Development Of Male Sexual Characteristics Research Articles

Cell-specific functions of androgen receptor in skeletal muscles.

Androgens play a vital role not only in promoting the development of male sexual characteristics but also in exerting diverse physiological effects, including the regulation of skeletal muscle growth and function. Given that the effects of androgens are mediated through androgen receptor (AR) binding, an understanding of AR functionality is crucial for comprehending the mechanisms of androgen action on skeletal muscles. Drawing from insights gained using conditional knockout mouse models facilitated by Cre/loxP technology, we review the cell-specific functions of AR in skeletal muscles. We focus on three specific cell populations expressing AR within skeletal muscles: skeletal muscle cells, responsible for muscle contraction; satellite cells, which are essential stem cells contributing to the growth and regeneration of skeletal muscles; and mesenchymal progenitors, situated in interstitial areas and playing a crucial role in muscle homeostasis. Furthermore, the indirect effects of androgens on skeletal muscle through extra-muscle tissue are essential, especially for the regulation of skeletal muscle mass. The regulation of genes by AR varies across different cell types and contexts, including homeostasis, regeneration and hypertrophy of skeletal muscles. The varied mechanisms orchestrated by AR collectively influence the physiology of skeletal muscles.

A review of current chemistry, pharmacology, and regulation of endogenous anabolic steroids testosterone, boldenone, and nandrolone in horses.

Anabolic androgenic steroids are synthetic substances related to the male sex hormones (androgens). These agents promote the growth of skeletal muscle (anabolic effects) and the development of male sexual characteristics (androgenic effects). Anabolic steroids have been illegally used for many years as performance-enhancing drugs in human, equine, and canine sports and as growth promoters in livestock reared to provide meat for human consumption. The analytical challenge to developing effective means of control within these fields has been exacerbated by the reported endogenous nature of some of these steroids. Anabolic steroids have been employed extensively in equine practice over the past 50 years. Their usefulness is largely dependent on subjective opinions, as only minimal studies investigating pharmacodynamics have been carried out in horses. Therefore, their use will vary markedly between practitioners depending on their personal experiences and pressures by trainers to use them. They form part of rational therapy in a variety of conditions. In addition to their use for increasing muscle mass, they are used to varying extents in the raising of yearlings and in the training and racing of horses with the view of improving performance. The use of these agents is prohibited in the horseracing industry by the Association of Racing Commissioners International (ARCI), International Federation of Horseracing Authorities (IFHA), and Fédération Equestre Internationale (FEI).

Evaluation of Enzymatic Activity of Various HSD17B3 Mutants Using Androgen Receptor-Mediated Transactivation

17β-Hydroxysteroid dehydrogenases (17β-HSDs, HSD17B) catalyze the reduction of 17-ketosteroids and the oxidation of 17β-hydroxysteroids to regulate the production of sex steroids. Among HSD17B family, 17β-HSD type 3 (HSD17B3) is expressed in testicular Leydig cells and contributes to development of male sexual characteristics by converting androstenedione (A4) to testosterone (T). Mutations of HSD17B3 genes cause a 46,XY disorder of sexual development (46,XY DSD) as a result of low T production. Therefore, the evaluation of HSD17B3 enzymatic activity is important for understanding and diagnosing this disorder. Although various amino acid substitutions of HSD17B3 have been reported in previous studies, the enzymatic activities of these proteins were often not defined. This is probably due to the difficulties that such enzymatic activities have been evaluated by quantifying the conversion of A4 into T using radioactive isotopes and liquid chromatography-mass spectrometry-mass spectrometry (LC-MS/MS). We adapted a method that easily evaluates enzymatic activity of HSD17B3 proteins by quantifying the conversion from A4 to T using androgen receptor (AR)-mediated transactivation. HEK293 cells were transfected to express human HSD17B3, and incubated medium containing A4. Depending on the incubation time with HSD17B3-expressing cells, the culture media progressively increased luciferase activities in CV-1 cells, transfected with the AR expression vector and androgen-responsive reporter. These luciferase activities reflected T concentrations in culture media defined by LC-MS/MS. This system is also applicable to detect the conversion of A4 to T by HSD17B1 and HSD17B5. In addition, it can evaluate the conversion of 11-ketoandrostenedione to 11-ketotestosterone by HSD17B family. Establishment of HEK293 cells expressing various missense mutations in the HSD17B3 gene with (N74T, A188V, M197K, A200V,, V225M, H271R) or without (V31I, E67K and G289S) the manifestation of 46,XY DSD revealed that this system is effective to evaluate the enzymatic activities of mutant proteins. A188V, A200V, V225M and H271R mutations completely inactivated the enzymatic function. N74T and M197K mutations showed some residual activities. In contrast, V31I, E67K and G289S substitutions showed similar activities as the wild-type protein.

