Quantification of müllerian inhibiting substance in developing chick gonads by a competitive enzyme-linked immunosorbent assay

Investigations of the function of AMH in granulosa cells in hens

Anti-mullerian hormone (AMH) plays a crucial role in follicle regulation in mammals by preventing premature primordial follicle activation and restricting follicle development through reduction of FSH sensitivity and inhibition of FSH-induced increase of steroidogenic enzymes. AMH is produced by granulosa cells from growing follicles and expression declines at the time of selection in both mammalian and avian species. The role of AMH in chicken granulosa cells remains unclear, as research is complicated because mammalian AMH is not bioactive in chickens and there is a lack of commercially available chicken AMH. In the current experiments, we used RNA interference to study the role of AMH on markers of follicle development in the presence and absence of FSH. Cultured chicken granulosa cells from 3-5 mm follicles and 6-8 mm follicles, the growing pool from which follicle selection is thought to occur, were used. Transfection with an AMH-specific siRNA significantly reduced AMH mRNA expression in granulosa cells from 3-5 mm and 6-8 mm follicles. Genes of interest were only measured in granulosa cells of 3-5 mm follicles due to low expression of AMH mRNA at the 6-8 mm follicle stage. Knockdown of AMH mRNA did not affect markers of follicle development (follicle stimulating hormone receptor, FSHR; steroidogenic acute regulatory protein, STAR; cytochrome P450 family 11 subfamily A member 1, CYP11A1; bone morphogenetic protein receptor type 2, BMPR2) or FSH responsiveness in granulosa cells from 3-5 mm follicles, indicating that AMH does not regulate follicle development directly by affecting markers of steroidogenesis, FSHR or BMPR2 at this follicle stage in chickens.

Ultrastructure of human ovarian tissues and risk of cancer cells re-implantation after transplantation to chick embryo chorioallantois membrane (CAM) following vitrification or slow freezing

Ovarian follicle depletion and premature ovarian failure are significant challenges in cancer patients subjected to radio- or chemotherapy. Ovarian tissue (OT) cryopreservation would be an option when other fertility preservation methods are not accessible. This study aimed to analyze the structure and ultrastructure of human OTs transplanted onto chick embryo chorioallantois membrane (CAM) after cryopreservation by vitrification or slow freezing. OTs from 10 cancer patients underwent cryopreservation. CAM transplantation was done on fresh and cryopreserved OTs, to assign samples to nine study groups as follows: 1) FI-FIII = fresh, 5- and 10-days post-CAM transplantation groups; 2) VI-VIII = vitrified, 5- and 10-days post-transplantation vitrified groups; 3) SFI-SFIII: slow frozen, 5- and 10-days post-transplantation slow freezing groups. Proliferation ability, folliculogenesis, and structural and ultrastructure were analyzed. The density of primordial follicles did not change after both freezing methods, but reduced after 5 (P ≥ 0.05) and 10 days (P ≤ 0.05) post-CAM transplantation. The follicular grade significantly decreased in all transplanted tissues (P ≤ 0.0). The proliferation marker increased after cryopreservation, but reduced after transplantation (P ≤ 0.05). TEM evaluation showed better follicular ultrastructure in the fresh group, after transplantation. Stromal ultrastructure appeared more preserved after vitrification compared with slow freezing. There was no sign of malignant cell contamination after transplantation. Some follicular TEM abnormalities were found in both methods of freezing, with a better transplantation rate after vitrification. Also, enhanced follicular activation resulted in faster follicular depletion in this method. The information regarding post grafting events would improve our knowledge for longer OTs' lifespans.

Anti-Müllerian hormone inhibits activation and growth of bovine ovarian follicles in vitro and is localized to growing follicles

STUDY QUESTION

Does anti-Müllerian hormone (AMH) inhibit activation (initiation of growth) of primordial follicles and attenuate the growth of primary follicles in cattle, an excellent animal model for human ovarian follicular development?

SUMMARY ANSWER

AMH inhibited activation of bovine primordial follicles and attenuated the growth of activated follicles in vitro.

WHAT IS KNOWN ALREADY

In mice null mutant for AMH, the pool of primordial follicles is depleted prematurely and AMH inhibits follicle activation in vitro. Results of studies with human ovarian tissue in vitro were inconsistent. Our previous work provided indirect evidence that AMH inhibits follicle activation in bovine ovaries.

