The spatio-temporal brain dynamics of processing and integrating sound localization cues in humans.

Interaural intensity and time differences (IID and ITD) are two binaural auditory cues for localizing sounds in space. This study investigated the spatio-temporal brain mechanisms for processing and integrating IID and ITD cues in humans. Auditory-evoked potentials were recorded, while subjects passively listened to noise bursts lateralized with IID, ITD or both cues simultaneously, as well as a more frequent centrally presented noise. In a separate psychophysical experiment, subjects actively discriminated lateralized from centrally presented stimuli. IID and ITD cues elicited different electric field topographies starting at approximately 75 ms post-stimulus onset, indicative of the engagement of distinct cortical networks. By contrast, no performance differences were observed between IID and ITD cues during the psychophysical experiment. Subjects did, however, respond significantly faster and more accurately when both cues were presented simultaneously. This performance facilitation exceeded predictions from probability summation, suggestive of interactions in neural processing of IID and ITD cues. Supra-additive neural response interactions as well as topographic modulations were indeed observed approximately 200 ms post-stimulus for the comparison of responses to the simultaneous presentation of both cues with the mean of those to separate IID and ITD cues. Source estimations revealed differential processing of IID and ITD cues initially within superior temporal cortices and also at later stages within temporo-parietal and inferior frontal cortices. Differences were principally in terms of hemispheric lateralization. The collective psychophysical and electrophysiological results support the hypothesis that IID and ITD cues are processed by distinct, but interacting, cortical networks that can in turn facilitate auditory localization.

Distinct subcellular localization of beta-tubulin epitopes in the adult mouse brain.

A panel of monoclonal antibodies specific of alpha-tubulin (TU-01, TU-09) and beta-tubulin (TU-06, TU-13) subunits was used to study the location of N-terminal structural domains of tubulin in adult mouse brain. The specificity of antibodies was confirmed b immunoblotting experiments. Immunohistochemical staining of vibratome sections from cerebral cortex, cerebellum, hippocampus, and corpus callosum showed that antibodies TU-01, TU-09, and TU-13 reacted with neuronal and glial cells and their processes, whereas the TU-06 antibody stained only the perikarya. Dendrites and axons were either unstained or their staining was very weak. As the TU-06 epitope is located on the N-terminal structural domain of beta-tubulin, the observed staining pattern cannot be interpreted as evidence of a distinct subcellular localization of beta-tubulin isotypes or known post-translational modifications. The limited distribution of the epitope could, rather, reflect differences between the conformations of tubulin molecules in microtubules of somata and neurites or, alternatively, a specific masking of the corresponding region on the N-terminal domain of beta-tubulin by interacting protein(s) in dendrites and axons.

Dominant negative MyD88 proteins inhibit interleukin-1beta /interferon-gamma -mediated induction of nuclear factor kappa B-dependent nitrite production and apoptosis in beta cells.

Insulin-dependent diabetes mellitus is an autoimmune disease in which pancreatic islet beta cells are destroyed by a combination of immunological and inflammatory mechanisms. In particular, cytokine-induced production of nitric oxide has been shown to correlate with beta cell apoptosis and/or inhibition of insulin secretion. In the present study, we investigated whether the interleukin (IL)-1beta intracellular signal transduction pathway could be blocked by overexpression of dominant negative forms of the IL-1 receptor interacting protein MyD88. We show that overexpression of the Toll domain or the lpr mutant of MyD88 in betaTc-Tet cells decreased nuclear factor kappaB (NF-kappaB) activation upon IL-1beta and IL-1beta/interferon (IFN)-gamma stimulation. Inducible nitric oxide synthase mRNA accumulation and nitrite production, which required the simultaneous presence of IL-1beta and IFN-gamma, were also suppressed by approximately 70%, and these cells were more resistant to cytokine-induced apoptosis as compared with parental cells. The decrease in glucose-stimulated insulin secretion induced by IL-1beta and IFN-gamma was however not prevented. This was because these dysfunctions were induced by IFN-gamma alone, which decreased cellular insulin content and stimulated insulin exocytosis. These results demonstrate that IL-1beta is involved in inducible nitric oxide synthase gene expression and induction of apoptosis in mouse beta cells but does not contribute to impaired glucose-stimulated insulin secretion. Furthermore, our data show that IL-1beta cellular actions can be blocked by expression of MyD88 dominant negative proteins and, finally, that cytokine-induced beta cell secretory dysfunctions are due to the action of IFN-gamma.

