Biomedical subjects

James Carter

Publications and source records attributed to James Carter.

4 recordsLinked to original sources

PubMed2006

Distance-based clustering of CGH data.

MOTIVATION: We consider the problem of clustering a population of Comparative Genomic Hybridization (CGH) data samples. The goal is to develop a systematic way of placing patients with similar CGH imbalance profiles into the same cluster. Our expectation is that patients with the same cancer types will generally belong to the same cluster as their underlying CGH profiles will be similar. RESULTS: We focus on distance-based clustering strategies. We do this in two steps. (1) Distances of all pairs of CGH samples are computed. (2) CGH samples are clustered based on this distance. We develop three pairwise distance/similarity measures, namely raw, cosine and sim. Raw measure disregards correlation between contiguous genomic intervals. It compares the aberrations in each genomic interval separately. The remaining measures assume that consecutive genomic intervals may be correlated. Cosine maps pairs of CGH samples into vectors in a high-dimensional space and measures the angle between them. Sim measures the number of independent common aberrations. We test our distance/similarity measures on three well known clustering algorithms, bottom-up, top-down and k-means with and without centroid shrinking. Our results show that sim consistently performs better than the remaining measures. This indicates that the correlation of neighboring genomic intervals should be considered in the structural analysis of CGH datasets. The combination of sim with top-down clustering emerged as the best approach. AVAILABILITY: All software developed in this article and all the datasets are available from the authors upon request. CONTACT: juliu@cise.ufl.edu.

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PubMed2005

The effect of sweetness on the efficacy of carbohydrate supplementation during exercise in the heat.

The aim of the present study was to investigate potential mechanisms responsible for the improvement in prolonged exercise capacity in hot environments with exogenous carbohydrate. Eight endurance-trained men (VO(2)max 60.5 +/- 2.4 ml.kg(-1).min(-1), mean +/- SE) cycled to exhaustion on three occasions at 60% VO(2)max at an ambient temperature of 35 degrees C. They ingested either a sweet 6.4% carbohydrate solution (SC), a nonsweet 6.4% carbohydrate solution (NSC), or water (W). Exercise capacity was significantly increased with SC and NSC compared to W, the improvements corresponding to 15.8% and 11.8%, respectively. No difference in exercise capacity was seen between SC and NSC solutions. Plasma glucose concentrations were higher during the SC and NSC trials compared to W, significantly so at 10 min and at fatigue. Rates of carbohydrate oxidation were higher in the SC and NSC trials, although the rates never declined below 2.1 +/- 0.2 g.min(-1) in the W trial. There was no difference in the rate of rise of rectal temperature between trials, but there was a trend for subjects to fatigue at higher temperatures during the two carbohydrate trials. In conclusion, exogenous carbohydrate, independent of sweetness, improves exercise capacity in the heat compared to water alone.

Adult↗

PubMed2003

Carbohydrate supplementation improves moderate and high-intensity exercise in the heat.

The aim of the present study was to clarify the effect of carbohydrate (CHO) supplementation on moderate and high-intensity endurance exercise in the heat. Eight endurance-trained men [maximal oxygen uptake ( VO(2max)) 59.5+/-1.6 ml kg(-1) bw(-1), mean+/-SE] cycled to exhaustion twice at 60% VO(2max) and twice at 73% VO(2max) at an ambient temperature of 35 degrees C. Subjects ingested either a 6.4% maltodextrin solution (CHO) or an artificially flavoured and coloured placebo (PLA). Time to fatigue was significantly greater with CHO in both the 60% and 73% VO(2max) trials (14.5% and 13.5% improvement, respectively). Heart rate and oxygen uptake ( VO(2)) did not differ at any point between PLA and CHO. Hypoglycaemia was not seen in any condition but plasma glucose concentrations tended to be higher at both intensities when CHO was fed. CHO oxidation rates were similar at 60% VO(2max) between CHO and PLA. There were no differences between PLA and CHO in the rate of rise of rectal temperatures ( T(rec)) at either intensity but there was a trend for subjects to fatigue at a high temperature when taking CHO. Ratings of perceived exertion (RPE) tended to be lower throughout both CHO trials; this was significant at 80 min and at fatigue at 60% VO(2max). It is concluded that supplementation with CHO improves exercise performance in the heat at both moderate and high endurance intensities. In the absence of a clear metabolic explanation, a central effect involving an increased tolerance of rising deep body temperature merits further investigation.

Adult↗

PubMed2002

Validity and reliability of three commercially available breath-by-breath respiratory systems.

Information concerning the validity and reliability of commercial on-line gas analysis systems is limited. The aim of this study was to provide a comparison of the validity and reliability of three on-line systems (Oxycon Alpha, Oxycon Pro and Pulmolab EX670) with that of Douglas bags. Two separate studies were conducted. In study 1, the three gas analysis systems were compared with Douglas bags using a metabolic simulator over four increases in ventilation. In study 2, ten subjects were split into equal groups exercising at 100 W or 150 W for 85 min on three separate occasions. Each system was used twice per visit. Study 1 demonstrated that the Oxycon Alpha and Douglas bags produced similar respiratory values over all levels of ventilation. The Oxycon Pro tended to slightly overestimate mean expiratory flow (V(E) ), oxygen uptake ( VO2), carbon dioxide production (VCO2) and respiratory exchange ratio (RER) at the higher ventilations. The Pulmolab produced large overestimations at all ventilations for and RER (up to 26.3% away from expectations), whilst values for, and were slightly underestimated at higher ventilations (up to 7.5% from expectations). The results of study 2 support the findings of study 1, with the Oxycon Pro and Oxycon Alpha producing similar results compared to Douglas bags for, and RER. The coefficients of variation for and measured using Douglas bags, Oxycon Pro and Oxycon Alpha were 3.3-5.1%, 4.7-7.0% and 4.5-6.3%, respectively, whilst that for the Pulmolab was highly variable (26.8-45.8%). The exercise study showed the Oxycon Pro and Oxycon Alpha to be both valid and reliable on-line systems for the measurement of parameters of respiration, at least at workloads up to 150 W.

Adult↗