Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Formazans”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1999

Detection of immobilized proteins on nitrocellulose membranes using a biotinylation-dependent system.

Proteins are biotinylated after immobilization on nitrocellulose sheets by reaction with a biotinyl-succinimide ester. The biotinyl residues are visualized by streptavidin-peroxidase-based detection systems either by deposition of a colored formazan dye or by enhanced chemiluminescence (ECL), the latter being 10-fold more sensitive. The sensitivity of the staining procedure is dramatically improved by the inclusion of the reporter deposit technique into the staining procedure: the initially bound peroxidase generates phenolic radicals from biotinyltyramide, enhancing the number of biotinyl residues in the vicinity of the first biotinylation site. Thus the detection limit is lowered to 1 pg of protein with the ECL detection. The new method is compared with silver stain and immunochemical staining in Western blots and furthermore its suitability is demonstrated for 2-D gel electrophoresis.

Biotin↗
PubMed1997

Generation of active oxygen species from advanced glycation end-products (AGE) under ultraviolet light A (UVA) irradiation.

To clarify a possible role of advanced glycation end-products (AGE) on photoaging of human skin, the interaction between AGE and ultraviolet A light (UVA) was examined from both a biological and chemical perspective. Human dermal fibroblasts that were exposed to UVA in the presence of AGE bound with bovine serum albumin (AGE-BSA) exhibited a significant decrease of cell viability as compared to control cells, which were exposed to UVA in the absence of AGE-BSA. Further, UVA-irradiated AGE-BSA reduced nitroblue tetrazolium to its formazan, but the reaction was inhibited by addition of superoxide dismutase in the system. UVA dose-dependent formation of H2O2 in AGE-BSA was also observed. An ESR spin-trapping study revealed the generation of unstable free radicals in AGE-BSA under UVA irradiation. After addition of Fe2+ in the system, an ESR spectrum due to the formation of hydroxyl radicals was observed. On the basis of these results, the authors propose that AGE is an important factor for promoting photoaging in the skin via generation of active oxygen species involving .O2-, H2O2, and .OH.

Cell Survival↗
PubMed2001

Bcl-2 overexpression protects photooxidative stress-induced apoptosis of photoreceptor cells via NF-kappaB preservation.

We recently showed that photooxidative stress on cultured photoreceptor cells results in down-modulation of NF-kappaB activity which then leads to apoptosis of cultured 661W photoreceptor cells. In an effort to further delineate the mechanism of photoreceptor cell death, we sought to determine the effects of Bcl-2 overexpression on cell survivability. Wild-type 661W cells were transfected with the plasmid construct pSFFV-neo-Bcl-2 and several clones were isolated. All clones demonstrated increased Bcl-2 mRNA and protein levels, with the B4 clone exhibiting the greatest enhancement. On exposure to visible light the B4 cells were protected from undergoing apoptosis when compared with the mock transfected cells, as ascertained by TUNEL apoptosis assay and formazan based estimation of cell viability. The Bcl-2 overexpressing cells also maintained a higher Bcl-2/Bax ratio, suggesting that this ratio is important in protection from photooxidative stress. Electrophoretic mobility shift assays for NF-kappaB demonstrated higher activity in both nuclear and cytosolic fractions of the B4 photoreceptors compared with the 661W wild-type cells at all light exposure time points. Furthermore, the findings of the gel shift assays were further supported by immunocytochemistry for NF-kappaB which revealed that protein levels of the RelA subunit of NF-kappaB were protected in the nucleus as well as in the cytoplasm of Bcl-2 overexpressing B4 cells exposed to light compared to the 661W cells. These results suggest that Bcl-2 overexpression protects NF-kappaB protein levels and activity in the nucleus, indicating that preservation of NF-kappaB binding activity in the nucleus may be essential for photoreceptor cells to survive photooxidative damage induced apoptosis.

Animals↗
PubMed2001

Evaluation of a tetrazolium salt test to determine absence of live mycobacteria in tuberculin purified protein derivative.

