Efficacy of Colloidal Silver-Hydrogen Peroxide and 2-Bromo-2-nitroporopane-1,3-diol Compounds Against Different Serogroups of Legionella pneumophila Strains.

Cooling towers are considered as amplifier and disseminator sources for Legionella spp. despite preventive treatments. Information which was obtained from biocidal tests could improve the effectiveness of treatments. Therefore, the choice of appropriate biocides and the applying of biocides in correct dosages and contact times are important. Various oxidizing and non-oxidizing biocides have been investigated in vitro for their effectiveness against legionellae. Colloidal silver-hydrogen peroxide (CSHP) and 2-bromo-2-nitroporopane-1,3-diol (BNPD) biocides were selected as an example for oxidizing and non-oxidizing agents, respectively, in view of bactericidal action against different serogroups of L. pneumophila strains [serogroup 1 (S1) and serogroup 2-14 (S2)] which are isolated different cooling towers in the vicinity of Istanbul, Turkey and reference strain. In the current study, oxidizing biocide was found more effective than non-oxidizing biocide in terms of contact times, log reductions and recommended dosages. At the recommended concentrations for cooling towers (100 ppm), while CSHP compound killed all strains in 3 h contact time, BNPD compound killed S2 and reference strain in the same contact time, S1 strain after 6 h contact time. The results of the present study showed that effective biocide applications can be achieved by pre-determining minimum inhibitory concentration (MIC) and minimum contact time of different biocides to kill target bacteria.

The application of viable count procedures for measuring viable cells in the various marine environments.

AIMS: To investigate whether the use of direct viable count (DVC), quantitative viable count (qDVC), colony-forming units and the contribution of capsule-bearing bacteria to the total number of bacteria and esterase-active bacteria could be used to clearly differentiate viable cells in various trophic status of seawater. METHODS AND RESULTS: Hundred and four marine isolates from various marine environments in Turkey (Western Black Sea, northern part of the Sea of Marmara, Northern Aegean Sea and eastern part of the Sea of Marmara) were screened. Seawater samples were taken from the surface (the upper 0-30 cm) and deeper layers (from 5 to 500 m) of the sea at different time periods between February 2002 and June 2007. For the assessment of cell elongation, minor modifications were made on DVC procedure in order to optimize the concentration of yeast extract and incubation time for enumeration of bacteria in response to nutrient addition. The best results were obtained when the yeast extract was used at a final concentration of 250 mg l(-1) (at 35 degrees C 24 h incubation) for bacteria isolated from eutrophic areas and a final concentration of 50 mg l(-1) for those selected from oligotrophic areas. A positive correlation was found between the trophic level and the level of metabolically active bacteria. Among these methods, the bacterial number obtained by qDVC is higher than those gained by other methods. CONCLUSIONS: The results indicate that the qDVC procedure could easily differentiate between viable cells and dormant or dead cells. We suggest that this method may be applicable to detecting the level of metabolic potential of bacterial communities in marine environments. SIGNIFICANCE AND IMPACT OF THE STUDY: The study resulted in increased knowledge on the applicability of the qDVC method that arranges the substrate amount and incubation time as well as on the comparison of various viable bacteria count procedures related to trophic situation of seawater samples.

Cx36 and the function of endocrine pancreas.

The secretory, duct, connective and vascular cells of pancreas are connected by gap junctions, made of different connexins. The insulin-producing beta-cells, which form the bulk of endocrine pancreatic islets, express predominantly Cx36. To assess the function of this connexin, we have first studied its expression in rats, during sequential changes of pancreatic function which were induced by the implantation of a secreting insulinoma. We observed that changes in beta-cell function were paralleled by changes in Cx36 expression. We have also begun to investigate mutant mice lacking Cx36. The absence of this protein did not affect the development and differentiation of beta-cells but appeared to alter their secretion. We have studied this effect in MIN6 cells which spontaneously express Cx36. After stable transfection of a construct that markedly reduced the expression of this connexin, we observed that MIN6 cells were no more able to secrete insulin, in contrast to wild type controls, and differentially displayed a series of still unknown genes. The data provide evidence that Cx36-dependent signaling contributes to regulate the function of native and tumoral insulin-producing cells.

Cx36 preferentially connects beta-cells within pancreatic islets.

Previous studies have provided evidence for the transcripts of Cx43 and Cx45 within pancreatic islets. As of yet, however, it has proven difficult to unambiguously demonstrate the expression of these proteins by islet cells. We have investigated whether Cx36, a new connexin species recently identified in mammalian brain and retina, may also be expressed in pancreatic islets. Using probes that permitted the original identification of Cx36 in the central nervous system, we show that a transcript for Cx36 is clearly detectable in rat pancreatic islets. Using novel and affinity-purified polyclonal antibodies, we have found that Cx36 is actually expressed in pancreatic islets. Both in situ hybridization and immunolabeling indicated that this connexin is abundant in the centrally located insulin-producing beta-cells and is expressed much less, if at all, by the other endocrine cell types. This differential expression was further confirmed on fluorescence-activated cell sorter-purified preparations enriched in either beta- or non-beta-cells. The finding of a differential distribution of Cx36 within distinct regions of pancreatic islets creates the possibility that this connexin may provide the establishment of selective pathways of communication between the different types of endocrine cells comprising the pancreatic islet.

