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At least 19 recordsLinked to original sources
PubMed1977

Inhibition of carcinogenic effects of polycyclic hydrocarbons by benzyl isothiocyanate and related compounds.

Benzyl isothiocyanate and phenethyl isothiocyanate, two compounds found in cruciferous plants, and phenyl isothiocyanate, a synthetic compound, all inhibit 7,12-dimethylbenz[a]anthracene (CMBA)-induced mammary tumor formation in female Sprague-Dawley rats when administered 4 hours prior to the DMBA. Comparable studies in which benzyl isothiocyanate was administered 24 hours before or 4 hours after DMBA showed almost complete loss of inhibition. Additions of benzyl isothiocyanate or phenethyl isothiocyanate to a diet containing CMBA inhibited formation of neoplasms of the forestomach and pulmonary adenomas in female ICR/Ha mice. Addition of benzyl isothiocyanate to a diet containing benzo[a]pyrene also inhibited carcinogenesis of the mouse forestomach due to this carcinogen. The finding of two additional anutrient dietary compounds which inhibit chemical carcinogenesis focuses on the possibility that dietary constituents of this nature may diminish the impact of exposures to chemical carcinogens.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Inhibition of separated forms of phosphodiesterases from pig coronary arteries by uracils and by 7-substituted derivatives of 1-methyl-3-isobutylxanthine.

A series of 7-substituted 1-methyl-3-isobutylxanthines was designed in an attempt to increade the specificity of the 1-methyl-3-isobutylxanthine (MIX) structure for one of the two cyclic nucleotide phosphodiesterase peaks isolated by DEAE-cellulose chromatography of the soluble fraction of the intima + media layer of pig coronary arteries. A series of 1,3-dialkyluracils was of low potency as inhibitors of either peak I or peak II. The 7-substituted xanthines were prepared by alkylation of MIX with the corresponding alkyl or aralkyl halide in DMF containing K2CO3. These compounds were, in general, much less potent inhibitors of peak II activity than was MIX, but some of them retained the potency of MIX as inhibitors of peak I and, therefore, were relatively specific for inhibition of peak I. 7-Bzl-MIX was the most selective compound tested; it was a potent inhibitor of peak I activity but was much less effective as an inhibitor of peak II activity. Substitution of either electron-withdrawing (nitro) or electron-donating (methoxy) groups on the 7-benzyl moiety reduced the effectiveness of the 7-benzyl compounds as inhibitors of peak I. Chlorobenzyl substitution increased the potency slightly over the benzyl but not the selectivity between peaks.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

[Effect of thiol-oxidizing agents on several enzymes in rat liver mitochondria].

The sulphydryl groups of nonprotein thiols and proteins of mitochondria, activity of enzymes, oxidative phosphorylation and swelling of these organellas were studied as affected by the thiol-oxidizing agents. Diamide and azoester are shown to oxidize SH-groups of mitochondria, inhibit isocytrate dehydrogenase and succinate: cytochrome oxidation and inhibits energy-dependent swelling of mitochondria. Under the effect of azoester the rate of oxygen consumption by mitochondria increases and there occurs their sharp swelling.

Animals↗
PubMed1977

Chemical modification of cellulase from Aspergillus niger.

N-Bromosuccinimide completely inactivated the cellulase, and titration experiments showed that oxidation of one tryptophan residue per cellulase molecule coincided with 100% inactivation. CM-cellulose protected the enzyme from inactivation by N-bromosuccinimide. The cellulase was inhibited by active benzyl halides, and reaction with 2-hydroxy-5-nitrobenzyl bromide resulted in the incorporation of 2.3 hydroxy-5-nitrobenzyl groups per enzyme molecule; one tryptophan residue was shown to be essential for activity. Diazocarbonyl compounds in the presence of Cu2+ ions inhibited the enzyme. The pH-dependence of inactivation was consistent with the reaction occurring with a protonated carboxyl group. Carbodi-imide inhibited the cellulase, and kinetic analysis indicated that there was an average of 1 mol of carbodi-imide binding to the cellulase during inactivation. Treatment of the cellulase with diethyl pyrocarbonate resulted in the modification of two out of the four histidine residues present in the cellulase. The modified enzyme retained 40% of its original activity. Inhibition of cellulase activity by the metal ions Ag+ and Hg2+ was ascribed to interaction with tryptophan residues, rather than with thiol groups.

