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Biomedical subjects

I Koyama

Publications and source records attributed to I Koyama.

At least 19 recordsLinked to original sources
PubMed2007

Improved outcomes of renal transplantation from cardiac death donors: a 30-year single center experience.

Outcomes of renal transplantation from donation after cardiac death (DCD) donors over 30 years were analyzed. Between 1975 and 2004, 256 renal transplantations from DCD donors were performed. The recipients were divided into four groups according to a time period as follows: 1975-1979 (Group 1; n = 18), 1980-1989 (Group 2; n = 81), 1990-1999 (Group 3; n = 84) and 2000-2004 (Group 4; n = 73). Of the 256 transplanted kidneys from DCD donors, 38 (15%) functioned immediately after transplantation. The incidence of delayed graft function (DGF) was 72%. Warm ischemic time and total ischemic time were 7.4 +/- 9.4 min and 11.9 +/- 5.6 h, respectively. The overall graft survival rates at 1, 5 and 10 years were 80%, 72% and 53%, respectively. Graft survival rates in each group have continually improved over time (5-year graft survival; 23% vs. 64% vs. 74% vs. 91%, respectively). However, there was no significant difference in graft survival rates between the groups of patients who survived with a functioning graft for more than 1 year. A multivariate Cox regression analysis showed acute rejection and donor age to be independently associated with graft outcome. DCD donors are a valuable source of kidneys for transplantation with promising long-term outcomes.

Adult↗
PubMed2005

Cyclosporine-sparing effect of basiliximab in renal transplant recipients with mycophenolate mofetil.

UNLABELLED: Basiliximab added to a maintenance regimen consisting of cyclosporine microemulsion and mycophenolate mofetil was studied for its effectiveness in allowing early steroid withdrawal in renal transplantation. Furthermore, the cyclosporine-sparing effects between groups with and without basiliximab induction therapy were compared. PATIENTS: Between September 2001 and June 2003, 90 patients underwent renal transplants with cyclosporine-based immunosuppression, namely, cyclosporine, mycophenolate mofetil, and methylprednisolone, (group 1; n = 25). During the latter half of the study basiliximab was administered during the induction phase (group 2; n = 65). In group 2, steroids were completely withdrawn on postoperative day 14 in 57 patients. RESULTS: The incidence of acute rejection was significantly higher among group 1 patients (P = .005). The incidence of steroid-resistant rejection in group 1 patients was significantly higher (P = .025). At each time point cyclosporine levels in group 1 patients were significantly higher (P < .01). The incidence of infection was comparable between the groups. Patient and graft survival rates in group 1 were 100% and 100%; in group 2, they were 99% and 99%, respectively. In group 2, steroids were discontinued in 57 patients with permanent withdrawal achieved in 32 patients (56%). CONCLUSION: The use of basiliximab, together with mycophenolate mofetil allowed for a significant reduction in the cyclosporine dose without increasing the risk of acute rejection. Although further follow-up is necessary to confirm the effect, this regimen may attenuate cyclosporine nephrotoxicity thereby affecting the long-term outcomes of renal transplantation.

Antibodies, Monoclonal↗
PubMed2005

Comparative study of clinical outcome in kidney transplantation between early steroid withdrawal protocol using basiliximab, calcineurin inhibitor, and mycophenolate mofetil and triple regimen consisting of calcineurin inhibitor, mycophenolate mofetil, and steroid.

