scholarly journals Cell suspensions from porcine olfactory mucosa. Changes in membrane potential and membrane fluidity in response to various odorants.

1987 ◽  
Vol 89 (3) ◽  
pp. 443-457 ◽  
Author(s):  
M Kashiwayanagi ◽  
K Sai ◽  
K Kurihara
Keyword(s):  
Membrane Potential ◽  
Cell Suspension ◽  
Membrane Fluidity ◽  
Fluorescent Dyes ◽  
External Medium ◽  
Olfactory Mucosa ◽  
Dose Dependent Fashion ◽  
K Concentration ◽  
Induced Changes ◽  
Dose Dependent

A suspension of olfactory epithelial cells was prepared from porcine olfactory mucosa and the physiological functions of the suspension were examined. The membrane potential of the cell suspension, which was monitored by measuring the fluorescence changes of rhodamine 6G, was depolarized by an increase in the K+ concentration in the external medium. Various odorants depolarized the cell suspension in a dose-dependent fashion. The magnitude of depolarization by odorants was either unchanged or slightly increased by a reduction of the concentration of Na+, Ca2+, and Cl- in the external medium, which suggests that changes in the permeabilities of specific ions are not involved in depolarization by odorants. The application of various odorants to the cell suspension induced changes in the membrane fluidity at different sites of the membrane that were monitored with various fluorescent dyes [8-anilino-1-naphthalene sulfonate, n-(9-anthroyloxy) stearic acids, 12-(9-anthroyloxy) oleic acid, and (1,6-diphenyl-1,3,5-hexatriene)], which suggests that the odorants having different odors are adsorbed on different sites in the membrane. On the basis of these results, a possible mechanism of odor discrimination is discussed.

Apamin, a highly specific Ca2+ blocking agent in heart muscle

1985 ◽  
Vol 248 (6) ◽  
pp. H961-H965 ◽  
Author(s):  
G. Bkaily ◽  
N. Sperelakis ◽  
J. F. Renaud ◽  
M. D. Payet
Keyword(s):  
Heart Muscle ◽  
Blocking Agent ◽  
Tyrode Solution ◽  
Tetraethylammonium Chloride ◽  
Naturally Occurring ◽  
Ventricular Cells ◽  
Dose Dependent Fashion ◽  
K Concentration ◽  
Dose Dependent ◽  
Slow Action Potentials

Apamin, a bee venom polypeptide, was recently reported to block specifically the Ca2+-dependent K+ channels that are not blocked by tetraethylammonium chloride in muscle cells. We report here that apamin blocked the naturally occurring slow action potentials (APs) in cultured cell reaggregates from chick hearts. The effects of apamin were not reversible on washout with Tyrode solution only (up to 24 h), but quinidine (10(-8) M) reversed the apamin blockade of the slow channels. Apamin also blocked the isoproterenol-induced slow APs in freshly isolated chick ventricular cells depolarized by 22 mM extracellular K+ concentration ([K+]o) in a dose-dependent fashion (10(-12) to 10(-10) M). Apamin at 5 X 10(-11) M blocked the isoproterenol-induced slow APs without affecting the membrane potential. Washout (with Tyrode solution containing 22 mM [K+]o and 10(-6) M isoproterenol) did not recover the slow APs. However, recovery of the slow APs was possible only when quinidine (10(-8) M) was added to the superfusion medium. The fast APs were rapidly restored by washout with Tyrode solution only. The present data show that apamin is a highly specific compound that tightly binds to the Ca2+ slow channels, thus blocking the slow APs in heart muscle. In addition, quinidine antagonizes the apamin binding on the slow APs.

Accumulation of D-arginine by rat liver mitochondria

1987 ◽  
Vol 65 (12) ◽  
pp. 1057-1063 ◽  
Author(s):  
Rafael Villalobos-Molina ◽  
J. Pablo Pardo ◽  
Alfredo Saavedra-Molina ◽  
Enrique Piña
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Mitochondrial Respiration ◽  
Mitochondrial Membrane ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Osmotic Swelling ◽  
Dose Dependent Fashion ◽  
Dose Dependent

The permeability of the inner mitochondrial membrane from rat liver to D-arginine was studied. By using safranin as a probe of the membrane potential, depolarization of energized liver mitochondria occurred in a dose-dependent fashion starting at 3.3 mmol/L of D- or DL-arginine. When ethidium bromide fluorescence was employed, a decrease in the membrane potential due to D- or DL-arginine was observed. A parallel significant change in succinate-induced respiration in rat liver mitochondria was found in response to osmotic swelling in 125 mmol/L of D-arginine salts. L-Arginine, L-glutamine, L-asparagine, L-ornithine, D-ornithine, and L-lysine did not modify the membrane potential at the concentrations tested. D-Arginine was not transformed into citrulline, but 1.0 mmol/L of the D-amino acid inhibited, by 42%, the state 3 of mitochondrial respiration using succinate as substrate. When D-arginine was used in combination with nigericin, a 40% inhibition of mitochondrial respiration in state 3 was recorded with succinate and with glutamate–malate as substrates.

