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Wear EE, Song J, Zynda GJ, Mickelson-Young L, LeBlanc C, Lee TJ, Deppong DO, Allen GC, Martienssen RA, Vaughn MW, Hanley-Bowdoin L, Thompson WF. Comparing DNA replication programs reveals large timing shifts at centromeres of endocycling cells in maize roots. PLoS Genet 2020; 16:e1008623. [PMID: 33052904 PMCID: PMC7588055 DOI: 10.1371/journal.pgen.1008623] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 10/26/2020] [Accepted: 08/28/2020] [Indexed: 12/20/2022] Open
Abstract
Plant cells undergo two types of cell cycles–the mitotic cycle in which DNA replication is coupled to mitosis, and the endocycle in which DNA replication occurs in the absence of cell division. To investigate DNA replication programs in these two types of cell cycles, we pulse labeled intact root tips of maize (Zea mays) with 5-ethynyl-2’-deoxyuridine (EdU) and used flow sorting of nuclei to examine DNA replication timing (RT) during the transition from a mitotic cycle to an endocycle. Comparison of the sequence-based RT profiles showed that most regions of the maize genome replicate at the same time during S phase in mitotic and endocycling cells, despite the need to replicate twice as much DNA in the endocycle and the fact that endocycling is typically associated with cell differentiation. However, regions collectively corresponding to 2% of the genome displayed significant changes in timing between the two types of cell cycles. The majority of these regions are small with a median size of 135 kb, shift to a later RT in the endocycle, and are enriched for genes expressed in the root tip. We found larger regions that shifted RT in centromeres of seven of the ten maize chromosomes. These regions covered the majority of the previously defined functional centromere, which ranged between 1 and 2 Mb in size in the reference genome. They replicate mainly during mid S phase in mitotic cells but primarily in late S phase of the endocycle. In contrast, the immediately adjacent pericentromere sequences are primarily late replicating in both cell cycles. Analysis of CENH3 enrichment levels in 8C vs 2C nuclei suggested that there is only a partial replacement of CENH3 nucleosomes after endocycle replication is complete. The shift to later replication of centromeres and possible reduction in CENH3 enrichment after endocycle replication is consistent with a hypothesis that centromeres are inactivated when their function is no longer needed. In traditional cell division, or mitosis, a cell’s genetic material is duplicated and then split between two daughter cells. In contrast, in some specialized cell types, the DNA is duplicated a second time without an intervening division step, resulting in cells that carry twice as much DNA. This phenomenon, which is called the endocycle, is common during plant development. At each step, DNA replication follows an ordered program in which highly compacted DNA is unraveled and replicated in sections at different times during the synthesis (S) phase. In plants, it is unclear whether traditional and endocycle programs are the same, especially since endocycling cells are typically in the process of differentiation. Using root tips of maize, we found that in comparison to replication in the mitotic cell cycle, there is a small portion of the genome whose replication in the endocycle is shifted in time, usually to later in S phase. Some of these regions are scattered around the genome and mostly coincide with active genes. However, the most prominent shifts occur in centromeres. The shift to later replication in centromeres is noteworthy because they orchestrate the process of separating duplicated chromosomes into daughter cells, a function that is not needed in the endocycle.
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Affiliation(s)
- Emily E. Wear
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
- * E-mail:
| | - Jawon Song
- Texas Advanced Computing Center, University of Texas, Austin, Texas, United States of America
| | - Gregory J. Zynda
- Texas Advanced Computing Center, University of Texas, Austin, Texas, United States of America
| | - Leigh Mickelson-Young
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Chantal LeBlanc
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Tae-Jin Lee
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - David O. Deppong
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - George C. Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Robert A. Martienssen
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Matthew W. Vaughn
- Texas Advanced Computing Center, University of Texas, Austin, Texas, United States of America
| | - Linda Hanley-Bowdoin
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - William F. Thompson
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America
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Wear EE, Song J, Zynda GJ, LeBlanc C, Lee TJ, Mickelson-Young L, Concia L, Mulvaney P, Szymanski ES, Allen GC, Martienssen RA, Vaughn MW, Hanley-Bowdoin L, Thompson WF. Genomic Analysis of the DNA Replication Timing Program during Mitotic S Phase in Maize ( Zea mays) Root Tips. Plant Cell 2017; 29:2126-2149. [PMID: 28842533 PMCID: PMC5635974 DOI: 10.1105/tpc.17.00037] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 07/31/2017] [Accepted: 08/24/2017] [Indexed: 05/19/2023]
Abstract
All plants and animals must replicate their DNA, using a regulated process to ensure that their genomes are completely and accurately replicated. DNA replication timing programs have been extensively studied in yeast and animal systems, but much less is known about the replication programs of plants. We report a novel adaptation of the "Repli-seq" assay for use in intact root tips of maize (Zea mays) that includes several different cell lineages and present whole-genome replication timing profiles from cells in early, mid, and late S phase of the mitotic cell cycle. Maize root tips have a complex replication timing program, including regions of distinct early, mid, and late S replication that each constitute between 20 and 24% of the genome, as well as other loci corresponding to ∼32% of the genome that exhibit replication activity in two different time windows. Analyses of genomic, transcriptional, and chromatin features of the euchromatic portion of the maize genome provide evidence for a gradient of early replicating, open chromatin that transitions gradually to less open and less transcriptionally active chromatin replicating in mid S phase. Our genomic level analysis also demonstrated that the centromere core replicates in mid S, before heavily compacted classical heterochromatin, including pericentromeres and knobs, which replicate during late S phase.
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Affiliation(s)
- Emily E Wear
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - Jawon Song
- Texas Advanced Computing Center, University of Texas, Austin, Texas 78758
| | - Gregory J Zynda
- Texas Advanced Computing Center, University of Texas, Austin, Texas 78758
| | - Chantal LeBlanc
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724
| | - Tae-Jin Lee
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - Leigh Mickelson-Young
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - Lorenzo Concia
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - Patrick Mulvaney
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - Eric S Szymanski
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - George C Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina 27695
| | | | - Matthew W Vaughn
- Texas Advanced Computing Center, University of Texas, Austin, Texas 78758
| | - Linda Hanley-Bowdoin
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - William F Thompson
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27695
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Wear EE, Concia L, Brooks AM, Markham EA, Lee TJ, Allen GC, Thompson WF, Hanley-Bowdoin L. Isolation of Plant Nuclei at Defined Cell Cycle Stages Using EdU Labeling and Flow Cytometry. Methods Mol Biol 2016; 1370:69-86. [PMID: 26659955 DOI: 10.1007/978-1-4939-3142-2_6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
5-Ethynyl-2'-deoxyuridine (EdU) is a nucleoside analog of thymidine that can be rapidly incorporated into replicating DNA in vivo and, subsequently, detected by using "click" chemistry to couple its terminal alkyne group to fluorescent azides such as Alexa Fluor 488. Recently, EdU incorporation followed by coupling with a fluorophore has been used to visualize newly synthesized DNA in a wide range of plant species. One particularly useful application is in flow cytometry, where two-parameter sorting can be employed to analyze different phases of the cell cycle, as defined both by total DNA content and the amount of EdU pulse-labeled DNA. This approach allows analysis of the cell cycle without the need for synchronous cell populations, which can be difficult to obtain in many plant systems. The approach presented here, which was developed for fixed, EdU-labeled nuclei, can be used to prepare analytical profiles as well as to make highly purified preparations of G1, S, or G2/M phase nuclei for molecular or biochemical analysis. We present protocols for EdU pulse labeling, tissue fixation and harvesting, nuclei preparation, and flow sorting. Although developed for Arabidopsis suspension cells and maize root tips, these protocols should be modifiable to many other plant systems.
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Affiliation(s)
- Emily E Wear
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Lorenzo Concia
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, 27695, USA
| | - Ashley M Brooks
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, 27695, USA
| | - Emily A Markham
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Tae-Jin Lee
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
- Syngenta Crop Protection, LLC, Research Triangle Park, NC, 27709, USA
| | - George C Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, NC, 27695, USA
| | - William F Thompson
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Linda Hanley-Bowdoin
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, 27695, USA.
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Bass HW, Hoffman GG, Lee TJ, Wear EE, Joseph SR, Allen GC, Hanley-Bowdoin L, Thompson WF. Defining multiple, distinct, and shared spatiotemporal patterns of DNA replication and endoreduplication from 3D image analysis of developing maize (Zea mays L.) root tip nuclei. Plant Mol Biol 2015; 89:339-51. [PMID: 26394866 PMCID: PMC4631726 DOI: 10.1007/s11103-015-0364-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 08/19/2015] [Indexed: 05/09/2023]
Abstract
Spatiotemporal patterns of DNA replication have been described for yeast and many types of cultured animal cells, frequently after cell cycle arrest to aid in synchronization. However, patterns of DNA replication in nuclei from plants or naturally developing organs remain largely uncharacterized. Here we report findings from 3D quantitative analysis of DNA replication and endoreduplication in nuclei from pulse-labeled developing maize root tips. In both early and middle S phase nuclei, flow-sorted on the basis of DNA content, replicative labeling was widely distributed across euchromatic regions of the nucleoplasm. We did not observe the perinuclear or perinucleolar replicative labeling patterns characteristic of middle S phase in mammals. Instead, the early versus middle S phase patterns in maize could be distinguished cytologically by correlating two quantitative, continuous variables, replicative labeling and DAPI staining. Early S nuclei exhibited widely distributed euchromatic labeling preferentially localized to regions with weak DAPI signals. Middle S nuclei also exhibited widely distributed euchromatic labeling, but the label was preferentially localized to regions with strong DAPI signals. Highly condensed heterochromatin, including knobs, replicated during late S phase as previously reported. Similar spatiotemporal replication patterns were observed for both mitotic and endocycling maize nuclei. These results revealed that maize euchromatin exists as an intermingled mixture of two components distinguished by their condensation state and replication timing. These different patterns might reflect a previously described genome organization pattern, with "gene islands" mostly replicating during early S phase followed by most of the intergenic repetitive regions replicating during middle S phase.
