Cell Viability

The corrosion resistance of AISI 304 stainless steel (AISI 304 SS) and manganese stainless steel (low-nickel SS) brackets in artificial saliva was investigated. The cytotoxic effects of their corrosion products on L929 cell culture were compared by two assays, crystal violet, to evaluate cell viability, and MTT (3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide), for cell metabolism and proliferation. The atomic absorption spectroscopic analysis of the corrosion products demonstrated that nickel and manganese ion concentrations were higher for the AISI 304 SS-bracket immersion solution as compared with the low-nickel SS brackets. Scanning electron microscopy and energy-dispersive spectroscopy demonstrated less corrosion resistance for the AISI 304 SS brackets. Although none of the bracket extracts altered L929 cell viability or morphology, the AISI 304 SS-bracket extracts decreased cellular metabolism slightly. The results indicated that the low-nickel SS presents better i...

We examined the cytotoxic potential of nine N-[2-substituted-2-(2-thienyl) ethyl] piperazinyl quinolone derivatives on human oral epithelial mouth carcinoma (KB) and human squamous carcinoma (A431) cell lines. Phototoxic properties of these compounds were ...

The differentiation and proliferation of neural stem/progenitor cells (NPCs) depend on various in vivo environmental factors or cues, which may include an endogenous electrical field (EF), as observed during nervous system development and repair. In this study, we investigate the morphologic, phenotypic, and mitotic alterations of adult hippocampal NPCs that occur when exposed to two EFs of estimated endogenous strengths. NPCs treated with a 437 mV/mm direct current (DC) EF aligned perpendicularly to the EF vector and had a greater tendency to differentiate into neurons, but not into oligodendrocytes or astrocytes, compared to controls. Furthermore, NPC process growth was promoted perpendicularly and inhibited anodally in the 437 mV/mm DC EF. Yet fewer cells were observed in the DC EF, which in part was due to a decrease in cell viability. The other EF applied was a 46 mV/mm alternating current (AC) EF. However, the 46 mV/mm AC EF showed no major differences in alignment or differentiation, compared to control conditions. For both EF treatments, the percent of mitotic cells during the last 14 h of the experiment were statistically similar to controls. Reported here, to our knowledge, is the first evidence of adult NPC differentiation affected in an EF in vitro. Further investigation and application of EFs on stem cells is warranted to elucidate the utility of EFs to control phenotypic behavior. With progress, the use of EFs may be engineered to control differentiation and target the growth of transplanted cells in a stem cell-based therapy to treat nervous system disorders.

Haem oxygenase-1 (HO1) is a heat-shock protein that is induced by stressful stimuli. Here we demonstrate a cytoprotective role for HO1: cell death produced by serum deprivation, staurosporine or etoposide is markedly accentuated in cells from mice with a targeted deletion of the HO1 gene, and greatly reduced in cells that overexpress HO1. Iron efflux from cells is augmented by HO1 transfection and reduced in HO1-deficient fibroblasts. Iron accumulation in HO1-deficient cells explains their death: iron chelators protect HO1-deficient fibroblasts from cell death. Thus, cytoprotection by HO1 is attributable to its augmentation of iron efflux, reflecting a role for HO1 in modulating intracellular iron levels and regulating cell viability.

This report describes the use of the fluorescent probe, 5(6)-carboxyfluorescein diacetate succinimidyl ester (CFDA-SE), to determine pHi in growing cells of the spoilage yeast Saccharomyces cerevisiae. The technique is based on the pH-dependent intracellular fluorescence of the probe in the cytosol of the cell. The major advantage of this probe over other derivatives is the presence of a succinimidyl group which binds to aliphatic amines in cellular proteins. This allows for the determination of pHi under conditions that either permeabilise the cell membrane, or increase active extrusion, and would otherwise result in loss of the intracellular probe to the external medium. Optimal loading of the probe into cells only occurred after exposure to a mild stress regime of 37°C for 24 h in 100 mM citric/phosphate buffer, pH 4.0. This loading regime was selected because there was no appreciable effect on cell viability or subsequent growth rate in batch culture under optimal conditions. The pHi of yeast cells was measured after incubation in citric/phosphate buffer and gave values comparable to those measured by other techniques in the literature. Also, we were able to detect rapid changes in pHi induced by the addition of a known disruptor of pHi homeostasis in yeast, the weak-acid food preservative, sorbic acid. Finally, successful determination of pHi was made in growing cells of an isogenic parent (PMA1) and a mutant with reduced-expression of the membrane H+-ATPase, pma1-205. As might be expected, the pHi in the mutant strain was reduced compared to the parent. Comparison of growth and pHi in growing cells of either strain revealed no correlation between pHi and exit from lag phase. These results are discussed in relation to previous findings.

Polyclonal stimuli like phorbol myristate acetate (PMA) plus calcium ionophore (Ca-I), concanavalin A (ConA) or anti-CD3 plus anti-CD28 (alphaCD3/alphaCD28) are widely used T cell stimuli. All three stimuli act at different sites and in different ways to activate the T cell receptor pathway and are widely used in different concentrations, stimulation durations and read-out systems. This study was designed to establish the most suitable polyclonal stimulus in human peripheral blood mononuclear cells (PBMC) experiments by assessing the kinetics of cell viability, present immunophenotypes, proliferation, and cytokine production of the PBMC. In addition, changes in these read-out parameters due to cryopreservation have been investigated by comparing fresh and cryopreserved PBMC cultures at days 1, 3, 5, and 7. This study showed a reduction in the cytokine levels after cryopreservation of PMA/Ca-I stimulated PBMC, whereas no significant differences due to the cryopreservation were observed in ConA or alphaCD3/alphaCD28 stimulated PBMC. Cryopreservation did not alter the maximal proliferation capacity of ConA or alphaCD3/alphaCD28 stimulated PBMC, whereas it did delay the proliferation. Although cryopreservation had no effect on the CD3+CD4+ or CD3+CD8+ T cell subsets, PMA/Ca-I significantly reduced the amount of both T cell subsets over time. In conclusion, PMA/Ca-I is suitable as a positive control in experiments where high cytokine production is expected and only fresh PBMC are used. Proliferation and effects on the T cell subsets in long-term PBMC cultures should use ConA or alphaCD3/alphaCD28 as positive control.

Cell viability was improved by supplemental feeding of amino acids and vitamins in batch culture of hybridoma cells. Cells could be maintained over a 10 day period following exponential growth at a constant viable cell concentration of 2.1×106 cells/ml. Concentrations of monoclonal antibody (MAb) reached 140 mg/l, a value of nearly four times that found in typical batch culture. Lactate formation appeared to occur only during active exponential growth and not during the stationary phase.