Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.36 (hyaluronidase)
 4,606 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Corneas from mouse, rat and rabbit were analysed quantitatively and/or qualitatively for collagen and acid glycosaminoglycans. They were examined by light and electron microscopy, using Alcian blue and Cupromeronic blue, in critical electrolyte concentration methods, with or without digestion by hyaluronidase, chondroitinases and keratanase, for their sulphated glycosaminoglycan distributions. Glycosaminoglycan patterns were very different in the three species. Mouse lacked chemically detectable keratan sulphate, which was present in considerable amounts in rat and rabbit stroma. Mouse corneal stroma proteoglycan filaments were located predominantly at the gap zone of the collagen fibrils, mainly at the d band, with few at the a and c bands. Rat and rabbit micrographs were more complicated, with many proteoglycan filaments at the a and c, as well as the d and e bands. These findings support the proposal that the a and c bands were specific binding sites for keratan sulphate proteoglycan (Scott & Haigh, 1985b). Evidence from studies on cornea and cartilage suggests that keratan sulphate, rather than chondroitin sulphate is produced in conditions of O2 lack. Metabolic mechanisms which could account for this balance are proposed The production of uridine diphosphate glucuronic acid is the key step, which is sensitive to hypoxia, lactate and NAD:NADH ratios.
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PMID:Keratan sulphate and the ultrastructure of cornea and cartilage: a 'stand-in' for chondroitin sulphate in conditions of oxygen lack? 297 65

This paper examines the role of the extracellular matrix (ECM) in the development of the cornea. After a brief summary of the corneal structure and ECM, we describe evidence suggesting that the differentiation of neural crest (NC) cells into endothelium and fibroblasts is under the control of ocular ECM. We then examine the role of collagen I in stromal morphogenesis by comparing normal corneas with those of homozygous Mov 13 mice which do not make collagen I. We report that, in spite of this absence, the cellular morphology of the Mov13 eye is indistinguishable from that of the wild type. In the 16-day mutant stroma, however, the remaining collagens form small amounts of disorganized, thin fibrils rather than orthogonally organized 20 nm-diameter fibrils; a result implying that collagen I plays only a structural role and that its absence is not compensated for. It also suggests that, because these remaining collagens will not form the normal fibrils that they will in vitro, fibrillogenesis in the corneal stroma differs from that elsewhere. The latter part of the paper describes our current work on chick stromal deposition using corneal epithelia isolated with an intact basal lamina that lay down in vitro approximately 3 microns-thick stromas of organized fibrils similar to that seen in vivo. This experimental system has yielded two unexpected results. First, the amount of collagen and proteoglycans produced by such epithelia is not dependent on whether its substratum is collagenous and we therefore conclude that stromal production by the intact epithelium is more autonomous than hitherto thought. Second, chondroitin sulphate (CS), the predominant proteoglycan, appears to play no role in stromal morphogenesis: epithelia cultured in testicular hyaluronidase, which degrades CS, lay down stromas whose organization and fibril-diameter distribution are indistinguishable from controls. One possible role for CS, however, is as a lubricant which facilitates corneal growth: it could allow fibrils to move over one another without deforming their orthogonal organization. Finally, we have examined the processes of fibrillogenesis in the corneal stroma and conclude that they are different from those elsewhere in the embryo and in vitro, perhaps because there is in the primary stroma an unidentified, highly hydrated ECM macromolecule that embeds the fibrils and that may mediate their morphogenesis.
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PMID:The extracellular matrix of the developing cornea: diversity, deposition and function. 325 Aug 51

Microfibrils have been identified within and between corneal collagen lamellae in a number of vertebrate species in a variety of developmental and pathological conditions, but they are relatively rare in normal adult animals. The present study was undertaken to analyze corneal microfibrils in adult rabbits using enzymatic digestion techniques. Transmission electron microscopy (TEM) showed clusters of 10-15 nm microfibrils arranged in quasi-parallel bundles within or between orthogonally arranged stromal collagen lamellae. When corneas were fixed with tannic acid/glutaraldehyde, the entire stroma showed increased electron density and microfibrillar bundles were heterogeneously stained. Peripheral fibrils were more electron-dense than those located more centrally. Following sequential detergent solubilization of unfixed corneas, all cellular elements were removed and collagen lamellae were distorted. Microfibrillar bundles remained intact, however, and resembled untreated controls. Subsequent treatment with pepsin, trypsin or elastase resulted in swollen corneal tissues in which collagen lamellae were no longer distinguishable but individual collagen fibrils maintained their morphological integrity. In these tissues microfibrillar bundles were rarely identifiable and were reduced to randomly oriented fragments or clusters of filamentous material. Testicular hyaluronidase or chondroitinase ABC did not affect the fibrils. These data indicate that rabbit corneal microfibrils are proteinaceous and that the tannic acid-staining component of the bundles is not glycosaminoglycan. The fibrils are indistinguishable from those identified as oxytalan in cornea and other ocular tissues. Moreover, their sensitivity to elastase and preferential staining with tannic acid/glutaraldehyde strongly suggest they may be related to the elastic system of fibrils.
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PMID:Ultrastructural analyses of enzyme-treated microfibrils in rabbit corneal stroma. 328 15

