Biomedical subjects

S Kubota

Publications and source records attributed to S Kubota.

At least 37 records · Page 2Linked to original sources

PubMed2001

Observation of compressional Alfvén modes during neutral-beam heating on the national spherical torus experiment.

Neutral-beam-driven compressional Alfvén eigenmodes at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment. The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2omega(ci) to approximately 1.2omega(ci). The frequency has a scaling with toroidal field and plasma density consistent with Alfvén waves. The modes have been observed with high bandwidth magnetic pickup coils and with a reflectometer.

Journal Article↗

PubMed2001

Protective effect of tamoxifen on 1-methyl-4-phenylpyridine-induced hydroxyl radical generation in the rat striatum.

We examined whether tamoxifen could suppress 1-methyl-4-phenylpyridine (MPP(+))-induced hydroxyl radical generation in the extracellular fluid of rat striatum, using in vivo microdialysis system. MPP(+) (5 mM) enhanced generation of hydroxyl radicals with concomitant increased efflux of dopamine. Tamoxifen (1--100 microM) dose-dependently suppressed the hydroxyl radical formation induced by MPP(+). Tamoxifen (100 microM) significantly attenuated dopamine efflux induced by MPP(+). The result in the present study is the first demonstration showing the protective effect of tamoxifen on hydroxyl radical generation induced by MPP(+) by suppressing dopamine efflux.

1-Methyl-4-phenylpyridinium↗

PubMed2001

Allopurinol suppresses para-nonylphenol and 1-methyl-4-phenylpyridinium ion (MPP(+))-induced hydroxyl radical generation in rat striatum.

We recently demonstrated that para-nonylphenol, an environmental estrogen-like chemical, enhances hydroxyl radical (*OH) generation in the rat striatum. In the present study we have examined whether para-nonylphenol enhanced 1-methyl-4-phenylpyridinium ion (MPP(+))-induced *OH generation in the rat striatum using a microdialysis technique. Para-nonylphenol significantly enhanced MPP(+)-induced *OH generation. Further, we studied the effect of allopurinol, a xanthine oxidase inhibitor, on para-nonylphenol and MPP(+)-induced *OH generation. Allopurinol significantly suppressed para-nonylphenol and MPP(+)-induced *OH generation. The results indicate that para-nonylphenol enhanced *OH generation based on superoxide anion production, and allopurinol may have preventive effect on para-nonylphenol and MPP(+)-induced *OH generation.

1-Methyl-4-phenylpyridinium↗

PubMed2001

Calreticulin is directly involved in anti-alpha3 integrin antibody-mediated secretion and activation of matrix metalloprotease-2.

Matrix metalloprotease-2 (MMP-2) plays a pivotal role in cancer invasion and metastasis. Invasive human rhabdomyosarcoma cells (RD) secrete proMMP-2. We recently reported that anti-alpha3 integrin antibody induced the activated form of MMP-2 and enhanced proMMP-2 secretion by RD cells with concomitant enhancement of RD cell invasion. Since recent studies showed that calreticulin interacts with integrin alpha subunit, we hypothesized that calreticulin may be involved in signal transduction of anti-alpha3 integrin antibody-mediated MMP-2 secretion and activation. Here we demonstrate that anti-alpha3 integrin antibody induced a transient enhanced interaction of calreticulin with alpha3 integrin. Transfection of antisense oligonucleotides of calreticulin in RD cells abrogated the interaction between calreticulin and alpha3 integrin, and completely suppressed activation of MMP-2 and enhanced secretion of proMMP-2 induced by anti-alpha3 integrin antibody. Transient overexpression of calreticulin cDNA in RD cells significantly increased secretion of proMMP-2. The results demonstrate for the first time that calreticulin is directly involved in MMP-2 secretion and activation.

Antibodies↗

PubMed2001

p53 independent G(1) arrest induced by DL-alpha-difluoromethylornithine.