AIMS: Effect of early steroid withdrawal protocol using basiliximab in kidney transplantation (KTx) on the clinical outcomes was investigated as compared with triple regimen. METHODS: Kidney transplant patients in group 1 (n = 62) were treated with 8 mg/kg of cyclosporine (CsA), 2000 mg of MMF, two bolus IV injections of 20 mg of basiliximab and 500 mg of methylprednisolone (MP) rapidly tapered and withdrawn at 14 postoperative days (POD). Group 2 (n = 56) was treated with same dose of CsA and MMF, and 250 mg of MP tapered and continued. Acute rejection (AR) episodes were treated with MP pulse therapy followed by muromonab CD3 (OKT3) in case of steroid-resistant rejection. RESULTS: In 46 of 62 cases (74.2%) in group 1, steroid was successfully withdrawn at 13.7 +/- 1.7 POD. Graft survival at 3, 6, and 12 months in group 1 was 100%, 100%, and 98.4% (one death with functioning graft), and 100%, 98.2%, and 96.4% in group 2, respectively. The incidence of AR was 12.9% for group 1 and 42.9% for group 2, among which 21 cases in group 2 were treated with ALG or OKT3; no patient needed ALG or OKT3 in group 1. Fifteen cases in group 1 and 13 cases in group 2 developed CMV antigenemia, among which febrile episode was exhibited in 3 cases (4.8%) in group 1 and 5 cases (8.9%) in group 2. CONCLUSIONS: Early steroid withdrawal protocol using basiliximab is promising for reducing the incidence of AR (especially steroid-resistant rejection), CMV diseases, and steroid-related complications.

Adrenal Cortex Hormones↗
PubMed2005

Effect of mechanical stress imposition on co-culture of hepatic parenchymal and nonparenchymal cells: possibility of stimulating production of regenerating factor.

The effect of mechanical stress generated within a three-dimensional bioreactor on the co-culture of hepatic parenchymal cells (PC) and hepatic nonparenchymal cells (NPC) was assessed to develop a bioartificial liver that can produce factors accelerating liver regeneration. A rotating radial flow bioreactor was used to provide mechanical stress to a co-culture of PC and NPC that were isolated from rats. They were co-cultured in the reactor under static or dynamic conditions. Albumin, interleukin-6 (IL-6), hepatocyte growth factor (HGF), and lactate dehydrogenase (LDH) were measured at intervals. Electron microscopy was also performed. LDH was not significantly different between the static and mechanical stress-loaded cultures, while albumin and interleukin-6 levels were higher in the latter at all sampling times. Only the co-cultures loaded with mechanical stress produced HGF in the early stage of culture (hours 3 and 6). Histologically, the cells retained their structure when cultured under dynamic conditions. These results suggested that an appropriate level of mechanical stress enabled co-cultures of PC and NPC to produce IL-6, HGF, and other factors that accelerate liver regeneration.

Coculture Techniques↗
PubMed2005

Effect of continuous application of shear stress on liver tissue: continuous application of appropriate shear stress has advantage in protection of liver tissue.

Rapid blood flow changes occur in the liver following a massive resection or in the grafted liver following transplantation, under which shear stress (SS) change induced by the flow change may determine the postoperative results. We observed changes in liver tissue structure and liver-specific function, and consequently assessed SS effect. The cultured liver tissue exposed to continuous application of moderate SS was shown to express and maintain a long-term liver-specific function. There was also evidence showing that destruction of the liver structure was inhibited. However, the cultured liver tissue not exposed to SS or exposed to high SS was shown to lose liver-specific function soon after expression. The liver structure was destroyed in the early stage of incubation. These results suggested that continuous application of appropriate SS has advantages over other types of stresses to protect liver tissue.

Animals↗
PubMed2001

Glycated high-density lipoprotein induces apoptosis of endothelial cells via a mitochondrial dysfunction.

