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T Kijima

Publications and source records attributed to T Kijima.

100 records · Page 6Linked to original sources
PubMedDate not supplied

In vitro studies of immobilized heparin and sulfonated polyurethane using epifluorescent video microscopy.

In situ surface modification techniques to improve the blood compatibility of blood contacting surfaces of medical devices have been developed by the authors. The techniques include heparin immobilization and sulfonated polymer grafting onto a polyurethane (PU) surface by using either ozone oxidation or photo reaction. These modified PUs were evaluated using an epifluorescent video microscope combined with a parallel plate flow cell. The epifluorescent video microscope system measured the amount of platelet coverage on the PU surfaces using whole human blood containing mepacrine labeled platelets perfused at a wall shear rate of 100 sec-1 for 20 min. Platelet activation and complement activation were also measured. Both immobilized heparin and sulfonated PUs showed significantly lower levels of platelet adhesion than the control PU. The platelet activation levels of these modified PUs also correspond to the results of the platelet adhesion. As for complement activation, heparin the immobilized surface showed the least complement activation, while sulfonated PU and the control PU showed higher levels of complement activation. In situ surface modification techniques, which use either ozone oxidation or photo reaction, are useful in a variety of medical devices even of a complex design, such as membrane oxygenators or artificial hearts.

Allylamine↗
PubMedDate not supplied

Can heparin immobilized surfaces maintain nonthrombogenic activity during in vivo long-term implantation?

The authors previously demonstrated that heparin immobilized surfaces showed excellent nonthrombogenic properties for extracorporeal membrane oxygenation experiments as long as 168 hr. The characteristics of the heparin immobilized surfaces include high heparin bioactivity and prevention of platelet adhesion and complement activation. However, it is not known whether the heparin immobilized surfaces would be effective for in vivo long-term implantation. Heparin bioactivity may be lost because of complete degradation or blocking of binding sites on heparin by adsorbed proteins. This study attempted to elucidate the in vivo long-term fate of heparin immobilized surfaces. The blood contacting surfaces of the ventricular assist device (VAD) made from polyurethane was modified with heparin immobilization and evaluated in a long-term sheep left VAD (LVAD) model for as long as 3 months. After removal of the VAD, heparin bioactivity was measured by Factor Xa assay. The blood contacting surfaces were analyzed with a scanning electron microscope, and the adsorbed proteins on the surfaces of the diaphragm were analyzed by SDS-PAGE and Western blotting. The thickness of adsorbed proteins on the surfaces also was measured by a confocal laser microscope. For the control ventricular assist devices, thrombus formation was observed within 1 month, whereas heparin immobilized VADs were able to operate thrombus free for periods as long as 3 months. The control surfaces demonstrated a thick adsorbed protein layer on thin surfaces, whereas heparin immobilized surfaces maintained thinner adsorbed proteins on thin surfaces. Anti Factor Xa activity of the heparinized surfaces disappeared after 15 days, but the surfaces remained nonthrombogenic even after heparin bioactivity was completely lost. The protein composition analyzed by SDS-PAGE showed an albumin dominant pattern on the heparinized surfaces. The band of 110 kD corresponding to C3b was detected only on the control surfaces, which possibly activated complement, and subsequently activated platelets and coagulation. Immunoblot showed degradation products of fibronectin and vitronectin on the control surfaces, which probably were promoted by surface generated protease, whereas the heparinized surfaces showed minimal degradation throughout the experimental periods. These results suggest that the heparin moiety has an ability to control adsorbed proteins, thereby inhibiting thrombus formation during in vivo long-term implantation.

Adsorption↗
PubMedDate not supplied

Recent progress in the development of Terumo implantable left ventricular assist system.

