Adaptation of rat jaw muscle fibers in postnatal development with a different food consistency: an immunohistochemical and electromyographic study
Adaptation of rat jaw muscle fibers in postnatal development with a different food consistency: an immunohistochemical and electromyographic study
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DOI：
10.1111/j.1469-7580.2010.01235.x
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发表时间：
2010-06-01
影响因子：
2.4
通讯作者：
Tanaka, Eiji
中科院分区：
文献类型：
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作者：
Kawai, Nobuhiko;Sano, Ryota;Tanaka, Eiji
颅面系统的发育，除其他原因外，是对功能需求的反应。特别是，缺乏适当的咀嚼刺激会影响生长。本研究的目的是将出生后发育过程中肌肉活动的变化与肌纤维的适应性变化联系起来。14只21日龄Wistar系雄性大鼠随机分为两组，分别饲喂固体（硬饲料组）和粉末（软饲料组）饲料63天。植入一个无线电遥测装置，连续记录肌肉活动的浅表咬肌，二腹肌前腹和颞肌前。通过每天肌肉活动的总持续时间（工作时间）、总爆发次数及其超过峰值活动指定水平（5%、20%和50%）的平均长度来量化每日肌肉使用的程度。通过免疫组织化学染色的肌球蛋白重链含量检查肌肉的纤维类型组成，并测量其横截面积。所有肌纤维被鉴定为慢型I和快型IIA、IIX或IIB（分别具有增加的抽搐收缩速度和疲劳性）。在较低的活动水平（超过峰值活动的5%），二腹肌前腹的工作时间在软饮食组显著高于硬饮食组（P < 0.05）。在较高活动水平（超过峰值活动的20%和50%）时，软质饮食组的浅层咬肌工作时间显著低于硬质饮食组（P < 0.05）。在任何肌肉活动水平下，颞肌前肌的工作时间均无差异。软食组咬肌表浅部IIA型纤维的百分比显著低于硬食组（P < 0.01），IIB型纤维的百分比则相反（P < 0.05）。软食组咬肌浅层IIX型和IIB型纤维的截面积显著小于硬食组（P < 0.05）。二腹肌和颞肌前腹的肌纤维组成和横截面积无差异。总之，对于软食饲养的雄性大鼠的下颌肌，肌纤维的慢到快的转变仅在浅表咬肌中显示。因此，减少肌肉收缩的数量可能对肌纤维中肌球蛋白重链同种型从慢到快的转变很重要。
The development of the craniofacial system occurs, among other reasons, as a response to functional needs. In particular, the deficiency of the proper masticatory stimulus affects the growth. The purpose of this study was to relate alterations of muscle activity during postnatal development to adaptational changes in the muscle fibers. Fourteen 21-day-old Wistar strain male rats were randomly divided into two groups and fed on either a solid (hard-diet group) or a powder (soft-diet group) diet for 63 days. A radio-telemetric device was implanted to record muscle activity continuously from the superficial masseter, anterior belly of digastric and anterior temporalis muscles. The degree of daily muscle use was quantified by the total duration of muscle activity per day (duty time), the total burst number and their average length exceeding specified levels of the peak activity (5, 20 and 50%). The fiber type composition of the muscles was examined by the myosin heavy chain content of fibers by means of immunohistochemical staining and their cross-sectional area was measured. All muscle fibers were identified as slow type I and fast type IIA, IIX or IIB (respectively, with increasing twitch contraction speed and fatigability). At lower activity levels (exceeding 5% of the peak activity), the duty time of the anterior belly of the digastric muscle was significantly higher in the soft-diet group than in the hard-diet group (P < 0.05). At higher activity levels (exceeding 20 and 50% of the peak activity), the duty time of the superficial masseter muscle in the soft-diet group was significantly lower than that in the hard-diet group (P < 0.05). There was no difference in the duty time of the anterior temporalis muscle at any muscle activity level. The percentage of type IIA fibers of the superficial masseter muscle in the soft-diet group was significantly lower than that in the hard-diet group (P < 0.01) and the opposite was true with regard to type IIB fibers (P < 0.05). The cross-sectional area of type IIX and type IIB fibers of the superficial masseter muscle was significantly smaller in the soft-diet group than in the hard-diet group (P < 0.05). There was no difference in the muscle fiber composition and the cross-sectional area of the anterior belly of the digastric and anterior temporalis muscles. In conclusion, for the jaw muscles of male rats reared on a soft diet, the slow-to-fast transition of muscle fiber was shown in only the superficial masseter muscle. Therefore, the reduction in the amount of powerful muscle contractions could be important for the slow-to-fast transition of the myosin heavy chain isoform in muscle fibers.