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  • Cell & Developmental Biology  (2)
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  • 1
    ISSN: 0730-2312
    Keywords: tetracycline ; MMTV-LTR ; tTA ; MMTV-tTA ; β-galactosidase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Molecular mechanisms of development and disease can be studied in transgenic animals. Controlling the spatial and temporal expression patterns of transgenes, however, is a prerequisite for the elucidation of gene function in the whole organism. Previously we reportted that mice carrying a tetR/VP16 hybrid gene (tTA), under the control of the hunman cytomegalovirus immediate early 1 (HCMV-IE1) gene promoter, can be used to temporally activate the expression of transgenes under the control of a promoter containing tetop sequences. We now show that the MMTV-LTR can be used to target expression of tTA to the epthelial cells of secretory organs and skin in transgenic mice. Notably, nearly uniform expression of a tetop-lacZ transgene was found in seminal vesicle, salivary gland, and Leydig cells of mice carrying also the MMTV-tTA transgene. More heterogeneous patterns of gene expression were observed in mammary epithelial cells and nasal cells of the epidermis. Different MMTV-tTA lines had conparable tissue expression patterns. Transcriptional activation mediated by tTA was up to several hundred fold and it was abrogated after the administration of tetracycline. The MMTV-tTA mice established in this work will be useful for experiments examining the roles of biological factors at defined developmental stages in the epithelial cells of salivary gland, seminal vesicle, mammary gland, and skin and the Leydig cells of testes in addition, in combination with the CRE/lox recombnation system, these mice will be useful to achieve gene deletions at defined time points in these organs. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 164 (1995), S. 1-8 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Antiprogestins possess a potent antitumor activity in hormone-dependent experimental breast cancer models. Though the underlying mechanism is not clear, induction of functional differentiation seems to be a major event. This study attempts to test directly for antiproliferative and differentiation promoting activities of antiprogestins on the normal mammary gland. To this end, whole organ cultures of mammary glands from estradiol/progesterone-primed virgin mice maintained in a serum-free medium with aldosterone, prolactin, insulin, and hydrocortisone were exposed to the antiprogestin ZK114043. A 4-day treatment of organ cultures led to a strong inhibition of epithelial DNA synthesis. In parallel, ZK114043 caused alveolar cells to acquire a more differentiated phenotype distinguished by secretory active alveoli composed of single cell layers with increased fat droplet accumulation and enhanced expression of the milk proteins b̃-casein and whey acidic protein (WAP). Particularly strong effects were found on the expression of mammary-derived growth inhibitor (MDGI). Both half-maximal inhibition of epithelial DNA synthesis and stimulation of MDGI mRNA expression were found at about 5 ng/ml of ZK114043. Presence in the medium of 5 m̈g/ml hydrocortisone rendered antiglucocorticoid effects of ZK114043 highly unlikely. Furthermore, prevention of action of ZK114043 by the progesterone agonist R5020 and ZK114043 stimulated expression of b̃-casein and MDGI mRNA in cultured glands of 10-week-old unprimed virgin mice suggest a progesterone receptor-mediated mechanism of antiprogestin action. Two other antiprogestins, Mifepristone and Onapristone, likewise stimulated MDGI expression. The data provide direct evidence that antiprogestins act like a differentiation factor in the normal mammary gland. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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