Abstract
A simple method is described for growing rat embryos in vitro for 48 hr from head-fold to early limb-bud stages at rates of development and protein synthesis indistinguishable from those in vivo. Culture of the embryos can be continued for longer periods but at a reduced growth rate. Preheating the culture serum to 56 degrees C for 30 min improves embryonic development, but raising the culture temperature 2-3 degrees C or exposing the presomite embryos to 20% O2 (160 mm Hg) causes malformations, particularly of the brain and spinal cord. The value of such culture methods for teratology is briefly discussed.