Search PubMed⌕ Search

Biomedical subjects

R Takahashi

Publications and source records attributed to R Takahashi.

At least 37 records · Page 2Linked to original sources
PubMed2001

The membrane-anchored MMP inhibitor RECK is a key regulator of extracellular matrix integrity and angiogenesis.

Matrix metalloproteinases (MMPs) are essential for proper extracellular matrix remodeling. We previously found that a membrane-anchored glycoprotein, RECK, negatively regulates MMP-9 and inhibits tumor invasion and metastasis. Here we show that RECK regulates two other MMPs, MMP-2 and MT1-MMP, known to be involved in cancer progression, that mice lacking a functional RECK gene die around E10.5 with defects in collagen fibrils, the basal lamina, and vascular development, and that this phenotype is partially suppressed by MMP-2 null mutation. Also, vascular sprouting is dramatically suppressed in tumors derived from RECK-expressing fibrosarcoma cells grown in nude mice. These results support a role for RECK in the regulation of MMP-2 in vivo and implicate RECK downregulation in tumor angiogenesis.

Animals↗
PubMed2001

3D grazing collision of two black holes.

We present results for two colliding black holes (BHs), with angular momentum, spin, and unequal mass. For the first time, gravitational waveforms are computed for a grazing collision from a full 3D numerical evolution. The collision can be followed through the merger to form a single BH, and through part of the ringdown period of the final BH. The apparent horizon is tracked and studied, and physical parameters, such as the mass of the final BH, are computed. The total energy radiated in gravitational waves is shown to be consistent with the total initial mass of the spacetime and the apparent horizon mass of the final BH.

Journal Article↗
PubMed2001

Green fluorescent protein-transgenic rat: a tool for organ transplantation research.

The purpose of this study is to evaluate green fluorescent protein (GFP) transgenic rats for use as a tool for organ transplantation research. The GFP gene construct was designed to express ubiquitously. By flow cytometry, the cells obtained from the bone marrow, spleen, and peripheral blood of the GFP transgenic rats consisted of 77, 91, and 75% GFP-positive cells, respectively. To examine cell migration of GFP-positive cells after organ transplantation, pancreas graft with or without spleen transplantation, heart graft with or without lung transplantation, auxiliary liver and small bowel transplantation were also performed from GFP transgenic rat to LEW (RT1(1)) rats under a 2-week course of 0.64 mg/kg tacrolimus administration. GFP-positive donor cells were detected in the fully allogenic LEW rats after organ transplantation. These results showed that GFP transgenic rat is a useful tool for organ transplantation research such as cell migration study after organ transplantation without donor cell staining.

Animals↗
PubMed2001

Plunge waveforms from inspiralling binary black holes.

We study the coalescence of nonspinning binary black holes from near the innermost stable circular orbit down to the final single rotating black hole. We use a technique that combines the full numerical approach to solve the Einstein equations, applied in the truly nonlinear regime, and linearized perturbation theory around the final distorted single black hole at later times. We compute the plunge waveforms, which present a non-negligible signal lasting for t approximately 100M showing early nonlinear ringing, and we obtain estimates for the total gravitational energy and angular momentum radiated.

Journal Article↗
PubMed2001

A possible novel isoform of peripheral myelin P0 protein: a target antigen recognized by an autoantibody in a patient with malignant lymphoma and peripheral neuropathy.

