Biomedical subjects

Y Hashimoto

Publications and source records attributed to Y Hashimoto.

At least 127 records · Page 7Linked to original sources

PubMed2000

Transformation of BALB3T3 cells caused by over-expression of rat CD98 heavy chain (HC) requires its association with light chain: mis-sense mutation in a cysteine residue of CD98HC eliminates its transforming activity.

CD98 is a 125-kDa glycoprotein (GP125) consisting of an 85-kDa heavy chain (HC) and a 40-kDa light chain (LC), and is highly expressed on the cell surface of activated lymphocytes and various tumor cells. In addition to the regulatory role of CD98HC in L-, y(+)L- and Xc-amino-acid transport systems, which are principally mediated by CD98LC, we have reported transforming activity of human CD98HC. In this study, we established and analyzed BALB3T3 clones transfected with cDNAs encoding wild-type and mutated rat CD98HC proteins designated as BrH/Wild, C103S, C325S and 103/325, in which 103 and/or 325 cysteine were intact or replaced with serine. Flow cytometry with anti-rat CD98HC MAb B3 revealed that wild-type and mutated CD98HC transfectants expressed almost the same amounts of rat CD98HC proteins on the cell surface. Immunoprecipitation with B3 revealed that exogenous rat CD98HC proteins were associated with endogenous mouse CD98LC by a disulfide bond in BrH/Wild and C325S, but not in C103S and 103/325 transfectants. These transfectants showed similar doubling times and leucine and arginine transport activities, as compared with BALB3T3 and control transfectants in monolayer culture. Wild-type and C325S transfectants, however, formed much larger anchorage-independent colonies than C103S, 103/325 and control transfectants in soft agar. In addition, wild-type and C325S transfectants showed tumorigenicity in nude mice, although C103S, 103/325 and control transfectants did not. These findings indicate that over-expression of CD98HC and its disulfide-linkage with CD98LC at the cell surface result in malignant transformation of murine fibroblasts.

Amino Acid Substitution↗

PubMed2000

Further studies on nociceptin-related peptides: discovery of a new chemical template with antagonist activity on the nociceptin receptor.

Three series of nociceptin (NC)-related peptides were synthesized and their abilities (i) to bind to the NC sites expressed in mouse forebrain membranes, (ii) to inhibit the electrically evoked contraction of the mouse vas deferens, and (iii) to inhibit forskolin-stimulated cAMP accumulation in Chinese hamster ovary cells expressing the human recombinant NC receptor (CHONCR) were investigated. The compounds of the first series (a series) have an ordinary Xaa1-Gly2 bond, those of the second series (b series) have a Xaa1psi(CH2-NH)Gly2 pseudopeptide bond, and those of the third series (c series) have a peptoid (Nxaa1-Gly2) structure. The affinity values measured in the binding assay and in the two functional assays with the compounds of the three series showed high levels of correlation. Thus, (I) the compounds of the a series in which Phe1 was substituted with Tyr, Cha, or Leu acted as potent NC receptor agonists; (II) the b series compounds behaved as NC receptor antagonists in the mouse vas deferens and as full agonists in CHO(NCR) cells with different potencies depending on the first amino acid residue, [Phe1psi(CH2-NH)Gly2]NC(1-17)NH2 and [Phe1psi(CH2-NH)Gly2]NC(1-13)NH2 being the most potent compounds; (III) the compounds of the third series were all inactive both as agonists and as antagonists with the exception of [Nphe1]NC(1-17)NH2 and [Nphe1]NC(1-13)NH2, which behaved as NC receptor antagonists both in the isolated tissue and in CHO(NCR) cells (pKB 6.1-6.4). In conclusion, this study demonstrates that chemical requirements for NC receptor agonists are different from those of antagonists. Moreover, modifications of the steric orientation of the aromatic residue Phe1 in the NC sequence as obtained with the pseudopeptide bond between Phe1 and Gly2 or with the displacement of the benzyl side chain by one atom, as in Nphe1, lead respectively to reduction or elimination of efficacy. Indeed, in contrast to [Phe1psi(CH2-NH)Gly2]NC(1-13)NH2 which has been reported to exhibit agonist activity in several assays involving either central or recombinant NC receptors, [Nphe1]NC(1-13)NH2 antagonizes the effect of NC at human recombinant NC receptors and in the mouse tail withdrawal assay.

Animals↗

PubMed2000

Interface characterization of the type II module pair from fibronectin.

