Home About us Contact
|
Home About us Contact | ||
|
|
||
Membrane Disruption (membrane + disruption)
Selected AbstractsSupported Lipid Bilayer on Nanocrystalline Diamond: Dual Optical and Field-Effect Sensor for Membrane DisruptionADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Priscilla Kailian Ang Abstract It is demonstrated that a good biomimetic model lipid membrane with dynamic fluidity can be established on optically transparent nanocrystalline diamond (OTND) with surface roughness below 10,nm. Maigainin II, an antimicrobial peptide, is chosen to investigate the permeation of artificial bacterial membranes constructed on OTND. Due to the unique combination of optical transparency and highly sensitive surface conducting channel, intrinsic OTND affords the possibility of dual-mode sensing based on optical and field effect properties. This opens up new possibilities for making integrated biomolecule,semiconductor microdevices, or sensors where the binding of biomolecules can be tracked using confocal microscopy whilst the associated changes in charge density during membrane perforation can be tracked using the space charge effect in the semiconductor. Such a synergistic approach may provide a powerful methodology for the screening of specific bactericidal activity on biomimetic membrane systems. [source] Cellular effects of monohydrochloride of l -arginine, N, -lauroyl ethylester (LAE) on exposure to Salmonella typhimurium and Staphylococcus aureusJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004E. Rodríguez Abstract Aims:, Here we study the effect of monohydrochloride of l -arginine, N, -lauroyl ethylester (LAE), a cationic preservative derived from lauric acid and arginine, on the cell envelopes of Salmonella typhimurium and Staphylococcus aureus at sub-lethal concentration such as their respective minimal inhibitory concentrations, 32 and 8 ,g ml,1, respectively. Methods and Results:, Bacterial populations were studied by using transmission electron and fluorescence microscopy (TEM and FM), flow cytometry (FC) and ion-flux across the cellular membrane. Cell integrity was altered mainly in the outer membrane of S. typhimurium, but there was no significant change in the cytoplasm. However, in Staph. aureus, clear zones, abnormal septation and mesosome-like structures were observed in the cytoplasm. Bacterial populations were double-stained with propidium iodide (PI) and SYTO-13 for FC analysis. In S. typhimurium the proportion of damaged cells after 24 h was 97% and in Staph. aureus 56·3%. LAE induced transmembrane ion flux, the increase of potassium leakage after 30 min of contact was 7·7 and 3·34 ,g ml,1 for Staph. aureus and S. typhimurium, respectively. Membrane disruption was detected by measuring the proton flow across the membrane. Conclusions:, Disturbance in membrane potential and structural changes was caused by LAE, although cells were not disrupted. Significance and Impact of the Study:, This is the first time the cellular effects of LAE on bacterial cells were studied. [source] Anthracene photoinduced toxicity to plhc-1 cell line (Poeciliopsis lucida) and the role of lipid peroxidation in toxicityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2000Jonghoon Choi Abstract Many polycyclic aromatic hydrocarbons (PAHs) are acutely toxic to fish and other aquatic organisms in the presence of solar ultraviolet radiation (SUVR) of environmentally realistic intensities. In the present study, the photoinduced toxicity of a PAH (anthracene; ANT) to topminnow hepatoma cell line (PLHC-1) was assessed. After the toxicity was characterized, the role of lipid peroxidation in PAH photoinduced toxicity was examined by measuring lipid peroxidation products and by assessing the effect of lipid peroxidation antagonist (Trolox) treatment. In cytotoxicity tests using two assays (MTT, neutral red), the SUVR/ANT treatment elicited toxicity to PLHC-1 cells in a concentration- and SUVR (exposure duration and intensity)-dependent pattern. As found in previous organism-level studies, no significant cytotoxicity was observed in the cells exposed either to fluorescent light/ANT or to SUVR only. The SUVR/ANT treatment elicited the lipid peroxidation process and Trolox pretreatment significantly reduced SUVR/ANT-induced cell mortality. Microscopic observation showed that Trolox pretreatment relieved the SUVR/ANT-inflicted damage, such as cell shrinkage and membrane disruption. Together with a recent finding in our lab that increased production of superoxide anion and a lipid peroxidation product (malondialdehyde) was found in SUVR/ANT-treated fish microsomes, the present study suggests that reactive oxygen radical-induced lipid peroxidation is an important factor in PAH photoinduced toxicity to fish. [source] Hypoxia induces complex I inhibition and ultrastructural damage by increasing mitochondrial nitric oxide in developing CNSEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2008Sebastián Giusti Abstract NO-mediated toxicity contributes to neuronal damage after hypoxia; however, the molecular