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PubMed1992

The role of maternal stimulation in the development of sexual behavior and its neural basis.

Both sexual differentiation, which is a matter of individual development, and sexual dissimilation, which is a matter of individual differences, result from developmental processes that are open to input from the early maternal environment. There are reliable features in both the dam and the young that ensure that males receive more perineal stimulation from maternal licking than is necessary for survival and normal growth. This stimulation contributes toward the development of masculine sexual behavior and mechanisms in the central nervous system that control copulatory reflexes. Because of differences in signals that they produce, males receive more stimulation than females. This bias in early stimulation accounts for some of the dissimilarity between the sexes in nervous system morphology and behavior. The same processes that produce sex differences can also produce individual differences among males. These differences are likely to have significant functional consequences in rats, a species in which males have a high level of intrasexual reproductive competition. Future research will be directed toward testing this functional hypothesis and toward exploring the extent of stimulative effects on the development of the sexually dimorphic brain regions that function in sexual behavior.

Afferent Pathways↗
PubMed2003

New paradigms for research on heterosexual and sexual-minority development.

As psychological research on sexual-minority (i.e., nonheterosexual) adolescents has increased over the past 20 years, it has become increasingly segregated from research on mainstream heterosexual youths, as if the knowledge gleaned from each population had nothing to offer our understanding of the other. To the contrary, understanding of both populations would be greatly improved by integrating investigations of sexual-minority issues into mainstream psychological research on adolescents. I outline 4 weaknesses in contemporary research on sexual-minority youth that stem from--and perpetuate--its historical isolation from mainstream developmental research: misspecification of the populations under study, lack of attention to within-group diversity, failure to test alternative explanations for--and moderators of--"sexual-minority effects," and insufficient attention to the underlying processes and mechanisms through which sexual-minority effects operate. Correcting these weaknesses has important implications for future research on how same-sex and other-sex sexuality shape adolescent psychosocial development and clinical child and adolescent problems.

Adolescent↗
PubMed1997

Rapamycin specifically interferes with the developmental response of fission yeast to starvation.

Rapamycin is a microbial macrolide which belongs to a family of immunosuppressive drugs that suppress the immune system by blocking stages of signal transduction in T lymphocytes. In Saccharomyces cerevisiae cells, as in T lymphocytes, rapamycin inhibits growth and cells become arrested at the G1 stage of the cell cycle. Rapamycin is also an effective antifungal agent, affecting the growth of yeast and filamentous fungi. Unexpectedly, we observed that rapamycin has no apparent effect on the vegetative growth of Schizosaccharomyces pombe. Instead, the drug becomes effective only when cells experience starvation. Under such conditions, homothallic wild-type cells will normally mate and undergo sporulation. In the presence of rapamycin, this sexual development process is strongly inhibited and cells adopt an alternative physiological option and enter stationary phase. Rapamycin strongly inhibits sexual development of haploid cells prior to the stage of sexual conjugation. In contrast, the drug has only a slight inhibitory effect on the sporulation of diploid cells. A genetic approach was applied to identify the signal transduction pathway that is inhibited by rapamycin. The results indicate that either rapamycin did not suppress the derepression of sexual development of strains in which adenylate cyclase was deleted or the cyclic AMP-dependent protein kinase encoded by pka1 was mutated. Nor did rapamycin inhibit the unscheduled meiosis observed in pat1-114 mutants. Overexpression of ras1+, an essential gene for sexual development, did not rescue the sterility of rapamycin-treated cells. However, expression of the activated allele, ras1Val17, antagonized the effect of rapamycin and restored the ability of the cells to respond to mating signals in the presence of the drug. We discuss possible mechanisms for the inhibitory effect of rapamycin on sexual development in S. pombe.

Adenylyl Cyclases↗
PubMed2006

Embryonic gonadal and sexual organ development in a small viviparous skink, Niveoscincus ocellatus.

