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Chan Wah Hak C, Dean JA, Hill MA, Somaiah N. The National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group Workshop: Translating Novel Discoveries to and from the Clinic. Clin Oncol (R Coll Radiol) 2023; 35:769-772. [PMID: 37741714 DOI: 10.1016/j.clon.2023.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 08/30/2023] [Indexed: 09/25/2023]
Affiliation(s)
- C Chan Wah Hak
- Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK
| | - J A Dean
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - M A Hill
- Department of Oncology, University of Oxford, Oxford, UK
| | - N Somaiah
- Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK; The Royal Marsden NHS Foundation Trust, London, UK.
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Giardina TD, Hunte H, Hill MA, Heimlich SL, Singh H, Smith KM. Defining Diagnostic Error: A Scoping Review to Assess the Impact of the National Academies' Report Improving Diagnosis in Health Care. J Patient Saf 2022; 18:770-778. [PMID: 35405723 PMCID: PMC9698189 DOI: 10.1097/pts.0000000000000999] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Standards for accurate and timely diagnosis are ill-defined. In 2015, the National Academies of Science, Engineering, and Medicine (NASEM) committee published a landmark report, Improving Diagnosis in Health Care , and proposed a new definition of diagnostic error, "the failure to ( a ) establish an accurate and timely explanation of the patient's health problem(s) or ( b ) communicate that explanation to the patient." OBJECTIVE This study aimed to explore how researchers operationalize the NASEM's definition of diagnostic error with relevance to accuracy, timeliness, and/or communication in peer-reviewed published literature. METHODS Using the Arskey and O'Malley's framework framework, we identified published literature from October 2015 to February 2021 using Medline and Google Scholar. We also conducted subject matter expert interviews with researchers. RESULTS Of 34 studies identified, 16 were analyzed and abstracted to determine how diagnostic error was operationalized and measured. Studies were grouped by theme: epidemiology, patient focus, measurement/surveillance, and clinician focus. Nine studies indicated using the NASEM definition. Of those, 5 studies also operationalized with existing definitions proposed before the NASEM report. Four studies operationalized the components of the NASEM definition and did not cite existing definitions. Three studies operationalized error using existing definitions only. Subject matter experts indicated that the NASEM definition functions as foundation for researchers to conceptualize diagnostic error. CONCLUSIONS The NASEM report produced a common understanding of diagnostic error that includes accuracy, timeliness, and communication. In recent peer-reviewed literature, most researchers continue to use pre-NASEM report definitions to operationalize accuracy and timeliness. The report catalyzed the use of patient-centered concepts in the definition, resulting in emerging studies focused on examining errors related to communicating diagnosis to patients.
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Affiliation(s)
- Traber D. Giardina
- From the Center for Innovations in Quality, Effectiveness and Safety, Michael E. DeBakey Veterans Affairs Medical Center
- Baylor College of Medicine, Houston, Texas
| | - Haslyn Hunte
- MedStar Institute for Quality and Safety (MIQS), Columbia
- Medstar Health, Baltimore, Maryland
| | - Mary A. Hill
- MedStar Institute for Quality and Safety (MIQS), Columbia
- Medstar Health, Baltimore, Maryland
| | | | - Hardeep Singh
- From the Center for Innovations in Quality, Effectiveness and Safety, Michael E. DeBakey Veterans Affairs Medical Center
- Baylor College of Medicine, Houston, Texas
| | - Kelly M. Smith
- MedStar Institute for Quality and Safety (MIQS), Columbia
- Medstar Health, Baltimore, Maryland
- Michael Garron Hospital–Toronto East Health Network
- Institute of Health Policy, Management & Evaluation, University of Toronto, Toronto, Ontario, Canada
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Abstract
e19243 Background: Patient and family-centered care (PFCC) is grounded in the concepts of dignity and respect, information sharing, and active participation and collaboration in their health care. Efforts to engage patients and family members as part of the healthcare team as part of robust multidisciplinary breast cancer care (MBCC), including in multidisciplinary tumor boards, is an extension of PFCC for breast cancer care. Our team explored multi-stakeholder perspectives of engaging patients as partners on a virtual multidisciplinary tumor board (MTB) using an mHealth application. Methods: We conducted a prospective cohort study employing semi-structured interviews and focus group methodology to explore stakeholder (patients with Stage 0-III breast cancer, family members/caregivers, clinicians, and tumor board staff) perspectives of engaging patients in a virtual MTB. Interviews and focus groups were audiotaped, transcribed, and analyzed using concurrent content analysis to identify common themes. Recruitment continued until saturation of themes was achieved. Results: We conducted 22 interviews and 5 focus groups with 49 participants. Patients and family members reported discomfort with idea of engaging in MTB discussions about their cancer. Disease burden, limited understanding of medical terminology, and not wanting to be a part of the early discussions about their disease (e.g., being overwhelmed, need to trust clinician’s advice) were commonly reported. Clinicians and staff also reported concerns about patient engagement in MTB. Clinicians reported that it may change the candor of the discussions at MTB and obfuscate the problems/issues if they needed to modify their language to accommodate patients’ sensitivities. Clinicians and staff were also concerned about patient’s perception of discordance within the MTB clinician members and how to explain this uncertainty to patients. Staff concerns centered around the use of medical terminology which may create anxiety and result in patient misunderstanding. Conclusions: Clinicians, staff, patients and family members were overwhelmingly concerned about adding patients to the MTB. Engaging patients in the frank and candid early treatment planning discussions may need further evaluation in a clinical environment and among different patient cohorts.
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Affiliation(s)
- Kelly M Smith
- MedStar Institute for Quality and Safety (MIQS), Columbia, MD
| | - Mary A Hill
- MedStar Institute for Quality and Safety (MIQS), Columbia, MD
| | - Kelly Rosendall
- MedStar Institute for Quality and Safety (MIQS), Columbia, MD
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Abstract
e19244 Background: mHealth interventions support patient behavior change, promote adherence to treatment provide patient education, and clinical decision support. Research on mHealth interventions has focused on unidirectional communication from providers to patients. mHealth to support patient navigation through multidisciplinary breast cancer care (MBCC) has not been realized. Our team explored the information needs and perceived benefits and barriers to the design and adoption of mHealth solutions to support patient-centered MBCC. Methods: We conducted a prospective cohort study with patients and family members of patients with breast cancer (Stage 0-III), clinicians and practice staff participated semi-structured interviews/focus group to explore stakeholder perceptions of mHealth across the domains of: information needs, communication, technology preferences, and barriers and facilitators to adoption and implementation. Transcripts were analyzed using concurrent content analysis and recruitment continued until saturation of themes was achieved within each stakeholder group. Results: We conducted 22 interviews and 5 focus groups with 49 participants generating 466 individual responses. Patients, clinicians, and staff found existing communication pathways (e.g., calls to office, patient portal) sufficient in meeting patient’s needs. Family members and caregivers saw the potential of mHealth as beneficial to decision-making and treatment adherence. Patient access to health information on a smartphone between visits was perceived positive to support care organization. Clinicians and staff recognized the need for patient engagement to optimize treatment outcomes. Concerns about workload, privacy and security, and misinterpretation of information shared in mHealth apps were perceived as barriers to adoption. Recommendations included EHR integration, existing “in-box” management workflow, and team engagement in information management processes. Conclusions: mHealth can play a pivotal role in supporting patient-clinician-family dynamics for MBCC. Designers of mHealth should carefully consider the relative value of applications to the clinical workflow, patient and family needs, and identify team-based approaches to supporting adoption and implementation.
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Affiliation(s)
| | - Mary A Hill
- MedStar Institute for Quality and Safety (MIQS), Columbia, MD
| | - Kelly Rosendall
- MedStar Institute for Quality and Safety (MIQS), Columbia, MD
| | - Kelly M Smith
- MedStar Institute for Quality and Safety (MIQS), Columbia, MD
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Hill MA. Radiation Track Structure: How the Spatial Distribution of Energy Deposition Drives Biological Response. Clin Oncol (R Coll Radiol) 2020; 32:75-83. [PMID: 31511190 DOI: 10.1016/j.clon.2019.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/04/2019] [Accepted: 07/08/2019] [Indexed: 12/22/2022]
Abstract
Ionising radiation is incredibly effective at causing biological effects. This is due to the unique way energy is deposited along highly structured tracks of ionisation and excitation events, which results in correlation with sites of DNA damage from the nanometre to the micrometre scale. Correlation of these events along the track on the nanometre scale results in clustered damage, which not only results in the formation of DNA double-strand breaks (DSB), but also more difficult to repair complex DSB, which include additional damage within a few base pairs. The track structure varies significantly with radiation quality and the increase in relative biological effectiveness observed with increasing linear energy transfer in part corresponds to an increase in the probability and complexity of clustered DNA damage produced. Likewise, correlation over larger scales, associated with packing of DNA and associated chromosomes within the cell nucleus, can also have a major impact on the biological response. The proximity of the correlated damage along the track increases the probability of miss-repair through pairwise interactions resulting in an increase in probability and complexity of DNA fragments/deletions, mutations and chromosomal rearrangements. Understanding the mechanisms underlying the biological effectiveness of ionising radiation can provide an important insight into ways of increasing the efficacy of radiotherapy, as well as the risks associated with exposure. This requires a multi-scale approach for modelling, not only considering the physics of the track structure from the millimetre scale down to the nanometre scale, but also the structural packing of the DNA within the nucleus, the resulting chemistry in the context of the highly reactive environment of the nucleus, together with the subsequent biological response.
