Ovulation blockade through synergism of cycloheximide with assorted anesthetics.

This report addresses the following question: Can ovulation be blocked through a combined action of two drugs, which individually have no effect on ovulation. Ovulation blockade in hamsters was achieved through synergism of two drugs that individually had no effect on ovulation. Treatments were given at 18:00 h on pro-estrus.

Climacteric in women: an evolutionary defect?

This is a theoretical paper. Climacteric in women has two basic consequences: (i) Sterility, which is interpreted here as a positive feature, because it protects the older woman from the hardships of pregnancy. (ii) Hormonal deficiency, which is interpreted here as a negative feature, because it leads to deleterious changes in various parts of the body.

Regulatory enzymes of carbohydrate and energy metabolism in the rabbit blastocyst.

The activities of phosphofructokinase, pyruvate kinase, citrate synthase and creatine kinase were determined in blastocysts from rabbits at 144 h post coitum and in similar blastocysts cultured for 24 h with or without oestradiol-17beta (1 microgrm/ml). There was a significant increase in all the enzymes during the 24-h culture period but oestradiol had no effect.

Cyclic AMP and cyclic GMP in rabbit blastocysts.

Concentrations of both nucleotides were significantly higher in Day-6 than in Day-5 blastocysts but the ratio of cAMP to cGMP changed from 0.5 to 1.5.

Evidence that "embryonic estrogen" is a factor which controls the development of the mouse preimplantation embryo.

4- to 8-cell mouse PIE's (preimplantation embryos) were cultured in vitro for 48 hr in media containing various concentrations of the anti-estrogen CI-628. Graded effects of the various concentrations were observed with the highest concentration (1.5 microng/ml) being 100% effective in blocking development to the blastocyst stage.

Does "blastocyst estrogen" initiate implantation?

Fertilized eggs were incubated for 2 hours in a medium containing estradiol-17beta and then transferred into the uteri of day 5 pseudopregnant rats. These eggs, but not estrogen-free control eggs, induced a local increase in capillary permeability. We suggest that the blastocyst factor which induces the local increase in capillary permeability during early pregnancy is estrogen synthesized by the blastocyst.

Evidence that the maintenance of early pregnancy in the rabbit requires ""blastocyst estrogen''.

It has been shown by others that treatment with only progesterone is sufficient to induce implantation and maintain pregnancy in ovariectomized-adrenalectomized rabbits. Based on these results, it was deduced that induction of implantation in the rabbit does not require estrogen. In making this deduction, ""blastocyst estrogen'' was not taken into account.

Prostaglandins in rabbit blastocyst.

Rabbit blastocysts recovered at 144 hours post coitum contained the prostaglandins F and E-A. We suggest that one or more of these prostaglandins act as mediators in blastocyst steroidogenesis. (In another study we have demonstrated steroidogenesis in rabbit blastocysts).

Steroidogenesis in rabbit preimplantation embryos.

Rabbit preimplantation embryos were flushed from the reproductive tract at 24 hr (1- to 2-cell stage), 48 hr (morula), 72 hr (morula), 96 hr (blastocyst), 120 hr (blastocyst), and 144 hr (blastocyst) post coitum. At 168 hr (early postimplantation period), gestation sacs were excised, frozen, and sectioned in a cryostat. Delta5-3beta-Hydroxysteroid dehydrogenase [3(or 17)beta-hydroxysteroid:NAD(P) oxidoreductase, EC 1.