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H Matsubara

Publications and source records attributed to H Matsubara.

At least 271 records · Page 15Linked to original sources
PubMed1990

Diabetes-induced alterations in atrial natriuretic peptide gene expression in Wistar-Kyoto and spontaneously hypertensive rats.

We investigated the effects of streptozotocin-induced diabetes on atrial natriuretic peptide (ANP) synthesis, hemodynamic parameters, blood volume, and histopathology, as well as the reversibility of such effects with insulin therapy in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). The biatrial ANP messenger RNA (mRNA) levels in the diabetic WKY rats increased by 16-17% compared with those in the age-matched WKY rats at 12 weeks after the onset of diabetes, whereas their ventricular ANP mRNA levels showed increases of 190% in left ventricles and 160% in right ventricles at 8 weeks. In the diabetic SHRs, the left atrial ANP mRNA levels increased by 36% compared with those in the age-matched SHRs, as early as 4 weeks after diabetes onset. Their ventricular ANP mRNA levels also showed 80-82% increases in left and right ventricles at 4 weeks. In proportion to changes in cardiac ANP synthesis, the biventricular end-diastolic pressures were significantly elevated at 8 weeks in the diabetic WKY rats and at 4 weeks in the diabetic SHRs. The blood volume significantly increased at 8 weeks in the diabetic WKY rats and remained higher thereafter, whereas it did not change in the diabetic SHRs throughout the experimental period. The left ventricular peak dP/dt was depressed in the 8-week diabetic SHRs, whereas in the diabetic WKY rats, its depression was observed at 12 weeks after diabetes onset. Histopathological studies showed that diabetic changes in ANP synthesis and hemodynamic parameters described above occurred before the cardiomyopathic histological changes. Cardiac ANP synthesis in the diabetic rats completely reverted to control levels after insulin therapy, accompanied by normalization of hemodynamic parameters. The present study indicates that 1) ANP synthesis is significantly augmented in the streptozotocin-induced diabetic rat compared with that in the normal rat, and the combination of diabetes and hypertension produces an earlier and greater effect in stimulating cardiac ANP synthesis than does either disease alone; 2) an elevation in the intraventricular filling pressure that occurs before observable cardiomyopathic histopathological alterations might be involved partially in the augmented ANP synthesis; and 3) the reversibility with insulin therapy suggests that the streptozotocin-induced alterations observed in cardiac ANP synthesis and hemodynamics result from insulin-deficient diabetes mellitus, not from cardiac toxicity of streptozotocin.

Animals↗
PubMed1990

Stimulation of rat atrial natriuretic peptide (rANP) synthesis by triiodothyronine and thyroxine (T4): T4 as a prohormone in synthesizing rANP.

Thyroid hormones have been reported to increase the secretion and synthesis of atrial natriuretic peptide (ANP) in vitro. In this study, we focused on the role of type I T4 5'-deiodinase to investigate the stimulating effects of T4 on ANP synthesis and secretion by measuring cellular content and secretion into the medium of immunoreactive rat ANP (IR-rANP) and rANP mRNA levels in cultured rat neonatal atrial myocytes. Both T3 (10(-9)-10(-7) M) and T4 (10(-8)-10(-6) M) increased cellular content and secretion into the medium of IR-rANP in a dose-dependent manner. However, these effects of T4 were completely inhibited by the addition of propylthiouracil, which selectively suppressed type I T4 5'-deiodinase activity. Methimazole, which did not alter T4 5'-deiodinase activity, had no effects on T4-induced IR-rANP increase. In the measurements of rANP mRNA levels by dot blot analysis, T3 (10(-8) and 10(-7) M) and T4 (10(-7) and 10(-6) M) increased rANP mRNA levels in the same way as they increased IR-rANP content. Although T4-increased rANP mRNA levels were also inhibited by propylthiouracil, methimazole did not alter the effect of T4. Moreover, T4-induced rANP mRNA accumulation in atrial myocytes was further stimulated by the addition of dithiothreitol, suggesting that the deiodinating activity was thiol sensitive. These data suggest that the stimulating effect of T4 on cellular IR-rANP content and rANP mRNA levels is entirely induced after it is converted to T3 by type I T4 5'-deiodinase in atrial myocytes and that T4 serves as a prohormone for T3 in synthesizing rANP.

