Brain inflammation plays a central role in multiple sclerosis (MS). Besides lymphocytes, the astroglia and microglia mainly contribute to the cellular composition of the inflammatory infiltrate in MS ...lesions. Several studies were able to demonstrate that cortical lesions are characterized by lower levels of inflammatory cells among activated microglia/macrophages. The underlying mechanisms for this difference, however, remain to be clarified. In the current study, we compared the kinetics and extent of microglia and astrocyte activation during early and late cuprizone-induced demyelination in the white matter tract corpus callosum and the telencephalic gray matter. Cellular parameters were related to the expression profiles of the chemokines
Ccl2
and
Ccl3
. We are clearly able to demonstrate that both regions are characterized by early oligodendrocyte stress/apoptosis with concomitant microglia activation and delayed astrocytosis. The extent of microgliosis/astrocytosis appeared to be greater in the subcortical white matter tract corpus callosum compared to the gray matter cortex region. The same holds true for the expression of the key chemokines
Ccl2
and
Ccl3
. The current study defines a model to study early microglia activation and to investigate differences in the neuroinflammatory response of white vs. gray matter.
Excessive low-affinity Na+ uptake is toxic to the growth of glycophytic plants. Recently, several reports have suggested that the interaction between K+ and Na+ uptake might represent a key factor in ...determining the Na+ tolerance of plants. We investigated the effects of K+ starvation on Na+ and K+ uptake mechanisms in the plasma membrane of wheat (Triticum aestivum L.) root cortex cells using the patch-clamp technique. Unexpectedly, K+ starvation of wheat seedlings was found to enhance the magnitude and frequency of occurrence of time-dependent inward-rectifying K+ channel currents ($\text{I}_{\text{K}}{}^{+}{}_{\text{in}}$). We examined whether the transcription of a wheat root $\text{K}^{+}{}_{\text{in}}$ channel gene is induced by K+ starvation. A cDNA coding for a wheat root K+ channel homolog, TaAKT1 (accession no. AF207745), was isolated. TaAKT1 mRNA levels were up-regulated in roots in response to withdrawal of K+ from the growth medium. Furthermore, K+ starvation caused an enhancement of instantaneous Na+ currents ($\text{I}_{\text{Na}}{}^{+}$). Electrophysiological analyses suggested that $\text{I}_{\text{K}}{}^{+}{}_{\text{in}}$ and $\text{I}_{\text{Na}}{}^{+}$ are not mediated by the same transport protein based on: (a) different activation curves, (b) different time dependencies, (c) different sensitivities to external Ca2+, and (d) different cation selectivities. These data implicate a role for $\text{I}_{\text{Na}}{}^{+}$ in Na+ uptake and stress during K+ starvation, and indicate that $\text{K}^{+}{}_{\text{in}}$ channels may contribute to K+-starvation-induced K+ uptake in wheat roots.
In this paper, we introduce a new sensor technology for measuring plethysmographic parameters, i.e., for pulse oximetry, particularly in mobile people. The sensor uses the auditory canal as a ...measuring site, plus a novel light path through the tissue of the auditory canal's wall for continuously and reliably measuring arterial oxygen saturation and heart rate under mobile conditions. Measurements with this sensor technology reveal a good ratio in combination with excellent signal quality - ideal prerequisites to make pulse oximetry a continuous unobtrusive mobile monitoring technology.
Major plasmalemma ion transporters in plants are voltage-gated. Such gating behavior can lead to sustained oscillations of membrane voltage, which allows long-term osmotic adjustment by switching ...between periods of net uptake and net release of salt. The aim of this study was to investigate the mechanisms behind the oscillatory behavior by means of a minimal model. According to general preconditions for sustained oscillations such a model must consist of two ion transporters with very different equilibrium voltage and one of them acting as positive feedback. Such a positive feedback can be detected as negative slope of the steady-state I-V curves. Discussing the stability properties of the main electrogenic ion transporters in plants we found that a membrane with a predominant pump and a predominant channel would be a realistic paradigm for a minimal system with inherent oscillatory characteristics. This two-variable model was examined by phase-plane analysis. Parameter ranges for sustained oscillations could be determined via bifurcation analysis. These parameter ranges include physiologically relevant parameter sets for pump/cation-channel and pump/anion-channel systems. Finally, membrane voltage oscillations in systems without sufficient positive self-coupling mechanisms of the electrogenic ion transporters are discussed.
