Androgens increase survival of adult-born neurons in the dentate gyrus by an androgen receptor-dependent mechanism in male rats.

Gonadal steroids are potent regulators of adult neurogenesis. We previously reported that androgens, such as testosterone (T) and dihydrotestosterone (DHT), but not estradiol, increased the survival of new neurons in the dentate gyrus of the male rat. These results suggest androgens regulate hippocampal neurogenesis via the androgen receptor (AR). To test this supposition, we examined the role of ARs in hippocampal neurogenesis using 2 different approaches. In experiment 1, we examined neurogenesis in male rats insensitive to androgens due to a naturally occurring mutation in the gene encoding the AR (termed testicular feminization mutation) compared with wild-type males. In experiment 2, we injected the AR antagonist, flutamide, into castrated male rats and compared neurogenesis levels in the dentate gyrus of DHT and oil-treated controls. In experiment 1, chronic T increased hippocampal neurogenesis in wild-type males but not in androgen-insensitive testicular feminization mutation males. In experiment 2, DHT increased hippocampal neurogenesis via cell survival, an effect that was blocked by concurrent treatment with flutamide. DHT, however, did not affect cell proliferation. Interestingly, cells expressing doublecortin, a marker of immature neurons, did not colabel with ARs in the dentate gyrus, but ARs were robustly expressed in other regions of the hippocampus. Together these studies provide complementary evidence that androgens regulate adult neurogenesis in the hippocampus via the AR but at a site other than the dentate gyrus. Understanding where in the brain androgens act to increase the survival of new neurons in the adult brain may have implications for neurodegenerative disorders.

'Idiopathic' partial androgen insensitivity syndrome in 28 newborn and infant males: impact of prenatal exposure to environmental endocrine disruptor chemicals?

OBJECTIVE: 46,XY disorders of sex differentiation (46,XY DSD) can be due to a testis determination defect, an androgen biosynthesis defect, or androgen resistance (complete or partial androgen insensitivity syndrome (PAIS), or 5α reductase deficiency). We aimed to evaluate the impact of a prenatal contamination by environmental xenoestrogens in 'idiopathic' PAIS-like phenotype. SUBJECTS: We investigated 28 newborn/infant males with 46,XY DSD, normal androgen production, and no androgen receptor or steroid-5αR type II enzyme (SRD5A2) gene mutations. METHODS: To exclude other genetic defects, we sequenced the steroidogenic factor 1 (SF1) and mastermind-like domain-containing 1 (MAMLD1) genes, which were recently found to be associated with the PAIS-like phenotype. Parents were interviewed about their environmental/occupational exposure to endocrine disrupting chemicals (EDCs) before/during the patients' fetal life. Total estrogenic bioactivity of patient serum was analyzed by ultrasensitive bioassay. RESULTS: All the patients had normal SF1 sequence and one patient showed a double polymorphism of MAMLD1. Eleven (39.3%) of the 28 patients had reported parental fetal exposure to EDCs. The mean estrogenic bioactivity in these 11 patients with fetal EDC exposure (6.65 ± 8.07 pg/ml) versus 17 cases without contamination (1.27 ± 0.34 pg/ml) and controls (1.06 ± 0.44 pg/ml; P<0.05) was elevated. CONCLUSIONS: Our results indicate that the 'idiopathic' PAIS-like phenotype may in some cases be related to EDC contamination during fetal life.

Hidden in plain sight: the mammary line in males may be the missing link regulating inguinoscrotal testicular descent.

BACKGROUND/PURPOSE: Inguinoscrotal testicular descent is controlled by androgens and the genitofemoral nerve, but the trigger for what makes the gubernaculum become a migratory organ like a limb bud remains unknown. Recent observations in the flutamide-treated rat suggested a link with the mammary line. We aimed, therefore, to reassess histologic anatomy in 2 different rodent models of androgen blockade, the testicular feminisation mouse (TFM) and the flutamide-treated rat. METHODS: Neonatal TFM mice and fetal and neonatal rats after pretreatment of dams with an antiandrogen, flutamide (75 mg/kg; sunflower oil; days 16-19), were prepared for histologic analysis of the inguinal region and compared with fetal and neonatal controls. RESULTS: Fetal control rats (E15.5 days) showed a mammary bud just outside the future inguinal canal adjacent to the gubernaculum. Neonatal TFM mice showed persistence of the inguinal breast bud supplied by the genitofemoral nerve. Flutamide-treated rats (D2) showed the gubernaculum surrounded by a persisting breast bud. CONCLUSIONS: The inguinal mammary line is adjacent to the gubernaculum in fetal rodents, and after androgen blockade, the gubernaculum becomes connected to the breast. The male mammary line, which is hidden in plain sight outside the inguinal canal, is made visible by androgen blockade. It may be the missing link in testicular descent, regulating gubernacular migration.

