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Biomedical subjects

N Light

Publications and source records attributed to N Light.

14 recordsLinked to original sources
PubMed1986

Collagen and elastin changes in D-penicillamine-induced pseudoxanthoma elasticum-like skin.

A patient with cystinuria who was treated with large doses of D-penicillamine for 19 years developed skin abnormalities resembling those seen in pseudoxanthoma elasticum. Biochemical and histological examination of the dermis showed that the collagen content, the ratio of the major genetic forms of collagen and the distribution of collagen types was normal. Light microscopy demonstrated the presence of vastly increased amounts of elastin in the dermis, and the individual elastin fibres were shown by electron microscopy to be abnormal; chemical analysis showed the elastin to be poorly cross-linked. Some of the collagen also appeared structurally abnormal, and biochemically resembled that seen in the dermis of a young child with respect to cross-linking and hexosyl-lysine content. The therapy led to an increased deposition of collagen and elastin fibres which appeared abnormal, and resulted in an increase in total skin surface area. These data indicate that D-penicillamine was not fully effective in inhibiting collagen and elastin cross-linking, and appeared to prevent or inhibit the natural maturation process of the collagen.

Aged↗
PubMed1985

Collagen cross-links: location of pyridinoline in type I collagen.

Collagen from bone, dentine and tendon (type I), all of which contain the pyridinoline cross-link at varying levels, were each digested with CNBr. The resulting peptide mixtures were resolved by gel filtration on A1.5m agarose and assayed for pyridinoline. The polymeric cross-linked peptide complex, poly alpha 1CB6 [(1980) Biochem. J. 189, 111] isolated from each of these tissues did not contain pyridinoline. Only one peptide fraction contained the pyridinoline cross-link; that identified as alpha 2CB3,5. However, this peptide showed only a small increase in Mr in its cross-linked form (approx. 2000-5000) demonstrating that pyridinoline is not involved in the formation of polymeric structures like poly alpha 1CB6. These data, considered in the light of the recent finding that pyridinoline is present in type I collagens from different sources in widely varying amounts, cast doubt on its role in collagen maturation.

Amino Acids↗
PubMed1984

Characterization of muscle epimysium, perimysium and endomysium collagens.

In the past it has been proven difficult to separate and characterize collagen from muscle because of its relative paucity in this tissue. The present report presents a comprehensive methodology, combining methods previously described by McCollester [(1962) Biochim. Biophys. Acta 57, 427-437] and Laurent, Cockerill, McAnulty & Hastings [(1981) Anal. Biochem. 113, 301-312], in which the three major tracts of muscle connective tissue, the epimysium, perimysium and endomysium, may be prepared and separated from the bulk of muscle protein. Connective tissue thus prepared may be washed with salt and treated with pepsin to liberate soluble native collagen, or can be washed with sodium dodecyl sulphate to produce a very clean insoluble collagenous product. This latter type of preparation may be used for quantification of the ratio of the major genetic forms of collagen or for measurement of reducible cross-link content to give reproducible results. It was shown that both the epimysium and perimysium contain type I collagen as the major component and type III collagen as a minor component; perimysium also contained traces of type V collagen. The endomysium, the sheaths of individual muscle fibres, was shown to contain both type I and type III collagen as major components. Type V collagen was also present in small amounts, and type IV collagen, the collagenous component of basement membranes, was purified from endomysial preparations. This is the first biochemical demonstration of the presence of type IV collagen in muscle endomysium. The preparation was shown to be very similar to other type IV collagens from other basement membranes on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and was indistinguishable from EHS sarcoma collagen and placenta type IV collagen in the electron microscope after rotary shadowing.

Animals↗
PubMed1984

Investigation of the parameters for reversed-phase high-performance liquid chromatography of collagen types I and III.

A detailed study was carried out on the behaviour of collagen and its subcomponents on large pore size reversed-phase high-performance liquid chromatographic columns. Investigation of laboratory-prepared C18 and CN 50-nm pore size supports using a simple solvent system showed that heat-denatured collagen chains could be retained and resolved and that the C18 packing had a greater selective capacity. However, because of inconsistencies in the chromatography obtained using laboratory-prepared supports commercial 33-nm pore size packings were subsequently studied with both pyridine-based and trifluoroacetic acid-based solvent systems. An optimised solvent was defined and used to check the resolving capacity of both C18 and CN commercial columns. These studies led to the description and interpretation of the effects of pH, counter-ion concentration, solvent strength, type of support and molecular weight of protein solutes on the chromatographic behaviour of this large protein and its CNBr peptides. An explanation of the major forces acting to bring about retention and resolution is presented and suggestions are made for the application of this methodology to other proteins.

Animals↗
PubMed1984

Cross-linking in type IV collagen.

Type IV collagen could not be extracted from human placenta using 6M-urea containing 10mM-dithiothreitol, indicating that the type IV molecule is stabilized within the basement membrane by covalent cross-links. However, various forms of type IV collagen molecule were extractable by means of increasingly severe proteolytic conditions. Type IV collagen tetramers ('spiders') lacking only the C-terminal globular region (NC1) were further digested to the 'long-form' 7S fragment and an assortment of helical rod-like molecules derived from the 'leg' region. These molecules were separated by salt fractionation and examined by rotary-shadowing electron microscopy. Isolation of these fractions from placenta which had been reduced with NaB3H4 revealed that both the 7S (N-terminal) and C-terminal regions contained significant proportions of reducible lysine-derived cross-links. These cross-links were shown to be exclusively the stable oxo-imine hydroxylysino-5-oxonorleucine. The number of the cross-links per molecule was significantly lower than might be expected in order to fully stabilize the molecule. These results suggest that the keto-imine cross-links in type IV collagen have been stabilized in part by conversion into an unknown non-reducible form, although a sensitive immunoassay failed to show the presence of any pyridinoline. Comparison with the fibrous collagen from placenta suggested that the rate of this conversion is much greater in basement-membrane collagen.

Basement Membrane↗
PubMed1979

Life table analysis of membership in an HMO retention.

The retention patterns of the Kaiser Foundation Health Plan (Oregon Region) were studied over a six-year period using a life table analysis. A 5% random sample, consisting of subscriber units that were enrolled at the initiation of the study of subsequently joined during the six-year period, were followed with respect to enrollment retention. The analysis presented here focuses on the 2,112 subscribers enrolled during the 1967-1970 period. These subscribers were characterized by the year they joined the plan and by their age and sex. The analyses showed that age of the subscriber and length of time on the plan consistently affected the probability of continued enrollment. The sex of the subscriber and the initial year of enrollment showed only a slight differential affect. A general pattern of high attrition in the first year, but rapid slackening thereafter, existed in all subgroup specific analyses. The utility of the analyses and the impact of the effect of differential membership retention on the plan are discussed.

Actuarial Analysis↗