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Biomedical subjects

K Okadome

Publications and source records attributed to K Okadome.

At least 55 records · Page 3Linked to original sources
PubMed1991

Significance of the endothelial lining in prevention of intimal thickening of autogenous vein grafts in dogs.

To better comprehend the role of the endothelial lining in occurrence and development of intimal thickening in arterially implanted autogenous vein grafts, two models of canine femoral arteries were prepared. In the Group I model, the implanted autogenous vein graft was kept under a normal flow condition for 2 to 4 weeks after implantation, then was exposed to an abnormal flow (poor run-off). In case of a 3- to 4-week normal flow, intimal thickening was practically nil. Scanning electron microscopic studies showed that this 3- to 4-week period corresponded to that of re-endothelialization of the autogenous vein grafts. Immunohistochemical studies of fibrinogen distribution in the autogenous vein graft wall in the Group II model revealed that the permeation of fibrinogen was enhanced in case of an abnormal flow condition for about 2 weeks after the implantation. We interpret these observations to mean that intimal thickening was induced by an accelerated permeability in the presence of abnormal flow conditions until full re-endothelialization after the implantation.

Animals↗
PubMed1991

Laser thermal angioplasty for early repair of anastomotic stenosis after lower extremity arterial reconstruction: initial experience.

Laser thermal angioplasty with a sapphire hot-tip Nd-YAG laser system was effectively used for five grafts with anastomotic stenotic lesions which occurred after femoro-popliteal arterial reconstructions. Stenotic lesions were detected by a combination of Doppler flow waveform analysis and ankle/brachial index measurement in 32 femoro-popliteal and five femoro-tibial arterial bypass grafts in the postoperative period. The laser probe used was 3 to 4 mm in diameter. There were no perforations of the arterial wall caused by thermal ablation, even with repeated pulses of 40 watts of laser energy for 3 s. Contact Nd-YAG laser thermal angioplasty using this rounded, 3-4 mm hot-tip facilitated effective widening of the lumen of the anastomotic stenotic lesion. All patients remain well at follow-up from 9 to 20 months after laser thermal angioplasty.

Aged↗
PubMed1991

Simulated blood flow and the effects on prostacyclin production in the dog femoral artery.

Effects of blood flow on the production of prostacyclin (PGI2) were examined in the canine femoral artery perfused ex vivo. Each artery was perfused in situ with medium 199, under conditions of simulated blood flow. To simulate the normal and abnormal blood flow waveforms at the same mean flow rate, we developed a flow apparatus capable of making various waveforms by changing the duration when the electromagnetic valve in the circuit was open. Group I (n = 7) was exposed to a steep acceleration waveform followed by a steep deceleration, as the normal flow waveform; group II (n = 7) was exposed to a gentle sloping waveform in the deceleration phase, as the abnormal flow waveform. PGI2 was measured as 6-ketoprostaglandin F1 alpha. PGI2 production was estimated as the cumulative production for the first 5 minutes (acute response) and as the production rate after the first 30 minutes (stable production rate). Under conditions of normal flow, the acute response was 5.87 +/- 2.16 ng/cm2/5 min, whereas under conditions of abnormal flow, the rate was 2.20 +/- 0.27 ng/cm2/5 min (p less than 0.01). Stable production rates were 82.5 and 37.5 pg/cm2/min, respectively (p less than 0.05). Both the acute response and the stable production rate of PGI2 production were greater under conditions of simulated normal flow as compared with findings in the case of an abnormal flow. Our working hypothesis is that the decreased production of PGI2, as well as a deterioration in the implanted graft, under conditions of abnormal blood flow leads to a loss of late patency of the reconstructed arteries.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Possible transmission of serum hepatitis in liver surgery with the ultrasonic dissector.

When the ultrasonic dissector is used during liver surgery, the possibility exists of the transmission of virus to the attending hospital personnel because of unavoidable splashing of the irrigating solution. It becomes apparent from this study that the titer of hepatitis B surface antigen in the aspirated irrigating solution is almost the same level as that in the serum. We therefore strongly recommend that eye shields should be used in hepatic surgery when the ultrasonic dissector is in use.

Adult↗
PubMed1990

Computational simulation method of intraluminal velocity profile proved by laser Doppler velocimeter.

Measurement of the intraluminal velocity profile within an artery may provide insight into predicting the prognosis of arterial reconstruction. To confirm the results of the computer simulation method a laser Doppler velocimeter using an optical fiber was applied to canine femoral arteries with good or poor runoff, and the intraluminal velocity profile was measured directly. Under normal flow conditions, remarkable fluctuation was obtained at the layer adjacent to the wall, whereas under poor runoff conditions, stagnation of flow was seen at the layer adjacent to the wall. These results showed that our computational simulation method which calculates the intraluminal velocity profile was a reliable, valid method of on-line analysis of the intraluminal velocity profile.

