Neuronal and astroglial correlates underlying spatiotemporal Intrinsic Optical Signal in the rat hippocampal slice

Widely used for mapping afferent activated brain areas in vivo, the label-free intrinsic optical signal (IOS) is mainly ascribed to blood volume changes subsequent to glial glutamate uptake. By contrast, IOS imaged in vitro is generally attributed to neuronal and glial cell swelling, however the relative contribution of different cell types and molecular players remained largely unknown. We characterized IOS to Schaffer collateral stimulation in the rat hippocampal slice using a 464-element photodiode-array device that enables IOS monitoring at 0.6 ms time-resolution in combination with simultaneous field potential recordings. We used brief half-maximal stimuli by applying a medium intensity 50 Volt-stimulus train within 50 ms (20 Hz). IOS was primarily observed in the str. pyramidale and proximal region of the str. radiatum of the hippocampus. It was eliminated by tetrodotoxin blockade of voltage-gated Na+ channels and was significantly enhanced by suppressing inhibitory signaling with gamma-aminobutyric acid(A) receptor antagonist picrotoxin. We found that IOS was predominantly initiated by postsynaptic Glu receptor activation and progressed by the activation of astroglial Glu transporters and Mg2+-independent astroglial N-methyl-D-aspartate receptors. Under control conditions, role for neuronal K+/Cl- cotransporter KCC2, but not for glial Na+/K+/Cl- cotransporter NKCC1 was observed. Slight enhancement and inhibition of IOS through non-specific Cl- and volume-regulated anion channels, respectively, were also depicted. High-frequency IOS imaging, evoked by brief afferent stimulation in brain slices provide a new paradigm for studying mechanisms underlying IOS genesis. Major players disclosed this way imply that spatiotemporal IOS reflects glutamatergic neuronal activation and astroglial response, as observed within the hippocampus. Our model may help to better interpret in vivo IOS and support diagnosis in the future

Complements and adjuncts in machine translation

A significant number of natural language processing applications cannot work without syntactic parsing. The automatic syntactic analysis of natural language texts in turn requires an efficient method for differentiating between elements that belong to the predicate's argument structure and those that are attached to it as adjuncts. The focus of our paper is a specific method we are working on for differentiating between verbal complements and adjuncts, which we intend to use for the elaboration of a Hungarian verbal argument structure database, particularly suited for machine translation purposes

Extracting information from participial structures

Our applied linguistic research aims at increasing the efficiency of a rule-based information extraction (IE) system by enhancing it with further grammatical knowledge. The input of the IE system is made up of sentences of business news. The event of the piece of news is identified through the main verb of the sentence, while parti'cipants and circumstances of the event through arguments and adjuncts of the main verb. Our objective was to unfold the hidden information, contained by NPs within which non-finite verbs (e.g. participles) appear. Thus, we invented a rule-system to transform participial structures into sentences with a finite verb, so that they could serve as input of the IE system. To tackle this task we had to be able to distinguish between real participles and adjectives. According to us there are some distributional criteria which can be used as the basis for creating the right classification

Extracting information from participial structures

Our applied linguistic research aims at increasing the efficiency of a rule-based information extraction (IE) system by enhancing it with further grammatical knowledge. The input of the IE system is made up of sentences of business news. The event of the piece of news is identified through the main verb of the sentence, while parti'cipants and circumstances of the event through arguments and adjuncts of the main verb. Our objective was to unfold the hidden information, contained by NPs within which non-finite verbs (e.g. participles) appear. Thus, we invented a rule-system to transform participial structures into sentences with a finite verb, so that they could serve as input of the IE system. To tackle this task we had to be able to distinguish between real participles and adjectives. According to us there are some distributional criteria which can be used as the basis for creating the right classification

Complements and adjuncts in machine translation

A significant number of natural language processing applications cannot work without syntactic parsing. The automatic syntactic analysis of natural language texts in turn requires an efficient method for differentiating between elements that belong to the predicate's argument structure and those that are attached to it as adjuncts. The focus of our paper is a specific method we are working on for differentiating between verbal complements and adjuncts, which we intend to use for the elaboration of a Hungarian verbal argument structure database, particularly suited for machine translation purposes

