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Y Kawabe

Publications and source records attributed to Y Kawabe.

At least 55 records · Page 3Linked to original sources
PubMed1999

LbrA, a protein predicted to have a role in vesicle trafficking, is necessary for normal morphogenesis in Polysphondylium pallidum.

The fruiting body of Polysphondylium pallidum is composed of whorls of branches along the axis of a central stalk. In the course of fruiting body formation, the interval between neighboring whorls, and the number and the spacing of branches in a whorl are highly regulated. In this study, using the REMI (restriction-enzyme-mediated integration) insertional mutagenesis method, we obtained a mutant (strain M2323) with longer branches than those of the wild-type strain PN500. The sequence analyses revealed the presence of an ORF of 206 aa residues (23 kDa) near the vector insertion site. Disruption of the gene, lbrA (long branch A), by homologous recombination causes the same phenotype as that of M2323. A lbrA transcript is expressed maximally at the early aggregation stage in the parental strain, but is not detectable in the REMI mutant. A homology search showed that LbrA is a member of the p24 family proteins, which have been proposed to function as receptors for cargo proteins that are transported by COP I- (coat protein I) and/or COP II-coated vesicles between the endoplasmic reticulum and the Golgi complex. As far as we know, this is the first paper to show that a p24 family member is implicated in morphogenesis.

Amino Acid Sequence↗
PubMed1999

FK506 markedly enhances apoptosis of antigen-stimulated peripheral T cells by down-regulation of Bcl-xL.

BACKGROUND: FK506 is a clinically effective immunosuppressive agent and promoter of immunologic tolerance. However, limited information is available about the mechanism of FK506-induced immunosuppression. METHODS: In the present study, we investigated the molecular mechanism of FK506-mediated enhancement of apoptosis using in vivo activated T lymphocytes. We examined the effects of FK506 on apoptosis-related proteins in superantigen-stimulated peripheral T cells. RESULTS: Injection of staphylococcal enterotoxin B (SEB) into BALB/c mice resulted in a selective apoptosis of splenic Vbeta8-positive T cells after 48 hr. Injection of FK506 within 36 hr of SEB injection resulted in a marked enhancement of DNA fragmentation of splenic Vbeta8+ T cells. FK506 did not affect the expression of Fas antigen on SEB-activated Vbeta8+ T cells. As Bcl-2-related proteins are involved in apoptotic process, we also evaluated their role by examining the expression of Bcl-2, Bcl-X(L), and Bax on SEB-FK506-treated murine splenic T cells. Although SEB injection slightly increased the expressions of Bcl-2 and Bax on V138+ T cells, FK506 did not modulate Bcl-2 or Bax expression in these cells. In contrast, the expression of Bcl-x(L) on Vgamma8+ T cells, which was markedly induced by SEB, was abrogated by FK506. CONCLUSIONS: Our findings indicate FK506-induced enhancement of apoptosis of activated T cells is mediated by down-regulation of Bcl-X(L) expression on these cells. Our results also suggest that Bcl-x(L) is a critical determinant of apoptosis of activated T cell and may represent a potential target for new therapies designed to achieve immunological tolerance.

Animals↗
PubMed1999

Characterization of cleavage enzymes for sterol regulatory element binding protein in hamster liver microsomes.

Sterol regulatory element binding proteins (SREBP-1 and SREBP-2) are the key transcription factors for the regulation of the cellular cholesterol level. To identify proteolytic enzymes for SREBPs, a fluorogenic peptide substrate, MOCAc-GRSVLSFK(Dnp)rr-NH2, was synthesized according to the proposed cleavage site of human SREBP-2. In microsome fractions from hamster liver, we found a peptidase activity inhibitable by the synthetic inhibitor Ac-GRSVL-aldehyde with an IC50 of 40 nM. This peptidase separated into three peaks of approximately 400 kDa, 60 kDa, and 30 kDa (Mp400, Mp60 and Mp30 respectively) upon gel permeation chromatography. Mp30 was purified to apparent homogeneity with an Mr of 32 kDa. The partial amino acid sequence of Mp30 possessed homology to cathepsin B (EC 3.4.22.1). A 109 kDa protein band on SDS-PAGE which corresponded to Mp400 exhibited homology to neprilysin (EC 3.4.24.11) in partial amino acid sequence. These findings suggest several degradative pathways for SREBP in liver microsome membranes.

