Mechanisms of ouabain-induced arterial muscle contraction

1980 ◽  
Vol 239 (2) ◽  
pp. H199-H205 ◽  
Author(s):  
N. Toda
Keyword(s):  
Muscle Contraction ◽  
Contractile Response ◽  
Cerebral Arteries ◽  
Peripheral Arteries ◽  
Femoral Arteries ◽  
Low Concentrations ◽  
Electrogenic Na Pump ◽  
High Concentrations ◽  
Free Media ◽  
Alpha Antagonist

Ouabain caused dose-related contractions in helically cut strips of cerebral, mesenteric, renal, and femoral arteries isolated from dogs and monkeys; the contractions were elicited at lower concentrations in cerebral than in the peripheral arteries. Contractions induced by ouabain were abolished by exposure of cerebral arteries to Ca2+-free media. Contractions induced by Ca2+ in Ca2+-free media were potentiated by ouabain. Substitution of LiCl for NaCl and reduction of [K+]0 suppressed the contractile response of cerebral arteries to ouabain. Pretreatment of dogs with reserpine abolished the response of peripheral arteries to ouabain but not the cerebroarterial response. Phentolamine also abolished the response of peripheral arteries. Once oubain-induced contractions were stabilized, the alpha-antagonist caused a marked relaxation in peripheral but not in cerebral arteries. Ouabain-induced contractions appear to be mediated by an increase in the Ca2+ influx that results mainly from an inhibition of the electrogenic Na+ pump in low concentrations (cerebral arteries) and from a release of norepinephrine from nerves in high concentrations (mesenteric, renal, and femoral arteries).

Effects of cytochalasin B on the aggregation, electrophoretic mobility and surface morphology of chick neural retina cells

1975 ◽  
Vol 17 (3) ◽  
pp. 371-379
Author(s):  
G.E. Jones
Keyword(s):  
Surface Morphology ◽  
Electrophoretic Mobility ◽  
Cytochalasin B ◽  
Neural Retina ◽  
Initial Rise ◽  
Low Concentrations ◽  
Significant Difference ◽  
Site Of Action ◽  
High Concentrations ◽  
Free Media

Over a concentration range of o-5-10 mug/cm-3, cytochalasin B caused a biphasic change in the electrophoretic mobility of disaggregated neural retina cells. An initial rise in anodal mobility at low concentrations of the drug was transformed into a reduction in the mobility below that of the control at a concentration of 10 mug/cm-3. The effect of cytochalasin B was found to be reversible by washing treated cells in cytochalasin B-free media. This was investigated at a concentration of cytochalasin at which the greatest difference existed between the mobilities of the control and experimental cell suspensions. Reaggregation of cell dispersions failed to show any significant difference in the rate of aggregation between cytochalasin B-treated cells and the control. Scanning electron microscopy of cells fixed while in suspension also showed little significant change in the surface morphology upon application of cytochalasin B. In high concentrations of the drug cells appeared somewhat smoother in outline, but no correlation was found between changes in surface morphology and the variations in cell electrophoretic mobility. It is concluded that the observed changes in electrophoretic mobility may be attributed to a binding of cytochalasin B to the cell membrane. This lends support to the hypothesis that the primary site of action of cytochalasin B may be the plasma membrane.

Heterogeneity in the response to dopamine of monkey cerebral and peripheral arteries

1983 ◽  
Vol 245 (6) ◽  
pp. H930-H936 ◽  
Author(s):  
N. Toda
Keyword(s):  
Renal Arteries ◽  
Mesenteric Arteries ◽  
The Other ◽  
Dopaminergic Receptors ◽  
Alpha Adrenoceptors ◽  
Femoral Arteries ◽  
Prostaglandin F2 Alpha ◽  
Low Concentrations ◽  
Responses To Dopamine ◽  
High Concentrations

