scholarly journals The low KM-phosphodiesterase inhibitor denbufylline enhances neuronal excitability in guinea pig hippocampus in vitro

1990 ◽  
Vol 342 (3) ◽  
pp. 349-356 ◽  
Author(s):  
B. Sutor ◽  
C. Alzheimer ◽  
A. Ameri ◽  
G. ten Bruggencate
Keyword(s):  
Guinea Pig ◽  
Neuronal Excitability ◽  
Phosphodiesterase Inhibitor

EFFECTS OF LOW CONCENTRATIONS OF THYROID STIMULATING HORMONE: PHARMACOLOGICAL EXPERIMENTS IN VITRO

1970 ◽  
Vol 64 (1) ◽  
pp. 133-149 ◽  
Author(s):  
M.-L. Desbarats-Schönbaum ◽  
E. A. Sellers ◽  
Malle Laansoo ◽  
Eva Koves ◽  
E. Schönbaum
Keyword(s):  
Guinea Pig ◽  
Thyroid Tissue ◽  
Phosphodiesterase Inhibitor ◽  
Thyroid Stimulating Hormone ◽  
Low Concentration ◽  
Low Concentrations ◽  
Stimulating Hormone

ABSTRACT In guinea pig thyroid tissue incubated at 25°C for forty hours the binding (organification) of iodide appears to be the step most sensitive to TSH. Binding is independent of uptake in this system and physiological doses of TSH can stimulate binding while uptake is partially inhibited. At a suitably low concentration of PTU, the addition of TSH can counteract the effect of this drug. At less than maximal concentrations, the effects of TSH and theophylline (a phosphodiesterase inhibitor) are additive, which supports the hypothesis that TSH acts by stimulating the production of cyclic 3′,5′-AMP. The effect of TSH appears to be exerted equally on any iodide present in the thyroid at the beginning of, or taken up during, incubation in vitro. In this system deiodination has been excluded as a major complicating factor.

Parathyroid hormone (PTH) fragments relax the guinea-pig trachea in vitro

1983 ◽  
Vol 61 (11) ◽  
pp. 1324-1328 ◽  
Author(s):  
Y. C. Yen ◽  
May C. M. Yang ◽  
Alexander D. Kenny ◽  
Peter K. T. Pang
Keyword(s):  
Amino Acids ◽  
Hydrogen Peroxide ◽  
Parathyroid Hormone ◽  
Guinea Pig ◽  
Phosphodiesterase Inhibitor ◽  
Blocking Agent ◽  
No Inhibition ◽  
Per Se ◽  
Bovine Parathyroid Hormone

Synthetic bovine parathyroid hormone fragment containing the N-terminal 1 – 34 amino acids (bPTH-(1 – 34)) relaxed the guinea-pig trachea constricted with histamine in vitro. Peptides with bovine and human sequences purchased from Peninsula Laboratories and Beckman Bioproducts produced similar effects. Substitution of methionine in positions 8 and 18 by norleucine did not affect this property of bPTH-(1 – 34). However, when the methionines were oxidized by treating the peptide with hydrogen peroxide, the peptide could no longer produce relaxation in the trachea. Oxidation of the methionine-replaced analog did not affect the action of the peptide on the trachea. It seems that the methionines per se are not necessary, but once oxidized the conformation of the molecule may be sufficiently altered to affect its ability to relax the trachea. While propranolol can block the relaxing action of isoproterenol, this blocking agent produces no inhibition of the bPTH-(1 – 34) effect. This action of PTH on the trachea may be related to cAMP because isobutyryl-methylxanthine, a phosphodiesterase inhibitor, potentiates and imidazole, a phosphodiesterase stimulator, inhibits the trachea relaxing action of bPTH-(1 – 34).

Inhibition of Human and Animal Platelet Adhesiveness to Glass Bead Columns by Adenosine, Dipyridamole, Chlorpromazine and Acetylsalicylic Acid

1976 ◽  
Vol 36 (02) ◽  
pp. 401-410 ◽  
Author(s):  
Buichi Fujttani ◽  
Toshimichi Tsuboi ◽  
Kazuko Takeno ◽  
Kouichi Yoshida ◽  
Masanao Shimizu
Keyword(s):  
Guinea Pig ◽  
Acetylsalicylic Acid ◽  
Guinea Pigs ◽  
Glass Bead ◽  
Animal Species ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Platelet Adhesiveness

SummaryThe differences among human, rabbit and guinea-pig platelet adhesiveness as for inhibitions by adenosine, dipyridamole, chlorpromazine and acetylsalicylic acid are described, and the influence of measurement conditions on platelet adhesiveness is also reported. Platelet adhesiveness of human and animal species decreased with an increase of heparin concentrations and an increase of flow rate of blood passing through a glass bead column. Human and rabbit platelet adhesiveness was inhibited in vitro by adenosine, dipyridamole and chlorpromazine, but not by acetylsalicylic acid. On the other hand, guinea-pig platelet adhesiveness was inhibited by the four drugs including acetylsalicylic acid. In in vivo study, adenosine, dipyridamole and chlorpromazine inhibited platelet adhesiveness in rabbits and guinea-pigs. Acetylsalicylic acid showed the inhibitory effect in guinea-pigs, but not in rabbits.

