模拟失重对大鼠咬肌超微结构的影响

Effects of simulated weightlessness to the ultrastructures of masseter muscle in rats

目的:应用透射电镜观察模拟失重对大鼠咬肌超微结构的影响。方法:24只Wistar大鼠,随机分为4组:模拟失重1w组,模拟失重2w组,模拟失重4w组和正常对照组。4组大鼠的饲养条件相同,分别于实验第1w、第2w和第4w处死大鼠,通过光镜和透射电镜分别观察大鼠咬肌组织病理学以及超微结构的变化情况。结果:实验第1w、2w和4w,对照组大鼠体重为328.67±15.65、330.00±12.38和326.33±15.88,实验组大鼠体重分别为274.50±41.66、295.00±19.92和288.84±22.41,后者大鼠体重增长速度明显下降,与对照组相比差异具有统计学意义(P<0.05)。光镜下观察,1w组大鼠咬肌部分肌纤维溶解、粗细不均,横纹不清晰;其他各实验组肌纤维横纹清晰,无明显肌纤维溶解破坏现象。透射电镜下观察,1w组大鼠咬肌肌原纤维溶解,Z线不连续,线粒体重度肿胀,基质密度降低,线粒体嵴减少,严重者可见空泡化;2w组大鼠线粒体轻度肿胀,肌原纤维周围线粒体数目增多;4w组大鼠咬肌线粒体未见明显肿胀。结论:模拟失重可导致大鼠咬肌发生可逆性的损伤。

Objective： To study the influence of simulated weightlessness by tail-suspension to the ultrastructures of mas- seter muscle in rats. Method： 24 Wistar rats were randomly divided into three groups： lw simulated weightlessness group, 2w simulated weightlessness group, 4w simulated weightlessness group and control group. All the rats were raised under the same conditions and executed at the one weeks, the two weeks and the four weeks. The histopathological changes and ul- trastructures ofmasseter muscle were observed under microscope and electron microscope respectively. Result： At lw, 2w and 4w, the weight of rats were 328.67±15.65,330.00± 12.38 and 326.33±15.88 in the control group and 274.50±41.66, 295.00± 19.92 and 288.84±22.41 in the experimental groups. The rate of weight decreased, which showed statistically sig- nificant difference between the control group and the experimental groups. H＆E showed that there were the discontinuous Z-line, some dissolved and uneven myofibrils, and the abnormal striated structure in lw simulated weightlessness group. We observed no obvious inflammation or solution of muscle fibers in the other groups. By electron microscope, the severe swollen mitochondria with cristae loss, degrade of matrix density and even vacuolus degeneration were found in lw simu- lated weightlessness group. The mitochondria was slight swollen, of which the number increased around the myofibrils in 2w simulated weightlessness group. There was no obvious swollen in the mitochondria in 4w simulated weightlessness group. Conclusion： The simulated weightlessness can lead the reversible injury to the ultrastructures of masseter muscle.