scholarly journals Heterogenous distribution of free calcium and propagation of calcium transient in gastric parietal cells revealed by digital imaging microscopy.

1989 ◽  
Vol 37 (7) ◽  
pp. 999-1005 ◽  
Author(s):  
Y Tsunoda ◽  
S Yodozawa ◽  
Y Tashiro
Keyword(s):  
Digital Imaging ◽  
Resting State ◽  
Calcium Concentration ◽  
Gastric Gland ◽  
Calcium Transient ◽  
Parietal Cells ◽  
Free Calcium ◽  
Marked Contrast ◽  
Free Calcium Concentration ◽  
Gastric Parietal Cells

Spatial and temporal changes of cytoplasmic free calcium concentration ([Ca2+]i) in single parietal cells of guinea pig were investigated with a digital imaging microscope equipped with a microspectrofluorometer, using a Ca2+-sensitive dye, fura-2. Intracellular distribution of [Ca2+]i was not homogeneous, but there were two kinds of [Ca2+]i gradient in the resting parietal cells, one a continuous gradient increasing towards the plasma membrane and a second discontinuous gradient (Ca2+ plateau) in some restricted regions of the cytoplasm. When treated with gastrin, only about 40% of parietal cells in the gastric gland responded with an almost twofold increase in the average resting [Ca2+]i of 52.4 +/- 7.1 nM. In the responding cells, the discontinuous plateaus transiently enlarged to the entire cytoplasm. In marked contrast, all of these cells responded to Ca2+ ionophore ionomycin. We also found that when provoked by gastrin Ca2+ transient in the parietal cells in the gastric gland often propagated to some adjacent cells, and occasionally spontaneous Ca2+ transient and oscillation were observed even in the resting state.

189 CHARACTERIZATION OF THE FIRST SPERM-INDUCED CALCIUM TRANSIENT IN PIG OOCYTES

2016 ◽  
Vol 28 (2) ◽  
pp. 225
Author(s):  
C. Wang ◽  
Z. Machaty
Keyword(s):  
Calcium Concentration ◽  
Calcium Transient ◽  
Calcium Oscillations ◽  
Calcium Transients ◽  
Intracellular Free Calcium ◽  
Calcium Signal ◽  
Free Calcium ◽  
Essential Information ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

Fertilization in mammals is associated with repetitive elevations in the oocytes’ intracellular free calcium concentration. The elevations are triggered by the fertilizing sperm and are responsible for stimulating embryo development. In mouse oocytes, the sperm-induced calcium signal starts with a calcium rise that is larger and longer in duration than any succeeding transients. It also has unique characteristics: it begins with a rapid increase for 2–3 s followed by a shoulder, which is an inflection point that represents a brief decline in the rise of calcium levels. Once calcium level reaches its maximum, it decreases but remains elevated for several minutes while it is superimposed by several smaller calcium spikes. In bovine oocytes the situation is somewhat different. In this species, the first sperm-induced calcium transient is larger than the additional spikes but it lacks the sustained elevation phase and is not superimposed by small calcium rises. In the present study our purpose was to characterise the first sperm-induced calcium transient in pig oocytes. Oocytes were obtained from ovaries of prepubertal gilts collected at an abattoir and matured in vitro for 44 h. Mature oocytes were loaded with the calcium indicator dye fura-2; subsequently, they were either IVF or used for intracytoplasmic sperm injection (ICSI). Changes in their intracellular free calcium concentration were then immediately monitored using InCyt Im2, a dual-wavelength fluorescence imaging system. Characteristics of the first transients (including amplitude and duration) were compared to those of the additional ones using Student’s t-test. We found that in oocytes that underwent IVF (n = 11), the oscillations started 83.4 ± 23.2 min after adding the sperm to the oocytes. In the ICSI group (n = 10 oocytes) the calcium oscillations started sooner, 27.1 ± 17.7 min after injection. The average peak amplitude and the mean interval between the calcium transients varied among individual oocytes, but no significant differences were found between the IVF and ICSI groups (which on average were fluorescence ratio of 2.6 ± 1.1 and 23.5 ± 11.4 min, respectively; P > 0.1). The oscillation patterns showed slight differences between individual oocytes in terms of spike frequency, which has been described before and may be due to variations in the amount of sperm-derived activating factor present in the ooplasm. Most importantly, in all oocytes measured, the initial calcium spike showed no differences when compared to subsequent calcium transients: its amplitude and duration was similar to the additional transients. This points at potential species-specific differences in the regulation of calcium signalling in oocytes and provides essential information for the better understanding of the fertilization process. This work was supported by Agriculture and Food Research Initiative Competitive Grant 2011–67015–30006 from the USDA National Institute of Food and Agriculture.

scholarly journals Muscle calcium transient. Effect of post-stimulus length changes in single fibers.

