小白鼠运动终板和肌梭的发育

OBSERVATIONS ON THE DEVELOPMENT OF MUSCLE SPINDLES AND MOTOR END PLATES OF THE MICE

哺乳类骨骼肌神经损伤或实验性切除肌神经以后,不但出现肌功能障碍,而且不久发生肌萎缩。这种现象许多学者认为是神经对肌肉的营养性影响(Stocker^([1]))。它的机制至今还不十分清楚。“神经营养性关系的问题与发育分化这个生物学基本问题有密切关系”(冯德培^([2]))。观察骨骼肌神经的发育是探讨神经对肌肉的营养性影响的基础研究的一个方面。文献上研究骨骼肌神经的发育主要集中在运动终板和肌梭两方面。

Fourty-eight prenatal and postnatal mice were used to observe the development of muscle spindles and motor end plates.Muscle tissues were embedded in paraffin,serially sectioned and impregnated with urea silver nitrate.Three categories of nerve fibres were seen to enter a muscle spindle,i e,1)Coarse fibre.It distributes over the equatorial region of the spindle.It does not show spirality untill the age of fifteenth day after birth;2)Median fibre.3)Fine fibre.The latter two distribute beyond the equatorial region.There is dotted enlargements at the end of each fine fibre.We could not find out the endings of median fibers.During the prenatal and postnatal stages of development the shape of motor end plates displays several transitional forms before they reach the mature ones.At about the postnatal age of fifth day,the motor endings of extrafusal fibre have the shape of bulb or leaf.At the age of fifteenth day after birth,they show the form of basket or glo-merulus;at the end of first month after birth the motor endings begin to show dicho-tomus plasmodesma.At the advanced ages,The muscle fibres become wider,the plasmodesma of motor end plate increase up to 8~16 branches in number at the end of third month after birth.Even at this time the motor end plates still give rise to new buds as the muscle fibre increases in width.Teloglia nuclei and soleplasm nuclei increase in number gradually after birth in accord with repeated dichotomy of the motor end plate.