Utilització de plantes d'Arabidopsis thaliana mutants de CK2 per a l'establiment de línies cel·lulars i per a l'estudi de la implicació de la CK2 en l'estructuració de la cromatina

La proteïna CK2 és una Ser/Thr fosfotransferasa evolutivament conservada. Està formada per dues subunitats diferents, α (catalítica) i β (reguladora), que s’associen en un complex heterotetramèric (α2β2). L’activitat d’aquest enzim està regulada per varis mecanismes que la modulen diferencialment en funció del substrat, entre ells, la localització subcel·lular de les diferents subunitats. A partir de plantes transgèniques que contenen les subunitats de CK2 fusionades a una proteïna fluorescent (GFP o YFP) hem establert línies cel·lulars que permetran analitzar, en treballs futurs, els canvis de localització subcel·lular de les subunitats de CK2 provocats per diferents estímuls. La CK2 intervé en un gran nombre de processos cel·lulars, entre d’altres, metabolisme, transport a nucli, control del cicle cel·lular i reparació del DNA. Amb la finalitat d’estudiar el paper de la CK2 en el desenvolupament de les plantes, membres del grup van generar un mutant dominant negatiu per transformació estable de plantes d’Arabidopsis thaliana. Estudis previs mostraven que la pèrdua d’activitat CK2 en aquestes plantes provocava una alteració de l’activitat mitòtica i un bloqueig del cicle cel·lular. Els resultats obtinguts en aquest treball indiquen que aquests fenotips podrien ser conseqüència de la implicació de la CK2 en processos d’estructuració de la cromatina.

Transportin regulates nuclear import of CD44.

CD44 is a facultative cell surface proteoglycan that serves as the principal cell surface receptor for hyaluronan (HA). Studies have shown that in addition to participating in numerous signaling pathways, CD44 becomes internalized upon engagement by ligand and that a portion of its intracellular domain can translocate to the nucleus where it is believed to play a functional role in cell proliferation and survival. However, the mechanisms whereby fragments of CD44 enter the nucleus have not been elucidated. Here we show that CD44 interacts with two import receptors of the importin β superfamily, importin β itself and transportin. Inhibition of importin β-dependent transport failed to block CD44 accumulation in the nucleus. By contrast, inhibition of the transportin-dependent pathway abrogated CD44 import. Mutagenesis of the intracellular domain of CD44 revealed that the 20 membrane-proximal residues contain sequences required for transportin-mediated nuclear transport. Our observations provide evidence that CD44 interacts with importin family members and identify the transportin-dependent pathway as the mechanism whereby full-length CD44 enters the nucleus.

Maintenance of hepatic nuclear factor 6 in postnatal islets impairs terminal differentiation and function of beta-cells.

The Onecut homeodomain transcription factor hepatic nuclear factor 6 (Hnf6) is necessary for proper development of islet beta-cells. Hnf6 is initially expressed throughout the pancreatic epithelium but is downregulated in endocrine cells at late gestation and is not expressed in postnatal islets. Transgenic mice in which Hnf6 expression is maintained in postnatal islets (pdx1(PB)Hnf6) show overt diabetes and impaired glucose-stimulated insulin secretion (GSIS) at weaning. We now define the mechanism whereby maintenance of Hnf6 expression postnatally leads to beta-cell dysfunction. We provide evidence that continued expression of Hnf6 impairs GSIS by altering insulin granule biosynthesis, resulting in a reduced response to secretagogues. Sustained expression of Hnf6 also results in downregulation of the beta-cell-specific transcription factor MafA and a decrease in total pancreatic insulin. These results suggest that downregulation of Hnf6 expression in beta-cells during development is essential to achieve a mature, glucose-responsive beta-cell.