1984 ◽  
Vol 83 (1) ◽  
pp. 75-103 ◽  
Author(s):  
E B Ridgway ◽  
A M Gordon
Keyword(s):  
Strong Correlation ◽  
Calcium Binding ◽  
Time Course ◽  
Calcium Concentration ◽  
Muscle Length ◽  
Calcium Transient ◽  
Free Calcium ◽  
Free Calcium Concentration ◽  
Length Changes ◽  
Stimulus Length

We examined the effects of post-stimulus length changes on voltage-clamped, aequorin-injected single muscle fibers from the barnacle Balanus nubilus. Extra light (extra calcium) is seen when the fiber is allowed to shorten (a small percentage) during the declining phase of the calcium transient. The opposite is observed when the fiber is stretched. Increasing the extent of shortening increases the amount of extra calcium, as does decreasing the temperature. The extra calcium probably comes from the myofilaments and not from the sarcoplasmic reticulum because (a) there is a strong correlation between the extra calcium and the level of activation; (b) there is a strong correlation between the extra calcium and the amount of force redeveloped after a length change; and (c) the time course of the appearance of the extra calcium is intermediate between that of the free calcium concentration and that of force. We suggest (a) that the calcium binding to the activating myofibrillar proteins is sensitive to muscle length or muscle force, and (b) that there is a pool of bound calcium (activating calcium) that waxes and wanes with a time course intermediate between the free calcium concentration and force.

Hypothalamic Hypophyseal Inhibitory Factor (HHIF) Increases Intrasynaptosomal Free Calcium Concentration

Hypertension ◽  
1997 ◽  
Vol 29 (6) ◽  
pp. 1337-1343 ◽  
Author(s):  
Mercedes Ricote ◽  
Elena Garcia-Martin ◽  
Jose Sancho ◽  
Carlos Gutierrez-Merino
Keyword(s):  
Calcium Concentration ◽  
Inhibitory Factor ◽  
Free Calcium ◽  
Free Calcium Concentration

Identification of ecto-PKC on surface of human platelets: role in maintenance of latent fibrinogen receptors

2000 ◽  
Vol 278 (6) ◽  
pp. H2008-H2019 ◽  
Author(s):  
Anna Babinska ◽  
Michael V. Hogan ◽  
Tomasz Sobocki ◽  
Malgorzata B. Sobocka ◽  
Yigal H. Ehrlich ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Calcium Concentration ◽  
Surface Protein ◽  
Human Platelets ◽  
Surface Proteins ◽  
Free Calcium ◽  
Platelet Surface ◽  
Inhibitory Peptides ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration

Human platelets express a protein phosphorylation system on their surface. A specific protein kinase C (PKC) antibody, monoclonal antibody (MAb) 1.9, which binds to the catalytic domain of PKC and inhibits its activity, causes the aggregation of intact platelets while inhibiting the phosphorylation of platelet surface proteins. Photoaffinity labeling with 100 nM 8-azido-[α32P]ATP identified this ecto-PKC as a single surface protein of 43 kDa sensitive to proteolysis by extracellular 0.0005% trypsin. Inhibition of the binding of 8-azido-[α32P]ATP to the 43-kDa surface protein by MAb 1.9 identified this site as the active domain of ecto-PKC. Covalent binding of the azido-ATP molecule to the 43-kDa surface protein inhibited the phosphorylative activity of the platelet ecto-PKC. Furthermore, PKC pseudosubstrate inhibitory peptides directly induced the aggregation of platelets and inhibited azido-ATP binding to the 43-kDa protein. Platelet aggregation induced by MAb 1.9 and by PKC inhibitory peptides required the presence of fibrinogen and resulted in an increase in the level of intracellular free calcium concentration. This increase in intracellular free calcium concentration induced by MAb 1.9 was found to be dependent on the binding of fibrinogen to activated GPIIb/IIIa integrins, suggesting that MAb 1.9 causes Ca2+flux through the fibrinogen receptor complex. We conclude that a decrease in the state of phosphorylation of platelet surface proteins caused by inhibition of ecto-PKC results in membrane rearrangements that can induce the activation of latent fibrinogen receptors, leading to platelet aggregation. Accordingly, the maintenance of a physiological steady state of phosphorylation of proteins on the platelet surface by ecto-PKC activity appears to be one of the homeostatic mechanisms that maintain fibrinogen receptors of circulating platelets in a latent state that cannot bind fibrinogen.