We tried to characterize a 35-kD antigen recognized by the serum IgG of a patient with malignant lymphoma and peripheral neuropathy. By Western blotting, the serum IgG reacted with the 35-kD antigen in the human, bovine and mouse peripheral nerve (PN) but not with other neural and non-neural tissues. Immunohistochemical analysis showed immunoreactivity of the IgG in the compact myelin of PN. We constructed a human sciatic nerve cDNA library and screened it using IgG of the patient. Three independent clones were obtained. Sequence alignment indicated that the inserts of these clones were homologous to the P0 cDNA, but that all three corresponded to the 3'-untranslational region of the P0 cDNA. To biochemically analyze the 35-kD antigen, myelin fractions of the human and bovine PN were prepared. The 35-kD antigen was purified from the crude myelin fraction by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. When the immunoreactivities of the 35-kD antigen for the IgG of the patient and a monoclonal anti-P0 antibody were compared with those of P0 protein for these antibodies, the 35-kD antigen reacted with both antibodies, but the P0 protein reacted with only the monoclonal anti-P0 antibody. These results suggest that the 35-kD antigen is an isoform of P0 protein. Although it is unlikely that the autoantibody may be the primary cause of neuropathy, because they were also detected in patients with lymphoma without overt neuropathy, they appear to be a modifying factor in the progression of neuropathy.

Adult↗
PubMed2001

Ubiquitin-protein ligase activity of X-linked inhibitor of apoptosis protein promotes proteasomal degradation of caspase-3 and enhances its anti-apoptotic effect in Fas-induced cell death.

The inhibitor of apoptosis (IAP) family of anti-apoptotic proteins regulate programmed cell death and/or apoptosis. One such protein, X-linked IAP (XIAP), inhibits the activity of the cell death proteases, caspase-3, -7, and -9. In this study, using constitutively active mutants of caspase-3, we found that XIAP promotes the degradation of active-form caspase-3, but not procaspase-3, in living cells. The XIAP mutants, which cannot interact with caspase-3, had little or no activity of promoting the degradation of caspase-3. RING finger mutants of XIAP also could not promote the degradation of caspase-3. A proteasome inhibitor suppressed the degradation of caspase-3 by XIAP, suggesting the involvement of a ubiquitin-proteasome pathway in the degradation. An in vitro ubiquitination assay revealed that XIAP acts as a ubiquitin-protein ligase for caspase-3. Caspase-3 was ubiquitinated in the presence of XIAP in living cells. Both the association of XIAP with caspase-3 and the RING finger domain of XIAP were essential for ubiquitination. Finally, the RING finger mutants of XIAP were less effective than wild-type XIAP at preventing apoptosis induced by overexpression of either active-form caspase-3 or Fas. These results demonstrate that the ubiquitin-protein ligase activity of XIAP promotes the degradation of caspase-3, which enhances its anti-apoptotic effect.

Apoptosis↗
PubMed2001

An unfolded putative transmembrane polypeptide, which can lead to endoplasmic reticulum stress, is a substrate of Parkin.

A putative G protein-coupled transmembrane polypeptide, named Pael receptor, was identified as an interacting protein with Parkin, a gene product responsible for autosomal recessive juvenile Parkinsonism (AR-JP). When overexpressed in cells, this receptor tends to become unfolded, insoluble, and ubiquitinated in vivo. The insoluble Pael receptor leads to unfolded protein-induced cell death. Parkin specifically ubiquitinates this receptor in the presence of ubiquitin-conjugating enzymes resident in the endoplasmic reticulum and promotes the degradation of insoluble Pael receptor, resulting in suppression of the cell death induced by Pael receptor overexpression. Moreover, the insoluble form of Pael receptor accumulates in the brains of AR-JP patients. Here, we show that the unfolded Pael receptor is a substrate of Parkin, the accumulation of which may cause selective neuronal death in AR-JP.

Acetylcysteine↗
PubMed2001

Characterization of two genes, Sig1 and Sig2, encoding distinct plastid sigma factors(1) in the moss Physcomitrella patens: phylogenetic relationships to plastid sigma factors in higher plants.

