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Biomedical subjects

K Ohtani

Publications and source records attributed to K Ohtani.

At least 55 records · Page 3Linked to original sources
PubMed2000

The complete DNA sequence of the O antigen gene region of Plesiomonas shigelloides serotype O17 which is identical to Shigella sonnei form I antigen.

We cloned and determined the sequence of a DNA region of approximately 15-kb containing the cluster of genes required for O17 antigen expression in the Escherichia coli K-12 strain from the chromosome of Plesiomonas shigelloides serotype O17:H2 strain. The sequencing analysis revealed that the minimum essential region of the P. shigelloides O17 antigen gene cluster had a size of approximately 11.5-kb and contained 9 contiguous open reading frames (ORFs), which were almost identical to the corresponding ORFs of Shigella sonnei form I antigen gene region, except for IS630 sequence, at the DNA as well as amino acid levels. The putative function of most of the ORFs could be determined on the basis of amino acid sequence similarities and characteristics. In addition, the G+C content of the P. shigelloides O17 antigen genes was lower than that of the chromosomal DNA of P. shigelloides and S. sonnei, suggesting that both P. shigelloides O17 and S. sonnei form I antigen genes had been derived from the same origin with a low G+C content.

Amino Acid Sequence↗
PubMed2000

Genetic analysis of the ycgJ-metB-cysK-ygaG operon negatively regulated by the VirR/VirS system in Clostridium perfringens.

The 5'-flanking region of the metB-cysK-ygaG operon, whose expression is negatively regulated by the VirR/VirS system in C. perfringens, was analyzed. The region contained the ycgJ, mscL, and colA genes encoding a hypothetical protein, a large conductance mechanosensitive channel protein, and kappa-toxin (collagenase), respectively. Northern analysis revealed that the ycgJ gene was transcribed as a 4.9-kb operon together with the metB-cysK-ygaG genes and that this operon was negatively regulated by the VirR/VirS system. It is indicated that the pfoA (theta-toxin or perfringolysin O), colA, and ycgJ-metB-cysK-ygaG genes that belong to the VirR/VirS regulon are situated very close together in a 26.5-kb region of the chromosome, but do not form a pathogenic island.

Bacterial Proteins↗
PubMed2000

Some factors which influence intrinsic factor content and its mRNA level in the rat stomach.

Factors which regulate Intrinsic Factor (IF) content and IF mRNA level were examined with an abc-ELISA and Northern blot analysis in growing rats, and compared with pepsinogen (Pg) and in terms of the increased need for vitamin B12 (V.B12). Increases in IF content and IF mRNA level gradually occurred from day 13 after birth, whereas those of Pg and Pg mRNA started from day 16. The effects of a few related hormones on the expression of IF mRNA were examined. The injection of hydrocortisone induced IF and Pg mRNA expression in 5-d-old postnatal rats. Furthermore, adrenalectomy-induced decreases in IF content and IF mRNA level in adult male rats were recovered with hydrocortisone administration. IF content and IF mRNA level were measured in the artificially and physiologically created needs for V.B12, the first being regeneration of the liver, the V.B12 storing tissue, following partial hepatectomy, and the second pregnancy or lactation. During regeneration of the liver, increases in IF content and IF mRNA level were marked, followed by reduction toward the original level after accomplishment of regeneration. Increases in IF content and IF mRNA level were also seen in lactating rats, but no increases were obtained in pregnant rats. These results suggest that the IF content and IF mRNA level are regulated not only by corticosteroids but also by the increased need for V.B12.

Adrenalectomy↗
PubMed2000

Sphingosine 1-phosphate stimulates insulin secretion in HIT-T 15 cells and mouse islets.

Sphingosine is involved in the regulation of cellular processes as a second messenger in various kinds of cells. Since the possible involvement of sphingosine has not been investigated in pancreatic beta-cells, we determined the expression of putative sphingosine 1-phosphate (S1P) receptors and the effect of sphingosine on pancreatic beta-cell function using a clonal Hamster beta-cell line, HIT-T 15 cells and isolated mouse islets. We showed the expression of putative S1P receptors, Edg-3 and AGR16/H218 in HIT-T 15 cells. Ten and 20 microM S1P significantly stimulated insulin secretion for 10 minutes in HIT-T 15 cells. Ten microM S1P significantly increased insulin secretion from isolated mouse islets. Ten microM S1P obviously increased intracellular Ca2+ concentration ([Ca2+]i). Fifty nM nifedipine did not affect the S1P stimulation of insulin secretion in HIT-T 15 cells. Two microM U73122 (phospholipase C inhibitor) completely deleted 10 microM S1P-induced stimulation of insulin secretion for 10 minutes, but U73343 (an inactive analogue of U73122) did not. S1P dose-dependently inhibited intracellular cyclic AMP levels. Pretreatment with 100 ng/ml pertussis toxin (PTX) partially, but significantly attenuated an increase of insulin secretion by 10 microM S1P. These data suggested that PTX-sensitive G-protein-dependent pathway may, at least in part, be involved in an increase of non-glucose stimulated insulin secretion by S1P through the activation of phospholipase C-Ca2+ system.

