Effect of hyperthermia on somatosensory evoked potentials in the anaesthetized rat.

In the rat heat stroke model, established by heating to a climatic chamber temperature of 42 degrees C, the brain temperature was found to be consistently lower than the rectal temperature, suggesting efficient brain cooling mechanisms in the rat. In response to heating, with increasing brain temperature, the latencies of the somatosensory evoked potentials (SEPs) showed an initial decrease followed by an increase (inflection point). Studies were done on rats heated up to, before, or after the inflection point and then cooled. Reversibility with cooling of functional and structural changes induced by heat was evaluated by analysis of SEPs, survival time, brain blood perfusion and histopathology. The evidence from these studies demonstrated that the brain temperature at which the inflection in wave P2 latency occurred was critical, beyond which hyperthermia produced irreversible changes in the SEP, shorter survival time, relative reduction in brain blood perfusion and evidence of brain histopathological damage. The suggestion that endorphins may mediate brain dysfunction in hyperthermia was investigated. In rats heated and then cooled after wave P2 latency inflection naloxone, the endorphin antagonist, was injected (10 mg/kg, intravenously) just prior to the inflection. It produced reversibility of SEP changes as well as longer survival time (P less than 0.001) compared to saline-treated rats.

Comparison of exercise effects on the hemodynamics of the Bio 14.6 cardiomyopathic hamster.

1. Comparisons of the effects of 4 and 16 weeks of exercise were made on; cardiac output, stroke volume, heart rate, left intraventricular systolic and diastolic pressures, dP/dt, and heart calcium in the Bio 14.6 cardiomyopathic and F1 B hamsters. 2. In the cardiomyopathic hamster the cardiac output, stroke volume, left intraventricular systolic pressure and dP/dt, which were all depressed in the age related sedentary animals, were increased by both periods of exercise. The left intraventricular diastolic pressure which was elevated was likewise decreased by both exercise periods. Only the 16 week exercise period decreased the resting heart rate. 3. In the normal F1 B hamster, both periods of exercise increased the cardiac output and stroke volume while the left intraventricular systolic pressure was decreased. Only the 16 week exercise decreased the resting heart rate and left intraventricular diastolic pressure and increased the left ventricular dP/dt. 4. Both periods of exercise increased the total heart calcium in the Bio 14.6 hamster while the heart calcium in the F1 B was increased only by the 16 week exercise period.

Exercise time relationship to coronary risk factors in Kuwaiti adult males 1985-1986.

Two hundred and sixty-nine apparently healthy Kuwaiti men, aged 20-49, from 800 randomly selected Kuwaiti families, were examined for cardiovascular fitness and risk factors for coronary heart diseases (CHD). The risk factors were examined by exercise stress test on Quinton-2000 ECG monitor and treadmill Q-model 24-26, Bruce protocol, along with Ergo-oxyscreen, by laboratory tests of fasting blood lipid levels, and by interview using a questionnaire. The sample was stratified into three age groups, 20-29, 30-39, and 40-49. For the entire sample, the results showed that a number of the investigated factors were significantly correlated with the duration of treadmill exercise time. Univariate analysis indicated that performance was inversely correlated with age, cholesterol levels, cholesterol:HDL ratio, triglycerides and uric acid, weight, body-build indexes, body density, resting heart rate, blood pressure (BP), personal history of CHD, and smoking habits. Most of the observed significant correlations were particularly pronounced in the younger age groups, 20-39 years. In this group, significant results in the analysis of variance were found between the treadmill performance time and a number of risk factors, including: cholesterol levels, age, cholesterol:HDL ratios, triglycerides, uric acid, heart rate, elevated systolic blood pressure, and obesity.