We isolated the cDNA for a sigma factor from the moss Physcomitrella patens, which possesses unusually large N-terminal extension and the conserved subdomains 1.2-4.2. Phylogenetic analyses indicated that this novel sigma factor and PpSIG1*(2), a plastid sigma factor previously identified from Physcomitrella, were classified into SigA and SigB groups, two major classes of higher plant plastid sigma factors, respectively. According to the nomenclature recently proposed, we renamed PpSIG1* into PpSIG2, and named the novel sigma factor PpSIG1. A transient expression assay using a green fluorescent protein showed that the N-terminal region of PpSIG1 acts as a chloroplast-targeting signal. Reverse transcription-PCR experiments showed that light induces the expression of the Sig1 and Sig2 genes encoding PpSIG1 and PpSIG2, respectively. Thus, PpSIG1 and PpSIG2 are likely plastid sigma factors regulating plastid gene expression in response to light signals.

Amino Acid Sequence↗
PubMed2001

X-linked inhibitor of apoptosis protein (XIAP) inhibits caspase-3 and -7 in distinct modes.

The inhibitor of apoptosis proteins (IAP) regulates cell death by inhibiting caspases. The region of X-linked (X) IAP containing the second baculovirus IAP repeat domain (BIR2) is sufficient for inhibiting caspase-3 and -7. In this study, we found that the modes of inhibition of these two caspases were different: caspase-3 is inhibited in a competitive manner whereas caspase-7 inhibition occurs through a mixed competitive and noncompetitive mechanism. Binding assays revealed that the inhibition of caspase-3 by XIAP was totally dependent on the interaction between the active site of caspase-3 and the linker region between the BIR1 and BIR2 domains of XIAP. In contrast, the active site and the NH(2)-terminal region of caspase-7 bound to the linker region and the BIR2, respectively. Moreover the BIR2 with a mutated linker region, which inhibited caspase-3 very weakly, still bound to and inhibited caspase-7. Furthermore, a chimeric caspase-7/3 comprising the NH(2)-terminal portion of caspase-7 and COOH-terminal portion of caspase-3 was inhibited by XIAP by a mixed competitive and noncompetitive mechanism. Our results suggest that the linker region between BIR1 and BIR2 domains is responsible for active site-directed, competitive inhibition of both caspase-3 and -7, whereas the BIR2 itself is involved in noncompetitive inhibition of caspase-7.

Base Sequence↗
PubMed2001

Stable operation of a 300-m laser interferometer with sufficient sensitivity to detect gravitational-wave events within our galaxy.

TAMA300, an interferometric gravitational-wave detector with 300-m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations; the interferometer was operated for over 10 hours stably and continuously. With a strain-equivalent noise level of h approximately 5x10(-21)/sqrt[Hz], a signal-to-noise ratio of 30 is expected for gravitational waves generated by a coalescence of 1.4M-1.4M binary neutron stars at 10 kpc distance. We evaluated the stability of the detector sensitivity with a 2-week data-taking run, collecting 160 hours of data to be analyzed in the search for gravitational waves.

Astronomy↗
PubMed2001

cAMP and calcium ionophore induce outgrowth of neuronal processes in PC12 mutant cells in which nerve growth factor-induced outgrowth of neuronal processes is impaired.

During continuous culturing, PC12 cells are subject to spontaneous mutations. We obtained PC12m3 cells, clone cells in which outgrowth of neuronal processes (dendrites and axons) under the condition of nerve growth factor (NGF) treatment was highly stimulated by various inducers, such as cyclic adenosine monophosphate (cAMP), calcium ionophore, steroid and high osmolarity. The number of cells with neuronal processes in the presence of cAMP was approximately twenty-fold greater than PC12 parental cells and other PC12 mutant cells. In PC12m3 cells, NGF-induced outgrowth of neuronal processes was reduced by cytotoxic solanine, whereas the effect of NGF was unaffected by hyaluronic acid. In PC12m3 cells, various inducers of neurite outgrowth, such as cAMP, calcium ionophore and high osmolarity, activated mitogen activated protein (MAP) kinase, whereas solanine and hyaluronic acid did not cause any significant activation of MAP kinase. However, PC12m3 cells, in which NGF-induced outgrowth of neuronal processes were impaired, had strong NGF-induced MAP kinase activity as PC12 parental cells had. These findings suggest that cAMP, calcium influx and high osmolarity induce outgrowth of neuronal processes in PC12m3 cells through activation of the downstream target of MAP kinase or through a novel pathway independent of NGF activation.

