1,589 research outputs found
Ouabain-induced cytoplasmic vesicles and their role in cell volume maintenance
Cellular swelling is controlled by an active mechanism of cell volume regulation driven by a Na+/K+-dependent ATPase and by
aquaporins which translocate water along the osmotic gradient. Na+/K+-pump may be blocked by ouabain, a digitalic derivative,
by inhibition of ATP, or by drastic ion alterations of extracellular fluid. However, it has been observed that some tissues are still able
to control their volume despite the presence of ouabain, suggesting the existence of other mechanisms of cell volume control. In
1977, by correlating electron microscopy observation with ion and water composition of liver slices incubated in differentmetabolic
conditions in the presence or absence of ouabain, we observed that hepatocytes were able to control their volume extruding water
and recovering ion composition in the presence of ouabain. In particular, hepatocytes were able to sequester ions and water in
intracellular vesicles and then secrete themat the bile canaliculus pole.We named this “vesicularmechanismof cell volume control.”
Afterward, thismechanism has been confirmed by us and other laboratories in several mammalian tissues.This review summarizes
evidences regarding this mechanism, problems that are still pending, and questions that need to be answered. Finally, we shortly
review the importance of cell volume control in some human pathological conditions
Ions and energy metabolism in duck salt‐gland: possible role of furosemide‐sensitive co‐transport of sodium and chloride
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110010/1/tjp19823251333.pd
User interfaces for computational science: a domain specific language for OOMMF embedded in Python
Computer simulations are used widely across the engineering and science disciplines, including in the research and development of magnetic devices using computational micromagnetics. In this work, we identify and review different approaches to configuring simulation runs: (i) the re-compilation of source code, (ii) the use of configuration files, (iii) the graphical user interface, and (iv) embedding the simulation specification in an existing programming language to express the computational problem. We identify the advantages and disadvantages of different approaches and discuss their implications on effectiveness and reproducibility of computational studies and results. Following on from this, we design and describe a domain specific language for micromagnetics that is embedded in the Python language, and allows users to define the micromagnetic simulations they want to carry out in a flexible way. We have implemented this micromagnetic simulation description language together with a computational backend that executes the simulation task using the Object Oriented MicroMagnetic Framework (OOMMF). We illustrate the use of this Python interface for OOMMF by solving the micromagnetic standard problem 4. All the code is publicly available and is open source
Indinavir/Low-dose Ritonavir Containing HAART in HIV-1 Infected Children has Potent Antiretroviral Activity, but is Associated with Side Effects and Frequent Discontinuation of Treatment
We here present the study results of 21 HIV-1 infected children who were treated with indinavir plus low-dose ritonavir and two nucleoside reverse transcriptase inhibitors (NRTIs) for 48 weeks. Although this q12h HAART regimen had potent antiretroviral activity, it was frequently associated with side effects and discontinuation of therapy
Equilibrium Properties of Temporally Asymmetric Hebbian Plasticity
A theory of temporally asymmetric Hebb (TAH) rules which depress or
potentiate synapses depending upon whether the postsynaptic cell fires before
or after the presynaptic one is presented. Using the Fokker-Planck formalism,
we show that the equilibrium synaptic distribution induced by such rules is
highly sensitive to the manner in which bounds on the allowed range of synaptic
values are imposed. In a biologically plausible multiplicative model, we find
that the synapses in asynchronous networks reach a distribution that is
invariant to the firing rates of either the pre- or post-synaptic cells. When
these cells are temporally correlated, the synaptic strength varies smoothly
with the degree and phase of synchrony between the cells.Comment: 3 figures, minor corrections of equations and tex
Variability of cardioinhibition in vasovagal syncope:differences between subgroups during cardioinhibition and beyond
Purpose: We compared hemodynamic parameters between subjects with marked, intermediate and minimal cardioinhibition during vasovagal syncope.Methods: The study included subjects with a decrease in heart rate while experiencing a complete vasovagal syncope during tilt-table testing. The subjects were classified as having marked, intermediate or minimal cardioinhibition, based on tertile values of the decrease in heart rate. Hemodynamic parameters between these groups were compared before tilt in the supine position, shortly after tilt and during cardioinhibition. Results:A total of 149 subjects with a median age of 43 (interquartile range 24–60) years were included in the study. Among the three groups with different levels of cardioinhibition, the highest heart rate was observed in subjects with marked cardioinhibition both before and shortly after tilt and at the start of cardioinhibition. The heart rate decrease in these subjects was both larger and faster compared to subjects with minimal and intermediate cardioinhibition. Conclusion: Subjects with marked cardioinhibition have both a larger and faster decrease in heart rate compared to subjects with intermediate and minimal cardioinhibition, as early as from the start of cardioinhibition. Marked cardioinhibition is related to differences in hemodynamic profiles already present well before the start of cardioinhibition.</p
Random Walks for Spike-Timing Dependent Plasticity
Random walk methods are used to calculate the moments of negative image
equilibrium distributions in synaptic weight dynamics governed by spike-timing
dependent plasticity (STDP). The neural architecture of the model is based on
the electrosensory lateral line lobe (ELL) of mormyrid electric fish, which
forms a negative image of the reafferent signal from the fish's own electric
discharge to optimize detection of sensory electric fields. Of particular
behavioral importance to the fish is the variance of the equilibrium
postsynaptic potential in the presence of noise, which is determined by the
variance of the equilibrium weight distribution. Recurrence relations are
derived for the moments of the equilibrium weight distribution, for arbitrary
postsynaptic potential functions and arbitrary learning rules. For the case of
homogeneous network parameters, explicit closed form solutions are developed
for the covariances of the synaptic weight and postsynaptic potential
distributions.Comment: 18 pages, 8 figures, 15 subfigures; uses revtex4, subfigure, amsmat
Light transport in cold atoms: the fate of coherent backscattering in the weak localization regime
The recent observation of coherent backscattering (CBS) of light by atoms has
emphasized the key role of the velocity spread and of the quantum internal
structure of the atoms. Firstly, using highly resonant scatterers imposes very
low temperatures of the disordered medium in order to keep the full contrast of
the CBS interference. This criterion is usually achieved with standard laser
cooling techniques. Secondly, a non trivial internal atomic structure leads to
a dramatic decrease of the CBS contrast. Experiments with Rubidium atoms (with
a non trivial internal structure) and with Strontium (with the simplest
possible internal structure) show this behaviour and confirm theoretical
calculations
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