The mechanism of tetrodotoxin on the in situ acetylcholinesterase in the vagal heart system ofRana pipiens

Zusammenfassung Am isolierten Vagus-Herzen vonRana pipiens wird die Wirkung der Vagusreizung gemessen: Konzentrationen unter 4×10^–10 g/ml Tetrodotoxin erhöhen die vagale Reizungswirkung, nicht aber die Herzkontraktionen.     

The influence of hyperosmolality on heart function

Summary Hyperosmolality produces a reduction in myocardial water content, an increase in ventricular stiffness and coronary blood flow, and a decrease in ventricular performance. The alterations of myocardial dehydration and ventricular stiffness are more pronounced in glucose-induced, and those of ventricular performance in urea-induced hyperosmolality.     

Transmural pressure as a determinant of basic intrinsic heart rate

Summary It was observed the heart rate was minimum at zero transmural pressure. The mean heart rate at zero transmural pressure was 23±5/min. This mean heart rate increased from 23±5/min to a peak value of 40±6/min (74% acceleratin) when the transmural pressure was raised from 0 to +4 mm Hg and to a similar peak value of 36±8/min (56% acceleration) when the transmural pressure was lowered from 0 to –4 mm Hg. The peak values attained at ±4 mm Hg were higly significant (p<0.001). It is concluded that the heart rate at zero transmural pressure represents the basic intrinsic pacemaker frequency independent of neural, humoral, thermal and haemodynamically induced mechanical influences.     

Effects ofl-dopa alone and in combination with dopa decarboxylase inhibitors on the arterial pressure and heart rate of dogs

Zusammenfassung Nach Vorbehandlung mitl-HMD (peripherer Hemmer der Dopa-Dekarboxylase) wird mitl-Dopa (25 und 50 mg/kg i.v.) Blutdruck und Herzfrequenz herabgesetzt.     

The rate of action of cyclic ammonium and sulfonium analogues of acetylcholine

Summary The rate of action of cyclic acetylcholine analogues in the 4-acetoxypiperidine and 4-acetoxythiacyclohexane series has been determined by using the isolated left guinea-pig atrium. The kinetic data obtained has been correlated with the experimental ED₅₀-value on the muscarinic receptor.Structure and Conformation Activity Relationships of Cyclic Acetylcholine Analogues.VI.We thank the German Research Association for supporting this work, and Mrs Ch. Röttger for her valuable assistance in carrying out the investigations.     

The effect of some neurohormones on the heart rate of spiders

Résumé Les auteurs ont étudié l'effet de l'adrénaline et de l'acétylocholine sur le rythme du cur chez l'araignéeTegenaria atrica C. L. Koch. L'enregistrement s'est fait au moyen de l'électroencephalographe. L'injection de l'adrénaline provoquait l'accélération du rythme du cur, l'acétylocholine — son ralentissement.     

The effect of sleep deprivation upon variations in heart rate and respiration rate

Summary Variations in heart rate and respiration rate were found to be responsive to total sleep deprivation, particularly under experimental conditions more realistic to everyday life.     

Stretch sensitive intrinsic autoregulatory mechanisms for rhythmicity and contractility of the heart

Résumé L'étirement mécanique est une force motrice fondamentale pour l'autorégulation intrinsèque du rhythme du cur en modifiant l'activité du «pacemaker» de la même manière que la distension du myocarde influe sur le réponse inotropique. L'étirement est un mécanisme biologique de base pour la rythmicité cardiaque et la contractilité et il met en interdépendance positive le retour veineux et le débit sanguin. La sensibilité à l'étirement est une propriété des réponses chronotropiques. Elle fait du cur une pompe autorégulatrice unique en son genre.     

The rate of action of cyclic ammonium and sulfonium analogues of acetylcholine.

The rate of action of cyclic acetylcholine analogues in the 4-acetoxypiperidine and 4-acetoxythiacyclohexane series has been determined by using the isolated left guinea-pig atrium. The kinetic data obtained has been correlated with the experimental ED50-value on the muscarinic receptor.     

The influence of incubation temperature on the rate of human lymphocyte proliferation in vitro

Summary Using the FPG staining technique we have confirmed that incubation temperature has a marked effect on the proliferation rate of cultured lymphocytes. With 48 h-cultures the proportion of 2nd-cycle cells increases linearly over the temperature range 36–39°C. However the absolute size of the increase exhibits interdonor variability.We would like to acknowledge the assistance of the Commission of the European Communities for their provision of a travel grant.     

Cardiopulmonary origin of vagal afferent fibers exerting a tonic reflex influence on the circulation

Riassunto Le fibre afferenti presenti nel vago cervicale, e dotate di tonica attività inibitrice sui fenomeni circolatori, originano da aree recettrici intratoraciche, non provengono in misura importante dall'arco aortico, ma si dipartono da ampie zone della regione cardio-polmonare.

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This research has been sponsored in part by Wright Air Development Division of the Office of Aerospace Research, United States Air Force, through its European Office, with Contract No. AF 61 (052)-253, and by Consiglio Nazionale delle Ricerche.     

Serotonin levels in fish brain: Effects of hydrostatic pressure and water temperature

Summary The contents of serotonin (5 HT) and its metabolite 5 hydroxy indoleacetic acid (5 HIAA) have been measured (HPLC technique) in the brains of eels exposed to different conditions of hydrostatic pressure and temperature (HP=1 or 101 ATA in winter, Tw=14°C, and in summer, Tw=19°C). It appears that an increase of Tw induces a significant increase of the 5 HT/5 HIAA ratio. In contrast, eels exposed at 101 ATA of HP for 1 h do not exhibit any modification in the 5 HT/5 HIAA brain ratio at a given temperature. The involvement of 5 HT under the conditions studied is discussed.     

The effect of pressure changes on esterification of cholesterol and hydrolysis of cholesterol esters in rat aorta and serum

Zusammenfassung Experimente in vitro zeigen, dass unter Überdruck von 200 mm Hg die Hydrolyse von Cholesteropalmitat in den Aorten und im Blutserum von Ratten gehemmt wird: Die Esterifikation von Cholesterin, in Aorten ebenfalls erniedrigt, zeigt im Serum einen deutlichen Anstieg.

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The skillful technical asistance of Mrs.J. Malíková andJ. Straková is gratefully acknowledged.