scholarly journals Regulation of Cellular Calcium in Vestibular Supporting Cells by Otopetrin 1

2010 ◽  
Vol 104 (6) ◽  
pp. 3439-3450 ◽  
Author(s):  
Euysoo Kim ◽  
Krzysztof L. Hyrc ◽  
Judith Speck ◽  
Yunxia W. Lundberg ◽  
Felipe T. Salles ◽  
...  
Keyword(s):  
Culture System ◽  
Calcium Concentration ◽  
Vestibular Function ◽  
Cytosolic Calcium ◽  
Extracellular Calcium ◽  
Dependent Manner ◽  
Supporting Cells ◽  
Calcium Dependent ◽  
Organ Culture System ◽  
High Concentrations

Otopetrin 1 (OTOP1) is a multitransmembrane domain protein, which is essential for mineralization of otoconia, the calcium carbonate biominerals required for vestibular function, and the normal sensation of gravity. The mechanism driving mineralization of otoconia is poorly understood, but it has been proposed that supporting cells and a mechanism to maintain high concentrations of calcium are critical. Using Otop1 knockout mice and a utricular epithelial organ culture system, we show that OTOP1 is expressed at the apex of supporting cells and functions to increase cytosolic calcium in response to purinergic agonists, such as adenosine 5′-triphosphate (ATP). This is achieved by blocking mobilization of calcium from intracellular stores in an extracellular calcium-dependent manner and by mediating influx of extracellular calcium. These data support a model in which OTOP1 acts as a sensor of the extracellular calcium concentration near supporting cells and responds to ATP in the endolymph to increase intracellular calcium levels during otoconia mineralization.

scholarly journals Specificity and Prevalence of Natural Bovine Antimannan Antibodies

1999 ◽  
Vol 6 (6) ◽  
pp. 946-952 ◽  
Author(s):  
Abhay Srinivasan ◽  
Yawei Ni ◽  
Ian Tizard
Keyword(s):  
Age Groups ◽  
Inhibitory Effect ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Serum Samples ◽  
Adult Cattle ◽  
Calcium Dependent ◽  
High Concentrations ◽  
Carbohydrate Components ◽  
A Minor

ABSTRACT Immune responses to the carbohydrate components of microorganisms, mediated both by antibodies and by lectins, are an important part of host defense. In the present experiments, the specificity and presence of natural bovine antibodies against mannan, a common fungal antigen, were examined by enzyme-linked immunosorbent assay (ELISA), usingSaccharomyces cerevisiae mannan as an antigen. The results showed that all serum samples from animals of three age groups (newborn, calf, and adult) tested contained antimannan antibodies, and the titer of these antibodies increased significantly in adults. However, titers among individual adult cattle differed widely. Inhibition assays showed that yeast mannan was the strongest inhibitor.d-Mannose exhibited only a minor inhibitory effect at high concentrations. This suggests that most of these antibodies recognize an oligosaccharide-based epitope(s) different from those recognized by lectins. Cattle possess three serum C-type lectins (collectins) capable of recognizing mannan in a calcium-dependent manner. Addition of EDTA to the reaction did not reduce antibody binding, suggesting that the binding of these antibodies to mannan was not affected by the presence of collectin. The antibodies purified from either calf or adult serum by mannan-Sepharose affinity chromatography consisted of mainly immunoglobulin G (IgG) and a smaller amount of IgM. IgG1 was shown to be the dominant antimannan IgG isotype by isotype-specific ELISA. Together, these results demonstrate the production of natural antimannan antibodies in cattle in an age-dependent manner. These antibodies might be involved in defending the host against mannan-containing pathogens as a specific line of defense in conjunction with the innate response by lectins.