Animals↗
PubMed1990

Flow waveform analysis and long-term results of autogenous saphenous vein and polytetrafluoroethylene grafts in 140 arterial reconstructions of the lower limbs.

In previous work we have found that the outcome of grafts in the lower limbs correlated with the flow waveform pattern of the artery. We have retrospectively reviewed 140 femoro-popliteal bypass operations involving the use of 75 saphenous vein grafts and 65 polytetrafluoroethylene (PTFE) grafts. For grafts with type 0 or I flow waveform pattern the patency at 4 years (56%) was superior to grafts with the type II, III or IV flow waveform (35%) patterns (P less than 0.05). For saphenous vein grafts with type 0 or I flow, the patency rate was 78% at 3 years and 69% at 5 and 8 years. In contrast with type II, III or IV flow the patency rate was 52% at 3 years, 48% at 5 years and 34% at 8 years, with a statistical significance at 4 years (P less than 0.05). PTFE grafts with type 0 or I flow showed a tendency toward an increased patency which was not significant in comparison with the grafts with type II, III or IV flow (P = 0.12). Saphenous vein grafts with type II flow patterns had an increased occlusive rate in the first year whereas PTFE grafts had the same tendency within 2 years. In both types of graft, early occlusions within a month of operation were encountered in grafts with a type III or IV flow waveform pattern. These results indicate that the fate of the reconstructed arteries of the lower limb could be predicted by flow waveform analysis, and a careful and serial postoperative evaluation of the graft should be made, particularly those with type II, III or IV flow waveform patterns.

Blood Vessel Prosthesis↗
PubMed1990

Intimal thickening and permeability of arterial autogenous vein graft in a canine poor-runoff model: transmission electron microscopic evidence.

The relationship between development of intimal thickening and permeability of an arterial autogenous vein grafts in dogs' limbs was examined with horseradish peroxidase used as a tracer. The transendothelial transports increased under conditions of abnormal blood flow, compared with findings with a normal blood flow, and a large amount of horseradish peroxidase infiltrated the subendothelial spaces for 4 weeks after implantation, a time when intimal thickening progressed rapidly. It would thus appear that, under conditions of abnormal blood flow, intimal hyperpermeation would be a contributing factor to the intimal thickening of an autogenous vein graft before an autovein graft had completely adapted to the new environment.

Animals↗
PubMed1989

Venous reconstruction for iliofemoral venous occlusion facilitated by temporary arteriovenous shunt. Long-term results in nine patients.

In nine patients with iliofemoral venous occlusion, venous reconstructions using a temporary arteriovenous shunt were performed by open thromboendvenectomy with autogenous vein patch angioplasty in four, expanded polytetrafluoroethylene (ePTFE) bypass grafts (including two with external ring-supported ePTFE) in four, and Palma's procedure in one patient. There was an adequate function in the reconstructed venous segments in two of four who underwent thromboendvenectomy and in all four with ePTFE bypass grafting for nine months to 13 years after surgery. In those with a temporary arteriovenous shunt, prepared to maintain patency of the reconstructed venous segments, blood flow through the shunt exceeded 100 mL/min, determined by an electromagnetic flowmeter. Postoperative shunt closure was readily facilitated, using a looping technique and a 2-0 nylon. The increased blood flow through the graft made feasible by the temporary arteriovenous shunt enhanced the patency of the reconstructed venous graft and hence there was an improvement in the affected limb.

Adolescent↗
PubMed1988

Intimal hyperplasia: the permeation of serum-derived substance into the arterial autovein graft under abnormal blood flow.

The etiology of intimal hyperplasia in autogenous vein grafts used for arterial replacement was experimentally studied in dogs. We previously developed an experimental model, which mimicked a human extremity with poor run-off of peripheral arteries. This model characterized the abnormal flow by a weak fluctuation of wall shear stress at the site adjacent to the vessel wall. In this model we found that an autogenous vein implanted into the femoral artery under such abnormal flow conditions exhibited remarkable intimal thickening; 200-400 micron at 1 month and 300-500 micron at 6 months. A fluorescence microscopic study revealed that Evans blue-albumin complex entered the inner wall of vein grafts transplanted in abnormal flow conditions until about 2 weeks after implantation, after which further permeation was no longer observed. A similar observation was made in the fibrinogen distribution of subendothelial tissue. These results showed that abnormal flow conditions enhance the permeation of certain substances into immaturely repaired intimal tissues of autovein grafts. This phenomenon is thought to be responsible for the proliferation of smooth muscle cells, leading to hyperplasia of autovein grafts.