The research group of the Terumo Corporation, the NTN Corporation, and Setsunan University (T. Akamatsu) has been developing an implantable left ventricular assist system (ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The impeller of the MSCP is suspended by a magnetic bearing, providing contact-free rotation of the impeller inside the pump housing. Thus the MSCP is expected to provide years of long-term durability. Ex vivo chronic sheep experiments using the extracorporeal model (Model I) demonstrated long-term durability, nonthrombogenicity, and a low hemolysis rate (plasma free Hb <6 mg/dl) for more than 2 years. The prototype implantable model (Model II; 196 ml, 400 g) was evaluated ex vivo in 2 sheep and intrathoracically implanted in a small sheep (45 kg). These experiments were terminated at 70, 79, and 17 days, respectively, because of blood leakage through the connector system within the housing of Model II. There was no thrombus formation on the retrieved pump surfaces. A new connector system was introduced to the Model II pump (modified Model II), and the pump was intrathoracically implanted in a sheep. Pump flow rate was maintained at 3-7 L/min at 1700-1800 rpm. The temperature elevation on the surfaces of the motor and the electromagnet inside the pump casing was kept less than 6 degrees C. The temperature of the tissue adjacent to the pump casing became normal 10 days postoperatively. The sheep survived for more than 5 months without any sign of mechanical failure or thromboembolic complication. In vitro real-time endurance tests of motor bearings made of stainless steel and silicone nitride have been conducted for more than 1 year without any sign of bearing wear. The next prototype system (Model III), with an implantable controller and a new MSCP with reduced input power, has been developed with a view toward a totally implantable LVAS.

Alanine Transaminase↗
PubMedDate not supplied

Terumo implantable left ventricular assist system: results of long-term animal study.

The research group of Terumo Corporation, NTN Corporation, and the Setsunan University have been developing an implantable left ventricular assist system (T-ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The present study describes results of chronic animal experiments using the MSCP. The MSCP has been tested ex vivo and in vivo in 6 sheep as a left heart bypass between the left ventricular apex and descending aorta. Ex vivo chronic sheep experiments using Model I demonstrated long-term durability, nonthrombogenicity, low hemolysis (<6 mg/dl), and excellent stability of the magnetic bearing with long-term survival for up to 864 days. Average pump flow rate was 4 L/min at a fixed rotational speed of 2000 rpm. Power spectral analyses of heart rate, aortic pressure, and blood temperature maintained normal 1/f fluctuation during the study. The retrieved pump was completely free from thrombus formation and there was no evidence of infarct in major organs. The implantable Model II was evaluated ex vivo in two sheep and intra-thoracically implanted in a sheep. These experiments were terminated at 70, 79, and 17 days due to blood leakage through the connector system within the housing. No thrombus formation was observed in any of the retrieved pumps. A modified Model II with a new connector system was subsequently intra-thoracically implanted in a sheep. The sheep survived for 482 days without any sign of thromboembolic complication or hemolysis at a fixed rotational speed of 1700 rpm and an average pump flow rate of 5 L/min. There was no intra-device thrombus formation or infarct in major organs. The Model III system, consisting of an implantable controller and a new MSCP with a reduced input power of 13 W, has been developed and implanted in a chronic sheep model. The MSCP was implanted in the left pleural space and the controller in the abdominal wall. The experiment is still in progress for more than 30 days without any significant complication to date. These animal studies strongly suggest the feasibility of the MSCP for use as long-term circulatory assist.

Animals↗
PubMedDate not supplied

Activated c-Met signals through PI3K with dramatic effects on cytoskeletal functions in small cell lung cancer.

