RESUMEN
We have cloned a full-length complementary DNA from the chicken (Gallus gallus domesticus), which encodes a polypeptide that exhibits approximately 75% identity to the product of the mammalian gene Arc (activity-regulated cytoskeleton-associated protein), also known as arg3.1 (activity-regulated gene). Since this gene is an immediate-early gene that has been suggested to play a role in synaptic plasticity and learning and memory processes, its expression has been analyzed in a juvenile form of learning, namely, filial imprinting. Our results demonstrate that Arc/arg3.1 mRNA is detectable in the newborn chick brain, and that at this early age the level of this transcript can be altered by brief sensory/emotional experience. After postnatal exposure to a novel 30-min auditory imprinting stimulus, Arc/arg3.1 mRNA was found to be significantly increased in two higher associative areas, the mesopallium intermediomediale (P = 0.002) and the nidopallium dorso-caudale (P = 0.031), compared with naïve controls. The transcript level was also significantly elevated after imprinting in Area L pallii (P=0.045), which is analogous to the mammalian auditory cortex. In addition, increases were seen in the medio-rostral nidopallium/mesopallium (P = 0.054), which is presumed to be the analog of the mammalian prefrontal cortex, and the hyperpallium intercalatum (P = 0.054), but these did not quite reach significance. We discuss these data in the light of those obtained in an earlier study, in the same paradigm, for the avian immediate-early gene, zenk (an acronym for zif-268, egr-1, ngfi-a and krox-24, which are different names for the orthologous mammalian gene). We conclude that, although both the Arc/arg3.1 and zenk genes are induced by auditory imprinting, they are significantly up-regulated in different learning-relevant brain regions. It is, therefore, evident that they must be activated by different mechanisms.
Asunto(s)
Encéfalo/fisiología , Proteínas del Citoesqueleto/genética , Regulación del Desarrollo de la Expresión Génica , Impronta Psicológica/fisiología , Proteínas del Tejido Nervioso/genética , Conducta Social , Estimulación Acústica , Secuencia de Aminoácidos , Animales , Animales Recién Nacidos , Aprendizaje por Asociación/fisiología , Encéfalo/crecimiento & desarrollo , Pollos , Proteínas de Unión al ADN/genética , Proteína 1 de la Respuesta de Crecimiento Precoz , Biblioteca de Genes , Genes Inmediatos-Precoces/fisiología , Proteínas Inmediatas-Precoces/genética , Datos de Secuencia Molecular , Plasticidad Neuronal/fisiología , ARN Mensajero/análisis , Ratas , Factores de Transcripción/genéticaRESUMEN
In experiments on 72 rabbits, the LD50 of sodium selenite by intravenous injection was found to be 2.24 mg/kg body weight. The clinical picture and pathological changes associated with acute selenium poisoning are described. The increase in selenium concentration was up to nine times the normal in liver and up to six times in kidney and muscle. There was no sign of a return to normal values 24 hours after administration.