Ornithine decarboxylase (ODC), which catalyzes polyamine biosynthesis, plays an essential role in cell growth. DL-alpha-Difluoromethylornithine (DFMO), a synthetic inhibitor of ODC, inhibits cell growth. However, the exact mechanism by which polyamine depletion by DFMO results in growth inhibition remains to be elucidated. We clarified the mechanisms by which DFMO inhibits human gastric cancer cell (MKN45) growth. DFMO induced MKN45 cell G(1) phase arrest after 48 h, and the percentage of G(1) arrest cells continued to increase until 72 h. Expression of p21 and phosphorylation of Stat1 were significantly induced by DFMO at 24 h. Luciferase assay and gel shift assay showed specific binding of Stat1 to the p21 promoter, and promoter activity was activated at 24 h. In dominant negative p53 expressing cells, DFMO significantly induced p21 expression, arrested cells at G(1) phase, and suppressed cell growth effectively. These results suggest that DFMO induced MKN45 cell arrest at G(1) phase in a p53 independent manner, and Stat1 is, at least in part, involved in G(1) arrest.

Cell Division↗

PubMed2001

Change in cellular localization of a rheumatoid arthritis-related antigen (RA-A47) with downregulation upon stimulation by inflammatory cytokines in chondrocytes.

We previously isolated a rheumatoid arthritis-related antigen (RA-A47) protein that had reactivity with RA sera from a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8. Sequencing analysis of ra-a47 cDNA revealed RA-A47 as a product of the colligin-2 gene, which is also known as the human heat shock protein (HSP) 47 gene. Expression of hsp47 has been shown to be cooperatively altered with that of collagen genes upon stimulation. In this study, it was confirmed that the mRNA expression of ra-a47 and COL2A1, a type II collagen gene, was upregulated on stimulation with transforming growth factor (TGF) beta in chondrocytes. However, in contrast, inflammatory cytokines such as tumor necrosis factor (TNF) alpha, interferon (IFN) beta, and interleukin (IL)-6 downregulated the expression of ra-a47 mRNA, whereas the expression of COL2A1 mRNA was not repressed, or even upregulated, in HCS-2/8 cells. Of note, inducible NO synthase (iNOS) and matrix metalloproteinase (MMP)-9 mRNAs were strongly stimulated by TNFalpha. We also found that cell-surface type II collagen disappeared upon such a stimulation, suggesting that decrement of RA-A47 may inhibit the secretion of type II collagen and lead to its accumulation inside the cells. RA-A47 was detected in the cultured medium of TNFalpha-treated HCS-2/8 cells and of IL-1-treated rabbit chondrocytes by Western blot analysis. Under the same conditions, RA-A47 was detected on the cell surface by immunofluorescence staining. These findings demonstrate that the RA-A47 chaperone protein is specifically downregulated, causing the intracellular accumulation of unsecretable type II collagen, while the extracellular matrix (ECM) is degraded by MMPs and iNOS through the stimulation of chondrocytes by TNFalpha. The altered localization of RA-A47 to the surface or outside of cells may represent the mechanism for the recognition of RA-A47 as an autoantigen during rheumatoid arthritis.

Animals↗

PubMed2001

Thymic carcinoma with tumor thrombus into the superior vena cava.

Tumor thrombus into the vena cava have been reported in cases with renal cell carcinoma, thyroid tumor and in those with thymoma. These tumors are frequently invasive and continuous from the main tumor that shows direct vessel wall invasion. Here, we report a case of thymic carcinoma with superior vena cava syndrome, which was caused by a tumor thrombus in the superior vena cava without vessel wall invasion. The main mediastinal tumor did not show innominate vein invasion, and the superior vena cava syndrome was a result of separate tumor thrombus that was free of vessel wall invasion. The tumor thrombus could be removed through a simple venotomy. To prevent stenosis in the superior vena cava and the left innominate vein, we used a pericardial patch to close the venotomy site.

Carcinoma, Renal Cell↗

PubMed2001

Repair of false para-anastomotic aortic aneurysms using an endovascular stent graft technique in a patient with severe pulmonary disease: report of a case.

Conventional surgery for para-anastomotic aortic aneurysms is technically challenging, and is associated with high morbidity and mortality. This report describes the case of a patient with severe pulmonary diseases in whom false para-anastomotic aortic aneurysms were successfully repaired using an endovascular stent graft technique.

