Regulation of the formation and water permeability of endosomes from toad bladder granular cells.

Osmotic water permeability (Pf) in toad bladder is regulated by the vasopressin (VP)-dependent movement of vesicles containing water channels between the cytoplasm and apical membrane of granular cells. Apical endosomes formed in the presence of serosal VP have the highest Pf of any biological or artificial membrane (Shi and Verkman. 1989. J. Gen. Physiol. 94:1101-1115). We examine here: (a) the influence of protein kinase A and C effectors on transepithelial Pf (Pfte) in intact bladders and on the number and Pf of labeled endosomes, and (b) whether endosome Pf can be modified physically or biochemically. In paired hemibladder studies, Pfte induced by maximal serosal VP (50 mU/ml, 0.03 cm/s) was not different than that induced by 8-Br-cAMP (1 mM), forskolin (50 microM), VP + 8-Br-cAMP, or VP + forskolin. Pf was measured in endosomes labeled in intact bladders with carboxyfluorescein by a stopped-flow, fluorescence-quenching assay using an isolated microsomal suspension; the number and Pf (0.08-0.11 cm/s, 18 degrees C) of labeled endosomes was not different in bladders treated with VP, forskolin, and 8-Br-cAMP. Protein kinase C activation by 1 microM mucosal phorbol myristate acetate (PMA) induced submaximal bladder Pfte (0.015 cm/s) and endosome Pf (0.022 cm/s) in the absence of VP, but had little effect on maximal Pfte and endosome Pf induced by VP. However, PMA increased by threefold the number of apical endosomes with high Pf formed in response to serosal VP. Pf of endosomes containing the VP-sensitive water channel decreased fourfold by increasing membrane fluidity with hexanol or chloroform (0-75 mM); Pf of phosphatidylcholine liposomes (0.002 cm/s) increased 2.5-fold under the same conditions. Endosome Pf was mildly pH dependent, strongly inhibited by HgCl2, but not significantly altered by GTP gamma S, Ca, ATP + protein kinase A, and phosphatase action. We conclude that: (a) water channels cycled in endocytic vesicles are functional and not subject to physiological regulation, (b) VP and forskolin do not have cAMP-independent cellular actions, (c) activation of protein kinase C stimulates trafficking of water channels, but does not increase the number of apical membrane water channels induced by maximal VP, and (d) water channel function is sensitive to membrane fluidity. By using VP and PMA together, large quantities of endosomes containing the VP-sensitive water channel are labeled with fluid-phase endocytic markers

Modelling of sediment nutrient fluxes for a pulsed organic load

A sediment model has been developed to simulate the Sediment Oxygen Demand (SOD) and sediment nutrient fluxes after a sudden input of Particulate Organic Matter (POM). Compared with previous sediment models, the main advances are the use of a continuous function to represent the kinetics of POM diagenesis and inclusion of the biomass content in POM diagenesis. Laboratory experiments were also carried out to investigate the SOD dynamics and sediment nutrient fluxes after an input of fish food pellets into the sediment. The simulation results of SOD and nutrient fluxes compared fairly well with the experimental measurements. Copyright © 2011 Inderscience Enterprises Ltd.postprin

Novel Z2 Topological Metals and Semimetals

© 2016 American Physical Society.We report two theoretical discoveries for Z2 topological metals and semimetals. It is shown first that any dimensional Z2 Fermi surface is topologically equivalent to a Fermi point. Then the famous conventional no-go theorem, which was merely proven before for Z Fermi points in a periodic system without any discrete symmetry, is generalized so that the total topological charge is zero for all cases. Most remarkably, we find and prove an unconventional strong no-go theorem: all Z2 Fermi points have the same topological charge νZ2=1 or 0 for periodic systems. Moreover, we also establish all six topological types of Z2 models for realistic physical dimensions.postprin

Organizing the innovation process : complementarities in innovation networking

This paper contributes to the developing literature on complementarities in organizational design. We test for the existence of complementarities in the use of external networking between stages of the innovation process in a sample of UK and German manufacturing plants. Our evidence suggests some differences between the UK and Germany in terms of the optimal combination of innovation activities in which to implement external networking. Broadly, there is more evidence of complementarities in the case of Germany, with the exception of the product engineering stage. By contrast, the UK exhibits generally strong evidence of substitutability in external networking in different stages, except between the identification of new products and product design and development stages. These findings suggest that previous studies indicating strong complementarity between internal and external knowledge sources have provided only part of the picture of the strategic dilemmas facing firms

