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Bhardwaj M, Lee JJ, Versace AM, Harper SL, Goldman AR, Crissey MAS, Jain V, Singh MP, Vernon M, Aplin AE, Lee S, Morita M, Winkler JD, Liu Q, Speicher DW, Amaravadi RK. Lysosomal lipid peroxidation regulates tumor immunity. J Clin Invest 2023; 133:164596. [PMID: 36795483 PMCID: PMC10104903 DOI: 10.1172/jci164596] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 02/14/2023] [Indexed: 02/17/2023] Open
Abstract
Lysosomal inhibition elicited by palmitoyl protein transferase 1 (PPT1) inhibitors such as DC661 can produce cell death, but the mechanism is not completely understood. Programmed cell death pathways (autophagy, apoptosis, necroptosis, ferroptosis, and pyroptosis) were not required to achieve the cytotoxic effect of DC661. Inhibition of cathepsins, or iron or calcium chelation, did not rescue DC661-induced cytotoxicity. PPT1 inhibition induced lysosomal lipid peroxidation (LLP), which led to lysosomal membrane permeabilization and cell death that could be reversed by the antioxidant N-acetylcysteine (NAC), but not by other lipid peroxidation antioxidants. The lysosomal cysteine transporter MFSD12, was required for intralysosomal transport of NAC and rescue of LLP. PPT1 inhibition produced cell-intrinsic immunogenicity with surface expression of calreticulin that could only be reversed with NAC. DC661-treated cells primed naïve T cells, and enhanced T cell-mediated toxicity. Mice vaccinated with DC661-treated cells, engendered adaptive immunity and tumor rejection in "immune hot" tumors but not in "immune cold" tumors. These findings demonstrate LLP drives lysosomal cell death, a unique immunogenic form of cell death, pointing the way to rational combinations of immunotherapy and lysosomal inhibition that can be tested in clinical trials.
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Affiliation(s)
- Monika Bhardwaj
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
| | - Jennifer J Lee
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
| | - Amanda M Versace
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
| | - Sandra L Harper
- Proteomics & Metabolomics Facility, The Wistar Institute, Philadelphia, United States of America
| | - Aaron R Goldman
- Proteomics & Metabolomics Facility, The Wistar Institute, Philadelphia, United States of America
| | - Mary Ann S Crissey
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
| | - Vaibhav Jain
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
| | - Mahendra Pal Singh
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
| | - Megane Vernon
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, United States of America
| | - Andrew E Aplin
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, United States of America
| | - Seokwoo Lee
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States of America
| | - Masao Morita
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States of America
| | - Jeffrey D Winkler
- Department of Chemistry, University of Pennsylvania, Philadelphia, United States of America
| | - Qin Liu
- Proteomics & Metabolomics Facility, The Wistar Institute, Philadelphia, United States of America
| | - David W Speicher
- Proteomics & Metabolomics Facility, The Wistar Institute, Philadelphia, United States of America
| | - Ravi K Amaravadi
- Department of Medicine, University of Pennsylvania, Philadelphia, United States of America
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2
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Jain V, Harper SL, Versace AM, Fingerman D, Brown GS, Bhardwaj M, Crissey MAS, Goldman AR, Ruthel G, Liu Q, Zivkovic A, Stark H, Herlyn M, Gimotty PA, Speicher DW, Amaravadi RK. Targeting UGCG Overcomes Resistance to Lysosomal Autophagy Inhibition. Cancer Discov 2023; 13:454-473. [PMID: 36331284 PMCID: PMC9905280 DOI: 10.1158/2159-8290.cd-22-0535] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [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: 05/08/2022] [Revised: 08/10/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022]
Abstract
Lysosomal autophagy inhibition (LAI) with hydroxychloroquine or DC661 can enhance cancer therapy, but tumor regrowth is common. To elucidate LAI resistance, proteomics and immunoblotting demonstrated that LAI induced lipid metabolism enzymes in multiple cancer cell lines. Lipidomics showed that LAI increased cholesterol, sphingolipids, and glycosphingolipids. These changes were associated with striking levels of GM1+ membrane microdomains (GMM) in plasma membranes and lysosomes. Inhibition of cholesterol/sphingolipid metabolism proteins enhanced LAI cytotoxicity. Targeting UDP-glucose ceramide glucosyltransferase (UGCG) synergistically augmented LAI cytotoxicity. Although UGCG inhibition decreased LAI-induced GMM and augmented cell death, UGCG overexpression led to LAI resistance. Melanoma patients with high UGCG expression had significantly shorter disease-specific survival. The FDA-approved UGCG inhibitor eliglustat combined with LAI significantly inhibited tumor growth and improved survival in syngeneic tumors and a therapy-resistant patient-derived xenograft. These findings nominate UGCG as a new cancer target, and clinical trials testing UGCG inhibition in combination with LAI are warranted. SIGNIFICANCE We discovered UGCG-dependent lipid remodeling drives resistance to LAI. Targeting UGCG with a drug approved for a lysosomal storage disorder enhanced LAI antitumor activity without toxicity. LAI and UGCG inhibition could be tested clinically in multiple cancers. This article is highlighted in the In This Issue feature, p. 247.
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Affiliation(s)
- Vaibhav Jain
- Abramson Cancer Center and Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Amanda M. Versace
- Abramson Cancer Center and Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | - Monika Bhardwaj
- Abramson Cancer Center and Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mary Ann S. Crissey
- Abramson Cancer Center and Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Gordon Ruthel
- Department of Pathobiology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA
| | - Qin Liu
- The Wistar Institute, Philadelphia, PA 19104, USA
| | - Aleksandra Zivkovic
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Universitaetsstr. 1, 40225, Düsseldorf, Germany
| | - Holgar Stark
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Universitaetsstr. 1, 40225, Düsseldorf, Germany
| | | | - Phyllis A. Gimotty
- Department of Biostatistics, Epidemiology, and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David W. Speicher
- The Wistar Institute, Philadelphia, PA 19104, USA
- Corresponding authors: Ravi K. Amaravadi, MD, University of Pennsylvania, 852 BRB 2/3, 421 Curie Blvd, Philadelphia, PA 19104, Tel: 215-796-5159, ; David W. Speicher, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, Tel: 215-898-3972,
| | - Ravi K. Amaravadi
- Abramson Cancer Center and Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Corresponding authors: Ravi K. Amaravadi, MD, University of Pennsylvania, 852 BRB 2/3, 421 Curie Blvd, Philadelphia, PA 19104, Tel: 215-796-5159, ; David W. Speicher, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, Tel: 215-898-3972,
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3
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Sharma G, Ojha R, Noguera-Ortega E, Rebecca VW, Attanasio J, Liu S, Piao S, Lee JJ, Nicastri MC, Harper SL, Ronghe A, Jain V, Winkler JD, Speicher DW, Mastio J, Gimotty PA, Xu X, Wherry EJ, Gabrilovich DI, Amaravadi RK. PPT1 inhibition enhances the antitumor activity of anti–PD-1 antibody in melanoma. JCI Insight 2022; 7:165688. [DOI: 10.1172/jci.insight.165688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Harper SL, Cunsolo A, Babujee A, Coggins S, De Jongh E, Rusnak T, Wright CJ, Domínguez Aguilar M. Trends and gaps in climate change and health research in North America. Environ Res 2021; 199:111205. [PMID: 33961824 DOI: 10.1016/j.envres.2021.111205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 04/16/2021] [Accepted: 04/17/2021] [Indexed: 06/12/2023]
Abstract
The Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (2014) assessed the state of climate change and health knowledge, globally through the Human Health: Impacts, Adaptation, and Co-Benefits Chapter and regionally through chapters, such as the North America Chapter. With IPCC's 6th Assessment Report scheduled to be released in 2021-22, we asked: how has climate change and health research in North America advanced since the IPCC's 5th Assessment Report in 2014? Specifically, we systematically identified and examined trends in the extent, range, and nature of climate-health research conducted in North America. We used a scoping review methodology to systematically identify literature and map publication trends. A search string was used to search five academic databases. Two independent reviewers first screened titles and abstracts, and then the full texts of articles for relevance. Research articles and reviews using systematic methods published since 2013 were eligible for inclusion, and no language restrictions were applied. To be included, articles had to measure and link climatic variables or hazards to health outcomes in North America. Relevant articles were analysed using descriptive statistics to explore publication trends. The number of climate-health articles has significantly increased since the last IPCC Assessment Report. Published research about climate change impacts, heat-related mortality and morbidity, and respiratory illness taking place in urban centres and in the USA continue to dominate the North American climate-health literature, reflected by the high proportion of articles published. Important research gaps on previously neglected climate-sensitive health outcomes, however, are beginning to be filled, including climate change impacts on mental health, nutrition, and foodborne disease. We also observed progress in research that included future projections of climate-health risks; however, projection research is still relatively nascent and under-studied for many climate-sensitive health outcomes in North America, and would benefit from considering social and demographic variables in models. Important research disparities in geographical coverage were noted, including research gaps in Canada and Mexico, and in rural and remote regions. Overall, these publication trends suggest an improved understanding of exposure-response relationships and future projections of climate-health risks for many climate-sensitive health outcomes in North America, which is promising and provides an evidence-base to inform the IPCC 6th Assessment Report. Despite these advancements and considering the urgent policy and practice implications, more research is needed to deepen our understanding of climate-sensitive health outcomes, as well as examine new arising issues that have limited evidence-bases. In particular, transdisciplinary and cross-sector research, that includes the social sciences, examining current and future climate-health adaptation, mitigation, and the adaptation-mitigation nexus should become a top priority for research, given the urgent need for this evidence to inform climate change policies, actions, and interventions.
