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A. BARTKE

Summary.

Dwarf mice with hereditary prolactin deficiency were rendered fertile by implanting normal mouse pituitary under the kidney capsule. The grafts were removed by unilateral nephrectomy between Days 9 and 16 of pregnancy. All females carried to term and delivered litters. The young died within 2 to 8 days, apparently from lack of milk. The comparison of these results with the effects of hypophysectomy during pregnancy suggests that the mouse placenta produces prolactin-like hormone before it can provide full luteotrophic complex. The involution of mammary glands is slower in dwarfs deprived of the source of prolactin but secreting lh, fsh and acth than in the hypophysectomized animals.

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A. BARTKE

In the laboratory mouse, formation of spermatozoa from type A spermatogonia requires 34·5 days (Oakberg, 1956b; Clermont & Trott, 1969). Early spermatids appear in the mouse testis at the age of 22 to 24 days (Nebel, Amarose & Hackett, 1961) and 2 weeks later, the testicular histology has been reported to reach the adult state (Molne & Brabrand, 1968). Fertility is usually attained before the age of 60 days, depending mainly on the genetic constitution and diet. The yield of spermatogenesis was studied quantitatively during the period of rapid growth of the testes before the animal becomes fertile. Groups of CD-1 random-bred male mice (Charles River Breeding Laboratories) were killed at the age of 27, 32, 39 and 44 days. Two 4-month-old males were included for comparison. Germinal cells were counted on 5-μ cross-sections of the testes stained with haematoxylin and PAS, using ten tubules in stage VII of spermatogenesis (Clermont & Morgentaler, 1955; Oakberg, 1965a). The crude counts of type A spermatogonia (A), preleptotene spermatocytes (PL), pachytene spermatocytes (P) and step 7 spermatids (ST) were converted into true counts using the Abercrombie formula (Abercrombie, 1946) and corrected for the differences in the number of Sertoli cells using the `Sertoli cell factor' (Clermont & Morgentaler, 1955). The values were expressed per 10·1 Sertoli cells, i.e. the number observed in adult males. The differences between the ratios of different cell types were compared by Χ2 and the mean
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A. BARTKE

Summary.

Female mice had unilateral, silk thread IUDs removed 1, 2, 3 or 4 days after mating and were killed 1 to 5 days later. Histological sections of both uterine horns, or the uterine contents flushed out with water, were examined for the presence of leucocytes. Polymorphonuclear leucocytes which are invariably present in the lumen and endometrium of all horns containing an IUD and in a proportion of contralateral untreated horns, had usually disappeared in less than 48 hr after removing the IUD. This may explain the occurrence of implantations in mice from which the IUDs were removed 1 to 3 days after mating.

The duration of pseudopregnancy in mice with IUDs was increased and was more variable than in untreated mice.

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A. BARTKE

In the mouse, lh depletes cholesterol esters while prolactin promotes their accumulation in the testes (Bartke, 1969, 1971). In prepuberal mice, the concentration of total cholesterol in the testes has been reported to decrease (Simmons, 1969) and to increase with age (Ichihara, 1969). After weaning, the concentration of total cholesterol has been reported to remain approximately the same until the age of 90 days (Simmons, 1969) or to increase more than two-fold between the ages of 42 and 49 days (Ichihara, 1969). No information is available on the amounts of free and esterified cholesterol in the testes of immature mice. The concentration of esterified and free cholesterol in the testes of mice between the ages of 5 and 120 days has, therefore, been studied.

Random-bred mice derived from crossing YS/ChWf, YS/ChWf-dw and Dw/Wf strains were mated after 2 months of age and, thereafter, kept in pairs. The litters were weaned at the age of 21 to 23 days. Animals were killed by cervical dislocation and the concentration of free and esterified cholesterol was measured as previously described (Bartke, 1969). In mice less than 3 weeks old, the testes from two to eight animals were used for each determination. For statistical calculations and presentation, the results were pooled into nine groups. Within each group, there were no differences in the concentration of

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G. LAPINSKY and A. BARTKE

Summary.

The influence of the removal of the uterus and of the interruption of its vascular supply on the ovulatory response to pregnant mare serum gonadotrophin (pmsg) and human chorionic gonadotrophin (hcg) was studied in adult female rats. Both procedures significantly decreased the proportion of rats ovulating after pmsg/hcg treatment. In intact animals, the number of ova shed differed when pmsg was administered at different stages of the oestrous cycle but no such relationship existed in operated rats.

