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Biomedical subjects

T Endo

Publications and source records attributed to T Endo.

At least 577 records · Page 32Linked to original sources
PubMed1995

Increase in oxygen tension after intraperitoneal N-methyl-DL-aspartate in rat cerebral cortex.

An oxygen electrode equipped with a thermocouple enabled us to determine the absolute oxygen tension (PO2) in brain regions by taking account of local changes in temperature. Under urethane anesthesia, the PO2 of rat cerebral cortex was significantly increased up to 90 min after N-methyl-DL-aspartate administration (200 mg/kg, i.p.). This suggests that stimulation of NMDA receptors enhances oxygen supply to the cerebrum in vivo.

Animals↗
PubMed1995

Interindividual variation in carboxylesterase levels in human liver microsomes.

Microsomal carboxylesterase activities in 12 human livers were determined using 10 kinds of carboxylesterase substrates (p-nitrophenylacetate, p-nitrophenylpropionate, p-nitrophenylbutyrate, butanilicaine, isocarboxazid, palmitoyl-coenzyme-A, malathion, clofibrate, acetanilide, and phenacetin). There were large individual differences in the 12 humans based on experimental results in the past several years in our laboratory. We found that all human liver microsomes have RH1-immunoreactive carboxylesterase, and the carboxylesterase content in liver also showed large individual differences. The RH1-immunoreactive carboxylesterase concentration correlated well with those of p-nitrophenylesters, clofibrate, butanilicaine, and isocarboxazid, and anti-RH1 immunoglobulin G strongly inhibited human liver hydrolase activity. These findings indicate that one major carboxylesterase isozyme that is immunoreactive with anti-RH1 in human liver microsomes has catalytic activity on major carboxylesterase substrates, and thus hydrolase activity in human liver depends on the expression level of this carboxylesterase isozyme. These observations should be useful in understanding the action of carboxylesterases on drug metabolism in humans.

Adult↗
PubMed1995

Biological effects of diesel exhaust particles (DEP) on tissues and cells isolated from respiratory tracts of guinea pigs.

Diesel engine-powered vehicles emit some 30 to 100 times more particles than do gasoline engine cars. We previously reported that diesel exhaust particles (DEP) instilled intratracheally into mouse caused lung edema accompanying endothelial cell damage. In order to clarify further the biological effects of DEP on the respiratory system, the primary target of DEP instillation, we examined the direct action of DEP on isolated tissues and the cytotoxicity of DEP on cultured cells of respiratory tracts in guinea pigs. DEP were collected on glass fiber filters from a light-duty (2730 cc), four cylinder diesel engine. DEP induced a dose-dependent relaxation in tracheal smooth muscle and lung parenchymal preparations from guinea pigs. Neither propranolol nor ranitidine inhibited the relaxing effect of DEP on tracheal preparations. DEP also exhibited concentration- and time-dependent cytotoxicity on cultured tracheal smooth muscle cells and lung fibroblasts from guinea pigs, as assessed by specific [51Cr] release. These cytotoxicities induced by DEP were significantly inhibited by catalase, deferoxamine and MK-447, whereas SOD and mannitol had little effect. These inhibitory effects were blunted by the higher concentration of DEP. These results suggest that the cytotoxicity of DEP may cause dysfunction of respiratory tissues, which are mediated via oxygen radicals, probably hydroxyl radicals or hydrogen peroxides.

Animals↗
PubMed1995

[Increased production of nitric oxide in the immediate and late asthmatic responses in models of guinea pig experimental asthma].

Nitric oxide is produced in mammalian airways by constitutive and inducible nitric oxide synthase, and endogenous nitric oxide can be detected as exhaled gas. Patients with asthma have large numbers of airway epithelial cells and inflammatory cells that contain nitric oxide synthase, and nitric oxide levels in exhaled air are high during immediate asthmatic responses. To examine the dynamics of nitric oxide synthase in the tracheas of guinea pigs, cumulative dose-response studies of 5-HT were done on tracheal strips, in the presence or absence of arginine and its analogues. This assay indicated that relative the activity of nitric oxide synthase was greater 6 hr after the challenge than immediately after, which suggests that nitric oxide is involved in the pathogenesis of bronchial asthma attacks.

Animals↗
PubMed1994

Identification of the SecA protein homolog in pea chloroplasts and its possible involvement in thylakoidal protein transport.

