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Biomedical subjects

H Iwao

Publications and source records attributed to H Iwao.

At least 127 records · Page 7Linked to original sources
PubMed1990

Effects of cromakalim, a potassium channel opener, on regional blood flow in conscious spontaneously hypertensive rats.

We studied the effects of cromakalim, a potassium channel opener, on regional blood flow in conscious spontaneously hypertensive rats using microspheres. Cromakalim produced significant hypotension and increased blood flow in the stomach, skeletal muscle and skin. Calculated vascular resistances decreased in many organ vascular beds. Although nifedipine also showed a similar hemodynamic profile, differences were observed in the brain, gastrointestinal tract and skin.

Animals↗
PubMed1990

Endogenous angiotensin II regulates hepatic angiotensinogen production.

We have investigated the effects of endogenous angiotensin II (ANG II) on hepatic angiotensinogen mRNA levels in rats. Changes in endogenous ANG II were induced by various sodium intakes (standard-, low-, and high-sodium) or by enalapril treatment. In a low sodium state for 2 weeks, angiotensinogen mRNA levels and plasma ANG II concentration increased 1.3-fold and 1.6-fold compared to those in standard sodium state, respectively. In a high sodium state, angiotensinogen mRNA levels and plasma ANG II concentration decreased by 42% and 56% compared to the standard sodierm state, respectively. Four hours after treatment with enalapril (3 mg/kg), angiotensinogen mRNA level and plasma ANG II concentration decreased by 25% and 12% compared to the standard sodium state, respectively. There was a close correlation between angiotensinogen mRNA level and plasma ANG II concentration (r = 0.79, P less than 0.01). These results suggest that endogenous ANG II may play an important role in the regulation of hepatic angiotensinogen synthesis.

Angiotensin II↗
PubMed1990

Effect of angiotensin II on angiotensinogen production in adrenalectomized rats.

The present study was performed to examine the effect of angiotensin II on hepatic angiotensinogen production in adrenalectomized rats. The hepatic angiotensinogen mRNA levels in rats without adrenal glands increased 2.8-fold 4 h after the start of angiotensin II infusion. In intact rats with adrenal glands, the hepatic angiotensinogen mRNA levels increased 2.7-fold 4 h after the start. The angiotensin II infusions did not only increase angiotensinogen mRNA levels in intact rats but also increased those in adrenalectomized rats. The results suggest that the angiotensinogen response to ANG II was not dependent on adrenal glucocorticoid.

Adrenalectomy↗
PubMed1990

Regulation of liver angiotensinogen and kidney renin mRNA levels by angiotensin II.

The current study was designed to evaluate the role of angiotesin II (ANG II) in the regulation of renin mRNA and angiotensinogen mRNA levels. We investigated the changes in renin mRNA levels in the kidney and angiotensinogen mRNA levels in the liver induced by ANG II infusion and by inhibition of the endogenous renin-angiotensin system with enalapril or saralasin in rats. mRNAs for angiotensinogen and renin were measured by densitometric analysis of Northern blot hybridization. After a 4-h intravenous infusion of ANG II (0.2 micrograms.kg-1.min-1), angiotensinogen mRNA level in the liver increased 2.5-fold to the control level, and renin mRNA level in the kidney decreased by 45%. Four hours after treatment with a single dose of enalapril (3 mg/kg po), angiotensinogen mRNA level in the liver decreased by 50%, and renin mRNA level in the kidney increased 1.5-fold to the control level. These mRNA levels returned to control levels 8 h after treatment. After a 4-h infusion of saralasin (2.5 micrograms.kg-1.min-1) in the low-sodium state, angiotensinogen mRNA level in the liver decreased by 45%, and renin mRNA level in the kidney increased twofold to the control level. These findings suggest that ANG II is one of the factors that regulate angiotensinogen mRNA level in the liver and renin mRNA level in the kidney.

Angiotensin II↗
PubMed1990

Elevated angiotensinogen mRNA levels in rat liver by nephrectomy.

The expression of the angiotensinogen gene was studied in nephrectomized rats with and without adrenal glands. Angiotensinogen mRNA was measured by a sensitive radiodensitometric hybridization assay. Angiotensinogen mRNA levels in the liver increased 5 times by nephrectomy alone and 2.6 times by nephrectomy with adrenalectomy in acute experiments. Brain mRNA levels remained the same in both groups. When nephrectomy was performed 7 days after adrenalectomy, mRNA level increased by 50%. Angiotensinogen mRNA increased 5 times in the liver and 2.3 times in the brain by the administration of dexamethasone. An additive effect on liver angiotensinogen mRNA level was observed in nephrectomy with dexamethasone treatment. These results suggest that in nephrectomy, a synergetic action of glucocorticoids and other unknown factors increase hepatic angiotensinogen mRNA levels.

