RESUMO
The aim of this study was to examine the effects of first exogenous nutrients on the mRNA levels of muscle atrophy F-box (atrogin-1/MAFbx) and glucose transporters (GLUTs) in the skeletal muscles of newly hatched chicks with no feed experience. In experiment 1, newly hatched chicks had free access to feed or were fasted for the first 24h. The chicks having free access to feed for the first 24h increased their body weight and had decreased atrogin-1/MAFbx mRNA levels in their sartorius and pectoralis major muscles compared with the fasted chicks. In experiment 2, newly hatched chicks received a single feed via intubation into the crop. Three hours after intubation, levels of atrogin-1/MAFbx mRNA in the sartorius muscle were decreased whereas the plasma insulin concentration and phosphorylated AKT levels in the sartorius muscle were increased. In addition, the mRNA levels of GLUT1 and GLUT8 were increased in the sartorius muscle after the intubation. However, in the pectoralis major muscle, AKT phosphorylation and levels of atrogin-1/MAFbx, GLUT1 and GLUT8 mRNA were not affected 3h after intubation. The first exogenous nutrients increased the level of phosphorylated AKT in the sartorius muscle of newly hatched chicks, possibly because of the decrease in atrogin-1/MAFbx mRNA levels. Furthermore, the sartorius muscle in newly hatched chicks appeared to be more susceptible to the first feed compared with the pectoralis major muscle.
Assuntos
Proteínas Aviárias/genética , Galinhas/genética , Proteínas F-Box/genética , Transportador de Glucose Tipo 1/genética , Proteínas Musculares/genética , Ração Animal , Fenômenos Fisiológicos da Nutrição Animal , Animais , Animais Recém-Nascidos , Proteínas Aviárias/metabolismo , Galinhas/metabolismo , Expressão Gênica , Masculino , Músculo Esquelético/metabolismo , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Group I self-splicing intron constitutes an important class of functional RNA molecules that can promote chemical transformation. Although the fundamental mechanism of the auto-excision from its precursor RNA has been established, convenient assay systems for its splicing activity are still useful for a further understanding of its detailed mechanism and of its application. Because some host RNA sequences, to which group I introns inserted form stable three-dimensional (3D) structures, the effects of the 3D structures of exonic elements on the splicing efficiency of group I introns are important but not a fully investigated issue. We developed an assay system for group I intron self-splicing by employing a fluorescent aptamer RNA (spinach RNA) as a model exonic sequence inserted by the Tetrahymena group I intron. We investigated self-splicing of the intron from spinach RNA, serving as a model exonic sequence with a 3D structure.
RESUMO
To investigate the intracellular signaling mechanisms by which clenbuterol reduces muscle protein degradation, we examined the phosphorylation level and intracellular localization of FOXO1 in the sartorius muscle of neonatal chicks. One-day-old chicks were given a single intraperitoneal injection of clenbuterol (0.1 mg/kg body weight). Three hours after injection, AKT protein was phosphorylated in the sartorius muscle by clenbuterol injection. Coincidentally, clenbuterol increased cytosolic level of phosphorylated FOXO1 protein, while it decreased nuclear level of FOXO1 protein in the sartorius muscle. Furthermore, clenbuterol decreased the expression of mRNAs for muscle-specific ubiquitin ligases (atrogin-1/MAFbx and MuRF1) in the sartorius muscle accompanied by decreased plasma 3-methylhistidine concentration, an index of muscle protein degradation, at 3 h after injection. These results suggested that, in the sartorius muscle of the chicks, clenbuterol changed the intracellular localization of phosphorylated FOXO1, and consequently decreased protein degradation via suppressing the expression of genes encoding muscle-specific ubiquitin ligases.
Assuntos
Proteínas Aviárias/genética , Clembuterol/farmacologia , Proteína Forkhead Box O1/genética , Músculo Esquelético/efeitos dos fármacos , Proteínas Ligases SKP Culina F-Box/genética , Simpatomiméticos/farmacologia , Ubiquitina-Proteína Ligases/genética , Animais , Animais Recém-Nascidos , Proteínas Aviárias/metabolismo , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/metabolismo , Galinhas , Citoplasma/efeitos dos fármacos , Citoplasma/metabolismo , Proteína Forkhead Box O1/metabolismo , Regulação da Expressão Gênica , Injeções Intraperitoneais , Metilistidinas/sangue , Músculo Esquelético/metabolismo , Fosforilação/efeitos dos fármacos , Proteólise/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Ligases SKP Culina F-Box/antagonistas & inibidores , Proteínas Ligases SKP Culina F-Box/metabolismo , Ubiquitina-Proteína Ligases/antagonistas & inibidores , Ubiquitina-Proteína Ligases/metabolismoRESUMO
Tertiary interactions between a new RNA motif and RNA tetraloops were analyzed to determine whether this new motif shows preference for a GCGA tetraloop. In the structural context of a ligase ribozyme, this motif discriminated GCGA loop from 3 other tetraloops. The affinity between the GCGA loop and its receptor is strong enough to carry out the ribozyme activity.