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Query: CAS:7440-70-2 (calcium)
 333,191 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

GABA evoked a reversible rise of free intracellular calcium concentration ([Ca]i) in cultured rat hippocampal neurons, detected with Fluo-3 fluorescence in a confocal laser scanning microscope. The GABA-evoked change of [Ca]i was mimicked by muscimol and not by baclofen, but was only minimally affected by picrotoxin or bicuculline, indicating that this effect of GABA is not likely to be mediated by activation of GABAB receptor or by a conventional chloride-linked GABAA receptor. GABA-evoked rise of [Ca]i expressed a marked desensitization; only 10-20 minutes after a previous exposure to GABA was the response to a subsequent application fully expressed. This desensitization was not seen in electrophysiological responses to GABA or in [Ca]i changes evoked by NMDA in the same neurons. The GABA response appeared to be developmentally regulated and was seen in 1-7-day-old more than in 21-28-day-old cells. It is suggested that GABA evokes a unique change of [Ca]i in young hippocampal neurons.
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PMID:GABA induces a unique rise of [Ca]i in cultured rat hippocampal neurons. 835 6

Freshly isolated rat hepatocytes, loaded with the Ca2+ probe Fluo-3, responded to homologous pancreastatin with a sudden increase in free cytosolic Ca2+ ([Ca2+]i) as well as glucose release. Addition of rat pancreastatin (0.1 microM) to hepatocytes resulted in an increase in [Ca2+]i from 150 nM to 700 nM, which declined back to nearly basal values within 2-3 min. Half-maximal and maximal effects were observed at 0.3 and 100 nM pancreastatin respectively. The increase in [Ca2+]i induced by vasopressin and noradrenaline was very similar in extent (from 150 to 800 nM) to that produced by pancreastatin. Neither the alpha 1-adrenergic blocker prazosin nor the vasopressin antagonist V1 modified the increase in [Ca2+]i induced by pancreastatin. Pig pancreastatin and its 33-49 C-terminal fragment produced about 65 and 75% of the effect of homologous pancreastatin respectively. Glucose production correlated with changes in [Ca2+]i in the same order of potency: vasopressin > rat pancreastatin > pig 33-49 pancreastatin > pig 1-49 pancreastatin. The effect of pancreastatin on [Ca2+]i was decreased by 50% when Ca2+ was omitted from the medium, and totally abolished when hepatocytes were depleted of internal Ca2+ stores by preincubation without Ca2+ and with 2 mM EGTA. When hepatocytes were preincubated for 5 min with PMA, the effects of ATP and noradrenaline were prevented, and those of vasopressin and pancreastatin remained unchanged. The pretreatment of hepatocytes with pertussis toxin diminished the response to pancreastatin and vasopressin. These results suggest that pancreastatin is a new Ca(2+)-mobilizing glycogenolytic hormone acting through a specific receptor which may involve both pertussis-toxin-sensitive and -insensitive GTP-binding regulatory proteins.
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PMID:Pancreastatin increases free cytosolic Ca2+ in rat hepatocytes, involving both pertussis-toxin-sensitive and -insensitive mechanisms. 837 59

Recent studies indicate that depressed macrophage (M phi) immune responses following hemorrhage can be restored by the administration of interferon (IFN)-gamma as an adjuvant to resuscitation. However, the mechanism of these effects remains unknown. An important component of the process of M phi activation in response to pathogens is the mobilization of intracellular calcium ([Ca2+]i). Since hemorrhage alters the M phi signal transduction system, the aim of this study, therefore, was to determine whether administration of IFN-gamma after hemorrhage restores this mode of macrophage signal transduction. To assess this, C3H/HeN mice were bled to and maintained at a mean blood pressure of 35 mm Hg for 1 hr and then adequately resuscitated. Mice then received either 40,000 units IFN-gamma/kg body wt or saline vehicle and were killed 2 hr posthemorrhage to obtain splenic M phi. These M phi were loaded with Fluo-3 AM (fluorescent [Ca+2]i probe) and their capacity to mobilize [Ca+2]i in response to stimulation with f-met-leu-phe (FMLP; bacterial peptide) was assessed on a laser cytometer. The results indicated that IFN-gamma restored the capacity of splenic M phi to mobilize [Ca+2]i in response to FMLP. Moreover, the results demonstrated that hemorrhage produced a marked increase in resting cAMP levels in these cells that were lowered to sham levels by the administration of IFN-gamma. Thus, it appears that IFN-gamma acts to restore M phi signal transductional capacity, thereby improving M phi-mediated immune functions following hemorrhage and resuscitation.
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PMID:Insights into the mechanism by which interferon-gamma improves macrophage function following hemorrhage and resuscitation. 839 49

