Female Sexual Development Research Articles

Mutations in the TSPYL1 gene associated with 46,XY disorder of sex development and male infertility

We screened 100 individuals with anomalies of testicular development or function for mutations in the TSPYL1 gene. A 46,XY female with complete gonadal dysgenesis carried a p.K320R mutation in the highly conserved NAP domain, and a 46,XY male with idiopathic azoospermia harbored a p.R89H mutation, and this data supports the hypothesis that mutations in TSPYL1 may contribute to anomalies of testicular development/function.

Effect of the Gene doublesex of Anastrepha on the Somatic Sexual Development of Drosophila

BackgroundThe gene doublesex (dsx) is at the bottom of the sex determination genetic cascade and is transcribed in both sexes, but gives rise to two different proteins, DsxF and DsxM, which impose female and male sexual development respectively via the sex-specific regulation of the so-called sexual cyto-differentiation genes. The present manuscript addressed the question about the functional conservation of the tephritid Anastrepha DsxF and DsxM proteins to direct the sexual development in Drosophila (Drosophilidae).MethodologyTo express these proteins in Drosophila, the GAL4-UAS system was used. The effect of these proteins was monitored in the sexually dimorphic regions of the fly: the foreleg basitarsus, the 5th, 6th and 7th tergites, and the external terminalia. In addition, we analysed the effect of Anastrepha DsxF and DsxM proteins on the regulation of Drosophila yolk protein genes, which are expressed in the fat body of adult females under the control of dsx.ConclusionsThe Anastrepha DsxF and DsxM proteins transformed doublesex intersexual Drosophila flies into females and males respectively, though this transformation was incomplete and the extent of their influence varied in the different sexually dimorphic regions of the adult fly. The Anastrepha DsxF and DsxM proteins also behaved as activators and repressors, respectively, of the Drosophila yolk protein genes, as do the DsxF and DsxM proteins of Drosophila itself. Finally, the Anastrepha DsxF and DsxM proteins were found to counteract the functions of Drosophila DsxM and DsxF respectively, reflecting the normal behaviour of the latter proteins towards one another. Collectively, these results indicate that the Anastrepha DsxF and DsxM proteins show conserved female and male sex-determination function respectively in Drosophila, though it appears that they cannot fully substitute the latter's own Dsx proteins. This incomplete function might be partly due to a reduced capacity of the Anastrepha Dsx proteins to completely control the Drosophila sexual cyto-differentiation genes, a consequence of the accumulation of divergence between these species resulting in the formation of different co-adapted complexes between the Dsx proteins and their target genes.

FXYD1, a Modulator of Na+,K+‐ATPase Activity, Facilitates Female Sexual Development by Maintaining Gonadotrophin‐Releasing Hormone Neuronal Excitability

The excitatory tone to gonadotrophin-releasing hormone (GnRH) neurones is a critical component underlying the pubertal increase in GnRH secretion. However, the homeostatic mechanisms modulating the response of GnRH neurones to excitatory inputs remain poorly understood. A basic mechanism of neuronal homeostasis is the Na(+),K(+)-ATPase-dependent restoration of Na(+) and K(+) transmembrane gradients after neuronal excitation. This activity is reduced in a mouse model of Rett syndrome (RTT), a neurodevelopmental disorder in which expression of FXYD1, a modulator of Na(+),K(+)-ATPase activity, is increased. We now report that the initiation, but not the completion of puberty, is advanced in girls with RTT, and that, in rodents, FXYD1 may contribute to the neuroendocrine regulation of female puberty by modulating GnRH neuronal excitability. Fxyd1 mRNA abundance reaches maximal levels in the female rat hypothalamus by the fourth postnatal week of life (i.e., around the time when the mode of GnRH secretion acquires an adult pattern of release). Although Fxyd1 mRNA expression is low in the hypothalamus, approximately 50% of GnRH neurones contain Fxyd1 transcripts. Whole-cell patch recording of GnRH-EGFP neurones revealed that the neurones of Fxyd1-null female mice respond to somatic current injections with a lower number of action potentials than wild-type cells. Both the age at vaginal opening and at first oestrous were delayed in Fxyd1(-/-) mice, but adult reproductive capacity was normal. These results suggest that FXYD1 contributes to facilitating the advent of puberty by maintaining GnRH neuronal excitability to incoming transsynaptic stimulatory inputs.

