Biomedical subjects
T Azuma
Publications and source records attributed to T Azuma.
Cofilin and gelsolin segment-1: molecular dynamics simulation and biochemical analysis predict a similar actin binding mode.
An understanding of the actin-depolymerizing function attributed to members of the ADF/cofilin/destrin superfamily requires a structural model of these proteins in complex with actin. As a step toward defining actin-cofilin interactions, the complex of yeast cofilin with monomeric actin was predicted, starting with the actin-gelsolin segment-1 binding mode recently suggested for the actin-destrin complex. After refinement by molecular dynamics simulation, the structure of cofilin converged in a new binding mode that required only minimal changes induced in the actin-cofilin interface. The predicted complex exhibits strong interactions between the N termini of actin and cofilin, mediated by a salt bridge of cofilin Arg3 with actin Asp1. The forming of this salt bridge could be prevented by the phosphorylation of cofilin Ser4, which is believed to inhibit cofilin depolymerization activity. Recent mutagenesis studies, crosslinking experiments and peptide binding studies are consistent with the predicted model of the actin-cofilin complex. The structural homology between cofilin and gelsolin segment-1 binding to actin was confirmed experimentally by two types of competitive binding assays.
Clinical and molecular genetic study in seven Japanese families with spinocerebellar ataxia type 6.
We report on seven Japanese families with spinocerebellar ataxia type 6 (SCA6) carrying small CAG repeat expansions in the calcium channel alpha1A subunit gene. The number of the expanded CAG repeat, ranged from 22 to 25, showed no intergenerational instability and had a significant inverse correlation with the age of onset. The clinical features of these patients were late onset progressive pure cerebellar ataxia with dysarthria and nystagmus, and are consistent with autosomal dominant cerebellar ataxia type III (ADCA type III). Magnetic resonance imaging scan of the brain demonstrated cerebellar atrophy with no evidence of brainstem involvement. We propose that clinical phenotype of SCA6 is compatible with ADCA type III and SCA6 is one of the most common types of ADCA in Japan.
The role of the HLA-DQA1 gene in resistance to atrophic gastritis and gastric adenocarcinoma induced by Helicobacter pylori infection.
BACKGROUND: It has been suggested that immunogenetic factors for susceptibility or resistance to disease caused by Helicobacter pylori exist in the host. To examine host genetic factors that increase the risk of gastric adenocarcinoma among H. pylori-infected persons, the HLA-DQA1 locus was examined in patients with gastric adenocarcinoma. METHODS: Eighty-two gastric adenocarcinoma patients and 167 unrelated controls were examined for H. pylori infection and HLA-DQA1 genotyping. In addition, serum pepsinogen A (PGA) and pepsinogen C (PGC) values and the PGA/PGC ratio, which have been characterized as markers of gastric mucosal atrophy, also were analyzed. RESULTS: Of the 167 controls, 121 were H. pylori positive (+) and 46 were H. pylori negative (-). All H. pylori (-) individuals had normal endoscopic and histologic findings. Among the 121 H. pylori (+) controls, 36 had superficial gastritis and 85 had atrophic gastritis. The allele frequency of DQA1*0102 was significantly lower in the H. pylori (+) atrophic gastritis group than in the H. pylori (+) superficial gastritis and H. pylori (-) normal control groups. In addition, the allele frequency of DQA1*0102 also was significantly lower in the H. pylori (+) intestinal type gastric adenocarcinoma group than in the H. pylori (-) normal control, H. pylori (+) superficial gastritis, and H. pylori (-) diffuse type gastric adenocarcinoma groups. Serum PGA and PGC values and the PGA/PGC ratio did not differ significantly among HLA-DQA1 genotypes; however, the PGA/PGC ratio was significantly lower in the H. pylori (+) atrophic gastritis and H. pylori (+) intestinal type gastric adenocarcinoma groups than in the H. pylori (-) normal control and H. pylori (+) superficial gastritis groups. CONCLUSIONS: The DQA1*0102 allele may contribute to resistance against H. pylori-associated gastric atrophy and its association with intestinal type gastric adenocarcinoma, whereas the absence of DQA1*0102 may be a host genetic risk factor for H. pylori-associated atrophic gastritis and intestinal type gastric adenocarcinoma.
