Morphometric study of glomerular slit diaphragms fixed by rapid-freezing and freeze-substitution

Morphometric study of glomerular slit diaphragms fixed by rapid-freezing and freeze-substitution. The widths of slit diaphragms in rat glomeruli were quantitatively measured on electron micrographs obtained by the rapid-freezing and freeze-substitution (FS) fixation method and compared to those prepared by conventional chemical fixation procedures, such as tannic acid, glutaraldehyde and osmium tetroxide (TGO) or glutaraldehyde and osmium tetroxide (GO) fixation. When fixed by FS using 2% osmium tetroxide, glomerular slit diaphragms had widths of 33.8 ± 3.6 nm, but when fixed by TGO or GO they had widths of 47.0 ± 4.3 and 48.7 ± 5.5 nm, respectively. The width of slit diaphragms was significantly narrower after cryofixation than after conventional TGO or GO fixation (P