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Biomedical subjects

H Oku

Publications and source records attributed to H Oku.

At least 37 records · Page 2Linked to original sources
PubMed2001

Total cavopulmonary connection using a pedicled pericardial conduit for a patient with apicocaval juxtaposition.

A 5-year-old boy, with a double inlet solitary ventricle, pulmonary atresia, and apicocaval juxtaposition underwent an extracardiac total cavopulmonary connection. A pedicled pericardial conduit was placed behind the ventricle to make a straight pathway between the inferior vena cava and pulmonary artery. This report presents a solution for managing patients with complicated heart defects with apicocaval juxtaposition during the completion of a total cavopulmonary connection.

Angiography↗
PubMed2001

Experimental heterotopic heart transplantation without cardiopulmonary bypass: auxiliary support for the recipient heart.

BACKGROUND: Auxiliary cardiac support using heterotopic heart transplant is of considerable interest, but the outcome is not known. To investigate technical feasibility and the possibility of using auxiliary support from heterotopic heart transplantation without cardiopulmonary bypass, we evaluated hemodynamics including the pressure-volume relationship in experimental animals. METHODS: In heterotopic heart transplantation, we tailored the donor heart by removing the pulmonary and tricuspid valves, and by wide removal of the inter-atrial septum. Next, we anastomosed the descending aorta and left atrium of the donor heart to the descending aorta and left atrium of the recipient, without using cardiopulmonary bypass. Consequently, declamping the recipient's descending aorta allowed the donor heart to fill with blood and to start beating. We performed hemodynamic assessments including the effects of adrenergic stimulation. We measured the pressure and volume relationship of the recipient heart by closing and opening inflow of the donor left atrium to change the pre-load of the donor left ventricle. RESULTS: The donor left ventricle produced a systolic blood pressure that was augmented by the recipient blood pressure and responded to adrenergic stimulation. When inflow of the donor left atrium was opened, the pressure-volume loop of the recipient heart shifted to the left and pressure-volume area decreased. Simultaneously, the mechanical efficiency and E(max) (the slope of the end-systolic pressure-volume relationship) of the recipient heart increased when inflow of the donor left atrium was opened. CONCLUSIONS: This transplant model, without cardiopulmonary bypass, is feasible and can be applied to transplant investigations as a working heart model on the basis of the response of adrenergic stimulation. The increased pre-load of the donor left atrium from the recipient left atrium resulted in a recipient leftward shift of the pressure-volume relationship, suggesting that this transplant model with adequate pre-load acts as auxiliary assistance in the recipient intrathoracic cavity.

Animals↗
PubMed2001

Surgical treatment of pacemaker induced left innominate vein occlusion using a spiral vein graft.

Superior vena cava syndrome due to transvenous pacing leads is an uncommon but potentially life-threatening complication. This case involves a 54-year-old man who developed left innominate vein occlusion due to a pacemaker lead. This complication induced a progressive swelling on the left side of his face, neck, arm, and upper chest. The left innominate vein occlusion was surgically treated using a composite spiral saphenous vein graft. Postoperatively, the patient has received anticoagulation therapy with warfarin to prevent thrombosis and, thereby, the long-term patency of the graft. He has undergone follow-up on a regular outpatient basis without showing any recurrence of clinical symptoms.

Brachiocephalic Veins↗
PubMed2001

A case of Standford type B aortic dissection involving a right-sided aortic arch with mirror-image branching and right-sided descending aorta.

Isolated right aortic arch with mirror-image branching is a rare congenital anomaly. To date, no case has been reported for aortic dissection involving a right aortic arch with mirror-image branching. We report here on a case involving a 58-year-old man in whom expanding type B aortic dissection was demonstrated in the right aortic arch with mirror-image branching and a right descending aorta. The patient was successfully treated by interposition of a prosthetic graft via a right posterolateral thoracotomy approach. We also reviewed the literature.

Aortic Dissection↗
PubMed2001

Follow-up study of coronary artery bypass grafting in patients with Kawasaki disease.