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Affiliation(s)
- M A Hill
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford, UK.
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Hill MA, Thompson JM, Kavanagh A, Tullis IDC, Newman RG, Prentice J, Beech J, Gilchrist S, Smart S, Fokas E, Vojnovic B. The Development of Technology for Effective Respiratory-Gated Irradiation Using an Image-Guided Small Animal Irradiator. Radiat Res 2017; 188:247-263. [PMID: 28715250 DOI: 10.1667/rr14753.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The development of image-guided small animal irradiators represents a significant improvement over standard irradiators by enabling preclinical studies to mimic radiotherapy in humans. The ability to deliver tightly collimated targeted beams, in conjunction with gantry or animal couch rotation, has the potential to maximize tumor dose while sparing normal tissues. However, the current commercial platforms do not incorporate respiratory gating, which is required for accurate and precise targeting in organs subject to respiration related motions that may be up to the order of 5 mm in mice. Therefore, a new treatment head assembly for the Xstrahl Small Animal Radiation Research Platform (SARRP) has been designed. This includes a fast X-ray shutter subsystem, a motorized beam hardening filter assembly, an integrated transmission ionization chamber to monitor beam delivery, a kinematically positioned removable beam collimator and a targeting laser exiting the center of the beam collimator. The X-ray shutter not only minimizes timing errors but also allows beam gating during imaging and treatment, with irradiation only taking place during the breathing cycle when tissue movement is minimal. The breathing related movement is monitored by measuring, using a synchronous detector/lock-in amplifier that processes diffuse reflectance light from a modulated light source. After thresholding of the resulting signal, delays are added around the inhalation/exhalation phases, enabling the "no movement" period to be isolated and to open the X-ray shutter. Irradiation can either be performed for a predetermined time of X-ray exposure, or through integration of a current from the transmission monitor ionization chamber (corrected locally for air density variations). The ability to successfully deliver respiratory-gated X-ray irradiations has been demonstrated by comparing movies obtained using planar X-ray imaging with and without respiratory gating, in addition to comparing dose profiles observed from a collimated beam on EBT3 radiochromic film mounted on the animal's chest. Altogether, the development of respiratory-gated irradiation facilitates improved dose delivery during animal movement and constitutes an important new tool for preclinical radiation studies. This approach is particularly well suited for irradiation of orthotopic tumors or other targets within the chest and abdomen where breathing related movement is significant.
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Affiliation(s)
- M A Hill
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - J M Thompson
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - A Kavanagh
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - I D C Tullis
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - R G Newman
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - J Prentice
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - J Beech
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - S Gilchrist
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - S Smart
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - E Fokas
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
| | - B Vojnovic
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford OX3 7DQ, United Kingdom
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Hill MA, O'Neill P, McKenna WG. Comments on potential health effects of MRI-induced DNA lesions: quality is more important to consider than quantity. Eur Heart J Cardiovasc Imaging 2016; 17:1230-1238. [PMID: 27550664 PMCID: PMC5081138 DOI: 10.1093/ehjci/jew163] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 07/13/2016] [Indexed: 01/01/2023] Open
Abstract
Magnetic resonance imaging (MRI) is increasingly being used in cardiology to detect heart disease and guide therapy. It is mooted to be a safer alternative to imaging techniques, such as computed tomography (CT) or coronary angiographic imaging. However, there has recently been an increased interest in the potential long-term health risks of MRI, especially in the light of the controversy resulting from a small number of research studies reporting an increase in DNA damage following exposure, with calls to limit its use and avoid unnecessary examination, according to the precautionary principle. Overall the published data are somewhat limited and inconsistent; the ability of MRI to produce DNA lesions has yet to be robustly demonstrated and future experiments should be carefully designed to optimize sensitivity and benchmarked to validate and assess reproducibility. The majority of the current studies have focussed on the initial induction of DNA damage, and this has led to comparisons between the reported induction of γH2AX and implied double-strand break (DSB) yields produced following MRI with induction by imaging techniques using ionizing radiation. However, γH2AX is not only a marker of classical double-ended DSB, but also a marker of stalled replication forks and in certain circumstances stalled DNA transcription. Additionally, ionizing radiation is efficient at producing complex DNA damage, unique to ionizing radiation, with an associated reduction in repairability. Even if the fields associated with MRI are capable of producing DNA damage, the lesions produced will in general be simple, similar to those produced by endogenous processes. It is therefore inappropriate to try and infer cancer risk by simply comparing the yields of γH2AX foci or DNA lesions potentially produced by MRI to those produced by a given exposure of ionizing radiation, which will generally be more biologically effective and have a greater probability of leading to long-term health effects. As a result, it is important to concentrate on more relevant downstream end points (e.g. chromosome aberration production), along with potential mechanisms by which MRI may lead to DNA lesions. This could potentially involve a perturbation in homeostasis of oxidative stress, modifying the background rate of endogenous DNA damage induction. In summary, what the field needs at the moment is more research and less fear mongering.
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Affiliation(s)
- M A Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK
| | - P O'Neill
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK
| | - W G McKenna
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK
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Mariotti LG, Abdelrazzak AB, Ottolenghi A, O'Neill P, Hill MA. Stimulation of intercellular induction of apoptosis in transformed cells at very low doses of ionising radiation: spatial and temporal features. Radiat Prot Dosimetry 2015; 166:161-164. [PMID: 25883313 DOI: 10.1093/rpd/ncv176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The ultimate response of a cell or tissue to radiation is dependent in part on intercellular signalling. This becomes increasingly important at low doses, or at low dose rates, associated with typical human exposures. In order to help characterise the underlying mechanism of intercellular signalling, and how they are perturbed following exposure to ionising radiation, a previously well-defined model system of intercellular induction of apoptosis (IIA) (Portess et al. 2007, Cancer Res. 67, 1246-1253) was adopted. The aim of the present work is to evaluate the signalling mechanisms underpinning this process through exploring the variables that can affect the IIA, i.e. dose, time and space.
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Affiliation(s)
- L G Mariotti
- Dipartimento di Fisica, Universit Degli Studi di Pavia, via Bassi 6, Pavia I-27100, Italy Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Pavia, via Bassi 6, Pavia I-27100, Italy CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford OX3 7DQ, UK
| | - A B Abdelrazzak
- CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford OX3 7DQ, UK Physics Research Division, National Research Centre, Giza, Egypt
| | - A Ottolenghi
- Dipartimento di Fisica, Universit Degli Studi di Pavia, via Bassi 6, Pavia I-27100, Italy Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Pavia, via Bassi 6, Pavia I-27100, Italy
| | - P O'Neill
- CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford OX3 7DQ, UK
| | - M A Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford OX3 7DQ, UK
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Abstract
The target theory of radiation-induced effects has been challenged by numerous studies, which indicate that in addition to biological effects resulting from direct DNA damage within the cell, a variety of non-DNA targeted effects (NTE) may make important contributions to the overall outcome. Ionising radiation induces complex, global cellular responses, such as genomic instability (GI) in both irradiated and never-irradiated 'bystander' cells that receive molecular signals produced by irradiated cells. GI is a well-known feature of many cancers, increasing the probability of cells to acquire the 'hallmarks of cancer' during the development of tumours. Although epidemiological data include contributions of both direct and NTE, they lack (i) statistical power at low dose where differences in dose response for NTE and direct effects are likely to be more important and (ii) heterogeneity of non-targeted responses due to genetic variability between individuals. In this article, NTE focussing on GI and bystander effects were critically examined, the specific principles of NTE were discussed and the potential influence on human health risk assessment from low-dose radiation was considered.
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Affiliation(s)
- M A Kadhim
- Genomic Instability Group, Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford OX3 0BP, UK
| | - M A Hill
- CRUK/MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK
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10
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Abstract
The yield of chromosome aberrations is not only dependent on dose but also on radiation quality, with high linear energy transfer (LET) typically having a greater biological effectiveness per unit dose than those of low-LET radiation. Differences in radiation track structure and cell morphology can also lead to quantitative differences in the spectra of the resulting chromosomal rearrangements, especially at low doses associated with typical human exposures. The development of combinatorial fluorescent labelling techniques (such as mFISH and mBAND) has helped to reveal the complexity of rearrangements, showing increasing complexity of observed rearrangements with increasing LET but has a resolution limited to ∼10 MBp. High-LET particles have not only been shown to produce clustered sites of DNA damage but also produce multiple correlated breaks along its path resulting in DNA fragments smaller than the resolution of these techniques. Additionally, studies have shown that the vast majority of radiation-induced HPRT mutations were also not detectable using fluorescent in situ hybridisation (FISH) techniques, with correlation of breaks along the track being reflected in the complexity of mutations, with intra- and inter-chromosomal insertions, and inversions occurring at the sites of some of the deletions. Therefore, the analysis of visible chromosomal rearrangements observed using current FISH techniques is likely to represent just the tip of the iceberg, considerably underestimating the extent and complexity of radiation induced rearrangements.
