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You searched for +publisher:"Virginia Tech" +contributor:("McFadden, T. B."). Showing records 1 – 2 of 2 total matches.

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Virginia Tech

1. Ellis, Steven E. Mechanisms Controlling Ductal Morphogenesis in the Ruminant Mammary Gland.

Degree: PhD, Dairy Science, 1998, Virginia Tech

Basic research into the histology, endocrine control, and local regulation of prepuberal ruminant mammogenesis was conducted to provide a better understanding of this important developmental period. Histologic features of prepuberal ruminant mammary parenchymal morphogenesis were examined in tissue samples taken from ewe lambs at 2 (n = 5), 3 (n = 15), 6 (n = 26), 9 (n = 7), 12 (n = 5), and 13 wk (n = 20), and from Holstein heifers at 4 (n = 1) and 6 mo (n = 2). Examination of approximately 8000 histologic sections revealed that mammary parenchymal morphogenesis in sheep and cattle occurs through the proliferation of highly arborescent ductal structures embedded in a dense stroma. These observations contrast strongly with models of mammogenesis based on murine mammary development. The formation of luminal spaces and the expansion of ducts also differed from murine mammogenesis models. Luminal spaces were shown to develop through a progressive separation of opposing sides in initially solid ductal structures. Likewise, our investigation of prepubertal ovine mammogenesis revealed that parenchymal weight, 3H-thymidine labeling, stromal weight, and parenchymal DNA were all unaffected by ovariectomy (P > 0.05), in marked contrast to the dramatic reduction in mammary development following ovariectomy in rats, mice, and heifers. Responsiveness to exogenous estrogen (0.1 mg/kg) was demonstrated by increased 3H-thymidine labeling (P < 0.05) in both intact and ovariectomized lambs. Three dimensional collagen gel cultures of bovine mammary organoids from the peripheral (OUTER) and medial (INNER) parenchymal zones were used to characterize the proliferative and morphogenetic responses to local-acting growth factors. The proliferation of OUTER cells was 2 to 3 times greater than INNER cells (P < 0.0001) in response to IGF-I stimulation. Dramatic differences in the morphology of INNER and OUTER organoids were also observed. INNER cells grew into smooth-edged colonies when treated with heifer serum but stellate colonies when treated with other mitogens. OUTER cells grew into stellate colonies regardless of mitogen treatment. These investigations highlight the fact that a great deal more research into the basic physiology of prepuberal ruminant mammogenesis is required and that dogma developed in murine model systems may not be applicable to ruminant mammary physiology. Advisors/Committee Members: Akers, Robert Michael (committeechair), Caceci, Thomas (committee member), Lewis, Gregory S. (committee member), Gwazdauskas, Francis C. (committee member), McFadden, T. B. (committee member), Vinson, William E. (committee member).

Subjects/Keywords: Prepuberal Mammogenesis; Ovariectomy; Collagen Gel Cultures

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APA (6th Edition):

Ellis, S. E. (1998). Mechanisms Controlling Ductal Morphogenesis in the Ruminant Mammary Gland. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30728

Chicago Manual of Style (16th Edition):

Ellis, Steven E. “Mechanisms Controlling Ductal Morphogenesis in the Ruminant Mammary Gland.” 1998. Doctoral Dissertation, Virginia Tech. Accessed April 10, 2021. http://hdl.handle.net/10919/30728.

MLA Handbook (7th Edition):

Ellis, Steven E. “Mechanisms Controlling Ductal Morphogenesis in the Ruminant Mammary Gland.” 1998. Web. 10 Apr 2021.

Vancouver:

Ellis SE. Mechanisms Controlling Ductal Morphogenesis in the Ruminant Mammary Gland. [Internet] [Doctoral dissertation]. Virginia Tech; 1998. [cited 2021 Apr 10]. Available from: http://hdl.handle.net/10919/30728.

