Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: CAS:7440-70-2 (calcium)
 333,191 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enzymatically disaggregated, electrically stimulated cardiomyocytes from adult rats were examined by television-mediated vital microscopy for intracellular Ca2+ concentration and contractile activity. Using an inverted microscope in the epifluorescence mode, the Ca2+ signal was imaged with a low-light-level CCD camera and traced by means of the intracellular concentration of the fluorescent complex of Ca2+ with its indicator Fluo-3. Using the transmitted-light mode, cardiomyocytes that were not loaded were imaged with a conventional CCD camera with automatic gain control and traced by length measurements. Optical images of at least 40 cardiomyocytes per batch of cells from one heart were recorded in up to 20 microscopic fields of observation on videotape within 20 min. They were consecutively analysed by a personal computer installed with an image analysis card at a time-resolution of 20 ms, employing a discrete convolution operation, filtering and threshold setting for fluorescence measurements, and contour description and vectorial analysis for length measurements. Frames of fluorescent images were corrected for the halo effect caused by the increase in the Ca(2+)-dependent fluorescence signal after electrical stimulation. The cell contraction had to be measured in the transmission mode without Fluo-3 due to the inhibition caused by the intracellular Fluo-3. The following coefficients of variation (V) were determined: Vfluorescence < 0.033 and Vtransmission < 0.003 for the precision of measurement, and Vfluorescence < 0.05 and Vtransmission < 0.04 for the reproducibility. The system was validated with isoprenaline and ouabain as agents to modify the Ca(2+)-signal and the contraction. The response of cardiomyocytes of various rats to electrical stimulation, with respect to amplitude and its time point, had a V < 0.08 for both the Ca(2+)-signal and the contraction.
 ...
PMID:Kinetics of intracellular Ca2+ concentration changes and cell contraction of electrically stimulated cardiomyocytes as analysed by automated digital-imaging microscopy. 796 51

We developed an optical system for the measurement of the Ca2+ content of sarcoplasmic reticulum (SR) in saponin-treated ventricular muscles of ferrets. After the SR was loaded with Ca2+ by activating the Ca2+ pump of SR, caffeine (50 mM) was applied to release the accumulated Ca2+ from the SR into the bathing solution containing the fluorescent Ca2+ indicator, Fluo-3. As Fluo-3, at high concentrations (approximately 200 microM), predominantly binds most of the Ca2+ released from the SR, the Fluo-3 fluorescence change upon Ca2+ binding gave an estimate of the amount of accumulated Ca2+ in SR before caffeine application. The maximal Ca2+ content of SR, thus estimated, was about 370 mumol/l cytoplasm. The amount of Ca2+ loaded in SR showed bell-shaped dependence on the free Ca2+ concentration ([Ca2+]) of the loading solution, reflecting Ca(2+)-induced Ca2+ release at high [Ca2+] (> or = 1 microM). Mg2+ and H+ decreased the rate of Ca2+ uptake by SR. The present system provides a relatively direct means of measurement of the Ca2+ content of SR, and allows examination of the effects of various interventions on SR Ca2+ uptake, bypassing the large influence of intracellular Ca2+ buffer sites.
Cell Calcium 1994 Aug
PMID:Measurement of sarcoplasmic reticulum calcium content in skinned mammalian cardiac muscle. 798 63

1. The reliability of the propagation of action potentials (AP) through dorsal root ganglion (DRG) cells in embryonic slice cultures was investigated during repetitive stimulation at 1-20 Hz. Membrane potentials of DRG cells were recorded intracellularly while the axons were stimulated by an extracellular electrode. 2. In analogy to the double-pulse experiments reported previously, either one or two types of propagation failures were recorded during repetitive stimulation, depending on the cell morphology. In contrast to the double-pulse experiments, the failures appeared at longer interpulse intervals and usually only after several tens of stimuli with reliable propagation. 3. In the period with reliable propagation before the failures, a decrease in the conduction velocity and in the amplitude of the afterhyperpolarization (AHP), an increase in the total membrane conductance, and the disappearance of the action potential "shoulder" were observed. 4. The reliability of conduction during repetitive stimulation was improved by lowering the extracellular calcium concentration or by replacing the extracellular calcium by strontium. The reliability of conduction decreased by the application of cadmium, a calcium channel blocker, 4-amino pyridine, a fast potassium channel blocker, or apamin or muscarine, the blockers of calcium-dependent potassium channels. The reliability of conduction was not effected by blocking the sodium potassium pump with ouabain or by replacing extracellular sodium with lithium. 5. In the period with reliable propagation cadmium, apamin, and muscarine reduced the amplitude of the AHP. The shoulder of the action potential was more pronounced and not sensitive to repetitive stimulation when extracellular calcium was replaced by strontium. It disappeared when cadmium was applied. 6. In DRG somata changes of the intracellular Ca2+ concentration were monitored by measuring the fluorescence of the Ca2+ indicator Fluo-3 with a laser-scanning confocal microscope. During repetitive stimulation, an accumulation of intracellular calcium occurred that recovered very slowly (tens of seconds) after the AP trains. 7. Computer model simulations performed in analogy to the experimental protocols produced conduction failures during repetitive stimulation only when the calcium currents during the APs were reduced. 8. From these findings it is concluded that conduction failures during repetitive stimulation are dependent on an accumulation of intracellular calcium leading to an inactivation of calcium currents, combined with small contributions of an accumulation of extracellular potassium and a summation of slow potassium conductances.
 ...
PMID:Action potential propagation through embryonic dorsal root ganglion cells in culture. II. Decrease of conduction reliability during repetitive stimulation. 798 25

