Conformational features of the Dippu-AST 8 neuropeptide from the cockroach Diploptera punctata

Spatial structure and conformational properties of the Dippu-AST 8 (allatostatin III) neuropeptide have been investigated by the molecular mechanics method. The conformational energy and geometrical parameters corresponding to the low-energy states of the molecule are obtained. A single backbone conformation with a very restricted set of Ser 3, Phe 4 and Leu 9 amino acids positions is observed for Dippu-AST 8 neuropeptide.     

Role of protein-tyrosine phosphatase SHP2 in focal adhesion kinase down-regulation during neutrophil cathepsin G-induced cardiomyocytes anoikis

Inflammatory cells and their proteases contribute to tissue reparation at site of inflammation. Although beneficial at early stages, excessive inflammatory reaction leads to cell death and tissue damage. Cathepsin G (Cat.G), a neutrophil-derived serine protease, has been shown to induce neonatal rat cardiomyocyte detachment and apoptosis by anoikis through caspase-3 dependent pathway. However the early mechanisms that trigger Cat.G-induced caspase-3 activation are not known. This study identifies focal adhesion kinase (FAK) tyrosine dephosphorylation as an early mechanism that regulates Cat.G-induced anoikis in cardiomyocytes. Both FAK tyrosine phosphorylation at Tyr-397 and kinase activity decrease rapidly upon Cat.G treatment and was associated with a decrease of FAK association with adapter and cytoskeletal proteins, p130(Cas) and paxillin, respectively. FAK-decreased tyrosine phosphorylation is required for Cat.G-induced myocyte anoikis as concurrent expression of phosphorylation-deficient FAK mutated at Tyr-397 or pretreatment with a protein-tyrosine phosphatase (PTP) inhibitor, pervanadate, blocks Cat.G-induced FAK tyrosine dephosphorylation, caspase-3 activation and DNA fragmentation. Analysis of PTPs activation shows that Cat.G treatment induces an increase of SHP2 and PTEN phosphorylation; however, only SHP2 forms a complex with FAK in response to Cat.G. Expression of dominant negative SHP2 mutant markedly attenuates FAK tyrosine dephosphorylation induced by Cat.G and protects myocytes to undergo apoptosis. In contrast, increased SHP2 expression exacerbates Cat.G-induced FAK tyrosine dephosphorylation and myocyte apoptosis. Taken together, these results show that Cat.G induces SHP2 activation that leads to FAK tyrosine dephosphorylation and promotes cardiomyocyte anoikis.     

The interplay between environmental and host factors during an outbreak of visceral leishmaniasis in eastern Sudan

Parasitic diseases, including human visceral leishmaniasis, are multifactorial. Factors that are expected to play an important role in the parasite-human interaction are exposure, parasite "virulence" and host resistance factors. In populations exposed to Leishmania donovani most subjects do not allow the parasites to establish themselves or remain asymptomatic. Some individuals, however, fail to control parasite expansion and dissemination and develop a visceral disease. We report here the results of a longitudinal survey whose aims were to identify risk factors underlying visceral leishmaniasis (VL) susceptibility during an outbreak that occurred in a Sudanese village between 1995 and 1999. Most of the 660 subjects (90%) living in the central district were exposed to Leishmania and 20.9% (n = 138), mostly teenagers, developed VL. VL cases increased markedly in adults late in the outbreak, suggesting some changes in adult resistance status or in Leishmania "virulence" during the epidemic. Age and ethnic origin of the patients were the most important critical risk factors to account for the distribution of the VL cases that were recorded during the whole epidemic. This and the high frequency of VL in certain families suggest that host genetic factors played an important role in shaping the outbreak in this village. However, environmental factors (the presence of cows and neems in the households) that increase/decrease exposure to the parasite had significant effects on the distribution of VL cases in the village in the first phase of the outbreak.     

