Effects of ionophore A23187 on ciliary activity of Paramecium caudatum

1988 ◽  
Vol 34 (2) ◽  
pp. 169-179 ◽  
Author(s):  
Michael J. Doughty
Keyword(s):  
Extracellular Calcium ◽  
Ion Concentration ◽  
Ciliary Activity ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
Paramecium Caudatum ◽  
Alkaline Ph ◽  
Ph Values ◽  
Swimming Motion ◽  
Ciliary Reversal

The ciliated protozoan Paramecium caudatum (suspended in buffered solutions of pH 4.5–9.5) was treated with the ionophore A23187. With calcium and sodium as the only added extracellular cations, A23187 stopped ciliary motion and immobilized the cells. The rate of immobilization increased as a function of A23187 concentration (0.5–16 μg/mL) and extracellular calcium concentration (0.016–4 mM), but decreased as a function of increasing extracellular pH. The rate of immobilization was markedly sensitive to the extracellular calcium ion concentration at alkaline pH, but showed only slight calcium sensitivity at acid pH values. Continuous ciliary reversal (and thus backward swimming motion of the cells) was not observed under these conditions. However, extracellular magnesium ions (in a concentration-dependent manner) attenuated and even prevented the immobilization induced by calcium–A23187 treatment. In addition, in the presence of 1 mM Mg2+, a periodic ciliary reversal response was induced by calcium–A23187 treatment. At neutral pH values, the duration of this response increased as a function of extracellular calcium, but not magnesium, ion concentration. At neutral to alkaline pH values, a sustained slow backward swimming or circling motion (partial ciliary reversal) occurred after the period of periodic ciliary reversal.

EFFECTS OF DILAZEP ON CYTOPLASMIC CALCIUM ION CONCENTRATION AND ARACHIDONIC ACID METABOLISM IN HUMAN PLATELETS AND NEUTROPHILS.

1987 ◽  
Author(s):  
M Okuma ◽  
K Kanaji ◽  
S Sensaki ◽  
H Uchino
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Calcium Ionophore ◽  
Leukotriene B4 ◽  
Human Platelets ◽  
Ion Concentration ◽  
Antiplatelet Drug ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
Concentration Dependent Manner

We studied effects of dilazep(DZ), an antiplatelet drug, on the cytoplasmic Ca2+ concentration ([Ca2+]-i) and arachidonic acid (AA) metabolism in human platelets and neutrophils. [Ca2+]i of aequor-in-loaded platelets was estimated by using the platelet ionized calcium aggregometer. AA metabolism was studied by the determination of AA metabolites including hydroxyheptadecatrienoic acid (HHT), hydroxyeicosatetraenoic acid (HETE) and leukotriene B4 (LTB4) by reversed-phase high-performance liquid chromatography. When aequorin-loaded platelets were preincubated with DZ (0−0.5 mM) for 1 min at 37°C, both platelet aggregation and [Ca2+]i elevation induced by thrombin, AA and collagen were inhibited by DZ in a concentration dependent manner, while only aggregation was inhibited after stimulation by the calcium ionophore A23187 (1 yM). Both influx and release of Ca2+ into platelet cytoplasm induced by thrombin or AA were inhibited by DZ, while neither of them was affected when induced by A23187. The production of HHT and 12-HETE by the reaction of 100 yM AA with platelets preincubated with DZ (0−1 mM) was not inhibited, whereas their production by throirfbin (10 u/ml) was remarkably inhibited by DZ in a concentration dependent manner. When DZ (0−0.3 mM)-treated neutrophils were incubated with 5 μM A23187 in the presence or absence of 20 μM AA, the production of LTB4 and 5-HETE was increased by DZ in the presence of AA, whereas their production was inhibited by DZ in its absence. When platelet/neutrophil mixtures preincubated with DZ (0−0.3 mM) and cytochalasin B were stimulated by thrombin (5 u/ml) in the presence of FMLP, DZ inhibited LTB4 production in a concentration dependent manner, while 5S,12S-diHETE synthesis was enhanced by lower concentrations of DZ and inhibited by its higher concentrations (> 0.1 mM).Thus, DZ inhibits platelet aggregation induced by any agonist including A23183, while [Ca2+]i elevation is inhibited by the drug only when it is induced by the receptor-mediated agonist. Furthermore, it was suggested that AA liberation from phospholipids in platelets and neutrophils was inhibited by DZ, leading to reduced production of all endogenous AA metabolites by these cells after appropriate stimulation, although lipoxygenase metabolites of liberated or exogenous AA could be increased.

