Quantitative Participation of Placental Mammotropic Hormones in Mammary Development During Pregnancy of Mice

Nagasawa, Hiroshi; Yanai, Reiko

doi:10.1507/endocrj1954.18.507

Cited by 31 publications

(22 citation statements)

References 8 publications

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“…In mice, the mass of the mammary tissue has long been established to be related to litter size at birth (Bateman, 1957). Nagasawa and Yanai confirmed that this correlation in mice occurs because of the effect of the number of placentas on mammary growth by surgically removing some embryos and their placentas, and thereby reducing lactogenic activity (Nagasawa and Yanai, 1971). They found that both prepartum and postpartum mammogenesis were reduced in relation to the number of placentas removed.…”

Section: Introductionmentioning

confidence: 94%

Limits to sustained energy intake. XVII. Lactation performance in MF1 mice is not programmed by fetal number during pregnancy

Duah

Monney

Hambly

et al. 2013

Journal of Experimental Biology

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SUMMARYSeveral studies have suggested that lactation performance may be programmed by the number of fetuses during pregnancy, whereas other studies indicate that processes during lactation are more important. As gestation litter size and litter size in lactation are usually strongly correlated, separating the roles of pregnancy and lactation in lactation performance is difficult. To break this link, we experimentally manipulated litter size of MF1 mice to five or 16 pups per litter by cross-fostering. Litter size and mass at birth were recorded on day 1 of lactation prior to litter size manipulation. Maternal body mass and food intake, litter size and litter mass were measured daily throughout. After weaning, the potential differential utilisation of body tissues of the mothers was investigated. Relationships between maternal mass and food intake, including asymptotic daily food intake at peak lactation, offspring traits and other maternal parameters suggested that the number of fetuses the females had carried during pregnancy had no effect on lactation performance. Litter mass increases depended only on maternal food intake, which was highly variable between individuals, but was independent of fetal litter size. The sizes of key organs and tissues like the liver and alimentary tract were not related to maximal food intake at peak lactation or to fetal litter size, but the masses of the pelage, mammary glands and retroperitoneal fat pad were. These data suggest that while growth of the mammary glands and associated structures may be initiated in gestation, and vary in relation to the number of placentas, the ultimate sizes and activities of the tissues depends primarily on factors during lactation.

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Section: Introductionmentioning

confidence: 94%

Limits to sustained energy intake. XVII. Lactation performance in MF1 mice is not programmed by fetal number during pregnancy

Duah

Monney

Hambly

et al. 2013

Journal of Experimental Biology

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“…Placental lactogen secretion is unlikely to be simply a function of placental mass (and hence fetal number) in all species. Experiments in mice have demonstrated that fetal number and mammary growth are correlated up to a maximum of 8 feto-placental units; thereafter either placental lactogen secretion is not enhanced or the gland is unable to respond further to the hormone (Nagasawa & Yanai, 1971b). Rats need a minimum of only 3 feto-placental units to ensure maximum mammary development (Anderson, 1975a), and prolactin secretion may be enhanced in pregnant rats by self-licking of nipples, a phenomenon which is apparently necessary for normal mammogenesis, since if it is prevented mammary growth is reduced (Roth & Rosenblatt, 1968).…”

Section: Systemic Endocrine Controlmentioning

confidence: 99%

Development of the mammary gland

Knight¹,

Peaker²

1982

Reproduction

139

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“…The DNA content of lactating mammary glands of rats is also directly related to the number of young suckled (Tucker, 1966). There is an apparent dichotomy of opinion concerning fetal effects in mice, for although a clear relationship has been established between fetal number and mammary development during gestation (Nagasawa & Yanai, 1971), there is apparently little or no correlation between the number of fetuses carried and milk yield (Nagai, 1978;Eisen, Nagai, Bakker & Hayes, 1980 Surgical procedure. Mice were used on day 8 of pregnancy.…”

Section: Introductionmentioning

confidence: 99%

Mammary development in mice: effects of hemihysterectomy in pregnancy and of litter size post partum

Knight

Peaker

1982

The Journal of Physiology

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SUMMARY1. Mice were hemihysterectomized on day 8 of pregnancy to reduce the number of feto-placental units.2. Fetal mortality was not affected by hemihysterectomy; mean single-pup weight at birth was increased when compared with sham-operated controls.3. Pregnant sham-operated and hemihysterectomized animals were killed on days 13 and 18 of gestation, and their mammary glands were analysed for total DNA (DNAt) and RNA (RNAt). Both were significantly lower in the hemihysterectomized group on day 18, but not on day 13. 4 Milk yield was assessed, by daily weighing ofthe litter, in groups ofsham-operated and hemihysterectomized lactating animals suckling nine pups each. There was no difference in yield between the two groups.5. One group ofsham-operated mice suckling nine pups, one ofhemihysterectomized mice suckling nine pups and one of hemihysterectomized mice suckling four pups were killed on day 5 of lactation for mammary gland analysis. There was no significant difference in mammary weight or DNAt between the sham-operated and hemihysterectomized animals suckling nine pups, although RNAt was still reduced in the latter. Mammary weight, DNAt and RNAt were all significantly lower in the hemihysterectomized group suckling four pups than in either of the other two groups.6. It is concluded that the less well developed mammary glands of mice which give birth to small litters are capable of compensatory growth during the first few days of lactation if a sufficiently strong suckling stimulus is given.7. It is suggested that control of mammary development by the fetus during gestation and by the suckling young during early lactation are both mechanisms designed to ensure that milk yield is appropriate to the needs of the young.

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Quantitative Participation of Placental Mammotropic Hormones in Mammary Development During Pregnancy of Mice

Cited by 31 publications

References 8 publications

Limits to sustained energy intake. XVII. Lactation performance in MF1 mice is not programmed by fetal number during pregnancy

Limits to sustained energy intake. XVII. Lactation performance in MF1 mice is not programmed by fetal number during pregnancy

Development of the mammary gland

Mammary development in mice: effects of hemihysterectomy in pregnancy and of litter size post partum

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