Search Results

You are looking at 1 - 2 of 2 items for

  • Author: S. Sugawara x
Clear All Modify Search
Free access

K. Hashizume, S. Sugawara and S. Takeuchi

Laboratory of Animal Reproduction, Faculty of Agriculture, Tohoku University, Sendai, Japan

We have previously described studies of parturition and subsequent reproductive phenomena in rats which showed that the time of the LH surge and post-partum ovulation are related to the time of parturition (Hashizume, Sugawara & Takeuchi, 1973a, b, 1975). In an attempt to clarify further the factors governing the timing of the post-partum ovulation in rats, we have examined the effects of an oestrogen antagonist, clomiphene (see Labhsetwar, 1970), on the time of parturition and the post-partum ovulation.

Rats of the Wistar strain, bred in our own laboratory and kept in controlled lighting (lights on 06.00-18.00 hours), were used. Rats which had experienced three consecutive 4-day cycles were caged at pro-oestrus with fertile males and mating was verified by finding spermatozoa in the vaginal smear the following morning. This day was designated Day 1 of pregnancy.

Clomiphene citrate (Clomid

Free access

H. Matsumoto, N. Shoji, S. Sugawara, M. Umezu and E. Sato

A developmental block is induced by phosphate in rat embryos at the late two-cell stage. The present study was designed to examine the energy metabolism of rat two-cell blocked and non-blocked embryos. Enzyme activity was measured in individual embryos by histochemical techniques. The activities of malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, pyruvate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, and phosphorylase did not differ among non-blocked and blocked embryos. However, the activity of succinate dehydrogenase was significantly decreased in blocked embryos compared with non-blocked embryos. In blocked embryos, cytochrome oxidase activity was distributed homogeneously, but was located at the perinuclear region in non-blocked embryos. Active mitochondrial organization was visualized using the fluorescent probe rhodamine 123 and laser scanning confocal microscopy. In both non-blocked and blocked embryos, mitochondria were distributed homogeneously. The concentration of H2O2 measured fluorometrically in embryos cultured without phosphate did not change significantly during the culture period, but decreased in embryos cultured with phosphate. The timing corresponded to the occurrence of the two-cell block. In summary, these results suggest that the developmental block in rat two-cell embryos is induced by disturbance of mitochondrial energy metabolism.