Amino Acid Sequence↗
PubMed1999

Detection by epitope-defined monoclonal antibodies of Werner DNA helicases in the nucleoplasm and their upregulation by cell transformation and immortalization.

We prepared several monoclonal antibodies (mAbs) specific for the NH2- and COOH-terminal regions of the DNA helicase (WRN helicase) responsible for Werner's syndrome known as a premature aging disease. With these antibodies, we detected by immunoblot analysis the endogenous WRN helicase of a relative mass of 180 kD in several lines of cultured cells, but not in patient cells with a defined mutation. Immunocytochemical staining of proliferating fibroblasts and tumor cells showed that the major part of WRN helicase is in the nucleoplasm and not in the nucleolus. Similar experiments with a rat mAb specific to the mouse homologue of human WRN helicase yielded an identical conclusion. Although this nucleoplasmic staining was evident in cells in interphase, the condensed chromatin structure in metaphase was not stained by the same mAbs, suggesting that WRN helicases exist perhaps in a soluble form or bound to the unfolded chromatin structure. From quantitative immunoblot analysis, higher levels of WRN helicase were observed in all transformed cells and tumor cells examined than those of normal cells. The expression of WRN helicase was enhanced consistently in fibroblasts and B-lymphoblastoid cells by transformation with SV-40 and Epstein-Barr virus, respectively, suggesting that rapidly proliferating cells require a high copy numbers of WRN helicase.

Animals↗
PubMed1999

The physiological role of sterol regulatory element-binding protein-2 in cultured human cells.

To clarify the role of the sterol regulatory element-binding protein-2 (SREBP-2), we established cell lines in which human SREBP-2(1-481) could be induced by isopropyl-beta-D-thiogalactopyranoside (IPTG). The range of IPTG-induced changes in SREBP-2(1-481) levels in '23-11' cells, one of these cell lines, was almost the same as that of sterol-induced changes in the levels of mature SREBP-2, indicating that IPTG was able to regulate the expression of SREBP-2(1-481) within the normal physiological range in this cell line. Sterols regulate the expression of the LDL receptor, HMG-CoA reductase, squalene synthase and fatty acid synthase in 23-11 cells as they also do in the parental cell line HeLa S3. IPTG increased mRNA levels of the LDL receptor and HMG-CoA reductase but not squalene synthase both in the presence or absence of excess sterols. Fatty acid synthase mRNA was increased 2 h after the IPTG addition in the absence of excess sterol (10% FBS), but was slightly increased 6 h after the IPTG addition in the presence of excess sterols. In the absence of excess sterols, both SREBP-2(1-481) and endogenous mature SREBP-2 exist in the nucleus. This suggests that an increased amount of SREBP-2 over the normal physiological range is required for the regulation of fatty acid synthase. IPTG increased both the surface binding of 125I-LDL and cholesterol biosynthesis from [14C]acetate significantly in a similar time course. In contrast, fatty acid biosynthesis from [14C]acetate was almost unchanged by IPTG during the same incubation period. These results suggest that physiological amounts of SREBP-2 play a key role in the regulation of cholesterol but not fatty acid metabolism.

Cell Line↗
PubMed1999

Route of TT virus infection in children.

