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Biomedical subjects

Peter James

Publications and source records attributed to Peter James.

At least 19 recordsLinked to original sources
PubMed2007

Binding of calcium ions and SNAP-25 to the hexa EF-hand protein secretagogin.

Secretagogin is a hexa EF-hand protein, which has been identified as a novel potential tumour marker. In the present study, we show that secretagogin binds four Ca2+ ions (log K1=7.1+/-0.4, log K2=4.7+/-0.6, log K3=3.6+/-0.7 and log K4=4.6+/-0.6 in physiological salt buffers) with a [Ca2+](0.5) of approx. 25 microM. The tertiary structure of secretagogin changes significantly upon Ca2+ binding, but not upon Mg2+ binding, and the amount of exposed hydrophobic surface in secretagogin increases upon Ca2+ binding, but not upon Mg2+ binding. These properties suggest that secretagogin belongs to the 'sensor' family of Ca2+-binding proteins. However, in contrast with the prototypical Ca2+ sensor calmodulin, which interacts with a very large number of proteins, secretagogin is significantly less promiscuous. Only one secretagogin-interacting protein was reproducibly identified from insulinoma cell lysates and from bovine and mouse brain homogenates. This protein was identified as SNAP-25 (25 kDa synaptosome-associated protein), a protein involved in Ca2+-induced exocytosis in neurons and in neuroendocrine cells. K(d) was determined to be 1.2x10(-7) M in the presence of Ca2+ and 1.5x10(-6) M in the absence of Ca2+. The comparatively low Ca2+ affinity for secretagogin and the fact that it undergoes Ca2+-induced conformational changes and interacts with SNAP-25 raise the possibility that secretagogin may link Ca2+ signalling to exocytotic processes.

Calcium↗
PubMed2006

Proteome analysis of cultured fibroblasts from type 1 diabetic patients and normal subjects.

CONTEXT: Protein profiling of diabetic tissues could provide useful biomarkers for early diagnosis, therapeutic targets, and disease response markers. Cultured fibroblasts are a useful in vitro model for proteome analysis and study of the molecular mechanisms involved in diabetes. OBJECTIVE: The objective of the study was to isolate and characterize the proteins of cultured fibroblasts, obtained by skin biopsy, from long-term type 1 diabetic patients without complications and age- and sex-matched normal subjects as controls. DESIGN: Proteins were separated by two-dimensional electrophoresis (2-DE), and the gel images were qualitatively and quantitatively analyzed. Protein identification was performed by matrix-assisted laser desorption/ionization mass spectrometry. RESULTS: Reproducible protein maps of fibroblasts from diabetic and healthy subjects were obtained. A total of 125 protein spots were isolated and identified, among them 27 proteins not previously reported in published human fibroblast 2-DE maps, including 20 proteins never reported previously in the literature in human skin fibroblasts. Quantitative analyses revealed six protein spots differentially expressed in the fibroblasts from the diabetic vs. the control subjects (P < 0.05), representing glycolytic enzymes and structural proteins. An increase of triosephosphate I isomerase of two splice isoforms of pyruvate kinase and alpha-actinin 4 and a decrease of tubulin-beta2 and splice isoform 2 of tropomyosin beta-chain were detected. CONCLUSIONS: We generated 2-DE reference maps of the proteome of human skin fibroblasts from both normal and uncomplicated type 1 diabetic patients. Differences in glycolytic enzymes and structural proteins were found. The functional implications of the identified proteins are discussed.

Adult↗
PubMed2006

Chemical derivatization of phosphoserine and phosphothreonine containing peptides to increase sensitivity for MALDI-based analysis and for selectivity of MS/MS analysis.