Photoreceptors of dissociated Drosophila retinae were loaded with the fluorescent Ca2+ indicators, fluo-3 and Calcium Green-5N. In fluo-3-loaded, wild-type photoreceptors, a rapid increase in fluorescence (Ca2+ signal) accompanied the light-evoked inward current. Removal of extracellular Ca2+ greatly reduced the Ca2+ signal, indicating Ca2+ influx as its major cause. In Calcium Green-5N-loaded trp mutants, which lack a large fraction of the Ca2+ permeability underlying the light-evoked inward current, the Ca2+ signal was smaller relative to wild-type photoreceptors. Fluo-3-loaded norpA mutant photoreceptors, which lack a light-activated phospholipase C, generated no light-evoked inward current and no Ca2+ signal. The phosphoinositide pathway therefore appears necessary for both excitation and changes in cytosolic free Ca2+ concentration.
 ...
PMID:The light response of Drosophila photoreceptors is accompanied by an increase in cellular calcium: effects of specific mutations. 801 36

Loaded under whole cell patch-clamp configuration, the caged Ca2+ molecule DM-nitrophen was used to increase [Ca2+]i rapidly and reversibly in isolated Deiters cells of the organ of Corti. Photolysis of DM-nitrophen increased [Ca2+]i from resting concentrations of 20-50 nM to values above microM, as measured with the fluorescent indicator Fluo-3. Immediately after the photoliberation of Ca2+, a movement of the head of the phalangeal process could be observed in 75% of cells (n = 28). This mechanical movement, with an amplitude ranging between 0.5 to 1 micron within few hundred of ms, consisted of an extension of the phalanges away from the cell body. Measurement of phalangeal stiffness in transversal flexion toward the cell body ranged between 15-440 pN/micron. Stiffness can increase by 28 to 51% after rising [Ca2+]i. The results suggest Ca2+ as a potential intracellular messenger for active mechanical responses in Deiters cells.
 ...
PMID:Photo-released intracellular Ca2+ evokes reversible mechanical responses in supporting cells of the guinea-pig organ of Corti. 802 70

The intracellular calcium concentration [Ca2+]i in olfactory receptor neurones of Xenopus laevis was imaged with high spatial and temporal resolution. A new method using a mixture of the calcium indicator dyes Fluo-3 and Fura-Red was employed. The fluorescence patterns in two wavelength bands were measured on the emission side of a confocal laser scanning microscope, and the ratio R of the fluorescence intensities was taken as an estimate of [Ca2+]i. When the neurones were depolarized by elevating the extracellular potassium concentration [K+]o they showed one of three types of responses: a fast increase in [Ca2+]i, a slow increase in [Ca2+]i, or no change in [Ca2+]i. The fast increase in [Ca2+]i took place in the soma compartment. For at least 4 s after the onset of depolarization the calcium distribution in the dendrite remained essentially unchanged. To study the fast increase with high time resolution, line scan images were taken. The neurones were depolarized for brief periods applying a solution containing high [K+] onto the soma from an application pipette. The fast increase in [Ca2+]i began with a delay of about 200 ms and went from the resting concentration to about 110 nM above resting concentration. Following the depolarization, recovery from elevated [Ca2+]i to resting levels had a time constant of about 15 s. The slow response seemed to depend on the removal of [Na+] from the bath rather than on the elevated [K+] in the bath. The response was also observed with Cd2+, Ni2+, and Co2+ (1.5 mM each) in the bath.(ABSTRACT TRUNCATED AT 250 WORDS)
Cell Calcium 1994 May
PMID:Localization of calcium entry through calcium channels in olfactory receptor neurones using a laser scanning microscope and the calcium indicator dyes Fluo-3 and Fura-Red. 803 92

A method is described to facilitate flow cytometric analysis of calcium mobilization upon stimulation of murine T cell hybrids. In these transformed cell lines, the accuracy of cytometric measurement of free cytoplasmic calcium with Fluo-3 is compromised by the rapid loss of the intracellular dye. We have found that the addition of sulfinpyrazone, a known organic-anion transporter inhibitor in epithelial cells and in macrophages, severely impairs the leakage of the Fluo-3 probe from the cytoplasmic matrix. Under appropriate conditions, sulfinpyrazone has little effect on the cell physiology and permits the detection of calcium influx in a variety of murine T cell hybrids.
 ...
PMID:Flow cytometric measurement of calcium influx in murine T cell hybrids using Fluo-3 and an organic-anion transport inhibitor. 803 84