STUDY DESIGN, SIZE, DURATION

Pieces of fetal bovine ovarian cortex (2 pieces/culture well), obtained during mid or late pregnancy, were cultured in control medium or with graded doses of AMH for 2, 10 or 12 days. Effects of treatment on follicle activation and growth were determined by histological morphometry; follicles in every 20th histological section were staged (primordial or primary), counted, and measured. In addition, AMH was immunolocalized in bovine ovaries obtained at various times during pregnancy (n = 20 ovaries).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Bovine fetal ovaries at mid or late gestation were obtained at a commercial abattoir. Pieces of ovarian cortex were cultured without or with AMH and fixed for histological morphometry on Day 0 and at the end of culture. Treatments were applied to duplicate cultures from each of two or three fetuses. In 12-day cultures, addition of AMH was delayed until the third day. Histological analysis provided information about the types, numbers and sizes of follicles in cortical pieces before and after treatments. Ovaries obtained during the second and third trimesters were assessed for the presence of AMH by immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

AMH (100-500 ng/ml) inhibited follicle activation in response to an activator (insulin) in ovarian cortical pieces from fetal ovaries in late gestation. Dose-dependent inhibitory effects on the diameters of primary follicles and their oocytes were also observed. These results were obtained only when AMH was added to cultures in advance of insulin (presumably because it penetrates tissue more slowly than insulin). Results of experiments with cortical pieces from fetal ovaries at mid-gestation, when follicles are forming, showed that AMH did not inhibit the formation of follicles. Immunohistochemical localization of AMH showed that it is not present in fetal ovaries until the third trimester, when it was localized to the granulosa cells of secondary and small antral follicles.

LIMITATIONS REASONS FOR CAUTION

The experiments were performed with fetal ovaries because follicles form and follicle activation begins during fetal life in cattle (as it does in humans), so fetal ovarian cortex of later gestation provides tissue rich in primordial follicles. We assume, but have no experimental evidence, that our findings also apply to post-natal ovaries.

WIDER IMPLICATIONS OF THE FINDINGS

Although circulating AMH is used as an indication of the follicular reserve in women, little is known about AMH in human ovaries. Cattle are an excellent non-primate model for human ovarian follicular development and, hence, the findings suggest similar roles for AMH in human follicular development.

LARGE SCALE DATA

Not applicable.

STUDY FUNDNG/COMPETING INTEREST(S)

This research was supported by National Research Initiative Competitive Grants no. 00-35203-9151, 2003-35203-13532, and 2008-35203-05989) from the U.S. Dept. of Agriculture's National Institute of Food and Agriculture to JEF and by an NIH National Research Service Award (F32 HD08264) to RAC. There are no conflicts of interest or competing interests.

Immunohistochemical localization of progesterone receptor isoforms and estrogen receptor alpha in the chicken oviduct magnum during development

In this work, the immunohistochemical expression of progesterone receptor (PR) isoforms and estrogen receptor alpha (ER-α), as well as the histomorphometric changes of the magnum region of the left oviduct from 8-day-old chicken embryos to one-month-old chickens were evaluated. Results indicate evident histological changes in the oviduct magnum during development mainly in the magnum's mucosa. Immunohistochemical analysis showed that the oviduct magnum from 8-day-old chicken embryos to one-day-old chickens did not present any PR isoform, but the oviduct magnum of one-week and one-month-old chickens expressed PR in the nuclei of all cell types. In epithelial cells, PR-B was the only isoform expressed; in muscle and serosa cells, PR-A isoform was the only isoform expressed; and stromal cells expressed both isoforms. The results also demonstrate positive ER-α immunostaining in the nuclei of different cells from embryonic life to later developmental stages of the oviduct magnum. Data indicate that the variations of ER-α or PR expression or dominance of either PR expression is differentially regulated depending on the cell type, the development of the oviduct, and in an age-specific manner. These variations in sex steroids hormone receptors are related with histological changes of the oviduct magnum through development.

Spatiotemporal expression patterns of doublesex and mab-3 related transcription factor 1 in the chicken developing gonads and Mullerian ducts

Sex of birds is genetically determined by the inheritance of sex chromosomes (ZZ for male and ZW for female), and the Z-linked gene named doublesex and mab-3 related transcription factor 1 (DMRT1) is a candidate sex-determining gene in avian species. However, the mechanisms underlying sex determination in birds are not yet understood, and the expression patterns of the DMRT1 protein in urogenital tissues have not been identified. In the current study, we used immunohistochemistry to investigate the detailed expression patterns of the DMRT1 protein in the urogenital systems (including Müllerian ducts) in male and female chicken embryos throughout embryonic development. Gonadal somatic cells in the male indifferent gonads showed stronger expressions of DMRT1 compared with those in the female indifferent gonads well before the presumptive period of the sex determination, and Sertoli cells forming testicular cords expressed DMRT1 in the testes after sex determination. Germ cells expressed DMRT1 equally in males and females after sex determination. The expression was continuous in males, but in females it gradually disappeared from the germ cells in the central part of the cortex of the left ovary toward both edges. The DMRT1 was also detected in the tubal ridge, which is a precursor of the Müllerian duct, and at the mesenchyme and outermost coelomic epithelium of the Müllerian duct in both sexes. Strong expression was observed in the males, but it was restricted to coelomic epithelium after the regression of the duct started. Thus, we observed the detailed spatiotemporal expression patterns of DMRT1 in the developing chicken urogenital systems throughout embryonic development, suggesting its various roles in the development of urogenital tissues in the chicken embryo.

