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Biomedical subjects

A Takao

Publications and source records attributed to A Takao.

At least 91 records · Page 5Linked to original sources
PubMed1990

Myocardial perfusion after aortic implantation for anomalous origin of the left coronary artery from the pulmonary artery.

Postoperative myocardial perfusion and function were evaluated using thallium-201 myocardial imaging and technetium-99m cardiac pool imaging in five patients with an anomalous left coronary artery arising from the pulmonary artery. The patients underwent reimplantation of the left coronary artery at an age ranging from 10 months to 13 years. Postoperative electrocardiographic and radionuclide studies were performed both at rest and during stress 1 to 4 years after the operation. Electrocardiograms which were abnormal preoperatively returned to normal after surgery except that the T wave in lead aVL remained negative. Postoperatively, left ventricular ejection fraction measured by technetium-99m cardiac pool imaging was normal in all patients. Postoperative thallium-201 myocardial imaging, however, showed a perfusion defect with incomplete redistribution at the high-lateral or antero-lateral segment in all patients after a stress test. These data suggest that although myocardial ischaemic change decreases and global cardiac function improves after establishment of a dual coronary artery system, severe myocardial damage remains at the high-lateral or antero-lateral segment.

Adolescent↗
PubMed1990

Fetal cardiovascular cross-sectional morphology of tetralogy of Fallot in rats.

In order to clarify cross-sectional morphology of tetralogy of Fallot in the fetus, 202 rat fetuses with tetralogy of Fallot induced by maternal administration of bis-diamine were studied using cesarean section, the whole body freezing method and by photographing cross sections of the fetal heart on a freezing microtome. Some characteristic features such as large subaortic ventricular septal defects, aortic overriding over the ventricular septum, aortomitral fibrous continuity, and narrow infundibulum and pulmonary valve were found. Moreover, three subtypes were noticed. In classic tetralogy of Fallot with stenotic infundibulum, the size of the pulmonary arteries was smaller in proportion to the infundibular stenosis. In the second type with absent infundibular septum and severe valvular pulmonary stenosis, the pulmonary arteries were most hypoplastic. In the third type with absent pulmonary valve, the pulmonary arteries were dilated forming aneurysms. In the last type only, ventricles were dilated and grossly hypertrophic.

Animals↗
PubMed1990

Ventricular volume characteristics in double-inlet left ventricle before and after septation.

Septation is one of the surgical choices for double-inlet left ventricle, yet postoperative hemodynamics have not been well defined. We studied ventricular volume characteristics in 10 patients with double-inlet left ventricle before and after septation. Preoperative end-diastolic volume (EDV) of the ventricle was 291 +/- 111% (+/- SD) of normal and ejection fraction (EF) was 0.59 +/- 0.07. Postoperatively, EDV of the right-sided ventricle (RV) was 82 +/- 24%, and EDV of the left-sided ventricle (LV) was 153 +/- 41%. Ejection fraction of the RV was 0.77 +/- 0.10, and LVEF was 0.49 +/- 0.13. On the short-axis view of two-dimensional echocardiography, fractional change of the cross-sectional area was 0.65 +/- 0.16 for the RV and 0.23 +/- 0.11 for the LV. Fractional shortening of the septum-to-ventricular free wall axis was 0.51 +/- 0.17 in the RV and -0.05 +/- 0.09 in the LV. Analysis of the curvature of the new septum during cardiac cycle on two-dimensional echocardiography revealed that the septum shifted to the right side during systole in all patients in whom the systolic LV/RV pressure ratio was larger than 1.0. The septum shifted toward the LV during diastole in eight patients in whom end-diastolic pressure in the RV was higher than or equal to that in the LV, whereas it remained in the right side in two patients with higher left-side pressure. The cardiac index of these two patients was 2.4 and 2.6 l/min/m2, respectively, whereas it averaged 4.4 +/- 1.0 l/min/m2 in the other eight patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Fetal cardiac morphology of tetralogy of Fallot with absent pulmonary valve in the rat.