Protein phosphorylation is one of the most important and common ways of regulating protein function in cells. However, phosphopeptides are difficult to analyse, ionising poorly under standard MALDI conditions. Several methods have been developed to deal with the low sensitivity and specificity of phosphopeptide analysis. Here, we show an approach using a simple one-step beta-elimination/Michael addition reaction for the derivatization of phosphoserine and phosphothreonine. The substitution of the negatively charged phosphate group by a positively charged S-ethylpyridyl group greatly improves the ionisation of the modified peptides, especially in MALDI MS, increasing the sensitivity of the analysis. The modification allows the formation of a unique fragment ion at m/z 106 under mild collisional activation conditions, which can be used for parent (precursor) ion scanning in order to improve both the sensitivity and the selectivity of the analysis. The optimisation of the approach is described for a standard model peptide and protein and then applied to phosphorylation analysis in two biologically derived proteins purified from different experimental systems.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2006

Report. Proteomics education, an important challenge for the scientific community: report on the activities of the EuPA Education Committee.

The main missions of the EuPA Education Committee (EuPA-EC) are to promote and enhance the quality of proteomics knowledge by creating educational programs and to initiate European-wide scientific exchange programs for young proteomics researchers. In this first report we present the initial actions we have undertaken in relation to the missions of the EuPA-EC, and the educational activities that have been planned for 2007-2008. These activities include courses (basic and advanced courses and a summer school), workshops, laboratory networking and tutorials.

Curriculum↗
PubMed2006

140 mouse brain proteins identified by Ca2+-calmodulin affinity chromatography and tandem mass spectrometry.

Calmodulin is an essential Ca2+-binding protein that binds to a variety of targets that carry out critical signaling functions. We describe the proteomic characterization of mouse brain Ca2+-calmodulin-binding proteins that were purified using calmodulin affinity chromatography. Proteins in the eluates from four different affinity chromatography experiments were identified by 1-DE and in-gel digestion followed by LC-MS/MS. Parallel experiments were performed using two related control-proteins belonging to the EF-hand family. After comparing the results from the different experiments, we were able to exclude a significant number of proteins suspected to bind in a nonspecific manner. A total of 140 putative Ca2+-calmodulin-binding proteins were identified of which 87 proteins contained calmodulin-binding motifs. Among the 87 proteins that contained calmodulin-binding motifs, 48 proteins have not previously been shown to interact with calmodulin and 39 proteins were known calmodulin-binding proteins. Many proteins with ill-defined functions were identified as well as a number of proteins that at the time of the analysis were described only as ORFs. This study provides a functional framework for studies on these previously uncharacterized proteins.

Animals↗
PubMed2006

Comparison of MS/MS methods for protein identification from 2D-PAGE.

We have compared the use of a low resolution MALDI-Ion Trap MS/MS and a high-resolution ESI-TOF-MS/MS for the analysis of spots from 2D gels. The main criteria were speed and accuracy of protein identification. The results obtained using the MALDI-MS/MS system are comparable to those from the LC-MS/MS system in terms of accuracy, but less low-level proteins are identified while the time required for the analysis is dramatically reduced.

Computational Biology↗
PubMed2006

Systemic administration of alcohol to adult rats inhibits leydig cell activity: Time course of effect and role of nitric oxide.

