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PubMed1976

Calcitonin-biochemistry and physiology.

Calcitonin is still a mysterious protein hormone. Secreted by the C-cell in ultimobranchial body or thyroid glands, it seems to act as a hypocalcemic antagonist against parathyroid hormone by inhibiting osteolysis. This concept which was developed especially in small mammals like the rat, does not entirely fit the results gained from other species: in fish, CT levels change in connection with the reproductive cycle in the female, in amphibians, buffering capacity of the organism is bound to the ultimobranchial body, and in birds, sexual development in the male is accompanied by increasing calcitonin levels.

Amphibians↗
PubMed1998

The Y-chromosome and reproductive disorders.

Over the past decade the tools of modern molecular biology have provided unique insights into our fundamental understanding of developmental systems. These insights have been gleaned from the study of a wide variety of model organisms including yeast (Saccharomyces cerevisiae), fly (Drosophila), worm (Caenorhabditis elegans), and mouse. In man, the first analysis of developmental systems started with sexual differentiation and focused on the role of Y-linked genes. The presence of living developmental mutants in man affecting sexual development and the early technology of deletion mapping facilitated the isolation and identification of small segments of putative DNA suspected to contain sex-determining genes. The isolation of genes such as SRY (Sex Related gene on Y) has provided the first insights into the molecular biology of human sexual differentiation. The focus on the Y chromosome has brought further insights into chromosomal pairing, statural determinants in man, oncogenesis, spermatogenesis, haploid genomes, and the lineage of man himself. This paper provides the circumstantial and direct evidence to illustrate the importance of the Y chromosome in reproductive disorders, and in the analysis of haploid genomes.

Animals↗
PubMedDate not supplied

Trace minerals in human growth and development.

Trace mineral deficiencies may affect several biological functions in humans, including physical growth, psychomotor development and immunity. We have reviewed the mechanisms whereby several trace mineral deficiencies may affect these biological functions at different ages (fetal life, infancy, childhood and adolescence), as well as the evidence supporting this association. We describe the effects of zinc deficiency on the hormonal regulation of growth and sexual development in both humans and animal models. We provide data regarding the effects of iron deficiency on growth and psychomotor development. We mention the effects of copper, manganese, selenium and iodine deficiencies on growth and development. We conclude that iron deficiency may affect psychomotor development, but does not appear to affect growth. Zinc deficiency may cause growth retardation and psychomotor delay.

Child↗
PubMed1999

Trace minerals in human growth and development.

Trace mineral deficiencies may affect several biological functions in humans, including physical growth, psychomotor development and immunity. We have reviewed the mechanisms whereby several trace mineral deficiencies may affect these biological functions at different ages (fetal life, infancy, childhood and adolescence), as well as the evidence supporting this association. We describe the effects of zinc deficiency on the hormonal regulation of growth and sexual development in both humans and animal models. We provide data regarding the effects of iron deficiency on growth and psychomotor development. We mention the effects of copper, manganese, selenium and iodine deficiencies on growth and development. We conclude that iron deficiency may affect psychomotor development, but does not appear to affect growth. Zinc deficiency may cause growth retardation and psychomotor delay.

Adolescent↗
PubMed2003

Sry expression level and protein isoform differences play a role in abnormal testis development in C57BL/6J mice carrying certain Sry alleles.

