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PubMed1969

The influence of drugs on the uptake of acetylcholine by slices of rat cerebral cortex.

1. The acetylcholine content of cortical slices from rat brain, was determined after incubation for 30 min in a medium containing acetylcholine (4 mug/ml.). The cholinesterase activity of the slices had been inhibited by pretreatment with 3,3-dimethyl-n-butyl 2-methylphosphonofluoridate (soman).2. Acetylcholine accumulated in the tissue slices, up to a concentration of about six times that in the medium.3. The uptake of acetylcholine was partly inhibited by potassium in high concentrations.4. Hemicholinium-3, O-ethyl S-diethylaminoethyl ethylphosphonothiolate, physostigmine, atropine and choline, in that order of potency, inhibited the accumulation of acetylcholine in the cortical slices, but soman and ethyl N,N-dimethyl phosphonoamidocyanate (tabun) had no effect on the uptake of acetylcholine.5. Substances interfering with energy metabolism, such as 2,4-dinitrophenol, oligomycin, sodium azide, amylobarbitone sodium and p-chloromercuribenzoate inhibited the uptake of acetylcholine. Ouabain had little inhibitory effect.6. In anaerobic conditions the accumulation of acetylcholine in the tissue slices was nearly blocked.7. The uptake of acetylcholine in the tissue slices was dependent on temperature. The Q(10) was about 2.8. Autoradiography of sections from slices in which (3)H-acetylcholine had accumulated showed a diffuse distribution of radioactivity in the cytoplasm of all cells. There was no visible preference for certain cells or cell structures.

Acetylcholine↗

PubMed1980

Effect of human gastric juice on the mutagenicity of chemicals.

10 mutagens were assayed in the Salmonella test after a pre-incubation step with human gastric juice. Such treatment affected the activity of 4 compounds, with different mechanisms, either in the sense of deactivation (sodium azide and sodium dichromate), of stabilization (captan), or even of potentiation (ICR-170). Conversely, the mutagenicity of other compounds (folpet, sodium nitrite, ICR-191, nitrofurantoin and a related drug) was unchanged. The stability of 2 carcinogens requiring metabolic activation, namely benzo[a]pyrene and aflatoxin B1, provided evidence that pre-incubation of compounds with gastric juice is compatible with the subsequent addition of liver post-mitochondrial preparations, thus reproducing in vitro 2 consecutive metabolic steps occurring in the organism. These findings lead us to report an improved correlation between assays in vivo and in vitro, in particular by explaining the lack of carcinogenicity of some mutagens introduced orally or by gastric intubation. Therefore, the Salmonella/gastric juice test is proposed as an additional assay for predicting the potential health hazards of chemicals.

Biotransformation↗

PubMed1988

Synaptosomal calcium influx is activated by sodium fluoride.

Neuronal calcium channels can be modulated by changes in membrane potential or by activation of channel-associated receptors. The latter may be modulated by guanine nucleotide binding proteins. NaF, which activates guanine nucleotide binding proteins, caused a large stimulation of 45Ca2+ uptake by synaptosomes prepared from rat brain. Stimulation of 45Ca2+ influx by NaF (i) was apparent in media containing either 5 mM-K+ or 50 mM-K+, (ii) was slower than the fast-phase of voltage-dependent 45Ca2+ influx but continued for a longer period of time than did depolarization-induced 45Ca2+ influx, and (iii) was not mimicked or modified by a number of drugs, including ouabain, dinitrophenol, sodium azide or sodium vanadate. These results are consistent with the hypothesis that NaF activates a guanine nucleotide binding protein associated with receptor-coupled calcium channels, resulting in stimulation of calcium influx.

Animals↗

PubMed1986

Attempts for light microscopical demonstration of guanylate cyclase activity in rat cerebellum.

Guanylate cyclase in rat cerebellum was investigated on the light microscopical level with guanylyl imidodiphosphate as substrate. Several attempts for activation of enzymatic activity and delimitation to other enzymes were made by sodium azide, aminophylline, sodium fluoride and dithioerythrole. The localization was similar but less strong compared to adenylate cyclase (Poeggel and Luppa 1984) and differs in behaviour to the above mentioned substances. Nucleotide pyrophosphatases seem to play an unimportant role in guanylyl imidodiphosphate conversion, while alkaline phosphatase is possibly of more importance. A light microscopical demonstration of guanylate cyclase by its enzymatic activity must be considered with caution. Main reasons are the low activity and therefore the great importance of interfering enzymes with high activities.

