The Subplate, A Transient Neocortical Structure: Its Role in the Development of Connections between Thalamus and Cortex

The functioning of the mammalian brain depends upon the precision and accuracy of its neural connections, and nowhere is this requirement more evident than in the neocortex of the cerebral hemispheres. The neocortex is a structure that is divided both radially, from the pial surface to the white matter into six cell layers, and tangentially into more than 40 different cytoarchitectural areas (Brodmann 1909). For instance, within the cerebral hemispheres, sets of tangential axonal connections link neurons within a given cortical layer to each other and also link neurons of different cortical areas; sets of radial connections link neurons of different layers together. In addition, the major input to the neocortex arises from neurons in the thalamus, which in tum receive a reciprocal set of connections from the cortex. These connections are highly restricted: In the radial domain, thalamic axons make their major projection to the neurons of cortical layer 4, and the neurons of cortical layer 6 project back to the thalamus. Connections are also restricted tangentially, in that neurons located in specific subdivisions of the thalamus send their axons to specific cortical areas. For instance, neurons in the lateral geniculate nucleus (LGN) of the thalamus connect with primary visual cortex, whereas those situated in the ventrobasal complex connect with somatosensory cortex. There are also local patterns of connections within a given cortical area, for example, the ocular dominance columns in primary visual cortex of higher mammals, or the barrels in rodent somatosensory cortex (Woolsey & van der Loos 1970). The ocular dominance columns are based on the fact that the inputs of LGN axons representing the two eyes are segregated from each other in layer 4 and their terminal arbors are clustered together in patches (LeVay et al 1980). A primary question is how these sets of connections form during development. The purpose of this review is to consider this question as it pertains specifically to the formation of connections between thalamus and cortex [for a more general review of the formation of connectivity, see Goodman & Shatz (1993)]. Several major steps are involved in this developmental process. First, the constituent neurons of the thalamus and cortex must be generated. Next, axons must grow along the appropriate pathways and select the appropriate targets. In the visual system, this means that LGN axons must grow up through the internal capsule, bypass many other inappropriate cortical areas, and then select visual cortex. Finally, the axons must enter the cortical plate, recognize and terminate within layer 4, and segregate to form ocular dominance columns. Thus, in addition to the general problems of pathfinding and target selection faced by all developing neurons, thalamic neurons are faced with a series of tangential and radial decisions as they form the final pattern of connections within neocortex: they must choose the correct cortical area and the correct layer, and must restrict the extent of their terminal arbors. In addition, similar problems must be solved by the neurons of cortical layer 6 as they grow towards and invade their thalamic targets. A growing body of evidence suggests that the formation of connections between thalamus and cortex requires the presence of a specific and transient cell type, subplate neurons. These neurons are present early in development, but by adulthood the majority have disappeared. Here we consider their life history and review the evidence for their role in the patterning of connections

FORSE-1, an Antibody That Labels Regionally Restricted Subpopulations of Progenitor Cells in the Embryonic Central Nervous System, Recognizes the Le^x Carbohydrate on a Proteoglycan and Two Glycolipid Antigens

A key problem in nervous system development is how distinct subpopulations of progenitor cells give rise to different adult brain structures. The labeling pattern of the FORSE-1 antibody subdivides the neuroepithelium of the embryonic forebrain into domains resembling those of certain transcription factors, suggesting that the FORSE-1 epitope may be involved in the specification of developmental compartments. Therefore, it is important to determine the identity of the antigen(s) recognized by FORSE-1. On immunoblots, FORSE-1 recognizes a single, high-molecular-weight species, which we have identified as phosphacan, a brain-specific chondroitin sulfate proteoglycan that binds neural cell adhesion molecules. This identification is based on cross-immunoprecipitations and immunoblotting using an anti-phosphacan antibody and FORSE-1. FORSE-1 also recognizes two major neutral glycolipids in embryonic brain. The FORSE-1 epitope is sensitive to endo-β-galactosidase, suggesting that the epitope corresponds to a carbohydrate moiety. Moreover, immunoprecipitates of the proteoglycan bearing the FORSE-1 epitope bind antibodies that recognize the Lex carbohydrate, and immunostaining patterns of embryonic brain sections by FORSE-1 and a known anti-Le^x antibody are identical. Finally, purified FORSE-1 specifically recognizes Le^x-containing glycoconjugates in ELISAs. The pattern of FORSE-1 labeling, the identification of its epitope as Le^x, which has been implicated in cell adhesion, and the presence of Le^x on phosphacan suggest that this carbohydrate epitope may play a role in adhesive interactions important for proliferation, cell migration, or axon guidance

Morphological Domains of Lewis-X/FORSE-1 Immunolabeling in the Embryonic Neural Tube Are Due to Developmental Regulation of Cell Surface Carbohydrate Expression

The Lewis-X (LeX) carbohydrate epitope, recognized by the FORSE-1 monoclonal antibody (mAb), shares expression boundaries with neural regulatory genes and may be involved in patterning the neural tube by creating domains of differential cell adhesion. The present experiments focus on the question of what determines the expression pattern of LeX in embryonic rat brain. Comparisons of FORSE-1-positive glycolipid and protein antigens in embryonic, early postnatal, and adult tissues show that the LeX epitope is carried primarily by glycolipids during embryonic development and by a proteoglycan and glycoproteins in postnatal and adult tissue. Immunohistochemistry using FORSE-1 and an antibody to the proteoglycan phosphacan, which carries LeX, shows that the distribution of LeX is more restricted than phosphacan. These observations suggest that the precise spatial regulation of FORSE-1 binding in the embryonic forebrain is due to the expression pattern of the LeX carbohydrate on glycolipids, rather than to the transcriptional regulation of a carrier protein

