Remodeling of mammary tissue and lactation persistency / Remodelage de la glande mammaire et persistance de la lactation

这项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过程的了解，并开发经济上可行且消费者可以接受的技术或实践，以改善奶牛的哺乳持久性，并使奶牛能够更长时间地哺乳。延长哺乳时间会减少奶牛在哺乳早期的生命比例，从而减少与这一时期相关的疾病、代谢紊乱和繁殖失败的发生。细胞凋亡发生在哺乳期晚期，是哺乳期下降时分泌细胞逐渐丧失的原因。因此，有相当大的动机来确定调控乳腺细胞凋亡的因素。 最近在我的实验室进行的工作表明，催乳素(PRL)是乳用反刍动物的乳汁生成激素，也是乳房细胞的生存因素。因此，PRL，特别是挤奶诱导的PRL，可能通过限制细胞丢失和维持细胞分化而成为持续哺乳的重要因素。我们还发现，催乳素的生乳作用是在乳腺水平上调节的。 我的假设是：-有可能通过降低乳腺细胞死亡率来减少产奶量下降的速度；挤奶诱导的催乳素释放对乳腺细胞的分化和生存非常重要；几个因素通过改变腺体对催乳素的敏感性来影响产奶量和哺乳持久性。 短期目标是：1-确定控制挤奶诱导的催乳素释放的因素。2-确定乳腺对催乳素的敏感性是如何调节的。3-确定影响产奶量的因素是否也影响PRL分泌和/或敏感性。4-确定干燥期对乳腺的影响。

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. Apoptosis occurs in late lactation and accounts for the progressive loss of secretory cells in declining lactation. Therefore, there are considerable incentives to identify the factors which regulate mammary apoptosis. Recent work carried out in my laboratory, have shown that the hormone prolactin (PRL) is galactopoietic in dairy ruminants and a survival factor for mammary cells. 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. We also found that the galactopoietic action of PRL is modulated at the level of the mammary gland. My hypotheses are: -It is possible to reduce the rate of decline in milk production by reducing the rate of mammary cell death; the milking-induce PRL release is important for the differentiation and the survival of the mammary cells and; several factors affect milk production and lactation persistency by modifying gland sensitivity to PRL. The short range objectives are: 1- To determine the factors controlling the milking-induced release of PRL. 2- To determine how sensitivity of the mammary gland to PRL is modulated. 3- To determine if factors that affects milk production affects also PRL secretion and/or sensitivity. 4- To determine the effect of the dry period on the mammary gland.