The lone (1)F2(2)F2 modular pair of fibronectin is found in the collagen-binding region. This exclusive localization suggests the (1)F2(2)F2 pair plays an important role in the recognition of collagen. However, no information is currently available about the interaction between the two F2 modules and, thus, the orientation of their putative collagen-binding sites with respect to one another. Comparison of a variety of high-resolution NMR parameters from the F2 modules in isolation and the (1)F2(2)F2 pair was used to establish the extent of interaction between the F2 modules in the pair. Chemical shifts of the F2 modules and the (1)F2(2)F2 pair indicate that the structures of the modules are preserved in the pair and that, with the exception of the covalent linkage, they do not interact. (15)N NMR relaxation data identify significant motion occurring in the linker region of the (1)F2(2)F2 pair, and analyses of the anisotropic diffusion properties of the (1)F2(2)F2 pair are consistent with the modules in the F2 pair tumbling independent of one another.

Binding Sites↗

PubMed2000

Inhibitory effect of anti-diabetic agents on rat organic anion transporter rOAT1.

The interactions of sulfonylureas and a novel anti-diabetic drug, nateglinide, with rat renal organic anion transporter (rOAT1) expressed in Xenopus laevis oocytes were studied. Uptake of p-aminohippurate via rOAT1 was markedly inhibited by glibenclamide and nateglinide, and moderately by chlorpropamide and tolbutamide. The inhibition constant values (K(i)) for chlorpropamide, glibenclamide, tolbutamide and nateglinide were 39.5, 1.6, 55.5 and 9.2 microM, respectively. Kinetic analysis showed that the inhibition of p-aminohippurate uptake by glibenclamide was competitive. Sulfonylureas examined and nateglinide did not show a trans-stimulation effect on [14C]p-aminohippurate efflux from rOAT1-expressing oocytes. There was no stimulation of [3H]glibenclamide uptake via rOAT1. These findings suggested that sulfonylureas and nateglinide interact with rOAT1, but these drugs are not translocated via the transporter.

Animals↗

PubMed2000

Relationship between cytogenetic aberrations by CGH coupled with tissue microdissection and DNA ploidy by laser scanning cytometry in head and neck squamous cell carcinoma.

BACKGROUND: The relationship between DNA sequence copy number aberrations (DSCNAs) and DNA ploidy in head and neck squamous cell carcinomas (HNSCCs) is still controversial. Materials and Methods We analyzed DSCNAs by comparative genomic hybridization (CGH) combined with microdissection and DNA ploidy by laser scanning cytometry (LSC) in 18 surgically removed HNSCCs and compared the data. RESULTS: Copy number increases were most frequently observed on chromosomes 3q (16 cases), 8q (13 cases), and 12p (11 cases). Copy number decreases were observed on chromosome 3p (14 cases). LSC revealed DNA aneuploidy in 10 of the 18 cases. All DNA aneuploid tumors exhibited gain or amplification of DNA copy number at 12p11-12.1, whereas gain of DNA copy number was found in only 1 of 8 diploid tumors. DSCNAs were more frequent in DNA aneuploid tumors than in diploid tumors (P < 0.005). CONCLUSIONS: The present observations indicate a close relationship between DSCNAs and DNA ploidy in HNSCCs.

Aged↗

PubMed2000

Induction of KAI-1 expression in metastatic cancer cells by phorbol esters.

KAI-1 is a tumor suppressor gene whose down-regulation has been shown to be associated with the development of metastases of cancer cells. Here, we demonstrated that KAI-1 expression was induced by activating protein kinase C even in metastatic prostate cancer cell lines in which its expression was significantly down-regulated. KAI-1 expression was enhanced in a dose-dependent manner by PMA, and its induction is at least in part due to transcriptional activation. Pretreatment with calphostin C abrogated its induction by PMA. Our findings may provide useful information for developing a novel drug capable of inducing KAI-1 expression and thereby inhibiting metastasis.

Antigens, CD↗

PubMed2000

Novel alpha-glucosidase inhibitors with a tetrachlorophthalimide skeleton.

Novel alpha-glucosidase inhibitors with a tetrachlorophthalimide skeleton were prepared and their structure-activity relationships were analyzed. Among them, N-phenyl-4,5,6,7-tetrachlorophthalimide (CPOP: 2) and N-(4-phenylbutyl)-4,5,6,7-tetrachlorophthalimide (CP4P: 6) showed very potent inhibitory activity, being more potent than 1-deoxynojirimycin (dNM: 1). Mechanistic studies revealed that CPOP (2) and CP4P (6) inhibit alpha-glucosidase non-competitively and competitively, respectively.

1-Deoxynojirimycin↗

PubMed2000

Glyoxalase I is involved in resistance of human leukemia cells to antitumor agent-induced apoptosis.