BACKGROUND: The purpose of this study was to assess the long-term clinical outcome of coronary artery bypass grafting in pediatric patients with Kawasaki disease. METHODS: Six patients (mean age, 9.3 +/- 1.6 years) underwent coronary artery bypass grafting between September 1985 and December 1992. The number of bypass grafts placed was 1 to 2 per patient (mean 1.3 +/- 0.5). The left internal mammary artery (IMA) was used as a bypass graft in 3 patients, bilateral IMA in 1, and saphenous vein in 3. All patients underwent postoperative evaluations after 1 month and between 5 and 10 years. RESULTS: Follow-up ranged between 9 and 16 years (mean 12.6 +/- 2.7 years). Stress myocardial scintigraphy identified 2 patients with transient ischemia, one of whom died suddenly after 16 postoperative years. Coronary angiography demonstrated that the grafts of 5 patients were patent at both the short- and long-term follow-up. However, in 1 patient, the IMA that was grafted to the diagonal artery was occluded 1 month after surgery. Five survivors are in good health, without clinical angina. CONCLUSIONS: We consider that coronary revascularization with bilateral IMA grafts may provide a more favorable prognosis in patients with severe Kawasaki coronary artery disease. Stress myocardial scintigraphy and echocardiography can be used effectively to follow such patients.

Adolescent↗
PubMed2001

The mechanism and change in the optic nerve head (ONH) circulation in rabbits after glucose loading.

PURPOSE: To assess the influence of the blood glucose level on ocular capillary circulation, we induced clinically significant hyperglycemia (200--300 mg/dl) in rabbits and investigated the changes in the optic nerve head (ONH) circulation. METHODS: Hyperglycemia was induced by injection of glucose (5.6 mmol/kg) into an auricular vein of healthy albino rabbits and changes in the ONH circulation were measured by the laser speckle method. In order to examine the role of nitric oxide (NO), glucose was administered after intravenous injection of an NO synthetase inhibitor (N(G)-nitro-L-arginine methyl ester, L-NAME, 1 mg/kg), then changes in the ONH circulation were measured. RESULTS: The blood glucose level reached a peak at 30 min after glucose loading and returned to its initial level by 2 hours. ONH circulation showed a 60% increase compared with its initial level at 15 min after glucose loading and subsequently remained almost unchanged throughout the 2-hour observation period. There were no significant changes of the blood pressure, heart rate, or intraocular pressure. The glucose-induced increase of ONH circulation was completely inhibited by pretreatment with L-NAME. CONCLUSIONS: ONH circulation was increased by administration of glucose to healthy rabbits. A high blood glucose level seems to promote ocular capillary circulation and NO as well as insulin appear to have a role in this process.

Animals↗
PubMed2001

Platelet-derived growth factor-BB: a survival factor for the retinal microvasculature during periods of metabolic compromise.

PURPOSE: The aim of this study was to test the hypothesis that platelet-derived growth factor (PDGF) reduces ischemia-induced damage to cells in the retinal microvasculature. METHODS: As a model of ischemia, pericyte-containing microvessels freshly isolated from the adult rat retina were exposed to the inhibitors of ATP synthesis, iodoacetate and antimycin A. Cell viability was assayed by trypan blue exclusion. RESULTS: PDGF-BB significantly reduced cell death induced by chemical ischemia. The half-maximally effective concentration was approximately 15 pM. In contrast to PDGF-BB, which is the specific ligand for PDGF-beta receptors, ischemic death was not reduced by PDGF-AA, which does not activate the beta-receptors. The protective effect of PDGF-BB was blocked by tolbutamide, which is an inhibitor of ATP-sensitive potassium (K(ATP)) channels and mimicked by the K(ATP) channel opener, pinacidil. Nifedipine, which blocks voltage-gated calcium channels (VGCC's), also mimicked the protective effect of PDGF-BB. Consistent with PDGF-BB and nifedipine preventing cell death via a common mechanism, i.e., reducing VGCC activity, the maximal effects of this growth factor and the calcium channel blocker were not additive. CONCLUSIONS: Our results indicate that PDGF-BB significantly reduces the vulnerability of retinal microvessels to damage caused by profound ischemia. During episodes of metabolic compromise, it appears likely that the opening of K(ATP) channels via activation of PDGF-beta receptors initiates an adaptive mechanism to enhance the survival of the retinal microvasculature.