mechanisms involved are still a matter of controversy. Since mitochondria play a key role in signalling neuronal death, we aimed to determine the role of nitrative stress in hypoxia-induced mitochondrial damage. Therefore, we analysed the biochemical and ultrastructural impairment of these organelles in the optic lobe of chick embryos after in vivo hypoxia,reoxygenation. Also, we studied the NO-dependence of damage and examined modulation of mitochondrial nitric oxide synthase (mtNOS) after the hypoxic event. A transient but substantial increase in mtNOS content and activity was observed at 0,2 h posthypoxia, resulting in accumulation of nitrated mitochondrial proteins measured by immunoblotting. However, no variations in nNOS content were observed in the homogenates, suggesting an increased translocation to mitochondria and not a general de novo synthesis. In parallel with mtNOS kinetics, mitochondria exhibited prolonged inhibition of maximal complex I activity and ultrastructural phenotypes associated with swelling, namely, fading of cristae, intracristal dilations and membrane disruption. Administration of the selective nNOS inhibitor 7-nitroindazole 20 min before hypoxia prevented complex I inhibition and most ultrastructural damage. In conclusion, we show here for the first time that hypoxia induces NO-dependent complex I inhibition and ultrastructural damage by increasing mitochondrial NO in the developing brain. [source] Differential responses to NMDA receptor activation in rat hippocampal interneurons and pyramidal cells may underlie enhanced pyramidal cell vulnerabilityEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005E. Avignone Abstract Hippocampal interneurons are generally more resistant than pyramidal cells to excitotoxic insults. Because NMDA receptors play a crucial role in neurodegeneration, we have compared the response to exogenous NMDA in CA1 pyramidal cells and interneurons of the stratum oriens using combined whole-cell patch-clamp recording and ratiometric Ca2+ imaging. In voltage-clamp, current-clamp or in nominally Mg2+ -free medium, NMDA (10 µm; 3,5 min exposure in the presence of tetrodotoxin) induced a markedly larger inward current and Ca2+ rise in pyramidal cells than in interneurons. Pyramidal cells also showed a more pronounced voltage dependence in their response to NMDA. We hypothesized that this enhanced response to NMDA receptor activation in pyramidal cells could underlie their increased vulnerability to excitotoxicity. Using loss of dye as an indicator of degenerative membrane disruption, interneurons tolerated continuous exposure to a high concentration of NMDA (30 µm) for longer periods than pyramidal cells. This acute neurodegeneration in pyramidal cells was independent of intracellular Ca2+, because high intracellular BAPTA (20 mm) did not prolong survival time. Thus, a plausible explanation for the enhanced sensitivity of pyramidal neurons to excitotoxic insults associated with cerebral ischemia is their greater response to NMDA receptor activation, which may reflect differences in NMDA receptor expression and/or subunit composition. [source] Multifunctional host defense peptides: intracellular-targeting antimicrobial peptidesFEBS JOURNAL, Issue 22 2009Pierre Nicolas There is widespread acceptance that cationic antimicrobial peptides, apart from their membrane-permeabilizing/disrupting properties, also operate through interactions with intracellular targets, or disruption of key cellular processes. Examples of intracellular activity include inhibition of DNA and protein synthesis, inhibition of chaperone-assisted protein folding and enzymatic activity, and inhibition of cytoplasmic membrane septum formation and cell wall synthesis. The purpose of this minireview is to question some widely held views about intracellular-targeting antimicrobial peptides. In particular, I focus on the relative contributions of intracellular targeting and membrane disruption to the overall killing strategy of antimicrobial peptides, as well as on mechanisms whereby some peptides are able to translocate spontaneously across the plasma membrane. Currently, there are no more than three peptides that have been convincingly demonstrated to enter microbial cells without the involvement of stereospecific interactions with a receptor/docking molecule and, once in the cell, to interfere with cellular functions. From the limited data currently available, it seems unlikely that this property, which is isolated in particular peptide families, is also shared by the hundreds of naturally occurring antimicrobial peptides that differ in length, amino acid composition, sequence, hydrophobicity, amphipathicity, and membrane-bound conformation. Microbial cell entry and/or membrane damage associated with membrane phase/transient pore or long-lived transitions could be a feature common to intracellular-targeting antimicrobial peptides and mammalian cell-penetrating peptides that have an overrepresentation of one or two amino acids, i.e. Trp and Pro, His, or Arg. Differences in membrane lipid composition, as