BACKGROUND: Alcohol has been shown to interfere with testosterone (T) release from Leydig cells. However, the mechanisms responsible for this phenomenon, which may include decreased activity of the luteinizing hormone-releasing hormone (LHRH)-LH axis, as well as a direct influence of the drug on the testes, are not fully understood. In this work, we investigated the influence of alcohol, administered intragastrically (i.g.) or delivered via vapors, on Leydig cell activity and T release. Leydig cell function was studied by measuring changes in the levels of the steroidogenic proteins steroidogenic acute regulatory (StAR), the peripheral-type benzodiazepine receptor (PBR), and the cytochrome P450 side-chain cleavage enzyme (P450scc). Testosterone release was studied under basal conditions or in response to human chorionic gonadotropin (hCG). Finally, to identify potential factors mediating the influence of alcohol, we measured the testicular variant of the neuronal nitric oxide (NO) synthase (NOS), TnNOS, in semipurified Leydig cells. METHODS: Adult male Sprague-Dawley rats were either injected with alcohol i.g. once or exposed to alcohol vapors (4 h/d) for 1 or 5 days. Controls received the vehicle (i.g. model) or were kept in boxes through which no vapors were circulated. Following these treatments, one series of experiments was devoted to investigate Leydig cell responsiveness by measuring plasma T levels before or after the intravenous injection of hCG (1 U/kg). In another series of experiments, we used semipurified Leydig cell preparations to measure StAR, PBR, P450scc, and TnNOS by Western blot analysis. RESULTS: In the i.g. model, the T response to hCG was blunted for 12 hours following alcohol injection, but showed a rebound at 48 hours. Levels of StAR protein and of PBR, but not of P450scc, were significantly decreased within 10 minutes of drug administration. While StAR then remained depressed for 24 hours, PBR values were variable over this time course. By 48 hours, StAR, PBR, and P450scc levels had increased above control values. Both StAR and PBR levels showed correlations with plasma T levels. In the alcohol vapor models, both regimens of the drug also significantly depressed StAR and PBR protein concentrations, blunted the T response to hCG, and did not alter P450scc. Finally, we observed that alcohol delivered i.g. or via vapors up-regulated TnNOS levels in Leydig cells, but that blockade of NO formation failed to restore a normal T response to hCG. CONCLUSIONS: Collectively, these results suggest that (a) the ability of Leydig cells to release T does not show a simple correlation with changes in StAR, PBR, and P450scc levels; (b) the time course of the alcohol-induced changes were protein-specific; and (c) despite the ability of alcohol to stimulate TnNOS expression, NO does not appear to mediate the inhibitory influence of this drug on testicular steroidogenesis in the models that we studied.

Administration, Inhalation↗
PubMed2005

Predictors of quality of life in ulcerative colitis: the importance of symptoms and illness representations.

BACKGROUND: Establishing predictors of quality of life (QoL) in individuals with inflammatory bowel disease could help to identify those patients who are most likely to experience poor QoL and to target therapeutic interventions appropriately. We aimed to investigate how disease-specific QoL depends on demographic, diseaserelated, and physiological markers of disease activity, cognitive representations of illness, and perceived general health status. METHODS: A total of 111 individuals completed the Inflammatory Bowel Disease Questionnaire (IBDQ), the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and the Illness Perception Questionnaire (IPQ). The extent of disease was determined from records, and disease activity was determined by a symptom index. Bivariate analyses and multivariate regression models were used to identify predictors of disease-specific QoL. RESULTS: Bivariate analyses showed that symptom-related disease activity, elements of illness representation measured by the IPQ, and elements of physical and mental health measured by the SF-36 were the only variables that were strongly or moderately correlated with disease-specific QoL. Multivariate regression modeling showed that disease activity was the major explanatory variable for each of the 4 domains and for the total score on the IBDQ. CONCLUSION: This study highlights the strong relationship between individuals' symptoms and all domains of their health-related QoL, but shows little association with age, gender, physiological markers of disease activity, or anatomic disease extent. Perceptions of the condition were relatively weak predictors of self-reported QoL. The best strategy for improving QoL among individuals with ulcerative colitis may be to find ways to reduce their symptoms.

Adult↗
PubMed2005

Caring for carers of people with stroke: developing a complex intervention following the Medical Research Council framework.

OBJECTIVE: To develop an intervention, using the first three phases of the Medical Research Council (MRC) framework for complex interventions, to facilitate coping skills in new carers of stroke patients. METHODS: In the preclinical (theoretical) phase, a theoretically based framework for a small group course for carers of people with stroke was developed. The intervention was grounded in a cognitive behavioural model and included carers' needs identified from a literature review. Phase I (modelling phase) comprised a qualitative study involving one-to-one semi-structured interviews with a purposive sample of informal carers of people with stroke. Following this, the intervention was modified. In phase II (exploratory phase), the modified intervention was delivered by a clinical psychologist and stroke nurse practitioner to five carers. Following postcourse interviews the course was further refined and delivered to seven new carers who subsequently completed a satisfaction questionnaire. RESULTS: Carers' needs identified from the literature included information provision; managing emotions; social support; health maintenance; and practical problem solving. Consultation with existing carers confirmed these as important issues with a strong emphasis on finding niches of control in life, becoming an expert carer, and dealing with emotional upheaval. Participants reported feeling more optimistic and empowered subsequent to the course. CONCLUSIONS: The MRC framework provided a useful methodology for the development of a complex intervention. The course aimed to assist carers to regain control over aspects of their lives and manage their emotions. It was feasible to run and acceptable to carers; however a randomized controlled trial (RCT) is required to evaluate its effectiveness.

