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At least 163 records · Page 9Linked to original sources
PubMed2000

Effect of phospholipase A2 inhibitors on the release of arachidonic acid and cell viability in cold-stored hepatocytes.

We investigated the effect of phospholipase A(2) (PLA(2)) inhibitors on PLA(2) activity and cell viability in cold-stored rat hepatocytes. The cells were radiolabeled with [(3)H] arachidonic acid (AA) and cold stored in the University of Wisconsin (UW) solution containing various PLA(2) inhibitors. PLA(2) activity was determined by measuring the total free (cellular + supernatant) AA by thin-layer chromatography after inhibiting reacylation of free AA with inhibitors of energy production (carbonyl cyanide m-chlorophenylhydrazone + iodoacetate). Aristolochic acid, chlorpromazine, and quinacrine in the UW solution showed a significant inhibitory effect throughout 48 h cold storage but only at relatively high concentration. PLA(2) activity was also suppressed (58% of control) by trifluoperazine (50 microM), but its effect was limited to only 24 h. In contrast, pretreatment of the cells prior to hypothermic preservation with trifluoperazine (10 to 100 microM) suppressed PLA(2) activity during 48 h storage. Inclusion of calmodulin antagonist W-7 did not affect PLA(2) activity. Thus, the inhibitory activity of these agents appears unrelated to Ca-calmodulin-phospholipid interaction but to have an inhibitory effect on PLA(2) activity. To study the effects of PLA(2) inhibitors on cell viability, lactate dehydrogenase (LDH) release was measured in the presence or absence of inhibitors upon rewarming cold-stored cells in Krebs-Henseleit buffer for 2 h at 37 degrees C. None of the inhibitors tested improved cell viability after 48 h storage. Thus, although PLA(2) inhibitors blocked PLA(2) activity, there was no suppression of LDH release. PLA(2) may play a minor role in preservation/reperfusion injury to cold-stored hepatocytes.

Animals↗
PubMed2000

Comparison of the effects of bile acids on cell viability and DNA synthesis by rat hepatocytes in primary culture.

Bile acid-induced inhibition of DNA synthesis by the regenerating rat liver in the absence of other manifestation of impairment in liver cell viability has been reported. Because in experiments carried out on in vivo models bile acids are rapidly taken up and secreted into bile, it is difficult to establish steady concentrations to which the hepatocytes are exposed. Thus, in this work, a dose-response study was carried out to investigate the in vitro cytotoxic effect of major unconjugated and tauro- (T) or glyco- (G) conjugated bile acids and to compare this as regards their ability to inhibit DNA synthesis. Viability of hepatocytes in primary culture was measured by Neutral red uptake and formazan formation after 6 h exposure of cells to bile acids. The rate of DNA synthesis was determined by radiolabeled thymidine incorporation into DNA. Incubation of hepatocytes with different bile acid species - cholic acid (CA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA), in the range of 10-1000 microM - revealed that toxicity was stronger for the unconjugated forms of CDCA and DCA than for CA and UDCA. Conjugation markedly reduced the effects of bile acids on cell viability. By contrast, the ability to inhibit radiolabeled thymidine incorporation into DNA was only slightly lower for taurodeoxycholic acid (TDCA) and glycodeoxycholic acid (GDCA) than for DCA. When the effect of these bile acids on DNA synthesis and cell viability was compared, a clear dissociation was observed. Radiolabeled thymidine incorporation into DNA was significantly decreased (-50%) at TDCA concentrations at which cell viability was not affected. Lack of a cause-effect relationship between both processes was further supported by the fact that well-known hepatoprotective compounds, such as tauroursodeoxycholic acid (TUDCA) and S-adenosylmethionine (SAMe) failed to prevent the effect of bile acids on DNA synthesis. In summary, our results indicate that bile acid-induced reduction of DNA synthesis does not require previous decreases in hepatocyte viability. This suggests the existence of a high sensitivity to bile acids of cellular mechanisms that may affect the rate of DNA repair and/or proliferation, which is of particular interest regarding the role of bile acids in the etiology of certain types of cancer.

Animals↗
PubMed1996

Overlapping functions for recF and priA in cell viability and UV-inducible SOS expression are distinguished by dnaC809 in Escherichia coli K-12.

