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J. D. SKINNER

Reports of abnormal reproductive development in feral antelope are rare. Skinner & Huntley (1971) have given details of an intersex kudu but there have been no reports of such abnormalities in gazelle. During recent studies on the reproduction of the springbok (Skinner & van Zyl, 1970, 1971) 250 rams were shot. Of these, one was found to be bilaterally cryptorchid and is the subject of this communication.

Apart from the fact that no scrotum or pouch formation was present, the ram was phenotypically identical to normal rams. It weighed 36·4 kg compared with 36·7 ± 1·1 kg for six normal rams shot at the same time. The pituitary gland weighed only 0·2 g compared with 0·5 ± 0·1 g for normal rams. After cutting through the pubic symphysis,

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J. D. SKINNER

Marshall (1922) stated that: "in those animals in which during immaturity the testicles remain in the body cavity, it is at puberty that these organs first descend into the scrotal sacs". Subsequent work has shown that in the rabbit the growth of testes follows a sigmoid curve, increasing rapidly during puberty (Lipschütz, 1924; Kuboshima, 1951; Gaddum, 1964). Brief reports have been published by Lipschütz (1924) and Davies & Mann (1947) on the endocrine function of the pubescent rabbit testis. The object of the present study was to investigate the time-relationship between the androgenic and gametogenic function of the rabbit testis during puberty.

The rabbits came from the Unit's own closed colony which originated from cross-bred rabbits, and in which males reach a mature weight of 3 to 4 kg at 7 months of age. Weaned rabbits were transferred in groups to colony pens. It was observed that fighting began amongst these animals at 60 days of age and `bucking' (attempts to mount) about 10 days later. At this stage seven bucks were separated and trained to ejaculate into an artificial vagina, and thereafter, ejaculates were collected at weekly intervals until autopsy at 126 days. The following were determined: Volume of semen (seminal gel, if present, was included) ; sperm density, in a haemacytometer; the percentage of live and abnormal spermatozoa, as described by Glover (1960); and fructose and citric acid (Mann, 1964). The main results of semen analyses appear in Text-fig.

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J. D. SKINNER and J. BOWEN

Relatively little is known about the time when the stallion reaches puberty. In the Anglo-Norman breed the testes have been shown to increase gradually in weight from the 11th month onwards, and then more rapidly from the 16th month (Nishikawa & Horie, 1955). Large amounts of testosterone have been found in the spermatic vein blood of mature stallions (Lindner, 1959, 1961). It has also been postulated that the rise in urinary oestrogen excretion accompanies sexual maturation at 20 months (Zondek, 1934; Pigon, Lunaas & Velle, 1961). The object of the present experiment was to study sexual development in living pony stallions from birth until the time when spermatozoa appear in ejaculates, and to define the time relationship between the onset of androgenic and gametogenic testicular functions. In addition, a study was made of the effects of season on

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M. Lindeque and J. D. Skinner

Summary. Sexual differentiation of the Müllerian duct system and gonad in female fetuses conformed to the general mammalian pattern, whereas the external genital anlage in male and female fetuses developed into the male facies. Interstitial cells occurred in the primary germinal cords of both male and female fetal gonads and are suggested to be the source of androgen production in spotted hyaena fetuses. Maternal transfer of androgens to the fetus via the placenta was negligible. Male fetuses had higher gonadal and plasma concentrations of testosterone than female fetuses, and vice versa for androstenedione. Plasma testosterone was nearly as high in a female 31-day-old fetus as in the twin male, and masculinization of the genital tubercle probably results from an episode of androgen secretion by the fetal gonad although the Wolffian ducts in the female do not respond.

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R. J. van Aarde and J. D. Skinner

Summary. The reproductive tract of the male Cape porcupine is morphologically and histologically similar to that of New World hystricomorph rodents. Males are reproductively active throughout the year and attained sexual maturity (complete spermatogenesis) at an age of 8–18 months. Testes weight, epididymides weight and seminiferous tubule diameter attained asymptotic values at the age of 23–30 months. A tendency towards seasonality in the activity of accessory glands, preceded and accompanied by an increase in circulating plasma testosterone values, may be considered as a factor enforcing seasonal breeding in females. Testosterone concentrations in pubertal males were significantly higher than those recorded in sexually mature males.

