Biomedical subjects

Z Dische

Publications and source records attributed to Z Dische.

At least 19 recordsLinked to original sources

PubMed1985

Differences between two fractions of glycosaminoglycans of the corneal stroma in their structural relation to collagen.

Glycosaminoglycans (GAG) of bovine cornea were sequentially extracted by 0.15 M NaCl and by 1 M CaCl2, pH 8. The amounts of hexosamine (HexN) and hexuronic acid (HexUA), specific hexoses (Hex), and protein were determined in the extracts. The ultrastructure of the corneal stroma after NaCl and NaCl/CaCl2 extraction was also studied. Approximately 70% of the Hex-HexN extractable by 0.15 M NaCl is removed in the first NaCl extract, with the amount decreasing rapidly to the fifth NaCl extract. Only 20-30% of the extractable HexUA-HexN is removed in the first NaCl extract; subsequent extraction removes successively less HexUA-HexN. There is a sharp increase, however, in both Hex-HexN and HexUA-HexN removed in the first 1 M CaCl2 extract, ranging from 25 to 40% of the total extractable with NaCl. The stroma retained lamellar organization and normal spacing, diameter, and length of collagen fibers after NaCl extraction. Visibility of the 64-nm periodicity was enhanced because of loss of density in the ground substance. CaCl2 extraction led to loss of lamellar organization and apparent disruption of the collagen fibers. Only short thin fibrils remained, embedded in a material having the density and very fine fibrillar organization of basal lamina. Disruption of the collagen fibers is probably due to removal of a specific GAG component necessary to maintain the collagen as an extended morphologic structure but may also be due to a specific degradative effect of CaCl2 on collagen no longer covered by a protective layer of GAG and glycoproteins.

Animals↗

PubMed1983

Studies on the cornea. X. Incorporation of 14C-glucosamine into glycosaminoglycans and glycoproteins of elasmobranch corneas, extractability of these components and morphological effects of such extractions.

Incorporation of 14C-glucosamine into dogfish (Squalus acanthias) corneas occurs primarily in the glycosaminoglycans (GAG) and glycoproteins (GP) extractable with elasmobranch Ringer's solution but the rate at which this component can be extracted varies inversely with the age (size) of the fish. Whereas this fraction represents only one-fourth of the total hexosamine (Hex-N) it contains nearly three-fourths of the newly incorporated 14C-glucosamine. The CaCl2-extractable HexN contains only 13% of the incorporated radioactivity. Collagen-associated GAG in both soluble and insoluble collagen fractions contain keratan sulfate, dermatan sulfate and chondroitin-4-sulfate, with the GAG associated with the salt-insoluble collagen having only half the radioactivity of those associated with the soluble fraction. However, the specific activities of both the salt-insoluble and the salt-soluble fractions were very low, suggesting that the GAG-GP which are tightly bound to collagen may have a high degree of stability. Partially de-epithelialized corneas incorporated 14C-glucosamine at rates ranging from 22% to 58% of the efficiency of intact corneas, suggesting a possibly significant role of the epithelium in the biosynthesis of GAG-GP in the adult dogfish. Morphologic results exactly paralleled those previously reported by us for the bovine cornea with the exception that the effects of CaCl2 extraction of GAG-GP were not evident on the collagen fibers until the second to fifth sequential CaCl2 extraction. The morphologic findings, therefore, exactly parallel the analytic findings which show that a significant portion of the collagen and collagen-associated GAG-GP of the dogfish cornea remains after the double extraction. How much of this remaining material represents sutural fibers and their associated GAG-GP is yet to be determined.

Animals↗

PubMed1975

Some biochemical aspects of light effects on transparent eye tissues.

The usefulness of biochemical studies on effects of light on transparent tissues of the mammalian eye is discussed in relation to the possible role of photobiological phenomena in aging and pathology of the eye. Particular emphasis is on effects of light on interaction between different cellular constituents of the corneal stroma which appear as a factor in regulation of the corneal metabolism. Daylight filtered through the walls of glass vessels was found to depress the incorporation of 14-C glucosamine into keratansulfate fraction of the bovine corneal stroma which appears not to be bound to collagen fibrils as it is extracted by 0.15M NaC1 at 4 degrees C without any morphological change in these fibrils. Since this depression was not found in the absence of the epithelium, secretions by the epithelium of specific substances affecting the keratoyctes are suggested. The possible relation of light effects on the hydration of the cornea is discussed.

Animals↗

PubMed1975