正常人周围神经内膜中的纤维性长间距体及神经束膜细胞的超微结构

ULTRASTRUCTURE OF PERINEURIAL CELLS AND FIBROUS LONG-SPACING BODIES (FLS) IN ENDONEURIUM OF NORMAL HUMAN PERIPHERAL NERVE

本文报道在电镜下观察了正常人腹壁神经小分支的神经束膜细胞的超微结构,并在神经内膜间质中发现了纤维性长间距体(FLS)。1.2~5层神经束膜细胞紧密地包绕着神经束。束膜细胞呈扁平样排列,胞质内有丰富的微丝和吞饮小泡,基膜明显而连续。紧贴其外的和神经内膜中的成纤维细胞均无基膜。两相贴的束膜细胞之间可见缝管连接和丰富的桥粒,也可见胶原纤维。神经内膜间质中胶原原纤维细,有FLS体存在;而束膜外侧的胶原原纤维较粗,未见FLS体。2.多数FLS体与无髓神经纤维的Schwann细胞基膜相连,个别处周围为一般胶原原纤维,未见基膜;有髓神经纤维的Schwann细胞处未见FLS体。纵切面上,多数FLS体呈纺锤状,大小不等,其长轴与相邻胶原原纤维的长轴平行,有时可见两者相互延续移行。偶见FLS体呈桥样架于两Schwann细胞之间,FLS体的暗带与两侧Schwann细胞的基膜相延续。还见2~3个FLS体并为一体,但横纹错开。FLS体的斜断面近似长方形,也呈横纹样结构,与纵断面没有很大区别。FLS体的横纹周期长约133nm,暗带约53nm,主要由电子较密的颗粒状物构成;明带约80nm,由方向大致相同的微丝网构成;横纹周期中无细横纹存在。本文并对神经束膜细胞可能的作用、FLS体与基膜的关系、FLS体的横纹周期问题进行了讨论。

The perineurial cells of the small nerve branch of the normal human abdominal wall are observed with electron microscope.The fibrous long-spacing bodies(FLS)are found within the interstitial substance of the endoneurium.1.2-5 layers of the perineurial cells surround the nerve fasciculus.The perineurial cells are squamous in shape and the cytoplasm contains microfilaments and pinocytotic vesicles.Each perineurial cell has an obvious basement membrane on its basal surface but the fibroblasts,whatever situated in the endoneurium or on the outer surface of the perineurium,has no basement membrane.Numerous desmosome and some gap junctions between the close attached perineurial cells are demostrated.The collagen fibrils between perineurial cells can be often shown.FLS bodies and collagen fibrils about 45 nm in diameter in the interstitial substance of endoneurium inside perineurial cells are demonstrated.In the connective tissue surrounding the outside of perineurial cells,the collagen fibrils of 80 nm in diameter can be seen,but no FLS bodies present there.2.FLS bodies in the endoneurial matrix can be demostrated.Most of them closely associated with the basement membrane of the Schwann cells surrounding the unmyelinated nerves but no FLS bodies are found associate with those of the myelinated nerves.A few FLS bodies do not relate to basement membrane and they are invested only with the collagen fibrils.In the longitudinal sections,most of FLS bodies are in spindle shape of various sizes,their longitudinal axes parallel to that of the adjoining collagen fibrils.Sometimes the FLS bodies continue with the collagen fibrils are found.Occasionally,FLS body like a bridge locate between two Schwann cells and its dark bands continue to the basement membrane of the Schwann cells.Two or three FLS bodies may fuse together but their cross bands do not registered at the same level.In the oblique sections,FLS bodies are nearly rectangular in shape,with the cross bands shown,and their appearance do not show greaty difference from those in longitudinal sections.The periodicity of FLS bodies is about 133nm in length;the dark band in it is about 53 nm,which is made of the dense granular substance;the light band is about 80 nm,which is made of a network with approximated parallel microfilaments.There are no further crossstriated structures within the periods.Some problems,such as the role of the perineurial cells,the relationship of FLS bodies with basement membrane,are briefly discussed.