Fingers as a marker of prenatal androgen exposure.

Interest in biological substrates of sex-related variations in psychological and physiological characteristics has led to a search for biomarkers of prenatal hormone exposure that can be measured postnatally. There has been particular interest in digit ratio, the relative lengths of the second and fourth fingers (2D:4D), but its validity as a measure of prenatal androgen has not been established. We report the strongest evaluation of the value of 2D:4D as a biomarker for early androgen exposure. Individuals with 46,XY karyotype but no effective prenatal androgen exposure due to complete androgen insensitivity syndrome had digit ratios that were feminized: they were higher than those of typical men and similar to those of typical women. Nevertheless, the effect was modest in size, and there was considerable within-group variability and between-group overlap, indicating that digit ratio is not a good marker of individual differences in prenatal androgen exposure.

The avian egg as a test system for endocrine disrupters: effects of diethylstilbestrol and ethynylestradiol on sex organ development.

Many environmental contaminants are known or suspected to interfere with hormonal function in animals. In vivo test methods to detect and characterize chemicals that disrupt the endocrine system are therefore urgently needed. In this study, we assessed the usefulness of abnormalities of the reproductive organs as test endpoints for estrogenic activity of xenobiotics in Japanese quail embryos. Two synthetic estrogens, diethylstilbestrol (DES) and ethynylestradiol (EE2), were injected into the yolks of embryonated eggs. At a dose as low as 2 ng EE2/g egg, all male embryos became feminized, containing ovary-like tissue in the left testis. The extent of feminization of the testes was determined by measuring the relative area of the ovary-like component. Persistent Müllerian ducts (oviducts) in male embryos, and malformations of the Müllerian ducts in females occurred at 2 ng EE2/g egg and higher doses. DES was approximately one-third to one-tenth as potent as EE2. The morphological changes studied were dose-dependent, indicating that they are useful as test endpoints for estrogenic activity. Feminization of the left testis in males proved to be the most sensitive endpoint. We propose the quail egg as a simple in vivo test system for estrogenic compounds.

Action of testosterone on the estradiol-induced feminization of the male chick embryo.

The early treatment of male chick embryos with estradiol induces the feminization of their sex tract, i.e. both their gonads and müllerian tract exhibit female features. The additional treatment of estrogenized male embryos with testosterone propionate antagonizes the effects of estradiol on both gonads and müllerian ducts. Our data give further support to the view that testosterone and estrogens act respectively as agonist and antagonist modulators of the secretion of the anti-müllerian hormone.

Disturbed testicular descent in the rat after prenatal exposure to the antiandrogen flutamide.

Exposure of rats in utero to the anti-androgen flutamide resulted in feminization of the external genitalia that was noticeable at birth. This exposure also resulted in a high degree of cryptorchidism during adulthood. In most affected animals, testes were lying in 'ovary position' close to the caudal pole of the ipsilateral kidney. Cryptorchidism occurred despite normal prenatal development of the gubernacular cones and the transformation of these structures, postnatally, into muscular cremaster sacs. Inter- and intralitter variation in the response to prenatal exposure to flutamide was observed as well as intra-individual variation. Cryptorchidism frequently occurred unilaterally with right side cryptorchidism predominating. Cryptorchidism occurred in association with marked suppression of the growth of the ipsilateral epididymis and deferent duct. The possibility is considered that the poor development or absence of these structures contributes to cryptorchidism. Intra-individual variation supports the concept of the local nature of the influence of testis hormones in stabilization and further differentiation of the ipsilateral Wolffian duct derivatives. Cryptorchidism was enhanced when rats were treated postnatally with testosterone or oestradiol. The effect of testosterone was unexpected in view of the generally held hypothesis that androgens enhance testis descent. The effect of oestradiol was as expected: other animal models have been described in which induction of cryptorchidism by oestradiol occurs. Additional treatment with oestradiol caused further suppression of growth of the epididymis and deferent duct. The response to prenatal exposure to flutamide was not altered by further injections of flutamide postnatally. Such injections were without effect in males not exposed to flutamide prenatally except for minor, but statistically significant, testicular enlargement during adulthood. A model is thus presented that describes cryptorchidism as an endogenous developmental disorder.

