Biomedical subjects

Toshikazu Suzuki

Publications and source records attributed to Toshikazu Suzuki.

At least 19 recordsLinked to original sources

PubMed2005

Leupeptin-sensitive proteases involved in cell survival after X-ray irradiation in human RSa cells.

Proteases have received attention as important cellular components responsible for stress response in human cells. However, little is known about the role of proteases in the early steps of cell response after X-ray irradiation. In the present study, we first searched for proteases whose activity levels are changed soon after X-ray irradiation in human RSa cells with a high sensitivity to X-ray cell-killing. RSa cells showed an increased level of fibrinolytic protease activity within 10 min after irradiation with X-ray (up to 3 Gy). The induced protease activity was proved to be inhibited by leupeptin. We next examined whether this protease inducibility is related to the X-ray susceptibility of cells. Treatment of RSa cells with leupeptin prior to X-ray irradiation resulted in lowered colony survival and an increased ratio of G(2)/M-arrested cells and apoptotic cells. These results suggest that leupeptin-sensitive proteases are involved in the resistance of human RSa cells to X-ray cell-killing.

Apoptosis↗

PubMed2005

Increased expression of GRP94 protein is associated with decreased sensitivity to X-rays in cervical cancer cell lines.

PURPOSE: Radiation therapy is one of the standard treatments for cervical cancer. Glucose regulated protein 94 (GRP94) is a molecular chaperone, which increases in amount after X-ray irradiation. This study examined the involvement of GRP94 in radio-resistance in human cervical cancer cells. MATERIALS AND METHODS: Seven human cervical carcinoma cell lines (HeLa, SKG-I, SKG-IIIb, QG-U, Caski, SiHa and C33A) were examined for basal levels of GRP94 protein by western blotting analysis. Sensitivity to X-ray irradiation of these cell lines was determined with a colony survival assay. The suppression of GRP94 expression was performed using specific small-interfering RNA (siRNA) in HeLa and Caski cells. RESULTS: HeLa cells and QG-U cells, with higher basal levels of GRP94, exhibited a low sensitivity to X-ray cell killing. In HeLa cells, the sensitivity increased when protein GRP94 levels were reduced by specific siRNA transfection. However, a reduction in GRP94 protein had little effect on the X-ray sensitivity of Caski cells, which expressed low basal GRP94 protein levels but showed a low sensitivity to X-rays. CONCLUSIONS: High basal protein levels of GRP94 were correlated with a modest decrease in sensitivity to X-ray cell death in some cervical cancer cell lines. These results suggest that higher GRP94 protein expression is one of the molecular mechanisms causing resistance to radiation, and therefore GRP94 siRNA might be useful in tumor-specific gene therapy by reversing radio-resistance prior to radiation in cervical cancer.

Biomarkers, Tumor↗

PubMed2005

Histologic evaluation of temporomandibular arthritis induced by mild mechanical loading in rabbits.

BACKGROUND: We still lack knowledge of causative factors in arthritis related to temporomandibular disorders (TMD). The goal of the present study was to investigate whether applying a mechanical loading on the glenoid fossa can induce arthritis. METHODS: Coil springs were placed in 24 rabbits so as to exert a force of 100 g between the orbital edge and the antegonial notch. At 1, 2, 4 and 8 weeks after the surgery, six samples of the temporomandibular joint (TMJ) were removed for histologic examination. RESULTS: The results showed that mild synovitis began 1-2 weeks after the start of loading, and the degree of synovitis was significant at 4 weeks, and that morphologic changes occurred in the articular eminence and condyle, while type II collagen in the cartilage of the articular eminence degraded prior to that in the condyle. CONCLUSIONS: Our results revealed that mild, continuous mechanical loading to the glenoid fossa induces synovitis of the articular capsule, and induces organic changes of the articular cartilage without destroying these tissues.

Animals↗

PubMed2005

Enhanced expression of transferrin receptor confers UV-resistance in human and monkey cells.

