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Biomedical subjects

K Ikegami

Publications and source records attributed to K Ikegami.

At least 109 records · Page 6Linked to original sources
PubMed1982

Effects of acetylcholine on the tone and miniature contractions of isolated dog urinary bladder.

Effects of acetylcholine on the tone and miniature contractions of dog urinary bladder were investigated in vitro. In both dome and trigone preparations, cumulative administrations of acetylcholine produced dose-dependent increases in the tone, which were dose-dependently depressed by prior administration of atropine and augmented by neostigmine. The frequency of miniature contractions in the dome and trigone was dose-dependently increased by acetylcholine. The dose-response curves of the frequency for acetylcholine were shifted to the right by atropine and to the left by neostigmine in both preparations. The amplitude of miniature contractions in both preparations was not significantly changed by acetylcholine. A computer analysis showed that changes in the tone of the bladder had the positive correlation to the frequency of miniature contractions. The results indicate that acetylcholine would act on the urinary bladder through activation of muscarinic receptors, and that there is the positive correlation between changes in the tone and the frequency of miniature contractions.

Acetylcholine↗
PubMed1982

Effects of adrenergic drugs on miniature contractions of isolated dog urinary bladder.

Isolated dog urinary bladder showed spontaneous miniature contractions under a steady state. In dome preparations, norepinephrine and isoproterenol decreased the frequency of miniature contractions, while epinephrine produced biphasic responses on it; increase by low concentration and decrease by high concentrations. The height of miniature contractions was decreased by these drugs. In trigone preparations, norepinephrine and epinephrine increased the frequency of miniature contractions, while isoproterenol decreased it. These drugs decreased the height of miniature contractions. In both preparations, phentolamine enhanced the decreases in frequency and height by norepinephrine, epinephrine and isoproterenol, while propranolol depressed or reversed them. A computer analysis showed positive and significant correlations between changes in tension development of bladder and frequency and height of miniature contractions. Results indicate that miniature contractions in both dome and trigone of isolated dog urinary bladder are increased by activation of alpha-adrenoceptors and decreased by activation of beta-adrenoceptors.

Animals↗
PubMed1982

A possible mechanism involved in generation of automaticity of isolated human renal artery.

A possible mechanism involved in generation of automaticity of isolated human renal arteries was investigated qualitatively. Helical strips of human renal arteries showed rapid contractions followed by marked oscillations in the tension by administrations of vasoconstrictor agents such as norepinephrine, epinephrine, dopamine and 5-HT. Vasodilator agents such as acetylcholine and isoproterenol did not produce any change in these strips, but high doses of acetylcholine and isoproterenol evoked marked oscillations together with increases in the vascular tone. Prostaglandins E1, E2 and F2 alpha increased the vascular tone of the renal arterial strips, and generated marked oscillations in their contractions which were inhibited by aspirin or indomethacin. Two renal arterial strips showed marked oscillations in the tension by passive elevation of the basal tone of the strips. The marked oscillations did not appear when indomethacin was previously administered. The results indicate that mechanical stimulation of renal arterial smooth muscle, such as contractions, may induce enhancement of endogenous prostaglandin biosynthesis, resulting in generation of automaticity of isolated human renal arteries.

Acetylcholine↗
PubMed1981

Intrarenal prostaglandins E2 and F2 alpha in experimental renovascular hypertension.

To study the role of renal prostaglandins (PGs) in renovascular hypertension, PGE2 and PGF2 alpha concentrations in both inner and outer medullae of the kidney were measured by radioimmunoassay in rabbits with hypertension produced by left renal artery constriction. In the acute phase, a week after surgery, PGE2 in the inner and outer medullae and PGF2 alpha in the inner medulla were significantly increased in both the constricted and opposite kidneys (p less than 0.01). In chronic phase, 5 weeks after surgery, PGs returned to normal concentrations with the exceptions of PGE2 in the outer medulla and PGF2 alpha in the inner medulla of the constricted kidney. These results suggest that increased renal PGs may not be the cause of hypertension but a defensive reaction to renal ischemia, hypertension and sodium load.

Animals↗
PubMed1981

Effects of some autonomic drugs on the isolated human minor calyx.

The effects of some autonomic drugs on the isolated human minor calyceal strips were investigated quantitatively. Norepinephrine, epinephrine and phenylephrine dose dependently increased the basal tone and the frequency of spontaneous contractions and decreased their amplitudes, which were depressed by phentolamine. Acetylcholine at high doses increased the basal tone and decreased the amplitude, which were depressed by atropine without changing the frequency. These findings indicate the existence of alpha-adrenoceptors and muscarinic receptors in the human minor calyceal smooth muscles.

Acetylcholine↗
PubMed1981

Actions of some autonomic drugs on isolated dog quiescent ureter.

Actions of some autonomic drugs on upper, middle and lower portion of isolated dog ureters under quiescent state were investigated quantitatively. Noradrenaline and adrenaline at lower concentrations evoked contractions in each portion of the ureters and increased the concentration-dependent frequency and tension of these contractions, but attenuated them at higher concentrations. Phentolamine significantly depressed these contractions, while propranolol enhanced them. Phenylephrine increased the concentration-dependent frequency and tension of contractions, which were suppressed by phentolamine. Acetylcholine at higher concentrations produced contractions of the ureters, and phentolamine or hexamethonium suppressed them. The results indicate that ureteral contractions may be stimulated through an activation of alpha-adrenoceptors and be attenuated through an activation of beta-adrenoceptors, and that acetylcholine may release noradrenaline from sympathetic nerve endings through an activation of presynaptic nicotinic receptors, resulting in ureteral contractions.

