Morphology and histology of the male reproductive tract of Caecilia thompsoni (amphibia: Gymnophiona).

We studied the male reproductive tract of individuals of different body sizes of Caecilia thompsoni to describe morphological characteristics in comparison to other Gymnophiona. The reproductive tract consists of paired testes segmented into chains of primary and secondary lobes, sperm ducts that empty to Wolffian ducts, the cloaca that receives the Wolffian ducts and possesses a phallodeum. Müllerian ducts are present and develop into paired glands that empty into the cloacal urodeum. Testicular secondary lobes contain lobules with cysts of the entire germinal cell line, whereas primary lobes, in the terminal ends of the chains, only have spermagonia, Sertoli cells, and connective tissue. The smallest individual examined (21 cm body length) was immature and only possessed a few testicular primary lobes. Once the individuals reach sexual maturity, the morphological characteristics are quite consistent at macroscopic and histological level among males of very different body sizes. The histological features of the Wolffian and Müllerian glands suggest a complementary secretory role between the two ducts. In the cloaca we found the propulsor muscle, venous sinuses, and blind sacs in the phallodeum, which differentiate C. thompsoni from other species of the genus. Despite these slight differences, the general morphological characteristics, both macroscopic and microscopic, of the reproductive tracts of adult males of C. thompsoni follow the pattern known for the reproductively active males of Gymnophiona.

Molecular characteristics and alterations during early development of the human vagina.

Unresolved questions remain concerning the derivation of the vagina with respect to the relative contributions from the Müllerian ducts, the urogenital sinus, and the Wolffian ducts. Recent molecular and cellular studies in rodents have opened up a large gap between the level of understanding of vaginal development in mice and understanding of human vaginal development, which is based on histology. To compare the findings in mice with human vaginal development and to address this gap, we analysed molecular characteristics of the urogenital sinus, Wolffian ducts, and Müllerian ducts in 8-14-week-old human specimens using immunohistochemical methods. The monoclonal antibodies used were directed against cytokeratin (CK) 14, CK19, vimentin, laminin, p63, E-cadherin, caspase-3, Ki67, HOX A13, and BMP-4. The immunohistochemical analysis revealed that, during weeks 8-9, the epithelium of the Müllerian ducts became positive for p63 as p63-positive cells that originated from the sinus epithelium reached the caudal tip of the fused Müllerian ducts via the Wolffian ducts. The lumen of the fused Müllerian ducts was closed by an epithelial plug that contained both vimentin-positive and vimentin-negative cells. Subsequently, the resulting epithelial tube enlarged by proliferation of basal p63-positive cells. The first signs of squamous differentiation were detected during week 14, with the appearance of CK14-positive cells. According to our results, all three components, namely, the urogenital sinus, Wolffian ducts, and Müllerian ducts, interacted during the formation of the human vagina. The sinus epithelium provided p63-positive cells, the Wollfian ducts acted as a 'transporter', and the Müllerian ducts contributed the guiding structure for the vaginal anlagen. Epithelial differentiation began at the end of the period studied and extended in a caudo-cranial direction. The present study is one of the first to provide up-to-date molecular correlates for human vaginal development that can be compared with the results of cell biological studies in rodents.

PAX8 and PAX2 immunostaining facilitates the diagnosis of primary epithelial neoplasms of the male genital tract.

PAX8 and PAX2 are cell-lineage-specific transcription factors that are essential for the development of Wolffian and Müllerian ducts and have recently emerged as specific diagnostic markers for tumors of renal or Müllerian origin. Little is known about their expression in the Wolffian duct-derived human male genital tract. We report our findings of PAX8 and PAX2 expression in the epithelium of the normal male genital tract and in epithelial tumors derived therefrom using immunohistochemistry (IHC). We found that PAX8 and PAX2 were expressed in the epithelium of the male genital tract from the rete testis to the ejaculatory duct. Rare glands in the prostatic central zone, a tissue of purported Wolffian duct origin, were focally positive for PAX2, but no PAX8 was detected in this area, a finding that may warrant further study. We found diffuse expression of PAX8 and PAX2 in 1 case each of serous cystadenoma of the epididymis, carcinoma of the rete testis, Wolffian adnexal tumor of the seminal vesicle, and endometrioid carcinoma of the seminal vesicle. Neither PAX8 nor PAX2 was detected in the seminiferous tubules and interstitium of the normal testis, nor in Leydig cell tumors (n=6), Sertoli cell tumors (n=2), or 48 of 49 germ cell tumors. One pediatric yolk sac tumor showed focal and weak staining for PAX8. Tumors of mesothelial origin, that is, adenomatoid tumors (n=3) and peritoneal malignant mesotheliomas (n=37) in men, were negative for PAX2 and PAX8. Neither PAX2 nor PAX8 was present in other areas of the prostate. Expression of PAX8 and PAX2 in these primary epithelial neoplasms of the male genital tract is due to their histogenetic relationship with Wolffian or Müllerian ducts. PAX8 and PAX2 IHC may facilitate the diagnosis of these tumors and should be included in the differential diagnostic IHC panel.

