The effect of hyperthermia on the neuroepithelium of the 21‐day guinea‐pig foetus: Histologic and ultrastructural study

Abstract

Huperthermia was induced in guinea-pigs on day 21 of gestation by placing them in an incubator set at 42.5.degree.-43.0.degree. C for 1 h. At intervals fetuses were removed from the uterus and sections of the telencephalon were prepared for light microscopy and EM. The histologic and ultrastructural appearance of the telencephalon of the normal 21-day guinea-pig fetus was described for comparative purposes. Damage to cells in mitosis characterized by clumping of chromosomes, and dispersal of polysomes in interphase cells, were observed immediately after hyperthermia. Breakdown of the network of junctional complexes was apparent at 4 h and cellular proliferation was inhibited for 6-8 h. Degenerative changes and cell deaths were observed deep in the ventricular zone after 8 h; the extent of cell death was related to the post-stressing temperature. Proliferation was resumed at 8 h and damaged and dead cells moved outward toward the intermediate zone. Phagocytosis of debris by large mononuclear cells was a common finding. Cytoplasmic inclusions, some of which were Feulgen-positive, were present in otherwise normal ventricular cells. Occasional dead cells and empty spaces were present in the ventricular zone at 24 h and by 48 h the ventricular zone was normal in appearance. Previously observed micrencephaly in the offspring of guinea-pig mothers which were heat stressed on day 21 of gestation probably resulted from a temporary cessation of proliferation and partial depopulation of the proliferating neuroepithelium.