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Affiliation(s)
- M A Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK
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Underwood TSA, Thompson J, Bird L, Scott AJD, Patmore P, Winter HC, Hill MA, Fenwick JD. Validation of a prototype DiodeAir for small field dosimetry. Phys Med Biol 2015; 60:2939-53. [DOI: 10.1088/0031-9155/60/7/2939] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Underwood TSA, Winter HC, Hill MA, Fenwick JD. Mass-density compensation can improve the performance of a range of different detectors under non-equilibrium conditions. Phys Med Biol 2013; 58:8295-310. [DOI: 10.1088/0031-9155/58/23/8295] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Underwood TSA, Winter HC, Hill MA, Fenwick JD. TU-C-108-03: Beyond the Alfonso Formalism for Small Field Dosimetry: A New Metric, New Detectors, Or Both? Med Phys 2013. [DOI: 10.1118/1.4815367] [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: 11/07/2022] Open
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Woo GA, Hill MA, de Medina MD, Schiff ER. Screening for hepatitis B virus and hepatitis C virus at a community fair: a single-center experience. Gastroenterol Hepatol (N Y) 2013; 9:293-299. [PMID: 23943664 PMCID: PMC3740805] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Despite recommendations for screening for hepatitis B virus (HBV) and hepatitis C virus (HCV), most individuals are still unaware of their infection status. The disparities in screening for HBV and HCV can be attributed to lack of awareness, language barriers, and difficulty in accessing healthcare. To address these issues, an exhibit booth was set up at an annual cultural festival to promote awareness about HBV and HCV and also provide free screening for a local Floridian community. Recruitment was conducted in various languages by physicians and nurses who specialize in hepatology. All materials associated with the screening process were sponsored by the Schiff Center for Liver Diseases, which is located at the University of Miami Miller School of Medicine in Florida. In the first year of the screening initiative, 173 of 11,000 fair attendees were screened for HBV. Twenty-nine (17%) of those screened tested positive for antibodies to hepatitis B core antigen (anti-HBc), and only 1 individual tested positive for chronic HBV, with positive hepatitis B surface antigen (HBsAg). Screening for HCV and an extended patient questionnaire were added to the screening program in the second year of the initiative. A total 231 of 9,000 fair attendees volunteered to be screened for both HBV and HCV. Twenty-nine (13%) of these people tested positive for anti-HBc, and 3 tested positive for HBsAg. Only 1 person tested positive for anti-HCV, but this individual had undetectable HCV RNA levels. Our single-center experience illustrates that, despite efforts to improve access to screening, only 2-3% of attendees at a cultural fair embraced the screening efforts. Other strategies will be required to enhance participation in screening programs for viral hepatitis.
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Affiliation(s)
- Garmen A Woo
- Dr. Woo is a Fellow in the Division of Hepatology, Ms. Hill is the Manager and Ms. de Medina is the Director of the Research Laboratory in the Hepatology Diagnostic Laboratory, and Dr. Schiff is the Director of the Schiff Center for Liver Diseases, all at the University of Miami Miller School of Medicine in Miami, Florida
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Hill MA, Griffin CS, Pyke EL, Stevens DL. Chromosome aberration induction is dependent on the spatial distribution of energy deposition through a cell nucleus. Radiat Prot Dosimetry 2011; 143:172-176. [PMID: 21183544 DOI: 10.1093/rpd/ncq517] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The importance of the spatial distribution of energy deposition through the nucleus in determining the resultant chromosome rearrangements was investigated using fluorescent in situ hybridisation technique following either uniform or partial irradiation of HF19 human fibroblast cells with low-LET 1.5 keV ultrasoft X-rays. Irradiations were performed with and without a copper irradiation mask with a Poisson distribution of micron-sized holes immediately below the irradiation dish and the results are compared with previous results obtained following exposure to a Poisson distribution of alpha particles. For the same radiation quality, the spatial distribution of energy deposition within the nucleus was found to be important in determining the ultimate biological response, with an increased ratio of complex-to-simple aberrations observed for partial compared to uniform irradiation. Comparisons between low-LET ultrasoft X-rays and high-LET alpha particles indicate that the sub-micron clustering of damage along the alpha particle track is more important than just the total number of double-strand breaks produced.
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Affiliation(s)
- M A Hill
- CRUK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK.
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Young EJ, Hill MA, Wiehler WB, Triggle CR, Reid JJ. Reduced EDHF responses and connexin activity in mesenteric arteries from the insulin-resistant obese Zucker rat. Diabetologia 2008; 51:872-81. [PMID: 18324386 DOI: 10.1007/s00125-008-0934-y] [Citation(s) in RCA: 40] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 12/17/2007] [Indexed: 01/18/2023]
Abstract
AIMS/HYPOTHESIS The objective of this study was to examine the effect of insulin resistance on endothelium-derived hyperpolarising factor (EDHF) and small mesenteric artery endothelial function using 25-week-old insulin-resistant obese Zucker rats (OZRs) and lean littermate control rats (LZRs). The involvement of gap junctions and their connexin subunits in the EDHF relaxation response was also assessed. METHODS Mesenteric arteries were evaluated using the following assays: (1) endothelial function by pressure myography, with internal diameter recorded using video microscopy; (2) connexin protein levels by western blotting; and (3) Cx mRNA expression by real-time PCR. RESULTS Relaxations in response to acetylcholine were significantly smaller in mesenteric arteries from the OZRs than the LZRs, whereas there was no difference in relaxations in response to levcromakalim. Responses to acetylcholine were not altered by nitric oxide inhibitors, but were abolished by charybdotoxin in combination with apamin, which blocked the EDHF component of the response. 40Gap27 significantly attenuated the response to acetylcholine in the LZRs, but had no effect in the OZRs. Connexin 40 protein and Cx40 mRNA levels in mesenteric vascular homogenates were significantly smaller in the OZRs than in the LZRs, with no difference in connexin 43 or Cx43 mRNA levels. CONCLUSIONS/INTERPRETATION These findings demonstrate that endothelial dysfunction in mesenteric arteries from the insulin-resistant OZRs can be attributed to a defect in EDHF. The results also suggest that the defective EDHF is at least partly related to an impairment of connexin 40-associated gap junctions, through a decrease in connexin 40 protein and Cx40 mRNA expression in the OZRs.
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Affiliation(s)
- E J Young
- School of Medical Sciences, RMIT University, Melbourne, Victoria, Australia.
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17
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Braun A, Sheng JZ, Ella S, Davis MJ, Hill MA. Activators of SK
Ca
and IK
Ca
channels enhance agonist‐evoked vasodilation and endothelial NO synthesis. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.749.13] [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)
- Andrew Braun
- Pharmacology and TherapeuticsUniversity of CalgaryCalgaryCanada
| | - JZ Sheng
- Pharmacology and TherapeuticsUniversity of CalgaryCalgaryCanada
| | - S Ella
- University of Missouri‐ColumbiaColumbiaMO
| | - MJ Davis
- University of Missouri‐ColumbiaColumbiaMO
| | - MA Hill
- University of Missouri‐ColumbiaColumbiaMO
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18
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Murphy TV, Kotecha N, Hill MA. Endothelium-independent constriction of isolated, pressurized arterioles by Nomega-nitro-L-arginine methyl ester (L-NAME). Br J Pharmacol 2007; 151:602-9. [PMID: 17471179 PMCID: PMC2013995 DOI: 10.1038/sj.bjp.0707262] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Nitric oxide synthase (NOS) inhibitors cause vasoconstriction in pressurized arterioles with myogenic tone. This suggests either tonic production of NO modulates myogenic tone or a direct, NOS-independent effect of the NOS inhibitors. The nature of the contractile effect of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM) on pressurised arterioles was investigated. EXPERIMENTAL APPROACH Segments of rat cremaster muscle first-order arteriole were cannulated on glass micropipettes and maintained at an intraluminal pressure of 50, 70 or 120 mmHg. KEY RESULTS L-NAME and the related compound L-NA (100 microM) constricted pressurized vessels with myogenic tone. Removal of the endothelium did not cause constriction or alter myogenic tone, however the constrictor effect of L-NAME persisted. The constrictor effect of L-NAME was abolished by L-arginine (1 mM). Other NO and cGMP pathway inhibitors, including the nNOS inhibitor 7-nitroindazole (100 muM), the NO scavenger carboxy-PTIO (100 microM), the guanylate cyclase inhibitor ODQ (10 microM) and the cGMP inhibitor Rp-8CPT-cGMPS (10 microM) did not cause constriction of the arterioles. L-NAME caused a small (3-4 mV) but not statistically significant depolarization of the arteriolar smooth muscle at both pressures. The constrictor effect was not prevented by the K(+)-channel antagonist tetraethyl ammonium (TEA, 1 mM) or the K(ATP) channel antagonist glibenclamide (1 microM). CONCLUSIONS AND IMPLICATIONS These observations demonstrate that L-NAME causes an endothelium- and NOS-independent contraction of vascular smooth muscle in isolated skeletal muscle arterioles. It is suggested that the underlying mechanism relates to an arginine binding interaction.