Requirement for transmembrane sodium flux in maintenance of cytosolic calcium levels in rat Sertoli cells

1993 ◽  
Vol 264 (6) ◽  
pp. E863-E867 ◽  
Author(s):  
E. Gorczynska ◽  
D. J. Handelsman
Keyword(s):  
Sertoli Cells ◽  
Calcium Concentration ◽  
Cytosolic Calcium ◽  
Ruthenium Red ◽  
Extracellular Calcium ◽  
Isolated Cells ◽  
Acetoxymethyl Ester ◽  
Calcium Fluxes ◽  
Calcium Exchange ◽  
Extracellular Sodium

The prompt rise in cytosolic calcium induced by follicle-stimulating hormone (FSH) in rat Sertoli cells suggests a role for calcium in FSH signal transduction. To evaluate the requirement for sodium in transmembrane calcium fluxes in Sertoli cells, we measured intracellular calcium concentration under sodium-free conditions and during stimulation by monensin and veratridine, used to elevate cytosolic sodium. Cytosolic calcium levels were measured by dual-wavelength spectrofluorimetry using freshly isolated cells loaded with fura-2 acetoxymethyl ester. Whereas, removal of extracellular sodium lowered cytosolic calcium in unstimulated cells from 89 +/- 4 to 75 +/- 8 nM, treatment with monensin and veratridine increased cytosolic calcium to 142 +/- 19 and 126 +/- 13 nM, respectively. Without extracellular calcium, monensin still produced 47% of the rise in cytosolic calcium observed in the presence of extracellular calcium, indicating approximately equal contributions of calcium from intracellular and extracellular sources. Blockade of voltage-sensitive or/and voltage-insensitive calcium channels by verapamil and ruthenium red was unable to completely prevent the monensin-induced elevation of cytosolic calcium. In addition tetrodotoxin failed to block the FSH-induced rise in cytosolic calcium. These observations, together with the considerable reduction in monensin-induced rise in cytosolic calcium under extracellular sodium-free condition, support the hypothesis that sodium-calcium exchange rather than the specific calcium or sodium channels regulate basal and monensin-induced transmembrane sodium and calcium fluxes in Sertoli cells.

Cholecystokinin increases cytosolic calcium in a subpopulation of cultured vagal afferent neurons

2002 ◽  
Vol 283 (6) ◽  
pp. R1303-R1313 ◽  
Author(s):  
Steven M. Simasko ◽  
Jason Wiens ◽  
Adrienne Karpiel ◽  
Mihai Covasa ◽  
Robert C. Ritter
Keyword(s):  
Cytosolic Calcium ◽  
Threshold Concentration ◽  
Extracellular Calcium ◽  
Calcium Stores ◽  
Afferent Neurons ◽  
Sensory Stimuli ◽  
Adult Rat ◽  
Nodose Ganglia ◽  
Vagal Afferent ◽  
High Concentrations

Imaging fluorescent measurements with fura 2 were used to examine cytosolic calcium signals induced by sulfated CCK octapeptide (CCK-8) in dissociated vagal afferent neurons from adult rat nodose ganglia. We found that 40% (184/465) of the neurons responded to CCK-8 with a transient increase in cytosolic calcium. The threshold concentration of CCK-8 for inducing the response varied from 0.01 to 100 nM. In most neurons (13/16) the response was eliminated by removing extracellular calcium. Depleting intracellular calcium stores with thapsigargin slightly augmented the response. Most neurons were unresponsive to nonsulfated CCK-8. The response was eliminated by the CCK-A receptor antagonist lorglumide. Low concentrations of JMV-180 had no effect; however, high concentrations of JMV-180 reduced responses to CCK-8. These results demonstrate that CCK acts at the low-affinity site of the CCK-A receptor to trigger the entry of extracellular calcium into vagal afferent neurons. Increased cytosolic calcium may participate in acute activation of vagal afferent neurons, or it may initiate long-term changes, which modulate future neuronal responses to sensory stimuli.

scholarly journals Effects of caffeine, tetracaine, and ryanodine on calcium-dependent oscillations in sheep cardiac Purkinje fibers.

1985 ◽  
Vol 86 (6) ◽  
pp. 877-889 ◽  
Author(s):  
C J Nieman ◽  
D A Eisner
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Oscillation Amplitude ◽  
Membrane Current ◽  
Inward Current ◽  
Purkinje Fibers ◽  
Calcium Dependent ◽  
Cardiac Purkinje Fibers ◽  
High Concentrations

