scholarly journals Active extrusion of Ca2+ from epiphysial chondrocytes of normal and rachitic chickens

1982 ◽  
Vol 202 (2) ◽  
pp. 303-307 ◽  
Author(s):  
M Zanetti ◽  
R Camerotto ◽  
D Romeo ◽  
B De Bernard
Keyword(s):  
Electrode System ◽  
Metabolic Inhibitors ◽  
Ionophore A23187 ◽  
Small Decrease ◽  
Selective Electrode ◽  
Pump System ◽  
Epiphysial Cartilage ◽  
Highly Sensitive

Chondrocytes isolated from the epiphysial cartilage of chickens were exposed to either the ionophore A23187 or KCN, in the presence of 0.4 mM-extracellular Ca2+. This treatment elicits a prompt release of cell Ca2+, which can be measured as net cation efflux by a highly sensitive Ca2+-selective electrode system. Pre-exposure of chondrocytes to the metabolic inhibitors 2-deoxy-D-glucose or oligomycin causes a parallel decrease in both cell ATP and ionophore-mediated Ca2+ extrusion. Conversely, substitution of extracellular Na+ with choline produces only a very small decrease in the rate of Ca2+ efflux. This indicates that the ionophore A23187 and cyanide induce the mobilization of intracellular Ca2+, which is then extruded from the cell mainly by an ATP-driven pump system. Chondrocytes isolated from the cartilage of rachitic chickens also exhibit the capacity for extruding Ca2+ by the same mechanism, with an efficiency comparable with that of their normal counterpart.

scholarly journals Intracellular calcium and adenosine 3′,5′-cyclic monophosphate as mediators of potassium-induced aldosterone secretion

1985 ◽  
Vol 228 (1) ◽  
pp. 69-76 ◽  
Author(s):  
I Kojima ◽  
K Kojima ◽  
H Rasmussen
Keyword(s):  
Arachidonic Acid ◽  
Cyclic Amp ◽  
Intracellular Calcium ◽  
Secretory Response ◽  
Ionophore A23187 ◽  
Small Decrease ◽  
Aldosterone Secretion ◽  
Cyclic Monophosphate ◽  
A Value ◽  
Glomerulosa Cells

We compared the action of K+ on aldosterone secretion from isolated bovine adrenal glomerulosa cells with that of ionophore A23187. Addition of either 50 nM-A23187 or 8 mM-K+ to perifused cells induces a similar initial aldosterone-secretory responses, and a similar sustained increases in Ca2+ entry. However, K+-induced secretion is more sustained than is A23187-induced secretion, even though each agonist appears to act by increasing Ca2+ entry into the cells. When [3H]inositol-labelled cells are stimulated by 8 mM-K+, a small decrease in phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] is observed. This decrease is not accompanied by an increase in inositol trisphosphate (InsP3) concentration. Also, if [3H]arachidonic acid-labelled cells are exposed to 8 mM-K+, there is no increase in [3H]diacylglycerol production. When [3H]inositol-labelled cells are stimulated by 50 nM-A23187, a small decrease in PtdIns(4,5)P2 is observed. This decrease is not accompanied by an increase in InsP3. The cyclic AMP content of K+-treated cells was approximately twice that in A23187-treated cells. If cells are perifused simultaneously with 50 nM-forskolin and 50 nM-A23187, the initial aldosterone-secretory response is similar to that induced by A23187 alone, and the response is sustained rather than transient, and is similar to that seen during perifusion of cells with 8 mM-K+. This dose of forskolin (50 nM) causes an elevation of cyclic AMP concentration in A23187-treated cells, to a value similar to that in K+-treated cells. These results indicate that, in K+-treated cells, a rise in cyclic AMP content serves as a positive sensitivity modulator of the Ca2+ message, and plays a key role in mediating the sustained aldosterone-secretory response.

Human High Molecular Weight Kininogen - A Secreted Platelet Coagulant Protein

1981 ◽  
Author(s):  
A H Schmaier ◽  
J Kuchibhotla ◽  
R W Colman
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Gel Filtration ◽  
Human Platelets ◽  
Metabolic Inhibitors ◽  
Ionophore A23187 ◽  
High Molecular Weight Kininogen ◽  
Contact Phase ◽  
Platelet Factor ◽  
Coagulant Activity

Platelets have been shown to contain a number of secret- able coagulant proteins, which participate as substrates or cofactors in plasma coagulation reactions. Since we have previously demonstrated that high molecular weight kininogen (HMWK) is immunochemically present in platelet extracts, we posited that HMWK is secreted during activation of platelets. Fresh normal platelets were washed by a combination of albumin-gradient and gel-filtration procedures. In 11 experiments the supernates of freeze-thaw lysates of normal human platelets contained a mean of 5.7 Units (range 3.16 to 8.14) of HMWK coagulant activity/3 × 1011 platelets. This coagulant activity was neutralized by a goat antiki- ninogen antibody. Using a 125I-HMWK tracer in PRP, the supernate of washed activated platelets contained 0.082% radioactivity as the starting PRP, suggesting that 14% of the total HMWK coagulant activity could be accounted for by plasma contamination. In four experiments, ionophore A23187 (15μM) induced a net secretion of 39% of the total platelet HMWK (range 16 to 49%). Platelet HMWK secretion by A23187 was concentration dependent (1 to 15 μM) . At A23187 (15μM) platelets released 75% 14C-5HT (range 61 to 99%) and 81% low affinity platelet Factor 4 (range 60 to 99%). Ninety-five percent of A23187-induced secretion of HMWK could be blocked by platelet pretreatment with metabolic inhibitors. LDH determinations indicated that only 5% (range 0 to 10%) of total secreted platelet HMWK could be attributed to lysis. Collagen and PGH2 also caused secretion of platelet HMWK coagulant activity. This study indicates that human platelets contain functional HMWK which may be secreted locally to modulate the reactions of the contact phase of plasma proteolysis.

scholarly journals Calcium transport of Plasmodium chabaudi-infected erythrocytes.