The majority of research into the timing of gonad differentiation (and sex determination) in reptiles has focused on oviparous species. This is largely because: (1) most reptiles are oviparous; (2) it is easier to manipulate embryonic developmental conditions (e.g., temperature) of eggs than oviductal embryos and (3) modes of sex determination in oviparous taxa were thought to be more diverse since viviparity and environmental sex determination (ESD)/temperature-dependent sex determination (TSD) were considered incompatible. However, recent evidence suggests the two may well be compatible biological attributes, opening potential new lines of enquiry into the evolution and maintenance of sex determination. Unfortunately, the baseline information on embryonic development in viviparous species is lacking and information on gonad differentiation and sexual organ development is almost non-existent. Here we present an embryonic morphological development table (10 stages), the sequence of gonad differentiation and sexual organ development for the viviparous spotted snow skink (Niveoscincus ocellatus). Gonad differentiation in this species is similar to other reptilian species. Initially, the gonads are indifferent and both male and female accessory ducts are present. During stage 2, in the middle third of development, differentiation begins as the inner medulla regresses and the cortex thickens signaling ovary development, while the opposite occurs in testis formation. At this point, the Müllerian (female reproductive) duct regresses in males until it is lost (stage 6), while females retain both ducts until after birth. In the later stages of testis development, interstitial tissue forms in the medulla corresponding to maximum development of the hemipenes in males and the corresponding regression in the females.

Animals↗
PubMed1990

Sex steroid profiles of coho salmon (Oncorhynchus kisutch) during early development and sexual differentiation.

Sex steroids were measured by radioimmunoassay in whole-body extracts of coho salmon, Oncorhynchus kisutch, during early development and sexual differentiation. Profiles were developed for fish from the time of fertilization until 87 days postfertilization (dpf) for six steroids: testosterone (T), 11-ketotestosterone (KT), androstenedione (A), progesterone (P4), 17 alpha-hydroxy-20 beta-dihydroprogesterone (DHP), and 17 beta-estradiol (E2). Ovarian fluid was also examined for steroid content. Steroid profiles of unfertilized eggs essentially paralleled those of ovarian fluid. In one experiment, steroids in developing embryos declined precipitously after fertilization until 30 dpf; at hatching, all steroids increased slightly and then declined during yolk sac absorption. Results from a second experiment basically supported those of the first except that only testosterone increased at the time of hatching. Bimodality was evident in the data on steroid levels for fish collected between 42 and 56 dpf and again after 87 dpf. The hormone levels generally decreased or remained constant after the onset of exogenous feeding. Histological analyses during the first experiment showed the presence of undifferentiated gonads between hatching and 70 dpf, but by 77 dpf ovarian development was evident. In the second experiment, in which fish were more frequently sampled for histological analysis, undifferentiated gonads were present from hatching to 59 dpf. Development of oogonia was observed between 66 and 73 dpf and by 75 dpf ovarian development could be easily discerned. The sex of fish sampled at 101 dpf was determined by examining gonadal morphology, and steroid levels of those fish were determined. A sexual dimorphism was apparent in levels of T, KT, and A, but not of DHP or E2. The dynamics of steroid content of developing coho salmon at hatch, coupled with their bimodal distributions during yolk sac absorption, may suggest a role of sex steroids in the process of sexual differentiation apparent later in development. Changes in whole-body steroid levels at hatch may also be indicative of the onset of sexual differentiation even though no signs of gondal differentiation were histologically discernible at that time.

Androstenedione↗
PubMed1998

Sexually dimorphic development of the mammalian reproductive tract requires Wnt-7a.

An important feature of mammalian development is the generation of sexually dimorphic reproductive tracts from the Müllerian and Wolffian ducts. In females, Müllerian ducts develop into the oviduct, uterus, cervix and upper vagina, whereas Wolffian ducts regress. In males, testosterone promotes differentiation of Wolffian ducts into the epididymis, vas deferens and seminal vesicle. The Sertoli cells of the testes produce Müllerian-inhibiting substance, which stimulates Müllerian duct regression in males. The receptor for Müllerian-inhibiting substance is expressed by mesenchymal cells underlying the Müllerian duct that are thought to mediate regression of the duct. Mutations that inactivate either Müllerian-inhibiting substance or its receptor allow development of the female reproductive tract in males. These pseudohermaphrodites are frequently infertile because sperm passage is blocked by the presence of the female reproductive system. Here we show that male mice lacking the signalling molecule Wnt-7a fail to undergo regression of the Müllerian duct as a result of the absence of the receptor for Müllerian-inhibiting substance. Wnt7a-deficient females are infertile because of abnormal development of the oviduct and uterus, both of which are Müllerian duct derivatives. Therefore, we propose that signalling by Wnt-7a allows sexually dimorphic development of the Müllerian ducts.

