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C Führer

Publications and source records attributed to C Führer.

12 recordsLinked to original sources
PubMed1987

[Structure of cholesterol-containing creams].

The colloidal structure of a four-component system consisting of cholesterol, fatty alcohol, petrolatum and water was studied. Depending on the variation of temperature, chain length of the fatty alcohol and concentration of all components, creamy systems of w/o type could be prepared, which present different structural features. Liquid phases as well as crystalline and/or liquid crystalline phases participate in the structure of the creams. The liquid phases are represented by water and by liquid hydrocarbons of low molecular weight of petrolatum. Part of the surfactants is dissolved in this latter phase. The liquid crystalline phase is formed by cholesterol and fatty alcohol together. The characterization of the lamellar liquid crystalline phase was performed by polarized light microscopy and small angle x-ray diffraction. The formation of the lamellar liquid crystals is favoured in a certain molar concentration range of cholesterol and fatty alcohol. The liquid crystalline region is largest with tetradecanol. The lamellar liquid crystals swell with water up to a certain limit. This incorporation of water stabilizes the lamellar liquid crystals so that they are stable in a larger temperature range. The crystalline structures form a network consisting of solid hydrocarbons and the eutectic mixture of cholesterol and fatty alcohol. If water is present the surfactants crystallize as hydrates. A surplus of water can be dispersed as droplets mechanically. Referring to maximum capacity of water incorporation, systems with lowest crystalline amounts (only the network of petrolatum) were best. The surfactants should be completely dissolved.

Chemistry, Pharmaceutical↗
PubMed1978

Kinetic studies of ampicillin action on Escherichia coli and their spheroplasts.

Kinetic studies of ampicillin action were made on exponentially growing Escherichia coli and on E. coli-spheroplasts using a range of inhibitory and subinhibitory concentrations of ampicillin. For each concentration, the value (ko--ka) representing the difference in generation rates of ampicillin-free culture (ko) and the generation rate of the culture with ampicillin (ka) was calculated and plotted against ampicillin concentration. A straight line relation was obtained with E. coli cells, its intersection with the abscissa, where (ko--ka) = o, give the concentration of ampicillin which exerts no inhibitory action on the cells (0.25 microgram/ml). When ka was plotted against ampicillin concentration, the relation was also linear. Its intersection with the abscissa gives the minimum lethal concentration of ampicillin on the bacterial cells (1.05 microgram/ml). With E. coli-spheroplasts such plots were non-linear which means that a different order of reaction was involved. This difference is probably due to a different mechanism of ampicillin action as revealed by the electroscanning microscopy.

Ampicillin↗