Current methodology to determine absence of live mycobacteria in tuberculin purified protein derivative (PPD) takes up to 8 weeks to perform and may also involve testing on animals. In this paper we describe an in vitro test utilising the tetrazolium salt, 2,3-bis-(2-methoxy-4-nitro-5-sulphenyl)-(2H)-tetrazolium-5-carboxanilide (XTT) to monitor the absence of live Mycobacterium tuberculosis (Mtb) in PPD. In the presence of live cells XTT is converted to a coloured formazan product that can be measured spectrophotometrically. Live mycobacteria present in spiked PPD were detected by a marked change in optical density above background levels. This test is easy to perform and is complete in just 48 hr.

Evaluation Studies as Topic↗
PubMed1994

Nitric oxide synthase localization in cultured cerebrovascular endothelium during mitosis.

Nitric oxide synthase (NOS) is present in cultured endothelial cells of cerebrovascular origin in a unique membrane-bound subcellular distribution. The enzyme can be detected by its ability to reduce nitro blue tetrazolium to an insoluble dense blue formazan precipitate. In resting cells, enzyme is located adjacent to the nuclear membrane in a single focus with very faint staining in the cytoplasm. During the various stages of cell division, however, NOS becomes redistributed in a pattern which appears similar to that of the Golgi complex. Enzyme is found concentrated near the spindle during early prophase and metaphase. During anaphase and telophase, NOS appears to also spread into the cytoplasm for redistribution into the daughter cells.

Amino Acid Oxidoreductases↗
PubMed1993

Quantitative reduction of MTT by hearts biopsies in vitro is an index of viability.

The aim of this study is to evaluate the use of tetrazolium reductase (TR) activity as an indicator of myocardial viability in an isolated arrested pig heart biopsy model. Methyl Tetrazolium (MTT) is cleaved by an enzyme in the presence of coenzymes NAD, NADP. Cleavage yields a highly colored formazan product which is DMSO soluble. Efficient bioreduction of MTT has been investigated with heart biopsies. The relationship between MTT reduction and (1) oxygen consumption (r = 0.96, P < 0.001), (2) the sum of the adenine nucleotide levels (r = 0.87, P < 0.001) and (3) localization of coloration, has been established. The use of MTT in colorimetric assays offers high sensitivity. MTT reduction is a valid method. It is rapid and reproducible, and can be used as an indicator of myocardial viability. The MTT test has been used to rapidly compare the effect of different cardioplegic solutions (St Thomas and improved St Thomas) on hypothermic cardiac preservation. Significant differences have been established between the two solutions (P < 0.01).

Adenine Nucleotides↗
PubMed1997

Use of the MTT assay in adult ventricular cardiomyocytes to assess viability: effects of adenosine and potassium on cellular survival.

This study used the colorimetric MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide)] assay to assess cell viability in isolated quiescent adult guinea-pig ventricular myocytes exposed to different insults or cardioprotective conditions, including adenosine and hyperkalemic-cardioplegia. Optical density (OD), reflecting intracellular reduction of MTT into formazan pigment formation, was a function of the number of viable cells (coefficient of linear correlation approximately 0.99), with MTT reduction preferentially carried out by rod-shaped cardiomyocytes (absorbance at 1.009 +/- 0.013 and 0.006 +/- 0.001 OD units for populations containing 50 and 0% of rod-shaped cells). Following prolonged mechanical (pressure of 1 lb/min for 40 min), chemical (10% DMSO or ethanol) or hypoxic injury (N2-saturated solution), the MTT reductase activity reflected reduction in the number of viable cells by 87%, >50%, and 77%, respectively. In cardiomyocytes exposed to a 40 min hypoxia (with CO2), the MTT reductase activity was 0.056 +/- 0.009 in the absence, and 0.074 +/- 0.008 OD units in the presence of adenosine (1 mM), i.e. adenosine reduced the number of non-viable cells. Also, the MTT assay revealed that the effect of potassium-containing solutions (16 and 32 mM K+) on cellular viability may depend on the extent of insult imposed on cardiomyocytes; i.e. a approximately 24% and 49% increase under mild hypoxia (0.03% CO2), or an 18% decrease in cell viability under severe hypoxia (N2) in pre-injured cells. Thus, the MTT assay used to assess viability of isolated adult cardiomyocytes revealed a direct cytoprotective effect of adenosine and hyperkalemic-cardioplegia by promoting cell survival under certain conditions in vitro.