Expression of connexin36 in the adult and developing rat brain.

The distribution of connexin36 (Cx36) in the adult rat brain and retina has been analysed at the protein (immunofluorescence) and mRNA (in situ hybridization) level. Cx36 immunoreactivity, consisting primarily of round or elongated puncta, is highly enriched in specific brain regions (inferior olive and the olfactory bulb), in the retina, in the anterior pituitary and in the pineal gland, in agreement with the high levels of Cx36 mRNA in the same regions. A lower density of immunoreactive puncta can be observed in several brain regions, where only scattered subpopulations of cells express Cx36 mRNA. By combining in situ hybridization for Cx36 mRNA with immunohistochemistry for a general neuronal marker (NeuN), we found that neuronal cells are responsible for the expression of Cx36 mRNA in inferior olive, cerebellum, striatum, hippocampus and cerebral cortex. Cx36 mRNA was also demonstrated in parvalbumin-containing GABAergic interneurons of cerebral cortex, striatum, hippocampus and cerebellar cortex. Analysis of developing brain further revealed that Cx36 reaches a peak of expression in the first two weeks of postnatal life, and decreases sharply during the third week. Moreover, in these early stages of postnatal development Cx36 is detectable in neuronal populations that are devoid of Cx36 mRNA at the adult stage. The developmental changes of Cx36 expression suggest a participation of this connexin in the extensive interneuronal coupling which takes place in several regions of the early postnatal brain.

Glycyl-L-glutamine [beta-endorphin-(30-31)] attenuates hemorrhagic hypotension in conscious rats.

The profound hypotension caused by acute hemorrhage is thought to involve opioid peptide neurons. In this study, we tested whether glycyl-L-glutamine [Gly-Gln; beta-endorphin-(30-31)], a nonopioid peptide derived from beta-endorphin processing, prevents the cardiovascular depression induced by hemorrhage in conscious and anesthetized rats. Previously, we found that Gly-Gln inhibits the hypotension and respiratory depression produced by beta-endorphin and morphine but does not affect opioid antinociception. Hemorrhage (2.5 ml/100 g body wt over 20 min) lowered arterial pressure in conscious rats (from 120.1 +/- 2.9 to 56.2 +/- 4.7 mmHg) but did not change heart rate significantly. Intracerebroventricular Gly-Gln (3, 10, or 30 nmol) pretreatment inhibited the fall in arterial pressure and increased heart rate significantly. The response was dose related and was sustained during the 35-min posthemorrhage interval. Pentobarbital sodium anesthesia potentiated the hemodynamic response to hemorrhage and attenuated the effect of Gly-Gln. Gly-Gln (10 or 100 nmol icv) did not influence arterial pressure or heart rate in normotensive rats. These data indicate that Gly-Gln is an effective antagonist of hemorrhagic hypotension.

Intracerebroventricular injection of choline increases plasma oxytocin levels in conscious rats.

In the present study, we examined the effect of intracerebroventricularly (i.c.v.) injected choline on both basal and stimulated oxytocin release in conscious rats. I.c.v. injection of choline (50-150 micrograms) caused time- and dose-dependent increases in plasma oxytocin levels under normal conditions. The increase in plasma oxytocin levels in response to i.c.v. choline (150 micrograms) was greatly attenuated by the pretreatment of rats with atropine (10 micrograms; i.c.v.), muscarinic receptor antagonist. Mecamylamine (50 micrograms; i.c.v.), a nicotinic receptor antagonist, failed to suppress the effect of 150 micrograms choline on oxytocin levels. Pretreatment of rats with 20 micrograms of hemicholinium-3 (HC-3), a specific inhibitor of choline uptake into nerve terminals, greatly attenuated the increase in plasma oxytocin levels in response to i.c.v. choline injection. Osmotic stimuli induced by either oral administration of 1 ml hypertonic saline (3 M) following 24-h dehydration of rats (type 1) or an i.c.v. injection of hypertonic saline (1 M) (type 2) increased plasma oxytocin levels significantly, but hemorrhage did not alter basal oxytocin concentrations. The i.c.v. injection of choline (50, 150 micrograms) under these conditions caused an additional and significant increase in plasma oxytocin concentrations beyond that produced by choline in normal conditions. These data show that choline can increase plasma oxytocin concentrations through the stimulation of central cholinergic muscarinic receptors by presynaptic mechanisms and enhance the stimulated oxytocin release.