Mechanism of the Effect of Acetate on Frog Ventricular Muscle

1974 ◽  
Vol 52 (3) ◽  
pp. 404-423 ◽  
Author(s):  
Esther R. Anderson ◽  
J. G. Foulks
Keyword(s):  
Membrane Potential ◽  
Resting Membrane Potential ◽  
Acetate Solution ◽  
Tension Development ◽  
Electrogenic Transport ◽  
K Concentration ◽  
Reduced Rate ◽  
Induced Changes ◽  
The Relationship ◽  
Frog Ventricle

Substitution of acetate for external Cl produced a large persistent increase in the resting membrane potential (R.M.P.) of frog ventricle and a somewhat steeper relation between membrane potential (M.P.) and [K]o (external K concentration). An increased K conductance or reduced permeability to other ions could account for most of these results, but not for hyperpolarizations as great as −110 mV. Potentials of this size suggested a contribution from an active electrogenic transport system, but they were unaffected by several treatments including exposure to ouabain (10−7 M − 5 × 10−6 M), dinitrophenol (10−6 M, 10−5 M) or 30 mM tetraethylammonium.Acetate caused a prolongation of the action potential (A.P.) and a change in its configuration. Acetate also enhanced twitch tension and increased the rate of tension development. Similar changes are produced by removal of [K]o. The effects of both acetate and K removal on A.P. configuration were prevented by a reduced rate of stimulation.When acetate-induced hyperpolarization was reversed by raising [K]o to 10–15 mM, the configuration of the A.P. resembled that of controls and twitch tension did not increase. Thus, acetate-induced changes in the shape of the A.P. and in twitch tension appeared to be secondary to the increase in R.M.P. However, the relationship does not seem to be direct because these changes were temporary, whereas hyperpolarization was persistent.The character of the acetate-induced changes in A.P. configuration, and the dependence on stimulation rate and [Ca]o (external Ca concentration), suggested a raised [Ca]i (internal Ca concentration) and a possible increase in Ca influx. However, addition of Mn to the acetate solution did not prevent initial acetate-induced changes in the shape of the A.P. plateau and in twitch tension. Also in the absence of [Ca]o, disappearance of twitch tension was slowed by acetate. But acetate decreased the contracture tension produced in response to either increased [K]o or Na removal. Acetate may cause a redistribution of Ca within the cell.

scholarly journals Glucose stimulates voltage- and calcium-dependent inositol trisphosphate production and intracellular calcium mobilization in insulin-secreting β TC3 cells

1996 ◽  
Vol 314 (1) ◽  
pp. 339-345 ◽  
Author(s):  
Jesper GROMADA ◽  
Jørgen FRØKJÆR-JENSEN ◽  
Steen DISSING
Keyword(s):  
Membrane Potential ◽  
Resting Potential ◽  
Glucose Stimulation ◽  
Calcium Dependent ◽  
Cellular Processes ◽  
Intracellular Calcium Mobilization ◽  
Inositol 1,4,5 Trisphosphate ◽  
Voltage Dependent ◽  
K Concentration ◽  
Induced Changes

The cellular processes leading to a rise in the intracellular free Ca2+ concentration ([Ca2+]i) after glucose stimulation and K+ depolarization were investigated in insulin-secreting βTC3 cells. Stimulation with 11.2 mM glucose causes inositol 1,4,5-trisphosphate production and release of Ca2+ from intracellular stores. A strong correlation was observed between the changes in Ins(1,4,5)P3 concentration and the rise in [Ca2+]i, consistent with the former compound being responsible for release of Ca2+ from intracellular stores. The increase in Ins(1,4,5)P3 production was reduced by 68±4% when [Ca2+]i was kept low on glucose stimulation by loading cells with the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-NNN´N´-tetra-acetic acid (BAPTA). The Ins(1,4,5)P3 production was prevented in cells hyperpolarized with diazoxide, an opener of ATP-sensitive K+-channels, consistent with the membrane potential controlling the rate of Ins(1,4,5)P3 synthesis. Depolarizing K+ concentrations evoked changes in [Ca2+]i and Ins(1,4,5)P3 production in both the presence and the absence of extracellular Ca2+, and from the relation between the extracellular K+ concentration and membrane potential we found a half-maximal Ins(1,4,5)P3 production by a 28 mV depolarization from a resting potential of -56 mV and by a rise in [Ca2+]i of 390 nM. We conclude that stimulation-induced changes in membrane potential and [Ca2+]i are important in controlling Ins(1,4,5)P3 production in βTC-3 cells and that glucose-stimulated Ca2+ mobilization from intracellular stores is due to voltage-dependent Ins(1,4,5)P3 production and depends on the concurrent increase in [Ca2+]i.

