SEARCH · PubMed Health

Results for “Formazans”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 919 records · Page 51Linked to original sources

PubMed1987

Time study of macroscopic identification of experimental cerebral infarction in rat.

Cerebral infarctions were induced in rats by injection of Sephadex G-200 into the internal carotid artery. Unfixed slices of brain were stained with nitro blue tetrazolium (nitro-BT). Tissue dehydrogenase in normal regions reacts with this chemical and changes from a pale yellow color to dark blue consequent to formation of formazan. However, the color changes do not develop in infarcted tissue as there is depletion of tissue dehydrogenase in these regions. Ischemic lesions are identifiable by this method in over half the brain 2 to 4 hours after the embolization, but are seen in all brains 6 hours or more following the embolization. The procedure is simple, requires 30 minutes, and is useful for identification of small or acute cerebral infarction.

Animals↗

PubMed1996

Effect of antibacterial antibody on bactericidal activities of superoxide and lysosomal enzyme from alveolar macrophages in rabbits.

Alveolar macrophages (AM) have many Fc receptors for IgG, but are less reactive to lymphokines. They have a well-developed oxidative metabolism and contain large amounts of lysosomal enzyme. This suggests that the antibacterial antibody plays an important role in early resistance by AM to intracellular bacterial infection and that a bactericidal agent, dependent on oxygen and lysosomal enzyme, participates in the effects of the antibacterial antibody on bactericidal activities of superoxide (O2-) and lysosomal enzyme from rabbit AM. The number of Listeria monocytogenes in AM increased after pretreatment with saline or normal IgG but decreased by 60% after pretreatment with anti-Listeria and 120 min incubation. Alveolar macrophage-phagocytized Listeria monocytogenes and Bacille Calmette Guérin (BCG) bound with antibacterial antibody enhanced release of O2-, and nitroblue tetrazolium (NBT) formazan reduced by O2- was observed around the bacteria in the phagosomes of AM. We also confirmed that Listeria and BCG were killed extracellularly by O2-released by a superoxide-generating system in vitro and/or by lysosomal concluded that the antibacterial antibody of the IgG class enhances the antibacterial activity of AM thereby increasing the production of 02- and lysosomal enzyme in the phagosome. This finding may be important in the early resistance to intracellular bacteria infection by AM in the alveolar spaces.

Animals↗

PubMed1993

Decolorization of industrial effluents containing reactive dyes by actinomycetes.

Actinomycete strains have been identified which decolorize effluents containing different types of reactive dyes. Adsorption of anthraquinone, phthalocyanine and azo dyes to the cells of some of the strains resulted in the decolorization of the effluents, but no degradation of the dyes was observed. In contrast, effluents containing an azo-copper complex and a formazan-copper complex dye were almost completely decolorized by several of the strains without adsorption to the cells. The observed changes in the visible spectra indicated a degradation during incubation with the strains.

Actinomycetales↗

PubMed1994

Evaluation of a new cytotoxicity assay for Clostridium perfringens type D epsilon toxin.

A new cytotoxicity assay for determining the activity of epsilon toxin produced by Clostridium perfringens type D has been developed. Viability of cultured cells was determined by the ability of only live cells to convert 5-(3-carboxymethoxyphenyl)-2-(4,5-dimethylthiazolyl)-3-(4- sulfophenyl)tetrazolium to the coloured product formazan in the presence of phenazine methosulfate. Of the 12 cell lines tested, only the MDCK cell line was susceptible to epsilon toxin. Specificity was confirmed by the ability of only specific monoclonal antibodies to inhibit cytotoxicity. Good correlation was obtained with the mouse lethality assay (r = 0.991) and over a wide range of viability (15-75%) as determined by ethidium bromide/acridine orange staining (r = 0.995).

Animals↗

PubMed1981

Histochemical studies of lysosomal enzyme and nitroblue tetrazolium reduction of phagocytes in the cerebrospinal fluid of patients with infectious diseases of the central nervous system.

