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Biomedical subjects

M C Chang

Publications and source records attributed to M C Chang.

At least 289 records · Page 16Linked to original sources
PubMed1975

Temporal relationship between insemination and sperm penetration in immature rats, with special reference to the effect of incubation of spermatozoa.

Superovulated immature rats (24 to 25 days old) were inseminated with epididymal sperm before or after ovulation and their eggs were examined at various times. When inseminated before ovulation, the interval between insemination and sperm penetration was 7 to 9 hours; the sperm penetration began approximately 2 hours after the first appearance of eggs in the oviducts and ceased 4 to 6 hours later. When inseminated after ovulation, the interval between insemination and sperm penetration was 5 to 6 hours; sperm penetration started 5 to 9 hours after ovulation and the proportion of penetrated eggs was not increased 4 hours later. The fertilizing capacity of sperm in the immature female tract lasted for 10 to 14 hours, which is shorter than in the mature animals, and sperm penetration occurred 2 to 10 hours after ovulation. The proportion of eggs fertilized, however, was not higher than 55%. A significant greater number of eggs was penetrated by more than one sperm but the number of polyspermic eggs was not increased when insemination was delayed. Epididymal sperm were incubated for various lengths of time and similarly inseminated into the uterine horns of immature rats. The fertilizing capacity of sperm could be maintained in culture for 10 hours but the proportion of fertilized eggs decreased sharply after incubation for 8 hours. Although rat epididymal sperm in a concentrated form could not be capacitated in vitro, they could be capacitated after incubation by intrauterine insemination.

Animals↗
PubMed1975

Effects of indomethacin and prostaglandin F2alpha on parturition in the hamster.

In the hamster administration of indomethacin twice a day on days 14 to 16 of pregnancy delayed the onset of parturition; a delay of 5 and 8 hours was observed following treatments of 300 or 600 mug/injection of indomethacin, respectively. Injection of PGF2alpha to the indomethacin treated hamsters on day 15 of pregnancy, on the other hand, advanced the onset of parturition. Treatments of indomethacin and/or PGF2alpha did not affect the duration of parturition.

Animals↗
PubMed1975

Effect of indomethacin, an inhibitor of prostaglandin biosynthesis on the length of pseudopregnancy in rats and hamsters.

Pseudopregnancy (PSP) in rats was significantly lengthened after subcutaneous administration of 0.2-1.0 mg indomethacin/day, starting on day 5 of PSP. Injections of 1 mg indomethacin on days 5 and 6 or days 7 and 8, as well as a single injection of 2 mg indomethacin on day 6, also produced a significant increase of the duration of PSP. In hamsters, doses of 300-500 mug indomethacin per day starting on day 5 of PSP did not alter the length of PSP, but a significant prolongation varying from 11 to more than 30 days was observed after a treatment with 1 mg of indomethacin daily. It was further observed that the ovaries of hamsters autopsied on day 31 of PSP were very small and the uteri resembled those of ovariectomized animals. It is concluded that indomethacin lengthens pseudopregnancy in both rats and hamsters and that the latter species showed a more variable response. It seems that chronic administration of indomethacin in hamsters caused a long-lasting suppression of ovarian hormone production.

Animals↗
PubMed1975

Effect of indomethacin on blood plasma levels of LH and testosterone in male rats.

Treatment of adult male rats with indomethacin, an inhibitor of prostaglandin (PG) synthesis, caused a significant decrease in LH and testosterone levels in the blood plasma and in the weight of the seminal vesicles, but the weight of the testes and ventral prostate, the levels of FSH in the plasma and fertility were not affected. The concentration of PGF in the blood plasma of the treated animals was reduced, even though measurable amounts of PGs were present in every group. The results of this study, together with the known effects of PG administration on LH release, suggest that the reduction of plasma LH levels in rats injected with indomethacin was due to decreased PG synthesis. It appears that PGs are normally involved in the regulation of LH release.

Animals↗
PubMed1975

Effect of 4-chloromethyl-2-methyl-2-pentyl- 1,3-dioxolane (AY-22,352) on the fertilizing ability of hamster epididymal spermatozoa.

Fertile male hamsters were injected subcutaneously with AY-22,352 to determine the minimal antifertility dose, the site of action and the onset and duration of infertility. Fertility tests showed that 37 mg AY-22,352/kg/day induced sterility within 4 days. None of the males became infertile within the first 2 days but marked loss of sperm fertilizing ability had occurred by 24 hr from the second injection; all males were sterile after the fourth dose. Comparable daily treatment procuded the same antifertility effect subsequent to bilateral ligation of the corpus epididymidis and fertilization did not occur after artificial insemination with spermatozoa from the cauda epididymidis of such animals. The prompt recovery of fertilizing ability of spermatozoa in males which receoved four daily doses of AY-22,352 (37 mg/kg) and had ligated ductuli efferentes shows that transport of epididymal spermatozoa and their acquisition of fertilizing ability are not influenced by the drug.

Animals↗
PubMed1975

Fertilization of rat eggs in vitro at various times before and after ovulation with special reference to fertilization of ovarian oocytes matured in culture.

Oocytes recovered at various times from immature rats treated with PMSG and HCG were incubated with capacitated epididymal spermatozoa of mature rats. In the presence of follicular cells, sperm penetration was not observed 4 hr after incubation in the oocytes at stages from the intact germinal vesicle to the chromatin mass, but 7 to 55% of oocytes were penetrated at stages from the condensed germainal vesicle to metaphase II. After the removal of follicular cells, 15 to 72% of the oocytes at any stage were penetrated. After further incubation for 15 hr, the proportion of penetrated oocytes increased from 8 to 98% from early to late stages and that of penetrated oocytes with a male and female pronucleus increased from 9 to 100% as maturation progressed. Although the average number of spermatozoa/oocyte was not correlated with its maturation, transformation of the sperm head into a male pronucleus was retarded or failed, especially in the younger oocytes. Following incubation in a defined medium for 13 hr, 85% of oocytes at the intact germinal vesicle stage matured to the stage of the first polar body formation, but only 18 to 22% of these mature oocytes were penetrated by spermatozoa and only a few of the penetrated oocytes cleaved into normal two-cell eggs. When eggs recovered from oviducts 14 to 20 hr after ovulation were exposed to capacitated spermatozoa, the proportion of penetrated eggs (86 to 98%) and that of polyspermic eggs (11 to 27%) were not related to the ages of the eggs, but failure of transformation of the sperm head and the proportion of abnormal eggs increased 14 to 20 hr after ovulation.

Animals↗
PubMed1975

Prostaglandin F2-alpha for induction of midterm abortion: a comparative study.

The action of prostaglandin F2alpha (PGF2-alpha) to induce midterm abortion in rabbits, rats, hamsters, and mice using different methods and routes of administration was studied. Administration of PGF-alpha in a Silastic-PVP implant was more effective than was the parenteral injection at the same dose levels. The efficacy of PGF2alpha was optimum when deposited locally in the uterine lumen as a Silastic-PVP implant, a condition comparable to a continuous intra-amniotic or extra-amniotic administration of PGF2alpha in women. It is possible that the insertion of a Silastic-PVP implant into the uterine lumen results in a continuous PGF2alpha release and a high local PGF2alpha concentration which minimizes such factors as dilution and the short half life displayed in the general circulation. PGF2alpha contained in a Silastic-PVP implant and inserted into the uterine lumen may effectively induce abortion with a comparatively lower dose than that necessary for parenteral routes of administration.

Abortion, Induced↗