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Affiliation(s)
- T V Murphy
- Department of Physiology and Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
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19
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Abstract
Genomic instability (GI) is a hallmark of tumorigenic progression and is observed as delayed genetic damage in the progeny of irradiated and unirradiated bystander cells. The expression of GI can be influenced by genotype, cell type and radiation quality. While several studies have demonstrated the induction of GI by high and low-linear energy transfer (LET) radiation, our work on human and mouse primary cell systems has shown LET-dependent differences in the induction and expression of GI. These differences might be attributed to differences in radiation track structure, dose rate, contribution of bystander cells and radiation dose. This paper reviews the role of radiation quality in the induction of GI and describe the possible mechanisms underlining the observed differences between radiation types on its induction. The experimental results presented suggest that dose might be the most significant factor in determining induction of GI after low-LET radiation.
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Affiliation(s)
- M A Kadhim
- Radiation and Genome Stability Unit, Medical Research Council, Harwell, Oxfordshire, UK.
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20
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Pyke EL, Stevens DL, Hill MA. Keeping up with the neighbours--measuring the bystander response. Radiat Prot Dosimetry 2006; 122:266-70. [PMID: 17132670 DOI: 10.1093/rpd/ncl430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Ionising radiation can induce responses within non-exposed neighbouring (bystander) cells, which potentially have important implications on the estimates of risk at environmentally relevant doses. Using human skin fibroblasts (AG1522), a range of methods were used to investigate the nature of the signal(s) arising from the exposed cells. The signal(s) can be transmitted by direct cell-cell communication (investigated by using partial dish irradiations) or by medium-borne factors (a co-culture system where two monolayers share the same medium but only one monolayer is exposed to ionising radiation). CDKN1A was found to be up-regulated in both directly exposed and non-exposed cells. The data suggest that direct cell-cell communication dominates for these confluent cells, with medium-borne factors also contributing.
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Affiliation(s)
- E L Pyke
- MRC Radiation & Genome Instability Unit, Harwell, Oxfordshire OX11 0RD, UK.
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21
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Hill MA, Stevens DL, Kadhim M, Blake-James M, Mill AJ, Goodhead DT. Experimental techniques for studying bystander effects in vitro by high and low-LET ionising radiation. Radiat Prot Dosimetry 2006; 122:260-5. [PMID: 17164272 DOI: 10.1093/rpd/ncl429] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Ionising radiation can induce responses within non-exposed neighbouring (bystander) cells which potentially have important implications on the estimates of risk from low dose or low dose rate exposures of ionising radiations. A range of strategies have been developed for investigating bystander effects in vitro for both high-LET alpha particles or low-LET ultrasoft X rays using either partial shielding (grids, half-shields and slits) or by using a co-culture system where two physically separated populations of cells can be cultured together, allowing one population of cells to be irradiated while the second population remains unirradiated. The techniques described provide a useful tool to study bystander effects and complement microbeam studies. Studies using these systems show significant increases in the unirradiated bystander cells for various end points including the induction of chromosomal instability in haemopoetic stem cells and transformation in CGL1 cells.
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Affiliation(s)
- M A Hill
- MRC Radiation and Genome Instability Unit, Harwell, Oxfordshire OX11 0RD, UK.
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22
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Abstract
BACKGROUND/AIM Alpha-2alpha adrenergic receptor (alpha(2)-AR) agonists are thought to be neuroprotective, preventing retinal ganglion cell death independent of pressure reduction. Previous studies have identified alpha(2)-ARs in rat retina. The authors aimed to demonstrate the presence and localisation of alpha(2)-ARs in human and rat retina and on the rat retinal ganglion cell line, RGC-5. METHODS Seven postmortem human and three postmortem rat eyes were paraformaldehyde fixed and frozen. RGC-5 cells were also paraformaldehyde fixed. The expression of alpha(2A)-ARs was determined by antibody immunofluorescence. RESULTS alpha(2A)-AR expression was identified in the human retina, on ganglion cells, and cells in the inner and outer nuclear layers (INL, ONL). Differential alpha(2A)-AR staining patterns in the INL and ONL suggest a further restriction to as yet unidentified neuronal subclasses. The RGC-5 cell line also expressed alpha(2A)-ARs in undifferentiated cells and an increased expression upon fully differentiated cells. CONCLUSION alpha(2)-AR agonists in addition to their pressure lowering effects in the eye, may act directly upon retinal neurons, including retinal ganglion cells. The presence of alpha(2)-ARs on the RGC-5 cell line allows future investigation of these possible direct effects using in vitro glaucoma model systems.
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Affiliation(s)
- F B Kalapesi
- Department of Anatomy, University of New South Wales, Sydney NSW 2052, Australia
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23
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Hill MA, Ford JR, Clapham P, Marsden SJ, Stevens DL, Townsend KMS, Goodhead DT. Bound PCNA in nuclei of primary rat tracheal epithelial cells after exposure to very low doses of plutonium-238 alpha particles. Radiat Res 2005; 163:36-44. [PMID: 15606305 DOI: 10.1667/rr3282] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Bystander effects from ionizing radiation have been detailed for a number of cell systems and a number of end points. We wished to use a cell culture/ex vivo rat model of respiratory tissue to determine whether a bystander effect detected in culture could also be shown in a tissue. Examination by immunofluorescence techniques of tracheal cell cultures after exposure to very low doses of alpha particles revealed a large proportion of cells with proliferating cell nuclear antigen (PCNA) bound in their nuclei. PCNA was selected as an end point because it is involved in both DNA repair and the changes in cell cycle that are typical of many reported bystander effects. Maximum response can be detected in up to 28% of the cells in sub-confluent cultures with a dose of only 2 mGy. At this dose less than 2% of the cell nuclei have experienced a particle traversal and less than 6% of the cells have experienced an alpha-particle traversal through either their nucleus or some part of their cytoplasm. The hypothesis that this bystander response in nontargeted cells is mediated through secreted factor(s) is presented, and supporting evidence was found using partial irradiation and co-culture experiments. Examination of the effect with excised pieces of trachea demonstrated a response similar to that seen in culture.
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Affiliation(s)
- M A Hill
- Medical Research Council, Radiation and Genome Stability Unit, Harwell, Oxfordshire, OX11 0RD, United Kingdom
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24
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Abstract
Risk factors for the microvascular complications (nephropathy and retinopathy) of Type 1 and Type 2 diabetes mellitus and the associated accelerated atherosclerosis include: age, diabetes duration, genetic factors, hyperglycaemia, hypertension, smoking, inflammation, glycation and oxidative stress and dyslipoproteinaemia. Hypertriglyceridaemia, low HDL and small dense LDL are common features of Type 2 diabetes and Type 1 diabetes with poor glycaemic control or renal complications. With the expansion of knowledge and of clinical and research laboratory tools, a broader definition of 'lipid' abnormalities in diabetes is appropriate. Dyslipoproteinaemia encompasses alterations in lipid levels, lipoprotein subclass distribution, composition (including modifications such as non-enzymatic glycation and oxidative damage), lipoprotein-related enzymes, and receptor interactions and subsequent cell signaling. Alterations occur in all lipoprotein classes; chylomicrons, VLDL, LDL, HDL, and Lp(a). There is also emerging evidence implicating lipoprotein related genotypes in the development of diabetic nephropathy and retinopathy. Lipoprotein related mechanisms associated with damage to the cardiovascular system may also be relevant to damage to the renal and ocular microvasculature. Adverse tissue effects are mediated by both alterations in lipoprotein function and adverse cellular responses. Recognition and treatment of lipoprotein-related risk factors, supported by an increasing array of assays and therapeutic agents, may facilitate early recognition and treatment of high complication risk diabetic patients. Further clinical and basic research, including intervention trials, is warranted to guide clinical practice. Optimal lipoprotein management, as part of a multi-faceted approach to diabetes care, may reduce the excessive personal and economic burden of microvascular complications and the related accelerated atherosclerosis.
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Affiliation(s)
- A J Jenkins
- University of Melbourne, Department of Medicine, St Vincent's Hospital, 3065 Melbourne, Australia.
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25
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Neff GW, O'Brien CB, Cirocco R, Montalbano M, de Medina M, Ruiz P, Khaled AS, Bejarano PA, Safdar K, Hill MA, Tzakis AG, Schiff ER. Prediction of sustained virological response in liver transplant recipients with recurrent hepatitis C virus following combination pegylated interferon alfa-2b and ribavirin therapy using tissue hepatitis C virus reverse transcriptase polymerase chain reaction testing. Liver Transpl 2004; 10:595-8. [PMID: 15108250 DOI: 10.1002/lt.20115] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The optimal duration of therapy for pegylated interferon combined with ribavirin in recurrent Hepatitis C virus (HCV) following liver transplantation is not known. We wanted to determine if testing for HCV in liver tissue by reverse transcriptase polymerase chain reaction (RT-PCR) was superior in predicting sustained virological response (SVR) in comparison to standard HCV ribonucleic acid (RNA) detection in the serum. All recipients received combination pegylated alpha-2b interferon (1.5 mcg/kg) and ribavirin (200-600 mg/d) therapy for at least 48 weeks of therapy and were found to have nondetectable HCV RNA by PCR serum testing at the end of therapy. Sustained virological response (SVR) was defined as nondetectable serum HCV RNA at 6 months post treatment withdrawal. Ten liver transplant recipients were included in the study; mean time from transplantation was 29.2 months. All had nondetectable serum HCV RNA by RT-PCR. In hepatic tissue 7/10 patients HCV RNA was found to be positive by RT-PCR while 3/10 had nondetectable HCV RNA in their liver by RT-PCR. SVR was attained in all 3/10 that were hepatic tissue HCV PCR negative after 12 months of combination therapy. In conclusion, direct detection of HCV RNA by RT-PCR of liver tissue appears to more effectively predict SVR following pegylated interferon and ribavirin therapy than the conventional use of serum.