Site-specific conjugation of a radioiodinated phenethylamine derivative to a monoclonal antibody results in increased radioactivity localization in tumor.

The preparation of a novel radioiodination reagent, the (aminooxy)acetyl derivative of (p-[125]-iodophenyl)ethylamine, is described. Conventional radioiodination of proteins involves the formation of iodotyrosine residues, but for in vivo applications such as thyroid or stomach immunoscintigraphy, the susceptibility of these residues to tissue dehalogenases constitutes a serious disadvantage. Using our new compound, which has a particularly nonreactive aromatic ring, we confirm and extend studies published by other workers indicating the much greater in vivo stability of iodophenyl compounds compared to the more conventional iodophenolic ones. In addition, the aminooxy group of our reagent gives a stable and specific linkage to aldehyde groups formed by periodate oxidation on the sugar moiety of antibody molecules. In vitro, favorable binding activity and high stability was obtained with a (([125I]iodoaryl)amino)oxy labeled monoclonal antibody directed against carcinoembryonic antigen. In vivo, using paired labeling experiments in nude mice bearing colon carcinoma xenografts, the (([125I]iodoaryl)amino)oxy-MAb (MAb = monoclonal antibody) was compared with the same MAb 131I-labeled by conventional chloramine-T method. Tumor 125I concentration of (arylamino)oxy MAb (measured as percent injected dose per gram) was significantly higher as compared to values obtained with a conventionally labeled 131I antibody. Additionally, thyroid uptake, an indicator of iodine release from the antibody, was up to 25 times lower after injection of 125I-MAb obtained by the new method as compared to the conventionally iodinated 131I-MAb.

Differential regulation of the Hippo pathway by adherens junctions and apical-basal cell polarity modules.

Adherens junctions (AJs) and cell polarity complexes are key players in the establishment and maintenance of apical-basal cell polarity. Loss of AJs or basolateral polarity components promotes tumor formation and metastasis. Recent studies in vertebrate models show that loss of AJs or loss of the basolateral component Scribble (Scrib) cause deregulation of the Hippo tumor suppressor pathway and hyperactivation of its downstream effectors Yes-associated protein (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ). However, whether AJs and Scrib act through the same or independent mechanisms to regulate Hippo pathway activity is not known. Here, we dissect how disruption of AJs or loss of basolateral components affect the activity of the Drosophila YAP homolog Yorkie (Yki) during imaginal disc development. Surprisingly, disruption of AJs and loss of basolateral proteins produced very different effects on Yki activity. Yki activity was cell-autonomously decreased but non-cell-autonomously elevated in tissues where the AJ components E-cadherin (E-cad) or α-catenin (α-cat) were knocked down. In contrast, scrib knockdown caused a predominantly cell-autonomous activation of Yki. Moreover, disruption of AJs or basolateral proteins had different effects on cell polarity and tissue size. Simultaneous knockdown of α-cat and scrib induced both cell-autonomous and non-cell-autonomous Yki activity. In mammalian cells, knockdown of E-cad or α-cat caused nuclear accumulation and activation of YAP without overt effects on Scrib localization and vice versa. Therefore, our results indicate the existence of multiple, genetically separable inputs from AJs and cell polarity complexes into Yki/YAP regulation.

The Trypanosoma cruzi Genome Project: Nuclear Karyotype and Gene Mapping of Clone CL Brener

By using improved pulsed field gel electrophoresis conditions, the molecular karyotype of the reference clone CL Brener selected for Trypanosoma cruzi genome project was established. A total of 20 uniform chromosomal bands ranging in size from 0.45 to 3.5 Megabase pairs (Mbp) were resolved in a single run. The weighted sum of the chromosomal bands was approximately 87 Mbp. Chromoblots were hybridized with 39 different homologous probes, 13 of which identified single chromosomes. Several markers showed linkage and four different linkage groups were identified, each comprising two markers. Densitometric analysis suggests that most of the chromosomal bands contain two or more chromosomes representing either homologous chromosomes and/or heterologous chromosomes with similar sizes