Animals↗
PubMed2001

IL-12 and IL-18 are increased and stimulate IFN-gamma production in sarcoid lungs.

Sarcoidosis is a systemic chronic granulomatous disease of unknown cause. Recent investigations revealed that the cytokine profile in inflamed lesions of sarcoidosis is Th1 dominant. To obtain better immunopathologic understanding of sarcoidosis, we examined the expression of IL-12 and IL-18 and their roles in IFN-gamma production in pulmonary sarcoidosis. Sarcoid cases had significantly elevated levels of IL-12 (p40 and p70) and IL-18 in bronchoalveolar lavage (BAL) fluids compared with healthy subjects. IL-12 p70 and IL-18 were immunohistochemically expressed in the epithelioid cells and giant cells of sarcoid granulomas. Significant induction of IFN-gamma, IL-12 p70, and IL-18 was observed from sarcoid BAL fluid cells with LPS stimulation, whereas LPS tended to induce only IL-12 p70 in BAL fluid cells from healthy subjects. Sarcoid cases had significantly greater IFN-gamma induction with LPS stimulation than healthy subjects did. IL-18 mRNA expression was observed in freshly isolated sarcoid BAL fluid cells as well as in LPS-stimulated sarcoid BAL fluid cells, but IFN-gamma and IL-12 mRNA expression was observed only in LPS-stimulated BAL fluid cells. Treatment with anti-IL-12- and anti-IL-18-neutralizing Abs significantly inhibited IFN-gamma production from LPS-stimulated BAL fluid cells of sarcoid cases. Coadministration of rIL-12 or rIL-18 induced greater IFN-gamma production in sarcoid BAL fluid cells than in normal BAL fluid cells. We concluded that bioactive IL-12 and IL-18 were produced in sarcoid BAL fluid cells and synergistically induced IFN-gamma production, indicating important cytokines in the Th1 response of sarcoidosis.

Adjuvants, Immunologic↗
PubMed2001

The anxiolytic effect of Sho-ju-sen, a Japanese herbal medicine, assessed by an elevated plus-maze test in mice.

Sho-ju-sen (SK), a Japanese herbal medicine with a nourishing tonic action, is composed of a water extract of Kumazasa leaves (Sasa kurinensis Makino et Sibata) (SS), and ethanol extracts of Japanese red pine needles (Pinus densiflora Sieb. et Zucc) (PN) and Ginseng roots (Panax ginseng C. A. Meyer) (PX) in the ratio 8:1:1. In this study, an elevated plus-maze test in mice was carried out to assess whether SK had an anxiolytic effect. No significant change was observed in either the plus-maze or activity test following a single administration of SK (10 and 20 mL/kg p.o.). However, mice allowed a free intake of SK (10% solution) for 5 days and longer showed a significant prolongation of the time spent in the open arms (an anxiolytic effect), as long as that caused by the benzodiazepine anxiolytic diazepam (1 mg/kg p.o.). SK (1%, 3% and 30% solutions for 7 days) tended to develop the anxiolytic effect. Of the constituents of SK, SS (8% solution), but not PN (1% solution) or PX (1% solution), resulted in the anxiolytic effect. Except for a slight acceleration in the motor activity by PN (1% solution), no significant change in the motor activity was produced by any treatment with SK, SS or PX. The combined treatment of SK (10% solution) or SS (8% solution) with 1 mg/kg diazepam enhanced the anxiolytic effect. Flumazenil (0.1 mg/kg s.c.), a benzodiazepine receptor antagonist, alone did not change the time spent in the open arms. However, it completely reversed the anxiolytic effect of SK, SS and diazepam. The present results suggest that: (1) long-term treatment with SK develops an anxiolytic effect, (2) SS is the main constituent for the anxiolytic effect of SK, and (3) benzodiazepine receptors are involved in the anxiolytic effect of SK and SS.