Abnormality in the machinery of apoptosis is associated with a resistant phenotype of the tumor cell to chemotherapy. To determine the molecular basis of resistance to antitumor agent-induced apoptosis, we performed a complementary DNA (cDNA) subtractive hybridization with messenger RNA (mRNA) from human monocytic leukemia U937 and its variant UK711, which is resistant to apoptosis induced by antitumor agents. We found that glyoxalase I (GLO1), an enzyme that detoxifies methylglyoxal, is selectively overexpressed in the apoptosis-resistant UK711 cells. The GLO1 enzyme activity was significantly elevated in UK711 and UK110 cells, another drug-resistant mutant, as well as in K562/ADM, adriamycin-resistant leukemia cells, compared with their parental cells. When overexpressed in human Jurkat cells, GLO1 inhibited etoposide- and adriamycin-induced caspase activation and apoptosis, indicating the involvement of GLO1 in apoptosis suppression caused by these drugs. Moreover, cotreatment with S-p-bromobenzylglutathione cyclopentyl diester (BBGC), a cell-permeable inhibitor of GLO1, enhanced etoposide-induced apoptosis in resistant UK711 cells but not in parental U937 cells. Taken together, these results indicate that GLO1 is a resistant factor to antitumor agent-induced apoptosis in human leukemia cells and that the GLO1 inhibitor could be a drug resistance-reversing agent.

Antineoplastic Agents↗

PubMed2000

A lectin from an edible mushroom Pleurotus ostreatus as a food intake-suppressing substance.

In an experiment in which rats were allowed free access to food and water, the rats did not eat the diet containing a mushroom Pleurotus ostreatus even if they were emaciated. A P. ostreatus lectin (POL) was isolated from the mushroom as the food intake-suppression principle. In hemagglutination inhibition assays, Me-alphaGalNAc was the most potent inhibitor among the monosaccharides tested. Among all the sugars tested, 2'-fucosyllactose (Fucalpha1-->2Galbeta1-->4Glc) was the strongest inhibitor and its inhibitory potency was five times greater than that of Me-alphaGalNAc. POL exhibited a binding ability to bovine submaxillary mucin (BSM) and asialo-BSM and the other glycoproteins were inert to the binding. The food intake-suppressing activity of POL was dependent on the dose. The diet containing 0.1% POL caused a 50% decrease in the food intake of rats against the control.

Amino Acids↗

PubMed2000

Amino acid substitutions in the VanS sensor of the VanA-type vancomycin-resistant Enterococcus strains result in high-level vancomycin resistance and low-level teicoplanin resistance.

The vancomycin-resistant enterococci GV1, GV2 and GV3, which were isolated from droppings from broiler farms in Japan have been characterized as VanA-type VRE, which express high-level vancomycin resistance (256 or 512 microg ml(-1), MIC) and low-level teicoplanin resistance (1 or 2 microg ml(-1), MIC). The vancomycin resistances were encoded on plasmids. The vancomycin resistance conjugative plasmid pMG2 was isolated from the GV2 strain. The VanA determinant of pMG2 showed the same genetic organization as that of the VanA genes encoded on the representative transposon Tn1546, which comprises vanRSHAXYZ. The nucleotide sequences of all the genes, except the gene related to the vanS gene on Tn1546, were completely identical to the genes encoded on Tn1546. Three amino acid substitutions in the N-terminal region of the deduced VanS were detected in the nucleotide sequence of vanS encoded on pMG2. There were also three amino acid substitutions in the vanS gene of the GV1 and GV3 strains in the same positions as in the vanS gene of pMG2. Vancomycin induced the increased teicoplanin resistance in these strains.

Amino Acid Sequence↗

PubMed2000

The effect of growth hormone on the proliferation of human Th cell clones.

The effects of human growth hormone (hGH) on human Th cell clones were examined. Both 20K and 22K hGH stimulated the proliferation of Th2 and Th0 cells in the presence of mite antigen, whereas they did not stimulate the proliferation of Thl cells. Because the effect of 20K hGH was almost the same as that of 22KhGH, it was suggested that the action of hGH was not mediated through prolactin receptor but through hGH receptors. The application of growth hormone binding protein (GHBP) inhibited the cell growth of Th1 clones. In Th2 and Th0 cells GHBP inhibited the hGH-stimulated cell proliferation. However, GHBP alone did not affect the proliferation of Th2 and Th0 cells. hGH was detected in the supernatant of Th1 clones in the presence of mite antigen but it was not detected in Th2 clones. hGH was detected in one out of 4 batches of Th0 clones. These data indicated that hGH was secreted from Thl clones, and that Th0 clones possessed characteristics of both Th2 and Th0 clones.