Animals↗
PubMed1981

Further investigations on potassium-induced automaticity of isolated human renal artery.

Experiments were designed to investigate generation of automaticity of isolated human renal arteries induced by administration of potassium in vitro. Helical strips of human renal arteries showed marked oscillations in the potassium-induced contractions which persisted for 2 hr. Indomethacin and aspirin dose-dependently inhibited these oscillations. Tranylcypromine and mepacrine also had an inhibitory action on the oscillations of the strips induced by potassium. In the strips which reached a steady state 2 hr after administration of potassium, phospholipase A2 and bradykinin produced marked oscillations. Our results indicate that human renal arteries can generate automaticity in the contractions induced by potassium, and that such automaticity may be related to the biosynthesis of prostaglandins.

Adult↗
PubMed1980

Simple pelvic arteriography using a disposable elastic vein needle.

A new method for pelvic arteriography using a disposable elastic vein needle is presented. The technique is carried out by percutaneous transfemoral artery puncture and contrast medium is injected by a power air-driven injector which makes bilateral pelvic arteriography possible. Neither a radioopaque long catheter nor a guide wire are necessary in the present method. No major complications have been observed in a series of 162 cases. The present method is advantageous due to its simplicity and safety compared with ordinary Seldinger's method which is not always free of complications.

Angiography↗
PubMed1979

Effects of prostaglandin E1 on isolated dog renal artery.

Actions of prostaglandin (PG) E1 were investigated using isolated dog renal arterial strips. Norepinephrine increased the tension of the renal arterial strips contracted with potassium, and this response was depressed by phentolamine. Isoproterenol produced relaxant effects on these arteries, and this response was converted to contractile one by propranolol. Diltiazem dose dependently relaxed the potassium-contracted strips. PGE1 (10(-9)-3 X 10(-8) Gm./ml.) constricted the renal arterial strips, while in higher concentrations (10(-7)-3 x 10(-7) Gm./ml.) it caused relaxations of them. Contractile responses by PGE1 were not affected by phentolamine or phenoxybenzamine, but were suppressed by diltiazem. On the other hand, relaxant effects of PGE1 were not changed by propranolol. Papaverine or theophylline significantly inhibited the contractions induced by PGE1. From these results it is suggested that (1) in the dog renal artery adrenergic alpha-receptors must be more dominant than beta-receptors; (2) PGE1 will produce a depolarization of renal arterial smooth muscle and/or increase an active transport of calcium ions into smooth muscle cells; and (3) the relaxant responses by PGE1 may be related to an increase in cellular cyclic adenosine monophosphate (AMP) contents.

Animals↗
PubMed1979

Intrarenal prostaglandins: effect of sodium and indomethacin on PGE2 and PGF2 alpha in rabbits.

The levels of prostaglandins (PGs) E2 and F2 alpha in different parts of the rabbit kidney were determined to observe the effect of sodium and indomethacin. After the pretreatment with injections of saline or with indomethacin, tissues from inner and outer medulla and cortex were separated, extracted, analyzed for PGE2 and PGF2 alpha by radioimmunoassay. In the normal rabbit kidney, the greatest amount of PG was found in the inner medulla. Saline injections appeared to increase PGE2 (but not PGF2 alpha), especially in the inner medulla. Repeated injections of saline, on the other hand, markedly reduced PGE2 in the inner medulla but increased outer medullary PGE2. Indomethacin reduced the production of PGs in all kidney segments. These results suggest the bidirectional effect of sodium on PG concentration in the rabbit kidney. Acute administration of sodium may directly stimulate the synthesis of PGE2 in the inner medulla but chronic stimulation with sodium may alter the pattern of PGE2 synthesis.

Animals↗
PubMed1979

Studies on intrarenal prostaglandins. Effect of unilateral renal artery constriction on lipid droplets in the medullary interstitial cells of the 'opposite' kidney in rabbits.

The unilateral renal artery in rabbits was constricted, and lipid droplet count in the medullary interstitial cells of the 'opposite' kidney was performed 1 week after surgery. Lipid droplet count in hypertensive rabbits was less than that in both nonhypertensive and normal rabbits and was inversely proportional to the mean blood pressure. Lipid droplet count was significantly correlated with the juxtaglomerular granulation index and the sodium content in the inner medulla. The present results suggest that, in the opposite kidney of rabbits hypertensive due to unilateral constriction of the renal artery, the enhanced release of prostaglandins and the washout of solute in the renal medulla may be induced as a response to increased perfusion pressure and elevated circulating angiotensin.

Animals↗
PubMed1979

Studies on intraarenal prostaglandins. Influence of unilateral ureteral obstruction on prostaglandins E2 and F2 alpha in the rabbit kidney.

Prostaglandins (PGs) E2 and F2 alpha in the rabbit kidney were determined by radioimmunoassay to study the effects of unilateral ureteral obstruction on intrarenal PGs. An increase of PGE2 in the inner medulla was observed in the hydronephrotic kidney. When isotonic glucose solution was infused after the release of ureteral obstruction, an elevation of PGE2 in the outer medulla occurred in the hydronephrotic kidney. Under water diuresis immediately following the release of obstruction, PGE2 in the inner medulla showed significant correlations to urinary flow rate, urinary osmolar concentration and free water clearance. The present study indicates that PGE2 in the inner medulla is enhanced by ureteral obstruction and may have a close relation to renal functional damage in mild hydronephrosis.

Animals↗