Adenylyl Cyclases↗

PubMed1999

Glucose and non-glucidic nutrients exert permissive effects on 2-keto acid regulation of pancreatic beta-cell function.

Insulin-releasing effects of straight and branched chain 2-keto acids were assessed using clonal glucose-responsive beta-cells. Pyruvic acid (PA), 2-ketovaleric acid (KV), 2-ketoisovaleric acid (KIV) or 2-keto-3-methylvaleric acid (KMV) dose-dependently promoted the stimulatory effects of D-glucose, whereas 2-ketobutyric acid (KB) did not affect insulin release. The stimulatory 2-keto acids also promoted the stimulatory activity of D-glyceraldehyde, L-leucine or L-arginine. Responses to PA, KV, KIV or KMV were significantly reduced by transport inhibition with 2-cyano-3 hydroxycinnamate, glucokinase inhibition with mannoheptulose or metabolic inhibition with sodium azide or sodium cyanide. Membrane hyperpolarisation with K+ depletion or diazoxide reduced insulin output, but failed to abolish secretory responses to KV, KIV and KMV. Secretory effects of these 2-keto acids also persisted in beta-cells depolarised with high KCl and glucose. Voltage-dependent Ca2+ channel blockade, with verapamil, or depletion of extracellular Ca2+ abolished the secretory activity of 2-keto acids. Collectively, these results indicate that glucose and metabolisable nutrients exert permissive effects on 2-keto acid-induced insulin release. In addition, KV, KIV and KMV can regulate beta-cell function at least partially independently of K+-ATP channel activity, both through their mitochondrial metabolism and regulation of Ca2+ influx.

Animals↗

PubMed2002

Experimental and theoretical characterization of cationic, neutral, and anionic binary arsenic and antimony azide species.

Cationic, neutral, and anionic arsenic and antimony halides formed binary arsenic and antimony azide species M(N(3))(4)(+), M(N(3))(4)(-), and M(N(3))(6)(-) (M = As, Sb) upon reaction with trimethylsilyl azide or sodium azide. The compounds were obtained as pure substances or salts, and their identity was established by vibrational spectroscopy and multinuclear NMR spectroscopy and partially by elemental analysis. Attempts to synthesize pentaazides, M(N(3))(5) (M = As, Sb), failed due to spontaneous decomposition of the compounds. Density functional theory (B3LYP) was applied to calculate structural and vibrational data. Vibrational assignments of the normal modes for the isolated azide compounds were made on the basis of their vibrational spectra in comparison with computational results. The molecular structures and vibrational spectra of the arsenic and antimony pentaazides have been investigated theoretically. These calculations (B3LYP) show minima structures (NIMAG = 0) for all reported compounds. It is shown that the M(N(3))(4)(+) (M = As, Sb) cations exhibit ideal S(4) symmetry and the M(N(3))(6)(-) anions (M = As, Sb) ideal S(6) symmetry. The structure of the hexaazidoarsenate(V) has been determined by X-ray diffraction as its pyridinium salt. [py-H][As(N(3))(6)] crystallizes in the triclinic space group P with a = 6.8484(7), b = 7.3957(8), and c = 8.0903(8) A, alpha = 91.017(2), beta = 113.235(2), and gamma = 91.732(2) degrees, V = 376.29(7) A(3), and Z = 1. The structure of the As(N(3))(6)(-) anion exhibits only S(2) symmetry but shows approximately S(6) symmetry. The calculated and experimentally observed structure as well as the calculated and observed IR and Raman frequencies for all azide species (except M(N(3))(5)) are in reasonable agreement.

Journal Article↗

PubMed1998

Aerobic chromate reduction by Bacillus subtilis.

We have studied the reduction of hexavalent chromium (chromate) to the less toxic trivalent form by using cell suspensions and cell-free extracts from the common soil bacterium, Bacillus subtilis. B. subtilis was able to grow and reduce chromate at concentrations ranging from 0.1 to 1 mM K2CrO4. Chromate reduction was not affected by a 20-fold excess of nitrate-compound that serves as alternate electron acceptor and antagonizes chromate reduction by anaerobic bacteria. Metabolic poisons including sodium azide and sodium cyanide inhibited chromate reduction. Reduction was effected by a constitutive system associated with the soluble protein fraction and not with the membrane fraction. The reducing activity was heat labile and showed a Km of 188 microns CrO4(2)-. The reductase can mediate the transfer of electrons from NAD(P)H to chromate. The results suggest that chromate is reduced via a detoxification system rather than dissimilatory electron transport.