Transfer of certain Mus domesticus-derived Y chromosomes (Sry(DOM) alleles, e.g., Sry(POS) and Sry(AKR)) onto the C57BL/6J (B6) mouse strain causes abnormal gonad development due to an aberrant interaction between the Sry(DOM) allele and the B6-derived autosomal (tda) genes. For example, B6 XY(POS) fetuses develop ovaries and ovotestes and B6 XY(AKR) fetuses have delayed testis cord development. To test whether abnormal testis development is caused by insufficient Sry(DOM) expression, two approaches were used. First, gonad development and relative Sry expression levels were examined in fetal gonads from two strains of B6 mice that contained a single M. domesticus-derived and a single M. musculus-derived Sry allele (B6-Y(POS,RIII) and B6-Y(AKR,RIII)). In both cases, presence of the M. musculus Sry(RIII) allele corrected abnormal testis development. On the B6 background, Sry(POS) was expressed at about half the level of Sry(RIII) whereas Sry(AKR) and Sry(RIII) were equally expressed. On an F(1) hybrid background, both Sry(POS) and Sry(RIII) expression increased, but Sry(POS) expression increased to a greater extent. Second, sexual development and Sry expression levels were determined in XX mice carrying a transgene expressing Sry(POS) controlled by POS-derived or MUS-derived regulatory regions. In both cases one B6 transgenic line was recovered in which XX transgenic mice developed only testicular tissue but cord development was delayed despite normal Sry transcriptional initiation and overexpression. For three transgenes where B6 XX transgenic mice developed as females, hermaphrodites, or males, the percentage of XX transgenic males increased on an F(1) background. For the one transgene examined, Sry expression increased on an F(1) background. These results support a model in which delayed testis development is caused by the presence of particular DOM SRY protein isoforms and this, combined with insufficient Sry expression, causes sex reversal. These results also indicate that at least one tda gene regulates Sry expression, possibly by directly binding to Sry regulatory regions.

Animals↗
PubMed1991

Interstitial collagen synthesis by somatic testicular cells in culture.

The synthesis, distribution and types of collagen produced by somatic testicular cells in culture was studied. To investigate whether changes in collagen synthesis correlate with the age of the animal, cultures derived from immature and pubertal rats were established. Immature rats synthesize 40 per cent more collagen than pubertal rats. Both groups of animals synthesize procollagen types I and III. Pro-collagen type I is present in the culture medium as well as in the cell fraction, while type III is only detected in the culture medium. In the transition from immature to pubertal rat, the ratio of procollagen type III to procollagen type I diminishes from 5.7 to 1.7. These results indicate that the synthesis, distribution and molecular characteristics of interstitial collagens changes with the age of the animal. Since, the content of other extracellular matrix components such as proteoglycans and collagen type IV also varies with age, we postulate that the composition of the extracellular matrix in the testes is not constant but changes with sexual development.

Animals↗
PubMed2007

Sexual behavior in high-functioning male adolescents and young adults with autism spectrum disorder.

Group home caregivers of 24 institutionalized, male, high-functioning adolescents and young adults with Autism Spectrum Disorder, were interviewed with the Interview Sexuality Autism. Most subjects were reported to express sexual interest and to display some kind of sexual behavior. Knowledge of socio-sexual skills existed, but practical use was moderate. Masturbation was common. Many subjects were seeking physical contact with others. Half of the sample had experienced a relationship, while three were reported to have had sexual intercourse. The number of bisexual orientations appeared high. Ritual-sexual use of objects and sensory fascination with a sexual connotation were sometimes present. A paraphilia was present in two subjects. About one third of the group needed intervention regarding sexual development or behavior.

Adolescent↗
PubMed2004

ATRX and sex differentiation.

Most interest in the gene encoding the alpha-thalassemia, mental retardation, X-linked protein (ATRX) has traditionally been focused on its role in brain development and globin regulation. However, mutations in the ATRX gene also cause varying degrees of gonadal and urogenital abnormalities. These range from small testes to ambiguous external genitalia in XY individuals. ATRX is of great interest because this very large protein is one of the least understood proteins involved in mammalian sexual development. Although the biochemical role of ATRX remains unknown, recent and emerging evidence implicates ATRX in chromatin remodeling. We review what is known about ATRX as a chromatin remodeling protein, and its role in mammalian sex differentiation.

Chromatin↗
PubMed1999

Amphibians as a model to study endocrine disruptors: I. Environmental pollution and estrogen receptor binding.

