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Biomedical subjects

M Tokunaga

Publications and source records attributed to M Tokunaga.

At least 19 recordsLinked to original sources
PubMed2006

Prednisolone inhibits hyperosmolarity-induced expression of MCP-1 via NF-kappaB in peritoneal mesothelial cells.

The mechanism of peritoneal fibrosis in patients on continuous ambulatory peritoneal dialysis (CAPD) is poorly elucidated. We investigated the cellular mechanism of high-glucose-induced expression of monocyte chemoattractant protein-1 (MCP-1), which is important in recruiting monocytes into the peritoneum and progression of peritoneal fibrosis, and examined the inhibitory mechanism of glucocorticoids. Rat peritoneal mesothelial cells were cultured in high-glucose-containing medium and then analyzed for phosphorylation levels of p42/44 and p38 mitogen-activated protein (MAP) kinases (MAPK), MAPK or extracellular signal-regulated kinase kinase (MEK)1/2, c-Jun N-terminal kinase (JNK)1/2, and protein kinase C (PKC) by Western blotting. Expression of MCP-1 was examined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. DNA-binding activity of nuclear factor (NF)-kappaB was measured by electrophoretic mobility shift assay. High glucose increased MCP-1 mRNA and MCP-1 protein expression. Although glucose increased phosphorylation of MEK1/2, p42/44 MAPK, p38 MAPK, JNK1/2, and PKC, and DNA-binding activity of NF-kappaB, its effect on MCP-1 expression was suppressed only by PKC and NF-kappaB inhibitors. Mannitol caused a similar increase in PKC and NF-kappaB activation and MCP-1 synthesis. Prednisolone increased I-kappaB-alpha expression and inhibited glucose/mannitol-induced NF-kappaB DNA binding and MCP-1 expression without affecting PKC phosphorylation. The inhibitory effects of prednisolone on MCP-1 expression were reversed by mifepristone, a glucocorticoid receptor antagonist. Our results indicate that glucose induces MCP-1 mainly through hyperosmolarity by activating PKC and its downstream NF-kappaB, and that such effect was inhibited by prednisolone, suggesting the efficacy of prednisolone in preventing peritoneal fibrosis in patients on CAPD.

Animals↗
PubMed2005

Current oscillation and low-field colossal magnetoresistance effect in phase-separated manganites.

Current-induced switching from a metallic to an insulating state is observed in phase-separated states of (La(1-y)Pr(y))0.7Ca0.3MnO3 (y=0.7) and Nd(0.5)Ca(0.5)Mn(1-z)Cr(z)O3 (z=0.03) crystals. The application of magnetic fields to this current-induced insulating state causes a pronounced low-field negative magnetoresistance effect [rho(H)/rho(0)=10(-3) at H=1 kOe]. The application of a constant voltage also causes the breakdown of the Ohmic relation above a threshold voltage. At voltages higher than this threshold value, oscillations in currents are observed. This oscillation is well reproduced by a simple model of local switching of a percolative conduction path.

Journal Article↗
PubMed2004

Down-regulation of CD40 and CD80 on B cells in patients with life-threatening systemic lupus erythematosus after successful treatment with rituximab.

OBJECTIVES: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoreactive T cells and polyclonally activated B cells that produce autoantibodies. Five SLE patients who failed to respond to conventional immunosuppressants were treated with anti-CD20 antibody (rituximab) and their clinical manifestations and laboratory data were evaluated, including phenotypic analysis of B cells. METHODS: Rituximab (375 mg/m(2)) was administered weekly for 2 weeks in five SLE patients who developed severe manifestations despite intensive treatment. RESULTS: Rituximab resulted in rapid improvement (within several days) in clinical manifestations such as consciousness disorder, seizures, progressive sensory disorder, haemolytic crisis, cardiac function and laboratory data. The effects lasted 20 months in one patient; other patients were in remission for more than 6 months. Flow cytometric analysis revealed down-regulation of CD40 and CD80 expression on CD19-positive B cells 1 week after infusion of rituximab, and such down-regulation was seen for more than 7 months in two patients. CONCLUSIONS: Our pilot study provides sufficient evidence of excellent tolerability and high efficacy of rituximab therapy in refractory SLE. Rituximab not only reduced B-cell number and IgG levels but down-regulated CD40 and CD80 on B cells, suggesting possible disturbance of T-cell activation through these costimulatory molecules. Reduction of both quantity and quality of B cells suggests that rituximab could improve the disease course in patients with refractory SLE.