Adenosine↗
PubMed1997

Protection by inhibition of poly (ADP-ribose) synthetase against oxidant injury in cardiac myoblasts In vitro.

Peroxynitrite and hydroxyl radical are reactive oxidants produced during myocardial reperfusion injury. In various cell types, including macrophages and smooth muscle cells, peroxynitrite and hydrogen peroxide cause DNA single strand breakage, which triggers the activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS), resulting in cytotoxicity. Using 3-aminobenzamide and nicotinamide, inhibitors of PARS, we investigated the role of PARS in the pathogenesis of myocardial oxidant injury in H9c2 cardiac myoblasts in vitro. Peroxynitrite (100-1000 microM), hydrogen peroxide (0.3-10 microM) and the NO donor compounds S-nitroso-N-accetyl-DL-penicillamine (SNAP) and diethyltriamine NONOate all caused a dose-dependent reduction of the mitochondrial respiration of the cells, as measured by the mitochondrial-dependent conversion of MTT to formazan. Peroxynitrite and hydrogen peroxide, but not the NO donors caused activation of cellular PARS activity. The suppression of mitochondrial respiration by peroxynitrite and hydrogen peroxide, but not by the NO donors, was ameliorated by pharmacological inhibition of PARS. The protection by the PARS inhibitors diminished at extremely high concentrations of the oxidants. Hypoxia (1 h) followed by reoxygenation (1-24 h) also resulted in a significant activation of PARS, and caused a suppression of mitochondrial respiration, which was prevented by inhibition of PARS. Similar to the results obtained with the pharmacological inhibitors of PARS, a fibroblast cell line which derives from the PARS knockout mouse was protected against the suppression of mitochondrial respiration in response to peroxynitrite and reoxygenation, but not to NO donors, when compared to the result of cells derived from wild-type animals. Based on our data, we suggest that activation of PARS plays a role in the myocardial oxidant injury.

Animals↗
PubMed1995

Quantitating intestinal ischemia with nitroblue tetrazolium salts.

We evaluated a spectrophotometric nitroblue tetrazolium (NBT) reduction assay as a technique to quantitate experimental intestinal ischemic injury. NBT is a tetrazolium salt that is reduced by mitochondrial coenzymes to form a blue formazan dye which can be measured on a spectrophotometer. We used a rat model of progressive intestinal ischemia to compare NBT reduction with standard histologic grading by light microscopy. Isolated segments of small intestine were made ischemic for periods of 15, 30, 60, 90, and 120 min in each of five rats (no reperfusion). A portion of each segment was prepared for both NBT reduction assay and blinded histologic grading. The reproducibility of these results was then tested in a second identical study of four rats (Part 2). When compared to nonischemic segments of intestine, NBT reduction was significantly decreased after 30 min of ischemia (P < 0.05, ANOVA) and continued to decrease as ischemic time increased. These findings were reproduced in the second experimental group. Overall, NBT reduction correlated closely with duration of ischemia (r = 0.81, P < 0.001) and histologic grade (r = 0.77, P < 0.001). Based on criteria developed in Part 1, NBT reduction had a sensitivity of 100% and a specificity of 94% for detecting ischemia > or = 30 min in Part 2. We conclude that the spectrophotometric NBT assay in an accurate technique for quantitating small intestinal ischemic injury which also gives useful information about the functional status of mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed2001

Intralobular heterogeneity of oxidative stress and cell death in ischemia-reperfused rat liver.

The relationship between zonal oxidative stress and cell death after ischemia-reperfusion injury in rat liver was investigated. Oxidative stress was detected in situ by perfusion with nitroblue tetrazolium, which is converted to insoluble blue formazan by reducting agents. Cell death was detected in situ by perfusion with trypan blue. When isolated liver was perfused after 30 or 60 min of warm ischemia, oxidative stress was detected in periportal parenchymal cells after 30 min of reperfusion. It spread in the shape of a doughnut to midzonal cells after 60 min of reperfusion. On the other hand, cell death was observed in parenchymal cells that were within the doughnut-like area in which oxidative stress was detected. The extent of oxidative stress and cell death was higher after 60 min of ischemia than after 30 min of ischemia. In nonparenchymal cells, oxidative stress was observed in midzonal and pericentral regions after only 12 min of reperfusion, but minor cell death was observed only in periportal and midzonal regions after 30 min of reperfusion. Administration of allopurinol, an inhibitor of xanthine oxidase, suppressed oxidative stress and cell death in periportal parenchymal cells. These findings indicate that periportal and midzonal parenchymal cell death can be caused by zone-specific and xanthine-oxidase-mediated oxidative stress in parenchymal cells.