The activities of the major ion pathways in the plasma membranes of plants are sensitive to the membrane voltage, V. Therefore, these 'electroenzymes' interact with each other via the free running ...voltage under physiological conditions. A physical background is given here, of how to calculate these interactions on the basis of experimental data on these electroenzymes. Simplifying model calculations with five major electroenzymes from plant cells (H⁺ pump, inward and outward rectifying channels for K⁺, a Cl⁻ channel, and a 2H⁺/Cl⁻ symporter) show that osmotic relations are balanced in the long-term not by an appropriate steady-state, but by alternation between a state of salt uptake at V < < EK (the Nernst equilibrium voltage for K⁺ diffusion) and a state of salt loss at V > EK. Several specific properties of the model are discussed numerically, e.g. minimum configuration for oscillations (with two electroenzymes), temperature-compensation, the physiological impact of fast gating in plant membranes, and solution of possible paradoxes, such as flux stimulation by conductance inhibition.
Pulse oximetry is a valuable monitoring technology used at present mainly for immobile patients. The reason for the limitation concerning the user's mobility is due principally to unsuitable sensors ...and sensor locations. This is particularly the case with finger sensors, which tend to work best in respect to signal quality i.e. modulation depth, but are quite susceptible to motion artifacts. In order to achieve mobility for pulse oximetry monitoring, an ear canal sensor was developed. This area was chosen based on the assumption that intensive movement and acceleration of this part of the body is generally avoided as it produces unpleasant feelings. An unusual and so far unknown light path had to be used in the ear canal sensors for which we suggest the expression "circummission pulse oximetry", since the optoelectronic components face outside the canal and away from each other, generating a minimal effective light path of a semicircle within the auditory canal's wall. Surprising findings included modulation depth and omega values, indicating shunt levels even lower than in transmission pulse oximetry finger sensors. We concluded that finger sensors, which have so far been considered free of shunt light by many researchers, actually do involve some shunt light. Circummission pulse oximetry proved impressively resistant to motion and revealed good signal quality even when heavily moving the entire trunk/body. Therefore we believe that the mobile pulse oximetry monitoring system presented here might open up possibilities for a variety of monitoring applications: extending from medical to leisure settings, from inpatients to outpatients, from rehab-training to mountain climbing, from fire fighting to sleep apnea screening.
This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the process for centre-of-mass energies above the Z ...resonance, from -207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for scattering and several models which include physics beyond the Standard Model: the exchange of Z′ bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of in R-parity violating supersymmetry.This paper is dedicated to the memory of Alan Segar.
Heterotrimeric GTPases (G-proteins) are implicated in many cellular signalling processes. In plants, a function of a specific G-protein has only recently been characterized. A cDNA clone encoding a ...G-protein alpha-subunit was isolated from tobacco (Nicotiana tabacum L.). The deduced amino acid sequence of this alpha-subunit (NtGPalpha1) has 91% homology to GPalpha1 from Arabidopsis thaliana. Sequence comparisons with other plant G-proteins show that these two alpha-subunits belong to the only class of plant G-proteins known to date. The NtGPalpha1 cDNA was placed under the control of the CaMV 35S promoter both in sense and antisense orientation. These constructs were stably transformed into tobacco plants. As shown by patch-clamp experiments, mesophyll protoplasts of transformed tobacco plants over-expressing NtGPalpha1 sense or antisense RNA exhibited enhanced plasmalemma K<+< conductances compared to the wild type. By contrast, mesophyll protoplasts of transformed tobacco plants expressing the cholera toxin A1-subunit, a G-protein activator, exhibited a reduced plasmalemma K<+< conductance. These results indicate for the first time a role of a specific G-protein in the regulation of K<+< channels. Keywords:G-protein, cloning, antisense, K<+< channel regulation, Nicotiana tabacum.
Fresh-water plants generate extraordinarily high electric potential differences at the plasma membrane. For a deeper understanding of the underlying transport processes a mathematical model of the ...electrogenic plasmalemma ion transport was developed based on experimental data mainly obtained from Egeria densa. The model uses a general nonlinear network approach and assumes coupling of the transporters via membrane potential. A proton pump, an outward-rectifying K+ channel, an inward-rectifying K+ channel, a Cl- channel and a (2H-Cl)+ symporter are considered to be elements of the system. The model takes into consideration the effects of light, external pH and ionic content of the bath medium on ion transport. As a result it does not only satisfactorily describe the membrane potential as a function of these external physiological factors but also succeeds in simulating the effects of specific inhibitors as well as I-V-curves obtained with the patch-clamp technique in the whole cell mode. The quality of the model was checked by stability and sensitivity analyses.
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