Fetal in situ cardiovascular and bronchial morphologies were studied in rats with tetralogy of Fallot and absent pulmonary valve to clarify the prenatal pathology of this complex. There were 42 fetal rats with this complex among 300 fetuses treated with N,N'-bis-(dichloroacetyl)-1,8-octamethylenediamine (bis-diamine) (200 mg) on the 10th day of pregnancy. After undergoing rapid whole-body freezing on the 21st day, they were studied by means of serial cross-sectional photographs of the frozen thorax. Fetuses with normal heart treated with bis-diamine served as control. Tetralogy of Fallot and absent pulmonary valve in the fetus was associated with absence of the ductus arteriosus, enlargement and hypertrophy of both ventricles, and enlargement of the pulmonary arteries that compressed the bronchial trees. These abnormalities were inversely correlated with the degree of pulmonary stenosis. Milder stenosis (pulmonary valve ring greater than 50% of control, n = 28) was associated with larger pulmonary arteries (250 +/- 12% of control) (mean +/- SEM) and larger ventricles (volume, 200 +/- 15%; mass, 130 +/- 4%). Severe stenosis (pulmonary valve ring less than 50% of control, n = 14) was associated with mildly enlarged pulmonary arteries and mild bronchial compression. We concluded that enlargement of the pulmonary arteries and bronchial compression develop in fetal life and are associated with mild pulmonary stenosis in tetralogy of Fallot and absent pulmonary valve.

Animals↗
PubMed1990

Local response to cardiac overload on myosin heavy chain gene expression and isozyme transition.

It is uncertain whether the shift of cardiac myosin heavy chain (MHC) during pressure overload can be induced by some intrinsic factors or by the stress imposed directly on the individual myocytes. To study whether the changes in cardiac MHC gene expression produced by one-sided overload are limited to the involved ventricle or extend to the other ventricle, we examined MHC gene expression and isozyme transition in the left and right ventricles in aortic coarctated and pulmonary artery-banded rats. It has been confirmed that the pressure overload is indeed limited to the loaded ventricle. The results showed that, compared with sham-operated rats, there was no significant induction of the beta-MHC messenger RNA and corresponding protein in the unloaded ventricle, whereas significant induction was observed in the overloaded ventricle. These results demonstrated that the changes in MHC gene expression and isozyme produced by one-sided ventricular overload are limited to the involved ventricle. We conclude that the MHC gene regulation during hemodynamic overload may not be induced by intrinsic factors, such as hormones, catecholamine, or atrial natriuretic peptide, but is induced by direct local response to increased load.

Animals↗
PubMed1990

Effect of acidosis on intracellular pH and calcium concentration in the newborn and adult rabbit myocardium.

This study investigated developmental changes in the effect of acidosis on intracellular pH (pHi) and [Ca]i in the isolated heart and isolated myocyte preparations. The whole heart or myocytes of newborn (5-7 days old) and adult rabbits were loaded with the fluorescent pH indicator 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) or calcium indicator fura-2. Left ventricular pressure in the isolated heart preparation and the magnitude of cell contraction in the single-cell preparation were monitored. The heart and single cell were illuminated with excitation lights (340 and 380 nm, respectively, for fura-2 and 438 and 490 nm for BCECF). The intensity of fluorescence from the ventricular surface or from the cell was detected. [Ca]i was estimated from the following ratio: fluorescence at 505 nm during excitation at 340 nm/fluorescence at 505 nm during excitation at 380 nm. pHi was estimated from the following ratio: fluorescence at 530 nm during excitation at 490 nm/fluorescence at 530 nm during excitation at 438 nm. In the newborn, depression of contractile function during respiratory acidosis or metabolic acidosis was less than in the adult. Diastolic and systolic [Ca]i increased during respiratory acidosis in both the newborn and adult, and the net changes in [Ca]i were similar in the two age groups. During respiratory or metabolic acidosis, pHi decreased, but the decrease in the newborn was significantly less than in the adult. These data suggest that the greater resistance of the newborn myocardium to acidosis is due to the smaller change of pHi in this age group and not due to the difference in [Ca]i alteration.

Acidosis↗
PubMed1990

Effect of atrial natriuretic peptide on hemodynamics of the stage 21 chick embryo.

