Search PubMed⌕ Search

Biomedical subjects

T Iwasaki

Publications and source records attributed to T Iwasaki.

At least 37 records · Page 2Linked to original sources
PubMed2003

Inactivation differences of microorganisms by low pressure UV and pulsed xenon lamps.

UV disinfection has been applied to water treatment in recent years with low-pressure and medium-pressure UV lamps mainly used as the light source. In general, UV disinfection is considered to be inefficient with water of high turbidity because of inhibition of light penetration. Additionally, photoreactivation may be a problem that should be considered in case a disinfected water is discharged to the environment where sunlight causes reactivation. Recently, other types of lamps have been proposed including a flush-type lamp (such as a pulsed-xenon lamp) that emits high energy and wide wavelength intermittently. In this study, the difference between inactivation efficiencies by low-pressure UV (LPUV) and pulsed-xenon (PXe) lamps was investigated using two coliphage types and three strains of Escherichia coli. PXe had a suppressive effect on photoreactivation rate of the E. coli strains even though there was no significant effect on inactivation rate and maximum survival ratio after photoreactivation. PXe also had a benefit when applied to high turbidity waters as no tailing phenomena were observed in the low survival ratio area although it was observed in LPUV inactivation. This efficiency difference was considered to be due to the difference in irradiated wavelength of both lamps.

Escherichia coli↗
PubMed2002

Src kinase induces calcium release in Xenopus egg extracts via PLCgamma and IP3-dependent mechanism.

Mobilization of intracellular calcium is an indispensable step of fertilization-induced egg activation. Recently, this process has been shown to require the sequential activation of Src family tyrosine kinases, phospholipase Cgamma (PLCgamma), and inositol-1,4,5-trisphosphate (IP3)-dependent receptor of endoplasmic reticulum. In the present study, we made an attempt to recapitulate the early events of egg activation by stimulating Src kinase activity in the cell-free extracts of Xenopus eggs. We found that enhanced Src kinase activity can initiate calcium response of low magnitude in cytostatic factor (CSF)-arrested mitotic extracts without releasing them into interphase. The addition of catalytically active recombinant Src kinase, as well as the activation of endogenous Xenopus Src family kinase by hydrogen peroxide (H2O2), increased total tyrosine phosphorylation, tyrosine phosphorylation of PLCgamma, and IP3 production in the extracts. The treatment with the Src family kinase-specific inhibitor, PP1, or PLC inhibitor, U73122, or IP3 receptor antagonist, heparin, prevented calcium release in the extracts. We conclude, therefore, that possible mechanism of Src/H2O2 action in the extracts might involve tyrosine phosphorylation and activation of PLCgamma, accompanied by the increase in IP3 content and subsequent calcium release from IP3-regulated calcium stores. These results also suggest that monitoring calcium signals induced in the Xenopus egg extracts by various components of signaling pathways may provide a particularly useful approach to investigating their role in the signal transduction.

Animals↗
PubMed2002

Interleukin-18 and interleukin-12 synergistically inhibit osteoclastic bone-resorbing activity.

The effect of interleukin (IL)-18 on osteoclastic bone-resorbing activity was investigated in vitro. Osteoclast-enriched cells, about 70% of which were tartrate-resistant acid phosphatase (TRAP)-positive, were cultured on dentine slices, and then the total volume of resorption pits on each dentine slice was measured as bone-resorbing activity. When the effects of IL-18 alone at 1, 10, 100, and 1000 ng/mL were examined, bone-resorbing activity was significantly reduced only at 1000 ng/mL, by about 50%. However, IL-18 plus IL-12 (10 ng/mL each) reduced bone-resorbing activity by about 70%, whereas IL-12 alone had no significant effect. When the concentration of interferon (IFN)-gamma in the medium was measured, IL-18 or IL-12 was found to increase it slightly, and the combination of these two cytokines synergistically increased it. The inhibitory effect of the combination of the two cytokines was completely abolished by the addition of an anti-IFN-gamma neutralizing antibody to the medium, but IFN-gamma by itself did not inhibit osteoclastic bone resorption. IL-18 alone or in combination with IL-12 did not affect the number of TRAP-positive cells in culture of osteoclast-enriched cells. Osteoclasts prepared from osteoclast-enriched cells expressed mRNAs of IL-18 receptor, MyD88, and cathepsin K. Furthermore, IL-18 receptor protein was detected on the cell surface of osteoclasts. The present results indicate that the combination of IL-18 and IL-12 synergistically inhibits osteoclastic bone-resorbing activity, suggesting that IFN-gamma participates in the mechanism underlying this inhibition.

