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Biomedical subjects

F Miyawaki

Publications and source records attributed to F Miyawaki.

At least 19 recordsLinked to original sources
PubMed2003

Development of a vibratory microinjection method.

To reduce cellular damage by pronuclear microinjection and nuclear transfer, we have recently developed a vibratory microinjection method. A micropipette was fixed to a piezoelectric ceramic with a resonance frequency of 70 kHz. When this micropipette was vibrated, it easily entered a mouse-fertilized egg without any sharp depression of the cell body, whereas a sharp, deep depression at the insertion site was observed when the micropipette was not vibrated. A depression rate defined as a rate of a depth of depression over an original cell diameter was utilized as an index of cellular deformation. The depression rates with and without vibration were 11.1 +/- 5.2% (N = 24) and 40.4 +/- 8.8% (N = 16), respectively (P < 0.0001, Student's t-test). In conclusion, the vibratory microinjection method is a new, useful option for gene transfer because it resulted in much less cellular deformation, therefore implicating less cellular damage.

Animals↗
PubMed2001

Experience of vein grafting in Göttingen minipigs.

We experimented with vein grafting surgery on Göttingen minipigs. Using the internal jugular vein for the tissue graft, we performed side-to-side anastomosis to the carotid artery, to which it runs parallel. One key point in this surgery was to prevent vasospasm of the carotid artery so as to keep the lumen sufficiently patent during anastomosis. The histopathological findings in the grafts which remained patent resembled those of vein grafts in humans. We therefore considered that this technique in minipigs can be applied for the study of coronary artery bypass surgery in humans.

Animals↗
PubMed1994

[Diagnosis of perioperative myocardial infarction by cardiac troponin T following coronary artery bypass grafting].

The determinations of cardiac troponin T provide the highest diagnostic efficiency for the detection of myocardial cell necrosis. To assess perioperative myocardial infarction, serum levels of cardiac troponin T were determined in 14 patients undergoing coronary artery bypass grafting (CABG). The patients were divided into two groups: group I (n = 9), those whose troponin T was less than 1.00 ng/ml on the first postoperative day; group II (n = 5), those whose troponin T was more than 1.00 ng/ml on the first postoperative day. Troponin T levels in group II patients were significantly higher than in group I from the second to the seventh postoperative day. Two patients in group II had specific changes on the electrocardiogram detecting perioperative myocardial infarction as a new Q wave and R wave reduction. These results suggest that troponin T is a valuable marker of perioperative myocardial infarction following CABG.

Adult↗
PubMed1993

[A case of right ventricular outflow reconstruction surgery using an autologous pericardial non-valved conduit to treat pulmonary atresia with uncommon systemic-pulmonary collateral artery].

A 11-year-old girl diagnosed as having pulmonary atresia with uncommon systemic-pulmonary artery underwent on March 6, 1991. The collateral artery was derived from the left subclavian artery and divided from the descending aorta. Right ventricular outflow reconstruction was performed using a non-valved conduit of the autologous pericardium, and anastomosis of the conduit and pulmonary artery was successfully performed prior to extracorporeal circulation, because of the conduit's flexibility. Thus, we could reduce extracorporeal circulation time. Postoperative course was excellent, and patient is free from the morbidity associated with prosthetic valve. It is considered that a non-valved conduit of the autologous pericardium may be effective, but will require a long term follow-up.

Blood Vessel Prosthesis↗
PubMed1992

[Mitral valve surgery using combined superior-transseptal approach to the left atrium].

Although various approaches to the mitral valve surgery have been tried in the past, it still may be difficult to obtain a good surgical field, particularly in cases of small left atrium or reoperation. We performed mitral valve surgery in 6 patients using the combined superior-transseptal approach to the left atrium proposed by Berreklouw. Exposure of the mitral valve was excellent and the operative procedure was simple in all cases. There were no differences in bleeding volume, length of operation or complication of arrhythmia between patients treated with this new approach and a group treated with conventional approach in our institute.

Adult↗
PubMed1990

Effect of compliance mismatch on flow disturbances in a model of an arterial graft replacement.

Flow disturbances in a model of an interposition graft in an arterial segment were measured using an ultrasound Doppler velocimeter. The effect of the degree of compliance mismatch between a stiff' graft' and compliant 'arterial' segments was investigated. In steady flow, disturbances were detected when the compliance ratio (stiff to compliant segments) was less than or equal to 0.1 and the Reynolds number greater than or equal to 2200. A recirculation zone just downstream of the distal anastomosis was observed at a Reynolds number greater than or equal to 2400. Disturbances were also measured under pulsatile flow which consisted of a time-varying component superimposed on a steady flow component. The time-varying flow component was either quasiphysiological or sinusoidal in shape. The Reynolds number was 500 but the frequency parameter varied from 4.2 to 8.5. Significant disturbances were observed for conduits with compliance ratio less than or equal to 0.19. The disturbance intensity tended to increase as the compliance ratio decreased and the frequency parameter increased. The magnitude of the disturbance was also greater with the quasiphysiological than the sinusoidal input flow waveform.

