A galactosamine containing proteoglycan in human vitreous

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Morphologic and molecular changes during the post-natal development of the rabbit vitreous

Rabbits aged 1, 4, 10, 15, and 20 days, and 4 months were anesthetized and perfused with 4% formaldehyde. One eye of each rabbit was processed for paraffin embedding, while the other eye was embedded intact in methacrylate. Rabbits aged 1 and 15 days and 4 months were perfused with 2.5% glutaraldehyde, and the eyes were processed for Epon embedding. The paraffin sections were immunostained to allow detection of a high molecular weight cartilage matrix glycoprotein (CMGP), which is synthesized by the ciliary body and found in the vitreous in adult animals, using a specific mouse monoclonal antibody. CMGP was identified in the vitreous and in the inner layer of the ciliary epithelium only after the fifteenth day of life in amounts comparable to those detected in adult rabbits. Before this time immunostaining with the monoclonal antibody was seen only in the apical region of the inner ciliary epithelial cells. However, electron microscopic observations revealed that the cytoplasmic organelles responsible for the secretion of glycoproteins, i.e. the rough endoplasmic reticulum, Golgi apparatus, and vesicles, were present in the inner layer of ciliary epithelial cells as early as the first day of life. Anteroposterior sections of whole eyes embedded in methacrylate revealed a relatively dense meshwork of vitreous fibrils on the first day of life. The blood vessels were concentrated at the posterior region of the lens, and isolated cells were visible. The blood vessels were not seen after the age of 15 days, and the fiber meshwork and cells were inconspicuous by then.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial characterization, origin and turnover of glycoproteins of the rabbit vitreous body

L-[3H]fucose was injected intravitreally into rabbits that were killed from 1 hr to 28 days after injection. The vitreous bodies were processed for radiometric techniques, and electrophoresis followed by fluorography. Unbound [3H]fucose remained at a high level up to 1 day, whereas the peak of [3H]fucose bound to glycoproteins was observed at 3 days after injection with a continuous decrease afterwards. The turnover rate of vitreous glycoproteins was estimated at 4.37% per day and their turnover time at 22.85 days. Electrophoresis and fluorography combined revealed about 14 bands of glycoproteins with fucose residues and there were strong indications of differences in turnover rate among individual glycoproteins. The most prominent band in the Coomassie blue-stained gels was the one having a molecular weight of 69 kDa and it was not labeled with [3H]fucose. This band was tentatively identified as serum albumin. On the other hand, the 14 bands labeled with [3H]fucose were glycoproteins originating from within the eye, that is, they are intrinsic constituents of the vitreous body.

Vitreous contains a cartilage-related protein

The vitreous is a clear, gel-like mass in the posterior cavity of the eye. Its major components are type II collagen, hyaluronic acid, and water. A small amount of proteoglycan is also present. All of these molecules are found in cartilage as well. We have now identified a non-collagenous protein in bovine and human vitreous samples which has hitherto been found only in hyaline cartilage and fibrocartilage. This protein has a molecular weight of 550,000 and subunits of 130,000 MW and appears to be a shared cartilage and eye antigen. Its role, if any, in ocular disease associated with rheumatic disorders remains to be determined.

Histochemical demonstration of hyaluronic acid molecules by alcian blue

Specimens of vitreous humour (monkey eye), Wharton jelly (human umbilical cord) and commercial hyaluronates were immersed in buffered fixative solutions containing either aldehydes and Alcian Blue, or aldehydes and Alcian Blue with MgCl2 as electrolyte. Two MgCl2 concentrations were used, 0.025 M and 0.3 M. Immersion in both solutions induced formation of precipitates which were postfixed in OsO4, dehydrated and embedded for thin section electron microscopy. The use of the same fixative solution produced morphologically comparable precipitates from all three materials. The precipitates, especially after fixation in the presence of electrolyte, were composed of linear, unbranched filaments, frequently aggregated into bundles. The filaments were considered to be molecules of hyaluronic acid.

