ABSTRACT
Electrophoretic and biochemical techniques were applied to homogenates of the visceral yolk-sac of rat embryos at various gestational ages.
Alkaline phosphatase was shown by starch gel electrophoresis of normal yolk-sacs to undergo specific sequential changes from day 10 to day 20 of gestation. The isozyme repertory on any given day of gestation was achieved by deletions from, or additions to, that of the previous day.
Glucose-6-phosphate dehydrogenase was shown, by polyacrylamide gel electrophoresis of normal yolk-sacs, to achieve early in gestation a qualitatively constant number of enzyme forms. Quantitative changes among the enzyme forms occurred as gestation proceeded.
A teratogenic folic acid deficiency resulted in the delayed appearance of some enzyme forms as well as the premature disappearance of others in the two enzyme systems studied. The effects of the treatment were selective in that not all of the enzyme forms of the treated material were affected.
