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A. Halling and J.-G. Forsberg

Summary. Female mice of the NMRI strain were treated with the synthetic oestrogen diethylstilboestrol (DES) for the first 5 days after birth. Pools of ovaries were removed from groups of 6-, 12-, 21-, 28- and 56-day-old females. An homogenate of an ovarian pool was incubated for 1 h in the presence of [3H]pregnenolone. Synthesized steroids were extracted and separated in a two-dimensional thin-layer chromatography system. Homogeneity of tentative steroids was verified with recrystallization to constant specific activity. Synthesis of [3H]progesterone and [3H]testosterone was demonstrated at 6 days, [3H]androstenedione at 12 days, [3H]17α-hydroxyprogesterone at 21 days, and [3H]oestradiol-17β at 28 days. Up to 28 days (21 days for progesterone), the synthetic activity was lower in homogenates of DES-exposed ovaries than in control homogenates. After 28 days, values for recovered [3H]progesterone, [3H]androstenedione and [3H]oestradiol-17β were higher in DES homogenates than in control homogenates while the reverse was true for [3H]17α-hydroxyprogesterone and [3H]testosterone. The results are compatible with an early and direct DES inhibitory effect on ovarian steroidogenesis and, later in immature life, a DES-induced disruption of the normal FSH–LH stimulation of ovarian development.

Keywords: steroids; synthesis; ovary; mouse; diethylstilboestrol

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H. BOYD, A. JAMIESON and J. G. HALL

Summary.

The sera of ninety-six reproductively normal cows and twenty-sex artificial insemination bulls were typed for transferrin and for J antigen. Fertility of the cows was measured by examination of the genital tracts between 2 and 26 days after insemination at post-mortem or laparotomy. No significant relationship was observed between fertility and transferrin type or J antigen in these experimental animals. The results of approximately 90,000 inseminations with semen from the twenty-six bulls were also studied in relation to these types and again there was no useful association.

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ELEANOR PIGHILLS, J. L. HANCOCK and J. G. HALL

Summary.

Transfers were made to twenty-two ewes of pairs of sheep eggs which had been fused in vitro after mechanical removal of the zona pellucida. The zona pellucida of the sheep egg unlike that of the mouse egg could not be removed by pronase digestion. Single lambs were born to three ewes. Transferrin typing was used to identify the genotypes of the lambs.

The transferrin findings on one (still-born) lamb were in accord with expectations for a chimaeric lamb.

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G. T. Taylor, J. Weiss, T. Frechmann and J. Haller

Summary. The temporal changes in epididymal sperm numbers during the month after sexual contact were examined in 80 adult albino rats. The comparably sexually experienced males in 6 experimental groups were allowed 3 ejaculations with ovariectomized females in which oestrus was induced by hormone injections. Epididymides were removed from the experimental males 1 h, 1 day, 2 days, 3 days, 7 days or 30 days later. Control males were sexually inexperienced or sexually experienced and living with females. Epididymal sperm counts revealed a pattern that resembled an inverted V-shaped function with a peak at 48 h after copulation. We suggest that sexual activity provokes an acute attentuation of sperm disposal within the epididymis with the result that more spermatozoa are available for ejaculation during sexually active times.

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P. A. Jewell, S. J. G. Hall and M. M. Rosenberg

Summary. Ewes were each mated on four separate occasions, at 3, 9, 15 and 21 h after the start of oestrus and at each time by a different ram. The progeny were assigned to sires by blood typing, supplemented by resemblance between lambs and rams. The paternity of 64 lambs, born to 41 ewes, was established: 2 were conceived at a 3-h mating, 27 at 9 h, 23 at 15 h and 12 at 21 h. The optimum time for a ram to inseminate, when in competition with others, is therefore 9–15 h after onset of oestrus, and this finding accords with behavioural observations. Ewes tended to lamb during the same half of the day as that when they had come into oestrus.

