Functions spermatogenesis

It is widely accepted that men with testicular cancer have a higher incidence of abnormalities associated with impaired spermatogenesis, both in the cancerous testis but also in the contralateral testis. Men diagnosed as having testicular cancer often have very poor semen quality, with sperm concentrations of less than 10 million/ml compared to healthy men with > 50 million/ml." It is thought that gonadal function is abnormal even before testicular cancer develops, ... 

Winer, M. A., and Wolgemuth, D. J. (1993). Patterns of expression and potential functions of proto-oncogenes during mammalian spermatogenesis. In The Molecular Biology of the Male Reproductive System (De Kretser, D. M., ed.), pp. 143-179. Academic Press, San Diego. 

Yoshinaga, K., Nishikawa, S., Ogawa, M., Hayashi, S.-I., Kunisada, T Fujimoto, T and Nishikawa, S-I. (1991). Role of c-kit in mouse spermatogenesis identification of spermatogonia as a specific site of c-kit expression and function. Development 113 689-699. 

The major FSH target in the male is the Sertoli cells, found in the walls of the seminiferous tubules of the testis. They function to anchor and nourish the spermatids, which subsequently are transformed into spermatozoa during the process of spermatogenesis. Sertoli cells also produce inhibin (discussed later), which functions as a negative feedback regulator of FSH. The major physiological effect of FSH in the male is thus sperm cell production. 

New guidelines for fertility assessment (traditional Segment I) studies that have shortened the premating dosing schedule (for example, in male rats from 10 weeks to 4 weeks). There has been an increased interest in assessment of spermatogenesis and sperm function. 

The blood-testes barrier separates two parts of the seminiferous tubules, the part in which the spermatozoa are produced from the outer part which provides the blood supply. It has two functions (i) it prevents spermatozoa leaking into the blood or lymph, since proteins on the surface could act as antigens (ii) it maintains the distinct composition of fluid inside the tubules, which is necessary for spermatogenesis. 

Studies over the last 10 years clearly demonstrate the importance of histone variants in modifying nucleosome structure and function. They play specialized roles in diverse chromatin functions including transcriptional regulation, DNA repair, chromosome segregation, spermatogenesis, and histone replacement. 

In addition to leukopenia and manifestations of neurotoxicity (tremor, ataxia), monkeys treated with vincristine had degenerative changes in the liver and kidney. Vindesine at doses in the range of 0.1-0.3 mg/kg weekly produced leukopenia and reduced spermatogenesis in rats but apparently did not alter neural function 42). The acute intravenous LD50 for vindesine in mice is 6.3 mg/kg, and that for the congener in which two vindesine units are linked by a disulfide bridge is 6.9 mg/kg 32). 

Human sexual function and fertility disorders include, e.g., spontaneous abortions, impaired spermatogenesis, menstrual disorders, impotence, and early menopause. 

Functional disturbances in spermatogenesis and morphologic abnormalities of sperm were observed among workers occupationally exposed to 0.28 and 1.94ppm chloroprene. A threefold excess of miscarriages in the wives of these workers also was reported. 

Oral administration of 3 mg uranium/ %/day as uranyl acetate dihydrate to pregnant mice on gestation days 6-15 caused an increase in fetotoxicity (stunted fetuses, external and skeletal malformations, and developmental variations) and maternal toxicity." In reproductive studies, no adverse effects were observed in testicular function or spermatogenesis in male mice treated with up to 80mg/kg/day uranyl acetate dihydrate for 64 days."... 

Chemicals such as l,2-dibromo-3-chloropropane can disrupt spermatogenesis, leading to impaired reproductive function, including sterility. Men and women undergoing cancer chemotherapy with alkylating drugs are at increased risk for sterility. 

Follicle stimulating hormone is responsible for the growth of testes. It promotes spermatogenesis. Along with LH, FSH plays an essential role in maintaining the normal testicular functions such as development of male sex organs e.g. penis, scrotum development of secondary sexual characters e.g. growth of facial. 

It has a potent antiandrogen and mild progestional activity. It can also inhibit gonadotropin secretion in larger dose and also suppresses spermatogenesis and Leydig cell function. It is used in precocious puberty in males, acne, carcinoma prostate and hirsutism and virilization in women. 

Since FSH and LH are involved in spermatogenesis, hypothalamic control of their release by the pituitary is important for testicular function. Both FSH and LH are secreted in a pulsatile fashion from the pituitary. Inhibin produced by Sertoli cells has the most important negative feedback effect on FSH secretion, while testosterone exerts negative feedback effects on secretion of GnRH by the hypothalamus, thus regulating secretion of LH and, to a lesser extent, FSH. 

The purpose of this chapter is to review the methods that are currently in use to evaluate sexual function and fertility. Sexual function and fertility are complex reproductive functions that can be affected by environmental exposures. Reproductive disorders include spontaneous abortions, impaired spermatogenesis, menstrual disorders, impotence, early menopause and others. Any disturbance in the integrity of the reproductive system can affect these functions. 

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