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Kariyawasam U, Gulati M, Wang Y, Bao H, Shan T, Li X, Cao X, Sumathipala N, Hu Y, Zhang X, Boons GJ, Jiang H. Preferential binding of DAP-PGs by major peptidoglycan recognition proteins found in cell-free hemolymph of Manduca sexta. Insect Biochem Mol Biol 2022; 148:103827. [PMID: 36007680 DOI: 10.1016/j.ibmb.2022.103827] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [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: 02/03/2022] [Revised: 07/09/2022] [Accepted: 08/07/2022] [Indexed: 06/15/2023]
Abstract
Peptidoglycan recognition proteins (PGRPs) detect invading bacteria to trigger or modulate immune responses in insects. While these roles are established in Drosophila, functional studies are not yet achieved at the PGRP family level in other insects. To attain this goal, we selected Manduca sexta PGRP12 and five of the nine secreted PGRPs for recombinant expression and biochemical characterization. We cloned PGRP2-5, 12 and 13 cDNAs, produced the proteins in full (PGRP2-5, 13) or in part (PGRP3s, 12e, 13N, 13C) in Sf9 cells, and tested their bindings of two muramyl pentapeptides by surface plasmon resonance, two soluble peptidoglycans by competitive ELISA, and four insoluble peptidoglycans and eight whole bacteria by a pull-down assay. Preferential binding of meso-diaminopimelic acid-peptidoglycans (DAP-PGs) was observed in all the proteins containing a peptidoglycan binding domain and, since PGRP6, 7 and 9 proteins were hardly detected in cell-free hemolymph, the reportoire of PGRPs (including PGRP1 published previously) in M. sexta hemolymph is likely adapted to mainly detect Gram-negative bacteria and certain Gram-positive bacteria with DAP-PGs located on their surface. After incubation with plasma from naïve larvae, PGRP2, 3f, 4, 5, 13f and 13N considerably stimulated prophenoloxidase activation in the absence of a bacterial elicitor. PGRP3s and 12e had much smaller effects. Inclusion of the full-length PGRPs and their regions in the plasma also led to proHP8 activation, supporting their connections to the Toll pathway, since HP8 is a Spӓtzle-1 processing enzyme in M. sexta. Together, these findings raised concerns on the common belief that the Toll-pathway is specific for Gram-positive bacteria in insects.
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Affiliation(s)
- Udeshika Kariyawasam
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA; Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Mansi Gulati
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Yang Wang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Haibo Bao
- Institute of Plant Protection, Jiangshu Academy of Agricultural Sciences, Nanjing, 210014, PR China
| | - Tisheng Shan
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Xiuru Li
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602, USA
| | - Xiaolong Cao
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA; Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Niranji Sumathipala
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Yingxia Hu
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA; Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Xiufeng Zhang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602, USA
| | - Haobo Jiang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA.
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Packer KF, Cramer MD. Quantifying N-loss by root abscission: consequences for wheat N budgets and δ 15N values. J Plant Physiol 2018; 231:49-56. [PMID: 30218929 DOI: 10.1016/j.jplph.2018.08.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 08/15/2018] [Accepted: 08/27/2018] [Indexed: 06/08/2023]
Abstract
Lower plant δ15N values relative to source δ15N are commonly attributed to 15N efflux. We determined the extent to which root abscission contributes to plant N-loss and consequences for plant δ15N. Wheat (Triticum aestivum L. cv. SST015) was grown in hydroponics with direct aeration, aeration constrained within a pipe and circulation of nutrient solution through sand, representing three levels of stability for root growth. The δ15N of nutrient solutions and root fragments were periodically determined, as well as root and shoot δ15N. Plants in solution had significantly more negative δ15N (-8.9 and -9.2‰) than plants in sand (-6.9‰), suggesting greater 15N-loss; root fragments were major biomass- (six-fold greater than root dry weight) and N-loss (two-fold greater than plant net N uptake) pathways in solution. These plants had more ephemeral roots and two-fold more root tips than the sand treatment. We estimated that root fragment loss decreased plant δ15N by at least -3.7, -2.6 and -1.0‰ in the direct, pipe and sand treatments, respectively. Positive nutrient solution δ15N in all treatments relative to the source δ15N suggests that plant N, probably derived from efflux, was present in solution. Despite this, root abscission and root turnover are also important N-loss pathways in plants, while plant δ15N values are probably influenced by a combination of root abscission and N efflux.
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Affiliation(s)
- Kirsten F Packer
- Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa.