Animals↗

PubMed2000

Synthesis of a novel class of cdc25A inhibitors from vitamin D3.

We have developed a novel class of cdc25A inhibitors by drastic modification of the hydrophobic and hydrophilic substructures of dysidiolide. The unsaturated derivative 3b strongly inhibited cdc25A (IC50 = 7.7 microM) and caused GI arrest of HL60 cells.

4-Butyrolactone↗

PubMed2000

Differential interaction of CrkII adaptor protein with platelet-derived growth factor alpha- and beta-receptors is determined by its internal tyrosine phosphorylation.

CrkII is an intracellular adaptor protein involved in signal transduction by various growth factors. Activation of PDGF alpha-receptor resulted in its association with CrkII in vivo. In contrast, binding of CrkII to the PDGF beta-receptor was negligible, despite its becoming prominently phosphorylated. Bacterially expressed GST-CrkII SH2 domain specifically bound to Tyr-762 and Tyr-771 in the activated PDGF alpha- and beta- receptors, respectively. GST fusion protein of full-length CrkII also bound to the activated PDGF beta-receptor. However, tyrosine phosphorylation of GST-CrkII diminished its binding to the beta-receptor. CrkI, a truncated version of CrkII lacking the phosphorylatable tyrosine residue, could bind to both PDGF alpha- and beta-receptors in vivo. In conclusion, tyrosine phosphorylation of CrkII negatively affects its binding to the PDGF receptors. The differential binding of CrkII to the PDGF alpha- and beta- receptors may be a rationale for functional diversity between the two receptors.

Animals↗

PubMed2000

Significance of cyclin D1 overexpression for the diagnosis of mantle cell lymphoma: a clinicopathologic comparison of cyclin D1-positive MCL and cyclin D1-negative MCL-like B-cell lymphoma.

Mantle cell lymphoma (MCL) is a distinct clinicopathologic entity of non-Hodgkin's lymphoma, characterized by a monotonous proliferation of small to medium-sized lymphocytes with co-expression of CD5 and CD20, an aggressive and incurable clinical course, and frequent t(11;14)(q13;q32) translocation. We examined 151 cases of lymphoma with MCL morphology from a viewpoint of cyclin D1 overexpression, which is now easily detectable by immunohistochemistry. 128 cases (85%) showed positive nuclear staining for cyclin D1, while the remaining 23 (15%) were negative. Except for cyclin D1 immunohistochemistry, current diagnostic methods, including morphological and phenotypical examinations, could not make this distinction. Although both the cyclin D1-positive and -negative groups were characterized by male predominance, advanced stages of the disease, frequent extranodal involvement, and low CD23 reactivity, the cyclin D1-positive group showed a higher age distribution (P =.04), larger cell size (P =.02), higher mitotic index (P =.01), more frequent gastrointestinal involvement (P =.05), higher international prognostic index score (P =.05), and lower p27(KIP1) expression (P <.0001). Of particular interest is that cyclin D1-positive MCL showed significantly worse survival than cyclin D1-negative lymphoma (5-year survival: 30% versus 86%, P =.0002), which was confirmed by multivariate analysis to be independent of other risk factors. These data suggest that cyclin D1-positive and -negative groups may represent different entities and that the former closely fits the characteristics of classical, typical MCL. We therefore propose that cyclin D1-positivity should be included as one of the standard criteria for MCL, and that innovative therapies for this incurable disease should be explored on the basis of the new criteria.

Adult↗

PubMed2000

Changes in the inactivation of rat Kv1.4 K(+) channels induced by varying the number of inactivation particles.

N-type inactivation of rat Kv1.4 channels with one, two, or four inactivation balls was investigated using homogeneous populations of channels expressed in Xenopus oocytes. Tandem dimeric and tetrameric constructs of Kv1.4 were made. Channels encoded by tandem cDNAs Kv1. 4-Kv1.4Delta1-145 and Kv1.4-[Kv1.4Delta1-145](3) have two or only one tethered inactivation ball, respectively, whereas Kv1.4 itself encodes channels having four inactivation balls. The time constants for inactivation of macroscopic currents were increased significantly as the number of inactivation balls was decreased, whereas the time constants for recovery from inactivation were not modified. The ratios of the rate constants of inactivation (k(inact)) of Kv1.4-Kv1.4Delta1-145 and Kv1.4-[Kv1.4Delta1-145](3) channels to that of the Kv1.4 channel were 0.65 and 0.4, respectively, whereas the ratios of the rate constant of recovery (k(rec)) of these channels to that of Kv1.4 were almost unity. The rate constants k(inact) for channels having two and four inactivation balls are smaller than those that would be expected if inactivation balls on each channel are independent, suggesting some interaction occurs between inactivation balls. Furthermore, noninactivating current became apparent as the number of inactivation balls on a channel was decreased.