Animals↗
PubMed1989

Structure of [4Fe-4S] ferredoxin from Bacillus thermoproteolyticus refined at 2.3 A resolution. Structural comparisons of bacterial ferredoxins.

The structure of a low-potential ferredoxin isolated from Bacillus thermoproteolyticus has been refined by a restrained least-squares method. The final crystallographic R factor is 0.204 for 2906 reflections with F greater than 3 sigma F in the 6.0 to 2.3 A resolution range. The model contains 81 amino acid residues, one [4Fe-4S] cluster, and 59 water molecules. The root-mean-square deviation from ideal values for bond lengths is 0.018 A, and the mean coordinate error is estimated to be 0.25 A. The present ferredoxin is similar in the topology of the polypeptide backbone to the dicluster-type ferredoxins from Peptococcus aerogenes and Azotobacter vinelandii, but has considerable insertions and deletions of the peptide segments as well as different secondary structures. Although all but the C-terminal C zeta atoms of P. aerogenes ferredoxin superpose on the C alpha atoms of A. vinelandii ferredoxin, only 60% superpose on the C alpha atoms of B. thermoproteolyticus ferredoxin, with a root-mean-square distance of 0.82 A for each pair. The conformations of the peptide segments surrounding the [4Fe-4S] clusters in these three ferredoxins are all conserved. Moreover, the schemes for the NH...S hydrogen bonds in these ferredoxins are nearly identical. The site of the aromatic ring of Tyr27 in B. thermoproteolyticus ferredoxin is close spatially to that of Tyr28 in P. aerogenes ferredoxin with reference to the cluster, but these residues do not correspond in the spatial alignment of their polypeptide backbones. We infer that in monocluster-type ferredoxins, the side-chain at the 27th residue has a crucial effect on the stability of the cluster. Of the four cysteine residues that bind to the second Fe-S cluster in the dicluster-type ferredoxins, two are conserved in the monocluster-type ferredoxins from Desulfovibrio gigas. D. desulfuricans Norway, and Clostridium thermoaceticum. The tertiary structure of B. thermoproteolyticus ferredoxin suggests that in such monocluster-type ferredoxins these two cysteine residues, which in it correspond to Ala21 and Asp53, form a disulfide bridge.

Amino Acid Sequence↗
PubMed1989

The amino acid sequence of a flavodoxin from the eukaryotic red alga Chondrus crispus.

The amino acid sequence of the constitutive flavodoxin from the red alga Chondrus crispus was determined from the analyses of peptide fragments derived by enzymic digestions of the carboxymethylated protein. This is the first sequence reported for a flavodoxin from a eukaryote. The protein is composed of 173 amino acid residues and is a member of the longer-chain group of flavodoxins. The extent of sequence homology to the three other flavodoxins in the group for which sequences are available is in the range 36-39%, with the most strongly conserved regions being those implicated in binding of the FMN, the redox-active prosthetic group. Nevertheless, Chondrus crispus flavodoxin stands apart in a number of respects, in particular the possession of an unusually high content of proline, with these residues distributed more or less regularly along the peptide chain.

Amino Acid Sequence↗
PubMed1989

A single amino acid substitution in B subunit of Escherichia coli enterotoxin affects its oligomer formation.

We isolated a mutant strain of enterotoxigenic Escherichia coli by nitrosoguanidine mutagenesis, which produces an immunologically altered B subunit of heat-labile enterotoxin. This mutant B subunit was detected as a monomer on sodium dodecyl sulfate-polyacrylamide gel electrophoresis even without prior heating, suggesting a problem in oligomer formation. Furthermore, this mutant B subunit could not form holotoxin with the native A subunit, and the affinity to GM1-ganglioside receptor was 10-fold lower than that of the native B subunit. The amino acid sequence analysis of this mutant B subunit revealed only one amino acid substitution compared with the native B subunit, at the 64th position from the N terminus (valine instead of alanine). These data suggest that the alanine at position 64 from the N terminus is important for the native B subunit to form an oligomer structure and express its functions.

Alanine↗
PubMed1989

Crystallization and preliminary X-ray diffraction study of the heat-labile enterotoxin B subunit produced by enterotoxigenic Escherichia coli.