One of the most intriguing biological subjects is cell-surface molecules that regulate the susceptibility of human cells to cell-killing effects after irradiation with far-ultraviolet light (UV, principally 254 nm wavelength). Human RSa cells have unusual sensitivity to UV-induced cell-killing. We searched for molecules on the cell-surface of RSa cells that were present in different amounts as compared to a variant of these cells, UV(r)-1 cells, which have increased resistance to UV cell-killing. Among the 21 molecules examined, the amount of transferrin receptor (TfR) protein was found to be 2-fold higher in UV(r)-1 cells compared with in RSa cells. The amounts of this protein were also higher in the UV-resistant hematopoietic cell lines, CEM6 and Daudi, as compared to the UV-sensitive cell lines, Molt4 and 697. Culturing of UV(r)-1 cells in a medium containing anti-transferrin antibodies resulted in sensitization of the cells to UV cell-killing as demonstrated by colony formation assay. Similar results were observed by treatment of the cells with TfR siRNA. In contrast, overexpression of TfR protein led to a resistance to UV cell-killing in RSa cells and monkey COS7 cells as demonstrated by both colony formation and apoptosis assay. In TfR-overexpressing cells, reduction of p53 and Bax protein was observed after UV-irradiation. Thus, TfR expression appears to be involved in the regulation of UV-resistance, possibly via modulation of the amount of p53 and Bax protein.

Animals↗

PubMed2004

Induction of uPA release in human peripheral blood lymphocytes by [deamino-Cysl,D-Arg8]-vasopressin (dDAVP).

[deamino-Cys(l),d-Arg(8)]-vasopressin (dDAVP), known to be an arginine vasopressin (AVP) V(2) receptor agonist, is an agent that increases fibrinolytic activity levels in plasma after its infusion into the human body. However, mechanisms underlying an increase and exact localization of the extrarenal dDAVP-responsive V(2) receptor remain unclarified. Two AVP receptors, V(1a) and V(2), and a related oxytocin (OT) receptor were found to be expressed in human lymphocytes. Furthermore, we found an increase of fibrinolytic activity in the medium of peripheral lymphocytes obtained from human volunteers less than 20 min after dDAVP infusion. The increased activity was also detected in the medium after incubating the lymphocytes in the presence of dDAVP in vitro, being highest at 20 min after the incubation. In accord with the increased fibrinolytic activity, the levels of urokinase-type plasminogen activator (uPA) in the medium were also increased. However, there was no significant difference of plasminogen activator inhibitor-1 (PAI-1), pro-uPA, and tissue-type plasminogen activator (tPA) concentrations in the medium between dDAVP treatment and control. When lymphocytes were preincubated with a V(2) receptor antagonist [Adamantaneacetyl(1),O-Et-d-Tyr(2),Val(4),Aminobutyryl(6),Arg(8,9)]-vasopressin, the dDAVP-induced uPA increase was diminished. In contrast, preincubation with a V(1) receptor antagonist, [beta-Mercapto-beta,beta-cyclopentamethylenepropionyl(1),O-Me-Tyr(2),Arg(8)]-vasopressin, prior to dDAVP treatment resulted in a greater increase of the uPA concentration in the medium than with the dDAVP treatment alone. Thus it was suggested that dDAVP may induce uPA release from human lymphocytes via V(2) receptor-mediated reaction, and also via cross-talk between V(1) and V(2) receptors.

Arginine Vasopressin↗

PubMed2004

Mutations in chemosensory cilia cause resistance to paraquat in nematode Caenorhabditis elegans.

The relationship between oxidative stress and longevity is a matter of concern in various organisms. We isolated mutants resistant to paraquat from nematode Caenorhabditis elegans. One mutant named mev-4 was long-lived and showed cross-resistance to heat and Dyf phenotype (defective in dye filling). Genetic and sequence analysis revealed that mev-4 had a nonsense mutation on the che-11 gene, homologues of which are involved in formation of cilia and flagella in other organisms. The paraquat resistance was commonly observed in various Dyf mutants and did not depend on the daf-16 gene, whereas the extension of life span did depend on it. Expression of antioxidant enzyme genes seemed normal. These results suggest that chemosensory neurons are a target of oxidative stress and influence longevity dependent on the daf-16 signaling in C. elegans.

