US EPA

Gestation day (GD) 10 rat embryos (10-12 somites) were exposed in vitro for 10 to 25 mins at 42 or 430C and evaluated 24 hrs later for alterations in growth and specific morphological parameters, using a modified Brown-Fabro scoring system that allowed evaluation of development relative to gestational age. t 420, crown-rump length appeared to be particularly sensitive, responding to only 10 mins exposure. 5-min exposure resulted in decreased total protein, somite number and morphological score. o system was uniquely sensitive, since all parameters demonstrated some degree of response. ather, systems affected were those that would be developing-most rapidly at this time in gestation. t 43 degrees C, all of the parameters measured were affected by a 10-min exposure. hese results demonstrate alterations in vitro after much shorter exposure periods than previously reported on GD10, which may be due, in part, to the use of a modified scoring system that permitted the evaluation of graded individual end point changes relative to gestational age. he response patterns demonstrated a clear temperature- and exposure duration-dependency, with a shift from a more shallow duration-response curve to a more dramatic inhibition of development as temperature increased from 42 degrees C to 43 degrees C.

Kimmel, G., J. Cuff, C. Kimmel, D. Heredia, N. Tudor, AND P. Silverman. EMBRYONIC DEVELOPMENT IN VITRO FOLLOWING SHORT-DURATION EXPOSURE TO HEAT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-93/186 (NTIS PB93194538), 1993.

Teratology 47:243-251, 1993