Lysosomal enzyme levels and nitroblue tetrazolium (NBT) reduction of phagocytes in the cerebrospinal fluid (CSF) of patients with infectious diseases of the central nervous system (CNS) were studied histochemically to evaluate the function of phagocytes. Lysosomal enzymes of acid phosphatase and beta-galactosidase were demonstrated in mononuclear phagocytes and leptomeningeal cells, but not in polymorphonuclear leukocytes (PMN) and lymphocytes. In tuberculous meningitis, more than 60% of the cells were positive for the enzymes as compared with less than 30% for other diseases. Besides, the cells which stained highly for the enzymes were often found in the CSF of tuberculous meningitis. The lysosomal enzyme levels in the cells were dependent on the nature of the infection rather than on the intensity of inflammation when judged by total cell count in the CSF. On the other hand, reduced NBT formazan was found in PMN, mononuclear phagocytes, and leptomeningeal cells. The intensity of NBT reduction by these cells correlated well with the total cell count in CSF; i.e., enhanced NBT reduction by phagocytes reflected the intensity of the inflammation in the subarachnoid space. Thus, histochemical study of phagocytes in CSF can provide useful additional aids to the diagnosis of the nature and stage of CNS infection.

Acid Phosphatase↗

PubMed1996

Biological and clinical significance of in vitro prednisolone resistance in adult acute lymphoblastic leukaemia.

It has been reported that in vitro prednisolone (PDN) resistance provides a prognostic value in childhood acute lymphoblastic leukaemia (ALL). This study aimed at investigating the biological and clinical significance of in vitro PDN resistance in adult ALL. Blast cells from 30 patients were exposed to PDN (0.1 microM-35 microM) and cytotoxicity was determined by the soluble tetrazolium formazan 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino) carbamyl]-2H-tetrazolium hydroxyde (XTT) colorimetric assay. The IC50 (defined as the drug concentration that results in 50% growth inhibition) varied greatly among the samples, from 0.3 microM to > 35 microM; 15 microM was subsequently chosen as IC50-cut-off point between in vitro resistant and sensitive cases. PDN-induced cytotoxicity was significantly related to apoptosis, as demonstrated by regression analysis; in sensitive cases, however, the percentage of apoptotic cells after in vitro PDN treatment was significantly increased compared with control (p = 0.002). Immunofluorescence evaluation of intracellular BCL-2 protein showed an equal percentage of positive cells in the two groups, but in resistant cells a higher mean fluorescence intensity (p = 0.04) was demonstrated. In vitro sensitive and resistant patients did not display differences in clinical characteristics, in cytological, karyotypic and immunophenotypic features and in the outcome of induction therapy. Disease-free survival (DFS), however, was significantly better in sensitive patients (p = 0.02).

Adolescent↗

PubMed1991

Evidence for enhanced secretory function of hepatic macrophages after long-term ethanol feeding in rats.

Rats were pair-fed nutritionally adequate liquid diets, containing ethanol as 36% of energy or an isocaloric amount of carbohydrate for 4-6 weeks. Ruffle formation of hepatic macrophages in the periportal area observed with a transmission electron microscope (which reflects their extent in activation) was more remarkable in ethanol-fed rats than in control rats. The ability of hepatic macrophages to produce superoxide anions assessed in situ by formazan deposition after liver perfusion with nitro-blue tetrazolium and phorbol myristate acetate was enhanced after such ethanol feeding. A similar result was seen 24 h after withdrawal of ethanol feeding. These findings suggest that long-term ethanol consumption may activate hepatic macrophages in secretory function.

Animals↗

PubMed1995

Melatonin protects neurons from singlet oxygen-induced apoptosis.