Adenosine Triphosphate↗
PubMed2001

Possible involvement of endothelin-1 and nitric oxide in the pathogenesis of proliferative diabetic retinopathy.

BACKGROUND: Overproduction of endothelin-1 (ET-1) and nitric oxide (NO) in the retina is demonstrated in experimental diabetic animals. To clarify the possible involvement of ET-1 and NO in the pathogenesis of diabetic retinopathy, the authors examined the vitreous levels of these principal endothelium-derived vasoactive substances in patients with proliferative diabetic retinopathy (PDR). METHODS: Vitreous fluid was taken from patients with PDR (ET-1, n = 12; NO, n = 12) and from patients with macular holes as controls (ET-1, n = 10; NO, n = 10) at vitreous surgery. Endothelin-1 and NO metabolites were measured by radioimmunoassay and high-performance liquid chromatography based on the Griess method, respectively. RESULTS: Endothelin-1 levels (mean +/- SE) were 21.5 +/- 1.7 pg/mL in the vitreous of patients with PDR and 16.7 +/- 0.7 pg/mL in the vitreous of patients with macular hole. There was a significant difference between patients with PDR and controls (P = 0.009, Mann-Whitney). Nitrate (NO3) was 49.8 +/- 5.0 micromol/L in patients with PDR and 24.2 +/- 2.8 micromol/L in patients with macula hole; it was also significantly elevated in patients with PDR (P = 0.004, Mann-Whitney), whereas nitrite (NO2) was not detected in this study. CONCLUSION: These results indicate that ET-1 and NO may be related in the pathogenesis of PDR.

Adult↗
PubMed2001

Postischemic reperfusion injury can be attenuated by oxygen tension control.

Oxygen-derived free radicals cause cytotoxic damage during reperfusion after a period of ischemia and the production of these free radicals may be proportionate to oxygen tension (PO2). The present study tested the hypothesis that oxidative damage may be limited by maintaining a more physiologic PO2 following ischemia. An experimental study in Wistar rats were mounted on a Langendorff apparatus was conducted to estimate baseline aortic flow (AF), coronary flow (CF), cardiac output (CO), systolic pressure (SP), heart rate (HR), and the rate-pressure product (RPP: HRxSP). The hearts were divided into 3 groups (n=7, hearts/group): group 1, hypoxic (PO2=300+/-50 mmHg) reperfusion; group 2, middleoxic (PO2=500+/-50 mmHg) reperfusion; and group 3, hyperoxic (PO2=700+/-50 mmHg) reperfusion. Following 30 min of warm ischemia, hearts in all groups were reperfused at each oxygen pressure. The recovery of cardiac function of each heart was measured at the end of reperfusion. Concentrations of lactate (LAC), lactate dehydrogenase (LDH), and creatine kinase (CK) in the coronary perfusate during reperfusion were measured. The recovery rate of CO, SP, and RPP in group 2 were all significantly better than in the other 2 groups. CK leakage in group 2 was significantly lower than in group 3. A clinical study was also conducted during elective coronary artery bypass grafts in 16 consecutive patients who underwent either hyperoxic (n=8, PO2=450-550 mmHg) or more physiologic (n=8, PO2=200-250 mmHg) cardiopulmonary bypass after aortic unclamping. The clinical study assessed CK-MB, LDH, LAC, and malondialdehyde (MDA) in patient blood prior to starting the surgical procedure and at 30 min and 3, 9, and 21 h after unclamping. Cardiac index (CI), central venous pressure, pulmonary capillary wedge pressure, systolic arterial pressure, and the dose of cathecholamines were also measured. Although no significant differences were present in the dose of cathecholamines, the CI in the more physiologic oxygen tension group was significantly higher than in the hyperoxic group at 3 and 6 h after unclamping. The levels of MDA in the more physiologic PO2 group was significantly lower at 30 min after aortic unclamping than in the hyperoxic group. The present results suggest that in the experimental as well as in the clinical study, high PO2 leads to myocardial reperfusion damage; however, maintaining a more physiologic PO2 during reperfusion following ischemia may attenuate reperfusion injury.