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Affiliation(s)
- S L Harper
- School of Public Health, University of Alberta, 11405 87 Ave NW, Edmonton, AB, T6G 1C9, Canada.
| | - A Cunsolo
- School of Arctic & Subarctic Studies, Labrador Institute of Memorial University, 219 Hamilton River Road, PO Box 490, Stn B, Happy Valley-Goose Bay, NL, A0P 1E0, Canada
| | - A Babujee
- School of Public Health, University of Alberta, 11405 87 Ave NW, Edmonton, AB, T6G 1C9, Canada
| | - S Coggins
- School of Public Health, University of Alberta, 11405 87 Ave NW, Edmonton, AB, T6G 1C9, Canada
| | - E De Jongh
- School of Public Health, University of Alberta, 11405 87 Ave NW, Edmonton, AB, T6G 1C9, Canada
| | - T Rusnak
- School of Public Health, University of Alberta, 11405 87 Ave NW, Edmonton, AB, T6G 1C9, Canada
| | - C J Wright
- School of Public Health, University of Alberta, 11405 87 Ave NW, Edmonton, AB, T6G 1C9, Canada
| | - M Domínguez Aguilar
- Unidad de Ciencias Sociales, Universidad Autónoma de Yucatán, Calle 61 X 66 # 525. Col. Centro, Mérida, Yucatán, Mexico
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5
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Gousiadou C, Marchese Robinson RL, Kotzabasaki M, Doganis P, Wilkins TA, Jia X, Sarimveis H, Harper SL. Machine learning predictions of concentration-specific aggregate hazard scores of inorganic nanomaterials in embryonic zebrafish. Nanotoxicology 2021; 15:446-476. [PMID: 33586589 DOI: 10.1080/17435390.2021.1872113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The possibility of employing computational approaches like nano-QSAR or nano-read-across to predict nanomaterial hazard is attractive from both a financial, and most importantly, where in vivo tests are required, ethical perspective. In the present work, we have employed advanced Machine Learning techniques, including stacked model ensembles, to create nano-QSAR tools for modeling the toxicity of metallic and metal oxide nanomaterials, both coated and uncoated and with a variety of different core compositions, tested at different dosage concentrations on embryonic zebrafish. Using both computed and experimental descriptors, we have identified a set of properties most relevant for the assessment of nanomaterial toxicity and successfully correlated these properties with the associated biological responses observed in zebrafish. Our findings suggest that for the group of metal and metal oxide nanomaterials, the core chemical composition, concentration and properties dependent upon nanomaterial surface and medium composition (such as zeta potential and agglomerate size) are significant factors influencing toxicity, albeit the ranking of different variables is sensitive to the exact analysis method and data modeled. Our generalized nano-QSAR ensemble models provide a promising framework for anticipating the toxicity potential of new nanomaterials and may contribute to the transition out of the animal testing paradigm. However, future experimental studies are required to generate comparable, similarly high quality data, using consistent protocols, for well characterized nanomaterials, as per the dataset modeled herein. This would enable the predictive power of our promising ensemble modeling approaches to be robustly assessed on large, diverse and truly external datasets.
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Affiliation(s)
- C Gousiadou
- School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - R L Marchese Robinson
- School of Chemical and Process Engineering, University of Leeds, Leeds, United Kingdom
| | - M Kotzabasaki
- School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - P Doganis
- School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - T A Wilkins
- School of Chemical and Process Engineering, University of Leeds, Leeds, United Kingdom
| | - X Jia
- School of Chemical and Process Engineering, University of Leeds, Leeds, United Kingdom
| | - H Sarimveis
- School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - S L Harper
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR, USA.,Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR, USA.,Safer Nanomaterials and Nanomanufacturing Initiative, Oregon Nanoscience and Microtechnologies Institute, Eugene, OR, USA
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6
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Sharma G, Ojha R, Noguera-Ortega E, Rebecca VW, Attanasio J, Liu S, Piao S, Lee JJ, Nicastri MC, Harper SL, Ronghe A, Jain V, Winkler JD, Speicher DW, Mastio J, Gimotty PA, Xu X, Wherry EJ, Gabrilovich DI, Amaravadi RK. PPT1 inhibition enhances the antitumor activity of anti-PD-1 antibody in melanoma. JCI Insight 2020; 5:133225. [PMID: 32780726 PMCID: PMC7526447 DOI: 10.1172/jci.insight.133225] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 07/24/2020] [Indexed: 12/30/2022] Open
Abstract
New strategies are needed to enhance the efficacy of anti–programmed cell death protein antibody (anti–PD-1 Ab) in cancer. Here, we report that inhibiting palmitoyl-protein thioesterase 1 (PPT1), a target of chloroquine derivatives like hydroxychloroquine (HCQ), enhances the antitumor efficacy of anti–PD-1 Ab in melanoma. The combination resulted in tumor growth impairment and improved survival in mouse models. Genetic suppression of core autophagy genes, but not Ppt1, in cancer cells reduced priming and cytotoxic capacity of primed T cells. Exposure of antigen-primed T cells to macrophage-conditioned medium derived from macrophages treated with PPT1 inhibitors enhanced melanoma-specific killing. Genetic or chemical Ppt1 inhibition resulted in M2 to M1 phenotype switching in macrophages. The combination was associated with a reduction in myeloid-derived suppressor cells in the tumor. Ppt1 inhibition by HCQ, or DC661, induced cyclic GMP-AMP synthase/stimulator of interferon genes/TANK binding kinase 1 pathway activation and the secretion of interferon-β in macrophages, the latter being a key component for augmented T cell–mediated cytotoxicity. Genetic Ppt1 inhibition produced similar findings. These data provide the rationale for this combination in melanoma clinical trials and further investigation in other cancers. Inhibiting palmitoyl-protein thioesterase 1 (PPT1), a target of CQ derivatives like hydroxychloroquine (HCQ), enhances the antitumor efficacy of anti-PD-1 Ab in murine melanoma models.
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Affiliation(s)
| | - Rani Ojha
- Abramson Cancer Center and Department of Medicine
| | | | | | - John Attanasio
- Department of Systems Pharmacology and Translational Therapeutics and Penn Institute for Immunology, and
| | - Shujing Liu
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Shengfu Piao
- Abramson Cancer Center and Department of Medicine
| | | | - Michael C Nicastri
- Department of Chemistry, College of Arts & Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | | | - Vaibhav Jain
- Abramson Cancer Center and Department of Medicine
| | - Jeffrey D Winkler
- Department of Chemistry, College of Arts & Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | | | - Phyllis A Gimotty
- Department of Biostatistics, Epidemiology & Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Xiaowei Xu
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - E John Wherry
- Department of Systems Pharmacology and Translational Therapeutics and Penn Institute for Immunology, and
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7
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Rivera-Santiago R, Harper SL, Sriswasdi S, Hembach P, Speicher DW. Full-Length Anion Exchanger 1 Structure and Interactions with Ankyrin-1 Determined by Zero Length Crosslinking of Erythrocyte Membranes. Structure 2016; 25:132-145. [PMID: 27989623 DOI: 10.1016/j.str.2016.11.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 11/02/2016] [Accepted: 11/18/2016] [Indexed: 11/26/2022]
Abstract
Anion exchanger 1 (AE1) is a critical transporter and the primary structural scaffold for large macromolecular complexes responsible for erythrocyte membrane flexibility and integrity. We used zero-length crosslinking and mass spectrometry to probe AE1 structures and interactions in intact erythrocyte membranes. An experimentally verified full-length model of AE1 dimers was developed by combining crosslink-defined distance constraints with homology modeling. Previously unresolved cytoplasmic loops in the AE1 C-terminal domain are packed at the domain-domain interface on the cytoplasmic face of the membrane where they anchor the N-terminal domain's location and prevent it from occluding the ion channel. Crosslinks between AE1 dimers and ankyrin-1 indicate the likely topology for AE1 tetramers and suggest that ankyrin-1 wraps around AE1 tetramers, which may stabilize this oligomer state. This interaction and interactions of AE1 with other major erythrocyte membrane proteins show that protein-protein contacts are often substantially more extensive than previously reported.
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Affiliation(s)
- Roland Rivera-Santiago
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Sandra L Harper
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Sira Sriswasdi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Peter Hembach
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - David W Speicher
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.
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8
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Rivera-Santiago RF, Sriswasdi S, Harper SL, Speicher DW. Probing structures of large protein complexes using zero-length cross-linking. Methods 2015; 89:99-111. [PMID: 25937394 PMCID: PMC4628899 DOI: 10.1016/j.ymeth.2015.04.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [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: 12/23/2014] [Revised: 04/10/2015] [Accepted: 04/24/2015] [Indexed: 02/02/2023] Open
Abstract
Structural mass spectrometry (MS) is a field with growing applicability for addressing complex biophysical questions regarding proteins and protein complexes. One of the major structural MS approaches involves the use of chemical cross-linking coupled with MS analysis (CX-MS) to identify proximal sites within macromolecules. Identified cross-linked sites can be used to probe novel protein-protein interactions or the derived distance constraints can be used to verify and refine molecular models. This review focuses on recent advances of "zero-length" cross-linking. Zero-length cross-linking reagents do not add any atoms to the cross-linked species due to the lack of a spacer arm. This provides a major advantage in the form of providing more precise distance constraints as the cross-linkable groups must be within salt bridge distances in order to react. However, identification of cross-linked peptides using these reagents presents unique challenges. We discuss recent efforts by our group to minimize these challenges by using multiple cycles of LC-MS/MS analysis and software specifically developed and optimized for identification of zero-length cross-linked peptides. Representative data utilizing our current protocol are presented and discussed.
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Affiliation(s)
- Roland F Rivera-Santiago
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, PA 19104, United States; Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Sira Sriswasdi
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, PA 19104, United States; Department of Biological Sciences, Graduate School of Sciences, The University of Tokyo, Tokyo 113-0032, Japan
| | - Sandra L Harper
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, PA 19104, United States
| | - David W Speicher
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, Philadelphia, PA 19104, United States; Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, Philadelphia, PA 19104, United States.
