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F. Schwarzenberger, R. Francke and R. Göltenboth

The analysis of reproductive hormones in faecal samples is a possibility for non-invasive monitoring of reproductive status in free-ranging or intractable species. In the present study, faecal samples from three black rhinoceroses (Diceros bicornis michaeli) were collected at about weekly intervals during oestrous cycles and pregnancy. Daily samples were taken during the week after parturition. Total immunoreactive progestagens in faecal extracts were analysed with three different enzymeimmunoassays (EIA) that had considerable specificity for progestagens containing either a 20α-hydroxyl or a 20-keto group. With each EIA it was possible to distinguish between the follicular and luteal phases of the oestrous cycle. Mating corresponded with low concentrations of faecal progestagens. Samples from five and six consecutive cycles were available from two rhinoceroses and cycle lengths of 24 and 26.5 days were calculated. All three animals became pregnant and the duration of gestation ranged from 440 to 470 days. After fertilization, the concentration of progestagens increased continuously, as in the luteal phase, reaching values 5–10 times higher between days 60 and 250. During the two weeks before parturition faecal progestagens declined and within 3–4 days post partum had reached follicular phase values. It was concluded that several immunoreactive progestagens are present in the faeces of black rhinoceroses and that their measurement with EIA enables non-invasive monitoring of the oestrous cycle and pregnancy.

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R. N. Murdoch and R. C. Jones

Summary. Cooling diluted boar semen to 5°C and the addition of glycerol at 20°C and 5°C all depressed the subsequent metabolism of glucose, but had no effect on total oxygen uptake or lactate production. Ultrastructural studies showed that although glycerol had no effect on middle-piece cytology, it increased the incidence of acrosomal vesiculation at 5°C. It is concluded that acrosomal vesiculation does not affect the metabolism of spermatozoa and it is suggested that the reported detrimental effect of glycerol on the fertilizing capacity of spermatozoa is related to its membrane activity.

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R. R. Maurer and H. M. Beier

Summary. The effects of isolated protein fractions from rabbit uteri (prealbumin, albumin, uteroglobin, and β-glycoprotein), unfractionated uterine proteins, progesterone, oestradiol-17β, and prostaglandin F-2α on the development of rabbit embryos in vitro were investigated. When exposed to individual protein fractions obtained from Day-6 uteri, 8-cell embryos did not develop into early blastocysts; morulae readily developed into early blastocysts, but further development was retarded. Progesterone (10−5–10−11 M) and prostaglandin F-2α (0·1–10 ng/ml) added to the medium slowed development of blastocysts to advanced stages. Growth of 8- to 16-cell embryos, morulae, and Day-4 blastocysts was stimulated by unfractionated uterine proteins obtained from Day-5 uterine flushings.

Although embryos cultured in medium containing BSA had similar rates of blastocyst formation and, ultimately, similar blastocyst expansion as did the embryos cultured in medium with unfractionated proteins, the radial and immediate expansion of the early blastocysts cultured in the latter approximated that found in utero.

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R. E. CHAPLIN and R. W. G. WHITE

Summary.

The growth and spermatogenic activity of the testes and epididymides of fallow deer of determined age were studied through the year in a cross section of British herds. Full spermatogenic activity for all populations was first found at 16 months of age though overall growth of the testes continued into middle age. The physiological ability to effect fertile matings is, however, mediated by social forces. Until puberty, growth of the testes is continuous and independent of seasonal factors. Development of the epididymides parallels that of the testes. After puberty, there is a seasonal cycle of growth and regression of the testes and epididymides with maximum weights associated with the mating period (rut) in October/November.

The fallow deer is shown to follow the pattern of other northern temperate deer and to differ in its pattern of spermatogenic activity from tropical deer, such as muntjac, living in Britain.

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R. J. Aitken and R. A. Elton

Summary. The value of Poisson distribution theory in describing and predicting the nature of sperm—egg interaction in vitro has been investigated using an interspecific in-vitro fertilization system, incorporating zona-free hamster oocytes and human spermatozoa. The frequency distribution of polyspermic oocyte penetrations in 72 experiments exhibited good agreement with the Poisson distribution at all levels of fertilization, indicating that each oocyte must be of equal penetrability and that there can be no block to polyspermy in this interspecific system. Poisson distribution theory also accurately described the relationship between oocyte penetration and sperm motility in 50 out of 54 separate experiments spread across 10 serial dilution curves. For each dilution series the shape of the fitted curve was fixed but its location along the x-axis varied from donor to donor. The fixed nature of the relationship between sperm motility and egg penetration enables the results of such in-vitro fertilization experiments to be corrected for the number of motile spermatozoa in the incubation media. On the basis of these findings a protocol is described for assessing the results of the zona-free hamster oocyte penetration assay, which involves analysis of the degree of polyspermy followed by the application of Poisson distribution theory to correct the results to a standard concentration of motile spermatozoa. Changes in the penetrating ability of human spermatozoa after vasectomy and characterization of the degree of inter-ejaculate variation in penetrating potential are two clinical examples of such analyses given in the text. The statistical methods described in this paper should also be of general relevance to the study of fertilization mechanisms, in providing a rationale by which to analyse the quantitative nature of sperm—egg interaction in vitro.