Aged↗

PubMed2001

Novel mode of processing and secretion of connective tissue growth factor/ecogenin (CTGF/Hcs24) in chondrocytic HCS-2/8 cells.

The synthesis, processing, and secretion of human connective tissue growth factor (CTGF/Hcs24) in a human chondrocytic cell line, HCS-2/8, were analyzed immunochemically. By metabolic pulse-labeling, chasing, and subsequent immunoprecipitation analyses, active synthesis of CTGF was observed not only in growing HCS-2/8 cells, but also in confluent cells. However, secretion and processing of CTGF were found to be regulated differentially, depending upon the growth status. During phases of growth, HCS-2/8 cells released CTGF molecules immediately without sequestering them within the cell layer. In contrast, after the cells reached confluence, the secretion slowed, resulting in an accumulation of CTGF in the cells or extracellular matrices (ECMs). Also, in confluent cell layers, a 10 kDa protein that was reactive to an anti-CTGF serum was observed. This CTGF-related small protein was not detected immediately after labeling, but gradually appeared within 6 h after chase, which suggests its entity as a processed subfragment of CTGF. Surprisingly, the 10 kDa protein was stable even 48 h after synthesis, and was not released by ECM digestion, suggesting an intracellular maintenance and function. Taken together, the behavior of CTGF in HCS-2/8 cells is remarkably different from that reported in fibroblasts, which may represent unique roles for CTGF in the growth and differentiation of chondrocytes.

Amino Acid Sequence↗

PubMed2001

Genetic analysis of phytosterolaemia.

Two women with multiple xanthomas, intermittent arthritis and thrombocytopenia were diagnosed as phytosterolaemia, an autosomal-recessive lipid storage disease, based on their increased serum concentrations of beta-sitosterol, campesterol and sitostanol. The gene responsible for this disease is located within a distance of 18 cM between microsatellite markers of D2S 1788 and D2S1352 at chromosome 2p21. We genotyped the patients and their family members with 16 microsatellite markers around this locus. The results from the homozygosity mapping of one family suggested that the gene was located within the distance of 12.6 cM between D2S2328 and D2S1352. We have shortened the genetic distance by 5.4 cM.

Adult↗

PubMed2001

Frontal lobe dementia with abnormal cholesterol metabolism and heterozygous mutation in sterol 27-hydroxylase gene (CYP27).

Of the primary dementing disorders that cause frontotemporal dementia, the best-known is Pick disease. We report on a 44-year-old woman with progressive frontal lobe dementia and spastic paraplegia. Examination revealed increased serum levels of cholestanol with abnormal cholesterol metabolism and a heterozygous mutation of the sterol 27-hydroxylase gene (CYP27). Biochemical findings were compatible with cerebrotendinous xanthomatosis (CTX); however, the clinical manifestations were very dissimilar. To our knowledge, a symptomatic carrier of this mutation among CTX patients has not been reported. We speculate that the present patient has a previously undescribed neurodegenerative disease related to abnormal cholesterol metabolism with this heterozygous mutation.

Adult↗

PubMed2001

Highly repetitive DNA families restricted to germ cells in a Japanese hagfish (Eptatretus burgeri): a hierarchical and mosaic structure in eliminated chromosomes.

It is known that in eight hagfishes chromosome elimination occurs during early embryogenesis. The eliminated chromosomes are mostly C-band positive, so that none of the somatic cells have any C-band-positive chromatin. Recently, some highly repetitive DNA sequences have been reported as eliminated elements in these hagfishes based on molecular biological methods. However, no germline-restricted repetitive DNA have been directly isolated from the Japanese hagfish Eptatretus burgeri, from which approximately 21% of the total DNA is eliminated from presumptive somatic cells. Through electrophoretic investigation after digestion with restriction endonucleases, two DNA families that are restricted to germline DNA were isolated. Molecular cloning and sequence analysis revealed that these families are composed of closely related sequences of 64 and 57bp in length, respectively. Southern blot hybridization revealed that the two DNA families are restricted to germline DNA and were thus named EEEb1 and EEEb2, respectively. Moreover, these eliminated elements were highly and tandemly repeated, and it is predicted that they might amplify by saltatory replication and have evolved in a concerted manner. By densitometric scanning, EEEb1 and EEEb2 were found to amount to make up approximately 18.5 and 0.024% of the total germline genomic DNA, accounting for 88.6% of the total eliminated DNA. A fluorescence in situ hybridization experiment demonstrated that EEEb1 is located on all C-band-positive chromosomes that are limited to germ cells, suggesting that EEEb1 is the primary component of eliminated DNA of E. burgeri.

