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Biomedical subjects

J C Martin

Publications and source records attributed to J C Martin.

At least 19 recordsLinked to original sources
PubMed2006

Use of clinical risk factors to identify postmenopausal women with vertebral fractures.

INTRODUCTION AND HYPOTHESIS: Previous studies have been unable to identify risk factors for prevalent vertebral fractures (VF), which are suitable for use in selection strategies intended to target high-risk sub-groups for diagnostic assessment. However, these studies generally consisted of large epidemiology surveys based on questionnaires and were only able to evaluate a limited number of risk factors. Here, we investigated whether a stronger relationship exists with prevalent VF when conventional risk factors are combined with additional information obtained from detailed one-to-one assessment. METHODS: Women aged 65-75 registered at four geographically distinct GP practices were invited to participate (n=1,518), of whom 540 attended for assessment as follows: a questionnaire asking about risk factors for osteoporosis such as height loss compared to age 25 and history of non-vertebral fracture (NVF), the get-up-and-go test, Margolis back pain score, measurement of wall-tragus and rib-pelvis distances, and BMD as measured by the distal forearm BMD. A lateral thoraco-lumbar spine X-ray was obtained, which was subsequently scored for the presence of significant vertebral deformities. RESULTS: Of the 509 subjects who underwent spinal radiographs, 37 (7.3%) were found to have one or more VF. Following logistic regression analysis, the four most predictive clinical risk factors for prevalent VF were: height loss (P=0.006), past NVF (P=0.004), history of back pain (P=0.075) and age (P=0.05). BMD was also significantly associated with prevalent VF (P=0.002), but its inclusion did not affect associations with other variables. Factors elicited from detailed one-to-one assessment were not related to the risk of one or more prevalent VFs. The area under ROC curves derived from these regressions, which suggested that models for prevalent VF had modest predictive accuracy, were as follows: 0.68 (BMD), 0.74 (four clinical risk factors above) and 0.78 (clinical risk factors + BMD). Analyses were repeated in relation to the subgroup of 13 patients with two or more VFs, which revealed that in this instance, the Margolis back pain score and rib-pelvis distance were associated with the presence of multiple VFs (P=0.022 and 0.026, respectively). Moreover, the predictive value as reflected by the ROC curve area was improved: 0.80 (BMD), 0.88 (the four most predictive clinical risk factors consisting of the height loss, past NVF, Margolis back pain score and rib-pelvis distance) and 0.91 (clinical risk factors + BMD). CONCLUSIONS: Evaluation of additional risk factors from detailed one-to-one assessment does not improve the predictive value of risk factors for one or more prevalent vertebral deformities in postmenopausal women. However, the use of factors such as the Margolis back pain score and rib-pelvis distance may be helpful in identifying postmenopausal women at high risk of multiple prevalent VFs.

Aged↗
PubMed2004

Fat-depleted CLA-treated mice enter torpor after a short period of fasting.

Resting energy expenditure (Resting-EE), EE with treadmill exercise, and post-prandial thermogenesis were continuously monitored by indirect calorimetry during a 24 h recording session in control (CT) and CLA-treated (CLA) (1% CLA in the food, by weight) C57Bl/6 male mice. After 15 days of CLA treatment, the fat content of CLA mice had fallen to 20% of that in CT mice. CLA mice were able to face the energy challenge of exercise but used less lipid than CT mice. Resting-EE values fell during the post-exercise period. The thermogenic response to a calibrated test meal given 5 h after the run abolished the differences in EE and substrate oxidation between CT and CLA mice. However, 2.5 h after ingestion of the test meal onward, CT mice gradually increased their lipid oxidation to sustain resting-EE levels. In contrast, CLA mice did not increase their lipid oxidation and their resting-EE levels fell significantly until they entered into torpor. Blood leptin was low but similar in CT and CLA-treated mice suggesting that leptin is not critical to induce torpor. We suggest that the durable inhibition of lipid oxidation in fasting CLA mice was an adaptive behaviour devoted at sparing the residual adipose deposits.