Allopurinol↗
PubMed1994

Activated THP-1 cells depress mitochondrial respiration in Hep G2 cells infected with influenza B virus.

Influenza B virus has been aetiologically linked to Reye Syndrome (RS), but the mechanism(s) by which this pathogen could disrupt liver metabolism and produce the hepatic mitochondrial injury characteristic of the syndrome are unknown. In this study, two mechanisms by which infection of hepatocytes with influenza B virus could disrupt cellular metabolism were investigated. (1) virus-induced increase in pro-oxidant iron with subsequent iron-induced lipid peroxidation (LP) and (2) increased membrane permeability. Hep G2 cells, a well-differentiated continuous human liver cell line derived from a hepatoblastoma, were infected with allantoic-fluid derived influenza B Lee/40 virus (AFDV) at a multiplicity of infection of 10 for 24 h; productive infection was confirmed by both haemagglutination of chick erythrocytes and by plaque assay. Infection of Hep G2 cells preloaded with 59Fe-transferrin resulted in increased release of 59Fe (153 +/- 17% of controls, P < 0.03). However, the iron released did not result in increased LP (assessed by thiobarituric acid reactive substances; TBARS). To confirm that this lack of of increase in TBARS was not due to insensitivity of the cell line to pro-oxidant iron, cells were exposed to 15 microM iron ascorbate for 60 min. Production of TBARS was increased (122 +/- 4% of controls, P < 0.0003). Release of 51Cr from infected cells was also increased (128 +/- 12% of controls, P < 0.05); thus the infected cells exhibited a generalized increase in membrane permeability. However, infection did not depress mitochondrial respiration (as assessed by the formation of MTT-f3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide-formazan. To determine if the combination of viral infection and soluble products of activated macrophages would affect mitochondrial respiration, infected hepatocytes were exposed to the supernatant fluid from THP-1 cells which had previously been incubated with lipopolysaccharide at 100 ng ml-1 for 18 h. This supernate did depress the formation of MTT-f (81 +/- 5% of controls, P < 0.03). We conclude that influenza B virus does productively infect Hep G2 cells, and does increase hepatocyte membrane permeability. This effect does not impair mitochondrial respiration directly. However, infection does act in concert with soluble products of activated macrophages to depress hepatic mitochondrial respiration. Whether this interaction can be explained by virus-induced permeability changes and/or other effects of infection deserves further investigation.

Animals↗
PubMed1999

Use of PNA oligonucleotides for the in situ detection of Escherichia coli in water.

A species-specific Peptide Nucleic Acid (PNA) oligonucleotide probe directed against the V(1)region of the 16S rRNA molecule was synthesized for the detection of Escherichia coli in water. The specificity of the probe was tested in dot blot hybridizations against a number of environmental isolates including those from the genera Escherichia, Klebsiella, Enterobacter and Citrobacter. In situ hybridization experiments were performed with biotinylated PNA oligonucleotide probes with subsequent detection of the biotin label using a combination of Streptavidin-Horseradish Peroxidase and a tyramide signal amplification system. The results obtained enabled the specific detection of E. coli in under 3 h. Hybridizations were also performed on cells which were treated with chlorine (1.5 mg l(-1)) for up to 30 min. Escherichia coli cells were still detected after storage for 14 days at room temperature. No cells were detected by conventional plate count or the < > assay, a method currently used for the routine detection of E. coli and coliforms in the water industry. Cell viability was assessed by the ability of cells to reduce 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) to highly fluorescent formazan crystals through bacterial respiration. Only cells that had not been chlorinated were detected. These results confirm that ribosomal RNA exists within the cell long after cell death has occurred and that rRNA cannot be used to assess the viability of individual cells. However rRNA probes in combination with viability markers should enable the specific detection of viable cells in situ. Hybridization experiments were also performed successfully on seeded tap water samples. The number of fluorescent cells detected correlated well with those obtained by plate count analysis. This represents the first reported use of PNA oligonucleotides for in situ detection of micro-organisms and offers a fast efficient alternative to conventional DNA approaches.