Recently, we identified the SecA and SecY proteins in the cyanobacterium Synechococcus PCC7942. Antibodies raised against cyanobacterial SecA specifically reacted with a 110-kDa protein of pea chloroplasts, suggesting the presence of SecA in higher plant chloroplasts. A part of the pea secA cDNA was polymerase chain reaction-amplified with degenerated oligonucleotide primers and with pea cDNA as a template. The deduced amino acid sequence shows 62% identity with cyanobacterial SecA and 52% identity with Escherichia coli SecA. Antibodies raised against the pea SecA fragment, which was expressed in E. coli cells from the obtained polymerase chain reaction-amplified cDNA, reacted with the 110-kDa chloroplast protein; the 110-kDa protein was mainly found in the stroma but partly in the thylakoid membrane. The anti-pea SecA IgG inhibited the in vitro import of the 33-kDa protein of the oxygen-evolving complex, but not of the 23-kDa protein of the oxygen-evolving complex, into thylakoids. These results suggest that SecA facilitates transport of a subset of thylakoid lumenal proteins including the 33-kDa protein into thylakoids. We propose that a bacterial-type Sec protein-dependent transport system operates for protein transport into thylakoids in higher plant chloroplasts.

Amino Acid Sequence↗
PubMed1994

Structure of the rat thyroid transcription factor-1 (TTF-1) gene.

TTF-1 is a homeodomain-containing thyroid transcription factor which activates the genes of thyroid specific protein, thyroglobulin, thyroid peroxidase and thyrotropin receptor. We have cloned the TTF-1 gene from rat liver genomic library, and the exon/intron organization and the structure of the 5' flanking region were determined. The clone contained the 5.2 kbp upstream sequence from translation initiation site, and we found that the gene has a single intron in the coding sequence. We found in the 5' flanking region the TTF-1 binding consensus sequence, CTCAAGC, at -175 to -169, which overlaps the consensus sequence of CAAT box, DNase I foot print analysis has revealed that the region is protected by nuclear extract from thyroid cells but not by the extract from the liver, suggesting that expression of the TTF-1 gene is autoregulated by TTF-1.

Animals↗
PubMed1994

Chloroplast protein import. Chloroplast envelopes and thylakoids have different abilities to unfold proteins.

Proteins have to be at least partially unfolded upon passage through the biological membranes. Previous studies with a dihydrofolate reductase fusion protein containing a chloroplast transit peptide showed that stabilization of the tertiary structure of the fusion protein by binding of a ligand, methotrexate, failed to block its translocation across the envelopes, suggesting that chloroplast envelopes have strong activity to unfold proteins [America, T., Hageman, J., Guéra, A., Rook, F., Archer, K., Keegstra, K. & Weisbeek, P. (1994) Plant Mol. Biol. 24, 283-294]. In the present study, we have analyzed in vitro translocation of a fusion protein consisting of the entire plastocyanin precursor and dihydrofolate reductase across the chloroplast envelope membranes and the thylakoid membrane. In the presence of methotrexate, the fusion protein was imported into the stroma but its translocation across the thylakoid membrane was blocked. The fusion protein that bound to the envelope became susceptible to digestion by thermolysin. These results suggest that, while the envelope membranes can unfold the methotrexate-bound fusion protein to allow its passage, the thylakoid membrane cannot unfold the fusion protein that has re-bound to methotrexate in the stroma.

Amino Acid Sequence↗
PubMed1994

Phosphorylation of a proline-directed kinase motif is responsible for structural changes in myogenin.

Myogenin, a member of the MyoD family which governs skeletal muscle differentiation, was identified as a pair of phosphorylated bands on SDS-PAGE during myogenesis. The slow migrating form was found to be hyperphosphorylated myogenin. In vitro phosphorylation by CDC2 kinase caused a prominent reduction in electrophoretic mobility of myogenin. Furthermore, we demonstrated that phosphorylation of the serine residue at position 43 contributes to the modification of myogenin in vivo and in vitro resulting in the reduction in electrophoretic mobility. We propose here that a CDC2-like proline-directed kinase regulates myogenin activity through its phosphorylation.

Amino Acid Sequence↗
PubMed1994

Increased expression of acidic ribosomal protein (P0) mRNA after phorbol ester treatment of cultured rat thyroid (FRTL-5) cells.