Animals↗
PubMed2004

No differences in cycling efficiency between world-class and recreational cyclists.

The aim of this experiment was to compare the efficiency of elite cyclists with that of trained and recreational cyclists. Male subjects (N = 69) performed an incremental exercise test to exhaustion on an electrically braked cycle ergometer. Cadence was maintained between 80 - 90 rpm. Energy expenditure was estimated from measures of oxygen uptake (VO (2)) and carbon dioxide production (VCO(2)) using stoichiometric equations. Subjects (age 26 +/- 7 yr, body mass 74.0 +/- 6.3 kg, Wpeak 359 +/- 40 W and VO(2)peak 62.3 +/- 7.0 mL/kg/min) were divided into 3 groups on the basis of their VO (2)peak (< 60.0 (Low, N = 26), 60 - 70 (Med, N = 27) and > 70 (High, N = 16) mL/kg/min). All data are mean +/- SE. Despite the wide range in aerobic capacities gross efficiency (GE) at 165 W (GE (165)), GE at the same relative intensity (GE (final)), delta efficiency (DE) and economy (EC) were similar between all groups. Mean GE (165) was 18.6 +/- 0.3 %, 18.8 +/- 0.4 % and 17.9 +/- 0.3 % while mean DE was 22.4 +/- 0.4 %, 21.6 +/- 0.4 % and 21.2 +/- 0.5 % (for Low, Medium and High, respectively). There was no correlation between GE (165), GE (final), DE or EC and VO(2)peak. Based on these data, we conclude that there are no differences in efficiency and economy between elite cyclists and recreational level cyclists.

Adult↗
PubMed2004

Using a representative sample of workers for constructing the SUMEX French general population based job-exposure matrix.

BACKGROUND: Job-exposure matrices (JEMs) applicable to the general population are usually constructed by using only the expertise of specialists. AIMS: To construct a population based JEM for chemical agents from data based on a sample of French workers for surveillance purposes. METHODS: The SUMEX job-exposure matrix was constructed from data collected via a cross-sectional survey of a sample of French workers representative of the main economic sectors through the SUMER-94 survey: 1205 occupational physicians questioned 48 156 workers, and inventoried exposure to 102 chemicals. The companies' economic activities and the workers' occupations were coded according to the official French nomenclatures. A segmentation method was used to construct job groups that were homogeneous for exposure prevalence to chemical agents. The matrix was constructed in two stages: consolidation of occupations according to exposure prevalence; and establishment of exposure indices based on individual data from all the subjects in the sample. RESULTS: An agent specific matrix could be constructed for 80 of the chemicals. The quality of the classification obtained for each was variable: globally, the performance of the method was better for less specific and therefore more easy to assess agents, and for exposures specific to certain occupations. CONCLUSIONS: Software has been developed to enable the SUMEX matrix to be used by occupational physicians and other prevention professionals responsible for surveillance of the health of the workforce in France.

Algorithms↗
PubMed2002

Indirect effects of heavy metals on parasites may cause shifts in snail species compositions.