Aspergillus niger↗
PubMed1977

The nature of the rate-limiting step in aniline hydroxylation involving cytochrome p-450 rat liver microsomes.

The kinetics of aniline hydroxylation was studied with: (1) rat liver microsomes involving NADPH and O2 (system 1), (2) hepatic microsomes and tert-butylhydroperoxide (system 2) and (3) microsomes and cumyl hydroperoxide (system 3) at 15--37 degrees C. The reactions were characterized by the values of the aniline oxidation rate constants, k2 = V/E0, where E0 is the initial concentration of cytochrome P-450: K 1/2 = 1.60 - 10(8) EXP (-13 400/RT) sec-1, k 2/2 = 1.66 - 10(9) exp (-14 500/RT) sec-1, k 3/2 = 6.83 - 10(9) exp (-15 300/RT) sec-1. The values of delta H0 and delta S0, were calculated and compared for the three systems. The evidence suggests that oxygen insertion into the substrate molecule is the rate-limiting step in the reaction of aniline oxidation for the mentioned systems. The nature of aniline binding to cytochrome P-450 and that of the hydroxylating agent have been discussed.

Aniline Compounds↗
PubMed1975

Synthesis of threo-4,5-dihydroxy diastereomers of sphinganine;.

The threo-4,5-dihydroxy diastereomers of sphinganine were prepared by the following sequence of reactions: (a) benzoylation of sphingenine to the tribenzoyl derivative; (b) osmylation followed by resolution of the mixture of threo-4,5-dihydroxy tribenzoyl (DHTBS) diastereomers; and (c) alkaline hydrolysis to yield the threo-4,5-dihydroxysphinganines (DHS). Carbon atoms 4 and 5 of the high and low melting threo-4,5-DHTBS diastereomers and the compounds derived from them were tentatively assigned 4R, 5S and 5R configurations, respectively;

Amino Alcohols↗
PubMed1975

Fluorimetric determination of dipeptidyl carboxypeptidase. (angiotensin-I-converting enzyme).

A fluorimetric assay of dipeptidyl carboxypeptidase is described. It involves incubation at 37 degrees C with the substrate, Z-Phe-His-Leu, and reaction of the dipeptide His-Leu which is released upon enzymatic hydrolysis, with o-phthalaldehyde to yield a fluorescent compound. The method is simple, precise and sensitive. The assay in serum is conveniently performed on 20 mul samples. Normal values in human serum range from 0.04 to 0.22 U/l.

Benzyl Compounds↗
PubMed1979

Arprinocoid evaluation in broiler chicken pen trials in Europe.

The effect of arpinocid (9-[2-chloro-6-fluorophenyl)methyl]-9H-purin-6-amine) on artificial and natural coccidial infections in broiler chickens was evaluated in a series of pen trials conducted in England, France, and Germany. In trials with induced infections, mortality attributable to coccidiosis did not occur at 50, 60, and 70 ppm although it ranged from 3.2 to 9% in unmedicated groups. At 7 to 8 weeks of age, birds receiving arprinocoid in feed at levels of 40, 50, 60, and 70 ppm had improved body weights and feed conversion compared with unmedicated birds, the differences being significant (P is less than .05) in 4 out of 5 trials. Productivity of birds on arprinocid was equivalent or significantly superior (P is less than 0.5) to those on halofuginone (3 ppm), monensin (100 ppm), nicarbazin (125 ppm), and PANCOXIN (165 ppm). Based on the results of these pen trials, arprinocid at levels of 50 to 70 ppm in feed is a highly efficacious compound for the prophylaxis of coccidiosis, preventing mortality, and permitting good growth and feed conversion under conditions of both mild and severe infection pressure.

Adenine↗
PubMed1979

[Oxidative degradation of dibenzylsulfide].

Dibenzylsulfid (DBS) as a model of the organic sulfur compounds in crude oil was converted by a mixed culture (containing Pseudomonas aeruginosa) into several water soluble organic substances. Whereas these compounds are detectable with DC- and IR-spectroscopic techniques, benzylmercaptoacetic acid (BMA) was the only isolated product of DBS utilization. Efficiency of degradation, respectively, accumulation of BMA were dependent on aeration and pH-regulation.

Acetates↗
PubMed1978

Affinity chromatography of trypsin and related enzymes. V. Basic studies of quantitative affinity chromatography.

