Androgens in the demography of male life course--a review.

While the basics of testosterone production, effects and metabolism have been known for decades, there has been a flow of novel insights in the genomics of testosterone action on a molecular and cellular level, as well as in the clinical effects from modern clinical trials, improving the understanding of the role of testosterone in male life course. Androgens are produced under the control of an endocrine cascade from GnRH via gonadotropins to the testicular Leydig cells. In some organs, testosterone is reduced to 5alpha-dihydrotestosterone prior to the receptor binding by the 5alpha reductase. The androgen receptor gene is located on the X chromosome in the q11-12 region, each mutation in the gene will induce phenotypic manisfestations. In the first stage of the male life course, testosterone moderates the male embryonic development under the control of a complex molecular genetic network. The next important phase of male maturation is the puberty, in which testosterone levels increase and induce the development of somatic and psychological characteristics of male sexuality. In the adult male, testosterone maintains sexual functions and fertility. In aging men, testosterone levels decrease slowly. Testosterone supplementation in the aging male is able to restore the function of androgen target organs only in part.

Mesenchyme of embryonic reproductive ducts directs process outgrowth of Retzius neurons in the medicinal leech.

In the two segments of the medicinal leech (Hirudo medicinalis) that contain the male (segment 5) and the female (segment 6) reproductive ducts, the paired Retzius (Rz) neurons are distinguished by several unique properties. For example, the muscles and glands of the body wall are the primary peripheral targets of Rz neurons in standard segments [Rz(X)], whereas the muscles and glands of the reproductive ducts are the primary peripheral targets of Rz neurons in the two reproductive segments [Rz(5,6)]. In this paper, we show that organogenesis and differentiation, which generate an epithelial tube surrounded by mesenchymal cells, occur in the embryonic reproductive ducts at approximately the time when Rz processes first contact these structures. The growth cones leading one branch of the posterior axon of Rz(5,6) contact the duct mesenchymal cells. Following initiation of this contact, these posterior growth cones enlarge and send out numerous filopodia. Secondarily, growth cones leading the anterior axon of each Rz(5,6) also modify their shapes and trajectories. When embryonic reproductive ducts were transplanted into posterior (nonreproductive) segments, the branch of the posterior Rz axon near the ectopic reproductive tissue produced enlarged growth cones and extended several secondary branches into the mesenchyme of the ectopic tissue. This result suggests that the reproductive mesenchyme is attractive to, and can modify the growth of, all Rz neurons. The behavior of Rz(5,6) growth cones suggests that the reproductive mesenchyme cells provide guidance cues that control the location in which Rz axons elaborate their peripheral arborization and form synapses, and that the mesenchyme may also stimulate the production of a densely branched arbor.

Arachidonic acid and male genital differentiation.

Arachidonic acid (AA) prevents neural tube/defects, cleft palate, and micrognathia in the rat models of diabetic embryopathy and neural tube defects in the mouse embryo culture model. In this study, the involvement of AA in the male genital differentiation was described. These observations raise the complementary possibility that the AA-prostaglandin biochemical pathway may be a major mechanism mediating many embryonic events that involve cellular movement and fusion.

Differentiation and development of the male.

Male differentiation and development takes place against a tendency towards neutral or feminine differentiation. At each step of development male differentiation results from a suspension of a basic female development and the imposition of male features for which a normal functioning testis is necessary. Once the testis has differentiated early in gestation the establishment and maintenance of normal testicular function will condition male sexual differentiation and maturation. Nature likes to express herself in a rhythmic fashion (circhoral, ultradian, circadian, menstrual, long-term rhythms). To epitomise testicular function throughout development we would propose the term 'ontogenic rhythms' to describe the three periods of maximal testicular activity, fetal, neonatal and adult. This results in the differentiation which eventually determines adult sexual activity.