Among the most important events in connective tissue physiology are the nucleation, growth and calcification of collagen fibrils. It has been speculated that all are associated with, or even controlled by collagen-proteoglycan interactions. We therefore developed methods for investigating these associations in tissues, particularly for understanding their significance for type I collagen, the commonest form of collagen in the body, especially predominant in bone. Using an electron-dense dye, Cupromeronic blue, in the 'critical electrolyte concentration' mode, and digestion by hyaluronidase, chondroitinase ABC or keratanase, supported by biochemical analyses, we found that dermatan sulphate proteoglycan of soft connective tissue (skin, tendon, cornea) was regularly and orthogonally arrayed at the fibril surface, at the d or e band. Keratan sulphate proteoglycan in the cornea associates orthogonally at the a and c bands. Bone, demineralized by a non-aqueous technique which retains proteoglycans in the tissue, does not contain orthogonal arrays; the interfibrillar proteoglycan filaments are oriented parallel to the fibril axis. The main proteoglycan in bone is chondroitin sulphate-rich. There are thus four separate specific binding sites on type I collagen fibrils, each one associating with one particular proteoglycan, and apparently no other. This implies that there are two corresponding binding sites in each proteoglycan. Available evidence shows that there are two species of small dermatan sulphate and keratan sulphate proteoglycans. It is suggested that each species is specific for its own band (a, c, d or e). Hyaluronate and chondroitin sulphate are probably mainly interfibrillar, acting in a space-filling capacity.
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PMID:Proteoglycan-collagen interactions. 381 15

The association of proteoglycans with type I collagen fibrils in skin, tendon, cornea and bone has been determined by electron microscopy using an electron-dense dye, Cupromeronic blue, in the critical electrolyte concentration mode, backed up by biochemical analysis and digestion by hyaluronidase or keratanase. A major proteoglycan of the soft tissues, containing dermatan sulphate, is shown to be regularly and orthogonally arranged at the surface of the fibrils. Uranyl acetate counterstaining revealed that the main specific binding site is the 'd' band, which previous work indicated is very close to the initial site of calcification of type I collagen fibrils. Bone, demineralized by a 'non-aqueous' technique which preserves the proteoglycan in the tissue, does not contain orthogonal arrays; the interfibrillar proteoglycan filaments are oriented parallel to the fibril axis. The main proteoglycan in bone is chondroitin sulphate-rich. It is suggested that dermatan sulphate proteoglycan plays a role in preventing soft connective tissues from calcifying.
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PMID:Proteoglycan-type I collagen fibril interactions in bone and non-calcifying connective tissues. 398 11

The ultrastructural distribution of proteoglycans around capillaries growing in the cornea of the rabbit eye was determined after staining with ruthenium red (RR). Proteoglycans were identified by digesting tissues with glycosaminoglycan-degradative enzymes. Sialoglycoproteins were differentiated from proteoglycans by neuraminidase digestion. The capillary sprouts demonstrated a luminal glycocalyx containing testicular hyaluronidase-sensitive proteoglycans but little or no sialoglycoprotein. At the capillary tips, where mitosing and migrating endothelial cells are located, the basal cell surface displayed a network of small RR-stained granules (8 nm in diameter), which was partially removed by streptomyces hyaluronidase but not by testicular hyaluronidase. Thin filaments connected the granules to the endothelial cell plasmalemma and to a similar network of granules that is normally present in the corneal stroma. The stroma granules were partially digested by testicular hyaluronidase. In older capillary regions, where endothelial cells ceased proliferation, the basal network of proteoglycan granules was gradually infiltrated by fibrillar material until a basal lamina was formed. The proteoglycan granules were then arranged on both sides of the lamina densa, and a thin glycocalyx covered the basal endothelial cell surface. Thus, proteoglycans and anionic materials associated with growing capillaries serve to link proliferating and migrating endothelial cells to the extracellular matrix, help to organize the capillary basal lamina, form an anionic surface along the luminal front of capillaries, and probably help stabilize the structure of the capillary wall after proliferation ceases.
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PMID:Proteoglycans in the microvascular. II. Histochemical localization in proliferating capillaries of the rabbit cornea. 616 47

