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| An Investigation of Skeletal Muscle Apoptosis during Postmortem Aging of Yak Meat |
| SUN Zhi-chang;YU Qun-li;HAN Lin;ZHANG Wen-hua;YANG Qin |
| 1. College of Food Science and Engineering, Gansu Agriculture University, Lanzhou 730070, China; 2. Ningxia Xiahua Meat Food
Co. Ltd., Zhongwei 755000, China; 3. Gannan Institute of Animal Science and Veterinary, Hezuo 747000, China |
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Abstract The purpose of this study was to shed light on the occurrence of skeletal muscle apoptosis in triceps brachi (TB), musculus longissimus (ML), semimembranosus (SM) muscles from yak meat during postmortem aging. Totally 24 Ganan black yaks were selected and slaughtered in the Islamic way, and different muscles were excised from each carcass and aged under the conditions of 0-4℃and 0.5 m/s for air lfow rate. Morphological observation of the cell nucleus was performed using He staining at different time points during the aging process, and apoptotic index was measured by in situ end-labeling. Meanwhile, caspase-3 activity was assayed. At 1 d postmortem, the structure of the cell nucleus in the skeletal muscles TB, ML and SM was complete and apparent with evenly distributed nucleoplasm. As the aging progressed, the chromatin inside the nucleus was agglomerated to form a crescent-like shape, the cell nucleus was concentrated and broken, forming apoptotic bodies, and as a result, the cells were shrunk. Almost no positive cell nuclei were observed in ML and SM muscles within the ifrst 3 d premortem. At 5 d postmortem, TB and SM muscles exhibited signiifcantly increased counts of TUNEL-positive nuclei (P<0.01), and at 7 d, a signiifcant difference in the count TUNEL-positive nuclei was noticed between TB and ML muscles (P<0.01). The caspase-3 activity was signiifcantly higher at 12 h postmortem than at 0.5 h (TB, P<0.01;ML, P<0.001;SM, P<0.01). In ML muscle, this enzyme activity reached the maximum level at 12 h postmortem, showing a 273.01%increase over that observed at 0.5 h. In contrast, the enzyme activity reached the maximum level at 1 h postmortem, which was higher by 273.93%and 386.17%than at 0.5 h, respectively. At 5 h, the minimum levels of caspase-3 activity were detected in all the three muscles. In conclusion, during postmortem aging, the concentration and breaking of the cell nuclei in yak skeletal muscles to form apoptotic bodies, increased levels of caspase-3 activity, and the detectable presence of TUNEL-positive nuclei, positively dependent on aging time, together conifrm the occurrence of skeletal muscle apoptosis, which offers a systematic and reasonable way to interpret the mechanism of postmortem aging of yak meat.
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2014, Vol. 28 
