Citation:

Cuff, J., G. Kimmel, D. Hereida, N. Tudor, AND J. Chen. RELATIONSHIP BETWEEN ABNORMAL SOMITE DEVELOPMENT AND THORACIC SKELETAL DEFECTS IN RATS FOLLOWING HEAT EXPOSURE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-93/508 (NTIS PB94135159).

Description:

The effects of in vivo heat exposure on gestation day (GD) 10 rat embryos were studied on GD 11 to determine the relationships between morphological effects following in vivo and in vitro exposures and between effects observed on GC 11 and those observed in PND 3 pups. nesthetized rats were exposed to 42 degrees C in a warm air incubator until their rectal temperatures reached 41 degrees C or until a rectal temperature of 42-42.5 degrees C had been maintained for 5 minutes. mbryos exhibited a significant decrease in growth parameters including head length, somite number, and protein content/embryo. hese effects correlated well with in vitro effects from an earlier study. ertain morphological endpoints were also slightly, but significantly, delayed in development. he only effect on the embryos that could not be explained as a transient delay in development induced by heat was the induction of unsegmented somites. nsegmented somites were observed in 47% of the embryos exposed to 42 degrees C. n addition, the unsegmented somites were exclusively in the 8-21 somite range, the somites that give rise to thoracic vertebrae and ribs. hese effects correlated well with effects seen after in vitro exposure of a group of embryos to 42 degrees C for 15-20 min, and with the thoracic skeletal malformations observed in PND 3 pups exposed to the same heat treatment on GD 10.

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