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Biomedical subjects

T Okoshi

Publications and source records attributed to T Okoshi.

At least 37 records · Page 2Linked to original sources
PubMed1990

[A case of aneurysm of the inferior left ventricular wall].

Aneurysms of the inferior left ventricular wall represent only a small fraction of all aneurysms that have been reported in surgical series. And in comparison to anterior left ventricular aneurysms, a comparatively higher percentage of reported inferior wall aneurysms was classified as false. A 73-year-old male was admitted for acute inferior myocardial infarction. Three weeks after admission, cardiac catheterization was carried out. Coronary arteriography revealed triple vessel disease and left ventriculography showed an aneurysm of the inferior left ventricular wall, whose feature near the mitral annulus was multiple fenestrations. Left ventricular aneurysmectomy and aortocoronary bypass grafting to the left anterior descending artery were simultaneously performed under cardiopulmonary bypass with moderate hypothermia. The pathological feature was a true aneurysm. The postoperative course was uneventful.

Aged↗
PubMed1989

[Aortic wall injury and thrombogenesis in catheterization: experimental study].

Arterial and venous catheterization is a very useful procedure in the diagnosis of heart diseases. However, some complications with thrombogenesis have been reported. Two kinds of Mikaelson-type non-heparin-coated angiographic catheters (with 6.5 Fr. and 80 cm length) were used for the experiments. One was of polyurethane (PUC) and the other of polyethelene (PEC). Eight experimental dogs were used for each group. The catheter was inserted into the ascending aorta through the femoral artery. No antithrombogenic drugs were given to the animal. One hour later, sodium heparin (100 U/kg) was administered intravenously. The animal was sacrificed by acute exanguination. The aorta was opened longitudinally. The position of the thrombi on the aortic wall was macroscopically observed and the weight of the thrombi attached to the catheters were measured. A piece of the aorta at each level was excised for light and scanning electron microscopic observations. Mural thrombi of various lengths still remained on the aortic wall of every dog after the removal of the catheters. Microscopic observation revealed that the mural thrombus was formed on the aortic wall, where the endothelial cells had peeled off and the internal elastic membrane was partially destroyed. SEM observation also showed that fibrin network on the aortic wall where the endotherial cells were peeled off. Microscopic observation of aortic wall also revealed intimal tears, inner elastic membrane injury and bleeding in the elastic membrane. This damage could worsen leading to dissection of the aorta, thrombosis of the abdominal organs. The injury is considered due to mechanical irriation by the catheter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Aortocoronary bypass grafting with hydrophilic small caliber vascular grafts.

Previous work showed that the authors' vascular graft had satisfactory antithrombogenicity because of high hydrophilicity. The authors developed a small-caliber xenograft using new technology and evaluated the potential application for aortocoronary bypass grafting. Fresh sheep carotid artery with an internal diameter of 3 mm was obtained, and cross-linked with hydrophilic polyepoxy compounds. A 6 cm segment of the graft was then used between the aorta and the left circumflex coronary artery without cardiopulmonary bypass in 17 dogs. Sodium heparin was given during the surgery, but no anticoagulant was used thereafter. After the surgery, the dogs were randomly assigned to two groups according to the observation period. In 11 animals (Group 1), the observation period was up to 24 hr, at which time the grafts were evaluated; the patency rate was 72.7%. The patent grafts were clean and without thrombi. At the distal anastomotic lines of the occluded grafts, a thrombus was observed and a technical error was highly suspected. In six dogs (Group 2), angiography was performed to confirm graft patency between 2 and 3 weeks. The patency rate was 50% during the mean observation period of 17.5 days. One graft was evaluated at postoperative day 23. It was patent and soft, and the inner surface was shiny and smooth. Microscopic observation showed nice healing characteristics. These results indicate that it is possible for this new graft to be used for aortocoronary bypass grafting.

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PubMedDate not supplied

Long-term results of a new antithrombogenic cardiac wall substitute.

