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At least 433 records · Page 24Linked to original sources
PubMed1982

[Properties of metlegoglobin reductase from lupin root nodules].

The interaction between metlegoglobin reductase from lupin root nodules cytosol and some substrates and inhibitors was studied. The Km values for electron acceptors: dichlorophenol indophenol, potassium ferricyanide, methylene blue and cytochrome c were 5.7 x 10(-5), 2.1 x 10(-5), 1.75 x 10(-4) and 2.5 x 10(-5) M, respectively. The Km value for electron donor NADH was 2.4 x 10(-5) M. Hydroxymercurybenzoate and ethylmaleimide inhibited the metlegoglobin reductase activity; the enzyme activity was also inhibited by NAD. Metlegoglobin reductase was inhibited by quinacrine, which confirmed the flavoproteid nature of the enzyme earlier discovered by the authors. Cytochrome b5 from rabbit liver microsomes can be an electron intermediate during cytochrome c reduction by metlegoglobin reductase. The temperature optimum of metlegoglobin reductase is 40 degrees. The enzyme is comparatively thermostable; and was inactivated by 85% only after 5 min heating at 100 degrees.

Animals↗
PubMed1980

Spectrophotometric determination of urea in urine stains on foods and containers.

Urea is extracted from rodent urine-contaminated material with hot acetone. After the extract is evaporated to dryness, aqueous urease solution is added to produce ammonia and carbon dioxide. A blue product, indophenol, is formed by the reaction of ammonia with phenol in the presence of hypochlorite. Absorbance is maximum at 625 nm. Presence of urea is easily detected at 4 microgram. Detection of urine contamination in various materials is compared with detection by the AOAC urease-H2PtCl6 test.

Animals↗
PubMed1994

Effects of anti-ulcer agents on antibiotic activity against Helicobacter pylori.

OBJECTIVE: To investigate the mechanism of action of a series of potential combination therapies for use against Helicobacter pylori. DESIGN: The effects of certain anti-ulcer agents on the antimicrobial activity of antibiotics effective against H. pylori were determined in vitro. METHODS: H. pylori was cultured on Skirrow's agar. Amoxycillin, clarithromycin, erythromycin and tetracycline were used. The anti-ulcer agents studied comprised aluminum chloride, sofalcone [2'-carboxymethyl 4,4'-bis(3-methyl-2-butenyloxy)chalcone] and zinc chloride. Urease activity was measured by the urease-indophenol method. The minimum inhibitory concentration was determined by a plating method, with H. pylori streaked on plates containing various concentrations of the antibiotics plus sublethal doses of the anti-ulcer agents. RESULTS: This in vitro study showed that sofalcone had a direct antibacterial effect and, in addition, inhibited the adhesive property of H. pylori. It did not inhibit the antimicrobial activity of the antibiotics amoxycillin, clarithromycin, erythromycin or tetracycline against H. pylori. The metal ions had inhibitory effects on the antimicrobial activity of amoxycillin, erythromycin and tetracycline, but not on that of clarithromycin. CONCLUSION: This study suggests that sofalcone is a suitable candidate for combination therapy.

Aluminum Chloride↗
PubMed1994

Effects of Cu(II) complexes on photosynthesis in spinach chloroplasts. Aqua(aryloxyacetato)copper(II) complexes.

The inhibitory effect of 14 aqua(aryloxyacetato) copper(II) complexes on oxygen evolution rate in spinach chloroplasts has been investigated. The inhibitory effect of these effectors on photosynthesis was confirmed by Hill reaction as well as by EPR and fluorescence spectroscopies. The results of the EPR study showed that the sites of action of the studied effectors are Z+ and Y+ intermediates at the donor side of the photosystem (PS) 2. The EPR study also showed that another site of action is the oxygen evolving complex, namely its manganese cluster. The above suggestions were supported by the results of the fluorescence study as well. Based on the restoring of the photosynthetic electron transport to 2,6-dichlorophenol-indophenol in chloroplasts inhibited by the studied Cu(II) complexes using sym-diphenylcarbazide it can be assumed that the own core of PS2 (P680) and a part of the electron transport chain-at least up to plastoquinone-remain intact.

Chloroplasts↗
PubMed1994

Purification and characterization of hepatic microsomal NADPH cytochrome c reductase from rhesus monkey (Macaca mulatta).

