196,038 research outputs found
Increased extracellular levels of glutamate in the hippocampus of chronically epileptic rats
No full textAn increase in the release of excitatory amino acids has consistently been observed in the hippocampus during seizures, both in humans and animals. However, very little or nothing is known about the extracellular levels of glutamate and aspartate during epileptogenesis and in the interictal chronic period of established epilepsy. The aim of this study was to systematically evaluate the relationship between seizure activity and changes in hippocampal glutamate and aspartate extracellular levels under basal and high K+-evoked conditions, at various time-points in the natural history of experimental temporal lobe epilepsy, using in vivo microdialysis. Hippocampal extracellular glutamate and aspartate levels were evaluated: 24h after pilocarpine-induced status epilepticus (SE); during the latency period preceding spontaneous seizures; immediately after the first spontaneous seizure; in the chronic (epileptic) period. We found that (i) basal (spontaneous) glutamate outflow is increased in the interictal phases of the chronic period, whereas basal aspartate outflow remains stable for the entire course of the disease; (ii) high K+ perfusion increased glutamate and aspartate outflow in both control and pilocarpine-treated animals, and the overflow of glutamate was clearly increased in the chronic group. Our data suggest that the glutamatergic signaling is preserved and even potentiated in the hippocampus of epileptic rats, and thus may favor the occurrence of spontaneous recurrent seizures. Together with an impairment of GABA signaling (Soukupova et al., 2014), these data suggest that a shift toward excitation occurs in the excitation/inhibition balance in the chronic epileptic state
Irreversible and reversible topoisomerase II DNA cleavage stimulated by clerocidin: Sequence specificity and structural drug determinants
No full textIn contrast to other topoisomerase II poisons, the microbial terpenoid clerocidin was shown to stimulate irreversible topoisomerase II-mediated DNA cleavage. To establish the structural determinants for drug activity, in this study we have investigated intensity patterns and sequence specificity of clerocidin-stimulated DNA cleavage using 5'-end P-32-labeled DNA fragments. At a majority of the sites, clerocidin-stimulated cleavage did not revert upon NaCl addition; nevertheless, at some sites, cleavage completely reverted. Statistical analyses showed that drug-preferred bases were different in the two cases: guanine and cytosine were highly preferred at position -1 at irreversible and reversible sites, respectively. These results demonstrated that cleavage irreversibility was site selective and required a guanine at the 3' end of the cut. Further experiments revealed that some irreversible sites showed an abnormal electrophoretic mobility in sequencing gels with respect to cleaved bands generated by 4-(9-acridinylamino)methanesulfon-m-anisidide, suggesting a chemical alteration of the DNA strand. Interestingly, the ability to stimulate irreversible cleavage progressively decreased over time when clerocidin was stored in ethanol. Under these conditions, nuclear magnetic resonance measurements demonstrated that the drug underwent structural modifications that involved the C-12-C-15 side chain. Thus, the results indicate that a specific moiety of clerocidin may react with the DNA (guanine at -1) in the ternary complex, resulting in cleavage irreversibility and in altered DNA mobility in sequencing gels
A protein-mediated mechanism for the DNA sequence-specific action of topoisomerase II poisons -
No full textEffects of common buffer systems on drug activity: the case of clerocidin.
