Search results for "membrane potentials"
showing 10 items of 149 documents
Characterization of cells with different mitochondrial membrane potential during apoptosis.
2005
Background Until now, the simultaneous analysis of several parameters during apoptosis, including DNA content and mitochondrial membrane potential (ΔΨ), has not been possible because of the spectral characteristics of the commonly used dyes. Using polychromatic flow cytometry based upon multiple laser and UV lamp excitation, we have characterized cells with different ΔΨ during apoptosis. Methods U937 cells were treated with the flavonoid quercetin (Qu) and stained with JC-1 to detect ΔΨ, propidium iodide (PI) for cell viability, Hoechst 33342 for DNA content, Annexin V conjugated with Alexa Fluor-647 for detection of phosphatidilserine (PS) exposure, marker of early apoptosis, or Mitotracke…
Dithiothreitol Treatment of Madin-Darby Canine Kidney Cells Reversibly Blocks Export from the Endoplasmic Reticulum but Does Not Affect Vectorial Tar…
1995
Addition of dithiothreitol (DTT) to the culture medium of Madin-Darby canine kidney (MDCK) cells blocks transport of newly synthesized gp80 (clusterin, apolipoprotein J), a soluble marker protein for apical exocytosis in this epithelial cell line. In cells treated with DTT during pulse labeling, gp80 is retained in the endoplasmic reticulum. After removal of the reducing agent, gp80 is posttranslationally oxidized and secreted at the apical surface of MDCK cell monolayers. This demonstrates that when folded and oxidized posttranslationally, gp80 can acquire a conformation that exhibits sorting signals for vectorial targeting. In the continuous presence of DTT, the transepithelial electrical…
Blocking of an ion channel by a highly charged drug: Modeling the effects of applied voltage, electrolyte concentration, and drug concentration
2005
We present a simple physical model to estimate the blocked pore probability of an ion channel that can be blocked by a highly charged drug in solution. The model is inspired by recent experimental work on the blocking of the ${\mathrm{PA}}_{63}$ channel, involved in the anthrax toxin infection, by a highly charged drug [Karginov et al. PNAS 102, 15075 (2005)]. The drug binding to the pore is highly specific but the strong dependence of blocking on the applied voltage and electrolyte concentration suggests that long range electrostatic interactions are important. Since basic electrostatic concepts rather than detailed molecular models are considered, the microscopic details of the channel bl…
Inhibition of neuronally mediated secretion in rat colonic mucosa by prostaglandin D2
1992
Abstract The effect of prostaglandin D 2 (PGD 2 ) on ion transport across the mucosa of the descending colon was studied in rats. PGD 2 dose-dependently decreased baseline short-circuit current of mucosa-submucosal preparations mounted either in the Ussing chamber or mounted as an everted sac. However, with the everted sac technique, the tissue was about 1000 times more sensitive to PGD 2 . Concomitant with the decrease in short-circuit current, PGD 2 increased the mucosal-to-serosal fluxes of sodium and chloride and decreased the serosal-tomucosal flux of chloride. PGD 2 inhibited the secretory action of the PGI 2 analogue iloprost, PGD 2α , and neurotensin. The action of these secretagogu…
Antidepressants are functional antagonists at the serotonin type 3 (5-HT3) receptor
2003
Antidepressants are commonly supposed to enhance serotonergic and/or noradrenergic neurotransmission by inhibition of neurotransmitter reuptake through binding to the respective neurotransmitter transporters or through inhibition of the monoamine oxidase. Using the concentration-clamp technique and measurements of intracellular Ca2+, we demonstrate that different classes of antidepressants act as functional antagonists at the human 5-HT3A receptor stably expressed in HEK 293 cells and at endogenous 5-HT3 receptors of rat hippocampal neurons and N1E-115 neuroblastoma cells. The tricyclic antidepressants desipramine, imipramine, and trimipramine, the serotonin reuptake inhibitor fluoxetine, t…
On a set of data for the membrane potential in a neuron
2006
We consider a set of data where the membrane potential in a pyramidal neuron is measured almost continuously in time, under varying experimental conditions. We use nonparametric estimates for the diffusion coefficient and the drift in view to contribute to the discussion which type of diffusion process is suitable to model the membrane potential in a neuron (more exactly: in a particular type of neuron under particular experimental conditions).
Ni2+ toxicity in rice: effect on membrane functionality and plant water content.
2007
The heavy metal nickel is an essential mineral trace nutrient found at low concentrations in most natural soils. However, it may reach toxic levels in certain areas and affect a number of biochemical and physiological processes in plants. Wilting and leaf necrosis have been described as typical visible symptoms of Ni(2+) toxicity. The plasma membrane (PM) of root cells constitutes the first barrier for the entry of heavy metals but also a target of their toxic action. This work studies the relationship between disturbances of membrane functionality and the development of the typical symptoms of Ni(2+) toxicity. Rice plants (Oryza sativa L. cv. Bahia) grown in nutrient medium containing 0.5m…
Modulation of intracellular calcium concentrations and T cell activation by prickly pear polyphenols.
2004
Opuntia ficus indica (prickly pear) polyphenolic compounds (OFPC) triggered an increase in [Ca2+]i in human Jurkat T-cell lines. Furthermore, OFPC-induced rise in [Ca2+]i was significantly curtailed in calcium-free buffer (0% Ca2+) as compared to that in 100% Ca2+ medium. Preincubation of cells with tyrphostin A9, an inhibitor of Ca2+ release-activated Ca2+ (CRAC) channels, significantly diminished the OFPC-induced sustained response on the increases in [Ca2+]i. Lanthanum and nifedipine, the respective inhibitors of voltage-dependent and L-type calcium channels, failed to curtail significantly the OFPC-induced calcium response. As OFPC still stimulated increases in [Ca2+]i in 0% Ca2+ medium…
Inter-Model Consistency and Complementarity: Learning from ex-vivo Imaging and Electrophysiological Data towards an Integrated Understanding of Cardi…
2011
International audience; Computational models of the heart at various scales and levels of complexity have been independently developed, parameterised and validated using a wide range of experimental data for over four decades. However, despite remarkable progress, the lack of coordinated efforts to compare and combine these computational models has limited their impact on the numerous open questions in cardiac physiology. To address this issue, a comprehensive dataset has previously been made available to the community that contains the cardiac anatomy and fibre orientations from magnetic resonance imaging as well as epicardial transmembrane potentials from optical mapping measured on a per…
Induction of apoptosis in human osteosarcoma Saos-2 cells by the proteasome inhibitor MG132 and the protective effect of pRb
2003
Induction of apoptosis in human osteosarcoma Saos-2 cells by the proteasome inhibitor MG132 and the protective effect of pRb