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Chalmers S, Hill J, Connell L, Ackerley S, Kulkarni A, Roddam H. The value of allied health professional research engagement on healthcare performance: a systematic review. BMC Health Serv Res 2023; 23:766. [PMID: 37464444 PMCID: PMC10355072 DOI: 10.1186/s12913-023-09555-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 11/07/2022] [Accepted: 05/16/2023] [Indexed: 07/20/2023] Open
Abstract
BACKGROUND Existing evidence suggests that clinician and organisation engagement in research can improve healthcare performance. With the increase in allied health professional (AHP) research activity, it is imperative for healthcare organisations, clinicians, managers, and leaders to understand research engagement specifically within allied health fields. This systematic review aims to examine the value of research engagement by allied health professionals and organisations on healthcare performance. METHODS This systematic review had a two-stage search strategy. Firstly, the papers from a previous systematic review examining the effect of research engagement in healthcare were screened to identify papers published pre-2012. Secondly, a multi-database search was used to conduct a re-focused update of the previous review, focusing specifically on allied health to identify publications from 2012-2021. Studies which examined the value of allied health research engagement on healthcare performance were included. All stages of the review were conducted by two reviewers independently. Each study was assessed using the appropriate Joanna Briggs Institute critical appraisal tool. A narrative synthesis was completed to analyse the similarities and differences between and within the different study types. RESULTS Twenty-two studies were included, comprising of mixed research designs, of which six were ranked as high importance. The findings indicated that AHP research engagement appears related to positive findings in improvements to processes of care. The review also identified the most common mechanisms which may link research engagement with these improvements. DISCUSSION This landmark systematic review and narrative synthesis suggests value in AHP research engagement in terms of both processes of care and more tentatively, of healthcare outcomes. While caution is required because of the lack of robust research studies, overall the findings support the agenda for growing AHP research. Recommendations are made to improve transparent reporting of AHP research engagement and to contribute essential evidence of the value of AHP research engagement. TRIAL REGISTRATION This systematic review protocol was registered with the international prospective register of systematic reviews, PROSPERO (registration number CRD42021253461 ).
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Affiliation(s)
- S Chalmers
- University of Central Lancashire; Allied Health Research Unit, School of Health Sciences, University of Central Lancashire, Fylde Rd, Preston, PR1 2HE, UK.
- Bolton NHS Foundation Trust, Minerva Road, Farnworth, Bolton, Greater Manchester, BL4 0JR, UK.
| | - J Hill
- University of Central Lancashire; Synthesis, Economic Evaluation and Decision Science (SEEDS) Group, University of Central Lancashire, Fylde Rd, Preston, PR1 2HE, UK
| | - L Connell
- University of Central Lancashire; Allied Health Research Unit, School of Health Sciences, University of Central Lancashire, Fylde Rd, Preston, PR1 2HE, UK
- East Lancashire Hospitals NHS Trust, Burnley, BB10 2PQ, UK
| | - S Ackerley
- University of Central Lancashire; Allied Health Research Unit, School of Health Sciences, University of Central Lancashire, Fylde Rd, Preston, PR1 2HE, UK
| | - A Kulkarni
- Royal College of Speech & Language Therapists, 2-3 White Hart Yard, London, SE1 1NX, UK
| | - H Roddam
- Subject Matter Expert for AHP Research, Health Education England, Manchester, UK
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McMullen CJ, Chalmers S, Wood R, Cunningham MR, Currie S. Sunitinib and Imatinib Display Differential Cardiotoxicity in Adult Rat Cardiac Fibroblasts That Involves a Role for Calcium/Calmodulin Dependent Protein Kinase II. Front Cardiovasc Med 2021; 7:630480. [PMID: 33598481 PMCID: PMC7882511 DOI: 10.3389/fcvm.2020.630480] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 12/29/2020] [Indexed: 01/13/2023] Open
Abstract
Background: Tyrosine kinase inhibitors (TKIs) have dramatically improved cancer treatment but are known to cause cardiotoxicity. The pathophysiological consequences of TKI therapy are likely to manifest across different cell types of the heart, yet there is little understanding of the differential adverse cellular effects. Cardiac fibroblasts (CFs) play a pivotal role in the repair and remodeling of the heart following insult or injury, yet their involvement in anti-cancer drug induced cardiotoxicity has been largely overlooked. Here, we examine the direct effects of sunitinib malate and imatinib mesylate on adult rat CF viability, Ca2+ handling and mitochondrial function that may contribute to TKI-induced cardiotoxicity. In particular, we investigate whether Ca2+/calmodulin dependent protein kinase II (CaMKII), may be a mediator of TKI-induced effects. Methods: CF viability in response to chronic treatment with both drugs was assessed using MTT assays and flow cytometry analysis. Calcium mobilization was assessed in CFs loaded with Fluo4-AM and CaMKII activation via oxidation was measured via quantitative immunoblotting. Effects of both drugs on mitochondrial function was determined by live mitochondrial imaging using MitoSOX red. Results: Treatment of CFs with sunitinib (0.1-10 μM) resulted in concentration-dependent alterations in CF phenotype, with progressively significant cell loss at higher concentrations. Flow cytometry analysis and MTT assays revealed increased cell apoptosis and necrosis with increasing concentrations of sunitinib. In contrast, equivalent concentrations of imatinib resulted in no significant change in cell viability. Both sunitinib and imatinib pre-treatment increased Angiotensin II-induced intracellular Ca2+ mobilization, with only sunitinib resulting in a significant effect and also causing increased CaMKII activation via oxidation. Live cell mitochondrial imaging using MitoSOX red revealed that both sunitinib and imatinib increased mitochondrial superoxide production in a concentration-dependent manner. This effect in response to both drugs was suppressed in the presence of the CaMKII inhibitor KN-93. Conclusions: Sunitinib and imatinib showed differential effects on CFs, with sunitinib causing marked changes in cell viability at concentrations where imatinib had no effect. Sunitinib caused a significant increase in Angiotensin II-induced intracellular Ca2+ mobilization and both TKIs caused increased mitochondrial superoxide production. Targeted CaMKII inhibition reversed the TKI-induced mitochondrial damage. These findings highlight a new role for CaMKII in TKI-induced cardiotoxicity, particularly at the level of the mitochondria, and confirm differential off-target toxicity in CFs, consistent with the differential selectivity of sunitinib and imatinib.
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Affiliation(s)
- Calum J McMullen
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Rachel Wood
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Margaret R Cunningham
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Susan Currie
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
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Casciano JC, Perry C, Cohen-Nowak AJ, Miller KD, Vande Voorde J, Zhang Q, Chalmers S, Sandison ME, Liu Q, Hedley A, McBryan T, Tang HY, Gorman N, Beer T, Speicher DW, Adams PD, Liu X, Schlegel R, McCarron JG, Wakelam MJO, Gottlieb E, Kossenkov AV, Schug ZT. MYC regulates fatty acid metabolism through a multigenic program in claudin-low triple negative breast cancer. Br J Cancer 2020; 122:868-884. [PMID: 31942031 PMCID: PMC7078291 DOI: 10.1038/s41416-019-0711-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 11/22/2019] [Accepted: 12/19/2019] [Indexed: 02/06/2023] Open
Abstract
Background Recent studies have suggested that fatty acid oxidation (FAO) is a key metabolic pathway for the growth of triple negative breast cancers (TNBCs), particularly those that have high expression of MYC. However, the underlying mechanism by which MYC promotes FAO remains poorly understood. Methods We used a combination of metabolomics, transcriptomics, bioinformatics, and microscopy to elucidate a potential mechanism by which MYC regulates FAO in TNBC. Results We propose that MYC induces a multigenic program that involves changes in intracellular calcium signalling and fatty acid metabolism. We determined key roles for fatty acid transporters (CD36), lipases (LPL), and kinases (PDGFRB, CAMKK2, and AMPK) that each contribute to promoting FAO in human mammary epithelial cells that express oncogenic levels of MYC. Bioinformatic analysis further showed that this multigenic program is highly expressed and predicts poor survival in the claudin-low molecular subtype of TNBC, but not other subtypes of TNBCs, suggesting that efforts to target FAO in the clinic may best serve claudin-low TNBC patients. Conclusion We identified critical pieces of the FAO machinery that have the potential to be targeted for improved treatment of patients with TNBC, especially the claudin-low molecular subtype.
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Affiliation(s)
- Jessica C Casciano
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Caroline Perry
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA.,Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Adam J Cohen-Nowak
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Katelyn D Miller
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Johan Vande Voorde
- The Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
| | - Qifeng Zhang
- The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, SIPBS Building, 161 Cathedral Street, Glasgow, G4 0RE, UK
| | - Mairi E Sandison
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, SIPBS Building, 161 Cathedral Street, Glasgow, G4 0RE, UK.,Department of Biomedical Engineering, University of Strathclyde, Wolfson Centre, 106 Rottenrow, Glasgow, G4 0NW, UK
| | - Qin Liu
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Ann Hedley
- The Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
| | - Tony McBryan
- The Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK.,Institute of Cancer Sciences, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, G61 1BD, UK
| | - Hsin-Yao Tang
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Nicole Gorman
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Thomas Beer
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - David W Speicher
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Peter D Adams
- Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Xuefeng Liu
- Center for Cell Reprogramming, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, 3900 Reservoir Road, Washington D.C., 20057, USA
| | - Richard Schlegel
- Center for Cell Reprogramming, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, 3900 Reservoir Road, Washington D.C., 20057, USA
| | - John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, SIPBS Building, 161 Cathedral Street, Glasgow, G4 0RE, UK
| | | | - Eyal Gottlieb
- The Beatson Institute, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK.,The Ruth and Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, 1 Efron St. Bat Galim, 3525433, Haifa, Israel
| | - Andrew V Kossenkov
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA
| | - Zachary T Schug
- The Wistar Institute, Molecular and Cellular Oncogenesis, 3601 Spruce Street, Philadelphia, PA, 19104, USA.
