The Role of Fluoroquinolones in the Promotion of Alginate Synthesis and Antibiotic Resistance in Pseudomonas aeruginosa

Treatment of nonmucoid Pseudomonas aeruginosa with gyrase inhibitors such as ciprofloxacin, norfloxacin, and ofloxacin, which target the A subunit of topoisomerase II, resulted in 100% conversion to the mucoid phenotype. However, antibiotics that partially inhibited growth and macromolecular synthesis (DNA, RNA, protein, or peptidoglycan) of nonmucoid isolates in a gluconate-limited chemostat culture system did not promote conversion to mucoid subpopulations. An increase in resistance was observed in populations that expressed the mucoid phenotype. Both mucoid conversion and antibiotic resistance were completely reversible when ciprofloxacin pressure was withdrawn, but only partially reversible by the removal of norfloxacin and ofloxacin. Thus, these experiments indicate that in the presence of some fluoroquinolones, a conditional response resulting in mucoid conversion and antibiotic resistance may occur. Received: 28 January 1997 / Accepted: 12 February 1997     

Cadmium removal from human plasma by Cibacron Blue F3GA and thionein incorporated into polymeric microspheres

Poly(2-hydroxyethylmethacrylate–ethyleneglycoldimethacrylate) [poly(HEMA–EGDMA)] microspheres carrying Cibacron Blue F3GA and/or thionein were prepared and used for the removal of cadmium ions Cd(II) from human plasma. The poly(HEMA–EGDMA) microspheres, in the size range of 150–200 μm in diameter, were produced by a modified suspension copolymerization of HEMA and EGDMA. The reactive triazinyl dye-ligand Cibacron Blue F3GA was then covalently incorporated into the microspheres. The maximum dye incorporation was 16.5 μmol/g. Then, thionein was bound onto the Cibacron Blue F3GA-incorporated microspheres under different conditions. The maximum amount of thionein bound was 14.3 mg/g. The maximum amounts of Cd(II) ions removed from human plasma by poly(HEMA–EGDMA)–Cibacron Blue F3GA and poly(HEMA–EGDMA)–Cibacron Blue F3GA–thionein were of 17.5 mg/g and 38.0 mg/g, respectively. Cd(II) ions could be repeatedly adsorbed and desorbed with both types of microspheres without significant loss in their adsorption capacity.     

Effect of organic and conventional farming on soil bacterial diversity of pecan tree (Carya illinoensis K. Kosh) orchard across two phenological stages

We described the bacterial diversity of walnut grove soils under organic and conventional farming. The bacterial communities of rhizospheric and nonrhizospheric soils of pecan tree (Carya illinoensis K. Koch) were compared considering two phenological stages (sprouting and ripening). Sixteen operational taxonomic units (OTUs) were identified significantly more abundant according to the plant development, only one according to the farming condition, and none according to the soil origin. The OTUs specificaly abundant according to plant development included Actinobateria (2) and Betaproteobacteria (1) related OTUs more abundant at the sprouting stage, while at the fruit ripening (FR) stage the more abundant OTUs were related to Actinobacteria (6), Alphaproteobacteria (6), and unclassified Bacteria (1). The Gaiellaceae OTU18 (Actinobacteria) was more abundant under conventional farming. Thus, our study revealed that the plant development stage was the main factor shaping the bacterial community structure, while less influence was noticed for the farming condition. The bacterial communities exhibited specific metabolic capacities, a large range of carbon sources being used at the FR stage. The identified OTUs specifically more abundant represent indicators providing useful information on soil condition, potential tools for the management of soil bacterial communities.     

Adiponectin Levels during Low‐ and High‐Fat Eucaloric Diets in Lean and Obese Women

Objective: Adiponectin influences insulin sensitivity (S_I) and fat oxidation. Little is known about changes in adiponectin with changes in the fat content of eucaloric diets. We hypothesized that dietary fat content may influence adiponectin according to an individual's S_I. Research Methods and Procedures: We measured changes in adiponectin, insulin, glucose, and leptin in response to high‐fat (HF) and low‐fat (LF) eucaloric diets in lean (n = 10) and obese (n = 11) subjects. Obese subjects were further subdivided in relation to a priori S_I. Results: We found significantly higher insulin, glucose, and leptin and lower adiponectin in obese vs. lean subjects during both HF and LF. The mean group values of these measurements, including adiponectin (lean, HF 21.9 ± 9.8; LF, 20.8 ± 6.6; obese, HF 10.0 ± 3.3; LF, 9.5 ± 2.3 ng/mL; mean ± SD), did not significantly change between HF and LF diets. However, within the obese group, the insulin‐sensitive subjects had significantly higher adiponectin during HF than did the insulin‐resistant subjects. Additionally, the change in adiponectin from LF to HF diet correlated positively with the obese subjects’ baseline S_I. Discussion: Although in lean and obese women, group mean values for adiponectin did not change significantly with a change in fat content of a eucaloric diet, a priori measured S_I in obese subjects predicted an increase in adiponectin during the HF diet; this may be a mechanism that preserves S_I in an already obese group.     

Effect of adenosine and inosine on ureagenesis in hepatocytes.

Adenosine and inosine produced a dose-dependent stimulation of ureagenesis in isolated rat hepatocytes. Hypoxanthine, xanthine and uric acid were without effect. Half-maximally effective concentrations were 0.08 microM for adenosine and 5 microM for inosine. Activation of ureagenesis by both nucleosides had the following characteristics: (a) it was observed with either glutamine or (NH4)2CO3, provided that glucose was present; (b) it was not detected when glucose was replaced by lactate plus oleate; (c) it was mutually antagonized by glucagon, but not by adrenaline; and (d) it was dependent on Ca2+. We suggest that the action of adenosine and inosine on ureagenesis might be of physiological significance.     

Influence of the solvent on the conformational-dependent properties of random-coil polypeptides. I. The mean-square of the end-to-end distance and of the dipole moment

Conformational energies for the N-acetyl-N'-methylamides of the 20 natural amino acids were calculated, including the solvent effects, as functions of the angles phi and psi for rotation of the main chain and for six positions chi 1 of the C alpha-C beta bond in the side chain (fixed values for chi 2, chi 3, ...). The computed energies were used to evaluate the mean-square end-to-end distance and mean-square dipole moment of homopolypeptides of the 20 natural amino acids. Ten proteins and three enzymes of current interest were also studied. Slight differences in both properties are found on taking the effects of solvent into consideration. Comparison with other computational and experimental results is made.