Atrial natriuretic peptide (ANP) is important in the modulation of hemodynamics and fluid balance in the mature subject, but its hemodynamic effects at early stages of morphogenesis are not defined. We studied the effect of rat atriopeptin III on hemodynamics in chick embryos at Hamburger-Hamilton stage 21. The cardiovascular system is not yet innervated, nor is the kidney formed in these embryos. The vitelline arterial and venous blood pressures were measured with a servo-null, micro-pressure system and the dorsal aortic blood flow was measured with a 20 MHz pulsed Doppler velocity meter. The peptide was infused into the vitelline vein with a microinjector at doses of 0.1, 1.0, and 10 ng. Doses normalized by body wt of embryos averaged 0.003, 0.035, and 0.32 ng/mg (n = 61), respectively. Vitelline arterial blood pressure decreased in a dose dependent manner [y = 55.8 - 9.9x; r = -0.49; p less than 0.01 (y = % of baseline, x = log ng/mg)], and dorsal aortic blood flow, a measure of cardiac output, decreased similarly (y = 39.6 - 16.2x; r = -0.47; p less than 0.01). Heart rate did not change. Ten ng of ANP increased the vitelline venous diameter, determined directly under a microscope, from 125 +/- 47 (SD) microns to 139 +/- 49 microns (n = 11; p less than 0.01), and decreased vitelline venous pressure from 0.34 +/- 0.05 mm Hg to 0.10 +/- 0.07 mm Hg (n = 5). We conclude that ANP exerts its hemodynamic effect by direct venodilation in the noninnervated and anephric circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Molecular cloning and chromosomal localization of a gene coding for human cardiac myosin heavy-chain.

alpha- and beta-human cardiac myosin heavy-chain (MHC) genes, which correspond to MYH6 and MYH7, respectively, according to Human Gene Mapping nomenclature, were isolated from human genomic and cDNA clones, using two rat cardiac pCMHC26: alpha-MHC type; and pCMHC5: beta-MHC type as probes, and characterized. The alpha-MHC type cardiac genomic DNA clone and the beta-MHC type cardiac cDNA clone were used as probes in the Southern analysis of human genomic DNA from human-Chinese hamster or human-mouse somatic cell hybrids. The results showed that the human cardiac MHC gene is assigned to chromosome 14 and the human cardiac and skeletal MHC genes do not cosegregate as do the mouse cardiac and skeletal MHC genes. For further analysis, a regional mapping method was used. DNA from 4 human deletion and 3 human duplication cell line were prepared for southern blotting, hybridized with human cardiac alpha- and beta-MHC DNA probes, and the hybridization intensity relative to 46, XX or 46, XY DNA was estimated. The results showed that two human cardiac MHC genes segregated with the 14cenq13 region of the long arm of human chromosome 14. In situ hybridization of 3H-labeled human cardiac alpha-MHC probe to normal human metaphase chromosome independently confirmed this result.

Animals↗
PubMed1990

[The indication and effects of palliative right ventricular outflow tract reconstruction for tetralogy of Fallot with pulmonary atresia].

Palliative right ventricular outflow reconstruction (RVOT) in 5 cases with tetralogy of Fallot with valvular pulmonary atresia and 5 cases with truncal pulmonary atresia were studied regarding indication and postoperative development of pulmonary artery. In 4 cases with valvular atresia, RVOT was performed following previous palliation such as Blalock-Taussig shunt, and resulted in improvement in clinical symptoms and in significant increase in postoperative PA-index from 105.4 mm2/m2 before operation to 159.4 mm2/m2. In one case, RVOT was performed as the first stage palliation and symmetrical development of pulmonary arteries were observed. All underwent successful total correction later. However, in 5 cases with the truncal atresia, 2 died after RVOT and postoperative development of pulmonary artery was insignificant. RVOT is indicated for cases with poor pulmonary arterial development despite of palliation, and in future, RVOT as an initial palliation will be indicated in infants with hypoplastic pulmonary artery.

Child↗
PubMed1990

Histopathologic findings of endomyocardial biopsies in pediatric patients with arrhythmias or conduction disturbances.

Histopathologic findings of endomyocardial biopsy in 23 pediatric patients with arrhythmias or conduction disturbance were analyzed. ECG abnormalities consisted of atrioventricular block (AVB) in 11, ventricular arrhythmia including premature ventricular contractions (PVC) and ventricular tachycardia in 7, sick sinus syndrome (SSS) in 3, and bundle branch block in 2 cases. Biopsy specimens were obtained from the right ventricle in all cases and, additionally, from the right atrium in SSS cases. Biopsy revealed significant pathology in 19 cases (83%). Advanced histologic changes, including myocyte hypertrophy, disarrangement of muscle bundles, and interstitial fibrosis with or without myocyte degeneration, were observed in 7/11 AVB cases and 1/6 PVC cases. SSS cases showed interstitial fibrosis with disarrangement of muscle bundles in the right atrium, but no significant pathologic changes were seen in the right ventricle. There was no clinical evidence of hypertrophic or dilated cardiomyopathy, cardiac defects, or other heart disease in these patients. It is suggested that these cases may fall under the arrhythmia-conduction disturbance type of cardiomyopathy.