3T3 Cells↗
PubMed2000

Interleukin-6 increases insulin secretion and preproinsulin mRNA expression via Ca2+-dependent mechanism.

Interleukin (IL)-6, one of the cytokines released from inflammatory cells, stimulates insulin secretion in a physiological concentration (1-100 pg/ml), but the exact mechanism is still unknown. The present studies were undertaken to investigate the mechanism of IL-6-induced stimulation of insulin secretion in HIT-T 15 cells. The effects of the addition of nifedipine on the IL-6 (100 pg/ml)-induced stimulation of insulin secretion were investigated. We also examined the possibility that IL-6 (1-100 pg/ml) may stimulate insulin messenger ribonucleic acid (mRNA) expression, using the reverse transcription-polymerase chain reaction method. The addition of 100 and 1000 nM nifedipine significantly attenuated the stimulatory effects of 100 pg/ml IL-6 on insulin secretion. The addition of 1-100 pg/ml IL-6 dose-dependently increased preproinsulin mRNA expression relative to beta-actin mRNA. IL-6 increased insulin gene promoter activity of fragments A (-2188 to +337 bp) and B (-1782 to +270 bp) but not fragments C (-1275 to +270 bp), D (-1138 to +270 bp), E (-880 to +236 bp) or F (-356 to +252 bp). The addition of 10 nM nifedipine completely abolished the stimulatory effect of 10-100 pg/ml IL-6 on relative preproinsulin mRNA expression. These data raised the possibility that IL-6 increased preproinsulin mRNA expression via the stimulation of Ca(2+) influx which enhances insulin gene expression.

Actins↗
PubMed2000

Triterpenoidal saponins from Cornulaca monacantha.

From the aerial parts of Cornulaca monacantha, three new triterpenoidal saponins have been isolated and their genuine structures were identified as 3-O-[beta-xylopyranosyl-(1-->3)-beta- glucuronopyranosyl]-30-methylphytolaccagenate (2), 3-O-[beta-xylopyranosyl- (1-->3)-beta-glucuronopyranosyl]-30-methylphytolaccagenate 28-O-beta-gluco-pyranoside (3) and 3-O-[beta-xylopyranosyl-(1-->3)-beta- glucurono-pyranosyl]-30-methylserjanate 28-O-beta glucopyranoside (4) together with nine known saponins of oleanolic acid (5-9), hederagenin (1, 10, 11) and 30-methyl phytolaccagenate (12).

Egypt↗
PubMed1999

Ezrin, a membrane-cytoskeletal linking protein, is involved in the process of invasion of endometrial cancer cells.

In order to study ezrin function in tumor growth and invasion, we used two cell lines of human endometrial cancers. Ishikawa, the low-metastatic endometrial cancer cell line, and its subclone (mEIIL) with high-metastatic activity and higher ezrin expression were treated with a ezrin antisense phosphorothioate oligonucleotides (ePONs) pulse four times before the in vitro growth assay and Matrigel invasion assay. ePONs significantly suppressed the number of both cells that penetrated through Matrigel membrane (inhibition rate; 40.1 +/- 7.5% (Ishikawa), 42.7 +/- 2.4% (mEIIL), mean +/- SD, n = 6, P < 0.05, Student's t-test), whereas they showed no effect on cell proliferation. Ezrin expression at the protein level was inhibited by ePONs. These data suggest that ezrin expression is required for invasion. The association of high ezrin expression in mEIIL and its higher ability to migrate through Matrigel may at least in part indicate functional significance of ezrin in endometrial cancer metastasis.

Adenocarcinoma↗
PubMed1999

Implication of transcription factor E2F in regulation of DNA replication.