Selective estrogen receptor alpha activation disrupts sex organ differentiation and induces expression of vitellogenin II and very low-density apolipoprotein II in Japanese quail embryos.

The Japanese quail (Coturnix japonica) is a widely used model species for studying the roles of steroid hormones in avian sex differentiation. The aim of the present study was to elucidate the significance of estrogen receptors alpha and beta (ERalpha and ERbeta) in normal sex differentiation of the reproductive organs in the Japanese quail and in xenoestrogen-induced disruption of reproductive organ differentiation. Real-time PCR indicated that ERalpha (ESR1) mRNA is expressed in both right and left gonads and Müllerian ducts (MDs) in both sexes during early morphological differentiation. ERbeta (ESR2) transcripts were also detected in gonads and MDs, but at very low levels. Both receptor subtypes were expressed in the liver and may therefore mediate the expression of estrogen-regulated egg-yolk proteins. Aromatase mRNA was expressed at much higher levels in female than male gonads as early as embryonic day 5, indicating early sex differences in estrogen synthesis. Treatment with the ERalpha-selective agonist propyl pyrazole triol showed that frequently reported xenoestrogen effects, such as ovotestis formation, abnormal MD development, and hepatic expression of egg-yolk proteins, were induced by selective activation of ERalpha. Taken together, our results suggest that activation of ERalpha is crucial for estrogen-dependent sex differentiation of the reproductive organs and that ERalpha mediates xenoestrogen-induced toxicity during reproductive development in birds.

Do we need a new classification for radical hysterectomy? Insights in surgical anatomy and local tumor spread from human embryology.

OBJECTIVE: Current surgical treatment of cervical carcinoma is based on the assumption of undirected intra- and transcervical local tumor propagation and is executed by tailored excision of the paracervical tissues. We have recently demonstrated that cervical carcinoma spreads for extended phases during its malignant progression within the permissive compartment of the Müllerian morphogenetic unit (Lancet Oncol 2005;6:751-56) and proposed Müllerian compartment resection as the new principle for surgical treatment of cervical cancer. Do we need a new classification of radical hysterectomy? METHODS: The therapeutic index of the surgical treatment of cervical carcinoma FIGO stages IB1-IIB by extirpation of the Müllerian compartment through total mesometrial resection (TMMR) without adjuvant radiation is evaluated by an ongoing controlled prospective trial at the University of Leipzig. RESULTS: From 7/1998 to 12/2006, 163 patients with cervical carcinoma, FIGO stages IB1 (n=94), IB2 (n=21), IIA (n=14) and IIB (n=34) have been treated with TMMR and nerve-sparing therapeutic lymph node dissection. Twenty-five patients received (neo)adjuvant chemotherapy. No patient underwent adjuvant radiotherapy although 95 patients (58%) would have needed this additional modality in case of conventional radical hysterectomy because of their high-risk histopathological tumor features. At a median follow-up time of 45 months (3-104 months), recurrence-free and disease-specific overall survival is 93% and 96%. Maximum treatment-related morbidity according to the Franco-Italian score has been grade 2 in 12 patients (8%). CONCLUSIONS: The developmental view of local tumor spread and surgical anatomy holds a great promise for improving the therapeutic index of surgical cervical cancer therapy and challenges both the classification of radical hysterectomy based on tailored paracervical resection and the indication for adjuvant radiation.

