12/19/2023 0 Comments Finding blueprints dead cells![]() We envisioned that extracellular changes could coordinate cell wall synthesis and PCD. If deletion mutations in plant cells occur at a significant frequency in spontaneous mutants, their isolation may be feasible without the use of mutagens. ![]() The selection of deletion mutations in plant cells may be desirable for some purposes. A significant proportion of spontaneous mutations that arise in bacteria are stable deletions ( Drake, 1970). Research is in progress in various laboratories to determine effective mutagens for use with cultured plant cells. The percentage of dead cells estimated by staining tobacco cells with Q.05% (w/v) phenosafranine correlated well with the percentage of dead cells determined by adding the percentage of cells with condensed cytoplasm to the percentage of cells that did not undergo plasmolysis (unpublished observations from our laboratory). ![]() Where the plant cells are highly dispersed, the percentage of live ones can be determined more rapidly by microscopic examination of cells that have been treated with a dye such as phenosafranine or fluorescein diacetate ( Widholm, 1972d). This method is particularly appropriate when the cultures contain highly aggregated cells. Another method of determining cell survival is the extrapolation of growth curves of suspension cultures of plant cells back to the time of treatment ( Sung, 1976). Variability in the plating efficiency of plant cells at low densities makes this a rather unreliable method for determining the number of viable cells in a population. Widholm (1972d) noted that the viability of different species of plant cells in vitro dropped considerably when the growth rate decreased in the latter stages of culture.Įstimation of bacterial survival of treatments with mutagens or selective agents is accomplished by counting the number of colonies on agar plates. With a cultured tobacco cell line, the percentage of dead cells in an untreated control population may be from 10 to 28% (unpublished observations from our laboratory). Viability counts are useful in doing reconstruction experiments with putative mutant cell lines. Knowing the number of live cells in a population permits one to determine the mutation frequency in terms of viable cells and to define the percentage of cells surviving a given treatment with mutagens or selective agents. CARLSON, in Physiological Genetics, 1979 D Determination of Viable Cell Number Generally these problems only occur at very high antibody concentrations more reliable cell counts are obtained at lower antibody concentrations when the percentage lysis is still on a plateau.ĭONNA PARKE, PETER S. Also, if a large number of contaminating lymphocytes have been killed by an antiserum, there is a tendency for the mononuclear phagocytes to be found in clumps with dead lymphocytes and it may be difficult to tell if these cells are dead or alive. This can occur for two reasons: The serum can be anticomplementary at high concentrations, or cell lysis can be so extensive that many of the dead cells are blown up and lost leaving a field with few cells, lots of free latex particles, and an artificially low dead cell count. It is not uncommon for high concentrations of alloantisera to give unexpectedly low percentage lysis. 90%) throughout the assay these controls should be counted regularly during cytotoxicity counting, as the percentage dead cells can increase with time. In order for the cytotoxicity data to be meaningful, cell viability in medium alone, C alone, and alloantiserum alone must remain high (approx. Carol Cowing, in Methods for Studying Mononuclear Phagocytes, 1981 E Critical Comments
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