title: Paracrine factors and the regulation of spermatogenesis.
abstract: OBJECTIVE
  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 of 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.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Scott Department of Urology, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: C S
authors.initials: CS
authors.lastname: Niederberger
authors.forename: S
authors.initials: S
authors.lastname: Shubhada
authors.forename: S J
authors.initials: SJ
authors.lastname: Kim
authors.forename: D J
authors.initials: DJ
authors.lastname: Lamb
mesh_terms: D000818:Animals; D004815:Epidermal Growth Factor / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000502:physiology; D007335:Insulin-Like Growth Factor II / Q000502:physiology; D008297:Male; D009414:Nerve Growth Factors / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019009:Proto-Oncogene Proteins c-kit; D012708:Sertoli Cells / Q000378:metabolism; D013091:Spermatogenesis / Q000502:physiology*; D016211:Transforming Growth Factor alpha / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology
chemical_list: D009414:Nerve Growth Factors; D011518:Proto-Oncogene Proteins; D016211:Transforming Growth Factor alpha; D016212:Transforming Growth Factor beta; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D019009:Proto-Oncogene Proteins c-kit