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At least 19 recordsLinked to original sources
PubMed1978

Synthesis and analgesic activity of 1,3-dihydro-3-(substituted phenyl)imidazo[4,5-b]pyridin-2-ones and 3-(substituted phenyl)-1,2,3-triazolo[4,5-b]pyridines.

In a study of nonsteroidal antiinflammatory and analgesic agents, a series of 1,3-dihydro-3-(substituted phenyl)imidazo[4,5-b]pyridin-2-ones-and 3-(substituted phenyl)triazolo[4,5-b]pyridines was prepared. Many of the imidazolones were alkylated on the free nitrogen. In a modified Randall-Selitto analgesic assay, the pain thresholds of both the inflamed and normal foot were elevated. This is not commonly observed with nonsteroidal antiinflammatory agents. The most active compounds were 1,3-dihydro-3[3,4-(methylenedioxy)phenyl]imidazo[4,5-b]pyridin-2-one (I-15) and its N-allyl (I-21) and N-isopropyl (I-121) derivatives. In the triazole series the 3-(2-fluoro- and 2,4-difluorophenyl)triazolo[4,5-b]pyridines (T-1 and T-8) were the best. The imidazole compounds were somewhat superior in analgesic activity to codeine and d-propoxyphene without showing any narcotic characteristics. Some of the compounds also possessed activity against carrageenan-induced foot edema in the rat, so these compounds represent a new class of nonnarcotic analgesic antiinflammatories, capable of producing a greater degree of analgesia than that obtainable with other nonsteroidal antiinflammatory agents.

Animals↗
PubMed1979

Some factors involved in the N-oxidation of 3-substituted pyridines by microsomal preparations in vitro.

1. Pyridine-N-oxides have been identified as metabolites in vitro of several 3-substituted pyridines. 2. Factors affecting the metabolism of these pyridines in vitro have been studied, and conditions which give the most metabolism have been established. 3. 'Pyridine-N-oxidase' activity resides mainly in the hepatic and pulmonary microsomal fractions. 4. A species difference was evident with 'pyridine-N-oxidase' activity decreasing in the order hamster, rabbit, mouse, guinea-pig and rat. 5. A sex difference in 'pyridine-N-oxidase' activity was also established in rats and mice. 6. The appropriate kinetic factors, Km and Vmax for the N-oxidation of pyridine, 3-methylpyridine and 3-chloropyridine are reported.

Animals↗
PubMed1978

Regulation of Ca2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides.

Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca(2+) and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca(2+) is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as beta-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca(2+). Successive cycles of Ca(2+) release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca(2+)-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca(2+), mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport.

Adenosine Triphosphate↗
PubMed1978

Pyridine interactions with phenolic groups in water: evidence for hydrogen bonding and hydrophobic association.

Pyridine interactions with phenol, substituted phenol, tyrosine and poly(Glu50,Tyr50) in aqueous solutions have been studied by ultraviolet (UV) difference spectroscopy, spectrophotometric pH titration, circular dichroism (CD) and proton magnetic resonance (PMR) spectroscopy. A red shift and spectral sharpening of the near-UV spectrum of phenol in water was noted at pyridine concentrations greater than 0.25 M. In addition, the spectrophotometric equivalence point for the phenol- or substituted phenol-phenolate equilibrium was increased about 0.5 pH units upon the addition of 1.0 M pyridine. PMR studies were consistent with the formation of a 1 : 1 phenol-pyridine hydrogen bonded complex. The equilibrium constant derived for this interaction, 0.6-0.7 M-1, is greater than the corresponding value for phenol-acetate hydrogen bonding in water. Enhancement of thepyridine hydrogen bond interaction with Tyr within poly(Glu50,Tyr50) was observed at pH greater than 12 due to a hydrophobic microenvironment produced by pyridine molecules intercalating between neighboring tyrosyl residues.

Circular Dichroism↗
PubMed1979

The effect of various potential inhibitors, activators and inducers on the N-oxidation of 3-substituted pyridines in vitro.

1. The N-oxidation of pyridine, 3-methylpyridine and 3-chloropyridine was inhibited by SKF525A and DPEA. The C-oxidation of 3-methylpyridine was also inhibited by these compounds. 2. The N-oxidation of these pyridines was also inhibited by various other nitrogenous substrates including n-octylamine. 3. Incubation in an atmosphere of carbon monoxide resulted in inhibition of both C- and N-oxidation of 3-methylpyridine. 4. Any treatment of microsomes which resulted in a reduction of cytochrome P-450 also produced a concomitant fall in N-oxidation of the pyridines. 5. Pretreatment of animals with phenobarbitone resulted in an increase in the N-oxidation of the pyridines. Pretreatment with 3-methylcholanthrene had no appreciable effect on the N-oxidation of the pyridines in vitro.

Animals↗
PubMed1975

Interaction of Sendai virus with human erythrocytes. III. Further investigation on the effects of pyridine on the virus envelope.

