Adenohypophysis of the elephant seal (<i>Mirounga leonina</i>): Morphology and seasonal histological changes

Griffiths, D. J.; Bryden, M. M.

doi:10.1002/aja.1001760410

Cited by 3 publications

(1 citation statement)

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“…Cooling is important for successful spermatogenesis since this vital process fails in naturally occurring cryptorchids or in animals rendered cryptorchid by a surgical approach. Indeed, in such animals, there is a progressive destruction of the germinal epithelium (Griffiths, 1893; Glover, 1960). However, not all mammals employ a scrotal strategy.…”

Section: Introductory Perspectivementioning

confidence: 99%

Pre‐ovulatory temperature gradients within mammalian ovaries: a review

Hunter¹,

Einer‐Jensen

2005

Animal Physiology Nutrition

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Introductory perspectiveA long-standing problem in reproductive physiology concerns the temperature at which mammalian gonads function after the onset of puberty. In a majority of species so far studied, the testes descend via the inguinal canals to become suspended in a scrotal sac. Under normal conditions, a gradient in temperature is demonstrable between the abdomen and the scrotal pole of the testis (Setchell, 1978;Waites and Setchell, 1990). Cooling is important for successful spermatogenesis since this vital process fails in naturally occurring cryptorchids or in animals rendered cryptorchid by a surgical approach. Indeed, in such animals, there is a progressive destruction of the germinal epithelium (Griffiths, 1893;Glover, 1960). However, not all mammals employ a scrotal strategy. For example, elephants, various species of Hyrax and marine mammals retain their testes within the abdomen (Millar and Glover, 1973;Harrison, 1975;Glover et al., 1990), and a question therefore arises as to the temperature of such gonads. Do they function at deep body temperature without consequent morphological or genetic lesions in the sperm cells (e.g. mutations) or might there be subtle physiological mechanisms at play to cool such testicular tissue?Turning to the female, do mammalian ovaries function at deep body temperature or might there be compartments within ovarian tissues that are cooler than elsewhere in the gonad? It could be argued that if a reduction in temperature is required in the male gonad for successful gametogenesis, then temperature gradients would be anticipated within mammalian ovaries in tissues directly associated with the complement of oocytes -that is in follicular tissues.In fact, there are diverse reports of cooler tissues in the ovaries of various mammals (Balin et al., 1965;Benoit et al., 1976), and specifically in preovulatory Graafian follicles of rabbits and women. As determined by infra-red scanning (thermo-sensing) or by microelectrodes introduced during mid-ventral laparotomy, pre-ovulatory follicles of rabbits could be SummaryThe existence of a temperature gradient between the testis and deep body temperature has been accepted for many years. It is based on two simultaneous principles: cooling of the testis through the scrotal wall and transfer of heat between the testicular blood vessels. The ovary is positioned in the abdomen; a temperature difference parallel to the male system therefore seems less likely. However, the temperature of large follicles has been found to be 0.5 to 1.5°C cooler than the ovarian stroma in rabbits, pigs and, probably, women. The temperature difference seems to be based on a heat-consuming process in the expanding follicullar fluid, and a local transfer of heat between intra-ovarian blood vessels. The reason for the temperature gradient is not yet known; one may speculate of a common reason for the cooling of the gamete in male and female.

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Section: Introductory Perspectivementioning

confidence: 99%