scholarly journals The extracellular calcium-sensing receptor is expressed in the cumulus–oocyte complex in mammals and modulates oocyte meiotic maturation

Reproduction ◽  
2009 ◽  
Vol 138 (3) ◽  
pp. 439-452 ◽  
Author(s):  
Teresa De Santis ◽  
Valeria Casavola ◽  
Stephan Joel Reshkin ◽  
Lorenzo Guerra ◽  
Barbara Ambruosi ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Signal Transduction Pathway ◽  
Cumulus Cells ◽  
Extracellular Calcium ◽  
Ion Concentration ◽  
Meiotic Maturation ◽  
Dependent Manner ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Oocyte Meiotic Maturation

The extracellular calcium-sensing receptor (CASR) plays an important role in cells involved in calcium (Ca2+) homeostasis by directly sensing changes in the extracellular Ca2+ion concentration. We previously reported the localization and quantitative expression of CASR protein in human oocytes. In this study, we examined the expression and the functional role of CASR during oocyte meiotic maturation in a large mammal animal model, the horse. As in humans, CASR protein was found to be expressed in equine oocytes and cumulus cells. Western-blot analysis revealed a single 130 kDa band in denuded oocytes and a doublet of 130–120 kDa in cumulus cells. CASR labeling was observed by confocal microscopy in cumulus cells and in oocytes on the plasma membrane and within the cytoplasm at all examined stages of meiosis. Functionally, the CASR allosteric effector NPS R-467, in the presence of 2.92 mM external Ca2+, increased oocyte maturation rate in a dose-dependent manner and its stimulatory effect was attenuated by pre-treatment with the CASR antagonist NPS 2390. NPS R-467 had no effect in suboptimal external Ca2+(0.5 mM), indicating that it requires higher external Ca2+to promote oocyte maturation. In oocytes treated with NPS R-467, CASR staining increased at the plasmalemma and was reduced in the cytosol. Moreover, NPS R-467 increased the activity of MAPK, also called ERK, in cumulus cells and oocytes. These results provide evidence of a novel signal transduction pathway modulating oocyte meiotic maturation in mammals in addition to the well-known systemic hormones.

scholarly journals Effect of alkaline pH on photosynthetic water oxidation and the association of extrinsic proteins with Photosystem Two

1989 ◽  
Vol 258 (2) ◽  
pp. 357-362 ◽  
Author(s):  
D J Chapman ◽  
J De Felice ◽  
K Davis ◽  
J Barber
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Binding Sites ◽  
Partial Recovery ◽  
Alkaline Ph ◽  
Ph Values ◽  
Extrinsic Proteins ◽  
Reversible Phase ◽  
Photosynthetic Water Oxidation ◽  
Optimal Ph

Incubation of a membrane preparation enriched in Photosystem Two (PSII) at alkaline pH inhibited the water-splitting reactions in two distinct steps. Up to pH 8.5 the inhibition was reversible, whereas at higher alkalinities it was irreversible. It was shown that the reversible phase correlated with loss and rebinding of the 23 kDa extrinsic polypeptide. However, after mild alkaline treatments a partial recovery was possible without the binding of the 23 kDa polypeptide when the assay was at the optimal pH of 6.5 and in a medium containing excess Cl-. The irreversible phase was found to be closely linked with the removal of the 33 kDa extrinsic protein of PSII. Treatments with pH values above 8.5 not only caused the 33 kDa protein to be displaced from the PSII-enriched membranes, but also resulted in an irreversible modification of the binding sites such that the extrinsic 33 kDa protein could not reassociate with PSII when the pH was lowered to 6.5. The results obtained with these more extreme alkaline pH treatments support the notion that the 23 kDa protein cannot bind to PSII unless the 33 kDa protein is already bound. The differential effect of pH on the removal of the 23 kDa and 33 kDa proteins contrasted with the data of Kuwabara & Murata [(1983) Plant Cell Physiol. 24, 741-747], but this discrepancy was accounted for by the use of glycerol in the incubation media.

