Browsing by Author "Vecchiola, A"

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    Differential regulation of μ-opioid receptor mRNA in the nucleus accumbens shell and core accompanying amphetamine behavioral sensitization
    (1999) Vecchiola, A; Collyer, P; Figueroa, R; Labarca, R; Bustos, G; Magendzo, K
    Repeated amphetamine (AMPH) administration results in behavioral sensitization. To investigate the participation of the opioid system in this phenomenon, we examined the effects of acute and repeated AMPH administration on mu-opioid receptor (MOR) mRNA levels in the nucleus accumbens (NAc) and striatum (STR) of rats, by quantitative non-radioactive in situ hybridization. Five injections of PAh IPH (1.5 mg kg(-1), i.p., once every other day), resulted in a sensitization response profile and a significant down-regulation of MOR mRNA levels in the NAc shell, whereas no change was observed in MOR mRNA levels in the NAc core compared to the saline controls. Conversely, MOR mRNA levels were up-regulated in the rostral STR of AMPH-sensitized rats compared to saline controls. No changes in MOR mRNA levels were observed after acute AMPH treatment in any of the brain regions studied. These results suggest that the opioid system participates in the neurobiological underpinnings of behavioral sensitization and that opioid receptor (OR) expression in the STR and NAc shell and core is differentially modulated by repeated AMPH exposure. (C) 1999 Elsevier Science B.V. All rights reserved.
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    Gibberellic acid decomposition and its loss of biological activity in aqueous solutions
    (1996) Perez, FJ; Vecchiola, A; Pinto, M; Agosin, E
    In addition to gibberellic acid (GA(3)), significant amounts of iso-GA(3), an isomer of GA(3), accumulated in cultures media of the fungus Gibberella fujikuroi. It has been reported that iso-GA(3) is an intermediate in the decomposition of GA(3) to gibberellenic acid, a dicarboxylic acid lacking the gamma-lactone ring. In this work, we studied the decomposition of GA(3) in buffered aqueous solutions at pH 5 and 7, both by spectrophotometry, measuring the appearance of gibberellenic acid at 254 nm, and using a bioassay by measuring the induction of alpha-amylase in barley endosperm. Results indicate that at both pH values, biological inactivation of GA(3) is more rapid than the appearance of gibberellenic acid, suggesting that inactivation is largely due to conversion to the intermediate, iso-GA(3). Furtheremore, no induction of alpha-amylase activity in barley endosperm was obtained in bioassays with iso-GA(3).
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    PIASγ represses the transcriptional activation induced by the nuclear receptor Nurr1
    (2004) Galleguillos, D; Vecchiola, A; Fuentealba, JA; Ojeda, V; Alvarez, K; Gómez, A; Andrés, ME
    Nurr1 is a transcription factor essential for the development of ventral dopaminergic neurons. In search for regulatory mechanisms of Nurr1 function, we identified the SUMO ( small ubiquitin-like modifier)-E3 ubiquitin-protein isopeptide ligase, PIASgamma, as an interaction partner of Nurr1. Overexpressed PIASgamma and Nurr1 co-localize in the nuclei of transfected cells, and their interaction is demonstrated through co-immunoprecipitation and glutathione S-transferase pulldown assays. Co-expression of PIASgamma with Nurr1 results in a potent repression of Nurr1-dependent transcriptional activation of an artificial NGFI-B response element (NBRE) reporter as well as of a reporter driven by the native tyrosine hydroxylase promoter. We identified two consensus sumoylation sites in Nurr1. The substitution of lysine 91 by arginine in one SUMO site enhanced the transcriptional activity of Nurr1, whereas the substitution of lysine 577 by arginine in the second SUMO site decreased transcriptional activity of Nurr1. Interestingly, PIASgamma-induced repression of Nurr1 activity does not require the two sumoylation sites, because each mutant is repressed as efficiently as the wild type Nurr1. In addition, the mutations do not alter Nurr1 nuclear localization. Finally, we provide evidence that Nurr1 and PIASgamma co-exist in several nuclei of the rodent central nervous system by demonstrating the co-expression of Nurr1 protein and PIASgamma mRNA in the same cells. In conclusion, our studies identified PIASgamma as a transcriptional co-regulator of Nurr1 and suggest that this interaction may have a physiological role in regulating the expression of Nurr1 target genes.