Search Results

You are looking at 1 - 10 of 3,014 items for

  • Author: R R x
Clear All Modify Search
Free access

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,

Free access

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.

Free access

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.

Free access

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.

Free access

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.

Full access

R Ivell

The relaxin-like factor (RLF) is a novel member of the insulin-IGF-relaxin family of hormones and growth factors. Also known as the Leydig cell insulin-like factor (Ley-I-L), this peptide and the mRNA encoding it appear to be expressed in very large quantities in the Leydig cells of the testis. However, it is also produced in the ovary of a number of species in both follicular theca cells and in the corpus luteum of the cycle and pregnancy. RLF gene transcripts have been identified at a much lower level of expression throughout the bovine female reproductive tract and also in the hypothalamus. Although data are limited, it would appear that RLF represents a new differentiation-related factor with specific functions linked to reproductive physiology in male and female mammals.

Free access

R. DEANESLY

Summary.

In guinea-pigs, low doses of oestradiol benzoate, given immediately after mating, inhibit pregnancy. This is not due to retention of eggs in the Fallopian tubes but to their expulsion. It is suggested on present evidence that the term 'tube-locking' should be dropped, unless it is clearly shown that eggs are detained in the Fallopian tubes beyond the usual period.

Once the fertilized eggs have passed normally into the uterus, implantation is not prevented by as much as 30 or 50 μg oestradiol in the guinea-pig, but later stages of development may be affected and the corpora lutea regress completely, either because of a failure of the placental luteotrophic hormone at about 10 days post coitum (p.c.) or through a direct effect of oestrogen on the secretion of pituitary gonadotrophins. In animals which aborted or resorbed their embryos, oestrus returned about Day 16.

Implantation was not inhibited by 20 μg oestradiol in guinea-pigs ovariectomized on Day 5 and injected on Days 6 and 7 p.c.

Free access

R. ELIASSON

Summary.

Human seminal plasma contains highly active glutamic oxaloacetic transaminase (aspartate aminotransferase). Using the splitejaculation method it has been demonstrated that the enzyme is largely concentrated in the first portion of the ejaculate, indicating that it is derived from the prostate gland.

Free access

R. Ghazi

Summary. In 6 adult camels (Camelus dromedarius) the uterus had 2 arteries on each side; one was the cranial uterine artery, which was a branch from the ovarian artery, and the other was the caudal uterine artery, which originated from the urogenital (vaginal) artery. There was no middle uterine artery, as is found in ruminants. The ovarian artery originated directly from the aorta and divided into 3 branches (ovarian proper, uterine and oviduct arteries) at a point approximately 5 cm before the ovary. The main drainage consisted of the utero-ovarian and caudal uterine veins. Although interconnections between arteries as well as between veins were numerous, no true veno-arterial anastomoses were found. These anatomical findings would suggest that there may be local unilateral uterine control of ovarian function in the camel.

Free access

R. Webb

Summary. Treatment of ewes with a 3β-hydroxysteroid dehydrogenase (3β-HSD) inhibitor (Epostane) resulted in a significant increase in both ovulation rate and in the mean number of lambs per ewe lambing. The progestagen sponge plus 3β-HSD inhibitor treatment also caused a significant increase in oestrous cycle duration of approximately 1·5 days. Treatment of ewes with the 3β-HSD inhibitor caused a significant decrease in peripheral progesterone concentrations, which were reduced even further when 3β-HSD inhibitor treatment was given to ewes after insertion of a progestagen sponge. However, mean oestradiol concentrations were significantly higher in the two treatment groups, both at the end of the luteal phase and during the follicular phase of the oestrous cycle. These results demonstrate that ovulation rate and the production of lambs per ewe lambing can be significantly increased by 3β-HSD inhibitor treatment.