Oscillatory thermopower of carbon chains: First-principles calculations

We investigate the thermoelectric transport through carbon chains connected by two Al leads. Using a Landauer-Buttiker-like formula, we calculate the thermopower and thermoconductance of Al-Cn-Al from first principles. We find that the charge transfer plays an important role in the thermoelectric transport. Because of the charge transfer, the thermopower changes sign for even-odd number of carbon atoms. The thermopower and electric conductance as a function of the gate voltage also exhibit oscillatory behaviors with a phase difference of pi/2.published_or_final_versio

Spin pump in the presence of a superconducting lead

We present a theoretical analysis of a spin pump in the presence of a superconducting lead. The spin pump is facilitated by a rotating magnetic field which provides a spin flip mechanism and hence can generate a spin current without an accompanying charge current. Using a nonequilibrium Green's function method, we obtain a general solution of the pumped charge current and spin current in both the adiabatic and non-adiabatic regimes. The numerical results for the charge current and spin current are presented as we vary different system parameters such as the gate voltage, the external magnetic field, and the pumping frequency. We find that for a quantum dot with a single resonant level in line with the Fermi energy of the left normal lead, a pure spin current is generated by a rotating magnetic field at any frequency. We have identified two kinds of photon-assisted processes which dominate at low pumping frequencies and high pumping frequencies, respectively.published_or_final_versio

Image processing methods to elucidate spatial characteristics of retinal microglia after optic nerve transection

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The effect of morphine upon DNA methylation in ten regions of the rat brain

Morphine is one of the most effective analgesics in medicine. However, its use is associated with the development of tolerance and dependence. Recent studies demonstrating epigenetic changes in the brain after exposure to opiates have provided insight into mechanisms possibly underlying addiction. In this study, we sought to identify epigenetic changes in ten regions of the rat brain following acute and chronic morphine exposure. We analyzed DNA methylation of six nuclear-encoded genes implicated in brain function (Bdnf, Comt, Il1b, Il6, Nr3c1 and Tnf) and three mitochondrially-encoded genes (Mtco1, Mtco2 and Mtco3), and measured global 5-methylcytosine (5-mc) and 5-hydroxymethylcytosine (5-hmc) levels. We observed differential methylation of Bdnf and Il6 in the pons, Nr3c1 in the cerebellum, and Il1b in the hippocampus in response to acute morphine exposure (all p<0.05). Chronic exposure was associated with differential methylation of Bdnf and Comt in the pons, Nr3c1 in the hippocampus and Il1b in the medulla oblongata (all p<0.05). Global 5-mc levels significantly decreased in the superior colliculus following both acute and chronic morphine exposure, and increased in the hypothalamus following chronic exposure. Chronic exposure was also associated with significantly increased global 5-hmc levels in the cerebral cortex, hippocampus and hypothalamus, but significantly decreased in the midbrain. Our results demonstrate, for the first time, highly localized epigenetic changes in the rat brain following acute and chronic morphine exposure. Further work is required to elucidate the potential role of these changes in the formation of tolerance and dependence

Antigenic cross-reactivity between severe acute respiratory syndrome-associated coronavirus and human coronaviruses 229E and OC43

Cross-reactivity between antibodies to different human coronaviruses (HCoVs) has not been systematically studied. By use of Western blot analysis, indirect immunofluorescence assay (IFA), and enzyme-linked immunosorbent assay (ELISA), antigenic cross-reactivity between severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV) and 2 HCoVs (229E and OC43) was demonstrated in immunized animals and human serum. In 5 of 11 and 10 of 11 patients with SARS, paired serum samples showed a ≥4-fold increase in antibody titers against HCoV-229E and HCoV-OC43, respectively, by IFA. Overall, serum samples from convalescent patients who had SARS had a 1-way cross-reactivity with the 2 known HCoVs. Antigens of SARS-CoV and HCoV-OC43 were more cross-reactive than were those of SARS-CoV and HCoV-229E. © 2005 by the Infectious Diseases Society of America. All rights reserved.published_or_final_versio

Solar influenced late Holocene temperature changes on the northern Tibetan Plateau

Considerable efforts have been made to extend temperature records beyond the instrumental period through proxy reconstructions, in order to further understand the mechanisms of past climate variability. Yet, the global coverage of existing temperature records is still limited, especially for some key regions like the Tibetan Plateau and for earlier times including the Medieval Warm Period (MWP). Here we present decadally-resolved, alkenone-based, temperature records from two lakes on the northern Tibetan Plateau. Characterized by marked temperature variability, our records provide evidence that temperatures during the MWP were slightly higher than the modern period in this region. Further, our temperature reconstructions, within age uncertainty, can be well correlated with solar irradiance changes, suggesting a possible link between solar forcing and natural climate variability, at least on the northern Tibetan Plateau. © 2013 The Author(s).published_or_final_versio