Chlorine↗
PubMed1993

Cytotoxic effect of peptidoglycan from Treponema denticola.

Peptidoglycan isolated from pathogenic bacteria has been previously found to exhibit various biological activities. The aim of this investigation was to evaluate the toxicity of Treponema denticola peptidoglycan towards epithelial cells. The cytotoxicity of a lipopolysaccharide-like material was also determined. Epithelial cells were incubated with the test substances and cell viability was assayed by measuring lactate dehydrogenase activity and the conversion of tetrazolium salt into blue formazan. Morphological changes in the epithelial cells were monitored by scanning and transmission electron microscopy. While lipopolysaccharide-like material exerted negligible toxic effects on the epithelial cells, peptidoglycan was highly toxic. This cytotoxicity was both time- and concentration-dependent and was higher in the presence of serum. The epithelial cells appeared to be unable to recover following a short period of incubation with peptidoglycan. The study demonstrated that peptidoglycan from T. denticola is a potent toxic factor for epithelial cells. This represents a potential new virulence factor for this suspected periodontopathogen.

Animals↗
PubMed1996

Cytotoxicity and membrane damage in vitro by inclusion complexes between gamma-cyclodextrin and siloxanes.

Inclusion complexes of gamma-cyclodextrin and octamethylcyclotetrasiloxane (D4), decamethyltetrasiloxane (M10TS), and 1,3,5,7-tetramethyltetravinylcyclotetra - siloxane (TMTV-D4) were prepared to compare the cytotoxic effects of siloxanes in vitro. In these preparations, the hydrophobic siloxanes are surrounded by a hydrophilic shell of eight circularly linked D-glucose molecules (gamma-cyclodextrin), and upon contact with plasma membranes the siloxane molecule can intercalate into the lipid bilayer of the cell membrane. XRPC24, 2-11 plasmacytoma, CH12.LX lymphoma and P388D1 macrophage-like cells were used as indicator cells in toxicity assays. Using an MTT tetrazolium reduction to formazan test, a colorimetric method to determine the number of viable cells, the 50% minimal lethal doses (CD50) for the siloxane compounds were found to range from 30 to 50 microM. Sublethal doses (e.g., 15 microM and lower) resulted in the loss of lactate dehydrogenase (LDH) and glutathione (GSH) from the cytosolic compartment of the target cells and thus indicated cytotoxicity. Treatment of macrophages with siloxanes resulted in a higher production of interleukin-6 (IL-6) than was exhibited by untreated macrophages. The B9 cell bioassay of these treated cells showed as much as a 10 fold higher production (500 U/ml) of IL-6 than did the untreated cells. The degree of increase was dependent on the compound and concentration used. The results of this study show that low molecular weight siloxanes produce lethal effects on B-lymphocyte derived target cells in vitro and permeabilize the plasma membranes at lower sublethal concentrations.

Animals↗
PubMed1997

Hypoxia modulates free radical formation in brain microvascular endothelium.

Although free radical species (ROS; i.e., .O2-. .OH.H2O2) among other mediators, may be involved in altering the blood-brain barrier (BBB), little is known about the endogenous ability of cerebromicrovascular endothelium to generate ROS. This study examines the capacity of rat endothelial cells (RBEC) to produce ROS in normoxia and hypoxia/reoxygenation. Cultured RBEC were exposed to an oxygen-depleted atmosphere (containing 95% N2 and 5% CO2) for 4 hr at 37 degrees C and air (10 min) at room temperature to simulate "ischemia/reperfusion". Nitroblue tetrazolium (NBT) reduction [formation of nitroblue formazan (NBF)] served as a marker for the production of ROS. The release of lactate dehydrogenase (LDH) and [3H]arachidonic acid (AA) was used to assess cellular integrity. RBEC exposed to hypoxia/reoxygenation produced up to 59% greater NBF formation than controls without affecting the LDH or AA release. The production of ROS was calcium-dependent and not affected by AA or its metabolites. The findings indicate that the RBEC can produce superoxide dismutase (SOD)-inhibitable ROS which are augmented by hypoxia/reoxygenation. It is suggested that in vivo cerebromicrovascular endothelium may contribute to the formation of ROS and play a role in ischemic brain edema.

