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Biomedical subjects

Y Shapiro

Publications and source records attributed to Y Shapiro.

At least 55 records · Page 3Linked to original sources
PubMed1990

Effects of caffeine ingestion on body fluid balance and thermoregulation during exercise.

This study investigated the effects of caffeine supplementation on thermoregulation and body fluid balance during prolonged exercise in a thermoneutral environment (25 degrees C, 50% RH). Seven trained male subjects exercised on a treadmill at an intensity of 70-75% of maximal oxygen consumption to self-determined exhaustion. Subjects exercised once after caffeine and once after placebo ingestion, given in a double-blind crossover design. Five milligrams per kilogram body weight of caffeine followed by 2.5 mg.kg-1 of caffeine were given 2 and 0.5 h before exercise, respectively. Rectal temperature was recorded and venous blood samples were withdrawn every 15 min. Water loss and sweat rate were calculated from the difference between pre- and post-exercise body weight, corrected for liquid intake. Following caffeine ingestion, when compared with placebo, no significant difference in final temperature or in percent change in plasma volume were found. No significant differences were observed in total water loss (1376 +/- 154 vs. 1141 +/- 158 mL, respectively), sweat rate (12.4 +/- 1.1 vs. 10.9 +/- 0.7 g.m-2.min-1, respectively), rise in rectal temperature (2.1 +/- 0.3 vs. 1.5 +/- 0.4 degrees C, respectively), nor in the calculated rate of heat storage during exercise (134.4 +/- 17.7 vs. 93.5 +/- 22.5 W, respectively). Thus, in spite of the expected rise in oxygen uptake, caffeine ingestion under the conditions of this study does not seem to disturb body fluid balance or affect thermoregulation during exercise performance.

Adult↗
PubMed1990

Effect of an acute bout of exercise on glucose disposal in human obesity.

The effect of acute exercise on insulin action has been studied in six obese (150-250% ideal body weight) non-insulin-dependent diabetics (OD), seven obese normoglycemics (ON), and six lean healthy controls (LC). Using a three-stage euglycemic clamp, the metabolic clearance rate (MCR) of glucose under increasing insulin concentrations was measured. The insulin dose-response curve was assessed on two separate occasions: 1) a base-line test and 2) 1 h after aerobic treadmill exercise at a steady-state heart rate of 150-160 beats/min. In the base-line test, under all insulin levels, glucose MCR was significantly lower in obese compared with lean individuals (P less than 0.01). Exercise increased glucose MCR at the highest hormonal concentrations applied to 124 and 134% of base line in OD and in ON, respectively (P less than 0.05); the insulin concentration required for one-half of the maximal clearance rate of glucose achieved in this study decreased from 200 to 130 and from 160 to 95 microU/ml in OD and ON, respectively (P less than 0.05). The changes in these parameters were insignificant in LC. It is suggested that acute exercise affected the insulin dose-response curve in OD and in ON but not in LC; although enhanced by exercise, glucose MCR remained significantly lower in both obese groups compared with control subjects. We concluded that insulin resistance, which accompanies extreme obesity, could be markedly decreased but not completely reversed by one bout of exercise.

Adult↗
PubMed1990

Energy expenditure in normal labor.

The energy expenditure in 23 healthy parturient women during spontaneous labor was assessed by continuous measurement of their O2 consumption and CO2 production. Due to the intermittent character of uterine contractions, normal labor and delivery did not impose high energy demands on the parturient, whereas a prolonged labor and delivery in which energy input was high led to maternal metabolic disturbances.

Adult↗
PubMed1990

Asymptomatic or mildly symptomatic effort-induced myocardial ischemia: plasma beta-endorphin and effect of naloxone.

The hypothesis that endogenous opioids may be involved in reduced exercise-induced ischemic pain or in silent ischemia was tested. Fifteen male patients with coronary artery disease were tested in a randomized, double-blind crossover study. After a preliminary screening effort test they were divided into two groups: the first group of nine patients received an i.m. injection of naloxone 0.4 mg, or saline as placebo, and the second group, comprising six patients, received 4 mg naloxone or saline i.v. Effort testing was performed at weekly intervals on an ergometric bicycle, following the Bruce protocol. ECG, heart rate, blood pressure and pain perception were monitored continually. Blood was sampled through an indwelling venous catheter for beta-endorphin determination before, at the peak of, and 10-20 min following exercise. ST depression, heart rate, blood pressure and the double product were similar after naloxone and following saline administration. Beta-endorphin concentrations in plasma were significantly increased following exercise in the second group of patients. The increase in beta-endorphin concentration was larger when the patients were pretreated with naloxone (4 mg) than with placebo. However, chest pain was not significantly altered by either dose of naloxone.

Angina Pectoris↗
PubMed1990

Field and clinical observations of exertional heat stroke patients.

