ISSN:
1432-0878
Keywords:
Capillary endothelium
;
(Retina)
;
Tight junction artefact
;
Sodium ions
;
Streptozotocin
;
Diabetes
;
Electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Retinal capillary junctions were analysed in normal and diabetic rats and in a human retina with the electron microscope. Diabetes mellitus was induced with Streptozotocin. The retinae were fixed in Palade's osmium tetroxide containing sodium or calcium ions and block-stained in uranyl acetate. With Ca-fixation, no significant difference in interendothelial cleft width was detected between retinal layers or between normal and diabetic retinae. Diabetes caused a narrowing of the clefts in the Na-fixed tissue (X±SE, n=375; Normal: 78.6±3.00 Å; Diabetic: 57.7 ±2.42 Å; p≪0.001). A significant correlation was found between cleft width and the length of the tight junctions or zonulae occludentes (p〈0.001). In the nerve fibre layer of the Nadiabetio retina, where cleft narrowing was greatest, there was an increase in length of the zonulae occludentes from 22.8±2.2% to 41.6±3.7% (p〈0.001). Ca-fixation prevented these changes, indicating that at least some zonulae occludentes were interendothelial extraction artefacts. In the normal retina, endothelial cell membrane thickness was greater with Ca-than Na-fixation (p〈0.001). Diabetes caused a decrease in membrane thickness of Ca-fixed tissue (p〈0.001). The diabetic decrease in membrane thickness may explain the increased fragility and increased permeability of diabetic capillaries. Calcium binding by endothelial cell membranes is of primary importance in anticoagulation which is defective in diabetes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00220007