Age Factors↗

PubMed2004

Achievement of ultralow emittance beam in the accelerator test facility damping ring.

For high luminosity in electron-positron linear colliders, it is essential to generate low vertical emittance beams. We report on the smallest vertical emittance achieved in single-bunch-mode operation of the Accelerator Test Facility, which satisfies the requirement of the x-band linear collider. The emittances were measured with a laser-wire beam-profile monitor installed in the damping ring. The bunch length and the momentum spread of the beam were also recorded under the same conditions. The smallest vertical rms emittance measured at low intensity is 4 pm at a beam energy of 1.3 GeV, which corresponds to the normalized emittance of 1.0x1.0(-8) m. It increases by a factor of 1.5 for a bunch intensity of 10(10) electrons. The measured data agreed to the calculation of intrabeam scattering within much better than a factor of 2.

Journal Article↗

PubMed2004

AT-hook proteins stimulate induction of senescence markers triggered by 5-bromodeoxyuridine in mammalian cells.

5-Bromodeoxyuridine (BrdU) induces a phenomenon similar to cellular senescence in mammalian cells. To address an underlying molecular mechanism in this phenomenon, we assessed the role of AT-hook proteins that bind to the minor grooves of specific AT-rich sequences. We expressed DsRed-tagged HMGI, MATH2, and MATH20 proteins in HeLa cells in a doxycycline dependent manner. Modest expression of these proteins revealed no apparent effect on the cells although high levels of expression were toxic to the cells. In contrast, their modest expression in the presence of low concentrations of BrdU similarly and dose-dependently induced senescence markers examined, although the same concentrations of BrdU alone showed no obvious effect. In both cases, DsRed fluorescence was mainly observed as foci or intense dots on Hoechst 33342-staining regions. These distribution patterns were not changed by addition of BrdU. Since AT-hook domains can displace chromatin compacting proteins pre-bound on AT-rich sequences, these results suggest that chromatin unpacking is one of the factors stimulating expression of the senescence markers in human cells.

AT-Hook Motifs↗

PubMed2004

Cyclic stretch induced MAPK phosphorylation stronger than static stretch.

The environment for living organism in space has microgravity and/or hypergravity and/or any kind of mechanical stresses. Cellular response may differ from the variety of mechanical stress. Mitogen-activated protein kinases (MAPKs) pathway is related to various cellular events. In the present study it was investigated the serial measurement of MAPK phosphorylation using western-blotting analysis following with three types of cyclic stretch, static, 0.1 Hz and 0.25 Hz. The result was that induction of MAPK phosphorylation had peaks within 2 to 4 hours and attenuated, while induction of p38 phosphorylation in 0.1 Hz stretch had a peak at 6 hours later and the strongest. Thus, there might be differential cellular response depends upon the frequency of cyclic stretch .

Blotting, Western↗

PubMed2003

Clinical evaluation of arthroscopic eminoplasty for habitual dislocation of the temporomandibular joint: comparative study with conventional open eminectomy.

OBJECTIVE: We sought to compare the clinical courses of patients who underwent arthroscopic eminoplasty and conventional open eminectomy for habitual dislocation of the temporomandibular joint (TMJ). STUDY DESIGN: Arthroscopic eminoplasty was performed by using Segami's method in 24 joints in 13 patients (arthroscopic group) with habitual dislocation of the TMJ, while conventional open eminectomy was performed by using Myrhaug's method in 18 joints in 11 patients (open group). Clinical factors were retrospectively compared between the 2 groups. RESULTS: The operation time per joint was, on average, 14 minutes shorter in the arthroscopic group (77 minutes versus 63 minutes), and the average blood loss was less in the arthroscopic group (2 g versus 15 g). During the follow-up period (mean, 41 months), dislocation recurred in 5 TMJs (28%) in the open group and in 6 TMJs (25%) in the arthroscopic group. No major postoperative complications were observed in either group. CONCLUSION: In treating patients with habitual dislocation of the TMJ, the use of arthroscopic eminoplasty produces clinical outcomes that are as effective as those obtained with the use of conventional open eminectomy.