Membrane current and tension were measured in voltage-clamped sheep cardiac Purkinje fibers. Elevating the intracellular calcium concentration ([Ca2+]i) results in oscillations of membrane current and tension both at rest and during stimulation. During stimulation, an oscillatory transient inward current and an after contraction follow repolarization. We have examined the effects on the oscillations of changing the extracellular calcium concentration ([Ca2+]o) and of adding various drugs. In agreement with previous work, high concentrations of drugs that affect the sarcoplasmic reticulum, namely caffeine (10-20 mM), tetracaine (1 mM), and ryanodine (10 microM), abolish the oscillations. However, at lower concentrations, these three drugs have different effects on the oscillations. Caffeine (1-2 mM) decreases the oscillation amplitude but increases the frequency. Tetracaine (100-500 microM) has little effect on the magnitude of the oscillations but decreases their frequency. Ryanodine, at all concentrations used (0.1-10 microM), eventually abolishes the oscillations but, in doing so, decreases the magnitude, leaving the frequency unaffected. When [Ca2+]o was changed in order to vary [Ca2+]i, both the frequency and the magnitude of the oscillations always changed in the same direction. This suggests that these three drugs have effects in addition to just changing [Ca2+]i.

Extracellular Ca2+ directly regulates tight junctional permeability in the human cervical cell line CaSki

1997 ◽  
Vol 272 (2) ◽  
pp. C511-C524 ◽  
Author(s):  
G. I. Gorodeski ◽  
W. Jin ◽  
U. Hopfer
Keyword(s):  
Tight Junctions ◽  
Calcium Concentration ◽  
Calcium Influx ◽  
Partial Agonist ◽  
Electrical Conductance ◽  
Cytosolic Calcium ◽  
Extracellular Calcium ◽  
Maximal Effect ◽  
Response Curves ◽  
Junctional Permeability

Lowering extracellular calcium concentration ([Ca2+]o) increases acutely and reversibly the transepithelial electrical conductance (G(TE)) and the epithelial permeability to pyranine (Ppyr) across CaSki cultures. Effects were already observed after lowering calcium from 1.2 to 1.0 mM and were maximal at 0.1 mM. The dose-response curves were sigmoidal (calcium concentration that produces half-maximal effect = 0.3 mM), and the time courses indicated simple exponential trends (time constants of 4-5 min). The effect of calcium was not mediated by mobilization of cytosolic calcium or altering calcium influx, and manganese was found to be a partial agonist to [Ca2+]o. The effects of [Ca2+]o, on permeability were additive to those of hypertonic conditions, indicating that calcium modulates junctional permeability. The experimental data were fitted to theoretical models that relate changes in G(TE) to the probability of assembled/disassembled tight junctions. The results suggest that calcium interacts directly and cooperatively at extracellular sites with junctional elements that are arranged in parallel, and it shifts the probability state of the junctions from "open" to "closed" state. Changes in extracellular calcium may affect the permeability of tight junctions of the cervical epithelium and may play a role in regulating production of cervical mucus.

scholarly journals The role of calcium in the age-related decline of neutrophil function

Blood ◽  
1988 ◽  
Vol 71 (3) ◽  
pp. 659-665 ◽  
Author(s):  
DA Lipschitz ◽  
KB Udupa ◽  
LA Boxer
Keyword(s):  
Calcium Homeostasis ◽  
Calcium Concentration ◽  
Cytochalasin B ◽  
Cytosolic Calcium ◽  
Neutrophil Function ◽  
Extracellular Calcium ◽  
Cytosolic Calcium Concentration ◽  
Age Related ◽  
Improved Function

Abstract Upon activation by formyl-methionyl-leucyl-phenylalanine (FMLP), either in the presence of absence of cytochalasin B, neutrophils from old subjects generated significantly less superoxide than did neutrophils from the young. This reduction in activity was associated with a significant decrease in the basal cytosolic calcium concentration and a diminished flux of calcium to the cytosol after activation. At all concentrations of FMLP tested, cytosolic calcium remained significantly lower in neutrophils from the old as compared with the young, whereas permeability to extracellular calcium and efflux of calcium from the cell were also significantly diminished. Pretreatment of the cell with the ionophore ionomycin elevated the cytosolic calcium concentration and significantly improved function in old neutrophils. These findings demonstrate that aging results in alterations in neutrophil calcium homeostasis that may play a role in the age-related decline in neutrophil function.