Adaptation, Psychological↗
PubMed2004

Molecular diffusion in sperm plasma membranes during epididymal maturation.

Fluorescence recovery after photobleaching (FRAP) analysis has been used to measure lipid diffusion in different regions of the sperm plasma membrane. Our goal has been to understand how some membrane components are confined to specific surface domains, whilst others are freely diffusing and in some cases are able to migrate against large concentration gradients. Results with a variety of fluorescent lipid reporter probes (ODAF, NBD-PC, NBD-cholesterol) show that diffusion coefficients (D) are generally three to four times higher on the sperm acrosome than on the principal piece of the tail and increase significantly during epididymal maturation (ram, mouse, goat, dog and monkey sperm). Cholesterol diffusion is approximately 10 times faster on the sperm head than the tail and has a heterogenous distribution when detected with filipin. Lipid diffusion is very temperature sensitive but remarkably insensitive to changes in external pH and osmotic pressure. There was no evidence that the posterior ring or annulus functioned as diffusion barriers to lipids. On this basis it was possible to construct models of increasing complexity to describe the behaviour of a lipid molecule on the sperm surface, beginning with simple linear diffusion progressing to random diffusion and eventually to constrained diffusion.

Animals↗
PubMed2004

Automated methods for improved protein identification by peptide mass fingerprinting.

In order to maximize protein identification by peptide mass fingerprinting noise peaks must be removed from spectra and recalibration is often required. The preprocessing of the spectra before database searching is essential but is time-consuming. Nevertheless, the optimal database search parameters often vary over a batch of samples. For high-throughput protein identification, these factors should be set automatically, with no or little human intervention. In the present work automated batch filtering and recalibration using a statistical filter is described. The filter is combined with multiple data searches that are performed automatically. We show that, using several hundred protein digests, protein identification rates could be more than doubled, compared to standard database searching. Furthermore, automated large-scale in-gel digestion of proteins with endoproteinase LysC, and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis, followed by subsequent trypsin digestion and MALDI-TOF analysis were performed. Several proteins could be identified only after digestion with one of the enzymes, and some less significant protein identifications were confirmed after digestion with the other enzyme. The results indicate that identification of especially small and low-abundance proteins could be significantly improved after sequential digestions with two enzymes.

Animals↗
PubMed2004

Acidic proteome of growing and resting Lactococcus lactis metabolizing maltose.

The acidic proteome of Lactococcus lactis grown anaerobically was compared for three different growth conditions: cells growing on maltose, resting cells metabolizing maltose, and cells growing on glucose. In maltose metabolizing cells several proteins were up-regulated compared with glucose metabolizing cells, however only some of the up-regulated proteins had apparent relation to maltose metabolism. Cells growing on maltose produced formate, acetate and ethanol in addition to lactate, whereas resting cells metabolizing maltose and cells growing on glucose produced only lactate. Increased levels of alcohol-acetaldehyde dehydrogenase (ADH) and phosphate acetyltransferase (PTA) in maltose-growing cells compared with glucose-growing cells coincided with formation of mixed acids in maltose-growing cells. The resting cells did not grow due to lack of an amino acid source and fermented maltose with lactate as the sole product, although ADH and PTA were present at high levels. The maltose consumption rate was approximately three times lower in resting cells than in exponentially growing cells. However, the enzyme levels in resting and growing cells metabolizing maltose were similar, which indicates that the difference in product formation in this case is due to regulation at the enzyme level. The levels of 30S ribosomal proteins S1 and S2 increased with increasing growth rate for resting cells metabolizing maltose, maltose-growing cells and glucose-growing cells. A modified form of HPr was synthesized under amino acid starvation. This is suggested to be due to alanine misincorporation for valine, which L. lactis is auxotrophic for. L. lactis conserves the protein profile to a high extent, even after prolonged amino acid starvation, so that the protein expression profile of the bacterium remains almost invariant.

