Distribution of Extracellular Glutamate in the Neuropil of Hippocampus

Reported values of extracellular glutamate concentrations in the resting state depend on the method of measurement and vary ∼1000-fold. As glutamate levels in the micromolar range can cause receptor desensitization and excitotoxicity, and thus affect neuronal excitability, an accurate determination of ambient glutamate is important. Part of the variability of previous measurements may have resulted from the sampling of glutamate in different extracellular compartments, e.g., synaptic versus extrasynaptic volumes. A steep concentration gradient of glutamate between these two compartments could be maintained, for example, by high densities of glutamate transporters arrayed at the edges of synapses. We have used two photon laser scanning microscopy and electrophysiology to investigate whether extracellular glutamate is compartmentalized in acute hippocampal slices. Pharmacological blockade of NMDARs had no effect on Ca2+ transients generated in dendritic shafts or spines of CA1 pyramidal neurons by depolarization, suggesting that ambient glutamate is too low to activate a significant number of NMDARs. Furthermore, blockade of transporters did not flood the synapse with glutamate, indicating that synaptic NMDARs are not protected from high concentrations of extrasynaptic glutamate. We suggest that, in the CA1 region of hippocampus, glutamate transporters do not create a privileged space within the synapse but rather keep ambient glutamate at very low levels throughout the neuropil

De la torre de marfil al laboratorio pop: estudiar la cultura popular hoy: Sección Investigar en Sociales

“Laboratorio pop” es una iniciativa innovadora y revulsiva dentro de la Facultad: desafía y problematiza la asimilación académica de un pensamiento de fronteras, muchas veces reacia a dialogar con lenguajes y conocimientos sociales, urbanos, populares. Para ello proyecta un mapa de la cultura apropiándose de los saberes disímiles y contradictorios, y así -según explican sus integrantes-, busca traducirlo en “canales de contacto con aquellas ‘masas’ de las que no podemos, en una suerte de afán intelectual, pensarnosseparadxs”.Este artículo presenta la perspectiva y algunas líneas de trabajo de un proyecto en curso en el marco del programa “Estudios sobre Cultura Pop.  Formas locales, diseños globales y semióticas de lo popular”, radicado en el Centro de Estudios Avanzados de la Facultad, integrado por docentes, egresades y estudiantes de Sociología, Semiótica, Ciencia Política, Ciencias de la Comunicación y Letras, entre otras carreras de la Universidad Nacional de Córdoba. Da cuenta del interés del espacio en las problemáticas de la cultura, particularmente en sus dimensiones popular y masiva, sistematizadas en la noción de “cultura pop” y presenta las bases de  un trabajo de comunicación pública de la ciencia impulsado desde dicho programa

Complete DNA Sequence of the Mitochondrial Genome of the Sea-Slug, Aplysia Californica: Conservation of the Gene Order in Euthyneura

We have sequenced and characterized the complete mitochondrial genome of the sea slug, Aplysia californica, an important model organism in experimental biology and a representative of Anaspidea (Opisthobranchia, Gastropoda). The mitochondrial genome of Aplysia is in the small end of the observed sizes of animal mitochondrial genomes (14,117 bp, NCBI Accession No. NC_005827). The Aplysia genome, like most other mitochondrial genomes, encodes genes for 2 ribosomal subunit RNAs (small and large rRNAs), 22 tRNAs, and 13 protein subunits (cytochrome c oxidase subunits 1–3, cytochrome b apoenzyme, ATP synthase subunits 6 and 8, and NADH dehydrogenase subunits 1–6 and 4L). The gene order is virtually identical between opisthobranchs and pulmonates, with the majority of differences arising from tRNA translocations. In contrast, the gene order from representatives of basal gastropods and other molluscan classes is significantly different from opisthobranchs and pulmonates. The Aplysia genome was compared to all other published molluscan mitochondrial genomes and phylogenetic analyses were carried out using a concatenated protein alignment. Phylogenetic analyses using maximum likelihood based analyses of the well aligned regions of the protein sequences support both monophyly of Euthyneura (a group including both the pulmonates and opisthobranchs) and Opisthobranchia (as a more derived group). The Aplysia mitochondrial genome sequenced here will serve as an important platform in both comparative and neurobiological studies using this model organism

NMDAR antagonism has no differential effect on bAP-evoked Ca²⁺ signals in dendrites or spines.

<p>A. Top left: 2PLSM image of a spine and dendrite with dashed line indicating line scan position. Bottom left: During a 500 Hz line scan through spine and dendrite, a bAP (arrow) evokes a Ca²⁺ transient in both compartments. Right: Somatic AP evoked by current injection. B, C. Average Ca²⁺ transients evoked by a bAP measured in the dendrite (left) and spine (right) from a P14 animal (B; n = 11 for both structures) and a P34 animal (C; spine, n = 17; dendrite, n = 13) in the presence and absence of D-AP5 (10–50 µM).</p