Electron Microscopic Studies of Mouse Oocytes and Two-cell Embryos exposed to Progesterone in Vitro

This experiment was undertaken in order to find out if there is any morphological change in oocytes and two-cell embryos whose development have been suppressed by progesterone for six hours in vitro. It can be observed that some part of the outer side of nuclear membrane of the suppressed oocytes was damaged. The number of nuclear pores has decreased in suppressed oocytes and this suggests that progesterone might suppress the transport of intermediary metabolites between cytoplasm and nucleus. Sometimes, closely packed aggregates of parallel or irregular endoplasmic reticula were observed in suppressed oocytes. Microvilli of suppresed oocytes showed signs of degradation and the perivitelline space became apparent. Thus it is presumed that the egg membrane has constricted during cultivation under progesterone in vitro. The other cell organelles such as mitochondria, multivesicular bodies, cortical granules and fibrillar lattices showed no difference in morphology between treated and control (intact) oocytes. In two-cell embryos, there was also no evident morphological change except for the fact that many vacuoles appeared clearly in suppressed embryonal cells. In brief, there was no fundamental morphological change in the oocytes and the embryonal cells exposed to progesterone for six hours even though it inhibits their development. The action of progesterone should be investigated thoroughly.

The Effects of Follicular Fluid on in Vitro Maturation of Bovine Follicular Oocytes

The present experiments were conducted to evaluate the effects of follicular fluid on maturation of bovine follicular oocytes. TC medium 199 seemed to be in adequate for this purpose since a high proportion (ranging 84.1. to 97.0%) of the oocytes were able to resume meiotic division in both media-with or without the addition of follicular fluid. This implies a possible similarity between TC medium 199 and follicular fluid with regard to the components initiating meiosis. Actually, TC medium 199 contains amino acids, vitamins and carbohydrates most of which are also found in follicular fluid. For this reason, the effect of follicular fluid on the ovum maturation was investigated by applying Krebs-Ringer bicarbonate solution (SECM), which was main1y composed of the salts, pyruvate and lactate. When the oocytes were cultured in SECM without the addition of follicular fluid, only 7-14% of them resumed meiotic division within 30 hours. However, when follicular fluid was added, the proportion of oocytes undergoing maturation was sharply increased to about 70%. Among the groups cultured in media containing different concentrations of follicular fluid, the proportion of the oocytes in meiosis remained constant, In pure follicular fluid, 87-89% of the oocytes showed enhancement of meiotic division. The presence of the follicular fluid contributed to a decrease in the production of degenerative oocytes. As a consequence it has been noted that addition of follicular fluid to the culture medium provides a more beneficial environment for cow oocytes. Meiotic division is initiated and production of degenerative oocytes is inhibited.

The Maturation in Vitro of The Rabbit Oocytes I. Amino Acids Support the Maturation In Vitro of the Rabbit Oocytes

Rabbit follicular oocytes were cultured in a medium supplemented with various elements such as bovine serum(RS), bovine serum albumin(BSA), amino acids and chorionic gonadotrophic hormone(HCG) in order to find which factors among them were most effective for oocyte maturation. The presence of BSA in the basic medium (modified Krebs-Ringer bicarbonate) did not elevate the proportion of oocyte maturation. When BS alone was added to the medium, only a few oocytes could reach to metaphase I and most of them were in degeneration. This implies that BS may act as an inhibitory or a toxic agent to the rabbit oocytes. It was found that the medium supplemented with 0.4% BSA and amino acids together raised the proportion of the oocyte maturation (54-62%). Especially the presence of proline, or of both proline and glutamine, gave a more favourable condition for the initiation of meiotic division than other amino acids. Addition of HCG to the medium did not promote the proportion of the oocyte maturation. As a consequence, it is apparent that amino acids in the medium are the most essential factors in inducing oocyte meiotic division.