Biomedical subjects

A J Kielblock

Publications and source records attributed to A J Kielblock.

7 recordsLinked to original sources

PubMed1992

Diagnostic and prognostic criteria for heat stroke with special reference to plasma enzyme and isoenzyme release patterns.

1. The aim of this study was to investigate the potential value of isoenzyme release patterns as parameters of hyperthermic injury in improving the diagnostic protocol for heat stroke. 2. Rats were exposed to combinations of exercise and hyperthermic stress. Following exposure, respective release patterns of isoenzymes were determined. 3. Isoenzyme release patterns following hyperthermic injury portray both the type and extent of tissue damage more clearly than do plasma total enzyme release patterns. 4. The sensitivity of isoenzymes as a diagnostic criterion is extended to include both a temporal component (i.e. an accurate diagnosis will be possible at an earlier stage subsequent to hyperthermic exposure) and at the same time to be indicative of the exposure.

Alanine Transaminase↗

PubMed1987

Effect of beta-adrenoceptor blockade and calcium antagonism, alone and in combination, on thermoregulation during prolonged exercise.

The effect of clinically used doses of propranolol, atenolol, nifedipine, propranolol plus nifedipine, and atenolol plus nifedipine on thermoregulatory responses of 11 healthy men was studied during 2-h block-stepping in heat. Drug intervention did not alter ventilation during exercise. In contrast, propranolol and atenolol produced equivalent reductions in exercise tachycardia, implying a similar level of beta 1-adrenoceptor blockade. The heart rate response to exercise was unaffected by nifedipine and during dual beta-adrenoceptor blockade and calcium antagonism was equivalent to that with beta-adrenoceptor blockade alone. While rectal temperature rises were not modified by drug ingestion, propranolol and, to a lesser degree, atenolol and combination therapy, but not nifedipine alone, attenuated skin temperature rises. Moreover, although atenolol, nifedipine, and their combination did not alter sweating, propranolol and its combination with nifedipine enhanced sweating during the 1st and 2nd h of exercise. This study concludes that nifedipine does not modify thermoregulation during exercise and allows for greater confidence of its use during cardiac rehabilitation. Furthermore, the present data confirm that propranolol does enhance sweating during exercise and demonstrate that this effect is not mediated simply by an earlier onset of rapid sweating nor abolished by concomitant calcium antagonism.

Adrenergic beta-Antagonists↗

PubMed1986

Body cooling as a method for reducing hyperthermia. An evaluation of techniques.

The most important objective in the treatment of heatstroke and related conditions is to reduce the body core temperature to safe levels. Subjects performed at an external work rate of 54 W in hot, humid conditions (dry-bulb 40 degrees C, wet-bulb 35 degrees C), and a recent innovation to achieve body cooling, i.e. strategically placing instant cold packs (ICPs) (Coldpak; Medac) over the large vessels of the neck, axillae and groin, was evaluated under controlled laboratory conditions. We found that this procedure was not significantly more effective (P greater than 0.5) than passive body cooling in bringing about a 2 degrees C reduction in rectal temperature. Moreover, covering the whole body with ICPs plus induced evaporative cooling produced higher cooling rates than those achieved by the strategic placement of ICPs (0.0340 degrees C/min and 0.0344 degrees C/min respectively) (P less than 0.01).

Adult↗

PubMed1986

Physiologic and biochemical changes during a triathlon competition.

The triathlon has come to be recognized as a distinct endurance event and although a substantial body of research information exists with regard to the individual components (canoeing, cycling, running, etc.), the physiologic demands imposed by combining the respective activities into one continuous event have not yet been assessed. Twenty-three male athletes (age = 33 +/- 5.2 yr; mass = 71.79 +/- 7.42 kg; height = 176.0 +/- 7.21 cm; means +/- SD) participated in the study on the basis of informed consent. Venous blood samples, taken immediately prior to and on completion of the Iron Man Triathlon held in Johannesburg during 1983, were assayed for parameters of energy metabolism, fluid and electrolyte balance, and stress (tissue enzymes in serum). On the basis of post-race blood glucose (6.17 mmol. l-1), free fatty acids (1943 mumol. l-1), and blood lactate (3.45 mmol. l-1) changes, it was concluded that the triathlon is primarily, in an overall sense, an aerobic event. With the exception of magnesium and iron, serum electrolyte changes agreed with literature findings. However, body mass reductions (average 3.23 kg, i.e., 4.5%) indicated that the extent of dehydration is more severe in the triathlon than in comparable endurance events. Post-race enzyme levels (LD, CK, and AST) were significantly elevated, and LD negatively correlated with total performance time (P less than 0.01). The general conclusion is that the physiologic demand of the triathlon exceeds that of other comparable endurance events.

Adult↗

PubMed1985

Effect of beta-adrenoceptor blockade on thermoregulation during prolonged exercise.

The effect of clinically used equipotent doses of nonselective (beta 1/beta 2; propranolol) and selective (beta 1; atenolol) beta-adrenoceptor blockers on thermoregulation was studied during prolonged exercise in the heat. Oral propranolol (160 mg/day), atenolol (100 mg/day) or matching placebo were taken for 6 days each by 11 healthy young adult caucasian males. Subjects participated in 2 h of block-stepping at a work rate of 54 W in an environmental chamber with a temperature of 33.2 +/- 0.3 degree C dry bulb and 31.7 /+- 0.3 degree C wet bulb, 2 h after ingestion of the final dose of each drug. Both active agents produced similar marked (P less than 0.001) increases in subjective perception of effort, the mechanism of which was not immediately evident from changes in serum electrolytes, blood glucose, blood lactate, or ventilatory parameters. Propranolol did, however, cause a greater rise in serum K+ than placebo (P less than 0.02) and atenolol (P = NS) after exercise. Although rectal and mean skin temperatures were insignificantly altered by beta-adrenoceptor blockade, an increased total sweat production was noted with propranolol (P less than 0.01 vs. placebo) and to a lesser degree atenolol (P = NS vs. placebo) therapy. Analysis of the time course of sweat production showed the propranolol-mediated enhancement of sweating to ensue largely during the initial hour of block-stepping and to be transient in nature. The scientific and clinical implications of this observation will be dependent upon the precise underlying mechanism, a factor not identified by the present study.

Adrenergic beta-Antagonists↗

PubMed1982

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.

Animals↗

PubMed1979

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.

Adult↗