Aerobiosis↗

PubMed1987

The Effect of Abscisic Acid and Other Inhibitors on Photosynthetic Capacity and the Biochemistry of CO(2) Assimilation.

Abscisic acid (ABA) was shown to reduce the photosynthetic capacity of a leaf through an apparent inhibition of ribulose 1,5-bisphosphate (RuBP) carboxylase (RuBPCase) activity, in addition to promoting stomatal closure. By comparison with the effects of other inhibitors of photosynthesis (cyanazine, methyl viologen, sodium azide, nigericin, sodium cyanide) on whole leaf photosynthesis, RuBPCase activity and metabolite pool sizes, it was demonstrated that the biochemical basis for the apparent effect of ABA on RuBPCase activity was not the result of reduced substrate availability, decarbamylation of the enzyme, or synthesis of carboxyarabinitol 1-phosphate, the naturally occurring tight-binding inhibitor of the enzyme. An inhibition of photosynthetic capacity showing the same biochemical characteristics as ABA-fed leaves was observed in plants grown under saline conditions. We suggest that the common link between environmental stress and reductions in photosynthetic capacity may be ABA. We hypothesize that ABA may affect plasma membrane function and thus indirectly RuBPCase activity through altered ion fluxes. The results of feeding cyanazine, methyl viologen, and nigericin provide additional evidence that regulation of RuBPCase activity by carbamylation/decarbamylation is related to the extent to which the capacity for ATP formation limits photosynthesis.

Journal Article↗

PubMed1991

Tegumental surface modulation in Schistosoma mansoni primary sporocysts in response to ligand binding.

The clearance of host molecules from the surface of a parasite constitutes a potential immune evasive strategy. The possibility that certain ligands, when bound to the tegument of Schistosoma mansoni primary sporocysts, could induce such a modulating effect was investigated. Live, in vitro cultured primary sporocysts were first treated with either snail host Biomphalaria glabrata plasma, an anti-sporocyst monoclonal antibody (MoAb III-1), or concanavalin A (con A). The capacity of these primary ligands to produce a modulating effect alone, or when subsequently crosslinked by secondary or tertiary ligands, was measured using quantitative fluorescence microscopy. Snail plasma alone, or plasma crosslinked at the sporocyst surface with a mouse anti-plasma MoAb had little or no modulating effect. However, a tertiary level of ligand crosslinking with an anti-mouse IgG antibody produced an average 1.8-fold decrease in surface fluorescence within 1 h post-labelling. The anti-sporocyst MoAb III-1 also required secondary antibody reactivity to induce an average 1.5-fold decrease in MoAb III-1 recognized epitopes. Sporocysts labelled with con A crosslinked by secondary and tertiary ligands showed inconsistent modulation, with a 1.5-fold decrease in fluorescence in one out of three replicates. Overall, however, analysis of combined data revealed no significant effect of tertiary ligand level crosslinkage on modulation of con A-tegumental receptor complexes. In contrast, con A binding alone to tegumental determinants induced a small, but significant, reduction in surface con A complexes. Modulation of ligand-receptor complexes on the sporocyst tegumental membrane appears to be an energy-requiring event, since clearance of surface complexes was inhibited in the presence of sodium azide and/or sodium iodoacetate, or when larvae were incubated at 4 degrees C. It is concluded that alterations in sporocyst tegumental surface components may be triggered by specific (but as yet undefined) signals. Sporocysts are capable of exhibiting different responses depending on the nature of the binding signal and reactive tegumental receptor, and the degree of ligand crosslinkage.

Animals↗

PubMed1967

Simple medium for the selective isolation of Bacteroides and related organisms, and their occurrence in sewage.

A medium composed of 0.009% sodium azide, 0.07% sodium deoxycholate, and 0.0007% ethyl violet in Brain Heart Infusion Agar (Difco) and a process of incubation in an atmosphere of 90% N(2) and 10% CO(2) for the selective isolation of certain members of the intestinal bacteroides are described. The medium appears to select predominantly members of the genus Bacteroides and a few of the genus Sphaerophorus. A survey of the occurrence of these organisms in sewage and various stages of sewage treatment indicates that they survive complete sewage treatment in low numbers and that their rate of decline parallels that of the coliforms. Large numbers were recovered from sludge digestion tanks, suggesting a possible role in the anaerobic breakdown of organic matter.

