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M. C. CHANG

The interruption of early pregnancy in the rabbit by oral administration of ethinyl oestradiol (ee) has been reported by Parkes, Dodds & Nobles (1938). Recent work by Chang & Harper (1966) has shown that rabbits fed with various oestrogens, especially ee, 1 to 3 days after insemination will induce the degeneration of blastocysts and that the effect is due to the rapid transport of eggs from the tube to the uterus and their expulsion from the uterus. Chang (1966) has further reported that administration of an orally effective progestin, medroxyprogesterone acetate (MPA, Upjohn Company), for 3 days before ovulation has an effect similar to that observed following the administration of oestrogen after ovulation in the rabbit. This communication describes an experiment concerning the fertilization and transport of ferret eggs following oral administration of MPA before ovulation, or of

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M. C. CHANG

Summary.

Intra-uterine insemination of ten Snowshoe hares with rabbit spermatozoa resulted in the fertilization of 10% of the eggs. Following the intravaginal insemination of Snowshoe hares with epididymal hare spermatozoa and intravenous injection of hcg about 90% of the eggs were fertilized and two living young were born in captivity. When eleven, two-cell hare eggs were transferred into the Fallopian tubes of four rabbits, development to the blastocyst stage was possible, but decidua formation and implantation failed.

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C. M. Lubicz-Nawrocki and M. C. Chang

Summary. Experiments with prepubertal hamsters were undertaken to determine if the appearance of spermatozoa with fertilizing capacity in the cauda epididymidis is related to age and/or body weight and whether the development of sperm function coincides with complete maturation of the mating behaviour pattern. At Week 6 after birth, intrauterine insemination of comparable numbers of spermatozoa showed that fertilizing capacity was related to body weight and not to age or seminal vesicular fructose concentration. In contrast to the low fertilization rate produced by spermatozoa from males weighing 80 g at Week 6 after birth, spermatozoa from 80-g males at Week 7 showed normal fertilizing capacity. Only 50% of 7-week-old males weighing 100–110 g produced fertile matings whereas all matings were fertile with males weighing 135 g and with males weighing 100 to 110 g that had received 7 consecutive daily injections of 50 μg testosterone beginning at Week 6 after birth. Comparison of sperm numbers in the cauda epididymidis and ductus deferens after mating at Week 7 showed that males which produced sterile matings were unable to terminate intromission with normal ejaculation of spermatozoa.

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C. M. Lubicz-Nawrocki and M. C. Chang

Summary. Spermatozoa in the vas deferens of the hamster lose their fertilizing capacity 3 days after ligation of the initial part of the duct and after 2 days if the testes are removed at the time of ligation. Sham-ligation had no effect on the fertilizing life of vasal spermatozoa on the contralateral side even 3 days after bilateral castration. Unilateral castration for 3 days had no effect on the fertilizing capacity of spermatozoa from the ipsilateral unobstructed duct, whereas no eggs were fertilized by spermatozoa from the contralateral ligated duct associated with the remaining testis. Unlike testosterone, 5α-dihydrotestosterone injected daily or implanted subcutaneously in Silastic tubes maintained normal fertilizing capacity for 2 days in castrates and for 3 days in intact males. Within each group, ligation had no effect on the level of fructose in the seminal vesicle on that side compared with the level in the gland on the other side.

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C. M. LUBICZ-NAWROCKI and M. C. CHANG

Summary.

Fertile male hamsters were injected daily with 66 mg α-chlorohydrin/kg to determine the onset and duration of infertility. None of the males became infertile within the first 2 days but marked loss of fertilizing ability of spermatozoa had occurred by 24 hr from the second injection. Infertility occurred in all five males after the fourth dose. The fertilizing ability of the spermatozoa was not impaired when the equivalent of four daily doses was given as a single dose, thus indicating that sequential daily treatment was necessary for the induction of infertility. The prompt recovery of fertilizing ability of spermatozoa in males which had ligated ductuli efferentes and were given four daily doses of α-chlorohydrin (66 mg/kg) shows that transport of epididymal spermatozoa and their acquisition of fertilizing ability are not influenced by the drug.

