scholarly journals POTASSIUM-DEPENDENT SODIUM EXTRUSION BY CELLS OF PORPHYRA PERFORATA, A RED MARINE ALGA

1958 ◽  
Vol 42 (2) ◽  
pp. 281-288 ◽  
Author(s):  
Richard W. Eppley
Keyword(s):  
Marine Alga ◽  
Sea Water ◽  
High Sodium ◽  
Low Concentrations ◽  
Carrier Mechanism ◽  
Low Potassium ◽  
Sodium Extrusion ◽  
Rubidium Accumulation ◽  
Red Marine Alga

Potassium-free artificial sea water causes a loss of cell potassium and a gain of cell sodium in Porphyra perforata, which is not attributable to an inhibition of respiration. On adding KCl or RbCl to such low potassium, high sodium tissues, net accumulation of potassium or rubidium takes place, accompanied by net extrusion of sodium. Rates of potassium or rubidium accumulation and sodium extrusion are proportional to the amount of KCl or RbCl added only at low concentrations. Saturation of rates is evident at KCl or RbCl concentrations above 20–30 mM, suggesting the role of an ion carrier mechanism of transport. Evidence for and against mutually dependent sodium extrusion and potassium or rubidium accumulation is discussed.

Role of the spleen in congenital stomatocytosis associated with high sodium low potassium erythrocytes

1981 ◽  
Vol 59 (4) ◽  
pp. 173-179 ◽  
Author(s):  
W. Schr�ter ◽  
K. Ungefehr ◽  
W. Tillmann
Keyword(s):  
High Sodium ◽  
Low Potassium

scholarly journals SODIUM EXCLUSION AND POTASSIUM RETENTION BY THE RED MARINE ALGA, PORPHYRA PERFORATA

1958 ◽  
Vol 41 (5) ◽  
pp. 901-911 ◽  
Author(s):  
Richard W. Eppley
Keyword(s):  
Concentration Gradient ◽  
Marine Alga ◽  
Metabolic Inhibitors ◽  
Reduced Sulfur Compounds ◽  
Concentration Gradients ◽  
Potassium Accumulation ◽  
Potassium Loss ◽  
Sodium Extrusion ◽  
Potassium Retention ◽  
Red Marine Alga

Cells of the red marine alga, Porphyra perforata, accumulate potassium and exclude sodium, chloride, and calcium. Various metabolic inhibitors including dinitrophenol, anoxia, and p-chloromercuribenzoate partially abolish the cells' ability to retain potassium and exclude sodium. Iodoacetate induces potassium loss only in the dark; reduced sulfur compounds offer protection against the effects of p-chloromercuribenzoate; dinitrophenol stimulates respiration at concentrations which cause potassium loss and sodium gain. Following exposure to anoxia potassium accumulation and sodium extrusion take place against concentration gradients. These movements are retarded by sodium cyanide, but are stimulated by light. Sodium entry, following long exposure to 0.6 M sucrose, occurs rapidly with the concentration gradient, while potassium entry against the concentration gradient takes place slowly, and is prevented by cyanide.

The role of the renal prostaglandins and thromboxanes during high sodium/low potassium and low sodium/high potassium

1984 ◽  
Vol 27 ◽  
pp. 91
Author(s):  
N. Papanicolaou ◽  
M. Tsigga ◽  
E-L. Gkika ◽  
C. Hatziantoniou ◽  
I. Darlametsos ◽  
...  
Keyword(s):  
High Potassium ◽  
High Sodium ◽  
Low Sodium ◽  
Renal Prostaglandins ◽  
Low Potassium

scholarly journals Potassium Accumulation and Sodium Efflux by Porphyra perforata Tissues in Lithium and Magnesium Sea Water

1959 ◽  
Vol 43 (1) ◽  
pp. 29-38 ◽  
Author(s):  
Richard W. Eppley
Keyword(s):  
Concentration Gradient ◽  
Marine Alga ◽  
Sea Water ◽  
Secondary Process ◽  
Na Transport ◽  
K Uptake ◽  
Potassium Accumulation ◽  
Sodium Efflux ◽  
Na Efflux ◽  
Red Marine Alga

Cells of Porphyra perforata, a red marine alga, accumulate K in the absence of concomitant Na or Li extrusion while immersed in Li- or Mg-sea waters lacking Na. This suggests that the coupling observed between K and Na transport is facultative. No evidence is obtained for net extrusion of Li. Na efflux, with the concentration gradient, is facilitated by K and is proportional to the cellular Na content. Either Na efflux does not involve an ion carrier or the number of Na sites is large. Because K accumulation has been observed in the absence of Na extrusion, but not vice versa, it seems that K uptake is the primary secretory event, with Na extrusion a secondary process dependent upon K accumulation.

