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Biomedical subjects

S W Wilde

Publications and source records attributed to S W Wilde.

11 recordsLinked to original sources
PubMed1991

Glutamine transport by basolateral plasma-membrane vesicles prepared from rabbit intestine.

L-Glutamine, a major energy substrate for intestinal epithelial cells, can be extracted from intraluminal contents across the brush-border membrane and from arterial blood via the basolateral membrane. The purpose of the present study was to characterize glutamine transport by the basolateral membrane of rabbit epithelial cells. Transport of glutamine by isolated basolateral-membrane vesicles was mediated by both Na(+)-dependent and Na(+)-independent carriers. Tests were performed to distinguish glutamine uptake by likely transport agencies, including Systems A, ASC, N, IMINO, NBB, L and asc. The Na(+)-dependent glutamine uptake was strongly inhibited by an excess of 2-(methylamino)isobutyric acid (MeAIB), and glutamine was equally effective in inhibiting MeAIB transport. The reciprocal inhibition analysis, as well as a sensitivity to increased H+ concentration, indicates that Na(+)-dependent glutamine transport across the basolateral membrane is mediated by System A. The saturable Na(+)-independent glutamine transport was markedly inhibited by 2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid ('BCH') and insensitive to changes in assay pH, suggesting uptake via System L rather than System asc. The presence of a Na(+)-dependent carrier to mediate active transport of glutamine across the basolateral membrane is probably essential to ensure a continuous supply of this vital substrate to the enterocyte in the post-absorptive state.

Animals↗
PubMed1982

Ventilation and acid-base equilibrium for upper body and lower body exercise.

The purpose of this study was to compare pulmonary ventilation and blood acid-base responses for upper and lower body exercise at a variety of metabolic intensities. Nine male subjects completed a progressive intensity, discontinuous test for arm crank (AC) and cycle (CY) ergometry. During submaximal exercise, oxygen uptake (VO2), pulmonary ventilation (VE), VE/VO2, alveolar ventilation (VA) and blood lactate (LA) values were found to increase, whereas arterial carbon dioxide partial pressure (PCO2) and arterial pH values were found to decrease with increasing power output for both modes of ergometry. Generally, for a given submaximal power output level, VO2, VE, VE/VO2, VA. and LA values were higher, but, PCO2 and pH values were lower for AC compared to CY exercise. During maximal exercise, VO2, VE, VA, LA, and PCO2 values were lower for AC than CY exercise. When VE, VA, LA, PCO2 and pH were expressed in relation to percent of peak VO2 (ergometer specific), nearly identical response patterns were found for both modes of exercise. These results indicate that pulmonary ventilation and blood acid-base responses are dependent upon relative exercise intensity rather than the muscle groups employed.

Acid-Base Equilibrium↗
PubMed1981

Energy cost and cardiopulmonary responses for wheelchair locomotion and walking on tile and on carpet.

The purpose of this study was to compare energy cost and cardiopulmonary responses to wheelchair locomotion and walking on tile and on carpet at 3.0 km . h-1. Nine wheelchair-dependent (WD) and ten able-bodied (AB) individuals served as test subjects. WD subjects were tested for wheelchair locomotion on tile and on carpet, and AB subjects were tested for walking over both floor surfaces. Studied variables included gross energy cost (GEC), net locomotive energy cost (NLEC), pulmonary ventilation (VE) and heart rate (HR) during all test conditions. On tile, GEC and NLEC were found to be lower, whereas VE and HR were higher for wheelchair locomotion than for walking. On carpet, wheelchair locomotion elicited higher values for all variables than walking. In going from tile to carpet, significant increases in these variables were found for wheelchair locomotion, whereas walking elicited similar response magnitudes on both floor surfaces. These results suggest that cardiopulmonary stresses for wheelchair locomotion are higher than for walking, and that a carpet can present an obstacle to wheelchair locomotion which may not be recognised by those who walk.

Adult↗
PubMed1981

Evaluation of myocardial performance during wheelchair ergometer exercise.

Since a relatively high incidence of cardiovascular disease is associated with wheelchair confinement, exercise stress testing techniques should be utilized to assess myocardial performance of wheelchair-dependent individuals. Therefore, the purpose of this study was to apply the techniques of impedance cardiography to graded wheelchair-type exercise. For this, 9 wheelchair-dependent volunteers completed a progressive intensity, discontinuous test on a wheelchair ergometer (WERG) at power outputs (PO) of 10, 20, and 30 watts. An impedance cardiogram (ZCG), electrocardiogram (ECG), and phonocardiogram (PCG) were recorded for 15 sec immediately following steady state exercise. Stroke volume (delta V) calculated from the ZCG was multiplied by steady state heart rate (HR) to estimate cardiac output (Q). The simultaneous recording of the ZCG, ECG, and PCG permitted calculation of systolic time intervals and impedance cardiography contractility indices. Values for delta V, HR, Q, arteriovenous oxygen difference, systolic and diastolic blood pressure, mean systolic ejection rate, the first derivative of the impedance change, and the Heather Index increased with increments in PO. The Q-S2 interval, left ventricular ejection time (LVET), the pre-ejection period (PEP), the ratio of PEP to LVET, and the R-Z interval decreased with increases in exercise intensity. A linear relationship was found between Q and oxygen uptake which was similar to that reported by other investigators for arm exercise. These data indicate that impedance cardiography may be used in conjunction with electrocardiography and phonocardiography for the non-invasive assessment of myocardial performance during wheelchair exercise testing.