Glycation of plasma proteins may contribute to an excess risk of developing atherosclerosis in patients with diabetes mellitus. Although it is believed that high-density lipoprotein (HDL) is nonenzymatically glycosylated at an increased level in diabetic individuals, little is known about a possible linkage between glycated HDL and endothelium dysfunction in diabetes. This study set out to clarify whether glucose-modified HDL affects the function of endothelial cells by examining the apoptosis of cultured human aortic endothelial cells (HAECs) exposed to a glycated-oxidized HDL (gly-ox-HDL) prepared in vitro. Incubation of HAECs with 100 microg/ml of gly-ox-HDL for 48 h showed apoptotic features, such as cell shrinkage, membrane blebbing, and concentration and fragmentation of the nucleus, and the degree of apoptosis was dose-dependent on the glucose used in the preparation of gly-ox-HDL. Stimulation of HAECs with gly-ox-HDL elicited a marked increase in caspase 3 activity and the expressions of active caspase 3 and caspase 9, whereas concomitant treatment with a caspase 3 inhibitor significantly blocked gly-ox-HDL-induced apoptosis of HAECs. The release of cytochrome c into cytosols markedly increased in HAECs during the treatment with gly-ox-HDL. The increased expressions of Bax and Bad were detected in HAECs incubated for 24 h with gly-ox-HDL, but gly-ox-HDL failed to interfere with the expression of Bcl-2 and Bcl-x. Moreover, in vitro experiments with HDL (gly-HDL) glycated in the presence of 2 mM EDTA and Cu(2+)-oxidized HDL suggested that the apoptotic effect of gly-ox-HDL on endothelial cells might be due to an additional oxidative modification of gly-HDL. Taken altogether, additional oxidation of HDL under hyperglycemic conditions may induce endothelial apoptosis through a mitochondrial dysfunction, following the deterioration of vascular function.

Aorta↗
PubMed2001

alpha-Amylase expressed in human liver is encoded by the AMY-2B gene identified in tumorous tissues.

BACKGROUND: An alpha-Amylase in human liver is detected with an anti-human salivary amylase antibody, but the enzyme activity is very low. We previously found that the rat liver contained an amylase which differed from the enzyme of mice. In this study, we characterized the human liver amylases biochemically and immunohistochermically. METHODS AND RESULTS: Although the amylase activity of human liver was much lower than that of rat, protein moiety and sugar chains of the human amylase were identified as similar to the rat liver enzyme with an anti-human salivary amylase antibody and by concanavalin A (Con A) affinity chromatography. Liver amylases from human and rat were the same size, 50 kDa, on Western blot analysis and had the same isoelectric points. The cytoplasm of hepatocytes was moderately stained immunohistochemically with the anti-human salivary amylase antibody. Intrahepatic bile ducts were also stained weak-to-moderately. RT-PCR, with a specific primer for the consensus sequence of human amylases, amplified a single 474-bp product from the human liver total RNA. The PCR product was sequenced and referred to the homology. Thirteen bases in the 434-bp fragment of the human liver amylase differed from the corresponding region of the AMY-1 gene transcript and the deduced amino acid sequence differed at five residues. The human liver amylase cDNA sequence was identical to the corresponding cDNA of the AMY-2B, which was known to expressed in tumorous tissues. In situ hybridization revealed the expression of AMY-2B mRNA in non-tumorous human liver. CONCLUSIONS: The present results suggest the possibility that a novel amylase detected in tumorous tissues and encoded by the AMY-2B gene is a liver-specific amylase expressed in the human liver.

Animals↗
PubMed2001

Expression of alpha-amylase gene in rat liver: liver-specific amylase has a high affinity to glycogen.

The reactivity of rat liver alpha-amylases with maltotriose (G3), maltopentose (G5) and glycogen has been investigated. Liver amylases were found to be glycosylated and to have a molecular mass of 50 kDa by Western blotting using an anti-human salivary amylase antibody. The glycosylated liver amylases were found to be capable of G3- and G5-hydrolysis and of glucose formation, as demonstrated by thin-layer chromatography. When the amylase preparation was exposed to different concentrations of glycogen and run on a cellulose acetate membrane, the mobilities of rat liver amylases significantly decreased with tailing directly from the point of origin. In contrast, rat salivary amylases were not so much. These results indicate that rat liver amylases have a strong affinity to glycogen. We confirmed the expression of liver-specific amylases in rat liver by reverse transcriptional-polymerase chain reaction (RT-PCR); PCR products showed one band of an expected size of 474 bp using primers tested in the present study. A partial nucleotide sequence was then determined. When compared with the gene of mouse liver amylase, the substitution of 26 bases out of 434 bases was elucidated. The present data demonstrate the presence of liver-specific amylases in rats.