[Ingestion of diethylstilbestrol during pregnancy. Its responsibility in the testicular feminization syndrome]. / Prise de diéthylstilbestrol pendant la grossesse. Sa responsabilité dans le syndrome du testicule féminisant.

We report the cases of two women who had testicular feminization with remnants of Müllerian ducts and whose mothers had received diethylstilbestrol (DES) during the first trimester of pregnancy. At laparotomy, masses were removed which had the microscopic appearances of testes and Fallopian tubes, and were confirmed as such at histology. There were three possible explanations for these genetic abnormalities: deficient antimüllerian hormone (AMH) secretion (or lack of sensitivity of Müllerian ducts to AMH); early testicular descent with regression of Müllerian ducts beyond the efficacy margin of AMH; exposure to DES in utero during the first trimester of pregnancy. In these two women, the most likely explanation seems to be the last one.

[Feminization of embryonic chicken testicle by diethylstilbestrol and antagonistic action of tamoxifen]. / Féminisation du testicule embryonnaire de poulet par le diéthylstilboestrol et action antagoniste du tamoxifène.

The question was asked whether the feminization of the chick embryo testis by diethylstilboestrol involves oestrogen secretion. The left gonads of male embryos treated with diethylstilboestrol at the stage of 5 days of incubation were removed at the stage of 17 days and cultured in vitro in the presence of radiolabelled androstenedione, dehydroepiandrosterone, progesterone or sodium acetate. Radiochromatography and repeated crystallizations to constant specific activity were used to demonstrate the formation of oestrone and oestradiol. The results show that oestrogen synthesis takes place from any of the 4 precursors. The normal testis does not produce oestrogens or produces them only in small amounts. Thus, it can be concluded that diethylstilboestrol induces oestrogen synthesis in the chick embryo testis. In a second part of the work, it is shown that tamoxifen antagonizes the feminizing action of diethylstilboestrol on the testes, both at the morphological and biochemical levels.

DDT-induced feminization of gull embryos.

Injection of DDT [1, 1, 1-trichloro-2,2-bis(p-chlorophenyl)ethane] into gull eggs at concentrations comparable to those found in contaminated seabird eggs in 1970 induces abnormal development of ovarian tissue and oviducts in male embryos. Developmental feminization of males is associated with inability to breed as adults and may explain the highly skewed sex ratio and reduced number of male gulls breeding on Santa Barbara Island in southern California.

Structural and functional factors related to testicular neoplasia in feminized rats.

Testicular tumors in King-Holtzman hybrid rats with testicular feminization (tfm) were seen as firm, rounded masses of tissue consisting of Leydig cells, myoid cells, and fibroblast-like cells. The cytoplasm of Leydig cells contained well-developed smooth endoplasmic reticulum, pleomorphic mitochondria with numerous cristae, and many lipid droplets. Mitochondria were numerous and varied in size and shape. Their cristae were in the form of tubules, and lipid-like inclusions were frequently seen in the mitochondrial matrix. Lysosomes, rough endoplasmic reticulum, and Golgi bodies were also scattered in the cytoplasm. An in vitro study showed that more testosterone was produced in the tumor than in the testes of rats with tfm; however, the amount in both was less than normal. Testicular tumor-bearing rats with tfm exhibited slightly higher levels of plasma testosterone than did non-tumor-bearing animals with tfm. Levels in both were significantly higher than normal. Testicular tumor cells growing in culture medium supplemented with luteinizing hormone (LH) contained more protein and synthesized more androgen and DNA than did those growing in culture medium without LH. Observed under the scanning and transmission electron microscopes, the LH-stimulated cells had well-developed cytoplasmic organelles and inclusions and surface specializations such as numerous microvilli, large blebs, and other microextensions. They adhered well to the glass surface. These results indicated that Leydig cells in testicular tumors of rats with tfm had morphologic characteristics of steroid-producing cells. In addition these cells were capable of producing steroids, and this capability was enhanced by the presence of LH.