Animals↗
PubMed1996

Glycine does not reverse the inhibitory actions of ethanol on NMDA receptor functions in cerebellar granule cells.

The effects of ethanol and/or glycine on NMDA-induced enhancement of cytoplasmic free Ca2+ concentrations ([Ca2+]i), 45Ca2+ influx, 4-b-[3H]phorbol-12,13-dibutyrate ([3H]PDBu) binding, and neuronal necrosis in cultured rat cortical and cerebellar granule neurons were examined. Using microfluorimetric techniques in combination with rapid perfusion of single brain neurons, we found that glycine (10 microM) was a necessary co-agonist for NMDA-induced depolarization in cerebellar granule cells. In contrast, depolarization with NMDA in cortical cells was observed even without the addition of exogenous glycine as well as in the absence or presence of 1 mM MgCl2. Ethanol (50 mM) inhibited the effects of NMDA in some, but not all, neurons indicative of the existence of ethanol-sensitive and ethanol-insensitive cortical and cerebellar granule neurons. In studies performed in monolayers of cortical and cerebellar granule cells, we observed that the presence of glycine (10 microM) was a necessary prerequisite to unmask inhibitory actions of ethanol on 45Ca2+ influx induced by NMDA. In another set of experiments, we noted that NMDA-induced stimulation of [3H]PDBu binding to monolayers of intact cerebellar granule cells was inhibited by ethanol (50 mM). Finally, we report that ethanol caused a concentration-dependent inhibition of NMDA-induced necrotic cell death, assessed by measuring the ability of cerebellar granule cells to transform 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) into formazan. In none of the four assays used to demonstrate the inhibitory effects of ethanol on NMDA receptor activity, the ethanol-induced inhibition was reversed by glycine (up to 100 microM). Thus, in contrast to earlier reports, our data suggest that ethanol and glycine produce their effects by acting at different regulatory sites within the NMDA receptor system in brain neurons.

Animals↗
PubMed1996

Localization of nitrergic neuronal and non-neuronal cells in the ultimobranchial glands of the chicken.

The ultimobranchial glands of 20 chickens, aged 2-3 months, were investigated for their nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH-d) reactivity and the distribution of nitric oxide synthase (NOS), using NADPH-d histochemistry and NOS immunocytochemistry respectively. Formazan, the blue reaction product of NADPH-d, was localised in the neuronal cell bodies and nerve fibres. Most of the cell bodies were found in the parenchyma. Some of them occurred in the wall of the ultimobranchial cysts, and a few in the immediate vicinity of the blood vessels. Labelled nerve fibres mostly travelled with blood vessels, while few of them appeared in the cystic lining. In addition to neuronal profiles, some C cells, cystic lining, and vascular endothelium were also labelled. NOS staining was found in neuron-like cells and fibres that were confirmed as neurons in adjacent sections stained with antibodies against neuron-specific enolase. It was also detected in cystic lining and in some C cells, but not in vascular endothelium. The distribution patterns of NADPH-d and NOS suggest that NO may play a role in the regulation of the secretory activity of and the blood flow through the ultimobranchial glands.

Animals↗
PubMed1986

Rapid chemosensitivity testing of human lung tumor cells using the MTT assay.

Numerous procedures have been described which test the chemosensitivity of tumor cell lines. A major disadvantage of most of these assays is that practical limitations prevent the testing of more than a few variables. We have adapted a rapid and efficient colorimetric assay for testing the chemosensitivity of human lung tumor cells. In this assay, a tetrazolium salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide, MTT) is converted to a colored formazan product by enzymes active only in living cells. The MTT assay may be carried out entirely in 96-well microtiter plates, so that large experiments examining a number of variables can be readily performed. Thus, drug concentration, time of exposure to drug, length of assay, and cell density can be varied and tested. Moreover, the simplicity of this assay allows simultaneous testing of multiple drugs on multiple cell lines. Finally, the MTT assay is useful for monitoring the development of multidrug-resistant cells in culture.

Antineoplastic Agents↗