From safety to frustration: The neural substrates of inhibitory learning in aversive and appetitive conditioning procedures.

Inhibitory associative learning counters the effects of excitatory learning, whether appetitively or aversively motivated. Moreover, the affective responses accompanying the inhibitory associations are of opponent valence to the excitatory conditioned responses. Inhibitors for negative aversive outcomes (e.g. shock) signal safety, while inhibitors for appetitive outcomes (e.g. food reward) elicit frustration and/or disappointment. This raises the question as to whether studies using appetitive and aversive conditioning procedures should demonstrate the same neural substrates for inhibitory learning. We review the neural substrates of appetitive and aversive inhibitory learning as measured in different procedural variants and in the context of the underpinning excitatory conditioning on which it depends. The mesocorticolimbic dopamine pathways, retrosplenial cortex and hippocampus are consistently implicated in inhibitory learning. Further neural substrates identified in some procedural variants may be related to the specific motivation of the learning task and modalities of the learning cues. Finally, we consider the translational implications of our understanding of the neural substrates of inhibitory learning, for obesity and addictions as well as for anxiety disorders.

Distributed Global Debris Thickness Estimates Reveal Debris Significantly Impacts Glacier Mass Balance.

Supraglacial debris affects glacier mass balance as a thin layer enhances surface melting, while a thick layer reduces it. While many glaciers are debris-covered, global glacier models do not account for debris because its thickness is unknown. We provide the first globally distributed debris thickness estimates using a novel approach combining sub-debris melt and surface temperature inversion methods. Results are evaluated against observations from 22 glaciers. We find the median global debris thickness is ∼0.15 ± 0.06 m. In all regions, the net effect of accounting for debris is a reduction in sub-debris melt, on average, by 37%, which can impact regional mass balance by up to 0.40 m water equivalent (w.e.) yr-1. We also find recent observations of similar thinning rates over debris-covered and clean ice glacier tongues is primarily due to differences in ice dynamics. Our results demonstrate the importance of accounting for debris in glacier modeling efforts.

Gallium-rich Pd-Ga phases as supported liquid metal catalysts.

A strategy to develop improved catalysts is to create systems that merge the advantages of heterogeneous and molecular catalysis. One such system involves supported liquid-phase catalysts, which feature a molecularly defined, catalytically active liquid film/droplet layer adsorbed on a porous solid support. In the past decade, this concept has also been extended to supported ionic liquid-phase catalysts. Here we develop this idea further and describe supported catalytically active liquid metal solutions (SCALMS). We report a liquid mixture of gallium and palladium deposited on porous glass that forms an active catalyst for alkane dehydrogenation that is resistant to coke formation and is thus highly stable. X-ray diffraction and X-ray photoelectron spectroscopy, supported by theoretical calculations, confirm the liquid state of the catalytic phase under the reaction conditions. Unlike traditional heterogeneous catalysts, the supported liquid metal reported here is highly dynamic and catalysis does not proceed at the surface of the metal nanoparticles, but presumably at homogeneously distributed metal atoms at the surface of a liquid metallic phase.

Early childhood malnutrition predicts depressive symptoms at ages 11-17.

BACKGROUND: We examined the prevalence of depressive symptoms in Barbadian youth with histories of infantile malnutrition and in a healthy comparison group and the extent to which the effect of malnutrition was mediated/moderated by maternal depression. METHODS: Depressive symptoms were assessed using a 20-item scale administered to youths (11-17 years of age) who had experienced an episode of protein-energy malnutrition (marasmus or kwashiorkor) during the first year of life and in a comparison group of healthy youths without a history of malnutrition. Their mothers completed the same questionnaire on the same test on three occasions when their children were 5-17 years of age at 2-5-year intervals. RESULTS: The prevalence of depressive symptoms was elevated among previously malnourished youth relative to healthy comparison children (p < .001). When youth depression scores were subjected to a longitudinal multiple regression analysis, adjusting for the effect of maternal depressive symptoms, significant effects due to the history of early childhood malnutrition remained and were not discernibly attenuated from an unadjusted analysis. We also found significant independent effects of maternal depressive symptoms on youth depressive symptoms. CONCLUSION: Early childhood malnutrition contributed independently to depressive symptoms in youths who experienced a significant episode of malnutrition in the first year of life. This relationship was not mediated or moderated by the effects of maternal depression. Whether the later vulnerability to depression is a direct effect of the episode of malnutrition and related conditions early in life or whether it is mediated by the more proximal neurobehavioral effects of the malnutrition remains to be determined.

