Avian Gonads Research Articles

Identification of genes related to sexual differentiation and sterility in embryonic gonads of Mule ducks by transcriptome analysis.

The key genes of avian gonadal development are of great significance for sex determination. Transcriptome sequencing analysis of Mule duck gonad as potential sterile model is expected to screen candidate genes related to avian gonad development. In this study, the embryonic gonadal tissues of Mule ducks, Jinding ducks, and Muscovy ducks were collected and identified. Six sample groups including female Mule duck (A), male Mule duck (B), female Jinding duck (C), male Jinding duck (D), female Muscovy duck (E), and male Muscovy duck (F) were subjected to RNA sequencing analysis. A total of 9,471 differential genes (DEGs) and 691 protein-protein interaction pairs were obtained. Totally, 12 genes (Dmrt1, Amh, Sox9, Tex14, Trim71, Slc26a8, Spam1, Tdrp, Tsga10, Boc, Cxcl14, and Hsd17b3) were identified to be specifically related to duck testicular development, and 11 genes (Hsd17b1, Cyp19a1, Cyp17a1, Hhipl2, Tdrp, Uts2r, Cdon, Axin2, Nxph1, Brinp2, and Brinp3) were specifically related to duck ovarian development. Seven genes (Stra8, Dmc1, Terb1, Tex14, Tsga10, Spam1, and Plcd4) were screened to be specifically involved in the female sterility of Mule ducks; eight genes (Gtsf1, Nalcn, Tat, Slc26a8, Kmo, Plcd4, Aldh4a1, and Hgd) were specifically involved in male sterility; and five genes (Terb1, Stra8, Tex14 Tsga10 and Spam1) were involved in both female and male sterility. This study provides an insight into the differential development between male and female gonads of ducks and the sterility mechanism of Mule ducks through function, pathway, and protein interaction analyses. Our findings provide theoretical basis for the further research on sex determination and differentiation of birds and the sterility of Mule ducks.

H3K27ac chromatin acetylation and gene expression analysis reveal sex- and situs-related differences in developing chicken gonads

BackgroundBirds exhibit a unique asymmetry in terms of gonad development. The female left gonad generates a functional ovary, whereas the right gonad regresses. In males, both left and right gonads would develop into testes. How is this left/right asymmetry established only in females but not in males remains unknown. The epigenetic regulation of gonadal developmental genes may contribute to this sex disparity. The modification of histone tails such as H3K27ac is tightly coupled to chromatin activation and gene expression. To explore whether H3K27ac marked chromatin activation is involved in the asymmetric development of avian gonads, we probed genome-wide H3K27ac occupancy in left and right gonads from both sexes and related chromatin activity profile to the expression of gonadal genes. Furthermore, we validated the effect of chromatin activity on asymmetric gonadal development by manipulating the chromatin histone acetylation levels.MethodsThe undifferentiated gonads from both sides of each sex were collected and subjected to RNA-Seq and H3K27ac ChIP-Seq experiments. Integrated analysis of gene expression and active chromatin regions were performed to identify the sex- and situs-specific regulation and expression of gonadal genes. The histone deacetylase inhibitor trichostatin A (TSA) was applied to the undifferentiated female right gonads to assess the effect of chromatin activation on gonadal gene expression and cell proliferation.ResultsEven before sex differentiation, the gonads already show divergent gene expression between different sexes and between left/right sides in females. The sex-specific H3K27ac chromatin distributions coincide with the higher expression of male/female specification genes in each sex. Unexpectedly, the H3K27ac marked chromatin activation show a dramatic difference between left and right gonads in both sexes, although the left/right asymmetric gonadal development was observed only in females but not in males. In females, the side-specific H3K27ac occupancy instructs the differential expression of developmental genes between the pair of gonads and contributes to the development of left but not right gonad. However, in males, the left/right discrepancy of H3K27ac chromatin distribution does not drive the side-biased gene expression or gonad development. The TSA-induced retention of chromatin acetylation causes up-regulation of ovarian developmental genes and increases cell proliferation in the female right gonad.ConclusionsWe revealed that left/right asymmetry in H3K27ac marked chromatin activation exists in both sexes, but this discrepancy gives rise to asymmetric gonadal development only in females. Other mechanisms overriding the chromatin activation would control the symmetric development of male gonads in chicken.

