Chapter

Physiology of Testicular Function

DOI: 10.1007/978-3-540-78355-8_2 In book: Andrology, pp.11-59

ABSTRACT

The testes produce the male gametes and the male sexual hormones (androgens). The term spermatogenesis describes and includes all the processes involved in the production of gametes, whereas steroidogenesis refers to the enzymatic reactions leading to the production of male steroid hormones. Spermatogenesis and steroido-genesis
take place in two compartments morphologically and functionally distinguishable from each other. These are the tubular compartment,
consisting of the seminiferous tubules (tubuli seminiferi) and the interstitial compartment (interstitium) between the seminiferous tubules (Figs. 2.1 and 2.2). Although anatomically separate, both compartments are closely connected
with each other. For quantitatively and qualitatively normal production of sperm the integrity of both compartments is necessary.
The function of the testis and thereby also the function of its compartments are governed by the hypothalamus and the pituitary
gland (endocrine regulation). These endocrine effects are mediated and modulated at the testicular level by local control mechanisms (paracrine and autocrine factors).

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    • "For human, originally 12 spermatid maturation steps were described. These steps include nucleus condensation, the formation of a flagellum and the extrusion of a large part of cytoplasm [3]. The differentiation into the extremely specialized sperm cells is one of the most significant cell developmental processes that occur in biological systems. "
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    ABSTRACT: Diabetes mellitus (DM) represents one of the most prevalent chronic diseases nowadays. It comprehends a group of metabolic disorders characterized by chronic hyperglycaemia resulting from defects in insulin secretion, insulin action, or both. Type 1 DM is a chronic autoimmune disease that results from the pathogenic action of T lymphocytes on pancreatic beta cells leading to impaired insulin production. On the other hand, the cause for type 2 DM (T2DM) is a combination between insulin resistance and insufficient insulin secretion. The complexity of DM led to the establishment of a transitional condition, known as pre-diabetes. This intermediate state is a reversible condition in which the progression to T2DM can be prevented or, at least delayed by drug-based and lifestyle interventions. It is well known that the metabolic cooperation established between testicular cells, particularly concerning glucose metabolism, is crucial for the occurrence of a normal spermatogenesis and consequently, for male fertility potential. Therefore, it is crucial to unveil these mechanisms in diabetic individuals and how they are affected by the disease and alter the fertility of the males. In the recent years, several studies have provided new information concerning pre-diabetes and DM-induced alterations in male reproductive health. Moreover, it was highlighted that testicular cells have several mechanisms that react to hormonal fluctuations and to counteract hyper- and hypoglycemic events. In this chapter, we will discuss the effects of pre-diabetes and DM in the regulation of testicular glucose metabolism and its implication in male reproductive health.
    Full-text · Chapter · Nov 2015
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    • "Type B spermatogonia then give rise to spermatocytes that progress into meiosis to form haploid round spermatids, which transcribe high levels of messenger ribonucleic acids (mRNAs) that are not translated until spermiogenesis (O'Donnell et al., 2006). During spermiogenesis, mature round spermatids transform into spermatozoa, which, in mammals, sequentially includes formation of the acrosome from the Golgi apparatus, elongation of the spermatids, and condensation of the nucleus, which becomes transcriptionally arrested as histones are replaced by protamines (Weinbauer et al., 2010). Elongation of the spermatids continues until the flagellum is fully formed, which is concomitant with extrusion of most of the cell cytoplasm, the so-called residual body, which is phagocytosed by the Sertoli cell (Weinbauer et al., 2010). "
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    ABSTRACT: Fluid homeostasis is recognized as a critical factor during the development, maturation, and function of vertebrate male germ cells. These processes have been associated with the presence of multiple members of the aquaporin superfamily of water and solute channels in different cell types along the reproductive tract as well as in spermatozoa. We present a comparative analysis of the existing knowledge of aquaporin biology in the male reproductive tissues of mammals and teleosts. Current data suggest that in both vertebrate groups, aquaporins may have similar functions during differentiation of spermatozoa in the germinal epithelium, in the concentration and maturation of sperm in the testicular ducts, and in the regulation of osmotically induced volume changes in ejaculated spermatozoa. Recent studies have also provided insight into the possible function of aquaporins beyond water transport, such as in signaling pathways during spermatogenesis or the sensing of cell swelling and mitochondrial peroxide transport in activated sperm. However, an understanding of the specific physiological functions of the various aquaporins during germ cell development and sperm motility, as well as the molecular mechanisms involved, remains elusive. Novel experimental approaches need to be developed to elucidate these processes and to dissect the regulatory intracellular pathways implicated, which will greatly help to uncover the molecular basis of sperm physiology and male fertility in vertebrates. © 2015 Marine Biological Laboratory.
    Full-text · Article · Aug 2015 · Biological Bulletin
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