Animals↗
PubMed2001

Single molecule imaging of green fluorescent proteins in living cells: E-cadherin forms oligomers on the free cell surface.

Single green fluorescent protein (GFP) molecules were successfully imaged for the first time in living cells. GFP linked to the cytoplasmic carboxyl terminus of E-cadherin (E-cad-GFP) was expressed in mouse fibroblast L cells, and observed using an objective-type total internal reflection fluorescence microscope. Based on the fluorescence intensity of individual fluorescent spots, the majority of E-cad-GFP molecules on the free cell surface were found to be oligomers of various sizes, many of them greater than dimers, suggesting that oligomerization of E-cadherin takes place before its assembly at cell-cell adhesion sites. The translational diffusion coefficient of E-cad-GFP is reduced by a factor of 10 to 40 upon oligomerization. Because such large decreases in translational mobility cannot be explained solely by increases in radius upon oligomerization, an oligomerization-induced trapping model is proposed in which, when oligomers are formed, they are trapped in place due to greatly enhanced tethering and corralling effects of the membrane skeleton on oligomers (compared with monomers). The presence of many oligomers greater than dimers on the free surface suggests that these greater oligomers are the basic building blocks for the two-dimensional cell adhesion structures (adherens junctions).

Animals↗
PubMed2001

Atypical alkaline phosphatase isozymes in serum and urine of patients with renal failure.

BACKGROUND: Alkaline phosphatases (ALPs) originating from different organs are frequently detected in the serum and urine of patients with renal failure. METHODS: We investigated the characteristics of ALPs in the serum and urine of 108 patients with chronic renal failure (CRF) and of 106 healthy control subjects. RESULTS: In polyacrylamide gel electrophoresis, three atypical ALP bands in serum of patients were designated as atypical-s1, -s2 and -s3, respectively. In contrast, five atypical bands (u1, u2, u3, u4 and u5) were detected in the urine of patients. The atypical ALPs were electrophoretically isolated and assayed to determine their biochemical properties, i.e., neuraminidase sensitivity, heat stability, reactivity to anti-intestinal or anti-tissue nonspecific ALP antibodies, molecular sizes and sugar chain heterogeneities. From these results, we found that atypical-s1 and -s2 were the intestinal-type ALP, while s3 was the tissue-unspecific type ALP. Atypical-u1, -u2 and -u3 were high-molecular type ALPs, which we suggested as the ones that originated from the intestine. Atypical-u4, a tissue-unspecific type ALP, was detected with considerable frequency in the urine of patients. In patients with CRF, the appearance of these atypical ALPs was accompanied by a deterioration of the creatinine clearance. CONCLUSIONS: The appearance of atypical ALPs in the serum and urine of patients with CRF may be a useful marker for renal disease.

Adult↗
PubMed2001

Hemodialysis paradox: survey on the incidence rate of hepatocellular carcinoma in antihepatitis virus C-antibody-positive chronic hemodialysis patients.

The prevalence of antihepatitis virus C (HCV) antibodies in chronic hemodialysis (HD) patients is higher than in normal populations, and yet hepatocellular carcinoma (HCC) is infrequent in chronic HD patients who are HCV antibody positive. In this study, we investigated the characteristics of HCV-antibody-positive patients with HCC on chronic HD. A total of 6,366 cases of HCV-antibody-positive patients on chronic HD therapy was analyzed on the basis of answers to questionnaires on the incidence rate of HCC in 314 Japanese dialysis institutions. HCC was a complication in 114 of 6,222 (1.8%) HCV-antibody-positive patients, and cirrhosis was a complication in 536 of 6,242 (8.6%). The incidence rate of both complications was significantly higher in males than in females, and the incidence rate in the chronic HD patients was much lower than in normal populations. Specific immunological status in patients on chronic HD therapy may be an important key for preventing the progression of chronic HCV hepatitis. However, further research is needed because this study was preliminary and excluded the type of HCV virus, pathological findings, and laboratory data.

