母鸡性行为反转机制的研究

The sex of the domestic animals was determined by genetic sex chromosomes, but the gonads can differentiate into a testis or ovary. During the development of.chicken embryos, estrogen synthesis is more active in the ovary than that in the testis. Such a difference may result in great impact on sexual differentiation of the central nervous system. In adult avians the function and sexual behavior are regulated by endogenous genetic, neural and endocrine factors as well as exogenous factors such as pesticides with endocrine-disrupting effects. After exposure to such endocrine disrupters in embryonic stage, reproduction and neural functions may be interfered, leading to.reproductive disorders in adulthood. To evaluate the effect of estrogen on differentiation of chicken gonads and sexual behavior fertilized Hyline chicken eggs were injected on Day 3 of incubation with an aromatase inhibitor (AI). The chickens were raised for 8 months after hatching. Sexual behavior and secondary sex characteristics were observed after sexual maturity. Serum E2 and T were measured by radioimmunoassay and gonads and brain were removed for histological studies. The results showed that:.masculinized secondary sex characteristics and copulation behavior were observed in the genetic female chickens after AI treatment before sexual differentiation. The serum E2 levels were in such an order as: incompletely reversed hen>normal hen>completely reversed hen>normal cock, and serum T levels as: completely reversed.hen>incompletely reversed hen>normal cock>normal hen. Frequency of male mating behavior correlated positively with the ratio of serum T/E2. Histological examinationmanifested different degree of gonadal reversal: completely reversed hens had right testis and left ovotestis. In both gonads there were seminiferous tubules, which were filled with germ cells, but the diameter of the tubules were less than that of the normal cock; incompletely reversed hens had regressed right gonad and intact left ovary..These results indicated inhibition of aromatase activity during the embryonic period caused masculinization of the phenotype and the sexual behaviors of the female chickens. Serum sex steroid levels were also changed. The concentration and ratio of the serum T and E2 regulate the frequency and intensity of male mating behavior. The structure of the POM in the brain also changed. The disrupting effects of polychlorinated biphynyls (PCB) were also investigated in chickens at different developmental stages. The results showed that: PCB damaged primordial germ cells via toxic action, and interfered in gamete differentiation and gonadal development at later embryonic stage via both estrogenic and toxic actions, causing pyknosis and vacuolations in germ cells. PCB could directly damage the cultured embryonic chicken testicular germ cells. In the adult chickens, PCBs manifested higher effects on spermatogenesis and induced a marked decrease in the testicular weight, severe damage of the seminiferous.tubules and decreased testosterone secretion. The above results indicated that the effect of PCB varied according to age and sex of the chickens. Elucidation of the mechanisms of endogenous and exogenous factors on gonadal development may facilitate prevention of the reproductive toxicity of endocrine disrupters and improvement of reproductive performance.

用母鸡性行为反转模型研究性行为反转与遗传性别、性腺性别和表型性别间的关系。比较性行为反转母鸡与正常公鸡和母鸡性激素及其受体、类固醇合成酶及性腺结构和功能的差异；性行为相关神经核团的形态和递质作用的变化；通过核型和性染色体分析检测遗传性别，综合研究性行为反转的内分泌、神经和遗传调控机制，探讨禽类有功能的性腺反转的可能性。