Sex Differentiation of Avian Gonads In Vitro

The analysis of avian sex differentiation in vitro has beenlimited to the following problems: morphological sex differentiationof gonads cultured in vitro; analysis of the chemical natureof the hormonal secretion; differentiation of germ cells inrelation to their somatic environment. Morphological sex differentiationof avian gonads occurs in vitro. Differentiated gonads of thechick embryo carry out biosynthesis of sex hormones from severalradioactive precursors. Female gonads in particular synthesizeestrogens while male gonads synthesize testosterone. Some experimentshave given evidence of estrogen synthesis by undifferentiatedfemale gonads. Embryonic gonads of quail, like those of chick,are able to synthesize sex steroids from radioactive precursors.However, in the quail and mainly in the testes, a delayed appearanceand a lower activity of the enzyme system 3ß-HSDHs-4-isomerase was found. Histoenzymological results corroboratethe biochemical ones. Combination of culture and grafting experimentshave shown that male germ cells when they are forced into femaledifferentiation by early colonization of a female gonad degenerateafter entering the premeiotic stage. The reasons for this delayedfailure of sex differentiation of "male oocytes" have certainlyto be searched for at the level of perturbation in the mechanismsof meiosis.     

鸟类性别决定机制及性别鉴定的研究进展

鸟类的性别决定是一个多基因参与的级联调控过程。这一过程受Z染色体连锁的DMRT1基因, W染色体连锁的PKC1W和其它多种因子共同调控。本文综述了性别决定基因及其功能、性别鉴定方法等方面的研究进展。Abstract： Avian sex determination is a multiple gene regulation cascade. Genes such as the Z chromosome-linked DMRT1 gene, W chromosome-linked PKCIW gene and other factors have been demonstrated to be involved in this process. In this paper, we review the recent progress in this field. The investigation of functions of sex determinate genes and methods of sexing birds are discussed here.     

Effect of Immobilization Stress on Gonadotropins and Sex Steroids

The effects of the acute immobilization stress on follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and testosterone levels in rats were evaluated. The male and female rats were grouped in control and stress groups (7 animals in each group). Vaginal smears were taken daily from female rats and the rats in the proestrus were involved in the experiments. After a 1-h immobilization stress, blood samples from the heart were taken and the serum FSH, LH, estradiol and testosterone levels were measured by radioimmunoassay (RIA). The results were statistically analyzed using the Mann–Whitney U-test. A statistically significant increase of the levels of FSH and estradiol, but not of LH, was found in the female rats after the stress. A statistically significant increase of the FSH concentration was also revealed in the male rats, but there were no significant changes of the LH and testosterone levels. The scientific and applied (medical) aspects of the data obtained are discussed.     

Neuroendocrine Systems and Avian Sexual Differentiation

Sexual differentiation of the endocrine and behavioral componentsof the avian reproductive system occurs throughout embryonicdevelopment, initiating some of the early cellular events thatform the central nervous system (CNS) and culminating in theorganization of male or female neuroendocrine responses. Earlycellular events have been studied intensively in recent yearsand these developmental processes appear to involve specificgrowth factors in the development of certain tissues. Subsequentto cellular differentiation, primordial germ cells migrate tothe appropriate anatomical location and contribute to the developmentof the single ovary or testes; steroidogenesis begins soon thereafter.Other portions of the hypothalamo-pituitary-gonad (HPG) axisalso appear during early embryonic development with migrationof the gonadotropin-releasing hormone (GnRH) neurons from theolfactory region of the CNS to the midbrain and separate formationof the pituitary gland. The gonadal steroid hormones affectdevelopment of accessory sex structures as well as the laterorganization of neuroendocrine regulatory systems and secondarysex characteristics. Manipulation of steroids during embryonicand early posthatch periods results in altered endocrine andbehavioral responses in adult birds. There are marked speciesdifferences in the timing of these events, especially when precocialand altricial species are compared. Altricial species hatchin a less developed state and as such are more dependent onparental care. Of necessity, the precocial species must be capableof feeding and other motor capabilities at hatch and coincidentallytheir other physiological systems also appear to be more matureat this time. Finally, there is the separate issue of song birdsversus those avian species that do not have elaborate learnedsongs. It appears that most of the species with elaborate neuralcircuitry responsible for song are altricial. This may benefitthem from the standpoint of gaining more time and contact withthe parents to enable them to learn the appropriate song. Thereare also hormonal and neuroendocrine components critical inthe process of song development. Finally, the effects of environmentalfactors, such as endocrine disrupting chemicals take on addedsignificance when viewed in the context of exerting permanentorganizational effects which are likely to alter endocrine andbehavioral components of reproduction in the adult     