Bacteroides↗

PubMed1994

Isolated fibrils rescue cohesion and development in the Dsp mutant of Myxococcus xanthus.

Extracellular fibrils are involved in cell cohesion and cell development in Myxococcus xanthus. One group of social motility mutants, Dsp, is unable to produce extracellular fibrils; these mutants also lose the abilities to cohere and to develop. Extracellular fibrils isolated from vegetative wild-type cells and added to Dsp cells fully restored the abilities of these cells to cohere and to undergo normal morphological development. The fibrils thus mimic the ability of intact, wild-type cells to carry out the same rescue. Optimal cohesion rescue by fibrils required calcium and magnesium ions, did not require protein synthesis, but was energy dependent, i.e., sodium azide and sodium cyanide blocked rescue. Cohesion rescue was also blocked by the diazo dye Congo red. Cohesion rescue is genus specific, i.e., isolated fibrils did not cause the cohesion of Pseudomonas aeruginosa, Bacillus subtilis, Proteus mirabilis, Escherichia coli, or the related myxobacterium Stigmatella aurantiaca. Developmental rescue of Dsp by isolated fibrils included aggregation, fruiting body formation, and myxospore morphogenesis. Developmental gene expression in the Dsp mutant was only partially rescued by the isolated fibrils.

Bacterial Adhesion↗

PubMed1981

Exchange of free cholesterol between low density lipoproteins and human adipocytes.

Free cholesterol uptake from low density lipoproteins (LDL) by fat cells was investigated using exchange-labelled [1,2-3H]cholesterol-LDL and isolated human adipocytes, prepared by collagenase digestion of subcutaneous fat tissue biopsies. Radioactivity appeared in the cellular lipids within 2 min and accumulated at a slower rate approaching linearity for 3 h. At 5 and 120 min, 90% of the recovered cellular radioactivity was found in the bulk lipid fraction and the remainder was distributed among organelle fractions. Uptake of [3H]cholesterol was linearly related to substrate concentrations up to 5 micrograms unesterified cholesterol - LDL . mL-1. At higher concentrations up to 22 micrograms unesterified cholesterol - LDL . mL-1, [1,2-3H]cholesterol accumulated more gradually but did not reach a plateau. Metabolic inhibitors, sodium azide plus sodium fluoride, had no effect on radiocholesterol uptake. Native LDL and high density lipoprotein at equivalent unesterified cholesterol concentrations decreased [1,2-3H]cholesterol uptake, to a similar extent suggesting isotope dilution. The results demonstrate a rapid, receptor-independent uptake of cholesterol from LDL by adipocytes, consistent with an exchange mechanism. This process could explain the rapid labelling of adipose tissue cholesterol in vivo following intravenous administration of radiocholesterol and efflux of free cholesterol from adipose tissue during starvation.

Adipose Tissue↗

PubMed1987

Endogenous peroxidase activity in human cutaneous and adenoidal mast cells.

We have studied peroxidase activity in human cutaneous and adenoidal mast cells using different methods, in order to determine the optimal technical conditions for its demonstration. In 1.25% glutaraldehyde-fixed cells, no peroxidase activity was seen. On the contrary, in tannic acid-aldehyde-fixed cells or in unfixed cells peroxidase activity was revealed independently of the DAB concentration or the incubation time in DAB medium. The reaction product was localized in perinuclear cisternae and endoplasmic reticulum. Granules were always unreactive with all techniques employed. Golgi apparatus was generally negative and only occasional cells exhibited one or two positive peripheral cisternae. This activity appears sensitive to fixation by glutaraldehyde and is inhibited by 3-amino-1,2,4-triazole (AMT) and by lack of H2O2 or DAB in the incubation medium, but not by potassium cyanide, sodium azide, or sodium pyruvate, at the concentrations used. The peroxidase activity described in this report is an endogenous peroxidase and is not related to uptake of exogenous peroxidase by mast cells. It can therefore be considered as an ultracytochemical marker of human mast cells.

Adenoids↗

PubMed1992

Characteristics of L-citrulline transport across rat small intestine in vitro.