The immunosuppressive synthetic methylated polycyclic aromatic hydrocarbon (PAH), 7,12-dimethylbenz[a]anthracene (DMBA), has been shown to cause both an immediate and a sustained elevation of free intracellular calcium (Ca2+) in human T cells. In the present studies, a series of anthracene- and pyrene-based PAHs were tested for rapid (3 min) and sustained (4 hr) Ca2+ mobilization in the HPB-ALL human T cell line measured by flow cytometry using Fluo-3 as a Ca2+ indicator. Immunosuppressive PAHs produced a sustained Ca2+ elevation for at least 4 hr, while weakly immunosuppressive PAHs caused only a transient increase in Ca2+. The immunosuppressive PAHs, DMBA, benzo[a]pyrene, dibenz[a,h]anthracene, and 9,10-dimethylanthracene, produced a sustained increase in intracellular Ca2+ in HPB-ALL cells. Those PAHs with moderate to minimal immunosuppressive properties (i.e., dibenz[a,c]anthracene, benz[a]anthracene, benzo[e]pyrene, and anthracene) produced small and transient Ca2+ mobilization responses in HPB-ALL cells. It appeared that methylation of anthracene at the 9,10-positions increased the duration of Ca2+ mobilization, whereas the addition of a benzene group in the "a" position was associated with a transient increase in Ca2+ levels. Genistein, a protein tyrosine kinase (PTK) inhibitor, partially inhibited the rapid and sustained PAH-induced Ca2+ mobilization responses, while the protein kinase C (PKC) inhibitors, staurosporine and calphostin C, had essentially no effect on PAH-induced Ca2+ elevation. It appears that the action of PAHs on PTKs is important in the rapid Ca2+ response of human T cells. However, additional biochemical mechanisms appear to be responsible for the sustained elevation of Ca2+ produced by PAHs in T cells. The results of these studies demonstrate that persistent elevation of intracellular Ca2+ by PAHs correlates with their known immunosuppressive properties.
 ...
PMID:Persistence of calcium elevation in the HPB-ALL human T cell line correlates with immunosuppressive properties of polycyclic aromatic hydrocarbons. 804 70

The ced-1 mutant of the free-living nematode, Caenorhabitis elegans, was used to study cell injury and cell death in relation to changes in intracellular ionized calcium ([Ca2+]i). This animal, which is being genetically characterized, may prove to be extremely useful for certain toxicologic studies because of its small size, optical transparency, rapid generation time, and the morphologic and genetic data currently available. During the development of this animal, 131 of 1,090 ultimate somatic cells undergo programmed cell death. Using mutagenesis techniques, several genes responsible for this death have been identified. In this study, we have taken advantage of the ced-1 mutant in which dead cells accumulate, as they cannot be phagocytized and removed. Although changes in [Ca2+]i have been studied in relation to cell injury and cell death, observations have been essentially restricted to in vitro monolayer cultures because of the methodology involved. To study the relationship between changes in [Ca2+]i and injury in vivo, we selected this animal model for further study and report here the morphological changes following the effects of ionomycin treatment in relation to increases of [Ca2+]i and cell death as measured using the fluorescent probes Fluo-3/AM and propidium iodide, respectively. The technique of confocal laser scanning microscopy is ideally adapted to such measurements in these living animals, and the results can be readily correlated with those made with Nomarski differential interference contrast microscopy as well as with transmission electron microscopy. The results support previous in vitro observations and show that early increases of [Ca2+]i accompany early reactions to injury. Furthermore, the results also show that changes in this small invertebrate metazoan parallel those seen in mammalian systems, including human. Thus, the current study indicates that ced-1 C. elegans can potentially serve as an in vivo model not only for evaluating the possible temporal relationship of [Ca2+]i elevation with cell death but also for evaluating the [Ca2+]i elevation observed in relation to other phenomena and in evaluating toxic agents.
 ...
PMID:The relationship between [Ca2+]i and cell death using an in vivo model: a study using the ced-1 mutant strain of C. elegans. 805 4

The mechanisms by which a sperm factor caused Ca2+ oscillations in unfertilized mouse eggs was investigated by monitoring the fluorescence of intracellular Fluo-3. Injecting sperm extracts triggered Ca2+ oscillations that varied in number and frequency rather than amplitude. All the sperm factor-induced Ca2+ transients showed a characteristic rapid increase and decline. The oscillations persisted for variable times in eggs bathed in Ca2+ free media and were distinct in character from those caused by inserting pipettes containing inositol 1,4,5-trisphosphate (InsP3). InsP3-induced Ca2+ oscillations were always of high frequency but varied considerably in form and amplitude depending upon InsP3 concentration. The oscillations produced by injecting Ca2+ into unfertilized eggs were similar to those produced with low doses of InsP3 but different from those caused by sperm extract injection. After injection of sperm extracts further injection of InsP3, or Ca2+, produced high frequency large amplitude Ca2+ transients. It is concluded that the sperm factor mediates its effects by sensitizing Ca2+ release mechanisms.
Cell Calcium 1994 Apr
PMID:Ca2+ oscillations and sensitization of Ca2+ release in unfertilized mouse eggs injected with a sperm factor. 805 49


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>