Heat-labile enterotoxin LT produced by enterotoxigenic Escherichia coli is composed of A and B subunits. The A subunit is enzymatically active; whereas, through the action of the B subunit, the toxin binds to the receptor, a GM1 ganglioside present on the cell surface. Crystals of the LT-B subunit were formed at room temperature by vapor diffusion with polyethylene glycol in the presence of the non-ionic detergent beta-octylglucoside. The crystals were characterized by X-radiation as orthorhombic, space group P2(1)2(1)2(1), with unit cell dimensions of a = 224.1 A, b = 65.3 A, c = 118.4 A. They diffract X-rays to a resolution of at least 2.5 A and are stable to X-rays.

Bacterial Toxins↗
PubMed1989

An atypical heme-binding structure of cytochrome c1 of Euglena gracilis mitochondrial complex III.

Complex III was purified from submitochondrial particles prepared from Euglena gracilis. The purified complex consisted of 10 subunits and lost antimycin sensitivity. The Euglena complex III showed an atypical difference absorption spectrum for cytochrome c1 with its alpha-band maximum at 561 nm. The pyridine ferrohemochrome prepared from covalently bound heme in the Euglena complex III had an alpha-peak at 553 nm. This wavelength is the same as that of pyridine ferrohemochrome prepared from Euglena mitochondrial cytochrome c (c-558), the heme of which is linked to only a single cysteine residue through a thioether bond. Cytochrome c1 which was a heme-stained subunit with a molecular mass of 32.5 kDa was isolated from the purified complex III and its N-terminal sequence of 46 amino acids was determined. On the basis of apparent homologies to cytochromes c1 from other sources, this sequence included the heme-binding region. However, the amino acid at position 36, corresponding to the first cysteine involved in heme linkage in other cytochromes c1, was phenylalanine. Position 39, corresponding to the second cysteine, was not identified despite the treatment for removal of the heme and carboxymethylation of the expected cysteine. The unidentified amino acid is assumed to be a derivative of cysteine to which the heme is linked through a single thioether bond. The histidine-40 corresponding to the probable fifth ligand for heme iron was conserved in Euglena cytochrome c1.

Amino Acid Sequence↗
PubMed1989

Capacities of a newly established thymic stromal cell clone to express Ia antigens and to produce interleukin-6, colony-stimulating factor, and thymic stroma-derived T-cell growth factor.

Thymic stromal cell lines, termed MRL104 and MRL28, have been isolated from long-term liquid cultures of thymic stromal cells from MRL/l mice. The capacities of these parental lines and derived clones to express Ia antigens and to produce cytokines involved in T-cell proliferation and/or differentiation were investigated. Parental lines and their clones did not exhibit a typical fibroblastic, macrophage-like, or epithelial appearance in electron as well as phase-contrast micrographs. These thymic stromal cells seemed to differ from established fibroblast lines in that these thymic stromal cells expressed Ia antigens after exposure to interferon-gamma (IFN-gamma), whereas fibroblast lines did not. They also appeared to differ from macrophage cell lines in that they lacked the expression of Mac-1 antigens on their cell surface and produced no detectable level of interleukin-1 (IL1) before or even after exposure to lipopolysaccharide. When these parental lines and its clones were tested for their ability to produce various types of cytokines, it was revealed that they were capable of producing colony-stimulating factor (CSF), IL6, and thymic stroma-derived T cell growth factor (TSTGF), which was recently described, but were unable to generate other lymphokines and IFNs. Thus these cell lines and clones represent unique features in that they have potentials to express Ia antigens and to produce CSF, IL6, and TSTGF. The biological significance for the expression of these features is discussed in the context of intrathymic T-cell maturation and T-cell repertoire selection.

Animals↗
PubMed1989

Identification of a novel nifH-like (frxC) protein in chloroplasts of the liverwort Marchantia polymorpha.

The frxC gene, one of the unidentified open reading frames present in liverwort chloroplast DNA, shows significant homology with the nifH genes coding for the Fe protein, a component of the nitrogenase complex (Ohyama et al., 1986, Nature 322: 572-574). A truncated form of the frxC gene was designed to be over-expressed in Escherichia coli and an antibody against this protein was prepared using the purified product as an antigen. This antibody reacted with a protein in the soluble fraction of liverwort chloroplasts, which had an apparent molecular weight of 31,000, as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in good agreement with a putative molecular weight of 31,945 deduced from the DNA sequence of the frxC gene. In a competitive inhibition experiment, the antigenicity of this protein was indicated to be similar to that of the over-expressed protein in E. coli. Therefore, we concluded that the frxC gene was expressed in liverwort chloroplasts and that its product existed in a soluble form. The molecular weight of the frxC protein was approximately 67,000, as estimated by gel filtration chromatography, indicating that the frxC protein may exist as a dimer of two identical polypeptides analogous to the Fe protein of nitrogenase. The results obtained from affinity chromatography supported the possibility that the frxC protein, which possesses a ATP-binding sequence in its N-terminal region that is conserved among various other ATP-binding proteins, has the ability to bind ATP.