Carcinoma, Hepatocellular↗
PubMed2001

Expression of pyrimidine 5'-nucleotidase subclass I during erythrocyte maturation in rats.

The subclass I enzyme of rat pyrimidine 5'-nucleotidase (P5N-I), which preferentially hydrolyzes (deoxy)CMP and UMP, is distributed specifically in red blood cells (RBCs), and its activity increases approximately six-fold as compared to the control value after erythropoietic induction by phenylhydrazine administration. In this study, we detected rat P5N-I protein by using antibodies against the chicken P5N-I enzyme. The molecular mass of rat P5N-I was approximately 37 kDa, as estimated by gel filtration chromatography and Western blot analysis. The pI value of the enzyme was approximately 5.7. This protein band was detected only in RBC lysate extract, i.e., not in cytosol from the erythropoietic spleen. Protein mass of the P5N-I enzyme, estimated by immunoblot analysis, was increased in proportion to the enzyme activity after erythropoietic induction in rats. No phosphorylation of the enzyme protein was detected by immunoblot analysis with anti-phosphoserine or anti-phosphotyrosine antibody. In conclusion, these findings indicate that the rat P5N-I enzyme is expressed specifically in reticulocytes and may therefore be essential in the maturation process of rat erythrocytes.

5'-Nucleotidase↗
PubMed2001

Modulation of reactive oxygen species in endothelial cells by peroxynitrite-treated lipoproteins.

Peroxynitrite has been implicated in the oxidative modification of low-density lipoprotein (LDL) particles, and nitrotyrosine residues in the LDL have been detected in atherosclerotic plaques. Studies have suggested that lipoproteins modified by peroxynitrite lead to the onset of atherosclerotic vascular disease. We therefore prepared in vitro lipoproteins oxidatively modified by peroxynitrite (NO(2)-lipoprotein) and investigated the effect of NO(2)-lipoprotein on the viability of cultured endothelial cells. After exposure of a high-density lipoprotein (HDL) to peroxynitrite, some intermolecular complexes of apolipoproteins in HDL were detected on immunoblotting with monoclonal antibodies against apolipoprotein AI and AII, suggesting that nitration of HDL by peroxynitrite causes intermolecular cross-linking of the apolipoproteins in the particles. Treatment with 1 mM peroxynitrite increased the 3-nitrotyrosine level to 28.5 mmol/mol of tyrosine residues in the prepared NO(2)-HDL, as quantitated by HPLC, and the amount in NO(2)-lipoprotein depended on the peroxynitrite concentration. HDL exhibited a shorter lag phase and the reaction plateaued more rapidly than that with LDL. To clarify whether or not NO(2)-lipoproteins affect the function of endothelial cells, we first examined the viability of cultured human aortic endothelial cells (HAECs) exposed to NO(2)-lipoproteins. Incubation with either NO(2)-HDL or NO(2)-LDL significantly reduced the HAEC viability at 72 h. The results of RT-PCR and Western blotting showed that NO(2)-HDL markedly suppressed at 48 h not only the expressed levels of mRNA and protein but also the activity of catalase in HAECs. In contrast, NO(2)-LDL significantly reduced the expression and activity of Cu(2+),Zn(2+)-superoxide dismutase (CuZn-SOD) in the cells. Neither NO(2)-HDL nor NO(2)-LDL interfered with nitric oxide production or expression of cyclooxygenases and NADPH oxidase in HAECs. Increased radical production in NO(2)-lipoprotein-treated HAECs implied that reactive oxygen species such as superoxide anions and hydroxyl radicals may contribute to the mechanism of the toxic effect induced in endothelial cells by NO(2)-lipoprotein. Overall, NO(2)-lipoprotein may lead to deterioration of the vascular function through these endothelial cell responses.

Arteriosclerosis↗