We evaluated the long-term results of a new antithrombogenic cardiac wall substitute which is composed of collagen-coated ultrafine polyester mesh cross-linked by a hydrophilic polyepoxy compound (CUFP), and compared it with glutaraldehyde-treated equine pericardium (GA graft). In an animal study, 20 CUFPs and 18 GA control grafts were implanted as patches in the right ventricular outflow tract in 38 dogs. In the CUFP at 28 days after implantation, a thin neointima, which was almost endothelialized, had been formed. Fibroblasts and vasa vasorum were seen inside both the neointima and the graft wall. At 168 days, transmission electron microscopy revealed smooth muscle-like cells in the neointima, with endothelialization. The CUFP at 486 days had maintained a white, shiny, smooth, thin, and uniform neointima with endothelialization. Neither ulcer nor thrombus formation was seen on the surface, while in the GA graft at 353 days, no endothelialization was noticed in the center and almost no fibroblasts had infiltrated into the graft wall. From these results, the CUFP should be an ideal candidate for cardiac wall substitution.

Animals↗
PubMedDate not supplied

A method to reduce thrombogenicity of a graft for small diameter arterial substitution seeded with autologous venous tissue fragments.

The authors successfully applied a method to accelerate endothelialization by tissue fragmentation to a small diameter fabric vascular prosthesis. Tissue fragment seeded grafts showed rapid healing of the neointima. The thrombogenicity of the collagen fibrils in the fragments, however, caused major problems when the method was applied to small diameter grafts: the positively charged collagen fibrils aggregated the negatively charged platelets. The authors masked the fibrils electrostatically with heparin molecules, which are negatively charged. A canine jugular vein was resected, minced into tissue fragments, and suspended in the heparin solution; it then was sieved through the wall of a fabric prosthesis. The grafts (4 mm internal diameter and 3.5 cm in length) were implanted into both carotid arteries of six dogs (12 grafts). Tissue fragment seeded grafts without heparin also were implanted into six dogs. As a control, preclotted fabric grafts were implanted into six dogs (12 grafts). These grafts occluded within 1 week, whereas all the masked grafts were patent without thrombi. In vitro examination of heparin release revealed that approximately 92% of heparin in the graft was released during the first 5 hr, but approximately 6% remained after 25 hr. These results indicate that the method is applicable to small diameter arterial grafts.

Animals↗
PubMedDate not supplied

Microporous small diameter PVDF-TrFE vascular grafts fabricated by a spray phase inversion technique.

Microporous prostheses of 1.5 mm internal diameter were fabricated with a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE)n co-polymer by the spray phase inversion technique. Some of the grafts were made piezoelectric by poling under a high electrical field. Overall, 24 poled grafts (P) and 24 unpoled grafts (UP) (15-22 mm in length) were implanted in the infrarenal aorta of 48 adult rats. Patency rates in P were 100% (8/8) at 2 days, 100% (8/8) at 2 weeks, 75% (6/8) at 6 months, and 92% total (22 of 24). Patency rates in UP were 100% (8/8) at 2 days, 63% (5/8) at 2 weeks, 100% (8/8) at 6 months, and 88% total (21 of 24). Thus there was no significant difference in patency between the two types of grafts. Both showed similar macroscopic and microscopic findings. At 2 days, fibrin deposition was somewhat heavier on the poled grafts, but no difference in surface platelet deposition could be detected. Endothelialization was observed from both anastomoses at 2 weeks and was almost complete at 6 months. The excellent biocompatibility of PVDF-TrFE and the microporous structure of the grafts were probably the dominant factors in success with these grafts. Although piezoelectric activity in excised cleaned poled prostheses remained significantly higher than that in the control UP, the charges developed may have been too small to exert a biologic effect, either because of insufficient dipole orientation or inadequate mechanical deformation.

Animals↗
PubMedDate not supplied

Development of a polyepoxy compound cross-linked heterologous connective tissue tube.

A heterologous connective tissue tube with "built-in" polyester mesh was developed using a rabbit subcutaneous tissue and polyepoxy compound cross-linking method. To evaluate the graft, 11 grafts were implanted end to end in the position of the thoracic aorta of 11 dogs and evaluated from 1 hr to 80 days after surgery. The graft was white and pliable, and the mesh was seen through the connective tissue. The handling characteristics were good, and no bleeding was observed from either the graft wall or suture holes. Macroscopically, at 1 hour, the luminal surface was covered with a thin thrombus layer. At 80 days, most of the inner surface of the explanted graft was white and shiny without irregularity, but a small area of blood stain was observed. Microscopically, fibroblasts were observed in the graft wall at 7 days; capillaries penetrating to the luminal surface appeared at 29 days. Bleeding was rarely observed around the fabric. A layer of donor connective tissue was still observed at 80 days. No foreign body reaction was observed except around the mesh. It was concluded that the graft healed well and could be an arterial substitute.