Prenatal development of the bovine oviduct.

In this study the development of the bovine Fallopian tube was investigated using light microscopic methods. Formation and differentiation of the Müllerian duct were studied in mesonephroi of 16 embryos and fetuses with a crown-rump lengths (CRL) of 0.9-8.4 cm. The funnel field, the rostral beginning of the Müllerian duct was first observed at a CRL of 0.9 cm. It appears as a thickening of the mesothelium on the craniolateral side of the mesonephros. During later development the Müllerian duct emerges by caudal outgrowth from the funnel field. Formation of a common basal lamina surrounding the caudal tips of Müllerian and Wolffian ducts could be observed at all stages up to CRL of 2.7 cm. The mesothelium and the epithelium of the Wolffian duct adjacent to the Müllerian duct showed a modification of epithelium height in all examined stages. Probably the Wolffian duct influences the growth of Müllerian duct by epithelio-mesenchymal interactions. Fetuses from a CRL of 12.0 to 94.0 cm were used for investigation of the prenatal differentiation of the oviductal mucosa. Folding of the oviductal mucosa started at a CRL of 29.0 cm and continued until birth. Individual primary, secondary and tertiary folds are formed in special proliferation zones and epithelium-folding buds. The cellular differentiation of the oviductal epithelium involves the formation of ciliated and secretory cells during different times of prenatal development. Ciliogenesis was first detected at a CRL of 33.0 cm. Active secretory cells could be observed in the oviductal epithelium from a CRL of 64.0 cm onwards.

Helper function of the Wolffian ducts and role of androgens in the development of the vagina.

The development of a vagina as a separate outlet of the birth canal evolves at the transition of egg laying species to eutherian mammals. The derivation of the vagina from the Wolffian and Müllerian ducts and the contribution of the urogenital sinus are still open questions. Here experiments with the complete androgen receptor defect in the testicular feminisation (Tfm) mouse are reported which show that the vagina is formed by caudal migration of Wolffian and Müllerian ducts. The cranial ends of the Wolffian ducts successively regress while the Müllerian ducts fuse to form the vagina. Immunohistochemistry of the androgen receptor reveals that the caudal ends of the Wolffian ducts remain in the indifferent stage and therefore have been mistaken as sinuvaginal bulbs. The Wolffian ducts do not contribute to the vagina itself but have a helper function during downward movement of the vaginal bud in the female. In the male the caudal ends serve as androgen operated switch for the negative control of vaginal development. The results indicate that the rudimentary vagina in the complete androgen insensitivity syndrome (CAIS) corresponds to non obliterated caudal ends of the Müllerian ducts. Selective atresia of the vagina in the MRKH (Mayer-Rokitansky-Kuster-Hauser) syndrome may be explained by the failure of Wolffian and Müllerian ducts to descend caudally.

The Müllerian duct: recent insights into its development and regression.

Several recent publications have contributed to our understanding of the processes involved in development of the Müllerian ducts in both sexes and regression of these structures in male embryos. Additionally, new insights in the regulation of the anti-Müllerian hormone (AMH) signaling pathway, the pathway, which mediates the male specific degeneration of Müllerian ducts, have been gained. It has become clear that the Müllerian duct is formed by invagination of the coelomic epithelium and elongates primarily by proliferation. Later on cells of the coelomic epithelium perform epithelial to mesenchymal transition and move around the epithelium of the Müllerian duct to induce degeneration of this structure in male embryos. Besides AMH and its specific type II receptor AMHR2 two different type I receptors as well as different SMAD family members have been shown to be involved in the AMH signaling cascade. Other factors including WT1, WNT7a, beta-catenin and MMP2 act upstream and downstream of AMH signaling. Here we try to draw an overall picture of Müllerian duct formation and regression by integrating the recent literature in the field.

Müllerian inhibiting substance regulates its receptor/SMAD signaling and causes mesenchymal transition of the coelomic epithelial cells early in Müllerian duct regression.