Animals↗
PubMed2002

Preoperative hepatic venous embolization for partial hepatectomy combined with segmental resection of major hepatic vein.

BACKGROUND: Liver resection of segments VII and/or VIII sometimes requires segmental resection of the right hepatic vein in patients with liver tumours invading or located close to the hepatic vein. In this situation, hepatic vein reconstruction is thought to have an important role in the postoperative function of segment VI. This study investigated whether preoperative embolization of the major hepatic vein could obviate the need for hepatic vein reconstruction after cranial partial resection of the liver including the major hepatic vein trunk in a preclinical model. METHODS: Sixteen beagles were divided into two groups of eight: control group (hepatectomy alone) and hepatic venous embolization (HVE) group (hepatectomy after HVE). HVE was performed 2 weeks before hepatectomy. All dogs underwent resection of the cranial third of the left lateral liver lobe together with the major trunk of the left hepatic vein. Following hepatectomy, survival, histological features, portal venous pressure and serum aspartate aminotransferase (AST) levels were determined. RESULTS: Six control animals and seven in the HVE group were alive 1 week after hepatectomy. Immediately after hepatectomy, portal venous pressure was significantly higher in the control group compared with the HVE group (mean(s.d.) 14.0(1.1) versus 8.1(1.0) mmHg; P < 0.01). Histological examination of the remnant left lateral lobe demonstrated patchy parenchymal haemorrhage in the control group and normal parenchymal architecture in the HVE group. Peak AST levels were observed on day 1 in both groups and were significantly higher in the control group (mean(s.d.) 182(42) versus 67(40) units/l; P < 0.01). CONCLUSION: In this model, preoperative HVE facilitated interlobar venous collateral formation and minimized the untoward effects of segmental hepatic vein resection. This procedure may obviate the need for hepatic vein reconstruction after cranial partial liver resection including the major hepatic vein.

Alanine Transaminase↗
PubMed2002

The molecular mechanism in activation-induced cell death of an Ag-reactive B cell clone.

TPA-1 is a subclone of B cell hybridomas established by somatic hybridization using B cells of A/J mice immunized with TNP-LPS, and expresses a receptor for TNP on the cell membrane. The present study showed that TPA-1 was induced to apoptotic cell death upon treatment with TNP-BSA. Therefore, TPA-1 is considered to provide a good model for the study on activation-induced cell death of mature B cells induced by soluble antigen. TNP-BSA treatment caused the generation of a large amount of intracellular reactive oxygen species (ROS) of TPA-1, and the addition of the monovalent thiol-reactive compound: monochlorobimane (MCB) rescued it from apoptosis as well as the antioxidant reagent: N-acetyl-L-cysteine. Furthermore, MCB markedly inhibited the generation of ROS and prevented the disruption of mitochondrial membrane potential that was induced by TNP-BSA treatment. In addition, it counteracted the effect of TNP-BSA on the expression of the Bcl-2 family, resulting in down-regulation of Bax and Bad and up-regulation of Bcl-XL. Taken together, these results suggest strongly that oxidative stress of mitochondria may be involved directly in apoptotic cell death by engagement of antigen receptors on mature B cells with soluble antigen.

Amino Acid Chloromethyl Ketones↗
PubMed2001

HeLa ZIP kinase induces diphosphorylation of myosin II regulatory light chain and reorganization of actin filaments in nonmuscle cells.

Dlk/ZIP kinase is a serine/threonine kinase highly homologous to DAP kinase. We have reported that HeLa ZIP kinase (hZIPK) phosphorylated the regulatory light chain of myosin II (MRLC) at both Ser19 and Thr18 in vitro. In this study, we demonstrate that hZIPK also induces the diphosphorylation of MRLC in nonmuscle cells. Peptide mapping revealed that transient transfection of hZIPK into HeLa cells caused diphosphorylation of MRLC. In contrast, transfection of the kinase inactive mutant of hZIPK did not induce any phosphorylation of MRLC. Using antibodies specific for mono- or diphosphorylated MRLC, we showed that diphosphorylated MRLC induced by the overexpression of hZIPK was concentrated in striking aggregates or bundles of actin filaments in HeLa cells, while monophosphorylated MRLC showed no prominent localization to these aggregates. Overexpression of hZIPK also induced dramatic changes in cell shape and disruption of nuclear morphology reminiscent of changes during apoptosis. These effects of hZIPK were suppressed by the coexpression of a mutant MRLC where both phosphorylation sites were replaced with alanine, indicating that the changes in actin organization were a consequence of MRLC diphosphorylation. These results suggested that hZIPK plays a role in regulating actin organization and cell morphology in non-muscles and at least part of its effects are mediated through the diphosphorylation of MRLC.