In helical strips of monkey cerebral and mesenteric arteries contracted with prostaglandin F2 alpha, dopamine in low concentrations produced a moderate relaxation but in high concentrations produced a contraction from the level of relaxation. On the other hand, coronary, renal, and femoral arterial strips responded to dopamine with only a concentration-dependent contraction. Treatment with phenoxybenzamine or phentolamine potentiated the dopamine-induced relaxation seen in cerebral and mesenteric arteries and reversed the contraction in the other arteries to a relaxation. After treatment with phenoxybenzamine, relaxant responses to dopamine of cerebral, mesenteric, and renal arteries were almost identical, and, compared with those, the responses of coronary and femoral arteries were appreciably less. Relaxations induced by dopamine were not influenced by propranolol, atropine, aminophylline, cimetidine, and aspirin but were markedly attenuated by droperidol. Adenosine-induced relaxations were not affected by droperidol. It is concluded that dopamine preferentially relaxes monkey cerebral and mesenteric arteries, possibly via dopaminergic receptors. It appears that the dopamine-induced contractions mediated by alpha-adrenoceptors predominate over the relaxation in coronary, renal, and femoral arteries, and dopaminergic receptor function is greater in cerebral, mesenteric, and renal arteries than in coronary and femoral arteries.

scholarly journals A cytosolic sperm factor triggers calcium oscillations in rat hepatocytes

1996 ◽  
Vol 313 (2) ◽  
pp. 369-372 ◽  
Author(s):  
Christopher P. BERRIE ◽  
K. S. Roy CUTHBERTSON ◽  
J. PARRINGTON ◽  
F. Anthony LAI ◽  
Karl SWANN
Keyword(s):  
Rat Hepatocytes ◽  
Calcium Oscillations ◽  
Dorsal Root Ganglion Neurons ◽  
Protein Factor ◽  
Mammalian Sperm ◽  
Low Concentrations ◽  
Sperm Factor ◽  
High Concentrations ◽  
Ganglion Neurons ◽  
Free Media

Previously it has been shown that injecting a cytosolic sperm protein factor into mammalian eggs induces sustained repetitive transients of cytosolic free Ca2+ ([Ca2+]i), or [Ca2+]i oscillations [Swann (1990) Development 110, 1295-1302]. These sperm-factor (SF)-induced [Ca2+]i oscillations are similar to those seen at fertilization. Here we demonstrate that injecting the same cytosolic extracts of mammalian sperm into single rat hepatocytes induces a series of [Ca2+]i oscillations, as measured by aequorin luminescence. SF injection into hepatocytes induced [Ca2+]i oscillations that were of longer duration, lower frequency and greater amplitude than those seen with the Ins(1,4,5)P3-generating agonist phenylephrine. The SF-induced [Ca2+]i responses appeared to be due to internal release of Ca2+, since transients could occur in Ca2+-free media. Addition of the phorbol ester phorbol 12,13-dibutyrate (PDBu) at low concentrations did not inhibit the SF-induced [Ca2+]i oscillations; high concentrations of PDBu led to a sustained increase in [Ca2+]i concentrations. These data demonstrate that sperm contain a protein factor capable of inducing a characteristic series of [Ca2+]i oscillations in a somatic cell, the hepatocyte. Along with previous observations in dorsal root ganglion neurons, the data suggest a widespread efficacy of the factor in triggering Ca2+ oscillations.

Dual contractile response of the aorta strip

1959 ◽  
Vol 197 (1) ◽  
pp. 241-246 ◽  
Author(s):  
Donald C. Brodie ◽  
David F. Bohr ◽  
Jeanette Smit
Keyword(s):  
Contractile Response ◽  
Rabbit Aorta ◽  
Electrolyte Composition ◽  
The Other ◽  
Low Concentrations ◽  
Dual Character ◽  
Chemical Stimuli ◽  
High Concentrations ◽  
Isotonic Contractions ◽  
Reduced Temperature