scholarly journals Inhibition by somatostatin of amylase secretion induced by calcium and cyclic AMP in rat pancreatic acini

1994 ◽  
Vol 304 (2) ◽  
pp. 531-536 ◽  
Author(s):  
H Ohnishi ◽  
T Mine ◽  
I Kojima
Keyword(s):  
Cyclic Amp ◽  
G Protein ◽  
Pertussis Toxin ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Amylase Secretion ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
Pancreatic Acini

It has recently been shown that somatostatin inhibits amylase secretion from isolated pancreatic acini by reducing cyclic AMP (cAMP) production [Matsushita, Okabayashi, Hasegawa, Koide, Kido, Okutani, Sugimoto and Kasuga (1993) Gastroenterology 104, 1146-1152]. To date, however, little is known as to the other mechanism(s) by which somatostatin inhibits amylase secretion in exocrine pancreas. To investigate the action of somatostatin independent of cAMP generation, we examined the effect of somatostatin in isolated rat pancreatic acini stimulated by 1 microM calcium ionophore A23187 and 1 mM 8-bromo-cyclic AMP (8Br-cAMP). Somatostatin inhibited amylase secretion evoked by a combination of A23187 and 8Br-cAMP in a dose-dependent manner. The maximum inhibition was obtained by 10(-7) M somatostatin, and at this concentration somatostatin inhibited the effect of A23187 and 8Br-cAMP by approximately 30%. In electrically permeabilized acini, an elevation of free calcium concentration resulted in an increase in amylase secretion and cAMP enhanced the secretion evoked by calcium. cAMP shifted the dose-response curve for calcium-induced secretion leftwards and elevated the peak value of secretion. Somatostatin inhibited the effect of cAMP on calcium-induced amylase secretion by shifting the dose-response curve to the right. To determine the involvement of a G-protein(s), we examined the effect of somatostatin in acini pretreated with pertussis toxin. Pretreatment of acini with pertussis toxin completely blocked somatostatin-inhibition of amylase-secretion evoked by A23187 and 8Br-cAMP. These results indicate that somatostatin decreases amylase secretion induced by cAMP and calcium by reducing the calcium sensitivity of exocytosis. A pertussis toxin-sensitive G-protein is also involved in this step.

Heterogeneous distribution of endothelium-dependent relaxations resistant to NG-nitro-L-arginine in rats

1992 ◽  
Vol 263 (4) ◽  
pp. H1090-H1094 ◽  
Author(s):  
T. Nagao ◽  
S. Illiano ◽  
P. M. Vanhoutte
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Calcium Ionophore ◽  
Renal Arteries ◽  
Mesenteric Arteries ◽  
K Channel ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
Arterial Tree ◽  
Heterogeneous Distribution

Endothelium-dependent relaxations that are resistant to inhibitors of nitric oxide synthase probably are mediated by endothelium-dependent hyperpolarization of the vascular smooth muscle. Experiments were performed to examine the distribution of this type of relaxation along the arterial tree of the rat by measuring changes in isometric force. Acetylcholine induced concentration- and endothelium-dependent relaxations in aortas and in pulmonary, common iliac, femoral, mesenteric, and renal arteries contracted with phenylephrine. In the presence of NG-nitro-L-arginine, the cumulative administration of acetylcholine induced relaxations only in the femoral, mesenteric, and renal arteries. The calcium ionophore A23187 relaxed mesenteric arteries contracted with phenylephrine in a concentration- and endothelium-dependent manner. The concentration-relaxation curve to A23187 was shifted to the right in the presence of NG-nitro-L-arginine. The maximal relaxations induced by lemakalim, a K+ channel opener, were smaller in those arteries that did not exhibit NG-nitro-L-arginine-resistant relaxations. These results suggest that NG-nitro-L-arginine-resistant relaxations are more frequently observed in smaller arteries. The arteries that exhibit NG-nitro-L-arginine-resistant relaxations may be more sensitive to an endothelium-derived substance that causes hyperpolarization of vascular smooth muscle cells.