Towards the Physical Map of the Trypanosoma cruzi Nuclear Genome: Construction of YAC and BAC Libraries of the Reference Clone T. cruzi CL-Brener

Strategies to construct the physical map of the Trypanosoma cruzi nuclear genome have to capitalize on three main advantages of the parasite genome, namely (a) its small size, (b) the fact that all chromosomes can be defined, and many of them can be isolated by pulse field gel electrophoresis, and (c) the fact that simple Southern blots of electrophoretic karyotypes can be used to map sequence tagged sites and expressed sequence tags to chromosomal bands. A major drawback to cope with is the complexity of T. cruzi genetics, that hinders the construction of a comprehensive genetic map. As a first step towards physical mapping, we report the construction and partial characterization of a T. cruzi CL-Brener genomic library in yeast artificial chromosomes (YACs) that consists of 2,770 individual YACs with a mean insert size of 365 kb encompassing around 10 genomic equivalents. Two libraries in bacterial artificial chromosomes (BACs) have been constructed, BACI and BACII. Both libraries represent about three genome equivalents. A third BAC library (BAC III) is being constructed. YACs and BACs are invaluable tools for physical mapping. More generally, they have to be considered as a common resource for research in Chagas disease

Cytochemical and immunocytochemical characterization of nuclear bodies during hibernation.

Brown adipose tissue and liver of hibernating, arousing and euthermic individuals of the dormouse Muscardinus avellanarius were studies using ultrastructural cytochemistry and immunocytochemistry with the aim to investigate possible fine structural modifications of the cell nucleus during the seasonal cycle. The general morphology of brown adipocyte and hepatocyte nuclei was similar in the three experimental groups. However, three nuclear structural constituents were identified only in hibernating individuals: coiled bodies (CBs) and amorphous bodies (ABs) were observed in hepatocytes and, together with bundles of nucleoplasmic fibrils (NF), were present in brown adipocytes of hibernating dormice. In arousing animals only some structural constituents suggestive of poorly structured CBs were found. The latter showed the same immunocytochemical features as CBs of hibernating individuals, suggesting that they are disappearing CBs. A possible involvement of CBs in storing and/or processing RNA which must be rapidly and abundantly released upon arousal is discussed. ABs similarly to CBs contain RNA and nucleoplasmic ribonucleoproteins (RNPs) and could also be involved in mRNA pathways. NF do not contain nucleic acids or RNPs and seem to be composed of protein-aceous material; their functional role in the nuclear metabolism of hibernating brown adipocytes remains unclear.

The problem of the competitiveness of nuclear energy: a biophysical explanation

In this study I try to explain the systemic problem of the low economic competitiveness of nuclear energy for the production of electricity by carrying out a biophysical analysis of its production process. Given the fact that neither econometric approaches nor onedimensional methods of energy analyses are effective, I introduce the concept of biophysical explanation as a quantitative analysis capable of handling the inherent ambiguity associated with the concept of energy. In particular, the quantities of energy, considered as relevant for the assessment, can only be measured and aggregated after having agreed on a pre-analytical definition of a grammar characterizing a given set of finite transformations. Using this grammar it becomes possible to provide a biophysical explanation for the low economic competitiveness of nuclear energy in the production of electricity. When comparing the various unit operations of the process of production of electricity with nuclear energy to the analogous unit operations of the process of production of fossil energy, we see that the various phases of the process are the same. The only difference is related to characteristics of the process associated with the generation of heat which are completely different in the two systems. Since the cost of production of fossil energy provides the base line of economic competitiveness of electricity, the (lack of) economic competitiveness of the production of electricity from nuclear energy can be studied, by comparing the biophysical costs associated with the different unit operations taking place in nuclear and fossil power plants when generating process heat or net electricity. In particular, the analysis focuses on fossil-fuel requirements and labor requirements for those phases that both nuclear plants and fossil energy plants have in common: (i) mining; (ii) refining/enriching; (iii) generating heat/electricity; (iv) handling the pollution/radioactive wastes. By adopting this approach, it becomes possible to explain the systemic low economic competitiveness of nuclear energy in the production of electricity, because of: (i) its dependence on oil, limiting its possible role as a carbon-free alternative; (ii) the choices made in relation to its fuel cycle, especially whether it includes reprocessing operations or not; (iii) the unavoidable uncertainty in the definition of the characteristics of its process; (iv) its large inertia (lack of flexibility) due to issues of time scale; and (v) its low power level.

