Inhibition of chromosome separation in cleaving Psammechinus eggs by elevated temperature

Effects of hyperthermia on the myelograms of adult and fetal guinea-pigs

The myelograms of adult guinea-pigs at various stages after brief exposure to hyperthermia were compared with those of control animals. The proportions of neutrophil and eosinophil metamyelocytes and of intermediate normoblasts were significantly reduced for at least 24 h after exposure and the proportions of neutrophil polymorphs and lobulated eosinophils were significantly increased over this period. The mitotic index was reduced for up to 5 h. Morphological changes in cells included hypersegmentation of nuclei, pyknosis, necrobiotic changes, development of pseudopodia, and abnormalities of mitosis. The myelograms of newborn guinea-pigs which had been heated on days 20-23 of pregnancy showed no significant changes.

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

Hyperthermia was induced in guinea-pigs on day 21 of gestation by placing them in an incubator set at 42-5 degrees-43-0 degrees C for 1 hr. At intervals thereafter foetuses were removed from the uterus and sections of the telencephalon were prepared for light and electron microscopy. The histologic and ultrastructural appearance of the telencephalon of the normal 21-day guinea-pig foetus was described for comparative purposes. Damage to cells in mitosis characterised 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 hr and cellular proliferation was inhibited for 6-8 hr. Degenerative changes and cell deaths were observed deep in the venticular zone after 8 hr; the extent of cell death was related to the post-stressing temperature. Proliferation was resumed at 8 hr 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 hr and by 48 hr the ventricular zone was normal in appearance. It was concluded that previously observed micrencephaly in the offspring of guine-pig mothers which were heat stressed on day 21 of gestation resulted from a temporary cessation of proliferation and partial depopulation of the proliferating neuroepithelium.