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Biomedical subjects

Y Epstein

Publications and source records attributed to Y Epstein.

At least 109 records · Page 6Linked to original sources
PubMed1981

Way of life as a determinant of physical fitness.

Four hundred and five urbanites and 302 communal agricultural settlement (Kibbutz) members participated in a study which examined their physical fitness. The subjects were divided into three subgroups according to age: 18-21 years, 22-30 years, and 31-40 years. No differences were found among the two populations in all three subgroups as concerns anthropometric data. In the youngest age group no differences in resting heart rate and VO2 max between urbanites and kibbutz dwellers were found. For those aged over 21 years the VO2 max (40.8 +/- 10.0 ml O2/kg body weight/min for those aged 22-30 years and 38.7 +/- 9.7 ml O2/kg body weight/min for those aged 31-40 years) was significantly higher (p less than 0.001) than that of the urbanites (35.6 +/- 7.0 for age 22-30 and 33.1 +/- 8.0 ml O2/kg body weight/min for age 31-40 years). The results confirm the notion that physical fitness is a good profile of habitual activity.

Activities of Daily Living↗
PubMed1981

The energy cost of walking and running with and without a backpack load.

The effect of backpack load (20 kg) on oxygen consumption while walking and running at different speeds was investigated. Fifteen males walked an ran (with and without load) up a 5% sloped treadmill at 6.4, 7.2, 8.0, 9.6, and 11.2 km/h (4, 4.5, 5, 6, and 7 mph). While walking VO2 rose at a rate of 0.6 (l/min)/(km/h) and while running 0.3 (l/min)/(km/h). The mean oxygen consumption at the various speeds was 28.65, 33.78, 40.64, 46.84, 54.48 ml O2/kg BW/min, respectively, for the whole group without load and 26.52, 32.26, 38.28, 44.26, 48.16, respectively, with load. The breaking point between walking and running was at about 8.2 km/h. Carrying the load increased VO2 at a constant rate, and induced a breaking point between walking and running at a significantly lower speed for the smaller subjects than for the more robust ones. The results indicate that for certain tasks involving endurance and heavy load carriage, people should be selected according to criteria which integrate aerobic capacity and anthropometrical features.

Adult↗
PubMed1981

Heat tolerance in patients with extensive healed burns.

Some thermoregulatory parameters of 10 subjects with healed burns were studied. The subjects, 4 of whom had healed burns of over 40 percent (group A) and 6 with burns smaller than 30 percent (group B) were assigned in a climatic chamber to 3 hours bench stepping (30 cm height) under 40 degrees C and 50 percent relative humidity. Rectal temperature, weighted skin temperature, heat storage, and heart rate were all found to be significantly higher in group A than in group B or group C (control group of normal subjects). No significant difference was observed between groups B and C. A highly significant linear correlation (r = 0.89) was found between the sweat rate and percentage of burned area. In addition, 3 subjects of group A terminated the study after less than 90 minutes. Two subjects in group B terminated the study after 120 and 135 minutes, while all subjects of group C finished the entire 3 hour work. The study indicates that subjects with burns of over 40 percent could be classified as heat intolerant due to a pronounced reduction in perspiration area.

Adult↗
PubMed1981

The effect of pure aerobic training on aerobic and anaerobic capacity.

Twenty men (Group I) and twenty-seven men (group II) took part in a 3-week training course. The training was aerobic and consisted of marching and hiking. The intensity of the training regimen in Group II was greater than for Group I. The maximal oxygen uptake (VO2 max) increased significantly in both groups, more in Group II than in Group I, though no significant change was found in anaerobic capacity. It can be concluded that aerobic training cannot induce improvement in anaerobic capacity.

Adult↗
PubMed1981

Inhibin-like activity and steroid content in human follicular fluid during the periovulatory period.