Repertoire of intensive care unit pneumonia microbiota

Despite the considerable number of studies reported to date, the causative agents of pneumonia are not completely identified. We comprehensively applied modern and traditional laboratory diagnostic techniques to identify microbiota in patients who were admitted to or developed pneumonia in intensive care units (ICUs). During a three-year period, we tested the bronchoalveolar lavage (BAL) of patients with ventilator-associated pneumonia, community-acquired pneumonia, non-ventilator ICU pneumonia and aspiration pneumonia, and compared the results with those from patients without pneumonia (controls). Samples were tested by amplification of 16S rDNA, 18S rDNA genes followed by cloning and sequencing and by PCR to target specific pathogens. We also included culture, amoeba co-culture, detection of antibodies to selected agents and urinary antigen tests. Based on molecular testing, we identified a wide repertoire of 160 bacterial species of which 73 have not been previously reported in pneumonia. Moreover, we found 37 putative new bacterial phylotypes with a 16S rDNA gene divergence ≥ 98% from known phylotypes. We also identified 24 fungal species of which 6 have not been previously reported in pneumonia and 7 viruses. Patients can present up to 16 different microorganisms in a single BAL (mean ± SD; 3.77 ± 2.93). Some pathogens considered to be typical for ICU pneumonia such as Pseudomonas aeruginosa and Streptococcus species can be detected as commonly in controls as in pneumonia patients which strikingly highlights the existence of a core pulmonary microbiota. Differences in the microbiota of different forms of pneumonia were documented.     

The association between N-acetyltransferase 2 gene polymorphisms and pancreatic cancer

Pancreatic cancer has been linked with exposure to environmental chemicals, which generally require metabolic activation to highly reactive toxic or carcinogenic intermediates. N-acetyltransferase 1 (NAT1) and N-acetyltransferase 2 (NAT2) are expressed primarily in extrahepatic and hepatic tissues, respectively. Both enzymes catalyze N- and O-acetylation of aromatic and heterocyclic amines. It is believed that these compounds are activated via O-acetylation and detoxified by N-acetylation. Several polymorphisms of these two genes have been associated with an increased risk of cancer. Twenty-seven cases of pancreatic cancer and 104 controls were included in this study. Blood was collected in EDTA-containing tubes, and genomic DNA was extracted from the white blood cells by using a high pure PCR template preparation kit. Genotyping of NAT2 polymorphisms was detected by a real time PCR instrument. There was a significant difference in the distribution of the NAT2*6A acetylators phenotype between cases and the controls. The odds ratio of pancreatic cancer for the NAT2*6A slow phenotype was 5.7 (95% CI = 1.27-25.55; p = 0.023) compared with the fast type. Our results suggest that slow acetylators have higher risk of developing pancreatic cancer than fast acetylators. NAT2 gene polymorphisms may be associated with genetic susceptibility to pancreatic cancer.     

Analysis of Cell Wall Constituents of Biocide-Resistant Isolates from Dental-Unit Water Line Biofilms

In past years, the significance of microbial resistance to biocides has increased. Twenty biocide-resistant bacterial strains were isolated from dental-unit water line biofilm. All strains resisted high biocide concentrations (up to 100 mug ml(-)1): sodium dodecyl sulphate, hydrogen peroxide, sodium hypochlorite, phenol, Tween 20, ethylenediaminetetraacetic acid, chlorohexidine gluconate, and povidine iodine. Among bacteria, biocide sensitivity is based on permeability of biocides through the cell wall. Gram-positive bacteria are more permeable and susceptible to biocides, whereas Gram-negative bacteria have a more complex cell wall and are the least sensitive bacteria. The present study was designed to study the effect of biocides on the cell wall of biocide-resistant bacteria. Peptidoglycan (PG), diaminopimelic acid (DAP), and teichoic acid contents of the cell wall were determined in L-broth and L-broth supplemented with biocides at different temperatures (37 degrees C and 45 degrees C) and pH levels (7 and 9). In general and Gram staining-specific comparison, a significant increase (p < 0.05) in the DAP content of biocide-resistant bacteria was observed at pH 7 and at both temperatures. In tubing-specific comparison, a significant increase in the amount of teichoic acid in air water tubing (37 degrees C at pH 9) and DAP in patient tubing (pH 7 at both temperatures) was observed. In main water pipe, a significant decrease (p > 0.05) in PG content was noticed at 45 degrees C and pH 9. Overall, a significant increase in DAP content may be an important constituent in the manifestation of isolate resistance against various biocides.     

Activation of the midbrain periaqueductal gray induces airway smooth muscle relaxation.