Extracellular ATP increases [Ca 2+]i in distal tubule cells. I. Evidence for a P2Y2 purinoceptor

2000 ◽  
Vol 279 (1) ◽  
pp. F92-F101 ◽  
Author(s):  
Michel Bidet ◽  
Guy De Renzis ◽  
Sonia Martial ◽  
Isabelle Rubera ◽  
Michel Tauc ◽  
...  
Keyword(s):  
Calcium Concentration ◽  
Distal Tubule ◽  
Calcium Flux ◽  
Free Calcium ◽  
Receptor Subtype ◽  
Cytoplasmic Calcium ◽  
P2y2 Receptor ◽  
Nucleotide Analogs ◽  
Flux Measurements ◽  
Free Calcium Concentration

Experiments were performed to characterize the P2 purinoceptor subtype responsible for cytoplasmic calcium mobilization in cells from the initial part of rabbit distal convoluted tubule (DCT). Free calcium concentration was measured in a DCT cell line (DC1) with the probe fura 2. Both ATP and UTP increased cytosolic Ca2+ concentration ([Ca2+]i; EC50 3 and 6 μM, respectively). The order of potency for nucleotide analogs was ATP = UTP > adenosine 5′- O-[thiotriphosphate] ≫ ADP > UDP, which is consistent with the pharmacology of the P2Y2 receptor subtype. The increased [Ca2+]iresponses to ATP and UTP were strongly inhibited by suramin. Pretreatment of cells with pertussis toxin (PTX) attenuated the action of both nucleotides. Inhibition of phospholipase C with U-73122 totally blocked the [Ca2+]i response to ATP. Thus ATP- and UTP-stimulated [Ca2+]i mobilization in DC1 cells appears to be mediated via the activation of P2Y2 purinoceptors coupled to a G protein mechanism that is partially sensitive to PTX. Calcium flux measurements showed that lanthanum- and nifedipine-sensitive calcium channels are involved in the [Ca2+]i response to ATP.

Platelet Cytosolic Free Calcium in Essential Hypertension: Responses to Vasopressin

1989 ◽  
Vol 77 (2) ◽  
pp. 183-188 ◽  
Author(s):  
A. F. Dominiczak ◽  
J. J. Morton ◽  
G. Murray ◽  
P. F. Semple
Keyword(s):  
Essential Hypertension ◽  
Arginine Vasopressin ◽  
Calcium Concentration ◽  
Systolic Pressure ◽  
Extracellular Calcium ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Hypertensive Patients ◽  
Free Calcium Concentration ◽  
The Difference

1. Resting and stimulated free calcium concentrations have been measured in platelets loaded with the fluorescent probe quin2 from 30 patients with essential hypertension and from 30 age-matched controls. 2. Cytosolic free calcium concentrations were 94.6 ± 2.7 (mean ± sem) in the hypertensive group and 91.7 ± 2.8 nmol/l in the normotensive group, the difference was not significant. 3. Arginine vasopressin caused a transient increase in platelet free calcium concentration in all subjects. In the presence of extracellular calcium the increase was significantly higher in the control subjects than in the hypertensive patients (P = 0.005). In the absence of extracellular calcium, arginine vasopressin caused much smaller increases, and there was then no difference between the responses of the two groups. 4. Platelet free calcium concentrations were measured again in 13 patients after 8 weeks treatment with either verapamil (n = 6) or atenolol (n = 7). The reductions in systolic pressure after drug treatment were correlated with the changes in cytosolic free calcium concentrations (r = 0.75, P < 0.01).

Colocalization of the apical Cl−/HCO 3 − exchanger PAT1 and gastric H-K-ATPase in stomach parietal cells

2002 ◽  
Vol 283 (5) ◽  
pp. G1207-G1216 ◽  
Author(s):  
Snezana Petrovic ◽  
Zhaohui Wang ◽  
Liyun Ma ◽  
Ursula Seidler ◽  
John G. Forte ◽  
...  
Keyword(s):  
Resting State ◽  
Parietal Cells ◽  
Immunocytochemical Staining ◽  
Cell Distribution ◽  
Sharp Reduction ◽  
Anion Transporter ◽  
Membrane Location ◽  
Immunofluorescence Labeling ◽  
Apical Membranes ◽  
Gastric Parietal Cells

The apical Cl−/HCO[Formula: see text] exchanger called the putative anion transporter (PAT1; SLC26A6) is expressed on apical membranes of villus cells in the duodenum, but its location in the stomach remains unknown. Here we examined the cell distribution and membrane location of PAT1 in mouse stomach. Immunofluorescence labeling studies with anti-PAT1 antibodies and Dolichos biflorusagglutinin indicated the exclusive expression of PAT1 in gastric parietal cells. Double immunocytochemical staining revealed colocalization of PAT1 with the gastric H-K-ATPase, consistent with expression in tubulovesicles and/or the secretory canaliculus. Radiolabeled 36Cl flux studies demonstrated the functional presence of Cl−/HCO[Formula: see text] exchange in purified tubulovesicles of parietal cells. The expression of PAT1 was significantly decreased in parietal cells of gastric H-K-ATPase-null mice, which exhibit a sharp reduction in tubulovesicle membranes. These data indicate that the Cl−/HCO[Formula: see text]exchanger PAT1 is localized on tubulovesicular membranes, and they are consistent with the hypothesis that it functions in the maintenance of intravesicular ion concentrations in the resting state and dehydration of vesicles derived from the secretory membranes following the transition from the stimulated to the resting state.

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