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R C Bray

Publications and source records attributed to R C Bray.

174 records · Page 10Linked to original sources
PubMed1967

Enzymes in cancer. Asparaginase from chicken liver.

1. A procedure for partial purification of asparaginase from chicken liver is presented. 2. The bulk of the enzyme is located in the soluble fraction of chicken liver. 3. Molecular weights of chicken-liver asparaginase and of the guinea-pig serum enzyme, estimated by gel filtration, were 306000 and 210000 respectively. The Michaelis constants (K(m)) at 37 degrees and pH8.5 were 6.0x10(-5)m and 7.2x10(-5)m respectively. 4. At 50 degrees the chicken-liver enzyme was moderately stable, some activity being lost by aggregation; in dilute electrolyte solutions the activity rapidly diminished. 5. The anti-lymphoma effect of guinea-pig serum in mice carrying the 6C3HED tumour was confirmed. Chicken-liver asparaginase also showed an effect but in this case the enzyme preparation had to be administered repeatedly. 6. Guinea-pig serum asparaginase was stable for several days in mouse blood, after intraperitoneal injection, whereas chicken-liver asparaginase rapidly disappeared. 7. Aspartic acid beta-hydrazide was shown to be a competitive inhibitor of chicken-liver asparaginase with K(i) approx. 5.6x10(-4)m. In mice it produced an anti-lymphoma effect, as reported previously.

Amidohydrolases↗
PubMed1967

Enzymes and cancer. Preparation and some properties of guanase from rabbit liver.

1. Guanase has been purified 200-fold in 20% yield from the supernatant fraction of rabbit-liver homogenates, by using ammonium sulphate fractionation, calcium phosphate-gel adsorption and chromatography on DEAE-cellulose and Sephadex G-200. 2. K(m) with guanine as substrate at the optimum pH of 7.7 was found to be 1.05x10(-5)m. Q(10) was 1.4 between 23 degrees and 48 degrees . 3. Substrate activity and pH optima of compounds related to guanine have been studied. 8-Azaguanine, 1-methylguanine, thioguanine and 1-methylthioguanine are all substrates.

Aminohydrolases↗
PubMed1966

The chemistry of xanthine oxidase. Reaction with iodoacetamide.

1. The reaction of milk xanthine oxidase with iodoacetamide has been studied with the silver-silver iodide electrode. 2. The reaction proceeds considerably faster in the presence of xanthine than in its absence. Anaerobically, with excess of xanthine, the reaction takes place as a rapid phase in which the enzyme is inactivated and in which approx. 1 thiol group/mol. of enzyme reacts and as a slower phase in which about 12 groups/mol. react. 3. The rapid reaction appears to be first-order with respect to xanthine oxidase and iodoacetamide and independent of the xanthine concentration with more than about 3mol. of xanthine/mol. of enzyme. 4. The velocity constant of the rapid phase is 0.26min.(-1) at 25 degrees and pH7.0, with 1mm-iodoacetamide and 17mum-xanthine oxidase. The velocity constant for the slower phase is about one-hundredth of this value. 5. The velocities of both phases increase with increasing pH in the range 5.0-9.6. 6. Xanthine may be replaced by salicylaldehyde without affecting the rate of loss of enzymic activity. With sodium dithionite as reducing agent, the reaction is slightly faster. 7. The possible function of thiol groups in the reaction mechanism of the enzyme is discussed.

Aldehydes↗
PubMedDate not supplied

Posterior cruciate ligament reconstruction by transfer of the medial gastrocnemius tendon.

A retrospective study to determine the efficacy of medial gastrocnemius tendon transfer for symptomatic PCL instability is presented. Results from a group of 31 patients undergoing this procedure were compared with a group of 8 patients managed conservatively while awaiting surgery. The mean injury to follow-up interval was 82 months in the operated group and 104 months in the nonoperated group. The mean surgery to follow-up interval was 53 months. Sixty-nine percent of surgical patients were subjectively improved; however, 29 (91%) continued to have pain and 19 (59%) continued to experience giving way. Thirteen patients from the operated group who had associated procedures performed were significantly better subjectively than those with no associated procedures (P less than 0.05). Physical examination demonstrated no difference in clinical laxity between the operated and nonoperated groups. Medial gastrocnemius transfer did not result in any significant reduction in anterior-posterior translation (KT-1000 assessment) when reconstructed knees were compared with control posterior cruciate deficient knees. Surgery, combined with subsequent immobilization, may have also been responsible for the significant reduction in lower limb function observed in the reconstructed patients. We do not recommend this procedure as a primary PCL reconstruction.

Adolescent↗