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Hargrave KE, Woods S, Millington O, Chalmers S, Westrop GD, Roberts CW. Multi-Omics Studies Demonstrate Toxoplasma gondii-Induced Metabolic Reprogramming of Murine Dendritic Cells. Front Cell Infect Microbiol 2019; 9:309. [PMID: 31572687 PMCID: PMC6749083 DOI: 10.3389/fcimb.2019.00309] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [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: 04/16/2019] [Accepted: 08/12/2019] [Indexed: 01/14/2023] Open
Abstract
Toxoplasma gondii is capable of actively invading almost any mammalian cell type including phagocytes. Early events in phagocytic cells such as dendritic cells are not only key to establishing parasite infection, but conversely play a pivotal role in initiating host immunity. It is now recognized that in addition to changes in canonical immune markers and mediators, alteration in metabolism occurs upon activation of phagocytic cells. These metabolic changes are important for supporting the developing immune response, but can affect the availability of nutrients for intracellular pathogens including T. gondii. However, the interaction of T. gondii with these cells and particularly how infection changes their metabolism has not been extensively investigated. Herein, we use a multi-omics approach comprising transcriptomics and metabolomics validated with functional assays to better understand early events in these cells following infection. Analysis of the transcriptome of T. gondii infected bone marrow derived dendritic cells (BMDCs) revealed significant alterations in transcripts associated with cellular metabolism, activation of T cells, inflammation mediated chemokine and cytokine signaling pathways. Multivariant analysis of metabolomic data sets acquired through non-targeted liquid chromatography mass spectroscopy (LCMS) identified metabolites associated with glycolysis, the TCA cycle, oxidative phosphorylation and arginine metabolism as major discriminants between control uninfected and T. gondii infected cells. Consistent with these observations, glucose uptake and lactate dehydrogenase activity were upregulated in T. gondii infected BMDC cultures compared with control BMDCs. Conversely, BMDC mitochondrial membrane potential was reduced in T. gondii-infected cells relative to mitochondria of control BMDCs. These changes to energy metabolism, similar to what has been described following LPS stimulation of BMDCs and macrophages are often termed the Warburg effect. This metabolic reprogramming of cells has been suggested to be an important adaption that provides energy and precursors to facilitate phagocytosis, antigen processing and cytokine production. Other changes to BMDC metabolism are evident following T. gondii infection and include upregulation of arginine degradation concomitant with increased arginase-1 activity and ornithine and proline production. As T. gondii is an arginine auxotroph the resultant reduced cellular arginine levels are likely to curtail parasite multiplication. These results highlight the complex interplay of BMDCs and parasite metabolism within the developing immune response and the consequences for adaptive immunity and pathogen clearance.
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Affiliation(s)
- Kerrie E Hargrave
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Stuart Woods
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Owain Millington
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Gareth D Westrop
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Craig W Roberts
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
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Casciano JC, Cohen-Nowak A, Voorde JV, Zhang Q, Chalmers S, Sandison M, Hedley A, McBryan T, Beer T, Tang HY, Speicher DW, Adams P, Liu X, Schlegel R, McCarron J, Wakelam MJ, Gottlieb E, Schug ZT. Abstract 1441: MYC expression promotes lipid metabolism and metabolic plasticity in human mammary epithelial cells. Cancer Res 2018. [DOI: 10.1158/1538-7445.am2018-1441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
MYC is one of the most commonly mutated and highly amplified oncogenes in human breast cancer. MYC amplifications occur most frequently in triple-negative breast cancers (TNBCs). TNBCs can be divided into two molecular subtypes: basal-like and claudin-low breast cancers. These cancers tend to be extremely aggressive and are strongly associated with disease recurrence, poor prognosis and high mortality. In particular, claudin-low tumors are classified by a loss of tight junctions and cell-to-cell contacts and an enrichment for genes associated with an epithelial-to-mesenchymal transition (EMT) and mammary stem cells (also known as tumor-initiating cells). Despite the high level of disease severity, there are no targeted therapies for claudin-low TNBCs. To address this unmet need, we utilized human mammary epithelial cells (HuMECs) that express oncogenic levels of MYC and a mutant MYC (T58A) to characterize the behavioral and metabolic changes that occur during the formation of MYC-driven breast cancers. We found that MYC regulates the expression of genes associated with cell stemness, EMT, lipid metabolism, and calcium (Ca2+) signaling and that the expression of this gene signature promotes cell growth, survival, migration, and metabolic plasticity. The gene signature of MYC-expressing HuMECs highly correlates with the gene signature of claudin-low breast cancers, therefore highlighting the relevance of our HuMEC model to human claudin-low breast cancer. We found the major drivers underlying the MYC-dependent changes in cell behavior to be stimulation of Ca2+ signaling and strong activation of lipid metabolism. Ca2+ signaling is stimulated through the MYC-dependent repression of Ca2+ efflux mechanisms; elevated cytosolic Ca2+ then consequently stimulates a Ca2+/calmodulin kinase kinase 2 (CAMKK2)/AMPK signaling axis that activates fatty acid scavenging and transport, as well as β-oxidation. Enhanced lipid metabolism thereby provides the necessary biomass (fatty acids) for phospholipid biosynthesis and energy (ATP) to support the metabolically demanding processes of cell growth, proliferation, and migration. In all, our findings provide a strong rationale for targeting lipid metabolism and the Ca2+/CAMKK2/AMPK signaling axis in MYC-driven, and potentially claudin-low, breast cancers.
Citation Format: Jessica C. Casciano, Adam Cohen-Nowak, Johan Vande Voorde, Qifeng Zhang, Susan Chalmers, Mairi Sandison, Ann Hedley, Tony McBryan, Thomas Beer, Hsin-Yao Tang, David W. Speicher, Peter Adams, Xiufeng Liu, Richard Schlegel, John McCarron, Michael J. Wakelam, Eyal Gottlieb, Zachary T. Schug. MYC expression promotes lipid metabolism and metabolic plasticity in human mammary epithelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1441.
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Affiliation(s)
| | | | | | - Qifeng Zhang
- 3The Babraham Institute, Cambridge, United Kingdom
| | - Susan Chalmers
- 4Strathclyde Institute of Pharmacy and Biomedical Sciences, Glasgow, United Kingdom
| | - Mairi Sandison
- 4Strathclyde Institute of Pharmacy and Biomedical Sciences, Glasgow, United Kingdom
| | - Ann Hedley
- 2The Beatson Institute, Glasgow, United Kingdom
| | | | | | | | | | - Peter Adams
- 5Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA
| | - Xiufeng Liu
- 6Georgetown University Medical Center, Washington, DC
| | | | - John McCarron
- 4Strathclyde Institute of Pharmacy and Biomedical Sciences, Glasgow, United Kingdom
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Patnaik SR, Zhang X, Biswas L, Akhtar S, Zhou X, Kusuluri DK, Reilly J, May-Simera H, Chalmers S, McCarron JG, Shu X. RPGR protein complex regulates proteasome activity and mediates store-operated calcium entry. Oncotarget 2018; 9:23183-23197. [PMID: 29796181 PMCID: PMC5955404 DOI: 10.18632/oncotarget.25259] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 04/07/2018] [Indexed: 11/25/2022] Open
Abstract
Ciliopathies are a group of genetically heterogeneous disorders, characterized by defects in cilia genesis or maintenance. Mutations in the RPGR gene and its interacting partners, RPGRIP1 and RPGRIP1L, cause ciliopathies, but the function of their proteins remains unclear. Here we show that knockdown (KD) of RPGR, RPGRIP1 or RPGRIP1L in hTERT-RPE1 cells results in abnormal actin cytoskeleton organization. The actin cytoskeleton rearrangement is regulated by the small GTPase RhoA via the planar cell polarity (PCP) pathway. RhoA activity was upregulated in the absence of RPGR, RPGRIP1 or RPGRIP1L proteins. In RPGR, RPGRIP1 or RPGRIP1L KD cells, we observed increased levels of DVl2 and DVl3 proteins, the core components of the PCP pathway, due to impaired proteasomal activity. RPGR, RPGRIP1 or RPGRIP1L KD cells treated with thapsigargin (TG), an inhibitor of sarcoendoplasmic reticulum Ca2+- ATPases, showed impaired store-operated Ca2+ entry (SOCE), which is mediated by STIM1 and Orai1 proteins. STIM1 was not localized to the ER-PM junction upon ER store depletion in RPGR, RPGRIP1 or RPGRIP1L KD cells. Our results demonstrate that the RPGR protein complex is required for regulating proteasomal activity and for modulating SOCE, which may contribute to the ciliopathy phenotype.