The transcription factor E2F plays crucial roles in induction of S phase in mammalian cells by regulating the expression of genes that encode molecules involved in cell cycle progression. E2F exerts a repressive effect on E2F-responsive genes in G0/G1 phase by associating with the retinoblastoma tumor suppressor gene product pRb and the related protein p130. This repression is relieved by phosphorylation of the pRb family proteins by G1 cyclin (cyclin D and cyclin E) -dependent kinases, resulting in expression of E2F-responsive genes in late G1 with a peak at the G1/S boundary. One group of genes influenced by E2F encode cell cycle regulatory molecules, including members of the E2F family and cyclin E, demonstrating a loop-type regulation of activities of E2F and cyclin E-dependent kinase at this stage in the cell cycle. Another group is involved in DNA replication, including genes for molecules regulating initiation of DNA replication. Overexpression of E2F is sufficient to induce DNA synthesis in serum starved fibroblasts. In addition, overexpression of cyclin E, which is essential for entry into S phase, overcomes G1 arrest caused by inhibition of E2F activity without resuming E2F mediated transcription, suggesting the mergence of the two pathways. Thus, E2F target-gene products and cyclin E-dependent kinase activity apparently co-operate to initiate replication of DNA.

Animals↗
PubMed1999

Molecular cloning of a novel human collectin from liver (CL-L1).

Collectins are a C-lectin family with collagen-like sequences and carbohydrate recognition domains. These proteins can bind to carbohydrate antigens of microorganisms and inhibit their infection by direct neutralization and agglutination, the activation of complement through the lectin pathway, and opsonization by collectin receptors. Here we report the cloning of a cDNA encoding human collectin from liver (CL-L1 (collectin liver 1)) that has typical collectin structural characteristics, consisting of an N-terminal cysteine-rich domain, a collagen-like domain, a neck domain, and a carbohydrate recognition domain. The cDNA has an insert of 831 base pairs coding for a protein of 277 amino acid residues. The deduced amino acid sequence shows that this collectin has a unique repeat of four lysine residues in its C-terminal area. Northern blot, Western blot, and reverse transcription-polymerase chain reaction analyses showed that CL-L1 is present mainly in liver as a cytosolic protein and at low levels in placenta. More sensitive analyses by reverse transcription-polymerase chain reactions showed that most tissues (except skeletal muscle) have CL-L1 mRNA. Zoo-blot analysis indicated that CL-L1 is limited to mammals and birds. A chromosomal localization study indicated that the CL-L1 gene localizes to chromosome 8q23-q24.1, different from chromosome 10 of other human collectin genes. Expression studies of fusion proteins lacking the collagen and N-terminal domains produced in Escherichia coli affirmed that CL-L1 binds mannose weakly. CL-L1 and recombinant CL-L1 fusion proteins do not bind to mannan columns. Analysis of the phylogenetic tree of CL-L1 and other collectins indicated that CL-L1 belongs to a fourth subfamily of collectins following the mannan-binding protein, surfactant protein A, and surfactant protein D subfamilies including bovine conglutinin and collectin-43 (CL-43). These findings indicate that CL-L1 may be involved in different biological functions.

Amino Acid Sequence↗
PubMed1999

Cell growth-regulated expression of mammalian MCM5 and MCM6 genes mediated by the transcription factor E2F.

Initiation of DNA replication requires the function of MCM gene products, which participate in ensuring that DNA replication occurs only once in the cell cycle. Expression of all mammalian genes of the MCM family is induced by growth stimulation, unlike yeast, and the mRNA levels peak at G1/S boundary. In this study, we examined the transcriptional activities of isolated human MCM gene promoters. Human MCM5 and MCM6 promoters with mutation in the E2F sites failed in promoter regulation following serum stimulation and exogenous E2F expression. In addition, we identified a novel E2F-like sequence in human MCM6 promoter which cooperates with the authentic E2F sites in E2F-dependent regulation. Forced expression of E2F1 could induce expression of all members of the endogenous MCM genes in rat embryonal fibroblast REF52 cells. Our results demonstrated that the growth-regulated expression of mammalian MCM5 and MCM6 genes, and presumably other MCM members, is primarily regulated by E2F through binding to multiple E2F sites in the promoters.

Animals↗
PubMed1999

Novel TSC2 mutation in a patient with pulmonary tuberous sclerosis: lack of loss of heterozygosity in a lung cyst.

A Japanese patient with tuberous sclerosis (TSC), who manifested with multiple lung cysts and pneumothorax, is described. All exons of two TSC genes, TSC1 and TSC2, in peripheral blood leukocytes from the patient were analyzed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). A novel T-to-G transition was found in exon 19 of TSC2 at nucleotide position 2168. This mutation caused an amino acid change, L717R. There was no such mutation in any other family members or in 100 normal Japanese. An automated sequencer-assisted quantitative analysis of normal and mutated SSCP-bands revealed no loss of heterozygosity (LOH) in the lung cyst tissue of the patient.