The recF and priA genes have roles in DNA repair and homologous recombination. Mutations in these genes also cause decreases in cell viability and alterations in UV-inducible sulAp-lacZ (SOS) expression. To find out if the two genes are in the same or different pathways for viability and SOS expression, the phenotypes of the double mutant strains were studied. The recF priA double mutant showed a lower viability and SOS expression level than either of the single mutants. In the case of cell viability, recF missense mutations decreased viability of a priA2::kan strain two to five-fold whereas recF null priA2::kan double mutants were not viable at all. dnaC809, a mutation that suppresses the UV-sensitive (UVs and Rec- phenotypes of priA2::kan, restored cell viability, but not UV-inducible SOS expression, to a priA recF strain. Since recF is epistatic with recO and recR (recOR) for UV resistance, recOR mutations were also tested with priA2::kan. No overlap was found between recOR and priA for viability and SOS expression. It is concluded that priA and recF have two different overlapping functions in viability and SOS expression that are distinguishable by the effects of dnaC809. The role of recF in a priA2::kan strain in cell viability is a new function for recF and unlike recF's other roles in DNA repair and recombination, is independent of recOR. A new role for priA in UV-inducible SOS expression in a recF mutant is also defined.

Bacterial Proteins↗
PubMed1987

Decreased cell viability of fibroblasts from two patients with a ring chromosome: an in vitro reflection of growth failure?

We found decreased cell viability in fibroblast cultures from two patients, one with ring chromosome 4, the other with ring chromosome 15, who had severe somatic retardation. Cell viability was studied with the trypan blue exclusion assay, and in comparison with matched control cells was found to be 72.0 vs. 93.1%, and 79.8 vs 90.2%, respectively. Cloning efficiency of fibroblasts from the patient with ring chromosome 15 was also decreased (12.3 vs. 25.7%). It is suggested that the decreased cell viability is due to a continuous production of hypomodal cells, a process related to the ring structure per se, and perhaps responsible for the severe somatic retardation frequently observed in patients with a ring chromosome.

Cell Survival↗
PubMed1993

Epidermal growth factor and insulin-like growth factor-1 preserve cell viability in the absence of protein synthesis.

Prolonged exposure of cells to the potent protein synthesis inhibitor cycloheximide (CHX) terminates in cell death. In the present study we investigated the effect of epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), and insulin on cell death induced by CHX in the human cancerous cell lines MDA-231 and MCF-7 (breast), KB (oral epidermoid), HEP-2 (larynx epidermoid), and SW-480 (colon), and correlated this effect to the inhibition rate of protein synthesis. Cell death was evaluated by measuring either dead cells by trypan blue dye exclusion test or by the release of lactic dehydrogenase into the culture medium. CHX was shown to induce cell death in a concentration (1 to 60 micrograms/ml) and time (24 to 72 h)-dependent manner in each of the five cell lines. EGF at physiologic concentrations (2 to 40 ng/ml) reduced cell death close to control level (without CHX) in the cell lines HEP-2, KB, MDA-231, and SW-480, but had almost no effect on cell death in the MCF-7 cells. IGF-1 at physiologic concentrations (2 to 40 ng/ml) reduced cell death nearly to control level in the MCF-7 cells, but had only a partial effect in the other four cell lines. Insulin at supraphysiologic concentration (10,000 ng/ml) mimicked the effect of IGF-1 in each of the cell lines. CHX at concentrations that induced about 60% cell death, inhibited about 90% of protein synthesis as measured by [3H]leucine incorporation. Protein synthesis remained inhibited although cell viability was preserved by EGF or IGF-1. These results indicated that the mechanism by which EGF or IGF-1 preserve cell viability does not require new protein synthesis and may be mediated via a posttranslational modification effect.

Breast Neoplasms↗
PubMed2006

Oxygen gradients correlate with cell density and cell viability in engineered cardiac tissue.

For clinical utility, cardiac grafts should be thick and compact, and contain physiologic density of metabolically active, differentiated cells. This involves the need to control the levels of nutrients, and most critically oxygen, throughout the construct volume. Most culture systems involve diffusional transport within the constructs, a situation associated with gradients of oxygen concentration, cell density, cell viability, and function. The goal of our study was to measure diffusional gradients of oxygen in statically cultured cardiac constructs, and to correlate oxygen gradients to the spatial distributions of cell number and cell viability. Using microelectrodes, we measured oxygen distribution in a disc-shaped constructs (3.6 mm diameter, 1.8 mm thickness) based on neonatal rat cardiomyocytes cultured on collagen scaffolds for 16 days in static dishes. To rationalize experimental data, a mathematical model of oxygen distribution was derived as a function of cell density, viability, and spatial position within the construct. Oxygen concentration and cell viability decreased linearly and the live cell density decreased exponentially with the distance from the construct surface. Physiological density of live cells was present only within the first 128 microm of the construct thickness. Medium flow significantly increased oxygen concentration within the construct, correlating with the improved tissue properties observed for constructs cultured in convectively mixed bioreactors.

