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Biomedical subjects

S Toyoshima

Publications and source records attributed to S Toyoshima.

At least 19 recordsLinked to original sources
PubMed1995

Methylmalonic acid inhibits respiration in rat liver mitochondria.

Methylmalonic acid (MMA), which accumulates and is excreted in urine in mammals during vitamin B-12 deficiency, has been reported to inhibit succinate dehydrogenase, an enzyme involved in the mitochondrial tricarboxylic acid (TCA) cycle in rat liver. The enzyme inhibition by MMA may lead to various metabolic disorders as well as inhibition of mitochondrial energy generation in vitamin B-12-deficient mammals. To clarify the inhibition of succinate dehydrogenase by MMA in intact rat liver mitochondria, the effect of MMA on mitochondrial respiration was studied. When 6 mmol/L MMA was added to the reaction mixture for measuring mitochondrial respiration with succinate as a substrate, MMA was taken up and accumulated by the mitochondria (34-53 mmol/L). The accumulation of mitochondrial MMA was stimulated by the addition of ADP. Methylmalonic acid competitively inhibited State 3 mitochondrial respiration, and the Ki for the acid was 4.2 +/- 0.4 mmol/L. Although the respiratory control ratio decreased with increasing MMA concentration, the acid did not affect the phosphorus/oxygen ratio. Mitochondrial MMA accumulation secondary to vitamin B-12 deficiency inhibits succinate dehydrogenase and may contribute to various metabolic disorders associated with vitamin B-12 deficiency.

Adenosine Diphosphate↗
PubMed1995

Recognition of consensus CHO structure in ligands for selectins by novel antibody against sialyl Lewis X.

The selectins (L, E, and P) play an important role in the earliest events of the inflammatory response, leading to the "rolling" phenomenon. All selectins react with sialyl Lewis X (SLex) in vitro, possibly suggesting that their ligands have a consensus structure. 2H5 is a monoclonal antibody against SLex that blocks L-selectin-mediated adhesion. 2H5 inhibited adhesion of HL-60 cells to P- and E-selectin-producing COS cells in vitro and immunoprecipitated a P-selectin glycoprotein ligand-1-like glycoprotein from HL-60 cell lysate, suggesting that it recognizes a functional consensus structure on the ligands for all selectins. 2H5 reacted not only with human but also with rat and mouse neutrophils. 2H5 is the first antibody against SLex that recognizes neutrophils of nonhuman mammals. The carbohydrate structure recognized by 2H5 was present not only on high endothelial venules of rat lymphoid organs but also on the endothelial cells of nonlymphoid organs. Furthermore, administration of the antibody markedly inhibited L- and P-selectin-mediated neutrophil rolling and adhesion in rat mesenteric venules in vivo. These results provide evidence for the presence of a consensus carbohydrate structure on the ligands for all selectins. The consensus structure thus has the potential to serve as a therapeutic target.

Animals↗
PubMed1992

Transcriptional regulation of the c-jun gene by retinoic acid and E1A during differentiation of F9 cells.

Differentiation of mouse F9 embryonal carcinoma (EC) cells can be induced by exposure to retinoic acid (RA) or by expression of adenovirus E1A. The transcription of the c-jun gene is stimulated by either RA or E1A. We report here that both RA and E1A strongly induce the expression of chloramphenicol acetyltransferase (CAT) from c-jun promoter/CAT reporter construct (c-jun/CAT), which is stably integrated into F9 cells, in a manner that is independent of both copy number and integration locus. The induction of c-jun/CAT expression is observed in undifferentiated F9 cells, but not in differentiated F9 cells, adenovirus-infected F9 cells or HeLa cells. Deletion analysis of the promoter region of the c-jun gene indicates that the sequence elements required for the RA- and E1A-mediated induction are identical and they have been defined as a region of 145 bp between -190 and -46 of the 5' flanking region of c-jun. This RA and E1A response element (RERE) contains five variants of the motif CGCGGTGACGNT. The upstream two motifs are adjacent and extend in opposite directions, creating an imperfect palindrome. The downstream four motifs are located at 35 or 36 bp intervals in the same orientation. Substitution and insertion analysis indicates that these motifs and their regular intervals are important for the activity of the RERE.

