Gap-junctional communication between neurons and astrocytes dissociated from rat brain was identified in culture by using dye-transfer assays and electrophysiological measurements. Cell types were identified by using antibodies against ␤-tubulin III, glial fibrillary acidic protein, and 2,3-cyclic-nucleotide phosphohydrolase, which are antigenic determinants of neurons, astroglia, and oligodendrocytes, respectively. Dye coupling was examined as a function of time after dissociated embryonic brain cells were plated onto confluent monolayers of postnatal astrocytes by intracellularly injecting the fluorochrome Lucifer yellow. Coupling of neurons to the astrocytic monolayer was most frequent between 48 h and 72 h in culture and declined over the next 4 days. This gradual uncoupling was accompanied by progressive neuronal maturation, as indicated by morphological measurements in camera lucida drawings. Dye spread was abolished reversibly by octanol, an agent that blocks gap junction channels in other systems. Double whole-cell voltage-clamp measurements confirmed the presence of heterocellular electrical coupling in these cocultures. Coupling was also seen between neurons and astrocytes in cocultures of cells dissociated from embryonic cerebral hemispheres but was rarely detectable in cocultures of postnatal brain cells. These data strongly suggest that junctional communication may provide metabolic and electrotonic interconnections between neuronal and astrocytic networks at early stages of neural development and that such interactions are weakened as differentiation progresses.The nervous system has great complexity in terms of the diversity of cellular contacts and the broad range of information processing performed by neural cells. Thoroughly debated and overwhelmingly accepted nearly a century ago, the neuron doctrine (1) not only established cellular individuality in the brain parenchyma but also designated neurons as the functional elements in signaling in the central nervous system (CNS). As a consequence, research has focused on elucidating the cellular and molecular details of neuronal pathways, whereas glial cells have been regarded as elements of structural and trophic support, with no direct influence in information processing. However, in the past few years, evidence has accumulated indicating that glial networks may provide functional support to neuronal activity and may constitute dynamic pathways for electrical and chemical signaling in the CNS. Studies showing synchronous metabolic and electrical responses in astrocytes mediated by neuronal-glial interactions demonstrate that, in culture, both slow and rapid calcium waves propagate through the functional syncytium provided by the astrocytic network in response to iontophoretic application of glutamate to astrocytes (2) and to firing of glutamatergic neurons (3, 4). Conversely, the propagation of astrocytic calcium waves to neurons has been more recently reported (5-7). Calcium signaling from astrocytes to neurons in culture was proposed to ...

Glioblastoma (GBM) is a grade IV astrocytoma. GBM patients show resistance to chemotherapy such as temozolomide (TMZ), the gold standard treatment. In order to simulate the molecular mechanisms behind the different chemotherapeutic responses in GBM patients we compared the cellular heterogeneity and chemotherapeutic resistance mechanisms in different GBM cell lines. We isolated and characterized a human GBM cell line obtained from a GBM patient, named GBM11. We studied the GBM11 behaviour when treated with Tamoxifen (TMX) that, among other functions, is a protein kinase C (PKC) inhibitor, alone and in combination with TMZ in comparison with the responses of U87 and U118 human GBM cell lines. We evaluated the cell death, cell cycle arrest and cell proliferation, mainly through PKC expression, by flow cytometry and western blot analysis and, ultimately, cell migration capability and F-actin filament disorganization by fluorescence microscopy. We demonstrated that the constitutive activation of p-PKC seems to be one of the main metabolic implicated on GBM malignancy. Despite of its higher resistance, possibly due to the overexpression of P-glycoprotein and stem-like cell markers, GBM11 cells presented a subtle different chemotherapeutic response compared to U87 and U118 cells. The GBM11, U87, U118 cell lines show subtle molecular differences, which clearly indicate the characterization of GBM heterogeneity, one of the main reasons for tumor resistance. The adding of cellular heterogeneity in molecular behaviour constitutes a step closer in the understanding of resistant molecular mechanisms in GBM, and can circumvents the eventual impaired therapy.

BackgroundGlioblastoma (GBM) is the most common primary brain tumor and the most aggressive glial tumor. This tumor is highly heterogeneous, angiogenic, and insensitive to radio- and chemotherapy. Here we have investigated the progression of GBM produced by the injection of human GBM cells into the brain parenchyma of immunocompetent mice.MethodsXenotransplanted animals were submitted to magnetic resonance imaging (MRI) and histopathological analyses.ResultsOur data show that two weeks after injection, the produced tumor presents histopathological characteristics recommended by World Health Organization for the diagnosis of GBM in humans. The tumor was able to produce reactive gliosis in the adjacent parenchyma, angiogenesis, an intense recruitment of macrophage and microglial cells, and presence of necrosis regions. Besides, MRI showed that tumor mass had enhanced contrast, suggesting a blood–brain barrier disruption.ConclusionsThis study demonstrated that the xenografted tumor in mouse brain parenchyma develops in a very similar manner to those found in patients affected by GBM and can be used to better understand the biology of GBM as well as testing potential therapies.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-923) contains supplementary material, which is available to authorized users.