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Affiliation(s)
- Hank W Bass
- Department of Biological Science, Florida State University, 319 Stadium Drive, King Life Sciences Building, Tallahassee, FL, 32306-4295, USA.
| | - Gregg G Hoffman
- Department of Biological Science, Florida State University, 319 Stadium Drive, King Life Sciences Building, Tallahassee, FL, 32306-4295, USA
| | - Tae-Jin Lee
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
| | - Emily E Wear
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
| | - Stacey R Joseph
- Department of Biological Science, Florida State University, 319 Stadium Drive, King Life Sciences Building, Tallahassee, FL, 32306-4295, USA
| | - George C Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, NC, 27695-7609, USA
| | - Linda Hanley-Bowdoin
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
| | - William F Thompson
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
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Patel TK, Krasnyanski SF, Allen GC, Louws FJ, Panthee DR, Williamson JD. Tomato Plants Overexpressing a Celery Mannitol Dehydrogenase (MTD) Have Decreased Susceptibility to <i>Botrytis cinerea</i>. ACTA ACUST UNITED AC 2015. [DOI: 10.4236/ajps.2015.68116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Bass HW, Wear EE, Lee TJ, Hoffman GG, Gumber HK, Allen GC, Thompson WF, Hanley-Bowdoin L. A maize root tip system to study DNA replication programmes in somatic and endocycling nuclei during plant development. J Exp Bot 2014; 65:2747-56. [PMID: 24449386 DOI: 10.1093/jxb/ert470] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The progress of nuclear DNA replication is complex in both time and space, and may reflect several levels of chromatin structure and 3-dimensional organization within the nucleus. To understand the relationship between DNA replication and developmental programmes, it is important to examine replication and nuclear substructure in different developmental contexts including natural cell-cycle progressions in situ. Plant meristems offer an ideal opportunity to analyse such processes in the context of normal growth of an organism. Our current understanding of large-scale chromosomal DNA replication has been limited by the lack of appropriate tools to visualize DNA replication with high resolution at defined points within S phase. In this perspective, we discuss a promising new system that can be used to visualize DNA replication in isolated maize (Zea mays L.) root tip nuclei after in planta pulse labelling with the thymidine analogue, 5-ethynyl-2'-deoxyuridine (EdU). Mixed populations of EdU-labelled nuclei are then separated by flow cytometry into sequential stages of S phase and examined directly using 3-dimensional deconvolution microscopy to characterize spatial patterns of plant DNA replication. Combining spatiotemporal analyses with studies of replication and epigenetic inheritance at the molecular level enables an integrated experimental approach to problems of mitotic inheritance and cellular differentiation.
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Affiliation(s)
- Hank W Bass
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA
| | - Emily E Wear
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
| | - Tae-Jin Lee
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
| | - Gregg G Hoffman
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA
| | - Hardeep K Gumber
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA
| | - George C Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695, USA
| | - William F Thompson
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
| | - Linda Hanley-Bowdoin
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
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7
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Pascuzzi PE, Flores-Vergara MA, Lee TJ, Sosinski B, Vaughn MW, Hanley-Bowdoin L, Thompson WF, Allen GC. In vivo mapping of arabidopsis scaffold/matrix attachment regions reveals link to nucleosome-disfavoring poly(dA:dT) tracts. Plant Cell 2014; 26:102-20. [PMID: 24488963 PMCID: PMC3963562 DOI: 10.1105/tpc.113.121194] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 11/25/2013] [Accepted: 01/10/2014] [Indexed: 05/21/2023]
Abstract
Scaffold or matrix attachment regions (S/MARs) are found in all eukaryotes. The pattern of distribution and genomic context of S/MARs is thought to be important for processes such as chromatin organization and modulation of gene expression. Despite the importance of such processes, much is unknown about the large-scale distribution and sequence content of S/MARs in vivo. Here, we report the use of tiling microarrays to map 1358 S/MARs on Arabidopsis thaliana chromosome 4 (chr4). S/MARs occur throughout chr4, spaced much more closely than in the large plant and animal genomes that have been studied to date. Arabidopsis S/MARs can be divided into five clusters based on their association with other genomic features, suggesting a diversity of functions. While some Arabidopsis S/MARs may define structural domains, most occur near the transcription start sites of genes. Genes associated with these S/MARs have an increased probability of expression, which is particularly pronounced in the case of transcription factor genes. Analysis of sequence motifs and 6-mer enrichment patterns show that S/MARs are preferentially enriched in poly(dA:dT) tracts, sequences that resist nucleosome formation, and the majority of S/MARs contain at least one nucleosome-depleted region. This global view of S/MARs provides a framework to begin evaluating genome-scale models for S/MAR function.
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Affiliation(s)
- Pete E. Pascuzzi
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695
| | | | - Tae-Jin Lee
- Department of Plant Biology, North Carolina State University, Raleigh, North Carolina 27695
| | - Bryon Sosinski
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina 27695
| | - Matthew W. Vaughn
- Texas Advanced Computing Center, University of Texas, Austin, Texas 78758
| | - Linda Hanley-Bowdoin
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695
| | - William F. Thompson
- Departments of Plant Biology, Genetics, and Crop Science, North Carolina State University, Raleigh, North Carolina 27695
| | - George C. Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina 27695
- Address correspondence to
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Scott TB, Petherbridge JR, Harker NJ, Ball RJ, Heard PJ, Glascott J, Allen GC. The oxidative corrosion of carbide inclusions at the surface of uranium metal during exposure to water vapour. J Hazard Mater 2011; 195:115-123. [PMID: 21862213 DOI: 10.1016/j.jhazmat.2011.08.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 08/03/2011] [Accepted: 08/04/2011] [Indexed: 05/31/2023]
Abstract
The reaction between uranium and water vapour has been well investigated, however discrepancies exist between the described kinetic laws, pressure dependence of the reaction rate constant and activation energies. Here this problem is looked at by examining the influence of impurities in the form of carbide inclusions on the reaction. Samples of uranium containing 600 ppm carbon were analysed during and after exposure to water vapour at 19 mbar pressure, in an environmental scanning electron microscope (ESEM) system. After water exposure, samples were analysed using secondary ion mass spectrometry (SIMS), focused ion beam (FIB) imaging and sectioning and transmission electron microscopy (TEM) with X-ray diffraction (micro-XRD). The results of the current study indicate that carbide particles on the surface of uranium readily react with water vapour to form voluminous UO(3) · xH(2)O growths at rates significantly faster than that of the metal. The observation may also have implications for previous experimental studies of uranium-water interactions, where the presence of differing levels of undetected carbide may partly account for the discrepancies observed between datasets.
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Affiliation(s)
- T B Scott
- Interface Analysis Centre, University of Bristol, 121 St Michaels Hill, Bristol, BS2 8BS, United Kingdom.
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Allen GC, Elkan GH. Growth, Respiration, and Polypeptide Patterns of Bradyrhizobium sp. (Arachis) Strain 3G4b20 from Succinate- or Oxygen-Limited Continuous Cultures. Appl Environ Microbiol 2010; 56:1025-32. [PMID: 16348154 PMCID: PMC184338 DOI: 10.1128/aem.56.4.1025-1032.1990] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Succinate- or oxygen-limited continuous cultures were used to study the influences of different concentrations of dissolved oxygen and ammonia on the growth, respiration, and polypeptide patterns of Bradyrhizobium sp. (Arachis) strain 3G4b20. During succinate-limited growth, molar growth yields on succinate (Y(succ)) ranged from 38.9 to 44.4 g (dry weight) of cells mol of succinate and were not greatly influenced by changes in dilution rates or changes in the oxygen concentrations that we tested. Succinate, malate, and fumarate induced the highest rates of oxygen uptake in all of the steady states in which the supply rates of (NH(4))(2)SO(4) ranged between 322 and 976 mumol h. However, the amino acids aspartate, asparagine, and glutamate could also be used as respiratory substrates, especially when the (NH(4))(2)SO(4) supply rate was decreased to 29 mumol h. Glutamine-dependent respiration was seen only when the (NH(4))(2)SO(4) supply rate was 29 mumol h and thus appears to be under tight ammonia control. Nitrogenase activity was detected only when the culture was switched from a succinate-limited steady state to an oxygen-limited steady state. Comparison of major silver-stained proteins from three steady states by two-dimensional gel electrophoresis revealed that nearly 60% were affected by oxygen and 24% were affected by ammonia. These data are consistent with reports that oxygen has a major regulatory role over developmental processes in Rhizobium sp. and Bradyrhizobium sp.
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Affiliation(s)
- G C Allen
- Microbiology Department, 4525 Gardner Hall, North Carolina State University, Raleigh, North Carolina 27695
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Allen GC, Grimm DT, Elkan GH. Oxygen Uptake and Hydrogen-Stimulated Nitrogenase Activity from Azorhizobium caulinodans ORS571 Grown in a Succinate-Limited Chemostat. Appl Environ Microbiol 2010; 57:3220-5. [PMID: 16348585 PMCID: PMC183951 DOI: 10.1128/aem.57.11.3220-3225.1991] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Succinate-limited continuous cultures of an Azorhizobium caulinodans strain were grown on ammonia or nitrogen gas as a nitrogen source. Ammonia-grown cells became oxygen limited at 1.7 muM dissolved oxygen, whereas nitrogen-fixing cells remained succinate limited even at dissolved oxygen concentrations as low as 0.9 muM. Nitrogen-fixing cells tolerated dissolved oxygen concentrations as high as 41 muM. Succinate-dependent oxygen uptake rates of cells from the different steady states ranged from 178 to 236 nmol min mg of protein and were not affected by varying chemostat-dissolved oxygen concentration or nitrogen source. When equimolar concentrations of succinate and beta-hydroxybutyrate were combined, oxygen uptake rates were greater than when either substrate was used alone. Azide could also used alone as a respiratory substrate regardless of nitrogen source; however, when azide was added following succinate additions, oxygen uptake was inhibited in ammonia-grown cells and stimulated in nitrogen-fixing cells. Use of 25 mM succinate in the chemostat resevoir at a dilution rate of 0.1 h resulted in high levels of background respiration and nitrogenase activity, indicating that the cells were not energy limited. Lowering the reservoir succinate to 5 mM imposed energy limitation. Maximum succinate-dependent nitrogenase activity was 1,741 nmol of C(2)H(4)h mg (dry weight), and maximum hydrogen-dependent nitrogenase activity was 949 nmol of C(2)H(4) h mg (dry weight). However, when concentration of 5% (vol/vol) hydrogen or greater were combined with succinate, nitrogenase activity decreased by 35% in comparison to when succinate was used alone. Substitution of argon for nitrogen in the chemostat inflow gas resulted in "washout," proving that ORS571 can grow on N(2) and that there was not a nitrogen source in the medium that could substitute.