Morphometric and gross anatomy studies of gonads in day-old Arabic chick (Gallus turcicus) lead to gonadal asymmetry

The differentiation of avian gonads occurred since the embryonic stage, resulted in asymmetric morphology. This study aimed to analyse the morphometric and gross anatomy of gonads in Day old Arabic chick. This study utilized 116 Day old Arabic chick. After necropsy, they were divided into 61 male and 55 female. The variables studies were length, width, volume, location, colour, and shape of the gonads. Data analysis used descriptive analysis and independent T test. The results showed a significant difference (P<0.01) between the right and left ovary lengths 1.67±0.08 mm and 3.69±0.05, respectively. A significant difference (P<0.01) between the width ovaries 0.64±0.03 mm (right ovary) and 1.18±0.03 mm (left ovary), respectively. It was found a significant difference (P<0.05) between the length of right and left testis 2.47±0.08 mm and 3.29±0.07mm, and between volume of testis 1.46±0.12 mm3 (right testis) and 2.03±0.13 mm3 (left testis). However, the right and left testes width was not significant (P>0.01). The testes colour was creamy white, sometimes pink, and grey to black, the colour of ovaries was creamy yellow and pink. Morphometric and gonadal morphology of Day old Arabic chick showed gonadal asymmetry, and the left side is larger than the right side.

FOXL2 antagonises the male developmental pathway in embryonic chicken gonads.

FOXL2 is a conserved transcription factor with a central role in ovarian development and function. Studies in humans and mice indicate that the main role of FOXL2 is in the postnatal ovary, namely folliculogenesis. To shed light on the function and evolution of FOXL2 in the female gonad, we examined its role in embryonic avian gonads, using in ovo over-expression and knockdown. FOXL2 mRNA and protein are expressed female-specifically in the embryonic chicken gonad, just prior to the onset of sexual differentiation. FOXL2 is expressed in the medullary cord cells, in the same cell type as aromatase (CYP19A1). In addition, later in development, expression also becomes localised in a subset of cortical cells, distinct from those expressing estrogen receptor alpha. Mis-expression of FOXL2 in the male chicken embryonic gonad suppresses the testis developmental pathway, abolishing local expression of the male pathway genes, SOX9, DMRT1 and AMH, and repressing Sertoli cell development. Conversely, knockdown of FOXL2 expression allows ectopic activation of SOX9 in female gonads. However, mis-expression of FOXL2 alone was insufficient to activate aromatase expression in male gonads, while FOXL2 knockdown did not affect aromatase expression in females. These results indicate that FOXL2 plays an important role in embryonic differentiation of the avian ovary via antagonism of SOX9, but may be dispensable for aromatase activation at embryonic stages. The data suggest that FOXL2 has different roles in different species, more central for embryonic ovarian differentiation in egg-laying vertebrates.

MiRNAome expression profiles in the gonads of adult Melopsittacus undulatus.

The budgerigar (Melopsittacus undulatus) is one of the most widely studied parrot species, serving as an excellent animal model for behavior and neuroscience research. Until recently, it was unknown how sexual differences in the behavior, physiology, and development of organisms are regulated by differential gene expression. MicroRNAs (miRNAs) are endogenous short non-coding RNA molecules that can post-transcriptionally regulate gene expression and play a critical role in gonadal differentiation as well as early development of animals. However, very little is known about the role gonadal miRNAs play in the early development of birds. Research on the sex-biased expression of miRNAs in avian gonads are limited, and little is known about M. undulatus. In the current study, we sequenced two small non-coding RNA libraries made from the gonads of adult male and female budgerigars using Illumina paired-end sequencing technology. We obtained 254 known and 141 novel miRNAs, and randomly validated five miRNAs. Of these, three miRNAs were differentially expressed miRNAs and 18 miRNAs involved in sexual differentiation as determined by functional analysis with GO annotation and KEGG pathway analysis. In conclusion, this work is the first report of sex-biased miRNAs expression in the budgerigar, and provides additional sequences to the avian miRNAome database which will foster further functional genomic research.

Ethylene Glycol and Dimethyl Sulfoxide Combination Reduces Cryoinjuries and Apoptotic Gene Expression in Vitrified Laying Hen Ovary.