Effects of histamine and histamine receptor antagonists on ion transport in rabbit descending colon

1984 ◽  
Vol 247 (4) ◽  
pp. G411-G418 ◽  
Author(s):  
R. D. McCabe ◽  
P. L. Smith
Keyword(s):  
Ion Transport ◽  
Receptor Antagonist ◽  
Prostaglandin E1 ◽  
Short Circuit ◽  
Bathing Solution ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
H2 Receptor Antagonist ◽  
Maximal Inhibition ◽  
Descending Colon

The effects of histamine on colonic ion transport were examined in in vitro preparations of rabbit descending colon. Serosal addition of histamine (10(-5) M) produced a transient increase in short-circuit current (Isc) and transepithelial conductance. The Isc response to histamine could be blocked by removing Cl from both bathing solutions, adding furosemide (10(-3) M) to the serosal bathing solution, adding indomethacin to the serosal and mucosal bathing solutions (10(-5) M), or removing Ca from the serosal bathing solution. In addition, the histamine-induced increase in Isc was inhibited in a dose-dependent manner by the H1-receptor antagonist diphenhydramine, with a maximal inhibition at 10(-4) M and a half-maximal inhibition at 3 X 10(-7) M. The H2-receptor antagonist cimetidine (10(-3) M) was without effect on the histamine response. Measurement of unidirectional Na, K, and Cl fluxes revealed that serosal addition of diphenhydramine (10(-3) M) reduced basal Isc due to a decrease in mucosal-to-serosal Na flux. Serosal addition of diphenhydramine (10(-3) M) also inhibited the increase in Isc produced by serosal addition of prostaglandin E1, 8-bromo-cAMP, cholera toxin, or the ionophore A23187. Measurement of unidirectional K and Cl fluxes revealed that prostaglandin E1 alone increased serosal-to-mucosal K and Cl fluxes and reduced the mucosal-to-serosal K flux, thereby increasing net K and Cl secretion. Serosal diphenhydramine (10(-3) M) abolished the changes in Cl fluxes produced by prostaglandin E1 and reduced the magnitude of the changes in K fluxes.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunologic mast cell-mediated responses and histamine release are attenuated by heparin

1992 ◽  
Vol 73 (3) ◽  
pp. 1093-1101 ◽  
Author(s):  
J. Lucio ◽  
J. D'Brot ◽  
C. B. Guo ◽  
W. M. Abraham ◽  
L. M. Lichtenstein ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Histamine Release ◽  
Immunoglobulin E ◽  
Specific Antigen ◽  
Calcium Ionophore ◽  
Intradermal Injection ◽  
Calcium Ionophore A23187 ◽  
Ionophore A23187 ◽  
Dependent Manner

Heparin has been shown to act as a competitive inhibitor of inositol 1,4,5-triphosphate (InsP3) receptors in various cell types. Because InsP3 is one of the second messengers involved in stimulus-secretion coupling in mast cells, it is possible that heparin may inhibit mast cell-mediated reactions. Therefore, in allergic sheep, we tested this hypothesis in two mast cell-mediated reactions induced by immunologic and nonimmunologic stimuli: immediate cutaneous reaction (ICR) and acute bronchoconstrictor response (ABR). In 12 sheep allergic to Ascaris suum antigen, the surface area of the skin wheal was determined 20 min after intradermal injection (0.05 ml) of increasing concentrations of specific antigen, compound 48/80, and histamine, without and after pretreatment with heparin (100, 300, or 1,000 U/kg i.v.). Antigen, compound 48/80, and histamine produced concentration-dependent increases in ICR. Heparin “partially” inhibited the ICR to antigen and compound 48/80 in a dose-dependent manner without modifying the ICR to histamine. The heparin preservative benzyl alcohol was ineffective. In 11 additional sheep, specific lung resistance was measured before and after inhalation challenges with antigen, compound 48/80, and histamine without and with aerosol heparin pretreatment (1,000 U/kg). Heparin blocked the antigen- and compound 48/80-induced bronchoconstriction without modifying the airway effects of histamine. In isolated human uterine mast cells, heparin inhibited the anti-immunoglobulin E- but not the calcium ionophore- (A23187) induced histamine release. These data suggest that heparin inhibits the ICR and ABR induced by stimuli that produce immunologic and nonimmunologic mast cell degranulation without attenuating the effects of histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals CpxP, a Stress-Combative Member of the Cpx Regulon