No full textTwo widely used biological buffers [tris(hydroxymethyl)aminomethane (TRIS) and phosphate] covalently react with the topoisomerase II inhibitor clerocidin, affecting the drug's reactivity profile. Comprehensive analytical and structural analysis obtained by LC/MS, MS/MS, NMR, and IR techniques shows that these buffers form reversible and irreversible adducts through reactions with chemical groups, such as carbonyls, aldehydes, and epoxide. Analysis of the kinetic data on adducts formation suggests two parallel mechanisms for the inhibition of drug activity. The first involves modulation of the reactivity of the epoxide group obtained by elimination of the spiro system and relief of ring strain. This effect does not abolish epoxide reactivity and is more evident for the TRIS adduct, which can count on intramolecular stabilization of the form devoid of the spiro system. The second mechanism involves the slow nucleophilic attack to the epoxide ring, which results in permanent deactivation of the functional group responsible for topoisomerase II inhibition. This effect is predominant in phosphate buffer and is more evident for longer reaction times. These results provide a compelling reminder that the activity of chemically complex drugs in biological systems can be severely altered by buffer interactions, which may not be immediately predictable from the identity of the active group(s) and may require a more detailed knowledge of the subtle effects induced by vicinal groups
Effects of common buffer systems on drug activity: the case of clerocidin
No full textTwo widely used biological buffers [tris(hydroxymethyl)aminomethane (TRIS) and phosphate] covalently react with the topoisomerase II inhibitor clerocidin, affecting the drug's reactivity profile. Comprehensive analytical and structural analysis obtained by LC/MS, MS/MS, NMR, and IR techniques shows that these buffers form reversible and irreversible adducts through reactions with chemical groups, such as carbonyls, aldehydes, and epoxide. Analysis of the kinetic data on adducts formation suggests two parallel mechanisms for the inhibition of drug activity. The first involves modulation of the reactivity of the epoxide group obtained by elimination of the spiro system and relief of ring strain. This effect does not abolish epoxide reactivity and is more evident for the TRIS adduct, which can count on intramolecular stabilization of the form devoid of the spiro system. The second mechanism involves the slow nucleophilic attack to the epoxide ring, which results in permanent deactivation of the functional group responsible for topoisomerase II inhibition. This effect is predominant in phosphate buffer and is more evident for longer reaction times. These results provide a compelling reminder that the activity of chemically complex drugs in biological systems can be severely altered by buffer interactions, which may not be immediately predictable from the identity of the active group(s) and may require a more detailed knowledge of the subtle effects induced by vicinal groups
La metamorfosi del dolore. Lacrime private e pubbliche virtù (di Filippo Binaschi ed Alda Torelli Lunati in particolare)
No full textIl nobiluomo pavese Giovanni Filippo Binaschi, divenuto cieco dopo il sacco di Pavia del 1527, espresse i propri sentimenti d’amore (in particolare per lAlda Torelli Lunati, m. 1580) in liriche di intonazione petrarchesca ricche di riminiscenze classiche e cristiane. Lettore appassionato di Petrarca, al quale aveva dedicato una delle ventitre letture tenute nell’Accademia degli Affidati di Pavia, sublimava l’amore profano in amore sacro trasformando in virtù le proprie passioni dentro la tradizione letteraria. Grazie al mito di Endimione, l’amante della Luna, gli fu anche possibile rendere visibile la propria passione per l’amata tramite il motto della sua impresa accademica ‘Illuminatio mea’ (ricordata da Luca Contile), creata secondo quel procedimento detto del ‘giocare seriamente’ insegnato da tempo da Marsilio Ficino, strettamente integrato nella tradizione cristiana e destinato a diventare una delle occupazioni letterarie preferite di accademie e salotti
Induction of B<sub>1</sub> bradykinin receptors in the kindled brain
No full textThe data suggest that the B1 BK receptors may play a role in the physiopathology of epilepsy, and may represent a new interesting therapeutic target. Tools are available to challenge this idea both pharmacologically (using B1 and B2 receptor antagonists) and genetically (using B1 and B2 receptor knock-outs)
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Interaction between the cytotoxic drug Clerocidin and DNA: evidence for covalent adduct formation
No full textThe diterpenoid Clerocidin causes DNA breaks by stimulating topoisomerase mediated DNA cleavage. The sequence analysis of the cleavage indicated the presence of two types of sites, one exhibtig easily reversible DNA cleavage, the other showing an irreversible cleavage, along with an abnormal migration during gel electrophoresis. This suggested an irreversible mcdification caused by the drug when interacting with the DNA-topoisomerase cleavable complex. Given the chemical structure of Clerocidin, it can be proposed that the dug is reactive towards DNA. To verify this hypothesis, the interaction of Clerocidin with single and double stranded DNA sequences, as well as with deoxyrihonucleatides, was investigated under various experimental conditions using gel electrophoresis, high-field NMR and high performance liquid chromatography coupled to mass spectrometry. Indeed, Clerocidin was able lo produce cleavage in the nucleic acid structure. In addition, the drug reacted with DNA bases giving several adducta, which were characterized and identified. In particular, our results suggest the formation of a covalent guanine-Clerocdin adduct to explain irreversible binding, and of a cytosine-Clerocidin Schiff base to account for reversible binding
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