Singlet oxygen (O2[1 delta g]) is a very reactive molecule that can be produced by living cells and may contribute to cytotoxicity. The pineal hormone melatonin has been reported to possess potent antioxidant activity, and to be capable of scavenging O2(1 delta g). We investigated whether melatonin might reduce the neurotoxic action of O2(1 delta g). The cytotoxic effect of singlet oxygen was studied in primary cultures of cerebellar granule neurons pretreated with a photosensitive dye, rose bengal, and exposed to light--a procedure that generates O2(1 delta g). We found that this procedure triggers neuronal death, which is preceded by mitochondrial impairment (assayed by the rate of the reduction of MTT, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, into formazan), and by DNA fragmentation--a marker of apoptosis. DNA fragmentation was determined in situ by terminal deoxynucleotidyl transferase assay; cell death was assayed with 0.4% trypan blue solution--viable cells with an intact membrane are not permeable to trypan blue; dead cells are, and thus, they are stained blue. Neuroprotection was obtained with the pineal hormone melatonin. In a cell-free system, melatonin also protected the enzyme creatine kinase (EC 2.7.3.2) from the rose bengal-induced injury. The results suggest that melatonin might counteract the cytotoxic action of singlet oxygen. Further studies are needed to clarify the exact role singlet oxygen and melatonin might play in neurodegenerative diseases.

Animals↗

PubMedDate not supplied

Characterization of the anti-cancer activity of transferrin-adriamycin conjugates.

The anthracycline anti-cancer drug adriamycin (Adr) was coupled to human transferrin (Trf) by using a glutaraldehyde technique. The effect of Trf-Adr conjugates and unconjugated Adr on human cells was determined by using normal peripheral blood mononuclear cells and chronic myelogenous K562 cells. Cytotoxicity was determined by using an assay that measures the conversion of a tetrazolium salt (MTT) into a purple product (formazan) by mitochondrial dehydrogenases in viable cells. We found that free Adr at a concentration of 1 x 10(-7) had little effect on K562 cells, while Trf-Adr conjugates inhibited 75% of cellular activity. When normal peripheral blood mononuclear cells were tested against Trf-Adr conjugates, the 50% inhibitory concentration was found to be 1.4-1.7 x 10(-6) M, at which concentration greater than 85% of K562 cells were inhibited. Interactions of Trf-Adr conjugates with plasma membrane energy-producing systems are the proposed mechanisms of cytotoxicity.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1997

Respiratory burst of neutrophils in diabetic patients with periodontal disease.

Periodontal disease, a frequent complication of diabetes mellitus, is the major cause of tooth loss. However, studies on neutrophil function in patients with this condition have yielded contradictory findings. The NADPH oxidase activity of 40 diabetic patients with periodontosis who were on metabolic control was evaluated and compared with that in 40 healthy subjects. Superoxide anion production was measured by a photometric method, with NBT reduction at 490 nm in a microplate reader and by a microscopic method, with a percentage of positive PMNs with granules of formazan in the cytoplasm. When the PMN respiratory burst was activated by phorbol myristate acetate (PMA), a protein kinase C (PKC) soluble activator, superoxide production of diabetics (4.31 +/- 1.67 A x 10(-3)/min) and normal subjects (4.25 +/- 1.25 A x 10(-3)/min) was comparable by photometric method, whereas a significantly defective response to opsonized zymosan was observed when the microscopic method was used (58 +/- 17% in diabetics and 66 +/- 18% in controls; p = 0.05). Therefore in patients with diabetes the impact on PMN function is of multifactorial origin, and is probably correlated to the glucose level and to glycation of PMN protein, such as NADPH oxidase or myeloperoxidase. Alternatively, glucose in PMN may be reduced by aldose reductase to polyols, and this pathway requires NADPH, the coenzyme for the respiratory burst. Moreover, we found that superoxide production in response to opsonized zymosan was reduced in diabetic patients. The activation of protein tyrosine kinase (PTK) is an important mechanism underlying transmembrane signaling and, moreover, protein tyrosine phosphorylations, stimulated by zymosan receptor-mediated activation, might be caused by the activation of specific PTK, whereas activation by PMA is probably mediated through another PKC type.

Chemotaxis, Leukocyte↗

PubMed2001

Cancer preventive effect of Morinda citrifolia (Noni).