Adenoviruses, Human↗
PubMed1992

Surface glycoprotein of human natural killer cells recognized by wheat germ agglutinin.

We analyzed surface glycoproteins of human natural killer (NK) cells by utilizing lectins. Among the lectins tested, wheat germ agglutinin (WGA) was found to bind preferentially to CD16(Leu11)-positive lymphocytes as determined by two-colour flow cytometry. Analysis of glycoproteins in the lysate prepared from NK cells with sodium dodecyl sulfate (SDS) gel electrophoresis followed by Western blotting and 125I labeled WGA staining revealed that a glycoprotein with an M(r) of 65 kDa was strongly bound to the lectin, but no corresponding glycoprotein was detected in the lysate of T lymphocytes. This glycoprotein (GP65) gave several spots in the pI range 4.1-4.6 on 2-dimensional gel electrophoresis. Sialidase treatment of GP65 resulted in a single spot on the 2-dimensional gel, suggesting that GP65 is heterogeneous in the degree of sialylation. GP65 was shown to be exposed on the cell surface, since it was radiolabeled with 125I by the lactoperoxidase-catalyzed method. We next isolated GP65 from human peripheral blood lymphocytes by a combination of chromatography on a cation-exchange column and a WGA-agarose column and preparative SDS gel electrophoresis. It is suggested that GP65 is a novel surface glycoprotein on human NK cells.

Chromatography, Affinity↗
PubMed1992

Purification and cDNA cloning of a novel factor produced by a human T-cell hybridoma: sequence homology with animal lectins.

We have purified a novel immunoregulatory factor (BMPG: bone-marrow proteoglycan) produced by a T-cell hybridoma, with a monoclonal antibody column. Using an oligonucleotide probe corresponding to the partial amino acid sequence of BMPG, we cloned, sequenced, and expressed a cDNA for BMPG. BMPG has 222 amino acid residues with a 16 N-terminal signal sequence, so the mature form has 206 amino acid residues. BMPG was found to have unique characteristics: it has three types of sugar chains and it shows a marked homology with animal lectins including the human asialoglycoprotein receptor, chicken hepatic lectin and the homing receptor of lymphocytes.

Amino Acid Sequence↗
PubMed1992

Subunit-specific sulphation of oligosaccharides relating to charge-heterogeneity in porcine lutrophin isoforms.

Lutrophin (LH) consists of an array of isoforms with different charges and bioactivities. This study was undertaken to clarify specifically how oligosaccharides of alpha and beta subunits contribute to LH isoform charges. Porcine LH (pLH) was separated into four isoforms by isoelectric focusing (IEF), followed by subunit isolation. Their oligosaccharides were released by hydrazinolysis, labelled by reduction with NaB3H4, and fractionated by HPLC with a Mono Q column into five populations differing in the number of sulphate (S) and sialic acid (N) residues, designated as Neutral, N-1, S-1, S-N and S-2. Oligosaccharides were predominantly sulphated (S-1 and S-2) and infrequently sialylated (N-1 and S-N). Further analysis, including concanavalin A (Con A) affinity chromatography, desialylation, desulphation, sequential exoglycosidase digestion and methylation, clarified the structures of the acidic oligosaccharides. All were of the biantennary complex type. Their two peripheral branches were SO4-4GalNAc beta 1-4Glc-NAc and GalNAc beta 1-4GlcNAc or GlcNAc in S-1, SO4-4GalNAc beta 1-4GlcNAc and Sia alpha 2-6Gal beta 1-4GlcNAc in S-N, and (SO4-4GalNAc beta 1-4GlcNAc)2 in S-2 (where GalNAc is N-acetylgalactosamine and GlcNAc is N-acetylglucosamine). Ten percent of S-1 and of S-N had a bisecting GlcNAc residue. Sulphate residues occurred in nearly the same amount for both subunits; however, the alpha and beta subunits were sulphated differently. S-1 predominated in the alpha subunit, while S-1 and S-2 were major components in the beta subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Molecular cloning and expression of cDNA encoding a galactose/N-acetylgalactosamine-specific lectin on mouse tumoricidal macrophages.

