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Biomedical subjects

K Nishigaki

Publications and source records attributed to K Nishigaki.

At least 91 records · Page 5Linked to original sources
PubMed1993

[Surgical management of tetralogy of Fallot with absent pulmonary valve in infancy].

Between November, 1987 and May, 1990, definitive operation was performed in 7 infants for tetralogy of Fallot with absent pulmonary valve. Preoperative respiratory failure was serious in 5 patients and semi-emergency operation was done. Surgical procedure consisted of closure of ventricular septal defect, reconstruction of right ventricular outflow tract using heterograft valved pericardial roll and plication of aneurysmally dilated pulmonary artery with or without pulmonary artery suspension in 5 infants with severe respiratory distress and heart failure, operated on 26 days to 5 months of age. In the other two less symptomatic infants, operated on at 13 months of age, reconstruction of right ventricular outflow tract was performed by transannular bovine pericardial patch with monocusp. There were no operative death and six infants are doing well 6 months to 3 years postoperatively, but one patient died of prolonged respiratory infection and respiratory failure one year after operation. Postoperative pulmonary arteriogram revealed a 42 to 61 (mean 54) percent reduction in right and left pulmonary artery size in 3 patients who underwent extensive plication of pulmonary artery. We suggest that definitive plication with or without suspension of pulmonary artery, together with closure of ventricular septal defect and reconstruction of right ventricular outflow tract is supposed to eliminate air way obstruction.

Bioprosthesis↗
PubMed1993

Intraventricular repair for Taussig-Bing anomaly.

Among 41 patients with Taussig-Bing anomaly who underwent intracardiac repair, 10 patients were treated by intraventricular rerouting repair. The ages at operation ranged form 1 month to 8 years (average 2 years 3 months). Primary repair was done in four (average age 2 years 7 months), and repair was done after pulmonary artery banding in six patients (average age 2 years 2 months). The relationship of the great arteries was side by side in nine patients and oblique in one. After extensive resection of the infundibular septum, a distance of 8 to 18 mm from the tricuspid ring or chordae to the pulmonary valve was obtained (24% to 71% of total circumference for the subaortic route). The subaortic route was created to obtain an internal diameter at least equal to that of the aortic route. Tricuspid chordal or papillary muscle reattachment was performed in two patients. There were no early or late deaths. Follow-up ranged from 1 year 4 months to 22 years 3 months (average 5 years 8 months), and reoperation was required in one patient for residual pulmonary stenosis. The intraoperative pressure gradient between the left ventricle and aorta was 0 to 24 mm Hg (average 10.3 mm Hg), and postoperative study showed the gradients to be less than 19 mm Hg (n = 8). The age at operation, left ventricular-aortic pressure gradient, and postoperative tricuspid regurgitation were not significantly affected by the presence of severe hypertrophy of the infundibular septum (n = 4). These results indicate that intraventricular rerouting may be feasible in most patients who have the Taussig-Bing anomaly with side-by-side or similar relationships of the great arteries, and the age and conal anatomic variations do not appear to be significant limiting factors.

Cardiac Catheterization↗
PubMed1993

[A case report of successfully corrected 26 days old infant of tetralogy of Fallot with absent pulmonary valve].

A female infant weighing 2.4 kg had respiratory distress at birth. She became dyspneic and hypercapnic and required intubation with assisted ventilation 11 days after birth. Because cardiac failure and respiratory failure did not improve, she underwent total correction at 26 days old, which consisted of VSD closure, right ventricular outflow tract reconstruction with valved porcine pericardial roll (VPR) and plication of both pulmonary arteries. She was weaned from the ventilator 11 days after operation and discharged at 12 weeks of age. One year later, reoperation was successfully performed for the replacement of the stenotic VPR with a transannular patch.

Blood Vessel Prosthesis↗
PubMed1992

Age-related increase in systolic fraction of pulmonary vein flow velocity-time integral from transesophageal Doppler echocardiography in subjects without cardiac disease.