We studied the direct and indirect effects of pollution on the distributions and abundances of two closely related species of pulmonate freshwater snails. Physella columbiana is more numerous at heavy metal-polluted lakes, and Lymnaea palustris is more numerous at reference lakes. Both species are present at all sites, as are predatory bluegill sunfish (Lepomis macrochirus). The direct effects examined included the snails' growth and reproduction in both the presence and absence of heavy metals and their short-term survival when exposed to large concentrations of heavy metals. The indirect effects were the species' ability to elude capture by sunfish and the diversity and abundance of parasites within the snails. We found that heavy metals had little direct effect on growth and reproduction and that both species acquired similar levels of metals in their tissues. Interestingly, P. columbiana (the more abundant species in polluted lakes) actually exhibited higher recruitment in the absence of metals than did L. palustris (reference lakes). L. palustris has life history characteristics that favor increased growth and reduced reproduction. These characteristics resulted in decreased predation of adults by gape-limited predators and a greater ability to cope with heavy parasite burdens. P. columbiana exhibited slower growth, which resulted in increased predation although higher reproduction rates may compensate.The major effect of heavy metals on species distributions was indirect on the snails' parasites. Parasites appeared to be very susceptible to metals, and this resulted in lower parasite diversity and intensities at polluted sites for both species of snails. P. columbiana may only be able to outcompete L. palustris at polluted sites due to the indirect effects of heavy metals; the negative effect of heavy metals on parasites, and a proposed negative effect of metals on the foraging ability of sunfish that favors the faster-reproducing P. columbiana.

Animals↗
PubMed2002

Effects of crank length on maximal cycling power and optimal pedaling rate of boys aged 8-11 years.

It is generally reported that cycle crank length affects maximal cycling power of adults and that optimal crank length is related to leg length. This suggests that the use of standard length cycle cranks may provide nonoptimal test conditions for children. The purpose of this study was to determine the effects of cycle-crank length on maximal cycling power and optimal pedaling rate of 17 boys aged 8-11 years. The boys performed maximal cycle ergometry with standard (170 mm) cycle cranks and with a crank length that was 20% of estimated leg length (LL20). Power produced when using the 170 mm cranks [mean (SEM)] [364 (18) W] did not differ from that produced with the LL20 cranks [366 (19)]. Optimal pedaling rate was significantly greater for the LL20 cranks [129 (4) rpm] than for the 170 mm cranks [114 (4) rpm]. These data suggest that standard 170 mm cranks do not compromise maximal power measurements in boys aged 8-11 years so that the test apparatus does not bias physiological or developmental inferences made from tests of maximal cycling power.

Age Factors↗
PubMed2002

A comparative study to assess the clinical use of Fluorescein Meniscus Time (FMT) with Tear Break up Time (TBUT) and Schirmer's tests (ST) in the diagnosis of dry eyes.

INTRODUCTION: The clinical diagnosis of dry-eye is confirmed by a suitable test of tear production and the technique commonly used today to diagnose dry eye is the Schirmer's test (ST). Although the ST is easy to perform it gives variable results, poor reproducibility and low sensitivity for detecting dry eyes. Another test, the tear break up time (TBUT) is used to assess the stability of tears which if abnormal may also cause symptomatic dry-eye. We present the results of both these tests and a new test, which shows greater sensitivity than the ST in detecting aqueous tear deficiency. The fluorescein meniscus time (FMT) is a new test developed in conjunction with one of the authors (CL) and the Department of Ophthalmology at the University Hospital of Wales. The FMT is a measure of the rate at which a fluorescent tear meniscus is formed using 2% sodium fluorescein, a stopwatch and suitable illumination with a slit lamp. METHOD: An open controlled study in 62 patients and 51 controls was conducted to compare the ability of ST, FMT and TBUT to detect dry-eye in a group of patients diagnosed with rheumatoid arthritis and symptomatic dry eyes for a minimum period of 6 months. A separate control group of 15 subjects was tested on three separate occasions to assess the reproducibility of the FMT test. RESULTS: All three tests showed a statistically significant difference between the patient and control populations; Mann-Whitney P < 0.001. There was a correlation between the right and left eye for all three tests in the control group (ST r(2) = 0.77, FMT r(2) = 0.98, TBUT r(2) = 0.94). This correlation was markedly reduced for FMT and TBUT in the patient population and was in keeping with the symptoms reported as being worse on one side in a proportion of the patients (FMT r(2) = 0.52, TBUT r(2) = 0.54, ST r(2) = 0.75). A correlation with age was also observed for all the three tests in the control group (ST r(2) = 0.74, FMT r(2)= 0.92, TBUT r(2) = 0.51), but not in the patient population (ST r(2) = 0.06, FMT r(2) = 0.18, TBUT r(2) = 0.03). A significant correlation was observed between the ST and FMT in both the control (ST vs FMT r(2) = 0.65) and patient population (ST vs FMT r(2) = 0.44). There was no value greater than 200 seconds for FMT recorded in the control group. Using this value to define an abnormal FMT, 85% of the patients (72% of the eyes tested) had an abnormal result. This was in contrast to 35% of patients (26% of the eyes tested) with abnormal results detected by ST. Using ANOVA and Student's paired t-test, there were no significant differences between the three sets of values recorded serially over 3 months to assess the reproducibility of the FMT. The average standard error of the mean was 2.72% and the average co-efficient of variation 4.07%. CONCLUSION: Our study suggests that the FMT is a more sensitive test with good reproducibility compared to the Schirmer's test. The FMT correlates with the ST and suggests that both tests measure aqueous tear deficiency. The FMT therefore is a better alternative to ST currently being used to test aqueous tear deficiency.