Actin Cytoskeleton↗
PubMed2001

Dominant autoimmune epitopes recognized by pemphigus antibodies map to the N-terminal adhesive region of desmogleins.

Desmoglein (Dsg) is a cadherin-type adhesion molecule found in desmosomes. Dsg1 and Dsg3 are the target Ags in the autoimmune blistering diseases pemphigus foliaceus (PF) and pemphigus vulgaris (PV), respectively. To map conformational epitopes of Dsg1 and Dsg3 in PF and PV, we generated Dsg1- and Dsg3-domain-swapped molecules and point-mutated Dsg3 molecules with Dsg1-specific residues by baculovirus expression. The swapped domains were portions of the N-terminal extracellular domains of Dsg1 (1-496) and Dsg3 (1-566), which have similar structures but distinct epitopes. The binding of autoantibodies to the mutant molecules was assessed by competition ELISAs. Domain-swapped molecules containing the N-terminal 161 residues of Dsg1 and Dsg3 yielded >50% competition in 30/43 (69.8%) PF sera and 31/40 (77.5%) PV sera, respectively. Furthermore, removal of Abs against the 161 N-terminal residues of Dsg1 by immunoadsorption eliminated the ability of PF sera to induce cutaneous blisters in neonatal mice. Within these N-terminal regions, most of the epitopes were mapped to residues 26-87 of Dsg1 and 25-88 of Dsg3. Furthermore, a point-mutated Dsg3 molecule containing Dsg1-specific amino acid substitutions (His(25), Cys(28), Ala(29)) reacted with anti-Dsg1 IgG, thus defining one of the epitopes of Dsg1. Using the predicted three-dimensional structure of classic cadherins as a model, these findings suggest that the dominant autoimmune epitopes in both PF and PV are found in the N-terminal adhesive surfaces of Dsgs.

Autoantibodies↗
PubMed2001

NMDA and muscarinic blockade in the perirhinal cortex impairs object discrimination in rats.

To determine the possible involvement of NMDA and muscarinic activation of the perirhinal cortex in object discrimination, an NMDA antagonist, D,L-2-amino-5-phosphonopentanoic acid (AP5), and a muscarinic antagonist, scopolamine (SCP) were injected into the perirhinal cortex of rats. Each drug at the higher dose (AP5 60 mM, SCP 80 mM) significantly decreased correct choices on the retention test of object discrimination. SCP, but not AP5, also significantly increased response latency, but this increase was not necessarily related to the time spent for a choice. These results suggest that activation of both NMDA and muscarinic receptors contributes to object discrimination.

Acetylcholine↗
PubMed2001

Effect of the deletion of US2 and US3 from herpes simplex virus type 2 on immune responses in the murine vagina following intravaginal infection.

We investigated the effects of US2 and US3 deficiencies of herpes simplex virus type 2 (HSV-2) on host immunity in a murine model of genital herpes infection. Viral clearance from the vaginal mucosa was more rapid in mice infected with a US3-deficient mutant L1BR1 as compared with a wild-type 186 or YY2 (US2-deficient mutant) infection, although there was no significant difference among them in initial growth in the early stage of infection. Flow cytometric studies revealed that the number of vaginal mononuclear cells in L1BR1-infected mice was significantly greater than that in 186- or YY2-infected mice. Dendritic cells, macrophages and T cells were induced more rapidly and in greater numbers within the vaginas of L1BR1-infected mice. Moreover, the levels of IL-12 and IFN-gamma increased in L1BR1-infected mice over levels in 186-infected mice. These results indicate that a US3 deficiency alters the induction of the host immune response; therefore, the inactivation of US3 may be a promising strategy in the development of novel vaccines for genital herpes.