Polyamidoamine dendrimer impairs mitochondrial oxidation in brain tissue

Background: The potential nanocarrier polyamidoamine (PAMAM) generation 5 (G5-NH2) dendrimer has been shown to evoke lasting neuronal depolarization and cell death in a concentration-dependent manner. In this study we explored the early progression of G5-NH2 action in brain tissue on neuronal and astroglial cells.Results: In order to describe early mechanisms of G5-NH2 dendrimer action in brain tissue we assessed G5-NH2 trafficking, free intracellular Ca2+ and mitochondrial membrane potential (ΨMITO) changes in the rat hippocampal slice by microfluorimetry. With the help of fluorescent dye conjugated G5-NH2, we observed predominant appearance of the dendrimer in the plasma membrane of pyramidal neurons and glial cells within 30 min. Under this condition, G5-NH2 evoked robust intracellular Ca2+ enhancements and ΨMITO depolarization both in pyramidal neurons and astroglial cells. Intracellular Ca2+ enhancements clearly preceded ΨMITO depolarization in astroglial cells. Comparing activation dynamics, neurons and glia showed prevalence of lasting and transient ΨMITO depolarization, respectively. Transient as opposed to lasting ΨMITO changes to short-term G5-NH2 application suggested better survival of astroglia, as observed in the CA3 stratum radiatum area. We also showed that direct effect of G5-NH2 on astroglial ΨMITO was significantly enhanced by neuron-astroglia interaction, subsequent to G5-NH2 evoked neuronal activation.Conclusion: These findings indicate that the interaction of the PAMAM dendrimer with the plasma membrane leads to robust activation of neurons and astroglial cells, leading to mitochondrial depolarization. Distinguishable dynamics of mitochondrial depolarization in neurons and astroglia suggest that the enhanced mitochondrial depolarization followed by impaired oxidative metabolism of neurons may be the primary basis of neurotoxicity. © 2013 Nyitrai et al.; licensee BioMed Central Ltd

Appearance of fast astrocytic component in voltage-sensitive dye imaging of neural activity.

BACKGROUND: Voltage-sensitive dye (VSD) imaging and intrinsic optical signals (IOS) are widely used methods for monitoring spatiotemporal neural activity in extensive networks. In spite of that, identification of their major cellular and molecular components has not been concluded so far. RESULTS: We addressed these issues by imaging spatiotemporal spreading of IOS and VSD transients initiated by Schaffer collateral stimulation in rat hippocampal slices with temporal resolution comparable to standard field potential recordings using a 464-element photodiode array. By exploring the potential neuronal and astroglial molecular players in VSD and IOS generation, we identified multiple astrocytic mechanisms that significantly contribute to the VSD signal, in addition to the expected neuronal targets. Glutamate clearance through the astroglial glutamate transporter EAAT2 has been shown to be a significant player in VSD generation within a very short (<5 ms) time-scale, indicating that astrocytes do contribute to the development of spatiotemporal VSD transients previously thought to be essentially neuronal. In addition, non-specific anion channels, astroglial K(+) clearance through Kir4.1 channel and astroglial Na(+)/K(+) ATPase also contribute to IOS and VSD transients. CONCLUSION: VSD imaging cannot be considered as a spatially extended field potential measurement with predominantly neuronal origin, instead it also reflects a fast communication between neurons and astrocytes

A szótárkészítés támogatása párhuzamos korpuszokon végzett szóillesztéssel

Cikkünkben egy kétnyelv szótárak készítésének gépi támogatására irányuló módszert ismertetünk. A javasolt megközelítés alapja a párhuzamos korpuszokon végzett automatikus szóillesztés. A korpuszvezérelt megközelítés, ezen belül különösen a párhuzamos korpusz használata több okból is hasznosnak bizonyult a lexikográfia számára. Ezek közül a legfontosabb, hogy – megfelel méret reprezentatív korpusz használatával – a javasolt megközelítés garantálja, hogy a legrelevánsabb fordítások fognak szerepelni a szótárban. További elnyt jelent, hogy az összes korpuszbeli példamondat könnyedén hozzáférhet, így a poliszém jelentések közül nagy mennyiség természetes adat alapján választhatjuk ki a legmegfelelbbet. A két fenti tulajdonság különösen alkalmassá teszi az általunk javasolt módszert aktív szótárak elállítására