Exertional heatstroke (EH) occurs when heat production, generated by muscular exercise, exceeds the body's heat dissipation capacities. This illness has been reported among young, active individuals, laborers, and religious pilgrims. Although EH includes a rectal temperature above 39.5 degrees C (depending on the timing of the measurement) and elevation of serum enzymes, altered mental status is the universally accepted sign which distinguishes EH from heat exhaustion. Once EH is suspected, cooling therapy should be initiated immediately and investigation of multiple-system involvement should be undertaken. Delay in diagnosis occurs more commonly in moderate environments, when suspicion of EH is low. Complications of EH include the central nervous, cardiovascular, pulmonary, and gastrointestinal systems, often with renal and hematologic involvement. Treatment at the point of collapse should focus on clearing the airway, measurement of rectal temperature, whole body cooling, intravenous therapy, and prompt evacuation. Hospital treatment should emphasize whole body cooling, control of convulsions, monitoring of acid-base status, cardiac function, and renal function. The incidence of EH has been reduced markedly in Israel, by using the following simple guidelines: rest periods during exercise in heat, medical monitoring of strenuous activities, use of meteorological indices, and evaluation of medical history.

Heat Exhaustion↗
PubMed1989

[Physiological responses to heat and effort and complaints of hyperperspiration].

The sensation of hyperperspiration is a common complaint in hot, humid climates. 54 men and 20 women, 18-47 years old, who had this complaint and 27 male control subjects were examined at rest and after 1 hour of mild exercise (40W) under conditions of heat stress (37 degrees C, 50% relative humidity). During exposure to heat rectal and skin temperatures and heart rate were measured every 15 min. Sweat rate was calculated for the entire period of exposure and sweat gland density was measured at 0, 60 and 120 min. Only insignificant deviations from baseline values were noted at rest. During exercise the sweat rate of the men with the complaint was within normal limits and similar to that of the control men (285 +/- 75 ml/m2 vs 272 +/- 48). Matching for age and V02 max revealed no significant differences in physiological responses of men with and those without the complaint. Women with the complaint lost 25-30% less fluid (226 +/- 67 ml/m2) and their concentrations of active sweat glands were lower than in either of the male groups. 2 men and 1 woman with the complaint and 1 control lost 400-425 ml/m2 during exercise, the upper limit of normal. Only 1 subject showed hyperperspiration (855 ml/m2) during the test. All physiological parameters examined in these 5 subjects were within normal limits. It is concluded that the complaint of hyperperspiration in our self-selected group is basically a subjective feeling and has no pathological basis. None of the subjects was heat intolerant.

Adult↗
PubMed1989

Plasma-cortisol levels in experimental heatstroke in dogs.

The effect of external heat-load, exercise and dehydration on dynamic changes in plasma cortisol during the development of heatstroke was investigated. Thirty-three unanesthetized dogs were tested under two sets of climatic conditions: comfort conditions and hot-dry climatic conditions, half of them while exercising. Half of the dogs in each group were rehydrated. None of the dogs that were investigated at room temperature suffered heatstroke. Of the dogs exposed to high ambient temperature, all of the exercising, as well as five out of six non-hydrated dogs and one rehydrated non-exercising dog suffered heatstroke. Significant dehydration (6%-7% of body weight), occurred only under high ambient temperature. Plasma cortisol levels of all dogs that suffered heatstroke rose conspicuously for at least 5 h and returned to normal levels 24 h later. Cortisol levels of dogs who did not experience heatstroke remained within the normal range. Cortisol levels correlated with the severity of the stress leading to heatstroke. High and rising levels of cortisol, several hours after body temperature returns to normal, may support the diagnosis of heatstroke.

Animals↗
PubMed1989

The effect of caffeine ingestion on physical performance after prolonged exercise.

The purpose of this study was to determine the effect of caffeine ingestion on physical performance after prolonged endurance exercise. Twenty three trained male volunteers participated in a 40-km march and were divided into two groups, matched for caffeine clearance rate and aerobic capacity. The experimental group ingested, prior to the march, a caffeinated drink at a dose of 5 mg.kg-1 body mass and at the 3rd and 5th h of marching an additional drink at a dose of 2.5 mg.kg-1 body mass. The control group ingested a drink of equal volume at the same times. Upon termination of the march each subject performed a cycle ergometer test at an intensity of 90% maximal oxygen consumption. Time to exhaustion and rate of perceived exertion (RPE) were recorded. Blood samples were drawn predrink, at the 3rd and 5th h of marching and immediately after the cycle ergometer test, and were analysed for caffeine, free fatty acids (FFA), lactate and glucose levels. Plasma FFA levels increased during the march (p less than 0.05), with no significant difference between groups. Lactate levels increased in the experimental group (p less than 0.05), with no significant change in the control group. Glucose levels did not change significantly in either group. After the cycle ergometer test, lactate levels were significantly higher in the experimental, as compared to the control group (3.77 +/- 0.33 vs 2.52 +/- 0.35 mmol.l-1, respectively). There was no significant difference between treatments in the time to exhaustion on the cycle ergometer, but RPE was different (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Clustering of strokes in association with meteorologic factors in the Negev Desert of Israel: 1981-1983.

