FUNCTIONAL CHANGES IN FROG NEUROMUSCULAR-JUNCTIONS STUDIED WITH FREEZE-FRACTURE
FUNCTIONAL CHANGES IN FROG NEUROMUSCULAR-JUNCTIONS STUDIED WITH FREEZE-FRACTURE
复制标题
DOI：
10.1007/bf01111936
复制
发表时间：
1974-01-01
期刊：
影响因子：
--
通讯作者：
LANDIS, DMD
中科院分区：
文献类型：
--
作者：
HEUSER, JE;REESE, TS;LANDIS, DMD
在冷冻断裂的青蛙缝匠肌中，运动轴突长终支的表面有一系列狭窄的横脊，其边界是突触前膜内一排排相对较大的颗粒。通过它们与肌肉褶皱相对的独特位置，很明显，这些脊代表了突触小泡聚集在其周围的电子致密细胞质带的正面。在静息状态的终末，除了偶尔有小泡挤压质膜外，没有迹象表明这些脊下有小泡；但在用固定剂短暂刺激的终末，脊被许多小酒窝包围，突触小泡附着在质膜上。当镁离子被用来阻止刺激产生的递质释放时，这种“囊泡位置”不会出现，因此它们可能代表了递质释放的位置。然而，在较慢作用的固定剂刺激的终末出现更多的囊泡位置，因此它们似乎在固定过程中积累了一段时间，并不表明递质释放的瞬时水平。小泡部位的大小和形状各不相同，可能代表了小泡排出的不同阶段。在Schwann突起下的刺激过程中出现的酒窝有时比囊泡位置大，但在其他方面看起来很相似；因此很难区分突触小泡放电的冰冻断裂图和该突触的涂层小泡形成的冰冻断裂图。神经末梢下的肌膜上铺满了较大的颗粒团，这些颗粒团大多出现在骨折后膜的胞浆半部。这些颗粒团出现在突触后膜上，这些区域被电子致密的细胞质绒毛斑块覆盖。紧接在星团周围的是一些紧密堆积的、由略小的粒子组成的正交聚集体。
In freeze-fractured frog sartorius muscles, the long terminal branches of motor axons possess a series of narrow transverse ridges on their surface, bordered by rows of relatively large particles within the presynaptic membrane. By their exclusive location opposite muscle folds, it is apparent that these ridges represent anen faceview of the electron-dense cytoplasmic bands around which synaptic vesicles cluster. In resting terminals there is no sign that vesicles underlie these ridges, except for an occasional bulge where a vesicle presses against the plasmalemma; but in terminals stimulated briefly in fixative, the ridges are surrounded by a number of small dimples where synaptic vesicles attach to the plasmalemma. Such ‘vesicle sites’ do not appear when Mg++is used to prevent the transmitter release that results from stimulation, so they presumably represent sites of transmitter discharge. However, more vesicle sites appear in terminals stimulated in more slowly acting fixatives, so they appear to accumulate for some time during fixation and do not indicate the instantaneous level of transmitter release. Vesicle sites occur in a variety of sizes and shapes that may represent different stages of vesicle discharge. Dimples which appear during stimulation under Schwann processes, where endocytosis of coated vesicles has been found to occur, are sometimes larger than vesicle sites but otherwise look much the same; so it is not possible to readily distinguish between the freeze fracture images of synaptic vesicle discharge and coated vesicle formation at this synapse. The muscle membrane beneath nerve terminals is paved with clusters of relatively large particles which mostly appear on the cytoplasmic half of the membrane after fracture. These clusters of particles occur in regions of the postsynaptic membrane that are coated by plaques of electron-dense cytoplasmic fuzz. Immediately around the clusters are a number of tightly-packed, orthogonal aggregates of slightly smaller particles.