Inosine nucleosidase from Azotobacter vinelandii. Purification and properties

An enzyme catalyzing the hydrolysis of purine nucleosides was found to occur in the extract of Azotobacter vinelandii, strain O, and was highly purified by ammonium sulfate fractionation, DEAE-cellulose chromatography, hydroxylapatite chromatography and gel filtration on Sephadex G-150. A strict substrate specificity of the purified enzyme was shown with respect to the base components. The enzyme specifically attacked the nucleosides without amino groups in the purine moiety: inosine gave the maximum rate of hydrolysis and xanthosine was hydrolyzed to a lesser extent. The pH optimum of inosine hydrolysis was observed from pH 7 to 9, while xanthosine was hydrolyzed maximally at pH 7. The Km values of the enzyme for inosine were 0.65 and 0.85 mM at pH 7.1 and 9.0, respectively, and the value for xanthosine was 1.2 mM at pH 7.1. Several nucleotides inhibited the enzyme: the phosphate portions of the nucleotides were suggested to be responsible for the inhibition by nucleotides. Although the inhibition of the enzyme by nucleotides was apparently non-competitive type with respect to inosine, allosteric (cooperative) binding of the substrate was suggested in the presence of the inhibitor. The physiological significance of the enzyme was discussed in connection with the degradation and salvage pathways of purine nucleotides.

[Alpha- and beta-adrenoceptor blocking actions of labetalol and effects on the myocardial function, coronary circulation and myocardial energy metabolism thereof (author's transl)]

In the isolated atria, trachea and aorta of the guinea pig and in the heart-lung preparation (HLP) of the dog, labetalol was 3.6 approximately 5.9 times less potent than phentolamine in blocking alpha-adrenoceptors, 1.4 approximately 3.6 times less potent as beta 1-blocker and 6 times less potent as beta 2-blocker than propranolol. Beta 1 and beta 2-blocking actions were 12 approximately 28 and 7 times more potent than alpha-blocking action, respectively. As regards beta 1-blockade, attenuation of the heart rate increase was more prominent than that of the augmentation of the contractile force. Both in the isolated atrial preparation of the guinea pig and in canine HLP, labetalol produced a positive inotropic and chronotropic effect and a slight increase in the coronary flow associated with a slight increase in the myocardial O2 consumption and improvement of the myocardial redox potential. Myocardial extraction and usage of lactate, pyruvate and glucose tended to be decreased and those of FFA decreased significantly. The positive inotropic and chrontropic effect was observed in HLP of 6-hydroxydopamine-pretreated dogs and was abolished with propranolol. Labetalol produced a relaxation of the isolated trachea of the guinea pig, which was inhibited with propranolol. In doses higher than those required for alpha- and beta-adrenoceptor blockade, labetalol produced calcium-antagonistic action.

Chronic lymphocytic leukemia showing pituitary tumor with massive leukemic cell infiltration, and special reference to clinicopathological findings of CLL

An autopsy case of a 33 years old doctor with chronic lymphocytic leukemia (CLL) was reported. Two remissions were noted with chemotherapy and irradiation. The special characteristic of this case was the tumor formation in the sellar fossa similating a pituitary tumor which was considered as a type of meningeal leukemia, showing visual disturbance. Leukemic cell infiltration was hardly observed in any other organs. From the analysis of five cases of CLL, the author proposes that CLL may be classified into two types: the one is the severe type showing a short clinical course and the other is a mild one, showing a long clinical course. Details such as histopathological findings, cause of death and clinical findings were discussed.

Hypotensive and vascular effects of labetalol in the normotensive rat and dog

A new antihypertensive agent, labetalol, has potent hypotensive effects in the anesthetized rat and dog when given intravenously and also in the unanesthetized beagle when given orally. Labetalol slightly increased renal blood flow of the anesthetized dog while decreasing blood pressure. Labetalol slightly increased blood flow of canine femoral artery under constant pressure perfusion. However as compared with hydralazine, labetalol seems to have no marked vasodilatatory effect which accounts for its hypotensive effect. Pharmacologically, labetalol possessed both alpha- and beta-blocking activities, though weaker than phentolamine and propranolol respectively. Another specific action of labetalol was that it has stronger beta-blocking action on beta1 receptor (heart rate response) than on beta2 receptor (blood pressure response). Like several other beta-blockers, labetalol seems to block neuronal uptake of noradrenaline.

