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At least 937 records · Page 52Linked to original sources
PubMed2001

Analgesic and toxic effects of neonicotinoid insecticides in mice.

Several nicotinic agonists with the 6-chloro-3-pyridinyl moiety are potent insecticides (e.g., the neonicotinoids imidacloprid and thiacloprid) while others are candidate nonopioid and nonantiinflammatory analgesics (i.e., epibatidine and several heterocyclic analogs). This study examines the hypothesis for the first time that the neonicotinoid insecticides and their imine metabolites and analogs display analgesic (antinociceptive) activity or adverse toxic effects associated with their action on binding to the alpha 4 beta 2 nicotinic acetylcholine receptor (AChR) subtype. Seven 6-chloro-3-pyridinyl compounds were studied, i.e., imidacloprid and thiacloprid, the corresponding imines and an olefin derivative, a nitromethylene analog, and (+/-)-epibatidine. Like (-)-nicotine and carbachol, they all act as full agonists in the (86)rubidium ion efflux experiment with intact mouse fibroblast M10 cells stably expressing the alpha 4 beta 2 nicotinic AChR. Their agonist action is correlated with binding affinity to the alpha 4 beta 2 receptor from M10 cells. Imidacloprid, thiacloprid, and their imine analogs are not antinociceptive agents in mice by abdominal constriction and hot plate analgesic tests. Their agonist actions at the alpha 4 beta 2 receptor correlate instead with their toxicity. Surprisingly, the nitromethylene analog, a weak agonist, is as potent as (-)-nicotine in inducing antinociception, and the effect persists longer than that caused by (-)-nicotine. However, mecamylamine (1 mg/kg) prevents antinociception induced by (-)-nicotine but not by the nitromethylene analog. Interestingly, this nitromethylene neonicotinoid insecticide gives 80-100% mortality within 15 min at 3 mg/kg with mecamylamine pretreatment at 2 mg/kg, doses at which each agent alone gives no lethality. Therefore, analgesic and toxic effects of the nitromethylene analog differ in their mechanism of action from (-)-nicotine and (+/-)-epibatidine.

Analgesics, Non-Narcotic↗
PubMed1975

[Nitroblue-tetrazolium test in isolated human monocytes].

Depending upon the NBT charge 50 to 80% of isolated non stimulated human monocytes reduce NBT ro morphologically demonstrable Formazan. Similar to neutrophils two different patterns of reaction are exhibited: discrete load with finely distributed Formazan granula surrounding the nucleus; massive reaction with large distributed Formazan granula surrounding the nucleus; massive reaction with large Formazan deposits throughout the cytoplasma. In a low percentage morphologically desintegrated, massive loaden cells appear. After an additional incubation in medium without NBT the number of these necrotic cells increases. The phagocytosis of IgG-coated red cells is impaired after incubation of the monocytes in NBT. In the presence of an alkylating agent not only the NBT-reaction is inhibited; the number of necrotic cells is also diminished. Apparently the Formazan is cytotoxic. The significance of these results in particular in cases of enhanced NBT reduction is discussed. Compared with the findings of other authors concerning the neutrophils the monocytes possess a markedly stronger NBT reducing activity. Considering the lower bactericidal capacity of the monocytes NBT reduction does not in every case parallel bactericidal activity.

Antineoplastic Agents↗
PubMed1995

Acceleration of nitric oxide (NO) release from FK409, a spontaneous NO releaser, in the presence of sulfhydryl-bearing compounds.

PURPOSE: Recently, we have reported that FK409 spontaneously releases nitric oxide (NO) in solution. In the present study, the influence of L-cysteine (Cys) and glutathione (GSH), which are typical sulfhydryl group-bearing compounds, on NO release from FK409 and biological action of FK409 was examined. METHODS: We evaluated the effects of Cys and GSH on NO release from FK409 by nitrite analysis or detection with a chemiiluminesence analyzer. In a biological study, the influence of Cys on inhibition of rat platelet aggregation of FK409 was investigated. In addition, the above mentioned characteristics of FK409 were compared with those of isosorbide dinitrate (ISDN). RESULTS: FK409 decomposed spontaneously with generation of nitrite in solution. Both Cys and GSH accelerated decomposition of FK409 and nitrite generation from FK409 in a concentration-dependent manner. When the NO levels in the headspace of FK409 solutions (0.5 mM) reached equilibrium with and without 25 mM Cys, the constant rate for NO release from FK409 in the presence of Cys was 13 times larger than that in the absence of Cys. In biological study, FK409 (100 microM) showed 56 and 90% inhibition of rat platelet aggregation in the absence and presence of 10 mM Cys, respectively, whereas ISDN (100 microM) showed 10 and 23% inhibition, respectively. CONCLUSIONS: Decomposition of FK409 with generation of NO is spontaneous, and is accelerated in the presence of sulfhydryl group-bearing compounds, thereby potentiating the biological action of FK409.

Animals↗
PubMed1980

New compounds: derivatives of fluorene XXXVII: 9-substituted 3-nitrofluorenes.

New 9-substituted 3-nitrofluorenes were prepared as potential intermediates in a study of modified electrophilicity and mutagenicity of the carcinogen 3-N,O-diacetylhydroxylaminofluorene. The reported derivatives, together with some already known 9-substituted 3-nitrofluorenes, were too unstable to survive the reducing conditions required to transform the nitro group to the corresponding hydroxylamine.