Council of Science Editors:

Ellis SE. Mechanisms Controlling Ductal Morphogenesis in the Ruminant Mammary Gland. [Doctoral Dissertation]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/30728


Virginia Tech

2. Berry, Sarah Dianne Knowles. Growth Factor and Extracellular Matrix Regulation of Heifer Mammary Development.

Degree: PhD, Dairy Science, 2002, Virginia Tech

The overall objective of this project was to investigate the role of locally derived growth factors and extracellular matrix proteins in regulating prepubertal heifer mammary development. In the first experiment, short-term treatment of heifers with GH or E increased proliferation of mammary epithelial cells. Coinciding with increased epithelial cell proliferation, IGF-I protein increased and IGFBP-3 protein decreased within mammary tissues. Thus, proliferation was associated with an apparent net increase in the biological availability of IGF-I within the mammary gland. In the second experiment, decreased mammary development and epithelial cell proliferation in response to ovariectomy coincided with decreased mammary expression of IGF-I mRNA and decreased binding of IGF-I to mammary microsomes. Taken together, these results imply an important role for locally derived IGF-I in regulating heifer mammary development. However, in contrast to our hypothesis, IGF-I mRNA did not differ between cleared or intact mammary fat pad, suggesting that expression of IGF-I mRNA is not regulated by epithelial:stromal interactions. Neither ovariectomy or epithelial:stromal interactions influenced the mRNA expression of IGFBP-3 or IGFBP-5 within mammary tissues. Ovariectomy increased the proportion of ERa positive mammary epithelial cells. In contrast, GH administration to prepubertal heifers did not influence the proportion of ERa-positive epithelial cells. Interestingly, mammary development was more severely affected in heifers ovariectomized before six weeks of age than heifers ovariectomized at three months of age, implying a critical period of ovarian stimulation during the first six weeks of age. Localization of laminin, fibronectin, and collagen in mammary parenchyma suggested specific roles for extracellular matrix proteins in regulating mammary development and ductal morphogenesis. Laminin was decreased and fibronectin was increased by ovariectomy, suggesting a possible role for interactions between the ovary and extracellular matrix proteins within the heifer mammary gland. Finally, the mitogenic capacities of mammary tissue extracts from control and ovariectomized heifers did not differ in their ability to stimulate in vitro proliferation of MAC-T cells. In conclusion, the overall results support the hypothesis that locally derived IGF-I regulates prepubertal heifer mammary development. However, ERa expression and extracellular matrix proteins also appear to be important regulators of heifer mammary development. Advisors/Committee Members: Akers, Robert Michael (committeechair), McFadden, T. B. (committee member), Wong, Eric A. (committee member), Pearson, Ronald E. (committee member), Howard, Rick Dale (committee member).

Subjects/Keywords: IGF-I; extracellular matrix; growth hormone; heifer; estrogen; mammary

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Berry, S. D. K. (2002). Growth Factor and Extracellular Matrix Regulation of Heifer Mammary Development. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28541

Chicago Manual of Style (16th Edition):

Berry, Sarah Dianne Knowles. “Growth Factor and Extracellular Matrix Regulation of Heifer Mammary Development.” 2002. Doctoral Dissertation, Virginia Tech. Accessed April 10, 2021. http://hdl.handle.net/10919/28541.

MLA Handbook (7th Edition):

Berry, Sarah Dianne Knowles. “Growth Factor and Extracellular Matrix Regulation of Heifer Mammary Development.” 2002. Web. 10 Apr 2021.

Vancouver:

Berry SDK. Growth Factor and Extracellular Matrix Regulation of Heifer Mammary Development. [Internet] [Doctoral dissertation]. Virginia Tech; 2002. [cited 2021 Apr 10]. Available from: http://hdl.handle.net/10919/28541.

Council of Science Editors:

Berry SDK. Growth Factor and Extracellular Matrix Regulation of Heifer Mammary Development. [Doctoral Dissertation]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/28541

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