Adult↗
PubMed1980

Physiological responses to maximal effort wheelchair and arm crank ergometry.

The purpose of this investigation was to compare physical work capacity (PWC), peak oxygen uptake (peak VO2), maximal pulmonary ventilation (VEmax), maximal heart rate (HRmax), and maximal blood lactate concentration (LAmax) for wheelchair ergometer (WERG) and arm crank ergometer (ACE) exercise. For this, wheelchair-dependent (n = 6) and able-bodied (n = 10) subjects completed a progressive intensity, discontinuous test for each mode of exercise. Each test was terminated by physical exhaustion and/or an inability to maintain a flywheel velocity of 180 m.min-1. Relatively high correlation coefficients were found between values obtained during the two modes of ergometry for PWC, peak VO2, VEmax, and HRmax. WERG exercise was found to elicit a significantly (P less than 0.05) lower PWC (by 36%), HRmax (by 7%), and LAmax (by 26%) than ACE exercise. Peak VO2 and VEmax, however, were similar for both exercise modes. These data suggest that either exercise mode may be used for fitness testing and training of people who cannot use their legs and that arm cranking may be a superior method to propel wheelchairs.

Adult↗
PubMed1980

Metabolic and circulatory responses to wheelchair and arm crank exercise.

To compare metabolic and circulatory responses for wheelchair ergometer (WERG) and arm crank ergometer (ACE) exercise at equal power-output (PO) levels, wheelchair-dependent (n = 7) and able-bodied (n = 10) subjects exercised at PO levels at 30, 90, 150, and 210 kpm times min-1 for each mode of ergometry. Steady-state values of oxygen uptake (VO2), pulmonary ventilation (VE), ventilatory equivalent of oxygen (VE times VO2-1), cardiac output (Q), stroke volume (SV), arteriovenous oxygen difference (a-VO2), heart rate (HR), systolic blood pressure (SBP), and rate pressure product (RPP) were determined at each PO. With the exception of VE times VO2-1 and a-VO2, each variable tended to increase with PO. Generally, VO2, VE, Q, SV, HR, SBP, and RPP responses were higher for WERG than ACE exercise at each PO level. When Q and RPP were expressed in relation to VO2, both variables were higher for WERG exercise. These data suggest that the wheelchair hand-rim system is inherently more strenuous than arm cranking, and that the latter should be studied further as an alternative method for wheelchair propulsion.

Adult↗
PubMed1980

Effects of toeclip use on metabolic and cardiopulmonary responses to bicycle ergometer exercise.

Toeclips secure the feet to bicycle pedals and are thought to enable greater anticipation of leg musculature in the pedaling motion. To determine the effects of toeclip use on metabolic and cardiopulmonary responses to BERG exercise, 13 female subjects, who had no prior experience with the devices, performed maximal and submaximal work with and without the use of toeclips. Similar oxygen uptake (V02), physical work capacity, pulmonary ventilation (VE), respiratory exchange ratio (R), heart rate (HR), and blood lactate concentration (LA) were found for maximal effort exercise under both conditions. For submaximal exercise (at 30, 60, and 80% maximal V02) performed with and without toeclips, no differences were found for V02, VE, R, HR, LA, cardiac output, stroke volume, and arteriovenous oxygen difference. These data suggest that toeclip use during BERG exercise may not alter metabolic and cardiopulmonary responses of individuals who have no prior experience with the devices.

Adult↗
PubMed1980

Physiological and performance characteristics of United States championship class orienteers.

The purpose of this investigation was to study the anaerobic and aerobic power of female and male United States championship orienteers and relate these data to competitive performance. In addition, it was considered valuable to obtain a general physical description of the athletes. Anthropometrically, neither the females (n=5) nor the males (n=13) conformed to a somatotype classification typical of endurance athletes. Although the mean anaerobic power values for the females (76.6 kg.m.sec-1) and the males (106.6 kg.m.sec-1) were consistent with what is known for distance runners, the respective aerobic powers of 46.1 and 61.6 ml.kg-1.min-1 were considerably below expectations for national class competitors. The explanation for this latter finding was attributed to their reported training programs. Partial residual plots and multiple regression procedures were used to determine the relationship between aerobic power and gender, respectively, with speed of competitive performance. The final equation to predict performance was P = -13.10 + 0.62(VO2max) + 0.26 (Experience, years) - 0.03 (Anaerobic power) + 1.21 (gender) - 0.01 (VO2max)2 with an R-square of 0.73 and P less than 0.01.

Adult↗
PubMed1979

Effect of prolonged running on physiological responses to subsequent exercise.

The purpose of this study was to compare metabolic and cardiopulmonary responses for submaximal and maximal exercise performed several days preceding (pre-test) and 45 min after (post-test) 21 miles of high intensity (70% VO2 max) treadmill running. Seven aerobically trained subjects' oxygen uptake, oxygen pulse, respiratory exchange ratio, heart rate, pulmonary ventilation, ventilatory equivalent of oxygen, and blood lactate concentration were determined for exercise during the pre- and post-test sessions. No differences were found for submaximal oxygen uptake, oxygen pulse, pulmonary ventilation and ventilatory equivalent of oxygen between the pre- and post-test values. Generally, submaximal heart rate responses were higher, and respiratory exchange ratio values were lower during the post-test. Reductions of maximal work time (12%), maximal oxygen uptake (6%) and maximal blood lactate concentration (47%) were found during the post-test. Thermal stress and glycogen depletion are possible mechanisms which may be responsible for these observed differences.

Adult↗