Pyridoxal 5′-phosphate related changes in retention of 1,25-dihydroxy vitamin D-receptor ligands in rat intestinal mucosa cell nuclei

After feeding rats a vitamin B-6-deficient diet, we observed a decrease in pyridoxal 5′-phosphate concentrations in intestinal mucosa cells to 32 and 48% of control in cytoplasm and cell nuclei, respectively. Correlation analysis suggested that there were two pyridoxal 5′-phosphate pools in the nuclei: a “mobile” pool (equivalent to about 5% the concentration of the cytoplasmic pyridoxal 5′-phosphate), and a “stable” pool, which was independent of cytoplasmic fluctuations of pyridoxal 5′-phosphate (about 9 pmol pyridoxal 5′-phosphate/mg DNA). Reduction in pyridoxal 5′-phosphate content in the cells of vitamin B-6-deficient animals was accompanied by a substantial increase in 1,25-dihydroxyvitamin D-receptor ligand concentration in the cell nuclei (76.6 ± 19.7 vs 762 ± 291 fmol/mg DNA, mean ± SEM). The degree of 1,25-dihydrovitamin D accumulation in the nuclei appeared to be an exponential function of the “mobile” nuclear pyridoxal 5′-phosphate concentration. Semilogarithmic transformation of the data yielded a straight line, representing an inverse correlation between the cytoplasm-related nuclear pool of pyridoxal 5′-phosphate and the logarithm of the 1,25-dihydroxyvitamin D concentration in the nuclei (r=−0.95). These data suggest that pyridoxal 5′-phosphate may be related to 1,25-dihydroxyvitamin D retention in the nuclei, possibly through interaction of the pyridoxal 5′-phosphate with the vitamin D receptor protein in the nuclei.     

The potential use of atomic force microscopy for studying corrosion of metals in the presence of bacterial biofilms — an overview

This communication outlines the principles of application of scanning probe microscopy (SPM) as a tool for studying physico-chemical and biological phenomena and discusses the potential use of atomic force microscopy (AFM) , a form of SPM, for investigation of bacterial biofilms formed on metal surfaces and for studying corrosion of these surfaces in the presence of such biofilms. AFM images showing biofilms developed in pure cultures of either Pseudomonas species on copper, or by a marine isolate of sulphate-reducing bacterium on 304 stainless steel are presented to demonstrate usefulness of the SPM technique for both quantitative and qualitative determination of biocorrosion.     

Epilithic and endolithic microorganisms and deterioration on stone church facades subject to urban pollution in a sub-tropical climate

Weathering of two church facades in Rio de Janeiro was caused substantially by salts, mainly halite and gypsum, detected by SEM and chemical analyses, which cause physical stresses by deposition within the rock. Biofilm populations, determined by SEM and as operational taxonomic units (OTUs), degraded stone by penetration, solubilization and redeposition of minerals on their surfaces. Endolithic cyanobacteria were associated with gypsum deposits. Microbiomes were typical for high-stress environments, high salt, intense insolation, low water and low nutrients (eg halophilic Rubrobacter, Salinicola, Sterigmatomyces). The main colonizers on the church most affected by traffic (Nossa Senhora da Candelária – CA) were Actinobacteria; Gammaproteobacteria (chiefly Pseudomonas) were predominant on the site situated in a leafy square (São Francisco de Paula – SF). Major Gammaproteobacteria on CA were halophilic Halomonas and Rhodobacteriaceae. Fungal OTUs on both churches were principally dimorphic, yeast-like basidiomycetes. Many OTUs of thermophilic microorganisms (eg the Thermomicrobia class, Chloroflexi) were present. This is the first use of next generation sequencing (NGS) to study microbial biofilm interactions with metamorphic and granite buildings in an intensely urban, sub-tropical climate.     

Wiedemannia pieninensis,a New Species of Aquatic Empidid (Diptera,Empididae) from Poland

Wiedemannia pieninensis spec. nov., a new aquatic dance fly (Diptera, Empididae, Clinocerinae) from Poland is described and figured.     

