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Biomedical subjects

T Okoshi

Publications and source records attributed to T Okoshi.

At least 19 recordsLinked to original sources
PubMed2002

[A case of ischemic dilated cardiomyopathy, mitral regurgitation and congestive heart failure successfully treated by Batista operation, coronary artery bypass grafting and mitral valve replacement; usefulness of myocardial scintigraphy].

A 75-year-old man diagnosed as having ischemic dilated cardiomyopathy, congestive heart failure and mitral regurgitation underwent left ventricle volume reduction operation (Batista), coronary bypass grafting and mitral valve replacement because myocardial infarction had developed at lateral, inferior and small area of apex wall, not at interventricular septum. Left ventricular endodiastolic volume index and left ventricular endosystolic volume index decreased from pre-operative values of 155, and 128 ml/m2 to post-operative values of 113, and 82 ml/m2, respectively. Left ventricular ejection fraction increased from a pre-operative value of 17% to a post-operative value of 27%. This evaluation was performed by myocardial scintigraphy (quantitative gated spect: QGS). This method was bloodless and useful for determination of indication of left ventricle volume reduction surgery including Batista operation and pre- and post-operative evaluation of this type of surgery. Today, Batista operation is, generally speaking, performed for non-ischemic dilated cardiomyopathy. In this case, however, Batista operation was applied to ischemic dilated cardiomyopathy and was very effective.

Aged↗
PubMed1999

[Recent trend development of vascular grafts].

Recent researches on vascular grafts are introduced in this paper. A goal in development of small diameter vascular graft is to obtain their long-term patency and various approaches have been tried. On the other hand, renovation has been made aiming at further refinement of middle to large diameter vascular grafts although their long-term patency have been almost satisfactory. Endothelialization at graft inner surfaces is a very important key to achieve long-term patency and to prevent graft infection. Tissue engineering, which includes technologies on proteins, cells, genes, adhesive proteins, cytokines and so on, has been recently induced in development of vascular grafts. It is expected that excellent vascular grafts would be fabricated in the near future.

Animals↗
PubMed1998

Succinylated collagen crosslinked by thermal treatment for coating vascular prostheses.

Vascular prostheses coated with collagen carefully prepared to avoid contamination were tested to see if it could induce endothelial cell lining throughout the graft surface in a natural way. The collagen fibers were succinylated. Hydrogel produced with the succinylated collagen was used for the sealant to reduce the amount of solid substance. To avoid contamination and the side effects of chemical reagents, the collagen thermally crosslinked under sterile conditions. A suspension of the collagen fibers was enmeshed in the interstices of Dacron fibers of fabric prostheses, which were then thermally crosslinked at 130 degrees C for 20 h. The prostheses were porous when the collagen fiber network was dry. Under wet conditions, however, the water permeability of the grafts was reduced to 0.1 ml/min from the 1,250 ml/min of the original prostheses. Three weeks after implantation in the abdominal aortas of dogs, 81.2 +/- 11% of the luminal surface was macroscopically thrombus free, and 56 +/- 14% was endothelialized. More than 95% of the coated collagen had been absorbed. Numerous fibroblasts had migrated into the graft walls, and capillary blood vessels had infiltrated the inside of the graft walls without foreign body reaction. In the controls, thrombus free areas averaged 9.0 +/- 5%, and endothelialized areas averaged 5.2 +/- 4%. Many giant cells, plasma cells, and lymphocytes had migrated into the graft walls, but no fibroblasts. These results suggest that rapid endothelialization is possible when clean collagen is used.

Animals↗
PubMed1998

Choice, isolation, and preparation of cells for bioartificial vascular grafts.

Preparation of cells and tissues for bioartificial vascular grafts is discussed from the viewpoint of tissue engineering. In general, a neointima is not formed on vascular prostheses except at the anastomotic sites. Graft surfaces do not heal and are covered with fresh thrombi for a long period of time after implantation. The delayed healing is, so to speak, an intractable ulcer of the vascular wall. To overcome this problem, we have developed a tissue fragment transplantation method. We consider that neointima formation of vascular prostheses after implantation is a product of tissue engineering in vivo. Therefore, 3 essential elements for tissue engineering, i.e., cells, extracellular matrices, and cytokines, are required for neointima formation. Synthetic vascular prostheses lack one or more of these elements. In this study we demonstrated a standard healing process of fabric vascular prostheses and an antithrombogenic polymer graft using animal models. Then we showed the tissue fragment transplantation method using venous tissues, adipose tissues, and bone marrow. This method provided the 3 essential elements to the prostheses. To allow these elements to be actively engaged in neointima formation, we treated cells and tissues as clumps without enzymatic digestion. We also took advantage of the in vivo environment. With the results we demonstrate our way of thinking in relation to bioartificial vascular grafts.

