[Ratio of concentration of ions of uni- and bivalent metals in the tissues of developing chick embryos and 1-day-old chickens].

The ratio of concentrations Na+/K+ decreases in the brain and liver and increases in the cardiac muscle during the chick embryogenesis. The maximum concentration of Ca2+ was noted in the tissues under study on 14th day of chick embryonic development and its content decreased reliably at the subsequent stages. The concentration of Mg2+ in the tissues under study decreased during the embryogenesis as well.

[Participation of thyroxine in the regulation of the rate of isocitrate dehydrogenase reactions in the brain and liver].

A study was made of the effect of thyroxin on the activity of NAD- and NADP-dependent isocitratedehydrogenases in the brain and the liver of chick embryos. It was found that in both of the organs thyroxin accelerated isocitrate oxidation in the mitochondria through the NAD-dependent route and elevated the velocity of the NADP-isocitratedehydrogenase reaction in the citoplasm. At the same time the activity of the mitochondrial NADP-dependent isocitratedehydrogenase increased after the administration of the hormone to the embryos only in the mitochondria of the brain cells; this was apparently associated with the intensive biosynthesis of specific lipids in the developing brain.