Examination of Müllerian inhibiting substance (MIS) signaling in the rat in vivo and in vitro revealed novel developmental stage- and tissue-specific events that contributed to a window of MIS responsiveness in Müllerian duct regression. The MIS type II receptor (MISRII)-expressing cells are initially present in the coelomic epithelium of both male and female urogenital ridges, and then migrate into the mesenchyme surrounding the male Müllerian duct under the influence of MIS. Expression of the genes encoding MIS type I receptors, Alk2 and Alk3, is also spatiotemporally controlled; Alk2 expression appears earlier and increases predominantly in the coelomic epithelium, whereas Alk3 expression appears later and is restricted to the mesenchyme, suggesting sequential roles in Müllerian duct regression. MIS induces expression of Alk2, Alk3 and Smad8, but downregulates Smad5 in the urogenital ridge. Alk2-specific small interfering RNA (siRNA) blocks both the transition of MISRII expression from the coelomic epithelium to the mesenchyme and Müllerian duct regression in organ culture. Müllerian duct regression can also be inhibited or accelerated by siRNA targeting Smad8 and Smad5, respectively. Thus, the early action of MIS is to initiate an epithelial-to-mesenchymal transition of MISRII-expressing cells and to specify the components of the receptor/SMAD signaling pathway by differentially regulating their expression.

Sexually dimorphic expression of secreted frizzled-related (SFRP) genes in the developing mouse Müllerian duct.

In developing male embryos, the female reproductive tract primordia (Müllerian ducts) regress due to the production of testicular anti-Müllerian hormone (AMH). Because of the association between secreted frizzled-related proteins (SFRPs) and apoptosis, their reported developmental expression patterns and the role of WNT signaling in female reproductive tract development, we examined expression of Sfrp2 and Sfrp5 during development of the Müllerian duct in male (XY) and female (XX) mouse embryos. We show that expression of both Sfrp2 and Sfrp5 is dynamic and sexually dimorphic. In addition, the male-specific expression observed for both genes prior to the onset of regression is absent in mutant male embryos that fail to undergo Müllerian duct regression. We identified ENU-induced point mutations in Sfrp5 and Sfrp2 that are predicted to severely disrupt the function of these genes. Male embryos and adults homozygous for these mutations, both individually and in combination, are viable and apparently fertile with no overt abnormalities of reproductive tract development.

Experimental contributions to the study of the embryology of the vagina.

BACKGROUND: Acién's hypothesis, deduced from patients with malformations of the female genital tract, especially those with renal agenesis and ipsilateral blind hemivagina, affirms the embryology of the human vagina as deriving from the Wolffian ducts and the Müllerian tubercle and could explain the embryological origin of all the female genital malformations reported. In this study, we investigated the hypothesis in rats. METHODS: Twenty-five pregnant rats were used to analyse female embryos (64) from day 15 (stage indifferent) to day 20 postcoitum (vagina completely formed). We performed transverse and longitudinal sections of embryos, haematoxylin-eosin tinction and immunohistochemical staining using markers specific to Wolffian derivatives. We also analysed the presence of these markers in the vagina of four adult rats. RESULTS: The Müller ducts converge until they fuse into one tube, but caudally they diverge and finally they fuse with the 'urogenital sinus bulbs' that are actually the distal portion of the Wolffian ducts according to the immunohistochemical marking with GZ1 and GZ2. The Müllerian tubercle is observed between those elements. Then, the immunohistochemical staining can be seen all along the completely formed vagina, which is also observed in the vagina of the adult rat. CONCLUSION: We prove the participation of Müller tubercle and Wolffian ducts in the formation of the vagina in rats, so we confirm experimentally Acién's hypothesis about the human vagina embryology.

Association between the mesenchymal compartment of uterovaginal organogenesis and local tumour spread in stage IB-IIB cervical carcinoma: a prospective study.

