PubMed Health⌕ Search

Biomedical subjects

E Y Cesar

Publications and source records attributed to E Y Cesar.

4 recordsLinked to original sources
PubMed1988

An integrated microcomputer system using immobilized cellular electrodes for drug screening.

Biosensors based on immobilized microbial cells were developed for drug screening in our laboratory. Compared with the conventional methods such as diffusion and dilution tests, biosensors have been demonstrated to be superior in sensitivity and require much shorter screening time. An integrated microcomputer system has been developed for data acquisition, database management, and mode of action estimation, which automates the screening processes and reduces the labor requirements significantly.

Anti-Bacterial Agents↗
PubMed1984

Powder suspension method for critically re-examining the two-site model for hydroxyapatite dissolution kinetics.

A powder dissolution method has been developed, and experiments with the hydroxyapatite suspensions confirm earlier conclusions based on dissolution from hydroxyapatite disks. Although a quantitative assessment of the properties of site 1 was not possible from the data obtained in the present study, a rather accurate and independent evaluation of the properties and the behavior of site 2 of the two-site model for hydroxyapatite dissolution was possible, and the results clearly validate the original two-site model. The present work together with the earlier disk studies show that dissolution from site 2 is well described by a first-order expression, rate = kc2 (Cs2-C), where kc2 is a first-order rate constant, Cs2 is the apparent solubility for site 2 (defined by an ion activity product, KHAP, of the form a10Ca2+PO43-a2OH-, and the solution conditions), and C is the microenvironmental solution concentration of hydroxyapatite. For four different precipitated hydroxyapatite preparations, a single KHAP value of 1 X 10(-128) +/- 1 was found to be consistent with experiments using solutions covering wide ranges of partial saturation and calcium-phosphate ratios. The hydroxyapatite powder and pellet methods (including the data evaluation procedures) now offer a powerful combination for investigating the complex kinetics associated with dental enamel dissolution in particular and enamel chemistry in general.

Calcium↗
PubMed1983

Correlation of microenvironmental drug concentration with inhibition of growth of microorganisms on surfaces.

Methodologies have been developed to study the concept of microenvironmental drug concentration (C*) near or around microorganisms. C* may be calculated from data on drug release from a depot site by using appropriate diffusion relationships. By following C* and correlating this with the minimum inhibitory concentration (CMIC), one could attempt to predict the effectiveness of an antiplaque agent. When C* is less than CMIC, growth would be expected to occur; when C* is higher than or equal to CMIC, growth would not be expected. Chlorhexidine diacetate was chosen for this study, which used a system involving microorganisms present on the surface of drug-treated hydroxyapatite pellets. CMIC, defined as the lowest concentration to inhibit bacterial growth, was determined independently and under conditions similar to those used in the C* experiments. Surface growth of adhering microorganisms (Streptococcus mutans SL1) was followed by scanning electron microscopy. The parameters used in the calculation of C* were determined independently. Diffusion coefficients of the drugs and the diffusion layer thickness were determined under conditions similar to those employed in the release rate studies. Surface growth was generally found to be inhibited whenever C* was significantly greater than CMIC, and growth occurred whenever C* was significantly smaller than CMIC. These findings demonstrate how C* may determine the action of a topically administered antimicrobial agent and how the various physical and chemical factors play roles in influencing this quantity.

Anti-Infective Agents, Local↗