Synthesis of chondroitin sulfate by fibrotic vitreous induced by monocytes and lymphocytes

Vitreous fibrosis was induced in rabbit eyes by intravitreal injection of monocytes and lymphocytes. The fibrotic vitreous and normal vitreous removed from experimental animals were then incubated with [3H]-glucosamine at 37 degrees C for 24 hr. The newly synthesized 3H-labeled glycosaminoglycans (GAGs) were isolated by 4 M GuHCl extraction followed by pronase digestion. The 3H-labeled GAGs were then characterized by gel-filtration column chromatography and by specific enzymatic degradation, i.e. hyaluronidase, chondroitinase AC and/or chondroitinase ABC. The disaccahrides derived from chondroitinase ABC degradation were identified by thin-layer chromatography. Our results indicated that 91% of the total glycosaminoglycan synthesized by normal vitreous was hyaluronic acid. In contrast, in the fibrotic vitreous, the synthesis of hyaluronic acid was decreased to 30% whereas the synthesis of chondroitin sulfate increased to 47% of the total newly synthesized glycosaminoglycans. Control vitreous which was injected with freeze-thawed monocytes and lymphocytes synthesized 70% hyaluronic acid and 12% chondroitin sulfate although no fibrosis was observed.

Glycosaminoglycan metabolism of cultured fibroblasts from bovine vitreous

Glycosaminoglycan metabolism of cultured vitreal cells of bovine origin was investigated with the following results: Cultured vitreal cells distributed the synthesized macromolecules after [35S] sulfate incorporation into the culture medium (extracellular pool), the membrane-bound proteoglycans (pericellular pool), and within the cells (intraocular pool). No extracellular plateau was reached after 3 days; the pericellular and intracellular pools showed a steady state of radioactivity after 48 and 24 h, respectively. Pulse-chase experiments exhibited a rapid turnover of intracellular polysaccharides and a slower metabolism of pericellular polymers. Pinocytosis, adsorption and degradation of vitreal and corneal cell secretion by vitreal cells were observed to a comparable extent. Chondroitin sulfate isomers and heparan sulfate could be detected in minor proportions. The relevance of glycosaminoglycan metabolism in the replacement of cultured vitreal cells into the vitreous cavity is discussed.

Degradation of glycosaminoglycans by extracts of calf vitreous hyalocytes

The ability of extracts of calf vitreous hyalocytes to catalyze the degradation of glycosaminoglycans was studied by incubation with radioactively labeled substrates. The degradation of the polymeric substrates to lower molecular weight products was assayed by three methods: (1) paper chromatographic separation of low molecular weight, mobile digestion products from undigested, high molecular weight material which remains at or near the origin; (2) loss of the ability of the glycosaminoglycan to be precipitated by cetylpyridinium chloride; (3) gel chromatography to separate low molecular weight digestion products, which appear in the retarded volume, from undegraded, high molecular weight material, which is eluted in the void volume. The acidic pH optimum of the reaction suggests a lysosomal origin of the enzyme activity.

Glycosaminoglycans: structure and interaction

In the last few years, there has been considerable progress in the studies on glycosaminoglycans, a group of acidic polysaccharides present in the intercellular matrix of connective tissue. X-ray diffraction studies have indicated that these polymers can exist in the condensed phase in some helical form. Chiroptical and hydrodynamic measurements have provided significant information regarding the molecular conformation in solution and other physicochemical properties of the polymers. Studies related to the interaction properties of glycosaminoglycans with polypeptides, metal ions, and other molecules are numerous. This review covers mainly the results and their interpretations of both published and as yet unpublished material of the 1970s, but certain previous data are also included. A present-day concept regarding the structure and interaction properties of these molecules on the basis of various physicochemical measurements is presented. The biosynthesis and metabolism of glycosaminoglycans, and the structure of proteoglycans and glycoproteins, are not discussed.