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Affiliation(s)
- Sarita Rani Patnaik
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
- Institute of Molecular Physiology, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
| | - Xun Zhang
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Lincoln Biswas
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Saeed Akhtar
- Cornea Research Chair, Department of Optometry, King Saud University, Riyadh 11433, Kingdom of Saudi Arabia
| | - Xinzhi Zhou
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Deva Krupakar Kusuluri
- Institute of Molecular Physiology, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
| | - James Reilly
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
| | - Helen May-Simera
- Institute of Molecular Physiology, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland
| | - John G. McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, Scotland
| | - Xinhua Shu
- Department of Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, Scotland
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Chalmers S, Debenedictis TA, Zacharia A, Townsley S, Gleeson C, Lynagh M, Townsley A, Fuller JT. Asymmetry during Functional Movement Screening and injury risk in junior football players: A replication study. Scand J Med Sci Sports 2018; 28:1281-1287. [DOI: 10.1111/sms.13021] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2017] [Indexed: 11/30/2022]
Affiliation(s)
- S. Chalmers
- Sport and Exercise Science; School of Science and Health; Western Sydney University; Sydney Australia
| | - T. A. Debenedictis
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
| | - A. Zacharia
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
| | - S. Townsley
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
| | - C. Gleeson
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
| | - M. Lynagh
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
| | - A. Townsley
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
| | - J. T. Fuller
- Alliance for Research in Exercise, Nutrition and Activity (ARENA); Sansom Institute for Health Research; University of South Australia; Adelaide Australia
- Faculty of Medicine and Health Sciences; Macquarie University; Sydney NSW Australia
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Chalmers S, Saunter CD, Girkin JM, McCarron JG. Age decreases mitochondrial motility and increases mitochondrial size in vascular smooth muscle. J Physiol 2016; 594:4283-95. [PMID: 26959407 PMCID: PMC4967731 DOI: 10.1113/jp271942] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 02/26/2016] [Indexed: 01/08/2023] Open
Abstract
KEY POINTS Age is proposed to be associated with altered structure and function of mitochondria; however, in fully-differentiated cells, determining the structure of more than a few mitochondria at a time is challenging. In the present study, the structures of the entire mitochondrial complements of cells were resolved from a pixel-by-pixel covariance analysis of fluctuations in potentiometric fluorophore intensity during 'flickers' of mitochondrial membrane potential. Mitochondria are larger in vascular myocytes from aged rats compared to those in younger adult rats. A subpopulation of mitochondria in myocytes from aged, but not younger, animals is highly-elongated. Some mitochondria in myocytes from younger, but not aged, animals are highly-motile. Mitochondria that are motile are located more peripherally in the cell than non-motile mitochondria. ABSTRACT Mitochondrial function, motility and architecture are each central to cell function. Age-associated mitochondrial dysfunction may contribute to vascular disease. However, mitochondrial changes in ageing remain ill-defined because of the challenges of imaging in native cells. We determined the structure of mitochondria in live native cells, demarcating boundaries of individual organelles by inducing stochastic 'flickers' of membrane potential, recorded as fluctuations in potentiometric fluorophore intensity (flicker-assisted localization microscopy; FaLM). In freshly-isolated myocytes from rat cerebral resistance arteries, FaLM showed a range of mitochondrial X-Y areas in both young adult (3 months; 0.05-6.58 μm(2) ) and aged rats (18 months; 0.05-13.4 μm(2) ). In cells from young animals, most mitochondria were small (mode area 0.051 μm(2) ) compared to aged animals (0.710 μm(2) ). Cells from older animals contained a subpopulation of highly-elongated mitochondria (5.3% were >2 μm long, 4.2% had a length:width ratio >3) that was rare in younger animals (0.15% of mitochondria >2 μm long, 0.4% had length:width ratio >3). The extent of mitochondrial motility also varied. 1/811 mitochondria observed moved slightly (∼0.5 μm) in myocytes from older animals, whereas, in the younger animals, directed and Brownian-like motility occurred regularly (215 of 1135 mitochondria moved within 10 min, up to distance of 12 μm). Mitochondria positioned closer to the cell periphery showed a greater tendency to move. In conclusion, cerebral vascular myocytes from young rats contained small, motile mitochondria. In aged rats, mitochondria were larger, immobile and could be highly-elongated. These age-associated alterations in mitochondrial behaviour may contribute to alterations in cell signalling, energy supply or the onset of proliferation.
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Affiliation(s)
- Susan Chalmers
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, G4 ONR, UK
| | | | - John M Girkin
- Department of Physics, Durham University, South Road, Durham, DH1 3LE, UK
| | - John G McCarron
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, G4 ONR, UK
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Caldwell ST, Cairns AG, Olson M, Chalmers S, Sandison M, Mullen W, McCarron JG, Hartley RC. Synthesis of an azido-tagged low affinity ratiometric calcium sensor. Tetrahedron 2015; 71:9571-9578. [PMID: 26709317 PMCID: PMC4660056 DOI: 10.1016/j.tet.2015.10.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [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] [Indexed: 11/16/2022]
Abstract
Changes in high localised concentrations of Ca2+ ions are fundamental to cell signalling. The synthesis of a dual excitation, ratiometric calcium ion sensor with a Kd of 90 μM, is described. It is tagged with an azido group for bioconjugation, and absorbs in the blue/green and emits in the red region of the visible spectrum with a large Stokes shift. The binding modulating nitro group is introduced to the BAPTA core prior to construction of a benzofuran-2-yl carboxaldehyde by an allylation–oxidation–cyclisation sequence, which is followed by condensation with an azido-tagged thiohydantoin. The thiohydantoin unit has to be protected with an acetoxymethyl (AM) caging group to allow CuAAC click reaction and incorporation of the KDEL peptide endoplasmic reticulum (ER) retention sequence.
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Affiliation(s)
- Stuart T Caldwell
- WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Andrew G Cairns
- WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Marnie Olson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK
| | - Mairi Sandison
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK
| | - William Mullen
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK
| | - Richard C Hartley
- WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
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10
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Chalmers S, Saunter C, Girkin J, McCarron J. Age‐Associated Alterations in Mitochondrial Architecture and Motility in Vascular Smooth Muscle. FASEB J 2015. [DOI: 10.1096/fasebj.29.1_supplement.884.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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11
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Pawar RD, Goilav B, Xia Y, Herlitz L, Doerner J, Chalmers S, Ghosh K, Zang X, Putterman C. B7x/B7-H4 modulates the adaptive immune response and ameliorates renal injury in antibody-mediated nephritis. Clin Exp Immunol 2015; 179:329-43. [PMID: 25205493 DOI: 10.1111/cei.12452] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2014] [Indexed: 12/12/2022] Open
Abstract
Kidney disease is one of the leading causes of death in patients with lupus and other autoimmune diseases affecting the kidney, and is associated with deposition of antibodies as well as infiltration of T lymphocytes and macrophages, which are responsible for initiation and/or exacerbation of inflammation and tissue injury. Current treatment options have relatively limited efficacy; therefore, novel targets need to be explored. The co-inhibitory molecule, B7x, a new member of the B7 family expressed predominantly by non-lymphoid tissues, has been shown to inhibit the proliferation, activation and functional responses of CD4 and CD8 T cells. In this study, we found that B7x was expressed by intrinsic renal cells, and was up-regulated upon stimulation with inflammatory triggers. After passive administration of antibodies against glomerular antigens, B7x(-/-) mice developed severe renal injury accompanied by a robust adaptive immune response and kidney up-regulation of inflammatory mediators, as well as local infiltration of T cells and macrophages. Furthermore, macrophages in the spleen of B7x(-/-) mice were polarized to an inflammatory phenotype. Finally, treatment with B7x-immunoglobulin (Ig) in this nephritis model decreased kidney damage and reduced local inflammation. We propose that B7x can modulate kidney damage in autoimmune diseases including lupus nephritis and anti-glomerular basement membrane disease. Thus, B7x mimetics may be a novel therapeutic option for treatment of immune-mediated kidney disease.