Antiarrhythmic effect of oxprenolol on halothane-epinephrine and coronary ligation induced ventricular arrhythmias in beagle dogs

Antiarrhythmic effects of oxprenolol, a beta-blocker, were studied quantitatively on arhythmias produced by epinephrine during halothane anesthesia and by two-stage coronary ligation, and were compared to those of other beta-blockers, propranolol and Kö 1400, which have been already reported. Though oxprenolol has potent beta-blocking activity, the antiarrhythmic effect on halothane-epinephrine arrhythmia was significantly weaker than those of propranolol and Kö 1400. The effective dose of oxprenolol was 60 +/- 18 microgram/kg (mean +/- S.E., N = 6), which is in the range of the so-called beta-adrenergic blocking dose. The weaker antiarrhythmic effect of oxprenolol as compared to propranolol and Kö 1400 is probably due to the intrinsic positive chronotropic effect, which is most clearly observed in oxprenolol as compared to the other two drugs. As for two-stage coronary ligation arrhythmia, oxprenolol suppressed only that observed 48 hours after coronary ligation using higher doses (5 to 10 mg/kg). Other beta-blockers also showed similar effects. Because of the high doses necessary for the antiarrhythmic effects on the coronary ligation arrhythmia, the mechanism for suppressing the arrhythmia is probably due to the local anesthetic action of the beta-blockers.

Effects of heart rate and isoproterenol on the functional refractory period of the AV node

The effects of heart rate and l-isoproterenol on the functional refractory period (FRP) of the atrioventricular (AV) node were analyzed in anesthetized dog. A rectangular hyperbola was adopted to express the relationship between the AV conduction time of the premature beats and the atrial coupling intervals. FRP was shown to be expressed as FRP = E + 2 square root of C - C/(T - E). Thus, it is a function of the effective refractory period (E), basic cycle length (T), and C, a constant. A decrease in the basic cycle length caused a decrease in the effective refractory period as well as FRP; the minimum conduction time remained unchanged. As expected from the above equation, relationship of FRP to the basic cycle length was curvilinear. The above equation also indicates that changes in FRP produced by a change in the basic cycle length were to be ascribed to the change in the AV conduction time of the basic beats. Therefore, FRP under this condition cannot be equated with the refractory period in its true sense. In the paced hearts, l-isoproterenol hydrochloride caused a decrease in the effective refractory period, FRP, C and the minimum conduction time, and the changes in FRP were shown to be correlated with the changes in the effective refractory period, indicating that the change in FRP attained in a given fixed cycle length may be due to a change in the effective refractory period.

Antiarrhythmic and electrophysiological effects of CH-200

A new antiarrhythmic drug CH-200, 5-phenacyl-thieno[3,2-c]yridinium, was compared with procainamide and lidocaine in a two-stage coronary ligation arrhythmia model for its efficacy and electrophysiological properties. CH-200 suppressed arrhythmia in beagle dogs more effectively than did procainamide and lidocaine. The antiarrhythmic effects of CH-200 and procainamide developed slowly and lasted longer than those of lidocaine. Electrophysiological studies with CH-200 showed that it decreased max dV/dt of the action potential. This effect was dependent on the heart rate: the higher the rate, the stronger the effect. CH-200, procainamide and lidocaine prolonged the effective refractory period and this effect seemed to be responsible for suppressing the arrhythmia after coronary ligation. CH-200 and procainamide increased the frequency of ventricular pacemaker activity, while lidocaine decreased it. These effects appear to be unimportant for the antiarrhythmic effects.

[Effects of a new adrenergic beta-blocking agent, Kö 1400 on the canine heart-lung preparation supported by a donor dog and the perfused hindlimb preparation of the dog (author's transl)]

Using the canine heart-lung preparation supported by a donor, effects of a new adrenergic beta-blocking agent, dl-1-(tert. butylamino)-3-[ (2-propinyloxy) phenoxy]-2-propanol hydrochloride (Kö 1400), on cardiac function, myocardial metabolism, and coronary circulation were studied and compared with those of propranolol. Effects of this substance on the peripheral vascular bed were also studied in the perfused hindlimb preparation of the dog. Kö 1400 produced a positive inotropic and chronotropic effect. Mechanical efficiency of the heart improved after Kö 1400, while it lessened after propranolol. A decrease in the coronary flow was observed in association with a slight increase in myocardial O2 consumption, indicating that the substance exerted a direct constrictive effect on the coronary vasculature. As a beta-blocker, Kö 1400 was found to be 2-3 times more effective than propranolol. The uptake of the free fatty acid (FFA) by the heart was increased by Kö 1400 and the myocardial redox potential improved. In the perfused hindlimb preparation, intraarterial injection of Kö 1400 resulted in a transient increase of the femoral blood flow for a decrease in the flow followed by a sustained decrease. With repeated administration a marked tachyphylaxis was observed.

