Initiation and Maintenance of Spermatogonial Mitotic Divisions

精子发生是产生精子的生殖过程， 它们是能够产卵的独特细胞， 开始一个新的生命。 在动物中， 精子发生是通过一些渐进的变化， 男性生殖细胞的形状和行为。 这些变化包括 两种细胞分裂 首先是一个简单的过程 产生大量的干细胞，称为精原细胞。 的 第二种是一种独特的分裂，称为减数分裂，发生在两个 阶段，导致4个精子，每个精子的数量减少 的染色体。 本项目的目标是 发现告诉精原细胞的化学信使（1） 改变它们的行为并开始开始细胞分裂 (2)这表明细胞分裂的时间 继续 因此，这些化学品在以下方面很重要：（1） （2）确定有多少精子产生; 精子产生了。 细胞的形成和维持 精原细胞的分裂过程在所有的 动物系统，包括哺乳动物。 步行者计划利用 北大西洋常见的海星星或海星，在研究中， 精子发生的基本生物学过程，因为每个动物 可以在5个月内产生数万亿的精子， 精子发生过程可以同时研究， 完整的，活的海星或使用培养的细胞， 从这些动物的实验中得出的结论。 没有其他动物 生精系统允许如此近距离地观察 精子发生的重要时期，精原细胞 开始细胞分裂 这项工作的重要性在于， 它应该识别出开始和维持 动物的精子生产。 至今还没有这样的信使 任何动物都可以识别。雌激素，而不是雄激素（如 睾丸激素）提供了导致 精原细胞开始分裂， 精原细胞或相关细胞产生的化学物质， 使精原细胞继续分裂。 两种化学 信使（也许还有其他人）参与了这个过程， 精子生产 PI最终可能会 建议在更多国家采用外部控制精子产生的方法 像哺乳动物这样复杂的动物。

Spermatogenesis is a reproductive process that yields sperm, which are unique cells capable of fertilizing eggs and thus beginning the life of a new individual. In animals, spermatogenesis occurs via a number of progressive changes in the shape and behavior of male sex cells. Among these changes are two kinds of cell division. The first is a simple process producing large numbers of stem cells called spermatogonia. The second is a unique division, called meiosis, which occurs in two stages and which results in 4 sperm, each with a reduced number of chromosomes. The objective of the current project is to discover the chemical messenger (1) that tells spermatogonia to change their behavior and to begin cell division and also the one (2) that indicates the amount of time such cell division should continue. Therefore, these chemicals are important (1) in causing sperm to be produced and (2) in determining how many sperm are produced. The beginning and maintenance of cell division in spermatogonia are poorly understood processes in all animal systems, including mammals. Walker plans to use the Common North Atlantic sea star or starfish in studies of the basic biological process of spermatogenesis because each animal can produce trillions of sperm in a 5 month period and because the spermatogenic process can be studied simultaneously using entire, living sea stars or using cells in culture which are derived from the tests of these animals. No other animal spermatogenic system permits such close observation of spermatogenesis during the important period when spermatogonia are beginning cell division. The importance of this work is that it should identify chemical messengers that begin and maintain sperm production in an animal. No such messengers have as yet been identified for any animal. Estrogens, not androgens (like testosterone) provide the initial signal that causes spermatogonia to begin to divide and that polyamines, which are chemicals produced by spermatogonia or associated cells, then cause spermatogonia to continue to divide. Two chemical messengers (and perhaps others) are involved in the process of sperm production. The PI may ultimately be in a position to suggest means for external control of sperm production in more sophisticated animals like mammals.