Inhibin-like activity as well as estradiol-17 beta and progesterone content were assayed in human follicular fluid obtained at different stages of the periovulatory period. Between the start of the midcycle estrogen surge in plasma and the subsequent gonadotrophin peak, follicular fluid was found to contain similar levels of estradiol-17 beta and progesterone (8.2 pmol/microliter) and to induce a marked (44%) inhibition of gonadotrophin-releasing hormone-stimulated release of FSH. The midcycle gonadotrophin peak was characterized by a drop in estradiol-17 beta levels and a tripling in progesterone levels, whereas inhibin-like activity fell to almost half the previous value.

Adult↗
PubMed1981

Temporary heat intolerance in a heatstroke patient.

A case history of recurrent heatstroke is presented. The first heatstroke was incurred during strenuous exercise following acute gastroenteritis; the second heatstroke happened 1 month later during a march in hot climatic conditions. Two heat tolerance tests were performed. On the first, 1 month after the second incidence, an intolerance to heat was observed which, on the second test 5 months after the incidence, had disappeared. It is proposed that acute intercurrent illness and heatstroke in itself cause temporary susceptibility to exercise in heat, and that every heatstroke patient should be examined to determine the efficiency of his thermoregulatory mechanisms.

Adult↗
PubMed1980

A comparison of various methods for the determination of VO2max.

Previous studies have shown that true maximal oxygen uptake (VO2max) obtained by means of cycle ergometer and step test are lower than the VO2max measured during uphill treadmill running. The predicted VO2max measured by ergometer was even lower. Four different methods for the determination of VO2max within the same group of examinees were compared: True VO2max by treadmill, ergometer, step test, and predicted VO2max (Astrand-Rhyming). This study was performed on 15 healthy non-professional sportsmen. They underwent progressive test protocols on alternating days and the results were as follows -- VO2max expressed in ml O2 kg BW/min (mean +/- SD): treadmill running 63.8 +/- 4.7; ergometer cycling 60.2 +/- 5.6; step test 59.6 +/-5.2 and predicted VO2max 59.9 +/- 6.9. The VO2max as determined by uphill treadmill running was significantly higher than with the other methods. No significant difference was found between true VO2max determined by the ergometer and step test. However, step test and properly executed Astrand-Rhyming test again proved to be reliable and deviate from the treadmill test by only 6%. Maximal heart rate was significantly higher in the treadmill and step tests than in the direct ergometer test.

Adult↗
PubMed1980

Orthostatic responses in heat tolerant and intolerant subjects compared by three different methods.

The orthostatic responses of 10 heat tolerant and five intolerant subjects were evaluated by three different test methods--standing, head-up tilt (HUT), and head-up tilt after prolonged exercise (HUTPE)--in a hot environment of 40 degrees C, 40% RH. No difference was found within the normal group between responses in the standing and HUT test. In the HUTPE test, orthostatic responses were inadequate and 5 of 10 subjects fainted. The heat intolerant subjects reacted to all three tests similarly to the normal group, though their heart rate was higher and 3 out of 5 fainted at an earlier phase in the HUTPE test.

Adult↗
PubMed1980

Psychomotor deterioration during exposure to heat.

The effect of different heat loads on vigilance and complex cognitive tasks involved in a mission of different intensities were examined. Nine healthy volunteers were randomly exposed for 2 h to three climatic conditions: comfort (21 degrees C ET), moderate heat load (30 degrees C ET) and severe heat load (35 degrees C ET). The subjects were assigned to missions of shooting at targets of three different sizes. Physiological parameters (HR, Tre, and sweat rate) and psychomotor ability were monitored. Exposure to 35 degrees C ET gave rise to elevated HR, Tre, and dehydration of 2.5%, while exposure to 21 degrees C and 30 degrees C ET caused no physiological burden. Speed of performance was significantly higher when the subjects were exposed to moderate heat load than to either comfort or severe heat load. Percentage of errors, however, rose gradually with the rise in heat load. The results indicate: a) The effect of the intensity of the task and heat load on deteriorating performance are synergistic; b) psychomotor performance deteriorates even before physiological parameters are impaired, possibly because of feelings of discomfort; c) even highly motivated subjects are effected by heat load, especially when assigned to complex missions which require a high state of vigilance, cooperation, and coordination.

