Kinetics of DNA repair synthesis in guinea-pig pancreatic slices following in vitro exposure to N-methyl-N-nitrosourethane

Summary In vitro exposure of guinea-pig pancreatic slices to NMUT resulted in an increase in hydroxyurea-insensitive³H-TdR incorporation into DNA; this represents DNA repair synthesis following NMUT-induced DNA damage. The kinetics of this hydroxyurea-insensitive³H-TdR incorporation suggest that the NMUT-induced DNA damage is largely repaired within 2 hours.Environmental Health Programs, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 (USA). These studies were supported by National Cancer Institute (Bethesda, Md., USA). Contract No. N01-CP-23284. Technical assistance of MS.Mary Majdan is gratefully acknowledged.     

Kinetics of interferon action

Summary A kinetic analysis of the action of interferon with different preparations in chick embryo fibroblast cell culture gives additional evidence for interaction of interferon with the cell surface, compatible with the idea that interferon is not taken up by the cells. With certain assumptions the binding constant is in the range of 10¹³ [l/Mol].Work supported by the Swiss National Science Foundation, grants 3.399, 3.1050 and 3.540.     

Fluorescing valvular nerves in the guinea-pig heart

Résumé Des plexus fluorescents de nerfs dans les valvules du cur du Cobaye sont décrits. Bien que du tissu musculaire et des nerfs cholinergiques fussent présents dans les valvules atrioventriculaires, les nerfs adrénergiques de la valvule pulmonaire ne se rapportaient qu'au tissu connectif fibreux. Puisque dans cette situation il n'y a pas d'emplacement effecteur évident ou que ces nerfs influencement des nerfs dont la présence n'est pas révélée par des techniques de cholinesterase ou qu'ils sont de caractère afférent.

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Acknowledgment. The author thanks Prof.G. A. G. Mitchell for his continued interest.     

Further support for the postsynaptic action of substance P and its blockade with baclofen in neurons of the guinea-pig hypothalamus in vitro

Effects of substance P on neurons of the guinea-pig hypothalamus in vitro and antagonism between substance P and baclofen were investigated. Substance P increased the firing rate of neurons in the medium containing 0 mM Ca2+ and 12 mM Mg2+. The excitatory action of substance P was antagonized by a low dose of baclofen whereas that of acetylcholine was not antagonized even by much higher doses of baclofen.     

An inhibitory action of caerulein on the isolated guinea-pig ileum

Riassunto La caeruleina provoca sull'ileo di cavia isolato una inibizione dello spasmo sostenuto da dosi massimali di istamina. Questo effetto inibitorio sembra connesso con le proprietà colecisto-chinino simili del peptide più che con quelle gastrino simili.     

Adenosine activates a potassium conductance in guinea-pig atrial heart muscle

Adenosine shortens the action potential and diminishes the force of contraction in guinea-pig left atria. These effects may be brought about by the activation of a potassium conductance. This assumption is supported by voltage clamp and 42K release experiments.     

Papaverine blockade of the calcium action in depolarized taenia coli of the guinea-pig

Zusammenfassung Es wird die muskellähmende Wirkung von Papaverin auf die depolarisierte Taenia coli durch die Blockade des Kalziumionenstromes durch die Zellmembran erklärt.     

Effect of fatty acids on the contraction of guinea-pig ileum in vitro

Zusammenfassung Untersuchung der Wirkung von essentiellen Fettsäuren auf die Kontraktion des isolierten Meerschwein-Ileums ergab, dass besonders die direkten Vorläufer von Prostaglandin E₁ und E₂, nämlich Dihomo--Linolensäure und Arachidonsäure, aktiv sind.     

A promoting action of cyclic GMP on contractions of guinea-pig vas deferens

Summary The effect of dbc-GMP has been studied in ductus deferens of the guinea-pig. The nucleotide potentiated the contractions induced by electrical field stimulation and by adrenergic agonists. The site of action was probably in the smooth muscle cell, since the release of excitatory transmittor was not influenced.This work was supported by the Swedish State Medical Research Council (04X-4498).     

Luminal alkalinization by guinea-pig cecum in vitro,an electro-neutral process

Summary Guinea-pig cecum was found to alkalinize its mucosal media in vitro at a chemical equivalents rate greater than the short circuit current (I_SC). Alkalinization was inhibited by conditions which did not affect I_SC and by low mucosal Na suggesting an electro-neutral process, dependent on Na.This study was supported in part by the National Science Foundation Grant BMS 74-08901. The authors appreciate the insight and encouragement of Dr Michael J. Jackson expressed in numerous conversations.     

Inhibitory effect of taurine on decrease in the inotropic action of ouabain at high concentrations in isolated atria

Summary In vitro, taurine was shown to inhibit the decrease in the inotropic effect of ouabain at large doses in the normal and also low K⁺ medium in which this decrease in the inotropism of ouabain was facilitated. This inhibitory effect of taurine was, at least in part, due to the inhibition of the efflux of intracellular K⁺ in the isolated heart.     

Effect of adrenaline on the in vitro enzyme secretion in the guinea-pig pancreas

Riassunto In un sistema di fette di pancreas di cavia incubate in vitro l'adrenalina non modifica l'attività secretoria delle cellule acinari né in condizioni basali né in risposta a farmaci segretagoghi (ceruleina e carbamoilcolina). Sembra quindi probabile che l'inibizione della secrezione pancreatica esocrina prodotta in vivo dalla iniezione di adrenalina sia dovuta ad un meccanismo indiretto, quale la vasocostrizione pancreatica e(o) l'inibizione della secrezione di acqua ed elettroliti a livello delle cellule acino-duttulari.     

Divergent effects of theophylline on adenylate cyclase preparations from guinea-pig heart and lung

Zusammenfassung Theophyllin verringert die Aktivität der Adenyl-Cyclase (AC) in der plasmamembranreichen Fraktion der Meerschweinchenlunge in Konzentrationen von 6–10 mM; es hat dagegen keinen Einfluss auf die Aktivität der AC in Meerschweinchenherzen. Diese Resultate weisen darauf hin, dass in verschiedenen Geweben geringe Unterschiede in der Enzym-Katalyse bestehen können.     

Correlation between inhibition of stimulatory membrane repolarization and positive inotropic response caused by ouabain in rat heart]

During a stimulus train, the diastolic membrane potential of rat atria exhibits a depolarization phase followed by a slower repolarization phase which has been attributed to the activation of an electrogenic sodium pump (ATPase Na+, K+). This pump seems to be all the more active as stimulation frequency is higher. The parallel evolution of the sodium pump inhibition and a positive inotropic effect in response to ouabain perfusion, suggests that the enzymatic inhibition is directly involved in the development of the cardiotonic effect of digitalis.