BACKGROUND: Macroscopic, microscopic, and occult local tumour spread might be restricted to a permissive territory related to the morphogenesis of the tissue or organ from which the tumour originates. We aimed to define such a morphogenetic unit in Müllerian development, and to assess the role of total mesometrial resection in the treatment of patients with stage IB-IIB cervical carcinoma. METHODS: We analysed uterovaginal development in serial sections of female human embryos and fetuses, and defined the distal Müllerian morphogenetic unit from the Müllerian mesenchyme. We assessed prospectively the histopathological and clinical findings from patients who underwent total mesometrial resection-modified surgery for stage IB-IIB cervical carcinoma that aims to remove the uterus, proximal vagina, and extracervical mesenchyme within the borders of the distal Müllerian morphogenetic unit. FINDINGS: The spatial extension of the Müllerian mesenchyme, its vascularisation, and its innervation during early uterovaginal organogenesis determine a tissue territory that can be followed during fetal development and identified in women as a morphogenetic unit. 105 of 106 patients who had total mesometrial resection, 63 of whom were classed as high risk, had microscopically tumour-free resection margins (ie, R0). 48 (96%) of 50 patients had pelvic recurrence-free survival at 3 years (95% CI 92-100) without adjuvant radiotherapy. INTERPRETATION: Radical en-bloc resection of a topographically defined anatomical territory derived from common precursor tissue leads to local tumour control, preservation of autonomic nerves, and a reduced need for adjuvant radiotherapy.

The prostatic utricle is not a Müllerian duct remnant: immunohistochemical evidence for a distinct urogenital sinus origin.

PURPOSE: The embryological origin of the utricle is thought to be a remnant of the fused caudal ends of the müllerian ducts (MDs). Others propose that the urogenital sinus (UGS) contributes either partially or totally to the development of this structure. Using immunohistochemical probes, we provide strong evidence that the utricle is of UGS origin only. MATERIALS AND METHODS: Human fetal prostates, gestational ages 9 to 24 weeks, were serially cross-sectioned. Representative sections were stained with antibodies to p63 (basal cell marker), vimentin (mesoderm marker), uroplakins (marker for urothelium) Pax-2 (expressed in ductal and mesenchyme of urogenital system including the MDs and wolffian ducts) and Ki67 (proliferation). Apoptosis was detected with the TUNEL assay. RESULTS: By 9 weeks there was weak expression of p63 in the basal layer of the UGS. At 11 weeks there was increased staining of p63 in the UGS and some p63 staining of the fused MDs, which expressed Pax-2 at this time. At 14 to 15 weeks as the MDs were undergoing apoptosis, there was an ingrowth of uroplakin-expressing UGS epithelium into the periurethral stroma, which formed a plate of p63 positive cells just beneath the UGS that was Ki67 positive. The remaining caudal MD epithelium was p63 negative and expressed vimentin and Pax-2. By 17 weeks the plate of p63 positive cells elongated forming the utricle that remained p63 positive but Pax-2 and vimentin negative. CONCLUSIONS: We show that the utricle forms as an ingrowth of specialized cells from the dorsal wall of the UGS as the caudal MDs regress.

The broad ligament: a review of its anatomy and development in different species and hormonal environments.

The broad ligament is a double fold of peritoneum forming a mesentery for the human female genital tract. We investigated the anatomy of the broad ligament in different species and its hormonal regulation to determine if it had a role in gonadal positioning. The medical and veterinary literature was reviewed for descriptions of broad ligament anatomy and development. In addition, four adult female rats were dissected to compare the macroscopic anatomy of the broad ligament with any homologous structures in the male (n = 2). Detailed review was made of human males with persistent Müllerian duct syndrome (PMDS) and of bovine freemartin calves to determine the effect of abnormal hormonal environments on broad ligament development. Human and veterinary texts show variable broad ligament development between species, most being consistent with the size and shape of the uterus and uterine tubes. The broad ligament in adult female rats is a simple peritoneal fold and is homologous with the mesentery of the testis and vas deferens in males. Patients with PMDS and bovine freemartins have a broad ligament with intermediate anatomy. In PMDS the broad ligament is elongated and narrow, and not attached to the pelvic wall. The broad ligament is the mesentery of the genital ducts, and its anatomy varies with the degree of Müllerian duct fusion. The absence of a human male homologue is unusual, as the genital mesentery persists in male rodents. Apparent lack of a male homologue in the human may relate to obliteration of the processus vaginalis. The variable development of the broad ligament in pathological conditions is consistent with a role for steroid hormones in its development.

