Lysis

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

Isolation of milligram quantities of nuclear DNA from tomato (Lycopersicon esculentum), A plant containing high levels of polyphenolic compounds

Abstract: We have developed a protocol for isolating milligram quantities of highly purified DNA from tomato nuclei. The protocol utilizes fresh seedlings or leaves without freezing. Tissues are treated with ethyl ether, thoroughly washed, and placed in a buffer containing the nuclear-stabilizing agent 2-methyl-1,4-pentanediol. Nuclei are liberated from tomato cells by homogenization in a Waring blender. The interaction of nuclear DNA with oxidized polyphenols is inhibited by compounds that adsorb polyphenols or prevent oxidation reactions. Chloroplasts and mitochondria are preferentially eliminated with Triton X-100. Nuclei are concentrated using a Percoll gradient and lysed with SDS. DNA is subsequently purified by RNase and protease digestions and phenol/chloroform extractions. The isolated DNA is essentially free of polyphenols and other major contaminants based upon its lack of coloration, A260/A280 ratio, digestibility with restriction enzymes, melting profile, and reassociation properties.

Lytic agents, cell permeability, and monolayer penetrability.

Abstract: Cell lysis induced by lytic agents is the terminal phase of a series of events leading to membrane disorganization and breadkdown with the release of cellular macromolecules. Permeability changes following exposure to lytic systems may range from selective effects on ion fluxes to gross membrane damage and cell leakage. Lysis can be conceived as an interfacial phenomenon, and the action of surface-active agents on erythrocytes has provided a model in which to investigate relationships between hemolysis and chemical structure, ionic charge, surface tension lowering, and ability to penetrate monolayers of membrane lipid components. Evidence suggests that lysis follows the attainment of surface pressures exceeding a "critical collapse" level and could involve membrane cholesterol or phospholipid. Similarities of chemical composition of membranes from various cell types could account for lytic responses observed on interaction with surface-active agents. Cell membranes usually contain about 20–30 % lipid and 50–75 % protein. One or two major phospholipids are present in all cell membranes, but sterols are not detectable in bacterial membranes other than those of the Mycoplasma group. The rigid cell wall in bacteria has an important bearing on their response to treatment with lytic agents. Removal of the wall renders the protoplast membrane sensitive to rapid lysis with surfactants. Isolated membranes of erythrocytes and bacteria are rapidly dissociated by surface-active agents. Products of dissociation of bacterial membranes have uniform behavior in the ultracentrifuge (sedimentation coefficients 2–3S). Dissociation of membrane proteins from lipids and the isolation and characterization of these proteins will provide a basis for investigating the specificity of interaction of lytic agents with biomembranes.

Studies on the mechanism of NK cell lysis.

Abstract: The mechanism of cytolysis by murine NK cells was analyzed using a variety of metabolic inhibitors that have proven informative in studying the lytic mechanism of CTL and the mechanism of histamine release by mast cells. Target cell binding occurred in the absence of calcium and was inhibited by only one of the agents studied, cytochalasin B. Lysis was initiated by addition of Ca2+ ions, as in the case of CTL. Subsequent to target cell binding, but prior to programming for lysis by Ca2+, NK cell lytic activity could be suppressed by inhibitors of chymotrypsin-like, but not trypsin-like proteases, in contrast to CTL. In addition, 3-deaza-SIBA, an inhibitor of transmethylation reactions and quinacrine, an inhibitor of phospholipase A2, appear to act before the Ca2+-dependent programming for lysis. Sr2+ ions blocked the lytic function, as did trifluoperazine (stelazine), the former presumably competing for ionic calcium, the latter known to block binding of Ca2+ to calmodulin. 8Br-cAMP and colchicine blocked later steps required for lysis. With the possible exception of trifluoperazine, all of the agents that blocked NK cell lysis are known to inhibit histamine release from mast cells. These results lend support to the stimulus-secretion model, originally proposed to explain the mechanism of CTL cytolysis, as relevant to the mechanism of lysis by NK cells.