TT virus (TTV) is a novel viral agent, detected recently in non-A to E hepatitis cases. Little is known about its natural history or routes of transmission in childhood. For the detection of serum TTV DNA, semi-nested polymerase chain reaction (PCR) was carried out using TTV-specific primers and TTV nucleotide sequences were determined by the dideoxy chain-mediated termination method. Five of the 70 children studied (including 20 hepatitis B virus [HBV] carriers, 40 children born to HBV carrier mothers and 10 children born to hepatitis C virus [HCV] carrier mothers) had serum TTV DNA. Three of the 5 children had siblings (4 in total), so that a total of 9 children were studied to determine the time of initial serum TTV DNA detection. In the 8 seropositive children, the time of serum TTV DNA detection ranged from 6 to 14 months after birth, and TTV DNA persisted thereafter throughout the follow-up period. The TTV DNA-negative child was assessed most recently at 6 months of age. TTV DNA was detected in only 2 of the 4 mothers tested (families 2 and 3). When 271-bp TTV DNA fragments from each of the 8 children were sequenced, the degree of homology between siblings in families 1-3 was 100%, 99.5%, and 92.3%, respectively. The degree of homology between child-mother pairs of families 2 and 3 was 99.5-100% and 62. 6-63.9%, respectively. The distribution of different TTV strains was consistent within families, except for family 3. None of the TTV-infected children had elevated levels of alanine aminotransferase or clinical signs of liver disease.

Adolescent↗
PubMed1999

Regulation of synovial cell apoptosis by proteasome inhibitor.

OBJECTIVE: Recent studies have shown the importance of proteasome function in the regulation of apoptosis. This study examined whether inhibition of proteasome function mediates apoptosis of synovial cells, and whether cytokines modulate this process. METHODS: Type B synovial cells (fibroblast-like synovial cells) were cultured with tumor necrosis factor alpha (TNF alpha) or transforming growth factor beta1 (TGFbeta1), and further incubated in the presence of variable concentrations of Z-Leu-Leu-Leu-aldehyde (LLL-CHO), a proteasome inhibitor. During this process, apoptosis of synovial cells was determined by Hoechst 33258 dye staining and 51Cr release assay. The involvement of caspase cascade was examined using enzyme activity assay and blocking experiments by peptide inhibitors. The expression of pro-caspases, Bcl-2-related proteins, and X chromosome-linked inhibitor of apoptosis (XIAP) in synovial cells was examined by Western blot analysis. RESULTS: Apoptosis of cultured synovial cells was induced in a dose-dependent manner by LLL-CHO. Activation of caspase cascade through caspase-8 to caspase-3 was essential during this process. Pretreatment of synovial cells with TNF alpha significantly augmented both the activation of caspases and the proportion of apoptosis in synovial cells induced by LLL-CHO, whereas TGFbeta1 pretreatment markedly suppressed these phenomena. The ratio of the expression of Bcl-2 to Bax or Bcl-xL to Bax, and XIAP expression in synovial cells may not be directly associated with the susceptibility of synovial cells to apoptosis by LLL-CHO. CONCLUSION: Apoptosis of synovial cells was induced by inhibition of proteasome function through the activation of caspase cascade, and this process was clearly modulated by cytokines. These data provide new insight into the regulatory mechanisms controlling synovial cells in rheumatoid synovitis by proteasome inhibitors, and might be useful for the design of new therapeutic strategies in rheumatoid arthritis.

Apoptosis↗
PubMed1999

Successful treatment of rapidly progressive lupus nephritis associated with anti-MPO antibodies by intravenous immunoglobulins.

We report a case of systemic lupus erythematosus (SLE) associated with crescentic glomerulonephritis and myeloperoxidase-specific anti-neutrophil cytoplasmic antibodies (MPO-ANCA). A 34-year-old Japanese female patient diagnosed with SLE developed rapidly progressive renal failure and nephrotic syndrome. Haemodialysis was required to restore renal function. Methylprednisolone pulse therapy followed by plasmapheresis did not suppress the progression of renal failure, so she was treated with high-dose intravenous immunoglobulin (IV-IG) therapy, which was well tolerated and effectively prevented renal failure. A renal biopsy showed diffuse proliferative lupus nephritis (WHO classification IVc) with predominant crescent formation and scant subendothelial immune deposits. These findings indicate that, in addition to lupus nephritis, which usually results from the deposition of circulating or locally formed immune complexes, MPO-ANCA may be involved in the pathogenesis of crescentic glomerulonephritis. Furthermore, we propose that IV-IG is an effective therapy for MPO-ANCA-related renal crisis in lupus nephritis.