Hepatic microsomal NADPH cytochrome c reductase from nonhuman primate (Macaca mulatta) has been purified 76 fold by the combination of anion exchange, affinity and molecular sieve chromatographies. The purified preparation had approximate molecular wt of 63 kDa and carried out NADPH oxidation, cytochrome c reduction, 2,6-dichlorophenol indophenol (DCIP) reduction and production of superoxide anions (O2-.). The enhancement in NADPH cytochrome c reductase catalyzed NADPH oxidation by metal chelators viz. ethylenediaminetetra-acetic acid (EDTA)-FeCl3 and diethylenetriaminepenta-acetic acid (DTPA)-FeCl3 was dramatically higher than the enhancement in the reduction of cytochrome c and DCIP. DTPA-FeCl3 was found to be more potent stimulator of NADPH oxidation as compared to EDTA-FeCl3, but both had similar potency as for reduction of cytochrome c and DCIP were concerned. Superoxide dismutase (SOD) decreased EDTA-FeCl3 enhanced reduction of cytochrome c by 15%, but had no effect on the NADPH oxidation and DCIP reduction, whereas it significantly enhanced DTPA-FeCl3 stimulated NADPH oxidation, decreased cytochrome c reduction by 8% and did not affect DCIP reduction. In addition, SOD almost completely blocked the NADPH cytochrome c reductase catalyzed superoxide anion production. The results demonstrate that like rodents and lagomorphs, the hepatic microsomal NADPH cytochrome c reductase in nonhuman primate, Macaca mulatta can carry out single electron reduction of molecular oxygen.

Animals↗
PubMed1975

Microperoxisomes in retinal pigment epithelium.

Microperoxisomes were found to be abundant in the retinal pigment epithelium of the human, rhesus monkey, mice, rats, domestic fowl, and frog by ultrastructural histochemistry. They were rare in other cells of the retina and choroid. These organelles had a granular matrix, ranged in diameter from 0.15 mum to 0.30 mum, and were bound by a single tripartite membrane which often maintained slender connections with the smooth endoplasmic reticulum and other microperoxisomes. They exhibited a positive reaction (electron opaque product) following incubation in diaminobenzidine and H2O2 for the demonstration of the peroxidatic activity of catalase (Novikoff et al., J. Histochem. Cytochem. 20: 1006, 1972). The reaction was inhibited by: (1) aminotriazole; (2) dichlorophenol-indophenol; (3) preheating at 95 degrees C.; or (4) elimination of H2O2. Microperoxisomes, like the well-known peroxisomes (microbodies) of liver cells have been inplicated in various aspects of lipid metabolism and the detoxification of H2O2. We demonstrated for the first time that microperoxisomes respond to drug-induced changes in lipid metabolism, as previously shown for peroxisomes. Nafenopin is a recently utilized drug which greatly decreases serum lipids, increases hepatic catalase activity, and induces an increased size and number of hepatic peroxisomes. Black, beige, albino, and obese mutant mice of the C57BL/6J strain treated with nafenopin for several weeks showed a two- to threefold increase in the number of microperoxisomes in the retinal pigment epithelium. Microperoxisomes of the retinal pigment epithelium may be involved in the transport, storage, and rapid turnover of lipids associated with the maintenance of photoreceptor outer segment disc membranes.

Adult↗
PubMed1977

Semiautomated method for the fluorometric determination of total vitamin C in food products.

A simple method employing simultaneous extraction and oxidation has been developed for the semiautomated determination of ascorbic and dehydroascorbic acids in food products. Recovery studies were conducted on ready-to-eat breakfast cereals and both fresh and canned fruits and vegetables, with average recoveries of 101, 100, and 102%, respectively. Reproducibility data were generated showing a relative standard deviation of 3.5%. The automated method was compared with the manual AOAC fluorometric method and with indophenol titration; correlation coefficients were 0.9960 and 0.9926, respectively. The hydrolysis product of dehydroascorbic acid, 2,3-diketogulonic acid, a reported interference in this method, was prepared and shown not to form an interfering fluorescent derivative.

Ascorbic Acid↗
PubMed1993

The use of trehalose-stabilized lyophilized methanol dehydrogenase from Hyphomicrobium X for the detection of methanol.

The enzyme methanol dehydrogenase (EC 1.1.99.8) from Hyphomicrobium X was used in an attempt to develop a rapid colorimetric test for methanol. The enzyme was stabilized for storage by lyophilization in the presence of the disaccharide trehalose. It was found that the enzyme retained significantly greater activity in the dried state with trehalose than without. The enzyme was partially purified by ammonium sulphate fractionation, after which it was found to be more stable in solution at pH 9 than at pH 7. A procedure is given which involves mixing a defined amount of enzyme with the methanol-containing water together with phenazine methosulphate (PMS), 2-6-dichlorophenol-indophenol (DCPIP) and cyanide, and observing the resultant colour change from blue to yellow if methanol is present. The sensitivity of the procedure is such that 9 mg L-1 of methanol can be readily detected.

2,6-Dichloroindophenol↗
PubMedDate not supplied

[Different aspects of the substrate specificity of the cholinesterase in the optical ganglia of the Pacific Ocean squid Todarodes pacificus].