Successful cryopreservation of avian gonads is important not only for avian breeding but is also crucial for preservation of species, especially of endangered birds. The aim of this study was to evaluate the effect of vitrification by several cryoprotectants on the ovarian tissues of laying hens. Ovarian tissues were randomly divided into six groups: control (nonvitrified: C), dehydrated using ethylene glycol (EG), dehydrated with propylene glycol (PROH), dehydrated using dimethyl sulfoxide (DMSO), and two combined groups, EG+DMSO and EG+PROH. The composition of vitrification solutions was as follows: EG group: V1 = 7.5% EG and V2 = 15% EG +0.5 M sucrose, DMSO group: V1 = 7.5% DMSO and V2 = 15% DMSO +0.5 M sucrose, PROH group: V1 = 7.5% PROH and V2 = 15% PROH +0.5 M sucrose, EG+DMSO group: V1 = 7.5% EG +7.5% DMSO and V2 = 15% EG +15% DMSO +0.5 M sucrose and EG+PROH group: V1 = 7.5% EG +7.5% PROH and V2 = 15% EG +15% PROH +0.5 M sucrose. Ovarian tissues of each group were dehydrated for 10 minutes with V1 solution and 2 minutes with V2. Among the vitrified groups, intact primordial and primary follicles showed significant increase in EG+DMSO, but follicular attrition had the highest rate in the PROH group (p < 0.05). Immunohistochemical analysis showed that the percentage of active caspase 3-positive cells was lower (p < 0.05) when using EG+DMSO versus PROH. Further gene expression of caspase 3, 8, and 9 was highest in the PROH group (p < 0.05). Vitrification of ovaries of laying hens using EG+DMSO can afford effective protection of primordial and primary follicles during preservation and may therefore be successfully used for storing avian gonadal tissues.

Nesfatin-1: Localization and expression in avian gonads and its modulation by temporal phase relation of neural oscillations in female Japanese quail, Coturnix coturnix japonica

In a search for new appetite-controlling signals, the peptide nesfatin-1, expressed in the brain and peripheral tissues of rodents and humans has been reported to regulate feeding by reducing food intake. Recently it has also been reported that nesfatin-1 might be involved in regulating the reproductive axis in fishes and mammals, but its expression and physiological role if any, is not yet known in birds. In the present study, localization and expression of nesfatin-1 was observed in the testis, ovary and shell gland of poultry species Japanese quail, Coturnix coturnix japonica.Our earlier studies have reported that serotonin precursor 5-HTP and dopamine precursor l-DOPA given 8h apart induces gonadal suppression, when given 12h apart leads to gonadal stimulation while other relationships were found ineffective. In the present study intense ir-nesfatin-1 was observed in the regressed ovary (stromal cells) and shell gland (endometrium) of 8-h Japanese quail while in 12-h quail, weak and scarce immunostaining for nesfatin-1 was detected in the hyperactive ovary and shell gland compared to control.These findings led us to conclude that, an inverse relationship exists between ovarian activity (both in the control and simulated conditions) and nesfatin-1 expression. Present avian study, first of its kind, also suggests the role of nesfatin-1 in reproductive regulation possibly via appetite control and energy balance in female Japanese quail and needs to be investigated further in relation to food intake.

Development of retroviral vectors for tissue-restricted expression in chicken embryonic gonads.

The chicken embryo has long been a useful model organism for studying development, including sex determination and gonadal differentiation. However, manipulating gene expression specifically in the embryonic avian gonad has been difficult. The viral vector RCASBP can be readily used for embryo-wide transgene expression; however global mis-expression using this method can cause deleterious off-target effects and embryo-lethality. In an attempt to develop vectors for the over-expression of sequences in chicken embryonic urogenital tissues, the viral vector RCANBP was engineered to contain predicted promoter sequences of gonadal-expressed genes. Several promoters were analysed and it was found that although the SF1 promoter produced a tissue-restricted expression pattern that was highest in the mesonephros and liver, it was also higher in the gonads compared to the rest of the body. The location of EGFP expression from the SF1 promoter overlapped with several key gonad-expressed sex development genes; however expression was generally low-level and was not seen in all gonadal cells. To further validate this sequence the key testis determinant DMRT1 was over-expressed in female embryos, which due to insufficient levels had no effect on gonad development. The female gene aromatase was then over-expressed in male embryos, which disrupted the testis pathway as demonstrated by a reduction in AMH protein. Taken together, although these data showed that the SF1 promoter can be used for functional studies in ovo, a stronger promoter sequence would likely be required for the functional analysis of gonad genes that require high-level expression.