The pulmonary vein flow velocity-time profile would be equivalent to the pulmonary vein flow volume-time profile, provided that the cross-sectional area of the pulmonary vein remains unchanged during 1 cardiac cycle. The systolic fraction of the pulmonary vein flow velocity-time integral, a ratio of velocity-time integral of the S wave to the sum of velocity-time integrals of the S and D waves, represents the ratio of left atrial storage volume to left ventricular stroke volume. This systolic fraction may help early filling of the left ventricle through an appropriate storage of blood and generation of driving pressure in the left atrium. Because early filling of the left ventricle is progressively impaired with age, it was hypothesized that this systolic fraction is increased with age. Forty-four noncardiac surgical patients (age range 17 to 70 years) who underwent transesophageal Doppler echocardiography under general anesthesia were studied, and left upper pulmonary vein flow and mitral inflow velocities were recorded. The ratio of peak velocity of the E wave to that of the A wave of mitral inflow velocity-time profile (y) decreased with age (y = -0.0245 x age + 2.41; r = -0.672, p < 0.01). Systolic fraction (y) increased with age (y = 0.00373 x age + 0.514; r = 0.656, p < 0.01). The age-related increase in the systolic fraction of pulmonary vein flow velocity-time integral may account for the compensation for impaired early filling of the left ventricle in elderly patients.

Adolescent↗
PubMed1992

New surgical technique for total-defect aortopulmonary window.

A new technique is described to repair aortopulmonary window with total defect in an 8-day-old baby. Because we expected the future growth of aorta, we used the anterior wall of the pulmonary artery as a large flap to reconstruct the posterolateral aortic wall. An equine pericardial patch was used to repair the defect in the pulmonary artery. This is a logically effective method for aortic reconstruction in a neonate with a large aortopulmonary septal defect.

Aortopulmonary Septal Defect↗
PubMed1992

Structural analysis of nucleic acids by precise denaturing gradient gel electrophoresis: I. Methodology.

A method to convert the conventional denaturing gradient gel electrophoresis into a highly reproducible experimental system was developed. It was based on the following experimental findings; (i) dyes, which are small molecules, do not exhibit mobility changes attributed to their conformational change while nucleic acids do; and (ii) most of the mobility shifts caused by experimental fluctuations could be cancelled by normalizing the mobility of a sample with respect to the corresponding one of a dye. The method involves co-migration of internal reference dyes with samples (nucleic acids), and computer-aided data processing, allowing us to obtain the relative mobility of nucleic acids with respect to a dye throughout the denaturing gradient. The overall pattern of the relative mobilities thus obtained, named the normalized mobility profile (NMP), corresponded well to conformational changes of a macromolecule induced by denaturing effects. This method provides us with objective data without using internal macromolecular references, which not only guarantees the precision but also extends the range of application of the denaturing gradient method.

Base Sequence↗
PubMed1992

Structural analysis of nucleic acids by precise denaturing gradient gel electrophoresis: II. Applications to the analysis of subtle and drastic mobility changes of oligo- and polynucleotides.

Precise denaturing gradient gel electrophoresis was effectively applied to various kinds of oligo- and polynucleotides. The analyses on oligonucleotides revealed that every oligonucleotide has its own characteristic normalized mobility profile (NMP), which can be used to identify, characterize and classify the molecules. The precise system also enabled us to obtain unequivocally the mobility transitions corresponding to the melting of hairpin structures of oligonucleotides, single-stranded (ss) DNAs, and RNAs. Another application to co-migration and separate migration experiments demonstrated that there were significant binding interactions between two species of ss molecules of similar mobility, even when they have little complementarity with each other. When the precise temperature gradient gel electrophoresis was applied to double-stranded DNAs, it could be confirmed with high reliability that the mobility transitions observed correspond to cooperative meltings and strand dissociations. Through these experiments, mu m, a parameter defined as a mobility transition point, was shown to be effective to deal with those phenomena quantitatively.

