Myostatin (MSTN)是骨骼肌生长发育的负调控因子。MSTN^-/-小鼠的骨骼肌明显肥大，同时II型肌纤维显著增多而I型肌纤维显著减少。然而，MSTN^-/-猪的肌纤维类型的变化情况，以及MSTN是调控肌纤维类型的机制目前尚不清楚，特别是在猪这样的大型动物中。本研究中，我们对实验室前期获得的MSTN^-/-猪的多个发育阶段的骨骼肌的肌纤维类型的变化情况进行了综合分析，结果发现与野生型猪相比，MSTN^-/-猪的骨骼肌总量和IIb型肌纤维的数量均显著上调(P<0.01)，而I型和Ⅱa型肌纤维的数量则显著下调(P<0.01)。此外，为了进一步探究MSTN在胚胎期对肌纤维类型的影响及调控机制，我们从前期获得的转录组差异表达基因数据中选取了部分调控肌纤维类型相关的基因（包括Myf5, Mef2d, MyoD 和 Six1），并通过荧光定量PCR方法检测其表达情况。我们发现肌纤维亚型的标志基因：Myh7、 Myh2、 Myh4 和Myh1 （分别对应I、IIa、IIb、IIx型肌纤维）在胚胎期65天的骨骼肌中已有表达，而且与野生型个体相比，MSTN^-/-个体的Myh7 表达量显著下调 (P<0.01)，Myh4 (P<0.001) 和Myh1 (P<0.05) 的表达量则显著上调；同时，MSTN^-/-个体骨骼肌中Myf5 (P<0.05), Mef2d (P<0.01) 和 Six1 (P<0.05)的表达量显著上调预示MSTN在胚胎发育早期即参与肌纤维类型定向发育的调控。 由此可见，MSTN^-/-猪骨骼肌中的II型肌纤维增多，而且这一增多开始于胚胎期。 该研究结果不仅能够为猪肉品质的改善提供有价值的参考依据，而且可为人类骨骼肌的发育和疾病治疗提供理论基础。

    Myostatin, a member of the transforming growth factor beta (TGF-β) superfamily, is a dominant inhibitor that acts to limit skeletal muscle growth and development. In this study, we generated transgenic mice that express porcine myostatin containg mutations at its cleavage site (RSRR) to evaluate its effect on muscle mass. Results showed that the weight of four skeletal muscles including gastrocnemius, rectus femoris, tibialis anterior, and pectoralis increased by 17.83 and 28.39%, 21.76 and 28.70%, 34.31 and 41.62%, 53.21 and 27.54% in transgenic male and female mice, respectively, compared to their corresponding non-transgenic control mice. Measurement of muscle fiber size and number indicated that the mean myofiber size increased by 50.73 and 61.30% in transgenic male and female mice respectively compared to the non-transgenic controls. However, there was no difference in the number of myofiber between transgenic and non-transgenic male mice. These results clearly demonstrated that the increase in skeletal muscle mass in transgenic mice is caused by hypertrophy instead of hyperplasia.

The objective of this study was to investigate the suitability of tiletamine/zolazepam-xylazine-tramadol combination for miniature pigs. Fourteen Chinese experimental miniature pigs subjected to this study received 3.5 mg tiletamine/zolazepam kg-1 bw, 1.32 mg xylazine kg-1 bw and 1.8 mg tramadol kg-1 bw intramuscularly, as a mixture of the drugs. Cardiopulmonary, biochemical and haematological parameters were recorded before drug administration and after anaesthesia. The combination of the compounds resulted in anaesthesia lasting about 87 min and a satisfactory immobilization for handling. Cardiopulmonary parameters were changed after administration, but there were within biologically acceptable limits. Biochemical and haematological values decreased after drug administration, however, they returned to the baseline at 24 h. At the doses described, tiletamine/zolazepam-xylazine-tramadol combination produced good immobilization in miniature pigs with minimal changes over time in cardiopulmonary, biochemical and haematological parameters.