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PubMed1981

A scanning electron microscopic study of the two-step effect of cytochalasin B on Ehrlich ascites tumor cells.

The effect of cytochalasin B (CB) on the surface structure of Ehrlich ascites tumor cells was investigated using the scanning electron microscope. The effect occurs in two steps: formation of zeiotic knobs on the cell surface and subsequent grouping of the knobs at one pole of the cell. The early step of zeiotic knob formation occurs at low concentrations of CB (0.5-1 microgram/ml) at 37 degrees C and at high concentrations of the drug (5-10 microgram/ml) at low temperature but within 1 min at 37 degrees C. This step is only partially inhibited by 5 x 10(-3) M sodium azide. The subsequent grouping of zeiotic knobs lasts for more than 2 min at 37 degrees C and occurs only in the case of high concentrations of CB. It is inhibited by sodium azide and is often associated with grouping of the microvilli, which are then lost from all of the cell surface except the area of knob-grouping.

Animals↗

PubMed1998

Role of xanthine oxidase in hydrogen peroxide production.

Increased production of oxygen free radicals may play a role in many diseases such as hypertension. As evidence indicates that xanthine oxidase may be involved in creating these reactive oxygen species, experiments were performed to additionally characterize hydrogen peroxide (H2O2) production in xanthine oxidase catalyzed reactions. In vitro measurements of hydrogen peroxide production from the xanthine/xanthine oxidase reaction were performed in buffered saline using an electrochemical technique, and the effect of allopurinol on inhibition of xanthine oxidase was determined. Experiments were also performed in blood plasma to characterize endogenous hydrogen peroxide producing capability and xanthine oxidase activity. In the presence of sodium azide, an inhibitor of catalase, peroxide production was measured in plasma after adding xanthine or xanthine oxidase and the results were similar to those obtained in buffered saline. When only sodium azide was added to plasma, hydrogen peroxide was produced at a level of 36.1 +/- 7.6 microM (n = 5). From these measurements, endogenous xanthine oxidase activity was estimated to be 6.5 +/- 0.3 mU/ml (n = 5). These results suggests that sufficient substrate exists in plasma to produce micromolar levels of hydrogen peroxide and xanthine oxidase may catalyze these reactions.

Allopurinol↗

PubMed1984

Rapid and easy separation of the subunits of bovine and human glycoprotein hormones by use of high performance liquid chromatography.

A single method of reverse phase high performance liquid chromatography is used to separate the subunits of human and bovine glycoprotein hormones. This rapid and easy method is applicable for the separation and detection of subunits from as little as 10 micrograms hormone or the isolation of subunits from as much as 100 mg hormone. Separation is achieved by chromatography on a Vydac 218TP1010 column with a linear (60-min) gradient of 0.1 M sodium phosphate, pH 6.8, plus 1 mM sodium azide to a solvent containing 50% acetonitrile and 50% 0.1 M sodium phosphate, pH 6.8, plus 1 mM sodium azide. Although in some cases the interaction between the hydrophobic support and the hormone is sufficient for dissociation, preincubation of the hormone with guanidine hydrochloride ensures optimum dissociation and improves resolution of the subunits. The subunits isolated by high performance liquid chromatography are functional in that they will reassociate with their counterpart subunits.

Animals↗

PubMed1993

Acrylamide as an inducer of metabolic activation system (S9) in rats.

The S9 fraction was prepared from rats i.p. injected with a single dose of 75 mg/kg acrylamide. The efficiency of the acrylamide induction procedure was verified on Salmonella mutagenicity testing (TA98 and TA100) using a number of known mutagens. These mutagens are aflatoxin B1, benzo[alpha]pyrene, 2-acetylaminofluorene and sodium azide. The activity of the mutagen is measured in terms of histidine revertant numbers which were found to be almost proportional to the concentration of acrylamide-induced S9. The maximum activation of the mutagens (except sodium azide) was recorded using around 50 microliters of S9 per plate. The efficiency of our prepared S9 fraction as a metabolic activator for some known mutagens is comparable to that of standard S9. On the basis of our results, acrylamide-induced S9 demonstrated considerable increase in the activation of the tested compounds. Accordingly, acrylamide could be used as an additional procedure for the induction of rat hepatic enzymes (S9).

