Criteria of placental endocrine activity in the mouse

Abstract

The suppression of oestrus in the mouse during placental retention (Newtoil, '35) implies a direct o r indirect relationship between placenta and ovary. In man, monkeys and some other animals in which the ovaries are unnecessary for continued gestation after the early stages of pregnancy, a case can be made out for a straightforward depression of the ovaries, particularly as these may show atrophic changes. N o such simple relationship can be postulated for the rat and mouse, since the ovaries of these animals cannot he removed without terminating pregnancy.Iilein ( '35) has shown very clearly that iii the rat with retained placentae mucification of the vaginal epithelium is dependent on the presence of the placentae, but cannot be maintained in the absence of the ovaries. Froin this and previous work on the endometrium of the rabbit ('33)' Klein suggests a stimulating action of the placenta on the corpus luteum. However, there have been indications that the placenta itself may also produce progesterone, o r exert an endocrine influence independently of the o17ary. Thus Selye, Collip and Thomson ( ' 3 5 ) on the grounds of endometrial changes and maintenance of the mammary glands in rats, and Haterius ( '36), who succeeded in maintaining gestation in oophorectomized rats from which all except one foetus, but

Placental Activity in the Mouse in the Absence of the Pituitary Gland

“…The maintenance of body-weight and reabsorption of the symphysis pubis in the presence of retained placentae, phenomena previously shown to be dependent on the simultaneous presence of the ovaries [Newton and Lits, 1938], are found to be independent of the presence of the pituitary. Implicit in these findings is the suggestion that, since the ovaries are still able to play their part, at least part of the synergism between ovaries and placentae is a trophic effect of the latter on the former.…”

“…Mammary development and ligamentous transformation of the symphysis pubis [Gardner, 1936] proceed normally, and 19 days after impregnation mammary glands and symphysis pubis are indistinguishable from those at the end of normal pregnancy [Newton and Lits, 1938]. Allowing for some difference in the choice of criteria, the same unimportance of the growing foetuses in maintaining the changes characteristic of the last week of pregnancy is found in the rat [Kirsch, 1938 ;Klein, 1935 ;Selye, Collip, and Thomson, 1935;McKeown and Zuckerman, 1938].With the object of finding whether the activity of the placentae was direct or indirect, Newton and Lits [1938] removed the ovaries shortly after foetal destruction on about the 12th day of pregnancy. They found that in the ensuing week the mammary glands did not undergo involution, and in some cases attained full-term development, provided placentae were retained.…”

“…In the interval between foetal destruction and delivery of the placentae the weight added during the first part of pregnancy is maintained and oestrus is suppressed [Newton, 1935 ;Brooksby and Newton, 1938]. Mammary development and ligamentous transformation of the symphysis pubis [Gardner, 1936] proceed normally, and 19 days after impregnation mammary glands and symphysis pubis are indistinguishable from those at the end of normal pregnancy [Newton and Lits, 1938]. Allowing for some difference in the choice of criteria, the same unimportance of the growing foetuses in maintaining the changes characteristic of the last week of pregnancy is found in the rat [Kirsch, 1938 ;Klein, 1935 ;Selye, Collip, and Thomson, 1935;McKeown and Zuckerman, 1938].…”

“…With the object of finding whether the activity of the placentae was direct or indirect, Newton and Lits [1938] removed the ovaries shortly after foetal destruction on about the 12th day of pregnancy. They found that in the ensuing week the mammary glands did not undergo involution, and in some cases attained full-term development, provided placentae were retained.…”

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

“…Thus there is scope for an influence of the fetuses in utero on mammogenesis during gestation and also for an effect of the suckling young on growthpost partum. The importance of the placenta(e) in mammogenesis has long been recognized (Selye, Collip & Thomson, 1934;Newton & Lits, 1938), and relationships between the number of fetuses carried and mammary growth and/or milk yield have been demonstrated in a number of polytocous species (goat: Hayden, Thomas & Forsyth, 1979; sheep: Rattray, Garrett, East & Hinman, 1974; guinea-pig: Davis, Mepham & Lock, 1979). The DNA content of lactating mammary glands of rats is also directly related to the number of young suckled (Tucker, 1966).…”