We previously reported that the mouse macrophage galacose and N-acetylgalactosamine-specific lectin (MMGL) may participate in the binding of the macrophages to tumor cells [Oda, S., Sato, M., Toyoshima, S., & Osawa, T. (1989) J. Biochem. 105, 1040-1043]. We now report the cloning and characterization of a cDNA encoding MMGL. The MMGL gene encoded a protein consisting of 304 amino acid residues with a molecular weight of 34,595. The deduced amino acid sequence indicated that MMGL had a single membrane-spanning region, three leucine zipper-like domains, and a carbohydrate recognition domain. Two N-glycosylation sites were found in the extracellular region of MMGL, corresponding to the heavy N-glycosylation in the native MMGL. Comparison of the amino acid sequence of MMGL with those of rat hepatic lectins revealed a high overall sequence homology. The sequence homology was especially high in the putative membrane-spanning region and carbohydrate recognition domain. There was, however, a region of 25 amino acids which did not exist on hepatic lectins. The MMGL cDNA without the region encoding the putative membrane-spanning region and intracellular region was expressed in Escherichia coli. The expressed protein had galactose-binding activity and its sugar-binding specificity was same as that of the native lectin.

Acetylgalactosamine↗
PubMed1992

Damage to mitochondrial respiration chain is related to phospholipase A2 activation caused by tumor necrosis factor.

Tumor necrosis factor (TNF) has been shown to be cytotoxic to tumor cell lines in vitro, but the mechanism by which TNF exerts its cell growth-regulatory effects is not known. In this report, we used various inhibitors to investigate the sequence of events that lead to cytotoxic effects of TNF on L.P3 cells, a highly sensitive, murine fibroblast cell line. Our results indicate that mitochondrial respiration chains are damaged by a hydroxyl radical at an early stage of the cell lysis after TNF treatment. This event is followed by the activation of phospholipase A2, and finally leads to cell lysis.

Animals↗
PubMed1992

Invasive ductal carcinoma of the breast with a predominant intraductal component: cooperative clinicopathologic study in seven Japanese centers.

A nationwide multicenter joint study was undertaken to investigate the clinicopathologic characteristics of invasive ductal carcinoma of the breast with a predominant intraductal component, a diagnostic entity proposed in the histologic typing of breast tumors by the World Health Organization in 1981. A total of 368 tumors, of which 218 were studied pathologically between 1983 and 1987 and 150 between 1971 and 1977, were accumulated for the present study from seven medical institutes in Japan. The incidence of such types of tumor was higher in the latter period than in the former, as was that of pure intraductal carcinomas. Seventy of the 368 tumors displayed metastatic nodal involvement and nine tumor deaths were observed from 150 tumors followed up for over 10 years following radical mastectomy, the overall quantity of the extraductal stromal invasion clearly acting on lymph node metastases and patients' outcome. We consider a total stromal invasion of greater than 5 mm to be critical in the prognosis of patients with tumor of this type.

Breast↗
PubMed1991

Enhancement by IL-1 beta and IFN-gamma of platelet activation: adhesion to leukocytes via GMP-140/PADGEM protein (CD62).