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R. J. DONOFRIO and R. J. REITER

Summary.

The effect of blinding combined with anosmia on pituitary prolactin levels was studied in prepuberal female rats. Pituitary prolactin content and concentration were significantly depressed and the animals also evinced a noticeable retardation in the growth of their reproductive organs. Pinealectomy, when performed concurrently with blinding and olfactory bulb removal, prevented the fall in prolactin levels and ovarian weights and resulted in uterine weight levels between those of blind anosmic and untreated animals.

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I. R. Fleet and R. B. Heap

Summary. Uterine blood flow and myometrial activity were measured simultaneously in anaesthetized sheep 15 days after a sterile (non-pregnant group) or fertile (pregnant) mating. During the peri-implantation period uterine blood flow was similar in both groups of animals, but spontaneous myometrial activity was greatly reduced in pregnant ewes. This 'block' of myometrial activity was associated with circulating levels of progesterone which were significantly higher (2·8 ± 0·8 ng/ml, mean ± s.e.m.) than those in non-pregnant animals (0·4 ± 0·3 ng/ml). Adenosine injected into the uterine artery produced uterine vasodilatation in both groups, but the log dose–response was significantly less in pregnant than in non-pregnant animals (P < 0·001). Myometrial activity was stimulated by adenosine, particularly in the pregnant group (P < 0·001). Vascular and myometrial effects were potentiated by a previous infusion of dipyridamole. Occlusion of the uterine artery produced reactive hyperaemia, and oestradiol infused close-arterially induced vasodilatation after a lag phase of about 30 min. Our results are consistent with a hypothesis that vascular and myometrial cells in the uterus may contain two types of adenosine receptor, one mediating excitatory and the other inhibitory responses, and that both responses are modified by the presence of a conceptus. The results also support the idea that oestrogens produce uterine vasodilatation by increasing the local concentration of vasoactive substances.

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W. R. ALLEN and R. M. MOOR

The gonadotrophin (pmsg) present in the serum of mares between the 40th and 120th days of pregnancy originates in the uterine endometrial cups. These structures begin to develop on the 36th day of pregnancy opposite a transitory, though well-defined, circumferential thickening of the chorion called the allantochorionic girdle (Ewart, 1897; van Niekerk, 1965; Allen, 1970). The endometrial cups are composed of a discrete and densely packed mass of very large, epithelioid, decidual-like cells. They develop before the allantochorion becomes attached to the endometrium and it has been widely accepted in the past that they are exclusively maternal in origin (Clegg, Boda & Cole, 1954; Amoroso, 1955). However, recent genetic evidence, derived from the study of interspecific equine hybrids, has indicated

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S. K. SAKSENA and R. R. CHAUDHURY

Summary.

Nine azasteroids have been evaluated for antifertility effect in rats when fed orally from Days 1 to 4 of pregnancy at the dose of 10 mg/kg body weight. The compounds 3β-hydroxy-androst-5-ene (16, 17-C)-5-methyl-pyrazole and 1,2,3,4-tetrahydro-N-tosyl-8-methoxy-4-oxo-benzo(b)quinoline inhibited pregnancy at that dose in a significant number of rats.

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R. J. Aitken and R. W. Kelly

Summary. Time-exposure photomicrography and interspecies in-vitro fertilization procedures have been used to examine the influence of prostaglandins on human sperm function. An analysis of variance indicated that the presence of PGs in the incubation media was associated with a significant increase in sperm velocity and the frequency of sperm head rotation, although there were no differences between individual PGs in the degree of stimulation observed. Changes in the penetrating ability of human spermatozoa were detected after exposure to PGs, particularly PGE-1 and PGE-2. PGE-2 induced a sustained increase in penetration rates at all doses of >8·4 μg/ml, while exposure to PGE-1 gave a bell-shaped dose—response curve which exhibited a peak between 8·4 and 33·3 μg/ml and progressively fell to reach control levels at the maximum concentration tested of 270 μg/ml. A combination of PGE-2 and PGE-1 produced a dose—response curve similar to that for PGE-1 alone, while exposure to PGF-2α was without effect. Seminal extracts containing predominantly 19-hydroxy PGE-1, or equal amounts of 19-hydroxy PGE-1 + 2 induced a slight, but significant, rise in penetration rates while a combination of PGs representing the major components of human seminal plasma was without significant effect. We conclude that certain prostaglandins may have a direct action on the functional competence of human spermatozoa.