[Experimental anti-arrhythmic effects of a new beta-adrenergic receptor blocking agent, dl-l-(tert. butylamino)-3-[(2-propinyloxy)phenoxy]2-propanol hydrochloride (dl Kö 1400-Cl)]

Antiarrhythmic property of a new adrenergic beta-blocking agent, dl-1-(tert.butylamino)-3[(2-propinyloxy) phenoxy]-2-propanol hydrochloride (Kö 1400-Cl) was studied, using 1) ouabain-induced arrhythmia in the guinea pig, 2) aconitine-induced arrhythmia in the rat, 3) arrhythmia induced by two-step ligation of coronary artery (Harris's method) in the dog and 4) halothane-adrenaline arrhythmia in the dog and was compared with those of propranolol, oxprenolol, procainamide and ajmaline. Procainamide and ajmaline produced a marked protective effect against aconitine-induced ventricular extrasystole, but were not so effective against aconitine-induced ventricular fibrillation, while oxprenolol and, to a lesser degree, propranolol were effective against the latter type of aconitine arrhythmias. Kö 1400-Cl proved to be ineffective. All the compounds tested produced a marked protective action against ouabain-arrhythmia. Whereas procainamide was most effective in abolishing the ventricular arrhythmia due to coronary-ligation even on the first postoperative day, Kö 1400-Cl and propranolol were almost ineffective on the first day. Even on the second postoperative day, the antiarrhythmic effects of these two beta-blockers were not remarkable, effective only in 2/4 animals in the case of Kö 1400-Cl and in 2/3 animals in the case of propranolol. On the contrary, all the beta-blockers tested produced a protective action against halothane-adrenaline arrhythmia at much lower doses than against coronary ligation arrhythmia. The potency ratio of Kö 1400-Cl and propranolol was 3 : 1, which paralleled with beta-blocking activity of these compounds.

Inotropic and chronotropic effects of antiarrhythmic agents onisolated blood-perfused canine ventricular tissue

In the isolated blood-perfused canine ventricular tissue, antiarrhythmic agents could be classified as having: 1) positive chronotropic and inotropic effects (procainamide), 2) negative chronotropic but positive inotropic effects (quinidine), and 3) negative chronotropic and inotropic effects (lidocaine, ajmaline, diphenylhydantoin, and propranolol).

[The relations between lactation and cyclic-AMP -- The influences of adenyl cyclase activity on casein biosynthesis ability in the organ culture of the mouse mammary gland (author's transl)]

The relationships between hormonal action and cyclic AMP as the second messenger of hormones have recently been discussed on many hormones. Lactation is influenced by various hormone, especially, insulin, prolactin, and hydrocortisone. Whether adenyl cyclase activity in the mammary gland of mouse epithelial cells has parallel relations with casein biosynthesis ability or not was examined using the mammary gland organ culture method. Female, mid-pregnant (11-14 days), mice of DDY strain were used. Organ culture was done by the Chen's floating lens' paper method, using the hormone-added MEM media and non-added ones. Casein biosynthesis ability was measured by observing 32P incorporation into the casein molecules. Adenyl cyclase activity was estimated by the amount of 14-C-cyclic AMP produced out of adenine-8-14C by the Kuo and Krishna's method. Radio isotope compounds were pulsed for 4 hours in the medium. The experiments revealed that the added hormones had a remarkable effect on caein biosynthesis ability, but none on adenyl cyclase activity. No parallel fluctuation was observed between adenyl cyclase activity and casein biosynthesis ability, that is, the change of adenyl cyclase activity was found to have nothing to do with casein biosynthesis ability. Consequently, the cyclic AMP addition to the media showed no effect on casein biosynthesis ability.