Animals↗

PubMed2001

Machado-Joseph disease with retinal degeneration and dementia.

OBJECTIVES: To clarify the phenotypic varieties in Machado-Joseph disease (MJD). MATERIALS AND METHODS: We studied a 64-year-old man with ataxia, retinal degeneration and dementia neurologically, ophthalmologically and genetically. RESULTS: The patient noted dysesthesia of his hands at age 57 and later had memory disturbance. He had gait disturbance and needed a wheelchair at age 64. His total IQ was 61 on the WAIS-R. He had loss of central vision, ophthalmoplegia, hearing impairment, dysarthria, truncal and limb ataxia, sensory disturbance, and mild weakness of the extremities. Electrophysiologically he was suspected to have polyneuropathy. Brain MRI showed marked atrophy of the cerebellum and pons with mild cerebral atrophy. Ophthalmologic evaluation revealed multiple chorioretinal atrophy. Expanded CAG repeat numbers in MJD1 were 64. CONCLUSION: These findings indicate that the clinical features of MJD might cover a wider spectrum than previously expected, though it is possible that these complications, namely retinal degeneration and dementia, were incidental findings in this patient.

Brain↗

PubMed2001

The extinction program for Homo sapiens and cloning humans: trinucleotide expansion as a one-way track to extinction.

It has been uncovered that expansion of trinucleotide repeats in the human genome are causing a variety of genetic diseases. They are also identified in other loci that are not clearly related to particular diseases, which indicates such repeat expansion is one of the general forms of evolution occurring throughout the human genome. Trinucleotide repeat expansion has been shown to occur during meiosis, and is generally irreversible. In consequence, every human chromosome suffers from the burden of accumulating trinucleotide repeats along with the passage of generation, which eventually ends up in a deficiency of replication. Thus, all the human chromosomes are predicted to be 'mortal', so far as they replicate through meiosis. Naturally, the mortality of human chromosomes leads to the mortality of Homo sapiens as a species on earth. Although it is quite controversial, a radical breakthrough for humans to survive might be found through cloning reproduction without meiosis.

Animals↗

PubMed2001

Anti-alpha2 integrin antibody induces secretion and activation of 72-kDa progelatinase by human fibroblasts.

We examined the effects of the extracellular matrix proteins fibronectin, laminin, and matrigel on 72-kDa progelatinase secretion by human lip fibroblasts (KD) and skin fibroblasts (MRC9 and HSF). By gelatin zymography, 1.7 +/- 0.2-fold, 1.7 +/- 0.2-fold, and 1.8 +/- 0.3-fold increases were observed in 72-kDa progelatinase secretion from KD cells treated with fibronectin, laminin, and matrigel, respectively. Laminin and matrigel, but not fibronectin, stimulated 72-kDa progelatinase secretion from HSF cells. Fibronectin, laminin, and matrigel did not stimulate 72-kDa progelatinase secretion by MRC9 cells. Anti-alpha2 integrin antibody-stimulated 72-kDa progelatinase secretion and induced the 62-kDa activated form of 72-kDa progelatinase by KD cells. Activated p42 MAP kinase (MAPK) expression was down-regulated by anti-alpha2 integrin antibody. Anti-alpha2 integrin antibody stimulated 72-kDa progelatinase secretion by HSF cells without inducing the 62-kDa activated form. The data suggest that interaction between fibroblasts and extracellular matrix components via alpha2 integrin plays an important role in regulating secretion and activation of 72-kDa gelatinase and that down-regulation of activated p42 MAPK may be involved in the 72-kDa progelatinase activation mechanism.