Animals↗
PubMed1993

Nitric oxide synthase induction and intestinal epithelial cell viability in rats.

The present study determined the presence of constitutive and inducible nitric oxide (NO) synthase activities in intestinal isolated epithelial cells and the effects of NO induction on intestinal epithelial cell viability. Epithelial cells were isolated from rat proximal small intestine by dispersion using citrate and EDTA. Constitutive NO synthase activity, determined by [14C]arginine conversion to citrulline that was inhibited by in vitro incubation with the arginine analogue NG-monomethyl-L-arginine (L-NMMA; 300 microM) or ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA; 1 mM), was observed in these cells. Administration of Escherichia coli lipopolysaccharide (LPS; 3 mg/kg iv) significantly augmented NO synthase activity (determined 4 h later), which was inhibited in vitro by incubation with L-NMMA but not by EGTA. The highest level of constitutive and inducible NO synthase activity occurred in intestinal villus cells, and the lowest was in crypt cells. Induction of NO synthase activity was associated with a decrease in cellular viability as assessed by a decrease in trypan blue exclusion. Dexamethasone pretreatment (1 mg/kg iv 2 h before LPS administration) significantly reduced both induction of NO synthase activity and the reduction in cellular viability. Likewise concurrent administration of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (10 mg/kg sc) ameliorated the reduction in cell viability induced by LPS administration, an effect abolished by pretreatment with the NO substrate L-arginine (350 mg/kg sc). Whereas constitutively formed NO may have a physiological role in these cells, the results in this study suggest that induction of NO synthase in epithelial cells may represent a mechanism of local intestinal damage.

Amino Acid Oxidoreductases↗
PubMed1995

Purification and characterization of an endothelial cell-viability maintaining factor from fetal bovine serum.

Serum is an essential requirement for the growth and long-term survival of human endothelial cells, even in the presence of such defined elements such as polypeptide growth factors and hormones. A polypeptide from fetal bovine serum was isolated and characterized on the basis of long-term survival of human endothelial cells in serum-free culture. The endothelial cell viability maintaining factor has been purified to homogeneity by a combination of polyethylene glycol precipitation, hydroxylapatite, gel permeation and reverse-phase high performance liquid chromatography. The final purified endothelial cell viability maintaining factor has a molecular weight of 65,000 (reduced) and has been identified as bovine apolipoprotein H by amino-terminal amino acid sequence analysis and Western blot analysis. Endothelial cell viability maintaining factor improved a long-term viability of human endothelial cells at maximal concentrations of 2.5-5 micrograms protein/ml in serum-free medium.

Amino Acid Sequence↗
PubMed1999

Effect of Salmonella typhimurium enterotoxin (S-LT) on lipid peroxidation and cell viability levels of isolated rat enterocytes.

Reactive oxygen species (ROS) are potent mediators of inflammatory disorders and may be of pathophysiological importance in S. typhimurium induced tissue damage. This study was carried out to investigate if ROS play a role in mediating the enterocyte damage during in vitro exposure to Salmonella typhimurium enterotoxin (S-LT). The ROS generation was detected by measuring the changes in the enterocyte arachidonic acid (AA) metabolism (measured indirectly by estimating the level of enterocyte damage in the absence and presence of the cyclooxygenase inhibitor, indomethacin) and xanthine oxidase activity. The enterocyte damage was estimated by measuring the changes in the level of lipid peroxidation and cell viability. The results obtained showed that the exposure of isolated rat enterocytes to S-LT resulted in an increased XO activity; an increased arachidonic acid metabolism, dose and time dependent increase in the level of lipid peroxidation and decreased cell viability. Lipid peroxidation decreased and cell viability increased in the presence of the antioxidant enzymes superoxide dismutase (SOD) or catalase. Thus the in vitro exposure of the enterocytes to S-LT is accompanied by an increased generation of ROS which may induce the lipid peroxidation of the enterocyte membrane thereby leading to a loss of cell viability.

Animals↗
PubMed2003

Bcl-2 prevents loss of cell viability and caspase activation induced by 3-nitropropionic acid in GT1-7 cells.

In this study, we analyzed the effect of Bcl-2 overexpression, an important anti-apoptotic protein, by using two hypothalamic cell lines, GT1-7puro or GT1-7bcl-2. 3-Nitropropionic acid (3-NP) mediated a dose-dependent decrease in cell viability in GT1-7puro cells, as determined by following the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction, which was significantly prevented in GT1-7bcl-2 cells. In addition, activation of caspases-2, -3, and -6 induced by 3-NP was prevented by Bcl-2 overexpression. The data suggest that irreversible inhibition of mitochondrial complex II induces apoptotic features of cell death in a process prevented by Bcl-2.