Localization of apoptotic and proliferating cells and mRNA expression of caspases and Bcl-2 in gonads of chicken embryos

The aim of the present study was to analyze participation of apoptosis and proliferation in gonadal development in the chicken embryo by: (1) localization of apoptotic (TUNEL) and proliferating (PCNA immunoassay) cells in male and female gonads and (2) examination of mRNA expression (RT-PCR) of caspase-3, caspase-6 and Bcl-2 in the ovary and testis during the second half of embryogenesis and in newly hatched chickens. Apoptotic cells were found in gonads of both sexes. At E18 the percentage of apoptotic cells (the apoptotic index, AI) in the ovarian medulla and the testis was lower (p<0.05) than in the ovarian cortex. In the ovarian medulla, the AI at E18 was lower (p<0.05) than on E12. In the testis, the AI was significantly lower (p<0.05) at E18 than at E15 and 1D. The percentage of proliferating cells (the proliferation index: PI) within the ovary significantly increased from E15 to 1D in the cortex, while proliferating cells in the medulla were detected only at E15. In the testis, the PI gradually increased from E12 to 1D. The mRNA expression of caspase-3 and -6 as well as Bcl-2 was detected in male and female gonads at days 12 (E12), 15 (E15) and 18 (E18) of embryogenesis and the day after hatching (1D). The expression of all analyzed genes on E12 was significantly higher (p<0.05) in female than in male gonads. This difference was also observed at E15 and E18, but only for the caspase-6. The results obtained showed tissue- and sex-dependent differences in the number of apoptotic and proliferating cells as well as mRNA expression of caspase-3, -6 and Bcl-2 genes in the gonads of chicken embryos. Significant increase in the number of proliferating cells in the ovarian cortex and lack of these cells in the ovarian medulla (stages E12, E18, 1D) simultaneous with decrease in the intensity of apoptosis only in the medulla indicates that proliferation is the dominant process involved in the cortical development, which constitutes the majority of the functional structure of the fully developed ovary. No pronounced changes in the expression of apoptosis-related genes found during embryogenesis suggest that they cannot be considered as important indicators of gonad development. The molecular mechanisms of the regulation of balance between apoptosis and proliferation in developing avian gonads need to be further investigated.

Cryoconservation of avian gonads in Canada

Avian genetic resources have declined dramatically over the past half century as the cost of maintaining populations has exceeded the perceived benefit of keeping them. Despite the early importance of poultry in the development of cryopreservation techniques, very little avian germplasm has been conserved. Cryopreservation and recovery of avian gonads preserve the W chromosome and overcome problems of freezing and recovering semen or conserving and manipulating embryonic cells, and the use of vitrification procedures for preserving gonads minimizes cellular damage. On the basis of research demonstrating the biological possibility of cryopreserving and transplanting avian gonads, 5,125 testicles and 2,667 ovaries from 10 populations of Japanese quail, 9 populations of chickens, and 1 population of Chilean tinamou were cryopreserved and sent to the Canadian Animal Genetic Resources program for long-term storage. These gonads represent 20 of the 33 distinct avian populations currently maintained at Canadian public institutions of agricultural research.

Expression of matrix metalloproteinase-13 (MMP-13) in the testes of growing and adult chicken

Although several matrix metalloproteinases (MMPs) have been implicated in testis development, the presence of MMP-13 protein has not been directly substantiated in the male avian gonads. In this study, we examined the expression patterns of MMP-13 and MMP inhibitors, TIMP-1 and TIMP-2, in immature (4weeks), pre-pubertal (16weeks), and mature (1year) chicken testes. Using RT-PCR analysis, we observed that MMP-13 mRNA was expressed in immature testis. In Western blot analysis, the expression level of MMP-13 protein peaked in the immature testes during marked tissue remodeling, whereas it gradually decreased during testis maturation. High expression levels of TIMP-1 (34-kDa) and TIMP-2 (55-kDa) were detected only in immature and pre-pubertal testes and not in adult testis. Four different forms of TIMP-2 protein were differentially detected in the testes of growing and adult chicken. Using immunohistochemistry we localized both secreted and intracellular forms of MMP-13, TIMP-1, and TIMP-2 proteins. These proteins were temporally and spatially distributed in growing and adult testes, and all their expression levels were similar to the expression profile of Western blot results. These findings suggest that age-related changes of MMP-13 with balance of TIMPs act in concert to effect the controlled testicular remodeling and maturation.