Evaluation of 17β-hydroxysteroid dehydrogenase activity using androgen receptor-mediated transactivation

17β-Hydroxysteroid dehydrogenases (17β-HSDs) catalyze the reduction of 17-ketosteroids and the oxidation of 17β-hydroxysteroids to regulate the production of androgens and estrogens. Among them, 17β-HSD type 3 (HSD17B3) is expressed almost exclusively in testicular Leydig cells and contributes to development of male sexual characteristics by converting androstenedione (A4) to testosterone (T). Mutations of HSD17B3 genes cause a 46,XY disorder of sexual development (46,XY DSD) as a result of low T production. Therefore, the evaluation of 17β-HSD3 enzymatic activity is important for understanding and diagnosing this disorder. We adapted a method that easily evaluates enzymatic activity of 17β-HSD3 by quantifying the conversion from A4 to T using androgen receptor (AR)-mediated transactivation. HEK293 cells were transduced to express human HSD17B3, and incubated medium containing A4. Depending on the incubation time with HSD17B3-expressing cells, the culture media progressively increased luciferase activities in CV-1 cells, transfected with the AR expression vector and androgen-responsive reporter. Culture medium from HSD17B1 and HSD17B5-expressing cells also increased the luciferase activities. This system is also applicable to detect the conversion of 11-ketoandrostenedione to 11-ketotestosterone by HSD17B3. Establishment of HEK293 cells expressing various missense mutations in the HSD17B3 gene associated with 46,XY DSD revealed that this system is effective to evaluate the enzymatic activities of mutant proteins.

Imposex in Stramonita haemastoma from coastal sites of Cartagena, Colombia.

Imposex is the development of male sexual characteristics caused by the toxic effects of some chemicals that acts as an endocrinal disruptor. Antifouling paints contain these chemicals. Cartagena lacks studies to indicate the extent of imposex in its coastal waters. The aim of this study was to determine the prevalence of imposex in the gastropod Stramonita haemastoma in Cartagena, Colombia. Specimens were collected during 2013 from locations of high and low influence of port activity. Morphometric measurements and the frequency of the occurrence of imposex were registered. The comparison among morphometric variables showed statistically significant differences between the two sites studied. Furthermore, the females of the S. haemastoma species presented an imposex frequency of 93.1% in Birds' Island, Cartagena Bay, compared to 31.8% in La Bocana. The relative penis size index or RPLI (10.145 and 3.231) and vas deferens sequence index or VDSI (2.83 and 1.16), showed possible contamination by organotin compounds in both places.

The Transcription Factor MEF2 Is a Novel Regulator of Gsta Gene Class in Mouse MA-10 Leydig Cells.

Testosterone is essential for spermatogenesis and the development of male sexual characteristics. However, steroidogenesis produces a significant amount of reactive oxygen species (ROS), which can disrupt testosterone production. The myocyte enhancer factor 2 (MEF2) is an important regulator of organogenesis and cell differentiation in various tissues. In the testis, MEF2 is present in Sertoli and Leydig cells throughout fetal and adult life. MEF2-deficient MA-10 Leydig cells exhibit a significant decrease in steroidogenesis concomitant with a reduction in glutathione S-transferase (GST) activity and in the expression of the 4 Gsta members (GST) that encode ROS inactivating enzymes. Here, we report a novel role for MEF2 in ROS detoxification by directly regulating Gsta expression in Leydig cells. Endogenous Gsta1-4 mRNA levels were decreased in MEF2-deficient MA-10 Leydig cells. Conversely, overexpression of MEF2 increased endogenous Gsta1 levels. MEF2 recruitment to the proximal Gsta1 promoter and direct binding on the -506-bp MEF2 element were confirmed by chromatin immunoprecipitation and DNA precipitation assays. In MA-10 Leydig cells, MEF2 activates the Gsta1 promoter and cooperates with Ca(2+)/calmodulin-dependent kinases I to further enhance Gsta1 promoter activity. These effects were lost when the -506-bp MEF2 element was mutated or when a MEF2-Engrailed dominant negative protein was used. Similar results were obtained on the Gsta2, Gsta3, and Gsta4 promoters, suggesting a global role for MEF2 factors in the regulation of all 4 Gsta genes. Altogether, our results identify a novel role for MEF2 in the expression of genes involved in ROS detoxification, a process essential for adequate testosterone production in Leydig cells.

Effect of environmental contaminants on mammalian testis.