Animals↗
PubMed2001

Ischemic preconditioning and nicorandil pretreatment improve donor heart preservation.

The present study investigated the effects of ischemic preconditioning (IPC) and nicorandil pretreatment on myocardial storage in a donor heart preservation model. Isolated rat hearts were separated into groups: group 1, non-preconditioned control group; group 2, 2.5 min of normothermic ischemia followed by 15 min of normothermic Langendorff perfusion (one IPC cycle); and group 3, 2 cycles of IPC. All hearts were subsequently stored in University of Wisconsin solution at 4 degrees C for 2, 4 and 6h, and the concentrations of high-energy phosphate metabolites were measured for each time point. Heart function parameters (aortic flow, coronary flow and cardiac output) were measured when the heart was reperfused following the 2, 4 or 6 h of preservation. The effects of nicorandil, an ATP-sensitive potassium channel opener, on heart function following preservation were also evaluated. Nicorandil was injected intravenously before heart harvesting. The results showed that the energy status was well preserved in the IPC groups. The 2-cycle IPC group showed better recovery of heart function following preservation. Pretreatment with nicorandil also improved functional recovery of the heart following preservation. The present study showed that IPC of the rat heart resulted in improved myocardial energy metabolism and functional recovery after hypothermic preservation, and that nicorandil has potential for pharmacological preconditioning in heart preservation for transplantation.

Adenosine Triphosphate↗
PubMed2001

Mycotic aneurysm of the palmar artery associated with infective endocarditis. Case report and review of the literature.

A 26-year-old man was diagnosed with mycotic aneurysm of the left hand associated with active infective endocarditis. Preoperative arteriography of the hand revealed aneurysm of the radial side of the deep arch of the palmar artery. We approached the aneurysm from the dorsal side of the hand in order to avoid damage to the collateral vascular supply of the superficial arch of the palmar artery and neurological structures. As a result, the aneurysm was excised simply by proximal and distal ligation of the vessel. During follow-up over 14 months, no evidence of recurrent aneurysm formation or ischemia of the fingers has been obtained.

Adult↗
PubMed2001

Diabetes-induced disruption of gap junction pathways within the retinal microvasculature.

PURPOSE: Microvascular damage caused by diabetes is a leading cause of visual loss. Identifying events early in the course of diabetic retinopathy may help in understanding and, perhaps, preventing this disorder. The hypothesis that cell-to-cell communication within the retinal microvasculature may be affected soon after the onset of diabetes was tested. METHODS: Streptozotocin was used to induce diabetes in rats. To assess cell-to-cell coupling the gap junction-permeant tracer, Neurobiotin, was delivered via patch pipettes into pericytes located on microvessels freshly isolated from the retinas of diabetic and control animals. Subsequently, immunohistochemical methods revealed the extent of the intercellular spread of the tracer. Electrophysiological methods were also used to detect intercellular communication. RESULTS: In retinal microvessels of control rats, Neurobiotin spread hundreds of micrometers from the tracer-loaded pericytes. However, within days after the onset of diabetes, this cell-to-cell coupling was dramatically reduced. In contrast, microvessels of insulin-treated diabetic rats showed no significant loss of intercellular communication. Consistent with protein kinase C (PKC) playing a role in the diabetes-induced inhibition of gap junction pathways, exposure of microvessels to a PKC activator (phorbol myristate acetate) markedly reduced tracer coupling. CONCLUSIONS: Within retinal microvessels there is extensive cell-to-cell coupling, which is markedly reduced soon after the onset of streptozotocin-induced diabetes. The closure of gap junction pathways disrupts the multicellular organization of retinal microvessels and may contribute to vascular dysfunction.

Animals↗
PubMed2001

[Two-cusp plasty using a pedicled auto pericardial patch for the right ventricular outflow tract in complete repair of tetralogy of Fallot].