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Affiliation(s)
- G C Allen
- Microbiology Department, 4525 Gardner Hall, North Carolina State University, Raleigh, North Carolina 27695
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Lee TJ, Pascuzzi PE, Settlage SB, Shultz RW, Tanurdzic M, Rabinowicz PD, Menges M, Zheng P, Main D, Murray JAH, Sosinski B, Allen GC, Martienssen RA, Hanley-Bowdoin L, Vaughn MW, Thompson WF. Arabidopsis thaliana chromosome 4 replicates in two phases that correlate with chromatin state. PLoS Genet 2010; 6:e1000982. [PMID: 20548960 PMCID: PMC2883604 DOI: 10.1371/journal.pgen.1000982] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 05/12/2010] [Indexed: 12/23/2022] Open
Abstract
DNA replication programs have been studied extensively in yeast and animal systems, where they have been shown to correlate with gene expression and certain epigenetic modifications. Despite the conservation of core DNA replication proteins, little is known about replication programs in plants. We used flow cytometry and tiling microarrays to profile DNA replication of Arabidopsis thaliana chromosome 4 (chr4) during early, mid, and late S phase. Replication profiles for early and mid S phase were similar and encompassed the majority of the euchromatin. Late S phase exhibited a distinctly different profile that includes the remaining euchromatin and essentially all of the heterochromatin. Termination zones were consistent between experiments, allowing us to define 163 putative replicons on chr4 that clustered into larger domains of predominately early or late replication. Early-replicating sequences, especially the initiation zones of early replicons, displayed a pattern of epigenetic modifications specifying an open chromatin conformation. Late replicons, and the termination zones of early replicons, showed an opposite pattern. Histone H3 acetylated on lysine 56 (H3K56ac) was enriched in early replicons, as well as the initiation zones of both early and late replicons. H3K56ac was also associated with expressed genes, but this effect was local whereas replication time correlated with H3K56ac over broad regions. The similarity of the replication profiles for early and mid S phase cells indicates that replication origin activation in euchromatin is stochastic. Replicon organization in Arabidopsis is strongly influenced by epigenetic modifications to histones and DNA. The domain organization of Arabidopsis is more similar to that in Drosophila than that in mammals, which may reflect genome size and complexity. The distinct patterns of association of H3K56ac with gene expression and early replication provide evidence that H3K56ac may be associated with initiation zones and replication origins. During growth and development, all plants and animals must replicate their DNA. This process is regulated to ensure that all sequences are completely and accurately replicated and is limited to S phase of the cell cycle. In the cell, DNA is packaged with histone proteins into chromatin, and both DNA and histones are subject to epigenetic modifications that affect chromatin state. Euchromatin and heterochromatin are chromatin states marked by epigenetic modifications specifying open and closed conformations, respectively. Using the model plant Arabidopsis thaliana, we show that the time at which a DNA sequence replicates is influenced by the epigenetic modifications to the surrounding chromatin. DNA replication occurs in two phases, with euchromatin replicating in early and mid S phase and heterochromatin replicating late. DNA replication time has been linked to gene expression in other organisms, and this is also true in Arabidopsis because more genes are active in euchromatin when compared to heterochromatin. The earliest replicating DNA sequences are associated with acetylation of histone H3 on lysine 56 (H3K56ac). H3K56ac is also abundant in active genes, but the patterns of association of H3K56ac with gene expression and DNA replication are distinct, suggesting that H3K56ac is independently linked to both processes.
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Affiliation(s)
- Tae-Jin Lee
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Pete E. Pascuzzi
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Sharon B. Settlage
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Randall W. Shultz
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Milos Tanurdzic
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Pablo D. Rabinowicz
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Margit Menges
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Ping Zheng
- Department of Horticulture and Landscape Architecture, Washington State University, Pullman, Washington, United States of America
| | - Dorrie Main
- Department of Horticulture and Landscape Architecture, Washington State University, Pullman, Washington, United States of America
| | - James A. H. Murray
- School of Biosciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Bryon Sosinski
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - George C. Allen
- Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Robert A. Martienssen
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Linda Hanley-Bowdoin
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Matthew W. Vaughn
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - William F. Thompson
- Departments of Plant Biology, Genetics, and Crop Science, North Carolina State University, Raleigh, North Carolina, United States of America
- * E-mail:
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12
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Shultz RW, Lee TJ, Allen GC, Thompson WF, Hanley-Bowdoin L. Dynamic localization of the DNA replication proteins MCM5 and MCM7 in plants. Plant Physiol 2009; 150:658-69. [PMID: 19357199 PMCID: PMC2689970 DOI: 10.1104/pp.109.136614] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 04/02/2009] [Indexed: 05/21/2023]
Abstract
Genome integrity in eukaryotes depends on licensing mechanisms that prevent loading of the minichromosome maintenance complex (MCM2-7) onto replicated DNA during S phase. Although the principle of licensing appears to be conserved across all eukaryotes, the mechanisms that control it vary, and it is not clear how licensing is regulated in plants. In this work, we demonstrate that subunits of the MCM2-7 complex are coordinately expressed during Arabidopsis (Arabidopsis thaliana) development and are abundant in proliferating and endocycling tissues, indicative of a role in DNA replication. We show that endogenous MCM5 and MCM7 proteins are localized in the nucleus during G1, S, and G2 phases of the cell cycle and are released into the cytoplasmic compartment during mitosis. We also show that MCM5 and MCM7 are topologically constrained on DNA and that the MCM complex is stable under high-salt conditions. Our results are consistent with a conserved replicative helicase function for the MCM complex in plants but not with the idea that plants resemble budding yeast by actively exporting the MCM complex from the nucleus to prevent unauthorized origin licensing and rereplication during S phase. Instead, our data show that, like other higher eukaryotes, the MCM complex in plants remains in the nucleus throughout most of the cell cycle and is only dispersed in mitotic cells.
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Affiliation(s)
- Randall W Shultz
- Department of Molecular and Structural Biochemistry , North Carolina State University, Raleigh, North Carolina 27695-7651, USA.
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13
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Allen GC, Flores-Vergara MA, Krasynanski S, Kumar S, Thompson WF. A modified protocol for rapid DNA isolation from plant tissues using cetyltrimethylammonium bromide. Nat Protoc 2007; 1:2320-5. [PMID: 17406474 DOI: 10.1038/nprot.2006.384] [Citation(s) in RCA: 567] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We describe a modification of the DNA extraction method, in which cetyltrimethylammonium bromide (CTAB) is used to extract nucleic acids from plant tissues. In contrast to the original method, the modified CTAB procedure is faster, omits the selective precipitation and CsCl gradient steps, uses less expensive and toxic reagents, requires only inexpensive laboratory equipment and is more readily adapted to high-throughput DNA extraction. This protocol yields approximately 5-30 microg of total DNA from 200 mg of tissue fresh weight, depending on plant species and tissue source. It can be completed in as little as 5-6 h.
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Affiliation(s)
- G C Allen
- Department of Horticultural Science and Crop Science, 1200 Partners II, Campus Box 7550, 840 Main Campus Drive, North Carolina State University, Raleigh, NC 27606-7550, USA.
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14
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Santos AP, Wegel E, Allen GC, Thompson WF, Stoger E, Shaw P, Abranches R. In situ methods to localize transgenes and transcripts in interphase nuclei: a tool for transgenic plant research. Plant Methods 2006; 2:18. [PMID: 17081287 PMCID: PMC1635696 DOI: 10.1186/1746-4811-2-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2006] [Accepted: 11/02/2006] [Indexed: 05/08/2023]
Abstract
Genetic engineering of commercially important crops has become routine in many laboratories. However, the inability to predict where a transgene will integrate and to efficiently select plants with stable levels of transgenic expression remains a limitation of this technology. Fluorescence in situ hybridization (FISH) is a powerful technique that can be used to visualize transgene integration sites and provide a better understanding of transgene behavior. Studies using FISH to characterize transgene integration have focused primarily on metaphase chromosomes, because the number and position of integration sites on the chromosomes are more easily determined at this stage. However gene (and transgene) expression occurs mainly during interphase. In order to accurately predict the activity of a transgene, it is critical to understand its location and dynamics in the three-dimensional interphase nucleus. We and others have developed in situ methods to visualize transgenes (including single copy genes) and their transcripts during interphase from different tissues and plant species. These techniques reduce the time necessary for characterization of transgene integration by eliminating the need for time-consuming segregation analysis, and extend characterization to the interphase nucleus, thus increasing the likelihood of accurate prediction of transgene activity. Furthermore, this approach is useful for studying nuclear organization and the dynamics of genes and chromatin.