Mechanism of avian sex determination and differentiation

Avian sex is determined by genes on the sex chromosomes (ZZ for male and ZW for female). In avian embryo stage, genes on one or two chromosomes control the sex differentiation. Gonad develops to testis in ZZ male and to ovary in ZW female. To date, DMRT1 (Doublesex and mab-3 related transcription factor 1) is considered to be the best candidate gene in controlling the avian gonad differentiation. However, recent study showed that avian sex might be determined by cell autonomous independent of sex hormone signal. Therefore, sex determination gene does not only control the gonadal differentiation, but also control body cells. From this sense, DMRT1 is not the switch gene of avian sex determination. What is the switch factor of avian sex determination, and what is the mechanism of avian sex determination? This review discussed the current progresses on avian sex determination and differentiation from three aspects: W chromosome and ovary development, Z chromosome and testis development, and avian sex determination and cell autonomous.

Novel techniques for preserving genetic diversity in poultry germplasm.

Abstract There have been massive losses of avian genetic material over the past several decades, partly because of a belief that cryoconservation techniques used for mammals do not work for birds. For several avian species, cryopreservation of semen may not be sufficiently efficient to use in commercial practice but the fertility it produces is fully adequate for conservation purposes. Technology around embryonic primordial germ cells, which will produce the gametes, has been used to produce transgenic birds. These cells can be isolated, cryopreserved and recovered in chimaeras but the efficiency of recovery is far too low for conservation purposes because several dozen individuals must be produced to recover the variation from the original population. Cryopreservation of avian gonads with subsequent recovery of the germline through transplantation has been demonstrated recently and should provide the ability to both cryoconserve and recover avian populations.

3β-HSD activates DHEA in the songbird brain

Dehydroepiandrosterone (DHEA) is an abundant circulating prohormone in humans, with a variety of reported actions on central and peripheral tissues. Despite its abundance, the functions of DHEA are relatively unknown because common animal models (laboratory rats and mice) have very low DHEA levels in the blood. Over the past decade, we have obtained considerable evidence from avian studies demonstrating that (1) DHEA is an important circulating prohormone in songbirds and (2) the enzyme 3β-hydroxysteroid dehydrogenase/isomerase (3β-HSD), responsible for converting DHEA into a more active androgen, is expressed at high levels in the songbird brain. Here, we first review biochemical and molecular studies demonstrating the widespread activity and expression of 3β-HSD in the adult and developing songbird brain. Studies examining neural 3β-HSD activity show effects of sex, stress, and season that are region-specific. Second, we review studies showing seasonal and stress-related changes in circulating DHEA in captive and wild songbird species. Third, we describe evidence that DHEA treatment can stimulate song behavior and the growth of neural circuits controlling song behavior. Importantly, brain 3β-HSD and aromatase can work in concert to locally metabolize DHEA into active androgens and estrogens, which are critical for controlling behavior and robust adult neuroplasticity in songbirds. DHEA is likely secreted by the avian gonads and/or adrenals, as is the case in humans, but DHEA may also be synthesized de novo in the songbird brain from cholesterol or other precursors. Irrespective of its source, DHEA seems to be an important prohormone in songbirds, and 3β-HSD is a key enzyme in the songbird brain.

