As previously demonstrated, ovariectomy of rats with 4-or 5-day estrous cycles at 1600 hr on the day before proestrus but not at 1000 hr on the morning of proestrus blocks vaginal cornification and mating. When performed at 1000 hr on the day prior to proestrus, ovariectomy also blocks the proestrous uterine weight increase and the drop in pituitary LH. A single injection of MER-25, a nonsteroidal estrogen antagonist, was given at specific times in the estrous cycle to investigate whether the responses blocked by ovariectomy might be attributed entirely to a loss of estrogen secretion at critical times. In general, MER-25 administered in a single injection of 20 mg blocked vaginal cornification and the proestrous uterine ballooning as ovariectomy does, but did not completely prevent mating behavior or ovulation; MER-25 induced higher than control levels of pituitary LH content at estrus even in the presence of ovulatory evidence of LH release in some rats. When the dosage was increased to 40 mg, there was virtually complete inhibition of ovulation, and mating as well. The rats with 4-day cycles differed from those with 5-day cycles in 3 respects after treatment. MER-25, when given on the afternoon before proestrus, blocked vaginal cornification in 5-day cyclers but not in 4-day cyclers. There was also a significantly greater inhibition of ovulation in 4-day cyclers. Finally, the 4-day cyclers showed higher pituitary LH contents at estrus than the 5-day cyclers. (Endocrinology 82: 959, 1968)

No abstract

The mammalian oviduct especially the ampulla part plays an essential role in female reproduction as fertilization, oocyte maturation and early embryonic development. The present study was focused on the microscopic changes of the rat ampulla epithelium during the oestrous cycle and correlates the findings with their possible functions. Twenty five rats of regular 5 day oestrous cycles were used in our study. They were divided into 5 groups; five rats in each phase of estrous cycle (early proestrus, late proestrus, estrus, metestrus and diestrus). They were sacrificed and the ampullae were excised, fixed and processed to be examined by light and electron microscopy. Marked changes in both relative number and the structure of ciliated and secretory cells throughout the estrous cycle were seen. Ciliated cells were increased in the relative number at the early proestrus till became the predominant cell type at the late proestrus then decreased at the estrus phase accompanied by deciliation. The secretory cells increased in the relative number and prevailed at the metestrus with increasing in the secretory activity. They became rare at the diestrus, a day on which the first sign of neociliogenesis was recorded. Intra epithelial glands were firstly appeared at the estrus phase which increased in number and size at the metestrus. The secretory material is showed PAS positive reaction in the estrus and the metestrus.

The mechanism by which cells in the ampullae of the rat oviducts undergo rapid deciliation during each estrous cycle and the effects of estrogen on the ciliated cells were examined. Untreated rats were killed on each day of the 5-day estrous cycle, and the ampullae of their oviducts were removed. Other rats were injected subcutaneously each day for 5 days with 0.3 microgram or 3.0 micrograms of estradiol benzoate or with 0.3 mg of tamoxifen, an estrogen antagonist, per kilogram of body weight. The ampullae of the oviducts of the treated rats were excised on the day following the last injection. The tissues from all the rats were fixed in glutaraldehyde, stained with uranyl acetate and lead citrate, and examined with a transmission electron microscope. Deciliation of cells was seen to occur by membrane-bound cilia packets (CPs) forming at the apices of cells and pinching off. Although CPs were more numerous at proestrus, they were also observed at estrus, diestrus-1, and diestrus-2, suggesting that the process of deciliation is an ongoing one that merely changes in rate. No evidence of resorption of cilia was seen. Estradiol treatment did not prevent CPs from forming, nor was tamoxifen treatment associated with any apparent enhancement of deciliation. Ciliated cells with CPs stained more darkly than ciliated cells that were without CPs, and the former appeared similar in their staining characteristics to secretory cells, most of which stain darkly. It was concluded that the cells of the ampulla deciliate rapidly by shedding their cilia into the lumen of the oviduct, that estrogen does not halt the process, and that ciliated cells may be transformed to secretory cells following loss of their cilia.

Experiments tested the hypothesis that one role of protein in embryo culture media is protection of embryos against potentially embryotoxic substances in the media. Mouse embryos were cultured in modified Krebs-Ringer bicarbonate medium and in modified Tyrode's medium, aliquots of which were supplemented with 4 mg/ml of the protein bovine serum albumin (BSA), while other aliquots were left protein free. The media were prepared using water samples that differed in purity, as reflected by differences in conductivity, with tap water being least pure (and considered to have the greatest potential for being embryotoxic) and water that had been purified by reverse osmosis, Milli-Q filtration, and triple distillation being most pure. Embryos were placed in the media while in the two-cell stage of development and their development was assessed after 24, 48, and 72 hr of culture. Rate of embryo development in BSA-supplemented media was greater than that in protein-free media only when the media were prepared with the least purified water samples. Because these water samples would have contained substances not contained in media prepared with purer water, or would have contained the substances in higher concentration, the data supported the hypothesis that protein can protect embryos during culture by negating effects of embryotoxic substances in the media.