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Affiliation(s)
- Ana Paula Santos
- Plant Genetic Engineering Laboratory, Instituto de Tecnologia Química e Biológica, UNL, Av. República, 2781-901 Oeiras, Portugal
| | - Eva Wegel
- Department of Cell and Developmental Biology, John Innes Centre, Colney, Norwich NR4 7UH, UK
| | - George C Allen
- Plant Transformation Laboratory (PTL), Departments of Crop Science and Horticultural Science, Campus Box 7550, North Carolina State University, Raleigh, NC 27695, USA
| | - William F Thompson
- Plant Gene Expression Laboratory, Campus Box 7550, North Carolina State University Raleigh, NC 27695, USA
| | - Eva Stoger
- Institute for Molecular Biotechnology, RWTH Aachen, 52074 Aachen, Germany
| | - Peter Shaw
- Department of Cell and Developmental Biology, John Innes Centre, Colney, Norwich NR4 7UH, UK
| | - Rita Abranches
- Plant Cell Biology Laboratory, Instituto de Tecnologia Química e Biológica, UNL, Av. República, 2781-901 Oeiras, Portugal
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15
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Lewis AC, Kilburn MR, Heard PJ, Scott TB, Hallam KR, Allen GC, Learmonth ID. The entrapment of corrosion products from CoCr implant alloys in the deposits of calcium phosphate: a comparison of serum, synovial fluid, albumin, EDTA, and water. J Orthop Res 2006; 24:1587-96. [PMID: 16779825 DOI: 10.1002/jor.20198] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Physical wear of orthopedic implants is inevitable. CoCr alloy samples, typically used in joint reconstruction, corrode rapidly after removal of the protective oxide layer. The behavior of CoCr pellets immersed in human serum, foetal bovine serum (FBS), synovial fluid, albumin in phosphate-buffered saline (PBS), EDTA in PBS, and water were studied using X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The difference in the corrosive nature of human serum, water, albumin in PBS and synovial fluid after 5 days of immersion was highlighted by the oxide layer, which was respectively 15, 3.5, 1.5, and 1.5 nm thick. The thickness of an additional calcium phosphate deposit from human serum and synovial fluid was 40 and 2 nm, respectively. Co and Cr ions migrated from the bulk metal surface and were trapped in this deposit by the phosphate anion. This may account for the composition of wear debris from CoCr orthopedic implants, which is known to consist predominantly of hydroxy-phosphate compounds. Known components of synovial fluid including proteoglycans, pyrophosphates, phospholipids, lubricin, and superficial zone protein (SZP), have been identified as possible causes for the lack of significant calcium phosphate deposition in this environment. Circulation of these compounds around the whole implant may inhibit calcium phosphate deposition.
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Affiliation(s)
- A C Lewis
- Interface Analysis Centre, University of Bristol, 121 St. Michael's Hill, Bristol, BS2 8BS, UK.
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16
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Kumar S, Allen GC, Thompson WF. Gene targeting in plants: fingers on the move. Trends Plant Sci 2006; 11:159-61. [PMID: 16530459 DOI: 10.1016/j.tplants.2006.02.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 01/09/2006] [Accepted: 02/24/2006] [Indexed: 05/07/2023]
Abstract
Zinc-finger endonucleases (ZFNs) make targeted double-stranded breaks in genomic DNA and, thus, stimulate recombination and repair processes at specific sites. ZFNs can now be harnessed to stimulate homologous recombination and gene targeting in plants, which represents a major step towards modifying the plant genome more precisely. ZFN-mediated gene targeting is likely to become a powerful tool for genome research and genetic engineering.
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Affiliation(s)
- Sandeep Kumar
- Department of Botany, North Carolina State University, Raleigh, NC 27695-7612, USA.
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17
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Abranches R, Shultz RW, Thompson WF, Allen GC. Matrix attachment regions and regulated transcription increase and stabilize transgene expression. Plant Biotechnol J 2005; 3:535-43. [PMID: 17173639 DOI: 10.1111/j.1467-7652.2005.00144.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Transgene silencing has been shown to be associated with strong promoters, but it is not known whether the propensity for silencing is caused by the level of transcription, or some other property of the promoter. If transcriptional activity fosters silencing, then transgenes with inducible promoters may be less susceptible to silencing. To test this idea, a doxycycline-inducible luciferase transgene was transformed into an NT1 tobacco suspension culture cell line that constitutively expressed the tetracycline repressor. The inducible luciferase gene was flanked by tobacco Rb7 matrix attachment regions (MAR) or spacer control sequences in order to test the effects of MARs in conjunction with regulated transcription. Transformed lines were grown under continuous doxycycline (CI), or delayed doxycycline induction (DI) conditions. Delayed induction resulted in higher luciferase expression initially, but continued growth in the presence of doxycycline resulted in a reduction of expression to levels similar to those found in continuously induced lines. In both DI and CI treatments, the Rb7 MAR significantly reduced the percentage of silenced lines and increased transgene expression levels. These data demonstrate that active transcription increases silencing, especially in the absence of the Rb7 MAR. Importantly, the Rb7 MAR lines showed higher expression levels under both CI and DI conditions and avoided silencing that may occur in the absence of active transcription such as what would be expected as a result of condensed chromatin spreading.
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Affiliation(s)
- Rita Abranches
- North Carolina State University, Department of Crop Science, Box 7620, Raleigh, North Carolina 27695-7620, USA
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18
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Barbour ME, Finke M, Parker DM, Hughes JA, Allen GC, Addy M. The relationship between enamel softening and erosion caused by soft drinks at a range of temperatures. J Dent 2005; 34:207-13. [PMID: 16112333 DOI: 10.1016/j.jdent.2005.06.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Accepted: 06/06/2005] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVES Investigations of the erosive potential of soft drinks are usually performed at room or body temperature, but drinks are more frequently served chilled, with ice, or hot. Since the rate of chemical reactions usually increases with temperature, it is predicted that erosion is more severe at high temperatures and reduced at low temperatures. The aim of this study was to investigate the correlation between enamel softening, enamel erosion, and temperature. METHODS Atomic force microscopy nanoindentation and non-contact optical profilometry were used to assess changes in enamel nanomechanical properties after 5 min and erosive material loss after 30 min exposure to two different non-carbonated soft drinks at 4, 25, 50 and 75 degrees C. RESULTS For one drink (Robinson's Original Juice Drink), there was a statistically significant difference between nanomechanical properties and erosion depth at all temperatures, with softening and erosion increasing with temperature. For another drink (Ribena ToothKind Juice Drink), there was a slight softening and virtually no material loss, and temperature had no statistically significant impact on erosion. There was a good linear correlation (R2 = 0.94) between nanomechanical properties and material loss. CONCLUSIONS The difference between the drinks can be explained by their composition. For the erosive drink, material loss increased, and nanohardness decreased, approximately linearly with temperature. The correlation between softening and erosion demonstrated that nanomechanical properties after very short erosion times can be considered a good predictor of bulk material loss after considerably longer erosion times.
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Affiliation(s)
- M E Barbour
- Department of Oral and Dental Science, University of Bristol, Bristol, BS1 2LY, UK.
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19
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Lewis AC, Kilburn MR, Papageorgiou I, Allen GC, Case CP. Effect of synovial fluid, phosphate-buffered saline solution, and water on the dissolution and corrosion properties of CoCrMo alloys as used in orthopedic implants. J Biomed Mater Res A 2005; 73:456-67. [PMID: 15900610 DOI: 10.1002/jbm.a.30368] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The corrosion and dissolution of high- and low-carbon CoCrMo alloys, as used in orthopedic joint replacements, were studied by immersing samples in phosphate-buffered saline (PBS), water, and synovial fluid at 37 degrees C for up to 35 days. Bulk properties were analyzed with a fine ion beam microscope. Surface analyses by X-ray photoelectron spectroscopy and Auger electron spectroscopy showed surprisingly that synovial fluid produced a thin oxide/hydroxide layer. Release of ions into solution from the alloy also followed an unexpected pattern where synovial fluid, of all the samples, had the highest Cr concentration but the lowest Co concentration. The presence of carbide inclusions in the alloy did not affect the corrosion or the dissolution mechanisms, although the carbides were a significant feature on the metal surface. Only one mechanism was recognized as controlling the thickness of the oxide/hydroxide interface. The analysis of the dissolved metal showed two mechanisms at work: (1) a protein film caused ligand-induced dissolution, increasing the Cr concentration in synovial fluid, and was explained by the equilibrium constants; (2) corrosion at the interface increased the Co in PBS. The effect of prepassivating the samples (ASTM F-86-01) did not always have the desired effect of reducing dissolution. The release of Cr into PBS increased after prepassivation. The metal-synovial fluid interface did not contain calcium phosphate as a deposit, typically found where samples are exposed to calcium rich bodily fluids.
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Affiliation(s)
- A C Lewis
- Interface Analysis Centre, University of Bristol, 121 St Michaels Hill, Bristol BS2 8BS, UK.
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20
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Barbour ME, Parker DM, Allen GC, Jandt KD. Human enamel erosion in constant composition citric acid solutions as a function of degree of saturation with respect to hydroxyapatite. J Oral Rehabil 2005; 32:16-21. [PMID: 15634296 DOI: 10.1111/j.1365-2842.2004.01365.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The objective of this study was to investigate human enamel erosion under constant composition conditions, as a function of solution degree of saturation (DS) with respect to hydroxyapatite. The experimental conditions were relevant to the initial stages of enamel erosion by soft drinks. Nanoindentation was used to compare enamel surface softening caused by a control mineral water and two citric acid solutions with DS = 0.000 and DS = 0.032, both having pH 3.30. Enamel hardness and reduced elastic modulus were measured after 0, 30, 60, 120, 300 and 600 s exposure. A statistically significant change in enamel hardness was detected after 30 s exposure to both citric acid solutions, indicating that nanoindentation is extremely sensitive to the initial stages of erosion. There was a statistically significant difference between the mechanical properties of enamel exposed to the two citric acid solutions after 30, 60 and 120 s. At these times, the solution with DS = 0.000 caused twice as much enamel softening as that with DS = 0.032. This demonstrates that it may be possible to design a soft drink with a low erosive potential and a good taste by a small change in DS, at a typical drink pH.
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Affiliation(s)
- M E Barbour
- Department of Oral and Dental Science, University of Bristol, Bristol, UK
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21
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Allen GC, Spiker S, Thompson WF. Transgene integration: use of matrix attachment regions. Methods Mol Biol 2005; 286:313-26. [PMID: 15310930 DOI: 10.1385/1-59259-827-7:313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Matrix attachment regions (MARs) are operationally defined as DNA elements that bind specifically to the nuclear matrix in vitro. When MARs are positioned at the 5'- and 3'-ends of a transgene higher more predictable expression of the transgene results. MARs are increasingly being applied to prevent unwanted transgene silencing, which is especially common when direct DNA transformation methods are used. This chapter describes methods for the isolation of MARs and the subsequent methods allowing the investigator to incorporate MARS into transformation strategies that can both improve transformation frequency and result in predictable, stable expression of the transgenic trait.
