126 research outputs found
Endoscopic sensing of alveolar pH
Previously unobtainable measurements of alveolar pH were obtained using an endoscope-deployable optrode. The pH sensing was achieved using functionalized gold nanoshell sensors and surface enhanced Raman spectroscopy (SERS). The optrode consisted of an asymmetric dual-core optical fiber designed for spatially separating the optical pump delivery and signal collection, in order to circumvent the unwanted Raman signal generated within the fiber. Using this approach, we demonstrate a ~100-fold increase in SERS signal-to-fiber background ratio, and demonstrate multiple site pH sensing with a measurement accuracy of ± 0.07 pH units in the respiratory acini of an ex vivo ovine lung model. We also demonstrate that alveolar pH changes in response to ventilation
Truncation Effects in the Functional Renormalization Group Study of Spontaneous Symmetry Breaking
We study the occurrence of spontaneous symmetry breaking (SSB) for O (N) models using functional renormalization group techniques. We show that even the local potential approximation (LPA) when treated exactly is sufficient to give qualitatively correct results for systems with continuous symmetry, in agreement with the Mermin-Wagner theorem and its extension to systems with fractional dimensions. For general N (including the Ising model N = 1) we study the solutions of the LPA equations for various truncations around the zero field using a finite number of terms (and different regulators), showing that SSB always occurs even where it should not. The SSB is signalled by Wilson-Fisher fixed points which for any truncation are shown to stay on the line defined by vanishing mass beta functions
Glutamate regulation of calcium and IP3 oscillating and pulsating dynamics in astrocytes
Recent years have witnessed an increasing interest in neuron-glia
communication. This interest stems from the realization that glia participates
in cognitive functions and information processing and is involved in many brain
disorders and neurodegenerative diseases. An important process in neuron-glia
communications is astrocyte encoding of synaptic information transfer: the
modulation of intracellular calcium dynamics in astrocytes in response to
synaptic activity. Here, we derive and investigate a concise mathematical model
for glutamate-induced astrocytic intracellular Ca2+ dynamics that captures the
essential biochemical features of the regulatory pathway of inositol
1,4,5-trisphosphate (IP3). Starting from the well-known two-state Li-Rinzel
model for calcium-induced-calcium release, we incorporate the regulation of the
IP3 production and phosphorylation. Doing so we extended it to a three-state
model (referred as the G-ChI model), that could account for Ca2+ oscillations
triggered by endogenous IP3 metabolism as well as by IP3 production by external
glutamate signals. Compared to previous similar models, our three-state models
include a more realistic description of the IP3 production and degradation
pathways, lumping together their essential nonlinearities within a concise
formulation. Using bifurcation analysis and time simulations, we demonstrate
the existence of new putative dynamical features. The cross-couplings between
IP3 and Ca2+ pathways endows the system with self-consistent oscillator
properties and favor mixed frequency-amplitude encoding modes over pure
amplitude modulation ones. These and additional results of our model are in
general agreement with available experimental data and may have important
implications on the role of astrocytes in the synaptic transfer of information.Comment: 42 pages, 16 figures, 1 table. Figure filenames mirror figure order
in the paper. Ending "S" in figure filenames stands for "Supplementary
Figure". This article was selected by the Faculty of 1000 Biology: "Genevieve
Dupont: Faculty of 1000 Biology, 4 Sep 2009" at
http://www.f1000biology.com/article/id/1163674/evaluatio
Simulation based energy-resource efficient manufacturing integrated with in-process virtual management
Supported by the EU 7th Framework ICT Programme under EuroEnergest Project (Contract No. 288102)
Carbon Monoxide Promotes Respiratory Hemoproteins Iron Reduction Using Peroxides as Electron Donors
