RESUMO
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.
Assuntos
Axônios/fisiologia , Moléculas de Adesão Celular Neuronais , Proteínas de Drosophila , Glicoproteínas de Membrana/fisiologia , Proteínas de Membrana/fisiologia , Fibras Nervosas Mielinizadas/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Neuroglia/fisiologia , Neuropeptídeos/fisiologia , Nervo Óptico/fisiologia , Receptores de Superfície Celular/fisiologia , Nervo Isquiático/fisiologia , Envelhecimento , Animais , Clonagem Molecular , Drosophila , Feminino , Biblioteca Genômica , Heterozigoto , Homozigoto , Humanos , Masculino , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Fibras Nervosas Mielinizadas/ultraestrutura , Proteínas do Tecido Nervoso/genética , Neuropeptídeos/deficiência , Neuropeptídeos/genética , Canais de Potássio/fisiologia , Receptores de Superfície Celular/genética , Mapeamento por RestriçãoRESUMO
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.