1982 ◽  
Vol 93 (3) ◽  
pp. 680-684 ◽  
Author(s):  
K Tanabe ◽  
R B Mikkelsen ◽  
D F Wallach
Keyword(s):  
Infected Erythrocyte ◽  
Calcium Content ◽  
Transport Processes ◽  
Metabolic Inhibitors ◽  
Parasite Development ◽  
Ionophore A23187 ◽  
Plasmodium Chabaudi ◽  
Carbonyl Cyanide ◽  
Flux Measurements ◽  
Infected Cells

The calcium content and transport processes of Plasmodium chabaudi-infected rat erythrocytes were analyzed by atomic absorption spectroscopy and 45Ca2+ flux measurements. Infected erythrocytes, after fractionation on metrizamide gradients according to stage of parasite development, exhibited progressively increasing levels of Ca2+ with schizont and gametocytes containing 10- to 20-fold greater calcium levels than normal cells (0.54 +/- 0.25 nmol/10(8) cells). 45Ca2+ flux experiments showed both increased influx and decreased efflux in infected erythrocytes. Tris/NH4Cl lysis of normal erythrocytes preloaded with 45Ca2+ with the Ca2+ ionophore A23187 released less than 90% of cell calcium after incubation in ethyleneglycol bis(aminoethylether) N,N'-tetraacetic acid containing buffer, whereas lysis of the infected erythrocyte membrane resulted in release of 10-20% cell Ca2+, with the remaining portion associated with the isolated parasite fraction. This information together with the effects of various metabolic inhibitors indicates the presence of a parasite Ca2+ compartment in P. chabaudi-infected erythrocytes. Dicyclohexylcarbodiimide (DCCD) an inhibitor of proton ATPases of chloroplasts, bacteria, yeast, and mitochondria, and the proton ionophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP), inhibited Ca2+ influx and stimulated efflux from infected cells. These results combined with evidence for a DCCD- and CCCP-sensitive membrane potential in P. chabaudi-infected cells (Mikkelsen et al., accompanying manuscript) suggest that Ca2+ transport of intraerythrocytic parasites is coupled to a proton-motive force across the Plasmodia plasma membrane.

Rapid measurement of serum water to assess pseudohyponatremia.

1986 ◽  
Vol 32 (6) ◽  
pp. 983-986 ◽  
Author(s):  
S Faye ◽  
R B Payne
Keyword(s):  
Electrode System ◽  
Diabetic Coma ◽  
Lipid Concentration ◽  
Selective Electrode ◽  
Direct Reading ◽  
Rapid Methods ◽  
Rapid Measurement ◽  
System A ◽  
Before And After ◽  
Space Occupying Lesion

Abstract Pseudohyponatremia is caused by an increased serum protein or lipid concentration producing a "space-occupying lesion" in serum water. Its presence and magnitude must be assessed in hyponatremic patients with, for example, paraproteinemia or hyperlipemic diabetic coma. In the absence of a direct-reading ion-selective electrode system, a method for measuring the water content of serum is required. We describe two rapid methods for measuring the diffusible water of serum: osmometry before and after dilution and chloride measurement before and after ultrafiltration. Either of these methods allows the true sodium status of a patient's serum to be determined.

scholarly journals Photoelectric current as a highly sensitive readout for potentiometric sensors

2020 ◽  
Vol 56 (27) ◽  
pp. 3879-3882 ◽  
Author(s):  
Xu Hun ◽  
Xiaoli Xiong ◽  
Jiawang Ding ◽  
Wei Qin
Keyword(s):  
Reference Electrode ◽  
Ion Selective Electrode ◽  
Potentiometric Sensors ◽  
Polymeric Membrane ◽  
Selective Electrode ◽  
Photoelectric Current ◽  
Working Electrode ◽  
Highly Sensitive

The photocurrent at a working electrode coated with a ZnSe/r-GO composite can be modulated by a polymeric membrane ion-selective electrode that works as a reference electrode.

Implementation of a Chloride‐selective Electrode Into a Closed Bipolar Electrode System with Fluorimetric Readout

2020 ◽  
Vol 32 (4) ◽  
pp. 812-819 ◽  
Author(s):  
Ewa Jaworska ◽  
Agata Michalska ◽  
Krzysztof Maksymiuk
Keyword(s):  
Electrode System ◽  
Bipolar Electrode ◽  
Selective Electrode

The effects of temperature upon the reproduction and respiration of a marine obligate psychrophile

1974 ◽  
Vol 20 (10) ◽  
pp. 1341-1345 ◽  
Author(s):  
R. R. Christian ◽  
W. J. Wiebe
Keyword(s):  
Growth Efficiency ◽  
Oxygen Electrode ◽  
Electrode System ◽  
Maximum Temperature ◽  
Respiration Rates ◽  
Highly Sensitive ◽  
Growth Respiration ◽  
Lower Temperature Range ◽  
Effects Of Temperature ◽  
Lower Temperature

The growth and respiration rates of a marine obligate psychrophile, Vibrio sp., were determined in a complex medium using optical density and viable counts and a polarized oxygen-electrode system. Growth rate was optimal at 7C and decreased at 10C, the maximum temperature for growth. Respiration increased continually from 1to 10C. Both growth and respiration rates were highly sensitive to small changes in temperature. For example, rates at 4C were 1.8 and 4.4 times higher than at 1C for growth and respiration, respectively. Growth efficiencies were calculated as generations per hour divided by respiration rate. Results indicated that the growth efficiency of this bacterium was much greater at the lower temperature range of growth.

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