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9
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Khanna MR, Mattie FJ, Browder KC, Radyk MD, Crilly SE, Bakerink KJ, Harper SL, Speicher DW, Thomas GH. Spectrin tetramer formation is not required for viable development in Drosophila. J Biol Chem 2014; 290:706-15. [PMID: 25381248 DOI: 10.1074/jbc.m114.615427] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The dominant paradigm for spectrin function is that (αβ)2-spectrin tetramers or higher order oligomers form membrane-associated two-dimensional networks in association with F-actin to reinforce the plasma membrane. Tetramerization is an essential event in such structures. We characterize the tetramerization interaction between α-spectrin and β-spectrins in Drosophila. Wild-type α-spectrin binds to both β- and βH-chains with high affinity, resembling other non-erythroid spectrins. However, α-spec(R22S), a tetramerization site mutant homologous to the pathological α-spec(R28S) allele in humans, eliminates detectable binding to β-spectrin and reduces binding to βH-spectrin ∼1000-fold. Even though spectrins are essential proteins, α-spectrin(R22S) rescues α-spectrin mutants to adulthood with only minor phenotypes indicating that tetramerization, and thus conventional network formation, is not the essential function of non-erythroid spectrin. Our data provide the first rigorous test for the general requirement for tetramer-based non-erythroid spectrin networks throughout an organism and find that they have very limited roles, in direct contrast to the current paradigm.
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Affiliation(s)
- Mansi R Khanna
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Floyd J Mattie
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Kristen C Browder
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Megan D Radyk
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Stephanie E Crilly
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Katelyn J Bakerink
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
| | - Sandra L Harper
- the Systems Biology Division, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - David W Speicher
- the Systems Biology Division, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - Graham H Thomas
- From the Department of Biology and the Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 and
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Sriswasdi S, Harper SL, Tang HY, Speicher DW. Enhanced identification of zero-length chemical cross-links using label-free quantitation and high-resolution fragment ion spectra. J Proteome Res 2014; 13:898-914. [PMID: 24369724 DOI: 10.1021/pr400953w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Chemical cross-linking coupled to mass spectrometry provides structural information that is useful for probing protein conformations and providing experimental support for molecular models. "Zero-length" cross-links have greater value for these applications than longer cross-links because they provide more stringent distance constraints. However, this method is less commonly utilized because it cannot take advantage of isotopic labels, MS-labile bonds, or enrichment tags to facilitate identification. In this study, we combined label-free precursor ion quantitation and targeted tandem mass spectrometry with a new software tool, Zero-length Cross-link Miner (ZXMiner), to form a multitiered analysis strategy. A major, critical objective was to simultaneously achieve very high accuracy with essentially no false-positive cross-link identifications while maintaining a good depth of analysis. Our strategy was optimized on several proteins with known crystal structures. Comparison of ZXMiner to several existing cross-link analysis software showed that other algorithms detected less true positive cross-links and were far less accurate. Although prior use of zero-length cross-linking was typically restricted to small proteins, ZXMiner and the associated strategy enable facile analysis of very large protein complexes. This was demonstrated by identification of zero-length cross-links using purified 526 kDa spectrin heterodimers and intact red cell membranes and membrane skeletons.
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Affiliation(s)
- Sira Sriswasdi
- Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute , 3601 Spruce Street, Philadelphia, Pennsylvania 19104, United States
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Harper SL, Edge VL, Cunsolo Willox A. 'Changing climate, changing health, changing stories' profile: using an EcoHealth approach to explore impacts of climate change on inuit health. Ecohealth 2012; 9:89-101. [PMID: 22526749 DOI: 10.1007/s10393-012-0762-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 01/24/2012] [Accepted: 03/11/2012] [Indexed: 05/25/2023]
Abstract
Global climate change and its impact on public health exemplify the challenge of managing complexity and uncertainty in health research. The Canadian North is currently experiencing dramatic shifts in climate, resulting in environmental changes which impact Inuit livelihoods, cultural practices, and health. For researchers investigating potential climate change impacts on Inuit health, it has become clear that comprehensive and meaningful research outcomes depend on taking a systemic and transdisciplinary approach that engages local citizens in project design, data collection, and analysis. While it is increasingly recognised that using approaches that embrace complexity is a necessity in public health, mobilizing such approaches from theory into practice can be challenging. In 2009, the Rigolet Inuit Community Government in Rigolet, Nunatsiavut, Canada partnered with a transdisciplinary team of researchers, health practitioners, and community storytelling facilitators to create the Changing Climate, Changing Health, Changing Stories project, aimed at developing a multi-media participatory, community-run methodological strategy to gather locally appropriate and meaningful data to explore climate-health relationships. The goal of this profile paper is to describe how an EcoHealth approach guided by principles of transdisciplinarity, community participation, and social equity was used to plan and implement this climate-health research project. An overview of the project, including project development, research methods, project outcomes to date, and challenges encountered, is presented. Though introduced in this one case study, the processes, methods, and lessons learned are broadly applicable to researchers and communities interested in implementing EcoHealth approaches in community-based research.
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Affiliation(s)
- S L Harper
- Department of Population Medicine, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Li D, Harper SL, Tang HY, Maksimova Y, Gallagher PG, Speicher DW. A comprehensive model of the spectrin divalent tetramer binding region deduced using homology modeling and chemical cross-linking of a mini-spectrin. J Biol Chem 2010; 285:29535-45. [PMID: 20610390 PMCID: PMC2937985 DOI: 10.1074/jbc.m110.145573] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [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: 05/19/2010] [Revised: 06/30/2010] [Indexed: 11/06/2022] Open
Abstract
Spectrin dimer-tetramer interconversion is a critical contributor to red cell membrane stability, but some properties of spectrin tetramer formation cannot be studied effectively using monomeric recombinant domains. To address these limitations, a fused αβ mini-spectrin was produced that forms wild-type divalent tetramer complexes. Using this mini-spectrin, a medium-resolution structure of a seven-repeat bivalent tetramer was produced using homology modeling coupled with chemical cross-linking. Inter- and intramolecular cross-links provided critical distance constraints for evaluating and optimizing the best conformational model and appropriate docking interfaces. The two strands twist around each other to form a super-coiled, rope-like structure with the AB helix face of one strand associating with the opposing AC helix face. Interestingly, two tetramer site hereditary anemia mutations that exhibit wild-type binding in univalent head-to-head assays are located in the interstrand region. This suggests that perturbations of the interstrand region can destabilize spectrin tetramers and the membrane skeleton. The α subunit N-terminal cross-links to multiple sites on both strands, demonstrating that this non-homologous tail remains flexible and forms heterogeneous structures in the tetramer complex. Although no cross-links were observed involving the β subunit non-homologous C-terminal tail, several cross-links were observed only when this domain was present, suggesting it induces subtle conformational changes to the tetramer site region. This medium-resolution model provides a basis for further studies of the bivalent spectrin tetramer site, including analysis of functional consequences of interstrand interactions and mutations located at substantial molecular distances from the tetramer site.
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Affiliation(s)
- Donghai Li
- From Center for Systems and Computational Biology, The Wistar Institute, Philadelphia, Pennsylvania 19104
- the Jiangsu Diabetes Center, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu 210093, China, and
| | - Sandra L. Harper
- From Center for Systems and Computational Biology, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - Hsin-Yao Tang
- From Center for Systems and Computational Biology, The Wistar Institute, Philadelphia, Pennsylvania 19104
| | - Yelena Maksimova
- the Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Patrick G. Gallagher
- the Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520
| | - David W. Speicher
- From Center for Systems and Computational Biology, The Wistar Institute, Philadelphia, Pennsylvania 19104
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Harper SL, Li D, Maksimova Y, Gallagher PG, Speicher DW. A fused alpha-beta "mini-spectrin" mimics the intact erythrocyte spectrin head-to-head tetramer. J Biol Chem 2010; 285:11003-12. [PMID: 20139081 DOI: 10.1074/jbc.m109.083048] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Head-to-head assembly of two spectrin heterodimers to form an actin-cross-linking tetramer is a physiologically dynamic interaction that contributes to red cell membrane integrity. Recombinant beta-spectrin C-terminal and alpha-spectrin N-terminal peptides can form tetramer-like univalent complexes, but they cannot evaluate effects of the open-closed dimer interactions or lateral associations of the two-spectrin strands on tetramer formation. In this study we produced and characterized a fused "mini-spectrin dimer" containing the beta-spectrin C-terminal region linked to the alpha-spectrin N-terminal region. This fused mini-spectrin mimics structural and functional properties of intact, full-length dimers and tetramers, including lateral association of the alpha and beta subunits in the dimer and formation of a closed dimer. High performance liquid chromatography gel filtration analyses of this mini-spectrin provide the first direct non-imaging experimental evidence for open and closed spectrin dimers and show that dimer-tetramer-oligomer interconversion is slow at low temperatures and accelerated at 30 degrees C, analogous to full-length spectrin. This protein exhibits wild type dimer-tetramer dissociation constants of approximately 1 mum at 30 degrees C, independent of initial oligomeric state. Conformational states of the mini-spectrin dimer were probed further using chemical cross-linking, which identified distinct groups of cross-links for "open" and "closed" dimers and confirmed the N-terminal region of alpha-spectrin remains highly flexible in the complex, exhibiting closely analogous structures to those observed for the isolated alpha-spectrin N-terminal using NMR (Park, S., Caffrey, M. S., Johnson, M. E., and Fung, L. W. (2003) J. Biol. Chem. 278, 21837-21844). This fusion protein should serve as a useful template for structural and functional studies of the divalent tetramer site.
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Affiliation(s)
- Sandra L Harper
- Center for Systems and Computational Biology, The Wistar Institute, 3601 Spruce St., Philadelphia, PA 19104, USA.
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Abstract
Recombinant proteins are subject to many forms of heterogeneity, including aggregation, proteolytic degradation, chemical modification, mutation, and incorrect translation. This unit describes methods for the detection and identification of these problems using analytical HPLC gel filtration and MALDI-MS. Preliminary characterization of recombinants is necessary before the structure or function of the protein can be investigated.