well as differential lipid recruitment by peptides, may provide a basis for microbial cell killing on one hand, and mammalian cell passage on the other. [source] Sustained calpain activation associated with lysosomal rupture executes necrosis of the postischemic CA1 neurons in primatesHIPPOCAMPUS, Issue 7 2003Tetsumori Yamashima Abstract Because of the paucity of primate experimental models, the precise molecular mechanism of ischemic neuronal death remains unknown in humans. This study focused on nonhuman primates to determine which cascade necrosis or apoptosis is predominantly involved in the development of delayed (day 5) neuronal death in the hippocampal CA1 sector undergoing 20 min ischemia. We investigated expression, activation, and/or translocation of ,-calpain, lysosome-associated membrane protein-1 (LAMP-1), caspase-3, and caspase-activated DNase (CAD), as well as morphology of the postischemic CA1 neurons and DNA electrophoresis pattern. Immunoblotting showed sustained (immediately after ischemia until day 5) and maximal (day 3) activation of ,-calpain. The immunoreactivity of activated ,-calpain became remarkable as coarse granules at lysosomes on day 2, while it translocated throughout the perikarya on day 3. The immunoreactivity of LAMP-1 also showed a dynamic and concomitant translocation that was maximal on days 2,3, indicating calpain-mediated disruption of the lysosomal membrane after ischemia. In contrast, immunoblotting demonstrated essentially no increase in the activated caspase-3 at any time points after ischemia, despite upregulation of pro-caspase-3. Although expression of CAD was slightly upregulated on day 1 or 2, or both, it was much less compared with lymph node or intestine tissues. Furthermore, light and electron microscopy showed eosinophilic coagulation necrosis and membrane disruption without apoptotic body formation, while DNA electrophoresis did not show a ladder pattern, but rather a smear pattern. Sustained calpain activation and the resultant lysosomal rupture, rather than CAD-mediated apoptosis, may cause ischemic neuronal necrosis in primates. © 2003 Wiley-Liss, Inc. [source] Chrysophanol induces necrosis through the production of ROS and alteration of ATP levels in J5 human liver cancer cellsMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 7 2010Chi-Cheng Lu Abstract Anthraquinone compounds have been shown to induce apoptosis in different cancer cell types. Effects of chrysophanol, an anthraquinone compound, on cancer cell death have not been well studied. The goal of this study was to examine if chrysophanol had cytotoxic effects and if such effects involved apoptosis or necrosis in J5 human liver cancer cells. Chrysophanol induced necrosis in J5 cells in a dose- and time-dependent manner. Non-apoptotic cell death was induced by chrysophanol in J5 cells and was characterized by caspase independence, delayed externalization of phosphatidylserine and plasma membrane disruption. Blockage of apoptotic induction by a general caspase inhibitor (z-VAD-fmk) failed to protect cells against chrysophanol-induced cell death. The levels of reactive oxygen species production and loss of mitochondrial membrane potential (,,m) were also determined to assess the effects of chrysophanol. However, reductions in adenosine triphosphate levels and increases in lactate dehydrogenase activity indicated that chrysophanol stimulated necrotic cell death. In summary, human liver cancer cells treated with chrysophanol exhibited a cellular pattern associated with necrosis and not apoptosis. [source] Force impairment in calpain 3,deficient mice is not correlated with mechanical disruptionMUSCLE AND NERVE, Issue 5 2003Françoise Fougerousse MD Abstract Defects in human calpain 3 are responsible for limb-girdle muscular dystrophy type 2A, an autosomal-recessive disorder characterized mainly by late-onset proximal muscular atrophy. A corresponding murine model has previously been generated by gene targeting. In this report, muscular activity of calpain 3,deficient (capn3,/,) mice was evaluated at different ages. Growth curves showed a progressive global muscular atrophy. Histological examination throughout the lifespan of mice confirmed the dystrophic lesions. Whole animal tests showed only a mild significant impairment of the forelimbs. Studies of the mechanical properties of selected isolated fast- and slow-twitch muscles demonstrated that slow-twitch muscles were significantly weaker in capn3,/, mice than in wild-type mice. Three different tests showed that there was no membrane disruption, suggesting a nonmechanical etiology of capn3,/, mice dystrophy. These findings are consistent with a mechanism involving signaling systems. Muscle Nerve 27: 616,623, 2003 [source] A sodium dodecyl sulfate,polyacrylamide gel electrophoresis,liquid chromatography tandem mass spectrometry analysis of bovine cartilage tissue response to mechanical compression injury and the inflammatory cytokines tumor necrosis factor , and interleukin-1,ARTHRITIS & RHEUMATISM, Issue 2 2008Anna L. Stevens Objective To