Antibodies↗

PubMed2001

Cell-type-specific trans-activation of herpes simplex virus thymidine kinase promoter by the human T-cell leukemia virus type I Tax protein.

The human T-cell leukemia virus type I Tax protein (HTLV-I Tax) is known as a trans-activating factor for a variety of genes, including those of cytokines. Here, we show that Tax is capable of activating the herpes simplex virus thymidine kinase (HSV-TK) promoter in certain mammalian cell lines. In murine NIH 3T3 fibroblasts and human HeLa cells, trans-activation by Tax was remarkably strong, whereas in human chondrocytic HCS-2/8 and monkey kidney Cos-7 cells, the responsiveness of the TK promoter to Tax was poor. Deletion analysis revealed that one of the two previously described Sp1 sites is required for the Tax responsiveness, whereas the CTF binding site is not. The results suggest possible interactions between the oncogenic Tax protein and the viral TK in coinfected cells in vivo. Care should be taken in the context of HTLV-I research, as the HSV-TK promoter has been widely used in molecular biology and gene therapeutics.

3T3 Cells↗

PubMed2001

Regulatory mechanism of human connective tissue growth factor (CTGF/Hcs24) gene expression in a human chondrocytic cell line, HCS-2/8.

CTGF/Hcs24 is a multi-functional growth factor that potentiates either the growth or differentiation of mesenchymal cells, according to the biological conditions. Among various functional aspects of CTGF/Hcs24, it is especially notable that CTGF/Hcs24 may promote endochondral ossification in growth cartilage through all stages, and it is highly expressed in a human chondrosarcoma-derived chondrocytic cell line (HCS-2/8). In this study, to clarify the regulatory mechanism of CTGF/Hcs24 gene expression in chondrocytes, we analyzed the transcriptional activity of the CTGF/Hcs24 promoter and the effect of the CTGF/Hcs24 3'-untranslated region (3'-UTR) on gene expression in HCS-2/8 by means of an established DNA transfection and luciferase reporter gene assay system. As a result, the luciferase activity of the CTGF/Hcs24 promoter was found to be remarkably high in HCS-2/8. The 3'-UTR of the CTGF/Hcs24 gene strongly repressed the luciferase activity in HCS-2/8, when it was linked to the downstream of the luciferase reporter gene, suggesting its functionality also in chondrocytic cells. Deletion analysis of the CTGF/Hcs24 promoter clarified a major segment responsible for the enhanced CTGF/Hcs24 promoter activity in HCS-2/8. The TGF-beta response element in the DNA segment was active in HCS-2/8, and point mutations in the element moderately decreased the highly maintained promoter activity with total loss of TGF-beta responsiveness. These results indicate that the strong expression of the CTGF/Hcs24 gene in HCS-2/8 was mainly caused by high transcriptional activity of the CTGF/Hcs24 promoter, and that the TGF-beta response element is one of the critical elements that support the high transcription activity.

3' Untranslated Regions↗

PubMed2001

Technical advance: an automated device for cryofixation of specimens of electron microscopy using liquid helium.

Metal-contact rapid freezing using liquid helium is theoretically the best method for preserving the fine structure of living cells with high temporal resolution in preparation of tissue samples for electron microscopy. However, this method is not commonly used, because of its technical difficulty and low reproducibility. We have designed and constructed an automatic device which allows simple, rapid and reproducible preparation of high-quality electron microscopic specimens by the non-specialist. We assessed the quality of cryofixation in samples prepared using this device by examining the preservation of cellular ultrastructure in relation to distance from the freezing block, and found that the region within 10 microm of the metal-contact plane was fixed with the highest quality. We applied this device, in combination with freeze-substitution methods and immunocytochemical techniques, to two phenomena involving rapid movement of subcellular components: (1) active movement of subcellular structures in the papillar cells of stigma and (2) light-induced rapid subcellular translocation of phytochrome A. Considering the importance of understanding subcellular processes of living cells for molecular and cell biology, this device will be a useful tool for diverse biological applications in the near future.

Arabidopsis↗