Sex Chromatin Frequency in the Avian Aminon

Conflicting results have been reported on the incidence of sexchromatin in avian cells. In this study the sex chromatin frequenciesare explored in the ammotic cells from two .Leghorn varietiesof domestic fowl, a species which is reported to possess anheterochromatic and late leplicating W sex chromosome. The incidenceof sex chromatin was also examined in the ammotic epitheliumof the Japanese quail throughout the incubation period. Thisspecies of quail possesses a W sex chromosome that is euchromaticat metaphase When the sex chromatin frequencies in the domestic fowl werecompared with the gonadal sex of the embryos, a nuclear sexualdimorphism was apparent with the high frequencies correspondingto embryos of the female sex. No such nuclear sexual dimorphismwas found in the quail, both male and female embryos had approximatelythe same incidence of sex chromatin in their ammotic cells These findings are interpreted in support of the idea that thecytological entity identified as sex chiomatin in the domesticfowl represents the W sex chromosome in the interphase nucleus     

Sex Steroids Mediate Bidirectional Interactions Between Hosts and Microbes

The outcome of microbial infections in mammals, including humans, is affected by the age, sex, and reproductive status of the host suggesting a role for sex steroid hormones. Testosterone, estradiol, and progesterone, signaling through their respective steroid receptors, affect the functioning of immune cells to cause differential susceptibility to parasitic, bacterial, and viral infections. Microbes, including fungi, bacteria, parasites, and viruses, can also use sex steroid hormones and manipulate sex steroid receptor signaling mechanisms to increase their own survival and replication rate. The multifaceted use of sex steroid hormones by both microbes and hosts during infection forms the basis of this review. In the arms race between microbes and hosts, both hosts and microbes have evolved to utilize sex steroid hormone signaling mechanisms for survival.     

The Evolution of Neuroanatomical Substrates of Reproductive Behavior: Sex Steroid and LHRH-Specific Pathways Including the Terminal Nerve

Fairly recent anatomical methods have made possible the mappingof neurobehavioral systems involving two types of reproductivehormones, gonadal steroids and the peptide luteinizing hormonereleasing hormone (LHRH). Brain sites of steroid uptake aredetected using autoradiography; LHRH is localized in cells andfibers using immunocytochemical procedures. Both hormone typesare known to strongly influence sex behavior and it can reasonablybe assumed that these effects are mediated in large part viasystems identified using the anatomical procedures. Analysisof the comparative anatomy of these systems should thereforeprovide information useful in the construction of models concerningthe evolution of neurohormonal control of reproductive behavior.The results of such a study are reported. Sex steroid and LHRHsystems in cyclostomes, teleosts, amphibians, reptiles, birdsand mammals are considered in detail. A synthesis of this informationhas led to the following ideas. Androgenic control of male reproductivesystems has evolved in a number of nonhomologous motor systemscontrolling male reproductive behavior. Sex steroid and LHRHsystems may interact at several different levels of the neuraxisbut the most obvious overlap of the systems occurs in the septaland POA areas. The latter especially is a fairly constant andperhaps primitive feature. LHRH secretion into the systemiccirculation was most likely the earliest means for LHRH modulationof both pituitary function and neural systems controlling reproductivebehavior.Pathways for more direct delivery of LHRH to pituitarycells and brain nuclei probably developed in the early gnathostomes.The terminal nerve appears to be a rather conservative LHRH-containingpathway connecting olfactory systems with septal-preoptic nuclei.A function in pheromonal control of sex behavior is suggested.The general distribution of steroid concentrating cells andLHRH pathways in tetrapods seems to be rather constant. Absenceof the systems in neocortical areas and their homologs is conspicuous.     

