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Facultad de Ingeniería y Facultad de Ciencias Médicas, Universidad de Mendoza, Mendoza, Argentina
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Facultad de Ingeniería y Facultad de Ciencias Médicas, Universidad de Mendoza, Mendoza, Argentina
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ovary, these findings might help devise some of the pleiotropic effects of neuroactive steroids on female reproduction. Moreover, ALLO modulation of ovarian physiology might help uncover novel treatment approaches for reproductive diseases
Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Sassari, Italy
Department of Neuroscience, ‘Tor Vergata’ University, Rome, Italy
Istituto Zootecnico Caseario della Sardegna, Bonassai, Sassari, Italy
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Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Sassari, Italy
Department of Neuroscience, ‘Tor Vergata’ University, Rome, Italy
Istituto Zootecnico Caseario della Sardegna, Bonassai, Sassari, Italy
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Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Sassari, Italy
Department of Neuroscience, ‘Tor Vergata’ University, Rome, Italy
Istituto Zootecnico Caseario della Sardegna, Bonassai, Sassari, Italy
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Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Sassari, Italy
Department of Neuroscience, ‘Tor Vergata’ University, Rome, Italy
Istituto Zootecnico Caseario della Sardegna, Bonassai, Sassari, Italy
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Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Sassari, Italy
Department of Neuroscience, ‘Tor Vergata’ University, Rome, Italy
Istituto Zootecnico Caseario della Sardegna, Bonassai, Sassari, Italy
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Istituto Zooprofilattico Sperimentale della Sardegna, Sassari, Sassari, Italy
Department of Neuroscience, ‘Tor Vergata’ University, Rome, Italy
Istituto Zootecnico Caseario della Sardegna, Bonassai, Sassari, Italy
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connection with light stimulation ( Wisor & Takahashi 1997 ). In the female rat anterior pituitary, VGF immunoreactivity was apparently restricted to gonadotropes and lactotropes, with striking VGF peptide/s degranulation at estrus in association with an
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It has long been recognized that one of the advantages of sexual reproduction, consisting of the fusion between a male and a female gamete derived from two different individuals, is the increased genetic diversity of the offspring resulting in improved adaptability to environmental changes (Maynard Smith, 1978).
The different genetic strategies
The existence of functional male and female individuals is essential for reproduction in mammals as well as the majority of species (though not all – parthenogenetic lizards are known; Cole, 1984) in other vertebrates. It might be supposed that the mechanisms of sex differentiation would be basically similar in all vertebrates. Instead of this, several variations on a theme exist for achieving what is effectively the same end. In both mammals and birds, sex is determined by specific, visibly distinguishable chromosomes. In mammals, males (the heterogametic sex) have an X and a Y chromosome, while females (homogametic) have two
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Department of Endocrinology, Growth and Reproduction, Faculty of Medicine, Erasmus University, P.O. Box 1738, Rotterdam, The Netherlands
(Received 14 June 1978)
Prenatal morphological and behavioural masculinization of female foetuses through exposure to androgen from the testes of male foetuses was first suggested by Clemens (1974). It was reported that female foetuses next to male foetuses in the uterus had a larger ano-genital distance at birth and displayed more (but not statistically significant) mounting behaviour in response to administration of testosterone in adult life than did female foetuses that had not been in such close proximity to foetal male rats. More recently, Gandelman, vom Saal & Reinisch (1977) also reported that in mice, the positions of the female foetuses in the uterus relative to the male foetuses determined the extent to which the female rat was masculinized in terms of both morphology (ano-genital distance at birth) and behaviour (testosterone-induced fighting in
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†Division of Clinical and Experimental Endocrinology, University Women's Hospital, 34 Göttingen, and ‡Section of Biology of Reproduction, Department of Animal Science, 34 Göttingen, Federal Republic of Germany
(Received 4 September 1975)
To obtain information on the pituitary-gonadal system during sexual maturation in the pig, we have determined plasma luteinizing hormone (LH) and gonadal steroid levels in foetal, neonatal and pubertal animals of both sexes. Blood was collected from 45 male and 34 female miniature pig (Göttingen strain) foetuses between days 61 and 110 of foetal life (by cardiac puncture or from umbilical vessels). The piglets were removed 5–8 min after initiation of halothane anaesthesia in the sow. Blood (2–5 ml) was taken once by venipuncture of the jugular vessels from 79 male and 72 female unanaesthetized animals, 2 h (only females) to 12 weeks after birth.