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Affiliation(s)
- R D Pawar
- The Division of Rheumatology, Albert Einstein College of Medicine, NY, USA; Department of Microbiology & Immunology, Albert Einstein College of Medicine, NY, USA
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12
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Chalmers S, Saunter C, Girkin J, McCarron J. Single organelle localisation microscopy in vascular smooth muscle reveals mitochondrial networks are multiple electrically‐discontinuous elements, with larger organelle dimensions and more extensive mitochondrial clustering occurring in hypertension (757.2). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.757.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - John Girkin
- Department of Physics Durham UniversityDurhamUnited Kingdom
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13
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Saunter C, Chalmers S, Girkin J, McCarron J. Quantitative analysis of mitochondrial dynamics illuminates links between mitochondrial dynamics and cell function, and allows single organelle localisation microscopy (759.2). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.759.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - John Girkin
- Department of Physics Durham UniversityDurhamUnited Kingdom
| | - John McCarron
- SIPBS University of Strathclyde GLASGOWUnited Kingdom
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14
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Sandison M, Chalmers S, Dempster J, McCarron J. Direct visualisation of smooth muscle cell phenotypic plasticity and migration by long‐term imaging (867.12). FASEB J 2014. [DOI: 10.1096/fasebj.28.1_supplement.867.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Mairi Sandison
- Strathclyde Institute of Pharmacy and Biomedical SciencesUniversity of Strathclyde GLASGOWUnited Kingdom
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical SciencesUniversity of Strathclyde GLASGOWUnited Kingdom
| | - John Dempster
- Strathclyde Institute of Pharmacy and Biomedical SciencesUniversity of Strathclyde GLASGOWUnited Kingdom
| | - John McCarron
- Strathclyde Institute of Pharmacy and Biomedical SciencesUniversity of Strathclyde GLASGOWUnited Kingdom
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15
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McCarron JG, Olson ML, Wilson C, Sandison ME, Chalmers S. Examining the role of mitochondria in Ca²⁺ signaling in native vascular smooth muscle. Microcirculation 2013; 20:317-29. [PMID: 23305516 PMCID: PMC3708117 DOI: 10.1111/micc.12039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 01/07/2013] [Indexed: 01/18/2023]
Abstract
Mitochondrial Ca2+ uptake contributes important feedback controls to limit the time course of Ca2+signals. Mitochondria regulate cytosolic [Ca2+] over an exceptional breath of concentrations (∼200 nM to >10 μM) to provide a wide dynamic range in the control of Ca2+ signals. Ca2+ uptake is achieved by passing the ion down the electrochemical gradient, across the inner mitochondria membrane, which itself arises from the export of protons. The proton export process is efficient and on average there are less than three protons free within the mitochondrial matrix. To study mitochondrial function, the most common approaches are to alter the proton gradient and to measure the electrochemical gradient. However, drugs which alter the mitochondrial proton gradient may have substantial off target effects that necessitate careful consideration when interpreting their effect on Ca2+ signals. Measurement of the mitochondrial electrochemical gradient is most often performed using membrane potential sensitive fluorophores. However, the signals arising from these fluorophores have a complex relationship with the electrochemical gradient and are altered by changes in plasma membrane potential. Care is again needed in interpreting results. This review provides a brief description of some of the methods commonly used to alter and measure mitochondrial contribution to Ca2+ signaling in native smooth muscle.
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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16
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McCarron JG, Wilson C, Sandison ME, Olson ML, Girkin JM, Saunter C, Chalmers S. From structure to function: mitochondrial morphology, motion and shaping in vascular smooth muscle. J Vasc Res 2013; 50:357-71. [PMID: 23887139 PMCID: PMC3884171 DOI: 10.1159/000353883] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 05/07/2013] [Accepted: 05/07/2013] [Indexed: 12/29/2022] Open
Abstract
The diversity of mitochondrial arrangements, which arise from the organelle being static or moving, or fusing and dividing in a dynamically reshaping network, is only beginning to be appreciated. While significant progress has been made in understanding the proteins that reorganise mitochondria, the physiological significance of the various arrangements is poorly understood. The lack of understanding may occur partly because mitochondrial morphology is studied most often in cultured cells. The simple anatomy of cultured cells presents an attractive model for visualizing mitochondrial behaviour but contrasts with the complexity of native cells in which elaborate mitochondrial movements and morphologies may not occur. Mitochondrial changes may take place in native cells (in response to stress and proliferation), but over a slow time-course and the cellular function contributed is unclear. To determine the role mitochondrial arrangements play in cell function, a crucial first step is characterisation of the interactions among mitochondrial components. Three aspects of mitochondrial behaviour are described in this review: (1) morphology, (2) motion and (3) rapid shape changes. The proposed physiological roles to which various mitochondrial arrangements contribute and difficulties in interpreting some of the physiological conclusions are also outlined.
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Affiliation(s)
- John G. McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, UK
| | - Calum Wilson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, UK
- Department of Biomedical Engineering, University of Strathclyde Wolfson Centre, Glasgow, UK
| | - Mairi E. Sandison
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, UK
| | - Marnie L. Olson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, UK
| | - John M. Girkin
- Centre for Advanced Instrumentation, Department of Physics, Durham University, Durham, UK
| | - Christopher Saunter
- Centre for Advanced Instrumentation, Department of Physics, Durham University, Durham, UK
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, UK
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17
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Abstract
Increases in bulk average cytoplasmic Ca(2+) concentration ([Ca(2+)](c)) are derived from the combined activities of many Ca(2+) channels. Near (<100 nm) the mouth of each of these channels the local [Ca(2+)](c) rises and falls more quickly and reaches much greater values than occurs in the bulk cytoplasm. Even during apparently uniform, steady-state [Ca(2+)] increases large local inhomogeneities exist near channels. These local increases modulate processes that are sensitive to rapid and large changes in [Ca(2+)] but they cannot easily be visualized with conventional imaging approaches. The [Ca(2+)] changes near channels can be examined using total internal reflection fluorescence microscopy (TIRF) to excite fluorophores that lie within 100 nm of the plasma membrane. TIRF is particularly powerful when combined with electrophysiology so that ion channel activity can be related simultaneously to the local subplasma membrane and bulk average [Ca(2+)](c). Together these techniques provide a better understanding of the local modulation and control of Ca(2+) signals.
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy & Biomedical Sciences, Strathclyde University, Glasgow, UK
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18
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Chalmers S, Saunter C, Wilson C, Coats P, Girkin JM, McCarron JG. Mitochondrial motility and vascular smooth muscle proliferation. Arterioscler Thromb Vasc Biol 2012; 32:3000-11. [PMID: 23104850 DOI: 10.1161/atvbaha.112.255174] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Mitochondria are widely described as being highly dynamic and adaptable organelles, and their movement is thought to be vital for cell function. Yet, in various native cells, including those of heart and smooth muscle, mitochondria are stationary and rigidly structured. The significance of the differences in mitochondrial behavior to the physiological function of cells is unclear and was studied in single myocytes and intact resistance-sized cerebral arteries. We hypothesized that mitochondrial dynamics is controlled by the proliferative status of the cells. METHODS AND RESULTS High-speed fluorescence imaging of mitochondria in live vascular smooth muscle cells shows that the organelle undergoes significant reorganization as cells become proliferative. In nonproliferative cells, mitochondria are individual (≈ 2 μm by 0.5 μm), stationary, randomly dispersed, fixed structures. However, on entering the proliferative state, mitochondria take on a more diverse architecture and become small spheres, short rod-shaped structures, long filamentous entities, and networks. When cells proliferate, mitochondria also continuously move and change shape. In the intact pressurized resistance artery, mitochondria are largely immobile structures, except in a small number of cells in which motility occurred. When proliferation of smooth muscle was encouraged in the intact resistance artery, in organ culture, the majority of mitochondria became motile and the majority of smooth muscle cells contained moving mitochondria. Significantly, restriction of mitochondrial motility using the fission blocker mitochondrial division inhibitor prevented vascular smooth muscle proliferation in both single cells and the intact resistance artery. CONCLUSIONS These results show that mitochondria are adaptable and exist in intact tissue as both stationary and highly dynamic entities. This mitochondrial plasticity is an essential mechanism for the development of smooth muscle proliferation and therefore presents a novel therapeutic target against vascular disease.
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Affiliation(s)
- Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
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19
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Olson ML, Sandison ME, Chalmers S, McCarron JG. Microdomains of muscarinic acetylcholine and Ins(1,4,5)P₃ receptors create 'Ins(1,4,5)P₃ junctions' and sites of Ca²+ wave initiation in smooth muscle. J Cell Sci 2012; 125:5315-28. [PMID: 22946060 PMCID: PMC3561854 DOI: 10.1242/jcs.105163] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Increases in cytosolic Ca2+ concentration ([Ca2+]c) mediated by inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3, hereafter InsP3] regulate activities that include division, contraction and cell death. InsP3-evoked Ca2+ release often begins at a single site, then regeneratively propagates through the cell as a Ca2+ wave. The Ca2+ wave consistently begins at the same site on successive activations. Here, we address the mechanisms that determine the Ca2+ wave initiation site in intestinal smooth muscle cells. Neither an increased sensitivity of InsP3 receptors (InsP3R) to InsP3 nor regional clustering of muscarinic receptors (mAChR3) or InsP3R1 explained the selection of an initiation site. However, examination of the overlap of mAChR3 and InsP3R1 localisation, by centre of mass analysis, revealed that there was a small percentage (∼10%) of sites that showed colocalisation. Indeed, the extent of colocalisation was greatest at the Ca2+ wave initiation site. The initiation site might arise from a selective delivery of InsP3 from mAChR3 activity to particular InsP3Rs to generate faster local [Ca2+]c increases at sites of colocalisation. In support of this hypothesis, a localised subthreshold ‘priming’ InsP3 concentration applied rapidly, but at regions distant from the initiation site, shifted the wave to the site of the priming. Conversely, when the Ca2+ rise at the initiation site was rapidly and selectively attenuated, the Ca2+ wave again shifted and initiated at a new site. These results indicate that Ca2+ waves initiate where there is a structural and functional coupling of mAChR3 and InsP3R1, which generates junctions in which InsP3 acts as a highly localised signal by being rapidly and selectively delivered to InsP3R1.