Base Sequence↗
PubMed1992

Interaction between microvascular alpha 1- and alpha 2-adrenoceptors and endothelium-derived relaxing factor.

Intravital microscopy was used to study the effect of endothelium-derived relaxing factor (EDRF) on microvascular adrenoceptor sensitivity in rat cremaster skeletal muscle. NG-Monomethyl L-arginine (L-NMMA, 1-300 microM), an inhibitor of EDRF formation, produced concentration-dependent constriction of arterioles and venules. When an intermediate amount of alpha 1- versus alpha 2-adrenoceptor tone was first produced with bath-added norepinephrine (NE) in the presence of rauwolscine or prazosin, L-NMMA caused constriction with greater potency and efficacy during alpha 2 than during alpha 1 tone. During localized alpha 1 or alpha 2 constriction along an arteriole by perivascular micropipette suffusion of NE in the presence of rauwolscine or prazosin, again, bath-added L-NMMA produced constriction with greater potency during alpha 2 than during alpha 1 constriction. Like L-NMMA, disruption of EDRF release by microembolization caused baseline arteriole constriction and selectively increased alpha 2 sensitivity 75-fold. Although these findings support the hypothesis that endothelial cells possess alpha 2-adrenoceptors that promote EDRF release, a greater susceptibility of alpha 2 than alpha 1 constriction to EDRF inhibition could also account for the results. In support of this latter possibility, alpha 2 constriction was approximately 50-fold more susceptible than alpha 1 constriction to inhibition by the EDRF-like nitrodilator nitroprusside. The similarity in magnitude of this difference in sensitivity with the difference obtained in the embolization experiments does not support the hypothesis that microvascular endothelial cells in skeletal muscle possess EDRF-promoting alpha 2-adrenoceptors. However, these data do suggest that endogenous EDRF release modulates basal arteriole and venule tone and that alpha 2-adrenoceptor constriction is more sensitive than alpha 1 constriction to inhibition by EDRF.

Animals↗
PubMed1992

[Total repair for truncus arteriosus].

Total repair for truncus arteriosus using an external conduit was performed in 12 patients from 1978 through 1989. Six cases were infants (mean age: 3.4 months) and 6 were children (mean age; 1 years 9 months). Two cases had Collet-Edwards type II truncus and the other 10 cases had type I truncus. One of the infants was associated with an interruption of the aorta and another had a severe regurgitation of the truncal valve (TrV). For external conduits, we used a non-valved conduit in one infant, a composite valved conduit of Dacron containing a heterograft valve in 4 children and a valved pericardial roll made of an autologous or porcine pericardium in 5 infants and 2 children. One infant with a severe regurgitation of the TrV needed valve replacement along with enlargement of the annulus of the TrV. One infant who had replacement of the TrV died early postoperatively. Another infant died 10 months after total repair due to an infection of an external conduit. Cardiac catheterization was performed in all 10 survivors. The mean value for the systolic pulmonary/systemic pressure ratio decreased from 0.98 +/- 0.09 preoperatively to 0.36 +/- 0.09 postoperatively. Replacement of an external conduit was performed due to a conduit stenosis in 2 children and 1 infant, 10 years and 2 months, 7 years and 9 months, and 1 year and 8 months after the total repair, respectively. In one of these 2 children, replacement of the aortic valve was performed due to a severe aortic regurgitation. We conclude that our results of total repair for truncus arteriosus were satisfactory. However, it remains to be solved how to manage an infant with truncus arteriosus associated with a severe regurgitation of the TrV.

Bioprosthesis↗
PubMed1991

Occlusion of cremaster collateral circulation alters microvascular reactivity.