Follicle selection in the avian ovary

Follicle development in the highly efficient laying hen is characterized by a well-organized follicular hierarchy. This is not the case in other chickens such as the broiler breeder hen that has excessive follicle development and lower reproductive efficiency. Although management practices can optimize egg production in less productive breeds of chickens, the factors that contribute to this difference are not known. Interactions between the oocyte and surrounding somatic cells are believed to be involved in promoting follicle selection. Anti-Müllerian hormone (AMH) has been shown to have a role in regulating rate of follicle development in mammals. In hens, the expression of AMH is restricted to the growing population of follicles and, similar to mammals, is markedly decreased at around the time of follicle selection. The oocyte factors, growth and differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), have been identified in the hen, and their expression pattern has been characterized. Anti-Müllerian hormone expression in hens is decreased by a protein factor from the oocyte (not GDF9) and is also decreased by vitamin D. Associated with the decrease in AMH expression by vitamin D, follicle-stimulating hormone receptor mRNA is increased. These data suggest that information about AMH regulation may enhance our understanding of follicle selection, particularly in birds with aberrant follicle development.

Current achievements and future research directions in ovarian tissue culture, in vitro follicle development and transplantation: implications for fertility preservation

BACKGROUND Female cancer patients are offered 'banking' of gametes before starting fertility-threatening cancer therapy. Transplants of fresh and frozen ovarian tissue between healthy fertile and infertile women have demonstrated the utility of the tissue banked for restoration of endocrine and fertility function. Additional methods, like follicle culture and isolated follicle transplantation, are in development. METHODS Specialist reproductive medicine scientists and clinicians with complementary expertise in ovarian tissue culture and transplantation presented relevant published literature in their field of expertise and also unpublished promising data for discussion. As the major aims were to identify the current gaps prohibiting advancement, to share technical experience and to orient new research, contributors were allowed to provide their opinioned expert views on future research. RESULTS Normal healthy children have been born in cancer survivors after orthotopic transplantation of their cryopreserved ovarian tissue. Longevity of the graft might be optimized by using new vitrification techniques and by promoting rapid revascularization of the graft. For the in vitro culture of follicles, a successive battery of culture methods including the use of defined media, growth factors and three-dimensional extracellular matrix support might overcome growth arrest of the follicles. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Large animals, including non-human primates, are essential working models. CONCLUSIONS Experiments on ovarian tissue from non-human primate models and from consenting fertile and infertile patients benefit from a multidisciplinary approach. The new discipline of oncofertility requires professionalization, multidisciplinarity and mobilization of funding for basic and translational research.

Expression of anti-Mullerian hormone in hens selected for different ovulation rates

In hens, the granulosa layer is the primary source of anti-Mullerian hormone (AMH), as it is in mammals. Small follicles express the greatest amount ofAmhmRNA with less in the larger follicles. Laying hens have a distinct ovarian hierarchy of follicles while broiler breeder hens often have excessive follicle growth with a disrupted hierarchy. The objective of Experiment 1 was to examineAmhexpression in two strains of hens differing in ovulatory efficiency.Amhexpression was greater (P<0.01) in broiler breeder hens (n=6) as compared with laying hens (n=6). Experiment 2 was designed to examine whether alterations in follicular development due to diet, within the broiler breeder hens, were correlated with changes in the expression ofAmh. Restricted feeding (RF) in broiler breeder hens promotes optimal follicular development. Egg production in broiler breeder hens on full feed (FF;n=8) was 78% that of hens on RF (n=9). The number of large follicles (P<0.05), total ovarian weight (P<0.01), andAmhmRNA expression were greater in FF hens as compared with RF hens (P<0.01). There was no difference in FSH receptor expression between the two groups. A direct nutritional effect was not supported because culture of granulosa cells with varying concentrations of glucose and insulin showed no effect on granulosaAmhexpression. Finally, testis-conditioned medium resulted in a dose-related increase in granulosa cell proliferation, which could be inhibited by preincubation with AMH antibody. AMH may enhance granulosa cell proliferation through an autocrine or paracrine mechanism although excessive AMH may inhibit optimal follicle selection.