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Affiliation(s)
- Marnie L Olson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, The Arbuthnott Building, 161 Cathedral Street, Glasgow G4 0RE, UK
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20
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Abstract
Ca2+ may selectively activate various processes in part by the cell's ability to localize changes in the concentration of the ion to specific subcellular sites. Interestingly, these Ca2+ signals begin most often at the plasma membrane space so that understanding subplasma membrane signals is central to an appreciation of local signaling. Several experimental procedures have been developed to study Ca2+ signals near the plasma membrane, but probably the most prevalent involve the use of fluorescent Ca2+ indicators and fall into two general approaches. In the first, the Ca2+ indicators themselves are specifically targeted to the subplasma membrane space to measure Ca2+ only there. Alternatively, the indicators are allowed to be dispersed throughout the cytoplasm, but the fluorescence emanating from the Ca2+ signals at the subplasma membrane space is selectively measured using high resolution imaging procedures. Although the targeted indicators offer an immediate appeal because of selectivity and ease of use, their limited dynamic range and slow response to changes in Ca2+ are a shortcoming. Use of targeted indicators is also largely restricted to cultured cells. High resolution imaging applied with rapidly responding small molecule Ca2+ indicators can be used in all cells and offers significant improvements in dynamic range and speed of response of the indicator. The approach is technically difficult, however, and realistic calibration of signals is not possible. In this review, a brief overview of local subplasma membrane Ca2+ signals and methods for their measurement is provided. © 2012 IUBMB IUBMB Life, 64(7): 573–585, 2012
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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21
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Abstract
The cytosolic Ca²⁺ concentration ([Ca²⁺]c) controls virtually every activity of smooth muscle, including contraction, migration, transcription, division and apoptosis. These processes may be activated by large (>10 μM) amplitude [Ca²⁺]c increases, which occur in small restricted regions of the cell or by smaller (<1 μM) amplitude changes throughout the bulk cytoplasm. Mitochondria contribute to the regulation of these signals by taking up Ca²⁺. However, mitochondria's reported low affinity for Ca²⁺ is thought to require the organelle to be positioned close to ion channels and within a microdomain of high [Ca²⁺]. In cultured smooth muscle, mitochondria are highly dynamic structures but in native smooth muscle mitochondria are immobile, apparently strategically positioned organelles that regulate the upstroke and amplitude of IP₃-evoked Ca²⁺ signals and IP₃ receptor (IP₃R) cluster activity. These observations suggest mitochondria are positioned within the high [Ca²⁺] microdomain arising from an IP₃R cluster to exert significant local control of channel activity. On the other hand, neither the upstroke nor amplitude of voltage-dependent Ca²⁺ entry is modulated by mitochondria; rather, it is the declining phase of the transient that is regulated by the organelle. Control of the declining phase of the transient requires a high mitochondrial affinity for Ca²⁺ to enable uptake to occur over the normal physiological Ca²⁺ range (<1 μM). Thus, in smooth muscle, mitochondria regulate Ca²⁺ signals exerting effects over a large range of [Ca²⁺] (∼200 nM to at least tens of micromolar) to provide a wide dynamic range in the control of Ca²⁺ signals.
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 161 Cathedral Street, Glasgow, G4 0NR, UK.
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Chalmers S, Caldwell ST, Quin C, Prime TA, James AM, Cairns AG, Murphy MP, McCarron JG, Hartley RC. Selective uncoupling of individual mitochondria within a cell using a mitochondria-targeted photoactivated protonophore. J Am Chem Soc 2011; 134:758-61. [PMID: 22239373 PMCID: PMC3260739 DOI: 10.1021/ja2077922] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
![]()
Depolarization of an individual mitochondrion or small
clusters
of mitochondria within cells has been achieved using a photoactivatable
probe. The probe is targeted to the matrix of the mitochondrion by
an alkyltriphenylphosphonium lipophilic cation and releases the protonophore
2,4-dinitrophenol locally in predetermined regions in response to
directed irradiation with UV light via a local photolysis system.
This also provides a proof of principle for the general temporally
and spatially controlled release of bioactive molecules, pharmacophores,
or toxins to mitochondria with tissue, cell, or mitochondrion specificity.
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Affiliation(s)
- Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK
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Dunsford A, Magarey M, Chalmers S, Boesch E. The incidence of injury in elite junior Australian Rules Football and correlation with screening findings and training loads: A pilot study. J Sci Med Sport 2011. [DOI: 10.1016/j.jsams.2011.11.129] [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: 10/28/2022]
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Chalmers S, Coats P, Saunter CD, McCarron JG. Mitochondrial Motility During Vascular Smooth Muscle Proliferation. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.453] [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: 11/27/2022] Open
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Abstract
Smooth muscle responds to IP(3)-generating agonists by producing Ca(2+) waves. Here, the mechanism of wave progression has been investigated in voltage-clamped single smooth muscle cells using localized photolysis of caged IP(3) and the caged Ca(2+) buffer diazo-2. Waves, evoked by the IP(3)-generating agonist carbachol (CCh), initiated as a uniform rise in cytoplasmic Ca(2+) concentration ([Ca(2+)](c)) over a single though substantial length (approximately 30 microm) of the cell. During regenerative propagation, the wave-front was about 1/3 the length (approximately 9 microm) of the initiation site. The wave-front progressed at a relatively constant velocity although amplitude varied through the cell; differences in sensitivity to IP(3) may explain the amplitude changes. Ca(2+) was required for IP(3)-mediated wave progression to occur. Increasing the Ca(2+) buffer capacity in a small (2 microm) region immediately in front of a CCh-evoked Ca(2+) wave halted progression at the site. However, the wave front does not progress by Ca(2+)-dependent positive feedback alone. In support, colliding [Ca(2+)](c) increases from locally released IP(3) did not annihilate but approximately doubled in amplitude. This result suggests that local IP(3)-evoked [Ca(2+)](c) increases diffused passively. Failure of local increases in IP(3) to evoke waves appears to arise from the restricted nature of the IP(3) increase. When IP(3) was elevated throughout the cell, a localized increase in Ca(2+) now propagated as a wave. Together, these results suggest that waves initiate over a surprisingly large length of the cell and that both IP(3) and Ca(2+) are required for active propagation of the wave front to occur.
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, Glasgow, UK.
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McCarron JG, Chalmers S, MacMillan D, Olson ML. Agonist-Evoked Calcium Wave Progression Requires Calcium and Ip3 in Smooth Muscle. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.1599] [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: 11/30/2022] Open
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Olson ML, Chalmers S, McCarron JG. Mitochondrial Ca2+ uptake increases Ca2+ release from inositol 1,4,5-trisphosphate receptor clusters in smooth muscle cells. J Biol Chem 2009; 285:2040-50. [PMID: 19889626 DOI: 10.1074/jbc.m109.027094] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [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
Smooth muscle activities are regulated by inositol 1,4,5-trisphosphate (InsP(3))-mediated increases in cytosolic Ca2+ concentration ([Ca2+](c)). Local Ca2+ release from an InsP(3) receptor (InsP(3)R) cluster present on the sarcoplasmic reticulum is termed a Ca2+ puff. Ca2+ released via InsP(3)R may diffuse to adjacent clusters to trigger further release and generate a cell-wide (global) Ca2+ rise. In smooth muscle, mitochondrial Ca2+ uptake maintains global InsP(3)-mediated Ca2+ release by preventing a negative feedback effect of high [Ca2+] on InsP(3)R. Mitochondria may regulate InsP(3)-mediated Ca2+ signals by operating between or within InsP(3)R clusters. In the former mitochondria could regulate only global Ca2+ signals, whereas in the latter both local and global signals would be affected. Here whether mitochondria maintain InsP(3)-mediated Ca2+ release by operating within (local) or between (global) InsP(3)R clusters has been addressed. Ca2+ puffs evoked by localized photolysis of InsP(3) in single voltage-clamped colonic smooth muscle cells had amplitudes of 0.5-4.0 F/F(0), durations of approximately 112 ms at half-maximum amplitude, and were abolished by the InsP(3)R inhibitor 2-aminoethoxydiphenyl borate. The protonophore carbonyl cyanide 3-chloropheylhydrazone and complex I inhibitor rotenone each depolarized DeltaPsi(M) to prevent mitochondrial Ca2+ uptake and attenuated Ca2+ puffs by approximately 66 or approximately 60%, respectively. The mitochondrial uniporter inhibitor, RU360, attenuated Ca2+ puffs by approximately 62%. The "fast" Ca2+ chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acted like mitochondria to prolong InsP(3)-mediated Ca2+ release suggesting that mitochondrial influence is via their Ca2+ uptake facility. These results indicate Ca2+ uptake occurs quickly enough to influence InsP(3)R communication at the intra-cluster level and that mitochondria regulate both local and global InsP(3)-mediated Ca2+ signals.
