Biomedical subjects
Publications and source records attributed to D C Williams.
Several media have been used in an attempt to assess the most appropriate combination of ingredients to effect good cell growth from human breast tumours. Good epithelial cell growth has been obtained in 60 out of a group of 160 tumours successfully cultured in four types of basic media. The other tumours were fibroblastic in nature or contained a mixture of epithelial and fibroblastic cells.
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1. The specific activity of yeast hexokinase A depends on the concentration of the protein in the solution being assayed. When a solution containing 13.5 mg of hexokinase A/ml is diluted 10--100-fold at various values of pH and temperature, there is a gradual decline in the specific activity of the enzyme until an equilibrium value is reached, which varies with the chosen experimental conditions. 2. The catalytic activity lost when hexokinase A (1 mg/ml) is incubated at 30degreesC is recovered by lowering the temperature to 25degreesC. 3. These concentration- and temperature-dependent phenomena are consistent with the existence of a monomer-dimer equilibrium in which the dimer alone is the catalytic form of the enzyme. 4. Glucose alone prevents the decline in specific activity of hexokinase A after dilution, but it does not re-activate dilute solutions solutions of the enzyme. It is concluded that glucose binds to both the dimer and the monomer and prevents both association and dissociation. 5. The progress curve describing the phosphorylation of glucose catalysed by hexokinase A does not attain a steady state. It is possible that dissociation of catalytically active dimers in a ternary complex with glucose and ATP (or glucose 6-phosphate and ADP) could explain the non-linearity of this progress curve.
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Cytoplasmic aspartate aminotransferase and malate dehydrogenase were purified from pig heart. Kinetic parameters were determined for the separate reaction catalysed by each enzyme and used to predict the course of the coupled reaction: (see article). Although a lag phase should have been easily seen, none was detected. The same coupled reaction was also carried out by using radioactive aspartate in the presence of unlabelled oxaloacetate. The reaction was quenched with HClO4 after 70 ms and the specific radioactivity of the malate produced in this system was found to be essentially the same as that of the original aspartate. These results show that oxaloacetate produced by the aspartate aminotransferase is converted into malate by malate dehydrogenase before it equilibrates with the pool of unlabelled oxaloacetate and are consistent with a proposal that the enzymes are associated in a complex. However, no physical evidence of the existence of a complex could be found. An alternative means of compartmentation of the intermediate as an unstable isomer is considered.
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A scanning electron-microscope study has established that there are major modifications in the surface membranes of malignant cells transformed from the pronephric kidney of the frog. Tumours were induced in vivo after exposure of embryos Lucké Herpes virus. A pronephric cell line from normal embryos and 3 tumour cell lines derived from experimentally induced adenocarcinomas of the pronephros were observed. The normal embryonic kidney cells have their surfaces covered with long fingerlike microvilli throughout the cell cycle. In contrast, the surface of the pronephric tumour cells are mainly covered by multiple, ruffled or parallel straight microridges and short, stubby microvilli. These comparisons were made on cells subject to similar culture conditions. The topographic changes in the tumour cells are considered significant since the characteristic microridges and stubby villi were consistently found in all 3 pronephric tumour lines.
Lymphocyte transformation, utilizing the mitotic index parameter has been assessed in newborns' cord blood, adults and women who had been on oral contraceptives and their babies. The results show that the newborns' cord blood response is significantly higher to PHA when compared with the respective adults' response. No significant difference was observed between the women taking oral contraceptives and their respective controls.
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A group of 18 long-stay hospital psycho-geriatric patients (aged 64-101 years) and a group of 10 healthy elderly subjects (aged 53-67 years) who were living in their own residence were studied. The group of geriatric patients were suffering from some degree of pressure sores, dementia, irritability and anorexia. Biochemical tests on vitamin adequacy with particular references to ascorbic acid, thiamine and retinal were performed in the subjects. The thiamine status was measured by determining the thiamine pyrophosphate stimulating effect of transketolase enzyme activity in whole blood. The ascorbic acid and retinal nutritures were determined by measuring their levels in plasma. From the biochemical data of the vitamins it would appear that a significant proportion of the long-stay hospital psycho-geriatric patients may be at risk of thiamine, ascorbic acid and retinol deficiencies.
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