Isotonic contractions of rabbit aorta strips recorded in response to chemical stimuli strongly suggest that the shortening process has a dual character, consisting of a fast (F-) and a slow (S-) component. In the current study evidence for a dual contractile mechanism was sought by attempting to separate one component from the other. The S-component is more altered than the F-component by shifts in electrolyte composition. The S-component is less activated than the F-component by low concentrations of epinephrine or norepinephrine. The F-component is less activated than the S-component by low concentrations of phenylephrine or isopropylarterenol. The differential effect of reduced temperature is the same as that produced by a decrease in concentration of the constrictor. Dibenamine blockade permits a differentiation of the two components since it seems to alter the ratio of available receptors which activate the two components. When norepinephrine was used in high concentrations after Dibenamine blockade it caused a separation of the F- and S-components by imposing a period of relaxation between the two.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

The Action of an Aniline Derivative (AN 162) on Blood Coagulation and on Platelets

1971 ◽  
Vol 26 (01) ◽  
pp. 145-166
Author(s):  
E Deutsch ◽  
K Lechner ◽  
K Moser ◽  
L Stockinger
Keyword(s):  
Blood Coagulation ◽  
Citric Acid Cycle ◽  
Second Phase ◽  
Aniline Derivative ◽  
Acid Cycle ◽  
Enhancing Effect ◽  
Low Concentrations ◽  
Dual Action ◽  
High Concentrations ◽  
Induced Aggregation

Summary1. The aniline derivative AN 162, Donau Pharmazie, Linz, Austria, has a dual action on the blood coagulation: an anticoagulant and an coagulation enhancing effect.2. The anticoagulant action may only be demonstrated with high concentrations (over 1 X 10”3 M related to plasma) preferentially in PPP. It is partially caused by an inhibition of the endogenous way of generation of the prothrombin converting principle. In addition it is suggested that it interferes with the fibrinogen-fibrin reaction in a manner not yet understood.3. The coagulant action is caused by a greater availability of platelet constituents at low concentrations of AN 162 (over 1 × 10-4 M) and by the induction of a release reaction at higher concentrations. The platelet factors 3 and 4, serotonin, adenine, and acid phosphatase are released.4. AN 162 inhibits platelet aggregation. This inhibition can be demonstrated by the PAT of Breddin and in the stirred aggregation test of Born. It is more effective to inhibit the collagen-induced and the second phase of the adrenaline-induced aggregation than the ADP induced one. The platelet retention (test of Hellem) is also reduced.5. The action of AN 162 on the platelets is caused by a damage of the platelet membrane which becomes permeabel for both, soluble platelet constitutents and granula.6. AN 162 interferes with the energy metabolism of the platelets. It causes a loss of ATP, and inhibits the key-enzymes of glycolysis, citric acid cycle, fatty acid oxydation and glutathione reduction.7. AN 162 inhibits the growth of fibroblasts without influence on mitosis.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

Biological Mechanisms of H2S Formation in Sewer Pipes

1992 ◽  
Vol 26 (3-4) ◽  
pp. 907-914 ◽  
Author(s):  
A. Attal ◽  
M. Brigodiot ◽  
P. Camacho ◽  
J. Manem
Keyword(s):  
Suspended Solid ◽  
Urban Wastewater ◽  
Biological Mechanisms ◽  
Sewer Pipes ◽  
Sulfate Reducing ◽  
Biological Phenomena ◽  
Low Concentrations ◽  
Production Of Hydrogen ◽  
High Concentrations ◽  
Reducing Bacteria

The purpose of this study is to gain a better understanding of the biological phenomena involved in the production of hydrogen sulfide in urban wastewater (UWW) systems. It is found that the UWW itself naturally possesses the biomass needed to consume the sulfates. These heterotrophic sulfate-reducing bacteria populations, though immediately active in strict anaerobic conditions, are present only in very low concentrations in the UWW. A concentration of them was studied within the pressure pipes, in the form of deposits, and this justifies the high concentrations of sulfides measured in certain wastewater networks. There are two reasons why the ferrous sulfate used as a treatment in any wastewater networks should not cause the production of additional sulfides. Firstly, the sulfate consumption kinetics are always too slow, relative to the residence time of the water in the pipe, for all of the sulfates to be consumed anyway. Secondly, the amount of assimilable carbon, soluble carbon, and carbon from suspended solid (SS) hydrolysis is insufficient.

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