Morinda citrifolia (Noni) has been extensively used in folk medicine by Polynesians for over 2,000 years. It has been reported to have broad therapeutic effects, including anticancer activity, in both clinical practice and laboratory animal models. The mechanism for these effects remains unknown. The hypothesis that Morinda citrifolia possesses a cancer preventive effect at the initiation stage of carcinogenesis was studied. Our preliminary data indicated that 10% Tahitian Noni Liquid Dietary Supplement or Tahitian Noni Juice (TNJ), made from Morinda citrifolia fruit by Morinda Inc, in drinking water for one week was able to prevent DMBA-DNA adduct formation. The levels of DMBA-DNA adducts were reduced by 30% in the heart, 41% in the lung, 42% in the liver, and 80% in the kidney of female SD rats. Even more dramatic results were obtained in male C57 BL-6 mice: 10% TNJ was able to reduce DMBA-DNA adduct formation by 60% in the heart, 50% in the lung, 70% in the liver, and 90% in the kidney. In order to explore the mechanism of this preventive effect, the antioxidant activity of TNJ was examined in vitro by lipid hydroperoxide (LPO) and tetrazolium nitroblue (TNB) assays. In the LPO assay, LPO oxidizes leucomethylene blue to methylene blue in the presence of hemoglobin. The resultant blue color was quantified at 660 nm spectrophotometrically. In the TNB assay, superoxide anion radicals (SAR) reduce TNB into formazan blue that was also measured by absorption at 602 nm. TNJ showed a dose-dependent inhibition of both LPO and SAR in our system. The antioxidant activity of TNJ was compared to the effects of vitamin C, grape seed powder (GSP), and pycnogenol (PYC) at the daily dose per serving level recommended by U.S.RDAs or manufacturers. The results suggest that prevention of carcinogen-DNA adduct formation and the antioxidant activity of TNJ may contribute to the cancer preventive effect of Morinda citrifolia.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1992

Spectrophotometric method for the determination of carbidopa using neotetrazolium chloride.

A new high-sensitive spectrophotometric method for the determination of microquantities of carbidopa is described. The method is based on the reduction of neotetrazolium chloride by carbidopa in an alkaline ethanolic medium. The formazan formed exhibits an absorption maximum at lambda = 507 nm, with an apparent molar absorptivity of epsilon = 6.63 x 10(4) M-1 cm-1 and a corresponding Sandell's sensitivity of 3.68 ng cm-2. Beer's law is obeyed over the range of 0.10-6.0 micrograms mL-1 while the optimum concentration range is 0.125-5.0 micrograms mL-1. The regression line equation was calculated as: A = 0.271C + 0.0023 with a correlation coefficient of 1.0000 (n = 28). The accuracy and the precision of the method were considered as very satisfactory. The results obtained from the determination of carbidopa using both the described procedure and the corresponding USP. XXII and BP 1988 clinical methods were statistically compared by means of Student's t-test as well as by the variance ratio F-test, and no significant difference was observed.

Carbidopa↗

PubMed1997

Endothelial-derived superoxide anions in pig coronary arteries: evidence from lucigenin chemiluminescence and histochemical techniques.

1. The generation of superoxide anions (O2-) by intact pig coronary artery rings was measured using a lucigenin-enhanced chemiluminescence technique and a histochemical technique with Nitroblue Tetrazolium (NBT) staining. 2. Isolated arteries with intact endothelium generated O2- at a rate of 9.0 +/- 0.8 pmol min-1 (mg dry weight)-1; this rate was diminished by about 24% when the endothelium was removed. The NBT staining of arterial ring preparations showed formazan precipitation mainly in the intima. Arterial rings were pretreated with diethylthiocarbamate in order to inhibit Cu-Zn superoxide dismutase (SOD) activity which increased the O2- generation by 184 +/- 55% (n = 10; P < 0.01). Stimulation of protein kinase C with phorbol 12-myristate 13-acetate (5 microM) enhanced endothelium-dependent O2- generation by 136 +/- 20% (n = 19; P < 0.01). Neither stimulation with bradykinin or substance P, nor inhibition with NG-nitro-L-arginine methyl ester of endothelial nitric oxide synthase had a significant effect on O2- generation. In contrast, the inhibition of flavoproteins with diphenyliodonium decreased concentration-dependent O2- generation (IC50, 1.85 +/- 5.33 microM). Inhibition of tetrahydrobiopterin synthesis with 2,4-diamino-6-hydroxy-pyrimidine resulted in a reduced generation of O2- by about 55%. 3. The addition of 100 microM NADH and 100 microM NADPH resulted in an excessive generation of O2- at a rate of 0.68 +/- 0.03 and 0.26 +/- 0.01 nmol O2- min-1 (mg protein)-1, respectively, in the membrane fraction, but not in the cytosolic fraction, of homogenates obtained from arteries. 4. The results suggest that intact coronary arteries do generate O2- under basal conditions and that the endothelial layer significantly contributes to this phenomenon. This generation of O2- is greatly influenced by intrinsic SOD activity. It is suggested that basal vascular O2- generation is mainly due to membrane-bound NAD(P)H oxidase activity and/or tetrahydrobiopterin-dependent processes.