Administration, Intravaginal↗
PubMed2001

Low density lipoprotein receptor-related protein is required for macrophage-mediated oxidation of low density lipoprotein by 12/15-lipoxygenase.

The oxidative modification of low density lipoprotein (LDL) has been implicated in the early stage of atherosclerosis through multiple potential pathways, and 12/15-lipoxygenase is suggested to be involved in this oxidation process. We demonstrated previously that the 12/15-lipoxygenase overexpressed in mouse macrophage-like J774A.1 cells was required for the cell-mediated LDL oxidation. However, the mechanism of the oxidation of extracellular LDL by the intracellular 12/15-lipoxygenase has not yet been elucidated. In the present study, we found that not only the LDL receptor but also LDL receptor-related protein (LRP), both of which are cell surface native LDL-binding receptors, were down-regulated by the preincubation of the cells with cholesterol or LDL and up-regulated by lipoprotein-deficient serum. Moreover, 12/15-lipoxygenase-expressing cell-mediated LDL oxidation was decreased by the preincubation of the cells with LDL or cholesterol and increased by the preincubation with lipoprotein-deficient serum. Heparin-binding protein 44, an antagonist of the LDL receptor family, also suppressed the cell-mediated LDL oxidation in a dose-dependent manner. The cell-mediated LDL oxidation was dose-dependently blocked by an anti-LRP antibody but not by an anti-LDL receptor antibody. Furthermore, antisense oligodeoxyribonucleotides against LRP reduced the cell-mediated LDL oxidation under the conditions in which the expression of LRP was decreased. The results taken together indicate that LRP was involved essentially for the cell-mediated LDL oxidation by 12/15-lipoxygenase expressed in J774A.1 cells, suggesting an important pathophysiological role of this receptor-enzyme system as the initial trigger of the progression of atherosclerosis.

Animals↗
PubMed2001

Identification and characterization of RRM-containing coactivator activator (CoAA) as TRBP-interacting protein, and its splice variant as a coactivator modulator (CoAM).

We previously cloned and characterized thyroid hormone receptor-binding protein (TRBP) as an LXXLL-containing general coactivator that associates with coactivator complexes through its C terminus. To identify protein cofactors for TRBP action, a Sos-Ras yeast two-hybrid cDNA library was screened using TRBP C terminus as bait. A novel coactivator was isolated, coactivator activator (CoAA), that specifically associates with TRBP. Human CoAA is composed of 669 amino acids with a TRBP-interacting domain and two highly conserved RNA recognition motifs (RRM) commonly found in ribonucleoproteins. A splice variant lacking the entire TRBP-interacting domain was also isolated as a coactivator modulator (CoAM), a 156-amino acid protein containing only the RRM region. Human CoAA and CoAM mRNAs are encoded by a single gene located on chromosome 11q13; alternative splicing in exon 2 of CoAA yields CoAM. CoAA interacts with both TRBP and p300 in vitro. In addition, CoAA potently coactivates transcription mediated by multiple hormone-response elements and acts synergistically with TRBP and CREB-binding protein (CBP). Furthermore, CoAA is associated with the DNA-dependent protein kinase-poly(ADP-ribose) polymerase complex. Strikingly, CoAM, which lacks a TRBP-interacting domain, strongly represses both TRBP and CBP action suggesting that CoAM may modulate endogenous CoAA function. These data suggest that CoAA may serve as a mediator of coactivators such as TRBP in gene activation.

Alternative Splicing↗
PubMed2001

Inhibition of epidermal growth factor-induced RhoA translocation and invasion of human pancreatic cancer cells by 3-hydroxy-3-methylglutaryl-coenzyme a reductase inhibitors.