2-Acetylaminofluorene↗

PubMed1983

Criteria for the standardization of Salmonella mutagenicity tests: results of a collaborative study. IV. Relationship between the number of his- bacteria plated and number of his+ revertants scored in the Salmonella mutagenicity test.

Five laboratories participated in a joint ring study to investigate the role of bacterial cell number in the Salmonella mutagenicity test. A strictly standardized protocol, using sodium azide and TA 1535, was developed and employed to test the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) with different dilutions of Salmonella typhimurium TA-100 and TA-1535 cultures. All laboratories detected the mutagenic activity of sodium azide with only a 2-fold variation of test results. For MNNG the interlaboratory variation was approximately 5-fold. Decreasing numbers of test bacteria employed resulted in lower numbers of MNNG-induced revertants in all laboratories. The number of preexisting revertants decreased in direct proportion to the reduced cell content, whereas the number of spontaneous revertants was not as greatly affected. A critical amount of test bacteria was required in order to obtain numbers of induced revertants which were equal to twice the number of spontaneous revertants. Two evaluation parameters which may be employed to describe the mutagenicity of a compound are compared.

Animals↗

PubMed2004

The assessment of the viability of the endospores of Rhinosporidium seeberi with MTT (3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide).

This report describes tests with Evan's Blue and MTT (3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide) for the assessment of the viability of rhinosporidial endospores. MTT stained a proportion of the spherical bodies that we regard as the Electron Dense Bodies (EDBs), and the cytoplasm of freshly prepared endospores or ones that were stored at 4 degrees. Slow-freezing at -20 degrees C, exposure to 10% formalin, or 0.1% sodium azide of the endospores abolished MTT-staining in both sites. Evan's Blue stained the EDBs and cytoplasm of fresh endospores or those stored at 4 degrees, and of sodium azide-treated or frozen (-20 degrees)-thawed endospores. TMRE (tetramethyl-rhodamine ethyl ester) specifically labelled the spherical bodies, supporting the conclusion that these spherical bodies have a mitochondrial-like structure. TMRE-staining was however retained in endospores after their treatment with formalin, sodium azide and slow-freezing while MTT-staining was abolished in all these treated endospores. These results indicate that EvB and TMRE were capable of revealing the morphological integrity of endospores but failed to identify the metabolic inactivation of the endospores after treatment with formalin, sodium azide or slow-freezing. Only MTT was capable of identifying metabolically active endospores and hence their viability and could prove to be of value in standardizing models of infection.

Evans Blue↗

PubMed1997

Indocyanine green: intracellular uptake and phototherapeutic effects in vitro.

Indocyanine green (ICG; absorption peak in human plasma 805 nm) was investigated for ICG-mediated phototherapy in vitro. The cellular uptake of ICG (1 microM-50 microM) into HaCaT keratinocytes after an incubation period of 24 h increased up to an intracellular ICG concentration of 12.1 +/- 1.3 nmol per 10(6) cells. To examine dose dependent phototoxic effects in vitro, keratinocytes were incubated with 0 microM-50 microM ICG for 24 h and irradiated by a diode laser (805 nm) with different energy densities (0, 12, 24, 48 J cm-2). All applied ICG concentrations except for 5 microM yielded a cell killing effect in combination with irradiation depending significantly on ICG concentration and light dose. Cell viability for dark control and cells incubated with 50 microM ICG and irradiated with 48 J cm-2 was 0.82 +/- 0.15 and 0.07 +/- 0.02, respectively. Sodium azide (100 mM), a quencher of reactive oxygen species, inhibited significantly the cell killing using 50 microM ICG and 24 J cm-2. Taken together, photoactivation of ICG by irradiation with a diode laser was shown to induce effectively cell killing of HaCaT keratinocytes. Moreover, this effect was inhibited by sodium azide, thus irradiation of ICG might induce a photodynamic reaction.