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Affiliation(s)
- George C Allen
- Department of Crop Science, North Carolina State University, Raleigh, USA
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Allen GC, Farnell Y, Bell-Pedersen D, Cassone VM, Earnest DJ. Effects of altered Clock gene expression on the pacemaker properties of SCN2.2 cells and oscillatory properties of NIH/3T3 cells. Neuroscience 2004; 127:989-99. [PMID: 15312911 DOI: 10.1016/j.neuroscience.2004.06.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2004] [Indexed: 01/08/2023]
Abstract
While peripheral tissues and serum-shocked fibroblasts express rhythmic oscillations in clock gene expression, only the suprachiasmatic nucleus (SCN) is capable of endogenous, self-sustained rhythmicity and of functioning as a pacemaker by imposing rhythmic properties upon other cells. To differentially examine the molecular elements necessary for the distinctive rhythm-generating and pacemaking properties of the SCN, the effects of antisense inhibition of Clock expression on the rhythms in 2-deoxyglucose uptake and Per gene expression were compared in immortalized SCN cells and a fibroblast cell line. Similar to changes in molecular and physiological rhythmicity observed in the SCN of Clock mutant mice, the rhythmic pattern of Per2 expression was disrupted and the period of metabolic rhythmicity was increased in SCN2.2 cells subjected to antisense inhibition of Clock. NIH/3T3 fibroblasts cocultured with antisense-treated SCN2.2 cells showed metabolic rhythms with comparable increases in period and decreases in rhythm amplitude. Per2 expression in these cocultured fibroblasts exhibited a similar reduction in peak levels, but was marked by non-24 h or irregular peak-to-peak intervals. In serum-shocked NIH/3T3 fibroblasts, oscillations in Per2, Bmal1, and Cry1 expression persisted with some change in rhythm amplitude during antisense inhibition of CLOCK, demonstrating that feedback interactions between Clock and other core components of the clock mechanism may be regulated differently in SCN2.2 cells and fibroblasts. The present results suggest that CLOCK is differentially involved in the generation of endogenous molecular and metabolic rhythmicity within SCN2.2 cells and in the regulation of their specific outputs that control rhythmic processes in NIH/3T3 cells.
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Affiliation(s)
- G C Allen
- Department of Human Anatomy and Medical Neurobiology, Texas A&M University Health Science Center, College of Medicine, College Station, TX 77843-1114, USA
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Shahwan T, Erten HN, Black L, Allen GC. ToF–SIMS depth profiling analysis of the uptake of Ba2+ and Co2+ ions by natural kaolinite clay. J Colloid Interface Sci 2004; 277:23-8. [PMID: 15276033 DOI: 10.1016/j.jcis.2004.04.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2004] [Accepted: 04/12/2004] [Indexed: 11/23/2022]
Abstract
The sorption behavior of Ba(2+) and Co(2+) ions on a natural clay sample rich in kaolinite was studied using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Depth profiling at 10-A steps was performed up to a 70-A matrix depth of the clay prior to and following sorption. The results showed that Co(2+) is sorbed in slightly larger quantities than Ba(2+), with significant numbers of ions fixed on the outermost surface of the clay. Depletion of the ions K(+), Mg(2+), and Ca(2+) from the clay lattice was observed to accompany enrichment with Co(2+) and Ba(2+) ions. The data obtained using X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) indicated insignificant structural and morphological changes in the lattice of the clay upon sorption of both Ba(2+) and Co(2+) ions. Analysis using energy dispersive X-ray spectroscopy (EDS) showed that the average atomic percentage (+/-S.D.) of Ba and Co on kaolinite surface were 0.49 +/- 0.11 and 0.61 +/- 0.19 , respectively, indicating a limited uptake capacity of natural kaolinite for both ions.
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Affiliation(s)
- T Shahwan
- Department of Chemistry, Izmir Institute of Technology, 35430 Urla, Izmir, Turkey.
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Abstract
We report here a preliminary study in which dynamic secondary ion mass spectrometry (SIMS) has provided images of boron-10 (10B) in biological tissue as used in research into boron neutron capture therapy. Cultured tumour cells incubated in media containing known concentrations of a 10B-containing compound, p-boronophenylalanine (BPA), and intracranial tumour tissue from animals previously injected with BPA were analysed by an in-house constructed SIMS. Investigations were conducted in positive secondary ion detection mode using a 25-keV, 5-nA gallium primary ion source. For calibration purposes, tissue standards were also analysed and their boron-to-carbon signal ratios correlated to bulk boron concentrations measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Ion maps of 10B, 12C, 23Na and 39K showing gross tissue and cell features were acquired. SIMS and ICP-AES standard measurements were in good agreement. Tissue regions with high or low 10B concentrations were identified along with 10B hotspots in normal brain areas. Cultured cells revealed the intracellular localization of 10B. SIMS is capable of producing images showing the distribution of 10B at p.p.m. levels in cells and in normal and tumour-bearing brain tissue.
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Affiliation(s)
- A C Oyedepo
- Interface Analysis Centre, University of Bristol, 121 St Michael's Hill, Bristol BS2 8BS, UK
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Ascenzi R, Ulker B, Todd JJ, Sowinski DA, Schimeneck CR, Allen GC, Weissinger AK, Thompson WF. Analysis of trans-silencing interactions using transcriptional silencers of varying strength and targets with and without flanking nuclear matrix attachment regions. Transgenic Res 2003; 12:305-18. [PMID: 12779119 DOI: 10.1023/a:1023310118231] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We investigated the effect of the Rb7 matrix attachment region (MAR) on trans-silencing in tobacco plants, comparing the effects of three transgene silencer loci on ten target loci. Two of the silencer loci, C40 and C190, contain complex and rearranged transgene arrays consisting of 35S:GUS or NOS:NPTII containing plasmids. The third silencer locus, V271, was previously characterized as a complex locus containing rearranged 35S:RiN sequences. Each of these silencers can reduce 35S promoter-driven expression at other loci, albeit with varying efficiencies. The presence of MARs at a target locus does not prevent trans-silencing by the V271 silencer. However, four of seven MAR-containing loci were at least partially resistant to silencing by the C40 and C190 loci. One MAR locus was unaffected by C40, our weakest silencer, and three were silenced only when the silencer locus was maternally inherited. Silencing is progressive in the F1 and F2 generations; two days after germination there is little or no difference between seedlings derived from crosses to silencing or control lines, but seedlings containing silencer loci slowly lose expression during subsequent development. These observations are compatible with the hypothesis that a product of the silencer locus must accumulate before unlinked loci can be affected. However, our silencer loci are themselves silenced for GUS transcription, and coding region homology is not required for their effects on target loci. Our results are consistent with a model in which transcriptional silencing is triggered by transcription of sequences during the early stages of embryo or seedling development.
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Affiliation(s)
- Robert Ascenzi
- Department of Botany, North Carolina State University, Raleigh, NC 27695-7612, USA.
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Mankin SL, Allen GC, Phelan T, Spiker S, Thompson WF. Elevation of transgene expression level by flanking matrix attachment regions (MAR) is promoter dependent: a study of the interactions of six promoters with the RB7 3' MAR. Transgenic Res 2003; 12:3-12. [PMID: 12650520 DOI: 10.1023/a:1022194120518] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have analyzed effects of a matrix attachment region (MAR) from the tobacco RB7 gene on transgene expression from six different promoters in stably transformed tobacco cell cultures. The presence of MARs flanking the transgene increased expression of constructs based on the constitutive CaMV 35S, NOS, and OCS promoters. Expression from an induced heat shock promoter was also increased and MARs did not cause expression in the absence of heat shock. There was also no effect of MARs on the pea ferredoxin promoter, which is not normally expressed in this cell line. Importantly, most transgenes flanked by RB7 MAR elements showed a large reduction in the number of low expressing GUS transformants relative to control constructs without MARs.
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Affiliation(s)
- S Luke Mankin
- Department of Botany, NC State University, Raleigh, NC 27695-7612, USA.
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Abstract
The effects of five tetracycline analogues, anhydrotetracycline, doxycycline, minocycline, oxytetracycline, and tetracycline, on Top10 promoter activity in NT1 tobacco tissue culture cells have been analysed. The concentration that repressed Top10 promoter activity, the level of transgene repression and the kinetics of transgene de-repression were determined for each analogue, and could not be predicted from in vitro binding affinity to the tetracycline repressor or from comparison with animal cells. Doxycycline had the most potent effect on the Top10 promoter and completely inhibited transgene expression at 4 nmol l(-1). Tetracycline was the most versatile of the analogues tested; tetracycline inhibited the Top10 promoter at 10 nmol l(-1) and was easily washed out to restore Top10-driven expression in 12-24 h. A study was also made of the suitability for plant research of a novel tetracycline analogue, GR33076X. In animal cells, GR33076X de-repressed Top10 promoter activity in the presence of inhibitory concentrations of anhydrotetracycline. In NT1, it is shown that GR 33076X can antagonize repression of the Top10 promoter in the presence of tetracycline, but not of anhydrotetracycline or of doxycycline. Different tetracycline analogues can therefore be used to regulate the Top10 promoter in plant cells and this property may be exploited in planning an optimum course of transgene regulation.
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Affiliation(s)
- John Love
- Department of Plant Sciences, University of Cambridge, Downing Site, Cambridge CB2 3EA, UK.
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Dalton JS, Janes PA, Jones NG, Nicholson JA, Hallam KR, Allen GC. Photocatalytic oxidation of NOx gases using TiO2: a surface spectroscopic approach. Environ Pollut 2002; 120:415-422. [PMID: 12395856 DOI: 10.1016/s0269-7491(02)00107-0] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The bandgap of solid-state TiO2 (3.2 eV) enables it to be a useful photocatalyst in the ultraviolet (lambda < 380 nm) region of the spectrum. A clean TiO2 surface in the presence of sunlight therefore enables the removal of harmful NOx gases from the atmosphere by oxidation to nitrates. These properties, in addition to the whiteness, relative cheapness and non-toxicity, make TiO2 ideal for the many de-NOX catalysts that are currently being commercially exploited both in the UK and Japan for concrete paving materials in inner cities. There is need, however, for further academic understanding of the surface reactions involved. Hence, we have used surface specific techniques, including X-ray photoelectron spectroscopy and Raman spectroscopy, to investigate the NOx adsorbate reaction at the TiO2 substrate surface.