Phorbol-stimulated influx of extracellular calcium in rat pulmonary artery endothelial cells

1994 ◽  
Vol 267 (2) ◽  
pp. L145-L151 ◽  
Author(s):  
H. S. Murphy ◽  
M. Maroughi ◽  
G. O. Till ◽  
P. A. Ward
Keyword(s):  
Endothelial Cells ◽  
Pulmonary Artery ◽  
Extracellular Calcium ◽  
Dependent Manner ◽  
Necrosis Factor Alpha ◽  
Calcium Dependent ◽  
High K ◽  
Voltage Dependent ◽  
Dependent Inhibition ◽  
Protein Kinase C Inhibitor

Stimulation of rat pulmonary artery endothelial cells (RPAEC) with phorbol 12-myristate 13-acetate (PMA) resulted in an increase in intracellular calcium ([Ca2+]i). Unlike the response to bradykinin, C5a and tumor necrosis factor-alpha (TNF-alpha) previously reported (15), the PMA-induced increase in [Ca2+]i was predominantly dependent on extracellular calcium. The PMA response paralleled the BAY K 8644-induced, extracellular calcium-dependent increase in [Ca2+]i. Pretreatment of endothelial cells with the protein kinase C inhibitor staurosporine resulted in a concentration-dependent inhibition of the increase in [Ca2+]i in response to PMA. The ability of PMA analogues to induce significant increase in [Ca2+]i paralleled their ability to induce O2- generation in neutrophils. The PMA-induced influx of extracellular Ca2+ was inhibited by the L-channel selective antagonists diltiazem, nifedipine, nicardipine, and verapamil in a dose-dependent manner. Depolarizing conditions induced by high [K+]o enhanced the calcium response to PMA. The data presented are consistent with the hypothesis that PMA-induced increases in [Ca2+]i in endothelial cells are the result of Ca2+ influx through voltage-dependent L-type Ca2+ channels.

Glomerular endothelial cells respond to calcium-mobilizing agonists with release of EDRF

1990 ◽  
Vol 258 (5) ◽  
pp. F1295-F1303 ◽  
Author(s):  
P. A. Marsden ◽  
T. A. Brock ◽  
B. J. Ballermann
Keyword(s):  
Endothelial Cells ◽  
Calcium Concentration ◽  
Mesangial Cells ◽  
Platelet Activating Factor ◽  
Cytosolic Calcium ◽  
Dependent Manner ◽  
Glomerular Mesangial Cells ◽  
Concentration Dependent Manner ◽  
Glomerular Function ◽  
Glomerular Endothelial Cells

To determine whether glomerular endothelial cells (GEN) may play a role in the local control of glomerular function by releasing endothelium-derived relaxing factor (EDRF), the effect of several agonists on GEN cytosolic calcium concentration ([Ca2+]i) and GEN EDRF release was determined. Bradykinin, ATP, thrombin, and platelet-activating factor (PAF) all increased [Ca2+]i in GEN in a concentration-dependent manner, whereas serotonin, acetylcholine, phenylephrine, and endothelin-1 were without effect. Coincubation of glomerular mesangial cells (GMC) with GEN augmented mesangial cell guanosine 3',5'-cyclic monophosphate (cGMP) content five- to sixfold, Bradykinin elicited a further concentration-dependent increase in GMC cGMP content in the presence but not absence of GEN. The GEN-dependent bradykinin-stimulated GMC cGMP accumulation was abolished by hemoglobin and methylene blue, blunted by gossypol, and augmented by superoxide dismutase. Other agonists capable of augmenting GEN [Ca2+]i also stimulated GMC cGMP accumulation in the presence but not in the absence of GEN. Thus cultured GEN release a factor that stimulates cGMP accumulation in adjacent mesangial cells which has the pharmacological characteristics of EDRF.