Adolescent↗
PubMed2002

Determinants of metabolic cost during submaximal cycling.

The metabolic cost of producing submaximal cycling power has been reported to vary with pedaling rate. Pedaling rate, however, governs two physiological phenomena known to influence metabolic cost and efficiency: muscle shortening velocity and the frequency of muscle activation and relaxation. The purpose of this investigation was to determine the relative influence of those two phenomena on metabolic cost during submaximal cycling. Nine trained male cyclists performed submaximal cycling at power outputs intended to elicit 30, 60, and 90% of their individual lactate threshold at four pedaling rates (40, 60, 80, 100 rpm) with three different crank lengths (145, 170, and 195 mm). The combination of four pedaling rates and three crank lengths produced 12 pedal speeds ranging from 0.61 to 2.04 m/s. Metabolic cost was determined by indirect calorimetery, and power output and pedaling rate were recorded. A stepwise multiple linear regression procedure selected mechanical power output, pedal speed, and pedal speed squared as the main determinants of metabolic cost (R(2) = 0.99 +/- 0.01). Neither pedaling rate nor crank length significantly contributed to the regression model. The cost of unloaded cycling and delta efficiency were 150 metabolic watts and 24.7%, respectively, when data from all crank lengths and pedal speeds were included in a regression. Those values increased with increasing pedal speed and ranged from a low of 73 +/- 7 metabolic watts and 22.1 +/- 0.3% (145-mm cranks, 40 rpm) to a high of 297 +/- 23 metabolic watts and 26.6 +/- 0.7% (195-mm cranks, 100 rpm). These results suggest that mechanical power output and pedal speed, a marker for muscle shortening velocity, are the main determinants of metabolic cost during submaximal cycling, whereas pedaling rate (i.e., activation-relaxation rate) does not significantly contribute to metabolic cost.

Adult↗
PubMed2002

Bronchial challenge with flour: early response is dependent on the dose of activated allergen inhaled.

Specific bronchial challenges provide information about the relationship between inhaled dose of allergen and change in lung function, but the intermediate pathways remain largely obscure. The aim of this study was to investigate the relationships between the early asthmatic response and 1) the inhaled dose of wheat flour, 2) the concentration of wheat flour, 3) the duration of the exposure, and 4) the deactivation of inhaled allergens and mediators. Thirty-one patients with occupational asthma to wheat flour were studied. Particle aerosols were generated by a computer-controlled aerosoliser and the results were expressed as the provocative dose causing a 20% fall in forced expiratory volume in one second (FEVi) (PD20). The cumulative dose (from the beginning of the challenge), the last inhaled dose, and an estimated dose (taking into account exponential deactivation), were calculated. Twenty patients had high reactivity to flour (reaching a PD20 value). Eleven patients had intermediate reactivity (no measurable PD20 but significantly greater fall in FEV1 compared with lactose challenge). A better correlation between change in FEV1 and dose was obtained for the estimated dose than for the cumulative or last inhaled dose. The bronchial response to wheat flour can be measured by the individual specific hyperreactivity and is expressed by provocative dose of flour. However, deactivation of the allergen and mediators has to be taken into account. This problem can be addressed by using a mathematical model.