Adipose Tissue↗
PubMed1998

Brain imaging of affective disorders and schizophrenia.

We review recent findings in human brain imaging, for example, which brain areas are used during perception of colors, moving objects, human faces, facial expressions, sadness and happiness etc. One study used fluorine-18-labeled deoxyglucose positron emission tomography (PET) in patients with unipolar depression and bipolar depression, and found hypometabolism in the left anterolateral prefrontal cortex. Another study reported increased regional cerebral blood flow in the amygdala in familial pure depressive disease. Using 11C-glucose PET, we reported that the glutamic acid pool was reduced in cortical areas of the brain in patients with major depression. We also found that the thalamic and cingulate areas were hyperactive in drug-naive (never medicated) acute schizophrenics, while the associative frontal, parietal, temporal gyri were hypoactive in drug-naive chronic schizophrenics. Brain biochemical disturbances of schizophrenic patients involved glutamic acid, N-acetyl aspartic acid, phosphatidylcholine and sphingomyelin which are important chemical substances in the working brain. The areas of the thalamus and the cingulate which become hyperactive in acute schizophrenic patients are important brain areas for perception and communication. The association areas of the cortex which become disturbed in chronic schizophrenia are essential brain areas in human creativity (language, concepts, formation of cultures and societies) and exist only in human beings.

Bipolar Disorder↗
PubMed1997

Surgical treatment of traumatic rupture of the normal aortic valve.

Blunt trauma followed by aortic valvular insufficiency is a rare occurence. In one case, a male high-school student who had sustained a non-penetrative chest injury suffered from aortic regurgitation resulting from the rupture of the normal aortic valve. A sizable tear in the non-coronary cusp caused aortic insufficiency. The case was treated successfully by surgical replacement of the aortic valve with a No. 21 SJM prosthesis.

Adolescent↗
PubMed1995

New concept of microporous structure in small diameter vascular prostheses.

Six types of skinned and microporous vascular prostheses (1.5 mm ID) with different hydraulic permeabilities (HP) were fabricated with either a polyurethane polydimethylsiloxane (PU-PDMS) or a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) by the spray phase inversion technique: skinned PU-PDMS grafts with an HP of 0 ml/min/cm2 (PU-PDMS-S-0), microporous surfaced PU-PDMS grafts with an HP of 2.7 ml/min/cm2 (PU-PDMS-2.7), microporous surfaced PU-PDMS grafts with an HP of 39 ml/min/cm2 (PU-PDMS-39), poled skinned PVDF-TrFE grafts with an HP of 0 ml/min/cm2 (poled PVDF-TrFE-S-0), poled microporous surfaced PVDF-TrFE grafts with an HP of 41 ml/min/cm2 (poled PVDF-TrFE-41), and unpoled microporous surfaced PVDF-TrFE grafts with an HP of 41 ml/min/cm2 (unpoled PVDF-TrFE-41). Straight segments of these grafts (1.5-2.2 cm in length) and one loop PU-PDMS-39 (10 cm in length) were implanted in the rat infrarenal aorta. Graft surface morphology and wall porosity as reflected by hydraulic permeability were the main determinants of early patency and completeness of healing including endothelialization.

Animals↗
PubMed1995

[Leukoencephalopathy in a patient being treated for small cell lung cancer].

A 62-year-old man was given a diagnosis of small cell lung cancer, and received 6 courses of combination chemotherapy (PE therapy) composed of cisplatin (80 mg/m2, day 1) and etoposide (100 mg/m2, days 1, 2, 3). Multiple brain metastases were found, and whole brain irradiation (44 Gy) was given. Eleven months after radiotherapy, he suffered from dizziness and abnormal gait. Enhanced CT of the head showed slight enlargement of the lateral ventricles and markedly low density of the white matter, but no evidence of intracranial tumor involvement. A magnetic resonance scan (axial T2-weighted) showed symmetric extensive hyperintensity in the white matter. Treatment-related leukoencephalopathy caused by the PE therapy and whole brain irradiation was diagnosed. He was alive 8 months after the appearance of neurological symptoms, without recurrence of lung cancer. A search of the literature revealed no previous report of leukoencephalopathy related to PE therapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Characterization of tumor necrosis factor alpha-induced alteration of glycosaminoglycans in cultured cells: comparison among vascular smooth-muscle cells, vascular endothelial cells, Chang liver cells and LLC-PK1 cells.

