Testes, spermatogenesis

Ovary follicle development, ovulation, estrogen synthesis testis spermatogenesis... 

Figure 4 Triantennary iV-glycans involved in germ cell and Sertoli cell interaction in the mouse testis. Spermatogenesis takes place in the tubal structure called seminiferous tube in the testis. Inside of seminiferous tube is lined by Sertoli cells, the tail epithelial cells. When germ stem cells at the base of Sertoli cells differentiate to spermatocytes, the cells move upward interacting with Sertoli cells. The MX gene knockout mouse revealed that fucosylated GlcNAc-terminated triantennary A-glycan (insert) plays an important role in germ cell adhesion to Sertoli cells (59).

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, ... 

ATANASSOVA N, MCKINNELL C, TURNER K J, WALKER M, FISHER J S, MORLEY M, MILLAR M R, GROOME N p, SHARPE R M (2000) Comparative effects of neonatal exposure of male rats to potent and weak (environmental) estrogens on spermatogenesis at puberty and the relationship to adult testis size and fertility evidence for stimulatory effects of low estrogen lew eh,. Endocrinology. 141 3898-907. 

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. 

The testes are suspended outside the abdomen, in the scrotum, which is divided into two sacs, one for each testis. This location outside the abdominal cavity helps to maintain the testes at a temperature below normal (about 6°C lower) which is essential for satisfactory spermatogenesis. Indeed, the arterial and venous supply is so organised that it provides a heat exchange mechanism in which the arterial blood is cooled and the venous blood is warmed. The... 

During embryonic development, the cells destined to become spermatozoa, i.e. the germ cells, divide to form spermatogonia, of which there are many thousands in each testis. Spermatogonia are, in fact, stem cells. Spermatogenesis begins at puberty and continues throughout life. It is divided, arbitrarily, into three parts ... 

Figure 19.11 Hormones secreted by the hypothalamus, anterior pituitary, ovary and testis and feedback regulation. GnRH is gonadotrophin-releasing hormone the gonadotrophins are follicle-stimulating hormone (FSH) and luteinising hormone (LH). The effect of these hormones on activities in the ovary and testes is shown. FSH stimulates synthesis and secretion of oestradiol from follicle, and spermatogenesis in testis. LH stimulates synthesis and secretion of progesterone from corpus luteum and synthesis and secretion of testosterone by the Leydig cells.

Kim, Y.-J., Hwang, I., Tres, L.L., Kierszenbaum, A.L., and Chae, C.-B. (1987) Molecular cloning and differential expression of somatic and testis-specific H2A histone genes during rat spermatogenesis. Dev. Biol. 124, 23-34. 

M (testicular atrophy decreased spermatogenesi s reduced testi cular wei ght)... 

Deficiency symptoms Bitot s spots, xerosis, night blindness, keratomalacia, diarrhoea, follicular hyperkeratosis, papular eruptions, drying of epidermis, urinary calculi, degeneration of testis, impaired spermatogenesis, sterility, abortion, impairment of smell and taste. 

Adult male albino rats received 0, 500 or 1000 mg/kg di(2-ethylhexyl) phthalate by gavage for 15 days and were killed 24 h later (Siddiqui Srivastava, 1992). Relative testis weight and epididymal sperm counts were reduced at the highest dose, as was the activity of several enzymes relevant to spermatogenesis (aldose reductase and sorbitol dehydrogenase). The activity of testicular lactate dehydrogenase was increased at this dose. 

FSH plays a key role in spermatogenesis it binds G-protein-coupled membrane-bound receptors on Sertoli cells and induces the Sertoli cells to proliferate during pre- and postnatal development. FSH also induces Sertoli cells to produce androgen binding protein (ABP), TGF-beta 1, MIS and other important signalling compounds. Sertoli cells also play an important role in spermiation and are the source of the seminiferous tubule fluid that provides nutrients to sperm cells as they travel from the testis to the epididymis. 

A dramatic increase (approx. 50-fold) of the activity of the sulfotransferase involved in the biosynthesis of the SGG also occurred when spermatocytes first began to appear in rat testis (19) the rise in the activity of this enzyme preceded by several days a marked rise in the amount of the SGG. Studies on pre-puber-tal human testis (which is temporarily blocked in spermatogenesis at a stage prior to the appearance of primary spermatocytes) have shown that neither SGG nor GG is present (15,26). Similarly, the testis of the pre-pubertal fowl also lacks sulfogalactosylceramide, the sulfatide found in mature fowl testis (26). All of these find-... 

Sarge, K.D., Park-Sarge, O.Y., Kirby, J.D., Mayo, K.E. and Morimoto, R.I. (1994) Regulated expression of heat shock factor 2 in mouse testis potential role as a regulator of HSP gene expression during spermatogenesis. Biol. Reproduct., 50, 1334-1343. 

Cyproterone inhibits the action of androgens and gossypol prevents spermatogenesis without altering the other endocrine functions of the testis (Figure 61.9). 

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