Preputialectomised and intact adult male mice exhibit an elevated urinary ratio of oestradiol to creatinine in the presence of developing females, whilst promoting uterine and ovarian growth of these females

Exposure to novel adult males and their urine can hasten the onset of sexual maturity in female mice. Some evidence implicates chemosignals from males' preputial glands, while other evidence suggests that male urinary steroids, especially 17beta-oestradiol, contribute to this effect. The present experiment was designed to determine whether preputial gland removal would influence the capacity of males to accelerate female sexual development, and to measure male urinary oestradiol and testosterone in the presence or absence of these glands. Juvenile females aged 28 days were housed for two weeks in isolation or underneath two outbred males that had undergone preputialectomy or sham surgery. Urine samples were collected non-invasively from males that were isolated or exposed to females, then assayed for oestradiol, testosterone and creatinine. Combined uterine and ovarian mass from females sacrificed at 43 days of age was increased by exposure to males, regardless of whether or not these males had been preputialectomised. Male urinary creatinine was reduced by exposure to developing females. Creatinine-adjusted oestradiol and testosterone were significantly greater in female-exposed than in isolated males, in both preputialectomised and intact males. These data suggest that the preputials are not necessary for the capacity of males to hasten female uterine and ovarian growth. As exogenous oestrogens can promote uterine growth and other parameters of female reproductive maturation, oestradiol in males' urine may contribute to earlier sexual maturity in male-exposed females.

Plasmodium male development gene-1 ( mdv-1) is important for female sexual development and identifies a polarised plasma membrane during zygote development

Successful development of Plasmodium sexual stages is essential for parasite survival, but the genes involved are poorly understood. We ‘knocked out’ the male development gene-1 ( mdv-1) locus in Plasmodium berghei and found it to be important in female gametocyte activation. Indirect immunofluoresence assays show MDV-1 has a punctate cytoplasmic distribution in gametocytes. After activation of both females and males, MDV-1 is more peripherally located but in males exclusively it becomes concentrated in a few large foci. In vitro ookinete conversion assays that test the ability of activated female gametocytes to develop into retort stage ookinetes, suggests a complicit role for MDV-1, with the knock-out parasite producing 86% reduction in ookinetes. The retort stage ookinete develops from the zygote by increasing growth of an apical protrusion and MDV-1 locates at the ‘leading’ extracellular apical pole of this protrusion. In the fully developed ookinete MDV-1 is localised to the posterior pole. In vivo, the knock-out parasites demonstrate a phenotype in which there is a 90% reduction of parasite transmission to oocysts in mosquitoes.

Exposure to developing females induces polyuria, polydipsia, and altered urinary levels of creatinine, 17β-estradiol, and testosterone in adult male mice ( Mus musculus)

Novel male mice can accelerate reproductive maturation in proximal developing females, an effect mediated by the chemistry of the males' urine. Exogenous estrogens can similarly accelerate female sexual development. In Experiment 1, adult male mice were housed across wire grid from either empty compartments or those containing post-weanling females. Proximity of females caused males to urinate more, progressively over days of exposure, with most urination directed towards females' compartments. Male urine collected after 5 days in these conditions was analyzed by enzyme immunoassay for 17β-estradiol, testosterone, and creatinine. Urinary creatinine of isolated males significantly exceeded that of female-exposed males. Unadjusted urinary steroids also trended toward higher levels in isolates, but creatinine-adjusted estradiol and testosterone of female-exposed males significantly exceeded that of isolated males. In Experiment 2, measurement of water consumption indicated significantly greater drinking by female-exposed as opposed to isolated males. In Experiment 3, males were housed in isolation or beside post-weanling intact (sham-operated) females, ovariectomized females, or intact (sham-operated) males. Male water consumption was elevated in all conditions involving social contact. Urinary creatinine was significantly lower in female-exposed males compared to isolated controls, while unadjusted testosterone was significantly lower in males in all social conditions. Again, creatinine-adjusted estradiol in female-exposed males significantly exceeded that of isolates. These data indicate that adult males drink and urinate more, have more dilute urine, and have a higher ratio of estradiol to creatinine when they are near developing females. These dynamics increase females' exposure to urinary steroids and other urinary constituents that can hasten sexual maturity.