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Affiliation(s)
- Marnie L Olson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, Glasgow G40NR, Scotland, United Kingdom
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Chalmers S, McCarron JG. Inhibition of mitochondrial calcium uptake rather than efflux impedes calcium release by inositol-1,4,5-trisphosphate-sensitive receptors. Cell Calcium 2009; 46:107-13. [PMID: 19577805 DOI: 10.1016/j.ceca.2009.05.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 05/07/2009] [Accepted: 05/31/2009] [Indexed: 10/20/2022]
Abstract
Mitochondria modulate cellular Ca2+ signals by accumulating the ion via a uniporter and releasing it via Na+- or H+-exchange. In smooth muscle, inhibition of mitochondrial Ca2+ uptake inhibits Ca2+ release from the sarcoplasmic reticulum (SR) via inositol-1,4,5-trisphosphate-sensitive receptors (IP(3)R). At least two mechanisms may explain this effect. First, localised uptake of Ca2+ by mitochondria may prevent negative feedback by cytosolic Ca2+ on IP(3)R activity, or secondly localised provision of Ca2+ by mitochondrial efflux may maintain IP(3)R function or SR Ca2+ content. To distinguish between these possibilities the role of mitochondrial Ca2+ efflux on IP(3)R function was examined. IP(3) was liberated in freshly isolated single colonic smooth muscle cells and mitochondrial Na+-Ca2+ exchanger inhibited with CGP-37157 (10microM). Mitochondria accumulated Ca2+ during IP(3)-evoked [Ca2+](c) rises and released the ion back to the cytosol (within approximately 15s) when mitochondrial Ca2+ efflux was active. When mitochondrial Ca2+ efflux was inhibited by CGP-37157, an extensive and sustained loading of mitochondria with Ca2+ occurred after IP(3)-evoked Ca2+ release. IP(3)-evoked [Ca2+](c) rises were initially unaffected, then only slowly inhibited by CGP-37157. IP(3)R activity was required for inhibition to occur; incubation with CGP-37157 for the same duration without IP(3) release did not inhibit IP(3)R. CGP-37157 directly inhibited voltage-gated Ca2+ channel activity, however SR Ca2+ content was unaltered by the drug. Thus, the gradual decline of IP(3)R function that followed mitochondrial Na+-Ca2+ exchanger inhibition resulted from a gradual overload of mitochondria with Ca2+, leading to a reduced capacity for Ca2+ uptake. Localised uptake of Ca2+ by mitochondria, rather than mitochondrial Ca2+ efflux, appears critical for maintaining IP(3)R activity.
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Affiliation(s)
- Susan Chalmers
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, UK
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Avlonitis N, Chalmers S, McDougall C, Stanton-Humphreys MN, Brown CTA, McCarron JG, Conway SJ. Caged AG10: new tools for spatially predefined mitochondrial uncoupling. Mol BioSyst 2009; 5:450-7. [DOI: 10.1039/b820415m] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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McCarron JG, Chalmers S, Muir TC. `Quantal' Ca2+ release at the cytoplasmic aspect of the Ins(1,4,5)P3R channel in smooth muscle. J Cell Sci 2008; 121:86-98. [DOI: 10.1242/jcs.017541] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Smooth muscle responds to activation of the inositol (1,4,5)-trisphosphate receptor [Ins(1,4,5)P3R] with a graded concentration-dependent (`quantal') Ca2+ release from the sarcoplasmic reticulum (SR) store. Graded release seems incompatible both with the finite capacity of the store and the Ca2+-induced Ca2+ release (CICR)-like facility, at Ins(1,4,5)P3Rs, that, once activated, should release the entire content of SR Ca2+. The structural organization of the SR and the regulation of Ins(1,4,5)P3R activity by inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] and Ca2+ have each been proposed to explain `quantal' Ca2+ release. Here, we propose that regulation of Ins(1,4,5)P3R activity by lumenal Ca2+ acting at the cytoplasmic aspect of the receptor might explain `quantal' Ca2+ release in smooth muscle. The entire SR store was found to be lumenally continuous and Ca2+ could diffuse freely throughout: peculiarities of SR structure are unlikely to account for `quantal' release. While Ca2+ release was regulated by [Ca2+] within the SR, the velocity of release increased (accelerated) during the release process. The extent of acceleration of release determined the peak cytoplasmic [Ca2+] and was attenuated by a reduction in SR [Ca2+] or an increase in cytoplasmic Ca2+ buffering. Positive feedback by released Ca2+ acting at the cytoplasmic aspect of Ins(1,4,5)P3Rs (i.e. CICR-like) might (a) account for the acceleration, (b) provide the regulation of release by SR [Ca2+] and (c) explain the `quantal' release process itself. During Ca2+ release, SR [Ca2+] and thus unitary Ins(1,4,5)P3R currents decline, CICR reduces and stops. With increasing [Ins(1,4,5)P3], coincidental activation of several neighbouring Ins(1,4,5)P3Rs offsets the reduced Ins(1,4,5)P3R current to renew CICR and Ca2+ release.
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Affiliation(s)
- John G. McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, UK
| | - Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, UK
| | - Thomas C. Muir
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, UK
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Abstract
Ca2+ uptake by mitochondria might both modulate the cytosolic Ca2+ concentration ([Ca2+]c) and depolarize the mitochondrial membrane potential (delta Psi m) to limit ATP production. To investigate how physiological Ca2+ signaling might affect energy production, delta Psi m was examined during Ca2+ oscillations in smooth muscle cells. In single, voltage-clamped smooth muscle cells, inhibition of mitochondrial Ca2+ accumulation inhibited inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3]-evoked Ca2+ release and prolonged the time required for restoration of [Ca2+]c following activation of plasmalemmal Ca2+ currents (ICa). Ca2+ could be released from mitochondria immediately (within 15 seconds) after a [Ca2+]c rise evoked by Ins(1,4,5)P3 or ICa. Despite this evidence of mitochondrial Ca2+ accumulation, no change in delta Psi m was observed during single or repetitive [Ca2+]c oscillations evoked by these conditions. Occasionally, spontaneous, repetitive, persistent Ca 2+ oscillations were observed. In these cases, mitochondria displayed stochastic delta Psi m depolarizations, which were independent both of events in neighboring mitochondria and of the timing of the [Ca 2+]c oscillations themselves. Such delta Psi m depolarizations could be mimicked by increased exposure to either fluorescence excitation light or the delta Psi m-sensitive dye tetramethylrhodamine ethyl ester (TMRE) and were inhibited by antioxidants (ascorbic acid, catalase, Trolox and TEMPO) or the mitochondrial permeability transition pore (mPTP)-inhibitor cyclosporin A (CsA). Individual mitochondria within smooth muscle cells might depolarize during repetitive Ca2+ oscillations or during oxidative stress but not during the course of single [Ca2+]c transients evoked by Ca2+ influx or store release.
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Affiliation(s)
- Susan Chalmers
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow, G4 0NR, UK
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Chalmers S, Olson ML, MacMillan D, Rainbow RD, McCarron JG. Ion channels in smooth muscle: regulation by the sarcoplasmic reticulum and mitochondria. Cell Calcium 2007; 42:447-66. [PMID: 17629940 DOI: 10.1016/j.ceca.2007.05.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 05/11/2007] [Accepted: 05/15/2007] [Indexed: 11/27/2022]
Abstract
In smooth muscle, Ca(2+) regulates cell division, growth and cell death as well as providing the main trigger for contraction. Ion channels provide the major access route to elevate the cytoplasmic Ca(2+) concentration ([Ca(2+)](c)) in smooth muscle by permitting Ca(2+) entry across the plasma membrane and release of the ion from intracellular Ca(2+) stores. The control of [Ca(2+)](c) relies on feedback modulation of the entry and release channels by Ca(2+) itself. Local rises in [Ca(2+)](c) may promote or inhibit channel activity directly or indirectly. The latter may arise from Ca(2+) regulation of ionic conductances in the plasma membrane to provide control of cell excitability and so [Ca(2+)](c) entry. Organelles such as mitochondria may also contribute significantly to the feedback regulation of ion channel activity by the control of Ca(2+) or redox status of the cell. This brief review describes the feedback regulation of Ca(2+) release from the internal Ca(2+) store and of plasma membrane excitability in smooth muscle.
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Affiliation(s)
- Susan Chalmers
- Division of Physiology and Pharmacology, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 0NR, UK
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McCarron JG, Olson ML, Rainbow RD, MacMillan D, Chalmers S. Ins(1,4,5)P3 receptor regulation during ‘quantal’ Ca2+ release in smooth muscle. Trends Pharmacol Sci 2007; 28:271-9. [PMID: 17482682 DOI: 10.1016/j.tips.2007.04.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Revised: 03/29/2007] [Accepted: 04/19/2007] [Indexed: 10/23/2022]
Abstract
Smooth muscle is activated by plasma-membrane-acting agonists that induce inositol (1,4,5)-trisphosphate [Ins(1,4,5)P(3)] to release Ca(2+) from the intracellular sarcoplasmic reticulum (SR) Ca(2+) store. Increased concentrations of agonist evoke a concentration-dependent graded release of Ca(2+) in a process called 'quantal' Ca(2+) release. Such a graded release seems to be incompatible with both the finite capacity of the SR store and the positive-feedback Ca(2+)-induced Ca(2+) release (CICR)-like process that is operative at Ins(1,4,5)P(3) receptors, which - once activated - might be expected to deplete the entire store. Proposed explanations of quantal release include the existence of multiple stores, each with different sensitivities to Ins(1,4,5)P(3), or Ins(1,4,5)P(3) receptor opening being controlled by the Ca(2+) concentration within the SR. Here, we suggest that the regulation of Ins(1,4,5)P(3) receptors by the Ca(2+) concentration within the SR explains the quantal Ca(2+)-release process and the apparent existence of multiple Ca(2+) stores in smooth muscle.