It is the first time when the substrate specificity is considered as a complex phenomenon, taking into account an influence of substrate structure on the rate of enzymatic hydrolysis and interaction of cholinesterases with reversible and irreversible inhibitors. Kinetic parameters of hydrolysis of 18 esters, including choline, ammonium and indophenol derivates, are presented, as affected by cholinesterase from optical ganglia of pacific squid Todarodes pacificus, by acetylcholinesterase from human erythrocytes and by butyrylcholinesterase from horse serum. Some peculiarities of the squid cholinesterase are revealed, which are as follows: a low specificity at a rather high hydrolytic efficiency, the sensitivity towards inhibitory effects of several substrates at high concentrations. Reversible inhibition of the squid enzyme by ammonium inhibitors was dependent on the nature of substrates to a greater extent than that of the other enzymes. The substrate structure also conditioned various aspects of "the protective effect" in the course of irreversible inhibition of the squid cholinesterase by organophosphorous inhibitors.

Animals↗
PubMed1997

[An experimental study of infection stone formation by Corynebacterium species].

The relationship between infection stone and Corynebacterium species was investigated in vitro and in vivo. Urease activity of urease-splitting Corynebacterium species was evaluated by 2 methods; an increase in pH of human urine after inoculation of Corynebacterium species and direct measurement of urease activity of 10(7) CFU organisms from amounts of ammonia by indophenol method. Formation of infection bladder stone was induced in male Wistar rats by implanting a zinc disc and inoculating 10(6) CFU organisms surgically into the bladder. Urine was alkalinized by the inoculation of Corynebacterium renale, C. pilosum and group D2 Corynebacterium. C. renale and C. pilosum had strong urease activity, and group D2 Corynebacterium had moderate activity. C. pseudodiphtheriticum did not produce the elevation of urinary pH and had little urease activity. Infection stones were formed in 100% of rats by inoculation of C. renale and C. pilosum and 88% of rats by group D2. Urinary pH was elevated in all inoculated rats. In conclusion, C. renale, C. pilosum and group D2 Corynebacterium may play a role in formation of infection stones.

Animals↗
PubMed1997

Reverse-micelle model: pH, electromagnetic field and inhibitor enzyme interaction.

The reverse micelle is one of many models thought to have properties more nearly resembling the biological cellular environment, than does the traditional dilute-solution biochemical reaction system. In order to evaluate the results of EMF perturbation of enzyme-catalyzed reactions, the description of the AOT reverse-micelle model, with respect to its internal pH, effect of chemical inhibitors, temperature, and electromagnetic-field perturbation has herein been extended. Acetylcholinesterase and NADPH cytochrome-P450 reductase, reacting within the AOT reverse-micelle, exhibit a temperature vs. activity profile equivalent to the same reaction in a buffered dilute-solution environment. In reverse micelles, some inhibitors of AChE (propidium, and d-tubocurarine) have much less effect upon indophenol-acetate hydrolysis than they do in a dilute solution environment. Other inhibitors act in the same manner within the structured environment of the reverse micelle as in the conventional dilute solution reaction model. These differences are explicable in terms of mechanism of action of the individual inhibitors. Perturbation by low-intensity microwave fields has a similar inhibitory effect upon dilute-solution reactions, as those in the 'low-water-activity' environment of the reverse micelle. However, the interactions between physical and chemical perturbants are differently limited by the structure of the aqueous phase of the reverse micelle. pH of the 'internal' reverse-micelle environment is a function of the availability of H-ions supplied by system components. Use of indicator dyes show that the low-molarity buffers which are compatible with reverse-micelle stability, are often insufficient to maintain a constant pH. Too, in the reverse micelle, reaction rate, for proton yielding reactions, is dramatically greater than the rate of the same reaction in dilute solution at the same acidic pH.

Animals↗
PubMedDate not supplied

[Effect of C-4'-modification of thiamine pyrophosphate on its coenzyme activity in the oxidative decarboxylation of pyruvic acid reaction].

Interaction was studied between pyruvate dehydrogenase (EC 1.2.4.1) and C-4'-substituted analogs of thiaminpyrophosphate, 4'-N (CH3)-TPP, 4'-N(CH3)2-TPP and OH-TPP. None of these analogs was found to replace TPP during the reduction of NAD and 2.6-dichlorophenol-indophenol as well as pyruvate decarboxylation. The decarboxylase activity of the pyruvate dehydrogenase component isolated from the pyruvate dehydrogenase complex was determined according to the 14CO2 yield and production of 2-C-oxoethyl-TPP using 1-14C-pyruvate and 2-14C-pyruvate, as substrates, respectively. All the analogs were found to competitively inhibit pyruvate dehydrogenase, Ki values for 4'-N(CH3)-TPP, 4'-N(CH3)2-TPP and 4'-OH-TPP being 4.1 X 10(-5) M, 8.5 X 10(-5) M and 2.9 X 10(-6) M, respectively; Km values for TPP was equal to 1-2 X 10(-7) M. It is assumed that the analogs of the holoenzymic complex formed by the pyruvate dehydrogenase component of the pyruvate dehydrogenase complex with mono-, dimethyl-TPP and oxo-TPP do not bind the substrate.

Animals↗