Adult↗
PubMed2004

Imaging of percolative conduction paths and their breakdown in phase-separated (La1-yPry)0.7Ca0.3MnO3 with y=0.7.

Local magnetization and current distribution in (La(1-y)Pr(y))0.7Ca0.3MnO3 (y=0.7) crystals are studied by a magneto-optical (MO) imaging technique. MO images below 120 K visualize inhomogeneous magnetization and conduction paths that manifest the percolative conduction originated from the mesoscopic phase separation into ferromagnetic metals and antiferromagnetic insulators. Application of large amounts of current switches the current distribution from inhomogeneous to homogeneous concomitantly with a steep increase in resistivity. These phenomena are discussed in view of current induced collapse of the phase separation through a local heating.

Journal Article↗
PubMed2004

Detection of Pneumocystis carinii by DNA amplification in patients with connective tissue diseases: re-evaluation of clinical features of P. carinii pneumonia in rheumatic diseases.

OBJECTIVES: We evaluated the polymerase chain reaction (PCR) detection of Pneumocystis carinii DNA in induced sputum of patients with connective tissue diseases and assessed the clinical features of patients positive for P. carinii. METHODS: Sputum was induced by nebulization in 29 in-patients with various connective tissue diseases who presented with symptoms suggestive of P. carinii pneumonia (PCP), and was examined by PCR. RESULTS: Detection of P. carinii DNA by PCR was significantly more sensitive than cytology; 54.5% patients were positive by PCR and only 4.5% by cytology. The prevalence of PCP was higher than previously considered and was especially high in patients receiving > 30 mg/day prednisolone with or without other immunosuppressants. P. carinii-positive patients had significant lymphocytopenia and a low serum IgG level compared with P. carinii-negative patients. P. carinii disappeared within 7-10 days after therapy with trimethoprim/sulfamethoxazole. CONCLUSION: We propose that the use of PCR for detection of P. carinii using induced sputum is a useful and non-invasive method that has high sensitivity and specificity for the early diagnosis of PCP.

Adult↗
PubMed2004

Beneficial effects of troglitazone on neutrophil dysfunction in multiple low-dose streptozotocin-induced diabetic mice.

Patients with poorly controlled diabetes are at high risk of acquiring bacterial infections. However, conflicting results have been reported on neutrophil function in diabetes. We periodically evaluated neutrophil dysfunction in multiple low-dose streptozotocin (STZ)-induced diabetic mice, and then evaluated the effects of troglitazone and other thiazolidinediones (TZDs) on the decline of neutrophil function. Zymosan was injected intraperitoneally and neutrophil infiltration and phagocytosis were evaluated. While phagocytosis of zymosan by peritoneal neutrophils was consistently reduced in diabetic mice, neutrophil infiltration was decreased on day 30, but increased on day 40 after STZ injection. The in vitro chemotactic and phagocytic activities of blood neutrophils in mice that did not receive zymosan were consistently reduced in diabetic mice. Phorbol myristate acetate (PMA)-stimulated superoxide production by zymosan-induced peritoneal neutrophils and the levels of zymosan-induced tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta in peritoneal exudate fluids were also reduced in the diabetic mice. Treatment of the diabetic mice with troglitazone beginning 2 weeks after STZ injection did not improve hyperglycaemia but did prevent the decline of zymosan-induced neutrophil infiltration on day 30, and additionally promoted the increased infiltration on day 40. Troglitazone also promoted the chemotactic activity of blood neutrophils isolated from normal mice in vitro. Rosiglitazone but not pioglitazone induced a similar effect. Neutrophil phagocytosis was not enhanced by troglitazone either in vivo or in vitro. Taken together, neutrophil function is impaired by STZ-induced diabetes, but inflammatory infiltration does not always vary with the chemotactic disability or cytokine levels. Furthermore, troglitazone and rosiglitazone were suggested to improve at least neutrophil chemotactic activity in these animals.