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Affiliation(s)
- J S Dalton
- Interface Analysis Centre, University of Bristol, UK
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Abstract
BACKGROUND The Le Fort I maxillary osteotomy approach for skull base tumor removal in the pediatric age group has not been widely discussed in the literature except for sporadic case reports and limited case series. OBJECTIVES To review our experience with the Le Fort I osteotomy and to propose that it be used as an alternative approach because of its many advantages for the removal of tumors of the central skull base and paranasal sinuses. DESIGN Case series. SETTING Tertiary academic center. PATIENTS AND METHODS A 5-year retrospective chart review of cases involving children who had undergone skull base tumor resection via the Le Fort I osteotomy approach. INTERVENTIONS Skull base tumor removal via the Le Fort I osteotomy approach. MAIN OUTCOME MEASURES Tumor type, location, and size; intraoperative and postoperative complications; and residual tumor and/or tumor recurrence associated with the surgical approach. RESULTS Eleven patients (9 boys and 2 girls; mean age, 14.3 years) were identified through the chart review. The tumor types included 8 angiofibromas, 1 malignant fibrous histiocytoma, 1 giant cell tumor, and 1 cavernous hemangioma. All these lesions had extensive tumor growth into at least 1 of the following sites: pterygomaxillary space, sphenoidal sinus, and areas adjacent to the optic nerve, cavernous sinus, clivus, and anterior cranial fossa. The mean follow-up for this cohort was 12.8 months. No intraoperative complications were noted. Postoperative complications were reviewed with respect to the approach. To date, there have been no cases of residual tumor or tumor recurrence that can be attributed to the procedure. CONCLUSIONS Our experience suggests that the Le Fort I osteotomy approach is a useful technique for the removal of extensive central skull base tumors and paranasal sinuses in the pediatric age group. It has distinct advantages over traditional anterior or lateral approaches, including a more direct line of vision and improved exposure and cosmesis.
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Affiliation(s)
- T M Lewark
- The Children's Hospital, Denver, CO 80218, USA
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Abstract
Matrix attachment regions (MARs) are operationally defined as DNA elements that bind specifically to the nuclear matrix in vitro. It is possible, although unproven, that they also mediate binding of chromatin to the nuclear matrix in vivo and alter the topology of the genome in interphase nuclei. When MARs are positioned on either side of a transgene their presence usually results in higher and more stable expression in transgenic plants or cell lines, most likely by minimizing gene silencing. Our review explores current data and presents several plausible models to explain MAR effects on transgene expression.
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Affiliation(s)
- G C Allen
- Department of Botany, North Carolina State University, Raleigh 27695, USA.
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Abstract
The history of pediatric airway management is inseparable from the history of medicine in general. Advancing medical technology and improved childhood survival gave impetus for pioneering physicians with a vision for the future to branch out and develop the specialty of pediatric otolaryngology. Institutions and organizations committed to research, uncompromised care, and training have provided a firm foundation for the future growth and development of the specialty.
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Affiliation(s)
- G C Allen
- Department of Otolaryngology-Head and Neck Surgery, University of Colorado School of Medicine, The Children's Hospital, Denver, CO 80218, USA
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Abstract
Varicella is a nearly ubiquitous acquired childhood disease. Infectious complications of varicella can be life- or limb-threatening. These complications appear 3 to 4 days after the appearance of varicella exanthem and are heralded by fever, pain, and erythema of the overlying skin. Airway complications of varicella are rare, rapidly evolving, and, unfortunately, difficult to visualize. We report a child who presented with a unique combination of varicella-induced airway complications-acute epiglottitis and subsequent necrotizing fasciitis of the head and neck. varicella, epiglottitis, necrotizing fasciitis, group A beta-hemolytic streptococcus, nasopharyngoscopy.
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Affiliation(s)
- C L Slack
- Department of Otolaryngology, University of Colorado School of Medicine, Children's Hospital, Denver, Colorado, USA.
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Michalowski SM, Allen GC, Hall GE, Thompson WF, Spiker S. Characterization of randomly-obtained matrix attachment regions (MARs) from higher plants. Biochemistry 1999; 38:12795-804. [PMID: 10504249 DOI: 10.1021/bi991142c] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Matrix attachment regions (MARs) can be operationally defined as DNA fragments that bind to the nuclear matrix. We have created a library of randomly obtained MARs from tobacco (Nicotiana tobacum) by cloning DNA fragments that co-isolate with nuclear matrixes prepared by a method involving lithium diiodosalicylate. The interactions of several of the cloned MARs with nuclear matrixes were tested by an in vitro binding assay in which genomic DNA was used as competitor. Based on this assay, the MARs were classified as strong, medium, and weak binders. Examples of each of the binding classes were further studied by in vitro binding using self- and cross-competition. Estimates of dissociation constants for several MARs ranged from 6 to 11 nM and correlated inversely with binding strength. The number of binding sites per matrix for several MARs ranged from 4 x 10(5) to 9 x 10(5) and correlated directly with binding strength. We conclude that binding strength, as we have measured it, is a function of both numbers of binding sites and affinity for the sites. The tobacco MARs were sequenced and analyzed for overall AT content, for distribution of AT-rich regions, and for the abundance of several MAR-related motifs. Previously identified MAR motifs correlate to various degrees with binding strength. Notably, the Drosophila topoisomerase II motif does not correlate with binding strength of the tobacco MARs. A newly identified motif, the "90%AT Box," correlates better with binding strength than any of the previously identified motifs we investigated.
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Affiliation(s)
- S M Michalowski
- Department of Genetics and Department of Botany, North Carolina State University, Raleigh, North Carolina 27695, USA
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Allen GC, Armfield DR, Bontempo FA, Kingsley LA, Goldstein NA, Post JC. Adenotonsillectomy in children with von Willebrand disease. Arch Otolaryngol Head Neck Surg 1999; 125:547-51. [PMID: 10326812 DOI: 10.1001/archotol.125.5.547] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To review the effectiveness of a perioperative management protocol and our experience with a large population of patients with von Willebrand disease (vWD) who require adenotonsillar surgery (T&A). DESIGN A retrospective review of the medical records of all patients having the diagnosis of vWD who underwent T&A between January 1, 1992, and July 31, 1996. SETTING A tertiary care, university-based children's hospital. INTERVENTIONS Patients having a preoperative diagnosis of vWD received a single intravenous dose of desmopressin acetate, 0.3 pg/kg, approximately 20 minutes before the induction of anesthesia. Beginning January 15, 1994, a standard management protocol involving the postoperative administration of fluids and electrolytes was followed. MAIN OUTCOME MEASURES Operative blood loss and the incidence of postoperative bleeding and of hyponatremia. RESULTS Of approximately 4800 patients who underwent T&A during the study period, 69 patients had a diagnosis of vWD. All 67 patients identified preoperatively received desmopressin; 2 were identified by postoperative workup as a result of excessive surgical bleeding. Minimal immediate postoperative bleeding was noted in 7 patients (10%), but none required intervention. Delayed bleeding occurred in 9 patients (13%); all were readmitted to the hospital for observation, 4 (6%) requiring operative cauterization. Substantial postoperative hyponatremia occurred in 3 patients, and 1 patient had seizure activity. Symptomatic hyponatremia has been avoided since a protocol of fluid and electrolyte administration was instituted. CONCLUSIONS Although T&A can be performed safely in patients with vWD, it is not without an increased risk of postoperative hemorrhage. The administration of desmopressin has been reported to reduce the risk of bleeding, but it is not without risk. A protocol for fluid and electrolyte management is recommended.
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Affiliation(s)
- G C Allen
- Department of Pediatric Otolaryngology, Children's Hospital of Pittsburgh, PA, USA.
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Abstract
Adult, male Syrian hamsters received daily subcutaneous melatonin (25 microg) injections or vehicle injections at 08:00 or 17:00 hr for 11 weeks. Body weights were measured weekly throughout the experiment and testes weights, spleen weights, and serum was collected at the end of the experiment. The spleens were sectioned and immunocytochemically analyzed for immunoglobulin G and serum levels of interferon-gamma, interleukin-2, and interleukin-4 were determined in heterologous mouse assays. Melatonin injections at 17:00 hr, but not at 08:00 hr, increased body weights, decreased testes weights and serum testosterone levels, and had no effect on immunoglobulin G content in the spleen. Likewise, melatonin injections at 17:00 hr, but not at 08:00 hr, increased serum interferon-gamma levels, had no effect on interleukin-2 levels, and appeared to increase interleukin-4 levels. Since melatonin injections at 08:00 hr were ineffective in altering immune measurements and correlations between reproductive measures and immune measures were high, the most parsimonious explanation for these results is that melatonin injections at 17:00 hr depressed reproductive hormone levels and these depressed levels altered immune measures.
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Affiliation(s)
- T H Champney
- Department of Human Anatomy and Medical Neurobiology, College of Medicine, Texas A&M University Health Science Center, College Station 77843-1114, USA.
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Petracek ME, Dickey LF, Nguyen TT, Gatz C, Sowinski DA, Allen GC, Thompson WF. Ferredoxin-1 mRNA is destabilized by changes in photosynthetic electron transport. Proc Natl Acad Sci U S A 1998; 95:9009-13. [PMID: 9671795 PMCID: PMC21193 DOI: 10.1073/pnas.95.15.9009] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/1998] [Indexed: 02/08/2023] Open
Abstract
In transgenic tobacco, pea Ferredoxin-1 (Fed-1) mRNA accumulates rapidly in response to photosynthesis even when the transgene is driven by a constitutive promoter. To investigate the role of photosynthesis on Fed-1 mRNA stability, we used the tetracycline repressible Top10 promoter system to specifically shut off transcription of the Fed-1 transgene. The Fed-1 mRNA has a half-life of approximately 2.4 hr in the light and a half-life of only 1.2 hr in the dark or in the presence of the photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). These data indicate that cessation of photosynthesis, either by darkness or DCMU results in a destabilization of the Fed-1 mRNA. Furthermore, the Fed-1 mRNA half-life is reduced immediately upon transfer to darkness, suggesting that Fed-1 mRNA destabilization is a primary response to photosynthesis rather than a secondary response to long-term dark adaptation. Finally, the two different methods for efficient tetracycline delivery reported here generally should be useful for half-life measurements of other mRNAs in whole plants.