BACKGROUND: Pulmonary stenosis (PS) and regurgitation (PR) are major concerns late after transannular patching for tetralogy of Fallot (TOF). In this study, we reviewed the TOF patients undergoing transannular patching to reveal whether the valvuloplasty technique (two cusp plasty) improved long-term results. We also reviewed potential for grow of the pedicled autopericardial patch. METHODS AND RESULTS: Since 1977, 151 patients underwent corrective surgery for TOF. Transannular patching was required in 58 (38.4%). PS and PR in the postoperative long-term period of these 59 cases were reviewed. 25 patients had the standard transannular patching (S-TAP), and 33 had two-cusp plasty (TCP). Pedicled autologous pericardial patch were used in 9 patients of TCP. Actuarial freedom from PS at 7 years was 70.8 +/- 9.2% in S-TAP and 79.2 +/- 8.3% in TCP, and there was no significant difference. Incidence of severe PR was significantly higher in S-TAP (7/24) than TCP (1/24) (p < 0.05). Actuarial freedom from PR at 7 year was 69.6 +/- 9.6% in the former and 95.8 +/- 4.2% in the later, respectively. The diameter of the pulmonary arterial annuals was augmented with the somatic growth in 6 patients with the pedicled pericardial patch. CONCLUSIONS: Two cusp plasty was more effective to prevent PR in the postoperative long-term period, comparing to S-TAP. As the material of the patch, pedicled autologous pericardium showed satisfactory outcome.

Blood Vessel Prosthesis Implantation↗
PubMed2001

Optic cup enlargement followed by reduced optic nerve head circulation after optic nerve stimulation.

PURPOSE: To investigate changes in optic nerve head (ONH) circulation, visual evoked potentials (VEPs), and ONH cupping after stimulation of the optic nerve. METHODS: Electrodes were fixed above the optic chiasma in rabbits under general anesthesia. Screw-type electrodes for VEP recording were fixed on the dura. ONH circulation, intraocular pressure (IOP), and blood pressure (BP) were measured after the passage of a current of 0.1 mA for 0.1 second (weak stimulation), 1 mA for 1 second (moderate), 5 mA for 10 seconds (strong), or 25 mA for 10 seconds (severe). Normalized blur (NB), indicative of tissue blood flow and velocity, was measured in the ONH after each stimulation, by using a laser speckle circulation analyzer. Changes in VEP and ocular fundus were also recorded. The ratio of cup area (CA) to disc area (DA) was measured before and 4 weeks after stimulation. After all experiments, the ONH was histologically examined. RESULTS: Weak stimulation increased NB in ONH for 10 minutes, whereas strong or severe stimulation significantly decreased NB for a longer time, in a dose-dependent manner. BP showed no significant change, except with severe stimulation. IOP was not significantly changed. VEP amplitude was reduced 30 minutes after strong stimulation. The CA-to-DA ratio was significantly increased 4 weeks after strong stimulation. In some rabbits, disc hemorrhage occurred, followed by enlargement of disc cupping, with slight gliosis. CONCLUSIONS: Electrical stimulation of the optic nerve changed ONH circulation and VEPs and increased disc cupping. This technique warrants further investigation as an experimental model for normal-tension glaucoma.

Animals↗
PubMed2001

Should the supplemental vein graft be anastomosed upstream or downstream of the internal thoracic artery (ITA) for ITA hypoperfusion?

BACKGROUND: This study was designed to compare internal thoracic artery (ITA) flow in different settings of supplemental vein grafting for ITA hypoperfusion. METHODS: Fourteen dogs each received two coronary bypass grafts to the circumflex artery (CFX), using left ITA and vein grafts, and then the proximal CFX was ligated. The animals were divided into two groups. G-I dogs receiving the vein graft proximally to the ITA graft and G-II receiving the vein distally. ITA flow was evaluated regarding 1) effects of competition from the vein graft, and 2) pharmacological or physiological effects on the ITA's contribution to distal perfusion. Flow is expressed as a mean (ml/min). RESULTS: ITA flow was 44.2+/-5.9 in G-I, and 45.7+/-6.5 in G-II (p=ns), when the vein graft was occluded. With a vein graft open, ITA flow decreased to 7.5+/-1.6 in G-I, and 6.8+/-1.8 in G-II (p=ns), and ITA's contribution to total perfusion requirements was 18% in G-I and 16% in G-II. Adenosine (0.2 mg/min/kg) increased the ITA flow in both groups, 18.4+/-3.2, and 16.3+/-3.8, respectively (p=ns), and ITA's contribution to distal perfusion was increased to 32% in G-I and 27% in G-II. In contrast, phenylephrine (0.003 mg/min/kg) decreased ITA flow and ITA's contribution to distal flow in both groups (6.1+/-1.1, 11% vs 6.2+/-1.4, 11%, p=ns), but increased vein flow significantly. Cardiac pacing (150 bpm) increased the ITA flow and ITA's contribution to distal perfusion equally in both groups (8.4+/-1.5, 16% vs 7.6+/-2.6, 15%, p=ns). CONCLUSIONS: Supplemental vein grafting, whether it is placed distally or proximally, limits ITA flow and ITA's contribution to distal perfusion both in the resting heart and during the increased myocardial oxygen demand.