Animals↗
PubMed2003

Arthroscopic management of tibial plateau fractures--comparison with open reduction method.

BACKGROUND: Arthroscopic treatment of tibial plateau fractures were compared with open traditional methods retrospectively. METHODS: Twenty-eight patients were included in this comparative study based on fracture patterns and divided into two groups. Using Schatzker's classification system, patients with type II (split depression), type III (isolated depression) fractures, or other fracture types were included. Nineteen of these patients were treated by arthroscopically assisted management (group S), and the remaining 9 underwent the conventional open method (group O). RESULTS: There was no significant difference between both groups in terms of duration of operation, postoperative flexion, and clinical results. In group S, however, the postoperative rehabilitation was easier and faster (the time to obtain 120 degrees of flexion was 4.6+/-3.9 weeks in group S, 9.1+/-8.6 weeks in group O). Furthermore, 16 of 19 patients (84%) in group S obtained an anatomical reduction (defined as <2 mm of residual displacement after surgery), whereas in group O, only 5 of 9 patients (55%) had an anatomical reduction. Also, accurate diagnosis and treatment of any associated joint pathology was possible with arthroscopic management. CONCLUSION: The arthroscopic procedure is recommended in selected tibial plateau fractures.

Adolescent↗
PubMed2003

FDG-PET for preoperative differential diagnosis between benign and malignant soft tissue masses.

OBJECTIVE: To evaluate the standardized uptake value (SUV) of [(18)F]2-deoxy-2-fluoro- d-glucose at positron emission tomography (FDG-PET) for preoperative differential diagnosis between benign and malignant soft tissue masses. DESIGN: One hundred and fourteen soft tissue masses (80 benign, 34 malignant) were examined by FDG-PET prior to tissue diagnosis. The SUVs were calculated and compared between benign and malignant lesions and among different histologic subgroups which included three or more cases. RESULTS: There was a statistically significant difference in SUV between benign (1.80+/-1.42 [SD]) and malignant (4.20+/-3.16) soft tissue masses in total (P<0.0001). However, a considerable overlap in SUV was observed between many benign and malignant lesions. Liposarcomas (2.16+/-1.72) and synovial sarcomas (1.60+/-0.43) did not show significantly higher SUV than any benign lesions. Metastases (4.23+/-2.35) showed no statistically significant difference in SUV as compared with schwannomas (1.75+/-0.84), desmoids (2.77+/-1.32), sarcoidosis (3.62+/-1.53), or giant cell tumors of tendon sheath (GCT of TS; 5.06+/-1.63). Even malignant fibrous histiocytomas (5.37+/-1.40) could not be differentiated from sarcoidosis or GCT of TS, based on the SUV. CONCLUSIONS: A large accumulation of FDG can be observed in both benign and malignant histiocytic, fibroblastic, or neurogenic lesions. SUV at conventional FDG-PET is limited to differentiating benign from malignant soft tissue masses, when all kinds of histologic subtypes are included.

Diagnosis, Differential↗
PubMed2002

Role of cytoplasmic calcium in platelet aggregation.