Clinical study of mini-nutritional assessment for older Chinese inpatients.

BACKGROUND: Malnutrition is a common problem in older patients. Early detection of malnutrition is an important task in clinical practice. The MNA has become an extensively used tool to evaluate nutritional status in European countries and the United States. OBJECTIVE: We evaluated the Mini-Nutritional Assessment (MNA) test and the short-form MNA (MNA-SF) test as screening tools for malnutrition in older Chinese inpatients and focused on finding an optimal cutoff point for MNA total score and MNA-SF score. DESIGN: One hundred eighty-four older Chinese inpatients were enrolled in this study from July to August 2006. Nutritional assessment included MNA, anthropometric measurements, and biochemical markers. RESULTS: According to the original cutoff point of the full MNA, 19.6% of those assessed were malnourished, 53.2% were at risk of malnutrition and 27.2% were well nourished. Correlations were found between MNA, MNA-SF and body mass index, triceps skinfold thickness, serum albumin, lymphocyte count, hemoglobin, lymphocyte ratio. With the most proper cutoff point lower than 19 indicating malnutrition, when using serum albumin (< 35.0 g/L) as the indicator, the sensitivity and specificity of the MNA total score were 0.6286 and 0.7466; when using BMI (< 18.5 kg/m2) as the indicator, the sensitivity and specificity were 0.8636 and 0.7469. The incidence rate of malnutrition was 32.6%. The most proper cutoff point of MNA-SF was lower than 12. CONCLUSION: The MNA and MNA-SF were useful tools to identify older Chinese inpatients with malnutrition. However, the cutoff point of the MNA should be modulated for this population.

Racemic salbutamol administration to guinea-pigs selectively augments airway smooth muscle responsiveness to cholinoceptor agonists.

1. An aim of this study was to investigate whether continuous in vivo administration of a low dose of salbutamol to guinea-pigs alters the responsiveness of airway smooth muscle in vitro. 2. Osmotic minipumps containing a solution of racemic salbutamol were implanted subcutaneously in guinea-pigs. The drug was infused at a dose of 0.2 mg kg(-1) day(-1) for 10 days and, at the end of that time, the trachea was isolated and concentration-response relationships to several contractile agonists were examined. 3. This treatment resulted in significant increases in the maximum tension developed by tracheal preparations in response to cholinoceptor agonists, carbachol and methacholine. 4. Cumulative concentration-response curves for histamine, leukotriene D4, and KCl were similar in tracheal segments from saline-control and salbutamol-infused animals. 5. Time course experiments showed that augmented airway contractile responsiveness to cholinoceptor agonists was reversible within 3 days after cessation of the 10 day salbutamol infusion. 6. Our findings support the hypothesis that beta2-adrenoceptor agonist drugs, administered over time in vivo, induce a transient hyperresponsiveness of airway smooth muscle to cholinergic bronchoconstrictor stimuli.

Dynamic binding of histone H1 to chromatin in living cells.

The linker histone H1 is believed to be involved in chromatin organization by stabilizing higher-order chromatin structure. Histone H1 is generally viewed as a repressor of transcription as it prevents the access of transcription factors and chromatin remodelling complexes to DNA. Determining the binding properties of histone H1 to chromatin in vivo is central to understanding how it exerts these functions. We have used photobleaching techniques to measure the dynamic binding of histone H1-GFP to unperturbed chromatin in living cells. Here we show that almost the entire population of H1-GFP is bound to chromatin at any one time; however, H1-GFP is exchanged continuously between chromatin regions. The residence time of H1-GFP on chromatin between exchange events is several minutes in both euchromatin and heterochromatin. In addition to the mobile fraction, we detected a kinetically distinct, less mobile fraction. After hyperacetylation of core histones, the residence time of H1-GFP is reduced, suggesting a higher rate of exchange upon chromatin remodelling. These results support a model in which linker histones bind dynamically to chromatin in a stop-and-go mode.

Localization of glucocorticoid hormone receptors in mitochondria of human cells.