Plasma LH and progesterone were measured by radioimmunoassay (Pomerantz, Ellendorff, Elsaesser, König & Smidt,
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Department of Endocrinology, Growth and Reproduction, Erasmus University, Medical Faculty, P.O. Box 1738, Rotterdam, The Netherlands
(Received 23 October 1975)
Normal cyclic ovarian activity stops in old female rats: cyclicity may be replaced by absence of ovulation and persistent vaginal cornification (Everett, 1939; Aschheim, 1964/5). In the present study, factors were examined which could contribute to the change from cyclicity to absence of ovulation. Vaginal cyclicity, ovarian microscopy, and the pro-oestrous surge of luteinizing hormone (LH) were compared between old and young rats. Locally bred (R × U)F 1 hybrid females were kept under standard lighting conditions (lights on at 05.00 h; off at 19.00 h). Three- to 5-month-old rats were all cyclic and showed predominantly 5-day cycles. From 7 months onwards a rapid increase occurred in the number of animals with persistent vaginal cornification; cyclic animals kept 5-day cycles (Table 1).
In the first experiment sodium pentobarbitone (Nembutal) was injected
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In a previous study (Bloch, 1971) we have suggested that the block to pregnancy brought about in newly mated mice by the odour of strange males, the 'Bruce effect' (Bruce, 1960), is provoked by a secretion of follicle-stimulating hormone (FSH) and, hence, oestrogen. This secretion inhibits nidation in non-lactating females, but hastens implantation in suckling animals, thus enhancing the occurrence of on-time nidations as was the case in our previous investigation. Oestrogen secretion would also agree with the 'Whitten effect'. Whitten (1956) established that females kept in groups without males and showing long periods of anoestrus showed synchronized oestrous cycles after the introduction of a male.
The editor of Research in Reproduction (1971, Vol. 3, No. 4) commenting on our findings, writes: 'Dominic had earlier ascribed the pregnancy block to lack of prolactin and this important controversy on the effect of odours on the pituitary will be resolved only by
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Most studies on the relationship between the pineal gland and reproductive function have been concerned with the effects of pinealectomy or pineal extracts on reproduction (for review see Kitay & Altschule, 1954), but the effects of the state of the reproductive system on the pineal gland have been little investigated. The effects of castration have been studied by Borell & Örström (1947) and Quay & Levine (1957), and the effects of sex hormone administration by Brewer & Quay (1958). However, no studies seem to have been made of the pineal body during pregnancy in the rat.
Fifty female rats, aged 3 months, were mated with males of similar age and thirty-eight became pregnant. The 1st day of pregnancy was defined as the 1st day on which sperms were found in vaginal smears, or vaginal plugs were seen. Twenty-five female rats of the same age and similar body weight served as
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In a single experiment, lasting for 18 months, male and female quail were exposed to an annual cycle of artificial photoperiod synchronized with sunrise and sunset, and their plasma levels of immunoreactive retinol-binding protein (IRBP) and LH were monitored at frequent intervals. Plasma levels of both IRBP and LH showed a repeating annual cycle with maximal levels during the spring/summer, the period of reproductive activity and highest rate of egg-laying, and minimal levels during the autumn/winter. Plasma levels of IRBP and LH were significantly, but only weakly, correlated with each other. The possible role of LH in the regulation of plasma IRBP during reproduction is discussed. Evidence is presented that the proportion of IRBP which does not carry retinol (retinol-binding apoprotein; apoRBP) varies throughout the female breeding cycle and that the high apoRBP concentration noted in the spring/summer period may be related to the deposition of retinol in the egg.
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SUMMARY
The effect of complete destruction of the thyroid gland by radioactive iodine on reproduction in the female mouse has been examined in detail. Possible direct effects of radiation on reproduction were differentiated from those due to thyroid destruction.
Destruction of the thyroid tissue in the male mouse had no effect on fertility.
In the thyroid-deficient female both fertility and litter frequency were unaffected, but the oestrous cycle was prolonged and the duration of 46% of gestations was longer than normal.
There was a general shift in the distribution of litter size towards small litters in the thyroid-deficient group which reduced the average number of young per litter.
Lactation, as judged by the weight of the offspring at weaning, was not affected by complete absence of the maternal thyroid gland.
After weaning the growth rate of offspring of either sex from both thyroid-deficient and normal mothers was the same.
Although the pituitary glands were enlarged in all the thyroid-deficient animals examined, tumours were not observed.
