RESUMO
The oligodendrocyte precursor cell (OPC) has until recently been regarded as a lineage-restricted precursor cell. Considerable interest has been generated by reports suggesting that OPCs may possess a wider differentiation potential than previously assumed and thus be considered a multipotential stem cell. This study examined the neuronal differentiation potential of rat, postnatal cortical OPCs in response to extracellular cues in vitro and in vivo. OPCs did not exhibit intrinsic neuronal potential and were restricted to oligodendrocyte lineage potential following treatment with the neural precursor mitogen fibroblast growth factor 2. In contrast, a postnatal hippocampal astrocyte-derived signal(s) is sufficient to induce functional neuronal differentiation of cortical OPCs in vitro in population and single cell studies. Co-treatment with Noggin, a bone morphogenetic protein antagonist, did not attenuate neuronal differentiation. Following transplantation to the adult rat hippocampus, cortical OPCs expressed doublecortin, a neuroblast-associated marker. The present findings show that hippocampal, astrocyte-derived signals can induce the neuronal differentiation of OPCs through a Noggin-independent mechanism.
Assuntos
Astrócitos/citologia , Diferenciação Celular/fisiologia , Neurônios/fisiologia , Oligodendroglia/fisiologia , Células-Tronco/citologia , Animais , Animais Recém-Nascidos , Cálcio/metabolismo , Proteínas de Transporte/metabolismo , Diferenciação Celular/efeitos dos fármacos , Sobrevivência Celular , Transplante de Células/métodos , Células Cultivadas , Córtex Cerebral/citologia , Técnicas de Cocultura/métodos , Meios de Cultivo Condicionados/farmacologia , Diagnóstico por Imagem/métodos , Proteína Duplacortina , Fator 2 de Crescimento de Fibroblastos/farmacologia , Citometria de Fluxo/métodos , Gangliosídeos/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Hipocampo/citologia , Hipocampo/fisiologia , Hipocampo/transplante , Imuno-Histoquímica/métodos , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Oligodendroglia/efeitos dos fármacos , RNA Mensageiro/biossíntese , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Fatores de Tempo , Transfecção/métodosRESUMO
PURPOSE: The CACNA1F gene encodes a voltage-gated calcium channel alpha1 subunit, alpha1F, which is expressed in the human retina. Mutations in this gene cause incomplete X-linked congenital stationary night blindness (CSNB2). The aim of this study was to obtain the sequence of the rat alpha1F cDNA and localize the encoded polypeptide in the rat retina. METHODS: The full-length rat alpha1F sequence was compiled from sequencing of overlapping alpha1F PCR fragments amplified from rat retinal cDNA. Antiserum was raised against a human alpha1F peptide. It was found that the human alpha1F peptide used to generate the antiserum was conserved at only 11 out of 19 residues in the cloned rat sequence. Therefore, antibodies were affinity purified against either the human alpha1F peptide or the equivalent rat peptide and used for immunofluorescent staining of rat retina sections. RESULTS: The rat alpha1F amino acid sequence was found to be 91% and 95% identical to the human and mouse alpha1F sequences, respectively. Antibodies affinity purified against the human alpha1F peptide stained both the outer nuclear layer (ONL) and outer plexiform layer of rat retina sections. In contrast, staining with antibodies affinity purified against the corresponding rat alpha1F peptide was restricted to the ONL. CONCLUSIONS: The rat alpha1F amino acid sequence is highly homologous to the human and mouse sequences. The immunohistochemical results indicate the existence of distinct alpha1F isoforms or alpha1F-like channels, which are differentially distributed in the cell bodies and synaptic terminals of photoreceptors in the rat retina.
Assuntos
Canais de Cálcio Tipo L , Canais de Cálcio/genética , Proteínas do Olho/genética , Células Fotorreceptoras de Vertebrados/metabolismo , Sequência de Aminoácidos , Animais , Anticorpos/imunologia , Anticorpos/isolamento & purificação , Sequência de Bases , Western Blotting , Cálcio/metabolismo , Canais de Cálcio/imunologia , Canais de Cálcio/metabolismo , Cromatografia de Afinidade , Primers do DNA/química , DNA Complementar/análise , Proteínas do Olho/imunologia , Proteínas do Olho/metabolismo , Técnica Indireta de Fluorescência para Anticorpo , Expressão Gênica , Humanos , Camundongos , Dados de Sequência Molecular , Cegueira Noturna/congênito , Fragmentos de Peptídeos/imunologia , Células Fotorreceptoras de Vertebrados/citologia , Reação em Cadeia da Polimerase , Terminações Pré-Sinápticas/metabolismo , RNA Mensageiro/biossíntese , Ratos , Ratos Endogâmicos WKY , Homologia de Sequência de Aminoácidos , OvinosRESUMO
OBJECTIVE AND METHOD: This article examines some of the ethical and legal issues which confront the psychiatrist who is asked to provide a forensic psychiatric assessment. Theory is explained and illustrated by way of a case study. RESULTS: Recent cases demonstrate a tendency by some psychiatrists to adopt an advocacy role in legal proceedings, to the potential disadvantage of not only those involved in the proceedings, but also to the wider community. CONCLUSION: Ideally, there is a need for a greater collaborative effort between the College's Ethics Committee and this Country's Courts and Law Societies to establish and monitor an ethical framework in the area of expert psychiatric evidence.