鸟类蛋黄中的类固醇性激素

介绍鸟类蛋黄中类固醇性激素的种类以及分布,并着重讨论其来源及其对幼鸟的重要生理意义.     

Sex Steroids Inhibit Osmotic Swelling of Retinal Glial Cells

Osmotic swelling of glial cells may contribute to the development of retinal edema. We investigated whether sex steroids inhibit the swelling of glial somata in acutely isolated retinal slices and glial cells of the rat. Superfusion of retinal slices or cells from control animals with a hypoosmolar solution did not induce glial swelling, whereas glial swelling was observed in slices of postischemic and diabetic retinas. Progesterone, testosterone, estriol, and 17ß-estradiol prevented glial swelling with half-maximal effects at approximately 0.3, 0.6, 6, and 20 μM, respectively. The effect of progesterone was apparently mediated by transactivation of metabotropic glutamate receptors, P2Y₁, and adenosine A₁ receptors. The data suggest that sex steroids may inhibit cytotoxic edema in the retina.     

圈养小熊猫繁殖行为变化及繁殖行为对策

In order to investigate the change of reproductive behaviors and understand reproductive strategies of both male and female red pandas, one-year behavioral observation was conducted through the focal sampling method in the Chengdu Research Base of Giant Panda Breeding from December 1999 to November 2000. Our results indicated that reproductive behaviors showed significant differences between the estrous and non-estrous seasons. Frequencies of the rubbing anogenital, sniffing and licking marking were much higher in estrus than in non-estrus. Bleating only appeared in the estrus and can be regarded as an estrous indicator.The result also demonstrated that both male and females applied different reproductive behavioral strategies. Frequencies of activity, rubbing anogenital, licking and sniffing marking, and bleat were much higher in the male than in the female. However, those of resting and investigating were much lower in the male than in the female. This indicated that the male was more active than the female during the estrus and might imply that the male acts mainly as an estrous message sender, and the female as a message receiver in the estrous season.     

Systemic Non-Reproductive Effects of Sex Steroids in Adult Males and Females

Sex steroids are well known for their reproductive actions, however, their roles are not confined to reproduction only and they have been shown to exert wide ranging effects on systemic physiology. Further, the effects of the so-called male and female sex steroids are not limited to their respective genders but they are present in both sexes where they have a significant impact upon systemic functions, reproductive as well as non-reproductive. This work reviews the existing knowledge base and recent reports on the effects of sex steroids on non-reproductive physiology.     

饲料中n-3 HUFA含量对花尾胡椒鲷亲鱼的生殖性能及血浆性类固醇激素水平季节变化的影响

以n-3 HUFA含量为0．16％、1．27％、2．36％和3．47％的4种人工配合饲料(D1～D4)及天然饲料(冰鲜杂鱼,D5)饲养花尾胡椒鲷(Plectorhynchus cinctus)雌亲鱼一周年,通过比较各饲料组亲鱼的产卵量、卵和仔鱼质量以及各月份的血浆性类固醇激素水平,研究n-3 HUFA对生殖性能及性类固醇激素水平季节性变化的影响。平均每kg雌鱼的产卵量、卵受精率、仔鱼存活率、开口仔鱼体长等,D2和D3组与D5组相近,但D1和D4组显著低于D5组;饲料中n-3 HUFA含量对血浆17β-雌二醇(E2)和睾酮(T)水平的季节性变化规律无明显影响,但亲鱼性腺发育与成熟时期的E2和T水平．D1和D4组较D5组显著降低。n-3 HUFA含量对亲鱼离体卵泡E2和T的分泌也有一定影响：D4组卵泡E2的基础分泌很少;绒毛膜促性腺激素(HCG,100IU／mL)可刺激D2-D5组卵泡分泌E2和T,但D1组卵泡对HCG无反应。结果提示,花尾胡椒鲷亲鱼饲料中n-3 HUFA的适宜含量为1．27％-2．36％,不足或过高对亲鱼的生殖性能均有不利影响;通过影响性类固醇激素的产生可能是饲料中n-3 HUFA含量影响鱼类生殖性能的机制之一。     

