TERATOGENIC AND LETHAL EFFECTS OF LONG-TERM HYPERTHERMIA AND HYPOTHERMIA IN THE CHICK-EMBRYO

The teratogenic effect of maternal hyperthermia is well known in labor atory animals and is presumed to exist also in humans, The aim of our study was to describe the embryotoxic effect of long-term higher and l ower incubation temperatures on the chick embryo, Chick embryos were i ncubated within days 1 to 9 at 12 different incubation temperatures ra nging from 31 to 42 degrees C, On the basis of our results, we estimat ed that there are three upper and lower critical thresholds of the inc ubation temperature: the first thresholds are 31 and 42 degrees C, at which all embryos died; the second thresholds are 32 and 41 degrees C, at which all living embryos were malformed; the third thresholds are 33 and 40 degrees C, at which some of the living embryos were without structural malformations, but their weight was shifted down and up wit h lower and higher temperature, respectively, The incubation temperatu re of 37 to 38 degrees C was optimal. Typical malformations detected o n day 9 of incubation were microphthalmia, gastroschisis, caudal regre ssion syndrome, and hyperlordosis, all of which occurred in dead embry os several times more frequently than in living embryos, CNS malformat ions were only sporadically present on day 9, as most of specimens bea ring CNS defects died during the first days of incubation.