1998 ◽  
Vol 180 (4) ◽  
pp. 831-839 ◽  
Author(s):  
Paul N. Danese ◽  
Thomas J. Silhavy
Keyword(s):  
Escherichia Coli ◽  
Envelope Protein ◽  
Periplasmic Protein ◽  
Dependent Manner ◽  
Alkaline Ph ◽  
Signal Transduction System ◽  
Two Component ◽  
Mutant Strains ◽  
Alkaline Conditions ◽  
Two Component Signal Transduction

ABSTRACT The CpxA/R two-component signal transduction system ofEscherichia coli can combat a variety of extracytoplasmic protein-mediated toxicities. The Cpx system performs this function, in part, by increasing the synthesis of the periplasmic protease, DegP. However, other factors are also employed by the Cpx system for this stress-combative function. In an effort to identify these remaining factors, we screened a collection of random lacZ operon fusions for those fusions whose transcription is regulated by CpxA/R. Through this approach, we have identified a new locus,cpxP, whose transcription is stimulated by activation of the Cpx pathway. cpxP specifies a periplasmic protein that can combat the lethal phenotype associated with the synthesis of a toxic envelope protein. In addition, we show that cpxPtranscription is strongly induced by alkaline pH in a CpxA-dependent manner and that cpxP and cpx mutant strains display hypersensitivity to growth in alkaline conditions.

scholarly journals The opposing Chloride Cotransporters KCC and NKCC control locomotor activity in constant light and during long days

2021 ◽  
Author(s):  
Anna Katharina Eick ◽  
Maite Ogueta ◽  
Edgar Buhl ◽  
James J. L. Hodge ◽  
Ralf Stanewsky
Keyword(s):  
Locomotor Activity ◽  
Circadian Clock ◽  
Opposite Effect ◽  
Neuronal Response ◽  
Reversal Potential ◽  
Ion Concentration ◽  
Day Length ◽  
Constant Light ◽  
Behavioral Activity ◽  
Dependent Manner

AbstractCation Chloride Cotransporters (CCC’s) regulate intracellular chloride ion concentration ([Cl−]i) within neurons, which can reverse the direction of the neuronal response to the neurotransmitter GABA. Na+ K+ Cl− (NKCC) and K+ Cl− (KCC) cotransporters transport Cl− into or out of the cell, respectively. When NKCC activity dominates, the resulting high [Cl−]i can lead to an excitatory and depolarizing response of the neuron upon GABAA receptor opening, while KCC dominance has the opposite effect. This inhibitory-to-excitatory GABA switch has been linked to seasonal adaption of circadian clock function to changing day length, and its dysregulation is associated with neurodevelopmental disorders such as epilepsy. Constant light normally disrupts circadian clock function and leads to arrhythmic behavior. Here, we demonstrate a function for KCC in regulating Drosophila locomotor activity and GABA responses in circadian clock neurons because alteration of KCC expression in circadian clock neurons elicits rhythmic behavior in constant light. We observed the same effects after downregulation of the Wnk and Fray kinases, which modulate CCC activity in a [Cl−]i-dependent manner. Patch-clamp recordings from clock neurons show that downregulation of KCC results in a more positive GABA reversal potential, while KCC overexpression has the opposite effect. Finally, KCC downregulation represses morning behavioral activity during long photoperiods, while downregulation of NKCC promotes morning activity. In summary, our results support a model in which the regulation of [Cl−]i by a KCC/NKCC/Wnk/Fray feedback loop determines the response of clock neurons to GABA, which is important for adjusting behavioral activity to constant light and long-day conditions.

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