We have examined the effect of inflammatory cytokines on the platelet activation. IL-1 beta and IFN-gamma were found to enhance the adhesion of thrombin-treated platelets to monocytic leukemia cells (U937), when the adhesion was assayed by platelet-mediated cell agglutination. The agglutination was inhibited by a monoclonal anti-GMP140 antibody or EDTA, suggesting that the enhanced platelet adhesion to the leukemic cells was mediated by GMP140. In addition, these cytokines also increased the release of 5-HT from platelets in the presence of a low concentration of thrombin. These data suggest that platelet functions are regulated by the cytokines and that activated platelets participate in inflammatory process.

Blood Platelets↗
PubMed1991

TNF-mediated cytotoxicity. Importance of intracellular cGMP level for determining TNF-sensitivity.

Previous work on the cytolytic action of activated macrophages indicated that tumor necrosis factor (TNF) showed synergistic cytolytic activity with NO, which has been shown to act as a cyclic GMP (cGMP) generator [Higuchi et al., J. Immun. 144, 1425-1431, (1990)]. In this study, we investigated the relationship between the accumulation of intracellular cGMP and the cytotoxic action of TNF. It was demonstrated that TNF-mediated cell lysis was closely related to the background level of intracellular cGMP, and that the accumulation of cGMP within TNF resistant cells induced TNF sensitivity. We reached these conclusions on the basis of the following results; (1) agents (sodium nitroprusside and isobutylmethylxantine) that cause the accumulation of cGMP intracellularly increased the TNF-sensitivity of TNF-resistant cells; (2) the addition of dibutyryl cGMP to TNF-resistant cells increased the TNF-sensitivity; and (3) treatment at 40 degrees C or agents such as interferon gamma and actinomycin D, that synergistically kill tumor cells together with TNF, potentially increased the cGMP level. Therefore, intracellular cGMP may be one of the key molecules that lead to cell death caused by TNF.

Animals↗
PubMed1991

Mechanism of immunosuppression by a murine non-specific suppressor T cell line, SB-1.

The mechanism of immunosuppression by a murine non-specific suppressor T cell clone (SB-1), which was established from concanavalin A (Con A)-activated murine spleen cells [Jpn. J. Exp. Med., 53, 139 (1983)], was investigated. SB-1-induced decrease of antigen non-specific plaque-forming cell (PFC) response was restored by the addition of 5 x 10(-6) M indomethacin, an inhibitor of cyclooxygenase. On the other hand, suppressive activity for antigen non-specific PFC response was found in the culture supernatant of SB-1 cells in the presence of proteose peptone-elicited macrophages. This induction of the suppressive activity was also inhibited by 5 x 10(-6) M indomethacin. Furthermore, 10(-5) M prostaglandine E2 (PGE2) was found to induce suppressive activity in the culture supernatant of SB-1 cells. 10(-5) M PGE2 did not suppress interleukin-2 (IL-2)-dependent proliferation of SB-1 cells, but increased a small quantity of protein synthesis and deoxyribonucleic acid (DNA) synthesis of SB-1 cells in the absence of IL-2. These results suggest that a cyclooxygenase product(s) such as PGE2 from macrophages may induce production of soluble suppressor factors in SB-1 cells. To characterize these suppressor factors, those in the culture supernatant of PGE2-stimulated SB-1 cells were partially purified by ammonium sulfate fractionation and sequential column chromatographies on diethylaminoethyl (DEAE)-cellulofine and Sephacryl S-200. Suppressor activities were eluted at the positions corresponding to the molecular masses of 10, 30, 70 and over 70 kilodalton (kDa) on Sephacryl S-200 column chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ductal carcinoma of the breast. An analysis of proportions of intraductal and invasive components.