Animals↗
PubMed1987

Development and regression of intimal thickening of arterially transplanted autologous vein grafts in dogs.

To investigate the influence of hemodynamic conditions on intimal thickening of arterially transplanted autologous vein grafts, two experimental models of canine femoral arteries were prepared. In group I, in which an autologous vein graft was transplanted under abnormal flow conditions (distal poor runoff), intimal thickening gradually developed and reached 358 +/- 33 microns at 8 months, whereas no thickening was observed under normal flow conditions at any time throughout the observation period. In group II the thickened intima, which developed under abnormal flow conditions for 1 month, was reimplanted into the contralateral leg under normal flow conditions. The thickness of the intima markedly regressed to about 66% at 1 month, 50% at 3 months, and 25% at 8 months, respectively, whereas no regression of the thickened intima was observed under continued abnormal flow conditions. Electron microscopic studies revealed that the thickened intima in group I was composed of proliferation of transformed smooth muscle cells with a marked increase in the mitochondria, the rough endoplasmic reticulum, and an abundant fibrous matrix, whereas with the regressed thickness of the intima of group II, the smooth muscle cells were spindle-shaped with distinct myofibrillae. These results provide pertinent data on the process involved in the intimal thickening in cases of graft placement.

Animals↗
PubMed1986

Modified vein allograft for small arterial reconstruction in dogs.

The ideal graft for peripheral arterial reconstruction has yet to be developed. We evaluated on the effectiveness of porosity to intimization of the graft. Modified vein allografts newly constructed through digestion of vein allografts with elastase, glutaraldehyde tanning and lyophilization were implanted in thirty-nine canine femoral arteries. These grafts had a higher porosity than conventional vein allografts and the overall patency rate was 70 per cent at 6 months after implantation. Microscopic examination showed that graft interstitial healing and subsequent intimization were completed by ingrowth of connective tissue from outside through the graft wall at 3 weeks and later. Aneurysmal change of the modified vein allografts was never evident. These results indicated that porosity of the graft is indeed an important factor for intimization and durability of grafts, even in bioderivative substitutes.

Animals↗
PubMed1986

Pathophysiological effects of fibrin on arterial endothelial cells in vivo: an electron microscopic study.

Interactions between fibrin and arterial endothelial cells of rat iliac arteries in vivo were studies electron microscopically using a newly devised method. The microvilli became attached to the fibrin threads in an initial period of fibrinolysis. These threads had a fine granular appearance in the lysed areas. Fibrinolytically active endothelial cells had an active vesicular transport for ferritin particles injected concomitantly with the fibrinogen-thrombin mixture, thereby implying the enhancement of endothelial permeability in the lysed areas. However, fibrinolytically inactive endothelial cells coexisted in the same arteries. The denuded intima showed no lytic changes in the fibrin threads. These results indicate that the microvilli of the endothelial cells may plan an important role in the releasing plasminogen tissue activator from the endothelial cells and that there is a heterogeneity with regard to reactivity of each endothelial cell to fibrin.

Animals↗
PubMed1986

Flow waveform assessment of polytetrafluoroethylene grafts for reconstruction of lower extremity arteries. A preliminary report.

On the basis of our findings that the outcome of reconstructive surgery for lower limbs could well be predicted by flow waveform analysis, we reviewed femoropopliteal arterial bypass operations involving the use of polytetrafluoroethylene (PTFE) grafts for 35 patients. Of 38 grafts, 26 were PTFE alone, and 12 were PTFE/vein composite grafts. Neither ankle pressure index nor angiographic distal runoff was of predictive value as a prognostic indicator. The cumulative patency rate, calculated by the life-table method, revealed the usefulness of flow waveform analysis for prediction of the outcome of PTFE grafts. In type 0 or I flow, the patency rate was 94% at 1 and 2 years and 79% at 3 years. In contrast, in type II flow, the patency rate was 74% at 1 year, 66% at 2 years, and 49% at 3 years, with a statistical significance at 2 and 3 years (p less than 0.05). Comparison of the result of PTFE grafts with that of PTFE/vein composite grafts showed superior results of composite grafts at 3 years after implantation (42% vs. 83%, p less than 0.05). These findings indicate that flow waveform analysis is useful for prediction of the outcome of PTFE grafts and that PTFE/vein composite grafts should probably be used, particularly in cases of abnormal blood flow.

Actuarial Analysis↗