Adult↗

PubMed2003

Does joint effusion on T2 magnetic resonance images reflect synovitis? Part 3. Comparison of histologic findings of arthroscopically obtained synovium in internal derangements of the temporomandibular joint.

OBJECTIVES: To evaluate the relationship between the volume of joint effusion (JE), determined by T2-weighted magnetic resonance imaging (MRI), and microscopic findings of synovial inflammation in internal derangement of the temporomandibular joint (TMJ). STUDY DESIGN: Magnetic resonance images of 53 symptomatic TMJs (53 patients) associated with painful hypomobility were taken to evaluate the degree of JE on a scale of 0 to 3. Within 2 months after MRI, biopsy specimens obtained by arthroscopy were quantitatively assessed, on the basis of Gynther's grading system, for severity of hyperplasia of synovial lining cell layers, vascularity, and the presence of inflammatory cells. Each synovitis score was compared among the 4 JE grades, as well as between 2 groups-effusion present (grades 2 and 3) and effusion absent (grades 0 and 1)-by using the Spearman correlation coefficiency and the Mann-Whitney U test. RESULTS: The distribution of JE was as follows: 14 joints had grade 0, 9 joints had grade 1, 19 joints had grade 2, and 11 joints had grade 3. Significant relationships were found between the grades of JE and scores of synovial lining cell layers (P =.0012) as well as between the grades of JE and scores of presence of inflammatory cells (P =.0064). The joints with effusion had significantly higher scores for synovial lining cell layers (2.0 +/- 0.2) than the joints without effusion (1.3 +/- 0.2) (P =.029). There was no statistically significant correlation between the scores of vascularity and JE (P =.394). CONCLUSIONS: The evidence of JE on MRI might correlate with synovial inflammatory activity. It confirms the common consensus that JE probably reflects synovitis, especially when synovial hyperplasia has a key role in the pathogenesis of JE.

Adolescent↗

PubMed2003

Bradykinin expression in synovial tissues and synovial fluids obtained from patients with internal derangement of the temporomandibular joint.

Bradykinin has been implicated in the pathogenesis of inflammatory arthritis by virtue of the potent pro-inflammatory properties. The purpose of this study is to investigate the expression of bradykinin in patients with internal derangement of the temporomandibular joint (TMJ). We examined 33 TMJ synovial biopsy specimens from 31 patients with internal derangement of the TMJ by an immunohistochemical technique using specific antibodies. We also determined the concentration of bradykinin in 20 synovial fluids from 18 patients with TMJ internal derangement by enzyme-linked immunosorbent assay. These data were compared with those of the control subjects. Bradykinin was predominantly localized in the synovial lining cell layer of TMJ samples obtained from patients with TMJ internal derangement. Bradykinin was also detected in 19 patients' TMJ synovial fluids and the average of bradykinin concentration in the synovial fluids of patients was higher than that of the healthy controls. Although a statistically significant correlation was not observed, these findings support the hypothesis that bradykinin may also be involved in the pathogenesis of TMJ pain and synovitis.

Adult↗

PubMed2002

Evaluation of the performance of polished mirror surfaces for the TAMA gravitational wave detector by use of a wave-front tracing simulation.

We evaluated the performance of polished mirror surfaces for the TAMA interferometric gravitational wave detector by comparing the experimental results with a wave-front tracing simulation. The TAMA mirror surfaces were polished to a roughness of a few nanometer rms. We confirmed that these polished mirrors do not limit the present TAMA sensitivity and that the target shot-noise sensitivity will be achieved with these mirrors, even if a power-recycling technique is introduced in the next stage of the TAMA.