Arteries↗
PubMed1990

[Postoperative long-term quality of life at present after total correction of tetralogy of Fallot].

We performed a questionnaire study in 47 patients who underwent corrective surgery for tetralogy of Fallot (TF) more than 10 years previously. To evaluate quality of life, we used well-being score advocated by Kaplan. 12 patients whose well-being score was 1.0 were in entirely good health without any complaints. Well-being score of patients averaged 0.773 with the range from 0.58 to 1.0. The patient with high RV/LV pressure ratio or large CTR tended to have a low well-being score. Grade of Lown classification did not correlate to well-being score.

Adolescent↗
PubMed1990

[A study of the long-term graft patency using a saphenous vein graft following aorto-coronary bypass surgery].

Long term graft patency after aorto-coronary (A-C) bypass surgery has been reported in the West and the data shows a lower patency rate in saphenous vein grafts (SVG) than internal mammary artery grafts. We studied the long term SVG patency in cases of Japanese patients at our institute, and we have compared our results with those in the West. The subjects, including children, were 211 cases who received A-C bypass surgery using at least one SVG from Jan., 1975 to Sept., 1989. 182 of these cases (examination rate: 86%) received a postoperative angiography one or three months after surgery. The postoperative study took the form of either a selective coronary angiography or a digital subtraction angiography. In 81 cases, using the same two methods, graft patency was reconfirmed from one to eleven years after surgery. Early graft patency including children was 95%. Long term graft patency in the adult cases was 89% from 1 to 2 years (mean: 1.3 years), 94% from 2 to 5 years (mean: 3.2 years), 88% from 6 to 11 years (mean: 7.1 years) following the operation. Six patients died during the post operative follow up period. Two cases were sudden death, one resulted from a reoperation for recurrent angina, two were caused by malignant neoplasm and other was the result of a cerebro-vascular accident. The results correlating the long term graft patency using a SVG and long term mortality were not as negative at our institute as they have been in studies done in the West.

Adult↗
PubMed1989

[Evaluation of antiplatelet drugs on platelet functions--comparison between ticlopidine and dipyridamole after prosthetic valve replacement].

We examined the efficacy of antiplatelet drugs after prosthetic valve replacement. As an early postoperative group (group E), 49 patients were divided into four groups. In group A only warfarin was given. In group B warfarin and dipyridamole 300 mg/day, in group C warfarin and ticlopidine 300 mg/day, in group D warfarin and ticlopidine 600 mg/day were administered respectively. As a late postoperative group (group L), 45 patients with prosthetic valves were divided into two groups. In group I dipyridamole 300 mg/day in group II ticlopidine 300 mg/day were administered. Both group I and II received warfarin. In group E platelet counts and platelet aggregability were examined to 22 POD. In group L starting two years after valve replacement, platelet counts were examined eight times by three-month intervals, and platelet aggregability, platelet adhesiveness were investigated 36 months in group I and 27 months in group II postoperatively. Results are the following. 1) Neither ticlopidine nor dipyridamole had any effects on the platelet counts through the postoperative period. 2) In the early postoperative period, the administration of antiplatelet drugs to groups B, C, and D suppressed platelet aggregability more than group A. 3) Ticlopidine (groups C and II) reduced ADP and collagen aggregabilities compared with dipyridamole (group B and I) both in the early and late postoperative period. 4) Ticlopidine 300 mg/day (group C) and ticlopidine 600 mg/day (group D) had no difference in ADP and Collagen aggregabilities. 5) No significant difference was shown between dipyridamole (group I) and ticlopidine (group II) in platelet adhesiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Wrapped-knitted Dacron and microporous EPTFE conduits for reconstruction of right ventricular outflow tract.

The use of the extracardiac conduit for the right ventricle to main pulmonary artery continuity facilitates repair of a wide variety of complex congenital cardiac malformations. Recently, concern has been directed to the appearance of proliferating and obstructive internal peels. In the present study on 18 mongrel dogs, wrapped-knitted Dacron, expanded polytetrafluoroethylene (EPTFE) and wrapped-knitted Dacron/EPTFE conduits were evaluated in the light of internal linings. Macroscopically, the wrapped-knitted Dacron conduits were covered with a thicker and poorly developed neointima, whereas, EPTFE conduits were internally covered with a thin neointima. Microscopically, the neointima on the former was not well healed, while that of the latter was well developed and anchored. Therefore, the EPTFE conduit seems to be superior to the wrapped-knitted Dacron conduit and EPTFE conduit can be used clinically.

Animals↗