Animals↗
PubMed1986

Physical growth and development in patients with Rett syndrome.

Linear growth and sexual development was assessed in 21 girls who fulfilled the clinical criteria of Rett syndrome. Ten (48%) showed growth retardation with length or height below the 5th centile and an additional 8 (38%) had shifted their linear growth downward sometime during the first years of life. All the girls had age-appropriate sexual development with menarche in 6 at a mean age of 11 2/12 years. Early deceleration of linear growth, growth retardation and normal sexual development appear to be useful markers in the clinical definition of Rett syndrome.

Adolescent↗
PubMed2002

Genes controlling hypothalamic development and sexual differentiation.

Steroid hormones dramatically influence the development of numerous sites in the nervous system. Basic mechanisms in neural development provide foci for understanding how factors related to sex can alter the ontogeny of these regions. Sex differences in neurogenesis, cell migration, cell differentiation, cell death, and synaptogenesis are being addressed. Any and all of these events serve as likely targets for genetic or gonadal steroid-dependent mechanisms throughout development. Although the majority of sexually dimorphic characteristics in brain have been described in older animals, many hormonal mechanisms that determine sexually differentiated brain characteristics occur during critical perinatal periods. Genes suggested to contribute to the development of specific hypothalamic nuclear groups have rarely been examined in the context of sex. The identification of sex differences in the expression of some of these genes may suggest early and likely transient molecular events that set the stage for later amplification by hormone actions. Sex differences in the positioning of cells in the developing hypothalamus further suggest that cell migration may be one key target for early gene actions that impact long-term susceptibility to brain sexual differentiation.

Animals↗
PubMed2001

"[A]re Norway rats...things?": diversity versus generality in the use of albino rats in experiments on development and sexuality.

In America by the 1930s, albino rats had become a kind of generic standard in research on physiology and behavior that de-emphasized diversity across species. However, prior to about 1915, the early work of many of the pioneer rat researchers in America and in central Europe reflected a strong interest in species differences and a deep regard for diversity. These scientists sought broad, often medical, generality, but their quest for generality using a standard animal did not entail a de-emphasis of organic diversity. They chose white rats as test animals for two primary reasons. First, rats develop very slowly. They therefore made features of physiological, neural and psychological development accessible to the experimental method at a time when its application to the phenomena of development remained controversial. Secondly, rats were thought to have unusually strong sex drives. For this reason they became central to the experimental study of sexuality and, in the work of the reproductive physiologist Eugen Steinach, sexual development. Connections among three research institutes that stressed experimental approaches to the study of brain and development demonstrate the importance of the rat's institutional role. As the emphasis on experimentation in the study of development grew, two of these institutes bred rats to provide uniform materials. Eventually, however, their reasons for selecting rats were lost; and the ready availability of a uniform test animal led to a shift in scientists' presumptions about diversity, as the standard rat became a tool for assuring generality.

Animals↗
PubMed2004

Sexual identity development in the context of compulsory heterosexuality.

This study analyzed the implications of sexual identity development for global, political, religious, and occupational identity development in 358 college students. Participants completed a written survey packet including the Extended Objective Measure of Ego Identity Status (EOM-EIS) and measures of sexual identity, physical/sexual preference, and emotional/affective preference. Data from the EOM-EIS suggest that having a sexual minority identity (lesbian, gay, bisexual, or "other" nonheterosexual identity) and reporting strong same-sex sexual or physical preferences are linked with more advanced global, political, religious, and occupational identity development. Heterosexual-identified participants were more likely to score high on identity foreclosure, moratorium, and diffusion, while sexual-minority-identified individuals scored higher on identity achievement. Individuals with strong same-sex physical/sexual preferences showed a pattern of results similar to those of sexual-minority-identified participants. Themes coded from a free-response question highlighted the finding that sexual-minority-identified participants more often viewed their sexual identity as salient and involving an effortful process. These individuals also stressed the importance of having support or modeling for their sexual identity.

Adolescent↗
PubMed1996

Is non-judgemental care possible in the context of nurses' attitudes to patients' sexuality?