| | - Michael D Cramer
- Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, South Africa
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Kruse J, Gao P, Eibelmeier M, Alfarraj S, Rennenberg H. Dynamics of amino acid redistribution in the carnivorous Venus flytrap (Dionaea muscipula) after digestion of 13 C/ 15 N-labelled prey. Plant Biol (Stuttg) 2017; 19:886-895. [PMID: 28727249 DOI: 10.1111/plb.12603] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [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: 06/12/2017] [Accepted: 07/17/2017] [Indexed: 06/07/2023]
Abstract
Amino acids represent an important component in the diet of the Venus flytrap (Dionaea muscipula), and supply plants with much needed nitrogen resources upon capture of insect prey. Little is known about the significance of prey-derived carbon backbones of amino acids for the success of Dionaea's carnivorous life-style. The present study aimed at characterizing the metabolic fate of 15 N and 13 C in amino acids acquired from double-labeled insect powder. We tracked changes in plant amino acid pools and their δ13 C- and δ15 N-signatures over a period of five weeks after feeding, as affected by contrasting feeding intensity and tissue type (i.e., fed and non-fed traps and attached petioles of Dionaea). Isotope signatures (i.e., δ13 C and δ15 N) of plant amino acid pools were strongly correlated, explaining 60% of observed variation. Residual variation was related to contrasting effects of tissue type, feeding intensity and elapsed time since feeding. Synthesis of nitrogen-rich transport compounds (i.e., amides) during peak time of prey digestion increased 15 N- relative to 13 C- abundances in amino acid pools. After completion of prey digestion, 13 C in amino acid pools was progressively exchanged for newly fixed 12 C. The latter process was most evident for non-fed traps and attached petioles of plants that had received ample insect powder. We argue that prey-derived amino acids contribute to respiratory energy gain and loss of 13 CO2 during conversion into transport compounds (i.e., 2 days after feeding), and that amino-nitrogen helps boost photosynthetic carbon gain later on (i.e., 5 weeks after feeding).
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Affiliation(s)
- J Kruse
- Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Universität Freiburg, Freiburg, Germany
| | - P Gao
- Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Universität Freiburg, Freiburg, Germany
| | - M Eibelmeier
- Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Universität Freiburg, Freiburg, Germany
| | - S Alfarraj
- College of Sciences, King Saud University, Riyadh, Saudi Arabia
| | - H Rennenberg
- Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Universität Freiburg, Freiburg, Germany
- College of Sciences, King Saud University, Riyadh, Saudi Arabia
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Zaia Alves GH, Hoeinghaus DJ, Manetta GI, Benedito E. Dry season limnological conditions and basin geology exhibit complex relationships with δ13C and δ15N of carbon sources in four Neotropical floodplains. PLoS One 2017; 12:e0174499. [PMID: 28358822 PMCID: PMC5373579 DOI: 10.1371/journal.pone.0174499] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [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: 12/21/2016] [Accepted: 03/10/2017] [Indexed: 11/27/2022] Open
Abstract
Studies in freshwater ecosystems are seeking to improve understanding of carbon flow in food webs and stable isotopes have been influential in this work. However, variation in isotopic values of basal production sources could either be an asset or a hindrance depending on study objectives. We assessed the potential for basin geology and local limnological conditions to predict stable carbon and nitrogen isotope values of six carbon sources at multiple locations in four Neotropical floodplain ecosystems (Paraná, Pantanal, Araguaia, and Amazon). Limnological conditions exhibited greater variation within than among systems. δ15N differed among basins for most carbon sources, but δ13C did not (though high within-basin variability for periphyton, phytoplankton and particulate organic carbon was observed). Although δ13C and δ15N values exhibited significant correlations with some limnological factors within and among basins, those relationships differed among carbon sources. Regression trees for both carbon and nitrogen isotopes for all sources depicted complex and in some cases nested relationships, and only very limited similarity was observed among trees for different carbon sources. Although limnological conditions predicted variation in isotope values of carbon sources, we suggest the resulting models were too complex to enable mathematical corrections of source isotope values among sites based on these parameters. The importance of local conditions in determining variation in source isotope values suggest that isotopes may be useful for examining habitat use, dispersal and patch dynamics within heterogeneous floodplain ecosystems, but spatial variability in isotope values needs to be explicitly considered when testing ecosystem models of carbon flow in these systems.
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Affiliation(s)
- Gustavo H. Zaia Alves
- Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais (PEA), Universidade Estadual de Maringá, Maringá, Paraná, Brasil
- Postdoctoral fellowship, National Council for Scientific and Technological Development (CNPq), Brasília, Distrito Federal, Brasil
- * E-mail:
| | - David J. Hoeinghaus
- Department of Biological Sciences and the Advanced Environmental Research Institute, University of North Texas, Denton, Texas, United States of America
| | - Gislaine I. Manetta
- Programa de Pós-Graduação em Biologia Comparada (PGB), Universidade Estadual de Maringá, Maringá, Paraná, Brasil
| | - Evanilde Benedito
- Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais (PEA), Universidade Estadual de Maringá, Maringá, Paraná, Brasil
- Programa de Pós-Graduação em Biologia Comparada (PGB), Universidade Estadual de Maringá, Maringá, Paraná, Brasil
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Cruz NF, Dienel GA, Patrick PA, Cooper AJL. Organ Distribution of 13N Following Intravenous Injection of [ 13N]Ammonia into Portacaval-Shunted Rats. Neurochem Res 2016; 42:1683-1696. [PMID: 27822667 DOI: 10.1007/s11064-016-2096-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/27/2016] [Accepted: 10/31/2016] [Indexed: 12/18/2022]
Abstract
Ammonia is neurotoxic, and chronic hyperammonemia is thought to be a major contributing factor to hepatic encephalopathy in patients with liver disease. Portacaval shunting of rats is used as an animal model to study the detrimental metabolic effects of elevated ammonia levels on body tissues, particularly brain and testes that are deleteriously targeted by high blood ammonia. In normal adult rats, the initial uptake of label (expressed as relative concentration) in these organs was relatively low following a bolus intravenous injection of [13N]ammonia compared with lungs, kidneys, liver, and some other organs. The objective of the present study was to determine the distribution of label following intravenous administration of [13N]ammonia among 14 organs in portacaval-shunted rats at 12 weeks after shunt construction. At an early time point (12 s) following administration of [13N]ammonia the relative concentration of label was highest in lung with lower, but still appreciable relative concentrations in kidney and heart. Clearance of 13N from blood and kidney tended to be slower in portacaval-shunted rats versus normal rats during the 2-10 min interval after the injection. At later times post injection, brain and testes tended to have higher-than-normal 13N levels, whereas many other tissues had similar levels in both groups. Thus, reduced removal of ammonia from circulating blood by the liver diverts more ammonia to extrahepatic tissues, including brain and testes, and alters the nitrogen homeostasis in these tissues. These results emphasize the importance of treatment paradigms designed to reduce blood ammonia levels in patients with liver disease.