Acute Kidney Injury↗
PubMed1999

Inhibitory effect of a new anti-rheumatic drug T-614 on costimulatory molecule expression, cytokine production, and antigen presentation by synovial cells.

The present study was undertaken to investigate the immunoregulatory effects of T-614 (3-formylamino-7-methylsulfonylamino-6-phenoxy-4H-1-benzopyran-4-o ne) on synovial cells in vitro. Synovial cells were cultured with T-614 in the presence or absence of various cytokines. After incubation, the costimulatory molecule expression on synovial cells and cytokine production in culture supernatants were analyzed by an indirect immunofluorescence method and enzyme-linked immunosorbent assay, respectively. We also examined the effect of T-614 on the function of synovial cells as antigen-presenting cells (APCs). The costimulatory molecules including CD54, CD58, and CD106 were constitutionally expressed on the surface of synovial cells. However, neither CD80 nor CD86 nor CD102 was found on the surface, and these costimulatory molecules could not be induced by any cytokines. T-614 itself did not affect the costimulatory molecule expression and cytokine production of unstimulated synovial cells. The stimulation of synovial cells with interferon-gamma (IFN-gamma), interleukin-1beta, or 12-O-tetradecanoyl phorbol 13-acetate enhanced the expression of costimulatory molecules and the proinflammatory cytokine production of these cells. Both the up-regulated expression of these costimulatory molecules and the enhanced production of proinflammatory cytokines were significantly inhibited by T-614. Autologous T cell proliferation in response to purified protein derivative by IFN-gamma-treated synovial cells was significantly suppressed by T-614. T-614 has considerable immunosuppressive effects on synovial cells by inhibiting the costimulatory molecule expression and cytokine production of these cells and the antigen-specific T cell proliferation mediated by the synovial cells. These results suggest that T-614 plays an important immunoregulatory role in rheumatoid synovial tissues.

Adjuvants, Immunologic↗
PubMed1999

Tumor necrosis factor-alpha and interleukin-1beta increase the Fas-mediated apoptosis of human osteoblasts.

Our recent work demonstrated functional Fas expression on human osteoblasts, and the histologic examination of the periarticular osteoporosis region in patients with rheumatoid arthritis (RA) showed apoptosis in osteoblasts. High concentrations of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6--which are thought to increase bone resorption--have been determined in RA synovium. We investigated the effect of these cytokines on the Fas-mediated apoptosis of human osteoblasts. The human osteoblastic cell line MG63 and human primary osteoblast-like cells from bone biopsy specimens were used as human osteoblasts. Fas expression on these cells was examined by flow cytometry, and Fas-mediated apoptosis induced by anti-Fas immunoglobulin M (IgM) was determined by a chromium 51 release assay, the presence of cells with hypodiploid DNA, staining with Hoechst 33258 dye, and the detection of DNA fragmentation on agarose gel electrophoresis. The proliferation of osteoblasts was analyzed by a tritiated thymidine incorporation assay. Spontaneous apoptosis was not found on cultured osteoblasts. The apoptosis of human osteoblasts was not induced by TNF-alpha, IL-1beta, or IL-6 alone in the absence of anti-Fas IgM. In addition, proliferation of the cells was not affected by these cytokines. Fas was constitutively expressed on unstimulated osteoblasts, and treatment of these cells with IL-1beta or TNF-alpha significantly augmented Fas expression. Human osteoblasts were committed to apoptosis with anti-Fas IgM, and the treatment of both IL-1beta and TNF-alpha markedly increased Fas-mediated apoptosis. TNF-alpha augmented both Fas expression and Fas-mediated apoptosis more efficiently than did IL-1beta. In addition, an additive effect on both Fas expression and Fas-mediated apoptosis was demonstrated when TNF-alpha and IL-1beta were added to osteoblasts. IL-6 influenced neither Fas expression nor the Fas-mediated apoptosis of osteoblasts. Furthermore, no synergistic effect of IL-6 with IL-1beta or TNF-alpha was observed. IL-1beta, TNF-alpha, or IL-6 did not change Bcl-2 expression. Our results suggest that IL-1beta and TNF-alpha regulate osteoblast cell number by up-regulating the Fas-mediated apoptosis of osteoblasts, one of the putative mechanisms inducing periarticular osteoporosis in patients with RA.

