Biochemical and ultrastructural study of human diabetic conjunctiva.
Combined biochemical and ultrastructural study of conjunctival biopsies of 27 normal subjects and 45 diabetics (40 to 60 years old) was made. The "in vitro" incorporation of 14C-glucosamine and 3H-proline in freshly excised conjunctival biopsies was studied. The alterations of the capillary basement membrane of the conjunctiva were studied by electron microscopy. The following results were obtained: 1) A decrease of the specific activity of 14C-glucosmaine incorporation was found in fractions of diabetic conjunctiva. 2) In diabetic conjunctiva the percentages of 3H-proline incorporation in polymeric collagen containing fraction and structural glycoproteins containing fraction were significantly increased with a parallel decrease of 3H-proline incorporation in "crude soluble collagen" fraction expressed as a percentage of total incorporation. 3) Significant thickening of capillary basement membrane was observed with the appearance of collagen-like fibrils within the basement membrane in diabetic conjunctiva. Such fibrils were not seen in normal basement membranes. A relation between the extent of basement membrane thickening and the appearance of collagen-like fibrils is suggested. 4) The higher percentage of incorporation of 3H-proline in polymeric collagen may be related to the appearance of collagen fibrils in thickened basement membranes of the diabetic conjunctival capillaries. 5) These results suggest an abnormal regulation of the relative rate of biosynthesis and/or excretion of intercellular matrix macromolecules (collagen, structural glycoproteins) as part of the metabolic disorders characterising diabetes.
D000328:Adult; D001485:Basement Membrane / Q000648:ultrastructure; D002196:Capillaries / Q000648:ultrastructure; D002250:Carbon Radioisotopes; D003094:Collagen / Q000096:biosynthesis / Q000378:metabolism; D003228:Conjunctiva / Q000098:blood supply / Q000648:ultrastructure*; D003920:Diabetes Mellitus / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000096:biosynthesis / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D014316:Tritium
D002250:Carbon Radioisotopes; D006023:Glycoproteins; D014316:Tritium; D003094:Collagen