Adult↗
PubMed1980

Tap water, an efficient method for cooling heatstroke victims--a model in dogs.

Forty experimentally heatstroke dogs were cooled by immersion in water at temperatures varying from 1-25 degrees C. At all water temperatures, cooling occurred at a much slower rate in comatose dogs in conscious ones. Dogs cooled in tap water (15-16 degrees C) had the same cooling rate as those cooled in ice water (1-3 degrees C). At water temperatures above 18 degrees C, cooling rates were considerably decreased. Since tap water cooled as efficiently as ice water, its use may prove the method of choice for human heatstroke victims. Its advantages are ready availability, simplicity of use, and its failure to cause shivering.

Animals↗
PubMed1979

Serum 3,5,3'-triiodothyronine and 3,3',5'-triiodothyronine concentrations during acute heat load.

To determine the changes in thyroid hormone metabolism during short periods of exposure to heat, 30 euthyroid healthy male volunteers (aged 23--40 yr) were placed in a climatic chamber for 2 h (35 C, 50% relative humidity). The subjects were at complete rest during the first hour and performed light work (40 watts) during the second hour. Blood samples for T4, T3 and rT3 were drawn at 0, 60, and 120 min. Rectal temperature and heart rate were monitored continuously. No significant changes in T4, T3, rT3, rectal temperature, or heart rate were observed after the first hour (basal levels, 8.5 +/- 0.3 microgram/dl, 160 +/- 5 ng/dl, 14.5 +/- 2.5 ng/dl, 37.2 +/- 0.1 C, and 78 +/- 8 beats/min, respectively; mean +/- SEM). During the second hour, a significant rise in body temperature was recorded (38.5 +/- 0.1 C), accompanied by a significant decrease in mean serum T3 concentration and a rise in mean serum rT3 concentration, T4 concentration remained unchanged. Our findings suggest that, parallel to the elevation in body temperature, there is a shift in the conversion of T4 to the noncalorigenic rT3 metabolite rather than to T3.

Body Temperature↗
PubMed1977

The effects of testosterone and its 5alpha-reduced metabolites on pituitary responsiveness to gonadotrophin-releasing hormone (Gn-RH).

The aim of this study was to investigate effects of androgens on gonadotrophin release in response to gonadotrophin-releasing hormone (Gn-RH) stimulation in vitro. Hemipituitaries of mature male rats were pre-incubated for 90 min with T, DHT, 3alpha- or 3beta-diol (4 ng or 4 microgram/ml medium), and the incubation continued for 240 min after adding Gn-RH (1 ng/ml medium). Gn-RH caused a 4-5-fold rise in the secretion of LH and a 2-fold rise in FSH secretion. The effect of the androgens was dose-dependent. At low levels, T and DHT exerted no effect on Gn-RH-stimulated gonadotrophin release, whereas the two androstanediols (3alpha- and 3beta-diol) augmented the Gn-RH stimulation of both gonadotrophins, though preferentially LH. With high doses of androgens, the results obtained showed: a) no effect of T; b) DHT suppression of the Gn-RH-stimulated FSH release; c) suppression of Gn-RH stimulation by 3alpha- and 3beta-diol regarding both LH and FSH. It is concluded that T exerts through its reduced metabolites a feedback effect on the pituitary gland responsiveness to Gn-RH stimulation.

Androstane-3,17-diol↗
PubMedDate not supplied

Principles of respiratory protection.

This review describes the various types of respiratory protective devices used in Israel during the Persian Gulf war, and summarizes the relevant physiological concepts of respiratory protection. Physiological principles of modern devices with powered air supply are discussed in detail. Our experience may be useful in the evaluation of new respirators and in finding solutions for problematic subpopulations.

Adult↗