compare the response of chondrocytes and cartilage matrix to injurious mechanical compression and treatment with interleukin-1, (IL-1,) and tumor necrosis factor , (TNF,), by characterizing proteins lost to the medium from cartilage explant culture. Methods Cartilage explants from young bovine stifle joints were treated with 10 ng/ml of IL-1, or 100 ng/ml of TNF, or were subjected to uniaxial, radially-unconfined injurious compression (50% strain; 100%/second strain rate) and were then cultured for 5 days. Pooled media were subjected to gel-based separation (sodium dodecyl sulfate,polyacrylamide gel electrophoresis) and analysis by liquid chromatography tandem mass spectrometry, and the data were analyzed by Spectrum Mill proteomics software, focusing on protein identification, expression levels, and matrix protein proteolysis. Results More than 250 proteins were detected, including extracellular matrix (ECM) structural proteins, pericellular matrix proteins important in cell,cell interactions, and novel cartilage proteins CD109, platelet-derived growth factor receptor,like, angiopoietin-like 7, and adipocyte enhancer binding protein 1. IL-1, and TNF, caused increased release of chitinase 3,like protein 1 (CHI3L1), CHI3L2, complement factor B, matrix metalloproteinase 3, ECM-1, haptoglobin, serum amyloid A3, and clusterin. Injurious compression caused the release of intracellular proteins, including Grp58, Grp78, ,4-actinin, pyruvate kinase, and vimentin. Injurious compression also caused increased release and evidence of proteolysis of type VI collagen subunits, cartilage oligomeric matrix protein, and fibronectin. Conclusion Overload compression injury caused a loss of cartilage integrity, including matrix damage and cell membrane disruption, which likely occurred through strain-induced mechanical disruption of cells and matrix. IL-1, and TNF, caused the release of proteins associated with an innate immune and stress response by the chondrocytes, which may play a role in host defense against pathogens or may protect cells against stress-induced damage. [source] The MACPF/CDC family of pore-forming toxinsCELLULAR MICROBIOLOGY, Issue 9 2008Carlos J. Rosado Summary Pore-forming toxins (PFTs) are commonly associated with bacterial pathogenesis. In eukaryotes, however, PFTs operate in the immune system or are deployed for attacking prey (e.g. venoms). This review focuses upon two families of globular protein PFTs: the cholesterol-dependent cytolysins (CDCs) and the membrane attack complex/perforin superfamily (MACPF). CDCs are produced by Gram-positive bacteria and lyse or permeabilize host cells or intracellular organelles during infection. In eukaryotes, MACPF proteins have both lytic and non-lytic roles and function in immunity, invasion and development. The structure and molecular mechanism of several CDCs are relatively well characterized. Pore formation involves oligomerization and assembly of soluble monomers into a ring-shaped pre-pore which undergoes conformational change to insert into membranes, forming a large amphipathic transmembrane ,-barrel. In contrast, the structure and mechanism of MACPF proteins has remained obscure. Recent crystallographic studies now reveal that although MACPF and CDCs are extremely divergent at the sequence level, they share a common fold. Together with biochemical studies, these structural data suggest that lytic MACPF proteins use a CDC-like mechanism of membrane disruption, and will help understand the roles these proteins play in immunity and development. [source] Degradation of normal and proliferated peroxisomes in rat hepatocytes: Regulation of peroxisomes quantity in cellsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2003Sadaki Yokota Abstract Degradation and turnover of peroxisomes is reviewed. First, we describe the historical aspects of peroxisome degradation research and the two major concepts for breakdown of peroxisomes, i.e., autophagy and autolysis. Next, the comprehensive knowledge on autophagy of peroxisomes in mammalian and yeast cells is reviewed. It has been shown that proliferated peroxisomes are degraded by selective autophagy, and studies using yeast cells have been especially helpful in shedding light on the molecular mechanisms of this process. The degradation of extraperoxisomal urate oxidase crystalloid is noted. Overexpressed wild-type urate oxidase in cultured cells has been shown to be degraded through an unknown proteolytic pathway distinct from the lysosomal system including autophagy or the ubiquitin-proteasome system. Finally, peroxisome autolysis mediated by 15-lipoxygenase (15-LOX) is described. 15-LOX is integrated into the peroxisome membrane causing focal membrane disruptions. The content of the peroxisomes is then exposed to cytosol proteases and seems to be digested quickly. In conclusion, the number of peroxisomes appears to be regulated by two selective pathways, autophagy, including macro- and microautophagy, and 15-LOX-mediated autolysis. Microsc. Res. Tech. 61:151,160, 2003. © 2003 Wiley-Liss, Inc. [source] | |||||||||||||