The fluorescent calcium ion indicator dye Fluo-3 and DNA-binding dye Hoechst 33342 were employed to determine, in a quantitative microspectrofluorometric study, the intracellular calcium ion concentration ([Ca2+]i) and the DNA content of individual living NIH3T3 cells. The well-separated excitation and emission properties of these dyes allowed us to establish for each cell both the phase of the cell cycle using DNA content and [Ca2+]i. We found that the transition from G1, through S, to the G2 phase is accompanied by a two-fold increase in [Ca2+]i. The [Ca2+]i was inhomologous in each phase of the interphase (G1, S and G2) although [Ca2+]i in the S and G2 phases was never lower than certain threshold values in the G1 and S phases respectively. [Ca2+]i in G0 cells was lower than that in G1 cells. These changes in [Ca2+]i suggest that [Ca2+]i may be an important regulator of cell cycle progression.
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PMID:Increase of calcium levels at interphase in NIH 3T3 cells. 839 2

A simple and relatively inexpensive system is described for obtaining quantitative fluorescence measurements on single living cells loaded with a fluorescent probe to study cell physiological processes. The light emitted from the fluorescent cells is captured by and transported through an optical fiber. After passage through appropriate filters the light is measured using a photomultiplier tube. The optical fiber is mounted in one of the microscope outlets. Signals derived from the photomultiplier are converted to voltage, amplified, and displayed on a recorder. In the excitation pathway a shutter control unit is mounted. With this control unit the period that the excitation pathway is 'opened' and 'closed' can be adjusted, to reduce cell damage and/or bleaching of the probe. This option allows time-lapse recording of experiments up to 1 h. We have used this set-up with a single and dual emission fluorescent probe to determine intracellular calcium concentrations and pH, respectively. In Fluo-3-loaded K562 target cells bound to natural killer cells, a temporary rise in [Ca2+]i was accompanied by bleb formation. The simple construction of this set-up is interchangeable between different types of fluorescence microscopes and can easily be combined with other microscopy techniques, e.g., patch clamp.
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PMID:A simple optical fiber device for quantitative fluorescence microscopy of single living cells. 844 47

New procedures are described for producing brief transients and reversible elevations in [Ca] that can be used to quantitatively control the concentration of cytoplasmic calcium. If the photolabile calcium chelator DM-nitrophen, partially bound to calcium, is exposed to steady illumination, [Ca] can be raised from a few nM to up to 10 microM for durations of 100 ms or longer, depending on light intensity and duration. An association rate of calcium with nitrophen of 1.5 x 10(6) M-1s-1 was estimated from measurements of [Ca] using the fluorescent indicator Fluo-3, and calcium was found to speed the photolysis of nitrophen 2.5-times. Partial photolysis of DM-nitrophen partly loaded with calcium elicits a [Ca] spike of over 100 microM lasting about 1 ms, depending on intensity and duration of the light flash. Simulations of the reactions involved predict changes in Fluo-3 fluorescence measured at high time resolution with a laser scanning confocal microscope. These procedures have been applied in physiological experiments to generate cytoplasmic [Ca] spikes and pulses and study the cellular responses to them.
Cell Calcium 1993 Feb
PMID:The calcium concentration clamp: spikes and reversible pulses using the photolabile chelator DM-nitrophen. 845 75

We describe a flow cytometric assay that enables one to follow conjugate formation between cytotoxic cells and their target cells during the cytotoxic process. In addition, the internal calcium concentration ([Ca2+]i) and internal pH (pHi) of the conjugated cells can be monitored and directly compared to the nonconjugated cells. This is achieved by labeling one cell type with the Ca(2+)-specific dye Fluo-3, while the other cell type is labeled with the pH-sensitive dye SNARF-1. As these fluorochromes have different emission spectra, events positive for both fluorochromes are identified as conjugates. The results show that the conjugates can be clearly distinguished from single cytotoxic cells [natural killer (NK) cells] and target cells [K562 cells, (TC)]. Upon binding, [Ca2+]i is increased in the NK cells as well as in the TC. In conjugated NK cells this increase of [Ca2+]i is temperature dependent and is followed by a decrease to a normal [Ca2+]i value later on. The [Ca2+]i in NK cells increases in 2 steps, which may be related to the binding--and lethal hit phase. Upon conjugate formation, NK cells show a slight increase in pHi (0.2-0.3 pH units). TC do not reveal a significant change in pHi.
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PMID:Flow cytometric measurement of [Ca2+]i and pHi in conjugated natural killer cells and K562 target cells during the cytotoxic process. 847 3

