Search results for "cyclic"
showing 10 items of 2439 documents
Characterization of oligomeric compounds in secondary organic aerosol using liquid chromatography coupled to electrospray ionization Fourier transfor…
2009
The components of secondary organic aerosols (SOAs) generated from the gas-phase ozonolysis of two C(10)H(16)-terpenes (alpha-pinene; sabinene) and a cyclic C(6)H(10) alkene (cyclohexene) were characterized by the use of a Fourier transform ion cyclotron mass spectrometer equipped with an electrospray ionization source operated in the negative ion mode. Reversed-phase high-performance liquid chromatography was used to achieve chromatographic separation of highly oxidized organic compounds. In addition to the well-known group of low molecular weight oxidation products (monomers; e.g. dicarboxylic acids), higher molecular weight compounds (dimers) were also detected and their exact elemental …
Cytogenetic effects of promutagens in genetically engineered V79 Chinese hamster cells expressing cytochromes P450.
1993
Abstract V79 Chinese hamster cell lines genetically engineered to express rat CYP2B1, CYP1A1, CYP1A2, and their parental cell lines V79-MZ, without acetyltransferase, and V79-NH, with acetyltransferase, were studied for chromosome aberrations and sister chromatid exchange induced by aflatoxin B 1 , cyclophosphamide, benzo[a]pyrene, 7,12-dimethylbenz[a]anthracene and dimethylnitrosamine. The parental V79 cell lines did not show clastogenic effects. Significant clastogenic effects were observed after an 18 h exposure to aflatoxin B 1 and cyclophosphamide in CYP2B1 expressing cells, to benzo[a]pyrene in CYP1A1 and CYP1A2 expressing cells, to 7,12-dimethylbenz[a]anthracene and dimethylnitrosami…
A53T-Alpha-Synuclein Overexpression Impairs Dopamine Signaling and Striatal Synaptic Plasticity in Old Mice
2010
BACKGROUND: Parkinson's disease (PD), the second most frequent neurodegenerative disorder at old age, can be caused by elevated expression or the A53T missense mutation of the presynaptic protein alpha-synuclein (SNCA). PD is characterized pathologically by the preferential vulnerability of the dopaminergic nigrostriatal projection neurons. METHODOLOGY/PRINCIPAL FINDINGS: Here, we used two mouse lines overexpressing human A53T-SNCA and studied striatal dysfunction in the absence of neurodegeneration to understand early disease mechanisms. To characterize the progression, we employed young adult as well as old mice. Analysis of striatal neurotransmitter content demonstrated that dopamine (DA…
Influence of gene action across different time scales on behavior.
2002
Genes can affect natural behavioral variation in different ways. Allelic variation causes alternative behavioral phenotypes, whereas changes in gene expression can influence the initiation of behavior at different ages. We show that the age-related transition by honey bees from hive work to foraging is associated with an increase in the expression of the foraging ( for ) gene, which encodes a guanosine 3′,5′-monophosphate (cGMP)–dependent protein kinase (PKG). cGMP treatment elevated PKG activity and caused foraging behavior. Previous research showed that allelic differences in PKG expression result in two Drosophila foraging variants. The same gene can thus exert different types of influe…
Developmental Changes and Daily Rhythm in Melatonin-Induced Inhibition of 3′,5′-Cyclic AMP Accumulation in the Rat Pituitary
1990
Melatonin's transduction mechanisms were investigated using in vitro cultured anterior hemipituitaries. Melatonin inhibited cAMP and 3',5'-cyclic GMP accumulation in neonatal rat anterior pituitary stimulated with LHRH. Maximal inhibitory effect was reached within 25 min and persisted for at least 20 min. Inhibition of cAMP accumulation is specific for melatonin because its analogs N-acetylserotonin and 5-methoxytryptamine are 1000 times less potent. Melatonin effect is age- and time-dependent. Marked inhibition was observed in 5-, 10-, and 14-day-old rats but not in 29-day-old ones. Melatonin was significantly more potent when applied at the end of the light period as compared with the fir…
Prostacyclin receptor desensitization is a reversible phenomenon in human platelets.