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C. M. LUBICZ-NAWROCKI and M. C. CHANG

Summary.

Male hamsters of known fertility were injected subcutaneously with α-chlorohydrin to determine the minimal antifertility dose and to elucidate its site of action. Fertility tests at 4-day intervals showed that α-chlorohydrin (66 mg/kg) induced infertility within 4 days and fertilization did not occur after artificial insemination with spermatozoa from the cauda epididymidis of such animals. Comparable daily treatment produced the same antifertility effect subsequent to bilateral ligation of the corpus epididymidis and also in castrated animals given daily treatment (100 μg/day) with either testosterone, 5α-dihydrotestosterone or 3α-androstanediol. The infertility was not related to deficiency of androgen, as judged by the concentration of fructose in the seminal vesicles, or to impaired ejaculation.

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C. M. LUBICZ-NAWROCKI and M. C. CHANG

Summary.

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 produced 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 received 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.

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A. Hanada and M. C. Chang

Summary.

Hamster eggs with follicular cells were fertilized by epididymal spermatozoa in two chemically defined media. The proportion of penetrated eggs was significantly higher in a medium for rabbit (16%) than in a medium for rat eggs (6%), but much lower than in Tyrode's solution containing follicular fluid or blood serum as reported by others. The optimal sperm concentration for sperm penetration ranged from 0·5 to 5 × 106/ml but penetration of denuded eggs failed in these media. When exposed to hamster spermatozoa in the rabbit medium containing living or dead spermatozoa of guinea-pig, rat, mouse or hamster, high proportions of denuded eggs (24-96 %) and eggs with follicular cells (93%) were penetrated. By exposure of denuded hamster eggs to hamster spermatozoa in supernatant fluid of frozen-thawed guinea-pig spermatozoa, 97% of eggs were penetrated in 8 hr compared to 0% in the control group. Sperm capacitation was also efficiently induced by preincubation of hamster spermatozoa in the supernatant fluid. The fertilizing capacity of hamster spermatozoa was maintained for 12 hr during incubation with frozen-thawed guinea-pig spermatozoa when the concentration of hamster spermatozoa ranged between 10 and 20 × 106/ml. The beneficial factor of guinea-pig spermatozoa appeared to be from spermatozoa themselves, not from the vasal or epididymal fluids. The presence of follicular cells, blood serum, bovine serum albumin, or even polyvinylpyrrolidone in the media is essential for the capacitation and acrosome reaction of hamster spermatozoa. The components of guinea-pig spermatozoa appear to maintain the fertilizing capacity of hamster spermatozoa and stimulate the process of capacitation.

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H. MIYAMOTO and M. C. CHANG

Summary.

Sperm penetration was not observed when newly ovulated eggs, together with spermatozoa suspended in Tyrode's solution, were deposited into uteri of hamsters. When epididymal spermatozoa preincubated for 1 to 3 hr in Tyrode's solution containing an equal volume of heated serum were used, 4 to 11% of eggs were penetrated 5 to 7 hr later, but signs of egg degeneration were observed.

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Y. Tsunoda and M. C. Chang

Summary.

The fertilizing ability of epididymal spermatozoa from rats and mice treated for 3 or 4 or 9 or 10 days with various doses of μ-chlorohydrin was tested in vitro, and in vivo by intrauterine insemination. The minimum doses (per kg/day) needed to affect fertilization significantly were: rat, in vitro, 8·8 mg for 3 or 4 days, 4·4 mg for 4 days and 2·7 mg for 9 or 10 days; in vivo, 4·4 mg for 3 or 4 days and 2·7 mg for 9 or 10 days: mouse, in vitro, 4·4 mg for 3 days and 13·3 mg for 9 days; in vivo, 44·2 mg for 3 days and 26·5 for 9 days. Rats were infertile for at least 18 days after receiving 44·2 mg μ-chlorohydrin/kg/day for 3 days, but fertilizing ability, tested in vivo and in vitro, was restored 10-11 days and 15-18 days, respectively, after daily treatment with 11·1 mg μ-chlorohydrin/kg for 3 days.