Acridines↗

PubMed2006

Biofilm formation by the emerging fungal pathogen Trichosporon asahii: development, architecture, and antifungal resistance.

Trichosporon asahii is the most common cause of fatal disseminated trichosporonosis, frequently associated with indwelling medical devices. Despite the use of antifungal drugs to treat trichosporonosis, infection is often persistent and is associated with high mortality. This drove our interest in evaluating the capability of T. asahii to form a biofilm on biomaterial-representative polystyrene surfaces through the development and optimization of a reproducible T. asahii-associated biofilm model. Time course analyses of viable counts and a formazan salt reduction assay, as well as microscopy studies, revealed that biofilm formation by T. asahii occurred in an organized fashion through four distinct developmental phases: initial adherence of yeast cells (0 to 2 h), germination and microcolony formation (2 to 4 h), filamentation (4 to 6 h), and proliferation and maturation (24 to 72 h). Scanning electron microscopy and confocal scanning laser microscopy revealed that mature T. asahii biofilms (72-h) displayed a complex, heterogeneous three-dimensional structure, consisting of a dense network of metabolically active yeast cells and hyphal elements completely embedded within exopolymeric material. Antifungal susceptibility testing demonstrated a remarkable rise in the MICs of sessile T. asahii cells against clinically used amphotericin B, caspofungin, voriconazole, and fluconazole compared to their planktonic counterparts. In particular, T. asahii biofilms were up to 16,000 times more resistant to voriconazole, the most active agent against planktonic cells (MIC, 0.06 microg/ml). Our results suggest that the ability of T. asahii to form a biofilm may be a major factor in determining persistence of the infection in spite of in vitro susceptibility of clinical isolates.

Antifungal Agents↗

PubMed1979

Rapid antimicrobial susceptibility test using tetrazolium reduction.

A rapid method of antimicrobial susceptibility testing has been developed, which uses a modified microdilution procedure and an inoculum of 10(7) bacteria per ml. Results are determined within 4 h with an indicator consisting of 2(p-iodophenyl)-3(p-nitrophenyl)-5-phenyltetrazolium chloride. The precipitation of a red formazan by bacteria uninhibited by antimicrobials is accelerated by the addition of phenazine methosulfate. Isolates are classified as resistant, indeterminate, or susceptible, based on growth in up to two antimicrobial concentrations which conform closely to concentrations which correlate with the millimeter breakpoints used in the Bauer-Kirby method. Results of testing 10 antimicrobial agents against 1,126 isolates were compared with results obtained when the Bauer-Kirby method and the agar dilution procedure were used as reference methods. Enterococci were excluded because of false resistance. Discrepancies were classified as very major (false susceptibility), major (false resistance), and minor (combinations of susceptibility or resistance with indeterminate results). The rapid method versus the agar dilution method yielded 2.3% very major, 0.7% major, and 2.9% minor discrepancies, for a total of 6.0%. Of 58 organism-antimicrobial agent combinations tested, 23 displayed 1% very major discrepancies between the rapid method and the agar dilution method. Six were not therapeutically important. The remainder involved Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter sp., and most organisms tested with chloramphenicol. It is suggested that adjustments in antibiotic concentrations and/or inoculum size may eliminate these discrepancies. The rapid method appeared economical when compared with Autobac 1 and the Bauer-Kirby procedure.