Carcinogens↗
PubMed2005

Biorational insecticides: mechanism and cross-resistance.

Potency and cross-resistance of various biorational insecticides, exemplified by the whitefly Bemisia tabaci, have been studied. Bemisia tabaci were exposed to the juvenile hormone mimic pyriproxyfen for the past 12 years resulting in an over 2,000-fold resistance, but there was no appreciable cross-resistance with the benzoylphenyl urea novaluron. Similarly, no cross-resistance was found between pyriproxyfen and the two neonicotinoids, acetamiprid and imidacloprid. On the other hand, a slight cross-resistance of 5-13-fold was observed with another neonicotinoid thiamethoxam. Among the neonicotinoids, a resistant strain of B. tabaci to thiamethoxam (approximately 100-fold) showed no appreciable cross-resistance to either acetamiprid or imidacloprid, while another strain 500-fold resistant to thiamethoxam resulted in a mild of 4-6-fold resistance to acetamiprid and imidacloprid. In other assays, B. tabaci strain resistant to thiamethoxam (approximately 100-fold) had no cross-resistance to pyriproxyfen. Our findings indicate that no appreciable cross-resistance was observed between the benzoylphenyl urea novaluron, the juvenile hormone mimic pyriproxyfen, and the neonicotinoids acetamiprid and imidacloprid. Hence, these compounds could be used as components in insecticide resistance management programs.

Animals↗
PubMed1985

Activation and inactivation of a variety of mutagenic compounds by the reconstituted system containing highly purified preparations of cytochrome P-450 from rat liver.

Six cytochrome P-450 preparations from phenobarbital (PB)-treated rats and two preparations from beta-naphthoflavone (BNF)-treated rats were purified. Using Salmonella typhimurium TA98 the ability of these cytochrome P-450 preparations to mutagenically activate and inactivate a variety of carcinogens was examined. High- and low-spin forms of cytochrome P-448 isolated from BNF-treated rats (BNF-IIa and IId) activated various carcinogens. Both forms activated 2-aminofluorene, benzo[a]pyrene, and dibenz[a,c]anthracene. However, o-aminoazotoluene and 2-nitrofluorene were activated only by the low-spin form, and aflatoxin B1 only by the high-spin form. In contrast, only limited carcinogens were activated by some preparations from PB-treated rats. 2-Aminofluorene was activated by four PB-inducible preparations (PB-Ia, Ic, Id, and IIa), but only moderately. Unexpectedly, however, the most prominent activation of benzo[a]pyrene was observed with one preparation (PB-Id) from PB-treated rats. Direct mutagens to the S. typhimurium, 4-NQO and AF-2, were markedly inactivated by NADPH-cytochrome c (P-450) reductase without cytochrome P-450. One PB-inducible form (PB-Ic) inactivated 2-nitrofluorene, and the high-spin form of P-448 (BNF-IIa) inactivated AF-2.

Aflatoxin B1↗
PubMed2006

Activity of and initial mechanistic studies on a novel antileishmanial agent identified through in silico pharmacophore development and database searching.

A 3D pharmacophore was generated to describe the antileishmanial activity of dinitroaniline sulfonamides by CATALYST 3D-QSAR methodology, and this pharmacophore was used to search the Maybridge database. Two compounds identified in this search, BTB 06237 and BTB 06256, were highly active with IC(50) values against L. donovani amastigotes of 0.5 +/- 0.2 and 2.3 +/- 0.8 microM, respectively. BTB 06237 also reduced parasite burdens in L. mexicana-infected J774 macrophages at low micromolar concentrations. Unlike the dinitroaniline sulfonamides, the active compounds did not display antimitotic effects against Leishmania. Transmission electron microscopy showed that the single parasite mitochondrion becomes dilated following incubation with BTB 06237, and fluorescence microscopy demonstrated that this organelle fragments into intensely staining spheres when treated with a mitochondrion-specific dye. The mitochondrial membrane potential was also dissipated in BTB 06237-treated parasites. These results indicate that BTB 06237 is an intriguing antileishmanial lead compound that likely interferes with mitochondrial function.

Aniline Compounds↗
PubMed1980

Effect of diet and Lactobacillus acidophilus supplements on human fecal bacterial enzymes.

The effect of diet and Lactobacillus acidophilus supplements on fecal microflora enzyme activity was studied in humans. The bacterial enzymes that were investigated are known to catalyze reactions that may result in formation of proximal carcinogens. Compared to vegetarians, omnivores eating a "Western-type" diet had higher levels of beta-glucuronidase, nitroreductase, azoreductase, and steroid 7-alpha-dehydroxylase in their fecal microflora. Removal of red meat or addition of fiber in the form of bran or wheat germ to the diet of omnivores for 30 days had no effect on beta-glucuronidase, nitroreductase, or azoreductase activity. However, removal of red meat or addition of fiber reduced fecal steroid 7-alpha-dehydroxylase activity. The addition of viable Lactobacillus acidophilus supplements to the diet of omnivores significantly decreased fecal bacterial beta-glucuronidase and nitroreductase activities. Thirty days after Lactobacillus supplements were curtailed, fecal enzyme levels returned to normal base-line activities. These findings suggested that the metabolic activity of the fecal microflora was influenced by diet and could be altered by Lactobacillus supplements and to a lesser extent by dietary fiber.

Adult↗