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Biomedical subjects

M Masada

Publications and source records attributed to M Masada.

61 records · Page 4Linked to original sources
PubMed1977

Gas chromatographic and gas chromatographic-mass spectrometric analysis of ampicillin.

A method was developed for the quantitative gas chromatographic (GC) determination of ampicillin. The procedure requires silylation iwth hexamethyldisilazane, trimethylchlorosilane, trimethylsilylimidazole and N,O-bis(trimethylsilyl)acetamide in pyridine and subsequent GC on an OV-17 column, using 5 alpha-cholestane as an internal standard. The method was applied to the determination of ampicillin in some pharmaceutical products. The characteristics of the mass spectra and the derivatization GC of ampicillin are also discussed.

Ampicillin↗
PubMed1975

Gas chromatographic determination and gas chromatographic-mass sepectrometric analysis of chloramphenicol, thiamphenicol and their metabolites.

A rapid and accurate gas chromatographic (GC) method is described for the determination of chloramphenicol, thiamphenicol and their metabolites excreted in human urine. These excretions were pre-treated with diazomethane and N,O-bis(trimethylsilyl)acetamide, so that they could be easily subjected to GC with satisfactory separation from each other and also from other urinary excretions, and could be determined simultaneously. The structures of the metabolites were confirmed by GC combined with mass spectrometric measurements of the GC peaks. The application of the method to urine specimens enabled more precise results for the amounts of metabolites present to be obtained; the excretion of thiamphenicol glucuronide was not observed.

Administration, Oral↗
PubMed1975

Cysteine synthase from rape leaves.

Cysteine synthase [O-Acetyl-L-serine acetate-lyase (adding hydrogen-sulfide) EC 4.2.99.8] has been highly purified from the extract of rape, Brassica chinensis var. Komatsuna. The purified preparation appeared to be homogeneous on Sephadex G-100 gel filtration and dodecylsulfate-polyacrylamide gel electrophoresis, showing a molecular weight of about 62,000. The latter method also suggested that this enzyme was composed of two identical subunits. The enzyme contained 2 moles of pyridoxal phosphate per mole of enzyme.

Chromatography, Gel↗
PubMedDate not supplied

Biosynthetic pathways of pteridines and their association with phenotypic expression in vitro in normal and neoplastic pigment cells from goldfish.

The distribution of GTP-cyclohydrolase I, pyruvoyl tetrahydropterin (dysopropterin) synthase, and pyruvoyl tetrahydropterin reductase in goldfish erythrophores, melanophores, and erythrophoroma cells in vitro has been revealed by specific biochemical assays. The activity of pyruvoyl tetrahydropterin synthase in the erythrophores is nearly the same as that in rat kidney and pineal gland. Results of the simultaneous quantification of unconjugated pteridines (biopterin, sepiapterin, neopterin, and pterin) by HPLC indicate that the total amounts of these derivatives present in these cells and in the respective culture media are closely correlated with the activities of these enzymes. These findings imply that these cells are capable of the autonomous synthesis of pteridines, which most likely proceeds from GTP to 6-lactoyl-5,6,7,8-tetrahydropterin (reduced sepiapterin), via dihydroneopterin triphosphate and pyruvoyl tetrahydropterin, through reactions catalyzed by these enzymes. A comparison of pteridine metabolism between clones of the stem cell type and the yellow-pigmented clones induced from erythrophoroma cells suggests that brightly colored pigmentation involves two separate phases: the biosynthesis of pteridines and their deposition in the pigment organelles. The presence of the highly active pteridine-synthesizing enzymes in melanophores and melanogenic erythrophoroma cells strongly suggests a loose commitment to the expression of pigment phenotypes in this species.

Alcohol Oxidoreductases↗