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Affiliation(s)
- Guy W Neff
- Center for Liver Diseases and Division of GI Transplant, Department of Medicine, University of Miami, FL 33136, USA
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26
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Abstract
The ICRP has attributed the same relative risk for all low-LET (linear energy transfer) radiations, including X and gamma radiations of all energies. However, very low energy X-rays are expected to be more biologically effective, per unit absorbed dose, than high energy X-rays or gamma rays due to the production of lower energy secondary electrons, with a correspondingly higher LET. This increase in relative biological effectiveness (RBE) is also seen experimentally for a range of biological end-points, however, a wide range of RBE values have been reported. The assessment of risks is particularly important due to the use of low energy X-rays for mammography screening. A review of the published data on the variation in biological effectiveness with energy is presented here.
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Affiliation(s)
- M A Hill
- MRC Radiation and Genome Stability Unit, Harwell, Oxfordshire OX11 0RD, UK.
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27
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Abstract
Carbon K ultrasoft x-rays (278 eV) interact with biological material producing random, isolated tracks of single electrons with a range < 7 nm (cf width of DNA helix approximately2 nm). The electron tracks produced by these ultrasoft x-rays are similar to the numerous secondary electrons and 'track ends' produced by essentially all ionizing radiations. They therefore provide a unique tool in the study of mechanisms of radiation action in the cell. Conventional carbon targets used with the Medical Research Councils cold-cathode discharge tubes have a limited lifetime of 40-50 min. We have investigated the use of thin, freestanding diamond films produced using chemical vapour deposition techniques as a new transmission target for a cold-cathode tube. We present here a novel use of diamond to produce CK ultrasoft x-rays for irradiation purposes. The system described produces an entrance absorbed dose rate to attached cells of approximately 0.2 Gy min(-1) which due to the long target lifetime is usable for low dose-rate CK x-ray studies.
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Affiliation(s)
- M A Hill
- Medical Research Council, Radiation & Genome Stability Unit, Harwell, Didcot, Oxfordshire OX11 0RD, UK.
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Hill MA, Stevens DL, Bance DA, Goodhead DT. Biological effectiveness of isolated short electron tracks: V79-4 cell inactivation following low dose-rate irradiation with Al(K) ultrasoft X-rays. Int J Radiat Biol 2002; 78:967-79. [PMID: 12456284 DOI: 10.1080/0955300021000016350] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE To investigate the biological effect of single, isolated, short electron tracks (<70 nm) relevant to practical human exposures to low-linear energy transfer radiation. MATERIALS AND METHODS An irradiation rig was constructed that allowed environmentally controlled, protracted irradiations with an individually prescribed dose to up to 20 samples over a period of days. Inactivation of V79-4 mammalian cells by Al(K) ultrasoft X-rays was studied at high and low dose-rates with a maximum exposure time of 42 h. RESULTS A significant increase in clonogenic survival was observed at the higher doses when the exposure time was increased from <6 min to 21 h, with no further increase observed for 42-h exposures. Despite the short range of the low-energy electrons produced (<70 nm), significant cell inactivation was observed for these low dose-rate exposures. CONCLUSIONS The results are consistent with the hypothesis that even individual tracks can be biologically effective.
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Affiliation(s)
- M A Hill
- MRC Radiation & Genome Stability Unit, Harwell, Didcot OX11 0RD, UK.
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29
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Hill MA, Stevens DL, Marsden SJ, Allot R, Turcu ICE, Goodhead DT. Is the increased relative biological effectiveness of high LET particles due to spatial or temporal effects? Characterization and OER in V79-4 cells. Phys Med Biol 2002; 47:3543-55. [PMID: 12408481 DOI: 10.1088/0031-9155/47/19/308] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The efficiency of producing biological damage varies with radiation quality. Conventional explanations rely on spatial differences in the radiation track structure; generally however there are also very large temporal differences in delivery of the radiation at the cellular level. High-LET radiation normally deposits substantial amounts of energy by individual heavily ionizing tracks on a timescale of the order of picoseconds. By contrast each low-LET radiation track deposits a small amount of energy. Many of these tracks, distributed over the whole cell, are required to deliver an equivalent dose to a high-LET track and they are usually delivered over much longer timescales (typically seconds) during which chemical, biochemical and biological processes are occurring. In this paper the design, characterization and initial application of a high-brightness, laser-plasma ultrasoft x-ray source is described. This has been used to investigate the importance of the temporal differences by irradiating mammalian cells with an energy deposition with spatial properties of low-LET radiation and temporal properties similar to high-LET radiation. The present system delivers a typical dose, to the incident surface of the cells, of 0.12 Gy per pulse delivered in <10 ps. The capabilities of the x-ray source were tested by determining the survival of V79-4 hamster cells irradiated with picosecond pulses of ultrasoft x-rays under aerobic and anaerobic conditions, which were found to be consistent with previously published non pulsed data with x-rays of similar energy. These results support the expectation that the disappearance of an oxygen effect for high-LET radiation particles is due to their spatial properties rather than the very short timescale of each particle traversal. For other effects, particularly non-targeted phenomena such as induced genomic instability, expectations may be less clear cut.
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Affiliation(s)
- M A Hill
- Medical Research Council, Radiation & Genome Stability Unit, Harwell, Didcot, Oxfordshire, UK.
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Fayard B, Touati A, Abel F, Herve du Penhoat MA, Despiney-Bailly I, Gobert F, Ricoul M, L'Hoir A, Politis MF, Hill MA, Stevens DL, Sabatier L, Sage E, Goodhead DT, Chetioui A. Cell inactivation and double-strand breaks: the role of core ionizations, as probed by ultrasoft X rays. Radiat Res 2002; 157:128-40. [PMID: 11835676 DOI: 10.1667/0033-7587(2002)157[0128:ciadsb]2.0.co;2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The large RBE (approximately 7) measured for the killing of Chinese hamster V79 cells by 340 eV ultrasoft X rays, which preferentially ionize the K shell of carbon atoms (Hervé du Penhoat et al., Radiat. Res. 151, 649-658, 1999), was used to investigate the location of sensitive sites for cell inactivation and the physical modes of action of radiation. The enhancement of the RBE above the carbon K-shell edge either may indicate a high intrinsic efficiency of carbon K-shell ionizations (due, for example, to a specific physical or chemical effect) or may be related to the preferential localization of these ionizations on the DNA. The second interpretation would indicate a strong local (within 3 nm) action of K-shell ionizations and consequently the importance of a direct mechanism for radiation lethality (without excluding an action in conjunction with an indirect component). To distinguish between these two hypotheses, the efficiencies of core ionizations in DNA atoms (phosphorus L-shell, carbon K-shell, and oxygen K-shell ionizations) to induce damages were investigated by measuring their capacities to produce DNA double-strand breaks (DSBs). The effect of photoionizations in isolated DNA was studied using pBS plasmids in a partially hydrated state. No enhancement of the efficiency of DSB induction by carbon K-shell ionizations compared to oxygen K-shell ionizations was found, supporting the hypothesis that it is the localization of these carbon K-shell events on DNA which gives to the 340 eV photons their high killing efficiency. In agreement with this interpretation, cell inactivation and DSB induction, which do not appear to be correlated when expressed in terms of yields per unit dose in the sample, exhibit a rather good correlation when expressed in terms of efficiencies per core event in the DNA. These results suggest that core ionizations in DNA, through core-hole relaxation in conjunction with localized effects of spatially correlated secondary and Auger electrons, may be the major critical events for cell inactivation, and that the resulting DSBs (or a constant fraction of these DSBs) may be a major class of unrepairable lesions.
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Affiliation(s)
- B Fayard
- Groupe de Physique des Solides, Universités Paris 7 et Paris (CNRS UMR 75-88, CEA LRC No. 6), Tour 23, 2 place Jussieu, 75251 Paris cedex 05, France
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Abstract
Ion channels are regulated by protein phosphorylation and dephosphorylation of serine, threonine, and tyrosine residues. Evidence for the latter process, tyrosine phosphorylation, has increased substantially since this topic was last reviewed. In this review, we present a comprehensive summary and synthesis of the literature regarding the mechanism and function of ion channel regulation by protein tyrosine kinases and phosphatases. Coverage includes the majority of voltage-gated, ligand-gated, and second messenger-gated channels as well as several types of channels that have not yet been cloned, including store-operated Ca2+ channels, nonselective cation channels, and epithelial Na+ and Cl- channels. Additionally, we discuss the critical roles that channel-associated scaffolding proteins may play in localizing protein tyrosine kinases and phosphatases to the vicinity of ion channels.