Small cell lung cancer (SCLC) is an aggressive illness with early metastases. There are several receptor tyrosine kinases (RTKs) overexpressed in SCLC, including c-Met. c-Met contains an external semaphorin-like domain, a cytoplasmic juxtamembrane domain, tyrosine kinase domain and multiple tyrosines that bind to adapter molecules. We have previously reported that c-Met is abundantly expressed in the NCI-H69 SCLC cell line and now have determined the downstream effects of stimulating c-Met via its ligand hepatocyte growth factor (HGF). Utilizing unique phospho-specific antibodies generated against various tyrosines of c-Met, we show that Y1003 (binding site for c-Cbl and a negative regulatory site), Y1313 (binding site for PI3K), Y1230/Y1234/Y1235 (autophosphorylation site), Y1349 (binding site for Grb2), Y1365 (important in cell morphogenesis) are phosphorylated in response to HGF (40 ng/ml, 7.5 min) in H69 cells. Since multiple biological and biochemical effects are transduced through the PI3K pathway, we determine the role of PI3K in the c-Met/HGF stimulation pathway. We initially determined that by inhibiting PI3K with LY294002 (50 microM over 72 hours), there was at least a 55% decrease in viability of H69 cells. Since H69 SCLC cells form clusters in cell culture, we determined the effects of HGF and LY294002 on cell motility of the clusters by time-lapse video microscopy. In response to HGF, SCLC moved much faster and formed more clusters, and this was inhibited by LY294002. Finally, we determined the downstream signal transduction of HGF stimulation of c-Met with and without inhibition of c-Met (with geldanamycin, an anisamycin antibiotic that inhibits c-Met in SCLC) or PI3K (with LY294002). We show that association of c-Met with PI3K and GAB2 is diminished by inhibiting c-Met. In summary, activation of the c-Met pathway targets the PI3K pathway in SCLC and this may be an important therapeutic target.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

Fibronectin enhances viability and alters cytoskeletal functions (with effects on the phosphatidylinositol 3-kinase pathway) in small cell lung cancer.

Small cell lung cancer (SCLC) is a rapidly progressive disease with ultimate poor outcome. SCLC has been shown to interact closely with the stromal and extracellular matrix (ECM) components of the diseased host. ECM consists of type I/IV collagen, laminin, vitronectin, and fibronectin (FN) among others. Herein, we investigated the behavior of a SCLC cell line (NCI-H446) on FN-coated surface. Over a course of 72 h, FN (10 micro g/ml) caused both increased survival and proliferation of NCI-H446 cells. Survival under serum-starved conditions increased 1.44-fold and proliferation in the presence of fetal calf serum increased by 1.30-fold. The phosphatidylinositol 3-kinase (PI3-K) inhibitor LY294002 reduced both survival and proliferation of NCI-H446 cells (0.48- and 0.27-fold, respectively), even on FN-coated surface. We next determined the effects of FN on cytoskeletal function such as cell motility/morphology and adhesion. Over a course of 24 h, FN reduced aggregation of NCI-H446 cells and induced flattened cellular morphology with neurite-like projections after 1 h, however, in the presence of LY294002, the cells rounded up. Adhesion of NCI-H446 cells also increased with FN (4.47-fold) which was abrogated with LY294002 treatment. This correlated with phosphorylation of the cytoskeletal protein p125FAK, on Tyr397, Tyr861 and Ser843 residues with FN. Even in the presence of LY294002, these serine/tyrosine residues were still phosphorylated on FN-coated surface. In contrast, the focal adhesion protein paxillin was not phosphorylated at Tyr31 with FN. In summary, FN stimulation of SCLC cells leads to enhancement of viability and changes in cytoskeletal function that are partially mediated through the PI3-K pathway.

Carcinoma, Small Cell↗
PubMedDate not supplied

Establishment of a CPT-11-resistant human ovarian cancer cell line.