Glucocorticoid hormones regulate the transcription of nuclear genes by way of their cognate receptors. In addition, these hormones also modulate mitochondrial gene transcription by mechanisms which are as yet poorly understood. Using immunofluorescence labeling and confocal laser scanning microscopy we show that the glucocorticoid receptor of HeLa and Hep-2 cells is specifically enriched at the sites of the mitochondria which were visualized by labeling with the vital dye CMX and antibodies against cytochrome oxidase subunit I. Immunogold electron microscopy demonstrated that the receptor was located within the inner space of the mitochondria. Immunoblotting experiments also revealed the presence of glucocorticoid receptor in mitochondria isolated from HeLa and Hep-2 cells. Finally, living HeLa cells expressing green fluorescent-glucocorticoid receptor fusion protein revealed a distinct mitochondrial GFP fluorescence. Our results support the concept of a receptor-mediated direct action of steroid hormones on mitochondrial gene transcription.

Storage of X-ray photons in a crystal resonator

The temporal structure and high brilliance of the X-ray beams produced by third-generation synchrotrons open up new possibilities in time-dependent diffraction and spectroscopy, where timescales down to the sub-nanosecond regime can now be accessed. These beam properties are such that one can envisage the development of the X-ray equivalent of optical components, such as photon delay lines and resonators, that have proved indispensable in a wide range of experiments--for example, pump-probe and multiple-interaction experiments--and (through shaping the temporal structure and repetition rate of the beams) time-dependent measurements in crystallography, physics, biology and chemistry. Optical resonators, such as those used in lasers, are available at wavelengths from the visible to soft X-rays. Equivalent components for hard X-rays have been discussed for more than thirty years, but have yet to be realized. Here we report the storage of hard X-ray photons (energy 15.817 keV) in a crystal resonator formed by two plates of crystalline silicon. The photons are stored for as many as 14 back-and-forth cycles within the resonator, each cycle separated by one nanosecond.

Measurement of albuterol in guinea pig serum by high performance liquid chromatography with fluorescence detection.

A sensitive, simple and reproducible high performance liquid chromatographic method for detecting and quantifying albuterol in guinea pig serum is described. A structurally related compound, bamethan, was used as an internal standard. The method employs ion-pair extraction with di(2-ethylhexyl)phosphate followed by chromatography on a Zorbax SB C18 reversed-phase column. Fluorescence detection was used to identify the compounds of interest. The calibration curve was linear between 1 and 50 ng/mL albuterol hemisulfate salt (0.83 and 41.50 ng/mL albuterol base), and the limit of detection for a 1 mL sample was 1 ng/mL albuterol hemisulfate salt (0.83 ng/mL albuterol base). Serum levels of albuterol were quantified from guinea pigs that had received the drug by continuous subcutaneous infusion at a dose of 0.2 mg/kg/day for 1, 5 or 10 days, or 10 days followed by a 24 h washout period.

Haploinsufficiency of CBFA2 causes familial thrombocytopenia with propensity to develop acute myelogenous leukaemia.

Familial platelet disorder with predisposition to acute myelogenous leukaemia (FPD/AML, MIM 601399) is an autosomal dominant disorder characterized by qualitative and quantitative platelet defects, and propensity to develop acute myelogenous leukaemia (AML). Informative recombination events in 6 FPD/AML pedigrees with evidence of linkage to markers on chromosome 21q identified an 880-kb interval containing the disease gene. Mutational analysis of regional candidate genes showed nonsense mutations or intragenic deletion of one allele of the haematopoietic transcription factor CBFA2 (formerly AML1) that co-segregated with the disease in four FPD/AML pedigrees. We identified heterozygous CBFA2 missense mutations that co-segregated with the disease in the remaining two FPD/AML pedigrees at phylogenetically conserved amino acids R166 and R201, respectively. Analysis of bone marrow or peripheral blood cells from affected FPD/AML individuals showed a decrement in megakaryocyte colony formation, demonstrating that CBFA2 dosage affects megakaryopoiesis. Our findings support a model for FPD/AML in which haploinsufficiency of CBFA2 causes an autosomal dominant congenital platelet defect and predisposes to the acquisition of additional mutations that cause leukaemia.

Structure and function of the nucleolus.

The activity of the ribosomal RNA genes generates a distinct subnuclear structure, the nucleolus, which is the site of ribosome biogenesis. The signals that target proteins and snoRNAs (small nucleolar RNAs) to the nucleolus, the nuclear import of ribosomal proteins, the export of the completed ribosomal subunits and the molecular organization of the nucleolus have been the subject of intense research during the past year. Evidence is accumulating that nucleoli functionally interact with coiled bodies and are also involved in the maturation of non-ribosomal RNA species.