Expression and regulation of anti-mullerian hormone in an oviparous species, the hen

Anti-mullerian hormone (AMH) has a critical role in regression of the mullerian duct system during development in male mammalian and avian species and in regression of the right oviduct in female avian species. AMH in adult female birds has not been investigated. Chicken-specific cDNA primers were used to isolate Amh by RT-PCR. This probe was used in Northern blot analysis to identify a 2.8-kb band with expression in total ovarian RNA and in granulosa cell RNA. Quantitative real-time PCR was used to assess Amh expression in follicles of different maturity (1, 3, 5, and 6-12 mm and the largest F1 follicle; n = 4-6 of each size). There was an increased amount of Amh mRNA in the granulosa layer of the smaller follicles and a lower amount in the granulosa layer of the larger follicles (P < 0.01). There was no difference in granulosa Amh expression between the germinal disc and non-germinal disc region of 6- to 12-mm follicles, although expression differed with follicle size (P < 0.01). To examine hormone regulation of Amh, granulosa cells (from 6- to 8-mm follicles) were cultured with various concentrations of estradiol (E(2)) and progesterone (P(4)), and Amh mRNA was assessed. Neither E(2) nor P(4) influenced Amh mRNA accumulation. Granulosa cells were also cultured in the presence of oocyte-conditioned medium (OCM), which decreased Amh mRNA expression in a dose-related manner (P < 0.05); FSH receptor expression was not affected. Heat treatment of OCM abolished the effect, but growth differentiation factor 9 antiserum did not block the suppression. Immunohistochemistry confirmed that the granulosa layer was the predominant source of AMH in the small follicles of the hen and indicated that AMH was present early in follicle development, with expression in very small follicles (approximately 150 mum).

Development of a Sexually Differentiated Behavior and Its Underlying CNS Arousal Functions

This chapter addresses questions regarding lordosis behavior, the most extremely sexually differentiated behavior that has been analyzed for its neural and molecular mechanisms. Analysis of this behavior has proved for the first time that specific biochemical reactions in specific nerve cell groups in the brain determine a mammalian behavior. Lordosis is done by the female but not by the male. How did the process of sexual differentiation occur? A large literature implicates high levels of testosterone during a critical period during development as being responsible for the defeminization of the brain. A new idea, however, offers the possibility of direct genetic influences independent of testosterone levels themselves. We propose here that Mullerian Inhibiting Substance (MIS) and its receptors could constitute an example of a nonandrogenic genetic influence. Further, specific sexual behaviors depend on underlying arousal states in the central nervous system (CNS). We have proposed the concept of generalized CNS arousal and provide information as to how generalized arousal forces interact with specifically sexual influences, thus to facilitate sexually differentiated mating behaviors.

Evidence for a role for anti-Müllerian hormone in the suppression of follicle activation in mouse ovaries and bovine ovarian cortex grafted beneath the chick chorioallantoic membrane

The first critical transition in follicular development, the activation of primordial follicles to leave the pool of resting follicles and begin growth, is poorly understood, but it appears that the balance between inhibitory and stimulatory factors is important in regulating the exodus of follicles from the resting pool. There is evidence that anti-Mullerian hormone (AMH; also known as MIS) inhibits follicle activation in mice, but whether it plays a similar role in non rodent species is not known. When pieces of bovine ovarian cortex, rich in primordial follicles, are cultured in serum-free medium, most follicles initiate growth, but when cortical pieces are grafted beneath the chorioallantoic membrane (CAM) of chick embryos, follicle activation does not occur. Since embryonic chick gonads of both sexes produce and secrete high levels of AMH, the hypothesis that the AMH in the chick circulation inhibits follicle activation was tested. In Experiment 1, whole newborn mouse ovaries were grafted beneath the CAM (placed "in ovo") or cultured in vitro for 8 days. In vitro (or after 8 days in vivo) follicles activated and proceeded to the primary or secondary stage, but activation was suppressed in ovo. This inhibition was reversed if ovaries were removed from beneath the CAM and cultured in vitro. In contrast, when ovaries from mice null mutant for the AMH type II receptor were CAM-grafted in Experiment 2, follicle activation occurred in a similar fashion to activation in vitro. This finding strongly implicates AMH as the inhibitor of follicle activation in ovo. Since chick embryonic gonads are the source of circulating AMH, chicks were gonadectomized in Experiment 3, prior to grafting of pieces of bovine ovarian cortex beneath their CAMs. Bovine primordial follicles activated in the gonadectomized chicks, similar to the results for mice lacking the AMH type II receptor. Taken together these experiments provide strong evidence that AMH is the inhibitor of mouse follicle activation present in the circulation of embryonic chicks and provide indirect, and hence more tentative, evidence for AMH as an inhibitor of bovine follicle activation.