Animals↗
PubMedDate not supplied

Rapid neointima formation with elastic laminae similar to the natural arterial wall on an adipose tissue fragmented vascular prosthesis.

A vascular prosthesis that can induce a neointima similar to a natural arterial wall is reported. The authors have developed a sealing method using autologous tissue fragments. The sealed graft showed many advantages, with characteristic neointima formation in an animal study. The grafts were implanted in the thoracic descending aortae of 40 dogs and were removed from 1 hour to 608 days after implantation. Another 40 dogs, used as controls, had a fabric graft implanted using the preclotting method. The luminal surface of the sealed graft was completely endothelialized and the original adipose tissue fragments were absorbed within 1 month. Smooth muscle cells infiltrated and proliferated at the same time as endothelialization took place. Most of the smooth muscle cells were arranged in parallel rows and oriented circumferentially within the graft. At 1 month, elastic fibers appeared around the smooth muscle cells near the anastomotic sites. In the long-term specimens, these elastic fibers constituted a fine lamina in the neointima. Intimal hyperplasia and degenerative changes in the neointima were not observed. These results indicated that the sealing method could induce a very stable neointima with a smooth muscle cell layer and elastic laminae similar to a natural arterial wall within a short period of time throughout the graft wall, with maintenance of the neointima for a long period of time after implantation.

Adipose Tissue↗
PubMedDate not supplied

Penetrating micropores increase patency and achieve extensive endothelialization in small diameter polymer skin coated vascular grafts.

This article points to the importance of penetrating micropores through the graft wall to minimize thrombosis and to enhance endothelialization in small diameter polymer skin coated vascular grafts. Four types of spongy polyurethane-polydimethylsiloxane vascular grafts (PUG) fabricated by a spray, phase-inversion technique, 1.5 mm inner diameter, 1.5-1.9 cm in length, were implanted end-to-end in the infrarenal aorta of 26 adult rats. Some had a continuous inner skin and a hydraulic permeability (HP) of 0 ml/min/cm2/ 120 mmHg (PUG-S-O). Some had an inner skin with varying amounts of isolated penetrating micropores and a mean hydraulic permeability of 11 (PUG-S-11), 37 (PUG-S-37), or 58 ml/min/cm2/120 mmHg (PUG-S-58). Twelve PUG-S-O, 6 PUG-S-11, 4 PUG-S-11, and 4 PUG-S-58 were evaluated between 2 hr and 3 months after implantation. All PUG-S-O occluded soon after implantation. The PUG that had a HP of more than 11 ml/min/cm2 showed acceptable patency. However, endothelialization was limited to anastomoses in patent PUG-S-11. In contrast, the patent PUG-S-37 and PUG-S-58 were largely endothelialized. In all patent grafts at 3 months, numerous host cells had migrated, and newly formed capillaries were seen in the voids of the graft wall, which appeared moderately to highly cellular. In conclusion, it appears that penetrating micropores through the graft wall increase patency and that a highly porous structure is needed to achieve extensive endothelialization in small diameter polymer skin coated vascular grafts.

Animals↗
PubMedDate not supplied

Endogenous basic fibroblast growth factor for endothelialization due to angiogenesis in fabric vascular prostheses.

Angiogenesis by basic fibroblast growth factor (bFGF) is important for endothelialization in vascular prostheses and is significant from shortly after implantation. Canine adipose tissue was resected, minced into fragments, and suspended. This mixture was sieved through the wall of a fabric vascular prosthesis. Tissue-fragmented grafts (TF-grafts, 6 mm internal diameter, 6 cm long) were implanted into the abdominal aortae of four dogs, and four preclotted grafts were used as control subjects. Grafts were removed at 1-7 days after implantation. Removed grafts were evaluated microscopically, immunohistologically, and by scanning electron microscope. At day 1, a thrombus layer was on the TF-graft lumen. At day 3, cell proliferation and migration were observed. At day 5, endothelial-like cells were extending onto the luminal thrombus. Cell proliferation around the fragments was active, and those cells were bFGF positive. In the control subjects, at day 7, the perigraft tissue was bFGF positive, whereas no endothelialization on the lumen or no capillary infiltration into the graft wall was observed. Furthermore, bFGF was negative in the sites of thrombus and infection. These results demonstrate that endogenous bFGF is important for endothelialization due to angiogenesis in fabric vascular prostheses, whereas thrombus and infection might have a negative effect.

Adipose Tissue↗