1997
Background Long-term exposure of platelets to endogenous or exogenous prostacyclin or its analogues might result in desensitization of the platelet prostacyclin receptor in vitro and in vivo accompanied by a loss in receptor density on the platelet surface and a reduced sensitivity toward the inhibitory effects of prostacyclins. However, the reversibility of this process in platelets has not yet been investigated. Methods and Results Human platelets desensitized by the chemically stable prostacyclin analogue iloprost showed a significant reduction in [ 3 H]-iloprost binding sites that was reversed by saponin permeabilization. This indicates functionally active internalized prostacyclin rec…
Role of CB2 receptors and cGMP pathway on the cannabinoid-dependent antiepileptic effects in an in vivo model of partial epilepsy.
2014
This study aimed at providing an insight on the possible role of cannabi-noid (CB) type 2 receptors (CB2R) and cGMP pathway in the antiepileptic activity ofWIN 55,212-2, (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl) pyrrolo[1,2,3-de]-1,4-benzoxazin-6-Yl]-1-naphthalenylmethanone, a non-selective CB agonist, in the maximal dentate activation (MDA) model of partial epilepsy in adult male rats. We evaluated the activity of a CB2 antagonist/inverse agonist AM630, [6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl](4-methoxyphenyl)methanone or 6-iodopravadoline, alone or in co-administration with WIN 55,212-2. Also, in the MDA model it was investigated the co-treatment of WIN55,212…
Coupling between agonist and chloride ionophore sites of the GABA(A) receptor: agonist/antagonist efficacy of 4-PIOL.
2000
Eight gamma-aminobutyric acid (GABA) mimetics were tested on their ability to differentiate native GABA(A) receptor subtypes present in various rat brain regions. In rat brain cryostat sections, little regional variations by the agonistic actions of muscimol, thiomuscimol, 4,5,6,7-tetrahydroisoazolo(5,4-c)pyridin-3-ol, piperidine-4-sulphonic acid, taurine and beta-alanine on [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to GABA(A) receptor channels were found. They were very similar to those found for GABA itself and indicated no direct correlation with single subunit distributions for any of these compounds. Only the low-efficacy GABA mimetic 5-(4-piperidyl)isoxazol-3-ol (4-PIOL…
Pharmacological characterization of uracil nucleotide-preferring P2Y receptors modulating intestinal motility: a study on mouse ileum.
2011
We investigated the possible modulation of the intestinal contractility by uracil nucleotides (UTP and UDP), using as model the murine small intestine. Contractile activity of a mouse ileum longitudinal muscle was examined in vitro as changes in isometric tension. Transcripts encoding for uracil-sensitive receptors was investigated by RT-PCR. UDP induced muscular contractions, sensitive to PPADS, suramin, or MRS 2578, P2Y(6) receptor antagonist, and mimicked by PSB 0474, P2Y(6)-receptor agonist. UTP induced biphasic effects characterized by an early inhibition of the spontaneous contractile activity followed by muscular contraction. UTP excitatory effects were antagonized by PPADS, suramin,…
Involvement of tachykinin NK2 receptors in the modulation of spontaneous motility in rat proximal colon.
2000
The role of endogenous tachykinins and the mechanisms whereby they act on NK2 receptors, modulating spontaneous motility, were investigated in rat isolated proximal colon. The mechanical activity was detected as changes in intraluminal pressure. The NK2 receptor antagonist, MEN 10627, produced a concentration-dependent reduction of the contraction amplitude. [beta-Ala8]-neurokinin A(4-10), an NK2 receptor agonist, and [Sar9, Met(O2)11]-Substance P ([Sar9, Met(O2)11]-SP), an NK1 receptor agonist, induced a concentration-dependent contractile response, characterized by an increase in basal tone with superimposed phasic contractions. MEN 10627 antagonized the response to [beta-Ala8]-neurokinin…