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Affiliation(s)
- M J Davis
- Department of Medical Physiology, Cardiovascular Research Institute, Texas A&M University System Health Science Center, College Station, Texas 77845, USA.
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32
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Abstract
Arterioles respond to increased transmural pressure with myogenic constriction. The present study investigated the role of tyrosine phosphorylation in myogenic activity. Cannulated segments of a rat cremaster arteriole were fixed under pressure, followed by incubation with fluorescein isothiocyanate (FITC)-conjugated anti-phosphotyrosine. Smooth muscle cell fluorescence intensity was measured with the use of confocal laser-scanning microscopy. Anti-phosphotyrosine fluorescence intensity in muscle cells of arterioles maintained at 100 mmHg was reduced by the tyrosine kinase inhibitor tyrphostin A47 (30 microM) and increased by the tyrosine phosphatase inhibitor pervanadate (100 microM). In time-course experiments, anti-phosphotyrosine fluorescence increased slowly (over 5 min) after an acute increase in intraluminal pressure, and was dissociated from myogenic contraction (within 1 min). In contrast, angiotensin II (0.1 microM) caused rapid constriction and increased tyrosine phosphorylation. Anti-phosphotyrosine fluorescence was also pressure dependent (10-100 mmHg). Abolition of myogenic activity, either through removal of extracellular Ca2+, or exposure to verapamil (5 microM) or forskolin (0.1 microM) caused a further increase in anti-phosphotyrosine fluorescence. We conclude that transmural pressure and/or wall tension in arterioles causes increased tyrosine phosphorylation; however, this is not involved in the acute phase of myogenic constriction but may be involved in later responses, such as sustained myogenic tone or mechanisms possibly related to growth.
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Affiliation(s)
- T V Murphy
- Microvascular Biology Group, School of Medical Sciences, RMIT University, Bundoora, Victoria 3083, Australia.
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33
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Hill MA, Zou H, Potocnik SJ, Meininger GA, Davis MJ. Invited review: arteriolar smooth muscle mechanotransduction: Ca(2+) signaling pathways underlying myogenic reactivity. J Appl Physiol (1985) 2001; 91:973-83. [PMID: 11457816 DOI: 10.1152/jappl.2001.91.2.973] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The smooth muscle of arterioles responds to an increase in intraluminal pressure with vasoconstriction and with vasodilation when pressure is decreased. Such myogenic vasoconstriction provides a level of basal tone that enables arterioles to appropriately adjust diameter in response to neurohumoral stimuli. Key in this process of mechanotransduction is the role of changes in intracellular Ca(2+). However, it is becoming clear that considerable complexity exists in the spatiotemporal characteristics of the Ca(2+) signal and that changes in intracellular Ca(2+) may play roles other than direct effects on the contractile process via activation of myosin light-chain phosphorylation. The involvement of Ca(2+) may extend to modulation of ion channels and release of Ca(2+) from the sarcoplasmic reticulum, alterations in Ca(2+) sensitivity, and coupling between cells within the vessel wall. The purpose of this brief review is to summarize the current literature relating to Ca(2+) and the arteriolar myogenic response. Consideration is given to coupling of Ca(2+) changes to the mechanical stimuli, sources of Ca(2+), involvement of ion channels, and spatiotemporal aspects of intracellular Ca(2+) signaling.
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Affiliation(s)
- M A Hill
- Microvascular Biology Group, School of Medical Sciences, RMIT University, Bundoora, Victoria 3083, Australia.
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de Dios ST, Hannan KM, Dilley RJ, Hill MA, Little PJ. Troglitazone, but not rosiglitazone, inhibits Na/H exchange activity and proliferation of macrovascular endothelial cells. J Diabetes Complications 2001; 15:120-7. [PMID: 11358680 DOI: 10.1016/s1056-8727(01)00141-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Diabetes is associated with a high level of mortality due to cardiovascular disease resulting from accelerated coronary artery atherosclerosis. A current focus for investigation of atherosclerotic mechanisms is the vascular endothelium since physical or functional injury may represent an initiating step for atherogenesis. Thiazolidinediones (TZDs) are the newest class of drugs for the treatment of insulin resistance and its metabolic consequences; they are peroxisome proliferator-activating receptor (PPAR)-gamma ligands that act as insulin-sensitizing agents. We are interested in the contribution of direct vascular actions to the clinical utility of these agents. We investigated the effect troglitazone and rosiglitazone on endothelial cell proliferation in low- and high-glucose media and further explored their action on the ubiquitous membrane transport system, the Na/H exchanger (NHE), which has been implicated in regulating the growth of vascular cells. Experiments were conducted in cultured bovine aortic endothelial cells (BAECs). Cell proliferation was assessed by cell counting, and NHE activity was determined in cells loaded with the pH-sensitive fluorescent dye, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester (BCECF-AM). Troglitazone caused a dose-dependent inhibition of endothelial cell proliferation with approximately 50% inhibition at 10 microM. Troglitazone inhibited endothelial cell proliferation with similar potency under low- (5 mM) and high-glucose (25 mM) concentrations. Rosiglitazone had no significant effect on endothelial cell proliferation at concentrations of up to 100 microM under low- or high-glucose concentrations. The NHE inhibitor, 3-metlylsulfonyl-4-piperidinobenzoyl guanidine (HOE 694), caused dose dependent inhibition of BAEC proliferation, which was independent of the media glucose concentration. Acute exposure of cells to troglitazone (10 microM) and rosiglitazone (30 microM) during recovery from acidosis showed slight but significant (P<.05) inhibition of NHE activity by troglitazone, but no significant (P>.05) effect by rosiglitazone. Exposure of cells to either drug for 24 h revealed no chronic regulation of NHE activity. Our data demonstrate that troglitazone has similar actions in endothelial cells as in vascular smooth muscle. The absence of rosiglitazone effects, a more potent PPAR-gamma activator, suggests that the observed actions of troglitazone may be at least partially independent of PPAR-gamma. The effects of troglitazone and rosiglitazone on endothelial cell proliferation and NHE activity, although contrasting, are consistent with a central signalling role of this transporter in cell proliferation.
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Affiliation(s)
- S T de Dios
- Cell Biology of Diabetes Laboratory, Baker Medical Research Institute, P.O. Box 6492, Victoria, Melbourne 8008, Australia
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35
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Abstract
This review summarizes what is currently known about the role of integrins in the vascular myogenic response. The myogenic response is the rapid and maintained constriction of a blood vessel in response to pressure elevation. A role for integrins in this process has been suggested because these molecules form an important mechanical link between the extracellular matrix and the vascular smooth muscle cytoskeleton. We briefly summarize evidence for a general role of integrins in mechanotransduction. We then describe the integrin subunit combinations known to exist in smooth muscle and the vascular wall matrix proteins that may interact with these integrins. We then discuss the effects of integrin-specific peptides and antibodies on vascular tone and on calcium entry mechanisms in vascular smooth muscle. Because integrin function is linked to the cytoskeleton, we discuss evidence for the role of the cytoskeleton in determining myogenic responsiveness. Finally, we analyze evidence that integrin-linked signaling pathways, such as those involving protein tyrosine phosphorylation cascades and mitogen-activated protein kinases, are required for myogenic tone.
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Affiliation(s)
- M J Davis
- Department of Medical Physiology, Cardiovascular Research Institute, Texas A&M University System Health Science Center, College Station, Texas 77845-1114, USA.
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36
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37
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de Lara CM, Hill MA, Jenner TJ, Papworth D, O'Neill P. Dependence of the yield of DNA double-strand breaks in Chinese hamster V79-4 cells on the photon energy of ultrasoft X rays. Radiat Res 2001; 155:440-8. [PMID: 11182795 DOI: 10.1667/0033-7587(2001)155[0440:dotyod]2.0.co;2] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [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: 11/03/2022]
Abstract
Induction of DNA DSBs by low-LET radiations reflects clustered damage produced predominantly by low-energy, secondary electron "track ends". Cell inactivation and induction of DSBs and their rejoining, assayed using pulsed-field gel electrophoresis, were determined in Chinese hamster V79-4 cells irradiated as a monolayer with characteristic carbon K-shell (CK) (0.28 keV), aluminum K-shell (AlK) (1.49 keV), and titanium K-shell (TiK) (4.55 keV) ultrasoft X rays under aerobic and anaerobic conditions. Relative to (60)Co gamma rays, the relative biological effectiveness (RBE) for cell inactivation at 10% survival and for induction of DSBs increases as the photon energy of the ultrasoft X rays decreases. The RBE values for cell inactivation and for induction of DSBs by CK ultrasoft X rays are 2.8 +/- 0.3 and 2.7 +/- 0.3, respectively, and by TiK ultrasoft X rays are 1.5 +/- 0.1 and 1.4 +/- 0.1, respectively. Oxygen enhancement ratios (OERs) of approximately 2 for cell inactivation and induction of DSBs by ultrasoft X rays are independent of the photon energy. The time scale for rejoining of DNA DSBs is similar for both ultrasoft X rays and 60Co gamma rays. From the size distribution of small DNA fragments down to 0.48 kbp, we concluded that DSBs are induced randomly by CK and AlK ultrasoft X rays. Therefore, ultrasoft X rays are more efficient per unit dose than gamma radiation at inducing DNA DSBs, the yield of which increases with decreasing photon energy.