Developments in nursing practice in the United Kingdom are increasingly focusing on holistic models and approaches to care. The recognition of the importance of sexuality and sexual orientation of patients is a significant aspect of holistic care. This paper explores and discusses the literature in the arena of nurses' attitudes to patients' sexuality. From this discussion the concept emerges that nursing needs to recognize the effect that attitudes towards patients' sexuality has on nursing care, and develop strategies that allow this to be reflected on. The use of reflection facilitated by clinical supervision will be presented as a potential way forward.

Attitude of Health Personnel↗
PubMed1997

The Wilms' tumor gene WT1 can regulate genes involved in sex determination and differentiation: SRY, Müllerian-inhibiting substance, and the androgen receptor.

Genital abnormalities associated with Wilms' tumors in the WAGR and Denys-Drash syndromes and the failure of the gonads to develop in Wilms' tumor gene (wt1)-homozygous mutant mice suggest that WT1 may also function in sexual development. To elucidate the mechanism of action of WT1 in embryonal sexual development, we examined how the four isoforms of WT1 regulate the transcription of several genes involved in sexual development using cotransfection assays. SRY (the sex-determining region of the Y chromosome) promoter was strongly activated by the WT1 isoforms without the KTS tripeptide, WT1(-)KTS, but was not activated by the WT1 isoforms with the KTS tripeptide, WT1(+)KTS, in all cells tested. The second alternative splicing site, which inserts the tripeptide KTS, alters the DNA binding capability. The MüAdullerian-inhibiting substance (MIS) promoter was strongly repressed by WT1(-)KTS isoforms and more weakly repressed by the WT1(+)KTS isoforms in Sertoli cells but not in HeLa cells. The androgen receptor (AR) promoter was strongly repressed by the WT1(-)KTS isoforms in all cells tested and was more weakly or not repressed by WT1(+)KTS isoforms depending on cell lines. Electrophoretic mobility shift assays showed strong binding by recombinant WT1(-)KTS protein and weaker or no binding by the WT1(+)KTS protein to DNA probes containing WT1 binding sites from these three promoters. The results of these functional and binding assays suggest that WT1 has an important role in regulation of genes involved in embryonal sexual development and that WT1 can function as a transcriptional activator.

Animals↗
PubMed2004

A putative high affinity hexose transporter, hxtA, of Aspergillus nidulans is induced in vegetative hyphae upon starvation and in ascogenous hyphae during cleistothecium formation.

Fungi employ different carbohydrate uptake systems to adapt to certain environmental conditions and to different carbon source concentrations. The hydrolysis of polymeric carbohydrates and the subsequent uptake of monomeric forms may also play a role in development. Aspergillus nidulans accumulates cell wall components during vegetative growth and degrades them during sexual development. We have identified the hxtA (high affinity hexose transporter) gene in a differential library, which was enriched for sexual-specific genes. The hxtA gene is disrupted by 6 introns and predicted to encode a 531 amino acid protein with high similarity to major facilitator superfamily members including the high affinity hexose transporter Gtt1 from Trichoderma harzianum. A. nidulans HxtA contains the 12 predicted transmembrane domains characteristic for this family. Deletion of hxtA did not impair growth of A. nidulans on a variety of carbon sources nor did it inhibit sexual development suggesting redundant sugar uptake systems. We found at least 17 putative hexose transporters in the genome of A. nidulans. Despite the high similarity of HxtA to fungal high affinity glucose transporters, the hxtA gene did not restore growth on glucose of a Saccharomyces cerevisiae mutant, in which all hexose transporters were deleted. Northern blot analysis revealed that the A. nidulans hxtA gene was repressed under high glucose conditions and expressed in vegetative hyphae upon carbon starvation and during sexual development. We found hxtA(p)::sgfp expression in developing cleistothecia specifically in ascogenous hyphae and propose that HxtA is a high affinity glucose transporter involved in sugar metabolism during sexual development.

Amino Acid Sequence↗
PubMed1990

Late effects of total body irradiation and cytostatic preparative regimen for bone marrow transplantation in children with hematological malignancies.

Twenty-seven children, surviving disease-free for more than 1 year after allogeneic bone marrow transplantation (BMT) for hematological malignancy were evaluated for the long-term effects on endocrine function, sexual development, physical growth, appearance of ocular cataract and psychological sequelae. The growth rate was not decelerated in the prepubertal period in children not affected by chronic graft-versus-host (GVH) disease and without previous cranial irradiation. Development of sexual characteristics was delayed in 4 relevant cases. Thyroid function was not adversely affected, gonadal function was impaired in girls, transplanted after menarche, ocular cataract developed in all cases, irradiated without shielding of the eyes after 4 years. Psychologically, children after BMT had an advantageous social development.

