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Biomedical subjects

F Takenaka

Publications and source records attributed to F Takenaka.

At least 37 records · Page 2Linked to original sources
PubMed1978

Comparison of myocardial and adipose tissue lipase activity in the rat.

Effects of catecholamines and iodoacetamide on lipase activity (pH 6.8) and triglyceride mobilization were investigated in adipose tissue, myocardial slice and isolated perfused heart preparation of the rat. Epinephrine and isoproterenol did not enhance myocardial lipase activity in vitro and in perfused hearts. No detectable amount of fatty acid was released from myocardial slice by epinephrine in vitro. Epinephrine, however, induced an increase in lipase activity and in the amount of fatty acid released from the adipose tissue. The results suggest a difference in properties of lipase present in the myocardium and in the adipose tissue. Iodoacetamide decreased lipase activity in vitro both in the myocardium and in the adipose tissue. Triglyceride content in the perfused heart receiving iodoacetamide at 30 min of perfusion was higher than that of the control. However, there was no correlation between triglyceride mobilization and lipase activity in these 2 tissues.

Adipose Tissue↗
PubMed1978

Effect of verapamil on the transmural energy metabolism in the isoproterenol-induced myocardial lesion.

The effect of verapamil on the isoproterenol (ISO)-induced transmural metabolic lesion in the left ventricular wall was investigated in the rat heart. The treatment with ISO 2.5 mg/Kg s.c. on 2 consecutive days resulted in significant decreases of creatine phosphate in the subendocardium (ENDO) and of adenosine triphosphate in the ENDO and the subepicardium. On the other hand, inorganic phosphate (Pi) and lactate (LA) were increased in both layers. These changes were more prominent in the ENDO. Pretreatment with verapamil 25 mg/Kg s.c. prevented the reduction of high energy phosphate compounds and the increases of Pi and LA in both layers by ISO.

Adenosine Triphosphate↗
PubMed1978

Effects of dobutamine on coronary circulation and cardiac metabolism of the dog.

Effects of (+/-)-4-[2-(3-p-hydroxyphenyl-1-methyl-amino)ethyl]pyrocatechol (dobutamine) on coronary circulation and cardiac metabolism were investigated using the heart in vivo and the isolated perfused heart of dogs. In the heart in vivo dobutamine 1--30 microgram/kg i.v. and 1--100 microgram i.c. produced dose-dependent increases in coronary perfusion pressure, coronary blood flow, heart rate and left intraventricular pressure. In the perfused heart dobutamine 10 microgram i.c. increased coronary flow, heart rate, cardiac contractility and myocardial oxygen consumption. Delta redox potentials decreased but did not show negative values. Propranolol 0.1 mg/kg i.v. and 0.1 mg i.c. inhibited these effects of dobutamine. Dobutamine shows basically the same actions as isoproterenol, but does not reduce the coronary perfusion pressure by the relatively high dose applied. The results suggest that dobutamine may have a selective adrenergic beta 1 receptor stimulating action on the heart and have a merit in maintaining the coronary perfusion pressure.

Animals↗
PubMed1978

Comparison of lactate pyruvate and potassium concentration in the cardiac lymph and, arterial and coronary sinus plasma in dogs.

Lactate (LA), pyruvate (PYR) and potassium (K) concentration in the cardiac lymph were compared with those in the arterial and coronary sinus plasma in dogs. In each substance, there was a good correlation between the plasma and cardiac lymph level in the control period. In respect to LA and PYR, the concentration in the cardiac lymph correlated more with that in the arterial plasma than in the coronary sinus one. During the infusion of isoproterenol, LA and PYR in the plasma increased, while K decreased. Each substance in the cardiac lymph changed to the same degree as in the plasma in mean values. Good correlation was also observed between the arterial plasma and cardiac lymph level during the administration of the agent. However, there was no correlation of PYR between the coronary sinus plasma and the cardiac lymph. During the administration of dipyridamole LA in the coronary sinus plasma increased and that in the arterial plasma decreased. LA in the cardiac lymph did decrease as in the arterial plasma. It is concluded that the concentrations of LA, PYR and K in the cardiac lymph can be changed depending upon changes in those in the plasma and the former two parameters seem to change depending upon those in the arterial plasma rather than the coronary sinus one.

Animals↗
PubMed1977

Activation of afferent cardiac sympathetic nerve fibers of the cat by pain producing substances and by noxious heat.