Adrenalectomy↗
PubMed1990

Effects of thyroid hormone on angiotensinogen and renin messenger RNA levels in rats.

We studied the expression of angiotensinogen and renin genes in rats treated with 3,3',5-triiodo-L-thyronine (T3) at doses of 0.1 and 1 mg/kg of body weight. Liver angiotensinogen mRNA increased by 2 to 3 times 8 to 12 hours after T3-treatment. This increase was dose-related. Plasma angiotensinogen concentration (PAC) increased 12 hours after T3-treatment. Brain and renal angiotensinogen mRNA levels and the renal renin mRNA level remained the same throughout the experimental periods. These results suggest that the thyroid hormone initially increases angiotensinogen mRNA and leads to an increase in the production of angiotensinogen in the liver followed by an elevation of PAC.

Angiotensinogen↗
PubMed1990

Intrarenal vascular sites of action of adenosine and glucagon.

Our purpose was to localize the intrarenal vascular sites of action of adenosine and glucagon. Renal blood flow (RBF) and glomerular filtration rate (GFR) were measured in anesthetized dogs, and renal perfusion pressure (RPP) was varied by an adjustable aortic clamp. At normal RPP, RBF was increased by all agents. In contrast, GFR was increased by glucagon, decreased by adenosine and unchanged by acetylcholine (ACh) or adenosine plus glucagon. The increases in RBF by glucagon occurred only at RPPs within the autoregulatory pressure range, and renal autoregulatory capability was attenuated during the infusion of glucagon. In contrast, adenosine increased RBF at RPPs both within and below the autoregulatory pressure range, and the autoregulatory capability was not perceptibly impaired. Superimposition of glucagon to adenosine caused further vasodilation, and the autoregulatory efficiency was completely attenuated. There was no difference between the RPP-RBF or RPP-GFR relations obtained during infusion of adenosine plus glucagon and ACh, which dilates both the afferent and efferent arterioles. It is generally accepted that afferent arteriolar resistance attains a minimum value at RPP near the lower limit of the autoregulatory range. Thus, our data indicate that glucagon and adenosine preferentially dilate the afferent arteriole and the efferent arteriole, respectively.

Adenosine↗
PubMed1990

[Surgical repair of total anomalous pulmonary venous connection in neonates and infants--prevention for pulmonary venous obstruction at the site of anastomosis].

From October, 1980, to June, 1987, thirty-eight infants less than one year old underwent correction for total anomalous pulmonary venous connection (TAPVC). Overall operative mortality and late mortality were 13% and 6%, respectively. Residual pulmonary hypertension was noted in 4 patients: three had pulmonary venous obstruction at the site of atrial anastomosis (PVOA) and one had supracardiac (Ia) lesion left after repair of mixed type (IV: Ia + III) of TAPVC. Two late deaths occurred in these with PVOA. Twenty-two patients with supracardiac (I) or infracardiac (III) TAPVC were divided into three groups according to the technical development in atrial anastomosis: the large anastomosis in which venous incision reached into at least one pulmonary vein beyond common pulmonary vein and the continuous running suture were used in 10 patients (group 1), the appropriate size of anastomosis in which venous incision limited within the common pulmonary vein and the continuous running suture used in 4 patients (group 2), and the appropriate size of anastomosis and the interrupted suture in 8 patients (group 3). PVOA were 3 (33%) in group 1, but 0 (0%) in group 2 and 3. Two late death occurred all in group 1 with PVOA. Cardiopulmonary bypass time and aortic clamp time in group 3 were 91 min and 74 min respectively, which did not become longer than those in both group 1 and group 2. Interrupted suture technique does not make operating time longer than continuous running suture one. PVOA is one of the important factors predicting late operative result.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1990

[Evaluation of left ventricular function after Jatene's operation for transposition of the great arteries--influence of age at repair].