线虫的性别分化和决定

线虫（Caeborhabditis elegans)是十分重要的模式生物。在遗传学,发育生物学以及神经生物学中有着广泛的应用。就线虫性别分化和性别决定相关基因的特性和功能进行了详细介绍,并在此基础上初步概括了其性别决定的分子机制。     

Swarming Behavior, Sexual Dimorphism, and Female Reproductive Status in the Sex Role-Reversed Dance Fly Species Rhamphomyia marginata

Dance flies are predaceous insects which often form male mating swarms. In many species males prior to swarming catch an insect prey, which is presented to the female at mating. In Rhamphomyia marginata, females in contrast to males gather to swarm, while males carrying a prey visit swarms for mating. Here I describe the swarming and courtship behavior in R. marginata and provide data on sexual dimorphism and swarming female reproductive status. Females swarm in small clearings in the forests. There was no specific swarm-maker. The swarming period lasted for 2–3 h and peaked around sunset. Identical swarm sites were used each evening and for several years. The mean number of females in swarms (swarm sites with at least one female) was 9.9 ± 9.1 (range, 1–40; n = 107) in 1993 and 7.1 ± 7.0 (range, 1–35; n = 68) in 1994. No obvious competition between females in swarms was observed. The operational sex ratio in swarms was extremely female biased (all swarms, 0.04). Less than one-third of male visits to swarms resulted in mating and males were found more often in larger swarms. Nuptial prey consisted of male midges. Females seem to mate more than once. Swarming females had undeveloped eggs, whereas mated females in swarms had further developed eggs than unmated females. Amount of sperm in the spermatheca was correlated with egg size. Amount of sperm and egg size did not correlate with wet weight, wing length, or wing load, except for egg size and weight. The wing coloration pattern and shape in R. marginata females are unique among dance flies, being greatly enlarged (1.6 times larger than that of males) and bicolored (gray part, 60% of wing area). When females, instead of males, possess extravagant secondary sexual characters, it is predicted from sexual selection theory that females should compete for males and that males should be selective in their choice of partner. A sex-role reversal will evolve when assess to males limit female reproductive success. The dance fly species R. marginata, like Empis borealis, another dance fly species studied earlier and discussed here, seems to fit these predictions.     

How Sex Selection Undermines Reproductive Autonomy

Non-medical sex selection is premised on the notion that the sexes are not interchangeable. Studies of individuals who undergo sex selection for non-medical reasons, or who have a preference for a son or daughter, show that they assume their child will conform to the stereotypical roles and norms associated with their sex. However, the evidence currently available has not succeeded in showing that the gender traits and inclinations sought are caused by a “male brain” or a “female brain”. Therefore, as far as we know, there is no biological reason why parents cannot have the kind of parenting experience they seek with a child of any sex. Yet gender essentialism, a set of unfounded assumptions about the sexes which pervade society and underpin sexism, prevents parents from realising this freedom. In other words, unfounded assumptions about gender constrain not only a child’s autonomy, but also the parent’s. To date, reproductive autonomy in relation to sex selection has predominantly been regarded merely as the freedom to choose the sex of one’s child. This paper points to at least two interpretations of reproductive autonomy and argues that sex selection, by being premised on gender essentialism and/or the social pressure on parents to ensure their children conform to gender norms, undermines reproductive autonomy on both accounts.     

黄颡鱼性腺分化的组织学观察

运用组织学方法,观察黄颡鱼(Pelteobagrus fulvidraco)性腺分化过程.结果表明,在水温(20±1)℃条件下,卵巢分化时间明显早于精巢.卵巢分化最早发生于孵出后13 d左右,其主要标志为原始性腺横切面上出现一个组织突起,进而形成卵巢腔;精巢分化的最早标志为精小叶和输精管的形成,开始于孵出后55 d.在发育早期,雌性生殖细胞的活动及分化明显早于雄性生殖细胞.孵出后25 d,卵原细胞开始通过有丝分裂快速增殖,孵出后34 d左右进入成熟分裂阶段;精原细胞在孵出后55 d时才开始大量增殖,成熟分裂最早发生于孵出后64 d.