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Affiliation(s)
- G E Begg
- The Wistar Institute, Philadelphia, Pennsylvania, USA
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15
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Peng H, Gibson LC, Capili AD, Borden KLB, Osborne MJ, Harper SL, Speicher DW, Zhao K, Marmorstein R, Rock TA, Rauscher FJ. The structurally disordered KRAB repression domain is incorporated into a protease resistant core upon binding to KAP-1-RBCC domain. J Mol Biol 2007; 370:269-89. [PMID: 17512541 DOI: 10.1016/j.jmb.2007.03.047] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [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: 11/27/2006] [Revised: 02/05/2007] [Accepted: 03/19/2007] [Indexed: 12/13/2022]
Abstract
The KRAB domain is a 75 amino acid transcriptional repression module that is encoded by more than 400 zinc finger protein genes, making it the most abundant repression domain in the human proteome. KRAB-mediated gene silencing requires a direct high affinity interaction with the RBCC domain of KAP-1 co-repressor. The structures of the free KRAB domain or the KRAB-RBCC complex are unknown. To address this, we have performed a systematic biophysical analysis of all KRAB isoforms using purified recombinant proteins. All KRAB domains are predominantly monomeric either alone or in a complex with KAP-1-RBCC protein, while a KRAB-SCAN isoform exists as a stable dimer. The KRAB:KAP-1-RBCC interaction requires only the A box in the context of the KRAB(Ab) or KRAB(AC) but both A and B boxes in the context of KRAB(AB). All isoforms bind the KAP-1-RBCC in a stable, zinc dependent fashion with a stoichiometry of KRAB1:3 RBCC with a zinc content of four atoms per RBCC monomer. Limited proteolysis, mass spectrometry and N-terminal sequence analyses suggest that a core complex comprises the entire RBCC domain of KAP-1 and the AB box of the KRAB domain rendering it resistant to proteolysis. NMR spectroscopy showed that unbound KRAB domain does not exist as a well-folded globular protein in solution but may fold into an ordered structure upon binding to the KAP-1-RBCC protein. This is the first example of a structurally disordered repressor domain that is the most widely conserved silencing domain in tetrapods.
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Affiliation(s)
- Hongzhuang Peng
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
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16
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Harper SL, Reiber CL. Metabolic, respiratory and cardiovascular responses to acute and chronic hypoxic exposure in tadpole shrimp Triops longicaudatus. ACTA ACUST UNITED AC 2006; 209:1639-50. [PMID: 16621945 DOI: 10.1242/jeb.02180] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [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: 11/20/2022]
Abstract
Hypoxic exposure experienced during sensitive developmental periods can shape adult physiological capabilities and define regulatory limits. Tadpole shrimp were reared under normoxic (19-21 kPa O(2)), moderate (10-13 kPa O(2)) or severe (1-3 kPa O(2)) hypoxic conditions to investigate the influence of developmental oxygen partial pressure (P(O(2))) on adult metabolic, respiratory and cardiovascular physiology. Developmental P(O(2)) had no effect on metabolic rate or metabolic response to hypoxic exposure in adults. All rearing groups decreased O(2) consumption as water P(O(2)) decreased. Heart rate, stroke volume and cardiac output were independent of P(O(2)) down to 5 kPa O(2) in all rearing groups. Below this, cardiac output was maintained only in tadpole shrimp reared under severe hypoxic conditions. The enhanced ability to maintain cardiac output was attributed to an increase in hemoglobin concentration and O(2)-binding affinity in those animals. Oxygen-delivery potential was also significantly higher in the group reared under severe hypoxic conditions (1,336 microl O(2) min(-1)) when compared with the group reared under normoxic conditions (274 microl O(2) min(-1)). Differences among the rearing groups that were dependent on hemoglobin were not considered developmental effects because hemoglobin concentration could be increased within seven days of hypoxic exposure independent of developmental P(O(2)). Hypoxia-induced hemoglobin synthesis may be a compensatory mechanism that allows tadpole shrimp to regulate O(2) uptake and transport in euryoxic (O(2) variable) environments. The results of this study indicate that increased hemoglobin concentration, increased O(2)-binding affinity and transient decreases in metabolic demand may account for tadpole shrimp hypoxic tolerance.
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Affiliation(s)
- S L Harper
- Department of Environmental and Molecular Toxicology, Oregon State University, Environmental Health Sciences Center, 1011 ALS, Corvallis, 97331, USA.
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Harper SL, Reiber CL. Cardiac development in crayfish: ontogeny of cardiac physiology and aerobic metabolism in the red swamp crayfish Procambarus clarkii. J Comp Physiol B 2006; 176:405-14. [PMID: 16397806 DOI: 10.1007/s00360-005-0062-7] [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] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 11/14/2005] [Accepted: 11/23/2005] [Indexed: 11/28/2022]
Abstract
The cardiovascular system performs key physiological functions even as it develops and grows. The ontogeny of cardiac physiology was studied throughout embryonic and larval development in the red swamp crayfish Procambarus clarkii using videomicroscopic dimensional analysis. The heart begins to contract by day 13 of development (at 25 degrees C, 20 kPa O2). Prior to eclosion, heart rate (fH) decreases significantly. Previous data suggests that the decrease in cardiac parameters prior to hatching may be due to an oxygen limitation of the embryo. Throughout development, metabolizing mass and embryonic oxygen consumption primarily increased while egg surface area remains constant. The limited area for gas exchange of the egg membrane, in combination with the increasing oxygen demand of the embryo could result in an inadequate diffusive supply of oxygen to developing tissues. To determine if the decrease in cardiac function was the result of an internal hypoxia experienced during late embryonic development, early and late stage embryos were exposed to hyperoxic water (PO2 = 40 kPa O2). The fH in late stage embryos increased significantly over control values when exposed to hyperoxic water suggesting that the suppression in cardiac function observed in late stage embryos is likely due to a limited oxygen supply.
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Affiliation(s)
- S L Harper
- Department of Environmental and Molecular Toxicology, Oregon State University, 1011 ALS, Corvallis, OR 97331, USA.
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Abstract
Crustacean embryonic and larval systems offer a unique and valuable tool for furthering our understanding of both developmental processes and physiological regulatory mechanisms. The diverse array of developmental patterns exhibited by crustaceans allows species choice to be based on the specific questions being investigated, where defined larval forms are chosen based on their developmental pattern, degree of maturation or regulatory capabilities. However, this great diversity in developmental patterns, as well as crustacean diversity, can also confound ones ability to define or identify species for investigation. These issues are addressed and suggestions put forth to clarify some of the problems. The complexity and overlapping nature of adult cardio-regulatory systems makes teasing them apart difficult. Embryonic and larval systems exhibit varying degrees of regulatory complexity depending on developmental stage and ontogenetic pattern. This can allow complex adult regulatory systems to be teased apart temporally, as the developing animal builds regulatory pathways. Equally important is the nature of crustacean larvae; many undergo dramatic metamorphoses in cases where the larvae have adaptations to environments different to those of the adult. During environmental transitions physiological adaptations to immediate change should take precedence over long-term adult adaptations. It is therefore possible to look at physiological responses as a function of developmental/environmental adaptation, independent of adult functions.
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Affiliation(s)
- C L Reiber
- University of Nevada, Department of Biological Sciences, Maryland Parkway, Las Vegas 89154-4004, USA.
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19
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Abstract
The cardiovascular system is the first system to become functional in a developing animal and must perform key physiological functions even as it develops and grows. The ontogeny of cardiac physiology was studied throughout embryonic and larval developmental stages in the red swamp crayfish Procambarus clarkii using videomicroscopic dimensional analysis. The heart begins to contract by day 13 of development (at 25 degrees C, 20 kPa O(2)). Cardiac output is primarily regulated by changes in heart rate because stroke volume remains relatively constant throughout embryogenesis. Prior to eclosion, heart rate and cardiac output decreased significantly. Previous data suggest that the decrease in cardiac parameters prior to hatching may be due to an oxygen limitation to the embryo. Throughout development, metabolizing mass and embryonic oxygen consumption increased, while egg surface area remained constant. The surface area of the egg membrane is a constraint on gas exchange; this limitation, in combination with the increasing oxygen demand of the embryo, results in an inadequate diffusive supply of oxygen to developing tissues. To determine if the decrease in cardiac function was the result of an internal hypoxia experienced during late embryonic development, early and late-stage embryos were exposed to hyperoxic water (PO(2) = 40 kPa O(2)). Heart rate in late-stage embryos exposed to hyperoxic water increased significantly over control values, which suggests that the suppression in cardiac function observed in late-stage embryos is due to a limited oxygen supply.
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Affiliation(s)
- S L Harper
- U.S. Environmental Protection Agency, Environmental Sciences Division/ORD, PO Box 93478, Las Vegas, Nevada 89193-3478, USA
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20
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Abstract
Adult crayfish have a neurogenic heart which is modulated via inputs from the central nervous system and neurohormones, which act on the cardiac ganglion or directly on the myocardium. This study investigates the ontogeny of cardiac regulation by exploring the temporal sequence of cardiac sensitivity to injections of cardioactive neurohormones (proctolin, serotonin and octopamine) and the neurotransmitter gamma-aminobutyric acid. The cardiac response (delta in heart rate, stroke volume, or in cardiac output) to each neurohormone at each developmental stage was assessed. The observed response elicited by each cardioactive drug was stage dependent and changed as the animals progressed from embryonic through larval and juvenile periods. During early developmental stages, octopamine, serotonin, and proctolin (10(-9)-10(-3) M) did not result in a modulation of stroke volume, yet in later developmental stages they caused significant increases in stroke volume, at comparable concentrations. Early developmental stages are capable of regulating cardiac function, however, the mechanisms appear to be quite different from those used by adults. Evidence is also provided to support the hypothesis that cardiac function is initiated prior to the establishment of an adult-like regulatory system.
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Affiliation(s)
- S L Harper
- Department of Biological Sciences, University of Nevada, Las Vegas 89154, USA.
