[Heat sensitivity of starred sturgeon follicles at different stages of their maturation period]. / Termochuvstvitel'nost' follikulov sevriugi na raznykh stadiiakh perioda sozrevaniia.

The influence of sharp temperature shift and proportioned keeping of the sevryuga females at a low temperature on the oocyte maturation and ovulation has been studied. The reaction of the follicles to similar influences was shown to differ at different stages of the period of maturation inertia: the follicles remained intact at the stages prior to the germinal vesicle (oocyte nucleus) breakdown, were damaged in a part of females at the prometa- and metaphase I and in the most females at the prometa- and metaphase II. The injection of triiodothyronine to the females subjected to cooling at different stages of the period of maturation inertia exerted no effect on the oocyte ovulation and the egg fertilizability.

[The effect of triiodothyronine on oocyte maturation in the starred sturgeon following exposure to low temperatures and female reservation]. / Vliianie triiodotironina na sozrevanie ootsitov sevriugi posle deistviia nizkikh temperatur i rezervatsii samok

A sharp cooling of the sevryuga females as well as their reservation at the spawning temperatures suppress the ability of oocytes coated by follicle membranes to mature under the effect of hypophyseal gonadotrophic hormones in vitro and in vivo. At the same time the oocytes from these females in both the types of experiments are able to mature in vitro in the Ringer solution with progesterone. The injection of triiodthyronine to cooled or reserved females restores the ability of their oocytes to mature under the effect of hypophyseal gonadotrophic hormones both in vivo and in vitro. Such oocytes in our experiments undergo normal development upon fertilization. The thyroid gland hormone (triiodthyronine) influences thus, the ability of follicle epithelium to respond to the effect of hypophyseal gonadotrophic hormones by stimulation of oocyte maturation; this influence of triiodthyronine appears to be indirect. Some practical aspects of this problem are discussed.