Kinesin Superfamily-Associated Protein 3 Is Preferentially Expressed in Glutamatergic Neurons and Contributes to the Excitatory Control of Female Puberty

It was earlier shown that expression of kinesin superfamily-associated protein 3 (KAP3), involved in the neuronal anterograde, microtubule-dependent transport of membrane organelles, increases in the hypothalamus of female rats during the juvenile phase of sexual development. KAP3 mRNA is abundant in the hypothalamus, suggesting that it might be expressed in broadly disseminated neuronal systems controlling neuroendocrine function. The present study identifies one of these systems and provides evidence for an involvement of KAP3 in the excitatory control of female puberty. In situ hybridization and immunohistofluorescence studies revealed that the KAP3 gene is expressed in glutamatergic neurons but not in GABAergic or GnRH neurons. Hypothalamic KAP3 mRNA levels increase during the juvenile period of female prepubertal development, remaining elevated throughout puberty. These changes appear to be, at least in part, estradiol dependent because ovariectomy decreases and estradiol increases KAP3 mRNA abundance. Lowering hypothalamic KAP3 protein levels via intraventricular administration of an antisense oligodeoxynucleotide resulted in reduced release of both glutamate and GnRH from the median eminence and delayed the onset of puberty. The median eminence content of vesicular glutamate transporter 2, a glutamate neuron-selective synaptic protein, and synaptophysin, a synaptic vesicle marker, were also reduced, suggesting that the loss of KAP3 diminishes the anterograde transport of these proteins. Altogether, these results support the view that decreased KAP3 synthesis diminishes GnRH output and delays female sexual development by compromising hypothalamic release of glutamate.

Testis-Specific Novel Transcripts in Chicken: In Situ Localization and Expression Pattern Profiling During Sexual Development1

Tissue-specific novel transcripts expressed during sexual development were examined by RT-PCR, quantitative RT-PCR (qRT-PCR), and in situ hybridization to provide data for chicken genomics. Public databases for transcript data have been constructed with known and unknown sequences of various tissues from different animals. However, the expression patterns and functions of the transcripts are less known. From the The Institute for Genomics Research Gallus gallus library, we examined 291 tentative consensus (TC) sequences that assembled 100% with transcripts by RT-PCR during male and female sexual development from Embryonic Day 6 to 25 wk of age. We found 85 TC sequences that were specific to testicular development; of these, 43 TC sequences were exclusively upregulated in 25-wk-old testis. Another 52 TC sequences were not specific to one tissue, but occurred in the testis and ovary at different developmental ages. Twelve testis-specific TC sequences upregulated in 25-wk-old testis were randomly selected and further examined with qRT-PCR. For precise localization, these 12 testis-specific TC sequences were examined by in situ hybridization with 25-wk-old adult testis. Six TC sequences were strongly expressed in secondary spermatocytes and haploid spermatids until spermatozoa release. Another six TC sequences were differentially expressed in the adluminal compartment of seminiferous tubules. Among the testis-specific TC sequences, TC120901 is a known gene, phospholipase C, zeta (PLCZ1). Our data provide potential insight into gene expression and genomic information on novel transcripts that are important to avian reproduction.

Nineteenth-century Attitudes to Female Sexuality

The nineteenth-century medical attitude to normal female sexuality was cruel, with gynaecologists and psychiatrists leading the way designing operations for the cure of the serious contemporary disorders of masturbation and nymphomania. The gynaecologist, Isaac Baker Brown (1811-1873), and the distinguished endocrinologist, Charles Brown-Séquard (1817-1894) advocated clitoridectomy to prevent the progression to masturbatory melancholia, paralysis, blindness and even death. Even after the public disgrace of Baker Brown in 1866-7, the operation remained respectable and widely used in other parts of Europe. This medical contempt for normal female sexual development was reflected in public and literary attitudes. Or perhaps it led and encouraged public opinion. There is virtually no novel or opera in the last half of the 19th century where the heroine with “a past” survives to the end. H G Well's Ann Veronica and Richard Strauss's Der Rosenkavalier, both of which appeared in 1909, break the mould and are important milestones. In the last 50 years new research into the sociology, psychology and physiology of sexuality has provided an understanding of decreased libido and inadequate sexual response in the form of Female Sexual Disorder (FSD) or Hypoactive Sexual Desire Disorder (HSDD). This is now regarded as a disorder worthy of treatment, either by various forms of counseling or by the use of hormones, particularly estrogens and testosterone.

