Nuclear maturation inhibitors in Bufo arenarum oocytes.

In Bufo arenarum, as in other amphibian species, nuclear maturation--characterized by germinal vesicle breakdown (GVBD) and meiosis resumption--is induced by progesterone. Seasonal variations in the sensitivity to progesterone were observed in Bufo arenarum oocytes. The gonadotropin FSH and drugs such as dbcAMP and xanthine did not affect nuclear maturation per se, although they acted as negative modulators of progesterone-induced nuclear maturation.

Effects of the pineal gland and melatonin on the metabolism of oocytes in vitro and on ovulation in Bufo arenarum.

The pineal gland and the hormone melatonin appear to be responsible to some extent for the metabolic behaviour of Bufo arenarum oocytes during the winter. This assumption is supported by the observation that, in isolated mitochondria, both elements stimulate the rate of oxidation of citrate and inhibit that of fumarate, thus raising the oxidizing ratio that relates these parameters (C/F) to values close to or above 1, which is characteristic of these animals in winter. The sensitivity of oocytes to melatonin, in terms of the C/F ratio, varies throughout the year.

Hydrosmotic effect of angiotensin II in the toad skin: role of cyclic AMP.

The mechanism of action of the hydrosmotic response of the isolated skin of the toad Bufo arenarum Hensel to angiotensin II was studied by means of an indirect pharmacological approach. Angiotensin II (2.10(-10) M), vasopressin (2.