385 research outputs found
Metabolism of Glycollate by Lemna minor L. Grown on Nitrate or Ammonium as Nitrogen Source
Marques, I. A., Oberholzer, M. J. and Erismann, K. H. 1985. Metabolism of glycollate by Lemna minor L. grown on nitrate or ammonium as nitrogen source.—J. exp. Bot. 36: 1685-1697. Duckweed, Lemna minor L., grown on inorganic nutrient solutions containing either NH4+ or NO3− as nitrogen source was allowed to assimilate [1-14C]- or [2-14C]glycollate during a 20 min period in darkness or in light. The incorporation of radioactivity into water-soluble metabolites, the insoluble fraction, and into the CO2 released was measured. In addition the extractable activity of phosphoenolpyruvate carboxylase was determined. During the metabolism of [2-14C]glycollate in darkness, as well as in the light, NH4+ grown plants evolved more 14CO2 than NO3− grown plants. Formate was labelled only from [2-14C]glycollate and in NH4+ grown plants it was significantly less labelled in light than in darkness. In NO3− grown plants formate showed similar radioactivity after dark and light labelling. The radioactivity in glycine was little influenced by the nitrogen source. Amounts of radioactivity in serine implied that the further metabolism of serine was reduced in darkness compared with its metabolism in the light under both nitrogen regimes. In illuminated NH4+ plants, serine was labelled through a pathway starting from phosphoglycerate. After [1-14C]glycollate feeding NH4+ grown plants contained markedly more radioactive aspartate and malate than NO3− plants indicating a stimulated phosphoenolpyruvate carboxylation in plants grown on NH4
Semiclassical structure of chaotic resonance eigenfunctions
We study the resonance (or Gamow) eigenstates of open chaotic systems in the
semiclassical limit, distinguishing between left and right eigenstates of the
non-unitary quantum propagator, and also between short-lived and long-lived
states. The long-lived left (right) eigenstates are shown to concentrate as
on the forward (backward) trapped set of the classical dynamics.
The limit of a sequence of eigenstates is found
to exhibit a remarkably rich structure in phase space that depends on the
corresponding limiting decay rate. These results are illustrated for the open
baker map, for which the probability density in position space is observed to
have self-similarity properties.Comment: 4 pages, 4 figures; some minor corrections, some changes in
presentatio
Alginate Microencapsulation of Human Islets Does Not Increase Susceptibility to Acute Hypoxia
Islet transplantation in diabetes is hampered by the need of life-long immunosuppression. Encapsulation provides partial immunoprotection but could possibly limit oxygen supply, a factor that may enhance hypoxia-induced beta cell death in the early posttransplantation period. Here we tested susceptibility of alginate microencapsulated human islets to experimental hypoxia (0.1–0.3% O2 for 8 h, followed by reoxygenation) on viability and functional parameters. Hypoxia reduced viability as measured by MTT by 33.8±3.5% in encapsulated and 42.9±5.2% in nonencapsulated islets (P<0.2). Nonencapsulated islets released 37.7% (median) more HMGB1 compared to encapsulated islets after hypoxic culture conditions (P<0.001). Glucose-induced insulin release was marginally affected by hypoxia. Basal oxygen consumption was equally reduced in encapsulated and nonencapsulated islets, by 22.0±6.1% versus 24.8±5.7%. Among 27 tested cytokines/chemokines, hypoxia increased the secretion of IL-6 and IL-8/CXCL8 in both groups of islets, whereas an increase of MCP-1/CCL2 was seen only with nonencapsulated islets. Conclusion. Alginate microencapsulation of human islets does not increase susceptibility to acute hypoxia. This is a positive finding in relation to potential use of encapsulation for islet transplantation
Semiclassical Theory of Quantum Chaotic Transport: Phase-Space Splitting, Coherent Backscattering and Weak Localization
We investigate transport properties of quantized chaotic systems in the short
wavelength limit. We focus on non-coherent quantities such as the Drude
conductance, its sample-to-sample fluctuations, shot-noise and the transmission
spectrum, as well as coherent effects such as weak localization. We show how
these properties are influenced by the emergence of the Ehrenfest time scale
\tE. Expressed in an optimal phase-space basis, the scattering matrix
acquires a block-diagonal form as \tE increases, reflecting the splitting of
the system into two cavities in parallel, a classical deterministic cavity
(with all transmission eigenvalues either 0 or 1) and a quantum mechanical
stochastic cavity. This results in the suppression of the Fano factor for
shot-noise and the deviation of sample-to-sample conductance fluctuations from
their universal value. We further present a semiclassical theory for weak
localization which captures non-ergodic phase-space structures and preserves
the unitarity of the theory. Contrarily to our previous claim [Phys. Rev. Lett.