We investigated the alteration of glycosaminoglycans (GAGs) induced by recombinant human tumor necrosis factor alpha (rhTNF alpha) using confluent cultures of bovine aortic smooth-muscle cells, bovine aortic endothelial cells, Chang liver cells and porcine kidney LLC-PK1 cells. It was found that the incorporation of both [35S]sulfate and [3H]glucosamine into GAGs in the trypsinate fraction of the cell layer was significantly decreased by rhTNF alpha in vascular smooth-muscle cells and vascular endothelial cells; the incorporation of [35S]sulfate was increased but that of [3H]glucosamine was unchanged in Chang liver cells; the incorporation of both [35S]sulfate and [3H]glucosamine was increased by rhTNF alpha in LLC-PK1 cells. In the conditioned medium, the incorporation of both [35S]sulfate and [3H]glucosamine was not greatly changed by rhTNF alpha in all tested cell types. Characterization of GAGs revealed that each cell type uniquely altered its GAGs after rhTNF alpha treatment; the cytokine-induced alteration of each GAG component was not necessarily the same among different cell types. It was therefore concluded that rhTNF alpha-induced alteration of GAGs is dependent upon cell type.

Animals↗
PubMed1993

Very small-diameter polyurethane vascular prostheses with rapid endothelialization for coronary artery bypass grafting.

Two types of spongy polyurethane-polydimethylsiloxane blend (Cardiothane 51, Kontron Instruments, Inc., Everett, Mass.) vascular grafts with an internal diameter of 1.5 mm were fabricated by a spray, phase-inversion technique. Low-porosity grafts with hydraulic permeability of 2.7 +/- 0.4 ml/min per square centimeter and medium-porosity grafts with hydraulic permeability of 39 +/- 8 ml/min per square centimeter displayed good handling properties and suturability. Twelve straight low-porosity grafts, 17 straight medium-porosity grafts (1.5 to 2.0 cm in length), and one loop medium-porosity graft (10 cm in length) were implanted by the same surgeon end to end in the infrarenal aorta of 30 male Sprague-Dawley rats. Three months after implantation, patency was 8% for low-porosity grafts (1/12) and 76% for straight medium-porosity grafts (13/17). The loop medium-porosity graft was also patent. The sole patent low-porosity graft showed neointimal hyperplasia and incomplete endothelialization. All but one of the patent straight medium-porosity grafts showed a glistening and transparent neointima with complete endothelialization and no anastomotic hyperplasia. The loop medium-porosity graft displayed endothelialization from each anastomosis and in many islands in the middle portion of the graft, totalling 47% of the luminal surface by morphometric analysis. Thick mural thrombus, anastomotic hyperplasia, or aneurysm formation were not observed in any patent medium-porosity graft. These data indicate that in the rat aortic replacement model it is possible to achieve patency and a high degree of endothelialization in very small-diameter prostheses of appropriate porosity.

Animals↗
PubMed1993

Acceleration of neointima formation in vascular prostheses by transplantation of autologous venous tissue fragments. Application to small-diameter grafts.

We have previously demonstrated rapid and complete endothelialization in synthetic fabric vascular prostheses that have been pretreated with autologous venous tissue fragments. However, significant thrombogenicity has been a major problem when this method has been applied to small-diameter grafts. By masking the positively charged collagen fibrils in the tissue fragments with negatively charged heparin, we were able to overcome this problem. A canine jugular vein was resected, minced into tissue fragments, and suspended. This mixture was sieved through the wall of a highly porous vascular prosthesis with a water porosity value of 4,000 ml/cm2 per minute by pressurized injection, which caused the tissue fragments to be trapped in the graft wall. Tissue-fragmented grafts (7 mm inside diameter, 5.7 cm long) were implanted into the thoracic aorta of 35 dogs. In addition, tissue-fragmented grafts of small diameter (4 mm inside diameter, 3.5 cm long) were pretreated with heparin and implanted into the carotid arteries of 16 dogs (32 grafts). Preclotted grafts without tissue fragmentation were implanted into the thoracic aorta (25 dogs) and carotid arteries (6 dogs, 12 grafts) as controls. Grafts were explanted from 1 to 495 days after implantation. New arterial wall formation was complete throughout the tissue-fragmented grafts within 2 weeks; however, in the control grafts, neointima formation was limited to the anastomotic sites even after 2 months. Twenty small-caliber tissue-fragmented grafts that were pretreated with heparin in the carotid position were patent, but all the control grafts were occluded within 1 week. These results demonstrate that neointima formation can be enhanced in synthetic fabric prostheses; furthermore, long-term patency of vascular grafts of small caliber is possible in dogs with this tissue-fragmentation technique.

Animals↗
PubMed1992

Rapid endothelialization of vascular prostheses by seeding autologous venous tissue fragments.

