Modulation of host cell membrane fluidity: a novel mechanism for preventing bacterial adhesion. (1/106)

Adhesion of bacterial enteropathogens to host mucosal surfaces is a critical primary step in the pathogenesis of diarrheal disease. We investigated the effects of altering the physical properties of eukaryotic cells on bacterial adhesion with the use of a series of three structurally dissimilar membrane fluidizers and several Escherichia coli as test strains. Lipid fluidity of the cell plasma membrane was measured by steady-state fluorescence anisotropy employing the probe 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3, 5-hexatriene. There was a dose-dependent and reversible inhibition of bacterial adhesion with increasing membrane fluidity. Time course experiments indicated that increasing membrane fluidity during the early stages of bacterial adhesion was essential for inhibition of attachment. None of the fluidizers affected the viability of either eukaryotic or prokaryotic cells. These findings demonstrate, for the first time, that changes in plasma membrane physical properties of epithelial cells can prevent microbial adhesion. This also suggests that altering the membrane properties of host cells could form a basis for novel strategies to prevent bacterial adhesion during infection in vivo.  (+info)

Protective effect of FR168888, a new Na+/H+ exchange inhibitor, on ischemia and reperfusion-induced arrhythmia and myocardial infarction in rats: in comparison with other cardioprotective compounds. (2/106)

We have studied the effects of FR168888 (5-hydroxymethyl-3-(pyrrol-1-yl)benzoylguanidine methanesulfonate), a new Na+/H+ exchange inhibitor, on ischemia and reperfusion-induced arrhythmia and myocardial infarction in anesthetized rats and compared them with those of other cardioprotective compounds. FR168888 had a potent inhibitory effect on Na+/H+ exchange of rat lymphocytes acidified with Na+-propionate with a Ki value of 6.4 nM. Pretreatment with FR168888 (0.032-0.32 mg/kg, i.v.) reduced or completely abolished the ventricular fibrillation (VF) induced by reperfusion after 5 min of regional ischemia, while lidocaine, a class I antiarrhythmic agent, showed less effect against VF as compared with FR168888. The size of myocardial infarction induced by 60-min ischemia and 60-min reperfusion was attenuated by FR168888 dose-dependently (1.0-10 mg/kg, i.v.), and ventricular tachycardia and VF were significantly reduced during the ischemic period. In contrast, propranolol and diltiazem did not show such protective effects on myocardial infarct size. In addition, FR168888 did not change hemodynamic parameters in rats. These results indicate that FR168888 has a strong inhibitory effect on Na+/H+ exchange and that treatment with FR168888 can protect the heart from arrhythmia and myocardial cell death in ischemic and reperfused situations.  (+info)

Cold shock in Bacillus subtilis: different effects of benzyl alcohol and ethanol on the membrane organisation and cell adaptation. (3/106)

A temperature shift-down of Bacillus subtilis from 40 to 20 degrees C induces an 80 min growth lag. Benzyl alcohol reduced this period to 51 min, whereas ethanol prolonged it up to 102 min. The effect of the two alcohols on the membrane state was investigated by measuring the steady-state fluorescence anisotropy and analysing the lifetime distribution of diphenylhexatriene (DPH) and its polar derivative, TMA-DPH. As followed from the fluorescence anisotropy, the two alcohols exerted similar (fluidizing) effects on the cytoplasmic membranes of B. subtilis. However, benzyl alcohol significantly shortened the main DPH lifetime component and widened its distribution, while ethanol had no effect. The benzyl alcohol activity was interpreted in terms of an increased membrane hydration due to disordering of the membrane structure. Such an effect imitates the cold shock induced synthesis of unsaturated fatty acids in B. subtilis. The fatty acid analysis revealed that ethanol hindered this adaptive synthesis of fatty acids. At the same time, its effect on the membrane state (membrane order) was very low and could not substitute the physiological response as was the case with benzyl alcohol. It can thus be concluded that the adaptation of the membrane physical state contributes significantly to the cold shock response of B. subtilis.  (+info)

Cloning and expression of ntnD, encoding a novel NAD(P)(+)-independent 4-nitrobenzyl alcohol dehydrogenase from Pseudomonas sp. Strain TW3. (4/106)

Pseudomonas sp. strain TW3 is able to metabolize 4-nitrotoluene to 4-nitrobenzoate and toluene to benzoate aerobically via a route analogous to the upper pathway of the TOL plasmids. We report the cloning and characterization of a benzyl alcohol dehydrogenase gene (ntnD) which encodes the enzyme for the catabolism of 4-nitrobenzyl alcohol and benzyl alcohol to 4-nitrobenzaldehyde and benzaldehyde, respectively. The gene is located downstream of the previously reported ntn gene cluster. NtnD bears no similarity to the analogous TOL plasmid XylB (benzyl alcohol dehydrogenase) protein either in its biochemistry, being NAD(P)(+) independent and requiring assay via dye-linked electron transfer, or in its deduced amino acid sequence. It does, however, have significant similarity in its amino acid sequence to other NAD(P)(+)-independent alcohol dehydrogenases and contains signature patterns characteristic of type III flavin adenine dinucleotide-dependent alcohol oxidases. Reverse transcription-PCR demonstrated that ntnD is transcribed during growth on 4-nitrotoluene, although apparently not as part of the same transcript as the other ntn genes. The substrate specificity of the enzyme expressed from the cloned and overexpressed gene was similar to the activity expressed from strain TW3 grown on 4-nitrotoluene, providing evidence that ntnD is the previously unidentified gene in the pathway of 4-nitrotoluene catabolism. Examination of the 14.8-kb region around the ntn genes suggests that one or more recombination events have been involved in the formation of their current organization.  (+info)