Apoptosis↗
PubMed1999

Enhancement of the specific growth rate of Thiobacillus ferrooxidans by diatomaceous earth.

Diatomaceous earth is an effective carrier with a large surface area on which Thiobacillus ferrooxidans adsorbs, and enhances the oxidation rate of ferrous ions by the bacterium. The adsorption of T. ferrooxidans on diatomaceous earth was expressed by the Henry isotherm, and reached equilibrium within five minutes. The enhancement was due to an increase in the growth rate of the adsorbed cells, which were so active that their specific growth rate calculated using a Monod-type equation was higher than that of the free cells in the liquid phase.

Journal Article↗
PubMed1999

Induction of cyclooxygenase-2 in human synovial cells by beta 2-microglobulin.

BACKGROUND: Prostaglandins (PGs) are important mediators of inflammation in arthritis. We evaluated the role of the cycloxygenase-2 (COX-2) enzyme, which regulates PG biosynthesis, in osteoarthropathy associated with hemodialysis-associated amyloidosis (HAA) by characterizing COX-2 expression in beta 2-microglobulin-treated human synovial cells. METHODS: We examined the effects of beta 2-microglobulin (beta 2m), a major constituent protein of amyloid fibrils in HAA, on the COX-2 protein and mRNA expression in human synovial cells using Western blot and reverse transcriptase-polymerase chain reaction. RESULTS: beta 2m selectively increased the biosynthesis of COX-2 protein and induction of COX-2 mRNA in a dose-dependent manner. Immunoabsorption of beta 2m-containing media by anti-beta 2m-specific antibody abrogated beta 2m-mediated COX-2 expression on synovial cells. On the other hand, dexamethasone markedly suppressed the induction of COX-2 protein and mRNA in beta 2m-stimulated synovial cells. CONCLUSIONS: Our results suggest that induction of COX-2 expression by beta 2m may be an important component of the inflammatory process in hemodialysis-associated osteoarthropathy.

Blotting, Western↗
PubMed1999

Lung cancer in patients who had received thoracoplasty for pulmonary tuberculosis.

BACKGROUND: In Japan in the 1950s, thoracoplasty was a powerful therapy for pulmonary tuberculosis. Now there are many aged people who have tuberculosis sequelae caused by thoracoplasty. We have encountered some cases of lung cancer among these people. METHODS: To elucidate the features of lung cancer occurring after thoracoplasty for pulmonary tuberculosis, we reviewed for analysis 20 such cases. RESULTS: There were 17 men and three women, aged 55 to 78 years (mean 65 years). All had respiratory dysfunction and most were cigarette smokers. Lung cancers were located in the upper lobes in nine cases, in the middle lobe in one and in the lower lobes in 10. Ten lung cancers were in the thoracoplastied lung and the remaining 10 in the opposite lung. Histologically, squamous cell carcinoma was predominant (11 cases). Eight lung cancers were detected in stages I and II and 12 in stages III and IV. Most cancer lesions were separate from tuberculosis lesions. Surgical resection was selected in only three of 11 stages I-IIIA cases in consideration of respiratory dysfunction and/or ventilatory impairment due to thoracoplasty. Chemotherapy and/or radiotherapy were performed in nine and supportive care alone was performed in eight. Fourteen patients died of lung cancer and four died of cor pulmonale due to tuberculosis sequelae. Five-year survival was achieved in only one surgical case. Eight of the nine patients who received chemotherapy or radiotherapy died within 1 year, and, further, seven of eight patients who received supportive care died within 6 months. CONCLUSION: Lung cancer in the patients who had received thoracoplasty occurred in each lung and every lobe, independent of thoracoplasty. In addition, delay of detection was such that stage III-IV cases were in the majority, there were some limitations in therapeutic benefits related to thoracoplasty and the prognosis was very poor. Physicians should avoid delay in the detection of lung cancer through careful follow-up of such patients.

