Molecular Sieve in Rat Tubular Basement Membrane as Revealed by Negative Staining

Abstract

Rat tubuli were isolated both by the method of Krisko and by a modified method of Cook and Pickering; renal tubular basement membrane (TBM) was isolated by sonic disruption and by the method of Carlson. Using electron microscopy after negative staining, TBM of rat kidney isolated under these different conditions was shown to be a fine meshwork. Strands of the meshwork were interwoven, apparently enclosing pores to make up whole basement membrane. These findings are compared with our previous observation that glomerular and alveolar basement membranes were made up of a similarly fine meshwork.

Meshwork Structures in Bovine Glomerular and Tubular Basement Membrane as Revealed by Ultra-High Resolution Scanning Electron Microscopy

“…The present findings obtained with HSEM confirm our previous study showing that the BM is a molecular sieve composed of pores and strands [9][10][11], The meshwork structure was not an artifact of the isolation procedure because similar meshwork structures 197 were observed in BMs isolated by two different procedures; we observed a similar meshwork structure using HSEM in untreated GBM specimens [Hironaka et al, unpubl. data].…”

“…We found that the meshwork structure was looser in the TBM than in the GBM in previous studies using negative staining and TEM [11,31]. A heterogeneous mesh structure was also observed in the present study.…”

Pores in the Glomerular Basement Membrane Revealed by Ultrahigh- Resolution Scanning Electron Microscopy

“…The presence of pores in the GBM has been postulated from physiological studies [I] and demonstrated by transmission electron microscopy (TEM) by us [2][3] and others [4][5][6], Although scanning electron microscopy (SEM) has an advantage over TEM in that topographical dissimilarity can be observed three-dimensionally, it failed to demonstrate the presence of pores in the GBM.In 1985, a new type of SEM, the ultrahighresolution SEM (HSEM), was developed by Tanaka et al [7]. It is equipped with a field emission source and an objective lens of very short focal length, and has a resolving power of 0.5 nm at 30 kV.…”

Definition of the Glomerular Basement Membrane

“…On electron microscopy, a lam ina rara externa is separated by the lamina densa from the lamina rara interna. The pores of the glomerular basement mem brane can be made visible showing the di mensions of 1 nanometer range [7]. Its func tional properties are the regulation of filtra tion and to serve as a scaffold.…”