Standardization of human diploid fibroblast cultivation: centrifugation procedure

Physical and chemical methods for enhancing rapid detection of viruses and other agents

Viral replication events can be enhanced by physical, chemical, or heat treatment of cells. The centrifugation of cells can stimulate them to proliferate, reduce their generation times, and activate gene expression. Human endothelial cells can be activated to release cyclo-oxygenase metabolites after rocking for 5 min, and mechanical stress can stimulate endothelial cells to proliferate. Centrifugation of virus-infected cultures can increase cytopathic effects (CPE), enhance the number of infected cells, increase viral yields, and reduce viral detection times and may increase viral isolation rates. The rolling of virus-infected cells also has an effect similar to that of centrifugation. The continuous rolling of virus-infected cultures at < or = 2.0 rpm can enhance enterovirus, rhinovirus, reovirus, rotavirus, paramyxovirus, herpesvirus, and vaccinia virus CPE or yields or both. For some viruses, the continuous rolling of infected cell cultures at 96 rpm (1.9 x g) is superior to rolling at 2.0 rpm for viral replication or CPE production. In addition to centrifugation and rolling, the treatment of cells with chemicals or heat can also enhance viral yields or CPE. For example, the treatment of virus-infected cells with dimethyl sulfoxide can enhance viral transformation, increase plaque numbers and plaque size, increase the number of cells producing antigens, and increase viral yields. The infectivity of fowl plague virus is increased by 80-fold when 4% dimethyl sulfoxide is added to culture medium immediately after infection. The heat shocking of virus-infected cells also has been shown to have a stimulatory effect on the replication events of cytomegalovirus, Epstein-Barr virus, and human immunodeficiency virus. The effects of motion, chemicals, or heat treatments on viral replication are not well understood. These treatments apparently activate cells to make them more permissive to viral infection and viral replication. Perhaps heat shock proteins or stress proteins are a common factor for this enhancement phenomenon. The utility of these treatments alone or in combination with other methods for enhancing viral isolation and replication in a diagnostic setting needs further investigation.

Effects of staphylococcal alpha-, beta-, delta-, and gamma-hemolysins on human diploid fibroblasts and HeLa cells: evaluation of a new quantitative as say for measuring cell damage

Human diploid embryonic lung fibroblasts and HeLa cells were cultivated in Eagle minimaĺ essential medium supplemented with 10% calf serum. Monolayer cultures were labeled with (3)H-uridine and treated with highly purified staphylococcal alpha-, beta-, delta-, or gamma-hemolysin. The release of soluble radioactive substances into the medium was used as an indicator of damage to the cell membrane after treatment with each hemolysin. The assay method described is simple, sensitive, and rapid. It allows quantitative estimation of changes in membrane permeability to be detected before a morphological damage is observed microscopically. Upon incubation for up to 30 min with highly purified staphylococcal hemolysins, only delta-hemolysin caused release of a significant amount of tritiated substances from fibroblasts. Such leakage occurred immediately after addition of delta-lysin and was independent of temperature. With minor exceptions, this was similar to the release of isotopes after treatment of the cells with the nonionic detergent Triton X-100. Treatment of fibroblasts with combinations of two or three of these toxins gave neither a synergistic nor an antagonistic effect. Evidence is presented which indicates that delta-hemolysin is the only important fibroblast damaging activity in crude preparations of extracellular proteins of four strains of S. aureus, whereas HeLa cells are susceptible also to purified alpha-toxin.