The postoperative left ventricular function (LV) of Jatene's operation for transposition of the great arteries (TGA) was evaluated by angiocardiography and echocardiography in 39 patients. In 16 patients repaired at less than 3 months of age, left ventricular endodiastolic volume (LVEDV) was significantly decreased at the angiography 2 months after repair: form 215 +/- 685% normal of preoperative LVEDV to 120 +/- 14% normal postoperatively (p less than 0.05) in 7 patients with simple TGA (Group IA), and from 220 +/- 64% normal to 130 +/- 33% normal (p less than 0.05) in 8 patients associated with ventricular septal defect (Group IIA). On the other hand, among 24 patients repaired at 3 or more months of age, 19 patients with simple TGA (Group IB) showed the significant increase of LVEDV (from 159 +/- 40% normal to 183 +/- 23% normal, p less than 0.05), and 5 patients associated with ventricular septal defect (Group IIB) showed no remarkable change (from 208 +/- 96% normal to 193 +/- 23% normal). There was no significant difference of postoperative pulmonary artery (PA) wedge pressure among the four groups. Postoperative left ventricular diastolic dimension (LVDd) revealed the tendency of normalization in all groups during the first postoperative year. Group IA and IIA completed the normalization of LVDd in 2 months and Group IIB in 6 months after the repair. However, LVDd in Group IB could not decrease to normal range even in 12 months after repair. There was a significant correlation between postoperative LVDd and the age at PA banding in 14 patients of Group IB, who had the preparatory PA banding for LV training.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

Renal hemodynamic responses to 5-hydroxytryptamine (5-HT): involvement of the 5-HT receptor subtypes in the canine kidney.

The study was designed to define the serotonin (5-HT) receptor subtypes in the canine kidney. An intrarenal infusion of 5-HT at a dose of 5 micrograms/min in anesthetized dogs resulted in a biphasic response of renal blood flow which decreased transiently then increased above the control level during prolonged infusion. The decrease of renal blood flow was abolished by infusion of methysergide but not by ketanserin, and the subsequent increase was abolished by infusion of either ketanserin or methysergide. Terazosin, an alpha1-adrenoceptor antagonist, did not modify the renal action of 5-HT. These findings suggest that the renal blood flow response induced by 5-HT did not depend on an indirect effect via the sympathetic nervous system, the initial vasoconstriction was mediated via a 5-HT1-like receptor, and that the latter vasodilatation was mediated via a 5-HT2 receptor. The infusion of 5-HT also increased urine flow and urinary excretion of sodium. These increases were reversed by pretreatment with ketanserin and abolished by methysergide. We propose that 5-HT may exert its antidiuretic action via a 5-HT1-like receptor in the tubules but that the renal hemodynamic changes induced by 5-HT may overcome its antidiuretic action. The present results suggest the existence of a 5-HT1-like and 5-HT2 receptor in the renal vasculature and a 5-HT1-like receptor in the renal tubules.

Adrenergic alpha-Antagonists↗
PubMed1989

Captopril and hydralazine suppress atrial natriuretic peptide (ANP) gene expression in the ventricles of spontaneously hypertensive rat.

We investigated the influences of captopril (CAP) and hydralazine (HYD) on the ANP mRNA level in the hypertrophied left ventricle (LV) of spontaneously hypertensive rats (SHR). Male SHRs (16 weeks of age) were given CAP (35 mg/kg/day) or HYD (3.5 mg/kg/day) for two weeks. Both drugs reduced blood pressure by a similar magnitude. Treatment with CAP caused a reduction in the ANP mRNA level in LV by 62%, and a reduction in the weight of the LV. The ANP mRNA level in LV of the HYD-treated rats was also decreased, but only by 31%. HYD did not affect LV hypertrophy. ANP gene expression in LV of SHR might be effectively suppressed by a reduction of blood pressure and also by the concomitant attenuation of hypertrophy.

Animals↗
PubMed1989

[Current status of Jatene's operation].

The current status of Jatene's operation for transposition of the great arteries was described by showing the analysis of our results of an arterial switch operation addition to the review of the literatures. The arterial switch operation recently has become the operation of first choice because of its low surgical mortality (4.5% in author's series) and low incidence of postoperative complication. Surgical techniques to avoid complications such as postoperative bleeding, kinking of the transplanted coronary arteries, aortic valve insufficiency and pulmonary arterial stenosis were presented. One-stage anatomic correction has been performed with low mortality less than 10% in centers dealing high volumes of neonatal surgery (7% in author's series). One-stage correction in the neonate is advocated in views of its low surgical mortality and excellent postoperative left ventricular function.

Aorta↗
PubMed1989

[Total repair of complete atrioventricular canal: relationship between age at operation and late results].

