RESUMO
Meditation is a conscious mental process that induces a set of integrated physiologic changes termed the relaxation response. Functional magnetic resonance imaging (fMRI) was used to identify and characterize the brain regions that are active during a simple form of meditation. Significant (p<10(-7)) signal increases were observed in the group-averaged data in the dorsolateral prefrontal and parietal cortices, hippocampus/parahippocampus, temporal lobe, pregenual anterior cingulate cortex, striatum, and pre- and post-central gyri during meditation. Global fMRI signal decreases were also noted, although these were probably secondary to cardiorespiratory changes that often accompany meditation. The results indicate that the practice of meditation activates neural structures involved in attention and control of the autonomic nervous system.
Assuntos
Atenção/fisiologia , Mapeamento Encefálico , Meditação , Descanso/fisiologia , Adulto , Tonsila do Cerebelo/fisiologia , Nível de Alerta/fisiologia , Gânglios da Base/fisiologia , Feminino , Lobo Frontal/fisiologia , Hipocampo/fisiologia , Humanos , Masculino , Mesencéfalo/fisiologia , Pessoa de Meia-Idade , RespiraçãoRESUMO
SurA is a periplasmic peptidyl-prolyl isomerase required for the efficient folding of extracytoplasmic proteins. Although the surA gene had been identified in a screen for mutants that failed to survive in stationary phase, the role played by SurA in stationary-phase survival remained unknown. The results presented here demonstrate that the survival defect of surA mutants is due to their inability to grow at elevated pH in the absence of sigmaS. When cultures of Escherichia coli were grown in peptide-rich Luria-Bertani medium, the majority of the cells lost viability during the first two to three days of incubation in stationary phase as the pH rose to pH 9. At this time the surviving cells resumed growth. In cultures of surA rpoS double mutants the survivors lysed as they attempted to resume growth at the elevated pH. Cells lacking penicillin binding protein 3 and sigmaS had a survival defect similar to that of surA rpoS double mutants, suggesting that SurA foldase activity is important for the proper assembly of the cell wall-synthesizing apparatus.
Assuntos
Proteínas de Transporte , Proteínas de Escherichia coli , Escherichia coli/enzimologia , Escherichia coli/crescimento & desenvolvimento , Peptidilprolil Isomerase/fisiologia , Proteínas de Bactérias/genética , Escherichia coli/genética , Concentração de Íons de Hidrogênio , Mutagênese , Peptidilprolil Isomerase/genética , Fator sigma/genética , TransposasesRESUMO
Many proteins require enzymatic assistance in order to achieve a functional conformation. One rate-limiting step in protein folding is the cis-trans isomerization of prolyl residues, a reaction catalyzed by prolyl isomerases. SurA, a periplasmic protein of Escherichia coli, has sequence similarity with the prolyl isomerase parvulin. We tested whether SurA was involved in folding periplasmic and outer membrane proteins by using trypsin sensitivity as an assay for protein conformation. We determined that the efficient folding of three outer membrane proteins (OmpA, OmpF, and LamB) requires SurA in vivo, while the folding of four periplasmic proteins was independent of SurA. We conclude that SurA assists in the folding of certain secreted proteins.