The ultrastructure of the pyridine-treated Sendai virus has further been investigated by electron microscopy of chemically fixed and negatively stained virions. Marked changes in the ultrastructural appearance of the viral envelope have been detected. The extent of these changes depends on pyridine dose and ranges from minor extraction of the outer track components to multiple breaks and disintegration of the whole envelope. At 16% pyridine a fragmentation of viral nucleocapsid has also been noted. Both the nature of these changes and the fact that even fully burst viral particles can eventually retain regularly-arranged spikes, strongly suggest that pyridine primarily affects the organization of the double-track viral membrane, probably by sequential extraction of lipids and protein components. The results are discussed in the light of the selective property of pyridine in discriminating among the biological activities of the Sendai virus and give additional support to the idea that phospholipids and a glycoprotein spike play cooperative roles in the hemolytic activity of the virus.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

Acid-fast properties and pyridine extraction of M. leprae.

The reportedly unique pyridine extractability of acid-fastness as an identifying characteristic for M. leprae was examined in the leprosy bacilli and in eight other strains of mycobacteria. The initial findings were, in general, in accord with previous reports except that M. smegmatis and M. phlei likewise demonstrated two hour pyridine extractability of acid-fastness. Perhaps, more significantly, it was found that this characteristic in M. leprae is related to aged, probably nonviable bacilli. Some other strains of mycobacteria when tested in aged cultures showed the same phenomenon while M. leprae cultivated in vitro in a recently developed medium resisted pyridine extraction up to three weeks of growth, but thereafter as the culture aged pyridine extractability became characteristic. It is concluded that this pyridine extractability of acid-fastness is a characteristic of aging or nonviable bacilli. As such it is not definitive in the determination of whether or not in vitro cultivation of M. leprae has been achieved.

Bacteriological Techniques↗
PubMedDate not supplied

Use of pyridine for differentiating Mycobacterium leprae from other mycobacteria in direct microscopy.

The loss of acid-fastness by M. leprae after two-hour pyridine extractions, reportedly a specific test for differentiating M. leprae from all other mycobacteria, was verified on different materials obtained from leprosy patients, histologic sections from a fatal post-BCG vaccination case and smears prepared from pure cultures of 32 strains of 18 different mycobacterial species. Under the conditions used, pyridine extraction led to complete loss of acid-fastness in M. leprae only in histologic sections of biopsy specimens from leprosy patients, whereas in direct smears from skin lesions containing M. leprae the number of acid-fast rods after pyridine extraction was either equal to or only slightly smaller than in control preparations. Moreover, since smears from pure cultures of M. avium, M. diernhoferi, M. fortuitum, M. scrofulaceum, M. vaccae and especially M. phlei displayed a smaller or greater number of nonacid-fast cells as well (in some instances only 10% to 20% of cells were found stained whereas control slides contained 90% to 100% acid-fast rods), loss of acid-fastness after two-hour pyridine extraction cannot be considered a property typical of M. leprae only.

BCG Vaccine↗
PubMed1975

Pyridine nucleotide metabolism in mitotic cells.

The biosynthesis and turnover of nicotinamide adenine dinucleotide (NAD) have been examined in mitotic cells of the human culture line, D98/AH2. No significant difference in the incorporation of nicotinic acid or nicotinamide could be detected between mitotic and interphase cells. The distribution of newly-incorporated nicotinic acid among the various pyridine nucleotides was also identical in mitotic and interphase cells. Whereas previous results have shown that the nucleus is necessary for NAD biosynthesis, the present results show that an intact nucleus is not required. In contrast to the equivalent rates of biosynthesis in mitotic and interphase cells, the pyridine ring of NAD was lost twice as fast from mitotic as from interphase cells. Loss of the pyridine ring to the medium is not necessarily an accurate measure of turnover, and the difference between mitotic and interphase cells may reflect differential reutilization of the pyridine ring within the cell. However, it is clear that NAD turnover is substantial in mitotic cells and possibly greater in mitotic cells than interphase cells.

Cell Line↗
PubMed1979

Pyridine nucleotide cycle of Salmonella typhimurium: regulation of nicotinic acid phosphoribosyltransferase and nicotinamide deamidase.

Nicotinic acid phosphoribosyl transferase (NAPRTase) and nicotinamide deamidase activities from Salmonella typhimurium were examined regarding their regulation by either feedback inhibition or repression mechanisms. The results indicate that neither enzyme is subject to feedback inhbition. Nicotinamide deamidase does not appear to be under repression control. NAPRTase, however, is repressed when cells are grown in minimal medium supplemented with various intermediates of the pyridine nucleotide cycle. The concentration of exogenously supplied pyridine nucleotide necessary to effect repression of NAPRTas was found to be that concentration which will result in a nadA mutant generation time of less than 60 min. Furthermore, the results presented indicate that nicotinamide adenine dinucleotide is the actual corepressor molecule. The analogs 6-aminonicotinic acid and 6-aminonicotinamide were also capable of repressing NAPRTase, but only when an intact pyridine nucleotide cycl permitted conversion to 6-aminonicotinamide adenine dinucleotide. The role of a repressible NAPRTase is discussed in relation to the overall functioning of the pyridine nucleotide cycle.