Acetates↗
PubMed2004

Diagnosis of type 2 diabetes at an older age: effect on mortality in men and women.

OBJECTIVE: To compare the mortality of people who were diagnosed with type 2 diabetes over 65 years of age with that of nondiabetic individuals. RESEARCH DESIGN AND METHODS: Using a population-based diabetes information system for an observational cohort study in Tayside, Scotland, people who were diagnosed with type 2 diabetes over the age of 65 years between 1993 and 2002 were identified. Nondiabetic comparators, matched for age and sex, were identified from the nondiabetic population. The two cohorts were followed up for mortality and cardiovascular mortality according to death certification records. RESULTS: There were 3,594 people with type 2 diabetes (48% male) and 7,188 matched comparators identified in the study. Over a mean follow-up period of 4.6 +/- 2.9 years for 3,594 people with type 2 diabetes and 7,188 comparators, 909 (25.3%) patients in the diabetic cohort and 1,651 (23.0%) in the nondiabetic cohort died. The adjusted relative risk for mortality in the diabetic cohort compared with the nondiabetic cohort was 1.06 (95% CI 0.94-1.19) for men and 1.29 (1.15-1.45) for women. Cardiovascular deaths accounted for 49.4% of the deaths in people with and 45.2% in those without diabetes (adjusted relative risk 1.01 [0.93-1.10]). CONCLUSIONS: Men diagnosed with type 2 diabetes over the age of 65 years have no excess mortality compared with their nondiabetic counterparts, a finding that was not replicated for women.

Aged↗
PubMed2003

Illness perceptions in people with acute bacterial gastro-enteritis.

Functional gastro-intestinal disorders (FGID) like irritable bowel syndrome (IBS) are common and can develop after gastro-enteritis. Illness representations may be important influences on the development of post-infectious FGIDs. Here, we studied both the relationship between prior chronic symptoms (FGIDs) and illness perception during an acute illness (bacterial gastro-enteritis) as well as the relationship between illness perception during an acute illness (bacterial gastro-enteritis) and the subsequent development of chronic abdominal symptoms. Two hundred and seventeen people with recent gastro-enteritis completed a questionnaire asking about gut symptoms consistent with a diagnosis of IBS, functional dyspepsia or functional diarrhoea and the Illness Perception Questionnaire. Those without a prior FGID were followed up and completed a similar gut questionnaire at six months. People with a prior FGID had significantly more symptoms and scored significantly higher on the timeline and consequence scores than those without. People who developed a FGID had a non-significantly higher number of symptoms and higher consequence and timeline scores than those who did not. Neither comparative group differed in the control/cure scores or causation scores. The implications of the findings are discussed.

Acute Disease↗
PubMed2003

Assertive outreach teams in London: models of operation. Pan-London Assertive Outreach Study, part 1.

BACKGROUND: Assertive outreach teams have been introduced in the UK, based on the assertive community treatment (ACT) model. It is unclear how models of community care translate from one culture to another or the degree of adaptation that may result. AIMS: To characterise London assertive outreach teams and determine whether there are distinct groups within them. METHOD: Semi-structured interviews with team managers plus one month's prospective process of care data collection were used to test for 'model fidelity' to ACT and, by cluster analysis, to identify groupings. RESULTS: Fidelity varied widely, with four teams (out of 24 studied) rated 'high fidelity' and three teams rated 'low fidelity' by US standards and 17 rated 'ACT-like'. Three clusters were identified, with voluntary sector teams being the most distinct group. CONCLUSIONS: There is wide variation in the practice of assertive outreach in London. The role of the voluntary sector requires increased attention. Heterogeneity in practice is a clinical challenge but a research opportunity in distinguishing effective from redundant components of the approach.

Adult↗
PubMedDate not supplied

Automating gel image acquisition.

We describe the design and implementation of a robotic solution to automate the acquisition of gel images. The soft- and hardware aspects are outlined together with the various safety aspects that need to be addressed.

Diagnostic Imaging↗