Neuroblastoma cells expressing mature IL-18, but not proIL-18, induce a strong and immediate antitumor immune response.

Retroviral constructs were designed to express the novel cytokine interleukin 18 (IL-18), also known as interferon-gamma-inducing factor, in a murine neuroblastoma cell line [neuro-2a (N-2a)] to examine the effects of IL-18 expression on tumorigenicity. N-2a cells expressing proIL-18 (N-2a/IL-18p) were as tumorigenic as parental N-2a cells, whereas N-2a cells engineered to secrete mature IL-18 (N-2a/IL-18m) were nontumorigenic. Inoculation of mice with N-2a/IL-18m generated immediate immunity to parental N-2a. N-2a/IL-18m formed tumors in mice depleted of CD4+ and CD8+ T cells, suggesting that the antitumor immune response was T cell mediated. The resulting T-helper (Th) immune response was also characterized in vitro and had a large Th1 component based on in vitro production of the cytokines IFN-gamma and granulocyte macrophage colony-stimulating factor in response to tumor cells and IL-18.

Architecture of the nuclear periphery of rat pachytene spermatocytes: distribution of nuclear envelope proteins in relation to synaptonemal complex attachment sites.

The nucleus of spermatocytes provides during the first meiotic prophase an interesting model for investigating relationships of the nuclear envelope (NE) with components of the nuclear interior. During the pachytene stage, meiotic chromosomes are synapsed via synaptonemal complexes (SCs) and attached through both ends to the nuclear periphery. This association is dynamic because chromosomes move during the process of synapsis and desynapsis that takes place during meiotic prophase. The NE of spermatocytes possesses some peculiarities (e.g., lower stability than in somatic cells, expression of short meiosis-specific lamin isoforms called C2 and B3) that could be critically involved in this process. For better understanding of the association of chromosomes with the nuclear periphery, in the present study we have investigated the distribution of NE proteins in relation to SC attachment sites. A major outcome was the finding that lamin C2 is distributed in the form of discontinuous domains at the NE of spermatocytes and that SC attachment sites are embedded in these domains. Lamin C2 appears to form part of larger structures as suggested by cell fractionation experiments. According to these results, we propose that the C2-containing domains represent local reinforcements of the NE that are involved in the proper attachment of SCs.

Dynamic relocation of chromosomal protein HMG-17 in the nucleus is dependent on transcriptional activity.

Chromosomal proteins HMG-14/-17 are nucleosomal binding proteins, which alter the structure of the chromatin fiber and enhance transcription, but only from chromatin templates. Here we show that in tissue culture cells, HMG-17 protein colocalizes with sites of active transcription. Incubation of permeabilized cells with a peptide corresponding to the nucleosomal binding domains of HMG-14/-17 specifically arrested polymerase II-dependent transcription. In these cells the peptide displaces HMG-17 from chromatin and reduces the cellular content of the protein. These results suggest that the presence of HMG-14/-17 in chromatin is required for efficient polymerase II transcription. In non-permeabilized, actively transcribing cells, the protein is dispersed in a punctate pattern, throughout the nucleus. Upon transcriptional inhibition by alpha-amanitin or actinomycin D, the protein gradually redistributes until it localizes fully to interchromatin granule clusters, together with the splicing factor SC35. The results suggest that the association of HMG-17 with chromatin is dynamic rather than static, and that in the absence of transcription, HMG-17 is released from chromatin and accumulates in interchromatin granule clusters. Thus, the intranuclear distribution of chromosomal proteins which act as architectural elements of chromatin structure may be dynamic and functionally related to the transcriptional activity of the cell.

Identification of a novel mRNA-associated protein in oocytes of Pleurodeles waltl and Xenopus laevis.

