ABSTRACT This study comprehensively explored muscle fibre characteristics and expression patterns of myosin heavy chain (MyHC) family in skeletal muscles of Large White and Mashen pigs exhibiting differences in muscle fibre development in postnatal muscle growth. Muscle fibre density and diameter were analysed using haematoxylin and eosin staining. The expression patterns of MyHCI, MyHCIIa, MyHCIIx and MyHCIIb were detected by quantitative real-time polymerase chain reaction. The muscle fibre diameter increased and density decreased gradually with aging. In individuals of the same age, the muscle fibre diameter was significantly lower and density was significantly higher in Mashen than in Large White pigs. The MyHCI expression increased, whereas that of MyHCIIa first increased and then decreased. The expression of MyHCI and MyHCIIa was significantly higher in Mashen. The expression of MyHCIIx and MyHCIIb decreased with increasing age; their expression was significantly lower in Mashen pigs. Muscle fibre diameter was negatively correlated with MyHCI expression and positively correlated with MyHCIIx and MyHCIIb expression (except the expression of MyHCI in psoas major). Muscle fibre diameter, muscle fibre density, and MyHCs expression follow certain patterns in skeletal muscles. These results provide valuable information for understanding the molecular mechanism responsible for pig growth performance and meat quality.

中文翻译：

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MyHCs发育表达模式及其对猪肌纤维特性的影响

摘要 本研究全面探讨了在出生后肌肉生长中肌肉纤维发育存在差异的大白猪和马神猪骨骼肌中肌球蛋白重链 (MyHC) 家族的肌纤维特征和表达模式。使用苏木精和伊红染色分析肌肉纤维密度和直径。MyHCI、MyHCIIa、MyHCIIx和MyHCIIb的表达模式通过定量实时聚合酶链反应检测。随着年龄的增长，肌纤维直径逐渐增大，密度逐渐减小。在同龄个体中，马神的肌纤维直径明显低于大白猪，密度明显高于大白猪。MyHCI 表达增加，而 MyHCIIa 表达先增加后减少。MyHCI 和 MyHCIIa 在 Mashen 中的表达显着较高。MyHCIIx和MyHCIIb的表达随年龄增长而降低；它们在马神猪中的表达显着降低。肌纤维直径与MyHCI表达呈负相关，与MyHCIIx和MyHCIIb表达呈正相关（除了腰大肌中MyHCI的表达）。肌肉纤维直径、肌肉纤维密度和 MyHCs 表达在骨骼肌中遵循某些模式。这些结果为理解影响猪生长性能和肉质的分子机制提供了有价值的信息。肌纤维直径与MyHCI表达呈负相关，与MyHCIIx和MyHCIIb表达呈正相关（除了腰大肌中MyHCI的表达）。肌肉纤维直径、肌肉纤维密度和 MyHCs 表达在骨骼肌中遵循某些模式。这些结果为理解影响猪生长性能和肉质的分子机制提供了有价值的信息。肌纤维直径与MyHCI表达呈负相关，与MyHCIIx和MyHCIIb表达呈正相关（除了腰大肌中MyHCI的表达）。肌肉纤维直径、肌肉纤维密度和 MyHCs 表达在骨骼肌中遵循某些模式。这些结果为理解影响猪生长性能和肉质的分子机制提供了有价值的信息。