Temozolomide,quercetin and cell death in the MOGGCCM astrocytoma cell line

The aim of the present study was to investigate the effect of Temozolomide (an alkylating chemotherapeutic agent) and quercetin (natural flavonoid) on cell death in the human astrocytoma cell line MOGGCCM (WHO grade III). Our results indicate that Temozolomide induces autophagy, while quercetin promotes severe necrosis in the cell line in a manner dependent on the drug concentration. We demonstrated for the first time that combinations of both drugs were much more effective in programmed cell death induction in glioma cells. At a low (5 μM) drug concentration, quercetin potentiated a pro-autophagic effect of Temozolomide, while after treatment with a higher drug concentration (30 μM), autophagy switched to apoptosis. Temozolomide attenuated the toxic effect of quercetin. Apoptosis was mediated by the mitochondrial pathway and the activation of caspase 3 and cytochrome C release, but no changes in caspase 8 expression was observed. It was accompanied by decreased mitochondrial membrane potential and inhibition of Hsp27 and Hsp72 expression. Autophagy was correlated with an increased level of LC3II. Temozolomide and quercetin also inhibited migratory phenotype of MOGGCCM cells and changed the nuclei morphology from a circular to an irregular shape. Our results indicate that quercetin acts in synergy with Temozolomide and when used in combination rather than in separate pharmacological application, both drugs are more effective in programmed cell death induction. Temozolomide administered with quercetin seems to be a potent and promising combination which might be useful in glioma therapy.     

The release of active substances from selected carbohydrate biopolymer membranes

As a biopolymer application to control release systems is increasing at present, flat matrices (transdermal systems) should be highlighted. They constitute one of the most friendly form of drug administration to the patient. The present results concern investigations on the active substance release (ibuprofen and salicylic acid) from film matrices made from biopolymers: polylactid acid (PLA), dibutyrylchitin (DBC) and chitosan (CH). The amount of released active substance was examined with UV-VIS spectrophotometer. The release process was conducted in the medium of pH = 5.6 as the transdermal systems are applied to human skin surface of pH value approximating 5.6. Swelling of polymer samples was confirmed in the buffer of pH = 5.6 as well.The paper comprises the analysis of obtained release results according to the proposed two stage complex diffusion model.     

Retigabine holds KV7 channels open and stabilizes the resting potential

The anticonvulsant Retigabine is a K_V7 channel agonist used to treat hyperexcitability disorders in humans. Retigabine shifts the voltage dependence for activation of the heteromeric K_V7.2/K_V7.3 channel to more negative potentials, thus facilitating activation. Although the molecular mechanism underlying Retigabine’s action remains unknown, previous studies have identified the pore region of K_V7 channels as the drug’s target. This suggested that the Retigabine-induced shift in voltage dependence likely derives from the stabilization of the pore domain in an open (conducting) conformation. Testing this idea, we show that the heteromeric K_V7.2/K_V7.3 channel has at least two open states, which we named O₁ and O₂, with O₂ being more stable. The O₁ state was reached after short membrane depolarizations, whereas O₂ was reached after prolonged depolarization or during steady state at the typical neuronal resting potentials. We also found that activation and deactivation seem to follow distinct pathways, suggesting that the K_V7.2/K_V7.3 channel activity displays hysteresis. As for the action of Retigabine, we discovered that this agonist discriminates between open states, preferentially acting on the O₂ state and further stabilizing it. Based on these findings, we proposed a novel mechanism for the therapeutic effect of Retigabine whereby this drug reduces excitability by enhancing the resting potential open state stability of K_V7.2/K_V7.3 channels. To address this hypothesis, we used a model for action potential (AP) in Xenopus laevis oocytes and found that the resting membrane potential became more negative as a function of Retigabine concentration, whereas the threshold potential for AP firing remained unaltered.