Apoptosis↗
PubMed2004

Cell size and water permeability as determining factors for cell viability after freezing at different cooling rates.

This work studied the viabilities of five types of cells (two yeast cells, Saccharomyces cerevisiae CBS 1171 and Candida utilis; two bacterial strains, Escherichia coli and Lactobacillus plantarum; and one human leukemia K562 cell) as a function of cooling rate during freezing. The range of investigated cooling rates extended from 5 to 30,000 degrees C/min. Cell viability was classified into three ranges: (i) high viability for low cooling rates (5 to 180 degrees C/min), which allow cell water outflow to occur completely and do not allow any intracellular crystallization; (ii) low viability for rapid cooling rates (180 to 5,000 degrees C/min), which allow the heat flow to prevail over water outflow (in this case, cell water crystallization would occur as water was flowing out of the cell); (iii) high viability for very high cooling rates (>5,000 degrees C/min), which allow the heat flow to be very rapid and induce intracellular crystallization and/or vitrification before any water outflow from the cell. Finally, an assumption relating cell death to the cell water crystallization as water is flowing out of the cell is made. In addition, this general cell behavior is different for each type of cell and seems to be moderated by the cell size, the water permeability properties, and the presence of a cell wall.

Candida↗
PubMed2004

Effect of amyloid peptides on serum withdrawal-induced cell differentiation and cell viability.

Abnormal deposition of amyloid-beta(A beta) peptides and formation of neuritic plaques are recognized as pathological processes in Alzheimer's disease (AD) brain. By using amyloid precursor protein (APP) transfected cells, this study aims to investigate the effect of overproduction of A beta on cell differentiation and cell viability. It was shown that after serum withdrawal, untransfected cell (N2a/Wt) and vector transfected cells (N2a/vector) extended long and branched cell processes, whereas no neurites was induced in wild type APP (N2a/APP695) and Swedish mutant APP (N2a/APPswe) transfected N2a cells. After differentiation by serum withdrawal, the localization of APP/A beta and neurofilament was extended to neurites, whereas those of APP-transfected cells were still restricted within the cell body. Levels of both APP and A beta were significantly higher in N2a/APP695 and N2a/APPswe than in N2a/Wt, as determined by Western blot and Sandwich ELISA, respectively. To further investigate the effect of A beta on the inhibition of cell differentiation, we added exogenously the similar level or about 10-times of the A beta level produced by N2a/APP695 and N2a/APPswe to the culture medium and co-cultured with N2a/Wt for 12 h, and we found that the inhibition of serum withdrawal-induced differentiation observed in N2a/APP695 and N2a/APPswe could not be reproduced by exogenous administration of A beta into N2a/Wt. We also observed that neither endogenous production nor exogenous addition of A beta 1-40 or A beta 1- 42, even to hundreds fold of the physiological concentration, affected obviously the cell viability. These results suggest that the overproduction of A beta could not arrest cell differentiation induced by serum deprivation and that, at least to a certain degree and in a limited time period, is not toxic to cell viability.

Amyloid beta-Peptides↗
PubMed2005

Adenovirus-mediated XIAP gene transfer reverses the negative effects of immunosuppressive drugs on insulin secretion and cell viability of isolated human islets.

Immunosuppressive drugs are routinely used to provide tolerance after whole pancreas and islet cell transplantations. While they are essential in inhibiting graft rejection, little is known about their effect on islet function and beta-cell viability. In this study, we report that tacrolimus, sirolimus, and mycophenolic acid, when added to cultures of freshly isolated human islets, induce a downregulation of the synthesis and secretion of insulin. These functional changes are associated with decreased islet cell viability. All three agents induce a decrease of intracellular levels of Bcl-2 and Bcl-xL, with an increased level of Smac, indicating that they are capable of promoting a downregulation of anti-apoptotic factors and an accumulation of pro-apoptotic mediators. Transduction of islet cells with the anti-apoptotic gene XIAP prevents the negative effects of these drugs on the function and viability of islets. XIAP-infected cells show a higher expression of phospho-CREB (cAMP-responsive element binding protein) and a reduced level of Smac, resulting in a significant reduction of apoptotic cells and a preservation of the glucose-dependent secretion of insulin. In conclusion, the present study demonstrates that genetically modified human islets expressing XIAP are resistant to the negative effects of immunosuppressive drugs on insulin secretion and cell viability.