α1-Adrenergic stimulation increases the Vmax of isolated myocardial papillary muscles

1991 ◽  
Vol 69 (12) ◽  
pp. 1804-1809 ◽  
Author(s):  
Kai Li ◽  
Jean L. Rouleau
Keyword(s):  
Calcium Concentration ◽  
Maximum Velocity ◽  
Cytosolic Calcium ◽  
Threshold Concentration ◽  
Extracellular Calcium ◽  
Papillary Muscles ◽  
Adrenergic Stimulation ◽  
Experimental Conditions ◽  
Extracellular Calcium Concentration ◽  
Rabbit Myocardium

α-Adrenergic agonists have been shown to increase the tension developed by myocardial muscle. However, their effects on the maximum velocity of unloaded muscle shortening (Vmax) have not been rigorously examined. In this study, the contractile effects of the α-adrenergic agonist phenylephrine were examined in the presence of propranolol in papillary muscles of two species, the dog and the rabbit. In rabbit papillary muscles studied at physiological calcium concentrations (1.25 mM), phenylephrine increased all indices of contractility (Vmax, tension, and maximum rate of tension developed (dT/dt)) starting at 10−8 M. The percent increase in Vmax (121 ± 8%) was less than that of tension (188 ± 20%, p < 0.05) and dT/dt (262 ± 35%, p < 0.01). These findings occurred at both 29 and 35 °C and were inhibited by adding 10−5 M prazosin. Increasing extracellular calcium concentration from 1.25 to 15 mM caused changes in twitch configuration that were significantly different from those of phenylephrine. Calcium increased all indices of contractility more than did phenylephrine. This was particularly true for dT/dt (502 ± 82 vs. 262 ± 35% for phenylephrine, p < 0.01). Nonetheless, the ratio of increase in tension to increase in Vmax under both experimental conditions was similar (the increase in Vmax was 64% of that of tension with phenylephrine and 69% with increased calcium). At 1.25 mM calcium, the increase in contractility caused by phenylephrine was much smaller in dog myocardium as compared with rabbit myocardium. Rather, the effects of phenylephrine on dog myocardium studied at 1.25 mM calcium resembled that of rabbit myocardium studied at 15 mM calcium. We conclude that (i) α1-adrenergic receptor stimulation increases all indices of contractility at a similar threshold concentration but increases Vmax relatively less; (ii) despite markedly different effects on the intensity of the cytosolic calcium transient and twitch configuration characteristics, the increase in Vmax relative to tension caused by phenylephrine is similar to that caused by increasing extracellular calcium concentration; (iii) species differences in myocardial contractile response to α1-adrenergic stimulation exist, and that some of these differences can be abolished by altering extracellular calcium.Key words: α1-adrenergic, Vmax, contractility, calcium.

scholarly journals Choline-Sigma-1R as an Additional Mechanism for Potentiation of Orexin by Cocaine

2021 ◽  
Vol 22 (10) ◽  
pp. 5160
Author(s):  
Jeffrey L. Barr ◽  
Pingwei Zhao ◽  
G. Cristina Brailoiu ◽  
Eugen Brailoiu
Keyword(s):  
Nucleus Accumbens ◽  
Calcium Concentration ◽  
Critical Role ◽  
Cytosolic Calcium ◽  
Dependent Manner ◽  
Ip3 Receptors ◽  
Orexin A ◽  
Signaling Mechanism ◽  
Orexin Receptors ◽  
Dose Dependent

Orexin A, an endogenous peptide involved in several functions including reward, acts via activation of orexin receptors OX1 and OX2, Gq-coupled GPCRs. We examined the effect of a selective OX1 agonist, OXA (17-33) on cytosolic calcium concentration, [Ca2+]i, in neurons of nucleus accumbens, an important area in the reward circuit. OXA (17-33) increased [Ca2+]i in a dose-dependent manner; the effect was prevented by SB-334867, a selective OX1 receptors antagonist. In Ca2+-free saline, the OXA (17-33)-induced increase in [Ca2+]i was not affected by pretreatment with bafilomycin A1, an endo-lysosomal calcium disrupter, but was blocked by 2-APB and xestospongin C, antagonists of inositol-1,4,5-trisphosphate (IP3) receptors. Pretreatment with VU0155056, PLD inhibitor, or BD-1047 and NE-100, Sigma-1R antagonists, reduced the [Ca2+]i response elicited by OXA (17-33). Cocaine potentiated the increase in [Ca2+]i by OXA (17-33); the potentiation was abolished by Sigma-1R antagonists. Our results support an additional signaling mechanism for orexin A-OX1 via choline-Sigma-1R and a critical role for Sigma-1R in the cocaine–orexin A interaction in nucleus accumbens neurons.

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