Cardiovascular origins of heatstroke pathophysiology: an anesthetized rat model.

Opinion is divided on issues concerning a cardiovascular origin of heatstroke pathophysiology as well as those concerning the mechanism of circulatory failure in heat. Such controversies seem to arise because of insufficient data covering the prodromal period of heatstroke. A reappraisal of the nature and sequence of early circulatory responses to heat stress was, consequently, undertaken by subjecting male albino rats to an environmental temperature of 45 degrees C at 15% relative humidity until overt circulatory failure occurred. Although the initial circulatory responses were normal for mild exertion, an inapparent circulatory crisis developed, probably a result of the abolishment of compensatory splanchnic vasoconstriction. The impending threat of functional hypovolemia was, temporarily at least, obscured by cardiac compensation and the extent of cardiovascular commitments may, therefore, have been underestimated. This also suggests that cardiovascular adjustments during the stress of heat may prove to be an essential feature of heatstroke pathophysiology.

Creatine phosphokinase and lactate dehydrogenase levels after ultra long-distance running. An analysis of iso-enzyme profiles with special reference to indicators of myocardial damage.

Blood samples obtained from 20 runners on completion or partial completion of a 160-km marathon were assayed for total serum creatine kinase (CK) and lactate dehydrogenase (LD), as well as for the respective iso-enzymes. Total CK was significantly elevated in all subjects, the mean value (2 243 U/l) constituting a 24-fold increase above the normal upper limit. In 65% of these cases, the cardiac-specific iso-enzyme of CK, MB, was present. The mean LD level (1 220 U/l) also exceeded the upper limit of normal significantly, 5 subjects presenting a 'flipped' LD pattern (LD1 greater than LD2). Three subjects exhibited the MB iso-enzyme in the presence of a flipped LD pattern. No electrocardiographic evidence of irreversible cardiac 'damage' could, however, be established after the race, nor any significant decrease in the Bruce protocol stress test rating. It is concluded that the MB iso-enzyme of CK, even in conjunction with a flipped LD pattern, may not represent unequivocal evidence of myocardial damage under all circumstances.

The relationship between scholastic progress and nutritional status. Part I. A study of 488 school beginners.

The reading progress of 488 Chatsworth Indian school beginners, in relation to their nutritional status, was assessed. It was found that the majority of the children were grossly growth-retarded and some 90% of them could be classified as slow learners. The significance of these findings is discussed. It is recommended that dietary supplementation be introduced for preschool as well as for school-going children in communities where growth retardation is prevalent.