P0, an acidic protein component of the ribosomal protein in eukaryotic 60 S ribosomal subunit, plays an important role in polypeptide chain elongation during translation. To investigate the role of protein kinase C in thyroid cell protein synthesis, we examined the effect of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on the expression of P0 mRNA and protein. RNA slot blot hybridization revealed that TPA induced the accumulation of P0 mRNA in FRTL-5 cells in a time- and dose-dependent manner. A maximal increase of 2-fold was observed 18 h after addition of TPA. Cycloheximide markedly inhibited the TPA-induced accumulation of P0 mRNA. Nuclear runoff transcription assays using nuclei prepared from TPA-treated FRTL-5 cells revealed that TPA increased the transcription of P0 mRNA but not of beta-actin. Immunoblotting experiments using anti-P protein antibody showed that TPA also increased the protein amount of P0. These results suggest that TPA activates protein synthesis in thyroid cells by inducing the expression of ribosomal proteins.

Actins↗
PubMed1994

Structural study on the glycosyl-phosphatidylinositol anchor and the asparagine-linked sugar chain of a soluble form of CD59 in human urine.

CD59 is an 18-kDa glycoprotein widely expressed on human cells. An important structural feature of CD59 is its attachment to the cell surface via a glycosyl-phosphatidylinositol (GPI) anchor. CD59, like many GPI-anchored proteins, has been found in urine, serum, and other body fluids. The structures of the GPI anchor and the asparagine-linked sugar chain of a soluble form of CD59 in urine, U-CD59, were determined. Purified U-CD59 released 1 mol of inositol per mole of protein by nitrous acid deamination, which cleaved between glucosamine and inositol present commonly in the GPI anchor. This indicates that a GPI anchor, which ended with inositol, is linked at the carboxy terminus of U-CD59. The peptide containing an asparagine-linked sugar chain and the peptide containing a glycan portion of the GPI anchor were isolated after trypsin digestion of U-CD59. The asparagine-linked sugar chains and the glycan portion of the GPI anchor were isolated from these peptides following hydrazinolysis or deamination and dephosphorylation, respectively. Their structures were analyzed by sequential exoglycosidase digestion and methylation analyses. The structures of the asparagine-linked sugar chains of U-CD59 were biantennary complex type, only 4.2% of which are monosialylated. The backbone structure of the GPI anchor was similar to that of Try-panosoma brucei variant surface glycoprotein, but showed significant variations in its side-chain moieties. This is the first detailed structural analysis of the human GPI anchor and the first detailed analysis of the carboxyl-terminal structure of the soluble-form GPI-anchored protein. The results indicate that the backbone structure of the GPI anchor is conserved from parasites to human and that at least a part of the soluble-form GPI-anchored protein has the structure produced by the action of glycan-phosphatidylinositol-specific phospholipase D.

Antigens, CD↗
PubMed1994

Studies on the induction of cyclooxygenase isozymes by various prostaglandins in mouse osteoblastic cell line with reference to signal transduction pathways.

A mouse osteoblastic cell line MC3T3-E1 has a cyclooxygenase enzyme, and produces prostaglandin E2. When the cells were cultured in the presence of iloprost (a stable analogue of prostacyclin) or prostaglandin E1 or F2 alpha, the activity of cyclooxygenase increased in a dose- and time-dependent manner. The increase of the enzyme activity was attributed mostly to the cyclooxygenase isoform-2 because immunoprecipitation using an anti-cyclooxygenase-2 antibody removed the majority of the cyclooxygenase activity from the solubilized enzyme fraction, and the corresponding activity was detected in the immunoprecipitant. In addition, there was a marked increase in the cyclooxygenase-2 protein which was demonstrated by Western blotting. As analyzed by Northern blotting, the cyclooxygenase-2 mRNA increased and reached a maximum 1 and 3 h after the addition of iloprost and prostaglandin F2 alpha (about 15- and 60-fold increase), respectively, whereas the cyclooxygenase-1 mRNA increased slowly and only by about 3-fold. Iloprost and prostaglandin E1 stimulated the production of cAMP by 60-fold over the basal level, whereas the cAMP level was almost unchanged by prostaglandin F2 alpha. In contrast, prostaglandin F2 alpha stimulated IP3 production more efficiently than iloprost and prostaglandin E1. These results suggest that the stimulated syntheses prominently of cyclooxygenase-2 and to a lesser extent of cyclooxygenase-1 are mediated by at least two distinct signal transduction pathways involving the cAMP-synthesis stimulated by iloprost and prostaglandin E1 and the phosphoinositide turnover stimulated by prostaglandin F2 alpha.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Activin A stimulates mitogenesis in Swiss 3T3 fibroblasts without activation of mitogen-activated protein kinases.