Antineoplastic Agents↗

PubMed1989

Interaction of mammalian cells with polymorphonuclear leukocytes: relative sensitivity to monolayer disruption and killing.

Monolayers of murine fibrosarcoma cells that had been treated either with histone-opsonized streptococci, histone-opsonized Candida globerata, or lipoteichoic acid-anti-lipoteichoic acid complexes underwent disruption when incubated with human polymorphonuclear leukocytes (PMNs). Although the architecture of the monolayers was destroyed, the target cells were not killed. The destruction of the monolayers was totally inhibited by proteinase inhibitors, suggesting that the detachment of the cells from the monolayers and aggregation in suspension were induced by proteinases releases from the activated PMNs. Monolayers of normal endothelial cells and fibroblasts were much resistant to the monolayer-disrupting effects of the PMNs than were the fibrosarcoma cells. Although the fibrosarcoma cells were resistant to killing by PMNs, killing was promoted by the addition of sodium azide (a catalase inhibitor). This suggests that the failure of the PMNs to kill the target cells was due to catalase inhibition of the hydrogen peroxide produced by the activated PMNs. Target cell killing that occurred in the presence of sodium azide was reduced by the addition of a "cocktail" containing methionine, histidine, and deferoxamine mesylate, suggesting that hydroxyl radicals but not myeloperoxidase-catalyzed products were responsible for cell killing. The relative ease with which the murine fibrosarcoma cells can be released from their substratum by the action of PMNs, coupled with their insensitivity to PMN-mediated killing, may explain why the presence of large numbers of PMNs at the site of tumors produced in experimental animals by the fibrosarcoma cells is associated with an unfavorable outcome.

Animals↗

PubMed1992

Potentiation of nicotinic transmission in the rat superior cervical sympathetic ganglion: effects of cyclic GMP and nitric oxide generators.

The efficacy of nicotinic transmission in the rat superior cervical ganglion in vitro (24-26 degrees C) was estimated by extracellular recording of the postganglionic compound action potential response to stimulation of the preganglionic nerve at a slow rate (one shock every 60 s). Atropine (2 microM) was included to block muscarinic transmission, and hexamethonium (200-250 microM) was used to produce a submaximal response sensitive to potentiation and inhibition of nicotinic transmission. Upon exposure to 1-100 microM 8-bromo-guanosine 3',5'-cyclic monophosphate (8-Br-cGMP), nicotinic transmission was potentiated by 6 +/- 1% (n = 4) to 89 +/- 5% (n = 5) in a dose-dependent manner. 8-Bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP, 10-100 microM) also potentiated nicotinic transmission (3.8 +/- 0.3% (n = 3) to 43 +/- 4% (n = 3)). However, 8-Br-cGMP was at least 2-fold more effective than 8-Br-cAMP. Sodium nitroprusside (0.1 microM to 1 mM) and sodium azide (0.1-100 microM) were used to stimulate the formation of endogenous cGMP52. Nicotinic transmission was potentiated by these substances also. The response was increased by 3.4 +/- 0.7% (n = 4) to 32 +/- 2% (n = 5) upon exposure to 0.1-100 microM sodium nitroprusside, and by 5.5 +/- 0.9% (n = 3) to 18 +/- 4% (n = 4) upon exposure to 0.1-100 microM sodium azide. Ferricyanide ion (10-100 microM) appeared to be ineffective, as would be expected if the effect of nitroprusside was due to the nitric oxide rather than the cyanide or ferric moieties.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1993

The filamentous bacteriophage assembly proteins require the bacterial SecA protein for correct localization to the membrane.