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Abstract
Human erythrocyte spectrin is an antiparallel heterodimer comprised of a 280 kDa alpha subunit and a 246 kDa beta subunit which further associates into tetramers in the red cell membrane cytoskeleton. Lateral association of the flexible rodlike monomers involves a multiple-step process that is initiated by a high affinity association near the actin-binding end of the molecule (dimer nucleation site). In this study, recombinant alpha and beta proteins comprising two or four "spectrin type" motifs with and without adjacent, terminal nonhomologous domains were evaluated for their relative contributions to dimer initiation, and the thermodynamic properties of these heterodimer complexes were measured. Sedimentation equilibrium studies showed that in the absence of the heterologous subunit, individual recombinant proteins formed weak homodimers (K(d) > 0.3 mM). When 2-motif (alpha20-21 and beta1-2) and 4-motif (alpha18-21 and beta1-4) recombinants lacking the terminal nonhomologous domains were paired with the complementary protein, high affinity heterodimers were formed in sedimentation equilibrium analysis. Both the alpha20-21/beta1-2 complex and the alpha20-21EF/betaABD1-2 complex showed stoichiometric binding with similar binding affinities (K(d) approximately 10 nM) using isothermal titration calorimetry. The alpha20-21/beta1-2 complex showed an enthalpy of -10 kcal/mol, while the alpha20-21EF/betaABD1-2 complex showed an enthalpy of -13 kcal/mol. Pull-down assays using alpha spectrin GST fusion proteins showed strong associations between all heterodimer complexes in physiological buffer, but all heterodimer complexes were destabilized by the presence of Triton X-100 and other detergents. Complexes lacking the nonhomologous domains were destabilized to a greater extent than complexes that included the nonhomologous domains. The detergent effect appears to be responsible for the apparent essential role of the nonhomologous domains in prior reports. Taken together, our results indicate that the terminal nonhomologous domains do not contribute to dimer initiation nor are they required for formation of high affinity spectrin heterodimers in physiological buffers.
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Affiliation(s)
- S L Harper
- The Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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Abstract
Chronic exposure of children to lead (Pb) can result in permanent physiological impairment. Since surfaces coated with lead-containing paints and varnishes are potential sources of exposure, it is extremely important that reliable methods for sampling and analysis be available. The sources of variability in the collection and preparation of samples were investigated to improve the performance and comparability of methods and to ensure that data generated will be adequate for its intended use. Paint samples of varying sizes (areas and masses) were collected at different locations across a variety of surfaces including metal, plaster, concrete, and wood. A variety of grinding techniques were compared. Manual mortar and pestle grinding for at least 1.5 min and mechanized grinding techniques were found to generate similar homogenous particle size distributions required for aliquots as small as 0.10 g. When 342 samples were evaluated for sample weight loss during mortar and pestle grinding, 4% had 20% or greater loss with a high of 41%. Homogenization and sub-sampling steps were found to be the principal sources of variability related to the size of the sample collected. Analysis of samples from different locations on apparently identical surfaces were found to vary by more than a factor of two both in Pb concentration (mg cm-2 or %) and areal coating density (g cm-2). Analyses of substrates were performed to determine the Pb remaining after coating removal. Levels as high as 1% Pb were found in some substrate samples, corresponding to more than 35 mg cm-2 Pb. In conclusion, these sources of variability must be considered in development and/or application of any sampling and analysis methodologies.
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Affiliation(s)
- S L Harper
- US Environmental Protection Agency, National Exposure Research Laboratory, Research Triangle Park, NC 27711, USA
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Letko E, Stechschulte SU, Kenyon KR, Sadeq N, Romero TR, Samson CM, Nguyen QD, Harper SL, Primack JD, Azar DT, Gruterich M, Dohlman CH, Baltatzis S, Foster CS. Amniotic membrane inlay and overlay grafting for corneal epithelial defects and stromal ulcers. Arch Ophthalmol 2001; 119:659-63. [PMID: 11346392 DOI: 10.1001/archopht.119.5.659] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVES To determine the effect of amniotic membrane transplantation (AMT) on persistent corneal epithelial defects (PEDs) and to compare the efficacy between inlay and overlay techniques. METHODS Thirty patients (30 eyes) underwent AMT for PED. The use of AMT was restricted to patients in whom all previous measures, including bandage contact lens and tarsorrhaphy, had failed. The amniotic membrane was placed on the surface of the cornea in overlay (group A) or inlay (group B) fashion. RESULTS The PED healed after the first AMT in 21 eyes (70%) within an average of 25.5 days after surgery and recurred in 6 eyes (29%). Among the 22 eyes treated with an overlay AMT (group A), the PED healed after the first AMT in 14 eyes (64%) within an average of 24.5 days and recurred in 4 eyes (29%). Among the 8 eyes treated with an inlay AMT (group B), the PED healed within an average of 27.4 days after AMT, which did not statistically significantly differ from group A (P = .72). The PED healed after the first AMT in 7 eyes (88%) and recurred in 2 (29%) of 7 eyes. CONCLUSIONS The AMT can be helpful in the treatment of PED in which all other conventional management has failed. However, the success rate in our study was not as high as that previously reported, and our results showed a high incidence of recurrences of epithelial defects. We did not find any difference between overlay and inlay techniques in terms of healing time and recurrence rate.
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Affiliation(s)
- E Letko
- Immunology Service, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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Harper SL, Letko E, Samson CM, Zafirakis P, Sangwan V, Nguyen Q, Uy H, Baltatzis S, Foster CS. Wegener's granulomatosis: the relationship between ocular and systemic disease. J Rheumatol 2001; 28:1025-32. [PMID: 11361183] [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: 04/16/2023]
Abstract
OBJECTIVE Wegener's granulomatosis (WG) is an etiologically obscure entity with multiple systemic manifestations. Ocular involvement is present in up to 58% of patients with WG. We describe a series of patients with ocular manifestations of WG to evaluate the presence of ocular lesions in the setting of systemic WG and to determine the value of ocular inflammation in the diagnosis of WG. METHODS A computerized database was used to generate a list of patients cared for in the Ocular Immunology Service of the Massachusetts Eye and Ear Infirmary during the 10 year period 1988-98 with a diagnosis of Wegener's granulomatosis. A detailed chart review was undertaken to determine demographic characteristics, history, initial manifestation of WG, initial ocular presentation, biopsy results, laboratory testing results, treatment, total followup period, and final outcome. RESULTS Forty-seven patients diagnosed with WG were identified. Twenty-eight were women (59.6%), 19 were men (40.4%). The average age was 53 years (range 18-90). Patients were divided into 4 groups. Group I included 27 patients (57.4%) who had systemic disease first and who subsequently developed an ocular lesion. Group II included 3 patients (6.3%) who had ocular inflammation first and who then subsequently developed systemic manifestations of WG. Group III included 3 patients (6.3%) who presented due to ocular symptoms but, on initial evaluation by us, were found to have occult systemic manifestations consistent with WG or biopsy evidence of WG. Group IV included 14 patients (30%) with ocular lesions and no history or presence of systemic disease at their last followup visit. CONCLUSION Ocular inflammation can occur with or without obvious systemic manifestations of WG. It may represent the first sign of WG that enables the knowledgeable physician to diagnose this potentially lethal disease.
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Affiliation(s)
- S L Harper
- Department of Ophthalmology, Uveitis and Immunology Service, The Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston 02114, USA
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Kim NN, Cox JD, Baggio RF, Emig FA, Mistry SK, Harper SL, Speicher DW, Morris SM, Ash DE, Traish A, Christianson DW. Probing erectile function: S-(2-boronoethyl)-L-cysteine binds to arginase as a transition state analogue and enhances smooth muscle relaxation in human penile corpus cavernosum. Biochemistry 2001; 40:2678-88. [PMID: 11258879 DOI: 10.1021/bi002317h] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [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: 11/30/2022]
Abstract
The boronic acid-based arginine analogue S-(2-boronoethyl)-L-cysteine (BEC) has been synthesized and assayed as a slow-binding competitive inhibitor of the binuclear manganese metalloenzyme arginase. Kinetic measurements indicate a K(I) value of 0.4-0.6 microM, which is in reasonable agreement with the dissociation constant of 2.22 microM measured by isothermal titration calorimetry. The X-ray crystal structure of the arginase-BEC complex has been determined at 2.3 A resolution from crystals perfectly twinned by hemihedry. The structure of the complex reveals that the boronic acid moiety undergoes nucleophilic attack by metal-bridging hydroxide ion to yield a tetrahedral boronate anion that bridges the binuclear manganese cluster, thereby mimicking the tetrahedral intermediate (and its flanking transition states) in the arginine hydrolysis reaction. Accordingly, the binding mode of BEC is consistent with the structure-based mechanism proposed for arginase as outlined in Cox et al. [Cox, J. D., Cama, E., Colleluori D. M., Pethe, S., Boucher, J. S., Mansuy, D., Ash, D. E., and Christianson, D. W. (2001) Biochemistry 40, 2689-2701.]. Since BEC does not inhibit nitric oxide synthase, BEC serves as a valuable reagent to probe the physiological relationship between arginase and nitric oxide (NO) synthase in regulating the NO-dependent smooth muscle relaxation in human penile corpus cavernosum tissue that is required for erection. Consequently, we demonstrate that arginase is present in human penile corpus cavernosum tissue, and that the arginase inhibitor BEC causes significant enhancement of NO-dependent smooth muscle relaxation in this tissue. Therefore, human penile arginase is a potential target for the treatment of sexual dysfunction in the male.
