Biomedical subjects

M Zacharias

Publications and source records attributed to M Zacharias.

6 recordsLinked to original sources

PubMed1992

Analysis of the Fis-dependent and Fis-independent transcription activation mechanisms of the Escherichia coli ribosomal RNA P1 promoter.

The role of the curved DNA sequence upstream to the Escherichia coli ribosomal RNA P1 promoter in transcription activation was studied. This sequence region had been shown to activate transcription from P1 in vivo and in vitro and to harbor binding sites for the trans-activating protein Fis. We have constructed a series of linker scanning mutants spanning the region -104 to -47, relative to the transcription start site. DNA fragments carrying the mutations show altered gel electrophoretic mobilities, consistent with reduced DNA bending angles compared to the wild-type sequence. Using gel retardation assays, qualitative as well as quantitative differences in the binding of the trans-activating protein Fis to the mutant DNA fragments could be observed. The effects of the mutations on rrnB P1 promoter activation were studied in vivo in fis+ and fis- backgrounds. A reduction in the promoter strength for some of the linker mutants correlates with altered Fis binding to two of the known Fis binding sites. Shifting the Fis binding region by half a helical turn, relative to the promoter core sequence, abolishes Fis-mediated activation almost totally, whereas activation is partly restored by a shift of a complete helical turn. For one mutant, which does not show alterations in Fis binding, a decrease in the promoter strength was observed in a fis- strain. From the results, we conclude that two upstream activating mechanisms, one Fis-dependent and one Fis-independent, influence the rrnB P1 promoter strength. Sequence determinants for the Fis-independent mechanism are closer to the promoter core region than the Fis binding sites. In addition, the study demonstrates that both the helical geometry and the absolute distance of the UAS region relative to the promoter are crucial for transcription activation.

Base Sequence↗

PubMed1992

Poisson-Boltzmann analysis of the lambda repressor-operator interaction.

A theoretical study of the ion atmosphere contribution to the binding free energy of the lambda repressor-operator complex is presented. The finite-difference form of the Poisson-Boltzmann equation was solved to calculate the electrostatic interaction energy of the amino-terminal domain of the lambda repressor with a 9 or 45 base pair oligonucleotide. Calculations were performed at various distances between repressor and operator as well as at different salt concentrations to determine ion atmosphere contributions to the total electrostatic interaction. Details in the distribution of charges on DNA and protein atoms had a strong influence on the calculated total interaction energies. In contrast, the calculated salt contributions are relatively insensitive to changes in the details of the charge distribution. The results indicate that the ion atmosphere contribution favors association at all protein-DNA distances studied. The theoretical number of ions released upon repressor-operator binding appears to be in reasonable agreement with experimental data.

Bacteriophage lambda↗

PubMed1992

Oxygen saturation during intravenous sedation using midazolam.

Intravenous sedation with midazolam was given to young, fit, adult patients undergoing third molar surgery; oxygen saturation (SpO2) was continuously measured during the surgery and for 30 minutes after the surgery. There were some instances of a brief fall in the oxygen saturation, during the surgery and in the immediate period following surgery. It is suggested that it may be necessary to observe and selectively monitor some patients in the immediate post-surgical period as well as during the period of operation. Although not addressed by this investigation, this would be particularly true of medically compromised patients and the elderly.

Adult↗

PubMed1979

Effect of preanaesthetic medication on etomidate.

The effects of diazepam and pethidine, when given as preanaesthetic medication, on the induction of anaesthesia and the postanaesthetic sequelae following etomidate were studied in women undergoing minor gynaecological procedures. Pain on injection was present in all the groups. However, the frequency was significantly less with the polyethylene glycol and propylene glycol formulations of the drug compared with the aqueous solution. A fast injection and pethidine premedication decreased the frequency also. The high frequency of excitatory phenomena in unpremedicated patients was decreased significantly by premedication with diazepam and pethidine, especially the latter. Respiratory and cardiovascular effects of the drug were not major problems. The frequency of emetic sequelae was high. Recovery was rapid even in the groups receiving sedative premedication.

Adolescent↗

PubMed1979

Venous sequelae following etomidate.

Five hundred patients receiving one of three different formulations of etomidate were observed on the 2nd and 3rd days after operation for possible venous sequelae. The total frequency of sequelae was 8% or more, the greatest being with the propylene glycol formulation (23%). Formulation of the drug and total dose employed were the most important factors influencing venous sequelae, which were not related to pain on injection.

Adolescent↗

PubMed1978

Evaluation of three preparations of etomidate.

Three formulations of etomidate were evaluated in unpremedicated patients undergoing minor gynaecological procedures. There was a high frequency of pain on injection (up to 50%) and excitatory phenomena (up to 95%) with all formulations. The frequency of excitatory phenomena was significantly greater than that after methohexitone. Recovery was rapid, but emetic sequelae were frequent and significantly more marked than after methohexitone.

Anesthesia, Intravenous↗