Search results for "cyclic"
showing 10 items of 2439 documents
Lymphatic absorption of phytosterol oxides in rats
1999
Two of the main classes of oxyphytosterols (7-keto and epoxides) were synthesized from sitosterol and campesterol and given to mesenteric duct-cannulated adult male rats. Lymph was collected during 24 h and was analyzed for oxysterols. The results showed that the lymphatic recovery of the phytosterol oxides was low: 4.7% of the given dose for epoxy derivatives and 1.5% for 7-keto compounds. The campesterol oxides presented a better absorption than the sitosterol oxides. During the process of absorption, the epoxyphytostanols were also partly transformed in campestanetriol and stigmastanetriol.
Rat liver endothelial and Kupffer cell-mediated mutagenicity of polycyclic aromatic hydrocarbons and aflatoxin B1.
1990
The ability of isolated rat liver endothelial and Kupffer cells to activate benzo(a)pyrene (BP), trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene (DDBP), trans-1,2-dihydroxy-1,2-dihydrochrysene (DDCH), and aflatoxin B1 (AFB1) to mutagenic metabolites was assessed by means of a cell-mediated bacterial mutagenicity assay and compared with the ability of parenchymal cells to activate these compounds. Endothelial and Kupffer cells from untreated rats were able to activate AFB1 and DDBP; DDBP was activated even in the absence of an NADPH-generating system. Pretreating the animals with Aroclor 1254 strongly enhanced the mutagenicity of the dihydrodiol, whereas the mutagenicity of AFB1 showed a sligh…
Interspecies differences in cancer susceptibility and toxicity.
1999
One of the most complex challenges to the toxicologist represents extrapolation from laboratory animals to humans. In this article, we review interspecies differences in metabolism and toxicity of heterocyclic amines, aflatoxin B1, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and related compounds, endocrine disrupters, polycyclic aromatic hydrocarbons, tamoxifen, and digitoxin. As far as possible, extrapolations to human toxicity and carcinogenicity are performed. Humans may be more susceptible to the carcinogenic effect of heterocyclic amines than monkeys, rats, and mice. Especially, individuals with high CYP1A2 and 3A4 activities and the rapid acetylator phenotype may be expected to have …
Mechanisms involved in the chemoprevention of flavonoids
2001
Flavonoids, widespread in edible plants, have been studied extensively for their anticarcinogenic properties. However, only few studies have been done with these constituents being administered by the dietary route. In our research, the effects of feeding rats with flavone, flavanone, tangeretin, and quercetin were investigated on two steps of aflatoxin B1 (AFB1)-induced hepatocarcinogenesis (initiation and promotion). Nonpolar flavonoids such as flavone, flavanone and tangeretin administered through the initiation period, decreased the number of -gamma-glutamyl transpeptidase-preneoplastic foci. In the same conditions of administration, quercetin, a polyhydroxylated flavonoid, showed no pr…
Characterization of γ-aminobutyrate type A receptors with atypical coupling between agonist and convulsant binding sites in discrete brain regions
2001
Abstract γ-Aminobutyric acid type A (GABA A ) receptor ionophore ligand t -[ 35 S]butylbicyclophosphorothionate ([ 35 S]TBPS) was used in an autoradiographic assay on brain cryostat sections to visualize and characterize atypical GABA-insensitive [ 35 S]TBPS binding previously described in certain recombinant GABA A receptors and the cerebellar granule cell layer. Picrotoxinin-sensitive but 1-mM GABA-insensitive [ 35 S]TBPS binding was present in the rat cerebellar granule cell layer, many thalamic nuclei, subiculum and the internal rim of the cerebral cortex, amounting in these regions up to 6% of the basal binding determined in the absence of exogenous GABA. Similar binding properties wer…
Benzimidazolones and renzapride facilitate acetylcholine release from guinea-pig myenteric plexus via 5-HT4 receptors
1995
The effects of the 5-HT4 receptor agonists BIMU 8, BIMU 1, renzapride and of the 5-HT1p receptor agonist 5-hydroxyindalpine on basal and electrically evoked outflow of tritium were studied in guinea-pig longitudinal muscle myenteric plexus preparations preincubated with [3H]choline. Muscle contractions were recorded simultaneously. BIMU 8 caused a calcium dependent and tetrodotoxin sensitive increase in basal [3H]outflow that was assumed to represent release of [3H]acetylcholine. In addition, BIMU 8 enhanced the release of [3H]acetylcholine and twitch contractions evoked by submaximal electrical stimulation. Ondansetron (1 μmol/l) did not change the effects of BIMU 8, but DAU 6285 and tropi…
Functional evidence of multidrug resistance transporters (MDR) in rodent olfactory epithelium.
2012
WOS: 000305340700029; International audience; BACKGROUND: P-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP1) are membrane transporter proteins which function as efflux pumps at cell membranes and are considered to exert a protective function against the entry of xenobiotics. While evidence for Pgp and MRP transporter activity is reported for olfactory tissue, their possible interaction and participation in the olfactory response has not been investigated. PRINCIPAL FINDINGS: Functional activity of putative MDR transporters was assessed by means of the fluorometric calcein acetoxymethyl ester (calcein-AM) accumulation assay on acute rat and mouse olfactory tissue slices.…
Micafungin (FK463), alone or in combination with other systemic antifungal agents, for the treatment of acute invasive aspergillosis
2006
Background: Micafungin (FK463) is a new lipopeptide compound (echinocandin) with activity against Aspergillus and Candida species. This study evaluated the safety and efficacy of micafungin in patients with proven or probable invasive aspergillosis (IA). Methods: A multinational, non-comparative study was conducted to examine proven or probable (pulmonary only) Aspergillus species infection in a wide variety of patient populations. The study employed an open-label design utilizing micafungin alone or in combination with another systemic antifungal agent. Criteria for IA and therapeutic responses were judged by an independent panel. Results: Of the 331 patients enrolled, only 225 met diagnos…
The nutrigenetic influence of the interaction between dietary vitamin E and TXN and COMT gene polymorphisms on waist circumference: a case control st…
2015
Background Abdominal obesity (AO) is a common modifiable risk factor for certain non-communicable diseases associated with enhanced oxidative stress (OS). The objective of this work was to investigate whether the interaction between antioxidant vitamin intake and OS-related polymorphisms modulates gene-associated anthropometry in a Spanish population. Methods A total of 246 subjects with AO, and 492 age and gender matched non-AO subjects were included in the study. Anthropometric, biochemical, and OS parameters, and antioxidant dietary intake data were assessed using validated procedures. DNA from white blood cells was isolated and the genotype of seven polymorphisms from genes involved in …
Metabolic Activation of the (+)-S,S- and (−)-R,R-Enantiomers of trans-11,12-Dihydroxy-11,12-dihydrodibenzo[a,l]pyrene: Stereoselectivity, DNA Adduct…
1997
Polycyclic aromatic hydrocarbons require metabolic activation in order to exert their biological activity initiated by DNA binding. The metabolic pathway leading to bay or fjord region dihydrodiol epoxides as ultimate mutagenic and/or carcinogenic metabolites is thought to play a dominant role. For dibenzo[a,l]pyrene, considered as the most potent carcinogenic polycyclic aromatic hydrocarbon, the formation of the fjord region syn- and/or anti-11,12-dihydrodiol 13,-14-epoxide (DB[a,l]PDE) diastereomers has been found to be the principal metabolic activation pathway in cell cultures leading to DNA adducts. In order to further elucidate the stereoselectivity involved in this activation pathway…