A diagnosis of Smith-Lemli-Opitz syndrome was made shortly after birth in a small-for-dates infant, on the basis of a characteristic face, penoscrotal hypospadias, bilateral postaxial hexadactyly, and bilateral syndactyly of toes 2-3. The clinical course was marked by failure to thrive, severe delay, refractory myoclonic jerks beginning at age 2 months, and increasing hepatosplenomegaly. He developed corneal clouding and increased gingival hypertrophy and died at age 18 weeks. Autopsy disclosed widespread storage of mucopolysaccharides and lipids within the macrophages and, to a lesser extent, parenchymal cells, of all organ systems. There was extensive demyelination of the cerebral white matter, and dystrophic calcification in the cerebrum, cerebellum, and brainstem. There was no evidence of primary neuronal involvement in the storage. Although the chance concurrence of 2 uncommon diseases is rare, a causal link between the clinical anomalies and the storage disorder cannot be argued convincingly on the basis of one case. Careful pathologic studies of other children who die with clinical signs compatible with Smith-Lemli-Opitz syndrome are indicated.
Cardiac performance was studied in the isolated perfused hearts of rats heat acclimated at 34 degrees C (AC) and their age-matched controls (C). The pressure-volume curves during isovolumetric conditions showed a shift to the right in AC compared with C hearts. At similar left ventricular (LV) volumes end-diastolic and peak systolic pressures of AC hearts were lower, but no difference was observed in the maximal pressure developed at the highest LV volumes measured. In both C and AC hearts the developed force decreased as pacing rate increased. AC and C heart responses were the same up to 250 pulses/min. At higher frequencies the amplitude of the developed force of AC hearts was smaller than that of the controls. In accordance the tension produced by very early premature beat reduced in AC compared with C hearts. Since no hypertrophy was observed in AC hearts, it is concluded that heat acclimation results in a change in the intrinsic properties of the AC hearts exhibited by increased compliance, reduced chamber stiffness, and a decrease in the tension developed for each volume load. It is also suggested that at a high beating rate AC hearts fail to restitute its contractility as quickly as C hearts.
Although the individual effects of heat acclimation and swimming exercise on cardiovascular reserve and efficiency have been studied, the relative and cumulative effects of these interventions have not. Myocardial developed force, coronary flow (CF), and oxygen consumption during baseline conditions and during pacing-induced tachycardia were therefore studied in isolated perfused hearts from four groups of rats: normothermic sedentary (C), heat acclimated sedentary (AC), normothermic swimmers (CS), and heat acclimated swimmers (ACS). Normothermic temperature was 24 degrees C. Heat acclimation was attained by continuous exposure to 34 degrees C for one and two months. Swimmers had two daily 75 minute sessions for five days a week with water temperatures of 33-35 degrees C and 36-38 degrees C for CS and ACS rats, respectively. After one month AC animals showed a remarkable decrease in O2 consumption. In contrast, ACS increased both O2 consumption and the maximal isometric force generated. After two months, O2 consumption of AC rats continued to be low. The heart failed to restitute the force developed at high pacing frequency. In these rats CF was remarkably low and remained unchanged with increased pacing. In contrast ACS maintained the ability to develop force at all pacing rates at a level similar to that of the normothermic C and ACS rat hearts, but at high oxygen cost. The data suggest that the AC heart is more efficient but cannot meet demands at high pacing rates. In contrast, swimming in the heat improved performance of ACS temporarily, without decreasing the metabolic rate.
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