Surgical preparation of the rat cremaster skeletal muscle for microvascular study usually involves occlusion of the deferential artery and vein which supply a collateral circulation to the tissue. This allows removal of the testis and ductus deferens, and permits direct observation of the cremaster microvasculature. We examined with intravital microscopy the effect of this occlusion on alpha-adrenergic and nonreceptor-mediated (KCl) constriction of large arterioles (1A, 136 microns i.d.) and venules (1V, 193 microns i.d.). The acutely denervated cremaster was suspended in a tissue bath containing propranolol to block beta-adrenergic receptors. alpha 1-adrenergic (norepinephrine (NE) + rauwolscine), alpha 2-adrenergic (NE + prazosin), and KCl (+ phentolamine) concentration-response curves were obtained for bath-added agonists before vs after occlusion of the deferential circulation. Occlusion had no effect on baseline 1A diameter but increased 1V diameter slightly. Arteriolar alpha 1- and alpha 2-adrenergic sensitivities were unaffected by occlusion, but venular sensitivities were reduced by the same amount (approximately fourfold) for both receptor types. Occlusion increased arteriolar sensitivity to KCl but had no effect of venular KCl sensitivity. These data indicate that occlusion of the deferential collateral circulation can produce significant and varied effects on alpha-adrenoceptor and nonreceptor-mediated constriction of cremaster large arteriolar and venular smooth muscle, and underscore the need to avoid collateral occlusion for certain studies of the cremaster microcirculation.

Animals↗
PubMed1991

Interactions between alpha-adrenoceptors and adenosine receptors on microvascular smooth muscle.

alpha 2-Adrenoceptor but not alpha 1-adrenoceptor constriction of arterioles is selectively inhibited by tissue acidosis, ischemia, and increased metabolic rate. To further examine neural-local interactions, we studied the effect of adenosine receptor stimulation on alpha 1- or alpha 2-adrenoceptor constriction. Intravital microscopy was used to study large arterioles (133 +/- 3 microns diam; mean +/- SE), small arterioles (16 +/- 1 microns), and large venules (178 +/- 3 microns) of rat cremaster skeletal muscle. Concentration-response (diameter change) curves were obtained for bath-added norepinephrine in the presence of either rauwolscine or prazosin to provide selective alpha 1- and alpha 2-constriction, respectively. The adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (2.24 x 10(-8) M) significantly attenuated both alpha 1- and alpha 2-constriction by 5- to 20-fold; alpha 1-constriction was three- to fourfold more sensitive than alpha 2-constriction. Similar inhibitory effects were obtained with adenosine (2.24 x 10(-6) M). The adenosine receptor antagonist 8-[4-[N(2-aminoethyl)carbamoylmethoxy]phenyl]-1,3-dipropylxanthine (0.7 microM) reversed the inhibitory effect of adenosine, which implicates extracellular A2 adenosine receptors. Intrinsic tone in large vessels was unaffected by adenosine receptor stimulation but was completely inhibited in small arterioles. These findings suggest that both alpha 2- and especially alpha 1-adrenoceptor constriction and intrinsic tone (of small but not large arterioles) are inhibited by physiologically relevant concentrations of adenosine.

Adenosine↗
PubMed1991

Differential activation of alpha 1- and alpha 2-adrenoceptors on microvascular smooth muscle during sympathetic nerve stimulation.

