Comparative evaluation of the cerebral state index and the bispectral index during target-controlled infusion of propofol.

BACKGROUND: Cerebral state index (CSI) has recently been introduced as an intra-operative monitor of anaesthetic depth. We compared the performance of the CSI to the bispectral index (BIS) in measuring depth of anaesthesia during target-controlled infusion (TCI) of propofol. METHODS: Twenty Chinese patients undergoing general anaesthesia were recruited. CSI and BIS, and predicted effect-site concentration of propofol were recorded. The level of sedation was tested by Modified Observer's Assessment of Alertness/Sedation Scale (MOAAS) every 20 s during stepwise increase (TCI, 0.5 microg ml(-1)) of propofol. The loss of verbal contact (LVC) and loss of response (LOR) were defined by MOAAS values of 2-3 and less than 2, respectively. Baseline variability and the prediction probability (P(K)) were calculated for the BIS and CSI. The values of BIS(05) and CSI(05), BIS(50) and CSI(50), BIS(95) and CSI(95) were calculated at each end-point (LVC and LOR). RESULTS: Baseline variability of CSI was more than that of BIS. Both CSI and BIS showed a high prediction probability for the steps awake vs LVC, awake vs LOR, and LVC vs LOR, and good correlations with MOAAS values. CONCLUSION: Despite larger baseline variation, CSI performed as well as BIS in terms of P(K) values and correlations with step changes in sedation.

Regulation of the rat cardiac troponin I gene by the transcription factor GATA-4.

Troponin I is a thin-filament contractile protein expressed in striated muscle. There are three known troponin I genes which are expressed in a muscle-fibre-type-specific manner in mature animals. Although the slow skeletal troponin I isoform is expressed in fetal and neonatal heart, the cardiac isoform is restricted in its expression to the myocardium at all developmental stages. To study the regulation of this cardiac-specific and developmentally regulated gene in vitro, the rat cardiac troponin I gene was cloned. Transient transfection assays were performed with troponin I-luciferase fusion plasmids to characterize the regulatory regions of the gene. Proximal regions of the upstream sequence were sufficient to support high levels of expression of the reporter gene in cardiocytes and relatively low levels in other cell types. The highest luciferase activity in the cardiocytes was noted with a plasmid that included the region spanning -896 to +45 of the troponin I genomic sequence. Co-transfection of GATA-4, a recently identified cardiac transcription factor, with troponin I-luciferase constructs permitted high levels of luciferase expression in non-cardiac cells. Electrophoretic mobility-shift assays demonstrated specific binding of GATA-4 to oligonucleotides representative of multiple sites of the troponin I sequence. Mutation of a proximal GATA-4 DNA-binding site decreased transcriptional activation in transfected cardiocytes. These results indicate that the proximal cardiac troponin I sequence is sufficient to support high levels of cardiac-specific gene expression and that the GATA-4 transcription factor regulates troponin I-luciferase expression in vitro.

A new mammalian DNA topoisomerase I poison Hoechst 33342: cytotoxicity and drug resistance in human cell cultures.

Hoechst dye 33342 (Ho33342), like many other DNA minor groove binding ligands and its parent compound Hoechst dye 33258 (Ho33258), nonspecifically inhibits the catalytic activities of many DNA enzymes. However, both Ho33258 and Ho33342 also specifically interrupt the breakage/reunion reaction of mammalian DNA topoisomerase I by trapping reversible topoisomerase I cleavable complexes. The enhanced membrane permeability of Ho33342 over its parent compound Ho33258 has allowed studies of the cellular action of Ho33342. Our results suggest that Ho33342 also traps topoisomerase I but not topoisomerase II into reversible cleavable complexes in human KB cells. Although Ho33342 shares a similar mechanism of action with camptothecin, a prototypic topoisomerase I poison, in trapping topoisomerase I cleavable complexes, Ho33342 differs from camptothecin in its effect on drug-resistant cells. Different from camptothecin, Ho33342 was shown to be about 200-fold less cytotoxic in MDR1-overexpressing human KB V1 cells relative to parental human KB 3-1 cells. Ho33342 is only 5-fold less cytotoxic for camptothecin-resistant CPT-K5 cells, which expresses a highly camptothecin-resistant from of topoisomerase I, than for the wild type human lymphoblast RPMI 8402 cells. Our studies suggest a potential use of Hoechst 33342 as a new topoisomerase I poison in antitumor chemotherapy.

Experimental parameters affecting the ultraviolet-induced tryptophan modification in the lens.

Experimental parameters affecting photolysis of tryptophan in the lens were evaluated, including: (a) the use of previously-frozen vs. freshly excised lenses, (b) the use of lenses in aqueous buffered solutions vs. in air, (c) the species source of the lens, and (d) the effects of oxygen depletion. Lenses were subjected to monochromatic ultraviolet radiation followed by monitoring of the tryptophan fluorescence spectra while exciting at two or more wavelengths. Previously frozen lenses showed faster UV-induced degradation of tryptophan, particularly in aqueous media. A rapid leakage of fluorescent components (including amino acids and peptides) from intact lenses was observed. Evidence for the artifactual production of free radicals during photometric monitoring of samples in solution was obtained. Species dependent differences were also observed.