Administration, Inhalation↗
PubMed2001

SPECT mapping of cerebral activity changes induced by repetitive transcranial magnetic stimulation in depressed patients. A pilot study.

Repetitive transcranial magnetic stimulation (rTMS) is being investigated as an alternative treatment for depression. However, little is known about the clinical role and the neurophysiological mechanisms of the action of rTMS in these patients. In this study, 99mTc-HMPAO single photon emission computed tomography (SPECT) was used to map the effects of left dorsolateral prefrontal rTMS on prefrontal activity in seven patients who met DSM-IV criteria for major depression resistant to pharmacological treatment. rTMS consisted of 30 trains of 2-s duration stimuli (20 Hz, 90% of motor threshold), separated by 30-s pauses. Each patient underwent three SPECTs: at baseline; during the first rTMS; and 1 week after 10 daily sessions of rTMS. Regional cerebral blood flow (rCBF) of each cerebral region was normalized to the rCBF value in the cerebellum and relative changes in normalized rCBF were addressed using a region-of-interest analysis. The Hamilton Depression Rating Scale (HDRS) was used for clinical evaluation before and after rTMS. A significant rCBF increase after the 10 sessions of rTMS was found in the left prefrontal region (MANOVA F=5.29, d.f.=2,10, P=0.027), but no significant rCBF changes were found during the first rTMS session. The remaining cerebral regions showed no significant rCBF changes at any time. Only two patients showed a clinical improvement after rTMS, with 50% reduction of the initial HDRS score. The study was repeated under placebo conditions (identical design but addressing coil discharges to the air) in these two patients, who failed to show any rCBF increase during sham-rTMS. No relationship was found between the percentage of left prefrontal rCBF change and the clinical findings. In conclusion, rTMS of the left prefrontal cortex induces a significant rCBF increase in this region, despite the limited clinical effect in our sample of depressed patients. Cerebral perfusion SPECT is a useful tool to map cerebral activity changes induced by rTMS.

Adult↗
PubMed2001

Determinants of maximal cycling power: crank length, pedaling rate and pedal speed.

The purpose of this investigation was to determine the effects of cycle crank length on maximum cycling power, optimal pedaling rate, and optimal pedal speed, and to determine the optimal crank length to leg length ratio for maximal power production. Trained cyclists (n = 16) performed maximal inertial load cycle ergometry using crank lengths of 120, 145, 170, 195, and 220 mm. Maximum power ranged from a low of 1149 (20) W for the 220-mm cranks to a high of 1194 (21) W for the 145-mm cranks. Power produced with the 145- and 170-mm cranks was significantly (P < 0.05) greater than that produced with the 120- and 220-mm cranks. The optimal pedaling rate decreased significantly with increasing crank length, from 136 rpm for the 120-mm cranks to 110 rpm for the 220-mm cranks. Conversely, optimal pedal speed increased significantly with increasing crank length, from 1.71 m/s for the 120-mm cranks to 2.53 m/s for the 220-mm cranks. The crank length to leg length and crank length to tibia length ratios accounted for 20.5% and 21.1% of the variability in maximum power, respectively. The optimal crank length was 20% of leg length or 41% of tibia length. These data suggest that pedal speed (which constrains muscle shortening velocity) and pedaling rate (which affects muscle excitation state) exert distinct effects that influence muscular power during cycling. Even though maximum cycling power was significantly affected by crank length, use of the standard 170-mm length cranks should not substantially compromise maximum power in most adults.

Adult↗
PubMed2001

Lifestyle behaviors affect cardiovascular risk status in men 1 year after kidney transplantation.