Journal Article↗

PubMed2002

Synergistic induction of the senescence-associated genes by 5-bromodeoxyuridine and AT-binding ligands in HeLa cells.

5-Bromodeoxyuridine induces a senescence-like phenomenon in mammalian cells. This effect was dramatically potentiated by AT-binding ligands such as distamycin A, netropsin, and Hoechst 33258. The genes most remarkably affected by these ligands include the widely used senescence-associated genes and were located on or nearby Giemsa-dark bands of human chromosomes. We hypothesize that AT-rich scaffold/nuclear matrix attachment region sequences are involved in this phenomenon. In fact, upon substitution of thymine with 5-bromouracil, a rat S/MAR sequence reduced its degree of bending and became insensitive to cancellation of the bending by distamycin A. The S/MAR sequence containing 5-bromouracil also bound more tightly to nuclear scaffold proteins in vitro and this binding was not inhibited by distamycin A. Under the same conditions, the S/MAR sequence containing thymine easily dissociated from the nuclear scaffold proteins. Taken together, the synergistic induction of the genes may be explained not only by opening of condensed chromatin by distamycin A but also by increase in the binding of 5-bromouracil-containing S/MAR sequences to the nuclear scaffolds.

AT Rich Sequence↗

PubMed2002

Extremely low vertical-emittance beam in the accelerator test facility at KEK.

Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.

Journal Article↗

PubMed2002

Overexpression of VDUP1 mRNA sensitizes HeLa cells to paraquat.

5-Bromodeoxyuridine (BrdU) induces or suppresses senescence-associated genes in any types of mammalian cells. From a cDNA library upregulated by BrdU in HeLa cells, we identified the gene encoding VDUP1 as a senescence-associated gene in normal human fibroblasts. To address a role of VDUP1 in senescence, we established HeLa cell clones, V7 and V27, which express its mRNA in a doxycycline-dependent manner. Although their growth in liquid culture was moderately retarded, colony formation on semi-solid medium was strongly inhibited by overexpression of the mRNA. We also examined susceptibility of these clones to various reagents. Consequently, colony formation in liquid culture was strongly inhibited by paraquat in these clones. Their superoxide dismutase activity was normal.

Bromodeoxyuridine↗

PubMed2002

Binding of 5-bromouracil-containing S/MAR DNA to the nuclear matrix.

Substitution of thymine with 5-bromouracil in DNA is known to change interaction between DNA and proteins, thereby inducing various biological phenomena. We hypothesize that A/T-rich scaffold/nuclear matrix attachment region (S/MAR) sequences are involved in the effects of 5-bromodeoxyuridine. We examined an interaction between DNA containing an intronic S/MAR sequence of the immunoglobulin heavy chain gene and nuclear halos prepared from HeLa cells. Upon substitution with 5-bromouracil, the S/MAR DNA bound more tightly to the nuclear halos. The multi-functional nuclear matrix protein YY1 was also found to bind more strongly to 5-bromouracil-substituted DNA containing its recognition motif. These results are consistent with the above hypothesis.

Bromouracil↗

PubMed2002

Changes in nuclear matrix proteins during the senescence-like phenomenon induced by 5-chlorodeoxyuridine in HeLa cells.

5-Chlorodeoxyuridine (CldU) immediately induces a senescence-like phenomenon in any type of mammalian cells probably due to a change in nuclear matrix structure. We thus examined nuclear matrix proteins in HeLa cells cultured with CldU by high-resolution two-dimensional gel electrophoresis and peptide mass spectrometry. Three proteins were found to be down-regulated and one protein up-regulated by addition of CldU. In addition, one acidic protein accumulated in the nuclear matrix, although not quantitatively changed in the nuclei. Since these alterations were observed within 24h after addition of CldU, these proteins may be involved in an early step of the senescence-like phenomenon.

Antigens, Nuclear↗