Voltage-dependent blockade of normal and mutant muscle sodium channels by benzylalcohol. (5/106)

1. We studied the effects of benzylalcohol on heterologously expressed wild type (WT), paramyotonia congenita (R1448H) and hyperkalaemic periodic paralysis (M1360V) mutant alpha-subunits of human skeletal muscle sodium channels. 2. Benzylalcohol blocked rested channels at -150 mV membrane potential, with an ECR(50) of 5.3 mM in wild type, 5.1 mM in R1448H, and 6.2 mM in M1360V. When blockade was assessed at -100 mV, the ECR(50) was reduced in R1448H (2 mM) compared with both wild type (4.3 mM; P<0.01) and M1360V (4.3 mM). 3. Membrane depolarization before the test depolarization significantly promoted benzylalcohol-induced sodium channel blockade. The values of K(D) for the fast-inactivated state derived from benzylalcohol-induced shifts in steady-state availability curves were 0.66 mM in wild type and 0.58 mM in R1448H. In the presence of slow inactivation induced by 2.5 s depolarizing prepulses, the ECI(50) for benzylalcohol-induced current inhibition was 0.59 mM in wild type and 0.53 mM in R1448H. 4. Recovery from fast inactivation was prolonged in the presence of drug in all clones. 5. Benzylalcohol induced significant frequency-dependent block at stimulating frequencies of 10, 50, and 100 Hz in all clones. 6. Our results clearly show that benzylalcohol is an effective blocker of muscle sodium channels in conditions that are associated with membrane depolarization. Mutants that enter voltage-dependent inactivation at more hyperpolarized membrane potentials compared with wild type are more sensitive to inhibitory effects at the normal resting potential.  (+info)

Functional analysis of an olfactory receptor in Drosophila melanogaster. (6/106)

Fifty nine candidate olfactory receptor (Or) genes have recently been identified in Drosophila melanogaster, one of which is Or43a. In wild-type flies, Or43a is expressed at the distal edge of the third antennal segment in about 15 Or neurons. To identify ligands for the receptor we used the Gal4/UAS system to misexpress Or43a in the third antennal segment. Or43a mRNA expression in the antenna of transformed and wild-type flies was visualized by in situ hybridization with a digoxigenin-labeled probe. Electroantennogram recordings from transformed and wild-type flies were used to identify cyclohexanol, cyclohexanone, benzaldehyde, and benzyl alcohol as ligands for the Or43a. This in vivo analysis reveals functional properties of one member of the recently isolated Or family in Drosophila and will provide further insight into our understanding of olfactory coding.  (+info)

Rate sensitivity of shear-induced changes in the lateral diffusion of endothelial cell membrane lipids: a role for membrane perturbation in shear-induced MAPK activation. (7/106)

Vascular endothelium transduces the temporal gradients in shear stress (tau) originating from unsteady blood flow into functional responses. We measured the effects of step-tau and ramp-tau (i.e., t with different temporal shear gradients) on the lipid lateral diffusion coefficient (D) in the apical membranes of confluent cultured bovine aortic endothelial cells by using fluorescence recovery after photobleaching. A step-tau of 10 dynes/cm2 elicited a rapid (5 s) increase of D in the portion of the cell upstream of the nucleus and a concomitant decrease in the downstream portion. A ramp-tau with a rate of 20 dynes/cm2 per min elicited a rapid (5 s) decrease of D in both the upstream and the downstream portions. The mitogen-activated protein kinases (MAPKs) ERK and JNK were activated by step-tau but not by ramping to the same tau level. Benzyl alcohol, which increases D, enhanced the activities of both MAPKs; cholesterol, which reduces D, diminished these activities. We conclude that the lipid bilayer can sense the temporal features of the applied tau with spatial discrimination and that the tau-induced membrane perturbations can be transduced into MAPK activation. These results have implications for understanding the role of t in modulating vascular functions in health and disease.  (+info)

Ten-nanosecond molecular dynamics simulation of the motions of the horse liver alcohol dehydrogenase.PhCH2O- complex. (8/106)

Molecular dynamics simulations have been carried out for a period of 10 ns with the dimeric enzyme horse liver alcohol dehydrogenase (HLADH) present as the reactive complex HLADH.NAD+. PhCH2O-. Cross-correlation analysis of the trajectory was carried out with the latter from 500 ps to 10 ns. The resulting cross-correlation map allowed the identification of the correlated and anticorrelated motions, which involve the entire protein. Anticorrelated and correlated motions are carried into the active site-aligned residues.  (+info)

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10