Endosalpingiosis: un dilema diagnóstico / Endosalpingiosis: a diagnostic dilemma

El término endosalpingiosis define la proliferación de epitelio tubárico en cualquier localización ectópica. Estas lesiones se consideran una curiosidad histológica debido a su poca frecuencia, aunque se han encontrado reiteradamente en especímenes de biopsias de casos de adenocarcinoma ovárico y endometrial. Se documenta un caso de Adenocarcinoma cervical con hallazgos de endosalpingiosis en ganglio pélvico y endometriosis cervical. Debido a lo inusual de esta patología y de que su diagnóstico diferencial con ADC metastásico es un reto para los patólogos se presenta y se hace revisión de la literatura

Androgens and masculinization of genitalia in the spotted hyaena (Crocuta crocuta). 1. Urogenital morphology and placental androgen production during fetal life.

According to common understanding of sexual differentiation, the formation and development of a penile clitoris in female spotted hyaenas requires the presence of naturally circulating androgens during fetal life. The purpose of the present study was to determine potential source(s) of such fetal androgens by investigating the timing of urogenital development and placental production of androgen during early and mid-gestation. Fetuses determined to be female by molecular techniques (lack of SRY gene) at days 33 and 48 of gestation had undifferentiated gonads, but the clitoris was already 'masculinized' and was generally similar to the phallus of a 50-day-old male fetus. Wolffian and Müllerian ducts terminated at the urogenital sinus in both sexes and a urethra was present along the entire length of the clitoris and penis. The adrenal gland was large and histologically differentiated at 33 days. Steroid gradients across the uterus (a drop in delta 4-androstenedione, with increases in oestrogen and androgen), and high androstenedione in ovarian veins indicated that ovarian androstenedione was metabolized and secreted as testosterone by the placenta throughout gestation. In vitro, whole or homogenized placentae at days 48 and 58 of gestation (110 days total) metabolized radiolabelled androstenedione into testosterone and oestradiol; the specific enzymatic activity of early placental tissues was higher than at later stages. A human placental homogenate had higher aromatase activity but did not produce testosterone unless aromatase was inhibited. Infusion of labelled androstenedione into the uterine arteries of hyaenas demonstrated the conversion of this substrate into testosterone and oestradiol and their secretion into the fetal circulation. Evidently, androgen is produced by the placenta and secreted into the fetal circulation from early in pregnancy when masculinization is first evident, before differentiation of the fetal ovary.

Localization of Bcl-2 in the human fetal müllerian tract.

OBJECTIVE: To determine if apoptosis is involved in development of the human fetal mullerian tract and regression of the uterine septum and to localize Bcl-2. a protein involved with regulating apoptosis. DESIGN: Descriptive controlled study. SETTING: Tertiary academic medical center. PATIENT(S): Eight human fetal uteri from 12 to 21 weeks' gestation. INTERVENTION(S): Immunohistochemistry using a monoclonal antibody for Bcl-2. MAIN OUTCOME MEASURE(S): Immunostaining. RESULTS: Bcl-2 was localized in endometrial cells, tubal muscularis and epithelium, and myometrial edges. It was absent from the septum of 4 uteri. CONCLUSIONS: The presence of Bcl-2 suggests that development of the human fetal müllerian tract involves apoptosis. Bcl-2 may protect the fetal endometrium from apoptosis as it continues to grow. The superior, inferior, and lateral myometrium as well as the tubal epithelium and muscularis also may represent active growth zones that are protected from apoptosis. The notable absence of staining for Bcl-2 in the embryonal uterine septum may indicate lack of protection from apoptosis in this area. This finding supports our hypothesis that apoptosis may be a mechanism by which the uterine septum regresses.

Interactions of gonadal steroids and pesticides (DDT, DDE) on gonaduct growth in larval tiger salamanders, Ambystoma tigrinum.

In view of the current worldwide decline in amphibian populations, exploratory studies are needed to assess the potential for environmental contaminants to act as endocrine disrupters of the amphibian reproductive system. The present study investigated the effects of DDT dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) on the development of amphibian gonaducts. Larval male and female tiger salamanders (Ambystoma tigrinum), with immature gonads, were immersed in a sublethal solution of p,p'-DDE or technical-grade DDT (80% p,p'-DDT and 20% o,p'-DDT). Additionally, larvae were injected with the steroid hormones estradiol or dihydrotestosterone (DHT). Morphometrics were used to analyze the effects and interactions of steroid and pesticide treatments on larval gonaducts. Estradiol and DHT stimulated cell proliferation and hypertrophy of the müllerian duct epithelium in both sexes. Wolffian duct epithelium, however, was stimulated only by DHT treatment. The pesticide DDT antagonized the estrogenic actions of the steroid treatments, and p,p'-DDE acted as an estrogen on the müllerian ducts of females only. The müllerian ducts of males, and the wolffian ducts of both sexes, were unaffected by DDT or DDE alone. While confirming the previously reported estrogenic actions of estradiol and DHT on urodelean gonaducts, the results contradict the expected estrogenic actions of DDT and antiandrogenic actions of p,p'-DDE. Instead, in A. tigrinum, technical-grade DDT had an antiestrogenic action and p,p'-DDE an estrogenic action.