Freud, Anna, and the Problem of Female Sexuality

Freud has been criticized for his failure to understand and write about femininity in ways that reflect the place of women in society. Indeed, although from the outset he worked with highly intelligent, articulate women analysands, his discussion of female sexuality was convoluted and did not take his clinical observations into account. His views of female sexual development focused on a picture of girls as defective boys. This article suggests that much of Freud's problem in understanding femininity was related to his relationship with his youngest child, daughter Anna (1895–1982), who was a part of psychoanalysis from her earliest childhood through her adult years, when she became his analysand and protégée, and later his guide and support. An admirer of Sophocles' drama Oedipus the King, Freud wrote of Anna as his Antigone. Reviewing Sophocles portrayal of Oedipus and Antigone, we show the parallel between this drama and that in Freud's own life through his own old age in exile from Vienna in London. … a natural predilection usually sees to it that a man tends to spoil his little daughters, while his wife takes her son's part. (S. Freud, 1900, p. 258) Unfortunately we can describe this state of things [the child's sexual theories] only as it affects the male child; the corresponding processes in the little girl are not known to us. (S. Freud, 1923, p. 142)

The Black Man and the Mermaid: Desire and Disruption in the Analytic Relationship

This paper considers the impact of desexualization of the maternal on the development of female sexuality. A “chance encounter” revealing a desire in the female analyst, previously unsuspected, disrupts a female patient's prior sense of homoerotic immersion with the analyst. I argue that a girl's would-be oedipal competition is encased within a patriarchal structuring of sexuality where the mother is rendered solely reproductive and preoedipal, not erotically sexual. I examine the meanings for a patient of internalizing a female figure, her analyst, who is viewed as both maternal and sexual. I suggest that a female sense of genital inadequacy and inferiority may have a component of not being able to link the mother's (and in the transference, the analyst's) use of her genitals with her use of her mind/maternal function. I unfold a thesis regarding maternal desexualization that I believe, given mother–infant symbiosis, has rather extensive applicability, and that can lead to viewing any third party as a “dark” interloper. An earlier version of this paper was given at Division 39 in Philadelphia, Pennsylvania, in 2006. I want to especially thank Will Bellot and Yojana Veeramasuneni, who have each challenged me with their respective contributions.

Oxytocin Facilitates Female Sexual Maturation through a Glia-to-Neuron Signaling Pathway

It has been earlier proposed that oxytocin could play a facilitatory role in the preovulatory LH surge in both rats and humans. We here provide evidence that oxytocin also facilitates sexual maturation in female rats. The administration of an oxytocin antagonist for 6 d to immature female rats decreased GnRH pulse frequency ex vivo and delayed the age at vaginal opening and first estrus. The in vitro reduction in GnRH pulse frequency required chronic blockade of oxytocin receptors, because it was not acutely observed after a single injection of the antagonist. Hypothalamic explants exposed to the antagonist in vitro showed a reduced GnRH pulse frequency and failed to respond to oxytocin with GnRH release. Prostaglandin E(2) (PGE(2)) mimicked the stimulatory effect of oxytocin on GnRH pulse frequency, and inhibition of PG synthesis blocked the effect of oxytocin, suggesting that oxytocin accelerates pulsatile GnRH release via PGE(2). The source of PGE(2) appears to be astrocytes, because oxytocin stimulates PGE(2) release from cultured hypothalamic astrocytes. Moreover, astrocytes express oxytocin receptors, whereas GnRH neurons do not. These results suggest that oxytocin facilitates female sexual development and that this effect is mediated by a mechanism involving glial production of PGE(2).

The role of cofactors in sex steroid action

Sex steroid signalling determines female and male sexual development and maintains the female and male phenotype in adults. Steroids carry out their function by activation of their cognate intracellular receptor, which is a ligand-dependent transcription factor. Steroid receptors function by binding to specific structural elements in the regulatory regions of target genes and by recruitment of cofactors by protein-protein interaction. Cofactors might display enzymatic activities that modify histones and other proteins. Cofactors also include proteins that modulate the chromatin structure and protein complexes that function as bridging factors between the multi-protein complexes. This review focuses mainly on the function of the androgen receptor and its cofactors and their role in androgen insensitivity syndrome.