Evaluation Studies as Topic↗

PubMed2001

Standardized method for in vitro antifungal susceptibility testing of Candida albicans biofilms.

Candida albicans is implicated in many biomaterial-related infections. Typically, these infections are associated with biofilm formation. Cells in biofilms display phenotypic traits that are dramatically different from those of their free-floating planktonic counterparts and are notoriously resistant to antimicrobial agents. Consequently, biofilm-related infections are inherently difficult to treat and to fully eradicate with normal treatment regimens. Here, we report a rapid and highly reproducible microtiter-based colorimetric assay for the susceptibility testing of fungal biofilms, based on the measurement of metabolic activities of the sessile cells by using a formazan salt reduction assay. The assay was used for in vitro antifungal susceptibility testing of several C. albicans strains grown as biofilms against amphotericin B and fluconazole and the increased resistance of C. albicans biofilms against these antifungal agents was demonstrated. Because of its simplicity, compatibility with a widely available 96-well microplate platform, high throughput, and automation potential, we believe this assay represents a promising tool for the standardization of in vitro antifungal susceptibility testing of fungal biofilms.

Amphotericin B↗

PubMed2005

Antiamoebic and toxicity studies of a carbamic acid derivative and its therapeutic effect in a hamster model of hepatic amoebiasis.

Amoebiasis is an important public health problem in developing countries. Entamoeba histolytica, the causative agent of amoebiasis, may develop resistance to nitroimidazoles, a group of drugs considered to be the most effective against this parasitic disease. Therefore, research on new drugs for the treatment of this common infection still constitutes an important therapeutic demand. In the present study we determined the effects of a carbamate derivative, ethyl 4-chlorophenylcarbamate (C4), on trophozoites of E. histolytica strain HM-1:IMSS. C4 was subject to various toxicity tests, including the determination of mutagenicity for bacterial DNA and changes in the enzymatic activities of eukaryotic cells. Genotoxicity studies were performed by the mutagenicity Ames test (plate incorporation and preincubation methods) with Salmonella enterica serovar Typhimurium, with or without metabolic activation produced by the S9 fraction of rat liver. C4 toxicity studies were performed by measuring enzymatic activity in eukaryotic cells by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-formazan test with Fischer 344 rat hepatocytes. C4 did not induce either frame-shift mutations in S. enterica serovar Typhimurium TA97 or TA98 or base pair substitutions in strains TA100 and TA102. The compound was not toxic for cultured rat hepatic cells. Trophozoites treated with 100 microg of C4 per ml were inhibited 97.88% at 48 h of culture; moreover, damage to the amoebae was also confirmed by electron microscopy. The antiamoebic activity of C4 was evaluated by using an in vivo model of amoebic liver abscess in hamsters. Doses of 75 and 100 mg/100 g of body weight reduced the extent of the amoebic liver abscess by 84 and 94%, respectively. These results justify further studies to clearly validate whether C4 is a new suitable antiamoebic drug.

Amebicides↗

PubMed1977

Generalized indicator plate for genetic, metabolic, and taxonomic studies with microorganisms.

We have developed an indicator plate that works well for diverse types of substrates and microorganisms. The plates are inexpensive and easy to prepare. The essential components are agar, buffer, growth-supporting nutrients, a test substrate, and 2,3,5-triphenyl tetrazolium chloride (TTC). Using various strains of Salmonella typhimurium and Escherichia coli, we have studied and defined the contribution of each component to the satisfactory function of the plate. Colonies capable of catabolizing the test substrate reduce TTC and produce a deep red formazan, whereas colonies failing to catabolize the substrate remain uncoloured. Those with intermediate rates of catabolism differ in rate and/or extent of color formation. In all cases the color is stable because TTC reduction is essentially irreversible. Since the mode of action of these plates is fairly well understood, alternative formulations can be devised to meet specific needs. The general applicability of this TTC indicator system makes it an extremely useful tool in microbial genetics, metabolism, and taxonomy.

Acinetobacter↗