The physiological role of the respiratory hemoproteins (RH), hemoglobin and myoglobin, is to deliver O2 via its binding to their ferrous (FeII) heme-iron. Under variety of pathological conditions RH proteins leak to blood plasma and oxidized to ferric (FeIII, met) forms becoming the source of oxidative vascular damage. However, recent studies have indicated that both metRH and peroxides induce Heme Oxygenase (HO) enzyme producing carbon monoxide (CO). The gas has an extremely high affinity for the ferrous heme-iron and is known to reduce ferric hemoproteins in the presence of suitable electron donors. We hypothesized that under in vivo plasma conditions, peroxides at low concentration can assist the reduction of metRH in presence of CO. The effect of CO on interaction of metRH with hydrophilic or hydrophobic peroxides was analyzed by following Soret and visible light absorption changes in reaction mixtures. It was found that under anaerobic conditions and low concentrations of RH and peroxides mimicking plasma conditions, peroxides served as electron donors and RH were reduced to their ferrous carboxy forms. The reaction rates were dependent on CO as well as peroxide concentrations. These results demonstrate that oxidative activity of acellular ferric RH and peroxides may be amended by CO turning on the reducing potential of peroxides and facilitating the formation of redox-inactive carboxyRH. Our data suggest the possible role of HO/CO in protection of vascular system from oxidative damage
Transcription forms and remodels supercoiling domains unfolding large-scale chromatin structures
DNA supercoiling is an inherent consequence of twisting DNA and is critical for regulating gene expression and DNA replication. However, DNA supercoiling at a genomic scale in human cells is uncharacterized. To map supercoiling we used biotinylated-trimethylpsoralen as a DNA structure probe to show the genome is organized into supercoiling domains. Domains are formed and remodeled by RNA polymerase and topoisomerase activities and are flanked by GC-AT boundaries and CTCF binding sites. Under-wound domains are transcriptionally active, enriched in topoisomerase I, “open” chromatin fibers and DNaseI sites, but are depleted of topoisomerase II. Furthermore DNA supercoiling impacts on additional levels of chromatin compaction as under-wound domains are cytologically decondensed, topologically constrained, and decompacted by transcription of short RNAs. We suggest that supercoiling domains create a topological environment that facilitates gene activation providing an evolutionary purpose for clustering genes along chromosomes
Nonlinear gap junctions enable long-distance propagation of pulsating calcium waves in astrocyte networks
A new paradigm has recently emerged in brain science whereby communications
between glial cells and neuron-glia interactions should be considered together
with neurons and their networks to understand higher brain functions. In
particular, astrocytes, the main type of glial cells in the cortex, have been
shown to communicate with neurons and with each other. They are thought to form
a gap-junction-coupled syncytium supporting cell-cell communication via
propagating Ca2+ waves. An identified mode of propagation is based on
cytoplasm-to-cytoplasm transport of inositol trisphosphate (IP3) through gap
junctions that locally trigger Ca2+ pulses via IP3-dependent Ca2+-induced Ca2+
release. It is, however, currently unknown whether this intracellular route is
able to support the propagation of long-distance regenerative Ca2+ waves or is
restricted to short-distance signaling. Furthermore, the influence of the
intracellular signaling dynamics on intercellular propagation remains to be
understood. In this work, we propose a model of the gap-junctional route for
intercellular Ca2+ wave propagation in astrocytes showing that: (1)
long-distance regenerative signaling requires nonlinear coupling in the gap
junctions, and (2) even with nonlinear gap junctions, long-distance
regenerative signaling is favored when the internal Ca2+ dynamics implements
frequency modulation-encoding oscillations with pulsating dynamics, while
amplitude modulation-encoding dynamics tends to restrict the propagation range.
As a result, spatially heterogeneous molecular properties and/or weak couplings
are shown to give rise to rich spatiotemporal dynamics that support complex
propagation behaviors. These results shed new light on the mechanisms
implicated in the propagation of Ca2+ waves across astrocytes and precise the
conditions under which glial cells may participate in information processing in
the brain.Comment: Article: 30 pages, 7 figures. Supplementary Material: 11 pages, 6
figure
Quantitative Structure–Property Relationship Studies on Ostwald Solubility and Partition Coefficients of Organic Solutes in Ionic Liquids
Article discussing quantitative structure-property relationship studies on Ostwald solubility and partition coefficients of organic solutes in ionic liquids
Individual and work-related risk factors for musculoskeletal pain: a cross-sectional study among Estonian computer users
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