[Intraepithelial filament bundles of the adult human kidney. Studies by light and electron microscopy and by diffraction analysis (author's transl)]

In studies of semi-thin sections of adult human kidney it is found that the structures formerly known as "Basalreifen" can be definitely related to basal cytoplasmic portions of the renal epithelium. Under the electron microscope they appear as bundles of filaments, usually having a width of 50-85 A. They are particularly well developed in the parietal layer of Bowman's capsule and are also present in the proximal and distal tubule where they are more abundant than in other parts of the nephron. The filament bundles proceed toward hemidesmosome-like structures at the basal border of the epithelia and sometimes contain dense bodies in the parietal capsular epithelium of the glomerulus; these bundles are probably responsible for local intra- and/or supravital protrusions of the cytoplasm. Findings in some diseased kidneys are also presented. Diffraction analysis of intrarenal vascular muscle cells and intraepithelial filament bundles gave comparable photographic records of the image structure spectrograms; it supports the assumption derived from the electron microscopic results that the intraepithelial filament bundles represent a contractile complex. However, the conclusiveness of image structure analysis in comparing the two biological objects is limited, as outlined in the discussion. With regard to renal function the significance of the intraepithelial filament bundles is still unclear. Periglomerular interstitial cells, which normally contain only narrow tracts of filaments in the periphery, had many of the characteristics of smooth muscle cells in a case of pyelonephritic renal cirrhosis. They are compared with myofibroblasts of a different origin.