Changes in mRNA expression of MMP-2 in the Müllerian duct of chicken embryo

Although asymmetric development of the ovary and the oviduct is a unique characteristic in birds, the mechanism of asymmetric development still remains unclear. Recently, degradation of extracellular matrix has been suggested as an important factor related to the regression of the Müllerian duct in mammals. The present study was conducted to examine a possible role of metalloproteinase-2 (MMP-2) in the regression of the right Müllerian duct in the developing chicken embryo. Morphological changes in the Müllerian ducts were studied on day 15 of incubation and mRNA expresseion of MMP-2 was studied on days 12, 15, and 18 of incubation. Morphological observation demonstrated the disappearance of basement membrane in the right Müllerian duct which undergoes the regression. RT-PCR analysis showed that MMP-2 mRNA expression of the right Müllerian duct increased on days 15 and 18 of incubation coincidently with the time of regression. In the right Müllerian duct, regression was prevented by diethylstilbestrol treatment on day 4 of incubation and a coincident decrease in MMP-2 expression was observed when compared to the control group. These results suggest that MMP-2 may be involved in the regression of the right Müllerian duct in the female embryos of the chicken.

The early stages of follicular development: activation of primordial follicles and growth of preantral follicles

Although enormous progress has been made in understanding the events and regulation of the later stages of ovarian follicular development, the early stages of development, to a large extent and particularly in large mammals, remain a mystery. Mechanisms that regulate the initiation of follicular growth (follicle activation) and the ensuing growth and differentiation of preantral follicles are of considerable interest, since their elucidation is a prerequisite to use of the primordial pool to enhance reproductive efficiency in domestic animals, humans, and endangered species. This review is an attempt to summarize the approaches that have been taken to further this goal and the results thus far of these efforts. Preantral follicular development can be divided into three stages: activation of primordial follicles, the primary to secondary follicle transition, and the development of secondary follicles to the periantral stage. The activation of primordial follicles in vitro has been achieved thus far in rodents, cattle, and primates, where it occurs spontaneously without the addition of growth factors or hormones. The ovaries of rodents are small enough to be cultured intact and, in that experimental situation, some follicles activate, while many remain in the resting pool, and the addition of specific factors can increase or decrease the number of follicles that leave the resting pool in vitro. In contrast, follicular activation in cattle and primates has been studied by culturing small pieces of the ovarian cortex, rich in primordial follicles, and the great majority of the primordial follicles activate in that situation, suggesting the importance of inhibitory factors to the normal, gradual exit of follicles from the resting pool. In cultured rodent ovaries, follicles appear to pass easily and spontaneously from the primary to the secondary stage, whereas few of the activated follicles in cultured cortical pieces from cattle or primates progress from the primary to the secondary stage. Understanding the requirements for the primary to secondary transition is critical for growing follicles activated in vitro to the late preantral and antral stages. In contrast, the requirements for the continued growth of larger preantral follicles, which can be isolated for in vitro studies, have been extensively explored in rodents and to a lesser extent in domestic species. A number of hormones and factors have been implicated and will be discussed. Taken together, the results highlight the need for a better understanding of the earliest stages of follicular development in domestic ruminants, particularly follicle activation and the primary to secondary follicle transition.

Simple assay method for endocrine disrupters by in vitro quail embryo culture: Nonylphenol acts as a weak estrogen in quail embryos

Many chemicals that are not structurally related to estrogen have estrogen-like activity. In this study, we tried to apply a quail embryo culture system for assessing the in vivo effects of such chemicals on the development of quail embryos. Beta-estradiol induced feminization of the gonads of genetically male embryos, which was confirmed by the increase in the size of the left gonad and female-specific aromatase expression, while male-specific SOX9 expression was not affected. Nonylphenol, which has a weak estrogenic activity, reduced the viability and body weight of embryos. Simultaneously, several genetically male embryos were feminized in terms of gonadal size and aromatase expression. These results indicate that the avian embryo culture system was useful for evaluating endocrine disrupters.

Hereditary persistent right oviduct in the chicken PNP/DO line

Hereditary, persistent, right oviduct manifested in an inbred line (PNP/DO line) from the Fayoumi breed of chickens was investigated for form of expression and mode of inheritance. Females in the PNP/DO line have varying lengths of elongated right oviducts, besides the normal left ovary, and oviducts that generally possess, irrespective of their total length, regions similar to those normally observed in a left oviduct. Observations of embryos indicated that the existence of right oviduct in this line could be attributed to the slow regression of right Müllerian duct during the embryonic stage, and left-right asymmetry in female genital system is intrinsic in this line. Intracrosses of the PNP/DO line produced 93% of female embryos with persistent right Müllerian ducts at the next generation, and reciprocal crosses of the PNP/DO line and control strains produced 5 and 30% of female embryos with persistent right Müllerian ducts in the F1 and N2 generations, respectively. Mating results suggested that this mutant trait is controlled by two pairs of autosomal recessive genes with major effects and numerous loci that have minor effects. Thus, expression of this trait is due to the interaction of major loci and the background genotype.