Adolescent↗
PubMed1999

High-level and effective production of human mannan-binding lectin (MBL) in Chinese hamster ovary (CHO) cells.

We have developed a high-expression system of recombinant human mannan-binding lectin (MBL) with CHO cells. Geneticin-resistant transformants harboring human MBL cDNA in the expression vector pNOW/CMV-A were screened by immunoblot analysis for secretion of recombinant MBL. Cloning and selection by both geneticin and methotrexate resulted in the production of recombinant MBL to a final concentration of 128.8 microg/ml in media after four days of culture. SDS-PAGE and gel-filtration analyses showed that recombinant MBL is characterized by two lower-order oligomeric structures (apparent molecular weights: 1150 kDa and 300 kDa) compared to native MBL (apparent molecular weight: 1300 kDa). The recombinant human MBL has both sugar-binding and complement activation activity and, like native MBL, can inhibit hemagglutination of influenza A virus. Lectin blots with recombinant MBL indicate that it can bind such microorganisms as HIV and influenza virus suggesting that it might inhibit their infection of hosts. This high-level expression of human MBL with the full range of biological activity will be useful for studies on the immunological role of MBL in humans.

Animals↗
PubMed1999

Thymidine phosphorylase expression is predominantly observed in stroma of well-differentiated adenocarcinoma of endometrium and correlates with a frequency of vascular involvement.

Thymidine phosphorylase (dThdPase) expression was studied in 20 cases of well-differentiated endometrial carcinomas to examine the clinicopathological significance. Immunohistochemical study showed predominant dThdPase expression in tumor stroma. No expression was detected in coexisting normal endometrial stroma or stroma of endometriosis. Seven cases (35%) showed strong stain and 13 (65%) showed weak stain. Based on the strength of immunoreactivity, patients were grouped into two groups: group S (strong) and group W (weak). In group S, 5 (71%) showed vascular involvement whereas in group W, only 3 (23%) cases were positive, giving a significant difference in the frequency of vascular involvement between the two groups (P < 0.03, chi2 analysis). No correlation was found between dThdPase expression and myometrial invasion. Patients with vascular involvement resulted in poorer outcome (P < 0.003) whereas between group S and W, there showed no difference in survival (group S vs group W; P < 0.15). A multivariate analysis including stage, vascular involvement, and dThdPase stain as variables showed none as independent risk factors. However, univariate analysis showed that the presence of a vascular involvement was a risk factor for a shorter survival (relative risk = 6.277, 95% range = 1.2-32.6, P < 0. 03). It is concluded that expression of dThdPase in endometrial carcinoma is a marker of a desmoreaction and a risk factor for vascular invasion. Since vascular invasion is a risk factor for poor outcome, the significance of dThdPase expression in endometrial carcinoma requires further clinical evaluations.

Adenocarcinoma↗
PubMed1999

Human mannan-binding lectin inhibits the infection of influenza A virus without complement.

Mannan-binding lectin (MBL) is a C-type serum lectin that is believed to play an important role in innate immunity. It is one of the collectin family, which is characterized by having a collagen-like sequence and a carbohydrate recognition domain. MBL can bind to sugar determinants of several micro-organisms, neutralize them and inhibit infection by complement activation through the lectin pathway and opsonization by collectin receptors. Bovine conglutinin and mouse MBL inhibit the infective and haemagglutinating activities of influenza A viruses. To identify the direct antiviral activity of human MBL against influenza A viruses that does not depend on complement activation or opsonization, we isolated native MBL from human serum and produced a recombinant MBL in Chinese hamster ovary (CHO) cells using a pNOW/CMV-A expression vector system. Native and recombinant human MBL exhibited neutralization activity against A/Ibaraki/1/90 (H3N2), with the plaque focus reduction assay at the viral attachment phase. Their activities were inhibited by EDTA, mannose and anti-human MBL antibody. Furthermore, at the viral expansion phase both MBL in culture medium prevented viral spreading from primary infected cells to neighbour cells. A virus recovery study using EDTA indicated that interaction between MBL and virus was reversible and non-damaging to the virus. Lectin blot and immunohistochemistry assays showed that these antiviral activities involved binding between MBL and two viral envelope proteins, haemagglutinin and neuraminidase. These findings suggest that human MBL can play an important role in innate immunity by direct viral neutralization and inhibition of viral spread, as well as an indirect role through opsonization and complement activation.