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Affiliation(s)
- M E Petracek
- Department of Botany, North Carolina State University, Raleigh, NC 27695, USA.
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Affiliation(s)
- G C Allen
- Department of Anesthesia, College of Medicine, The Pennsylvania State University, Hershey 17033, USA
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Allen GC, Tiu C, Koike K, Ritchey AK, Kurs-Lasky M, Wax MK. Transient-evoked otoacoustic emissions in children after cisplatin chemotherapy. Otolaryngol Head Neck Surg 1998; 118:584-8. [PMID: 9591854 DOI: 10.1177/019459989811800504] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Little is known about cisplatin ototoxicity in pediatric patients. Measurement of otoacoustic emissions is a rapid, reproducible, objective method of evaluating hearing. We examined whether transient-evoked otoacoustic emissions in pediatric patients exposed to cisplatin in the past correlated with audiographic findings. Twelve patients were entered into the study (mean age at treatment 7.8 years, mean cumulative dose 442.5 mg/mm2, mean 7.1 doses). Hearing at 3000 Hz was preserved in 82.6% of patients. In the higher frequencies significant sensorineural hearing loss was noted: 43.5% at 4 kHz; 81.0% at 6 kHz; and 90.5% at 8 kHz. Transient-evoked otoacoustic emissions were measurable in 11 of 12 patients. Middle ear disease accounted for abnormal otoacoustic emission seen in three patients (1 with effusion, 2 with significant negative middle ear pressure). When the middle ear was normal, a statistically significant correlation was seen between the transient-evoked otoacoustic emissions reproducibility and pure-tone threshold (correlation coefficient = -0.69, p = 0.008). Increased hearing loss was also associated with young age at first dose of cisplatin (p = 0.044), high number of chemotherapy cycles (p = 0.042), and high cumulative dose (p = 0.042).
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MESH Headings
- Adolescent
- Adult
- Age Factors
- Antineoplastic Agents/administration & dosage
- Antineoplastic Agents/therapeutic use
- Audiometry, Pure-Tone
- Audiometry, Speech
- Auditory Threshold/drug effects
- Auditory Threshold/physiology
- Bone Conduction/drug effects
- Bone Conduction/physiology
- Child
- Child, Preschool
- Cisplatin/administration & dosage
- Cisplatin/therapeutic use
- Cochlea/drug effects
- Cochlea/physiology
- Ear Diseases/physiopathology
- Ear, Middle/physiopathology
- Evoked Potentials, Auditory/drug effects
- Evoked Potentials, Auditory/physiology
- Female
- Hearing/drug effects
- Hearing/physiology
- Hearing Loss, High-Frequency/chemically induced
- Hearing Loss, High-Frequency/physiopathology
- Hearing Loss, Sensorineural/chemically induced
- Hearing Loss, Sensorineural/physiopathology
- Humans
- Male
- Otitis Media with Effusion/physiopathology
- Pilot Projects
- Pressure
- Reproducibility of Results
- Retrospective Studies
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Affiliation(s)
- G C Allen
- Department of Otolaryngology-Head and Neck Surgery, West Virginia University, Morgantown, USA
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Allen GC. Intraarticular controversy continues. Reg Anesth Pain Med 1998; 23:231. [PMID: 9570619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Allen GC, Larach MG, Kunselman AR. The sensitivity and specificity of the caffeine-halothane contracture test: a report from the North American Malignant Hyperthermia Registry. The North American Malignant Hyperthermia Registry of MHAUS. Anesthesiology 1998; 88:579-88. [PMID: 9523799 DOI: 10.1097/00000542-199803000-00006] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The caffeine-halothane contracture test (CHCT) is the only recognized laboratory test to diagnose malignant hyperthermia (MH). The authors report the results of their analysis of pooled data from the North American Malignant Hyperthermia Registry database to determine the sensitivity and specificity of the CHCT. METHODS The MH Clinical Grading Scale was used to identify 32 case subjects who were "almost certain" to be MH susceptible based on clinical criteria alone. Their CHCT results were compared with those of a group of 120 control subjects considered to be at low risk for MH. Diagnostic thresholds of the CHCT were adjusted, and its component tests were combined to generate receiver operating characteristic curves. The maximal Youden index for each component test was chosen as the diagnostic threshold indicative of MH susceptibility. RESULTS The highest sensitivity (97%; 95% CI, 84-100%) was achieved with a two-component test with thresholds of > or = 0.5 g contracture for 3% halothane, > or = 0.3 g contracture at 2 mM caffeine, or both, considered positive for MH. The test specificity was 78% (95% CI, 69-85%). The addition of other CHCT component tests did not improve CHCT sensitivity or specificity. CONCLUSION The CHCT achieves high sensitivity and acceptable specificity as a clinical laboratory diagnostic test when it is performed according to published standards. However, it cannot be used as a screening test because of the low prevalence of MH in the general population.
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Affiliation(s)
- G C Allen
- The North American Malignant Hyperthermia Registry, Department of Anesthesia, College of Medicine, The Pennsylvania State University, Hershey 17033-0850, USA.
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Goldstein NA, Armfield DR, Kingsley LA, Borland LM, Allen GC, Post JC. Postoperative complications after tonsillectomy and adenoidectomy in children with Down syndrome. Arch Otolaryngol Head Neck Surg 1998; 124:171-6. [PMID: 9485108 DOI: 10.1001/archotol.124.2.171] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To compare the postoperative course and complications after tonsillectomy or tonsillectomy and adenoidectomy in children with Down syndrome (group 1) with the postoperative course and complications in children in a control group (group 2). DESIGN Retrospective review of medical records for the period January 1, 1986, through March 30, 1996. SETTING Tertiary care children's hospital. PATIENTS The study included 87 children in group 1 and 64 children in group 2 matched for age, sex, and year of surgery. INTERVENTION Tonsillectomy and adenoidectomy (group 1, 79 children; group 2, 57 children) and tonsillectomy (group 1, 8 children; group 2, 7 children). MAIN OUTCOME MEASURES Length of hospitalization and postoperative complications. RESULTS The length of hospitalization was significantly increased for the children in group 1 compared with that of children in group 2 (1.6 vs 0.80 days; P=.001, Mann-Whitney U test). Twenty-two children (25%) in group 1 required airway management or observation in the pediatric intensive care unit compared with no children in group 2 who required such care (P<.001, Fisher exact test). None of the children in either group required reintubation, continuous positive airway pressure, or tracheotomy. Respiratory complications requiring intervention were 5 times more likely in group 1 (22 [25%] vs 3 [5%]; P<.001, Fisher exact test). The median time until intake of clear liquids and duration of intravenous therapy were significantly increased in group 1 compared with group 2 (5.0 vs 4.0 hours, P=.03; 23.5 vs 16.0 hours, P=.001, respectively; Mann-Whitney U test). CONCLUSIONS Although tonsillectomy and adenoidectomy can be performed safely in children with Down syndrome, the rate of postoperative respiratory complications is higher and the duration until adequate oral intake is resumed is longer. We therefore recommend that children with Down syndrome be admitted to the hospital overnight after undergoing tonsillectomy and adenoidectomy.
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Affiliation(s)
- N A Goldstein
- Department of Pediatric Otolaryngology, Children's Hospital of Pittsburgh, PA 15213, USA
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Abstract
In 1992, the Malignant Hyperthermia Association of the United States and The North American Malignant Hyperthermia Registry received reports of cardiac arrest in apparently healthy children given succinylcholine. Using data from 1990 to 1993, this study analyzes: (1) etiology of all reported pediatric arrests and (2) whether survival was associated with certain patient or treatment variables. We reviewed retrospectively all reports of pediatric (age < 18 years) arrests occurring within 24 hours of anesthesia. Etiology of arrests and presence of myopathy were determined. Twenty-five patients (92% male, median 45 months old) arrested; 23/25 (92%) were scheduled for minor surgery. Before receiving a potent inhalational anesthetic (92%) and/or succinylcholine (72%), these patients were evaluated by the anesthesiologist as being healthy with no personal or family history of myopathy. Serum potassium during arrest was measured in 18/25 (72%) patients; hyperkalemia (mean [K+] = 7.4 +/- 2.8, median 7.5 mmol/L) was detected in 13/18 (72%) patients. Postarrest resuscitations lasted a median of 42 minutes (range 10-296). Ten (40%) patients died, 1 (4%) is vegetative, and 14 (56%) returned to baseline neurologic function. A previously unrecognized Duchenne dystrophy (n = 8) or unspecified myopathy (n = 4) was diagnosed in 12 (48%) patients. Eight of these 12 patients' arrests were associated with hyperkalemia. Ten (40%) patients had no postarrest evaluation to exclude occult myopathy. No patient or treatment variables were statistically associated with survival. We conclude that, whenever possible, pediatricians should evaluate their patients (especially male infants and children) preoperatively for the presence of occult myopathy. During perianesthetic resuscitations, the pediatric advanced life support protocol should be modified to detect and treat hyperkalemia, a potentially reversible state even after prolonged resuscitation efforts. Following anesthetic deaths, pathologists should examine body fluid electrolytes and skeletal muscle for myopathy and dystrophin. If a preanesthetic creatine kinase screen for myopathy in male patients and restrictions on succinylcholine had been used, 64% of arrests and 60% of deaths might have been prevented. A formal prospective risk/benefit analysis for preventive measures is needed.
