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Search for other papers by RUBY R. ICHINOSE in
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SUMMARY
(1) To induce mammary differentiation in vitro, BALB/cCrgl mice were given hormones before incubation of their mammary glands in defined medium containing steroid hormones (oestradiol, progesterone and aldosterone), anterior pituitary hormones (prolactin and growth hormone), and insulin. The sequence of lobule development in vitro obtained in this way was determined by cultivation of tissues for 1, 2, 3, 4 and 5 days. Lobules appeared on the 3rd day of culture, although proliferation occurred throughout the 5-day period.
(2) In two other sets of experiments, mammary glands were exposed to various combinations of hormones in culture. Survival of cultured tissues required the presence of insulin, whereas differentiation required the presence of steroid hormones, anterior pituitary hormones, and insulin. Of the steroid hormones used, aldosterone alone fulfilled the minimum steroid hormone requirement for lobule formation in vitro.
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SUMMARY
1. Autoradiographs were made from thin thyroid sections of rats injected intraperitoneally with 20μc. 131I and killed at periods varying from 15 min to 16 days.
2. The concentrations of 131I in the thyroid sections were first deduced from G.M. counter measurements and then correlated with the average grain densities of their autoradiographs. From the observed grain densities in the colloid and cellular spaces of the thyroid follicles, the differential concentration of 131I in these sites was determined.
3. Each mm3 of thyroid tissue was found to fix about 0·1μc. in 15 min, 0·25μc. in 3 hr and 0·8μc. in 24 hr, out of the injected dose of 20μc. of 131I. The biological half-life of 131I in the thyroid was found to be 5·4 days.
4. From the knowledge of the total and differential concentrations of 131I, the partial volume of the colloid was calculated to be 66% of the whole thyroid volume, the rest being occupied by the cellular spaces. The latter was found to retain about half of the total 131I of the thyroid up to 15 min after the injection. But after 3 hr most of the 131I appeared in the colloid.
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Search for other papers by S Nandi in
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The proliferation of normal human breast epithelial cells in women is highest during the first trimester of pregnancy. In an attempt to analyze this hormonal environment in a model system, the effect of host mouse pregnancy and the administration of human chorionic gonadotropin (hCG) were assessed in normal human breast epithelial cells transplanted into athymic nude mice. Human breast epithelial cells, dissociated from reduction mammoplasty specimens and embedded inside the extracellular matrices comprised of collagen gel and Matrigel, were transplanted into nude mice. Proliferation was measured in vivo by BrdU labeling followed by immunostaining of sections from recovered gels in response to an altered hormonal environment of the host animal. The host animal was mated to undergo pregnancy and the complex hormonal environment of the host animal pregnancy stimulated growth of transplanted human cells. This effect increased with progression of pregnancy and reached the maximum during late pregnancy prior to parturition. In order to determine whether additional stimulation could be achieved, the transplanted human cells were exposed to a second cycle of host mouse pregnancy by immediately mating the animal after parturition. This additional exposure of host mouse pregnancy did not result in further increase of proliferation. The effect of hCG administration on transplanted human cells was also tested, since hCG level is highest during the first trimester of human pregnancy and coincides with the maximal breast cell proliferation. Administration of hCG alone stimulated proliferation of human cells in a dose-dependent manner, and could further enhance stimulation achieved with estrogen. The host mouse mammary gland also responded to hCG treatment resulting in increased branching and lobulo-alveolar development. However, the hCG effect on both human and mouse cells was dependent on intact ovary since the stimulation did not occur in ovariectomized animals. Although hCG receptor transcripts were detected in human breast epithelial cells, raising the possibility of a direct mitogenic action, the hCG effect observed in this study may have been mediated via the ovary by increased secretion of ovarian steroids. In summary, using our in vivo nude mice system, the proliferation of normal human breast epithelial cells could be stimulated by host mouse pregnancy and by administration of hCG.