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Affiliation(s)
- C M de Lara
- MRC Radiation and Genome Stability Unit, Harwell, Didcot, Oxfordshire, OX11 0RD, United Kingdom
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38
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Smith FA, Hill MA, Wilkinson I, Meek JH. A Monte Carlo simulation of fast neutron beams used for radiotherapy: I. Dose deposition by a collimated (d, t) beam. Phys Med Biol 2000. [DOI: 10.1088/0031-9155/34/8/001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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39
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40
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Abstract
1. Seizure threshold is an important variable in modern ECT treatment planning. To date, age, gender, and electrode placement have been used to predict seizure threshold, but the potential impact of ethnicity has received little attention. 2. In a retrospective pilot study of patients who received ECT, 20 pairs of first admission, right unilateral-treated, age- and sex-matched black and white patients were compared. 3. Black patients had higher seizure thresholds and were more likely to require restimulation, despite the finding that they were more likely to have been receiving concomitant medications which lower seizure threshold. However, ethnicity was confounded with variations in ECT dose titration, which were the strongest predictor of seizure threshold. 4. There were no differences in seizure length. Further study is necessary to confirm the impact of ethnicity on seizure threshold.
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Affiliation(s)
- K Dawkins
- Department of Psychiatry, University of North Carolina, Chapel Hill 27599-7160, USA.
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41
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Zou H, Ratz PH, Hill MA. Temporal aspects of Ca(2+) and myosin phosphorylation during myogenic and norepinephrine-induced arteriolar constriction. J Vasc Res 2000; 37:556-67. [PMID: 11146410 DOI: 10.1159/000054089] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Previous studies demonstrated that maintenance of steady-state myogenic tone requires Ca(2+)-dependent myosin phosphorylation. The present studies furthered these observations by examining temporal relationships among Ca(2+), myosin phosphorylation and vessel diameter during acute increases in intraluminal pressure and norepinephrine stimulation. Rat cremaster muscle arterioles were cannulated and loaded with the Ca(2+)-sensitive indicator fura-2. The extent of myosin phosphorylation was measured using two-dimensional gel electrophoresis. Acute increases in intraluminal pressure caused a biphasic increase in intracellular Ca(2+) ([Ca(2+)](i)), characterized by a transient peak followed by a decline to a steady-state level which remained significantly higher than control values. Peak [Ca(2+)](i) was significantly related to vessel distension and increased with the change in wall tension. Increased intraluminal pressure resulted in a monophasic increase in myosin phosphorylation that was significantly correlated with instantaneous wall tension. In general, norepinephrine induced larger [Ca(2+)](i) transients and a biphasic myosin phosphorylation pattern. The results demonstrate: (a) major roles for Ca(2+) and myosin phosphorylation in arteriolar myogenic and norepinephrine-induced responses; (b) that changes in Ca(2+) and phosphorylation during a myogenic response are related to changes in wall tension, and (c) differences in Ca(2+) and phosphorylation patterns between the two modes of contraction reflect possible differences in underlying signaling mechanisms. The data further emphasize that spontaneous arteriolar tone represents a state of maintained smooth muscle activation that requires increases in [Ca(2+)](i) and myosin light-chain phosphorylation.
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Affiliation(s)
- H Zou
- Department of Physiology, Eastern Virginia Medical School, Norfolk, Va., USA
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42
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Tos P, Battiston B, Geuna S, Giacobini-Robecchi MG, Hill MA, Lanzetta M, Owen ER. Tissue specificity in rat peripheral nerve regeneration through combined skeletal muscle and vein conduit grafts. Microsurgery 2000; 20:65-71. [PMID: 10702739 DOI: 10.1002/(sici)1098-2752(2000)20:2<65::aid-micr4>3.0.co;2-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [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: 01/09/2023]
Abstract
Diffusible factors from the distal stumps of transected peripheral nerves exert a neurotropic effect on regenerating nerves in vivo (specificity). This morphological study was designed to investigate the existence of tissue specificity in peripheral nerve fiber regeneration through a graft of vein filled with fresh skeletal muscle. This tubulization technique demonstrated experimental and clinical results similar to those obtained with traditional autologous nerve grafts. Specifically, we used Y-shaped grafts to assess the orientation pattern of regenerating axons in the distal stump tissue. Animal models were divided into four experimental groups. The proximal part of the Y-shaped conduit was sutured to a severed tibial nerve in all experiments. The two distal stumps were sutured to different targets: group A to two intact nerves (tibial and peroneal), group B to an intact nerve and an unvascularized tendon, group C to an intact nerve and a vascularized tendon, and group D to a nerve graft and an unvascularized tendon. Morphological evaluation by light and electron microscopy was conducted in the distal forks of the Y-shaped tube. Data showed that almost all regenerating nerve fibers spontaneously oriented towards the nerve tissue (attached or not to the peripheral innervation field), showing a good morphological pattern of regeneration in both the early and late phases of regeneration. When the distal choice was represented by a tendon (vascularized or not), very few nerve fibers were detected in the corresponding distal fork of the Y-shaped graft. These results show that, using the muscle-vein-combined grafting technique, regenerating axons are able to correctly grow and orientate within the basement membranes of the graft guided by the neurotropic lure of the distal nerve stump.
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Affiliation(s)
- P Tos
- Gruppo Interdivisionale di Microchirurgia (G.I.M), Ospedale C.T.O., Turin, Italy.
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43
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Gillespie RR, Hill MA, Kanitz CL, Knox KE, Clark LK, Robinson JP. Infection of pigs by Aujeszky's disease virus via the breath of intranasally inoculated pigs. Res Vet Sci 2000; 68:217-22. [PMID: 10877966 DOI: 10.1053/rvsc.1999.0364] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Aujeszky's disease is a worldwide problem in the pig industry. In this experiment, four pigs chosen to act as shedder pigs were intranasally infected with Aujeszky's disease virus. Next, on three consecutive days, eight recipient pigs were exposed to the breath of a pair of shedder pigs via a mask-to-mask module. Except for the virtual absence of CNS signs, shedder pigs expressed clinical signs that were similar to pigs infected naturally or experimentally. Only mild respiratory signs occurred in recipient pigs, but all were infected by aerosols of Aujeszky's disease virus as evidenced by seroconversion. The pig is a much more sensitive indicator of airborne virions than our aerosol collection methods. We conclude that the mild respiratory disease acquired by the aerogenous route in recipient pigs is an easily managed model for studying the transmission of airborne respiratory infections and the immune responses to this type of infection.
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Affiliation(s)
- R R Gillespie
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA
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44
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Abstract
Pressure is a crucial component of the cellular environment, and can lead to pathology if it varies beyond its normal range. The increased intra-ocular pressures in acute glaucoma are associated with the loss of neurons by apoptosis. Little is known regarding the interaction between pressure and apoptosis at the level of the cell. The model developed in this study examines the effects of elevated ambient hydrostatic pressure directly upon cultured neuronal lines. Conditions were selected to be within physiological limits: 100 mmHg over and above atmospheric pressure for a period of 2 hr, as seen clinically in acute glaucoma. This system can be used to investigate pressure relatively independently of other variables. Neuronal cell line cultures (B35 and PC12) were subjected to pressure conditions in specially designed pressure chambers. Controls were treated identically, except for the application of pressure, and positive controls were treated with a known apoptotic stimulus. Apoptosis was detected by cell morphology changes and by 2 specific apoptotic markers: TUNEL (Terminal transferase dUTP Nick-End Labeling) and Annexin V. These fluorescent markers were detected and quantified by automated Laser Scanning Cytometry. All techniques showed that increased pressure was associated with a greater level of apoptosis compared to equivalent controls. Our results suggest that pressure alone may act as a stimulus for apoptosis in neuronal cell cultures. This raises the possibility of a more direct relationship at the cellular level between pressure and neuronal loss.
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Affiliation(s)
- A Agar
- Cell Biology Lab, School of Anatomy, University of New South Wales, Sydney, Australia
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45
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Hill MA, Burke FJ, Cheung SW, Qualtrough AJ, Wilson NH. Techniques used by a group of United Kingdom-based dental practitioners during the provision of indirect tooth-coloured restorations. Prim Dent Care 2000; 7:77-82. [PMID: 11404971 DOI: 10.1308/135576100322732229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A number of techniques involving the use of various instruments, brushes and devices have been described for the removal of excess luting material and subsequent finishing around the margins of indirect tooth-coloured restorations. There is little information available on the clinical techniques employed by UK dental practitioners in the placement of these restorations, or on the effectiveness of these techniques. A questionnaire was designed to elicit such information. This was distributed to 500 UK-based dental practitioners. A total of 301 practitioners returned completed questionnaires, giving a response rate of 60%. The results indicated that 88% of the respondents routinely provided porcelain veneers for their patients, with 94% of these respondents indicating that they routinely prepared teeth during the provision of such restorations. A light-cured resin composite luting material was used by 29% of the respondents in placement of veneers, while 69% used a dual cured composite. Excess uncured luting material was removed by a number of methods and a variety of methods were used by respondents to finish the margins of the veneers after placement. Of the respondents 68% indicated that they routinely provided tooth-coloured inlays and onlays, with 89% indicating that they routinely used a dentine bonding system when luting their indirect tooth-coloured restorations. It is concluded that a high proportion of the practitioners surveyed were providing porcelain veneers and tooth-coloured inlays and that a wide variety of materials and finishing techniques were being used.
