【目的】研究慢性热应激对黄羽肉鸡肝脏和肌肉的抗氧化能力与内质网应激以及腓肠肌肌纤维类型的影响.【方法】试验选用20只47日龄黄羽肉鸡,随机分为常温组和慢性热应激组,每组10只.鸡只饲养在人工气候室,试验期30 d.试验结束采集血液、肝脏和腓肠肌样品,利用试剂盒法检测血清生化指标、血清激素以及血清和肝脏抗氧化指标.利用实时荧光定量PCR法检测内质网应激(Endoplasmic reticulum stress,ERS)相关基因和腓肠肌不同肌纤维肌球蛋白重链(Myosin heavy chain,My HC)基因mRNA的表达.【结果和结论】慢性热应激显著降低肉鸡平均日增质量、血清甘油三酯(TG)、甲状腺激素(T3和T4)、胰岛素样生长因子1(Insulin-like growth factor 1,IGF-1),显著升高血清皮质酮(CORT)水平(P<0.05).同时,慢性热应激显著升高血清中丙二醛(MDA)含量,降低血清和肝脏谷胱甘肽过氧化物酶(GSH-PX)活性和肝脏总抗氧化能力(T-AOC)(P<0.05).此外,慢性热应激显著提高肉鸡肝脏和腓肠肌中热休克蛋白70(Heat shock protein 70,HSP70)基因以及腓肠肌中转录激活因子4(Activating transcription factor 4,ATF4)基因mRNA的表达(P<0.05),降低腓肠肌中葡萄糖调节蛋白78(Glucose-regulated protein 78,GRP78)基因mRNA的表达,而对肝脏中ATF4和GRP78基因mRNA的表达量无显著影响.最后,慢性热应激显著降低腓肠肌慢肌(Slow myofiber,SM)My HC基因mRNA表达量(P<0.05)而对快红肌(Fast red myofiber,FRM)和快白肌(Fast white myofiber,FWM)My HC基因mRNA表达量无影响.研究结果提示,慢性热应激可能通过降低血清生长和代谢激素、机体抗氧化能力以及引发细胞内质网应激影响肉鸡生长和腓肠肌纤维类型.
Bone marrow mesenchymal stem cells （BMSCs） could differentiate into various cell types including adipocytes and myocytes, which had important scientific significance not only in the field of tissue regeneration, but also in the field of agricultural science. In an attempt to exhibit the characterization and differentiation into adipocytes and myocytes of porcine BMSCs, we isolated and purified porcine BMSCs by red blood cell lysis method and percoll gradient centrifugation. The purified cells presented a stretched fibroblast-like phenotype when adhered to the culture plate. The results of flow cytometry analysis and immunofluorescence staining demonstrated that the isolated cells were positive for mesenchymal surface markers CD29, CD44 and negative for hematopoietic markers CD45 and the adhesion molecules CD31. Cells were induced to differentiate into adipocytes with adipogenic medium containing insulin, dexamethasone, oleate and octanoate. Oil Red O staining demonstrated that the porcine BMSCs successfully differentiated to adipocytes. Moreover, the findings of real-time PCR and Western blotting indicated that the induced cells expressed adipogenic marker genes （PPAR-y, C/EBP-c~, perilipin, aP2） mRNA or proteins （PPAR-3,, perilipin, aP2）. On the other hand, porcine BMSCs were induced into myoctyes with myogenic medium supplemented with 5-azacytidine, basic fibroblast growth factor, chick embryo extract and horse serum. Morphological observation by hochest 33342 staining showed that the induced cells presented as multi-nucleus muscular tube structure. And myogenic marker genes （Myf5, desmin） mRNA or proteins （MyfS, MyoD, myogenin, desmin） were found in the induced cells. In addition, the results of immunofluorescence staining revealed that myogenic marker （Myf5, MyoD, myogenin, desmin, S-MyHC） proteins was positive in the induced cells. Above all, these results suggested that the isolated porcine BMSCs were not only consistent with the characterization of mesenchymal stem cells, but also e
