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. / Ph. D.

Orientador: Eunice Oba / Resumo: O objetivo do presente trabalho foi delinear parâmetros hemodinâmicos e avaliar sua relação com os principais hormônios envolvidos na mamogênese de búfalas mestiças Murrah em diferentes estágios fisiológicos. Utilizou-se 24 animais separados de acordo com a categoria (n= 6): bezerras, novilhas, gestantes e lactantes, com idades iniciais de zero, 12, 24 e 48 meses, respectivamente, criadas extensivamente. Realizou-se a cada 28 dias, ultrassonografia Doppler, colheita de sangue e pesagem, durante um ano (bezerras e novilhas) e 10 meses (gestantes e lactantes). Foram determinados os índices de resistividade (IR) e pulsatilidade (IP) e o diâmetro interno (DI) das artérias mamárias pela ultrassonografia. Foram mensuradas as concentrações plasmáticas de progesterona (P4), fator semelhante a insulina tipo I (IGF-I), insulina (IN), hormônio do crescimento (GH) e estradiol (17β-E2). Utilizou-se ANOVA com medidas repetidas, correlação de Spearman e regressão não linear múltipla, considerando nível de significância de 0,05. Nas bezerras e novilhas, houve redução de IR e IP e aumento do DI (P<0,0001) do primeiro ao último mês de avaliação, contudo, não houve diferença estatística para os índices hemodinâmicos entre as artérias mamárias cranial e caudal. Nas bezerras, detectou-se correlação do IR com o IP (r= 0,94; P<0,0001) e com o DI (r= -0,98; P<0,0001) e também, do IP com o DI (r= -0,98; P<0,0001). Nas novilhas o IR também correlacionou-se com o IP (r= 0,99; P<0,000... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to delineate hemodynamic parameters and toevaluate its relationship with key hormones involved in mammogenesis ofcrossbred Murrah buffaloes in different physiological stages. We used 24 animalsdivided according to the category (n= 6): calves, heifers, pregnant and lactatingfemales with early ages of zero, 12, 24 and 48 months, respectively, raisedextensively. Every 28 days, Doppler ultrasound examinations, blood analysis andweighing were held over one year (for calves and heifers) and over 10 months(for pregnant and lactating females). There were determined resistivity index (RI)and pulsatility index (PI) and internal vessel diameter (ID) of the mammaryarteries by ultrasound. Plasma concentrations of progesterone (P4), insulin-likegrowth factor 1 (IGF-I), insulin (IN), growth hormone (GH) and estradiol (17β-E2)were measured. We used repeated measures ANOVA, Spearman correlationand non-linear multiple regression considering 0.05 significance level. In calvesand heifers, a reduction of RI and PI and increased ID (P<0.0001) from first tolast month's assessment, however, there was no statistical difference inhemodynamic indices between the cranial and caudal mammary arteries. Allheifers, RI correlation was detected with PI (r= 0.94; P<0.0001), and ID (r= -0.98;P<0.0001) and also PI with ID (r= -0.98; P<0.0001). In heifers RI also correlatedwith PI (r= 0.99; P<0.0001) and DI (r= -0.95; P<0.0001) and PI with the ID... (Complete abstract click electronic access below) / Doutor