Functional responses to stimulation of rat 5-HT1C receptors expressed in A9 cells were studied using whole cell voltage clamp and calcium recording techniques. Stimulation of 5-HT1C receptors evoked outward currents clamped at -50 mV. The outward currents were reduced when GTP was excluded from the intracellular recording solution or when GDP-beta-S was added. 8-Bromo cyclic AMP (5 mmol/l) neither produced an effect per se nor affected the 5-HT-induced outward current in A9 cells, thus excluding cAMP as a second messenger involved in 5-HT1C receptor activation. Phorbol myristic acetate (PMA; 10 mumol/l) did not affect the electrical activity of the transfected A9 cells but reduced the 5-HT-induced current amplitude to 71 +/- 9% of the control value (n = 12). This indicates that activation of protein kinase C does not play a direct role in the 5-HT-induced response in these cells. The 5-HT induced currents mainly involved potassium ions, although a small contribution of chloride ions was also observed. The 5-HT-induced current was inhibited by the K+ channel blocking agents tetraethylammonium (1 mmol/l), apamin (0,5 mumol/l) and 4-aminopyridine (5 mmol/l). The 5-HT-induced currents recorded at -50 mV were unaffected by removal of extracellular calcium, but inclusion of the calcium chelator BAPTA (5 mmol/l) in the intracellular solutions abolished the current. Measurement with the calcium indicator Fluo-3 revealed a 5-HT-induced increase in intracellular calcium which was not affected by removal of extracellular calcium but declined after repeated stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of functional responses in A9 cells transfected with cloned rat 5-HT1C receptors. 847 32

The effect of hyposmotic conditions on the concentration of intracellular free calcium ([Ca2+]i) was studied in cultured cerebellar granule cells and cerebral cortical neurons after loading of the cells with the fluorescent Ca2+ chelator Fluo-3. It was found that in both types of neurons exposure to media with a decrease in osmolarity of 20 to 50% of the osmolarity in the isosmotic medium (320 mOsm) led to a dose dependent increase in [Ca2+]i with a time course showing the highest value at the earliest measured time point, i.e. 40 s after exposure to the hyposmotic media and a subsequent decline towards the basal level during the following 320 s. The response in the cortical neurons was larger than in the granule cells but both types of neurons exhibited a similar increase in [Ca2+]i after exposure to 50 mM K+ which was of the same magnitude as the increase in [Ca2+]i observed in the cortical neurons exposed for 40 s to a medium with a 50% reduction in osmolarity. In both types of neurons the blocker of voltage gated Ca2+ channels verapamil had no effect on the hyposmolarity induced increase in [Ca2+]i. On the contrary, this increase in [Ca2+]i was dependent upon external calcium and could be inhibited partly or completely by the inorganic blockers of Ca2+ channels Mg2+ and La3+. Dantrolene which prevents release of Ca2+ from internal stores had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Neurons respond to hyposmotic conditions by an increase in intracellular free calcium. 847 57

The free Ca2+ ion concentration, measured by means of the fluorescent indicators Indo-1 and Fluo-3, has been compared in normal and parasitized erythrocytes from synchronized in vitro cultures of human blood infected with Plasmodium falciparum. The cells were loaded with the calcium probes in the form of their acetoxymethylesters. P. falciparum-infected red blood cells gradually accumulate more free Ca2+ ions than uninfected cells. The increased Ca2+ concentration is preferentially located inside a rather large central area, corresponding to the position and size of the parasite. In contrast, the Ca2+ concentration outside this area is not higher than that in normal red blood cells. This rise in calcium content becomes significant at the end of the ring stage. The concentration measured in 36-hr schizonts reaches two times that measured in uninfected erythrocytes, and it peaks to four times control values in 44-hr schizonts. The Ca2+ channel blocker verapamil (10 to 20 microM), added on the 24th hr of culture, slows down or blocks the parasite's growth at the trophozoite stage. However, the free Ca2+ concentration measured on infected red blood cells at different times after verapamil addition does not differ from that obtained in the absence of verapamil. These results demonstrate that the bulk of the free Ca2+ load of P. falciparum-infected erythrocytes is located inside the parasite or its parasitophorous vacuole. These data also indicate that the increased Ca2+ influx in P. falciparum-infected erythrocytes does not take the route of verapamil-sensitive Ca2+ channels. It also appears that the inhibitory effect of verapamil on the parasite's maturation does not depend on a change in its Ca2+ content.
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PMID:Cytosolic free calcium in Plasmodium falciparum-infected erythrocytes and the effect of verapamil: a cytofluorimetric study. 850 May 85


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