Vitamin B 12 in developing chick embryos from vitamin B 12-deficient and control eggs

Abstract

The vitamin B 12 contents of the normal and vitamin B 12-deficient chick embryos and yolk sacs were determined at 12, 15, 18 and 21 days of age, by the use of Ochromonas malhamensis. From the 12th day of incubation on there was a decrease in the vitamin B 12 content of the yolk sac with the greatest reduction occurring between the 15th and 18th days. The greatest increase in the vitamin B 12 content of the control embryo occurred during the same period. In the deficient embryo the largest increase occurred between the 18th and 21st days. The vitamin B 12 content of the whole egg (embryo plus yolk sac) decreased between the 15th and 21st days of incubation. The fate of the vitamin B 12 not recovered is unknown, but it is possible that it was metabolized to a substance not utilized by the assay organism.