Adolescent↗
PubMed1986

Evidence that serotonin is involved in the sexually dimorphic development of the preoptic area in the rat brain.

To investigate the possibility that serotonin plays a role in the sexually dimorphic development of a nucleus in the medial preoptic area of the rat brain, p-chlorophenylalanine, an inhibitor of serotonin biosynthesis, was administered to pregnant dams from day 8 of gestation until parturition. This treatment did not alter plasma steroid levels but increased the volume of the sexually dimorphic nucleus in female neonates to that of control males. Thus, serotonin is implicated as a neurochemical which may be involved in the sexually dimorphic development of the preoptic area.

Animals↗
PubMed1997

Studies on the age of puberty of male camels (Camelus dromedaries) in Saudi Arabia.

Aspects of sexual development and attainment of sexual and breeding maturity were studied in two groups of Najdi camels (Mojaheem and Wadah), maintained in stalls under good nutritional conditions. Body weight, testes diameter and degree of penile freedom were recorded weekly. Sexual maturity was assessed by the examination of semen collected by an artificial vagina. Puberty was defined as the stage when the animal was able to produce viable sperms. Mating, followed by strong jerks and ejaculation of mature sperms, was taken to indicate onset of breeding maturity. Mojaheem camels reached sexual maturity at a significantly younger age and heavier weight (164 weeks and 360 kg) than Wadah camels (182 weeks and 336.5 kg) (P < 0.001). Complete separation of the penis from preputial adhesions occurred at an average age of 138.6 weeks in both breeds. At the point of sexual maturity, the mean percentage of live spermatozoa was 65.1 +/- 5.2 while percentage of abnormal sperms was 17.6 +/- 2.2; total motility was 40 +/- 16% and progressive motility (48 +/- 2.2% (semen pH range 7.8-8.2). The percentage of live sperm was 65 +/- 1.5 (normal sperms 82 +/- 4). It is suggested that the encouragement of rapid growth during the pubertal period in camels managed under good nutritional and environmental conditions could assist early sexual development and breeding maturity.

Aging↗
PubMed2005

Sexuality in children and adolescents with disabilities.

This review presents a discussion of the sexual development of children and adolescents with disabilities, described in the framework of body structure and function, individual activities, and societal perspectives presented in the World Health Organization's International Classification of Functioning, Disability and Health. Issues of sexual development, gynecological care and contraception, sexual functioning, societal barriers, sexual victimization, and sexuality education are presented. Overall, adolescents with disabilities seem to be participating in sexual relationships without adequate knowledge and skills to keep them healthy, safe, and satisfied. Although their sexual development may be hindered both by functional limitations and by intentional or unintentional societal barriers, the formal and informal opportunities for teenagers with disabilities to develop into sexually expressive and fulfilled persons do exist. Health care providers are urged to increase their awareness of this unmet need and to implement strategies that promote the physical, emotional, social, and psychosexual independence of children, teenagers, and young adults with disabilities.

Adolescent↗
PubMed2006

'Your true and proper gender': the Barr body as a good enough science of sex.

In the late 1940s, a microanatomist from London Ontario, Murray Barr, discovered a mark of sex chromosome status in bodily tissues, what came to be known as the 'Barr body'. This discovery offered an important diagnostic technology to the burgeoning clinical science community engaged with the medical interpretation and management of sexual anomalies. It seemed to offer a way to identify the true, underlying sex in those whose bodies or lives were sexually anomalous (intersexuals, homosexuals and transsexuals). The hypothesis that allowed the Barr body to stand in for 'chromosomal' or 'genetic' sex was provisional, but it supported the expectation that genetic information established one's primary identity, and the conviction that the animal world could be neatly divided into two, and only two, sexes. Ultimately, this provisional hypothesis, and its status as an unambiguous arbiter of true sex, was overturned. But during much of the 1950s, Barr's thesis about the identity of the Barr body was consistent with a coherent set of theories and evidence explaining sexual development and sexual pathology. Though provisional, the scientific status of the sex chromatin within this system of knowledge was good enough to support a flourishing research enterprise in the clinical sciences.

Animals↗