Adenoviridae↗
PubMed1989

Evidence that graft survival is not related to parenchymal cell viability in rat liver transplantation. The importance of nonparenchymal cells.

Injury to parenchymal and nonparenchymal cells of livers stored in cold Euro-Collins solution was assessed following reperfusion and compared with graft survival following orthotopic rat liver transplantation. Parenchymal cells maintained their viability nearly completely after up to 24 hr of cold storage as assessed by trypan blue exclusion (97% of cells) and LDH release (4% of total) from livers reperfused for 20 min following storage. Furthermore, hepatic glycolysis (rates of lactate plus pyruvate production), oxygen uptake and NADH redox state (lactate:pyruvate ratio) were in the normal range at all time points studied up to 24 hr of cold storage. In contrast, nonparenchymal cells lost viability as assessed from trypan blue staining beginning after 8 hr of storage: 40% were nonviable after 24 hr of storage. Since injury to nonparenchymal cells occurs only upon reperfusion, oxygen radicals may be involved. Accordingly, xanthine and hypoxanthine, substrates for oxygen radical formation, were measured in perfusate upon reperfusion. Both purines accumulated (up to 80 microM) with time of storage and were washed out rapidly (less than 10 min) upon reperfusion. Although parenchymal cell function was in the normal range in livers stored in the cold for 24 hr, liver grafts stored for 6 hr and longer in Euro-Collins solution could not be transplanted successfully. Thus, we conclude that viability of parenchymal cells in liver grafts prior to transplantation is a poor parameter to predict the outcome of transplantation. Therefore, assessment of parenchymal cell energy state (e.g., with 31P NMR and other methods) most likely will not predict survival reliably. On the other hand, nonparenchymal cells lose their viability significantly earlier following storage and reperfusion. These data suggest that preservation of nonparenchymal cell viability is critical for successful liver transplantation.

Animals↗
PubMed2003

A colorimetric assay for determination of cell viability in algal cultures.

In this work, we propose the determination of cell viability in algal cultures by using a colorimetric assay widely used for estimation of cell proliferation in animal cell cultures. The method is based on in vivo reduction by metabolically active cells of a tetrazolium compound (MTS=3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenil)-2H-tetrazolium, inner salt) to a colored formazan, with maximal absorbance at 490 nm, that is released to the culture medium. For this purpose, we have tested two microalgae with high commercial value (Dunaliella and Spirulina) and two seaweeds with different morphology (Ulva and Gracilaria). Color development in this assay is directly proportional to the number of viable cells, to the incubation time in the presence of the assay solution, and to the incubation temperature. A direct significant correlation was found between algal photosynthesis rate and color development in all species used through this work. Moreover, the intensity of absorbance at 490 nm was significantly lower in stressed cells (e.g. in nutrient-limited cultures, in the presence of toxic substances, and in osmotically-stressed cultures). We conclude that cell viability of algal cultures can be rapidly and easily estimated through colorimetric determination of the reduction of MTS to formazan.

Adaptation, Physiological↗
PubMed1999

DNA polymerase epsilon catalytic domains are dispensable for DNA replication, DNA repair, and cell viability.

DNA polymerase epsilon (Pol epsilon) is believed to play an essential catalytic role during eukaryotic DNA replication and is thought to participate in recombination and DNA repair. That Pol epsilon is essential for progression through S phase and for viability in budding and fission yeasts is a central element of support for that view. We show that the amino-terminal portion of budding yeast Pol epsilon (Pol2) containing all known DNA polymerase and exonuclease motifs is dispensable for DNA replication, DNA repair, and viability. However, the carboxy-terminal portion of Pol2 is both necessary and sufficient for viability. Finally, the viability of cells lacking Pol2 catalytic function does not require intact DNA replication or damage checkpoints.

Alleles↗
PubMed2001

Determination of cell viability in single or mixed samples using capillary electrophoresis laser-induced fluorescence microfluidic systems.

The advent of high-efficiency microbial separations will have a profound effect on both chemistry and microbiology. For the first time, it appears that it may be possible to obtain qualitative and quantitative information on microbial systems with the accuracy, precision, speed, and throughput that currently is found for chemical systems. Recently it was suggested that an analytical separations-based approach for determining the viability of cells would be advantageous. The feasibility of such an approach is demonstrated using CE-LIF of two bacteria and yeast. The analytical procedures and figures of merit are outlined. High-throughput analyses and evaluation of microorganisms now appear to be possible.

Bifidobacterium↗