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Allen GC, Lubas S, Wax MK, Devore RF. Epidermal growth factor regulates topoisomerase II activity and drug sensitivity in human KB cells. Otolaryngol Head Neck Surg 1996. [PMID: 8643303 DOI: 10.1016/s0194-5998(96)70102-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Because of its unique DNA-cleaving and strand-passing activities, topoisomerase II is involved in many aspects of DNA metabolism, including replication, transcription, recombination, and repair. The cytotoxic potential of topoisomerase II-targeted drugs, such as etoposide, is related to their ability to stabilize covalently linked enzyme-DNA complexes, which are intermediates in the enzyme's catalytic cycle. Epidermal growth factor receptor is expressed on the cell surface of the majority of squamous cell carcinomas, and epidermal growth factor binding is known to stimulate a number of cellular transduction pathways, including tyrosine kinase, protein kinase C, and phospholipase C. Because topoisomerase II is a proliferation-dependent protein and has been shown to be a high-affinity substrate for many of these cellular transduction pathways, the effects of epidermal growth factor on cellular regulation and sensitivity to etoposide were studied with the human oral cavity squamous cell line, KB. Topoisomerase II catalytic activity was rapidly and transiently inhibited after the addition of epidermal growth factor to the cellular growth media. Western blot on nuclear extracts did not demonstrate alterations in topoisomerase II polypeptide levels to account for changes in catalytic activity. Epidermal growth factor treatment also led to the formation of stabilized, covalently linked enzyme-DNA complexes. Furthermore, epidermal growth factor-induced, topoisomerase II-mediated DNA strand breaks were additive to those induced by etoposide. This study indicates that epidermal growth factor specifically regulates the catalytic and DNA-cleaving activities of topoisomerase II in KB cells. This may direct clinical strategies for circumventing the intrinsic cellular resistance to chemotherapy commonly observed in squamous cell carcinomas of the head and neck.
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Affiliation(s)
- G C Allen
- Department of Otolaryngology-Head and Neck Surgery, West Virginia University, Morgantown, WV 26506-9200, USA
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Süzer S, Toppare L, Hallam KR, Allen GC. X-ray photoelectron spectroscopic investigation of conducting polymer blends. Anal Bioanal Chem 1996; 355:387-9. [PMID: 15045422 DOI: 10.1007/s0021663550387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/1995] [Accepted: 11/10/1995] [Indexed: 11/24/2022]
Abstract
Electrochemically prepared films of conducting polymers of polypyrrole and polythiophene and their blends with polyamide have been investigated by X-ray photoelectron spectroscopy. In the N1s region of the spectra of films containing polypyrrole the peak corresponding to N(+) at 402.0 eV is separated from that of neutral N. The intensity of the N(+) peak can be correlated with the electrical conductivity of the films and the spectroscopically derived ratio of F/N(+) is close to 4 indicating that one BF(-)(4) dopant ion is incorporated for every oxidized nitrogen center. In the spectra of films of polythiophene and its blends peaks corresponding to S and S(+) can not be resolved but again the F/C ratio correlates with the electrical conductivity.
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Affiliation(s)
- S Süzer
- Department of Chemistry, Bilkent University, 06533, Ankara, Turkey
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Allen GC, Lubas S, Wax MK, Devore RF. Epidermal Growth Factor Regulates Topoisomerase II Activity and Drug Sensitivity in Human KB Cells. Otolaryngol Head Neck Surg 1996; 114:785-92. [PMID: 8643303 DOI: 10.1016/s0194-59989670102-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Because of its unique DNA-cleaving and strand-passing activities, topoisomerase II is involved in many aspects of DNA metabolism, including replication, transcription, recombination, and repair. The cytotoxic potential of topoisomerase II–targeted drugs, such as etoposide, is related to their ability to stabilize covalently linked enzyme-DNA complexes, which are intermediates in the enzyme's catalytic cycle. Epidermal growth factor receptor is expressed on the cell surface of the majority of squamous cell carcinomas, and epidermal growth factor binding is known to stimulate a number of cellular transduction pathways, including tyrosine kinase, protein kinase C, and phospholipase C. Because topoisomerase II is a proliferation-dependent protein and has been shown to be a high-affinity substrate for many of these cellular transduction pathways, the effects of epidermal growth factor on cellular regulation and sensitivity to etoposide were studied with the human oral cavity squamous cell line, KB. Topoisomerase II catalytic activity was rapidly and transiently inhibited after the addition of epidermal growth factor to the cellular growth media. Western blot on nuclear extracts did not demonstrate alterations in topoisomerase II polypeptide levels to account for changes in catalytic activity. Epidermal growth factor treatment also led to the formation of stabilized, covalently linked enzyme-DNA complexes. Furthermore, epidermal growth factor-induced, topoisomerase II–mediated DNA strand breaks were additive to those induced by etoposide. This study indicates that epidermal growth factor specifically regulates the catalytic and DNA-cleaving activities of topoisomerase II in KB cells. This may direct clinical strategies for circumventing the intrinsic cellular resistance to chemotherapy commonly observed in squamous cell carcinomas of the head and neck.
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MESH Headings
- Antineoplastic Agents, Phytogenic/pharmacology
- Blotting, Western
- Carcinoma, Squamous Cell/drug therapy
- Carcinoma, Squamous Cell/enzymology
- Carcinoma, Squamous Cell/pathology
- Catalysis
- Cell Division/drug effects
- DNA Damage
- DNA Topoisomerases, Type II/drug effects
- DNA Topoisomerases, Type II/metabolism
- DNA, Neoplasm/drug effects
- Drug Screening Assays, Antitumor
- Epidermal Growth Factor/pharmacology
- Epidermal Growth Factor/physiology
- Etoposide/pharmacology
- Head and Neck Neoplasms/drug therapy
- Head and Neck Neoplasms/enzymology
- Head and Neck Neoplasms/pathology
- Humans
- KB Cells
- Tumor Cells, Cultured
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Affiliation(s)
- G C Allen
- Department of Otolaryngology-Head and Neck Surgery, West Virginia University, Morgantown, WV 26506-9200, USA
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Süzer S, Voscoboinikov T, Hallam KR, Allen GC. Electron spectroscopic investigation of Sn coatings on glasses. Anal Bioanal Chem 1996; 355:654-6. [PMID: 15045334 DOI: 10.1007/s0021663550654] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/1995] [Revised: 10/13/1995] [Accepted: 11/08/1995] [Indexed: 10/26/2022]
Abstract
Float glasses of different thicknesses and a conducting tin oxide glass have been investigated using Photo and Auger Electron Spectroscopy induced by AlKalpha X-rays. On the basis of measured chemical XPS shifts in the binding energies the chemical state of Sn (+2 or +4) incorporated on the float glasses could not be assigned. The use of the Auger parameter allows to separate relaxation and chemical contributions. The derived true chemical shifts of Sn on float-glasses are larger than those of SnO and/or SnO(2) due to the larger ionic environment of the glass matrix. Ar(+) or HF etching reveals that the concentration of Sn decreases exponentially as a function of depth from the surface.
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Affiliation(s)
- S Süzer
- Chemistry Department, Bilkent University, 06533, Ankara, Turkey
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Allen GC, Hall G, Michalowski S, Newman W, Spiker S, Weissinger AK, Thompson WF. High-level transgene expression in plant cells: effects of a strong scaffold attachment region from tobacco. Plant Cell 1996; 8:899-913. [PMID: 8672887 PMCID: PMC161147 DOI: 10.1105/tpc.8.5.899] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We have previously shown that yeast scaffold attachment regions (SARs) flanking a chimeric beta-glucuronidase (GUS) reporter gene increased per-copy expression levels by 24-fold in tobacco suspension cell lines stably transformed by microprojectile bombardment. In this study, we examined the effect of a DNA fragment originally identified in a tobacco genomic clone by its activity in an in vitro binding assay. The tobacco SAR has much greater scaffold binding affinity than does the yeast SAR, and tobacco cell lines stably transformed with constructs containing the tobacco SAR accumulated greater than fivefold more GUS enzyme activity than did lines transformed with the yeast SAR construct. Relative to the control construct, flanking the GUS gene with plant SARs increased overall expression per transgene copy by almost 140-fold. In transient expression assays, the same construct increased expression only approximately threefold relative to a control without SARs, indicating that the full SAR effect requires integration into chromosomal DNA. GUS activity in individual stable transformants was not simply proportional to transgene copy number, and the SAR effect was maximal in cell lines with fewer than approximately 10 transgene copies per tobacco genome. Lines with significantly higher copy numbers showed greatly greatly reduced expression relative to the low-copy-number lines. Our results indicate that strong SARs flanking a transgene greatly increases expression without eliminating variation between transformants. We propose that SARs dramatically reduce the severity or likelihood of homology-dependent gene silencing in cells with small numbers of transgenes but do not prevent silencing of transgenes present in many copies.
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Affiliation(s)
- G C Allen
- Department of Botany, North Carolina State University, Raleigh 27695, USA
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50
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Allen GC, Hall G, Michalowski S, Newman W, Spiker S, Weissinger AK, Thompson WF. High-level transgene expression in plant cells: effects of a strong scaffold attachment region from tobacco. Plant Cell 1996. [PMID: 8672887 DOI: 10.2307/3870291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We have previously shown that yeast scaffold attachment regions (SARs) flanking a chimeric beta-glucuronidase (GUS) reporter gene increased per-copy expression levels by 24-fold in tobacco suspension cell lines stably transformed by microprojectile bombardment. In this study, we examined the effect of a DNA fragment originally identified in a tobacco genomic clone by its activity in an in vitro binding assay. The tobacco SAR has much greater scaffold binding affinity than does the yeast SAR, and tobacco cell lines stably transformed with constructs containing the tobacco SAR accumulated greater than fivefold more GUS enzyme activity than did lines transformed with the yeast SAR construct. Relative to the control construct, flanking the GUS gene with plant SARs increased overall expression per transgene copy by almost 140-fold. In transient expression assays, the same construct increased expression only approximately threefold relative to a control without SARs, indicating that the full SAR effect requires integration into chromosomal DNA. GUS activity in individual stable transformants was not simply proportional to transgene copy number, and the SAR effect was maximal in cell lines with fewer than approximately 10 transgene copies per tobacco genome. Lines with significantly higher copy numbers showed greatly greatly reduced expression relative to the low-copy-number lines. Our results indicate that strong SARs flanking a transgene greatly increases expression without eliminating variation between transformants. We propose that SARs dramatically reduce the severity or likelihood of homology-dependent gene silencing in cells with small numbers of transgenes but do not prevent silencing of transgenes present in many copies.
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Affiliation(s)
- G C Allen
- Department of Botany, North Carolina State University, Raleigh 27695, USA
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