Photobinding of 8-methoxypsoralen and 5,7-dimethoxycoumarin to DNA and its effect on template activity.
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Biomedical subjects
Publications and source records attributed to C N Ou.
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The photobinding of [3H]8MOP to tRNA upon irradiation at 365 nm in the absence of O2 was determined by gel filtration. The maximum photobinding was found to be ca. 4 mol of 8MOP er mol of tRNA and 5FU-tRNA, with an overall quantum yield of 2.3 X 10(-3). The photobinding kinetics for 8MOP-tRNA showed an apparent induction period or sigmoidal kinetic curve, indicating a specific initial photobinding site on tRNA which was identified as 4-thiouridine at position 8 from the 5'-end of Escherichia coli tRNA. Photobinding of 8MOP to 5FU-tRNA proceeded without an apparent induction period. 8MOP-tRNA and 8MOP-5FU-tRNA adducts were characterized by absorption, fluorescence, and CD spectroscopy. A modified procedure was also developed to analyze the nucleoside composition in modified 8MOP-tRNA and 8MOP-5FU-tRNA. The results showed that 8MOP photochemically added mainly to pyrimidine bases. The photobinding of 8MOP changed the conformation (secondary in particular) of tRNA and inhibited aminoacyl-tRNA synthetase activity.
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An optimized method for application of the EMIT reagent system to a COBAS-BIO centrifugal analyzer was developed to minimize reagent consumption while maintaining good precision and accuracy. Forty-one serum samples, previously analyzed for theophylline by HPLC, were assayed using the modified protocol on the COBAS-BIO centrifugal analyzer. Regression analysis of the results obtained from both methods yielded the following equation: y = 1.10x + 0.01, r = 0.964 (x = HPLC, y = COBAS-BIO centrifugal analyzer, EMIT). The COBAS-BIO centrifugal analyzer and EMIT methodology provided an efficient, inexpensive, and relatively effortless approach to drug monitoring in the routine clinical laboratory.
The short- and long-term effects of simultaneous administration of terbutaline and betamethasone were investigated in 8 gravidas treated for preterm labor. Their plasma concentrations of glucose, insulin, glucagon, C-peptide, lactate and potassium were compared to a control group receiving intravenous magnesium sulfate and betamethasone. The patients on terbutaline therapy had a marked hyperglycemia at 11 h which remained elevated for 48 h. There was a simultaneous rise in plasma insulin and C-peptide, and a fall in plasma glucagon. Lactate levels were markedly elevated. Only 1 of the 8 patients had an abnormal glucose tolerance test at 1 week of therapy. The metabolic changes of control patients were minimal in comparison and there was no lacticacidemia. This suggests that glucocorticoids potentiate the hyperglycemic response of terbutaline.