Amidohydrolases↗
PubMed1976

Pyridine nucleotide as an indicator of the oxygen requirements for energy-linked functions of mitochondria.

The responses of cardiac mitochondria to anoxia may be evaluated in terms of the oxidation-reduction state of the electron carriers and the ability of the mitochondria to function in energy-linked reactions. The previous detailed evaluation of the oxygen requirements for electron transfer in mitochondria is here extended to the oxygen requirements for energy-linked functions. Four functions are evaluated: the energy-dependent reduction of pyridine nucleotide, the phosphorylation of ADP, the retention of Ca2+, and the establishment of a membrane potential. All of these functions are half-maximally activated with 10-20% oxidation of cytochromes c and a + a3. Fifty percent oxidation of pyridine nucleotide is required for these functions. In a normoxic-anoxic titration, an increment of 50% in the reduction of pyridine nucleotide in intact tissue corresponds to the point at which the mitochondria are half-maximally active in energy coupling. Thus, the use of pyridine nucleotide fluorescence as an optimal indicator of tissue oxidation-reduction states has now been extended to the assay of energy-linked functions of mitochondria in situ in cardiac tissue.

Adenosine Triphosphate↗
PubMed1979

Kinetic and mechanistic studies on the reduction of melilotate hydroxylase by reduced pyridine nucleotides.

The reduction of the melilotate hydroxylase . 2-OH-phenyl propionate complex by NADH and reduced 3-acetyl pyridine adenine dinucleotide (AcPyNADH) has been investigated using steady state kinetic and rapid reaction techniques. Reduction by NADH appeared to involve only one charge-transfer-type intermediate (between reduced enzyme and NAD) as previously described (Strickland, S., and Massey, V. (1973) J. Biol. Chem. 248, 2953-2962). Reduction by AcPyNADH was shown to involve two charge-transfer-type intermediates. The first was between oxidized enzyme and AcPyNADH and the second was between reduced enzyme and AcPyNAD. Reaction of AcPyNADH with oxidized enzyme . 2-OH-phenyl propionate complex to form the first charge-transfer complex reached equilibrium within the mixing time of the stopped flow apparatus (5 ms). Subsequent steps in the reaction appeared to be first order and were independent of the AcPyNADH concentration. An 8-fold deuterium isotope effect on the step involving flavin reduction was found when reduced 3-acetyl[4A-2H]pyridine adenine dinucleotide (AcPyNADD) was used as the reductant. Analysis of the rapid reaction results for the reaction of oxidized pyridine nucleotide with reduced enzyme . 2-OH-phenyl propionate complex indicated the presence of two forms of reduced enzyme (in equilibrium) of which only one form was capable of reacting with the oxidized pyridine nucleotide. Based on the rapid reaction data, a mechanism for the reduction half-reaction is proposed. The turnover number calculated from this mechanism is in good agreement with that determined from the steady state data.

Electron Transport↗
PubMed1977

Characterization of C-4-methylated sterols by pyridine-induced solvent shifts in proton magnetic resonance spectroscopy.

The proton magnetic resonance (PMR) spectra were measured in deuterochloroform (CDC13) and pyridine solutions for some 4-desmethyl, 4alpha-methyl, 4beta-methyl, and 4,4-dimethyl sterols related to 5alpha-cholestane series as well as for their C-3-oxo derivatives. The influence of pyridine, relative to CDC13, on methyl group chemical shifts was discusssed. The technique utilizing pyridine-induced solvent shifts in PMR spectroscopy was found useful in characterizing the individual classes of sterols.

Chloroform↗
PubMed1978

Dehydrative metabolites of 1-(3-chlorophenyl)-1methyl-2-phenyl-2-(2-pyridine)ethanol as potential hypocholesteremic agents.

The E and Z isomers of 2-[2-(3-chlorophenyl)-1-phenyl-1-propenyl]pyridine (2a,b) and 2-[2-(3-chlorophenyl)-1-(4-hydroxyphenyl)-1-propenyl]pyridine (4a,b) were synthesized and separated as possible metabolites of 1-(3-chlorophenyl)-1-methyl-2-phenyl-2-(2-pyridine)ethanol (1a). Following administration of 1a to rats, a HPLC system was used to examine urine and serum specimens for the less polar metabolites of 1a. Isomers 2a and 2b were not detected but their hydroxylated derivatives 4a and 4b were observed as minor metabolites. Compounds 2a,b and 4a,b exhibited hypocholesteremic activity in rats; compounds 4a and 4b are of special interest because they possessed relatively low estrogenicity.

Animals↗