BACKGROUND: Although adherence and aggregation of platelets on an active surface such as exposed subendothelial matrix or foreign surfaces is integral to the occlusion of blood vessels, its mode of action is not fully understood. METHODS: The role of cytoplasmic ionized Ca(2+) concentration ([Ca(2+)](i)) in platelet activation induced by contact with a glass surface under shear-stress was studied by employing confocal laser scanning microscopy (CLSM) in conjunction with a parallel plate flow chamber. Changes in [Ca(2+)](i) and morphology of aggregating platelets on glass surface was simultaneously examined. RESULTS: Under static condition, contact with glass caused platelet adhesion to the surface, which was associated with [Ca(2+)](i) rise and morphological change; however, platelets did not develop a large aggregation on the surface. Under lower shear-stress, the number of the single platelets adsorbed on the surface was less than that under static condition. Although shear-stress increased the number of single platelets involved and enhanced morphological change in aggregating platelets in a shear-stress related manner, the peak [Ca(2+)](i) value in individual platelets were not increased. CONCLUSIONS: These observations may suggest the crucial roles of shear-stress in platelet aggregate formation at the site of arterial stenosis. Shear-stress might enhances platelet aggregate growth not through the enhancement of [Ca(2+)](i) rise.

Calcium↗
PubMed2001

Ruthenium-catalyzed hydration of 1-alkynes to give aldehydes: insight into anti-Markovnikov regiochemistry.

The mechanism of the selective conversion of 1-alkynes to aldehydes by hydration was investigated by isolating organic and organometallic byproducts, deuterium-labeling experiments, and DFT calculations. The D-labeled acetylenic hydrogen of 1-alkyne was found exclusively in the formyl group of the resulting aldehydes. After the reaction, the presence of metal-coordinated CO was confirmed. All of the experimental results strongly suggest the involvement of a metal-acyl intermediate with the original acetylenic hydrogen also bound to the metal center as a hydride, with the next step being release of aldehyde by reductive elimination. Theoretical analyses suggest that the first step of the catalytic cycle is not oxidative addition of acetylene C [bond] H or tautomerization of eta(2)-alkyne to a vinylidene complex, but rather protonation of the coordinated 1-alkyne at the substituted carbon to form a metal-vinyl intermediate. This cationic intermediate then isomerizes to Ru(IV)-hydride-vinylidene via alpha-hydride migration of the vinyl group to the metal center, followed by attack of the vinylidene alpha-carbon by OH(-) to give the metal-hydride-acyl intermediate.

Journal Article↗
PubMed2001

RNA polymerase II elongator holoenzyme is composed of two discrete subcomplexes.

Elongator is a histone acetyltransferase complex that associates with the elongating form of RNA polymerase II. We purified Elongator to virtual homogeneity via a rapid three-step procedure based largely on affinity chromatography. The purified factor, holo-Elongator, is a labile six-subunit factor composed of two discrete subcomplexes: one comprised of the previously identified Elp1, Elp2, and Elp3 proteins and another comprised of three novel polypeptides, termed Elp4, Elp5, and Elp6. Disruption of the yeast genes encoding the new Elongator proteins confers phenotypes indistinguishable from those previously described for the other elp mutants, and concomitant disruption of genes encoding proteins in either subcomplex does not confer new phenotypes. Taken together, our results indicate that holo-Elongator is a functional entity in vitro as well as in vivo. Metazoan homologues of Elp1 and Elp3 have previously been reported. We cloned the human homologue of yeast ELP4 and show that this gene is ubiquitously expressed in human tissues.

Acetyltransferases↗
PubMed2001

A multiprotein complex that interacts with RNA polymerase II elongator.

A three-subunit Hap complex that interacts with the RNA polymerase II Elongator was isolated from yeast. Deletions of genes for two Hap subunits, HAP1 and HAP3, confer pGKL killer-insensitive and weak Elongator phenotypes. Preferential interaction of the Hap complex with free rather than RNA polymerase II-associated Elongator suggests a role in the regulation of Elongator activity.

Amino Acid Sequence↗
PubMed2001

Localized activation of m-calpain in human umbilical vein endothelial cells upon hypoxia.