Activin A stimulated DNA synthesis and transient c-fos expression in quiescent Swiss 3T3 fibroblasts. The activin A-induced DNA synthesis was dose-dependent with a half-maximal effect obtained at 0.3 nM. The maximal response obtained at 10 nM was comparable with that induced by 5 ng/ml basic fibroblast growth factor. Swiss 3T3 fibroblasts expressed abundant high affinity binding sites for 125I-labeled activin A with a Kd value of 0.63 nM and the number of binding sites at 24,000/cell. Northern blot analysis revealed that Swiss 3T3 fibroblasts express a high level of type II activin receptor mRNA. In an attempt to elucidate the mechanism of mitogenic action of activin A, we examined the effect of activin A on mitogen-activated protein kinase activation. Unexpectedly, however, activin A did not induce kinase activation under conditions in which basic fibroblast growth factor and endothelin-1 at similar or even less potent mitogenic concentrations did. Furthermore, activin A did not induce phosphorylation of the Erk2 species of mitogen-activated protein kinase. These observations strongly suggest that the activation of mitogen-activated protein kinase is not a necessary step for activin A-induced DNA synthesis in Swiss 3T3 fibroblasts.

3T3 Cells↗
PubMed1994

Identification and characterization of the sec-A protein homologue in the cyanobacterium Synechococcus PCC7942.

The secA gene product mediates protein translocation across the cytoplasmic membrane in Escherichia coli. We have cloned a gene homologous to secA from the genome of the cyanobacterium Synechococcus PCC7942. The deduced amino acid sequence, 948 amino acids long, shows 43% homology with that of the E. coli secA and 47-48% homology with those of the algal plastid secA genes. Upon subcellular fractionation, the cyanobacterial SecA protein was mainly found as soluble homodimer in the cytosol, but the remaining small but distinct fraction was associated with both the cytoplasmic and thylakoid membranes. The SecA protein likely participates in protein translocation across both the cytoplasmic and thylakoid membranes in cyanobacterial cells.

Adenosine Triphosphatases↗
PubMed1994

Yge1p, a eukaryotic Grp-E homolog, is localized in the mitochondrial matrix and interacts with mitochondrial Hsp70.

Yeast Yge1p, the gene product of YGE1, is a eukaryotic GrpE homolog found recently (Ikeda et al., 1994). We have revealed here that Yge1p is a soluble protein in the mitochondrial matrix. Depletion of Yge1p in yeast cells resulted in accumulation of the precursor of F1-ATPase beta subunit in vivo, suggesting that Yge1p is involved in protein import into mitochondria. Overexpression of Yge1p in the temperature-sensitive mutant strains of mitochondrial hsp70, Ssc1p, caused hypersensitivity to temperature for cell growth, suggesting a genetic interaction between the YGE1 and SSC1 genes. A physical interaction between Yge1p and Ssc1p was directly demonstrated by co-immunoprecipitation of Ssc1p by the anti-Yge1p antibodies. We propose that Yge1p functions in cooperation with Ssc1p in a similar manner as bacterial GrpE with DnaK.

Bacterial Proteins↗
PubMed1994

alpha-Actinin and vinculin are PIP2-binding proteins involved in signaling by tyrosine kinase.

Western blot analysis of Balb/c 3T3 cell lysates by an antibody specific to phosphatidylinositol 4,5-bisphosphate (PIP2) showed that several proteins exist in a PIP2-bound form. Among them, two proteins, 100 and 115 kDa in molecular mass, were detected as PIP2 abundant proteins. These were identified as alpha-actinin and vinculin by their antibodies. In Balb/c 3T3 cells, alpha-actinin in the cytoskeleton contains PIP2, while alpha-actinin in cytosol does not. The levels of PIP2 bound to alpha-actinin decrease in response to platelet-derived growth factor (PDGF). Similarly, PIP2 bound to vinculin is decreased upon stimulation with PDGF. By immunofluorescent staining, PIP2 was found to be present densely in the central areas around nuclei, microfilament bundles, and focal contacts, where alpha-actinin and vinculin are distributed. PDGF stimulation decreases the intensity of PIP2 staining in these areas. In this paper we suggest that tyrosine kinase-activated phospholipase C hydrolyzes PIP2 bound to alpha-actinin and vinculin, leading to the simultaneous generation of second messengers and reorganization of the cytoskeleton.

3T3 Cells↗