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Affiliation(s)
- N N Kim
- Department of Urology, Boston University School of Medicine, 700 Albany Street, Boston, Massachusetts 02118, USA
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Gunn RA, Harper SL, Borntrager DE, Gonzales PE, St Louis ME. Implementing a syphilis elimination and importation control strategy in a low-incidence urban area: San Diego County, California, 1997-1998. Am J Public Health 2000; 90:1540-4. [PMID: 11029985 PMCID: PMC1446380 DOI: 10.2105/ajph.90.10.1540] [Citation(s) in RCA: 8] [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: 11/04/2022]
Abstract
OBJECTIVES This study assessed a strategy designed to contain imported cases of syphilis and prevent reestablishment of ongoing transmission. METHODS Reported syphilis cases during an endemic period (1990-1992) and an elimination period (1997-1998) were compared in San Diego, Calif. The elimination strategy, which focuses on rapid reporting of infectious syphilis cases by clinicians, prompt partner and sexual network management, outreach to marginalized populations, and implementation of an outbreak containment plan, was evaluated. RESULTS Infectious syphilis incidence rates declined from 18.3 per 100,000 in 1998 to 1.0 per 100,000 in 1998. Of the 46 cases involving probable infection during 1997-1998, 19 (41%) were imported, mostly (79%) from Mexico. Outbreak containment procedures were implemented successfully for 2 small clusters. Outreach workers provided sexually transmitted disease information to a large number of individuals; however, no cases of infectious syphilis were identified, suggesting that syphilis transmission was not occurring among marginalized groups. CONCLUSIONS This syphilis elimination and importation control strategy will require monitoring and adjustments. Controlling syphilis along the US-Mexico border is a necessary component of syphilis elimination in the United States.
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Affiliation(s)
- R A Gunn
- Centers for Disease Control and Prevention, Atlanta, Ga., USA.
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27
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Abstract
A laboratory system has been constructed that uniformly deposits dry particles onto any type of test surface. Devised as a quality assurance tool for the purpose of evaluating surface sampling methods for lead, it also may be used to generate test surfaces for any contaminant that uses particles or dust as a transport mechanism. Additionally, it may be used to spike surfaces for studies concerning particle transport, resuspension, reentrainment, and exposure. The electromechanical system includes a rugged aluminum chamber housing deposition equipment, a computer-controlled positioning system, and a 0.61 x 0.61 m target surface area (2 x 2 ft). Media used to evaluate the system have included glass beads of various size fractions (physical diameters between 30 and 500 microm), and Arizona Test Dust (aerodynamic diameters between 1 and 80 microm). Presieved particle size fractions may be used individually to study the effects of monodisperse particles, or may be mixed to create custom polydisperse size distributions. Using arrays of 16 coupons placed on the surface to collect representative samples from every test, the uniformity of the particle deposition can be quantified. The system achieved an average coefficient of variation of less than 20% for the 16 coupons for the particle types and sizes mentioned above and for a variety of total surface loadings (0.3-19 g/m2). Calculations of the system's repeatability (as the average coefficient of variation of mass gains for individual coupon locations compared across multiple identically configured runs) yielded approximately 10 +/- 5% (one standard deviation). Tests of the system's accuracy, defined as the absolute percentage difference between predicted surface loadings and actual loadings, yielded 3.7 +/- 1.3% (one standard deviation).
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Affiliation(s)
- J T Antley
- Center for Engineering and Environmental Technology, Research Triangle Institute, Research Triangle Park, NC 27709, USA
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28
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Abstract
PURPOSE To describe the ocular and systemic manifestations associated with systemic lupus erythematosus (SLE) choroidopathy. METHODS Three new cases of choroidopathy in patients with active SLE were described. Twenty-five published cases of lupus choroidopathy were summarized. RESULTS There have been 28 cases of lupus choroidopathy (47 involved eyes) that have been reported in the English literature since 1968, including the three current cases. Only two of the patients were male. The choroidopathy was bilateral in 19 patients (68%). All 28 patients (100%) had active systemic vascular disease at the onset of their choroidopathy; 18 (64%) had nephropathy and 10 (36%) had central nervous system (CNS) lupus vasculitis. All but one of the patients had a known diagnosis of SLE at the onset of choroidopathy. 30 of the 47 involved eyes had presenting visual acuity of 20/40 or better; 14 eyes showed improvement in visual acuity with therapy. 23 patients (82%) had resolution of their choroidopathy when their systemic disease was brought under control. Despite treatment, 4 of the 28 patients (14%) died from complications of SLE. CONCLUSIONS Although less known than retinopathy, lupus choroidopathy may be more common than generally appreciated. It usually serves as a sensitive indicator of lupus activity. The presence of SLE choroidopathy is generally indicative of coexistent (although sometimes occult) nephropathy, CNS vasculitis, and other SLE visceral lesions. Immunomodulation of the systemic disease can lead to improvement and resolution of the systemic vasculitis as well as the choroidopathy.
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Affiliation(s)
- Q D Nguyen
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
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29
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Peng H, Begg GE, Harper SL, Friedman JR, Speicher DW, Rauscher FJ. Biochemical analysis of the Kruppel-associated box (KRAB) transcriptional repression domain. J Biol Chem 2000; 275:18000-10. [PMID: 10748030 DOI: 10.1074/jbc.m001499200] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [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] Open
Abstract
The Kruppel-associated box (KRAB) domain is a 75-amino acid transcriptional repressor module commonly found in eukaryotic zinc finger proteins. KRAB-mediated gene silencing requires binding to the RING-B box-coiled-coil domain of the corepressor KAP-1. Little is known about the biochemical properties of the KRAB domain or the KRAB.KAP-1 complex. Using purified components, a combination of biochemical and biophysical analyses has revealed that the KRAB domain from the KOX1 protein is predominantly a monomer and that the KAP-1 protein is predominantly a trimer in solution. The analyses of electrophoretic mobility shift assays, GST association assays, and plasmon resonance interaction data have indicated that the KRAB binding to KAP-1 is direct, highly specific, and high affinity. The optical biosensor data for the complex was fitted to a model of a one-binding step interaction with fast association and slow dissociation rates, with a calculated K(d) of 142 nm. The fitted R(max) indicated three molecules of KAP-1 binding to one molecule of the KRAB domain, a stoichiometry that is consistent with quantitative SDS-polyacrylamide gel electrophoresis analysis of the complex. These structural and dynamic parameters of the KRAB/KAP-1 interaction have implications for identifying downstream effectors of KAP-1 silencing and the de novo design of new repression domains.
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Affiliation(s)
- H Peng
- Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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30
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Abstract
Visual rehabilitation after cataract surgery has been improved with the development of IOLs. These lenses are well tolerated in many uveitis patients when complete control of preoperative inflammation is achieved. However, in some patients, IOL placement after cataract extraction results in chronic inflammation, deposition of inflammatory cells and debris on the IOL surface, and inflammatory membrane formation despite antiinflammatory coverage. Patients with systemic diseases characterized by chronic inflammation, such as sarcoidosis and JRA, and those with chronic ocular inflammatory conditions or inflammation involving the intermediate segment of the eye may be at high risk for these complications. In patients in whom antiinflammatory therapy fails, adequate control of inflammation may be achieved after lens explantation.
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Affiliation(s)
- S L Harper
- Ocular Immunology and Uveitis Service, Massachusetts Eye and Ear Infirmary, Boston 02114, USA
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31
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Begg GE, Harper SL, Morris MB, Speicher DW. Initiation of spectrin dimerization involves complementary electrostatic interactions between paired triple-helical bundles. J Biol Chem 2000; 275:3279-87. [PMID: 10652315 DOI: 10.1074/jbc.275.5.3279] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [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: 11/06/2022] Open
Abstract
The spectrin heterodimer is formed by the antiparallel lateral association of an alpha and a beta subunit, each of which comprises largely a series of homologous triple-helical motifs. Initiation of dimer assembly involves strong binding between complementary motifs near the actin-binding end of the dimer. In this study, the mechanism of lateral spectrin association at this dimer nucleation site was investigated using the analytical ultracentrifuge to analyze heterodimers formed from recombinant peptides containing two or four homologous motifs from each subunit (alpha20-21/beta1-2; alpha18-21/beta1-4). Both the two-motif and four-motif dimer associations were weakened substantially with increasing salt concentration, indicating that electrostatic interactions are important for the dimer initiation process. Modeling of the electrostatic potential on the surface of the alpha20 and beta2 motifs showed that the side of the motifs comprising the A and B helices is the most favorable for association, with an area of positive electrostatic potential on the AB face of the beta2 motif opposite negative potential on the AB face of the alpha20 motif and vise versa. Protease protection analysis of the alpha20-21/beta1-2 dimer showed that multiple trypsin and proteinase K sites in the A helices of the beta2 and alpha21 motifs become buried upon dimer formation. Together, these data support a model where complementary long range electrostatic interactions on the AB faces of the triple-helical motifs in the dimer nucleation site initiate the correct pairing of motifs, i.e. alpha21-beta1 and alpha20-beta2. After initial docking of these complementary triple-helical motifs, this association is probably stabilized by subsequent formation of stronger hydrophobic interactions in a complex involving the A helices of both subunits and possibly most of the AB faces. The beta subunit A helix in particular appears to be buried in the dimer interface.
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Affiliation(s)
- G E Begg
- Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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32
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Affiliation(s)
- R Baggio
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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33
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Abstract
The inflammatory arthropathies that affect the eye most commonly are RA, JRA, and the seronegative spondyloarthropathies. These conditions not only cause devastating systemic findings but can be the source of damaging ocular disease. The inflammatory nature of these entities, with the accompanying liberation of mediators of inflammation, can result in a cycle of tissue destruction that culminates in blindness. The diseases reviewed can present first with systemic or ocular findings; thus, all physicians must be equipped with the appropriate knowledge to make accurate and timely diagnoses so that appropriate management strategies can be employed. The successful recognition and treatment of these conditions can prevent their associated systemic and ocular morbidity.