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Affiliation(s)
- M A Hill
- University of Birmingham School of Dentistry
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46
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Widmer WR, Buckwalter KA, Fessler JF, Hill MA, VanSickle DC, Ivancevich S. Use of radiography, computed tomography and magnetic resonance imaging for evaluation of navicular syndrome in the horse. Vet Radiol Ultrasound 2000; 41:108-16. [PMID: 10779069 DOI: 10.1111/j.1740-8261.2000.tb01463.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Radiographic evaluation of navicular syndrome is problematic because of its inconsistent correlation with clinical signs. Scintigraphy often yields false positive and false negative results and diagnostic ultrasound is of limited value. Therefore, we assessed the use of computed tomography and magnetic resonance imaging in a horse with clinical and radiographic signs of navicular syndrome. Cadaver specimens were examined with spiral computed tomographic and high-field magnetic resonance scanners and images were correlated with pathologic findings. Radiographic changes consisted of bony remodeling, which included altered synovial fossae, increased medullary opacity, cyst formation and shape change. These osseous changes were more striking and more numerous on computed tomographic and magnetic resonance images. They were most clearly defined with computed tomography. Many osseous changes seen with computed tomography and magnetic resonance imaging were not radiographically evident. Histologically confirmed soft tissue alterations of the deep digital flexor tendon, impar ligament and marrow were identified with magnetic resonance imaging, but not with conventional radiography. Because of their multiplanar capability and tomographic nature, computed tomography and magnetic resonance imaging surpass conventional radiography for navicular imaging, facilitating earlier, more accurate diagnosis. Current advances in imaging technology should make these imaging modalities available to equine practitioners in the future.
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Affiliation(s)
- W R Widmer
- School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA
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47
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Abstract
Studies were performed to determine the significance of temporal variation in vascular smooth muscle Ca(2+) signaling during acute arteriolar myogenic constriction and, in particular, the importance of the stretch-induced intracellular Ca(2+) concentration ([Ca(2+)](i)) transient in attaining a steady-state mechanical response. Rat cremaster arterioles (diameter approximately 100 microm) were dissected from surrounding tissues, and vessel segments were pressurized in the absence of intraluminal flow. For [Ca(2+)](i) measurements, vessels were loaded with fura 2 and fluorescence emitted by excitation at 340 and 380 nm was measured using video-based image analysis. Ca(2+) and diameter responses were examined after increases in intravascular pressure were applied as an acute step increase or a ramp function. Additional studies examined the effect of longitudinal vessel stretch on [Ca(2+)](i) and arteriolar diameter. Step increase in intraluminal pressure (from 50 to 120 mmHg) caused biphasic change in [Ca(2+)](i) and diameter. [Ca(2+)](i) transiently increased to 114.0 +/- 2.0% of basal levels and subsequently declined to 106.7 +/- 4.4% at steady state. Diameter initially distended to 125.4 +/- 2.1% of basal levels before constricting to 71.1 +/- 1.2%. In contrast, when the same pressure increase was applied as a ramp function (over 5 min) transient vessel distension and transient increase in [Ca(2+)](i) were prevented, yet at steady state vessels constricted to 71.3 +/- 2.5%. Longitudinal stretch resulted in a large [Ca(2+)](i) transient (158 +/- 19% of basal) that returned to baseline despite maintenance of the stretch stimulus. The data demonstrate that the initial vessel distension (reflecting myocyte stretch) and associated global [Ca(2+)](i) transient are not obligatory for myogenic contraction. Thus, although arteriolar smooth muscle cells are responsive to acute stretch, the resulting changes in myogenic tone may be more closely related to other mechanical variables such as wall tension.
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Affiliation(s)
- M A Hill
- Department of Human Biology and Movement Science, RMIT University, Bundoora 3083, Australia.
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48
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Abstract
The present study investigated the role of protein tyrosine phosphorylation in myogenic responsiveness of rat skeletal muscle arterioles. Arteriolar segments were cannulated and pressurized without intraluminal flow. All vessels studied developed spontaneous tone and demonstrated significant myogenic constriction to step changes in pressure with a resultant increase in myogenic tone over an intraluminal pressure range of 50-150 mmHg. Step increases in intraluminal pressure from 50 to 120 mmHg caused a rapid and sustained elevation in intracellular [Ca(2+)], as measured using fura 2. Vessels with myogenic tone dilated in response to tyrosine kinase inhibitors genistein (10 or 30 microM) and tyrphostin A47 (10 or 30 microM) and constricted to the tyrosine phosphatase inhibitor pervanadate (1 or 10 microM). Despite the dilator effect, myogenic reactivity was not blocked by the inhibitors. Daidzein (10 microM), a compound structurally similar to genistein but without tyrosine kinase-inhibiting activity, did not alter vessel tone or myogenic responses. Preincubation of arterioles with genistein or tyrphostin A47 did not significantly alter baseline arteriolar [Ca(2+)], and neither drug reduced the increase in [Ca(2+)] following an acute increase in intraluminal pressure. Constriction induced by pervanadate (10 microM) was not accompanied by a significant increase in intracellular [Ca(2+)], even though removal of extracellular Ca(2+) reversed the constriction. Examination of smooth muscle tyrosine phosphorylation, using a fluorescent phosphotyrosine antibody and confocal microscopy, showed that increased intraluminal pressure resulted in an increase in anti-phosphotyrosine fluorescence. Because manipulation of tyrosine kinase activity was found to alter vessel diameter, these data support a role for tyrosine phosphorylation in modulation of arteriolar tone. However, the results indicate that acute arteriolar myogenic constriction does not require tyrosine phosphorylation.
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Affiliation(s)
- B E Spurrell
- Microvascular Biology Group, Department of Human Biology and Movement Science, RMIT University, Bundoora, Victoria 3083, Australia
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49
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Abstract
Decreased arteriolar distensibility in diabetes may impair signal transduction mechanisms that are required for converting a pressure stimulus into smooth muscle contraction. These studies aimed to determine if pressure-induced increases in arteriolar intracellular Ca(2+) are altered in diabetes and whether diabetes is associated with alterations in composition of the extracellular matrix. Studies of mechanical properties used single, isolated, and cannulated cremaster arterioles from streptozotocin (60 mg/kg) diabetic rats and age-matched controls. To measure Ca(2+)(i), arterioles were loaded with Fura 2 (5 microM) after which preparations were examined by fluorescence microscopy and image analysis. Matrix protein (type IV collagen, laminin, fibronectin) deposition was studied by immunohistochemistry. Over a range of 30-120 mm Hg control vessels showed a linear relationship (r = 0.98, p < 0.01) between intraluminal pressure and Ca(2+)(i). Vessels from diabetic animals also showed a linear relationship (r = 0.99, p < 0.01), however, the mean slope was significantly (p < 0.02) less in the diabetic (0.17 +/- 0.05, n = 5) compared to controls (0.51 +/- 0.09, n = 7). Similarly, the slope of the wall tension-Ca(2+)(i) relationship was significantly decreased in vessels from diabetic animals. These differences were ameliorated by treatment of diabetic animals (n = 5) with aminoguanidine. Increased content of type IV collagen, laminin and fibronectin in vessel media was evident after 2 weeks of diabetes and showed a further increase with duration of diabetes. The data suggest that for a given increase in luminal pressure arterioles from diabetic animals response with an attenuated rise in smooth muscle Ca(2+)(i). This mechanotransduction defect may relate to alterations in the composition of the extracellular matrix within the arteriolar wall.
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Affiliation(s)
- G Yu
- Department of Physiology, Eastern Virginia Medical School, Norfolk, VA, USA
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50
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Abstract
Microtubules are important cytoskeletal elements that have been shown to play a major role in many cellular processes because of their mechanical properties and/or their participation in various cell signaling pathways. We tested the hypothesis that depolymerization of microtubules would alter vascular smooth muscle (VSM) tone and hence contractile function. In our studies, isolated cremaster arterioles exhibited significant vasoconstriction that developed over a 20- to 40-min period when they were treated with microtubule depolymerizing drugs colchicine (10 microM), nocodazole (10 microM), or demecolcine (10 microM). Immunofluorescent labeling of microtubules in cultured rat VSM revealed that both colchicine and nocodazole caused microtubule depolymerization over a similar time course. The vasoconstriction was maintained over a wide range of intraluminal pressures (30-170 cmH(2)O). The increased tone was not affected by endothelial denudation, suggesting that it was due to an effect on VSM. Microtubule depolymerization with demecolcine or colchicine had no effect on VSM intracellular Ca(2+) concentration ([Ca(2+)](i)). These data indicate that microtubules significantly interact with processes leading to the expression of vasomotor tone. The mechanism responsible for the effect of microtubules on vasomotor tone appears to be independent of both the endothelium and an increase in VSM [Ca(2+)](i).
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Affiliation(s)
- S H Platts
- Cardiovascular Research Institute and Department of Medical Physiology, Texas A&M University System Health Science Center, College Station, Texas 77843-1114, USA
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