A Contactin–Receptor‐Like Protein Tyrosine Phosphatase β Complex Mediates Adhesive Communication Between Astroglial Cells and Gonadotrophin‐Releasing Hormone Neurones

Although it is well established that gonadotrophin-releasing hormone (GnRH) neurones and astrocytes maintain an intimate contact throughout development and adult life, the cell-surface molecules that may contribute to this adhesiveness remain largely unknown. In the peripheral nervous system, the glycosylphosphatidyl inositol (GPI)-anchored protein contactin is a cell-surface neuronal protein required for axonal-glial adhesiveness. A glial transmembrane protein recognised by neuronal contactin is receptor-like protein tyrosine phosphatase beta (RPTP beta), a phosphatase with structural similarities to cell adhesion molecules. In the present study, we show that contactin, and its preferred in cis partner Caspr1, are expressed in GnRH neurones. We also show that the RPTP beta mRNA predominantly expressed in hypothalamic astrocytes encodes an RPTP beta isoform (short RPTP beta) that uses its carbonic anhydrase (CAH) extracellular subdomain to interact with neuronal contactin. Immunoreactive contactin is most abundant in GnRH nerve terminals projecting to both the organum vasculosum of the lamina terminalis and median eminence, implying GnRH axons as an important site of contactin-dependent cell adhesiveness. GT1-7 immortalised GnRH neurones adhere to the CAH domain of RPTPbeta, and this adhesiveness is blocked when contactin GPI anchoring is disrupted or contactin binding capacity is immunoneutralised, suggesting that astrocytic RPTP beta interacts with neuronal contactin to mediate glial-GnRH neurone adhesiveness. Because the abundance of short RPTP beta mRNA increases in the female mouse hypothalamus (but not in the cerebral cortex) before puberty, it appears that an increased interaction between GnRH axons and astrocytes mediated by RPTP beta-contactin is a dynamic mechanism of neurone-glia communication during female sexual development.

A Dynamical Systems Approach to the Development and Expression of Female Same-Sex Sexuality.

Researchers have documented substantial variability in the development and expression of same-sex sexuality, especially among women, posing challenges to traditional linear developmental models. In this article, I argue for a new approach to conceptualizing the development and expression of female same-sex sexuality over the life course, based in dynamical systems theory. Dynamical systems models seek to explain how complex patterns emerge, stabilize, change, and restabilize over time. Although originally developed by mathematicians and physicists to model complex physical phenomena in the natural world, they have increasingly been applied to social-behavioral phenomena, ranging from motor development to cognition to language. I demonstrate the utility of this approach for modeling change over time in female same-sex sexuality, reviewing extant published research and also introducing data collected from an ongoing, 10-year longitudinal study of young nonheterosexual women. I provide evidence that female same-sex sexuality demonstrates the emblematic features of a dynamical system: nonlinear change over time, spontaneous emergence of novel forms, and periodic reorganizations and phase transitions within the overall system. I highlight the specific contribution of a dynamical systems perspective for understanding such phenomena and suggest directions for future study.

Pituitary-adrenal axis during human development.

Investigation of early human fetal tissue has helped us elucidate the onset of the activation of the pituitary-adrenal axis during human development. Adrenal steroidogenesis and ACTH secretion from the pituitary starts at 7–8 weeks postconception, providing the rationale for prenatal treatment using dexamethasone offered to fetuses at risk of 21-hydroxylase deficiency (21-OHD). Fluctuation of 3beta-hydroxysteroid dehydrogenase (HSD3B2) in human fetal adrenal has several significant meanings. Its activity during early gestation is essential for inhibiting androgen production in the adrenal and safeguarding normal female sexual development. The enzyme may be reduced during mid-gestation in order to maintain pregnancy and to prevent preterm labor. Its reappearance in late gestation is also crucial for fetal maturation and parturition at term. Late-onset circulation failure observed in extremely low birth weight newborns may be associated with the paucity of HSD3B2 in their adrenals. In fetuses with 21-OHD, a proportion of increased 17alpha-hydroxyprogesterone may be converted to dihydrotestosterone through the backdoor pathway and contribute to the virilization of female fetuses.

Deletion of theTtf1Gene in Differentiated Neurons Disrupts Female Reproduction without Impairing Basal Ganglia Function

Thyroid transcription factor 1 (TTF1) [also known as Nkx2.1 (related to the NK-2 class of homeobox genes) and T/ebp (thyroid-specific enhancer-binding protein)], a homeodomain gene required for basal forebrain morphogenesis, remains expressed in the hypothalamus after birth, suggesting a role in neuroendocrine function. Here, we show an involvement of TTF1 in the control of mammalian puberty and adult reproductive function. Gene expression profiling of the nonhuman primate hypothalamus revealed that TTF1 expression increases at puberty. Mice in which the Ttf1 gene was ablated from differentiated neurons grew normally and had normal basal ganglia/hypothalamic morphology but exhibited delayed puberty, reduced reproductive capacity, and a short reproductive span. These defects were associated with reduced hypothalamic expression of genes required for sexual development and deregulation of a gene involved in restraining puberty. No extrapyramidal impairments associated with basal ganglia dysfunction were apparent. Thus, although TTF1 appears to fulfill only a morphogenic function in the ventral telencephalon, once this function is satisfied in the hypothalamus, TTF1 remains active as part of the transcriptional machinery controlling female sexual development.