L-Glutamine: an amino acid required for maintenance of the tegumental membrane potential of Schistosoma mansoni

Parasitology ◽  
1987 ◽  
Vol 94 (2) ◽  
pp. 233-242 ◽  
Author(s):  
Carolyn A. Lane ◽  
R. A. Pax ◽  
J. L. Bennett
Keyword(s):  
Amino Acids ◽  
Membrane Potential ◽  
Amino Acid ◽  
Schistosoma Mansoni ◽  
External Medium ◽  
Medium Ph ◽  
Organic Constituents ◽  
A Value ◽  
Dose Dependent ◽  
External Ph

SUMMARYThe tegumental membrane potential (–63±2·9 mV) of adult male Schistosoma mansoni in RPMI-1640 is significantly depolarized (–26±7·3 mV) when the parasite is incubated in inorganic media (Hank's Balanced Saline or RPMI-1640 without organic constituents). Of 9 amino acids (L-glutamine, D-glutamine, L-arginine, L-proline, L-aspartate, L-glutamate, L-asparagine, L-isoleucine and L-methionine) L-glutamine alone is sufficient to repolarize the membrane potential to a value (–56±4·5 mV) not significantly different from that found in RPMI-1640. Repolarization by glutamine is dose-dependent, with significant effects obtained as low as 0·10 mM. The concentration of phosphate in the medium also significantly alters the membrane potential. Physiological levels of phosphate (5·6 mM) are necessary in conjunction with L-glutamine to obtain the full repolarization of the membrane potential. In the absence of organic constituents, the membrane potential is strongly dependent on the external medium pH. When L-glutamine is present in the medium, the membrane potential becomes virtually independent of the external pH.

Dissociated response of acid and pepsin secretion to omeprazole in an in vitro perfused mouse stomach

1984 ◽  
Vol 247 (3) ◽  
pp. G240-G247
Author(s):  
C. J. Fimmel ◽  
M. M. Berger ◽  
A. L. Blum
Keyword(s):  
Acid Secretion ◽  
Parietal Cell ◽  
Pepsin Secretion ◽  
Weak Base ◽  
Carbonyl Cyanide ◽  
Luminal Perfusion ◽  
Dose Dependent Fashion ◽  
K Concentration ◽  
Dose Dependent

The effect of omeprazole, an inhibitor of the parietal cell H+-K+-ATPase, on pepsin and acid secretion was studied in an in vitro perfused whole mouse stomach model. Omeprazole inhibited basal and dibutyryl cAMP (DBcAMP)- and histamine-stimulated acid secretion in a dose-dependent fashion with a maximally effective dose of 10(-4) M. At the same time, omeprazole induced a dose-dependent increase of unstimulated pepsin release. This increase was not affected by pretreatment with 10(-3) M atropine or 10(-4) M cimetidine. It was, however, inhibited by preincubation with 10(-4) M carbonyl cyanide m-chlorophenylhydrazone (CCCP). Pepsin secretion after maximally effective doses of histamine or DBcAMP was not affected by 10(-4) M omeprazole. In a concentration of 10(-5) M, the effect of omeprazole was additive to the effect of submaximal concentrations of carbachol and histamine. NaSCN and imidazole mimicked the effect of omeprazole on acid secretion, but pepsin release was only stimulated with 10(-2) M imidazole. Another weak base, benzylamine, stimulated acid and pepsin in parallel. Luminal perfusion with solutions of high K+ concentration did not enhance basal pepsin release. The dissociated response of acid and pepsin secretion indicates that omeprazole does not act selectively on the parietal cell. The stimulation of pepsin secretion might be related to the weak base properties of the compound.

scholarly journals Increased corticosteroid binding capacity of plasma albumin but not of corticosteroid-binding globulin caused by ACTH-induced changes in free fatty acid concentrations in snowshoe hares and rabbits

1998 ◽  
Vol 156 (1) ◽  
pp. 205-212 ◽  
Author(s):  
R Boonstra ◽  
AA Tinnikov
Keyword(s):  
Protein Interactions ◽  
Binding Capacity ◽  
Plasma Albumin ◽  
Snowshoe Hares ◽  
Corticosteroid Binding Globulin ◽  
Dose Dependent Fashion ◽  
Steroid Binding ◽  
Endogenous Modulators ◽  
Induced Changes ◽  
Dose Dependent