94, 116801 (2005)], we find that the leading off-diagonal contribution to the
conductance leads to the exponential suppression of the coherent backscattering
peak and of weak localization at finite \tE. This latter finding is
substantiated by numerical magnetoconductance calculations.Comment: Typos in central eqns corrected (this paper supersedes
cond-mat/0509186) 20page
Ehrenfest time dependent suppression of weak localization
The Ehrenfest time dependence of the suppression of the weak localization
correction to the conductance of a {\em clean} chaotic cavity is calculated.
Unlike in earlier work, no impurity scattering is invoked to imitate
diffraction effects. The calculation extends the semiclassical theory of K.
Richter and M. Sieber [Phys. Rev. Lett. {\bf 89}, 206801 (2002)] to include the
effect of a finite Ehrenfest time.Comment: 3 Pages, 1 Figure, RevTe
Glucose-induced β cell production of IL-1β contributes to glucotoxicity in human pancreatic islets
Erratum / Corrigendu
Effect of incoherent scattering on shot noise correlations in the quantum Hall regime
We investigate the effect of incoherent scattering in a Hanbury Brown and
Twiss situation with electrons in edge states of a three-terminal conductor
submitted to a strong perpendicular magnetic field. The modelization of
incoherent scattering is performed by introducing an additional voltage probe
through which the current is kept equal to zero which causes voltage
fluctuations at this probe. It is shown that inelastic scattering can lead in
this framework to positive correlations, whereas correlations remain always
negative for quasi-elastic scattering.Comment: 5 pages latex, 5 eps figure
Shot Noise by Quantum Scattering in Chaotic Cavities
We have experimentally studied shot noise of chaotic cavities defined by two
quantum point contacts in series. The cavity noise is determined as 1/4*2e|I|
in agreement with theory and can be well distinguished from other contributions
to noise generated at the contacts. Subsequently, we have found that cavity
noise decreases if one of the contacts is further opened and reaches nearly
zero for a highly asymmetric cavity.Comment: 4 pages, 4 figures, REVTe
SMAD4 target genes are part of a transcriptional network that integrates the response to BMP and SHH signaling during early limb bud patterning
SMAD4 regulates gene expression in response to BMP and TGFβ signal transduction, and is required for diverse morphogenetic processes, but its target genes have remained largely elusive. Here, we identify the SMAD4 target genes in mouse limb buds using an epitope-tagged Smad4 allele for ChIP-seq analysis in combination with transcription profiling. This analysis shows that SMAD4 predominantly mediates BMP signal transduction during early limb bud development. Unexpectedly, the expression of cholesterol biosynthesis enzymes is precociously downregulated and intracellular cholesterol levels are reduced in Smad4-deficient limb bud mesenchymal progenitors. Most importantly, our analysis reveals a predominant function of SMAD4 in upregulating target genes in the anterior limb bud mesenchyme. Analysis of differentially expressed genes shared between Smad4- and Shh-deficient limb buds corroborates this function of SMAD4 and also reveals the repressive effect of SMAD4 on posterior genes that are upregulated in response to SHH signaling. This analysis uncovers opposing trans-regulatory inputs from SHH- and SMAD4-mediated BMP signal transduction on anterior and posterior gene expression during the digit patterning and outgrowth in early limb buds
- …