The effect of maternal hyperthermia on the development of the brain in the guinea pig.
The effect of maternal hyperthermia on the developmental state of newborn guinea pig brains has been studied. Mean litter size and mean body weights of young from control and experimental mothers did not differ. Mean brain weight of young from control mothers (2.72 +/- 0.02 g) was larger than that from experimental mothers (2.3 +/- 0.03 g). This reduced brain weight was expressed in terms of body weight and showed a mean deficit of 16.4 +/- 1% (range 3.4 to 36.1%). A good correlation was observed between the degree of microencephaly and brain DNA content in experimental young, and the mean reduction in DNA level was 14.9% which compares well with the mean weight reduction. Data from dissected brains indicate that much of the reduction in brain weight and DNA content observed following maternal hyperthermia was owing to an effect on the cerebral hemisphere. Specific activities of synaptic and microsomal membrane marker enzymes were similar in preparations from control and microencephalic young. However, the activities of the enzymes, when expressed in terms of DNA content, were higher in cerebral preparations from microencephalic young as compared with controls. Microencephaly is associated with a reduced cell number (DNA content) but a compensatory elaboration of neuronal dendritic processes also seems to occur.