A detailed study of the quantitative affinity chromatography of trypsin [EC 3.4.21.4] is reported here. Frontal chromatography using an enzyme solution of very low concentration on an affinity adsorbent gave the dissociation constant of the enzyme-immobilized ligand complex (Kd). Kd values determined under various conditions enabled us to discuss in detail the interaction of trypsin and affinity adsorbents (mainly Gly-Gly-Arg Sepharose). The pH dependence of Kd was consistent with that of the interaction of trypsin and product-type compounds. The effects of changes in temperature, ionic strength, dielectric constant, etc., were also studied. The Ki values of soluble competitive inhibitors can be determined by analysis of their effects on the elution volume of the enzyme. The values obtained were in good agreement with those obtained by kinetic analysis. The present method proved to be useful as a general procedure to investigate the interaction of a protein and a specific ligand.

Arginine↗
PubMed1979

[Comparative investigations on the organotropic carcinogenic effect of different N-nitroso compounds with rat after single and chronic treatment (author's transl)].

After the gavage of 200 mg N-nitrosodiethylamine per kg body weight only kidney tumors developed while long-term administration of 10 ppm N-nitrosodiethylamine induced esophageal tumors and hepatocellular carcinomas in female rats (SIV 50). This change of the organ-specific carcinogenic effect is not observed in experiments with N-methyl-N-nitrosobenzylamines substituted with a methyl group at the phenyl moiety. Both chronic treatment and single doses induced tumors of the esophagus and the pharynx.

Animals↗
PubMed1975

A pharmacologic comparison of histamine receptors in isolated extracranial and intracranial arteries in vitro.

Isolated segments of cat extracranial and intracranial arteries were tested simultaneously for circular motor activity in an aerated Krebs-Ringer organ bath at constant temperature and pH. Histamine produced a strong contraction (about 850 dyn) in the extracranial arteries but a considerably weaker contraction, with a high half maximum response, in the intracranial arteries. The mode of inhibition of the latter response by antihistaminic compounds (chlorpheniramine and mepyramine) showed the response to be nonspecific; the contraction in the extracranial arteries was inhibited in a competitive manner, demonstrating the presence of histamine H1 receptors. The dilatory response was studied after the vessels had been given a tonic contraction with serotonin. Histamine produced similar dilatory effects (about 200 dyn) in both types of arteries and competitive inhibitions were obtained with burimamide, showing that the dilation was mediated through histamine H2 receptors. Dissociation constants were calculated for the receptor-antagonist complex.

Animals↗
PubMedDate not supplied

The metabolic disposition of [14C]pivhydrazine, [14C]mebanazine, and [14C]benzylhydrazine in the rat.

The hydrazine drugs, [14C]pivhydrazine and [14C]mebanazine and the related compound [14C]benzylhydrazine were readily absorbed from the rat gut and the radioactivity was excreted mainly in urine. The major urinary metabolite of pivhydrazine and benzylhydrazine was [14C]hippuric acid, whereas mebanazine was shown to be excreted largely unchanged. Biliary excretion (21 and 24%, respectively) of radioactive material was observed after administration of [14C]pivhydrazine and [14C]mebanazine to bile duct-cannulated rats but only small amounts (approximately 3%) were excreted in bile after [14C]benzylhydrazine administration. The major biliary metabolites of pivhydrazine and mebanazine are acid-labile conjugates, possibly N-glucuronides. In vitro studies with rat liver homogenate suggest that benzylhyrazine may be an intermediate in the metabolism of pivhydrazine. The distribution of radioactivity in the rat 7 days after the administration of [14C]pivhydrazine and [14C]pivhydrazine and [14C]mebanazine is described.

Animals↗
PubMed1979

Quantitative analysis of tiamenidine in human plasma by gas chromatography mass spectrometry of a dibenzyl derivative.

A gas chromatography mass spectrometry method has been developed and evaluated for the quantitative analysis of tiamenidine in plasma. Tiamenidine and internal standard are extracted from basified plasma, converted to dibenzyl derivatives by reaction with benzyl bromide and potassium t-butoxide in the presence of 18-crown-6 ether prior to analysis by selected ion monitoring. The method can be used over the range 0.2--10 ng ml-1 with a coefficient of variation of better than 20% at 1 ng ml-1.

Alkylation↗