The P450 aromatase (P450 arom) gene is asymmetrically expressed in a critical period for gonadal sexual differentiation in the chick

Steroid hormones appear to play an important role in gonadal sex differentiation of birds. Here we studied the steady-state level of the P450 arom mRNA by reverse transcriptase polymerase chain reaction (RT-PCR) in the left and the right presumptive ovary and testis of developing chicken embryos. The gonads were evaluated every hour during the undifferentiated period, at 144-156 h of incubation (h/i), and every 24 h after sexual differentiation at 168 and 192 h/i. Activity of P450 arom was determined by estrone production from [3H]androstenedione at 144-192 h/i. Moreover, morphological development of the gonad was also examined by light microscopy. Results show that onset of P450 arom mRNA and its protein activity were simultaneously detected in the left and the right ovaries at 147 h/i. Asymmetric function of P450 arom gene expression was observed at 156 h/i when morphological gonadal differentiation is first recognized. Biotransformation of [3H]androstenedione to estrone was also asymmetrically detected between the left and right gonad at 156 h/i and asymmetry was maintained throughout the analyzed stages. It is proposed that there is a gene in birds that is asymmetrically expressed in the undifferentiated stage of the female and the male gonad. In the female this gene could promote P450 arom gene expression, increasing estrogen production, which in turn could induce ovarian cortex proliferation and expression of other structural estrogen-regulated genes involved in ovarian sexual determination.

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.

Expression of chicken steroidogenic factor-1 during gonadal sex differentiation

The orphan nuclear receptor, steroidogenic factor-1 (SF-1), regulates steroidogenic enzyme expression and is essential for gonadal and adrenal development in mammals. We have examined expression of the chicken homologue, cSF-1, during gonadal sex differentiation using whole mount in situ hybridisation and RNase protection assays (RPA). In the youngest embryos examined (day 3.5; stages 21-22), cSF-1 transcripts were already detectable by in situ hybridisation in the undifferentiated genital ridge of both sexes. Expression continued in the gonads of both sexes at the time of sexual differentiation (days 5.5-6.5; stages 28-30). Expression then became higher in developing ovaries compared to testes at days 6.5-8. 5 (stages 30-35). At day 13.5 (stage 40), when the gonads are well differentiated, both ovaries and testes showed cSF-1 expression, with higher levels of expression in the left ovary compared to the right (regressing) gonad in females and compared to testes. RPA analysis of isolated gonads confirmed higher expression of SF-1 in differentiating ovaries relative to testes. Expression of cSF-1 in the developing adrenal gland was similar for both sexes at all stages examined. In tissue sections of day 8.5 whole mount gonads, cSF-1 expression was localised in the medulla of the ovary and was weakly detectable in the testis. These observations indicate that SF-1 has a conserved role in early gonadal and adrenal development in vertebrates. However, upregulation of cSF-1 expression during ovarian differentiation is opposite to the pattern seen in mammals, in which SF-1 is downregulated in females. This difference between the birds and mammals may reflect differences in steroidogenic activity of the embryonic ovary versus the testis in the two groups.

Early expression of AMH in chicken embryonic gonads precedes testicular SOX9 expression

In mammals, anti-Müllerian hormone (AMH) is produced by Sertoli cells from the onset of testicular differentiation and by granulosa cells only after birth. SOX9, a transcription factor related to the testis-determining factor SRY, is expressed in mouse testis 1 day before AMH. To determine the relationship between AMH and SOX9 in birds, we cloned the AMH promoter in search of SOX9 response elements, and we compared the expression of AMH and SOX9 in the gonads of chick embryos using in situ hybridization. Potential SOX response elements were found in the AMH promoter; however, AMH is expressed in both sexes at stage 25, 1 day before the first SOX9 transcripts appear in the male gonads. SOX9 is never expressed in the female. These results do not support the hypothesis that SOX9 could trigger the expression of testicular AMH in the chick but does not exclude a later role in testis development.