Gelsolin is a downstream effector of rac for fibroblast motility.
Rac, a member of the rho family of GTPases, when activated transmits signals leading to actin-based membrane ruffling in fibroblasts. Compared with wild-type fibroblasts, gelsolin null (Gsn-) dermal fibroblasts have a markedly reduced ruffling response to serum or EGF stimulation, which signal through rac. Bradykinin-induced filopodial formation, attributable to activation of cdc42, is similar in both cell types. Wild-type fibroblasts exhibit typical lamellipodial extension during translational locomotion, whereas Gsn- cells move 50% slower using structures resembling filopodia. Multiple Gsn- tissues as well as Gsn- fibroblasts overexpress rac, but not cdc42 or rho, 5-fold. Re-expression of gelsolin in Gsn- fibroblasts by stable transfection or adenovirus reverts the ruffling response, translational motility and rac expression to normal. Rac migrates to the cell membrane following EGF stimulation in both cell types. Gelsolin is an essential effector of rac-mediated actin dynamics, acting downstream of rac recruitment to the membrane.
Cross-linking CD21/CD35 or CD19 increases both B7-1 and B7-2 expression on murine splenic B cells.
Activation of the complement cascade and ligation of complement C3 receptors on B cells represent an important bridge between innate and Ag-specific acquired immunity. We show here that cross-linking of mouse CD21 (complement receptor type 2, CR2, C3d receptor) and CD35 (complement receptor type 1, CR1, C3b/C4b receptor) or co-cross-linking of CD21/CD35 and surface IgM rapidly up-regulates both B7-1 and B7-2 expression on murine resting splenic B cells. CD21/CD35-mediated up-regulation of both B7-1 and B7-2 expression is observed within 14 h, while other stimuli up-regulate only B7-2 but not B7-1 at this early time point. Consistent with the increase in B7 levels, BALB/c B cells on which surface IgM and CD21/CD35 have been co-cross-linked stimulate C57BL/6 T cells more effectively than controls. This CD21/CD35-enhanced allogeneic MLR is blocked nearly completely by anti-B7-2 mAbs and partially by anti-B7-1 mAbs. In addition, cross-linking of CD19, which is physically associated with CD21/CD35, leads to increased B7-1 and B7-2 expression. These data suggest that CD21/CD35 ligation results in enhanced B cell Ag presentation using costimulatory mechanisms shared with other activators and thus works cooperatively in this process. Rapid up-regulation of B7-1 expression, a unique response to CD21/CD35 and CD19 cross-linking, may be a particularly important effect of C3-containing ligands. We propose that CD21/CD35- and CD19-mediated B7-1 and B7-2 up-regulation is an important mechanism by which complement activation links innate and acquired immunity.
Differential properties of D4/LyGDI versus RhoGDI: phosphorylation and rho GTPase selectivity.
RhoA/B/C and CDC42/Rac, which form two subgroups of the rho guanosine triphosphatase (GTPase) family, regulate various aspects of actin cytoskeleton organisation. In cytosol, guanosine diphosphate (GDP) dissociation inhibitor (GDI) interacts with and maintains rho GTPases in their inactive GDP-bound form. RhoGDI is a ubiquitously expressed GDI, whereas D4/LyGDI is hematopoietic cell-specific and 10-fold less potent than RhoGDI in binding to and regulating rho GTPases. We have combined microanalytical liquid chromatography with the use of specific antibodies in order to separate D4/LyGDI and RhoDGI-complexes from the cytosol of U937 cells and to demonstrate that the two GDIs associate with different rho protein partners. RhoGDI can form a complex with CDC42Hs, RhoA, Rac1 and Rac2, while none of these GTPases was found to interact with D4/LyGDI. In addition, we found that stimulation of U937 cells with phorbol ester leads to phosphorylation of D4/LyGDI. Our results suggest that LyGDI forms complexes with specific rho GTPases expressed in hematopoietic cells where it may regulate specific pathways.