Persons with end-stage renal disease have an accelerated risk for cardiovascular (CV) morbidity and mortality. Unfortunately, their accelerated CV risk persists even after kidney transplantation associated with pretransplant and post-transplant vascular disease. number of rejections treated with high-dose steroids, prolonged use of immunosuppressive therapy post-transplant, effects of comorbid chronic conditions and male gender. Unhealthy, modifiable lifestyle practices often augment their CV risk. The purpose of this study was to examine health-related lifestyle behaviors and estimate CV risks of men 1 year following kidney transplantation. Using the Healthier People Network Health Risk Appraisal (HPN-HRA), we examined CV risk characteristics of 34 men (M age=47.3 years) enrolled in an urban, mid-southern transplant center. Participants were assessed via self-administered paper-and-pencil questionnaires and medical record review provided biological data for analyses. HPN-HRA software was used to analyze biological and behavioral characteristics to compute CV risk estimates. Data were analyzed using descriptive, inferential and correlational analyses. The majority of participants reported smoke cessation (n= 19) or never having smoked (n = 8), and consumption of one or less alcoholic drinks per week (n=28). On the other hand, increased risk for heart attack and stroke were associated with advancing age (P<0.0001), white race (P<0.05) and higher systolic blood pressure (P<0.01). While risk for heart attack was associated with current cigarette smoking (P<0.01), risk for stroke was not. Conversely, risk for stroke was associated with higher BMI (P<0.05), risk for heart attack was not. Thus, the study provides evidence that male kidney transplant survivors exhibit a significant number of non-modifiable and modifiable characteristics that contribute to their posttransplant CV risk.

Cardiovascular Diseases↗
PubMed2001

Cellulosomal scaffoldin-like proteins from Ruminococcus flavefaciens.

Two tandem cellulosome-associated genes were identified in the cellulolytic rumen bacterium, Ruminococcus flavefaciens. The deduced gene products represent multimodular scaffoldin-related proteins (termed ScaA and ScaB), both of which include several copies of explicit cellulosome signature sequences. The scaB gene was completely sequenced, and its upstream neighbor scaA was partially sequenced. The sequenced portion of scaA contains repeating cohesin modules and a C-terminal dockerin domain. ScaB contains seven relatively divergent cohesin modules, two extremely long T-rich linkers, and a C-terminal domain of unknown function. Collectively, the cohesins of ScaA and ScaB are phylogenetically distinct from the previously described type I and type II cohesins, and we propose that they define a new group, which we designated here type III cohesins. Selected modules from both genes were overexpressed in Escherichia coli, and the recombinant proteins were used as probes in affinity-blotting experiments. The results strongly indicate that ScaA serves as a cellulosomal scaffoldin-like protein for several R. flavefaciens enzymes. The data are supported by the direct interaction of a recombinant ScaA cohesin with an expressed dockerin-containing enzyme construct from the same bacterium. The evidence also demonstrates that the ScaA dockerin binds to a specialized cohesin(s) on ScaB, suggesting that ScaB may act as an anchoring protein, linked either directly or indirectly to the bacterial cell surface. This study is the first direct demonstration in a cellulolytic rumen bacterium of a cellulosome system, mediated by distinctive cohesin-dockerin interactions.

Amino Acid Sequence↗
PubMed2001

Development of a Web site for transplant patient education.

The Internet is a global communication network used by more than 17.6 million adults as a major source of current health information. Both the number of health-related Web sites and the number of Web users are increasing exponentially as well as reports indicating a growth in the number of persons who access the Internet specifically to retrieve information about organ transplantation. However, few are using this medium for posttransplant educational or psychosocial purposes. Armed with this information, as well as a commitment from the transplant team, we chose to develop a Web-based educational program to facilitate posttransplant care for our transplant recipients. The purpose of this article is to describe the planning, development, and implementation of a Web-based education program for transplant recipients.

Health Plan Implementation↗