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Affiliation(s)
- Nancy F Cruz
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
- Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, NM, USA
| | | | - Arthur J L Cooper
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY, 10595, USA.
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Zhou S, Sakiyama Y, Riya S, Song X, Terada A, Hosomi M. Assessing nitrification and denitrification in a paddy soil with different water dynamics and applied liquid cattle waste using the ¹⁵N isotopic technique. Sci Total Environ 2012; 430:93-100. [PMID: 22634555 DOI: 10.1016/j.scitotenv.2012.04.056] [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] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 04/22/2012] [Accepted: 04/22/2012] [Indexed: 06/01/2023]
Abstract
Using livestock wastewater for rice production in paddy fields can remove nitrogen and supplement the use of chemical fertilizers. However, paddy fields have complicated water dynamics owing to varying characteristics and would influence nitrogen removal through nitrification followed by denitrification. Quantification of nitrification and denitrification is of great importance in assessing the influence of water dynamics on nitrogen removal in paddy fields. In this study, nitrification and nitrate reduction rates with different water dynamics after liquid cattle waste application were evaluated, and the in situ denitrification rate was determined directly using the (15)N isotopic technique in a laboratory experiment. A significant linear regression correlation between nitrification and the nitrate reduction rate was observed and showed different regression coefficients under different water dynamics. The regression coefficient in the continuously flooded paddy soil was higher than in the drained-reflooded paddy soil, suggesting that nitrate would be consumed faster in the flooded paddy soil. However, nitrification was limited and the maximum rate was only 13.3 μg Ng(-1)day(-1) in the flooded paddy soil with rice plants, which limited the supply of nitrate. In contrast, the drained-reflooded paddy soil had an enhanced nitrification rate up to 56.8 μg Ng(-1)day(-1), which was four times higher than the flooded paddy soil and further stimulated nitrate reduction rates. Correspondingly, the in situ denitrification rates determined directly in the drained-reflooded paddy soil ranged from 5 to 1035 mg Nm(-2)day(-1), which was higher than the continuously flooded paddy soil (from 5 to 318 mg Nm(-2)day(-1)) during the vegetation period. The nitrogen removal through denitrification accounted for 38.9% and 9.9% of applied nitrogen in the drained-reflooded paddy soil and continuously flooded paddy soil, respectively.
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Affiliation(s)
- Sheng Zhou
- Institute of Engineering, Tokyo University of Agriculture & Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
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Abstract
Loss of nitrogen (N) from land limits the uptake and storage of atmospheric CO(2) by the biosphere, influencing Earth's climate system and myriads of the global ecological functions and services on which humans rely. Nitrogen can be lost in both dissolved and gaseous phases; however, the partitioning of these vectors remains controversial. Particularly uncertain is whether the bacterial conversion of plant available N to gaseous forms (denitrification) plays a major role in structuring global N supplies in the nonagrarian centers of Earth. Here, we use the isotope composition of N ((15)N/(14)N) to constrain the transfer of this nutrient from the land to the water and atmosphere. We report that the integrated (15)N/(14)N of the natural terrestrial biosphere is elevated with respect to that of atmospheric N inputs. This cannot be explained by preferential loss of (14)N to waterways; rather, it reflects a history of low (15)N/(14)N gaseous N emissions to the atmosphere owing to denitrifying bacteria in the soil. Parameterizing a simple model with global N isotope data, we estimate that soil denitrification (including N(2)) accounts for approximately 1/3 of the total N lost from the unmanaged terrestrial biosphere. Applying this fraction to estimates of N inputs, N(2)O and NO(x) fluxes, we calculate that approximately 28 Tg of N are lost annually via N(2) efflux from the natural soil. These results place isotopic constraints on the widely held belief that denitrifying bacteria account for a significant fraction of the missing N in the global N cycle.
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Affiliation(s)
- Benjamin Z Houlton
- Department of Land, Air, and Water Resources, University of California, Davis, CA 95616, USA.
