An ultrasensitive assay for soluble sulfhydryl and its application to the study of glutathione levels during the HeLa life cycle

A 1H spin echo NMR study of the HeLa tumour cell

Phosphorylcholine, phosphorylcreatine, lactate, glutathione, glycine and leucine were identified in living HeLa cells in the first study of this cell type by 1H spin echo NMR spectroscopy. The technique has the advantage that it is non-invasive, providing detailed structural information on individual species present in the cell matrix. It has been used in this case to study the rate of energy consumption following the activation of the glycolytic pathway with glucose.

Mechanistic aspects on chemical induction of spindle disturbances and abnormal chromosome numbers

Work on the chemical induction of spindle disturbances and abnormal chromosome numbers, and work on the composition and biochemistry of the spindle are reviewed. Some early investigations have shown that there is an unspecific mechanism for chemical induction of spindle disturbances. This mechanism is based on the interaction of compounds with cellular hydrophobic compartments. Some compounds act differently and are more active than predicted from their lipophilic character. Selected compounds of that kind and their possible mechanisms of action are discussed. Changes in sulfhydryl and ATP levels, oxidative damage of membranes and impaired control of cytoplasmic Ca2+ levels are discussed in this context.

Differential sensitivity of metaphase to diamide and ouabain in HeLa cells

We have examined the effects of diamide, an oxidizer of glutathione, on the progress of HeLa cells through the cell cycle. At concentrations which do not significantly alter generation time, anaphase or cytokinesis, diamide causes a two-fold increase in the duration of metaphase. At 3 X 10(-8) M, ouabain also prolongs metaphase without effect on anaphase or cytokinesis, though with a different time course. The data suggest that the metaphase stage of mitosis is particularly sensitive to alterations in both sulfhydryl groups and Na+ levels but that the effects of diamide are probably not primarily due to the oxidation of sulfhydryl groups of the Na+/K+-ATPase.

Correlation between the radiobiological oxygen constant, K, and the non-protein sulphydryl content of mammalian cells

The value of the radiobiological oxygen constant K has been found to depend on the concentration of non-protein sulphydryl (NPSH) within the cell. Cells in the exponential phase of growth have a higher concentration of NPSH and a higher value of K than cells in plateau phase. Binding NPSH with N-ethylmaleimide reduced the value of K and conversely, addition of NPSH as dithioerythritol increased the value of K. K also rises with the same time course as NPSH increases, when plateau phase cells are replated into fresh medium. These results support the hypothesis that free-SH groups within the cell compete with oxygen to react with radiation damaged molecules.

Effects of caffeine and other methylxanthines on the development and metabolism of sea urchin eggs. Involvement of NADP and glutathione

Methylxanthines (MX) inhibit cell division in sea urchin and clam eggs. This inhibitory effect is not mediated via cAMP. MX also inhibit respiration in marine eggs, at concentrations which inhibit cleavage. Studies showed that no changes occurred in ATP and ADP levels in the presence of inhibitory concentrations of MX, indicating an extra-mitochondrial site of action for the drug. Subsequent studies revealed decreased levels of NADP+ and NADPH, when eggs were incubated with inhibitory concentrations of MX, but no change in levels of NAD+ and NADH. MX did not affect the pentose phosphate shunt pathway and did not have any effect on the enzyme NAD+ -kinase. Further studies showed a marked inhibitory effect on the glutathione reductase activity of MX-treated eggs. Reduced glutathione (GSH) could reverse the cleavage inhibitory effect of MX. Moreover, diamide, a thiol-oxidizing agent specific for GSH in living cells, caused inhibition of cell division in sea urchin eggs. Diamide added to eggs containing mitotic apparatus (MA) could prevent cleavage by causing a dissolution of the formed MA. Both MX and diamide inhibit a Ca2+-activated ATPase in whole eggs. The enzyme can be reactivated by sulfhydryl reducing agents added in the assay mixture. In addition, diamide causes an inhibition of microtubule polymerization, reversible with dithioerythritol. All experimental evidence so far suggests that inhibition of mitosis in sea urchin eggs by MX is mediated by perturbations of the in vivo thiol-disulfide status of target systems, with a primary effect on glutathione levels.

Cyclic nucleotides, thioldisulfide status of proteins, and cellular control processes

It is shown that cyclic nucleotides can have a variety of effects on cell division, cell shape, cell adhesion, and cell movement, depending on the cells selected and the conditions under which they are used. For example, while CHO cells elongate under the influence of exogenous dibutyryl CAMP, Y-1 adrenal tumor cells round up and polyoma-transformed 3T3 cells show no change in shape. The totality of experience with cyclic nucleotides suggests that where they have been used by cells as control elements involving the four processes listed above, they are superimposed on basic cellular processes that progress in their absence--that is, they must be acting indirectly. In attempting to understand the inhibitory action of methyl xanthines on egg development, we were forced to abandon the idea that they acted through cyclic nucleotides. We found that methyl xanthines inhibited the activation of glutathione reductase and that glutathione oxidizing agents act as mitotic inhibitors. Further, we found that tubulin polymerizability, NAD-kinase activity, and a mitotic apparatus associated Ca+2-ATP-ase were all inhibited by oxidation of some of their sulfhydryls and were activated by reduction of the resulting disulfides. These results are discussed in terms of reported cycles and activations of glutathione reductase (GR) in cells and reports that mixed disulfides of glutathione and proteins can act as substrates for GR. Using the fact that a CAMP-dependent protein kinase has been reported to be activated by glutathione, we have suggested potential sites where sulfhydryl control processes and cyclic nucleotide control processes and cyclic nucleotide control processes may interact in certain restricted cases.