In humans, early cortisol biosynthesis provides a mechanism to safeguard female sexual development

In humans, sexual differentiation of the external genitalia is established at 7-12 weeks post conception (wpc). During this period, maintaining the appropriate intrauterine hormone environment is critical. In contrast to other species, this regulation extends to the human fetal adrenal cortex, as evidenced by the virilization that is associated with various forms of congenital adrenal hyperplasia. The mechanism underlying these clinical findings has remained elusive. Here we show that the human fetal adrenal cortex synthesized cortisol much earlier than previously documented, an effect associated with transient expression of the orphan nuclear receptor nerve growth factor IB-like (NGFI-B) and its regulatory target, the steroidogenic enzyme type 2 3beta-hydroxysteroid dehydrogenase (HSD3B2). This cortisol biosynthesis was maximal at 8-9 wpc under the regulation of ACTH. Negative feedback was apparent at the anterior pituitary corticotrophs. ACTH also stimulated the adrenal gland to secrete androstenedione and testosterone. In concert, these data promote a distinctive mechanism for normal human development whereby cortisol production, determined by transient NGFI-B and HSD3B2 expression, provides feedback at the anterior pituitary to modulate androgen biosynthesis and safeguard normal female sexual differentiation.

Additional evidence for the genomic imprinting model of sex determination in the haplodiploid wasp Nasonia vitripennis: isolation of biparental diploid males after X-ray mutagenesis

The primary sex-determining signal in the haplodiploid wasp Nasonia vitripennis is not known. In haplodiploid reproduction, unfertilized eggs typically develop into uniparental haploid males and fertilized eggs into biparental diploid females. Although this reproductive strategy is common to all Hymenoptera, sex-determination is not strictly specified by the number of genome copies inherited. Furthermore, primary sex-determining signals differ among haplodiploid species. In the honeybee, for example, the primary signal is the genotype at a single, polymorphic locus: diploid animals that are homozygous develop into males while heterozygotes develop into females. Sex determination in Nasonia cannot be explained by this mechanism. Various lines of evidence show that the inheritance of a paternal genome is required for female sexual development and suggest a genomic imprinting mechanism involving an imprinted gene, expressed only from a paternal copy, that triggers female sexual development. In this model, haploid or diploid uniparental embryos develop into males due to a maternal imprint that silences this locus. The genomic imprinting model predicts that a loss-of-function mutation in the paternal copy of the imprinted gene would result in male sexual development in a biparental diploid embryo. In support of this model, we have identified rare biparental diploid males in the F1 progeny of X-ray mutagenized haploid males. Although uniparental diploid male progeny of virgin triploid females have been previously described, this is the first report of biparental diploid males in Nasonia. Our work provides a new, independent line of evidence for the genomic imprinting model of Nasonia sex determination.

Effects of peripubertal exposure to triphenyltin on female sexual development of the rat

Triphenyltin (TPT) belongs to the group of organotin compounds which have been shown to affect reproduction in mammals. It is used as a fungicide and antifouling agent and the main source of human exposure is via food. We studied the effects of 2 or 6 mg TPT/kg bw on female sexual development using a modification of the Rodent 20-Day Thyroid/Pubertal Female Assay. Moreover, the effect of TPT before the onset of puberty was investigated. Beginning at postnatal day (PND) 23 female Wistar rats were treated per gavage until either PND 33 or the first estrus after PND 53. A delay in the completion of vaginal opening (VO) was observed in the 6 mg TPT group, while the 2 mg TPT group showed advanced VO. Significantly increased ovarian weights were observed in both treatment groups. Steroid hormone levels and ovarian aromatase activity were affected after exposure to 6 mg TPT/kg bw, while treatment with 2 mg TPT/kg bw resulted in minor changes of these endpoints. We conclude that peripubertal exposure to 6 mg TPT/kg bw, and to a lesser extent to 2 mg TPT/kg bw, affects female sexual development.