A camptothecin analog, ((4s)-4,11-diethyl-4-hydroxy-9-[(4- piperidinopiperidino)carbonyloxy]dione hydrochloride trihydrate), (CPT-11), is a recently developed topoisomerase I (Topo I) inhibitor which attracts the attention of clinicians because of its high antitumor activity. We established a CPT-11-resistant human ovarian cell line, HAC2/CPT, from the parental HAC2 cell line. An in vitro drug sensitivity assay revealed that HAC2/CPT was 9.7 and 4.7 times as resistant as HAC2 to CPT-11 and 7-ethyl-10-hydroxy-CPT-11 (SN-38), an active metabolite of CPT-11, respectively. HAC2/CPT showed no cross-resistance to other drugs tested (adriamycin, etoposide, cisplatin and Taxol), suggesting that HAC2/CPT acquired a phenotype specifically resistant to the Topo I inhibitor. In order to elucidate the mechanism of the resistance, we measured Topo I activity of HAC2 and HAC2/CPT. The activity of Topo I of HAC2/CPT was reduced to half of that of the parental HAC2 cells. To determine the cause of the decreased activity of Topo I, the mutation of the Topo I gene was searched for by the polymerase chain reaction and the reverse transcriptase analysis. Topo I gene mutation was not detected. The amount of Topo I protein was measured by immunoblotting and a marked decrease of Topo I protein was observed in HAC2/CPT. These results suggest that the decreased protein content of Topo I causes the decreased activity of Topo I and the decreased sensitivity of HAC2/CPT to Topo I inhibitors.

Antineoplastic Agents, Phytogenic↗
PubMedDate not supplied

Classification of hematopoietic regions in out-of-phase T1-weighted images: a quantitative comparison study with T1-weighted and STIR images.

The hematopoietic regions were classified into two groups on the basis of out-of-phase T1-weighted images (op-T1WI): regions with lower intensity than that of muscle (LH) and regions with intensity equal to or higher than that of muscle (HH). We quantitatively evaluated the differences in signal intensity between LH and HH in order to examine this classification. Forty-two hematopoietic areas in aplastic anemia were classified into two groups of 23 LH and 19 HH. The signal ratios of hematopoietic areas to muscle on T1WI and STIR were calculated, and the differences between LH and HH were statistically evaluated. The signal ratios of LH were significantly higher on T1WI and lower on STIR than those of HH (unpaired t-test, p < 0.05). This result indicated that LH consisted of more hypocellular marrow than HH. Op-T1WI were useful in differentiating between LH and HH and defining the degree of hematopoiesis in aplastic anemia.

Adipose Tissue↗
PubMedDate not supplied

More than 1 year continuous operation of a centrifugal pump with a magnetically suspended impeller.

The authors have been developing a centrifugal pump with a magnetically suspended impeller (MSCP) designed for total artificial heart and long-term ventricular support. The MSCP consists of a magnetic bearing, an impeller and housing, and a driving motor. The impeller is suspended by a magnetic bearing, therefore providing contact free rotation of the impeller inside the pump. This study was designed to evaluate long-term durability and nonthrombogenicity of the MSCP in a chronic sheep model. The blood contacting surfaces of the pump and conduits were completely modified by a heparin immobilization technique (Hepaface). The MSCP was placed paracorporeally as a left heart bypass between left ventricle and descending aorta in three adult sheep. Coumadin was given orally to maintain prothrombin time at 15-20 sec. The coagulation and hematologic parameters, including plasma free hemoglobin, were periodically monitored throughout the experiment. Under daily movement in the cage, the pump could produce average flow rates of 3-6 L/min (50-100 ml/kg) at 1,700-2,000 rpm. Although the arterial pulse contour decreased, there was no physiologic deterioration. The axial impeller excursion monitored by a position sensor was < 25 microns. Plasma free hemoglobin level remained at < 5 mg/dl throughout the experiment. There was no increase in the motor current, which indicates no massive thrombus formation around the impeller. One experiment was terminated at 70 days due to Hall sensor dysfunction of the motor. The retrieved pump was entirely free from thrombus formation. There was no detectable thrombus formation inside the pump or the inflow and outflow conduits. Hematologic, renal, and hepatic parameters remained within the normal range throughout the experiment. The other two sheep have survived for more than 395 and 41 days without major complication. These studies demonstrated that the MSCP has significant potential for long-term use.

Animals↗