Myelodysplastic syndrome with translocation (8;21): a distinct myelodysplastic syndrome entity or M2-acute myeloid leukemia with extensive myeloid maturation?
We report a case of refractory anemia with excess of blasts in transformation with the translocation (8;21), which is frequent in acute myeloid leukemia (AML) but not in myelodysplastic syndromes (MDS). Bone marrow blasts were 1.6% and an extensive myeloid differentiation was noted. Fluorescence in situ hybridization analysis revealed the presence of 21q22 translocations in mature neutrophils, indicating that clonogenic blast progenitors could actively undergo terminal differentiation to mature end cells in vivo. We consider that t(8;21)+ MDS may represent a rare clinical manifestation of M2-AML, in which blast progenitors have an extensive differentiation potential to mature neutrophils without maturation arrests.
Systematic laparoscopic left lateral segmentectomy of the liver for hepatocellular carcinoma.
A systematic technique for the resection of hepatocellular carcinoma (HCC) prevents the dissemination of cancer cells through the portal vein of the remnant liver. We successfully performed a systematic laparoscopic left lateral segmentectomy in a 62-year-old man with HCC. The tumor was located in the left lateral segment of the liver, and measured approximately 4 cm in diameter. Since no other tumors were detected in the liver or in any distant organs, the patient was considered to be a candidate for surgery. A laparoscopic hepatic resection was selected as the procedure of choice. Prior to dissection of the liver parenchyma, the arteries and branches of the portal vein feeding the left lateral segment were divided and dissected, together with the branches of the biliary tree in the umbilical portion of the left pedicle of Glisson's capsule. The liver parenchyma was then dissected and the left hepatic vein divided and dissected, and transection of the left lateral segment was completed. The patient's postoperative course was uneventful and he was discharged on postoperative days 14. No evidence of recurrence has been noted in the 22 months after surgery (the time of this report). This less invasive surgery, taking into consideration the pathogenesis of HCC, may be a useful new approach in selected patients with this tumor.
Presence of CD4 suppressor T cells in rat liver transplantation.
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Potential candidates for small bowel transplantation: from our experience and survey of home parenteral nutrition in Japan.
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Nutritional effects of alanyl-glutamine after liver transplantation in pigs.
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Differences in cellular mechanisms between heart and skin graft rejection by in vitro and in vivo analyses.
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Caspase-3-induced gelsolin fragmentation contributes to actin cytoskeletal collapse, nucleolysis, and apoptosis of vascular smooth muscle cells exposed to proinflammatory cytokines.
Gelsolin, an 80 kDa actin-severing protein, has been recently identified as a substrate for the cell death-promoting cysteinyl protease caspase-3 (CPP32/apopain/YAMA). We investigated the role of gelsolin and its cleavage product in apoptosis of vascular smooth muscle cells (SMC) induced by the proinflammatory cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). Treatment with a combination of IFN-gamma and TNF-alpha reduced viability of SMC in a time- and concentration-dependent manner. Immunoblotting revealed that SMC treated with the cytokines generated a 41 kDa gelsolin fragment. The gelsolin fragmentation required activation of caspase-3, as the caspase-3 inhibitor diminished cytokine-induced cell death as well as the fragmentation. Gelsolin cleavage was accompanied by a reduction in F-actin content and by a marked disruption of cell structure. Adenovirus-mediated transfection of this N-terminal gelsolin fragment into SMC altered cell morphology, reduced cell viability, increased the number of TUNEL-positive cells, and promoted internucleosomal DNA fragmentation. Compared to wild-type cells, gelsolin-deficient SMC showed resistance to apoptosis induced by the inflammatory cytokines. These results suggest a mechanistic role for gelsolin cleavage during SMC apoptosis, a process implicated in vessel development as well as stability of atherosclerotic plaque.