Therapeutic efficacy of sonic hedgehog protein in experimental diabetic neuropathy

Orientadora : Drª Lucélia DonattiTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Biologia Celular e Molecular. Defesa: Curitiba, 31/07/2014Inclui referências : f. 71-83Resumo: Os peixes que habitam o Oceano Antártico são extremamente adaptados ao frio, sendo seu metabolismo, bioquímico e fisiológico, eficiente em baixas temperaturas. Oscilações sazonais de luminosidade e do suprimento alimentar são também apontados como fatores determinantes da biodiversidade e limitantes da biomassa e da produtividade primária do Oceano Antártico. A tolerância a temperaturas mais altas dos organismos marinhos antárticos tem sido estudada devido à preocupação dos pesquisadores frente ao aquecimento global e da Península Antártica. Os poucos resultados existentes têm demonstrado que esses organismos são extremamente estenotérmicos e que alterações de temperatura podem ser letais. O sistema antioxidante representa um importante marcador de resposta dos organismos submetidos a situações de estresse e alterações de temperatura podem promover a geração de espécies reativas de oxigênio ocasionando danos celulares. Atualmente, a extrema estenotermia dos organismos marinhos antárticos também tem sido estudada através da expressão das proteínas do choque térmico (HSPs). Dentre a família das HSPs, a HSP70 apresenta síntese rápida e significativa diante de diferentes estressores, por isso é uma ferramenta útil para quantificar e prever níveis de estresse em organismos. As coletas e os bioensaios deste trabalho, foram realizados na Baía do Almirantado, Ilha Rei George, no Arquipélago das Shetlands do Sul, Península Antártica, onde se localiza a Estação Antártica Comandante Ferraz (EACF). O presente trabalho tem como objetivo investigar variações nos níveis de HSP70, nos níveis de atividade de várias enzimas antioxidantes (SOD, CAT, GPx, GR e GST) e nos níveis dos marcadores não enzimáticos (GSH, PC e LPO) do estresse oxidativo nos peixes antárticos, Notothenia rossii e Nottohenia coriiceps em condições naturais e de estresse térmico. Para tanto, três capítulos compõem este trabalho, onde o primeiro analisa o efeito da temperatura no metabolismo oxidativo de N. rossii e N. coriiceps; o segundo avalia os níveis de expressão de HSP70 no fígado de N. rossii e N. coriiceps submetidos a estresse térmico e o terceiro analisa ao longo do ano os níveis de atividades dos marcadores de estresse oxidativo em diferentes órgãos de N. rossii e N. coriiceps da Baia do Almirantado, Ilha Rei George, Península Antártica. Palavras-chaves: temperatura, sazonalidade, estresse oxidativo, peixes antárticos, proteína do choque térmico.Abstract: The fish that inhabit the Southern Ocean are highly adapted to the cold, and its metabolism, biochemical and physiological, efficient at low temperatures. Seasonal fluctuations of light and food supply are determinants of biodiversity and limiting biomass and primary productivity of the Southern Ocean. The tolerance to higher temperatures of Antarctic marine organisms have studied due to the concern of researchers against global warming and the Antarctic Peninsula. The few results have demonstrated that these organisms are extremely stenothermal and rapid temperature change can be lethal. The antioxidant system is an important response marker of organisms subjected to stress and temperature changes situations can promote the generation of reactive oxygen species causing cell damage. Currently, the extreme stenothermal of Antarctic marine organisms has studied through the expression of heat shock proteins (HSPs). Among the family of HSPs, the HSP70 has significant and rapid synthesis on different stressors, so it is a useful tool to quantify and predict stress levels in organisms. The experiments of were performed in Admiralty Bay, King George Island, in the Archipelago of the South Shetlands, Antarctic Peninsula, where is the Comandante Ferraz Antarctic Station (EACF). This study aims to investigate variations in the levels of HSP70 in the activity levels of several antioxidant enzymes (SOD, CAT, GPx, GR and GST) and the levels of non-enzymatic markers (GSH, PC and LPO) oxidative stress in Antarctic fish, Notothenia rossii and Nottohenia coriiceps in natural and heat stress conditions. Therefore, three chapters make this work, where the first examines the effect of temperature on the oxidative metabolism of N. rossii and N. coriiceps; the second evaluates the HSP70 expression levels in liver N. rossii and N. coriiceps submited to thermal stress and the third analyzes throughout the year, the activity levels of oxidative stress markers in different tissues of N. rossii and N. coriiceps of Admiralty Bay, King George Island, Antarctic Peninsula. Keywords: temperature, seasonality, oxidative stress, Antarctic fish, heat shock proteins

Therapeutic efficacy of sonic hedgehog protein in experimental diabetic neuropathy

Hedgehog proteins modulate development and patterning of the embryonic nervous system. As expression of desert hedgehog and the hedgehog receptor, patched-1, persist in the postnatal and adult peripheral nerves, the hedgehog pathway may have a role in maturation and maintenance of the peripheral nervous system in normal and disease states. We measured desert hedgehog expression in the peripheral nerve of maturing diabetic rats and found that diabetes caused a significant reduction in desert hedgehog mRNA. Treating diabetic rats with a sonic hedgehog–IgG fusion protein fully restored motor- and sensory-nerve conduction velocities and maintained the axonal caliber of large myelinated fibers. Diabetes-induced deficits in retrograde transport of nerve growth factor and sciatic-nerve levels of calcitonin gene–related product and neuropeptide Y were also ameliorated by treatment with the sonic hedgehog–IgG fusion protein, as was thermal hypoalgesia in the paw. These studies implicate disruption of normal hedgehog function in the etiology of diabetes-induced peripheral-nerve dysfunction and indicate that delivery of exogenous hedgehog proteins may have therapeutic potential for the treatment of diabetic neuropathy