Adenosine Triphosphate↗
PubMed1989

Simultaneous measurement of alpha-human atrial natriuretic factor (hANF) and NH2-terminal fragment of pro-hANF in essential hypertension.

A radioimmunoassay specific for the N-terminal fragment of prohuman atrial natriuretic factor (hANF) was established with the use of antiserum for pro-hANF (1-30). Plasma levels of alpha-hANF-like immunoreactivity (LI) and pro-hANF (1-30)-Ll in patients with severe hypertension who were receiving a normal sodium diet were 56 +/- 5 pg/ml and 2710 +/- 118 pg/ml, respectively; these levels were significantly higher than control values. Levels of these peptides in patients with mild hypertension were similar to those of control subjects. Mean blood pressure correlated closely with alpha-hANF-Ll levels (r = 0.56, p less than 0.001) and pro-hANF (1-30)-Ll levels (r = 0.66, p less than 0.001) in patients receiving a normal sodium diet. Plasma alpha-hANF-Ll and pro-hANF (1-30)-Ll levels were significantly decreased 3 days in mild hypertension and 7 days in severe hypertension after initiation of a low-sodium diet with a decrease in blood pressure as compared to the initial values. These results suggest that plasma N-terminal fragment levels are elevated in proportion to the degree of hypertension, and they can be reduced by means of effective antihypertensive treatment.

Adult↗
PubMed1989

Immune dysfunction in hypophosphatemic vitamin D-resistant rickets: immunoregulatory reaction of 1 alpha(OH) vitamin D3.

We investigated immunologic function in six cases with hypophosphatemic vitamin D-resistant rickets (VDRR) before and after treatment with 1 alpha-hydroxycholecalciferol (1 alpha(OH) vitamin D3). All cases suffered frequent episodes of infection, which tended to be more severe in the older patients. OKT9-, OKT10-, and OKM1-positive cells and adenosine deaminase (ADA) were significantly increased, whereas numbers and activity of natural killer (NK) cells were lower than normal before treatment. After administration of 1 alpha(OH) vitamin D3, however, the susceptibility to infection apparently decreased, and NK cell number and activity increased in all patients. ADA was also significantly decreased and remained in the normal range after treatment. These results suggest that vitamin D plays a role in the impaired immunoregulatory functions of NK cells in VDRR. Furthermore, ADA may be one parameter reflecting this immunologic impairment.

Adenosine Deaminase↗
PubMed1989

Model for clonal elimination in the thymus.

A thymic stromal cell clone, MRL104.8a, expresses class I as well as class II H-2k antigens after exposure to gamma-interferon. This clone also produces thymic stroma-derived T-cell growth factor (TSTGF), which is distinct from other known interleukins and is capable of promoting the growth of various antigen-specific helper T cell (Th) clones without requiring a specific antigen or interleukin 2. When the keyhole limpet hemocyanin (KLH)-specific, I-Ek-restricted Th clone 9-16 was cultured on an Ia (I-Ak and I-Ek)-expressing MRL104.8a monolayer, potent proliferation of the 9-16 cells was induced by TSTGF produced by the monolayer. In contrast, the addition of KLH resulted in lethal growth inhibition of Th clone 9-16 cells. Another Th clone that is KLH-specific but I-Ab-restricted was capable of proliferating on the Iak-expressing MRL104.8a monolayer whether or not KLH was present. More importantly, death of Th clone 9-16 cells cultured on a MRL104.8a monolayer in the presence of KLH was almost completely prevented by the addition of anti-I-Ek or anti-CD3 monoclonal antibodies, which are capable of blocking antigen recognition by the T-cell receptor. However, when Th clone 9-16 cells were cultured in the presence of KLH but on a monolayer of MRL28.8a cells, another thymic stromal clone that expresses a comparable amount of I-Ek antigen but produces a marginal amount of TSTGF, cells did not die; a lethal effect was induced by adding TSTGF. These results indicate that the TSTGF-producing and Ia-expressing thymic stromal cells induce the continuous proliferation or selective elimination of each T-cell clone, depending on whether the T-cell receptor is stimulated by the relevant antigen associated with Ia molecules expressed on the stromal cell surface.