Animals↗

PubMed2000

Inhibitory effect of novel oral hypoglycemic agent nateglinide (AY4166) on peptide transporters PEPT1 and PEPT2.

The novel oral hypoglycemic agent nateglinide (AY4166) is a nonsulfonylurea insulin secretagogue, and its pharmacokinetic features include rapid absorption and elimination. As nateglinide is a dipeptide-like drug, we investigated the interaction of nateglinide with peptide transporters PEPT1 and PEPT2, which mediate the absorption of various peptide-like drugs. Nateglinide exhibited a potent inhibitory effect on [14C]glycylsarcosine uptake by the human colon adenocarcinoma cell line Caco-2 and rat PEPT-transfectants. Kinetic analysis revealed that these inhibitory effects were noncompetitive. Na(+)-coupled alanine or threonine uptake by Caco-2 cells was not inhibited by nateglinide, suggesting that the inhibitory effect of nateglinide on peptide transporters was not due to nonspecific interaction. There was little uptake of [14C]nateglinide by peptide transporters. Various sulfonylureas, such as glibenclamide, also inhibited [14C]glycylsarcosine uptake by rat PEPT-transfectants. In conclusion, nateglinide as well as sulfonylureas inhibit the transport activity of PEPT1 and PEPT2, although nateglinide itself is not transported by these transporters.

Administration, Oral↗

PubMed2000

Electrophysiological effect of l-cis-diltiazem, the stereoisomer of d-cis-diltiazem, on isolated guinea-pig left ventricular myocytes.

l-cis-Diltiazem, the stereoisomer of the L-type Ca(2+) channel blocker d-cis-diltiazem, protects cardiac myocytes from ischemia and reperfusion injury in the perfused heart and from veratridine-induced Ca(2+) overload. We determined the effect of l-cis-diltiazem on the voltage-dependent Na(+) current (I(Na)) and lysophosphatidylcholine-induced currents in isolated guinea-pig left ventricular myocytes by a whole-cell patch-clamp technique. l-cis-Diltiazem inhibited I(Na) in a dose-dependent manner without altering the current-voltage relationship for I(Na) (K(d) values : 729 and 9 microM at holding potentials of -140 and -80 mV, respectively). A use-dependent block of I(Na), the leftward shift of the steady-state inactivation curve and the delay of recovery from inactivation suggest that l-cis-diltiazem has a higher affinity for the inactivated state of Na(+) channels. In addition to I(Na), the lysophosphatidylcholine-induced currents were inhibited by l-cis-diltiazem in a similar concentration range. It is suggested that inhibition of both Na(+) channels and lysophosphatidylcholine-activated non-selective cation channels contributes to the cardioprotective effect of l-cis-diltiazem.

Animals↗

PubMed2000

NKT cells in the rat: organ-specific distribution of NK T cells expressing distinct V alpha 14 chains.

Rat invariant TCR alpha-chains and NKT cells were investigated to clarify whether CD1d-mediated recognition by NKT cells is conserved further in evolution. Rats had multiple-copies of TRAV14 genes, which can be categorized into two types according to the diversity accumulated in the CDR2 region. Rats retained invariant TCR alpha forms with the homogeneous junctional region similar to mouse invariant TRAV14-J281. The proportion of invariant TCR among V alpha 14+ clones was 12.9% in the thymus and increased in the periphery, 31% in the spleen and 95% in hepatic sinusoidal cells. The invariant TRAV14-J281 was expressed by liver sinusoidal and splenic NKT cells with CD8, CD44high, and TCR V beta 8. Type 1 invariant TCR alpha was expressed more frequently in hepatic lymphocytes, while type 2 invariant TCR alpha was expressed predominantly in the spleen. Both types of cells cytolyzed to and were stimulated to proliferate by CD1d-expressing cells in a CD1d-restricted manner. These results suggested that rat NKT cells bearing distinct V alpha 14 chains are distributed in a tissue-specific pattern. NKT cell populations in rats were more variable than those in mice, indicating that they play novel roles in nature. The implication of the molecular interaction between the structurally diverse invariant TCR alpha and CD1d/ligand complex in different organs is discussed.

Amino Acid Sequence↗