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R. R. UNNITHAN

Department of Zoology, University of Rajasthan, Jaipur, Rajasthan, India

(Received 10th June 1974)

An injection of 5 i.u. PMSG to 21-day-old mice greatly increases the number of large follicles in the ovary but does not cause any morphological change in the oocyte (Merchant & Chang, 1971; Cross, 1973). If an injection of HCG is given 48 hr later, the oocytes pass rapidly through the remaining stages of meiosis and reach the second metaphase in 12 to 14 hr (Edwards & Gates, 1959). Oocytes which are mechanically released from the follicles and cultured in an appropriate medium without any hormonal stimulation reach second metaphase in 14 to 17 hr (Donahue, 1968; Cross & Brinster, 1970). The present report deals with the fate of oocytes left in the follicles and their developmental potential at various times after an injection of PMSG.

Mouse oocytes have been matured in vitro by many workers (Edwards,

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R Gualtieri and R Talevi

Mammalian spermatozoa undergo a marked reduction in number during their journey through the female reproductive tract. One of the checkpoints in the selection of fertilizing spermatozoa may be the transient adhesion to the Fallopian tube epithelium, an event previously shown to play a key role in sperm storage. Bovine spermatozoa adhering to the Fallopian tube epithelium in vitro may be synchronously released by sulphated glycoconjugates. In the present study, experiments were designed to quantify the number of spermatozoa selected through adhesion, and to compare the zona pellucida (ZP) binding and fertilization competence of the initial sperm suspension versus the bound and unbound sperm subpopulations. Results showed that: (1) a fraction accounting for about 30% of the initial sperm suspension was selected by in vitro adhesion to oviductal epithelial cell monolayers; (2) selected spermatozoa, collected after heparin-induced release, had a significantly superior ZP binding and fertilization competence (mean +/- SD: 110 +/- 28 bound spermatozoa per oocyte; % cleavage, mean +/- SEM: 89 +/- 4) compared with both the initial sperm suspension (45 +/- 10 bound spermatozoa per oocyte, P < 0.001; % cleavage: 69 +/- 3, P < 0.05) and the unselected subpopulation (30 +/- 4 bound spermatozoa per oocyte, P < 0.001; % cleavage: 58 +/- 3, P < 0.01). These findings support the hypothesis that binding to oviductal cells is not only beneficial for sperm survival but also represents a crucial step for the selection of spermatozoa endowed with superior fertilization competence.

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R. R. MAURER and R. H. FOOTE

Summary.

Embryos from ageing (20 to 148 weeks of age) and young (20 to 30 weeks of age) donors were transferred to ageing (52 to 221 weeks of age) and young (18 to 30 weeks of age) recipients to partition the effects of ageing oocytes and uterine environment on embryo mortality. More than 3300 two- to eight-cell embryos collected following superovulation at six 6-month intervals were transferred. The average number of ovulation points per ageing donor doe superovulated at the six intervals declined with age and repeated superovulation. The average number of ovulations for the young donors at the six intervals also differed slightly, the low number (forty-one) for the last group possibly being due to the crossbred strain used. Both embryo recovery and cleavage rates usually exceeded 80% and did not differ between young and ageing donors. The percentage of viable young developing from embryos transferred from ageing and young donors showed that the potential for embryo development had not been impaired during 3 years of ageing. The percentage of viable young developing from embryos transferred to ageing and young recipients indicated that conditions for maintaining pregnancy had been impaired in the ageing recipients. The average number of ovulations for a group of old does superovulated for the first time at 229 weeks of age was fourteen compared to sixty-two for young controls, and only 26% of the embryos transferred from the old does developed into neonates, whereas 45% of those from young donors developed normally. As the female ages, the uterine environment may become less conducive to prenatal development and the oocytes then show the effects of the ageing process directly or as a result of exposure of the oocyte or young embryo to the ageing oviduct. At laparotomy 12 days after transfer, the ageing recipients had 45·3% pre- and 14·8% postimplantation mortality. Corresponding values for young recipients were 33·5 and 16·0% respectively. Laparotomy increased embryo mortality in ageing females only. The percentage of embryos which developed to blastocysts in vitro paralleled the development in vivo of embryos in ageing and young donors. The overall sex ratio of 81·6 males/100 females resulting from transferred embryos was significantly different (P<0·05) from the expected figure.

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R. R. MAURER and R. H. FOOTE

Summary.

Collagenase activity was measured 66 to 75 hr after parturition in does at 34, 167 and 204 weeks of age. Uteri of ageing does contained less collagenase than those of young does. Uterine collagen content tended to increase with age. At Day 12 of pregnancy, uterine acid-soluble collagen was higher in does 174 weeks old than in does at 38 weeks of age.

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R. R. MAURER and R. H. FOOTE

Summary.

Progesterone and 20α-hydroxypregn-4-en-3-one (20α-P) synthesis in vivo and in vitro was measured 12 days post coitum in does averaging 32 weeks (young) and 214 weeks old (ageing). Young pregnant does had an average of 7·7 corpora lutea and 7·3 implantations for a mortality rate of 4·3%. Similar values for ageing does were 7·7, 5·4 and 29%, respectively. The progesterone content of ovarian venous blood was higher in young pregnant does than ageing does but the 20α-P content did not differ. Administration of lh did not significantly alter progesterone blood levels in either age group but increased 20α-P levels in both groups. Synthesis of progesterone and 20α-P by interstitial tissue in vitro did not differ significantly between ages. Addition of lh to the incubation medium stimulated synthesis of progesterone by tissue from the ageing group whereas 20α-P synthesis was increased in the young group. There was a positive relationship between doe age and pituitary weight. The ageing does had heavier pituitary glands than the young does but there was no difference in total lh content.

