A new in vitro culture technique for rat embryos

A new technique for culturing embryos, which permits detailed observation and manipulation, is described. The method has been applied to rat embryos on day 10, 11, or 12 of gestation. Twenty‐four‐hour culture of day‐11 rat embryos resulted in nearly normal increases in somite number, and embryo length and protein increment of about half that occurring in vivo. After 24 h of culture the embryos generally were translucent and showed no apparent areas of gross tissue necrosis. Sections from representative embryos are presented. The apparatus is extremely compact and requires only about 9 ml of medium which is sufficient to support three embryos. The small volume allows the measurement of metabolites consumed or liberated with reasonable accuracy. The method permits a detailed and continuous record to be made of the heart rate and the addition of drugs to and sampling of the culture medium. The apparatus, named the PLASMOM, was used to measure the effect of changes in the ambient temperature on the heart rate of day‐11 rat embryos. The results showed a linear dependence of heart rate on temperature between 30 and 40° C.