The noncapsid assembly proteins pI and pI of the filamentous bacteriophage f1 are inserted into the inner membrane of Escherichia coli via an internal signal sequence. Inhibition of the activity of SecA with low concentrations of sodium azide results in rapid accumulation of pI and pI proteins in the cytoplasm. However, both proteins are inserted into the membrane under the same conditions when synthesized in bacteria containing a secA azide resistance mutation. The other noncapsid assembly protein, pIV, is an outer membrane protein synthesized with a cleavable signal sequence. Wild-type bacteria accumulate the precursor to pIV when protein synthesis is in the presence of low concentrations of sodium azide. These results suggest that the f1 bacteriophage assembly proteins require SecA and consequently the bacterial Sec system to reach their proper membrane location.

Adenosine Triphosphatases↗

PubMed2000

Laccase activity tests and laccase inhibitors.

Sulfhydryl organic compounds described as laccase inhibitors: dithiothreitol, thioglycolic acid, cysteine, diethyldithiocarbamic acid, and sodium azide were tested for their activity toward laccase of Trametes versicolor in different test systems utilising 2, 2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2, 6-dimethoxyphenol as enzyme substrates. Only sodium azide acted as a true laccase inhibitor and showed no significant interference with the enzyme tests. All other substances did not significantly inhibit the laccase activity and the previously reported inhibitory effects result from the reductions of the reaction products such as ABTS radical cation and diquinone or subsequent non-enzymatic interactions during substrate oxidation. The latter apparently forms a complex with unreacted ABTS displaying varied spectral characteristics and resulting in an underestimation of enzyme activity.

Benzothiazoles↗

PubMed1985

Cellular contribution to pH-mediated calcium flux in neonatal mouse calvariae.

Net calcium flux from cultured neonatal mouse calvariae into the culture medium is pH dependent, and acidified culture medium causes egress of calcium from bone. To determine whether calcium flux is mediated by pH effects on bone cell function, we cultured calvariae for 24 h with sodium azide, acetazolamide, parathyroid hormone (PTH), 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], or after three successive freeze-thaw cycles, treatments that would be expected to alter bone cell function. We recultured bones for 3 h with the respective treatment and measured calcium flux. Sodium azide and freeze-thaw cycles produced a net influx of calcium (JCa = -22 +/- 7 and -23 +/- 6 nmol X bone-1 X 3 h-1, respectively) compared with net efflux of control bones (JCa = 35 +/- 6) at a similar initial medium pH. Acetazolamide reduced net flux to 0 (JCa = 7 +/- 6). PTH and 1,25(OH)2D3 increased net calcium efflux from bone (JCa = 78 +/- 7 and 74 +/- 10, respectively). Despite changing net flux, the slope dependence of net flux on medium pH was the same in the control group and all five treated groups of bones. The similarity of slopes indicates that the pH dependence of net flux is not a result of pH acting on bone cells but probably an effect of altered mineral equilibria. The difference in net flux at similar pH indicates that calcium efflux is partially inhibited by acetazolamide and stimulated by both PTH and 1,25(OH)2D3.

Acetazolamide↗

PubMed1995

Isolation and characterization of a cDNA encoding the SecA protein from spinach chloroplasts. Evidence for azide resistance of Sec-dependent protein translocation across thylakoid membranes in spinach.

Thylakoid membranes of chloroplasts in higher plants harbor different pathways for the translocation of proteins. One of these routes is related to the prokaryotic Sec pathway, which mediates the secretion of particular proteins into the periplasmic space and involves the SecA protein as an essential component. We have isolated a full size cDNA of 3739 nucleotides encoding the SecA homologue from spinach. It contains an open reading frame of 1036 codons corresponding to a polypeptide with a calculated mass of 117 kDa. The deduced amino acid sequence shows between 43 and 49% identity to SecA proteins from bacteria and lower algae and 62% identity to SecA of the cyanobacterium Synechococcus sp. PCC7942. Compared with the Escherichia coli protein, spinach SecA carries an amino-terminal extension of approximately 80 residues. In organello experiments performed with the protein made in vitro by transcription of the cDNA and cell-free translation of the resulting RNA showed that this extension comprises a transit peptide that mediates the import of the protein into the chloroplast. The processed product of approximately 107 kDa accumulates predominantly in the stroma and to a lower extent associates with the thylakoid membrane. Comparably to E. coli, in which SecA activity can be inhibited by sodium azide, thylakoid translocation of a subset of lumenal proteins is sensitive to sodium azide in pea but not in spinach chloroplasts, suggesting that the latter contain an azide-resistant SecA variant.