Aged↗
PubMed1999

Age at time of hepatitis Be antibody seroconversion in childhood chronic hepatitis B infection and mutant viral strain detection rates.

BACKGROUND: Investigations of adult patients have demonstrated that with seroconversion, changes occur from wild-type strains of the infecting virus to mutant strains. However, to date, there have been few reports and insufficient investigation of this issue in children. METHODS: The presence or absence of nucleotide base and amino acid sequence mutations in a portion of the X region containing the core promoter region, the pre-C region, and the C region of HBV genomic DNA were investigated using a polymerase chain reaction-direct sequencing method on serum samples collected from 14 children who were hepatitis Be antibody (HBeAb)-positive carriers. Samples from three children who were HBe antigen (HBeAg)-positive carriers served as the control subjects. RESULTS: When patients were grouped based on whether they had had documented seroconversion before age 6 or at age 6 or older, differences in mutant viral detection rates involving the core promoter region and the pre-C region were apparent. Specifically, a mutant strain showing a G-to-A substitution at nucleotide 83 in the pre-C region, or a mutant strain showing an A-to-T substitution at nucleotide 1762 and a G-to-A substitution at nucleotide 1764, was detected in only two of eight cases (25%) from the HBeAb-positive carriers with documented seroconversion before age 6. In contrast, these findings were present in six of six patients (100%) with documented seroconversion at age 6 or older. CONCLUSIONS: The results of the present study suggest that the mechanism of onset of HBeAb seroconversion differs between children aged less than 6 years and those who are aged 6 or more.

Adolescent↗
PubMed1999

HTLV-I associated Sjögren's syndrome is aetiologically distinct from anti-centromere antibodies positive Sjögren's syndrome.

OBJECTIVE: To investigate whether Sjögren's syndrome (SS) with anti-HTLV-I antibodies is aetiopathologically distinguishable from SS without these antibodies, the study compared prevalence of autoantibodies in serum samples of SS patients with or without anti-HTLV-I antibodies. METHODS: The test group included 135 patients with primary SS and 97 patients with secondary SS. Serum samples of the patients were examined for the presence of anti-nuclear antibodies (ANA), anti-SS-A/Ro antibodies, anti-SS-B/La antibodies, anti-centromere antibodies (ACA), and anti-HTLV-I antibodies. RESULTS: Anti-HTLV-I antibodies were detected in 25.0% of primary SS patients and in 29.2% of secondary SS patients. There were no significant differences in the mean age, sex, values of asparate aminotransferase, alanine aminotransferase, alkaline phosphatase, serum complements and IgG between HTLV-I seropositive and seronegative SS patients. The rheumatoid factor, ANA, anti-SS-A/Ro, and anti-SS-B/La antibodies in serum samples of SS patients were detected in 60.0%, 84.0%, 51.9%, and 12.0%, respectively. There was no significant difference in the prevalence of these antibodies between HTLV-I seropositive and seronegative SS patients. Using the indirect immunofluorescence test, 14.2% showed a discrete speckled staining pattern. All serum samples contained significant amounts of ACA determined by enzyme linked immunosorbent assay. These antibodies were detected in only 4% of HTLV-I seropositive SS patients but were present in 19.9% of HTLV-I seronegative SS patients. Furthermore, the prevalences of anti-SS-A/Ro and anti-SS-B/La antibodies in serum samples of ACA positive patients were significantly lower than those in ACA negative SS patients. CONCLUSION: These results suggest that SS patients with anti-SS-A/Ro or anti-SS-B/La antibodies, or both, might be aetiopathologically distinct from SS patients with ACA. HTLV-I might be involved in the pathogenesis of SS in a subset of patients with anti-SS-A/Ro or anti-SS-B/La antibodies, or both, but not SS patients with ACA.

Aged↗