Muayad M. Abboud

Synchrony of G6PD activity and RBC fragility under oxidative stress exerted at normal and G6PD deficiency.

OBJECTIVES To investigative the effects of oxidative stress simultaneously on Glucose-6-phosphate dehydrogenase (G6PD) activity and RBC fragility under normal and G6PD defective conditions. METHODS The effects of several nitric oxide (NO) generating compounds and sulfhydryl blocking agents were simultaneously tested in vitro on hemolysate G6PD activities and RBC fragility. These effects were compared between normal subjects and patients with G6PD deficiency. RESULTS The NO donor compounds nitrosocysteine, nitrosoarginine and diethylamine caused strong inhibition on normal and defective G6PD activities, while a similar inhibition was observed only at higher concentrations of the sulfhydryl blocking agents: 2-mercaptoethanol , cysteine and reduced glutathione. All these oxidative compounds promoted RBC hemolysis in parallel to their inhibition extents on G6PD activities. The protection of RBC from this hemolysis was achieved by preincubation with NADPH or SNP but not NAD(+) compound. CONCLUSION A concomitant response of G6PD activities and RBC fragility towards the oxidative stress was established.

Biodegradation Kinetics of Four Substituted Chlorobenzoic Acids by Enterobacter aerogenes

ABSTRACT Enterobacter aerogenes is generally found in soil, sewage plants, and human gastrointestinal tract. Thus, this study was conducted to evaluate the ability of Enterobacter aerogenes to degrade four chlorobenzoic acid compounds (2-chlorobenzoic acid (2-CBA), 3-chlorobenzoic acid (3-CBA), 4-chlorobenzoic acid (4-CBA), and 3,4-dichlorobenzoic acid (3,4-dCBA)) in minimal salt medium. Enterobacter aerogenes was partially able to degrade and dechlorinate these CBAs at concentration of 3.5 mM within 72 h of incubation. According to Haldane single-substrate model, the values of maximum predicted growth rate (μmax), half saturation constant (K s), and inhibition constant (K i) fell in the range of 0.2–0.8 h−1, 8–41 mM, and 5–53 mM, respectively. Based on the estimated values of both α, a growth-associated constant, and β, a non–growth-associated constant, the production of chloride was predominantly growth associated, since negligible values of the β were determined. Haldane model gave a good prediction of the CBA substrate utilization and degradation, and was in a very good agreement with the experimental data. Because of the capability of Enterobacter aerogenes to utilize these aromatic compounds as carbon and energy sources, this microorganism can be a valuable and promising candidate for use in the biotreatment of wastewater and soil samples contaminated with mixtures of chlorobenzoates.