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Biomedical subjects

G Williamson

Publications and source records attributed to G Williamson.

151 records · Page 9Linked to original sources
PubMed1981

Home treatment of haemophilia. A follow-up study.

Twenty-four children and adolescents who have been receiving home treatment for haemophilia A and B, and were followed up for a median period of five years, have been assessed for physical activity, social adjustment, range of joint movement and infection with hepatitis viruses. They were treated with cryoprecipitate from 1972 to 1977, and since then with factor-VIII concentrates. The average dose of factor VIII was 20 units/kg body mass. It was found that there was near normal range of physical activity and school performance, and, in virtually all families, near normal family function could be preserved. Approximately one-third of the patients showed impairment of the normal range of joint movement in flexion and extension. Although there was no clinical evidence of liver disease, elevated aspartate aminotransferase (AST) levels were found in 14 patients. Evidence of past, or present, infection with hepatitis B was found in 19 patients, and of infection with hepatitis A in seven patients. Home treatment is associated with a reduced level of disability from haemophilia, but transfusion therapy continues to be associated with a high rate of liver function abnormalities, probably of infectious origin.

Adolescent↗
PubMedDate not supplied

Purification of a cytosolic enzyme from human liver with phospholipid hydroperoxide glutathione peroxidase activity.

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a selenoprotein which inhibits peroxidation of microsomes. The human enzyme, which may play an important role in protecting the cell from oxidative damage, has not been purified or characterized. PHGPx was isolated from human liver using ammonium sulphate fractionation, affinity chromatography on bromosulphophthalein-glutathione-agarose, gel filtration on Sephadex G-50, anion exchange chromatography on Mono Q resin and high resolution gel filtration on Superdex 75. The protein was purified about 112,000-fold, and 12 micrograms was obtained from 140 g of human liver with a 9% yield. PHGPx was active on hydrogen peroxide, cumene hydroperoxide, linoleic acid hydroperoxide and phosphatidylcholine hydroperoxide. The molecular weight, as estimated from non-denaturing gel filtration, was 16,100. The turnover number (37 degrees C, pH 7.6) on (beta-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl)-gamma-palmitoyl)-L-alpha-phosphatidylcho line was 91 mol mol-1 s-1. As reported for pig PHGPx, activity of the enzyme from human liver on cumene hydroperoxide and on linoleic acid hydroperoxide was inhibited by deoxycholate. In the presence of glutathione, the enzyme was a potent inhibitor of ascorbate/Fe induced lipid peroxidation in microsomes derived from human B lymphoblastic AHH-1 TK +/- CHol cells but not from human liver microsomes. Human cell line microsomes contained no detectable PHGPx activity. However, microsomes prepared from human liver contained 0.009 U/mg of endogenous PHGPx activity, which is 4-5 times the activity required for maximum inhibition of lipid peroxidation when pure PHGPx was added back to human lymphoblastic cell microsomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMedDate not supplied

Ferulic acid dehydrodimers from wheat bran: isolation, purification and antioxidant properties of 8-O-4-diferulic acid.

Wheat bran contains several ester-linked dehydrodimers of ferulic acid, which were detected and quantified after sequential alkaline hydrolysis. The major dimers released were: trans-5-[(E)-2-carboxyvinyl]-2-(4-hydroxy-3-methoxy-phenyl)-7-methoxy-2, 3- dihydrobenzofuran-3-carboxylic acid (5-8-BendiFA), (Z)-beta-[4-[(E)-2-carboxyvinyl]-2-methoxyphenoxy]-4-hydroxy-3-methox ycinnamic acid (8-O-4-diFA) and (E,E)-4,4'-dihydroxy-5,5'-dimethoxy-3,3'-bicinnamic acid (5-5-diFA). trans-7-hydroxy-1-(4-hydroxy-3methoxyphenyl)-6-methoxy-1,2-dihydro - naphthalene-2,3-dicarboxylic acid (8-8-diFA cyclic form) and 4,4'-dihydroxy-3,3'-dimethoxy-beta,beta'-bicinnamic acid (8-8-diFA non cyclic form) were not detected. One of the most abundant dimers, 8-O-4-diFA, was purified from de-starched wheat bran after alkaline hydrolysis and preparative HPLC. The resultant product was identical to the chemically synthesised 8-O-4-dimer by TLC and HPLC as confirmed by 1H-NMR and mass spectrometry. The absorption maxima and absorption coefficients for the synthetic compound in ethanol were: lambda max: 323 nm, lambda min: 258 nm, epsilon lambda max (M-1 cm-1): 24,800 +/- 2100 and epsilon 280 (M-1 cm-1): 19,700 +/- 1100. The antioxidant properties of 8-O-4-diFA were assessed using: (a) inhibition of ascorbate/iron-induced peroxidation of phosphatidylcholine liposomes and; (b) scavenging of the radical cation of 2,2'-azinobis (3-ethyl-benzothiazoline-6-sulphonate) (ABTS) relative to the water-soluble vitamin E analogue, Trolox C. The 8-O-4-diFA was a better antioxidant than ferulic acid in both lipid and aqueous phases. This is the first report of the antioxidant activity of a natural diferulate obtained from a plant.

Antioxidants↗
PubMedDate not supplied

alpha-Tocopherol enhances the peroxidase activity of hemoglobin on phospholipid hydroperoxide.

We have used direct separation of phospholipid hydroperoxide and phospholipid hydroxide by high performance liquid chromatography to examine the phospholipid hydroperoxide peroxidase activity of hemoglobin (Hb) in the presence of hydrogen donors. Hb exhibits phospholipid hydroperoxide peroxidase activity and rapidly breaks down phospholipid hydroperoxide to thiobarbituric acid-reactive substances. However, in the presence of alpha-tocopherol, some phospholipid hydroperoxide is converted to phospholipid hydroxide, which is more stable than the hydroperoxide and is much less reactive with thiobarbituric acid. Other electron donors such as glutathione and ascorbate are less effective than alpha-tocopherol. Free cysteine also shows some ability to reduce phospholipid hydroperoxides to corresponding hydroxides, but cys-93 beta of Hb did not participate in the reaction, as shown by N-ethylmaleimide modification. Hemin alone catalysed the reaction, in the absence of protein. The results therefore show that Hb catalyses an apparent phospholipid hydroperoxide alpha-tocopherol peroxidase reaction due to bound hemin, and that the reduction depends on the ability of hydrogen donors to react with the intermediate phospholipid alkoxyl radical and does not involve reduction by deprotonated sulfhydryl groups.

Hemoglobins↗