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Thesis (M.S.)—University of Nebraska—Lincoln, 1970. Department of Zoology.


Copyright 1970, the author. Used by permission.


DNA synthesis and growth profile were determined in MTV-free hormone-induced D1 hyperplastic alveolar mammary gland nodule of BALB/c mouse at weekly intervals following fat-pad transplantation. Methods used were autoradiography, liquid scintillation counting, and histology. The number of alveolar cells entering DNA synthesis determined by autoradiography in hormone-induced D1 outgrowths reached a peak two weeks after transplantation and this is followed by a plateau and finally a decline. Also, during the second week, alveolar cells are synthesizing DNA at a faster rate, as evidenced by an increase in the average number of silver grains per nucleus in D1 HAN. DNA synthesis (measured by radiochemical method) of the fat-pad containing the outgrowth reached a peak during the fourth week and this was followed by a plateau and finally a decline. The outgrowth does not grow exponentially, and there are periods of rapid proliferation followed by periods of less active growth. It has been suggested that there may be a relationship between rate of DNA synthesis in D1 HAN after transplantation and optimal time of application of the carcinogen 3-methylcholanthrene leading to tumor induction.

The effect of ovariectomy on two outgrowth lines of MTV-free, hormone induced D2 and D7 hyperplastic alveolar nodules (HAN) of BALB/c mouse mammary gland was determined by 3H-thymidine autoradiography. DNA synthesis in the cells of normal mammary glands collected from virgin hosts decreased significantly after bilateral ovariectomy. Frequency of alveolar cells labeled with 3H-TdR in the low tumor-producing D7 series dropped significantly following the ovaries in a manner similar to that of normal mammary tissue. DNA synthesis in the high tumor-producing D2 series continued in the absence of the ovaries as evidenced by the high values for frequency of 3H-TdR labeled nuclei five days following the operation. It is suggested that alveolar cells of the D2 outgrowth line have an altered response to host hormonal control on DNA synthesis. A possible relationship between tumor-producing capabilities and alterations in host hormonal control on DNA synthesis in BALB/c HAN tissues has been discussed.

Advisor: Mihir R. Banerjee