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Affiliation(s)
- John G McCarron
- Division of Physiology and Pharmacology, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 0NR, UK.
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Abstract
In smooth muscle, Ca(2+) controls diverse activities including cell division, contraction and cell death. Of particular significance in enabling Ca(2+) to perform these multiple functions is the cell's ability to localize Ca(2+) signals to certain regions by creating high local concentrations of Ca(2+) (microdomains), which differ from the cytoplasmic average. Microdomains arise from Ca(2+) influx across the plasma membrane or release from the sarcoplasmic reticulum (SR) Ca(2+) store. A single Ca(2+) channel can create a microdomain of several micromolar near (approximately 200 nm) the channel. This concentration declines quickly with peak rates of several thousand micromolar per second when influx ends. The high [Ca(2+)] and the rapid rates of decline target Ca(2+) signals to effectors in the microdomain with rapid kinetics and enable the selective activation of cellular processes. Several elements within the cell combine to enable microdomains to develop. These include the brief open time of ion channels, localization of Ca(2+) by buffering, the clustering of ion channels to certain regions of the cell and the presence of membrane barriers, which restrict the free diffusion of Ca(2+). In this review, the generation of microdomains arising from Ca(2+) influx across the plasma membrane and the release of the ion from the SR Ca(2+) store will be discussed and the contribution of mitochondria and the Golgi apparatus as well as endogenous modulators (e.g. cADPR and channel binding proteins) will be considered.
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Affiliation(s)
- John G McCarron
- Department of Physiology and Pharmacology, University of Strathclyde, SIPBS, Glasgow, UK.
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Abstract
The outcomes of 60 sets of monochorionic diamniotic (MCDA) twins were compared with 218 sets of dichorionic diamniotic (DCDA) twins. The caesarean section rates for MCDA were similar to those for DCDA twins (56.6 versus 53.6%, P > 0.1). Although the number of babies with 5-minute Apgar score of <7 was significantly higher for vaginally delivered MCDA twins compared with that of DCDA twins (12 versus 3.5%, P < 0.001), the umbilical artery pH of <7.2 was similar (20 versus 13%, P > 0.05). Admission to neonatal intensive care unit (NICU) and neonatal mortality were also similar in both groups. Delivery by caesarean section was associated with increased admission to the NICU and neonatal mortality for MCDA twins when compared with vaginal delivery group. From this retrospective cohort study, we can conclude that vaginal delivery for MCDA twins appeared to be a reasonable management option when similar selection criteria for vaginal delivery of DCDA twins were applied.
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Affiliation(s)
- A Sau
- Department of Obstetrics & Gynaecology, University Hospital Lewisham, London, UK.
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MacMillan D, Chalmers S, Muir TC, McCarron JG. IP3-mediated Ca2+ increases do not involve the ryanodine receptor, but ryanodine receptor antagonists reduce IP3-mediated Ca2+ increases in guinea-pig colonic smooth muscle cells. J Physiol 2005; 569:533-44. [PMID: 16195318 PMCID: PMC1464235 DOI: 10.1113/jphysiol.2005.096529] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Smooth muscle responds to IP3-generating (sarcolemma acting) neurotransmitters and hormones by releasing Ca2+ from the sarcoplasmic reticulum (SR) via IP3 receptors (IP3Rs). This release may propagate as Ca2+ waves. The Ca2+ signal emanating from IP3 generation may be amplified by its activating further Ca2+ release from ryanodine receptors (RyRs) in the process of Ca2+-induced Ca2+ release (CICR). Evidence for this proposal has relied largely on the use of blocking drugs such as ryanodine, tetracaine and dantrolene, reportedly specific inhibitors of RyRs. Here we have examined whether or not Ca2+ released via IP3Rs subsequently activates RyRs. In addition, the specificity of the blocking agents has been assessed by determining the extent of their ability to block IP3-mediated Ca2+ release under conditions in which RyRs were not activated. IP3-evoked Ca2+ release and Ca2+ waves did not require or activate RyRs. However, the RyR blocking drugs inhibited IP3-mediated Ca2+ signals at concentrations thought to be selective for RyRs. In single colonic smooth muscle cells, voltage clamped in the whole cell configuration, carbachol (CCh) evoked propagating Ca2+ waves which were not inhibited by ryanodine when the sarcolemma potential was -70 mV. At -20 mV, at which potential the SR Ca2+ content was increased and RyRs activated, ryanodine inhibited the Ca2+ waves. Photolysed caged IP3 increased [Ca2+]c; ryanodine, by itself, did not reduce the IP3-evoked [Ca2+]c increase when the sarcolemma potential was maintained at -70 mV. However, after activation of RyRs by caffeine, in the continued presence of ryanodine, the IP3-evoked [Ca2+]c increase was inhibited. In other experiments, RyRs were activated (as evidenced by the occurrence of spontaneous transient outward currents) by depolarizing the sarcolemma to -20 mV and again ryanodine was effective in inhibiting IP3-evoked Ca2+ increase. Thus while ineffective by itself, ryanodine inhibited IP3-evoked Ca2+ increases, presumably by causing persistent opening of the channel and depleting the SR of Ca2+, after RyRs were activated. These experiments establish that IP3-evoked Ca2+ release and Ca2+ waves do not activate RyRs; had they done so ryanodine would have inhibited the Ca2+ increase. However, under conditions where ryanodine was ineffective against the IP3-evoked Ca2+ transient (i.e. when RyRs were not activated, e.g. at a membrane potential of -70 mV) tetracaine and dantrolene each blocked IP3-evoked Ca2+ increases. The results show that although IP3-mediated Ca2+ release does not activate RyRs, RyR blockers can inhibit IP3-mediated Ca2+ signals.
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Affiliation(s)
- Debbi MacMillan
- Institute of Biomedical and Life Sciences, Neuroscience and Biomedical Systems, West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK
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Abstract
Neonatal cervical spinal cord injury occurring in the perinatal period is rare but has been described after both traumatic and atraumatic birth. Recently, a case of atraumatic, late third trimester, pre-labour presentation has been described. We report a second such case, but with important diagnostic differences and outcome. This case showed loss of foetal movements late in the third trimester. This was secondary to an extensive cervical lesion with no history of trauma. This emphasizes the need to consider cervical cord lesions when foetal or postnatal movements are reduced, even in the absence of trauma.
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Affiliation(s)
- T Hedderly
- Department of Neurology & Neonatology, Guys Hospital, London, UK.
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Abstract
The extraordinary capacity of isolated mitochondria to accumulate Ca(2+) has been established for more than 40 years. The distinct kinetics of the independent uptake and efflux pathways accounts for the dual functionality of the transport process to either modulate matrix free Ca(2+) concentrations or to act as temporary stores of large amounts of Ca(2+) in the presence of phosphate. One puzzle has been the nature of the matrix calcium phosphate complex, since matrix free Ca(2+) seems to be buffered in the region of 1-5 microM in the presence of phosphate while millimolar Ca(2+) remains soluble in in vitro media. The key seems to be the elevated matrix pH and the third-power relationship of the PO(4)(3-) concentration with pH. Taking this into account we may now finally have a model that explains the major features of physiological mitochondrial Ca(2+) transport.
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McCarron JG, Bradley KN, MacMillan D, Chalmers S, Muir TC. The sarcoplasmic reticulum, Ca2+ trapping, and wave mechanisms in smooth muscle. Physiology (Bethesda) 2004; 19:138-47. [PMID: 15143210 DOI: 10.1152/nips.01518.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [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: 11/22/2022] Open
Abstract
The sarcoplasmic reticulum (SR) and apposed regions of the sarcolemma passively trap Ca2+ entering the cell to limit the rise in cytoplasmic Ca2+ concentration without SR pump involvement. When "leaky," the SR facilitates Ca2+ entry to the cytoplasm. SR Ca2+ release via inositol 1,4,5-trisphosphate receptors (IP(3)Rs) propagates as calcium waves; IP(3)Rs alone account for wave propagation.
