Lysis

About: Lysis is a research topic. Over the lifetime, 6072 publications have been published within this topic receiving 216978 citations.

Interactions Between Sendai Virus and Human Erythrocytes

Abstract: Concentrated Sendai virus, when adsorbed to erythrocytes at 4 C, caused invaginations in the plasma membrane. Following elevation of the temperature to 37 C, the plasma membrane became fused with the viral envelope before dissolution of the virions and rupture of the cells. Cell lysis was accompanied by rapid and total loss of hemoglobin to the extracellular space. Following aqueous pyridine extraction, the hemoglobin-free ghosts remaining were found to be devoid of N-acetylneuraminic acid and to have solubility properties different from those of normal erythrocyte ghosts. By the action of viral neuraminidase, bound N-acetylneuraminic acid was also liberated from purified virus receptor substance whose electrophoretic mobility was thereby substantially reduced. Cu++ selectively inhibited hemolysis and neuraminidase without interfering with hemagglutination and attachment. Neuraminidase appeared to be essential for Sendai virus hemolysis; viral particle size may also be a critical factor in this process.

Kinetics of cell inactivation, toxin release, and degradation during permanganation of Microcystis aeruginosa.

Abstract: Potassium permanganate (KMnO4) preoxidation is capable of enhancing cyanobacteria cell removal. However, the impacts of KMnO4 on cell viability and potential toxin release have not been comprehensively characterized. In this study, the impacts of KMnO4 on Microcystis aeruginosa inactivation and on the release and degradation of intracellular microcystin-LR (MC-LR) and other featured organic matter were investigated. KMnO4 oxidation of M. aeruginosa exhibited some kinetic patterns that were different from standard chemical reactions. Results indicated that cell viability loss and MC-LR release both followed two-segment second-order kinetics with turning points of KMnO4 exposure (ct) at cty and ctr, respectively. KMnO4 primarily reacted with dissolved and cell-bound extracellular organic matter (mucilage) and resulted in a minor loss of cell viability and MC-LR release before the ct value reached cty. Thereafter, KMnO4 approached the inner layer of the cell wall and resulted in a rapid decrease of cell viability. Further increase of ct to ctr led to cell lysis and massive release of intracellular MC-LR. The MC-LR release rate was generally much slower than its degradation rate during permanganation. However, MC-LR continued to be released even after total depletion of KMnO4, which led to a great increase in MC-LR concentration in the treated water.

Acylation of SC4 dodecapeptide increases bactericidal potency against Gram-positive bacteria, including drug-resistant strains.

Abstract: We have conjugated dodecyl and octadecyl fatty acids to the N-terminus of SC4, a potently bactericidal, helix-forming peptide 12-mer (KLFKRHLKWKII), and examined the bactericidal activities of the resultant SC4 'peptide-amphiphile' molecules. SC4 peptide-amphiphiles showed up to a 30-fold increase in bactericidal activity against Gram-positive strains (Staphylococcus aureus, Streptococcus pyogenes and Bacillus anthracis), including S. aureus strains resistant to conventional antibiotics, but little or no increase in bactericidal activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Fatty acid conjugation improved endotoxin (lipopolysaccharide) neutralization by 3- to 6-fold. Although acylation somewhat increased lysis of human erythrocytes, it did not increase lysis of endothelial cells, and the haemolytic effects occurred at concentrations 10- to 100-fold higher than those required for bacterial cell lysis. For insight into the mechanism of action of SC4 peptide-amphiphiles, CD, NMR and fluorescence spectroscopy studies were performed in micelle and liposome models of eukaryotic and bacterial cell membranes. CD indicated that SC4 peptide-amphiphiles had the strongest helical tendencies in liposomes mimicking bacterial membranes, and strong membrane integration of the SC4 peptide-amphiphiles was observed using tryptophan fluorescence spectroscopy under these conditions; results that correlated with the increased bactericidal activities of SC4 peptide-amphiphiles. NMR structural analysis in micelles demonstrated that the two-thirds of the peptide closest to the fatty acid tail exhibited a helical conformation, with the positively-charged side of the amphipathic helix interacting more with the model membrane surface. These results indicate that conjugation of a fatty acid chain to the SC4 peptide enhances membrane interactions, stabilizes helical structure in the membrane-bound state and increases bactericidal potency.

High‐throughput laser‐mediated in situ cell purification with high purity and yield

Abstract: Background Technologies for purification of living cells have significantly advanced basic and applied research in many settings. Nevertheless, certain challenges remain, including the robust and efficient purification (e.g., high purity, yield, and sterility) of adherent and/or fragile cells and small cell samples, efficient cell cloning, and safe purification of biohazardous cells. In addition, existing purification methods are generally open loop and exhibit an inverse relation between cell purity and yield. Methods An automated closed-loop (i.e., employing feedback control) cell purification technology was developed by building upon medical laser applications and laser-based semiconductor manufacturing equipment. Laser-enabled analysis and processing has combined high-throughput in situ cell imaging with laser-mediated cell manipulation via large field-of-view optics and galvanometer steering. Laser parameters were determined for cell purification using three mechanisms (photothermal, photochemical, and photomechanical), followed by demonstration of system performance and utility. Results Photothermal purification required approximately 108 W/cm2 at 523 nm in the presence of Allura Red, resulting in immediate protein coagulation and cell necrosis. Photochemical purification required approximately 109 W/cm2 at 355 nm, resulting in apoptosis induction over 4 to 24 h. Photomechanical purification required more than 1010 W/cm2 independent of wavelength, resulting in immediate cell lysis. Each approach resulted in high efficiency purification (>99%) after a single operation, as demonstrated with eight cell types. An automated closed-loop process to re-image and irradiate remaining targets in situ was implemented, resulting in improved purification (99.5–100%) without decreasing cell yield or affecting sterility in this closed system. Efficient purification was demonstrated with B- and T-cell mixtures over a wide range of contaminating cell percentages (0.1–99%) and cell densities (104-106/cm2). Efficient cloning of 293T cells based on fluorescence with green fluorescent protein after plasmid transfection was also demonstrated. Conclusions In situ laser-mediated purification was achieved with nonadherent and adherent cells on the automated laser-enabled analysis and processing platform. Closed-loop processing routinely enabled greater than 99.5% purity with a greater than 90% cell yield in sample sizes ranging from 101 to 108 cells. Throughput ranged from approximately 103 to 105 total cells/s for contaminating percentages ranging from 99% to 0.1%, respectively. © 2004 Wiley-Liss, Inc.