Anastomosis, Surgical↗
PubMed2001

Intravenous nedaplatin and intraarterial cisplatin with transcatheter arterial embolization for patients with locally advanced uterine cervical cancer.

Nedaplatin is a platinum analog that has less renal toxicity and higher efficacy for uterine cervical cancer than cisplatin. Intraarterial cisplatin has been shown to be more effective than intravenous cisplatin in the treatment of cervical cancer. To improve the prognosis of cervical cancer, we studied combination chemotherapy of intravenous nedaplatin and intraarticular cisplatin with transcatheter arterial embolization (TAE). The criteria for selecting patients for this study were as follows: age 16-75 years, stage Ib2-IV according to the classification of the International Federation of Gynecology and Obstetrics (FIGO), performance status between 0 and 2, a creatinine clearance of >40 ml/min, adequate bone marrow and adequate renal and hepatic function. Thirty-two patients, aged 29-72 years (median: 55) were treated. FIGO stage was Ib2 in seven patients, IIa in seven patients, IIb in four, IIIa in one, IIIb in seven and IVa in six. Twenty-four patients had squamous cell carcinoma, three had adenocarcinoma and five had adenosquamous carcinoma. Written informed consent was obtained from all patients. Nedaplatin (30-70 mg/m2) was administered intravenously on day 1 and cisplatin (70 mg/m2) was administered intraarticularly via both uterine arteries on day 3 using the Seldinger method. TAE was then performed. This course of treatment was repeated every 3 weeks for 2-3 cycles. Response to the therapy was defined by magnetic resonance imaging. Partial response was found in 59% patients (19/32) and complete response in 34% (11/32), with an overall response rate of 94% (30/32). Myelosuppression was manageable. No grade 2 neurotoxicity was observed. The median follow-up was 32 months (6-53 months), with 84% of patients showing an overall survival of 1 year and 77% showing an overall survival of 2 years. These results show that this combination chemotherapy effected a high response rate. However, its influence on long-term survival remains to be determined.

Adenocarcinoma↗
PubMed2000

The major low molecular weight apolipoprotein from normal and hyperlipidemia atherosclerosis-prone (LAP) Japanese quail.

The low molecular weight (LMW) apolipoprotein of apo C plays an important role in the metabolism of triglyceride-rich lipoproteins. This study aimed at a characterization of the major LMW apolipoproteins from normal quail strain, and also from LAP (hyperlipidemia atherosclerosis-prone) strain to identify its genetic disorder. The major LMW apoprotein cDNA clone from normal quail comprised of approximately 500 bp, and encoded polypeptide of 78 amino acid residues containing 57 amino acids as a mature apolipoprotein. Although the quail LMW apoprotein showed a low homology to either apo C-I, C-II, or C-III of other animals, it retained a well-developed amphipathic alpha-helix structure. There was no difference in the deduced primary structure of the quail LMW apoprotein between LAP and normal strain. An analysis of the mRNA expression showed that the quail LMW apoprotein was only expressed in the liver of both LAP and normal Japanese quail. No difference was noted in the hepatic expression of the quail LMW apoprotein mRNA between normal and LAP strains with neither normal nor atherogenic dietary conditions. The structure and expression of the major LMW apoprotein thus had no relevance to higher susceptibility of LAP strain to the experimental atherosclerosis.

Amino Acid Sequence↗