FINE STRUCTURE OF MOTOR NERVE ENDINGS AT FROG MYONEURAL JUNCTIONS
FINE STRUCTURE OF MOTOR NERVE ENDINGS AT FROG MYONEURAL JUNCTIONS
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DOI：
10.1111/j.1749-6632.1966.tb45458.x
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发表时间：
1966-01-01
影响因子：
5.2
通讯作者：
BIRKS, RI
中科院分区：
文献类型：
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作者：
BIRKS, RI
单管成分和典型的突触小泡都是蛙肌神经交界处运动神经末梢超微结构的共同特征。小管通常位于轴膜非突触部分的轴浆中，而小泡通常聚集在轴膜的突触部分，甚至贴近轴膜的突触部分。这些小管的直径为400-600埃，约为一个小泡的直径，而上面提到的单管的直径通常较小，约为250-400埃。这些短小管存在的原因从未被认真研究过，尽管如果小泡是由简单小管萌芽形成的，就像其他细胞的内质网所提出的那样，那么短而大直径的小管可能是由于错误的出芽过程而产生的。这些实验的目的是为了进一步了解神经末梢中的这些细胞膜系统。采用了两种方法。首先，为了更好地保护神经末梢中的小管系统，青蛙缝纫肌被固定在丙烯醛中。这种固定剂最近被证明既保留了T小管，也保留了它与肌膜的连接。S的第二个结论是，在固定前，通过将肌肉浸泡在含有二氧化钍胶体颗粒(直径-100A)的林格液中，寻找有关可能的肾小管与轴膜连接的独立信息。第二种方法背后的原理类似于Huxley，8Page‘和Birks在展示这块肌肉中T管-肌膜连接的原理；即，如果神经末梢的小管连接到轴膜，如果它们开放到细胞外空间，这些颗粒应该扩散到它们里面。随后通过电子显微镜检测到小管中的颗粒，将为它们在生命中与细胞表面的联系提供推定证据。丙烯醛固定对神经末梢超微结构的整体保护作用并不比四氧化臭氧有明显改善。
Both simple tubular elements as well as the typical synaptic vesicles are common features of the ultrastructure of motor nerve endings at frog myoneural junctions.’The tubules usually lie in the axoplasm near the nonsynapsing portion of the axolemma, whereas the vesicles usually appear clustered towards, and even abutting on, the synapsing portion of the axolemma. Interspersed amongst this vesicle population, short tubular elements are also seen.’These latter tubules have a diameter of 400 to 600 A, about that of a vesicle, while the simple tubules referred to above are usually smaller in diameter, varying from about 250 to 400 A. The reason for the existence of these short tubular elements has never been seriously examined, although if vesicles were formed by budding off from the simple tubules, as has been proposed for the endoplasmic reticulum of other cells,’then the short, large diameter tubules might arise as a result of a faulty budding-off process. The purpose of the experiments to be reported here was to gain further information about these intracellular membrane systems in the nerve endings. Two methods have been employed. First, in the hope of better preserving the tubular system in the nerve endings, frog sartorius muscles were fixed in acrolein.‘This fixative has recently been shown to preserve both the T-iubules and their connections to the sarcolemma in this muscle. s ‘Second, independent information about possible tubular connections to the axolemma was sought by soaking muscles in Ringer solution’containing colloidal particles of thorium dioxide (-100 A diameter) prior to fixation. The rationale behind this second approach was similar to that of Huxley, 8 Page’and Birks’ in demonstrating the T-tubule-sarcolemmal connection in this muscle; namely, that if tubules in the nerve endings were connected to the axolemma, and if they opened into extracellular space, these particles should diffuse into them. The subsequent detection of particles in the tubules by electron microscopy would then provide presumptive evidence for their connection to the cell surface in life. The overall preservation of nerve ending ultrastructure is not noticeably improved by fixation with acrolein as compared with osmium tetroxide,