Afferent discharges of 64 single units were recorded from the left cardiac sympathetic nerve of anesthetized cats. Mechano-sensitive terminals of the afferent fibers were localized in the extrapulmonary part of the pulmonary artery, left atrium, left ventricle and left pericardium, as determined by direct mechanical probing of the heart after death of the animals. Conduction velocity of the fibers ranged from 2.5 to 14.6 m/s. Excitation of these Adelta-fibers with mechanically excitable endings was produced by intravenous injections of acetylcholine, 5-hydroxytryptamine, bradykinin, histamine and veratridine, and/or by topical application of these agents to the receptor region. Noxious heat to the mechanically excitable field in the wall of the pulmonary artery and the left ventricle also activated their afferent fibers. These observations provide evidence for a certain number of afferent units in the cardiac sympathetic nerve with polymodal sensitivity. These afferent fibers can provide the spinal cord with information not only on mechanical changes in cardiac events, but also changes in the chemical environment of the cardiac nerve ending, possibly produced by myocardial ischemia.

Acetylcholine↗
PubMed1977

Effects of increased cardiac mechanical performances on flow rates of cardiac lymph in dogs.

Relationship between flow rates of cardiac lymph (LF), and coronary blood flow (CF), coronary perfusion pressure (PP), left ventricular peak systolic pressure (LVSP) and heart rate (HR) was studied in open-chest dogs. Intra-coronary administration of catecholamines (CA) and electrical stimulation of the cardiac sympathetic nerve (ES) increased LF transiently with a concomitant rise in the cardiac mechanical performance, while dipyridamole induced no change in LF in spite of a marked increase in CF. Isoproterenol at does of 0.3 and 3x10(8) g/kg induced an increasein LF to 119 +/- 4 and 167 +/- 20% (mean +/- SE); norepinephrine, 0.3 and 3 X 10(7) g/kg, to 118 +/- r and 141 +/- 13%; ES AT 5 and 20 Hz, to 135 +/- 11 and 167 +/- 10%, respectively. Peak responses of LF correlated with changes in LVSP (R = 0.59, N l1,P less than 0.001), CF Tr = 0.53, n = 51, P less than 0.001), PP (r = 0.49, n = 51, P less than 0.001) but not with changes in HR (r = 0.27, n = 51, 0.05 less than P less than 0.10). Cardiac pacing also showed a poor correlation between the changes in LF and HR under the same LVSP within the changes in HR up to 134% of control value (r = -0.12, n = 17, P GREATER THAN 0.50). It is concluded that LF is independent of changes in HR, and increased LF after CA or ES may be caused mainly by an augmented propulsive force.

Animals↗
PubMed1977

Effects of dihydroergotamine methanesulfonate on the microcirculation of the rat cremaster muscle.

Effects of dihydroergotamine on the microcirculation of the rat cremaster muscle were investigated microscopically using colour photographic technique. 1. Dihydroergotamine 10(-4) g/ml constricted arterioles of the rat cremaster. 2. Dihydroergotamine 10(-4) g/ml produced a significant contraction of venules. 3. Dihydroergotamine 10(-4) g/ml markedly inhibited the contractile response of noradrenaline 10(-6) g/ml on arterioles of the rat cremaster. The results suggest that dihydroergotamine has an appreciable vasoconstrictive action, especially upon venules, and that dihydroergotamine also has an adrenergic alpha-receptor blocking action. By means of highly sensitive negative colour film we obtained a satisfactory photograph of the rat cremaster's circulation.

Animals↗
PubMed1977

Electrical activity of sinoatrial node cells of the rabbit surviving a long exposure to cold Tyrode's solution.

The right atrium including the sinoatrial node was excised from the rabbit heart, immersed in Tyrode's solution, and kept at 0-3 degrees C for several days. The tissue then was warmed to 36-37 degrees C in well oxygenated Tyrode's solution. Transmembrane potentials from cells in the sinoatrial node region and the right atrium were recorded with microelectrodes. After 3 days of storage, the maximum diastolic potential of cells in the sinoatrial node region decreased, but the configuration of the action potential was identical to that of the pacemaker pacemaker potential in the fresh preparation. After 5-7 days of storage, the sinoatrial node tissues in some preparations showed well preserved membrane potentials and pacemaker activity, while in others, the cells were electrically quiescent, or showed subthreshold oscillatory potentials of low amplitude. Transmembrane potentials could not be recorded from the right atrial tissue after storage for this period. Sinoatrial node action potentials with normal configuration were recorded from preparations stored for longer than 10 days. The sinoatrial cells in these preparations responded well to norepinephrine and acetylcholine, indicating that the reactivity of receptors was well preserved. The results provide electrophysiological evidence that cells in the sinoatrial node region can withstand long exposure to cold and retain their sensitivity to neuromediator action, but atrial myocardial cells cannot.