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Affiliation(s)
- S L Harper
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston 02114, USA
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35
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Wilmotte R, Harper SL, Ursitti JA, Maréchal J, Delaunay J, Speicher DW. The exon 46-encoded sequence is essential for stability of human erythroid alpha-spectrin and heterodimer formation. Blood 1997; 90:4188-96. [PMID: 9354690] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Human erythroid alpha-spectrin alleles responsible for hereditary elliptocytosis (alphaHE alleles) undergo increased incorporation into red blood cell membranes when the polymorphism alphaLELY (LELY: Low Expression LYon) occurs in trans. The alphaLELY polymorphism is characterized by a mutation in exon 40 at codon 1857 (CTA --> GTA, Leu --> Val) and the partial (50%) skipping of exon 46, which encodes residues 2177-2182 (Wilmotte et al, J Clin Invest 91:2091, 1993). Both of these peptide sequence alterations are located within the region of the alpha-chain involved in initiating heterodimer assembly, and either or both mutations could potentially contribute to decreased incorporation of alpha-chains from the alphaLELY allele in heterozygotes into red blood cell membranes. These possibilities were evaluated by testing the protease resistance and in vitro binding properties of normal and mutant recombinant 4-motif alpha subunit peptides containing the dimer initiation region. The two forms of alpha spectrin produced by alternative mRNA splicing of the alphaLELY allele were represented by alpha18-21(1857), a peptide with the codon 1857 mutation and retaining the exon 46 encoded sequence, and alpha18-21(1857-Delta46), a peptide carrying both the 1857 codon mutation and the exon 46 deletion. The properties of these two recombinant peptides were compared with alpha18-21, a peptide with the normal sequence at codon 1857 and retaining the exon 46 encoded sequence. The codon 1857 mutation does not adversely affect dimer formation, but it is responsible for the increased trypsin cleavage between the alphaIV and alphaV domains that was the characteristic feature initially used to identify the alphaLELY (SpalphaV/41) polymorphism (Alloisio et al, J Clin Invest 87:2169, 1991). Deletion of the six amino acids encoded by exon 46 perturbs folding of the alpha21 motif, because this region of the alpha18-21(1857-Delta46) peptide is rapidly degraded and this recombinant peptide is unusually prone to self-aggregation. Exon 46 deletion reduces, but does not eliminate, dimerization. Comparison of mild trypsin proteolytic products from an alphaLELY homozygote and the two alphaLELY recombinant peptides strongly suggests that little, if any, of the 50% of the alpha chains from the alphaLELY allele that contain the exon 46 deletion are incorporated into the mature erythroid membrane. Based on the in vitro analysis of recombinant alphaLELY peptides, the inability of detectable amounts of exon 46(-) alpha chains to assemble into the mature membrane skeleton in vivo is probably due to a combination of decreased dimer binding affinity and increased proteolytic degradation of these mutant chains.
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Affiliation(s)
- R Wilmotte
- Laboratoire de Génétique Moléculaire Humaine, CNRS URA 1171, Institut Pasteur de Lyon, Lyon, France
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36
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DeSilva TM, Harper SL, Kotula L, Hensley P, Curtis PJ, Otvos L, Speicher DW. Physical properties of a single-motif erythrocyte spectrin peptide: a highly stable independently folding unit. Biochemistry 1997; 36:3991-7. [PMID: 9092829 DOI: 10.1021/bi962412j] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [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: 02/04/2023]
Abstract
Spectrin is a long flexible rod-like actin cross-linking protein mostly comprised of many tandem homologous 106-residue motifs. In this study, the conformational stability and physical properties of a single homologous motif peptide, alpha1, were evaluated and compared to intact spectrin monomers and alphabeta heterodimers. It is interesting that while spectrin dimers elongate by about 3-fold in low ionic strength buffers relative to their size in physiological buffers, the single-motif peptide does not show significant changes in secondary structure in 10 mM phosphate buffer compared with isotonic buffer. This single-motif peptide is monomeric in physiological buffer as demonstrated by equilibrium sedimentation studies, and its hydrodynamic radius determined by gel filtration and dynamic light scattering of about 2.2 nm is consistent with an elongated rod-like shape. Unfolding of the single-motif peptide in urea solutions was similar to unfolding of intact heterodimers. Differential scanning calorimetry analyses showed that this single motif undergoes a reversible two-state transition with a Tm of 53 degrees C and an enthalpy of 65 kcal/mol in physiological buffer. Thermal stability was unaffected by ionic strength changes, but was decreased below physiological pH. These data show that this 13 kDa spectrin motif is a monomeric, highly stable, triple-helical, independently folding protein building block with physical characteristics that define many of the structural properties of the 526 kDa spectrin heterodimer. In contrast, interactions between adjacent motifs are probably responsible for spectrin's molecular flexibility and elasticity.
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Affiliation(s)
- T M DeSilva
- The Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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37
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Abstract
Thirty non-neoplastic ovarian cysts, discovered at laparotomy in association with 27 cases of tubal ectopic pregnancy, were examined to document changes seen in early pregnancy and possibly to identify precursor lesions to the luteinized cysts of later pregnancy. The ages of the patients ranged from 16 to 40 years, and length of gestation varied between 5 and 11 weeks. Of the 30 cysts, 12 were corpus luteum cysts; 10 were called lutein cysts, nonspecific, and had a lining of luteinized cells of a single cell type; three cysts were luteinized follicles; four cysts were unlined or lined by a single layer of cells. The origin of these four was not obvious, and they were called "simple cysts." The last was a granulosa-theca lutein cyst. Corpus luteum cysts are assumed to arise from the corpus luteum, and simple cysts appear to arise from both corpus luteum cysts and other follicular structures. The nonspecific lutein cysts appeared to arise from structures other than the corpus luteum or corpus luteum cysts; these nonspecific lutein cysts may be precursors to the so-called large solitary luteinized follicle cyst of pregnancy.
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Affiliation(s)
- S L Harper
- Department of Anatomical Pathology, University of Cape Town, Republic of South Africa
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38
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Harper SL, Klevans LR, Granger DN. Effects of the antihypertensive prostaglandin analog Ro 22-1327 on regional blood flows in the spontaneously hypertensive rat. J Cardiovasc Pharmacol 1987; 9:285-90. [PMID: 2437394 DOI: 10.1097/00005344-198703000-00004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The hemodynamic effects of Ro 22-1327 [nat-(15R,16R)-16-fluoro-15-hydroxy-9-oxoprosta-5(Z),1 3(E)-dienoic acid], a prostaglandin E2 analog, were evaluated in anesthetized spontaneously hypertensive rats (SHR). Within 3-4 h of topical application (1 and 3 mg/kg), a dose-dependent decrease in mean arterial blood pressure was observed. At 6 h following drug application, steady-state mean arterial pressure was 79-87% of control (pretreatment) values. Increments in blood flow, as well as reductions in vascular resistance, were apparent in the kidneys, skin, and the majority of the splanchnic organs. The magnitude of the drug-induced hyperemia decreased from the duodenum to the ileum. Significant elevations in colonic blood flow were not apparent with either dose, suggesting a proximal-to-distal gradient of response of the intestinal vasculature to the drug. The results of this study indicate that Ro 22-1327 is an effective antihypertensive agent when applied topically in SHR. Our results also imply that the splanchnic vascular bed contributes heavily to the antihypertensive activity of the compound.
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39
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Abstract
Experiments were performed in anesthetized 18-19-week-old spontaneously hypertensive rats (SHR) to evaluate the effects of delayed antihypertensive treatment on cerebrovascular function. Animals were treated for 25 +/- 1 days with an oral antihypertensive regimen consisting of hydralazine, reserpine, and chlorothiazide, resulting in normotension within 2 weeks. Cerebral arterioles were examined via a constantly suffused open cranial window and video microscopy. Resting cerebral blood flow was measured using radioactive microspheres and the reference organ method. While untreated SHR exhibited reductions in arteriolar diameter compared with normotensive Wistar Kyoto rats (WKY), treatment restored arteriolar dimensions to normal. Increments in microvascular wall area, associated with medial hypertrophy in untreated SHR, were completely reversed in treated SHR to a magnitude not different from control. Resting cerebral blood flow was, however, decreased in treated SHR compared with both untreated SHR and WKY; this was due to an increase in total cerebrovascular resistance compared with WKY. Additionally, microvascular pressure in the largest arterioles in treated SHR was reduced compared with both WKY and untreated SHR. There was a significant increase in the relative pressure drop accounted for by the arterial vessels upstream from the cerebral microcirculation in treated SHR. These results suggest that 1) cerebral microvascular abnormalities induced by chronic hypertension are reversed by delayed antihypertensive therapy, and 2) there is a persistent elevation in cerebrovascular resistance upstream from the microcirculation representing large vessel adaptations that may not be readily reversible with treatment.
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40
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Abstract
Studies were performed on anesthetized 16-18 week old normotensive Wistar-Kyoto rats, spontaneously hypertensive rats, and Goldblatt two-kidney one clip renal hypertensive rats, treated from age 4-5 weeks with an oral antihypertensive regimen consisting of hydralazine, reserpine, and chlorothiazide. Measurements of flow and intravascular pressure in the cerebral microvasculature were made via a constantly suffused open cranial window using video microscopy. A significant upward shift was seen in the pressure range for cerebral blood flow autoregulation in both groups of untreated hypertensive animals. Following treatment, the autoregulatory range in both hypertensive models was restored to a level nearly identical to control. The prevention of this shift in treated animals was due primarily to the prevention of structural microvascular adaptations that occur in untreated hypertensive animals. By preventing elevations in microvascular pressure, treatment may have eliminated the major stimulus for development of hypertrophy in resistance vessels. However, a persistent increment of arteriolar wall mass in treated spontaneously hypertensive rats may represent a hyperplastic response not influenced by treatment. Likewise, a persistent constriction of the smallest arterioles in treated renal hypertensive rats may represent a differential sensitivity of microvessels to circulating vasoactive agents. It appears that treatment initiated in the prehypertensive state, or before significant sustained hypertension has occurred, can markedly reduce the cerebrovascular morbidity associated with two different forms of hypertension.
