Abstract
Summary And Conclusions
(1) The muscles of the uterus of the ovariectomized mouse and rat undergo hyperplasia in response to ovarian follicular hormone (theelin) and a similar response is obtained in normal animals injected with prephysin and pregnant mares' serum. (2) The mitotic index, accentuated by arrest of mitosis in metaphase with colchicine, makes this new evidence especially convincing. (3) The highest index is obtained after 2 or more days of hormone action when the uterus is distended by secretion, as occurs at estrus in the mouse and rat. (4) The uterus of the ovariectomized rabbit, distended with paraffin pellets, but not treated with sex hormones, also shows hyperplasia at the sites of distention. As many as 50 mitoses may be counted in the muscle in one cross section of the uterus after 73 hours of distention. The endometrium in the same section contains few mitoses, is infiltrated with leucocytes and shows other signs of castrate atrophy. (5) Apparently both (a) endocrine stimulation and (b) distention are factors in hyperplasia of uterine muscles. The second factor alone induces hyperplasia in muscle tissue in the ovariectomized rabbit.
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