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Szczerba MW, Britto DT, Balkos KD, Kronzucker HJ. Alleviation of rapid, futile ammonium cycling at the plasma membrane by potassium reveals K+-sensitive and -insensitive components of NH4+ transport. J Exp Bot 2008; 59:303-13. [PMID: 18203690 DOI: 10.1093/jxb/erm309] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Futile plasma membrane cycling of ammonium (NH4+) is characteristic of low-affinity NH4+ transport, and has been proposed to be a critical factor in NH4+ toxicity. Using unidirectional flux analysis with the positron-emitting tracer 13N in intact seedlings of barley (Hordeum vulgare L.), it is shown that rapid, futile NH4+ cycling is alleviated by elevated K+ supply, and that low-affinity NH4+ transport is mediated by a K+-sensitive component, and by a second component that is independent of K+. At low external [K+] (0.1 mM), NH4+ influx (at an external [NH4+] of 10 mM) of 92 micromol g(-1) h(-1) was observed, with an efflux:influx ratio of 0.75, indicative of rapid, futile NH4+ cycling. Elevating K+ supply into the low-affinity K+ transport range (1.5-40 mM) reduced both influx and efflux of NH4+ by as much as 75%, and substantially reduced the efflux:influx ratio. The reduction of NH4+ fluxes was achieved rapidly upon exposure to elevated K+, within 1 min for influx and within 5 min for efflux. The channel inhibitor La3+ decreased high-capacity NH4+ influx only at low K+ concentrations, suggesting that the K+-sensitive component of NH4+ influx may be mediated by non-selective cation channels. Using respiratory measurements and current models of ion flux energetics, the energy cost of concomitant NH4+ and K+ transport at the root plasma membrane, and its consequences for plant growth are discussed. The study presents the first demonstration of the parallel operation of K+-sensitive and -insensitive NH4+ flux mechanisms in plants.
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Affiliation(s)
- Mark W Szczerba
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4
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Scaraffia PY, Zhang Q, Wysocki VH, Isoe J, Wells MA. Analysis of whole body ammonia metabolism in Aedes aegypti using [15N]-labeled compounds and mass spectrometry. Insect Biochem Mol Biol 2006; 36:614-22. [PMID: 16876704 DOI: 10.1016/j.ibmb.2006.05.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 05/02/2006] [Accepted: 05/08/2006] [Indexed: 05/11/2023]
Abstract
We have established a protocol to study the kinetics of incorporation of 15N into glutamine (Gln), glutamic acid (Glu), alanine (Ala) and proline (Pro) in Aedes aegypti females. Mosquitoes were fed 3% sucrose solutions containing either 80 mM 15NH4Cl or 80 mM glutamine labeled with 15N in either the amide nitrogen or in both amide and amine nitrogens. In some experiments, specific inhibitors of glutamine synthetase or glutamate synthase were added to the feeding solutions. At different times post feeding, which varied between 0 and 96 h, the mosquitoes were immersed in liquid nitrogen and then processed. These samples plus deuterium labeled internal standards were derivatized as dimethylformamidine isobutyl esters or isobutyl esters. The quantification of 15N-labeled and unlabeled amino acids was performed by using mass spectrometry techniques. The results indicated that the rate of incorporation of 15N into amino acids was rapid and that the label first appeared in the amide side chain of Gln and then in the amino group of Gln, Glu, Ala and Pro. The addition of inhibitors of key enzymes related to the ammonia metabolism confirmed that mosquitoes efficiently metabolize ammonia through a metabolic route that mainly involves glutamine synthetase (GS) and glutamate synthase (GltS). Moreover, a complete deduced amino acid sequence for GltS of Ae. aegypti was determined. The sequence analysis revealed that mosquito glutamate synthase belongs to the category of NADH-dependent GltS.
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Affiliation(s)
- Patricia Y Scaraffia
- Department of Biochemistry & Molecular Biophysics, The University of Arizona, Tucson, AZ 85721-0088, USA.
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Ingledew WJ, Smith SME, Gao YT, Jones RJ, Salerno JC, Rich PR. Ligand, cofactor, and residue vibrations in the catalytic site of endothelial nitric oxide synthase. Biochemistry 2005; 44:4238-46. [PMID: 15766252 DOI: 10.1021/bi047891y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [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: 11/29/2022]
Abstract
A study of bovine endothelial nitric oxide synthase by Fourier transform infrared (FTIR) spectroscopy in the 1000-2500 cm(-)(1) range is reported. Binding of CO to the reduced enzyme gives two heme(II)-CO nu(C)(-)(O) stretches (1927 and 1904 cm(-)(1)) which appear to be in rapid equilibrium. Photolysis of this heme(II)-CO compound is accompanied by perturbation of the local fine structure around the catalytic site giving vibrational changes of protein backbone, substrate, amino acid residues, and cofactors, to which heme, substrate arginine, and catalytic site residues contribute. Possible assignments of vibrations to heme, substrate arginine, and catalytic site residues are discussed. The discussion of assignments is informed by known structures, absorbance frequencies, and extinction coefficients of residues and cofactors, analysis of H(2)O-D(2)O exchange effects, analysis of substrate (14)N-(15)N (guanidinium)-arginine exchange effects, and comparison with the nNOS isoform (which differs in the replacement of asparagine 368 with an aspartate within the substrate binding site). The FTIR data can be modeled on the known structure of the catalytic site and indicate the extent of modulation of vibrational modes upon photolysis of the CO compound.
