On the postnatal development of the ovary (albino rat), with especial reference to the number of ova

Arai, Hayato

doi:10.1002/aja.1000270403

Cited by 98 publications

(21 citation statements)

References 26 publications

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“…An alternative view is that after hypophysectomy the total number of oocytes does not decrease with age, as it does in the normal animal [Arai, 1920; Mandi & Zucker¬ man, 1951 ]. Such an interpretation would be reinforced by the fact that hypo¬ physectomized animals in Swezy's experiment were in general younger than the controls, so that regardless of other physiological considerations, one would expect them to possess more oocytes.…”

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confidence: 50%

The Effect of Hypophysectomy on the Number of Oocytes in the Adult Albino Rat

Ingram¹

1953

J Endocrinol

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A comparison of the number of oocytes in fourteen pairs of hypophysectomized and litter-mate control rats showed that the number was greater in nine of the fourteen comparisons, and less in only five. This ratio is not significantly different from one of 7 : 7. The mean total number of oocytes was, on the othei hand, about 20 % greater in the operated animals, the statistical significance of the difference falling between P = 0\m=.\05-0\m=.\02.If any physiological significance attaches to this difference, the most likely explanation is that the rate of decline in the number of oocytes is less after removal of the pituitary than in normal animals.In the course of a review of the problem of mammalian oogénesis, in which it was shown that the now widespread belief that oocytes are produced throughout life is very insecurely based, Zuckerman [1951] referred to an unconfirmed observation by Swezy [1933] that in the adult rat, the numbers of oocytes increase after the removal of the pituitary. This worker estimated the number of oocytes in one of the ovaries (usually the left) of five normal and eight hypophysectomized animals, and showed that it was consistently greater in the hypophysectomized animals.The conclusion she drew, that 'after hypophysectomy the rate of ovogénesis increases ', is not, however, the only one that can be derived from this observation. An alternative view is that after hypophysectomy the total number of oocytes does not decrease with age, as it does in the normal animal [Arai, 1920; Mandi & Zucker¬ man, 1951 ]. Such an interpretation would be reinforced by the fact that hypo¬ physectomized animals in Swezy's experiment were in general younger than the controls, so that regardless of other physiological considerations, one would expect them to possess more oocytes. There are two further aspects to this matter of controls. The first is that the variation in the total number of oocytes is greater between than within litters [Mandi & Zuckerman, 1950]. Since Swezy apparently did not use htter-mate controls, the differences between the two groups of animals in her experiment would thus tend to be exaggerated. The second is that Swezy paid attention only to the number of oocytes in a single ovary of each animal she studied. Comparisons made in this way can, however, lead to misleading conclusions, for although the mean numbers of oocytes in the left and right ovaries, as derived from the study of a series of animals, do not differ significantly, there may be a considerable difference in the numbers of oocytes in the two ovaries of an individual animal. It is therefore prudent to deal always with the numbers of oocytes in both ovaries.In a similar study Paesi [1949] estimated the numbers of oocytes in four rats whose right ovaries were removed at the time of hypophysectomy and used as controls for the left, which were excised at autopsy 8 days later. Paesi did not

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confidence: 50%

The Effect of Hypophysectomy on the Number of Oocytes in the Adult Albino Rat

Ingram¹

1953

J Endocrinol

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“…Space flight during days 9-20 of gestation had no effect on the mass of these organs at postpartum on days 22-23. Rats have a period of oestrus and ovulation after delivery (Blandau and Soderwall, 1941), and the mechanisms that mediate postpartum ovulation are the same as those that control ovulation in normal cyclic rats (Ying et al, 1973 (Arai, 1920;Mandi and Shelton, 1959;Byskov, 1978), any disruption of this fundamental ovarian regulatory process could result in an increased or decreased number of ovulatory follicles and a resultant altered fecundity. However, space flight during days 9-20 of gestation had no effect on the numbers of ovarian follicles in any size range studied, either healthy or atretic, in ovaries approxi¬ mately 3 h postpartum.…”

Section: Discussionmentioning

confidence: 43%

Effects of space flight on ovarian-hypophyseal function in postpartum rats

Burden

Zary²,

Lawrence³

et al. 1997

Reproduction

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“…It was a commonly held belief throughout the first half of the 1900s that the ova initially present in the ovary at birth, the primitive ova, degenerated prior to sexual maturity and were replaced by new ova, the definitive ova. (2)(3)(4) The most commonly held view was that definitive ova arise from proliferation of the ovarian surface epithelium, (4)(5)(6)(7) though some investigators proposed that they arose from differentiation of somatic cells. (3) It was alleged that postnatal oogenesis occurs in a variety of mammalian species, including mice, (2,6) rats, (4,5,7) cats (4) and humans.…”

Section: Introductionmentioning

confidence: 41%

Renewed debate over postnatal oogenesis in the mammalian ovary

Greenfeld¹,

Flaws²

2004

BioEssays

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The central dogma of female reproductive biology has long held that oogenesis ceases prior to birth in mammals. During the first half of the last century, there was much debate about whether this was the case or whether oogenesis continued in the postnatal ovary. A report in 1951 effectively put an end to this debate and laid the foundation for the dogma. A new paper by Johnson et al. (2004) resurrects the debate over whether postnatal oogenesis occurs in the mammalian ovary. If confirmed, this would have tremendous impact on issues related to female fertility and reproductive longevity.

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On the postnatal development of the ovary (albino rat), with especial reference to the number of ova

Cited by 98 publications

References 26 publications

The Effect of Hypophysectomy on the Number of Oocytes in the Adult Albino Rat

The Effect of Hypophysectomy on the Number of Oocytes in the Adult Albino Rat

Effects of space flight on ovarian-hypophyseal function in postpartum rats

Renewed debate over postnatal oogenesis in the mammalian ovary

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