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A. Halling, C. von Mecklenburg and J-G. Forsberg

Neonatal female mice of the NMRI strain were treated s.c. with 5 μg of the synthetic oestrogen diethylstilboestrol (DES) or vehicle only (olive oil; controls) for the first 5 days after birth. Embryos at the two-cell stage from control females were transferred to the oviducts of control females or DES-treated females (6–8-weeks-old). Immediately after transfer, the oviducts were removed and incubated in vitro for 6 h. After incubation, slightly fewer embryos were recovered from oviducts exposed to DES compared with control oviducts (81% versus 92%; 0.05 > P > 0.01). When the recovered embryos were cultured in vitro, 64% of the embryos from control oviducts reached the blastocyst stage in contrast to only 24% of those from oviducts of DES-treated mice; slightly fewer of the latter showed trophoblastic outgrowth (76% versus 93%; 0.05 > P > 0.01). Oviductal transport and uterine attachment was studied by introduction of blue-stained dextran microspheres into the oviduct. The microspheres appeared earlier in the uteri of DES-treated females than in the uteri of controls. Moreover, the spheres were not captured in the uterus in most DES-treated females, but they were trapped when a piece of Spongostan was placed in the uterine lumen. Scanning electron microscope studies showed differences between controls and DES-treated females in uterine mucosal lining of possible importance for embryo attachment to the surface epithelium. These studies showed that neonatal DES treatment caused changes in the adult reproductive tract as revealed by a detrimental effect upon embryo development, more rapid oviductal transport and loss of embryos from the uterus.

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R. A. BEATTY, G. H. BENNETT, J. G. HALL, J. L. HANCOCK and D. L. STEWART

Summary.

Friesian cows were inseminated with semen mixtures containing equal numbers of spermatozoa from a Friesian and a Hereford bull. The five bulls of each breed gave twenty-five possible combinations. The paternity of calves was established by inspection of colour and conformation. Heterospermic indices were calculated to express the relative ability of sires to father offspring after mixed insemination. There were significant differences between the heterospermic indices of bulls, the maximum observed difference being twenty-one-fold. The indices were consistent over two series. The homospermic index was defined as the 16-week non-return rate after normal single first inseminations. The heterospermic index established differences between bulls more efficiently than the homospermic index; one estimate showed that the heterospermic method needed less than 1/170th the number of inseminations required by the homospermic method. The homospermic index was predictable from the heterospermic index, the regression coefficient having a significance level of 0·05 > P > 0·025. The initial spermatozoan concentration of a bull's semen (before dilution) was highly correlated with the heterospermic index. Measures of semen quality based on the morphology and staining affinity of spermatozoa predicted heterospermic and homospermic indices non-significantly but in the right direction.

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G. Almahbobi, L. J. Williams, X-G. Han and P. F. Hall

We have examined the distribution of lipid droplets and mitochondria in relation to the cytoskeletons of Leydig cells in primary culture by using light and electron microscopy on living, intact and detergent-extracted cells. After mild extraction with Triton X-100 lipid droplets and mitochondria retained their original distribution within the cell. Double immunofluorescent microscopy showed that both structures co-localise with intermediate filaments. Transmission electron microscopy of intact (unextracted) and mildly extracted Leydig cells showed that intermediate filaments are closely associated with mitochondria and lipid droplets. By examination of stereo pairs, intermediate filaments were shown to establish direct contact with mitochondria and lipid droplets. The association of droplets and mitochondria with intermediate filaments suggests possible mechanisms by which the transport of cholesterol takes place from droplets to mitochondria where this substrate enters the steroidogenic pathway.

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Lucinda C Aulsebrook, Michael G Bertram, Jake M Martin, Anne E Aulsebrook, Tomas Brodin, Jonathan P Evans, Matthew D Hall, Moira K O'Bryan, Andrew J Pask, Charles R Tyler and Bob B M Wong

Environmental pollution is an increasing problem for wildlife globally. Animals are confronted with many different forms of pollution, including chemicals, light, noise, and heat, and these can disrupt critical biological processes such as reproduction. Impacts on reproductive processes can dramatically reduce the number and quality of offspring produced by exposed individuals, and this can have further repercussions on the ecology and evolution of affected populations. Here, we illustrate how environmental pollutants can affect various components of reproduction in wildlife, including direct impacts on reproductive physiology and development, consequences for gamete quality and function, as well as indirect effects on sexual communication, sexual selection, and parental care. We follow with a discussion of the broader ecological and evolutionary consequences of these effects on reproduction, and suggest future directions that may enable us to better understand and address the effects of environmental pollution.