Ultrastructural study of the glomerular slit diaphragm in fresh unfixed kidneys by a quick-freezing method.
In normal kidneys fixed by perfusion with tannic acid and glutaraldehyde, glomerular slit diaphragms have been reported to consist of highly ordered and isoporous substructures with a zipper-like configuration. We have re-evaluated the ultrastructure of fixed or unfixed glomeruli using quick-freezing and deep-etching (QF-DE) and freeze-substitution (QF-FS) methods. In the fixed slit diaphragms, zipper-like substructures were often observed by the QF-DE method. In contrast, in fresh unfixed glomeruli the slit diaphragms mainly consisted of non-porous substructures. The slit diaphragms were more widely opened in the fixed glomeruli, as examined by the QF-FS method. These results suggest that the foot processes shrink during tissue preparation by conventional methods with chemical fixatives, and that the broadening of slit diaphragms and zipper-like substructures are formed by the pulling apart of adjacent foot processes due to shrinkage.
Ohno
S
S
Department of Anatomy, Shinshu University School of Medicine, Matsumoto, Japan.
Hora
K
K
Furukawa
T
T
Oguchi
H
H
D000818:Animals; D005613:Freeze Etching; D005614:Freeze Fracturing; D007678:Kidney Glomerulus / Q000502:physiology / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron / Q000379:methods; D009993:Osmium Tetroxide; D051381:Rats; D011919:Rats, Inbred Strains
D009993:Osmium Tetroxide