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Power M, Guiguer KRRA, Barton DR. Effects of temperature on isotopic enrichment in Daphnia magna: implications for aquatic food-web studies. Rapid Commun Mass Spectrom 2003; 17:1619-1625. [PMID: 12845588 DOI: 10.1002/rcm.1094] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Laboratory experiments were conducted with Daphnia magna and Hyalella sp. grown on a single food source of known isotopic composition at a range of temperatures spanning the physiological optima for each species. Daphnia raised at 26.5 degrees C were enriched in delta(13)C and delta(15)N by 3.1 and 2.8 per thousand, respectively, relative to diet. Daphnia raised at 12.8 degrees C were enriched 1.7 and 5.0 per thousand in delta(13)C and delta(15)N, respectively. Results imply a significant negative relationship between the delta(13)C and delta(15)N of primary consumers when a temperature gradient exists. Similar responses were observed for Hyalella. Results indicate a general increase in delta(13)C enrichment and decrease in delta(15)N enrichment as temperature rises. Deviations from the commonly applied isotopic enrichment values used in aquatic ecology were attributed to changes in temperature-mediated physiological rates. Field data from a variety of sources also showed a general trend toward delta(13)C enrichment with increasing temperature in marine and lacustrine zooplankton. Multivariate regression models demonstrated that, in oligotrophic and mesotrophic lakes, zooplankton delta(13)C was related to lake-specific POM delta(13)C, lake surface temperature and latitude. Temperature-dependent isotopic separation (enrichment) between predator and prey should be taken into consideration when interpreting the significance of isotopic differences within and among aquatic organisms and ecosystems, and when assigning organisms to food-web positions on the basis of observed isotope values.
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Affiliation(s)
- M Power
- Biology Department, University of Waterloo, 200 Avenue West, Waterloo, Ontario N2L 3G1, Canada.
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Korhonen M, Ahvenjärvi S, Vanhatalo A, Huhtanen P. Supplementing barley or rapeseed meal to dairy cows fed grass-red clover silage: II. Amino acid profile of microbial fractions. J Anim Sci 2002; 80:2188-96. [PMID: 12211389 DOI: 10.2527/2002.8082188x] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Four ruminally cannulated dairy cows were used to examine the effect of diet on the AA composition of rumen bacteria and protozoa, and the flow of microbial and nonmicrobial AA entering the omasal canal. Cows were offered grass-red clover silage alone, or that supplemented with 5.1 kg DM of barley, 1.9 kg DM of rapeseed meal, or 5.1 kg DM of barley and 1.9 kg DM of rapeseed meal according to a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. During the first 10 d of each period, cows had free access to silage and, thereafter intake was restricted to 95% of ad libitum intake. Postruminal digesta flow was assessed using the omasal canal sampling technique in combination with a triple marker method. Liquid- (LAB) and particle- (PAB) associated bacteria were isolated from digesta in the reticulorumen and protozoa from digesta entering the omasal canal. Microbial protein flow was determined using 15N as a microbial marker. Flows of AA entering the omasal canal were similar in cows fed silage diets supplemented with barley or rapeseed meal. However, rapeseed meal increased nonmicrobial AA flow while barley increased the flow of AA associated with LAB and protozoa. Diet had negligible effects on the AA profile of microbial fractions. Comparison of AA profiles across diets indicated differences between LAB and PAB for 10 out of 17 AA measured. Rumen bacteria and protozoa were found to be different for 14 out of 15 AA measured. For grass silage-based diets, energy and protein supplementations appear to alter postruminal AA supply through modifications in the proportionate contribution of microbial and nonmicrobial pools to total protein flow rather than as a direct result of changes in the AA profile of microbial protein.
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Affiliation(s)
- M Korhonen
- MTT Agrifood Research Finland, Jokioinen.
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Abstract
Previous studies have indicated that an increased asparagine to glutamine ratio (Asn : Gln) occurs in the xylem fluid of Lolium perenne 24 h after defoliation. However, the absolute changes in Asn and Gln leading to the increased Asn : Gln ratio are unknown. The present study tested the hypotheses that: (1) defoliation-induced changes in xylem amino acid composition occur in L perenne within the first 24 h following defoliation, irrespective of phasing with respect to the diurnal light/dark cycle; and (2) the increase in Asn : Gln ratio in the xylem fluid of L perenne following defoliation is due to an increase in Asn content. Plants of L perenne L. 'Aurora' were grown in flowing solution culture for 40 d. Plants were then either left intact, defoliated at the end of the light period or defoliated at the end of the dark period. 15N-labelled NO3- was supplied following defoliation to discriminate between the recovery of N absorbed prior to, and following, defoliation. Xylem samples were collected over the subsequent 24 h period with amino acids speciated by GC-MS. There was support for the first hypothesis: increased Asn : Gln ratios occurred within the first 24 h, irrespective of the phasing of defoliation with respect to light/dark cycles. The second hypothesis was not supported: the concentration of all amino acids in the xylem exudate declined after defoliation, and the increased Asn : Gln ratio was accounted for by a disproportionately large reduction in Gln levels. Low concentrations of amino acids in the xylem of defoliated plants precluded accurate discrimination of their nitrogen content into pre- and post-defoliation sources.