Sexual differentiation of the urogenital system of the fetal and neonatal tammar wallaby, Macropus eugenii.

In male tammar wallabies, the scrotum is the first organ to become sexually differentiated, 4-5 days before birth (day 22 of gestation). This is followed by enlargement of the gubernaculum and processus vaginalis one day before birth. However the indifferent gonad does not show any signs of testicular cord formation or androgen production until later, at around the time of birth; this is more pronounced at 2 days post-partum (p.p.), when the testis takes on a characteristic rounded appearance. Primordial germ cells proliferate throughout the testis at this time, although the testis does not become significantly heavier than the ovary until around 80 days p.p.. In females, the appearance of the mammary glands is the first sign of sexual differentiation 4-5 days before birth. The indifferent gonad first shows signs of developing an ovarian cortex and medulla 7 days after birth. The migrating germ cells are confined to the cortex, and first start to enter meiosis about 25 days after birth. The Wolffian (mesonephric) ducts are patent to the urogenital sinus in fetuses at day 21 of gestation. In the female they have started to regress by 10 days p.p. and only rudiments remain by day 25 p.p.. The Müllerian (paramesonephric) ducts develop adjacent to the cranial pole of the mesonephros at about day 25 of gestation and grow caudally to meet the urogenital sinus between days 2 and 7 p.p.. The Müllerian duct of the female develops a prominent ostium abdominale by day 9 p.p., but this structure has completely regressed in males by day 13 p.p.. The testis and ovary both migrate caudally, together with the adjacent mesonephros, at about day 10 p.p.. The ovaries remain around the level of lumbar vertebra 4 after about day 7 p.p., while the testes continue to descend. The testes enter the internal inguinal ring at about day 25 p.p., about the time that prostatic buds first appear in the urogenital sinus, and are in the inguinal canal from days 25 to 36 p.p.. They enter the scrotum at around day 36 p.p., and testicular descent is complete by days 65-72 p.p.. Melanin develops in the tunica vaginalis 72 days after birth. The overall development of the urogenital system in this marsupial is similar to that of eutherians but the sequence of events differs, with some aspects of genital differentiation preceding gonadal differentiation, apparently because they are directly controlled by X-linked genes, rather than indirectly controlled by gonadal steroids.

DiI analysis of cell migration during müllerian duct regression.

In most male vertebrates, the müllerian ducts, which are the embryonic oviducts, regress completely during embryogenesis or shortly thereafter. Müllerian duct regression is caused by the testicular hormone müllerian inhibiting substance. While the exact mechanism of müllerian duct regression is not well understood, it is theorized to involve active migration of at least some of the ductal epithelial cells following breakdown of the basement membrane, possibly through an interaction between the epithelial cells and the surrounding extracellular matrix. The purpose of the present study was (1) to confirm that müllerian duct regression is characterized by epithelial cell migration and (2) to determine the destination of these cells. The ductal epithelium of male alligator embryos was labelled with the fluorescent cell marker DiI and then allowed to undergo regression in vitro. DiI-labeled müllerian ducts from female embryos served as controls. An in vivo experiment also was performed in which the müllerian ducts of female hatchlings were injected with DiI prior to each female receiving a testicular implant from a male hatchling. Control females received a kidney implant instead. In both the in vitro and the in vivo experiments, DiI-labeled epithelial cells were observed migrating out from the duct during regression. In the in vitro experiment in which regression proceeded more rapidly, epithelial cells entered the mesonephric kidneys and were incorporated into the nephric tubule epithelium. No regression or cell migration was observed in the control müllerian ducts.