Amphibian oocytes accumulate a large pool of mRNA molecules for future embryonic development. Due to their association with specific proteins the stored maternal RNAs are translationally repressed. The identification of these RNA-binding proteins and the characterization of their functional domains may contribute to the understanding of the translational repression mechanisms and the subsequent activation processes during early embryogenesis. Here we present the complete Pleurodeles cDNA sequence of a cytoplasmic protein which is present in oocytes, eggs, and very early cleavage stage embryos but undetectable in postcleavage embryo and adult tissues. The predicted molecular mass of the protein is 55 kDa and the apparent molecular mass as determined by SDS-PAGE, 68 kDa. The deduced amino acid sequence reveals proline- and serine-rich domains in the aminoterminal part as well as two RGG boxes which represent characteristic motifs of several RNA-binding proteins. No distinct homologies to the consensus RNA recognition motif were found. The 55-kDa protein was recovered in cytoplasmic ribonucleoprotein (RNP) particles containing poly(A)+ RNA. It was therefore termed RAP55 for mRNA-associated protein of 55 kDa. However, a direct interaction of RAP55 with mRNA could not be demonstrated by UV-crosslinking experiments, indicating that it is bound to mRNP complexes via protein-protein interactions. RAP55 is evolutionarily conserved since antibodies raised against a recombinant Pleurodeles RAP55 fragment recognize the protein from Pleurodeles and Xenopus. The expression pattern and intracellular distribution of RAP55 suggest that it is part of those mRNP particles which are translationally repressed during oogenesis and become activated upon progesterone-induced oocyte maturation.

Chromosomal proteins HMG-14 and HMG-17 are released from mitotic chromosomes and imported into the nucleus by active transport.

The high mobility group 14/17 (HMG-14/-17) proteins form specific complexes with nucleosome core particles and produce distinct footprints on nucleosomal DNA. Therefore, they could be an integral part of the chromatin fiber. Here we show that during the cell cycle these proteins are transiently dissociated from chromatin. They colocalize with the nuclear DNA in interphase and prophase but not in metaphase and anaphase. They relocate into the nucleus and colocalize again with the DNA in late telophase, concomitantly with the appearance of the nuclear envelope. Thus, these nucleosomal binding proteins are not always associated with chromatin. Using reconstituted nuclei and permeabilized cells, we demonstrate that these two small proteins, with a molecular mass <10 kD, are actively imported into the nucleus. We identify the major elements involved in the nuclear import of these chromosomal proteins: HMG-14/-17 proteins contain an intrinsic bipartite nuclear localization signal, and their entry into the nucleus through nuclear pores requires energy and the participation of importin alpha. These findings suggest that the cell cycle-related association of HMG-14/-17 with chromatin is dependent on, and perhaps regulated by, nuclear import processes.

Genomic instability and catalase gene amplification induced by chronic exposure to oxidative stress.

Chronic exposure (>200 days) of HA1 fibroblasts to increasing concentrations of H2O2 or O2 results in the development of a stable oxidative stress-resistant phenotype characterized by increased cellular antioxidant levels, particularly catalase (D. R. Spitz et al, Arch. Biochem. Biophys., 279: 249-260, 1990; D. R. Spitz et al., Arch. Biochem. Biophys., 292: 221-227, 1992; S. J. Sullivan et al., Am. J. Physiol. (Lung Cell. Mol. Physiol.), 262: L748-L756, 1992). Acutely stressed cells failed to develop a stably resistant phenotype or increased catalase activity, suggesting that chronic exposure is required for the development of this phenotype. This study investigates the mechanism underlying increased catalase activity in the H2O2- and O2-resistant cell lines. In H2O2- and O2-resistant cells, catalase activity was found to be 20-30-fold higher than that in the parental HA1 cells and correlated with increased immunoreactive catalase protein and steady-state catalase mRNA levels. Resistant cell lines also demonstrated a 4-6-fold increase in catalase gene copy number by Southern blot analysis, which is indicative of gene amplification. Chromosome banding and in situ hybridization studies identified a single amplified catalase gene site located on a rearranged chromosome with banding similarities to Z-4 in the hamster fibroblast karyotype. Simultaneous in situ hybridization with a Z-4-specific adenine phosphoribosyltransferase (APRT) gene revealed that the amplified catalase genes were located proximate to APRT on the same chromosome in all resistant cells. In contrast, HA1 cells contained only single copies of the catalase gene that were not located on APRT-containing chromosomes, indicating that amplification is associated with a chromosomal rearrangement possibly involving Z-4. The fact that chronic exposure of HA1 cells to either HO2 or 95% O2 resulted in gene amplification suggests that gene amplification represents a generalized response to oxidative stress, contributing to the development of resistant phenotypes. These results support the hypothesis that chronic exposure to endogenous metabolic or exogenous environmental oxidative stress represents an important factor contributing to gene amplification and genomic instability.