One hundred and ninety patients with mammary ductal carcinoma were studied to evaluate the correlation of proportions of intraductal and invasive tumor growth to histologic and immunohistochemical features. Initially, attempts were made to divide the cases into 6 groups according to the proportion of extraductal invasive areas within the whole tumor. It has been found that ductal carcinoma could be divided, on this criterion, into 2 groups. One comprised tumors in which invasive areas made up less than 20% of the tumor, the other included those with invasive areas exceeding 20%. In the former, intraductal and invasive components exhibited a lower grade of nuclear and tumor component and a higher incidence of cells with CEA immune positivity. The latter manifested higher grades in both intraductal and invasive components and a lower incidence of CEA positive cells. Many of the latter tumors had a solid or comedo-like growing pattern of the intraductal component. There was a significant difference in the prognosis between the two categories. We conclude that like intraductal carcinomas, invasive ductal carcinomas with a predominant intraductal component should be considered a lower grade malignancy.

Adult↗
PubMed1990

Purification and partial amino acid sequences of phosphoinositide-specific phospholipase C of Drosophila eye.

To examine whether the norpA (no receptor potential A) gene encodes a phosphoinositide-specific phospholipase C (PLC) in the eye of Drosophila, a major PLC in the extract from normal Drosophila heads, which was absent in the extract from norpA mutant heads, and purified and its partial amino acid sequences were determined. The purification of the major PLC in KCl extract from normal Drosophila heads was achieved by sequential column chromatography on DEAE-Sepharose CL-6B, Mono Q, Superose 12, Mono S, second Mono S, and second Mono Q, followed by column chromatography on Superose 12 in the presence of 1% sodium cholate. The enzyme thus purified was found to be homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 98,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme hydrolyzed both phosphatidylinositol (PI) and phosphatidylinositol 4,5-bisphosphate (PIP2). Interestingly, the calcium and pH requirements for activation of the crude enzyme (KCl extract) were quite different from those of partially purified enzyme (active fraction from second Mono Q column). The maximal activity for PIP2 hydrolysis was observed at calcium concentrations between 10(-7) and 10(-5) M for both the crude and partially purified enzymes. On the other hand, the activity for PI hydrolysis of the crude enzyme increased with increasing calcium concentrations, while that of the partially purified enzyme reached a maximum at calcium concentrations between 10(-6) and 10(-4) M, and decreased at millimollar concentration. The pH dependences for PI hydrolysis of the crude enzyme and the partially purified enzyme were similar. The crude enzyme hydrolyzed PIP2 over a broad pH range from 6 to 8.5, while the activity of the partially purified enzyme monotonously increased with increasing pH. The partial amino acid sequences were determined by treating the purified enzyme with endopeptidase Lys-C; the resultant peptide fragments were purified on a high performance liquid chromatography-reverse phase column and then sequenced with sequencer. The obtained sequences were found to be a part of the deduced amino acid sequences of cDNA which was suggested to be norpA gene.

Amino Acid Sequence↗
PubMed1990

Concanavalin A-induced receptor aggregation stimulates the tyrosine kinase activity of the insulin receptor in intact cells.

Concanavalin A (ConA) stimulated the phosphorylation of the beta-subunit of the insulin receptor and an Mr-185,000 protein on serine and tyrosine residues in intact H-35 rat hepatoma cells. This Mr-185,000 protein whose phosphorylation was stimulated by ConA was identical to pp185, a protein reported previously to be a putative endogenous substrate for the insulin receptor tyrosine kinase in rat hepatoma cells. In Chinese hamster ovary (CHO) cells transfected with cDNA of the human insulin receptor, tyrosine-phosphorylation of pp185 was strongly enhanced by ConA compared with the controls, suggesting that the induction of tyrosine-phosphorylation of pp185 was due to stimulation of the insulin receptor kinase by ConA. Moreover, monovalent ConA only slightly induced the tyrosine-phosphorylation of pp185, which was enhanced by the addition of anti-ConA IgG, suggesting that ConA stimulated the insulin receptor kinase mainly by the receptor cross-linking or aggregation in intact cells. These data suggest that the insulin-mimetic action of ConA is related to the autophosphorylation and activation of the insulin receptor tyrosine kinase, as well as the subsequent phosphorylation of pp185 in intact cells.

Animals↗