Bleb formation is an early event of cellular damage observed in a variety of cell types upon hypoxia. Although we previously found the appearance of the localized cytoplasmic ionized Ca(2+) concentration ([Ca(2+)](i)) rise before bleb formation at the same loci of human umbilical vein endothelial cell (HUVEC) upon hypoxia, the mode of [Ca(2+)](i)-rise-induced cytoskeletal alteration remains ill-defined. The aim of this study is to clarify the mechanisms causing bleb formation after localized [Ca(2+)](i) rise. We studied the activation of m-calpain associated with the alteration of cytoskeleton-related proteins, F-actin, mu-actin, or ezrin by employing specific antibodies in conjunction with a confocal laser scanning microscopy (CLSM). Specific antibodies against 80-kDa-preactivated and 78-kDa-activated m-calpain clearly demonstrated redistribution of 80-kDa m-calpain followed by autoproteolytic activation of m-calpain to the 78-kDa form at the same loci of [Ca(2+)](i) rise in hypoxia-treated HUVECs, which was associated with the decrease of ezrin and the localized appearance of beta-actin at the same loci. In conclusion, hypoxia-induced localized [Ca(2+)](i) rise causes bleb formation at the same loci through m-calpain-catalyzed destruction of cross-linking between plasma membrane and actin filaments.

Actins↗
PubMed2001

NaCl-activated nucleoside diphosphate kinase from extremely halophilic archaeon, Halobacterium salinarum, maintains native conformation without salt.

Enzymes from extremely halophilic archaea are readily denatured in the absence of a high salt concentration. However, we have observed here that a nucleoside diphosphate kinase prepared from Halobacterium salinarum was active and stable in the absence of salt, though it has the amino acid composition characteristic of halophilic enzymes. Recombinant nucleoside diphosphate kinase expressed in Escherichia coli requires salt for activation in vitro, but once it acquires the proper folding, it no longer requires the presence of salts for its activity and stability.

Amino Acid Sequence↗
PubMed2001

Ruthenium complex-catalyzed anti-Markovnikov hydration of terminal alkynes.

[reaction: see text]. Highly regioselective, efficient, and substituent-tolerant anti-Markovnikov hydration of terminal alkynes occurs to give n-aldehyde by use of a catalytic amount of easily available cyclopentadienylruthenium complexes bearing appropriate bidentate or monodentate phosphine ligands. Typically, RuCpCl(dppm) (1 mol %) catalyzes the addition of water to 1-hexyne at 100 degrees C to give hexanal in 95% yield: 2-hexanone is not detected at all.

Journal Article↗
PubMed2001

Epstein-Barr virus in gastric carcinoma is associated with location in the cardia and with a diffuse histology: a study in one area of Chile.

Epstein-Barr virus (EBV) has been associated with the most common form of stomach neoplasms, the gastric carcinoma (GC). The presence of EBV-encoded small RNAtype-1 (EBER-1), a marker for EBV infection was analyzed by in situ hybridization (ISH) in 185 formalin-fixed and paraffin-embedded cases of GC from a high risk region. We found 31 (16.8%) EBV-positive cases with no relationship to age. Although male predominance (19% in males and 12.5% in females) was observed, the gender difference did not achieve statistical significance. Odds ratio (OR) for cardia location was 5.4 (95% CI 1.7-17.3) when antrum was used as referent category and the effects of gender and age were taken into account. The proportion of EBV-positive cases in diffuse histology was higher than intestinal type (OR = 4.8, 95% CI = 2.0-11.1). Our findings are contrary to a previously accepted hypothesis, that high-risk countries for GC have low rates of EBV-associated GC. In addition, our findings regarding location, histology and weak male predominance are different from what has been described in Asian and European countries, but similar to those described in Mexico and Mexican descendants living in the U.S. suggesting unique characteristics of EBV-associated GC in Latin-America.

Adult↗