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Biomedical subjects

S M Horvath

Publications and source records attributed to S M Horvath.

At least 19 recordsLinked to original sources
PubMed1979

Effect of marihuana on cardiorespiratory responses to submaximal exercise.

Six male chronic marihuana (MH) users exercised on a bicycle ergometer for 15 min at approximately 50% VO2max under 3 conditions: (1) not smoking (control), (2) after smoking MH containing 7.5 mg (-) delta-9-tetrahydrocannabinol, and (3) after smoking placebo marihuana (PL). The MH was administered double-blind in a counterbalanced repeated-measures design. Heart rates (HRs), arterial blood pressures (BPs), pulmonary ventilation (VE), and oxygen uptake (VO2) were measured during exercise and 15 min recovery. PL had no effect on any of the physiologic variables. Smoking MH had no effect on systolic blood pressure (SBP), diastolic blood pressure (DBP), VE, or VO2, but did induce a marked increase in heart rate which persisted throughout exercise and recovery periods, averaging 34% higher than control values at rest, 18% higher during exercise, and up to 50% higher during recovery. MH smoking increased the product of HR x SBP in all circumstances.

Adult↗
PubMed1979

Age and aerobic power in women: a longitudinal study.

Thirty-six women from an original cross-sectional population of 81 were retested after an average time span of 6.1 years to determine the longitudinal effects of aging on aerobic power. Women in their 20s maintained a constant level of VO2max. All other age groups showed a decrease in aerobic power (l . min-1 and ml . kg-1 . min-1) similar to that observed in the cross-sectional study. Although the decline in VO2max was similar for both groups, active women increased walk time on the treadmill, while sedentary women decreased in endurance time. Maximal heart rate also decreased with age but the rate of decrease was not constant across time. HRmax remained relatively steady during the middle years and then declined at a faster rate in the 50- and 60-year-old age groups. The results of the present study suggest that cross-sectional studies can provide valid information about the effect of age on response to maximal exercise provided that close attention is paid to the limitations underlying regression therapy. The data also indicate a need to consider alternatives to linear regression analysis of aging effects, since the rate of change of some variables is not constant across age.

Adolescent↗
PubMed1979

Thermoregulation in swimmers and runners.

Thermoregulatory responses of six trained swimmers and five runners to cold and heat were evaluated during 30 min of exercise (60% VO2max) while immersed to the neck in 20, 25, 30, and 35 degrees C water. Mean oxygen uptake was similar for both groups during all four trials. Changes in metabolic rate during the 8th to 28th min were significantly greater for the runners in 20 degrees C water, and swimmers in 30 and 35 degrees C water. Heart rates, Tsk, delta Tre, Tb, body heat content, and heat storage were dependent on water temperature. Runners were able to attain higher sweat rates than swimmers in 35 degrees C water. Swimmers had significantly greater tissue conductance values in the 35 degrees C exposure. Swimmers thermoregulated better in 20 degrees C water than runners, possibly due to a larger surface area-to-volume ratio, percentage body fat, subcutaneous fat, or improved vasomotor control. Exercise in the heat was better tolerated by runners. Physical training in water does not improve heat acclimatization to the extent of training in air, but does improve cold tolerance.

Adolescent↗
PubMed1979

Plasma volume changes during rest and exercise in different postures in a hot humid environment.

Plasma volume shifts were investigated in five male subjects who rested and exercised in the upright, low-sit, and supine postures in a hot humid environment (49.5 degrees C, 28.9 Torr). The resting and exercise periods were each 45 min in duration. Weight losses during rest were 0.3% with an additional weight loss of 1.1% during exercise. During exercise subjects worked at either 360 or 540 kpm.min-1 in each of three postures. Each experiment was preceded by a 30-min control period in the supine posture at an ambient temperature of 22 degrees C. At rest plasma volume was reduced 17.3% in the upright, 9.0% in the low-sit, and 2.2% in the supine postures (using the end of the supine rest as the zero reference point). Supine exercise resulted in a plasma volume decrease of 11%, the low-sit 7.1%, and the upright 2.7%. The total reduction in plasma volume during the rest and exercise period was 20% in the upright, 16.1% in the low-sit, and 13.3% in the supine. No significant differences in plasma volume shifts were observed between the high and low work loads. The results indicate that the plasma volume shifts observed during rest and exercise in the heat are qualitatively similar to those observed in a cool environment.