Acetylcholine↗
PubMed1977

Effects of diltiazem on high-energy phosphate contents reduced by isoproterenol in rat myocardium.

Effects of diltiazem on myocardial high-energy phosphate metabolism as well as on arterial blood pressure and heart rate were investigated in the rat treated with isoproterenol. Pretreatment with diltiazem prevented the reduction in both adenosine triphosphate and creatine phosphate induced by 2.5 mg/kg of isoproterenol. The ratio of creatine phosphate/inorganic phosphate in the rat receiving 100 mg/kg of diltiazem was higher than in the control. Heart rate was significantly decreased by the administration of 100 mg/kg of diltiazem not only in the non-pretreated rat but also in the rat given isoproterenol. This may partly account for the protective effect of diltiazem against the breakdown of high-energy phosphate in the isoproterenol-treated rat.

Adenosine Triphosphate↗
PubMed1976

Effects of propranolo, itramin tosylate and dipyridamole on myocardial phosphate metabolism in anoxic perfused rat hearts.

Effects of propranolo, itramin tosylate and dipyridamole on coronary flow, cardiac activity and phosphate metabolism were investigated in anoxic perfused rat hearts. During anoxia, heart contractions showed a transient increase followed by gradual declines in amplitude and frequency, while ATP and creatine phosphate (CP) contents strikingly decreased accompanying a pronounced increase in inorganic phosphate (Pi). Propranolol added to the anoxic perfusate attenuated the decrease in CP and increase in Pi, whereas heart contractions wre more markedly depressed than by anoxia alone. Similar effects were also seen in electrically paced anoxic hearts. Itramin decreased ATP contents in non-paced anoxic hearts, but did not in paced ones. Dipyridamole did not produce any significant effect on phosphate metabolism in anoxic myocardium. It was considered that propranolol prevented the anoxia-induced reduction in high-energy phosphates by antagonizing catecholamines released by anoxia and that itramin decreased ATP level by inhibiting ATP generation.

Adrenergic beta-Antagonists↗
PubMed1976

Possible mechanisms involved in the coronary vasodilatory response to dopamine.

Dopamine increased coronary blood flow in the dog heart pretreated with alpha-adrenoceptor blocking agents. The coronary vasodilator response was completely inhibited by indomethacin when pretreated with propranolol in addition to alpha blockade. The coronary vasodilation exerted by sodium nitrite was potentiated by indomethacin and adrenergic blockade. In coronary arterial strips, dopamine produced a contraction which was abolished by phenoxybenzamine. Dopamine elicited a dose-dependent relaxation in coronary arterial strips contracted previously by KC1 after pretreatment with phenoxybenzamine. The relaxation was potentiated by indomethacin; this effect was completely blocked by propranolol. Prostaglandin (PG)E1 produced a relaxing response but reduced the dopamine-induced relaxation. From the results it is suggested that beta-adrenoceptor stimulation and release of PG were involved in the coronary vasodilator response to dopamine. PG released by dopamine may increase coronary blood flow on the one hand and reduce beta-adrenoceptor stimulation by inhibiting adenyl cyclase on the other.

Adrenergic alpha-Antagonists↗
PubMed1976

Effects of iodoacetate and anoxia on phosphate metabolism in isolated perfused rat hearts.

When perfused with a solution equilibrated with 95% N2 and 5% CO2, the isolated rat heart was gradually depressed but continued to beat for longer than 30 min. Creatine phosphate content strikingly decreased, but lactate content was markedly elevated. When perfused with a fully oxygenated solution containing 0.5 mM of sodium iodoacetate (IAA) of the myocardial contractile force was almost unaltered and the heart rate decreased slightly within 10 min. Thereafter, the heart rate rapidly decreased, and soon cardiac arrest followed. Myocardial content of high-energy phosphates still remained at a considerably high level. The heart arrested by IAA responded to electrical stimulation, contracted and high-energy phosphates were well utilized. Addition of lactate to an oxygenated perfusate containing IAA improved myocardial performance. Citrate and palmitate did not restore the IAA-treated cardiac impairment. The results show that IAA disturbed cardiac conduction more markedly than contractility by blocking cytoplasmic glycolysis and that lactate, unlike citrate and palmitate, produced enough energy to recover cardiac activities in IAA-treated hearts.

Animals↗