Remodeling of mammary tissue and lactation persistency

本研究计划的长期目标是提高我们对控制乳腺退化所涉及的生物学过程的认识，并开发经济上可行且消费者可接受的技术或实践，以改善泌乳持续性并延长奶牛的泌乳时间。延长泌乳期将减少奶牛一生中处于泌乳早期的比例，从而减少与这一时期有关的疾病、代谢紊乱和繁殖失败的发生。虽然很少有人知道的生物控制persistivia，因素，如挤奶频率，完全的牛奶去除，奇偶性，光周期，营养摄入量和gestation. Recent工作进行了在我的实验室，已经证明，催乳素（PRL），相反，是galactoietic在奶牛反刍动物。如果PRL的基础水平与产奶量水平没有明显相关性，则挤奶诱导的PRL释放与产奶量水平相关。据报道，PRL在啮齿动物乳腺中具有抗细胞凋亡作用，因此，我们在PRL分泌受到抑制的奶牛腺体中发现了更多的细胞凋亡。因此，催乳素，尤其是泌乳诱导的催乳素，可能通过限制细胞损失和维持细胞分化而成为泌乳持续的重要因素。然而，我们还发现，催乳素的催乳作用是调制在乳腺水平的一种机制，仍有待阐明。** 我的假设是：*-挤奶诱导的激素释放对维持乳腺上皮细胞的分化、分泌活性和存活是重要的。*-有几个因素通过调节挤奶时释放的激素量和/或乳腺对激素的反应性来影响产奶量和持续泌乳。**我的短期目标是：*1-确定控制泌乳诱导的PRL释放量的因素 *2-确定局部因素影响泌乳持续性的机制。3-确定全身因素影响泌乳持续性的机制

The long range objectives of this research program are to improve our knowledge of the biological process involved in the control of mammary gland involution and to develop economically viable and consumer acceptable technologies or practices that would improve lactation persistency and enable longer lactation in dairy cows. Extended lactation would reduce the proportion of cow's lifetime spent in early lactation and, thus, the occurrence of disease, metabolic disorder and reproduction failure associated with this period.***Although little is known about the biological control of persistency, factors such as milking frequency, completeness of milk removal, parity, photoperiod, nutrient intake and gestation have been shown to affect it. Recent work carried out in my laboratory, have demonstrated that the hormone prolactin (PRL), contrary to what was believed, is galactopoietic in dairy ruminants. If basal level of PRL was not clearly associated with level of milk production, the milking-induced PRL release was correlated to level of milk production Anti-apoptotic effects of PRL have been reported in the mammary gland of rodents and, accordingly, we found more apoptosis in the glands of cows where PRL secretion was inhibited. Therefore, it is possible that PRL, especially the milking-induced PRL, is an important factor for lactation persistency by limiting the loss of cells and maintaining cell differentiation. However, we also found that the galactopoietic action of PRL is modulated at the level of the mammary gland by a mechanism that remains to be elucidated. ******My hypotheses are:***-The milking-induced release of hormone is important to maintain the differentiation, the secretory activity and the survival of the mammary epithelial cells.***- Several factors affect milk production and lactation persistency by modulating the amount of hormones release at milking and/or mammary gland responsiveness to them.******My short range objectives are:***1- To determine the factors controling the magnitude of milking-induced release of PRL***2- To determine the mechanisms by which local factors affect lactation persistency.***3- To determine the mechanism(s) by which systemic factors affect lactation persistency