Adult↗
PubMed1979

Maximal work capacity of women during acute hypoxia.

Six healthy women (22--34 yr of age) performed maximal bicycle work in a hypobaric chamber at sea level and at simulated altitudes of 2,130 and 3,050 m (barometric pressures, 758, 586, and 523 Torr). Maximal oxygen uptake (VO2max) decreased 10 and 15% from sea-level values at 2,130 and 3,050 m, respectively. At these altitudes minute ventilation (VEBTPS) increased 17 and 22% respectively, a consequence of increased respiratory rate (fR). Respiratory exchange ratios increased 10 and 14%, and oxygen pulse decreased 9 and 12%, respectively, at 2,130 and 3,050 m. Maximal blood lactates, heart rates, cardiac outputs, and plasma volume shifts were unaffected by these altitudes. Although during maximal work the percentage increases in VEBTPS, fR, and R that resulted from altitude exposure were greater in women than those previously reported for men, the decrements in VO2max were comparable to those in men. The results show that relative to their performance at sea level, men and women have equal ability to perform maximal work at altitudes up to 3,050 m.

Acute Disease↗
PubMed1979

Heat tolerance and aging.

Although children and older adults appear more susceptible to heat stress, the mechanisms responsible for their lower tolerance are not fully understood. Many studies dealing with the effect of age on temperature regulation have concluded that an inadequate sweating response is primarily responsible for the low tolerance of children and the elderly to exercise in the heat. However, the dependence of core temperature on relative exercise intensity and sweat rate on absolute exercise intensity makes it difficult to avoid the confounding effects of exercise on thermoregulation when aerobic power (Vo2max) varies across age groups. When 38 non-acclimatized females, ages 12 to 68 years, exercised at 30-35% Vo2max in the heat, the degree of cardiovascular stability was the primary predictor of tolerance time. Age was not a significant predictor. However, it was evident that individuals at either end of the age continuum were more likely to be at risk. For children this risk was associated with the instability of an immature cardiovascular system; for older women, a marked decrement in aerobic power. Sweat rate added significantly to the prediction of tolerance time for all subjects regardless of age. Whether the decrease in responsiveness of sweating noted for some older individuals is an age related change or a reflection of their lower fitness levels is not known.

Acclimatization↗
PubMed1979

Response of women mountaineers to maximal exercise during hypoxia.

Eight members of the American Women's Himalayan Expedition, ranging in age from 20-49, performed maximal exercise on a treadmill under normoxic and acute hypoxic (12.58% O2) conditions. Normoxic values for VO2 max were above average for all subjects and did not decline with age. The mean decrease in VO2 max (26.7%) during hypoxia was equivalent to that reported for younger males, which suggests that age was not a factor in response to hypoxia. Maximal heart rate, respiratory exchange ratio, oxygen pulse, and walk time were lower in hypoxia while ventilatory equivalent and blood lactate were higher. VEmax BTPS, was the same under both conditions. The combination of laboratory results and field observations by the Expedition physician suggest that women are capable of performing hard work at high altitude if they are in good condition and properly acclimatized.

Adult↗
PubMed1979

Visual evoked potentials and signal detection following a marathon race.

Five marathon runners participated in a visual sustained attention experiment 1 week prior to a competitive martathon race and from 1.5 to 8.5 h following the race. The task was designed to help assess changes in central nervous system function by examinining both behavioral deficits and electroencephalogram (EEG) visual evoked potentials as a function of the race. A significant increase in heart rate was observed during the behavioral task. No changes in any of the wave forms of the EEG visual evoked response were observed during the vigilance task as a function of the race. Sustained visual attention responses were unchanged for correct detections, but post-marathon performance gave significantly fewer false positive responses. The results provided evidence that central nervous system dysfunction was not observed following the completion of a competitive marathon race.

Adult↗
PubMed1979

Pulmonary function and maximum exercise responses following acute ozone exposure.

