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Biomedical subjects

J R Hassell

Publications and source records attributed to J R Hassell.

124 records · Page 7Linked to original sources
PubMed1980

Increased biosynthesis of specific glycoconjugates in rat corneal epithelium following treatment with vitamin A.

The biosynthesis of corneal epithelial proteins and glycoconjugates and their response to vitamin A were measured in vitamin A-deficient and normal rats. The synthesis of specific high-molecular-weight epithelial glycoconjugates was directly related to the levels of vitamin A administered. Protein synthesis, however, remained unaltered. Since vitamin A is known to reverse the keratinization process, the vitamin A-regulated high-molecular-weight glycoconjugates may play a role in modulating the expression of the keratinizing phenotype.

Animals↗
PubMed1979

Characterization and biosynthesis of proteoglycans of corneal stroma from rhesus monkey.

The proteoglycans of the Rhesus monkey corneal stroma were characterized by analyzing both radiolabeled proteoglycans synthesized by corneas in organ culture and native corneal proteoglycans obtained by large scale preparations. The analyses indicate that the proteoglycans synthesized in organ culture were similar to, if not identical with, their counterparts in the stroma although they are synthesized in different prportions in vitro than they acumulate in vivo. The corneal stroma contains two proteoglycans. The chondroitin-dermatan sulfate proteoglycan consists of approximately 70% protein and has a Mr = approximately 100,000 to 150,000. It contains one chondroitin-dermatan sulfate side chain of Mr = approximately 55,000. The keratan sulfate proteoglycan consists of approximately 74% protein and has a Mr = approximately -40,000 to 70,000. It contains one or two keratan sulfate side chains with a Mr = approximately 7,000 each. Radiolabeling indicates that both proteoglycans contain glycoprotein-type oligosaccharides as part of their structure.

Amino Acids↗
PubMed1979

Enhanced cellular fibronectin accumulation in chondrocytes treated with vitamin A.

Chick sternal chondrocytes cultured at high cell density lack fibronectin as a surface protein, while vitamin A-treated chondrocytes contain it as the major cell surface protein. We investigated the mechanism of fibronectin accumulation under these conditions. Control chondrocytes synthesized nearly as much fibronectin as vitamin A-treated chondrocytes, but it was secreted primarily into culture medium. Althought the fibronectin of control chondrocytes was of a slightly lower apparent molecular weight than the fibronectin synthesized by the treated cells, it bound as effectively to the cell layer of both normal and treated cells. In contrast, the vitamin A-treated cultures were 2.7 fold more effective in binding fibronectin synthesized by either control or treated cells. Thus in chondrocytes, vitamin A appears to regulate the cellular accumulation of fibronectin by increasing the ability of the cell layer to bind fibronectin rather than by altering its synthesis or its adhesivity for the cell layer.

Animals↗
PubMed1978

The in vivo stimulation of mannose incorporation into mannosylretinylphosphate, dolichylmannosylphosphate, and specific glycopeptides of rat liver by high doses of retinylpalmitate.

Excess vitamin A stimulated the incorporation of mannose into rat liver mannosylretinylphosphate (MRP), dolichylmannosylphosphate (DMP), and into glycoproteins by over 200% during a 20-min labeling period. The glycoproteins were digested with pronase and separated into three components by molecular sieve chromatography. The stimulation of mannose incorporation was greatest in the Peak II glycopeptide (Mr = 6500). In contrast, the incorporation of galactose into glycolipids or glycopeptides was not altered by vitamin A treatment. Analysis of the glycopeptide stimulated by vitamin A treatment showed it to contain mannose, glucose, galactose, and glucosamine in the respective molar ratios of 7:10:17:1 and to be rich in glutamic acid, serine, glycine, aspartic acid, and threonine. The results suggest that excess vitamin A stimulates the incorporation of mannose into glycoproteins by enhancing the synthesis of lipid intermediates involved in specific mannosyl transfer reactions.

Animals↗
PubMed1977

Inhibition of cranial neural crest cell development by vitamin A in the cultured chick embryo.

Chick embryos at stage 8, prior to neural crest cell migration, were explanted on whole egg medium with or without vitamin A and cultured for 3 days. Sections through the head regions showed that the cranial neural crest cells had migrated into the first visceral arch in the controls but were absent from this structure in the treated embryos. These observations suggest that vitamin A inhibits neural crest cell development or migration, an effect which may in part account for the facial malformations produced by excess vitamin A.

Animals↗
PubMed1976

Tissue fixation with diimidoesters as an alternative to aldehydes. II. Cytochemical and biochemical studies of rat liver fixed with dimethylsuberimidate.

Rat liver fixed with dimethylsuberimidate (DMS) was studied to investigate the use of diimidoesters as dixatives for light and electron microscopic cytochemistry. Paraffin sections of liver fixed with DMS at pH 9.5 were weakly stained with the ninhydrin-Schiff procedure, indicating extensive reaction of NH3+ groups with the fixative. Nuclei were strongly strained by the Feulgen procedure, with no background [corrected] reaction. In contrast, glutaraldehyde fixation resulted in a significant background reaction in the cytoplasm and nuclei in controls for the Schiff-based stains. DMS-fixed liver stained intensely for glycogen with the Periodic acid-Schiff procedure, and biochemical analysis of glycogen retention and extractability indicated that DMS retained considerably more glycogen in sections than glutaraldehyde. DMS-fixed liver incubated for thiamine pyrophosphatase activity revealed reaction product in ER cisternae, Goli saccules and bile canaliculi. Peroxisomes were strongly reactive for catalase activity after incubation in diaminobenzidine medium, and reaction product of glucose-6-phosphatase activity was considerably greater following DMS fixation than after glutaraldehyde. Biochemical studies revealed up to twice as musch residual activity of glucose-6-phosphatase after DMS fixation. These results suggest that DMS may be useful as a primary fixative for certain cytochemical procedures.

Aldehydes↗
PubMedDate not supplied

Corneal keratinization in the oel/ + mouse.

Several human diseases are accompanied by keratinization of the ocular surface and loss of corneal transparency. We describe a mouse strain in which 2/3 of the viable offspring manifest a corneal disease characterized initially by poor wetting followed by keratinization of the ocular surface, and progressive loss of corneal transparency. The corneal epithelium becomes vacuolated and the basement membrane thickened. Ulceration and perforation were seen in some cases. Standard bacterial cultures yielded no culpable pathogens. Blood antiviral titers and cultures of orbital and ocular tissues for herpes virus were negative. Double masked treatment trials with topical gentamicin, and topical and parenteral vitamin A had no significant effect on the course of the disease. The mouse strain exhibits corneal keratinization unresponsive to vitamin A therapy, and may serve as an excellent model of certain serious human ocular surface diseases.

Animals↗