5 research outputs found
The glial growth factors deficiency and synaptic destabilization hypothesis of schizophrenia
BACKGROUND: A systems approach to understanding the etiology of schizophrenia requires a theory which is able to integrate genetic as well as neurodevelopmental factors. PRESENTATION OF THE HYPOTHESIS: Based on a co-localization of loci approach and a large amount of circumstantial evidence, we here propose that a functional deficiency of glial growth factors and of growth factors produced by glial cells are among the distal causes in the genotype-to-phenotype chain leading to the development of schizophrenia. These factors include neuregulin, insulin-like growth factor I, insulin, epidermal growth factor, neurotrophic growth factors, erbB receptors, phosphatidylinositol-3 kinase, growth arrest specific genes, neuritin, tumor necrosis factor alpha, glutamate, NMDA and cholinergic receptors. A genetically and epigenetically determined low baseline of glial growth factor signaling and synaptic strength is expected to increase the vulnerability for additional reductions (e.g., by viruses such as HHV-6 and JC virus infecting glial cells). This should lead to a weakening of the positive feedback loop between the presynaptic neuron and its targets, and below a certain threshold to synaptic destabilization and schizophrenia. TESTING THE HYPOTHESIS: Supported by informed conjectures and empirical facts, the hypothesis makes an attractive case for a large number of further investigations. IMPLICATIONS OF THE HYPOTHESIS: The hypothesis suggests glial cells as the locus of the genes-environment interactions in schizophrenia, with glial asthenia as an important factor for the genetic liability to the disorder, and an increase of prolactin and/or insulin as possible working mechanisms of traditional and atypical neuroleptic treatments
Efeito da Ă©poca sobre a emergĂȘncia de Sida rhombifolia e Solanum viarum em diferentes profundidades de semeadura
O conhecimento da profundidade ideal de germinação de sementes de plantas daninhas Ă© importante para o desenvolvimento de estratĂ©gias de manejo eficientes, seguras e econĂŽmicas. Com o objetivo de estudar a emergĂȘncia de plĂąntulas de Sida rhombifolia L. e Solanum viarum Dunal, em resposta Ă Ă©poca (setembro de 2008 e janeiro de 2009) e Ă s profundidades de semeadura (0, 1, 2, 3, 4 e 5 cm), foram realizados dois experimentos em casa de vegetação. Sida rhombifolia mostrou-se sensĂvel Ă s variaçÔes de temperatura, em decorrĂȘncia das Ă©pocas de semeadura, e os maiores percentuais de emergĂȘncia ocorreram nas profundidades entre 1 e 4 cm. Para S. viarum, observou-se forte influĂȘncia da temperatura sobre a sua emergĂȘncia, sendo, observado o mĂĄximo de emergĂȘncia, nas profundidades de 1 a 5 cm e sua redução para as sementes locadas na superfĂcie do solo