The amino acid L-citrulline is an important intermediate of urea cycle and a key precursor for arginine biosynthesis. We have examined the characteristics of citrulline transport across the everted sacs of the rat small intestine. Our studies suggest that the optimal site of citrulline absorption is middle to lower ileum. It shows active transport, and this transport is predominantly Na+ dependent. Its uptake is significantly inhibited by ouabain, dinitrophenol, sodium azide, and sodium cyanide. Kinetic estimation reveal an apparent substrate concentration at 1/2 maximum velocity of 4.10 +/- 0.86 mM and a Vmax of 18.7 +/- 1.66 mumol/g wet weight tissue/30 min. Analog inhibition studies suggest that citrulline may share the neutral brush border system described for the mucosal brush border membranes of the rabbit jejunum or a system analogous to system ASC described for nonepithelial cells and for basolateral membranes of certain epithelia. In conclusion, the rat small intestine has developed a specific carrier-mediated, Na(+)-dependent pathway for citrulline absorption.

Amino Acids↗

PubMed1987

The roles of haemolymphatic lipoproteins in the oogenesis of Rhodnius prolixus.

The fates of purified 32P-vitellin and 32P-lipophorin were followed in vitellogenic females of Rhodnius prolixus. While the radioactivity from 32P-vitellin 6 hours after injection was found almost exclusively in the ovary, the radioactivity from injected 32P-lipophorin was found distributed among several organs. In the ovary, the radioactivity from 32P-vitellin was associated with the contents of the yolk granules. 32P-lipophorin delivered a great amount of radioactive phospholipids to the ovary with no accumulation of its protein moiety, as observed after its iodination with 131I. The delivery of phospholipids was inhibited at 0 degrees C and by the metabolic inhibitors, sodium azide and sodium fluoride. Comparison of the radioactivity incorporation from 32P-lipophorin with that of 14C-inulin suggests that the 32P-phospholipids from lipophorin are not taken up by fluid phase endocytosis. The data presented here are compatible with the concept of lipophorin as a carrier of lipids in insects and provide evidence that lipophorin transports phospholipids as shown previously for other classes of lipids. The utilization by the oocytes of the phospholipids transported by lipophorin is discussed.

Animals↗

PubMedDate not supplied

[Bicarbonate-stimulated ATP-ase from membranes of rat erythrocytes].

A bicarbonate-stimulating effect on the ATPase activity in membranes of rat erythrocytes depended upon pH, concentration of Mg2+ and HCO3-ions. Sodium azide and sodium thiocyanate distinctly inhibited the ATPase activity; pentachlorphenol and 2,4-dinitrophenol did not change it. Properties of the bicarbonate-stimulated ATPase from erythrocyte membranes were shown to be similar to the properties of the HCO3--ATPases from other cells.

Adenosine Triphosphatases↗

PubMed1992

In vitro stimulation of microsomal diethyl nitrosamine deethylase activity by vitamin K3 (menadione).

Vitamin K3 (menadione) has been found to stimulate diethyl nitrosamine (DEN)-deethylase activity in rat liver microsomes. The vitamin also takes care of the inhibitory effect of the anaerobic conditions as well as those of cytochrome poisons like sodium azide and sodium cyanide, possibly through production of active oxygen species. The enzyme was also stimulated by H2O2 and SOD and inhibited by catalase, thereby suggesting that H2O2 or some derivatives of it may be the active oxygen species involved in the reaction.

Animals↗

PubMed1987

Tyrosinase-catalyzed unusual oxidative dimerization of 1,2-dehydro-N-acetyldopamine.

Tyrosinase, which usually catalyzes the conversion of o-diphenols to o-benzoquinones, catalyzed an unusual oxidative dimerization of 1,2-dehydro-N-acetyl-dopamine to a benzodioxan derivative. The identity of the product was confirmed by UV, IR spectra, and NMR studies. During the oxidation, generation of a transient reactive intermediate could be witnessed by its characteristic visible absorption spectrum. Typical phenoloxidase inhibitors such as phenylthiourea, potassium cyanide, sodium azide, and sodium fluoride drastically inhibited the above reaction. Mimosine, a known competitive inhibitor of o-diphenoloxidase activity, also inhibited the new reaction competitively, suggesting that both the observed oxidative dimerization and the conventional quinone production are catalyzed by the same active site copper of tyrosinase. Based on our earlier findings (Sugumaran, M., and Lipke, H. (1983) FEBS Lett. 155, 65-68; Sugumaran, M. (1986) Biochemistry 25, 4489-4492) that phenoloxidases can produce quinone methides from certain 4-alkylcatechols, possible mechanisms for this new reaction are presented.

Binding Sites↗