Gene expression of sex-determining factors and steroidogenic enzymes in the chicken embryo: influence of xenoestrogens

Many genes involved in gonadal development have been proposed for mammals. To elucidate if those genes play any critical role in sexual differentiation of the avian gonad, we have examined expressions of the genes for proposed sex-determining factors (SF1, Sox9, DMRT1, Wpkci, and AMH), steroidogenic enzymes (P-450scc, 3β-HSD, P-450c17, 17β-HSD and aromatase) and the estrogen receptor in the urogenital system during chicken embryogenesis (days 4–16 of incubation), using a semi-quantitative reverse transcription-polymerase chain reaction. Transcripts of the genes for sex-determining factors except Wpkci and AMH were detected in both sexes but had no sexual dimorphism. Wpkci expression was female specific and constantly high throughout incubation. AMH was expressed in both sexes from the earliest stages but was higher in males than in females after the onset of gonadal differentiation. Expressions of the genes for more downstream enzymes in a steroidogenic pathway, such as P-450c17, 17β-HSD and aromatase, were clearly higher in females than in males. In particular, 17 β- HSD expression increased in the course of gonadal development in females, whereas it was constantly low in males. Aromatase was highly expressed in females during gonadal differentiation but not in males over the period. In addition, to elucidate the relationship between gene activation during embryogenesis and reproductive abnormalities in wild birds, we examined expressions of these genes in embryos treated with various doses of diethylstilbestrol (DES), as a representative estrogenic compound. DES had no effect on the expressions of all the genes in either sex during the periods of gonadal differentiation (days 8, 12, and 16). Sexual dimorphism of the gene expression for steroidogenic enzymes appeared to be closely related to gonadal development in the chicken embryo, especially in the female. However, all the genes examined here seem unlikely to respond to xenoestrogens.

Seasonal variation in size and function of the nasal salt gland of the franklin's gull ( Larus pipixcan)

1. 1. Extrarenal salt excretion through the nasal gland allows marine birds to drink salt water. Species inhabiting fresh water usually have small glands, although in many species studied, the glands increase in size in response to salt loads. 2. 2. The Franklin's gull ( Larus pipixcan) breeds in freshwater habitats and winters in marine habitats. Accordingly it shows an annual cycle in the size and function of the nasal gland. We found a large and active gland in gulls collected in April (just after arrival on the breeding ground) and in October (just prior to migration), while birds collected from late May to July had small and apparently inactive glands. 3. 3. Recrudescence of the gland occurred in wild-caught adults maintained in captivity on fresh water without a salt load. 4. 4. This appears to represent a cyclical phenomenon that is independent of actual salt loading. 5. 5. The glandular hypertrophy produced a histological picture similar to that of adaptive hypertrophy in response to salt loading. 6. 6. The increase was not inhibited by maintaining birds on a constant 16:8 light/dark cycle. This change is analagous to size changes in avian gonads. 7. 7. This cyclical phenomena may preadapt the Franklin's gull's salt gland to handle the slat load it will encounter when it reaches its winter quarters on the Pacific ocean shore.

Biological and binding activities of pituitary hormones from the ostrich, Struthio camelus

Biological and binding activities of adenohypophysial hormones purified from the ostrich (ost), Struthio camelus, were compared to those of the corresponding hormones derived from mammalian and other avian species. The potency of ostrich prolactin was comparable to those of other avian preparations and slightly less active than the ovine hormone when tested in the pigeon crop-sac assay, but ostrich growth hormone (GH) was more potent than several other avian preparations and was comparable to mammalian GH in the rat tibia bioassays. Marked discrepancies were evident in the activities of both ostrich gonadotropins (ostGn) when they were tested in a variety of in vivo and in vitro bioassays and radioreceptor assays (RRAs). Both the ostrich follicle-stimulating hormone (ostFSH) and luteinizing hormone (ostLH) were among the most potent tested thus far in in vivo bioassays for total gonadotropin in a lizard and a cockerel; a high sialic acid content may account for these high potencies. OstFSH was also the most potent nonmammalian Gn tested in two FSH specific mammalian bioassays, an in vivo (ovarian augmentation) and an in vitro (cAMP production) rat bioassay; in fact, ostFSH behaved more like a mammalian than an avian hormone in these assays. However, the binding activity of ostFSH was not unlike that of other avian FSH preparations when tested in either mammalian or nonmammalian FSH-RRA systems. OstLH was more potent than other avian preparations in an in vitro mammalian bioassay, but not in avian or amphibian LH bioassays; species specificity was pronounced among these LH assays. Binding activities of ostLH in mammalian and avian LH-RRAs were generally consistent with potencies in the two species of bioassays. However, a marked discrepancy was apparent in the behavior of ostLH in FSH-RRAs. Although ostLH had very low FSH activity when tested by radioimmunoassay, by bioassay, or by FSH-RRA with avian gonads, it was equipotent to ostFSH in competing for FSH-binding sites on the mammalian gonad; in this respect it was more like turkey than chicken LH. The ability of ostLH to antagonize the biological activities of ostFSH in the stimulation of cAMP by rat seminiferous tubules confirms that ostLH binds to the same functional receptors as FSH on the rat testis, even though it does not induce the characteristic physiological response associated with FSH.