Twenty five consecutive patients with complete atrioventricular canal (CAVC) underwent one-stage operation from April 1981 to Aug. 1987. Average ages at operation was 18 months (2 to 72) and average weight was 7.0 kg (2.8 to 13.8). Fifteen patients were infants and fifteen had Down syndrome. Conventional cardiopulmonary bypass with pulsatile bypass pump (PBP) and moderate hypothermia at 28 degrees C was utilized in all patients. Single patch technique (SPT) was adopted for initial five patients and two patch technique for the latter twenties. Two patients died perioperatively (operative mortality 8.0%), one of whom from mitral stenosis after SPT and the other from misdiagnosis of large subpulmonary VSD. There was no hospital death. Mean pulmonary artery pressure (mPA), pulmonary systolic pressure to systemic systolic pressure ratio (Pp/Ps) and pulmonary vascular resistance index (PVRI) were decreased remarkably from preoperative values of 56 +/- 14 mmHg, 0.92 +/- 0.13 and 6.2 +/- 4.9 WU.m2 to postoperative of 31 +/- 16 mmHg (p less than 0.001), 0.54 +/- 0.20 (p less than 0.001) and 4.6 +/- 4.0 WU.m2 (NS), respectively. Six patients had residual pulmonary hypertension in which mPA was more than 40 mmHg. One patient who was complicated with severe mitral regurgitation due to dehiscence of suture line and torn chordae had mitral valve replacement. Mean follow-up period was 26 months (5 to 63). The mean weights of 67%N at operation catched up with 87%N 3 years after operation. There were two late deaths, 4 and 20 months after operation between age at operation, both of whom had residual pulmonary hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1989

Arterial switch operation for transposition of the great arteries, with special reference to left ventricular function.

Between June 1984 and September 1987, 48 patients underwent Lecompte's modification of the arterial switch operation for transposition of the great arteries, including transposition with intact ventricular septum with preparatory pulmonary artery banding (n = 18), with patent ductus arteriosus (n = 11), with dynamic left ventricular outflow tract obstruction (n = 4), and transposition with ventricular septal defect (n = 15). Ages ranged from 12 days to 36 months (mean 8 months) and weights ranged from 2.7 to 12.8 kg (mean 5.7 kg). Two deaths occurred, yielding an operative mortality rate of 4.2%. Preparatory pulmonary artery banding resulted in an increase to 65 +/- 5 mm Hg in the left ventricular afterload. Linear regression of the optimum circumference of the band (Y, millimeters) against left ventricular end-diastolic volume (X, milliliters) yielded the following formula: Y = 0.23X + 19.7 (r = 0.885, p less than 0.001). Influence of left ventricular mass on cardiac function after anatomic correction was evaluated. The total amount of dopamine used after repair in patients in whom the left ventricular mass was less than 60% of normal was significantly larger than that in patients with a left ventricular mass greater than or equal to 60% of normal (p less than 0.002). The left ventricular end-diastolic volume in patients with a left ventricular mass less than 60% of normal increased significantly 2 months after operation (p less than 0.05), whereas it decreased in patients with a left ventricular mass greater than 60% of normal (p less than 0.01). We believe it is safe to perform this procedure in patients in whom the left ventricular mass is larger than 60% of normal. Most newborn infants with simple transposition can undergo correction between 10 and 20 days of life if the ductus arteriosus is kept patent with prostaglandin E1 and the left ventricle is thereby loaded. Preparatory pulmonary artery banding, when necessary, will be satisfactory if the left ventricular pressure is greater than 65 mm Hg and/or the left ventricular/right ventricular pressure ratio is greater than 0.8.

Aorta↗
PubMed1989

[Anatomic correction of transposition of the great arteries].

The present status of the surgical treatment of transposition of the great arteries was described by showing the analysis of our results of an arterial switch operation in addition to the review of the literatures. The arterial switch operation recently has become the operation of first choice because of its low surgical mortality (author 4.5%) and low incidence of postoperative complication. One-stage anatomic correction has been performed with low mortality less than 10% in centers dealing high volumes of neonatal surgery (author: 7%). One-stage correction is preferable and it can be accomplished with the cooperative treatment plan of surgeon and pediatrician, starting immediately after birth.

Humans↗
PubMed1988

Calcitonin gene-related peptide(CGRP) stimulates the release of atrial natriuretic peptide(ANP) from isolated rat atria.

The effect of calcitonin gene-related peptide(CGRP) on the release of atrial natriuretic peptide(ANP) was studied in spontaneously beating, isolated rat atria. CGRP stimulated the ANP release in a dose-dependent manner. When the atria were incubated with a combination of phentolamine, propranolol, and atropine, these antagonists blocked neither the rise in ANP release nor the positive chronotropic and inotropic effects of CGRP. Therefore, we conclude that CGRP stimulates ANP release as well as cardiac contractility independently of adrenergic and cholinergic receptors.

Animals↗