A method was developed to obtain rapid endothelialization of a fabric vascular prosthesis by seeding autologous venous tissue fragments into its wall. In an animal study, complete endothelialization was observed in the entire inner surface of the prosthesis within 2 weeks after implantation. A piece of peripheral vein was minced with scissors and then stirred into saline to create a tissue suspension. This suspension was enmeshed into the wall of a highly porous fabric vascular prosthesis by repeated pressurized injections with a syringe. The prostheses (7 mm inside diameter and 5.7 cm in length), seeded with tissue fragments, were implanted into the descending thoracic aorta of 25 dogs, and they were removed from 1 hour to 2 months after implantation. Twenty-five prostheses, preclotted with fresh blood, were used as control prostheses. In the seeded graft, a thin fibrin layer covered the inner surface just after implantation, but countless numbers of endothelial cells migrated from the fragments and came up to the luminal surface like multiple "mushrooms" under the fibrin layer. Smooth muscle cells made multiple layers underneath the endothelial cell layer. The healing proceeded equally at every part. By this active migration and proliferation, the inner surface was completely healed within 2 weeks.

Animals↗
PubMed1992

[A rabbit model for evaluation of a small-caliber vascular graft].

A method for experimental study for a long small-caliber vascular graft was developed and used to observe the healing process and antithrombogenicity of a high porosity fabric prostheses. Eight rabbits weighing 3 kg were used. A left thoracotomy was performed. The thoracic descending aorta was clamped with two vascular clamps and excised in the middle without temporary shunt. A 15 cm long by 4.0 mm ID segment of a fabric prostheses (porosity: 3000) was implanted end to end. After the blood flow of the aorta was restarted, the graft remained in a big loop shape in the thoracic cavity. Total operating time was less than one hour. Three animals were lost because of bleeding from the anastomotic sites (2) and bleeding from the lung (1) within 12 hrs, but paraplegia was not produced. One animal died because of an occlusion in the graft at 16 days after implantation. The remaining 4 animals survived. In two out of these four animals, an angiography was performed. Two grafts were still patent at four weeks. One of these two was explanted and its smooth surface was observed. The major advantage of this technique is that we could evaluate a long small-caliber vascular graft in a small animal.

Animals↗
PubMed1991

Rabbit model for evaluation of a long small-caliber vascular graft.

We developed an experimental method for evaluating the properties and healing process of a long, small-caliber vascular graft in a small animal. Eight rabbits were used. A left thoracotomy was performed and the thoracic aorta was isolated. The aorta was clamped and excised in the middle without a temporary shunt. A 15-cm-long by 4.0-mm-ID segment of a vascular graft was implanted end to end. After the blood flow of the aorta was restarted, the long graft remained in a big loop shape in the thoracic cavity and showed no tension. The major advantage of this technique is that, although it is simple, we are still able to evaluate a long, small-caliber vascular graft in a small animal.

Animals↗
PubMed1991

[Teflon mandril method for pre-clotting a highly porous small-caliber fabric prosthesis].

Healing characteristics in a highly porous fabric prosthesis are better than in a porous low one. However, bleeding from the highly porous graft wall after implantation has been a very big problem for surgeons, preventing them from using this prosthesis. When a small-caliber graft is pre-clotted and implanted, the condition of the inner surface, such as smoothness, enhances patency and anti-thrombogenicity. We developed a method for pre-clotting a highly porous small-caliber fabric prosthesis using Teflon Mandril. Before pre-clotting, a fabric vascular prosthesis was held end-to-end and stretched to make the crimp shallow. Teflon stick, which outer diameter was 0.5 mm smaller than the graft, was used to pre-clot. Fresh blood was poured into the space between the stick and the vascular graft. After 3 to 5 minutes, when the blood coagulated, the vascular graft with the stick inside was squeezed with a dry towel. Care was taken not to peel the fibrin attached to the graft. With this method, a smooth and tight fibrin meshwork was obtained at the inner surface. This procedure was repeated five times. As a control, pre-clotting was induced according to Yate's method using the same fabric prosthesis. Two groups of pre-clotted grafts were examined macroscopically and in a perfusion model. Macroscopically, the inside of the graft in the developed method was smooth and without thrombus. On the other hand, in the control grafts, the fibrin meshwork was observed and thrombus at the crimp was noticed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[A case of Klinefelter's syndrome with acute mitral regurgitation caused by idiopathic chordal rupture].

It has been reported that the incidence of mitral valve prolapse was remarkably increased in patients with Klinefelter's syndrome. Some cases which have been previously reported were associated with hemodynamically significant transvalvular regurgitation, however, none of them underwent a surgical treatment such as valvular replacement. Here we report a case of Klinefelter's syndrome which underwent MVR for mitral regurgitation caused by idiopathic chordal rupture. Pathological microscopic examination showed topical and minor myxomatous changes on the free edge of the leaflet and no inflammatory changes such as in infectious endocarditis. It is, therefore, suggested that an echocardiographic follow-up should be carried out in case of Klinefelter's syndrome during its life and also in the case treated by a prophylactic therapy for endocarditis with antibiotics. And when, unfortunately, surgical treatment is required, valve replacement would be preferable to valvuloplasty because of a fragility of leaflet.

Chordae Tendineae↗