玉米螟幼虫侧单眼的神经鞘和胶质细胞

THE NERVE SHEATH AND GLIAL CELLS OF THE STEMMATAL NERVE OF THE OSTRINIA NUBILALIS LARVA

用透射电镜观察了欧洲玉米螟Ostrinia nubilalis(Hbner)5龄幼虫侧单眼神经的神经围膜、周神经细胞和其他神经胶质。神经围膜与若干周神经细胞包围若42根轴突。周神经细胞的原生质膜在它们的侧面和内面高度卷曲,并与相邻细胞交错对插,这是细胞与细胞间的特殊连接方式;它们的外面以桥粒和半桥粒固定在神经围膜内面。周神经细胞由神经胶质细胞演化而来,所形成的膜称神经束膜,它与神经围膜组成围在侧单眼神经外面的神经鞘。侧单眼神经内的神经胶质细胞大而平整,具有许多突起物(相当于脊椎动物的少突神经胶质细胞),每一个突起物包被一个感光轴突。神经胶质细胞包被轴突的形式有三种不同的类型:一种是相邻轴突间插入15层神经胶质细胞突起物所形成的普通轴系膜形式,另两种是神经胶质细胞突起物在一个轴突的周围,由一些褶所形成的不同形式。最后,对这些神经胶质细胞以不同形式包被轴突的功能意义进行了讨论。

The neural lamella,perineurial cells and other glia of the stemmatal nerve of Ostrinia nu-bilalis larvae were observed with transmission electron microscope.The neural lamella and several perineural cells were found enveloping the core of forty-two axons.The plasma membranes of perineurial cells are very convoluted and interdigitafing on their lateral and interior borders to assure good cell to cell cohesion.These cells bind into each other and to the undely-ing neural lamella with spot desmosomes and hemi-desmosomes respectively The perineurial cells are derived from glia and also named perineurium.The interior glial cells,likened to vertebrate oligodendroglia,are large and flatened with numerous processes each of which wraps a different photoreceptor axon.Three different patterns of glial wrapping were noted.These ranged from a usual mesaxonal formation with up to 15 intervening glial processes between adjacent axons to a single glial envelopment of an axon but with glial pleats non-con-centrically around the axons.The functional significance of these diverse forms of glial enshea-thment is discussed.