The relative contribution of postjunctional alpha 1- and alpha 2-adrenoceptors to constriction of microvessels was examined during sympathetic nerve stimulation and sympathetic escape (difference between peak and steady-state constriction). Large arterioles (120 +/- 4 microns control diameter) and venules (174 +/- 6 microns) and small arterioles (13 +/- 4 microns) were examined in rat cremaster skeletal muscle during stimulation of the cremaster efferent innervation (decentralized lumbar sympathetic chain, 0.5-16 Hz, 2-minute train). The muscle was suspended in a tissue bath, and diameter was measured with intravital microscopy. Frequency-response curves were obtained after vehicle (prazosin or rauwolscine) was added to the bath. In large arterioles, prazosin (10(-7) M) significantly attenuated constriction by 60-80%; a fivefold higher concentration had no additional effect. In contrast, rauwolscine (1 to 5 x 10(-7) M) had no effect. Venules evidenced minimal response to nerve stimulation. In small arterioles, rauwolscine (5 x 10(-7) M) significantly attenuated constriction by 50-60%, while prazosin (10(-7) M) had no effect. These data suggest that for large arterioles, which are known to possess both receptors, alpha 1-adrenoceptors are preferentially stimulated by nerve-released norepinephrine. In contrast, sympathetic constriction of small arterioles is mediated by alpha 2-adrenoceptors. Compared with large arterioles, small arterioles exhibited greater peak and steady-state constriction at all frequencies, with maximal responses achieved over the 0.5-4 Hz range. Large arterioles exhibit graded constriction over the entire frequency range. Sympathetic escape exhibited a small, negatively correlated frequency dependence for large arterioles, tended to be greater for small arterioles, and was more evident in large arterioles during alpha 2-adrenoceptor constriction at low-frequency stimulation. This distinct neural control of large resistance vessels by alpha 1-adrenoceptors and small terminal arterioles by alpha 2-adrenoceptors may allow neurogenic regulation of these vessel segments to be differentially susceptible to modulation by other extrinsic and intrinsic vasoactive controls that preferentially interact with alpha 1- and alpha 2-adrenergic contractile mechanisms.

Animals↗
PubMed1990

The effect of left ventricular bypass on the right ventricular function: experimental analysis of the effects of ischemic injuries to the right ventricular free wall and interventricular septum.

The right ventricular (RV) function during left heart bypass (LHB) was examined in open-chest anesthetized mongrel dogs (average weight, 11.8 kg). The LHB was carried out by a left ventricle (LV) to femoral artery bypass using a centrifugal pump for 90 min, and the bypass flow was kept maximum to obtain almost complete decompression of the LV. The RV function was evaluated by hemodynamic parameters and pressure-dimension (sonomicrometry) relationship at pre-LHB (control) and 30, 60, and 90 min after LHB (LHB-30, LHB-60, and LHB-90). The materials were divided into three groups after LHB-30: intact heart (group 1, n = 5), RV free wall ischemia (group 2, n = 5), and interventricular septum (IVS) ischemia group (group 3, n = 8). No significant changes in mean right atrial pressure (mRAP), RV end-diastolic pressure (RVEDP), RV maximum derivative pressure, or RV fractional shortening (RVFS) were found between pre-LHB and post-LHB in groups 1 and 2. On the contrary, group 3 showed significant increases in mRAP and RVEDP, and a decrease in RVFS at LHB-90 compared to both pre-LHB and LHB-30. The RV end-systolic dimension (percentage of pre-LHB) showed significant increases at LHB-90 compared to LHB-30 in groups 2 and 3. These results indicate that the LHB itself does not depress the RV function in the intact heart and in the RV free wall ischemic heart, while the impairment of the IVS during LHB appears to lead to RV dysfunction.

Animals↗
PubMed1990

[Surgical therapy of congenital aortic valvular stenosis in neonates and infants].

The preoperative evaluation, surgical course, and early follow-up results of 5 infants less than 4 months of age who underwent aortic valvotomy for severe valvular stenosis between 1983 and 1985 were reviewed to determine the early prognosis of these neonates. Two of the 5 patients had been used respiratory support due to severe congestive heart failure and dyspnea. Emergency aortic valvotomy was performed in all during cardio-pulmonary bypass which achieve maximal relief of the stenosis without significant causing aortic insufficiency. There was a single operative death and there was one late death at 2 months after surgery who was regarded to have a extensive endocardial fibroelastosis. The other three patients have had a favorable early prognosis during mean follow-up period of 1.78 (0.4-3.8) years. They had been followed by means of two-dimensional and doppler echocardiography, which inferred that the aortic pressure gradient had been kept under 41 mmHg and which indicated that there were no LV enlargement to prove significant aortic valve insufficiency. These results indicate that early infants with severe valvular stenosis can undergo sufficient valvotomy safely and have a favorable early prognosis.

Aortic Valve↗