ISSN:
1433-8726
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Main problem: Although the gonadotropins and testosterone are required for normal spermatogenesis, it is believed that local control factors regulate spermatogenesis. For many years these regulatory factors had not been identified. Over the past five years, a number of growth factors have been identified in testis or isolated testicular cell types or secretions. Growth factors are key regulatory molecules which affect cell proliferation, meiosis, and differentiated function. These factors usually act in an autocrine (acting upon the cell which secreted it) or paracine (affecting another cell) manner and thus are involved in intercellular communications. Methods: Growth factor secretion by testicular cell types or testis tissue has been analyzed using a variety of assays measuring cell proliferation in vitro, as well as assays using immunocytochemicals. Growth factor gene expression in testis has been analyzed by Northern blot analysis and in situ hybridization, which gives information concerning the stage and cell specific expression of the gene. Inbred strains of mice with mutations or deletions in a growth factor gene has been used to suggest the function of two specific factors in testicular development and growth. Results: Among the growth factors expressed or secreted by testicular cell types, most are common to some other cell types in the body, such as transforming growth factors alpha and beta, epidermal growth factor, fibroblast-like growth factors, insulin-like growth factors, interleukins, endorphins, inhibin and activin, while others may be more testis specific such as mullerian inhibiting substance (anti-mullerian hormone) and Sertoli cell secreted growth factor. A variety of proto-oncogenes are expressed at discrete stages of spermatogenesis, as well as by the somatic cells of the testis. Many of these encode growth factors, receptors or other proteins involved in signal transduction. Conclusion: With the exception of the kit ligand and the c-kit proto-oncogene, which have been demonstrated to play a role in the survival of the primordial germ cell in the testis during embryogenesis, little is known of the direct role of the other growth factors in spermatogenesis. It is likely that in the near future that the function of many of these proteins in the regulation of spermatogenesis will be identified. Eventually, this information will be used to develop specific therapies and diagnostic procedures for the infertile male.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00182039
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