Many chemicals released into the environment without toxicological risks have the capacities to disrupt the function of endocrine systems. These endocrine disruptors disturb normal endocrine mechanisms and have been observed in nearly all classes of vertebrates. The aim of this research is to develop a comprehensive model to study endocrine disruption using the amphibian Xenopus laevis. The assessment of estrogenic potencies of endocrine disruptors includes several levels of investigation: (I) binding to liver estrogen receptor, (II) estrogenic activity in vitro by inducing vitellogenin synthesis in primary cultured hepatocytes, and (III) in vivo effects on sexual development caused by exposure of larvae. The present paper is focused on the first part by establishing a radioreceptorassay for [3H]17 beta-estradiol ([3H]E2) binding using liver cytosol fraction. In order to get optimum binding conditions we performed kinetic, saturation, and competitive displacement experiments. Association of [3H]E2 to estrogen receptor revealed that maximum specific binding is achieved between 18 and 48 h of incubation. Scatchard analyses of saturation experiments resulted in a homogenous saturable population of estrogen receptors having no significant differences of binding parameters between both sexes. The values of Kd (dissociation constant) in males and females were 22.4 +/- 6.0 and 15.0 +/- 2.8 nM (mean +/- S.E.M.; n = 5), respectively, while corresponding Bmax (maximum binding capacity) revealed 89 +/- 46 and 136 +/- 46 fmol [3H]E2/mg protein. The specificity of estrogen receptors as shown by competitive displacement experiments demonstrated receptors being highly specific just for estrogens, but not for other endogenous steroids having the following ranking of binding affinities: E2 > estrone > dehydroepiandrosterone > aldosterone > or = testosterone > or = corticosterone > or = progesterone. The affinity ranking of environmental chemicals compared to E2 was: E2 > tetrachlorbiphenyl > diethylphthalate > 2,2-bis-(4-hydroxyphenyl)-propan (bisphenol A) > or = 4-nonylphenol > or = 3-t-butyl-4-hydroxyanisole > or = 4-octylphenol > dichlor-diphenyl-trichlor-ethan (4,4'-DDT). Analyses of five sewage effluents for displacement of [3H]E2 binding resulted in three samples displacing more than 50% of specific binding at their original concentration. Taken together the established radioreceptorassay for [3H]E2 binding in Xenopus laevis liver cytosol is useful to screen estrogen receptor binding of pure compounds or complex mixtures of them, which is the prerequisite for causing either estrogenic or antiestrogenic effects.

Animals↗
PubMed2005

Aromatase pathway mediates sex change in each direction.

The enzyme aromatase controls the androgen/oestrogen ratio by catalysing the irreversible conversion of testosterone into oestradiol (E2). Therefore, the regulation of E2 synthesis by aromatase is thought to be critical in sexual development and differentiation. Here, we demonstrate for the first time that experimental manipulation of E2 levels via the aromatase pathway induces adult sex change in each direction in a hermaphroditic fish that naturally exhibits bidirectional sex change. Our results demonstrate that a single enzymatic pathway can regulate both female and male sexual differentiation, and that aromatase may be the key enzyme that transduces environmental, including social, cues to functional sex differentiation in species with environmental sex determination.

Animals↗
PubMed2001

Sexual maturation and fertility of male Nigerian Dwarf goat (Capra hircus) clones produced by somatic cell nuclear transfer.

Three, genetically identical, Nigerian Dwarf bucks produced by somatic cell nuclear transfer (NT) of fetal fibroblasts were monitored for sexual maturation and fertility. Starting at four months of age, these male clones were trained to serve an artificial vagina (AV). Average age of the NT-derived bucks at first semen collection was 20 weeks, which was not different from that of other young bucks of this breed (average age at first collection = 20 weeks). Average sperm production at 5 months of age for the NT-derived bucks was 5.0 x 10(8) spermatozoa, which was comparable to that of dwarf bucks of similar age (3.4 x 10(8) spermatozoa). At seven months of age, semen collected from two NT-derived bucks was used to artificially inseminate six females (three does per buck). Five does were confirmed pregnant by ultrasound at day 42. Nine healthy kids, four males and five females, were born in March and April 2000. Viable spermatozoa were collected from one of the F1 males at 28 weeks of age. These results demonstrated that NT-derived bucks and one of their male offspring developed sexually within the normal timeframe for their breed and that the clones were fertile.

