RESUMEN
Myelinated fibers are organized into distinct domains that are necessary for saltatory conduction. These domains include the nodes of Ranvier and the flanking paranodal regions where glial cells closely appose and form specialized septate-like junctions with axons. These junctions contain a Drosophila Neurexin IV-related protein, Caspr/Paranodin (NCP1). Mice that lack NCP1 exhibit tremor, ataxia, and significant motor paresis. In the absence of NCP1, normal paranodal junctions fail to form, and the organization of the paranodal loops is disrupted. Contactin is undetectable in the paranodes, and K(+) channels are displaced from the juxtaparanodal into the paranodal domains. Loss of NCP1 also results in a severe decrease in peripheral nerve conduction velocity. These results show a critical role for NCP1 in the delineation of specific axonal domains and the axon-glia interactions required for normal saltatory conduction.
Asunto(s)
Axones/fisiología , Moléculas de Adhesión Celular Neuronal , Proteínas de Drosophila , Glicoproteínas de Membrana/fisiología , Proteínas de la Membrana/fisiología , Fibras Nerviosas Mielínicas/fisiología , Proteínas del Tejido Nervioso/fisiología , Neuroglía/fisiología , Neuropéptidos/fisiología , Nervio Óptico/fisiología , Receptores de Superficie Celular/fisiología , Nervio Ciático/fisiología , Envejecimiento , Animales , Clonación Molecular , Drosophila , Femenino , Biblioteca Genómica , Heterocigoto , Homocigoto , Humanos , Masculino , Glicoproteínas de Membrana/deficiencia , Glicoproteínas de Membrana/genética , Proteínas de la Membrana/genética , Ratones , Ratones Noqueados , Fibras Nerviosas Mielínicas/ultraestructura , Proteínas del Tejido Nervioso/genética , Neuropéptidos/deficiencia , Neuropéptidos/genética , Canales de Potasio/fisiología , Receptores de Superficie Celular/genética , Mapeo RestrictivoRESUMEN
This study compared the performance of 18 elementary-age students with learning disabilities on the Stanford-Binet Intelligence Scale: Fourth Edition and the Kaufman Assessment Battery for Children. Correlations (corrected for restriction of range) between the two instruments were strong, r = .74, p less than .001 for Test Composite/Mental Processing Composite and r = .85, p less than .001 for Test Composite/Achievement.