Mechanism of the Antiplatelet Action of Dipyridamole in Whole Blood: Modulation of Adenosine Concentration and Activity

1986 ◽  
Vol 55 (01) ◽  
pp. 012-018 ◽  
Author(s):  
Paolo Gresele ◽  
Jef Arnout ◽  
Hans Deckmyn ◽  
Jos Vermylen
Keyword(s):  
Platelet Aggregation ◽  
Adenosine Receptor ◽  
Whole Blood ◽  
Blood Cells ◽  
Inhibitory Action ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effect ◽  
Adenosine Concentration ◽  
Pharmacological Studies

SummaryDipyridamole inhibits platelet aggregation in whole blood at lower concentrations than in plasma. The blood cells responsible for increased effectiveness in blood are the erythrocytes. Using the impedance aggregometer we have carried out a series of pharmacological studies in vitro to elucidate the mechanism of action of dipyridamole in whole blood. Adenosine deaminase, an enzyme breaking down adenosine, reverses the inhibitory action of dipyridamole. Two different adenosine receptor antagonists, 5’-deoxy-5’-methylthioadenosine and theophylline, also partially neutralize the activity of dipyridamole in blood. Enprofylline, a phosphodiesterase inhibitor with almost no adenosine receptor antagonistic properties, potentiates the inhibition of platelet aggregation by dipyridamole. An inhibitory effect similar to that of dipyridamole can be obtained combining a pure adenosine uptake inhibitor (RE 102 BS) with a pure phosphodiesterase inhibitor (MX-MB 82 or enprofylline). Mixing the blood during preincubation with dipyridamole increases the degree of inhibition. Lowering the haematocrit slightly reduces the effectiveness.Although we did not carry out direct measurements of adenosine levels, the results of our pharmacological studies clearly show that dipyridamole inhibits platelet aggregation in whole blood by blocking the reuptake of adenosine formed from precursors released by red blood cells following microtrauma. Its slight phosphodiesterase inhibitory action potentiates the effects of adenosine on platelets.

INHIBITION OF LIPOLYTIC ACTIVITY OF SYNTHETIC β1–24 AND β1–39 CORTICOTROPHIN BY ANTI-ACTH ANTISERUM

1966 ◽  
Vol 51 (1) ◽  
pp. 88-94 ◽  
Author(s):  
A. Villanueva ◽  
S. J. H. Ashcroft ◽  
J. P. Felber
Keyword(s):  
Guinea Pig ◽  
Lipolytic Activity ◽  
Peptide Hormones ◽  
Fat Pad ◽  
Double Antibody ◽  
Epididymal Fat ◽  
Antibody Complex ◽  
Radio Immunoassay ◽  
Antigen Antibody

ABSTRACT The synthetic ACTH peptides β1–39 and β1–24 stimulated lipolysis as determined by the rat epididymal fat pad in vitro. The stimulating effect of these peptides was diminished by prior incubation of the peptides with antibodies produced by the guinea-pig against ACTH. The stimulating effect of these hormones was also diminished by the double antibody system used in the radio-immunoassay of ACTH and other peptide hormones, in which incubation with antiserum is followed by precipitation of the antigen-antibody complex by rabbit anti-guinea-pig-γ-globulin.

Precision-cut Guinea-pig Liver Slices as a Tool for Studying the Toxicity of Volatile Anaesthetics

1990 ◽  
Vol 18 (1_part_1) ◽  
pp. 191-199
Author(s):  
Hanan N. Ghantous ◽  
Jeanne Fernando ◽  
Scott E. Morgan ◽  
A. Jay Gandolfi ◽  
Klaus Brandel
Keyword(s):  
Guinea Pig ◽  
Rank Order ◽  
Normal Liver ◽  
Liver Slice ◽  
Volatile Anaesthetics ◽  
Pig Liver ◽  
Liver Slices ◽  
Guinea Pig Liver ◽  
Krebs Henseleit Buffer

Cultured precision-cut liver slices retain normal liver architecture and physiological biochemical functions. Hartley male guinea-pig liver slices have proven to be a good model for studying the biotransformation and toxicity of halothane. This system was used to evaluate the biotransformation and toxicity of different volatile anaesthetics (halothane, enflurane, isoflurane and sevoflurane), and compare their effects to those of new anaesthetics (desflurane). Liver slices (250–300μm thick) were incubated in sealed roller vials, containing Krebs Henseleit buffer at 37°C under 95% O2:5% CO2 atmosphere. Volatile anaesthetics were delivered by volatilisation after pre-incubation for 1 hour to produce a constant concentration in the medium. Production of the metabolites, trifluroacetic acid and fluoride ion, was measured. Intracellular potassium ion content, protein synthesis and secretion were determined as indicators of viability of the slices. The rank order of biotransformation of anaesthetics by the liver slices was halothane >sevoflurane>isoflurane and enflurane>desflurane. The rank order of hepatotoxicity of these anaesthetics was halothane>isoflurane and enflurane>sevoflurane and desflurane. Halothane is the anaesthetic which is metabolised furthest and has the most toxic effect, while desflurane is the least metabolised anaesthetic and has the least toxicity. This in vitro cultured precision-cut liver slice system appears to be suitable for studying the biotransformation of volatile anaesthetics and correlating its role in the resulting toxicity.

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