Effects of embryonic estrogen on differentiation of the gonads and secondary sexual characteristics of male zebra finches

Male zebra finches sing to court females, whereas females do not normally sing. In parallel, the telencephalic brain regions that control song are larger in volume and contain larger cells in males than in females. The vocal control organ (syrinx) is also larger in males. Some evidence suggests that the sexual differentiation of both anatomy and behavior is under the regulation of gonadal hormones during early development, yet recent data conflict with the idea that the sole source of masculinization of the neural song system is the testes. In the present experiment, we treated genetic males with estradiol benzoate on embryonic day 5 and measured the volume of and neuron soma size in robust nucleus of the archistriatum (RA) and the high vocal center (HVC), two telencephalic song control nuclei. We also weighed the syrinx, the muscles of which are the target of the motor pathway containing the two brain regions. The estrogen treatment disrupted testicular morphology, and induced an oviduct in six of seven animals, but it had no effect on any of four measures of masculinization of the neural song system. These results suggest that normal testicular tissue is not required for masculine development of the neural song system.

Molecular cloning of an avian anti-Müllerian hormone homologue

Anti-Müllerian hormone (AMH) is responsible for regression of the Müllerian ducts in males during embryonic development. This peptide hormone of the transforming growth factor-beta family is also believed to play a broader role in sex determination, affecting differentiation and morphogenesis of the testes. Accordingly, in mammals, AMH is produced at much higher levels in male fetuses than in female fetuses. In contrast, in birds, both male and female embryonic gonads produce AMH at high levels, although in males it is still responsible for regression of the Müllerian ducts. Its persistent expression by the embryonic ovaries and its role in female sex determination in birds is not understood. We have cloned an avian homologue to AMH. Avian AMH cDNA encodes a 644 amino acid protein that is 42% identical to human AMH overall with increased identity at the carboxyl terminus. Similarities to human AMH include motifs of sequence identity, a conserved putative plasmin cleavage site and cysteine alignments, and similar genomic intron/exon structure. Antibodies to recombinant avian AMH cross-react with recombinant human AMH and were used to show that avian AMH is glycosylated as has been shown for the human form. The avian AMH gene is transcribed in both male and female gonads but not in liver, heart, kidney or muscle.

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.

Characterization of mullerian inhibiting substance binding on cervical carcinoma cells demonstrated by immunocytochemistry

Müllerian inhibiting substance (MIS) is a glycoprotein released from Sertoli cells or follicular cells of gonads, responsible for the regression of Müllerian ducts and/or Müllerian-derived tumor cells. Binding of MIS to target cells is essential for initiating regression. A human cervical carcinoma CaSki cell was examined by quantitative immunocytochemistry detected by anti-avian MIS antibody for MIS binding ability. Various treatments of WGA-peroxidase conjugate, enzyme digestion, sodium periodate or exogenous estrogen before antibody recognition were performed. It was found that the WGA partially blocked MIS binding to CaSki cell surfaces. Protease digestion of CaSki cell surfaces prior to addition of MIS or an anticervical carcinoma monoclonal antibody 1H10 (MAb 1H10), blocked the binding of MIS but not MAb 1H10 to cell surfaces. Sodium periodate and overnight exposure of CaSki cells to estrogen or diethylstilbestrol before or after fixation of the cells, did not influence MIS binding ability in vitro. MIS binding was higher on avian Müllerian duct compared with MIS binding to CaSki cells by quantitative immuno-gold labeling analysis. MAb 1H10 immuno-gold complexes binding to CaSki cells was also obtained and compared with MIS immuno-gold bindings. MIS binding site could be a polypeptide which survived sodium periodate treatment. The 'critical window' period, in which developing Müllerian ducts respond to exogenous estrogen protection from MIS regression, is possibly lost in CaSki cell.

Aromatase enzyme activity and sex determination in chickens

During development, the genotype of the zygote determines the nature of the gonad, which then determines the male or female phenotype. The molecular events underlying this process are just beginning to be defined. A single treatment of chicken embryos with an aromatase inhibitor (which blocks the synthesis of estrogen from testosterone) at a stage when their gonads were bipotential caused genetic females to develop a permanent male phenotype. These sex-reversed females developed bilateral testes that were capable of complete spermatogenesis and had the physical appearance and behavior of normal males. This result identifies aromatase as a key developmental switch in the sex determination of chickens.

Quantitative change in fibronectin in cultured müllerian mesenchymal cells in response to diethylstilbestrol and müllerian-inhibiting substance

I report on the synthesis of fibronectin in the developing chick Müllerian duct mesenchymal cells. Before the differentiation of female chick Müllerian duct, the amount of fibronectin in the cells of the right duct is 44% lower than in the left duct. While after differentiation, the amount of fibronectin in the right duct is 29% lower, as compared to the left duct. Estrogenic hormone diethylstilbestrol (DES) treatment was carried out at the 5th day of incubation when both female Müllerian ducts were undifferentiated. Three days after DES treatment, the regression of the right duct was prevented, and the amount of fibronectin was induced by 89%, while induction in the left duct was 11%. Eight days after DES administration, the amount of fibronectin in the right and left Müllerian duct was induced by 150 and 76%, respectively. After DES treatment in the male embryo, both Müllerian ducts were retained, and the capacity for fibronectin synthesis was preserved. Application of the indirect immunocytochemical labeling technique revealed Müllerian-inhibiting substance (MIS) binding sites on the membrane of the Müllerian mesenchymal cells. The addition of chick MIS in the culture medium reduced the amount of detectable fibronectin in the cultured mesenchymal cells. The synthesis of fibronectin in intestinal mesenchymal cells was not affected by DES or MIS.