In this study, we examined effects of chemical stimulation of the ventrolateral region of the midbrain periaqueductal gray (vl PAG) on airway smooth muscle tone. We observed that in anesthetized, paralyzed, and artificially ventilated ferrets, vl PAG stimulation elicited airway smooth muscle relaxation. To clarify the mechanisms underlying this observation, we examined the GABA-GABA(A) receptor signaling pathway by 1) examining the expression of GABA(A) receptors on airway-related vagal preganglionic neurons (AVPNs) located in the rostral nucleus ambiguus region (rNA), by use of receptor immunochemistry and confocal microscopy; 2) measuring GABA release within the rNA by using microdialysis; and 3) performing physiological experiments to determine the effects of selective blockade of GABA(A) receptors expressed by AVPNs in the rNA region on vl PAG-induced airway relaxation, thereby defining the role of the GABA(A) receptor subtype in this process. We observed that AVPNs located in the rNA region do express the GABA(A) receptor beta-subtype. In addition, we demonstrated that activation of vl PAG induced GABA release within the rNA region, and this release was associated with airway smooth muscle relaxation. Blockade of the GABA(A) receptor subtype expressed by AVPNs in the rNA by bicuculline diminished the inhibitory effects of vl PAG stimulation on airway smooth muscle tone. These data indicate, for the first time, that activation of vl PAG dilates the airways by a release of GABA and activation of GABA(A) receptors expressed by AVPNs.     

Protective Effects of Selenium and Vitamin E Combination on Experimental Colitis in Blood Plasma and Colon of Rats

Ulcerative colitis increases oxidative damage accompanied by production of free oxygen radicals. Selenium (Se) and vitamin E are two natural antioxidants. The present study was undertaken to investigate the possible protective role of Se and vitamin E combination in experimental colitis induced by acetic acid (AA) in rats. This study was carried out on three groups, namely the first (control), the second (experimental colitis group, 2 ml 5% acetic acid), and the third groups (2 ml 5% acetic acid, vitamin E (100 mg/kg body weight (bw)) plus Se (0.2 mg/kg bw)). The activities of catalase (CAT), prolidase (PRS), myeloperoxidase (MPO), total antioxidant capacity (TAC), total oxidant status (TOS), oxidative stress index (OSI), total thiol (T-SH) were determined in plasma and colon samples. Macroscopic and microscopic damages in colon were increased by AA treatment (p < 0.01 and p < 0.01, respectively), whereas they were decreased by selenium and vitamin E treatment (p < 0.05 and p < 0.01, respectively). The activities of CAT and PRS in the plasma and colon were significantly affected (p < 0.05 and p < 0.01) by treatment of AA, Se, and vitamin E. MPO activity in colon was increased (p < 0.01) by AA treatment and decreased (p < 0.05) by Se and vitamin E administration. The values of TOS and OSI in plasma were increased (p < 0.5) by AA. The TAC and T-SH in colon were decreased (p < 0.05) by AA and increased (p < 0.05) by Se and vitamin E. Based upon these results, Se and vitamin E may play an important role in preventive indication of the oxidative damage associated by acetic acid caused inflammation.     

Ionic blockade of the rat connexin40 gap junction channel by large tetraalkylammonium ions.

The rat connexin40 gap junction channel is permeable to monovalent cations including tetramethylammonium and tetraethylammonium ions. Larger tetraalkyammonium (TAA(+)) ions beginning with tetrabutylammonium (TBA(+)) reduced KCl junctional currents disproportionately. Ionic blockade by tetrapentylammonium (TPeA(+)) and tetrahexylammonium (THxA(+)) ions were concentration- and voltage-dependent and occurred only when TAA(+) ions were on the same side as net K(+) efflux across the junction, indicative of block of the ionic permeation pathway. The voltage-dependent dissociation constants (K(m)(V(j))) were lower for THxA(+) than TPeA(+), consistent with steric effects within the pore. The K(m)-V(j) relationships for TPeA(+) and THxA(+) were fit with different reaction rate models for a symmetrical (homotypic) connexin gap junction channel and were described by either a one- or two-site model that assumed each ion traversed the entire V(j) field. Bilateral addition of TPeA(+) ions confirmed a common site of interaction within the pore that possessed identical K(m)(V(j)) values for cis-trans concentrations of TPeA(+) ions as indicated by the modeled I-V relations and rapid channel block that precluded unitary current measurements. The TAA(+) block of K(+) currents and bilateral TPeA(+) interactions did not alter V(j)-gating of Cx40 gap junctions. N-octyl-tributylammonium and -triethylammonium also blocked rCx40 channels with higher affinity and faster kinetics than TBA(+) or TPeA(+), indicative of a hydrophobic site within the pore near the site of block.