Ultrastructural transition from the elastic to the muscular arteries

比较了肌动蛋白细丝(AFS)在主动脉(弹性动脉)和肾内动脉(肌动脉)内的分布。在成年大鼠，内皮AFS在这些动脉节段的分布模式几乎相同。相反，成人主动脉内皮细胞内的AFS由出生时的应力纤维向外周带重组。肾内动脉内皮下基底膜在动脉树的走行过程中表现出超微结构的异质性，为了比较弹性动脉和肌肉动脉的内侧超微结构，我们研究了肺内动脉，这两种类型的动脉的过渡可以在肺内追踪到。结果表明，这种转变发生在肺内，没有任何中间节段。对肌球蛋白重链异构体的免疫细胞化学研究表明，肾小球传入和传出小动脉之间存在分子异质性。详尽的形态计量学研究表明，在出生后大鼠肾脏的发育过程中，肾小球体积主要通过毛细血管的延长而增加，并伴随着肾小球基底膜的扩张。电子显微镜显示，肾小球足细胞内的细胞骨架主要分布在肾小球的外围，被认为是扩张的“基底膜外袋”。在孤立的灌流肾中，肾小球滤过屏障是可伸展的，足细胞中的细胞骨架被认为可以抵消这种过度伸展。在Masugi肾炎大鼠，足细胞足突的收缩伴随着足细胞的重组，这些足细胞可能阻止足细胞从基底膜脱离。

The distribution of actin filaments (AFs) in the endothelial cells was compared between in the aorta (elastic artery) and in the intrarenal arteries (muscular artery). In the adult rats, the distributional patterns of endothelial AFs in these arterial segments were almost identical. On the contrary, AFs in the aortic endothelial cells were shown to be reorganized from the stress fibers at birth to the peripheral bands in the adult. The subendothelial basement membranes of the intrarenal arteries showed the ultrastructural heterogeneity along the course of the arterial tree.For the comparison of the medial ultrastructure between elastic and muscular arteries, we studied the intrapulmonary arteries, where the transition of the two types of arteries could be traced within the lung. It was revealed that the transition occurs abruptly in the lung without any intermediary segment. An immunocytochemical study on the myosin heavy chain isoforms revealed a molecular heterogeneity between the renal glomerular afferent and efferent arterioles.An exhaustive morphometric study revealed that, during postnatal development of the rat kidney, the glomerular volume increased mainly through the elongation of capillaries, and the elongation was accompanied by expansion of glomerular basement membranes (GBM). Electron microscopy showed that "GBM-outpockets", where GBM are thought to be expanded, were distributed chiefly in the periphery of the glomeruli.The cytoskeletons in the renal glomerular podocyte was studied in experimental models. In the isolated perfused kidneys, the glomerular filtration barrier was shown to be extensible and the cytoskeletons in the podocyte was thought to counteract against the excessive extension. In the Masugi-nephritis rats, retraction of the foot processes of the podocytes was accompanied by the reorganization of AFs, and these AFs seem to prevent of the detachment of podocytes from GBM.