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J D McNeil

Publications and source records attributed to J D McNeil.

23 records · Page 2Linked to original sources
PubMed1986

The generation of reducing ends by exposure of hyaluronic acid to oxygen derived free radicals.

Enzymatic depolymerization of hyaluronic acid (HA) is accompanied by the release of reducing ends irrespective of the linkage cleaved. In this investigation we have examined HA exposed to oxygen-derived free radicals (oxy radicals) in order to determine whether reducing ends are released upon depolymerization. Reducing ends were detected by the assay of Park and Johnson, which is a non-specific but sensitive assay for reducing ends, but only to a minimal degree by the Reissig modification of the Morgan Elson reaction, which will detect N-acetylglucosamine at the reducing end. Exposure of a sample of HA, pre-exposed to streptomyces hyaluronidase, to an oxy radical flux did not result in a decrease in Morgan Elson reactivity thus indicating that post cleavage modification of the reducing end by further reaction with oxy radicals does not account for the lack of Morgan Elson reactivity. In addition reducing ends were also detected by reaction with radiolabelled cyanide to the degree predicted by molecular weight. These findings were interpreted as being consistent with the hypothesis that oxy radical induced depolymerization of HA occurs by preferential cleavage of the glucuronidic linkage thus leaving D-glucuronic acid at the reducing end.

Ferrous Compounds↗
PubMed1986

Abnormalities of gastric and esophageal emptying in polymyositis and dermatomyositis.

Gastric and esophageal emptying were assessed using scintigraphic techniques in 13 patients with polymyositis or dermatomyositis and in 13 normal volunteers. Esophageal emptying was significantly delayed in patients, with 8 of 13 patients being outside the normal range. Gastric emptying was also markedly slower in patients than in controls, with 8 patients being outside the normal range for solid emptying and 8 patients beyond the normal range for liquid emptying. The 5 patients with dysphagia all had delayed esophageal emptying, but both gastric and esophageal emptying were delayed in some asymptomatic patients. There was a significant correlation between esophageal emptying and both solid and liquid gastric emptying in the patients. Both gastric and esophageal emptying correlated with the severity of the peripheral (skeletal) muscle weakness. These results indicate that profoundly delayed gastric and esophageal emptying are common in polymyositis and dermatomyositis, implying frequent malfunction of the smooth muscle of the upper gastrointestinal tract in this disease.

Adolescent↗
PubMed1985

Depolymerisation products of hyaluronic acid after exposure to oxygen-derived free radicals.

Preparative chromatographic fractions of human umbilical cord hyaluronic acid (HA) of a molecular weight of 10(6) were subjected to graded oxygen-derived free radical (oxy radical) fluxes produced by: (a) the autoxidation of ferrous ions; (b) the action of xanthine oxidase (XO) on hypoxanthine (HX); and (c) by peripheral blood polymorphonuclear leucocytes that had been stimulated by phorbol myristate acetate (PMA). Analysis by gel chromatography of the products obtained with each of the oxy radical generating systems showed polydispersity in size. The smallest molecules detected had a molecular weight of 10(4). This limiting size was not reduced further by exposure to a second oxy radical flux. The relative proportions of large, medium, and small degradation products were established for various levels of oxy radical flux. Consistently a relatively rapid transition from large to small material was seen on Sepharose 2B chromatography, suggesting an ordered element to the breakdown process. Although the decrease in molecular weight after oxy radical exposure was confirmed by analytical ultracentrifugation, this procedure showed that those samples of lowest viscosity did not have the lowest sedimentation values, possibly reflecting oxy radical-induced repolymerisation. If the size and possibly the conformational characteristics of HA are altered, oxy radical exposure might be expected to alter its biological properties.

Biopolymers↗
PubMedDate not supplied

Osseous sarcoidosis--a magnetic resonance imaging diagnosis.

Bone involvement in sarcoidosis is not uncommon but may be overlooked as a cause of symptoms. Magnetic resonance imaging (MRI) is emerging as a sensitive diagnostic tool for osseous sarcoid. We document a case in which MRI suggested the diagnosis in the absence of abnormality with more conventional imaging techniques.

Azathioprine↗