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Affiliation(s)
- John G McCarron
- Institute of Biomedical and Life Sciences, Neuroscience and Biomedical Systems, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
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Meli M, Kipar A, Müller C, Jenal K, Gönczi E, Borel N, Gunn-Moore D, Chalmers S, Lin F, Reinacher M, Lutz H. High viral loads despite absence of clinical and pathological findings in cats experimentally infected with feline coronavirus (FCoV) type I and in naturally FCoV-infected cats. J Feline Med Surg 2004; 6:69-81. [PMID: 15123151 PMCID: PMC7128724 DOI: 10.1016/j.jfms.2003.08.007] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2003] [Indexed: 11/20/2022]
Abstract
Specified pathogen-free cats were naturally infected with FCoV or experimentally infected with FCoV type I. Seroconversion was determined and the course of infection was monitored by measuring the FCoV loads in faeces, whole blood, plasma and/or monocytes. Tissue samples collected at necropsy were examined for viral load and histopathological changes. Experimentally infected animals started shedding virus as soon as 2 days after infection. They generally displayed the highest viral loads in colon, ileum and mesenteric lymph nodes. Seroconversion occurred 3-4 weeks post infection. Naturally infected cats were positive for FCoV antibodies and monocyte-associated FCoV viraemia prior to death. At necropsy, most animals tested positive for viral shedding and FCoV RNA was found in spleen, mesenteric lymph nodes and bone marrow. Both experimentally and naturally infected cats remained clinically healthy. Pathological findings were restricted to generalized lymphatic hyperplasia. These findings demonstrate the presence of systemic FCoV infection with high viral loads in the absence of clinical and pathological signs.
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Affiliation(s)
- M Meli
- Clinical Laboratory, Faculty of Veterinary Medicine, University of Zurich, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
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McCarron JG, MacMillan D, Bradley KN, Chalmers S, Muir TC. Origin and Mechanisms of Ca2+ Waves in Smooth Muscle as Revealed by Localized Photolysis of Caged Inositol 1,4,5-Trisphosphate. J Biol Chem 2004; 279:8417-27. [PMID: 14660609 DOI: 10.1074/jbc.m311797200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytosolic Ca(2+) concentration ([Ca(2+)](c)) controls diverse cellular events via various Ca(2+) signaling patterns; the latter are influenced by the method of cell activation. Here, in single-voltage clamped smooth muscle cells, sarcolemma depolarization generated uniform increases in [Ca(2+)](c) throughout the cell entirely by Ca(2+) influx. On the other hand, the Ca(2+) signal produced by InsP(3)-generating agonists was a propagated wave. Using localized uncaged InsP(3), the forward movement of the Ca(2+) wave arose from Ca(2+)-induced Ca(2+) release at the InsP(3) receptor (InsP(3)R) without ryanodine receptor involvement. The decline in [Ca(2+)](c) (the back of the wave) occurred from a functional compartmentalization of the store, which rendered the site of InsP(3)-mediated Ca(2+) release, and only this site, refractory to the phosphoinositide. The functional compartmentalization arose by a localized feedback deactivation of InsP(3) receptors produced by an increased [Ca(2+)](c) rather than a reduced luminal [Ca(2+)] or an increased cytoplasmic [InsP(3)]. The deactivation of the InsP(3) receptor was delayed in onset, compared with the time of the rise in [Ca(2+)](c), persisted (>30 s) even when [Ca(2+)](c) had regained resting levels, and was not prevented by kinase or phosphatase inhibitors. Thus different forms of cell activation generate distinct Ca(2+) signaling patterns in smooth muscle. Sarcolemma Ca(2+) entry increases [Ca(2+)](c) uniformly; agonists activate InsP(3)R and produce Ca(2+) waves. Waves progress by Ca(2+)-induced Ca(2+) release at InsP(3)R, and persistent Ca(2+)-dependent inhibition of InsP(3)R accounts for the decline in [Ca(2+)](c) at the back of the wave.
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MESH Headings
- Animals
- Caffeine/pharmacology
- Calcium/analysis
- Calcium/metabolism
- Calcium/pharmacology
- Calcium Channels/drug effects
- Calcium Channels/physiology
- Carbachol/pharmacology
- Cell Membrane/metabolism
- Colon
- Electric Conductivity
- Enzyme Activation
- Feedback, Physiological
- Guinea Pigs
- Inositol 1,4,5-Trisphosphate/chemistry
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors
- Kinetics
- Male
- Muscle, Smooth/metabolism
- Photolysis
- Protein Kinase C/metabolism
- Receptors, Cytoplasmic and Nuclear/drug effects
- Receptors, Cytoplasmic and Nuclear/physiology
- Ryanodine Receptor Calcium Release Channel/physiology
- Sarcolemma/metabolism
- Signal Transduction
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Affiliation(s)
- John G McCarron
- Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
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Abstract
The mitochondrion has moved to the center stage in the drama of the life and death of the neuron. The mitochondrial membrane potential controls the ability of the organelle to generate ATP, generate reactive oxygen species and sequester Ca(2+) entering the cell. Each of these processes interact, and their deconvolution is far from trivial. The cultured cerebellar granule cell provides a model in which knowledge gained from studies on isolated mitochondria can be applied to study the role played by the organelles in the maintenance of Ca(2+) homeostasis in the cell under resting, stimulated and pathophysiological conditions. In particular, mitochondria play a complex role in the response of the neuron to excitotoxic stimulation of NMDA and AMPA-kainate selective glutamate receptors. One goal of research in this area is to provide clues as to possible ways in which modulators of mitochondrial function may be used as neuroprotective agents, since mitochondrial Ca(2+) accumulation seems to play a key role in glutamate excitotoxicity.
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Affiliation(s)
- David G Nicholls
- Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945, USA.
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45
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Abstract
Three sequential phases of mitochondrial calcium accumulation can be distinguished: matrix dehydrogenase regulation, buffering of extramitochondrial free calcium, and finally activation of the permeability transition. Relationships between these phases, free and total matrix calcium concentration, and phosphate concentration are investigated in rat liver and brain mitochondria. Slow, continuous calcium infusion is employed to avoid transient bioenergetic consequences of bolus additions. Liver and brain mitochondria undergo permeability transitions at precise matrix calcium loads that are independent of infusion rate. Cytochrome c release precedes the permeability transition. Cyclosporin A enhances the loading capacity in the presence or absence of acetoacetate. A remarkably constant free matrix calcium concentration, in the range 1-5 microM as monitored by matrix-loaded fura2-FF, was observed when total matrix calcium was increased from 10 to at least 500 nmol of calcium/mg of protein. Increasing phosphate decreased both the free matrix calcium and the matrix calcium-loading capacity. Thus the permeability transition is not triggered by a critical matrix free calcium concentration. The rate of hydrogen peroxide detection by Amplex Red decreased during calcium infusion arguing against a role for oxidative stress in permeability pore activation in this model. A transition between a variable and buffered matrix free calcium concentration occurred at 10 nmol of total matrix calcium/mg protein. The solubility product of amorphous Ca3(PO4)2 is consistent with the observed matrix free calcium concentration, and the matrix pH is proposed to play the major role in maintaining the low matrix free calcium concentration.
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Affiliation(s)
- Susan Chalmers
- Buck Institute for Age Research, Novato, California 94945, USA
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46
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Madigan JE, Hietala S, Chalmers S, DeRock E. Seroepidemiologic survey of antibodies to Ehrlichia equi in horses of northern California. J Am Vet Med Assoc 1990; 196:1962-4. [PMID: 2195000] [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: 12/30/2022]
Abstract
The prevalence of antibodies to Ehrlichia equi in horses from the foothill regions of northern California and from the Sacramento valley (non-foothill area) was determined, using an indirect fluorescent antibody test. Horses from foothill regions had a higher prevalence of seropositivity (10.4%) and higher titer (1:10 to 1:80) than did those from non-foothill regions (3.1%; titer less than or equal to 1:10). Fifty percent of healthy horses on a foothill farm enzootic for E equi had titer to E equi, suggesting that infection with E equi can be subclinical. Six veterinarians surveyed from northern California diagnosed clinical E equi infection in 38 horses during 1985-1986 based on clinical signs of infection and observation of E equi inclusion bodies in neutrophils on blood smears.
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Affiliation(s)
- J E Madigan
- Department of Medicine, School of Veterinary Medicine, University of California, Davis 05616
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Chalmers S, Schick RO, Jeffers J. Demodicosis in two cats seropositive for feline immunodeficiency virus. J Am Vet Med Assoc 1989; 194:256-7. [PMID: 2537276] [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: 01/01/2023]
Abstract
Two cats were diagnosed with generalized demodicosis. Serotest results were negative for FeLV and positive for feline immunodeficiency virus. In one cat, demodicosis resolved in response to topical application of lime-sulfur solution, but the other cat was euthanatized.
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Affiliation(s)
- S Chalmers
- Department of Small Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens 30602
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Supran EM, Gardner PS, Cayzer I, Court G, Chalmers S. Comparison of a modified microagglutination technique for HBsAg with the standard technique and a new RIA system. J Clin Pathol 1981; 34:1396-9. [PMID: 7328187 PMCID: PMC494616 DOI: 10.1136/jcp.34.12.1396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A further modification of the standard RPHA technique (Hepatest, Wellcome Reagents) for the detection of HBsAg is described. This modification does not require a centrifugation step which is required by the other modifications that have been described previously and consequently takes a little longer to perform. It does, however, retain the advantages of increased sensitivity and decreased costs which are also features of the other modifications. A series of 939 routine clinical specimens were used to evaluate the method described and to evaluate a new RIA kit for the detection of HBsAg (Hepatube, Wellcome Reagents). Of 53 specimens found to be positive for HBsAg by RIA, 50 (94% were detected by the modified Hepatest RPHA as opposed to 47 (89%) by the standard technique.
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