Animals↗
PubMed2001

Influence of humoral immunoreaction on hepatic nonparenchymal cells in ex situ xenoperfused rat livers.

BACKGROUND: The influence of xenogeneic humoral immunoreaction on hepatic nonparenchymal cells (NPCs) was evaluated ex situ in xenoperfused rat livers. METHODS: Isolated rat livers were perfused via the portal vein (PV) for 240 min. The perfusates consisted of fresh rat blood (group 1), fresh human blood (group 2), and fresh human blood containing 5 microg/mL soluble complement receptor type 1 (Group 3). RESULTS: Deposition of human IgM and C(5b-9) complement was observed in group 2, although only human IgM deposition was detected in group 3. Portal vein pressure in group 2 rose drastically during the first 10 min. Creatine kinase BB component gradually increased in all groups, followed by an elevation in alanine aminotransferase and both parameters were significantly higher in group 2 than in groups 1 and 3. In group 2, platelet thrombi in the peripheral PVs and periportal hemorrhage were observed after 10 min, and massive necrosis around the central veins after 240 min; these changes were not observed in group 1 or 3. Production of tumor necrosis factor alpha and alpha interferon and expression of intercellular adhesion molecule 1 (ICAM-1) were lower in group 2 than in groups 1 and 3. In group 2, there were negative areas for ICAM-1 and tumor necrosis factor alpha staining around the central veins after 240 min, which were consistent with necrotic areas. CONCLUSIONS: In xenoperfused rat livers, humoral mediators initially caused the disturbance of microcirculation, which would induce long ischemia in the pericentral areas, resulting in massive necrosis. NPC necrosis may be responsible for less production of cytokines and adhesion molecules in the xenoperfused livers.

Alanine Transaminase↗
PubMed2001

Aortic subannular left ventricular aneurysm in a patient of Asian ancestry.

An asymptomatic 50-year-old Japanese man was diagnosed with an aortic subannular left ventricular aneurysm during a routine physical checkup. Operative findings showed the subaortic aneurysm had developed beneath the noncoronary cusp of the aortic valve and expanded into the epicardium between the aortic root and left atrium. The operation involved patch closure of the orifice of the annular subaortic aneurysm, aortic valvuloplasty, and plication of the dilated ascending aorta.

Aortic Aneurysm↗
PubMed2001

Lethal adenovirus infection in a patient who had undergone nonmyeloablative stem cell transplantation.

We present a case of adenovirus (ADV) infection in a patient who had undergone nonmyeloablative stem cell transplantation (NST). A 50-year-old man with chronic myelogenous leukemia in the second chronic phase underwent NST from an HLA 2-loci-mismatched sibling. ADV hemorrhagic cystitis developed and progressed to lethal pneumonia. ADV was isolated from urine, bronchoalveolar lavage fluid, and postmortem specimens of kidney and liver. Because there are few reports of lethal pneumonia associated with ADV in Japan, we present the case and discuss the cause of and therapy for the infection.

Adenoviridae Infections↗
PubMed2001

A newly developed bisphosphonate, YM529, is a potent apoptosis inducer of human myeloma cells.

We examined the effect of YM529, a newly developed third-generation bisphosphonate (BP), on the growth of human myeloma cell lines using the trypan blue dye exclusion test and Alamar blue assay. BPs induced inhibition of proliferation in all cell lines dose-dependently, and YM529 had a most potent growth inhibitory effect, followed by incadronate and pamidronate. Flow cytometric analysis using annexinV and 7AAD showed that YM529 most significantly induced apoptosis of all myeloma cell lines. These observations suggested that YM529 is a potent apoptosis inducer of myeloma cells, and might have some benefit not only on the improvement of bone lesions but also on survival in some myeloma patients.

Antineoplastic Agents↗