Sex differences in nuclear receptor-regulated liver metabolic pathways.

Liver metabolism is markedly sex-dimorphic; accordingly, the prevalence of liver diseases is different between sexes. The superfamily of nuclear receptors (NRs) governs the proper expression of key liver metabolism genes by sensing lipid-soluble hormones and dietary lipids. When the expression of those genes is deregulated, disease development is favored. However, we lack a comprehensive picture of the differences between NR actions in males and females. Here, we reviewed explorative studies that assessed NR functions in both sexes, and we propose a first map of sex-dimorphic NR expression in the liver. Our analysis suggested that NRs in the female liver exhibited cross-talk with more liver-protective potential than NRs in male liver. This study provides empirical support to the hypothesis that women are more resilient to some liver diseases than men, based on a more compensative NR network. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

The expression of nuclear 3,5,3' triiodothyronine receptors is induced in Schwann cells by nerve transection.

The effects of thyroid hormones on the nervous system are mediated by the presence of nuclear T3 receptors (NT3R). In this study, the expression of NT3R was investigated in spinal cord, dorsal root ganglia (DRG), or sciatic nerve of adult rats after immunostaining with a 2B3-NT3R monoclonal antibody which recognizes both alpha and beta types of NT3R. The specificity of this monoclonal antibody was confirmed by Western blots. The 2B3-NT3R monoclonal antibody recognized one band corresponding to a molecular weight of 57 kDa in extract of spinal cord or DRG. No staining was observed on immunoblot of intact sciatic nerve. In the spinal cord, the nuclei of the neurons and glial cells including both astrocytes and oligodendrocytes exhibited 2B3-NT3R immunoreactivity. While all the nuclei of the DRG sensory neurons expressed the NT3R, all the nuclei of the satellite and Schwann cells were devoid of any immunoreaction. In the sciatic nerve, the nuclei of the Schwann cells also lacked 2B3-NT3R-immunoreactivity. After sciatic nerve transection in vivo, Schwann cell nuclei, which never expressed NT3R in intact nerves of adult rats, displayed a clear 2B3-NT3R immunoreaction in proximal and distal stumps adjacent to the section. Double immunostaining with antibodies raised to 3-sulfogalactosylceramide or S100 confirmed that most of the NT3R containing nuclei belong to Schwann cells. In dissociated cell cultures grown in vitro from sciatic nerves, Schwann cells exhibited 2B3-NT3R immunoreactivity. These data suggest that the inhibition of NT3R expression in Schwann cells ensheathing axons in intact nerve is reversed when the axons are degenerating or lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

Uranium reserve, nuclear fuel cycle delusion, CO2 emission from the sea, and electricity supply: reflections after the fuel meltdown of Fukushima nuclear power units

The Great Tohoku-Kanto earthquake and resulting tsunami has brought considerable attention to the issue of the construction of new power plants. We argue in this paper, nuclear power is not a sustainable solution to energy problems. First, we explore the stock of uranium-235 and the different schemes developed by the nuclear power industry to exploit this resource. Second, we show that these methods, fast breeder and MOX fuel reactors, are not feasible. Third, we show that the argument that nuclear energy can be used to reduce CO2 emissions is false: the emissions from the increased water evaporation from nuclear power generation must be accounted for. In the case of Japan, water from nuclear power plants is drained into the surrounding sea, raising the water temperature which has an adverse affect on the immediate ecosystem, as well as increasing CO2 emissions from increased water evaporation from the sea. Next, a short exercise is used to show that nuclear power is not even needed to meet consumer demand in Japan. Such an exercise should be performed for any country considering the construction of additional nuclear power plants. Lastly, the paper is concluded with a discussion of the implications of our findings.