Animals↗
PubMed1975

Genetic and hormonal control of male sexual differentiation.

Phenotypic sexual differentiation during embryogenesis is a complex process involving the action of at least 18 genes. These genes regulate gonadal differentiation, gonadal hormone formation, and in the male the cellular action of three necessary hormones, namely mullerian regression factor, testosterone, and dihydrotestosterone. Analysis of two of the mutations affecting sexual development is consistent with the thesis that the two androgens testosterone and dihydrotestosterone have separate and specific roles in virilization of the male urogenital tract, testosterone stimulating wolffian duct development and dihydrotestosterone mediating development of the urogenital sinus and external genitalia. In the disorder familial incomplete male pseudohermphroditism, type 2, deficient dihydrotestosterone formation is associated with a selective failure of virilization of the urogenital sinus and external genitalia, whereas the wolffian duct derivatives develop normally. On the other hand, in the testicular feminization syndrome there is a complete failure in the development of the male phenotype, indicating that the primary defect involves an abnormality in some biochemical step that is common to the action of both androgens. Evidence from studies in the submandibular gland of the mouse with testicular feminization suggest that the fundamental defect lies in the translocation and/or nuclear binding of the cytoplasmic androgen receptor. It remains to be proven whether these events in the postnatal, sexually dimorphic submandibular gland of the testicular feminization mouse reflect prenatal events occurring in the urogenital tissues during embryogenesis.

Age Factors↗
PubMed2004

Cultural sensitivity in providing reproductive care to adolescents.

PURPOSE OF REVIEW: To provide an exploration of the global attitudes towards reproductive healthcare by adolescent patients, and to review key points in promoting healthy sexual development among adolescents and appropriate guidelines for communicating within the adolescent population. RECENT FINDINGS: The adolescent's perception of healthcare providers and communication with adolescents are inextricably intertwined, hence the need to address both topics. In addition, we will briefly examine the topic of female circumcision and its impact on women's sexuality. It is necessary to approach this subject because of the increase in the number of individuals that emigrate each year to the United States and Canada from countries that still practise female circumcision. Providing reproductive care for these women has considerable implications for gynecologists and other healthcare providers dealing with reproductive care issues. SUMMARY: Healthcare providers who are aware of adolescent patients' developmental stage and cultural diversity are more able to gain the trust of their patients, and consequently are more effective at addressing their needs.

Adolescent↗
PubMed2001

Sexual activity during pregnancy and after childbirth: results from the Sexual Preferences Questionnaire.

The sexual relations of expectant and young parents have been researched relatively often, but most studies are restricted to female participants, samples from the USA, a short postpartum period and a reductionist view of sexuality as equivalent to intercourse. The aim of this study is to gain more knowledge about sexual activity of German couples with regard to non-genital tenderness, French kissing, breast stimulation, manual-genital stimulation, cunnilingus, fellatio, vaginal intercourse, anal intercourse and masturbation during pregnancy and the first 6 months postpartum. As part of a larger longitudinal study, 60 women and men (30 couples) answered a newly developed Sexual Preferences Questionnaire (SPQ) which assesses sexual activity and enjoyment. The frequency of most heterosexual activities declined during pregnancy, reached almost zero in the first 3 months postpartum, and then began to increase; male masturbation remained relatively constant. Agreement between the two members of each couple was assessed and SPQ data were validated with other questionnaire data and interview data. The results are discussed with regard to limitations of the sample. Future research should broaden the range of questions investigated, the range of research methods applied (questionnaires and interviews) and the range of persons researched (both partners).

Adult↗
PubMed2002

Issues in adolescent health: a challenge for nursing.

The young people of today are the greatest investment we as adults have in our future. The care and nurturing we afford the adolescent is just as important as that which we afford to children or the elderly. Although most adolescents have a preoccupation with their bodies, they do not always engage in activities that will protect and develop them. Adolescents are often exposed to peer pressure, the effects of which may impact negatively on their behaviour and their health. Many adolescent health and behavioural issues evolve from developmental changes and can manifest in a confrontational attitude toward society, parents and others. They are hormonally 'fully charged', and their adolescent sexuality can have enormous effects on their future physical, psychosocial, moral and sexual development. Nurses have a pivotal role to play in ensuring children and adolescents learn the facts relating to the consequences of engaging in unhealthy behaviour and lifestyle. Nurses must also encourage parents to model and reinforce good health practices, such as serving balanced and nutritious meals at regular times and planning positive family activities. In this paper we review some of the salient issues in adolescent health today.