Animals↗
PubMed1999

Induction of Bcl-x(L) expression by human T-cell leukemia virus type 1 Tax through NF-kappaB in apoptosis-resistant T-cell transfectants with Tax.

Human T-cell leukemia virus type 1 (HTLV-1) Tax is thought to play a pivotal role in immortalization of T cells. We have recently shown that the expression of Tax protected the mouse T-cell line CTLL-2 against apoptosis induced by interleukin-2 (IL-2) deprivation and converted its growth from being IL-2 dependent to being IL-2 independent. In this study, we demonstrate that constitutive expression of bcl-xl but not bcl-2, bcl-xs, bak, bad, or bax was associated with apoptosis resistance after IL-2 deprivation in CTLL-2 cells that expressed Tax. Transient-transfection assays showed that bcl-x promoter was transactivated by wild-type Tax. Similar effects were observed in mutant Tax retaining transactivating ability through NF-kappaB. Deletion or substitution of a putative NF-kappaB binding site identified in the bcl-x promoter significantly decreased Tax-induced transactivation. This NF-kappaB-like element was able to form a complex with NF-kappaB family proteins in vitro. Furthermore, Tax-induced transactivation of the bcl-x promoter was also diminished by the mutant IkappaBalpha, which specifically inhibits NF-kappaB activity. Our findings suggest that constitutive expression of Bcl-x(L) induced by Tax through the NF-kappaB pathway contributes to the inhibition of apoptosis in CTLL-2 cells after IL-2 deprivation.

Animals↗
PubMed1999

Human T-cell leukemia virus type 1 tax protein abrogates interleukin-2 dependence in a mouse T-cell line.

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia. Tax, the viral protein, is thought to be crucial in the development of the disease, since it transforms healthy T cells in vitro and induces tumors in transgenic animals. We examined the effect of Tax activity on the growth of the interleukin-2 (IL-2)-dependent T-cell line CTLL-2. Stable expression of Tax in CTLL-2 transformed cell growth from being IL-2 dependent to IL-2 independent. Tax stimulated transcription through NF-kappaB and the cyclic AMP-responsive element-like sequence in the HTLV-1 promoter. The finding of Tax mutants segregating these two pathways suggested that the NF-kappaB pathway was essential for IL-2-independent growth of CTLL-2 cells while the CRE pathway was unnecessary. However, both pathways were necessary for another transformation-related activity (colony formation in soft agar) of CTLL-2/Tax. Our results show that Tax has at least two distinct activities on T cells, and suggest that Tax plays a crucial role in IL-2-independent T-cell transformation induced by HTLV-1, in addition to its well-known IL-2-dependent cell transformation.

Animals↗
PubMed1999

Gene expression in primary, metastatic and recurrent lesions of endometrial cancer.

Seventeen patients with endometrial cancer were studied. Tissues of primary (P) and metastatic (M) lesions were obtained from 8 patients and complete sets of P, M and Recurrent (R) lesions were obtained from 9 patients during a follow-up period of 1-10 years. Expressions of estrogen receptors, progesterone receptors, multidrug resistance protein-1, multidrug resistance-related protein, c-erbB-2, membrane-type metalloproteinase, human telomerase RNA, human telomerase reverse transcriptase RNA, E-cadherin and autocrine motility factor receptor were studied by RT-PCR. Also, telomeric restriction fragment length (TRFL) and microsatellite instability were determined between P, M and R. The results indicate that there are significant differences in the gene expression frequency during tumor progression. The mismatch rate ranged from 0 to 47.1% between P and M and from 14.3% to 66.7% between P and R, respectively. The TRFL analysis showed a marked reduction in P and M (P vs. M: 8.2 +/- 0.9 vs. 5.6 +/- 0.4 kb, mean +/-SEM, n = 9, p = 0.002 by paired Student's t test). The length further decreased in R (P vs. R: 8.2 +/- 0.9 vs. 3.2 +/- 0.7, p = 0.01, M vs. R: 5.6 +/- 0.4 vs. 3.2 +/- 0.7, p = 0.005). The genomic instability/replication error was tested by AluI arbitrary primed polymerase chain reaction (AP-PCR). Five out of 17 patients showed an altered replication error pattern (29.4%). The mean number of abnormal AluI AP-PCR patterns in M and R compared to the P was 1.5 (M) and 4 (R). The difference between the P and R was statistically significant (p < 0.04). The present data indicate that biological behavior of cancer cells in P, M and R may differ significantly.

ATP Binding Cassette Transporter, Subfamily B, Mem↗