Adenosine Triphosphatases↗

PubMed1999

Effect of inhibitors on the biotransformation of tamoxifen by female rat and mouse liver slices and homogenates.

The metabolism of tamoxifen was studied in female Sprague-Dawley rat and mouse liver slices and homogenates, and the three principal tamoxifen metabolites, 4-hydroxytamoxifen, N-desmethyl-tamoxifen and tamoxifen N-oxide, were identified by HPLC using authentic standards. It was not possible to identify any of the minor metabolites such as the epoxides using this technique. The N-oxide metabolite only appeared when NADPH was added to the system; this is because the production of tamoxifen N-oxide is primarily mediated by microsomal flavin monooxygenase (FMO) which is NADPH dependent. However, this metabolite did appear in incubations with mouse liver slices only, because they are rich in flavin monooxygenases (FMOs). It did not appear in female rat or mouse liver homogenates, because the NADPH present is destroyed during homogenisation, therefore it was necessary to add NADPH to the system to produce the N-oxide metabolite. The purpose of this study was to investigate the effect of inhibitors on the biotransformation of tamoxifen by female rat and mouse liver slices and homogenates. Female rat liver slices and homogenates were incubated with the following inhibitors (1 mM): cimetidine, ascorbate, sodium azide and reduced glutathione. Cimetidine, a general P-450 inhibitor, inhibited the production of the N-desmethyl metabolite by about 80%; this is in agreement with the action of the other inhibitors. Reduced glutathione, ascorbate and sodium azide are mainly peroxidase inhibitors, so therefore from these novel and interesting results it was possible to suggest that peroxidases play a role in the metabolism of tamoxifen. This observation was also strengthened when the production of the N-desmethyl metabolite increased when horseradish peroxidase was added to the incubate. The production of 4-hydroxytamoxifen was reduced and the N-oxide metabolite was completely inhibited in the presence of peroxidase inhibitors. When rat liver homogenates was incubated with superoxide dismutase (SOD) and catalase, it was observed that the N-desmethyl metabolite disappeared completely at 60 min and the N-oxide and 4-hydroxy metabolites were completely inhibited. However, this phenomenon was only observed when SOD and catalase were preincubated for 30 min with the rat liver homogenate at 37 degrees C; without preincubation the production of these metabolites was unaffected. Finally, the effect of long incubation periods (300 min) on the production of metabolites was examined. It was found that there was a reduction in the concentration of metabolite produced after 60 min which was due to enzyme and co-factor degradation.

Animals↗

PubMed1993

Evaluation of the role of reactive oxygen species in the interactive toxicity of carbide-cobalt mixtures on macrophages in culture.

The lung toxicity of a carbide-cobalt mixture is more important than that of each individual component; the mechanism of this interaction is not understood. The capacity of cobalt metal particles alone and mixed with different carbides to generate hydroxyl radicals was examined with the deoxyribose assay. In a chemical system, cobalt ions and cobalt metal particles (Co) were found to catalyse the degradation of deoxyribose in the presence of hydrogen peroxide. Carbides were able to directly oxidize deoxyribose, but their respective activities did not support such a mechanism to explain the carbide-cobalt interactive toxicity, since there was no direct relationship between deoxyribose degradation ability and cytotoxicity toward macrophages. Tungsten, niobium, titanium and chromium carbides (interactive carbides) were only weak oxidants and conversely molybdenum, vanadium and silicon carbides (non-interactive carbides) were the most potent ones. The ability of cobalt metal to produce hydroxyl radicals in the presence of hydrogen peroxide was not increased by tungsten carbide. The role of reactive radical formation in the toxicity of these particles was further assessed in a macrophage culture model. Catalase (4000 U/ml), superoxide dismutase (300 U/ml), sodium azide (1 mM), sodium benzoate, mannitol, taurine and methionine (all 20 mM) were all unable to protect against the cytotoxic effects of cobalt ions and cobalt metal alone or mixed with tungsten carbide. In conclusion, no evidence was found that production of reactive oxygen species contributes to the elective toxicity of carbide-cobalt mixtures.