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L. Debeljuk and A. Bartke

In this investigation the concentrations of immunoreactive substance P and neurokinin A in the hypothalamus and anterior pituitary of the Siberian hamster were compared with those in the rat and Syrian hamster. The concentrations of immunoreactive neurokinin A in the hypothalamus of Siberian hamsters were significantly higher than those of rats and Syrian hamsters, while male Siberian hamsters had similar amounts of substance P in the hypothalamus to those of male Syrian hamsters, but had higher amounts than those in male rats. However, female Siberian hamsters had significantly higher hypothalamic concentrations of both substance P and neurokinin A than did female Syrian hamsters and rats. In the anterior pituitary glands of Siberian hamsters, concentrations of substance P and neurokinin A were markedly higher than they were in rats and even more so than in Syrian hamsters. Ovariectomy further increased tachykinin concentrations in the anterior pituitary gland of female Siberian hamsters, and this was completely prevented by oestradiol replacement. Female Siberian hamsters kept under conditions of reduced photoperiod had significantly higher tachykinin concentrations in the anterior pituitary than did animals kept under daily photoperiods of 16 h light:8 h dark. The incubation of anterior pituitaries from female Siberian hamsters with a neurokinin A receptor antagonist resulted in a partial blockade of the LH and FSH release in response to LHRH. Thus, the high concentration of tachykinins present in the anterior pituitary of the Siberian hamster may have a local role in modulating the secretion or release of gonadotrophins.

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B. T. CROFT and A. BARTKE

Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545, U.S.A.

(Received 2nd April 1975)

In the laboratory mouse, prolactin is indispensable for luteal function (Choudary & Greenwald, 1969), and pseudopregnancy can be induced by prolactin injections or by prolactin-producing pituitary grafts (Dresel, 1935; Browning & White, 1963; Bartke, 1966; Dominic, 1966). During pregnancy, the minimal daily requirement for exogenous prolactin is greater during the first 2 days than during the following 6 days (Bartke, 1973), and the present study was undertaken to check whether a similar difference also exists during pseudopregnancy.

Adult female mice of a random-bred stock were housed individually and vaginal smears were taken daily throughout the study. Ovine prolactin (NIH-PL-S10) dissolved in 0·9% saline (with a few drops of 0·1 n-NaOH) was injected intraperitoneally daily starting on the day of full vaginal cornification (oestrus) for 2 days or until the next oestrous smear. A treatment cycle of

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C. Sundqvist, A. G. Amador and A. Bartke

Department of Physiology, School of Medicine, Southern Illinois University, Carbondale, IL 62901-6512, USA

Page Introduction 413 The hypothalamus, pituitary and pineal 414 The hypothalamic–pituitary unit 414 Anatomy 414 Secretion of hormones 414 The pineal gland 416 Anatomy and secretion of hormones 416 Reproductive biology of the female 416 Oogenesis and ovulation 416 The phenomenon of delayed implantation 419 Fertilization, gestation and parturition 421 Other studies on the reproductive biology of the female 422 Reproductive biology of the male 422 Testicular development and spermatogenesis 422 Photoperiodic regulation of male reproduction 425 Other aspects of male reproductive biology 426 Reproductive problems in the female 427 Reproductive problems in the male 429 References 431

Keywords: mink; reproduction; fertility; seasonal breeder; review

Introduction

The mink (Mustela vison) is a seasonally breeding, semi-aquatic animal belonging to the mammalian order Carnivora. It is not a traditional laboratory animal, but nevertheless of great importance because it is

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B. BARCIKOWSKI, S. K. SAKSENA and A. BARTKE

Prostaglandins (PGs) can be synthesized by the testes (Ellis, 1972) and are present in the male accessory reproductive tissues and in the semen of various mammalian species (Bygdeman, Fredricsson, Svanborg & Samuelsson, 1970; Tan & Privett, 1972). Their physiological rôle in the male reproductive system is not understood but various effects of PG administration on the testes and male reproductive tract have been reported. These include decrease in plasma testosterone levels (Bartke, Musto, Caldwell & Behrman, 1973; Saksena, Safoury & Bartke, 1973), decrease in testicular blood flow (Free & Jaffe, 1972), and effects on contractions of the testis capsule (Seeley, Hargrove, Johnson & Ellis, 1972), on sperm transport (Hunt & Nicholson, 1972), and on contractile responses of the ductus deferens and seminal vesicles in vitro (Stahl, 1972; Taylor & Einhorn, 1972). In the human, certain cases of male infertility appear to be associated with a low seminal content of PGs

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S. C. Newton, M. J. Welsh and A. Bartke

Summary. To define a functional difference in Sertoli cells of animals exposed to different photoperiodic conditions, we isolated Sertoli cells from the testes of juvenile Siberian hamsters and cultured them in serum-free medium. In all age groups studied, Sertoli cells isolated from hamsters with delayed and normal puberty responded to follicle-stimulating hormone (FSH) with an increase in lactate production. The increase in lactate production induced by 1000 ng FSH ml−1 was significantly greater in Sertoli cells isolated from hamsters with delayed puberty than in those with normal puberty. These results suggest that Sertoli cells of Siberian hamsters exposed to short photoperiod in vivo may respond to increases in plasma FSH concentrations associated with photostimulation or spontaneous sexual maturation by an increase in secretory activity that may be critical for the initiation of spermatogenesis.

Keywords: Sertoli cells; Siberian hamster; photoperiodism; follicle-stimulating hormone; lactate