Adolescent↗
PubMed2003

Organochlorines affect the major androgenic hormone, testosterone, in male polar bears (Ursus maritimus) at Svalbard.

Normal sexual development and subsequent reproductive function are dependent on appropriate testosterone production and action. The regulation of steroid hormones, including androgens, can be influenced by both biological and environmental factors, including environmental chemicals. Concentrations of organochlorines are considerably greater in Svalbard polar bears than in polar bears from other regions. Between 1995 and 1998, samples were collected from 121 male polar bears (Ursus maritimus) from the Svalbard area. In this study, testosterone concentration variations were described for male polar bears during different seasons and for all age groups. To study possible relationships between plasma testosterone concentrations and biological factors, such as age, axial girth, and extractable plasma fat, and organochlorine contaminants including hexachlorocyclohexanes, hexachlorobenzene, chlordanes, p,p'-DDE, and 16 individual polychlorinated biphenyl (PCB) congeners, identical statistical analyses were performed on the total population and a subsample of reproductively active adults. Of the biological factors, axial girth showed a significant positive relationship and percentage extractable fat and a significant negative relationship with the testosterone concentrations. Both the epsilon pesticides and epsilon PCBs made significant negative contributions to the variation of the plasma testosterone concentration. The continuous presence of high concentrations of organochlorines in male polar bears throughout their life could possibly aggravate any reproductive toxicity that may have occurred during fetal and early postnatal development.

Age Factors↗
PubMedDate not supplied

Ornithine decarboxylase activity and polyamine levels in the epididymis of prepubertal rat after antiandrogen administration.

The antiandrogens flutamide and casodex have been administered subcutaneously (vehicle, 1, 5 or 10 mg per day) to prepubertal male rats for 10 days. A significant change of epididymal weight has been observed after both treatments, from the lowest dose used. Epididymal dihydrotestosterone concentrations were significantly increased in flutamide- or casodex-treated rats, while epididymal 3 alpha-androstanediol concentrations were affected only after flutamide administration, suggesting a differential effect on androgen metabolism between both antiandrogens. Ornithine decarboxylase (ODC) activity was significantly decreased by flutamide, and to a lesser extent by casodex. Antiandrogen administration resulted in a significant decrease in epididymal content of the polyamines putrescine, spermidine, and spermine. A slight but significant decrease in putrescine and spermidine concentrations, but not in spermine, was observed after flutamide treatment. However, casodex had no effects on polyamines levels. A decrease in putrescine concentration was detected only when ODC activity fell to rather low levels. Interference of the antiandrogens with the biological action of androgens on ODC activity was clearly seen in immature male rats. Therefore, both epididymal growth and differentiation, in correlation to ODC activity, would be severely affected at an early period of sexual development, such as prepuberty.

Androgen Antagonists↗
PubMed1995

Is ovarian adrenergic innervation essential to gonadal function in adult rats?

We studied the relative importance of ovarian innervation during different phases of female rat sexual development, 30, 40, 45 and 60-day-old. Chemical sympathectomy was promoted by long term postnatal treatment with guanethidine (GD), an adrenergic neuron blocking agent. The sympathectomized rats exhibited delayed puberty and alterations in estrous cycle. Reduced circulating E2, LH and Prl levels at 30 days of age were observed, besides decreased steroidal secretory responsiveness to gonadotropins in vitro. On the other hand, normal pituitary secretory responsiveness to LHRH in vivo and plasma gonadotropin concentrations were observed in 60-day-old rats. These data reinforce the view that ovarian sympathetic innervation contributes to the regulation of the prepubertal development of the ovarian functions.

Animals↗