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Biomedical subjects

J A Davis

Publications and source records attributed to J A Davis.

At least 271 records · Page 15Linked to original sources
PubMed1977

The influence of venous return on cardiac mechanical and sarcoplasmic reticulum function during endotoxemia.

E. coli endotoxin (0.03 mg/ml) added to blood perfusing a heart-lung preparation with a venous return of 600 ml/min produced a significant depression in ventricular function within 4 hours. Fragmented sarcoplasmic reticulum isolated from the myocardium of the endotoxin-perfused heart-lung preparations showed depressed calcium uptake rates and ATPase activity. When venous return was increased to 1,200 ml/min, gram-negative endotoxin had no effect on ventricular function, isolated fragmented sarcoplasmic reticulum calcium uptake, or ATPase activity. These observations suggest that gram-negative endotoxin or a product thereof acts in synergism with low venous return in order to depress myocardial function.

Adenosine Triphosphatases↗
PubMed1976

An automated system for assessing metabolic and respiratory function during exercise.

This paper provides a brief description of a new, totally automated system for assessing metabolic and respiratory function during exercise. This system was evaluated simultaneously against two established systems, one a computer-based system and the other a semiautomated system, to determine its validity over a wide range of metabolic levels, i.e., less than 2 to greater than 16 mets. A total of 112 males and females, 12-65 yr of age, performed either arm or leg exercises on a bicycle ergometer or treadmill, starting at approximately 2 mets and progressing by approximately 1 met/min to the point of volitional fatigue. Respiratory and metabolic assessments were made each minute during the entire exercise bout. Comparisons across the three systems demonstrated remarkable agreement, particularly when all potential sources of error for each system are considered. Although several statistically significant differences between two of the systems were noted at the lowest work levels, the difference in VO2 between any two systems never exceeded 1.1 ml/kg-min.

Adolescent↗
PubMed1976

Anaerobic threshold and maximal aerobic power for three modes of exercise.

Alterations in selected respiratory gas exchange parameters have been proposed as sensitive, noninvasive indices of the onset of metabolic acidosis (anaerobic threshold (AT) during incremental exercise. Our purposes were to investigate the validity and feasibility of AT detection using routine laboratory measures of gas exchange, i.e., nonlinear increases in VE and VCO2 and abrupt increases in FEO2. Additionally, we examined the comparability of the AT and VO2 max among three modes of exercise (arm cranking, leg cycling, and treadmill walk-running) with double determinations obtained from 30 college-age, male volunteer subjects. The AT's for arm cranking, leg cycling, and treadmill walk-running occurred at 46.5 +/- 8.9 (means +/- SD), 63.8 +/- 9.0, and 58.6 +/- 5.8% of VO2 max, respectively. No significant difference was found between the leg exercise modes (cycling and walk-running) for the AT while all pairwise arm versus leg comparisons were significantly different. Using nine additional subjects performing leg cycling tests, a significant correlation of r = 0.95 was found between gas exchange AT measurements (expressed as % VO2 max) and venous blood lactate AT measurements (% VO2 max). We conclude that the gas exchange AT is a valid and valuable indirect method for the detection of the development of lactic acidosis during incremental exercise.

Adult↗
PubMed1975

The community paediatrician in an integrated child health service.

A concept of Community Paediatrics has been described comprising clinical care to individual children including identification, diagnosis, and care of the handicapped child, expertise in preventive paediatric techniques, and the provision of investigation and advice in connexion with social and educational proboems. Its relationship to Community Medicine, General Practice, and Consulting Paediatrics has been discussed and a long-term training scheme is outlined. In the immediate future the deployment is envisaged of senior clinical Medical Officers now employed by Local Authorities.

Child↗
PubMed1975

A comparison of heart rate methods for predicting endurance training intensity.

Comparing results of various training studies is often confounded by use of different indices of exercise intensity. Two frequently used indices are: 1) the % HR max method (exercise at a HR corresponding to a chosen percentage of maximal HR), and 2) this study, % net VO2max was employed as the criterion measure of exercise intensity and a comparison was made between the prediction of % net VO2-MAXby the above two methods. Experiments were performed on nine males (M +/- SD age = 23.7 +/- 2.6 yrs) and consisted of double determinations of resting VO2 and multiple measurements of resting HR under five different conditions. Duplicate determinations of maximal VO2 and HR preceded a third treadmill test consisting of four, 5-minute workloads representing approx 25, 45, 65, and 85% net VO2max. The results demonstrated that the KM's prediction of exercise intensity was not significantly different (P greater than 0.05) from measured intensity at any of the four workloads. Additionally, the % HR max procedure yielded large, significant overpredictions of exercise intensity (29, 22, 16 and 8% overpredictions for the four submaximal intensities, respectively. These results suggest that the KM yields a training HR that reflects exercise intensity within reasonable limits of accuracy.

Adult↗