Graft rejection and recovery of host-derived hematopoiesis after allogeneic bone marrow transplantation: relation to conditioning with high dose etoposide and total body irradiation.
Engraftment failure following allogeneic bone marrow transplantation (BMT) is rare in patients with acute leukemia, after frequent conditioning with marrow-lethal chemoradiotherapy. We evaluated the efficacy of a preparatory regimen consisting of fractionated total body irradiation (TBI) (12 Gy in six fractions) and high dose etoposide (60 mg/kg) administered as an 8-h infusion for allogeneic BMT in 16 consecutive patients with acute leukemia. Although 14 patients showed complete and sustained engraftment, the remaining two patients rejected bone marrow grafts from HLA-identical sibling donors and showed subsequent recovery of host-derived hematopoiesis. Despite the limited number of patients, this observation suggests that the immunosuppressive potential of etoposide may be inferior to that of cyclophosphamide (CY) and that etoposide as an alternative to CY as an antileukemic and immunosuppressive agent in allogeneic BMT may increase the risk of graft rejection.
Deleted HTLV provirus in peripheral blood cells of a patient with T-cell prolymphocytic leukaemia.
We describe the first case of T-cell prolymphocytic leukaemia (T-PLL) in which the peripheral blood cells contained a human T-lymphotropic virus (HTLV) related tax sequence. Serum screening tests for anti-HTLV-I/II antibodies were negative. Polymerase chain reaction disclosed the presence of an HTLV-I tax sequence in the peripheral blood. Other sets of oligonucleotide primers for HTLV-I gag, pol, env and the long terminal repeat regions and for the HTLV-II pol region were negative in the DNA of the cells. Although patients with T-PLL have been reported to be seronegative for HTLV-I, our findings point to the possibility that HTLV-I infection might be involved in the aetiology of at least some cases of T-PLL and that there may be alternative mechanisms involved in HTLV-associated leukaemogenesis.
Full-length sequence analysis of the vacA gene from cytotoxic and noncytotoxic Helicobacter pylori.
Some clinical isolates of Helicobacter pylori fail to express vacuolating cytotoxin, despite possessing a copy of the vacA gene on the chromosome. To gain insight into the differences between vacA from cytotoxic and noncytotoxic strains, the vacA open-reading frames from 16 cytotoxic and 22 noncytotoxic strains were sequenced. Mutations that cause truncation of VacA in 11 of 22 noncytotoxic strains were identified, including internal duplication, large deletion, 1-bp insertion, and non-sense mutations. In contrast, none of the 16 cytotoxic strains had any truncation of VacA. Four cytotoxic strains had inserted sequences downstream of vacA. Three were mini-IS605, and the other was a putative rfaJ gene that encodes lipopolysaccharide glucosyltransferase. The rfaJ gene identified in this study had a poly(C) tract, resulting in premature termination of the gene product. The phylogenetic tree based on the vacA open-reading frame indicated that two different H. pylori lineages are circulating in Japan and the West.
Regulation of promoter and intron enhancer activity in immunoglobulin heavy-chain genes during B-cell differentiation.
Chloramphenicol acetyltransferase (CAT) transgenic mice, in which the transgene is regulated by the VH promoter and heavy-chain intron enhancer (E mu), were examined to investigate the variation of activity of these cis-acting elements during the late stage of B-cell development. CAT enzyme activity decreased when resting B cells were stimulated through B-cell receptors (BCR) with goat anti-mouse IgM antibodies in vitro. On the other hand, when these B cells were stimulated by lipopolysaccharide (LPS) in vitro, they showed enhanced CAT activity, accompanied by an increase in the number of CD43+ B220+ cells (pro-plasma and plasma cells). In addition, the CAT activities in CD43+ B220+ and PNAhi B220+ cells from immunized mice were higher than those in CD43- B220+ and PNAlo B220+ cells, respectively. These results suggest that the activity of E mu in the context of VH promoter was transiently down-regulated by stimulation through the BCR but enhanced at the pro-plasma and plasma stages.