Search results for "Porin"
showing 10 items of 260 documents
Vibrio cholerae cytolysin: assembly and membrane insertion of the oligomeric pore are tightly linked and are not detectably restricted by membrane fl…
2000
AbstractHemolytic strains of Vibrio cholerae secrete a cytolysin that, upon binding as a monomer, forms pentameric pores in animal cell membranes. Pore formation is inhibited at low temperature and in the absence of cholesterol. We here posed the following questions: firstly, can oligomerization be observed in the absence of pore formation? Secondly, is membrane fluidity responsible for the effect of temperature or of cholesterol upon pore formation? The first issue was approached by chemical cross-linking, by electrophoretic heteromer analysis, and by electron microscopy. None of these methods yielded any evidence of a non-lytic pre-pore oligomer. The second question was addressed by the u…
Further development of the β-lactamase MutaGen assay and evaluation by comparison with Ames fluctuation tests and theumu test
2005
A rapid, high-throughput bacterial mutagenicity test system has been developed (MutaGen test) that detects reversions of inactivating base-pair substitutions and frameshifts in a TEM-1 class A β-lactamase (ampicillinase) gene. To quickly and sensitively detect mutagens, the system utilises a series of plasmids that contain the mutated ampicillinase gene and the mucAB operon. Inactivating mutations in the ampicillinase gene include frameshifts integrated into repetitive GC-sequences and G-runs known to be mutagenic hot-spots, and base-pair substitutions inserted in or around the β-lactamase active site. Frameshift mutations completely inactivated the enzyme only when located downstream of th…
VIRULENCE FACTORS AND ANTIMICROBIAL RESISTANCE OF ESCHERICHIA COLI ST131 IN COMMUNITY-ONSET HEALTHCARE-ASSOCIATED INFECTIONS IN SICILY, ITALY
2017
Escherichia coli ST131 is an emerging resistant agent recently called “superbug” in England. This strain is responsible of community-acquired urinary tract infections and nowadays showing increasing resistance to antibiotics like fluoroquinolones and cephalosporins. Survey of virulent bacterial clone is relevant to control its spreading in community. We aim to assess the circulation of resistant clones Escherichia coli ST131 outside of the hospital to prompt control of outbreak in our geographical area. We selected 105 E. coli resistant isolates from community-acquired urinary infections and performed a multiplex PCR to evaluate if they belonged to the ST131 type. We investigated their set …
Evaluation of P-glycoprotein (abcb1a/b) modulation of [18F]fallypride in MicroPET imaging studies
2012
[(18)F]Fallypride ([(18)F]FP) is an important and routinely used D2/D3 antagonist for quantitative imaging of dopaminergic neurotransmission in vivo. Recently it was shown that the brain uptake of the structurally related [(11)C]raclopride is modulated by P-glycoprotein (P-gp), an important efflux transporter at the blood-brain barrier. The purpose of this study was to determine whether the brain uptake of [(18)F]FP is influenced by P-gp. For examination of this possible modulation microPET studies were performed in a rat and a mouse model. Hence, [(18)F]FP was applied to Sprague Dawley rats, half of them being treated with the P-gp inhibitor cyclosporine A (CsA). In a second experimental s…
Identification of P-glycoprotein substrates and inhibitors among psychoactive compounds--implications for pharmacokinetics of selected substrates.
2004
Abstract The pharmacokinetics of antipsychotic drugs has become an integral part in understanding their pharmacodynamic activity and clinical effects. In addition to metabolism aspects, carrier-mediated transport, particularly secretion by ABC transporters, has been discussed as potentially relevant for this group of therapeutics. In this study, the psychoactive compounds perphenazine, flupentixol, domperidone, desmethyl clozapine, haloperidol, fluphenazine, fluvoxamine, olanzapine, levome-promazine, perazine, desmethyl perazine, clozapine, quetiapine and amisulpride were characterized in terms of P-glycoprotein (P-gp) affinity and transport. Experimental methods involved a radioligand disp…
Staurosporine-induced apoptosis in Chang liver cells is associated with down-regulation of Bcl-2 and Bcl-XL.
2004
A potent inhibitor of serine/threonine kinases, staurosporine exerts antiproliferative and apoptotic effects in many cancer cells, although the exact mechanism of its action is still unclear. This study examines the effects of staurosporine on Chang liver cells, an immortalized non-tumor cell line, in comparison with those caused in HuH-6 and HepG2 cells, two human hepatoma cell lines. Our results provide evidence that staurosporine promotes apoptosis in Chang liver cells as observed by flow cytometric analysis and acridine orange/ethidium bromide staining. The effect appeared already after 8 h of treatment and increased with treatment time and dose. After 48 h of exposure to 200 nM stauros…
The tetrameric α-helical membrane protein GlpF unfolds via a dimeric folding intermediate.
2011
Many membrane proteins appear to be present and functional in higher-order oligomeric states. While few studies have analyzed the thermodynamic stability of α-helical transmembrane (TM) proteins under equilibrium conditions in the past, oligomerization of larger polytopic monomers has essentially not yet been studied. However, it is vital to study the folding of oligomeric membrane proteins to improve our understanding of the general mechanisms and pathways of TM protein folding. To investigate the folding and stability of the aquaglyceroporin GlpF from Escherichia coli, unfolding of the protein in mixed micelles was monitored by steady-state fluorescence and circular dichroism spectroscopy…
COVID-19, Cation Dysmetabolism, Sialic Acid, CD147, ACE2, Viroporins, Hepcidin and Ferroptosis: A Possible Unifying Hypothesis.
2022
Background: iron and calcium dysmetabolism, with hyperferritinemia, hypoferremia, hypocalcemia and anemia have been documented in the majority of COVID-19 patients at later/worse stages. Furthermore, complementary to ACE2, both sialic acid (SA) molecules and CD147 proved relevant host receptors for SARS-CoV-2 entry, which explains the viral attack to multiple types of cells, including erythrocytes, endothelium and neural tissue. Several authors advocated that cell ferroptosis may be the core and final cell degenerative mechanism. Methods: a literature research was performed in several scientific search engines, such as PubMed Central, Cochrane Library, Chemical Abstract Service. More than 5…
Cyclosporin A resistance of herpes simplex virus-induced "fusion from within" as a phenotypical marker of mutations in the Syn 3 locus of the glycopr…
1994
We here report research in which nine strains of Herpes simplex virus (HSV) with fusing activity were investigated in order to establish precise phenotypical markers of mutations in the carboxy terminus of glycoprotein B (gB). The gene region encoding the carboxy terminus of gB was isolated, then cloned, and finally sequenced. Our investigation showed that seven strains have different mutations in the syn 3 locus. We observed no base difference in the gB gene region encoding the carboxy terminus of gB of two other strains. Strains with a mutation in the carboxy terminus of gB induced fusion from within (FFWI) in the presence of Cyclosporin A (CyA) at a concentration up to 150 µM. There are …
The inhibition of glycerol permeation through aquaglyceroporin-3 induced by mercury(II)
2016
Mercurial compounds are known to inhibit water permeation through aquaporins (AQPs). Although in the last years some hypotheses were proposed, the exact mechanism of inhibition is still an open question and even less is known about the inhibition of the glycerol permeation through aquaglyceroporins. Molecular dynamics (MD) simulations of human aquaporin-3 (AQP3) have been performed up to 200 ns in the presence of Hg2+ ions. For the first time, we have observed the unbiased passage of a glycerol molecule from the extracellular to cytosolic side. Moreover, the presence of Hg2+ ions covalently bound to Cys40 leads to a collapse of the aromatic/arginine selectivity filter (ar/R SF), blocking th…