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Affiliation(s)
- B Thornton
- Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, UK.
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14
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Witte CP, Tiller SA, Taylor MA, Davies HV. Leaf urea metabolism in potato. Urease activity profile and patterns of recovery and distribution of (15)N after foliar urea application in wild-type and urease-antisense transgenics. Plant Physiol 2002; 128:1129-36. [PMID: 11891267 PMCID: PMC152224 DOI: 10.1104/pp.010506] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2001] [Revised: 10/10/2001] [Accepted: 11/21/2001] [Indexed: 05/18/2023]
Abstract
The influence of urease activity on N distribution and losses after foliar urea application was investigated using wild-type and transgenic potato (Solanum tuberosum cv Désirée) plants in which urease activity was down-regulated. A good correlation between urease activity and (15)N urea metabolism (NH(3) accumulation) was found. The general accumulation of ammonium in leaves treated with urea indicated that urease activity is not rate limiting, at least initially, for the assimilation of urea N by the plant. It is surprising that there was no effect of urease activity on either N losses or (15)N distribution in the plants after foliar urea application. Experiments with wild-type plants in the field using foliar-applied (15)N urea demonstrated an initial rapid export of N from urea-treated leaves to the tubers within 48 h, followed by a more gradual redistribution during the subsequent days. Only 10% to 18% of urea N applied was lost (presumably because of NH(3) volatilization) in contrast to far greater losses reported in several other studies. The pattern of urease activity in the canopy was investigated during plant development. The activity per unit protein increased up to 10-fold with leaf and plant age, suggesting a correlation with increased N recycling in senescing tissues. Whereas several reports have claimed that plant urease is inducible by urea, no evidence for urease induction could be found in potato.
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Affiliation(s)
- Claus-Peter Witte
- Unit of Plant Biochemistry, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, United Kingdom.
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Stoll HP, Hutchins GD, Winkle WL, Nguyen AT, Appledorn CR, Janzen I, Seifert H, Rübe C, Schieffer H, March KL. Advantages of short-lived positron-emitting radioisotopes for intracoronary radiation therapy with liquid-filled balloons to prevent restenosis. J Nucl Med 2001; 42:1375-83. [PMID: 11535728] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
UNLABELLED Balloon catheters filled with liquid radioisotopes provide excellent dose homogeneity for intracoronary radiation therapy but are associated with risk for rupture or leakage. We hypothesized that the safety of liquid-filled balloons may be improved once positron emitters with half-lives below 2 h are used instead of the high-energy beta-emitters 166Ho, 186Re, or 188Re, all of which have a longer half-life of at least 17 h. METHODS To support this concept, the suitability of 18F (half-life, 109.8 min), 68Ga (half-life, 67.6 min), 11C (half-life, 20.4 min), 13N (half-life, 9.97 min), and 15O (half-life, 2.04 min) for intracoronary radiation therapy was evaluated. Potential tissue penetration of positron radiation was assessed in a series of phantom experiments using Gafchromic film. Antiproliferative efficacy of positrons emitted by 68Ga was investigated in vitro using cultured bovine aortic smooth muscle cells (BASMCs), and was compared with gamma-radiation emitted by 137Cs. To characterize the remaining risk, we estimated radiotoxicity after accidental intravascular balloon rupture on the basis of tabulated isotope-specific doses (ICRP 53) and compared these values with 188Re. RESULTS Half-dose depth of tissue penetration measured in phantom experiments was 0.29 mm for 18F, 0.42 mm for 11C, 0.54 mm for 13N, 0.79 mm for 15O, and 0.9 mm for 68Ga. Irradiation of cultured BASMCs with positron radiation (68Ga) induced dose-dependent inhibition of proliferation with complete proliferative arrest at doses exceeding 6 Gy. ED(50) and ED(80) were 2.5 +/- 0.4 Gy (mean +/- SD) and 4.4 +/- 0.8 Gy, respectively. Antiproliferative efficacy was equal to that of the 662-keV gamma-radiation emitted by 137Cs (ED(50), 3.8 +/- 0.2 Gy; ED(80), 8.0 +/- 0.3 Gy). Estimates made for patient whole-body and organ doses were generally below 50 mSv/1.85 GBq for all investigated positron emitters. The same dose estimates for 188Re were 6-20 fold higher. CONCLUSION Among the studied radioisotopes, 68Ga is the most attractive source for liquid-filled balloons because of its convenient half-life, sufficient positron energy (2.92 MeV), documented antiproliferative efficacy, and uncomplicated availability from a radioisotope generator. The safety profile for 68Ga is significantly better than that of 188Re, which suggests this radioisotope should be evaluated further in preclinical studies.