Testosterone Potentiation of Ionophore and ADP Induced Platelet Aggregation : Relationship to Arachidonic Acid Metabolism

1981 ◽  
Vol 46 (02) ◽  
pp. 538-542 ◽  
Author(s):  
R Pilo ◽  
D Aharony ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Unsaturated Fatty Acids ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Arachidonic Acid Metabolism ◽  
Ionophore A23187 ◽  
Low Concentrations ◽  
Induced Aggregation

SummaryThe role of arachidonic acid oxygenated products in human platelet aggregation induced by the ionophore A23187 was investigated. The ionophore produced an increased release of both saturated and unsaturated fatty acids and a concomitant increased formation of TxA2 and other arachidonate products. TxA2 (and possibly other cyclo oxygenase products) appears to have a significant role in ionophore-induced aggregation only when low concentrations (<1 μM) of the ionophore are employed.Testosterone added to rat or human platelet-rich plasma (PRP) was shown previously to potentiate platelet aggregation induced by ADP, adrenaline, collagen and arachidonic acid (1, 2). We show that testosterone also potentiates ionophore induced aggregation in washed platelets and in PRP. This potentiation was dose and time dependent and resulted from increased lipolysis and concomitant generation of TxA2 and other prostaglandin products. The testosterone potentiating effect was abolished by preincubation of the platelets with indomethacin.

scholarly journals Impaired platelet responses to thrombin and collagen in AKT-1–deficient mice

Blood ◽  
2004 ◽  
Vol 104 (6) ◽  
pp. 1703-1710 ◽  
Author(s):  
Juhua Chen ◽  
Sarmishtha De ◽  
Derek S. Damron ◽  
William S. Chen ◽  
Nissim Hay ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Dense Granules ◽  
Fibrinogen Binding ◽  
Downstream Effectors ◽  
Low Concentrations ◽  
Phosphoinositide 3 Kinase ◽  
Deficient Mice ◽  
Granule Release

Abstract We investigated the role of Akt-1, one of the major downstream effectors of phosphoinositide 3-kinase (PI3K), in platelet function using mice in which the gene for Akt-1 had been inactivated. Using ex vivo techniques, we showed that Akt-1-deficient mice exhibited impaired platelet aggregation and spreading in response to various agonists. These differences were most apparent in platelets activated with low concentrations of thrombin. Although Akt-1 is not the predominant Akt isoform in mouse platelets, its absence diminished the amount of total phospho-Akt and inhibited increases in intracellular Ca2+ concentration in response to thrombin. Moreover, thrombin-induced platelet α-granule release as well as release of adenosine triphosphate from dense granules was also defective in Akt-1-null platelets. Although the absence of Akt-1 did not influence expression of the major platelet receptors for thrombin and collagen, fibrinogen binding in response to these agonists was significantly reduced. As a consequence of impaired αIIbβ3 activation and platelet aggregation, Akt-1 null mice showed significantly longer bleeding times than wild-type mice. (Blood. 2004;104:1703-1710)

scholarly journals CALCULATIONS OF BIOELECTRIC POTENTIALS

1939 ◽  
Vol 23 (1) ◽  
pp. 53-57 ◽  
Author(s):  
W. J. V. Osterhout
Keyword(s):  
Alkali Metals ◽  
Sea Water ◽  
Low Ph ◽  
Electrical Behavior ◽  
Low Concentrations ◽  
Alkaline Earths ◽  
Bioelectric Potentials

Interest in the study of Halicystis and of Valonia has been stimulated by discoveries of marked contrasts and striking similarities existing side by side. This is illustrated by new experiments with the alkali metals and alkaline earths. In Halicystis the apparent mobilities of K+, Rb+, Cs+, and Li+ (calculated by means of Henderson's equation from changes in P.D. produced by replacing sea water by a mixture of equal parts of sea water and 0.6 M of various chlorides) are as follows, uK, = 16, uRb = 16, uCs = 4.4, and uLi = 0.2; uNa is taken as 0.2. These values resemble those in Valonia except that in the latter uCs is about 0.2. No calculation is made for uNHNH4, because in these experiments even at low pH so much NH3 is present that the sign of the P.D. may reverse. This does not happen with Valonia. According to Blinks, NH4+ at pH 5 in low concentrations acts like K+. The calculation gives uMg = 1.9 which is similar to the value found for Valonia. No calculation can be made for CaCl2 since it produces protoplasmic alterations and in consequence Henderson's equation does not apply. This differs from Valonia. Evidently these plants agree closely in some aspects of electrical behavior but differ widely in others.

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