The macromolecular components of the extracellular matrix of avian ocular tissues undergo complex transitions during the course of development. Two of these tissues in particular, the cornea and vitreous body, have been studied in reference to their glycosaminoglycan and collagen components. During early stages of development, the corneal stroma is an acellular structure composed of orthogonally arranged fibrils containing types I and II collagens with associated chondroitin sulfate-proteoglycan. These are produced by the corneal epithelium. Type IV collagen and proteoglycan are also present in the epithelial basement membrane. The endothelium produces hyaluronate and possibly type IV collagen. Subsequently, the stroma becomes highly hydrated, swells and is invaded by mesenchymal cells which initially produce large amounts of hyaluronate. These cells then differentiate to corneal fibroblasts which synthesize mainly type I collagen and chondroitin sulfate and keratan sulfate-proteoglycans, the major components of the mature corneal matrix. At this time hyaluronidase activity increases in the cornea and the hyaluronate is removed; the tissue loses water, shrinks, and becomes transparent. Two major extracellular components of the avian vitreous body during the course of its development are chondroitin sulfate and type II collagen. Early in development these components are synthesized and secreted into the vitreous by the neural retina whereas subsequently they are derived from cells within the vitreous body itself. Possible structural and morphogenetic roles of these extracellular macromolecules relate to the stabilization of tissue phenotype and cellular migration.
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PMID:Transitions in extracellular macromolecules during avian ocular development. 681 Mar 70

Type VI collagen beaded microfibrils were extracted from bovine cornea or pig cartilage by limited collagenase digestion. Depolymerization of the microfibril, without strong denaturing reagents linke guanidinium hydrochloride or urea under mild acidic conditions, led to single tetramers and multiples of two to three. However, hyaluronidase digestion in accordance with a published method (Kielty et al. J. Cell Biol. 118:979-990, 1992) was unsuccessful in depolymerizing type VI collagen microfibrils. Also, repolymerization into microfibrils by incubation with hyaluronan was not observed. We further found no binding of native type VI collagen microfibrils to a hyaluronan-Sepharose column. Although a recombinant fragment comprising alpha 3(VI) domains N9-N2 showed apparent binding to the column, electron microscopy did not give any indication of binding of either type VI collagen or fragment N9-N2 to hyaluronan. The present findings suggest that the role of hyaluronan in polymerization of type VI collagen has been overestimated in previous work.
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PMID:Type VI collagen beaded microfibrils from bovine cornea depolymerize at acidic pH, and depolymerization and polymerization are not influenced by hyaluronan. 779 88

Changes in the distribution of keratan sulfate in the anterior segment of developing ocular tissue were investigated histochemically and immunohistochemically using human eyes from 5 weeks gestation to 2 years after birth. Enzyme digestion methods with streptomyces hyaluronidase, chondroitinase and keratanase showed that the main component of glycosaminoglycans in the cornea was hyaluronic acid at the early stage and chondroitin sulfate from the middle stage to the neonatal stage. Keratan sulfate was found at the neonatal stage. Immunohistochemical staining, however, showed that keratan sulfate was present from 6 weeks around mesenchymal cells which migrated into the anterior portion. The stroma and endothelial cells of the cornea, trabecular tissue, iris, choroidal tissue of the ciliary body and anterior tunica vasculosa lentis were the next tissues to show positive for immunostaining. Keratan sulfate became limited to the cornea and lumbus and mostly disappeared from the other anterior segment tissues after birth. These findings suggest that tissues which seem to originate from mesenchymal cells and surround the chamber space contain keratan sulfate during the developmental stage.
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PMID:Histochemical and immunohistochemical studies on keratan sulfate in the anterior segment of the developing human eye. 817 50

The development of iridocorneal angle and trabecular tissue was investigated histochemically and electron microscopically. Sixty-three human eyes at from 5 to 22 weeks of gestation were used in this study. For identifying glycosaminoglycans, alcian blue staining and enzyme digestion methods with hyaluronidase and chondroitinase AC and ABC were carried out light microscopically. Electron microscopically, specimens were stained with ruthenium red. In the early stage from 8 to 10 weeks, mesenchymal cells between the primordium of the cornea and the iris became elongated and connected with one another. Desmosome-like junctional complexes were observed in these cells. Schlemm's canal and para-canalicular tissue were observed at 20 weeks and the structure of the meshwork became similar that of adults. From findings of enzyme digestion methods, glycosaminoglycans in trabecular tissue seemed to be mainly hyaluronic acid in the early stage, which was replaced by chondroitin sulfate and dermatan sulfate afterwards. Substances positive for ruthenium red, which seemed to be glycosaminoglycans, was observed in intercellular spaces electron microscopically. They decreased according to development. These findings indicated that the beginning of aqueous outflow might be related to the decrease of glycosaminoglycans in trabecular tissue.
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PMID:[Histochemical and electron microscopic study of the formation of trabecular meshwork and changes of glycosaminoglycans]. 831 47


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