A lower concentration of lh was found in the pituitary gland and a lower progesterone content in the ovarian venous blood of old compared to young pregnant rabbits. While these differences may be partly responsible for the lowered reproductive efficiency of the ageing female, the evidence is somewhat equivocal since total pituitary lh and synthesis of progesterone in vitro were similar in the two age groups.

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R. ELIASSON

Summary.

Determinations of aspartate and alanine aminotransferase activity in human semen were carried out by the spectrophotometric and colorimetric methods. It was found that the occurrence of interfering substances in semen makes the spectrophotometric method unsuitable without prior partial purification of the enzyme. The mean activity determined colorimetrically in 417 samples of human semen was 320 Sigma-Frankel units/ml (s.e.m. ±8, range 10 to 1070) for aspartate aminotransferase and 30 units/ml (s.e.m. ±3, range 0 to 97, n = 40) for alanine aminotransferase. As regards aspartate aminotransferase, the activity of this enzyme was highest at +60° C. Pyridoxal phosphate increased the activity, particularly if added to semen samples with initially low activity. Gel electrophoresis of seminal plasma showed one band migrating towards the anode. However, in homogenized spermatozoa the bulk of enzyme migrated towards the cathode and only a weak band could be demonstrated on the side of the anode.

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R. DEANESLY

Luteinizing hormone (Ovine, nih-lh-s7 from the National Institutes of Health, Bethesda, U.S.A.) has been administered subcutaneously in normal saline (0·5 mg/ml) to female guinea-pigs for a study of its effects on ovulation and the cycle.

The animals were examined daily for vaginal changes; the first day of vaginal closure after oestrus (corresponding in general to the morning of the vaginal plug in mated females), was recorded as Day 0 and the following days as (luteal) Days 1, 2, etc. In most experiments a single dose of lh was given; the ovaries were examined at autopsy, and one or both sectioned serially after fixation in Bouin's fluid. Preliminary tests in cyclic females showed that 200 μg lh would stimulate ovulation within 24 hr and also follicular luteinization.

Fifteen unmated non-parous females with a regular cycle of about 16

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R. Billard

Summary. When trout (Salmo gairdneri) spermatozoa were diluted in coelomic fluid or saline diluents at high dilution rates of 10−3 and 10−2 for increasing periods of time before insemination, there was a rapid decline and loss of fertilizing ability. At a lower dilution rate of 10−1, there was partial or no loss of fertility. Dilution in a KCl-enriched saline diluent to inhibit sperm motility produced a slight decrease in fertility at a 10−3 dilution rate, indicating that the spermatozoa, although sensitive to dilution, were less so when they were kept immotile. A partial loss of fertility was observed after the spermatozoa or eggs had been washed with saline diluents. The loss of fertility was total when both gametes were washed. Removing the seminal fluid by centrifugation led to a significant decrease in the fertilizing ability of the spermatozoa when insemination was carried out in saline diluent but not in coelomic fluid. Adding BSA at high doses (10 mg BSA/ml) into the diluent led to longer survival of the diluted spermatozoa. We conclude that (1) sperm dilution rate is a major factor in the maintenance of fertilizing ability of diluted salmonid spermatozoa, (2) as reported in the literature, coelomic fluid is superior to mineral diluents only when the gametes have been washed, and (3) some substances (possibly proteins) present in seminal and coelomic fluids play a role in gamete protection. These findings may explain the discrepancies in the literature concerning the duration of motility and fertilizing ability of salmonid spermatozoa.

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R. ELIASSON

Summary.

The oxygen consumption of human spermatozoa has been determined polarographically with Clark electrodes both in whole semen and in a buffered Ringer solution. Washing of the spermatozoa caused an average decrease of 13% in the number of live cells. The oxygen consumption of the spermatozoa was two to three times higher in the Ringer solution than in the whole semen (P<0·001).

If the washed spermatozoa were returned to their own seminal plasma, the oxygen consumption also returned to the original level. These results indicated that human seminal plasma normally contains a factor that depresses sperm respiration.

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R. JONES

As yet, there is little knowledge as to the possible side effects of vasectomy on the function of the epididymis. In rats and bulls, it has been reported that vasectomy causes a spermatocoele to develop at the site of ligation on the vas deferens or in the epididymis (Amann & Almquist, 1962; Igboeli & Rakha, 1970; Hooker & Gilmore, 1972); in other species, notably the rabbit, this does not occur (Macmillan, Desjardins, Kirton & Hafs, 1968; Paufler & Foote, 1969). Some reports have claimed that vasectomy causes atrophy of the testis and disruption of spermatogenesis (Laumas & Uniyal, 1967; Sacher & Schilling, 1973) but most workers agree that, at least in the early stages, vasectomy only affects the terminal parts of the epididymis. It is not known what influence this might have