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R. J. van Aarde and J. D. Skinner

Summary. The constituent cell types of the ovary of the porcupine were similar to those of New World hystricomorph rodents and accessory corpora lutea and luteal bodies were formed through the luteinization of the membrana granulosa or theca interna of antral follicles. All luteal bodies were histologically similar. The total volume of luteal tissue per female was not affected by fetal age and was unrelated to circulating concentrations of maternal plasma progesterone. Maternal plasma progesterone concentrations were correlated with fetal age. Follicular activity occurred throughout pregnancy but was not affected by fetal age or related to circulating values of oestradiol-17β. The formation of accessory corpora lutea during pregnancy is regarded as important in supplementing progesterone during pregnancy.

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J. D. SKINNER and L. E. A. ROWSON

Summary.

The administration of chlormadinone acetate to pubescent lambs suppressed the growth of the reproductive tract as a whole, reduced both ejaculate volume and fructose concentration and delayed the appearance of spermatozoa. Following a period of suppression, a `rebound' effect was seen with fructose levels exceeding those of the controls for a short period and then returning to normal.

Sperm production and motility were reduced and the number of dead and abnormal spermatozoa increased.

Treatment was least effective after the onset of spermatogenesis and the inhibitory effect was counteracted by injection of pituitary gonado-trophin (icsh). There was no effect on growth rate.

Intravenous injection of methallibure appeared to have no effect on testicular growth, and did not delay the first appearance of spermatozoa, but fructose secretion by the seminal vesicles was increased. There was an increase in the number of spermatozoa produced and also in the numbers of dead and abnormal forms. Methallibure did not affect the growth rate.

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J. D. SKINNER and L. E. A. ROWSON

Summary.

Changes during puberty were studied in the live ram lamb by collecting electro-ejaculates and measuring fructose and citric acid concentration and sperm density and morphology. Fructose and citric acid secretion preceded spermatogenesis. Sperm motility improved with decreasing numbers of abnormal spermatozoa. Observations are included on the separation of the penis from the prepuce. In addition, the influence of season of birth on lamb ejaculates was studied. Reproductive development in lambs born in late summer was delayed, androgen secretion being more markedly affected than spermatogenesis. The results of these studies support the view that the onset of male puberty coincides with the time when the testes become androgenically active, the accessory glands begin to secrete fructose and citric acid, and the animal exhibits characteristic male behaviour.

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J. D. SKINNER and C. E. ADAMS

Summary.

The effect of CAP and of methallibure on sexual function was studied in the male rabbit. CAP was given as a single subcutaneous injection (2 mg or 10 mg/kg body weight) and methallibure as a single intravenous injection (1 mg or 10 mg/kg body weight) at birth, 42 days of age (before the onset of spermatogenesis) and at 63 days of age (after the onset of spermatogenesis). Surgically castrated males and controls were included for comparison. All bucks were subjected to autopsy at 133 days of age, 1 week after the appearance of spermatozoa in the ejaculate of the controls.

Both drugs suppressed male behaviour and testicular growth. Growth rate was adversely affected in bucks treated at birth or 42 days of age. The effect of the drugs was not so marked when given after the onset of spermatogenesis.

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D. C. Skinner and J. E. Robinson

The presence of melatonin-binding sites in the ovine pars tuberalis is well established, but data on melatonin binding in the pars distalis are inconsistent. The distribution of melatonin-binding sites in the ovine hypophysis was investigated using in vitro auto-radiography and the high-affinity, high specific-activity ligand 2-[125 I]iodomelatonin. The histology of sections was visualized with Heidenhain's azan stain and sections were immunoreacted against ovine LH (β-subunit) using standard immunocytochemical techniques. Melatonin binding in the hypophysis was restricted to the pars tuberalis and the zona tuberalis. The zona tuberalis is histologically similar to the pars tuberalis and appears to be a ventral extension of this region, although the shape and size of the zona tuberalis are extremely variable between individuals. Like the anteroventral pars tuberalis, there is a high concentration of immunoreactive gonadotrophs in the zona tuberalis. The density of immunoreactive gonadotrophs alone is sufficient to discriminate between the zona tuberalis and the pars distalis. Our data suggest that the zona tuberalis and the pars tuberalis are part of the same endocrine tissue and that melatonin-binding sites are not present in the pars distalis proper.