Exposure of humans and wildlife to pollutants released in the environment is a centre of attention nowadays. Many of these chemicals (generally referred to as environmental pollutants) have been shown to interfere with normal hormonal signalling and biological functions, leading to reproductive disorders or infertility, which has been a matter of concern within the recent decades. The present paper reviews adverse effects of these toxicants on mammalian testes, with emphasis on alteration of steroidogenesis, spermatogenesis, and histopathological effects. From the publications reviewed, it appears that environmental toxicants, especially heavy metals and organic chemicals of synthetic and microbiological origins, disrupt hormone production and action in the mammalian testes. Endocrine disruption leads to disorders of testicular function and thereby compromises the normal phenotypic development of male sexual characteristics, initiation and maintenance of spermatogenesis. The toxicants also induce impairment of testicular cells function, testicular histology, and sperm cells function directly. The release of the toxicants in the environment is still ongoing, despite alarming quantities that already exist in the atmosphere. If appropriate measures are not taken, their impact on the male reproductive function and especially on testicular function will be more serious.

Tributyltin exposure in early life stages induces the development of male sexual characteristics in the common whelk, Buccinum undatum

Common whelks ( Buccinum undatum) from the open North Sea show imposex; the development of male sexual characteristics in female prosobranch gastropods. A correlation with shipping intensities has been established (Ten Hallers-Tjabbes et al., 1994) and tributyltin (TBT), the active biocide in anti-fouling paints, was expected to be the cause. To study the supposed cause—effect relationship, adult whelks were experimentally exposed to TBT. Juvenile B. undatum, produced by the experimental specimens, were also exposed in ovo or just after hatching during this experiment and developed male sexual characteristics (a penis and/or a vas deferens) in a dose-dependent manner already after 10 months more than 80% of the young B. Undatum exposed to nominal TBT concentrations 100 ng TBT/litre developed these male sexual organs. Adult females, however, showed no signs of imposex, although they were exposed for 9 months to the same TBT concentrations as their offspring. In adult females exposed to a dose of 1 μg TBT/litre, a TBT body burden of > 300 ng Sn/g dry weight was measured.

Replacement therapy: arginine vasopressin (AVP), growth hormone (GH), cortisol, thyroxine, testosterone and estrogen.

Replacement therapy is routinely used to treat hormone deficiencies of patients who have had surgery or radiation therapy that damages the hypothalamus or pituitary gland. Hormones commonly replaced include: arginine vasopressin (AVP), growth hormone (GH), cortisol, thyroxine (T4), testosterone and estrogen. AVP, synthesized in the hypothalamus, is stored in and released by the posterior lobe of the pituitary gland. GH is synthesized and released by the anterior pituitary gland. The other hormones are produced and released by target glands each of which is stimulated by a specific anterior pituitary hormone, which in turn is controlled by release of a specific hypothalamic hormone. Feedback control by a high circulating concentration of the target gland's hormone regulates hypothalamic hormone release. Deficiency of AVP, important for water balance in the body, is restored with the synthetic analogue, 1-desamino-8-D-arginine vasopressin (DDAVP); it is given as a nasal spray or by injection. GH is required for normal growth in the developing child; recombinant GH, produced in bacteria, is injected subcutaneously. Adrenocorticotropic hormone (ACTH) controls release of cortisol which is produced by the adrenal cortex and enables the body to cope with stress; cortisol is replaced with prednisolone given orally. Thyroid stimulating hormone (TSH) controls release of the thyroid hormones, T4 and triiodothyronine (T3), which promote growth and development, and regulate energy metabolism; for replacement of T4, oral synthetic L-thyroxine is given. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) control release of testosterone, which promotes maturation of sperm and development of male sexual characteristics; replacement testosterone is administered intramuscularly. In females, FSH and LH control release of estrogens and progesterone which prepare the reproductive tract for release of the ovum, fertilization, implantation and development of the embryo, replacement by estrogen and progesterone preparations which are orally effective is given in a cyclic manner. A transdermal delivery system is available. Nursing implications include cautions and contraindications, potential problems of over-replacement, drug interactions as well as patient teaching points.

Specificity of testosterone and estradiol in the differentiating neonatal rat.

AbstractThose components of sexual behavior characteristic of the adult intact male such as intromission and ejaculation, were inhibited in males receiving estradiol dipropionate within the first week of life. Neonatal treatment with testosterone propionate at corresponding ages did not disrupt the capacity for homotypic behavior when the males became adult. The expression of female behavior during adulthood was suppressed in female rats treated during a critical period of early postnatal life with testosterone propionate or estradiol dipropionate.Spermatogenesis was suppressed in males receiving the estrogen but not the androgen in early postnatal life, whereas ovulation was suppressed in females receiving the estrogen or androgen at corresponding periods.It was concluded that testosterone is compatible with the normal development of male sexual characteristics but that estradiol is not compatible with development of female sexual characteristics when administered during a critical period of differentiation. The specificity for androgen in adult males is postulated to be partly due to the presence of androgens during the critical period. The specificity for estrogen shown by females in adulthood is thought to be dependent upon the absence of estrogen and androgen during a corresponding developmental stage.