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Affiliation(s)
- H P Stoll
- Medical Clinic III, Cardiology, Department of Radiation Oncology, University Hospital Homburg/Saar, Germany
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Mendum TA, Sockett RE, Hirsch PR. Use of molecular and isotopic techniques to monitor the response of autotrophic ammonia-oxidizing populations of the beta subdivision of the class proteobacteria in arable soils to nitrogen fertilizer. Appl Environ Microbiol 1999; 65:4155-62. [PMID: 10473429 PMCID: PMC99754 DOI: 10.1128/aem.65.9.4155-4162.1999] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.6] [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] [Indexed: 11/20/2022] Open
Abstract
This study examined the effects of NH(4)NO(3) fertilizer on the size and activity of nitrifying, autotrophic, ammonia-oxidizing populations of the beta subdivision of the class Proteobacteria in arable soils. Plots under different long-term fertilizer regimes were sampled before and after NH(4)NO(3) additions, and the rates of nitrification were determined by (15)N isotopic pool dilution assays. Ammonia-oxidizing populations in the plots were quantified by competitive PCR assays based on the amoA and ribosomal 16S genes. Prior to fertilizer addition, ammonium concentrations and nitrification rates in the plots were comparatively low; ammonia-oxidizing populations were present at 10(4) to 10(5) gene copies g of soil(-1). Three days after the application of fertilizer, nitrification rates had risen considerably but the size of the ammonia-oxidizing population was unchanged. Six weeks after fertilizer treatment, ammonium concentrations and nitrification rates had fallen while the ammonia-oxidizing populations in plots receiving fertilizer had increased. The rapidity of the rise in nitrification rates observed after 3 days suggests that it results from phenotypic changes in the ammonia-oxidizing bacterial population. Associated increases in population sizes were only observed after 6 weeks and did not correlate directly with nitrifying activity. Phylogenetic analyses of PCR products from one of the plots revealed a population dominated by Nitrosospira-type organisms, similar to those prevalent in other soils.
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Affiliation(s)
- T A Mendum
- IACR-Rothamsted, Harpenden, Hertfordshire AL5 2JQ, United Kingdom.
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17
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Abstract
[15N]Urea was introduced (in situ) into a ligated cecal pouch of chickens to determine if it is degraded therein and absorbed into the blood as ammonia during the following 60 min. A mean of 49% of the introduced urea-15N was recovered from the blood of the mesenteric vein draining the cecal pouch and 26% was recovered from the cecal lumen fluid. Of the urea-15N introduced into the pouch, 4%, 2%, 15% and 5% were detected as urea, ammonia and non-protein fractions, except urea and ammonia, and proteins in the lumen fluid, respectively. Non-protein-15N, except urea and ammonia, protein-15N, urea-15N and ammonia-15N values recovered in the cecal venous blood were 10%, 19%, 18% and 2% of the introduced 15N, respectively. Urea concentration in the cecal venous blood increased from 0.71 mg to 3.13 mg per 100 ml for the first 15 min after introduction of urea-15N (P < 0.01) then decreased until 60 min. No significant change was found in blood ammonia concentration, however, despite a small increase during the period 15-45 min after urea-15N introduction. Ammonia-15N increased in the caecal venous blood for the first 30 min then decreased to a plateau level of 43% of the peak level. The rates of increase of urea-15N and non-protein-15N concentrations attained maxima in the blood as early as 15 min, then decreased linearly (P < 0.05). It is concluded that, although urea is actively degraded to ammonia in the ceca, it is mostly absorbed from the ceca, not in the form of ammonia, but as protein, urea and amino acids.
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Affiliation(s)
- Y Karasawa
- Laboratory of Animal Nutrition and Feed Science, Faculty of Agriculture, Shinshu University, Nagano-Ken, Japan
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Schadereit R, Krawielitzki K, Herrmann U. [15N transamination in the administration of various tracer substances. 1. Whole body studies in rats]. Arch Tierernahr 1986; 36:783-92. [PMID: 3099731 DOI: 10.1080/17450398609434346] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
4 groups of 3 growing Wistar rats each were orally given either 15N methionine, 15N lysine, 15N glycine or 15N ammonia sulphate over 10 days. By means of measuring 15N, the 15N accumulation in the amino acids (AA) of the body protein, statements were to be made on the transamination of the individual 15N substances and thus their suitability as tracer substances for studies of N metabolism. None of the tested 15N AA achieved a proportionate labelling of all AA of the body protein. The AA used as tracer in each case showed the highest 15N labelling of all AA in the body. Of the amino 15N detected in the animal body, ca. 19% were found in Met after a 15N Met application, ca. 88% in Lys after a 15N Lys application and ca. 50% in Gly after a 15N Gly application. After the application of 15N ammonia sulphate ca. 42% of the body amino 15N are apportioned to the essential and ca. 58% to the non-essential AA. Thus this substance produces a more proportional labelling of the essential and non-essential AA of the body protein than 15N Gly. The following quotas of the 15N amounts applied were found in the AA of the animal bodies: tracer substance lysine 52%, glycine 32%, ammonia sulphate 24%, methionine 21%. After summing up the amino acid 15N amounts in the animal body, eliminating in each case the tracer AA and taking into account the molecular weight of the AA, there was a good agreement of the intensity of the accumulation of 15N in the individual AA, irrespective of the applied tracer substance: arginine, glutamic acid, cysteine and aspartic acid highest, threonine, phenylalanine and lysine lowest accumulation.
