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Biomedical subjects

J J Harding

Publications and source records attributed to J J Harding.

At least 109 records · Page 6Linked to original sources
PubMed1985

Aldehydes or dicarbonyls in non-enzymic glycosylation of proteins.

The non-enzymic post-translational glycosylation of certain proteins has been implicated in the production of diabetic sequelae. In the present paper the possibility that it is not the glucose aldehyde that binds to proteins but a dicarbonyl autoxidation product is investigated. Earlier experiments may not have distinguished between these two possibilities. The rate of binding of 2-deoxyglucose (a non-autoxidizable sugar) to lens alpha-crystallin is compared with that of glucose (an autoxidizable sugar). The stabilized Schiff-base adducts was investigated by using proton n.m.r. and fast-atom-bombardment mass spectroscopy to distinguish whether they are the product of aldehyde or dicarbonyl addition. We conclude that it is the open-chain aldehyde of glucose that binds initially to amino groups and that there is no participation of dicarbonyl autoxidation products in the initial non-enzymic protein glycosylation reaction.

Aldehydes↗
PubMed1985

Aspirin prevents carbamylation of soluble lens proteins and prevents cyanate-induced phase separation opacities in vitro: a possible mechanism by which aspirin could prevent cataract.

The carbamylation of lens proteins by cyanate causes conformational changes, and cyanate causes cataract. There is some evidence that aspirin is beneficial to cataract patients, so its effect on the carbamylation of lens proteins and on opacification produced by cyanate in vitro was studied. Aspirin decreased the phase separation temperature in lenses exposed to cyanate, and was found to reduce the rate of carbamylation of most, if not all, soluble lens proteins. Studies with radiolabelled aspirin lead to the conclusion that the drug achieves this protection by chemically modifying the proteins. The nature of this modification and the relevance of these results to human cataract is discussed.

Animals↗
PubMed1984

Conformational changes induced in bovine lens alpha-crystallin by carbamylation. Relevance to cataract.

Carbamylation of lens proteins may contribute to cataractogenesis in certain medical conditions where blood urea is elevated for prolonged periods. This paper reports on the effects of carbamylation on the physicochemical properties of one of the major lens structural proteins, alpha-crystallin. In particular it is shown that carbamylation alters the tertiary and secondary structure of the protein, leading to an increased reactivity of protein thiols, resulting in interchain disulphide bonding.

Animals↗
PubMed1982

The biochemical organization of the lens.

The metabolic pathways of the lens are similar to those found in other tissues but with changes of emphasis in keeping with its function. The mode of growth of the lens results in cells and proteins at the centre of the lens persisting throughout adult life. Changes seen in these proteins may be deleterious aging changes or may be adaptations to a developing environment. The blocked alpha-amino groups of two major groups of lens proteins serve to protect the lens against both amino-peptidases and chemical modification. An understanding of the biochemistry of the lens and the chinks in its protective devices leads to the idea that there may be common pathways in cataractogenesis.

Aging↗
PubMed1978

Isolation and hydroxylysine glycoside content of some cyanogen bromide-cleaved fragments of collagen from bovine corneal stroma.

Six CNBr-cleaved fragments of insoluble collagen from bovine cornea were isolated, characterized and examined for hydroxylysine glycosides. Thus the general distribution of most of the glycoside along the collagen molecule was determined. Collagen from bovine stroma is almost entirely type I. This work forms a basis for the pinpointing of glycoside-attachment sites along the collagen molecules of bovine cornea.

Amino Acids↗
PubMed1978

Chymotryptic and tryptic peptides of fragment alpha 1-CB3 from bovine corneal collagen. Pinpointing the sites of hexose attachment.

Tryptic peptides of citraconylated fragment alpha1-CB3 and chymotryptic peptides of fragment alpha1-CB3 of bovine corneal collagen were prepared, isolated and characterized. Their amino acid compositions were consistent with the amino acid sequence of fragment alpha1-CB3 from calf skin collagen. Two glycoside sites were identified in bovine corneal fragment alpha1-CB3, one of them being the first located in the overlap region of collagen. The results are related to the uniformly narrow collagen fibres found in cornea and essential for its transparency.

Amino Acid Sequence↗