This study determined the relationship between the duration and extent of temperature elevation, during a critical period of @entity35 embryonic development, and the induction of @entity600 . Pregnant @entity35 , at 9 days 12 hours gestation (gastrulation stage), were partially immersed in a water bath until their core temperature, monitored by a rectal thermistor probe, was elevated to a nominated temperature. Seven temperatures were tested from 40.5 degrees C to 43.5 degrees C, elevations of 2.0-5.0 degrees C in core temperature. Various durations at each of these temperatures were tested for potential teratogenicity. A single elevation of 5.0 degrees C or 4.5 degrees C needed only a "spike" in duration to be teratogenic, 4.0 degrees C was teratogenic within 5 minutes, 3.5 degrees C within 10 minutes, 3.0 degrees C within 20 minutes, and 2.5 degrees C within 1 hour. An elevation of 2.0 degrees C for 8 hours was not teratogenic. @entity4353 was the most common @entity600 at all teratogenic temperatures and was frequently the only @entity600 seen at the shortest time exposure for a particular temperature. Encephalocele, facial clefting, and @entity3573 were the other frequently seen @entity600 . Five control @entity35 were placed in the water bath for 2 hours at 38 degrees C so that their core temperature was not elevated. All the control fetuses were normal. An elevation of 2.5 degrees C for 1 hour was the threshold combination for teratogenesis. As the temperature increased above a 2.5 degrees C elevation the necessary duration of exposure for teratogenesis decreased.

Hyperthermia as a teratogen: parameters determining hyperthermia-induced head defects in the XXXX .

@entity35 :: ('10116', 'Species') :: ['rat', 'Sprague-Dawley rats', 'rats'] @entity4353 :: ('MESH:D008850', 'Disease') :: ['Microphthalmia'] @entity3573 :: ('MESH:D008439', 'Disease') :: ['maxillary hypoplasia'] @entity600 :: ('MESH:D000014', 'Disease') :: ['malformations', 'congenital malformations', 'malformation']
@entity35 :: (10116,Species) :: ['rat']
