Effects of acetylcholine and cyclic nucleotides on the bullfrog atrial muscle

Effects of ACh on the slow inward current and tension components of bullfrog atrial muscle were examined with voltage-clamp technique. ACh decreased the phasic component of contractile tension and the slow inward current with a reduction of gCa. Contracture tensions were augmented by ACh and decreased by adrenaline. Intracellularly injected cGMP through microelectrode decreased the overshoot and the plateau level of action potential without affecting the resting membrane potential, indicating a decrease in the slow inward current. cAMP enhanced the overshoot and the plateau. ACh seems to reduce the slow inward current through an elevation of intracellular cGMP concentrations.

Dual effects of fluoride on the action potential, contraction, and membrane currents in frog atrial muscle

The effects of NaF (10(-7) - 10(-2) M) on the membrane potential, current, and contractile tension in bullfrog atrial muscle were investigated under voltage-clamped or unclamped conditions. NaF showed two opposite actions, positive and negative inotropic effects, depending on the concentration of the drug. NaF in lower concentrations produced a marked increase in contractility, a moderate prolongation of action potential, an augmentation of calcium response, and an increase of ICa-dependent tension. Contrarily, NaF in higher concentrations produced an inhibition of contractile tension associated with a shortening of action potential, an increase in potassium conductance, and an inhibition of calcium response. These results indicate that NaF affects the contractile response by dual mechanisms.

Structure of wye (Yt base) and wyosine (Yt) from Torulopsis utilis phenylalanine transfer ribonucleic acid

A fluorescent base wye (Yt base) was isolated from Torulopsis utilis tRNAPhe. The structure was established as 4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazo[1,2-alpha]purine based on ultraviolet (uv), nuclear magnetic resonance (NMR), and mass spectra, and by direct comparison with synthetic material. The nucleoside, wyosine (Yt), was isolated from purified tRNAPhe by enzymatic degradations followed by column and thin-layer chromatographies. The structure of wyosine is proposed as 3-ribofuranosyl-4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazol[1,2-alpha]purine (the ribosyl group is attached to the N-9 position of guanine nucleus) on the basis of comparison with model compounds.

Cardiac involvement and prognosis in acute mucocutaneous lymph node syndrome

Cardiac involvement and prognosis were studied in the acute febrile mucocutaneous lymph node syndrome which recently has been found among Japanese infants and younger children. The reason for its particular predilection for the main coronary arteries and the pathologic process are discussed in relation to the pathogenesis and nutrient of the main coronary arteries.

A new assay method for hydrogenase based on an enzymic electrode reaction. The enzymic electric cell method

A new assay method for hydrogenase [EC 1.12.2.1] based on the enzymic electrode reaction of H2-H+ equilibrium has been established. The method is based on the experimental fact that the short-circuit current of the electric cell composed of an electrode with hydrogenase and methylviologen as the mediator of H2-H+ equilibrium and a saturated calomel electrode as the counter electrode, is practically proportional to the amount of hydrogenase in the cell. The new method is referred to as the "enzymic electric cell method." This technique has applications not only to routine activity assay but also to the direct determination of the time course of enzyme denaturation, which has not previously been possible.

Congenital left atrial enlargement. A case report with special reference to myocardial fine structure

A case of intrapericardial congenital left atrial enlargement was reported. The patient is an asymptomatic 3 year-old girl with abnormal cardiac silhouette seen on a chest roentgenogram. Angiography showed marked left atrial enlargement, and the diagnosis of intrapericardial congenital left atrial enlargement was confirmed on operation. Specimens of the atria were electron microscopically examined. Myocardiocytes of the left atrium showed marked increase of the mitochondria and decrease of myofibrils. Abnormal Z bands and disarrangement of myofibrils were often observed. Atrial specific granules in the left atrium were increased in size and number. The right atrium also showed same changes. The pathogenesis of this condition was discussed.

Right ventricular aneurysm with ventricular premature beats

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