Fenvalerate Exposure Alters Thyroid Hormone Status in Selenium- and/or Iodine-Deficient Rats

Considering the potential adverse effects of selenium and iodine deficiencies, and taking into account the widespread but often careless use of pyrethroid insecticides and their possible endocrine-disrupting effects, this study was undertaken to investigate the effects of fenvalerate on thyroid hormone parameters in both healthy and selenium- and/or iodine-deficient rats. Fenvalerate exposure had no effect on the TT4 levels of healthy controls but caused significant increases both in iodine deficiency (ID) and selenium plus iodine deficiency (ISeD), and a significant decrease in selenium deficiency (SeD). Dramatic increases in TT3 of all groups were observed by fenvalerate. Moreover, it caused insignificant decrease of thyroid stimulating hormone in healthy controls, no effect in SeD, and significant elevation in ID and ISeD. These results, thus, showed that the widely used pyrethroid insecticide fenvalerate has the potential to change significantly thyroid hormone parameters both in normal and deficiency states, and consequences of its thyroid status modifying effect might be of critical importance particularly in sensitive individuals and patients with thyroid dysfunction.     

The role of hemagglutination and effect of exopolysaccharide production on bifidobacteria adhesion to Caco-2 cells in vitro

It is believed that an important criterion for a potential probiotic strain is that it is capable of adhering to mucosal surfaces in the human gastrointestinal tract. The purpose of this study was to investigate a possible relationship between exopolysaccharide production and adhesion to Caco-2 cells by Bifidobacterium breve A28 and Bifidobacterium bifidum A10. In a preselection process, the hemagglutination abilities of these bacteria were determined prior to undertaking adhesion studies. B. breve A28, which produces large amounts of EPS (97.00 ± 2.00 mg/l) and has good hemagglutination abilities (+3) was found to adhere strongly to Caco-2 cells. Under gastrointestinal conditions, the high EPS producing- B. breve A28 was found to have better viability and adhesion to Caco-2 cells than the low EPS producing- B. bifidum A10. Also, B. breve A28 was found to be more effective at inhibiting Escherichia coli ATCC 11229 than B. bifidum A10. This investigation showed that high EPS production and adhesion ability may be important in the selection of bifidobacteria as probiotic strains.     

Prey processing in the Siamese fighting fish (Betta splendens)

We studied prey processing in the Siamese fighting fish (Betta splendens), involving slow, easily observed head-bobbing movements, which were compared with prey processing in other aquatic feeding vertebrates. We hypothesized that head-bobbing is a unique prey-processing behaviour, which alternatively could be structurally and functionally analogous with raking in basal teleosts, or with pharyngognathy in neoteleosts. Modulation of head-bobbing was elicited by prey with different motility and toughness. Head-bobbing involved sustained mouth occlusion and pronounced cranial elevation, similar to raking. However, the hyoid and pectoral girdle were protracted, and not retracted as in both raking and pharyngognathy. High-speed videofluoroscopy of hyoid movements confirmed that head-bobbing differs from other known aquatic prey-processing behaviours. Nevertheless, head-bobbing and other prey-processing behaviours converge on a recurrent functional theme in the trophic ecology of aquatic feeding vertebrates; the use of intraoral and oropharyngeal dentition surfaces to immobilize, reduce and process relatively large, tough or motile prey. Prey processing outside the pharyngeal region has not been described for neoteleosts previously, but morphological evidence suggests that relatives of Betta might use similar processing behaviours. Thus, our results suggest that pharyngognathy did not out-compete ancestral prey-processing mechanisms completely during the evolution of neoteleosts.     

Comparative evaluation of the microplate nitrate reductase assay and the rezasurin microtitre assay for the rapid detection of multidrug resistant Mycobacterium tuberculosis clinical isolates

The microplate nitrate reductase assay (MNRA) and the rezasurin microtitre assay (REMA) were used for the susceptibility testing of 73 clinical isolates and the results were compared with those that were obtained using the Bactec 460 TB and Bactec MGIT 960 systems. The REMA and the MNRA were performed in 96-well plates. For the REMA, the concentrations of isoniazid (INH) and rifampicin (RIF) ranged from 1.0-0.01 μg/mL and 2.0-0.03 μg/mL, respectively. For the MNRA, the INH concentration was between 1.0-0.03 μg/mL and the RIF concentration was between 2.0-0.06 μg/mL. For the MNRA, the sensitivity, specificity, positive predictive value, negative predictive value and INH/RIF agreement were 100/95.6, 97.6/100, 96.8/100, 100/98 and 98.6/98.6, respectively, and for the REMA, they were 100/91.3, 90.4/100, 88.5/100, 100/96.1 and 94.5/97.2, respectively. Our data suggest that these two rapid, low-cost methods may be inexpensive, alternative assays for the rapid detection of multidrug resistant tuberculosis in low-income countries.     

An Auto-Catalytic Surface for Conformational Replication of Amyloid Fibrils—Genesis of an Amyloid World?

