Development of terminal arbors of retino-geniculate axons in the kitten--II. Electron microscopical observations.
Development of terminal arbors of retino-geniculate axons in the kitten--II. Electron microscopical observations.
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小猫视网膜膝状体轴突末端乔木的发育--II。
DOI：
10.1016/0306-4522(82)90064-1
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发表时间：
1982
期刊：
影响因子：
3.3
通讯作者：
Mason,CA
中科院分区：
文献类型：
--
作者：
Mason,CA
出生后1至8周的小猫个体视网膜膝状体轴突乔木密集充满辣根过氧化物酶。不同类型的未成熟生长尖端的光镜外观与它们在电子显微镜中所见的突触关系相关。在出生后的前2周，广泛的不规则的喷雾状终端扩展以及叶状生长锥状终端的基础上，包含圆形的突触囊泡和苍白的线粒体特征的成人视网膜终端。它们形成基本的肾小球排列，其中它们是与树突轮廓突触的中心轮廓。许多突触后轮廓包含大的电子透明囊泡的特征生长的神经突，而不成熟的视网膜终端没有。数量较多的指状生长尖还含有圆形突触囊泡，并缩短了与树突和膝状体细胞胞体的接触。后一种接触在成人中未见，3周后，视网膜终末变大，并以明显的肾小球排列方式进行接触。神经胶质鞘首次出现。到6-8周，在光镜下出现细圆齿状的终末总是成熟肾小球的中心轮廓。较小的圆形终端简单的轴-树突接触在成人。8周时所见的少数未成熟终末结构也含有突触小泡，但它们的接触不像成年样，它们的突触排列也不完全被胶质细胞包围。这些发现，沿着前面的研究结果，17证明：（a）许多视网膜膝状体终末在达到成年形态之前很久就建立了突触接触;（B）在诱导跨板轴突发芽的最佳时期出生后1-2周，仅有少数未成熟终末形态参与初级肾小球;（c）第（1）款3周后，这些轴突的延展性下降，伴随着进入被胶质鞘包围的肾小球的细圆齿状终末的增加。星形胶质细胞的突触排列可能是随后阻碍老年动物轴突发芽的一个因素。
Individual retino-geniculate axon arbors from kittens of 1 to 8 postnatal weeks were densely filled with horseradish peroxidase. The light-microscopical appearance of various types of immature growing tips was correlated with their synaptic relations as seen in the electron-microscope. During the first 2 postnatal weeks, the broad irregular bases of spray-like terminal extensions as well as foliate growth-cone-like terminals contain the round synaptic vesicles and pale mitochondria characteristic of adult retinal terminals. They form elementary glomerular arrangements in which they are the central profile synapsing with dendritic profiles. Many postsynaptic profiles contain large electron-lucent vesicles characteristic of growing neurites, whereas the immature retinal terminations do not. The more numerous finger-like growing tips also contain round synaptic vesicles and make shorten passagecontacts onto dendrites and outgrowths of perikarya of geniculate cells. The latter type of contact is not seen in the adult.After 3 weeks, retinal terminals are larger and make contacts in distinctly glomerular arrangements. Glial sheaths are evident for the first time. By 6–8 weeks, the terminals which appear crenulated in the light-microscope are always the central profile in a mature glomerulus. Smaller rounder terminals make simple axo-dendritic contacts as in the adult. The few immature terminal structures seen at 8 weeks also contain synaptic vesicles, but their contacts are not adult-like, nor are their synaptic arrangements entirely surrounded by glia.These findings, along with those of the previous paper,17demonstrate that(a)many retino-geniculate terminals establish synaptic contacts long before attaining their adult form;(b)during the period optimal for induction of translaminar axon sprouting (1–2 weeks postnatal), only a few immature terminal forms participate in elementary glomeruli;(c)the decreasing malleability of these axons after 3 weeks is accompanied by an increase in crenulated terminals that enter glomeruli surrounded by glial sheaths.It is suggested that ensheathing of synaptic arrangements by astrocytic glia may be one factor which subsequently impedes axon sprouting in older animals.