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MESH Headings
- Adaptation, Physiological/drug effects
- Animals
- Antihypertensive Agents/therapeutic use
- Blood Flow Velocity/drug effects
- Cerebrovascular Circulation/drug effects
- Cerebrovascular Disorders/etiology
- Cerebrovascular Disorders/prevention & control
- Chlorothiazide/therapeutic use
- Drug Evaluation, Preclinical
- Drug Therapy, Combination
- Hydralazine/therapeutic use
- Hypertension/complications
- Hypertension/drug therapy
- Hypertension, Renal/complications
- Hypertension, Renal/drug therapy
- Hypertension, Renovascular/complications
- Hypertension, Renovascular/drug therapy
- Rats
- Rats, Inbred SHR/physiology
- Rats, Inbred Strains/physiology
- Rats, Inbred WKY
- Reserpine/therapeutic use
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41
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Abstract
Blood flow, arteriovenous O2 difference, and lumen pressure were measured in isolated loops of canine ileum. Ileal pressure was increased by an intra-arterial infusion of either Met-enkephalin or acetylcholine. Pressures were quantitated using a motility index (MI = mean of the pressure peaks divided by number of contractions per minute). Both Met-enkephalin and acetylcholine increased MI in a dose-dependent fashion. The highest MI achieved with acetylcholine was 37.9 mmHg, while Met-enkephalin produced a maximal MI of 8.1 mmHg. Ileal oxygen uptake increased when MI reached values greater than 6. There was a direct linear relationship between oxygen uptake and MI. Distension of the lumen in the absence of motility resulted in a decrease in oxygen uptake when lumen pressure reached 15-20 mmHg. The results of these studies indicate that contractions of intestinal smooth muscle can increase intestinal oxygen uptake and may contribute to the overall oxygen demands of the gut under conditions of fasting and feeding. Furthermore, large (greater than 20 mmHg) increments in lumen pressure during enhanced motility may compromise intestinal oxygenation.
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42
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Abstract
Pancreatic acinar tissue O2 tension (PO2) was measured in anesthetized rats using recessed-tip microelectrodes (tip diam 1-2 micron). Pancreatic blood flow was measured using radioactive microspheres. Volume rate of pancreatic secretion, as well as protein concentration, was also measured. Average resting PO2 was 24.8 +/- 1.6 mmHg, with relatively little variation evident within a given pancreas. Bolus intravenous infusion of cholecystokinin octapeptide (CCK-OP, 4 micrograms X kg body wt-1) induced a reduction in tissue PO2 and profoundly increased protein output, while not directly affecting pancreatic blood flow. By contrast, secretin infusion (1.0 CU X kg body wt-1 iv bolus) affected neither tissue PO2 nor blood flow, although secretory rate increased by nearly sevenfold. This difference in PO2 response to the two compounds is interpreted in light of the fact that CCK-OP primarily stimulates acinar cell function, while secretin preferentially activates secretory epithelium. Pancreatic PO2 was found to be linearly related to resting blood flow at flows above 44 ml X min-1 X 100 g-1. No regional differences in blood flow were found in the head, body, and tail of the pancreas.
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43
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Abstract
The intestinal vascular responses to graded reductions in arterial pressure and elevations in venous pressure were measured in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Blood flow and capillary pressure were measured in denervated, autoperfused segments of small intestine. Blood flow, capillary pressure, and total vascular resistance were significantly higher in SHR than WKY at the resting mean arterial pressures. Decrements in arterial pressure led to significant reductions in total vascular resistance in WKY but not in SHR. There was a significant tendency for capillary pressure autoregulation in WKY but not in SHR. Increments in venous pressure did not alter vascular resistance in WKY, yet significantly increased total vascular resistance in SHR. The latter effect was due entirely to a rise in precapillary resistance and is consistent with an enhanced sensitivity of the vasculature to myogenic factors. Intestinal blood flow, measured using 15-micro microspheres, was not significantly different between WKY and SHR in innervated preparations. However, in denervated preparations intestinal blood flow was significantly higher in SHR than WKY, indicating that there is a significant neural component to the increased intestinal vascular resistance in SHR.
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44
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Abstract
Vasoactive agents are known to have a variety of effects on the dynamics of the mesenteric microcirculation. We compare and contrast the effects of both vasodilators and vasoconstrictors on capillary filtration coefficient, vascular permeability, tissue oxygen tension, and microvascular pressure. The various methodologies used to determine the above quantities are discussed, as well as the limitations and advantages of each approach. Discrepancies between the results obtained with particular classes of vasoactive agents are discussed relative to both dosage and route of administration. In addition, data obtained for each parameter using both whole-organ and in vivo microscopic techniques are reconciled relative to the characteristics of each approach. Experimental designs are proposed that may help minimize future inconsistencies in the data, as well as maximize the relative advantages of available techniques.
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45
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Banks RO, Gallavan RH, Zinner MH, Bulkley GB, Harper SL, Granger DN, Jacobson ED. Vasoactive agents in control of the mesenteric circulation. Fed Proc 1985; 44:2743-9. [PMID: 2411604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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46
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Abstract
Arterial pressure, venous outflow pressure, blood flow, and arteriovenous oxygen difference were measured in autoperfused preparations of canine ileum while lumen temperature was altered in 1-5 degrees C increments (or decrements) between 31 and 40 degrees C. Neither blood flow nor vascular resistance was correlated to lumen temperature. However, both arteriovenous oxygen difference and oxygen uptake were linearly correlated with lumen temperature. The relation between ileal oxygen uptake and lumen temperature was consistent with a change in metabolic rate for a 10 degrees C change in temperature (Q10) for oxygen consumption of 2.7. These observations indicate that ambient temperature exerts a profound influence on intestinal oxygen consumption and that variations in temperature may explain the wide range of intestinal oxygen uptake values reported in the literature.
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47
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Abstract
Male rats were treated with daily subcutaneous injections (3 micrograms/kg) of cholecystokinin octapeptide (CCK-OP), a synthetic CCK analogue, for 2, 4, 7, and 14 days, while control rats were injected with saline over the same intervals. Regional blood flows were measured with Sc46-labeled microspheres using the reference-organ method. Pancreatic wet and dry weights were determined in each treatment group. Total pancreatic DNA content was estimated with the diphenylamine reaction. Significant hyperplasia and increases in pancreatic wet weight occurred at 7 and 14 days, although hypertrophy was not evident in any of the treatment groups. No increases in small intestine wet weight or DNA content were evident in any treatment group. CCK-OP treatment induced a significant pancreatic hyperemia at 2 and 4 days of treatment. Pancreatic blood flow at 7 and 14 days was not different from control when expressed per unit tissue weight. The hyperemia seen at 2 and 4 days was not due to either a direct vascular effect of CCK-OP or an increase in pancreatic exocrine secretion. The hyperemia is therefore due to the growth stimulus and may be related to vasodilator metabolite accumulation during pancreatic tissue proliferation.
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48
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Benoit JN, Barrowman JA, Harper SL, Kvietys PR, Granger DN. Role of humoral factors in the intestinal hyperemia associated with chronic portal hypertension. Am J Physiol 1984; 247:G486-93. [PMID: 6496739 DOI: 10.1152/ajpgi.1984.247.5.g486] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The role of neural, metabolic, physical, and humoral factors in the intestinal hyperemia associated with chronic portal hypertension was examined by use of the rat portal vein stenosis model. Intestinal blood flow and splenic pulp pressure were increased, while systemic arterial pressure and total vascular resistance were reduced in portal vein-stenosed rats as compared with controls. The reduction in total vascular resistance was entirely due to a fall in precapillary resistance and was accompanied by an increase in intestinal capillary pressure, which exceeded that produced by acute portal pressure elevation to the same level. Arteriovenous shunting of 15-micron microspheres was four times higher in portal-hypertensive rats. Cross-perfusion of control intestinal preparations with arterial blood from portal-hypertensive rats produced a 30% increase in blood flow. Plasma glucagon levels in portal-hypertensive rats were three times higher than in controls. Intra-arterial infusion of glucagon (at a rate that achieved the concentration measured in portal-hypertensive animals) produced a 20% reduction in intestinal vascular resistance. The results of these studies indicate that humoral factors, including glucagon, are primarily responsible for the hyperemia associated with portal hypertension.
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49
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Abstract
The potential presence of myogenic regulation in the cerebral microvasculature of the rat was investigated using a method which alters intravascular pressure without appreciably changing cerebral perfusion pressure (arterial minus venous pressure). The entire rat was placed in a sealed box, with the cranial cavity open to the atmosphere and prepared for in vivo microscopy. By increasing the ambient pressure in the box, both systemic arterial and venous pressure could be changed by nearly equal amounts (+/- 20 mm Hg). Heart and respiratory rates were not influenced by changing ambient pressure by +/- 20 mm Hg. At elevated ambient pressures, cortical arterioles constricted in linear proportion to the ambient pressure, whereas subatmospheric ambient pressures caused vasodilation whose magnitude was about equal at ambient pressures of -6 to -18 mm Hg. The calculated vessel wall tension typically remained within about +/- 10-15% of control during changes of transmural pressure of +/- 20-40%. In all cases, arteriolar responses to changes in ambient and intravascular pressure reached a new steady state within 10-15 seconds and were sustained for up to 30 minutes. These data are interpreted to indicate the presence of a myogenic vascular response in the brain vasculature of the rat.
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Granger DN, Barrowman JA, Harper SL, Kvietys PR, Korthuis RJ. Sympathetic stimulation and intestinal capillary fluid exchange. Am J Physiol 1984; 247:G279-83. [PMID: 6476118 DOI: 10.1152/ajpgi.1984.247.3.g279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Sympathetic nerve stimulation is generally considered not to alter intestinal capillary pressure or filtration rate because of appropriate adjustments in the pre-to-postcapillary resistance ratio. To directly assess this possibility, we measured lymph flow, capillary pressure, capillary filtration coefficient, and the transcapillary oncotic pressure gradient in the cat small intestine. Measurements were taken under control conditions and during the steady-state phase of periarterial nerve stimulation, i.e., following completion of the escape phase. Venous outflow pressure was held constant (0 mmHg) during the entire experiment. Nerve stimulation resulted in a significant reduction of lymph flow (by 65%), capillary filtration coefficient (by 75%), and capillary pressure (by 15%). Interstitial fluid pressure, calculated from the measured parameters in the Starling equation, was also reduced (from -0.74 to -2.53 mmHg) by nerve stimulation. The results of this study indicate that intestinal capillary pressure and capillary filtration rate are not "autoregulated" during sympathetic nerve stimulation. Capillary derecruitment appears to be largely responsible for the dramatic reduction in filtration rate associated with adrenergic stimulation.
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