Animals↗

PubMed1986

A high affinity calcium-stimulated ATPase in synaptic plasma membranes detectable in the presence and absence of exogenous magnesium.

A Ca2+-stimulated ATPase activity detectable in the presence of submicromolar free Ca2+ was characterized in synaptic plasma membrane preparations. In the absence of exogenous magnesium, Ca2+-stimulated ATPase showed a K0.5 Ca2+ of 0.1 microM, Vmax of 125 nmol Pi/mg per min and a Hill number of 1.2. The addition of 1 mM MgCl2 increased basal ATPase activity by about 10-fold. After this activity had been subtracted, apparent values for Ca2+-stimulated ATPase were 0.033 microM (K0.5 Ca2+), 172 nmol Pi/mg per min (Vmax) with a Hill number of 4. These activities were non-significantly affected by ouabain, sodium azide, theophylline and sodium fluoride. The results obtained indicated that high affinity Ca2+-stimulated ATPase activity could be in synaptic plasma membrane-enriched fraction detected both in the presence and absence of exogenous magnesium. Furthermore, the data indicated that magnesium was required for calcium transport.

Adenosine Triphosphatases↗

PubMed1981

In vitro synthesis of a mutagenic azide metabolite by cell-free bacterial extracts.

Cell-free extracts of Salmonella typhimurium synthesize a mutagenic azide metabolite from sodium azide and O-acetylserine. S. typhimurium mutant DW379 (O-acetylserine sulfhydrylase-deficient) extracts were neither able to carry out this reaction not produce the mutagenic azide metabolite in vivo. The in vitro reaction was inhibited by sulfide but not by L-cysteine. The catalytic activity responsible for the mutagenic metabolite synthesis was stable to brief heating up to 55 degrees C and had a pH optimum between 7-7.4. These results suggest that the enzyme O-acetylserine sulfhydrylase catalyzes the reaction of azide with O-acetylserine to form a mutagenic azide metabolite.

Azides↗

PubMed2004

Effects of cooling and ARL 67156 on synaptic ecto-ATPase activity in guinea pig and mouse vas deferens.

We have studied the influence of temperature and ARL 67156 on ATP hydrolysis in mouse and guinea pig vas deferens in order to explore the properties of the enzymatic inactivation mechanism proposed to regulate purinergic neurotransmission at the sympathetic neuromuscular junction of smooth muscle. The ectonucleotidase activity was determined by using the malachite green method to measure the inorganic phosphate (Pi) liberated with ATP used as a substrate. ATP hydrolysis in both species was found to be insensitive to ouabain (100 microM), sodium azide (1 mM), sodium vanadate (100 microM) and beta-glycerophosphate (10 mM) and was also found to depend on Ca2+ and Mg2+. V(MAX) of the ectonucleotidase activity for guinea pig and mouse vas deferens was 958.4+/-66.3 and 79.7+/-8.5 pmol/min/mg, while K(M) was 625.1+/-45.2 and 406.0+/-29.0 microM, respectively. Cooling the tissues from 35 to 25 degrees C reduced the enzyme activity significantly (P<0.01) by 52.7+/-9.2% in guinea pig vas deferens and 34.9+/-5.3% in mouse vas deferens. ARL 67156 (100 microM), the specific ecto-ATPase inhibitor, caused a reduction in enzyme activity in guinea pig and mouse vas of 54.1+/-16.4% and 53.0+/-7.6%, respectively (P<0.01). The degree of inhibition of ATP hydrolysis by lowered temperature and 100 microM ARL 67156 correlates well with the reported potentiation and prolongation of junction potentials under these conditions. It is concluded that ecto-ATPase or a closely related ectonucleotidase plays an important role in the physiological regulation of purinergic neurotransmission.

Adenosine Triphosphatases↗