Adolescent↗
PubMed1990

[A new noninvasive method for calculating pulmonary to systemic flow ratio (Qp/Qs) in patients with atrial septal defect using multigated Doppler echocardiography].

The number of patients with atrial septal defect (ASD) who undergo intracardiac repair without cardiac catheterization has been increasing. A noninvasive quantitative method to estimate the Qp/Qs ratio in this disease is therefore needed, but no simple, accurate method has yet been reported. The purpose of this study was to devise a new clinically useful method. Study materials consisted of 15 patients with ASD who were catheterized and five post-operative patients. For this study a multigated Doppler echocardiographic instrument (Fujitsu ME 120A) was used, which allowed us to ascertain Doppler shift frequency at 64 consecutive sampling volumes up to 13 cm in depth simultaneously. In the parasternal four-chamber view, the cursor was set so as to cross obliquely the right ventricular inflow tract just below the tricuspid valve and the left atrium, just above the mitral valve. Two blood flow profiles were obtained from the flow crossing the tricuspid and mitral valves. The multigated Doppler echocardiogram was recorded on videotape and then analyzed. (1) The encircling area between the profile and the base line was measured for tricuspid and mitral flow independently throughout diastole. After summing up each area of tricuspid (TA) and mitral (MA) flow profiles, the ratio TA/MA was obtained (area calculation method). (2) The flow volume passing through each tricuspid (TF) and mitral valve (MF) was calculated from the flow profile using the "ring approach" reported by Jenni, and the ratio TF/MF was obtained (flow calculation method).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Septation and Fontan repair of univentricular atrioventricular connection.

From April 1986 to September 1988, 12 patients with double- or common-inlet left ventricle and left anterior rudimentary right ventricle underwent septation while 17 patients with double- or common-inlet left or right ventricle underwent the Fontan operation. In the septation group, three patients who had pressure gradients ranging from 10 to 85 mm Hg between the left ventricle and the aorta underwent enlargement of the outlet foramen, and all survived. One of the 12 patients had a common atrioventricular valve that was repaired by separating the atrioventricular valve by the procedure used for atrioventricular septal defect. One had complete heart block before septation and the other one had it after separation. One 17-year-old woman, who had the smallest left ventricle (168% of normal), died in the hospital (mortality, 8.3%). In the Fontan group, one patient who died in the hospital (5.9%) had high pulmonary resistance of 4.4 U/m2, and one late death (5.9%) occurred in a patient who had complete heart block and a high mean pulmonary arterial pressure of 20 mm Hg. Because of suprasystemic pressure in the pulmonary ventricle, two patients had immediate takedown of the septation repair and substitution of the Fontan repair. Although right atrial pressure was almost equal in both groups after operation, the cardiac index was significantly higher in the septation group than in the Fontan repair group (p less than 0.01). These data suggest that patients who are candidates for either septation or Fontan repair might fare better with septation.

Adolescent↗
PubMed1990

Histopathological assessment of endomyocardial biopsy in children: I. Semiquantitative study on the hypertrophy of cardiac myocytes.

Over 200 endomyocardial biopsies in pediatric patients have been performed since 1962, and an appropriate interpretation of myocardial hypertrophy in biopsy specimens at different ages is now necessary. The diameter of myocytes was measured in 108 biopsy specimens and 209 autopsy specimens from pediatric cases. There was a gradual increase in the myocyte diameter according to age in the biopsy and autopsy specimens. The diameter became adult size at 13 to 15 years of age in the right ventricle and at 9 to 15 years in the left ventricle. The myocyte size of diseased hearts was greater than that of normal hearts at each age. The coefficient of variance of the mean myocyte diameter in heart muscle disease, including hypertrophic cardiomyopathy and dilated cardiomyopathy, was greater than in other hearts. These results suggested that it is possible to ascertain myocardial hypertrophy by measuring the diameter of cardiac myocytes. A proposed grading system of the degree of myocyte hypertrophy for the biopsy specimens at various pediatric ages is reported.