Lectin bindings and diethylstilbestrol effects on the recognition of mullerian inhibiting substance (MIS) on chick mullerian ducts by MIS-antiserum

A high intensity of lectin bindings was demonstrated on the epithelial cells and serosa cells of the regressing right Mullerian ducts (Mds) in the female chick embryos. The strong lectin bindings occurs on, or in the regressing Md cells along with marked surface MIS bindings at the age of day 13. However, at the age of days 5-7 1/2, bindings of lectins were weak. Neither Wheat-germ agglutinin (WGA) or Concanavalin A (Con-A) labelings before MIS-antiserum (MIS-Ab) incubation can block antibody recognitions to the antigens, including MIS and growth hormone at the age of day 13. Our previous studies indicated that after WGA labeling on the surfaces of Md epithelial cells prior to the incubation of MIS-Ab at day 10 did not prevent the recognition of MIS-Ab (Wang 1989). On the contrary, at day 7 1/2, the specific binding of MIS was eliminated after preincubations with lectins and prenatal diethylstilbestrol (DES) treatment at the age of day 5. It is suggested that DES provides a protection to the Mds from MIS-induced regression by preventing the MIS binding to its specific membrane receptors. An increase of extra- and intracellular glycoproteins or carbohydrates of regressing Md epithelial cells were suggested. Internalization of WGA but not MIS molecules was found in Md epithelial cells. The Golgi saccules were negative of lectin bindings.

Immunocytochemical demonstration of the binding of growth-related polypeptide hormones on chick embryonic tissues

The presence of endogenous growth-related polypeptide hormones, such as growth hormone (GH), somatomadin-C/insulin-like growth factor-1 (SM-C/IGF-1), prolactin (PRL) and Mullerian inhibiting substance (MIS) on chick embryonic tissues have been detected by electron microscopic (EM) immunocytochemistry. Antiserum against GH, anti-SM-C/IGF-1, anti-PRL and anti-MIS were used respectively as primary antibodies for immunolabeling probes by peroxidase (PO) and avidin-biotin complex (ABC)-gold ligands. Cross-reaction studies by ELISA showed negative or weak antigen-antibody interactions. Chick embryos, gonads, and Mullerian ducts (Mds) of various ages were fixed in 2.5% glutaraldehyde for 30 min. Washes in phosphate buffer were administered between each of the following incubations: (i) 2% BSA; (ii) primary antibody; (iii) biotinylated or PO-conjugated secondary antibody; (iv) avidin conjugated with gold particles. SM-C/IGF-1 bindings were negative on 1d embryonic disc, heavily stained on 2d endoderm. However, the GH bindings were found on the embryonic layers of 1d and 2d embryos, and increasing on the luminal epithelial cells of Mds during development. PRL was found in parallel with GH, but in less amount. The 10d Mds were double labeled with anti-SM-C/IGF-1-gold and anti-MIS-PO (MIS-PO), and the results showed SM-C/IGF-I negative, but MIS-PO positive bindings. This study provides the first immunocytochemical evidences for: (i) The presence of GH, SM-C/IGF-1, PRL and MIS bindings on chick embryonic tissues, and further supports their potential role as growth mediators during embryonic development. (ii) The amount of GH and MIS bindings were found correspondingly to their physiological status of Md growth or regression.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of chicken testicular müllerian inhibiting substance by ion exchange and high-performance liquid chromatography

A highly purified protein molecule was obtained from the secretory proteins of 8-week-old chicken testes using ion-exchange column chromatographic procedures, including DEAE Bio-Gel A, CM Bio-Gel A, wheat germ lectin columns, and high-performance liquid chromatographic (hplc) separation techniques. This protein molecule has a molecular weight of 74,000 Da (74K protein). The isolated 74K protein induces regression of chicken Müllerian ducts grown in vitro. The 74K protein does not cause regression of cultured embryonic intestine or Wolffian duct. When the total testicular secretory proteins are resolved in a two-dimensional gel electrophoresis, approximately 120 polypeptides are obtained. The purified 74K protein has a pI of 6.1. Analysis of amino acid composition indicates that the 74K protein is relatively acidic in nature with a ratio of acidic to basic amino acids of 1.93.