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors prevent the conversion of HMG-CoA to mevalonate and thereby inhibit the synthesis of other products derived from this metabolite. This includes a number of small prenylated GTPases involved in cell growth, motility, and invasion. We studied the effect of HMG-CoA reductase inhibitors (fluvastatin and lovastatin) on in vitro invasion of human pancreatic cancer PANC-1 cells. Epidermal growth factor (EGF) induced a dose-dependent increase of PANC-1 cell invasion in a modified Boyden chamber assay. Stimulation of cancer cells with EGF induced translocation of RhoA from the cytosol to the membrane fraction and actin stress fiber assembly. Furthermore, Clostridium botulinum C3 transferase, a specific inhibitor of Rho, inhibited the ability of EGF to promote invasion, indicating that EGF-induced cancer cell invasion is regulated by Rho signaling. Treatment of PANC-1 cells with fluvastatin markedly attenuated EGF-induced translocation of RhoA from the cytosol to the membrane fraction and actin stress fiber assembly, whereas it did not inhibit the tyrosine phosphorylation of EGF receptor and c-erbB-2. The induction of cancer cell invasion by EGF was inhibited by the addition of fluvastatin or lovastatin in a dose-dependent manner. The effects of fluvastatin or lovastatin on cell morphology and invasion were reversed by the addition of all-trans-geranylgeraniol but not by the addition of all-trans-farnesol. These results suggest that HMG-CoA reductase inhibitors affect RhoA activation by preventing geranylgeranylation, which results in inhibition of EGF-induced invasiveness of human pancreatic cancer cells.

ADP Ribose Transferases↗
PubMed2001

Correlation between p21(waf1) and p16(INK4a) expression in hepatocellular carcinoma.

Background: The cyclin dependent kinase p21(waf1) plays a crucial role in the regulation of cell cycle. The family of p53 proteins has the ability to induce p21(waf1), whereas p16(INK4a) modulates post-transcriptionally the expression of p21(waf1). Methods: Total 36 hepatocellular carcinomas (HCCs) and 24 paired adjacent liver tissues were evaluated for the following: (1) expression of p21(waf1) and p16(INK4a); (2) that of p21(waf1), p73 and p63 mRNAs; (3) genomic mutations and the loss of heterozygosity of p73 and p53; and (4) frequency of methylation in the 5'CpG promoter region of p16(INK4a). Results: In HCCs compared with the adjacent non-cancerous liver tissues, the expression of p21(waf1) and p16(INK4a) was reduced. Indeed, p21(waf1) was not detected in 36% (8/22) of HCCs in spite of the presence of p21(waf1) mRNA: among them, mutations of p53 gene were found in 50%, whereas a lack of p16(INK4a) expression in all of them. p21(waf1) and p16(INK4a) were reduced in proportion to the degree of methylation in p16(INK4a) gene. p73 did not mutated, and p63 did not expressed in HCCs. Conclusion: Methylation status of p16(INK4a) gene will play a part for reducing constitutive expression of p16(INK4a) and of p21(waf1) coordinately in HCCs.

Journal Article↗
PubMed2001

Comparison of neuropathogenicity of poliovirus type 3 in transgenic mice bearing the poliovirus receptor gene and cynomolgus monkeys.

To clarify the similarities of poliovirus infection in cynomolgus monkeys and transgenic mice bearing the poliovirus receptor, TgPVR21, we compared the pathological changes of these animals following intraspinal inoculation of two strains of poliovirus type 3 using immunohistochemical detection of the capsid antigen. All of the monkeys inoculated with 10(6) TCID(50) viruses showed flaccid paralysis 2 or 3 days post-inoculation (p.i.). TgPVR21 mice showed paralysis starting from 2 to 3 days p.i. Histologically, neurons having pyknotic nuclei and eosinophilic cytoplasm and neuronophagia were characteristically observed in both animals, but central chromatolysis was not observed in infected TgPVR21. The median lesion scores in the monkeys and TgPVR21 were well correlated, though the distribution of poliovirus-infected lesions in the central nervous system was different. In both animals the motor neurons and the brainstem nuclei responsible for flaccid paralysis were infected by the virus, while the cerebral cortex and thalamus were infected in the monkeys but not in TgPVR21. These results confirmed the reliability of neurovirulence tests using TgPVR21 as a substitute for monkeys, in respect to the spinal and brainstem lesions of poliovirus type 3.

Animals↗
PubMed2001

High-resolution soft X-ray absorption spectroscopy of solids.

The present research deals with the high-resolution soft x-ray absorption spectra (XAS) of Si, Ce- and Sm- compounds measured at BL25SU of SPring-8. The spectra are compared with theoretical results. The Si 1s spectrum shows good agreement with the calculated empty density of states so far reported. The Ce 3d spectra are very sensitive to the local electronic structure. The Sm 3d XAS of SmS shows clear temperature dependence, which is partly explained by a calculation for Sm2+ ion.

Journal Article↗