Adolescent↗
PubMed1989

Human cardiac myosin heavy chain gene mapped within chromosome region 14q11.2----q13.

Our previous report demonstrated that two human cardiac alpha- and beta-myosin heavy-chains (MHCs) which correspond to MYH6 and MYH7 respectively, according to Human Gene Mapping nomenclature, were mapped to human chromosome 14 and that human cardiac and skeletal MHC genes do not cosegregate. For further analysis, the regional mapping method was used. DNA from 4 human deletion and 3 human duplication cell lines were prepared for southern blotting, hybridized with human cardiac alpha- and beta-MHC DNA probes, and the hybridization intensity relative to 46,XX or 46,XY DNA was estimated. The results showed that two human cardiac MHC genes segregated with the 14cen----q13 region of the long arm of human chromosome 14. In situ hybridization of 3H-labeled human cardiac alpha-MHC probe to normal human metaphase chromosome independently confirmed this result.

Base Sequence↗
PubMed1989

Hemodynamic effects of acetylcholine in the chick embryo and differences from those in the rat embryo.

It has been reported that acetylcholine induces cardiac anomalies in the chick embryo. Thus, we studied hemodynamic effects of this drug in the chick embryo and also compared them with those in the rat embryo since we found that the effect of caffeine was different between the chick and rat embryos. Acetylcholine was given at doses of 5, 0.5, and 0.05 micrograms into the vitelline vein in chick embryos at Hamburger-Hamilton stage 21 and at a dose of 0.5 micrograms into the placenta in rat embryos at gestational day 12. In the chick embryo, heart rate was reduced to 91, 88, and 87% of control at the end of injection of 0.05, 0.5, and 5 micrograms, respectively, then returned to the baseline level. Vitelline arterial blood pressure was 110% of control with 0.05 micrograms, 134% with 0.5 micrograms, and 142% with 5 micrograms at 1 min after injection. The dorsal aortic blood flow decreased with time after injection, but it was increased only by a 5 micrograms dose at the end of injection. The vascular resistance increased in a dose-dependent manner. In the rat embryo, the change of heart rate was qualitatively similar to that of the chick embryo. The blood pressure did not change significantly. The blood flow velocity at the outflow tract decreased at the end of injection, which indicated the decrease in cardiac output, along with slowing of heart rate, then returned to the control level thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1989

Inotropic effect of phenylephrine and myocardial alpha-adrenergic receptor in newborn and adult animals.

Developmental changes in the myocardial alpha-receptor density were studied using rabbit, rat and dog hearts. In all species studied, alpha-receptor density in the newborn was greater than in the adult. The inotropic effect of phenylephrine was measured using the isolated arterially perfused heart preparation of rabbit and rat. The heart was stimulated electrically at 40/min. In the presence of propranolol, phenylephrine caused a significant positive inotropic effect which was significantly less in the newborn than in the adult. Since alpha-adrenergic stimulation activates protein kinase C, the inotropic effect of protein kinase C activation was studied in the rabbit and rat using phorbol myristate acetate (PMA). PMA caused a negative inotropic effect and the decrease in contractile function in the newborn was greater than in the adult. These data suggest that myocardial alpha-receptor density decreases and the positive inotropic effect of alpha-agonist increases with development. The reasons for this discrepancy remain unclear but there may be developmental differences in the signal transduction processes of alpha-stimulation. The greater negative inotropy of protein kinase C activation in the premature heart may be one of the mechanisms of the reduced inotropy of alpha-agonist in this age group.

Animals↗
PubMed1989

The teratogenic effect of forskolin on cardiovascular development in the chick embryo.

The cardiovascular teratogenicity and embryotoxicity of forskolin, a potent activator of adenylate cyclase, was studied in the chick embryo. The drug was topically applied to the surface of the chorioallantoic membrane in the vicinity of the embryonic heart on the 4th day of incubation (Hamburger-Hamilton developmental stage 24). Cardiovascular malformations were induced in 51% of embryos treated with forskolin doses larger than 1 x 10(-8) mol/egg. Major malformations included remnant of the left 4th aortic arch and ventricular septal defect. These results indicate that forskolin induces cardiovascular malformations in the chick embryo and suggest that increased levels of cyclic 3',5'-adenosine monophosphate produced by forskolin may be related to the malformations observed.

Abnormalities, Drug-Induced↗