Free fatty acids (FFAs) are rapidly mobilized by ACTH and have been shown to be potent endogenous modulators of steroid-protein interactions. We increased FFA in lagomorphs by ACTH and then separated the transient increase in glucocorticoid binding capacity of plasma into that accounted for by changes in binding to albumin and to corticosteroid-binding globulin (CBG). Sequential injections of dexamethasone and ACTH into both snowshoe hares and laboratory rabbits resulted in the rapid mobilization of FFA only after the ACTH injection. The maximum corticosteroid binding capacity increase paralleled that of the FFA increase in both species. In rabbits, CBG levels remained constant over the duration of the experiment. Corticosterone binding by rabbit albumin increased in a dose-dependent fashion in response to increases in FFA (oleic and linoleic acid) concentrations. Finally, by stimulating FFA release in snowshoe hares with ACTH and separating the increase in corticosteroid binding capacity through selective denaturing of CBG by heat, we determined that the increase in plasma binding capacity was a response to changes in binding by albumin, not CBG. Thus FFA released in response to stressors in lagomorphs may effect short-term increases in steroid binding.

Plasminogen Interactions with Immobilized Fibrinogen

1989 ◽  
Vol 62 (04) ◽  
pp. 1078-1082 ◽  
Author(s):  
Burt Adelman ◽  
Patricia Ouynn
Keyword(s):  
Immunosorbent Assay ◽  
Aminocaproic Acid ◽  
Enzyme Linked Immunosorbent Assay ◽  
Binding Regions ◽  
Dose Dependent Fashion ◽  
Epsilon Aminocaproic Acid ◽  
Dose Dependent

SummaryThis report describes the binding of plasminogen to fibrinogen adsorbed onto polystyrene wells. Binding was determined by enzyme linked immunosorbent assay. Both glu- and lys-plasminogen bound to immobilized fibrinogen in a dose-dependent fashion. However, more lys- than glu-plasminogen bound when equal concentrations of either were added to immobilized fibrinogen. Plasminogen binding was inhibited by epsilon aminocaproic acid indicating that binding was mediated via lysine-binding regions of plasminogen. Soluble fibrinogen added in excess of immobilized fibrinogen did not compete for plasminogen binding but fibrinogen fragments produced by plasmin digestion of fibrinogen did. Treatment of immobilized fibrinogen with thrombin caused a small but significant (p <0.01) increase in plasminogen binding. These studies demonstrate that immobilized fibrinogen binds both glu- and lys-plasminogen and that binding is mediated via lysine-binding regions. These interactions may facilitate plasminogen binding to fibrinogen adsorbed on to surfaces and to cells such as platelets which bind fibrinogen.

Soluble Thrombomodulin Purified from Human Urine Exhibits a Potent Anticoagulant Effect In Vitro and In Vivo

1995 ◽  
Vol 73 (05) ◽  
pp. 805-811 ◽  
Author(s):  
Yasuo Takahashi ◽  
Yoshitaka Hosaka ◽  
Hiromi Niina ◽  
Katsuaki Nagasawa ◽  
Masaaki Naotsuka ◽  
...  
Keyword(s):  
Human Urine ◽  
Specific Activity ◽  
Anticoagulant Activity ◽  
Rabbit Lung ◽  
Soluble Thrombomodulin ◽  
Molecular Weights ◽  
Dose Dependent Fashion ◽  
Dose Dependent

SummaryWe examined the anticoagulant activity of two major molecules of soluble thrombomodulin purified from human urine. The apparent molecular weights of these urinary thrombomodulins (UTMs) were 72,000 and 79,000, respectively. Both UTMs showed more potent cofactor activity for protein C activation [specific activity >5,000 thrombomodulin units (TMU)/mg] than human placental thrombomodulin (2,180 TMU/mg) and rabbit lung thrombomodulin (1,980 TMU/mg). The UTMs prolonged thrombin-induced fibrinogen clotting time (>1 TMU/ml), APTT (>5 TMU/ml), TT (>5 TMU/ml) and PT (>40 TMU/ml) in a dose-dependent fashion. These effects appeared in the concentration range of soluble thrombomodulins present in human plasma and urine. In the rat DIC model induced by thromboplastin, administration of UTMs by infusion (300-3,000 TMU/kg) restored the hematological abnormalities derived from DIC in a dose-dependent fashion. These results demonstrate that UTMs exhibit potent anticoagulant and antithrombotic activities, and could play a physiologically important role in microcirculation.

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