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Barrio JR, Baumgartner FJ, Henze E, Stauber MS, Egbert JE, MacDonald NS, Schelbert HR, Phelps ME, Liu FT. Synthesis and myocardial kinetics of N-13 and C-11 labeled branched-chain L-amino acids. J Nucl Med 1983; 24:937-44. [PMID: 6619964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Glutamate dehydrogenase (GDH), immobilized on CNBr-activated Sepharose supports, was used with N-13 ammonia to aminate alpha-ketoisocaproic acid (KIC), and alpha-ketoisovaleric acid (KIV) to produce N-13-labeled branched-chain L-amino acids with radiochemical yields ranging from 29% to 35%. From kinetic and practical considerations, pH 7.5-8.0 was established to be optimal for the synthesis of N-13-labeled branched-chain-L-amino acids. Myocardial time-activity curves in dogs at control, during low-flow ischemia, reperfusion, and after transaminase inhibition following intracoronary bolus injection of the N-13-labeled amino acids were biexponential. Higher retention of N-13 activity was observed in ischemic segments both during low-flow ischemia (29.2%) and reperfusion (23.2%) when compared with controls (20.0%), (n = 4). On the other hand, transaminase inhibition decreased residue fractions from 21.0% at control to 13.9% (n = 4). The residual activity with L-[1-11C]leucine allows for the calculation of protein synthesis rates.
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Gruhn K, Hennig A, Glotz D. [Studies of 15N-labeled lysine in colostomized laying hens. 3. 15N incorporation into the amino acids of the follicle, residual ovary and oviduct]. Arch Tierernahr 1983; 33:781-92. [PMID: 6422908 DOI: 10.1080/17450398309425162] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In a metabolism experiments with 15N-labelled lysine 3 colostomized laying hybrids received over 4 days 0.2% L-Lysine with 48 atom-% 15N-excess (15N') in addition to a ration conventionally produced and, subsequent to this, unlabelled lysine for four days. At the end of the experiment the hens were butchered: individual organs and tissues were prepared for 15N-analysis. The incorporation of the lysine-15N' into the further amino acids in the follicles, the ovary and the oviduct is described. The atom-% 15N' of the complete range of amino acids was analysed in the individual follicles. Various levels of heavy nitrogen could be detected in all essential and non-essential amino acids. Of the total amount of 15N' detected in the follicles 64.0% 65.0% and 61.2% resp. could be detected in lysine and 25.2%, 25.4%, 28.7% resp. in the other amino acids (hens 1 to 3). In the ovary on average 61.6% and on the oviduct 54.2% of the respective 15N'-amount was detected in lysine. In the ovary 10.9% and in the oviduct 8.4% 15N' of the total 15N' of these samples were incorporated into the arginine molecules.
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Abstract
An investigation was performed to correlate the regional uptake of N-13 L-glutamate with histologic changes in tumor tissue in patients undergoing adjuvant chemotherapy for osteogenic sarcoma. A parametric image was produced by calculating the ratio of N-13 uptake in the tumor in a pixel-by-pixel fashion, using the presurgical scan as the numerator and the pretherapy scan as the denominator. The change in N-13 uptake in 2 x 2-cm regions of the tumor was compared with residual cell viability as determined by microscopic examination of multiple thin sections obtained from the surgical specimens. Regions that showed decreases in N-13 uptake of more than 30% were frequently associated with areas of highly necrotic tumor, and regions that showed increasing uptake were associated with high residual cell viability and incomplete response to chemotherapy.
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Phelps ME, Huang SC, Hoffman EJ, Selin C, Kuhl DE. Cerebral extraction of N-13 ammonia: its dependence on cerebral blood flow and capillary permeability -- surface area product. Stroke 1981; 12:607-19. [PMID: 7303045 DOI: 10.1161/01.str.12.5.607] [Citation(s) in RCA: 74] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
13N-labeled ammonia was used to investigate 1) the cerebral extraction and clearance of ammonia, 2) the mechanism by which capillaries accommodate changes in cerebral blood flow (CBF) and 3) its use for the measurement of CBF. The unidirectional extraction of 13NH3 in rhesus monkeys was measured during PaCO2 induced changes in CBF and dog studies were performed using in vitro tissue counting techniques to examine 13NH3 extraction in gray and white matter, mixed tissue and cerebellum during variations in CBF produced by combinations of embolization, local brain compression, and changes in PaCO2. The single pass extraction fraction of 13NH3 varied from about 70 to 20% over a CBF range of 12 to 140 cc/min/100 g. Capillary permeability-surface area product (PS) estimates with a Renkin/Crone model show PS increasing with CBF. The magnitude and rate of increase in PS with CBF was highest in gray matter greater than mixed tissue greater than white matter. Tissue extraction of 13NH3 vs CBF relationship was best described by a unidirectional transport model in which CBF increases by both recruitment of capillaries and by increases of blood velocity in open capillaries. This saturable-recruitment model provides a possible explanation for the mechanism of flow changes at the capillary level. The net 13NH3 extraction subsequent to an i.v. injection increases non-linearly with CBF. Doubling or halving basal CBF produced from 35 to 50% changes in the 13N tissue concentrations with further increases in CBF associated with progressively smaller changes in 13N concentrations.
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