热应激对文昌鸡中枢免疫器官发育的影响及GABA调控机制

Due to the frequent and intense occurrence of heat waves caused by the global climate warming, the heat stress becomes a key issue to the animal production and reproduction as the high temperature environment has seriously impeded the productivity of domestic animals. In this study, experiments were conducted to investigate the effect of the heat stress on the growth of one-day-old Wenchang chickens, under a hot environment with a temperature of 40 C and a humidity of 80%. The laboratory investigation used variety of techniques including morphological anatomy,biochemistry, immunocytochemistry,in situ nick end-labeling,flow cytometry and cell culture. The impacts of heat stress on the development of the bursa of Fabricius and the thymus, central immune cell proliferation and apoptosis, and the development of cellular immunity and humoral immunity of Wenchang chickens were evaluated in this study as well as the regulatory mechanism of GABA at the individual and cellular level so as to reveal the law of development of the central immune organ in Wenchang chickens and its differences with other kinds of chickens, to understand the damage to the development process of the central immune organ and to clarify the regulatory mechanism of GABA in relieving the damage to the development of the central immune organ in Wenchang chickens under heat stress..New insights and evidences were obtained about the development of the central immune organ under heat stress and the regulatory mechanism of GABA in Wenchang chickens, so as to further understand the relationship between the development of the central immune organ and heat stress and to provide fresh ideas and data for easing the impact of the hot environment on the immunity of Wenchang chickens and providing effective precautions.

由于全球气候变暖,热浪袭击的频率和强度在逐年增加,高温环境严重地阻碍了畜禽生产力的发展,因此热应激是人们在动物生产繁殖过程中十分关注的重要问题。本项目拟选用1日龄文昌鸡为实验对象,采用温度40℃,湿度80%的热环境对雏鸡进行热应激，运用形态组织解剖学、生物化学、免疫细胞化学、原位缺口末端标记、流式细胞术和细胞培养技术等手段,在个体与细胞水平上,研究热环境下雏鸡胸腺和法氏囊的生长发育、免疫细胞增殖与凋亡、细胞与体液免疫等的变化以及GABA的调控作用，揭示文昌鸡中枢免疫器官发育的自然规律及与其他禽类发育规律的区别；弄清热应激对文昌鸡中枢免疫器官发育过程的损伤,阐明GABA缓解热应激文昌鸡中枢免疫器官发育的可能机制。本工作为阐明热应激对文昌鸡中枢免疫器官发育的影响及调控机制提供新的见解和证据，加深人们对热应激和中枢免疫器官发育关系的理解,为减轻热应激对动物免疫的损伤及预防措施提供新的思路和资料.

随着全球极端高温天气频发，动物的热应激时常发生,造成的经济损失越来越严重。热应激是导致动物免疫力下降的重要因素，严重地影响雏鸡免疫功能的发育。本项目通过组织解剖学、免疫组织化学、生物化学以及分子生物学等多种方法,探讨了热应激对文昌鸡雏鸡中枢免疫器官与功能发育的影响及其GABA的修复作用。结果显示:.1/.与对照组(CK)相比较,热应激组(HS)雏鸡的胸腺与法氏囊(BF)指数均下降,组织结构发育的完整性降低，雏鸡胸腺的皮质厚度、皮髓质比例、皮质淋巴细胞数均显著降低,BF的滤泡面积显著减小,凋亡细胞分布密度显著增大;而GABA+HS组雏鸡的胸腺指数、BF指数及组织结构发育的完整性均有不同程度的提高,而且BF脏器指数、滤泡面积增大,凋亡细胞分布密度显著地减小。 .2/. HS组雏鸡血清IL-2、IgA、IgG、IgM含量明显下降,新城疫抗体效价显著降低,而GABA+HS组雏鸡血清的以上各项指标与HS组雏鸡相比显著地提高。HS组雏鸡血浆中IL-4和IFN-γ的含量显著升高，TNF-α的含量降低，GABA+HS组显著降低了雏鸡血浆中IL-4和IFN-的含量。HS组雏鸡BF 的IL-1β水平在BF发育后期显著下调,而IL-6水平显著上升，TNF-α含量无显著差异,而GABA+HS组雏鸡BF 的IL-6水平显著下降、TNF-α水平显著上升。.3/. HS组雏鸡血液及组织内T、B淋巴细胞亚群的数量减少，而GABA+HS组雏鸡的这些细胞数量显著地升高；HS组雏鸡胸腺细胞凋亡率和S、G2/M期细胞数量显著增多，而GABA+HS组雏鸡胸腺细胞凋亡率和S、G2/M期细胞的数量均有所下降。.4/. HS组雏鸡胸腺组织中SOD、T-AOC、GSH-PX的活力均显著地下降,MDA含量显著地升高,而GABA+HS组雏鸡胸腺组织中抗氧化酶的活力却显著地升高,MDA含量显著地降低;各组雏鸡BF总SOD活力水平差异不大,但GABA+HS组于6周龄时总SOD活力上升,而且雏鸡GSH-PX酶活力在1-3周龄均具较高水平;GABA+HS组雏鸡BF组织中IL-6 mRNA水平均低于HS组。.结果表明：热应激严重影响文昌鸡雏鸡中枢免疫功能的发育，GABA通过提高组织的抗氧化能力、降低细胞凋亡率以及改变雏鸡细胞因子含量及其mRNA的表达等变化缓解热应激的损伤，增强了雏鸡中枢免疫功能的发育过程。

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