Nakano M, Atobe Y, Goris R C, Yazama F, Ono M, Sawada H, Kadota T, Funakoshi K, Kishida R
Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama, 236-004 Japan.
Anat Rec. 2000 Nov 1;260(3):299-307. doi: 10.1002/1097-0185(20001101)260:3<299::AID-AR67>3.0.CO;2-V.
The infrared sensory membranes of pit organs of pit vipers have an extremely rich capillary vasculature that forms many vascular loops, each serving a small number of infrared nerve terminals. We clarified the ultrastructure of capillary pericytes in the pit membranes by scanning and transmission electron microscopy, and examined the immunoreactivity in their cytoplasm to two contractile proteins: smooth muscle alpha-actin (SM alpha-actin) and desmin. The capillary pericytes had two major cytoplasmic processes: thickened primary processes that radiate to embrace the endothelial tube and flattened secondary processes that are distributed widely on the endothelium. Coexpression of SM alpha-actin and desmin was observed in the pericytes of entire capillary segments, and SM alpha-actin was characterized by prominent filament bundles directed mainly at right angles to the capillary long axis. This expression pattern was different from that of capillary pericytes of the scales, where SM alpha-actin was expressed diffusely in the cytoplasm. In a series of electron microscopic sections, we often observed the pericyte processes depressing the endothelial wall. We also observed a close relationship of the pericytes with inter-endothelial cell junctions, and pericyte processes connected with the endothelial cells via gap junctions. From these findings, we surmised that capillary pericytes in the pit membrane have a close functional relationship with the endothelium, and through their contractile and relaxing activity regulate capillary bloodflow to stabilize production of infrared nerve impulses.
蝰蛇颊窝器官的红外感觉膜具有极其丰富的毛细血管脉管系统，形成许多血管环，每个血管环为少量的红外神经末梢提供服务。我们通过扫描电子显微镜和透射电子显微镜阐明了颊窝膜中毛细血管周细胞的超微结构，并检测了它们的细胞质对两种收缩蛋白的免疫反应性：平滑肌α-肌动蛋白（SMα-肌动蛋白）和结蛋白。毛细血管周细胞有两个主要的细胞质突起：增厚的初级突起，呈放射状环绕内皮管；扁平的次级突起，广泛分布在内皮上。在整个毛细血管段的周细胞中观察到SMα-肌动蛋白和结蛋白的共表达，SMα-肌动蛋白的特征是有突出的细丝束，主要与毛细血管长轴成直角。这种表达模式与鳞片的毛细血管周细胞不同，在鳞片中SMα-肌动蛋白在细胞质中呈弥漫性表达。在一系列电子显微镜切片中，我们经常观察到周细胞突起压迫内皮壁。我们还观察到周细胞与内皮细胞间连接密切相关，周细胞突起通过缝隙连接与内皮细胞相连。根据这些发现，我们推测颊窝膜中的毛细血管周细胞与内皮具有密切的功能关系，并通过其收缩和舒张活动调节毛细血管血流，以稳定红外神经冲动的产生。