Animals↗
PubMed1989

Crystallization and preliminary X-ray diffraction studies of oxidized flavodoxin from Chondrus crispus, a red alga.

Crystals of the oxidized form of flavodoxin from a red alga, Chondrus crispus, have been grown in ammonium sulfate solution by the dialysis method. The crystals belong to the orthorhombic system, space group P2(1)2(1)2(1), with unit cell dimensions of a = 63.6, b = 48.8, and c = 56.8 A. The asymmetric unit contains one molecule of flavodoxin. The crystals diffract X-rays to about 2.0 A resolution and are stable to X-ray beams. The diffraction patterns changed significantly upon soaking the crystal in a solution of a platinum complex. The major heavy-atom sites in the platinum derivative crystal have been identified from the difference Patterson function calculated at 4 A resolution.

Crystallization↗
PubMed1989

Isolation and sequence studies of cysteinyl peptides from Spirulina glutathione reductase: comparison of active site cysteine peptides with those of other flavoprotein disulfide oxidoreductases.

The amino acid sequences of the cysteinyl peptides of Spirulina sp. glutathione reductase were determined. Spirulina glutathione reductase was covalently bound to Thiopropyl-Sepharose 6B in the presence of 8M urea through thiol-disulfide exchange. After tryptic digestion, 4 distinct cysteinyl peptides were finally isolated from NADPH-reduced glutathione reductase and 2 from oxidized glutathione reductase. The amino acid sequences of the two cysteinyl peptides which could not be isolated from the oxidized glutathione reductase were very similar to those around the active site disulfide of the other flavoprotein disulfide oxidoreductases and a unique replacement of asparagine and valine by isoleucine and arginine between the two cysteine residues was found. The other two peptides isolated from both oxidized and reduced glutathione reductase also show considerable homology to the corresponding parts of human and Escherichia coli glutathione reductases.

Amino Acid Sequence↗
PubMed1989

Precise determination of the mitochondrial import signal contained in a 70 kDa protein of yeast mitochondrial outer membrane.

A major 70 kDa protein of the yeast mitochondrial outer membrane is coded by a nuclear gene, synthesized on cytoplasmic ribosomes, and transported to the mitochondrial outer membrane. In order to investigate in detail the information necessary for localizing the 70 kDa protein at the outer membrane, we have examined the intracellular and intramitochondrial location of fusion proteins which consist of various lengths of the amino-terminal region of the 70 kDa protein with an enzymatically active beta-galactosidase. The results indicate that the extreme amino-terminal 12 amino acids of the 70 kDa protein function as a targeting sequence, whereas the subsequent uncharged region (up to residue 29) is necessary for "stop-transfer" and "anchoring" functions. Moreover, we have found that a fusion protein which contained the amino-terminal 19 amino acids of the 70 kDa protein is localized on the outer membrane as well as in the matrix space. Changes in the dual localization of this fusion protein accompanied its overproduction or expression in a respiration-deficient yeast mutant.

Base Sequence↗
PubMed1989

Amino acid sequences of ferredoxin isoproteins from radish roots.

Three ferredoxin isoproteins (R-Fd A, R-Fd B-1, and R-Fd B-2) were purified from white roots of radish (Raphanus sativus L. var. acantiformis cultivar Miyashige) and two isoproteins (L-Fd A and L-Fd B) from leaves. The amino acid sequences of three of them (L-Fd A, R-Fd B-1, and R-Fd B-2) were determined and compared with one another and with those of other higher plant ferredoxins so far studied. L-Fd A and R-Fd B-1 had heterogeneities at four and two amino acid sites, respectively. Two isoprotein (R-Fd B-1 and R-Fd B-2) were deduced to be expressed only in root tissue on the basis of sequence studies and amino acid compositions of all isoferredoxins isolated from the radish plant. The root ferredoxins sequenced in this study were similar to each other, but quite different from other higher plant ferredoxins, all of which were isolated from leaf tissue. The coupling activities of these ferredoxin isoproteins were measured in the NADP+-photoreduction system of radish chloroplasts and glutamate synthase [EC 1.4.7.1] systems isolated from radish leaf and root tissues. No distinctive physiological characteristics were observed among these isoferredoxins.

Amino Acid Sequence↗