Early sequential development in avian gonads. An ultrastructural study using selective glycogen labeling in the germ cells.

The early development of chick embryo gonads was studied by light and transmission electron microscopy and by cytochemical detection of glycogen in primordial germ cells (PGC's). The sequential events are presented from day 2 to day 5 (stages 14 to 27), together with the ultrastructural characteristics of the various cell populations. This study attempts to contribute data on the controversial origin of the avian gonadal medulla. It is shown that the main part of the primitive medulla arises from the association of the proliferating germinal epithelium (GE) and epithelioid cords (formed early from the condensed splanchnopleural mesenchyme); later deep cords, probably developed from the intermediate mesoderm mesenchyme, join the medulla. The process of mesenchymal condensation is described (cells aggregated by dense plaques and membrane anchorages, deposits of fibrillar extracellular material around the cords) together with ultrastructural changes in the GE basal lamina, which is progressively pushed back then disorganized. The study of the morphological relationships between the PGC's and the somatic cells has been facilitated by glycogen labeling in the former. Whereas the PGC's settled in the germinal epithelia do not display any junctional complex with the epithelial cells up to stage 26, those which are migrating through the dorsal mesentery and in the deep gonadal mesenchyme are associated to fibroblast-like somatic cells by dense plaques. The cytological characteristics of migrating PGC's (polymorphism, pseudopodia and filopodia, paucity of microfilaments, high alpha-glycogen particle content) have been described. In addition, the cell pattern in mesodermal tissues is thought well-suited to PGC invasion owing to a wide extracellular compartment, distributed in the mesenchyme and the early epithelium, and to discontinuities in the basal lamina.

Induction of H-Y Antigen in the Gonads of Male Quail Embryos by Diethylstilbestrol

In quails, H-Y antigen is induced by oestrogens in the gonads of the originally H-Y negative homogametic sex but not in non-gonadal tissues. This is consistent with the view that oestrogens act via H-Y antigen in the organization of the avian gonad.

Differences in the properties of FSH and LH binding sites in the avian gonad revealed by homologous radioligands

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the turkey, Meleagris gallopavo, were used as radioligands to study the characteristics of gonadotropin binding sites in avian and reptilian gonads. Scatchard analysis indicated the presence of multiple binding sites for each radioligand in the turkey and chicken gonad; the association constants ( K a ) for the high affinity, low capacity sites (10 9 to 10 10 M −1) were similar to those observed in gonads of other species. Phylogenetic differences were evident in the ability of gonads to bind turkey and mammalian radioligands; e.g., radioiodinated turkey hormones showed little binding to the pig ovary and radioiodinated human FSH showed little binding to the turkey gonad. Radioreceptor assays (RRAs) revealed the presence of separate binding sites with differential specificity for the two types of gonadotropins in the avian gonad. In particular, when turkey hormones were studied in the homologous RRA with 125I-labeled turkey LH as radioligand, gonadotropin binding sites appeared to be highly specific for LH. With 125I-labeled turkey FSH as radioligand, binding sites showed a relatively high affinity for FSH; but gonadotropin specificity of these sites was incomplete since turkey LH continued to show considerable activity in this FSH-RRA. Comparative studies with heterologous hormones (from chicken, sea turtle, and sheep) and heterologous receptor preparations (from chicken, sea turtle, lizard, and pig) gave variable results, depending on the source of both the hormone and receptor. For example, the specificity of FSH binding sites in the chicken testis was less pronounced than in the homologous turkey system; in fact, turkey LH was more potent than FSH in the chicken FSH-RRA. Binding in the turtle ovary did not show a clear specificity for either gonadotropin with either radioligand. The implications of these results for physiological actions of gonadotropins and evolution in gonadotropin structure are discussed.