Clinical observations of the apparent clustering of daily stroke admissions to a regional hospital in an arid climate prompted our investigation of possible meteorologic factors associated with stroke admissions. Daily hospitalization and meteorologic data were studied for 895 patients with stroke admitted to Soroka Medical Center, Beer-Sheva, Israel, during 1981, 1982, and 1983. The average daily incidence of stroke was about twice as great on relatively warm days as on relatively cold ones. This increase may be explained by increases in thromboembolic mechanisms secondary to physiologic changes in response to heat. When heat waves are predicted, information on the added risk for stroke needs to be disseminated to both the population and to health care providers so preventive measures can be instituted. Special attention should be devoted to air conditioning and adequate consumption of liquids, and antiplatelet aggregation medication such as aspirin should be considered.

Atmospheric Pressure↗
PubMed1987

Changes in serum magnesium concentration after strenuous exercise.

Serum magnesium concentration (S-Mg) was measured in 20 highly trained young men (mean age 19.5, +/- 0.5, range 18-20.5) before, and at 1 hour, 24 hours, 72 hours, and 3 months after a 120 km hike. As found in previous studies, S-Mg was significantly decreased at the end of the hike (p less than 0.001, [corrected] Student's t-test). In this group S-Mg had risen significantly after 24 hours in relation to the value at 1 hour (but not to starting value); yet, at 72 hours and 3 months later, it was once more significantly lower than the starting value (p less than 0.001 and p less than 0.05, respectively, Student's t-test). A marked elevation in serum creatine kinase activity (CK) suggests that the rise in S-Mg observed at 24 hours is the result of either exertional rhabdomyolysis or loss of membrane integrity, as a result of the strenuous exertion, since the CK had fallen sharply by 72 hours after the hike. The biphasic, statistically significant, lowering of S-Mg which persisted after 3 months suggests that strenuous exertion induces magnesium deficiency.

Adolescent↗
PubMed1987

Isotonic (dynamic) and isometric (static) effort in the assessment and evaluation of diastolic hypertension: correlation and clinical use.

We compared the effect of two exercise stress tests on blood pressure in normal and borderline populations. The aim of the trial was to determine if isometric exercise testing by handgrip can replace the isotonic exercise test in population screening for the detection of mild and latent hypertension. The study involved 150 subjects; 62 were normotensive and 88 were borderline hypertensive. No significant statistical difference was found in diastolic pressure between the tests. In normotensive subjects, the diastolic response after isotonic effort was 79.3 +/- 9.6 mm Hg and 89.0 +/- 9.7 mm Hg after the isometric test (p less than 0.05). However, both results did not pass 100 mm Hg. In borderline hypertensive patients the diastolic response to the isotonic test was 105.6 +/- 8.8 mm Hg and after the isometric test 107.7 +/- 10.6 mm Hg (NS). The results show that the handgrip isometric test can replace the complicated isotonic test for the screening detection and evaluation of hypertensives in the population.

Adult↗
PubMed1987

Surgical treatment of infants with esophageal atresia and VATER association.

Our surgical experience in 10 infants with esophageal atresia and the VATER association of multiple congenital anomalies is reviewed. Early recognition and evaluation of the various lesions enabled the planning of a staged surgical approach with a satisfactory outcome. Seven of the patients survived. There were no immediate postoperative deaths. Development and growth curves of the surviving patients are satisfactory. Despite multiple operative procedures infants with VATER association may lead a reasonably normal life.

Abnormalities, Multiple↗
PubMed1986

Increase in rat intestinal permeability to endotoxin during hyperthermia.

Victims of heat stroke exhibit several clinical features which are also encountered in endotoxaemia. In order to investigate these similarities hyperthermic rats were used to explore the possibility that high body temperature results in increased permeability of intestinal wall to endotoxin. 125I endotoxin was introduced into intestinal segments taken from non-heat exposed rats. The segments were then incubated at 37 degrees C or 45 degrees C. Intestinal segments from heat stressed rats were similarly prepared and incubated at 37 degrees C. Leakage of endotoxin from segments taken from heat stressed rats was three times greater than from those from non-heat stressed rats, as were the segments from non-heat stressed rats which were incubated at 45 degrees C. These results indicate that the intestinal membrane is damaged by heat and that an increase in outward leakage of microbial endotoxins from the gut then occurs. This might contribute to the pathophysiological picture of heatstroke.

Animals↗