We examined changes in pulmonary function during resting exposure to concentrations of ozone at 0.75, 0.50, 0.25, and 0.00 parts/million (ppm), and determined the effect these exposures had on a subsequent maximum exercise test using filtered air. In order to determine if recovery of pulmonary function would be facilitated by increased ventilation due to maximum exercise, a control condition was conducted with subjects resting for a period equivalent to the maximum exercise condition. Eight males and five females participated in eight different conditions in order to answer these two questions. Resting 2-h exposure to 0.75 and 0.50 ppm ozone caused significant decrements in forced vital capacity of 10% and 5%, respectively. However, 0.00 and 0.25 ppm ozone induced no pulmonary decrement. None of the pollutant conditions reduced subsequent maximum exercise performance (ml O2.min-1.kg-1, heart rate, and total performance time). The pulmonary function responses after the maximum capacity test returned to pre-ozone values for the 0.50 ppm condition, but were still significantly decreased for the 0.75 ppm condition. The increased ventilatory exchanges from maximum exercise did not facilitate the return of pulmonary function. It appeared that increased ventilation during ozone exposure plays a significant role only in inducing pulmonary function decrement, but not in facilitating the return of pulmonary function to normal values.

Adult↗
PubMed1979

Auditory and visual sustained attention during ozone exposure.

Experiments were conducted to determine the effects of different concentrations of ozone at 0.00, 0.25, 0.50, and 0.75 parts/million (ppm) on sustained visual and auditory attention tasks (vigilance performance). When the rate of signals to nonsignals was low, approximately 1 out of 30, ozone in concentrations as high as 0.75 ppm did not alter performance to either visual or auditory tasks. However, when the ratio of signals to non-signals was increased, a deficit in performance beyond that of the normal vigilance decline was observed during the 0.75 ppm ozone exposure. However, no changes in false positive responses occurred. The results were interpreted within the framework of an arousal hypothesis, suggesting that high concentrations of ozone may produce overarousal.

Adult↗
PubMed1978

Transcutaneous, noninvasive PO2 monitoring in adults during exercise and hypoxemia.

A new, commercially available, transcutaneous (tc) PO2 monitor was tested in adult females and in laboratory animals to assess its applicability in measuring arterial oxygen tension during physiological stress. Observed values on dogs correlated well with direct measurements of arterial PO2 and with previous data obtained from measurements of arterial blood during exercise and hypoxemia. In our female subjects the unit responded rapidly to changes in inspired ambient oxygen and electrical stability was excellent during maximal exercise tests. Transcutaneous PO2 decreased to an average of 87.8 Torr during maximum exercise breathing 20.9% O2, and to 32 Torr while breathing 12.6% O2 at maximum work. Two distinct patterns of response to tc PO2 were observed during hypoxic and normoxic exercise. The technique appears to have substantial future application both in clinical and physiological investigation involving adult subjects.

Adult↗
PubMed1978

Ileostomy of the distal end of the bypassed intestine in a patient with jejunoileal bypass for obesity.

Ileostomy of the distal end of the bypassed segment of small intestine was done twenty-three months after a 28 to 20 cm (12 to 8 inch) end-to-end jejunoileal bypass for obesity (Scott operation) in a forty-eight year old white female, thus creating a Thiry fistula. Weight prior to jejunoileal bypass was 130 kg (287 pounds). Before ileostomy it had stabilized at 80.3 kg (177 pounds). Indications for ileostomy were three episodes of blind loop syndrome and three episodes of severe bleeding from the ileotransverse colostomy anastomotic site. Culture of the bypassed segment at laparotomy revealed bacteroides, clostridia, and other anaerobes as well as the usual aerobic large bowel flora. After ileostomy the bypassed segment contained no anaerobic bacteria. Daily fluid output from the ileostomy has decreased with time, averaging 436 ml per day for the first postileostomy month and 50 ml per day for the ninth month. Beneficial effects of the ileostomy include: (1) better sense of well being; (2) no further episodes of blind loop syndrome or intestinal bleeding; and (3) cessation of anal itching. Nine months after ileostomy, hyperoxaluria and acquired megacolon were present. Weight was 5.9 kg (13 pounds) greater than before ileostomy.

Bacteroides Infections↗