Amyloid fibrils are composed of self assembled stacked peptide or protein molecules folded and trapped in a stable cross-beta-sheet conformation. The amyloid fibrillation mechanism represents an intriguing self-catalyzed process rendering replication of a molecular conformational memory of interest for prebiotic chemistry. Herein we describe how a solid surface can be rendered auto-catalytic for fibrillation of a protein solution. We have discovered that a hydrophobic silicon or glass surface can be made to continuously fibrillate solutions of insulin monomers under stressed conditions (pH 1.6, 65°C). It was found that the surface acts as a platform for the formation of nascent seeds that induce fibril replication on and at the surface. This autocatalytic effect stems from a layer a few insulin molecules thick representing an oligomeric layer of misfolded, conformationally trapped, insulin molecules that rapidly through epitaxial growth catalyze the rate determining step (nucleation) during fibril replication. This autocatalytic layer is generated by the protein-solid surface interaction and conformational changes of the adsorbed protein during exposure at the air-water interface. The resulting autocatalytic surface thus both initiates local conformational molecular self-replication and acts as a reservoir for fibril seeds budding off into solution spreading fibril replication entities to the surrounding medium. The possibility of catalysis of the conformational replication process by minute amounts of nucleation sites located on a recruiting surface can evade the issue of dramatic concentration dependence of amyloidogenesis.     

Characterization of vaginal lactobacilli coaggregation ability with Escherichia coli

The coaggregation abilities of probiotic strains might enable it to form a barrier that prevents colonization by pathogenic bacteria. In the present study, the characterization of the coaggregation ability of 19 vaginal lactobacilli was studied. Coaggregation ability of all lactobacilli with Escherichia coli ATCC 11229 was positive. Only the highest coaggregation percentage of Lactobacillus acidophilus S1 was obtained with E. coli ATCC 11229 under both aerobic (71%) and anaerobic conditions (62%). The coaggregation abilities of strains occurred higher at acidic pH than at basic pH values. Moreover, the coaggregation abilities of tested strains against E. coli decreased after heat treatment (70 or 85 °C). Also, the relationship between hydrophobicity and coaggregation of strains was found to be significant. The effect of sonication, some enzymes (lipase and pepsin) and sodium periodate on coaggregation ability of L. acidophilus S1, which is one of the highest potentials on coaggregation ability, was investigated. Sodium periodate did not have a significant effect on coaggregation ability of L. acidophilus S1. The sonicated cell showed lower coaggregation than the control, the supernatant fluid of this sonicated cells showed similar coaggregation ability to the control. Coaggregation abilities of bacteriotherapeutic lactobacilli with pathogenic bacteria can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human use against urogenital tract infections.     

σ-Amylase inactivation during corn starch hydrolysis process

The effects of operating conditions on the enzymatic hydrolysis of corn starch were investigated. A commercial α-amylase produced by Bacillus sp. was used for the hydrolysis experiments. The degree of starch hydrolysis (%) and residual α-amylase activity (%) was investigated versus process variables, including pH, temperature, viscosity, impeller speed, processing time and some materials added such as hydrolysate, maltose, glucose, ethanol and CaCl₂ using a stirred batch reactor. The mathematical models depending on the operating conditions were also derived using the experimental data of residual starch concentration. Some inactivation models were tested to determine the relationship between process variables and enzyme stability during the hydrolysis process.     

The effect of recombinant human erythropoietin on serum selenium levels in hemodialysis patients

Successful results in the treatment of anemia, one of the main complications of chronic renal failure, can be achieved by the use of recombinant human erythropoietin (RhEPO), which is available almost fifteen years in clinics. On the other hand, as both chronic renal failure and maintenance hemodialysis reduce the levels of trace elements, this study was designed to evaluate the interaction potential of RhEPO with serum concentrations of selenium (Se) during four months. Thirty one adult hemodialysis outpatients participated in the study. Ten of them, not on any drug therapy to interact with RhEPO, recruited as “Control Group”, and the remainder, on RhEPO therapy, as “RhEPO Group”. Blood was drawn from the Control Group at the beginning of the study, and from the RhEPO Group at every month for four months. Serum erythropoietin levels were measured by a radioimmunoassay method and Se status by a spectrofluorometric method. It was found that Se levels were not affected by RhEPO treatment during 3 months of therapy, while an increase was seen on the fourth month. The observation indicates that the increase in serum Se levels would be significant in longer than three-month RhEPO treatment.     

The effect of nitric oxide combined with fluoroquinolones against Salmonella enterica serovar Typhimurium in vitro

Two regulons, soxRS and marRAB, are associated with resistance to quinolones or multiple antibiotic in Salmonella enterica serovar Typhimurium. These regulons are activated by nitric oxide and redox-cycling drugs, such as paraquat and cause on activation of the acrAB-encoded efflux pump. In this study, we investigated the effect of nitric oxide (NO) alone and in combination with ofloxacin, ciprofloxacin, and pefloxacin against S. typhimurium clinical isolates and mutant strains in vitro. We did not observe synergistic effect against clinical isolates and SH5014 (parent strain of acr mutant), while we found synergistic effect against PP120 (soxRS mutant) and SH7616 (an acr mutant) S. typhimurium for all quinolones. Our results suggest that the efficiencies of some antibiotics, including ofloxacin, ciprofloxacin, and pefloxacin are decreased via activation of soxRS and marRAB regulons by NO in S. enterica serovar Typhimurium. Further studies are warranted to establish the interaction of NO with the genes of Salmonella and, with multiple antibiotic resistance.