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Biomedical subjects

T Sato

Publications and source records attributed to T Sato.

At least 19 recordsLinked to original sources
PubMed1992

Elevation of hepatic levels of metallothionein and zinc in mice bearing experimental tumors.

A tumor growth-dependent elevation in the hepatic levels of Zn and metallothionein (MT), without a change in the level of Cu, was found in mice and rats bearing solid tumors in the inguinal region. The levels of Zn and MT thus elevated gave a significant correlation (r = 0.95) between them. Nevertheless, when tumor-bearing mice and rats were fed a Zn-deficient diet, the hepatic levels of Zn and MT did not increase. In mice in which inflammation was induced at the same region, on the other hand, hepatic levels of Zn and MT increased transiently after the injection of turpentine or carrageenan even when they were fed the Zn-deficient diet. These results suggest that the elevation of MT and Zn levels can be a helpful marker for detecting malignancy.

Animals↗
PubMed1992

Purification and initial characterization of the proteasome from the higher plant Spinacia oleracea.

The proteasome (multicatalytic protease complex), a high molecular weight protein complex, has been purified from spinach leaves by successive chromatography on DEAE-cellulose, Bio-Gel A-1.5m, DEAE-TOYOPEARL 650C, and DEAE-5PW. The molecular mass was estimated to be 850 kDa by gel filtration. Polyacrylamide gel electrophoresis of the proteasome gave a single protein band under nondenaturing conditions and at least 10 bands in the range of 21-32 kDa in the presence of sodium dodecyl sulfate. By electron microscopy after negative staining with uranyl acetate, the proteasome from spinach appeared as symmetrical ring-shaped particles. The substrate specificity of proteasomes indicates that they contain at least three types of activity, namely, chymotrypsin-like, Staphylococcus aureus V8 protease-like, and trypsin-like activities. The former two activities were enhanced by poly-L-lysine or sodium dodecyl sulfate. Moreover, we examined the immunological reactivities of proteasomes from various eukaryotes. As a result, cross-immunoreactivities of some subunits were observed. These properties of the proteasome are similar to those of proteasomes isolated from various other eukaryotic sources.

Amino Acid Sequence↗
PubMed1992

Purification and properties of Aspergillus niger beta-glucosidase.

Beta-glucosidase was purified from a crude cellulase preparation from Aspergillus niger by affinity chromatography on a methacrylamide-N-methylene-bis-methacrylamide copolymer bearing cellobiamine. The purified enzyme was a dimer with an isoelectric point of 4.0. The molecular mass of the enzyme was estimated to be 240 kDa by gel-permeation chromatography. The enzyme hydrolyzed specifically beta-glucosidic bonds and catalyzed transglucosylation of the beta-glucosyl group of cellobiose to yield 4-O-beta-gentiobiosylglucose in the presence of organic solvents or under neutral conditions.

Aspergillus niger↗
PubMed1992

Estimation of a common risk ratio in stratified case-cohort studies.

The case-cohort study design is a useful modification of the case-control design, which allows direct estimation of the risk ratio without the rare-disease assumption. While several risk ratio estimation procedures have been proposed under large-strata settings, only the Mantel-Haenszel point estimator is available in sparse stratifications. This paper provides simple confidence limits methods, based on the large-sample distribution of the Mantel-Haenszel risk ratio, that apply to both large-strata and sparse-data situations. For the Tarone risk ratio, I give a new large-strata variance estimate.

Case-Control Studies↗
PubMed1992

Sequence of the Bacillus subtilis homolog of the Escherichia coli cell-division gene murG.

The Bacillus subtilis homology of the Escherichia coli murG gene [encoding UDP-N-acetylglucosamine:N-acetylmuramyl-(pentapeptide) pyrophosphoryl-undecaprenol N-acetylglucosamine transferase] was cloned in E. coli K-12 and sequenced. The murG homolog encodes a protein of M(r) 39,936 [363 amino acid (aa) residues] of which 108 aa residues (29.8%) are identical with the E. coli murG product.

Amino Acid Sequence↗
PubMed1992

Identification of osteopontin in isolated rabbit osteoclasts.

Bone remodeling is a complex process coupling bone formation and resorption. Osteoblasts, the bone-forming cells, are known to produce various bone matrix proteins and cytokines; however, little is known about protein factors produced by osteoclasts or bone-resorbing cells. A method utilizing the high affinity of osteoclasts for tissue culture dishes was developed to isolate a large number of pure osteoclasts from rabbit long bones. A cDNA library was then constructed from these isolated osteoclasts, and differential cDNA screening was performed between osteoclasts and spleen cells. Two clones representing osteoclast-specific clones, named OC-1 and OC-2, were isolated. By Northern blot analysis, OC-1 was expressed in osteoclasts and in kidneys, whereas OC-2 was specific for osteoclasts. OC-1 was found to encode osteopontin from its nucleotide sequence, and therefore, osteopontin may have other functions for osteoclastic bone resorption besides osteoclast attachment to bone.

Amino Acid Sequence↗
PubMed1992

Determination of dioxopiperazine metabolites of quinapril in biological fluids by gas chromatography-mass spectrometry.

The dioxopiperazine metabolites of quinapril in plasma and urine were extracted with hexane-dichloroethane (1:1) under acidic conditions. Following derivatization with pentafluorobenzyl bromide and purification of the desired reaction products using a column packed with silica gel, the metabolites were analysed separately by capillary column gas chromatography-electron-impact mass spectrometry with selected-ion monitoring. The limits of quantitation for the metabolites were 0.2 ng/ml in plasma and 1 ng/ml in urine. The limits of detection were 0.1 ng/ml in plasma and 0.5 ng/ml in urine, at a single-to-noise ratio of greater than 3 and greater than 5, respectively. The proposed method is applicable to pharmacokinetic studies.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Correlation of loss of alleles on the short arms of chromosomes 11 and 17 with metastasis of primary breast cancer to lymph nodes.

To examine the role of loss of heterozygosity (LOH) during tumor development and/or progression, we looked for correlations between metastasis of breast cancer to a regional lymph node(s) and LOH of chromosomal arms 11p, 13q, 16q, 17p, and 17q, where frequent losses in primary tumors have been detected. No correlation between lymph node metastasis and LOH of chromosomes 13q, 16q, or 17q was observed. However, tumors showing LOH of chromosomes 11p (chi 2 = 10.82, P less than 0.01) and 17p (chi 2 = 6.78, P less than 0.01) revealed a significantly higher incidence of metastasis to a regional lymph node(s) than tumors without LOH on these chromosomal arms. Furthermore, only four of 30 (13%) patients with tumors that retained both 11p and 17p had metastasis to a regional lymph node(s), compared with 24 of 32 (75%) patients with tumors that had lost both 11p and 17p. Analysis of LOH with markers on chromosomes 11p and 17p in a large number of tumors indicated that the peritelomeric region of each of these chromosomal arms contains a tumor suppressor gene that may be associated with tumor progression, particularly metastasis to a regional lymph node(s).

Alleles↗
PubMed1992

Biscoclaurine alkaloids inhibit receptor-mediated phospholipase A2 activation probably through uncoupling of a GTP-binding protein from the enzyme in rat peritoneal mast cells.

The mechanism underlying the inhibitory effect of biscoclaurine (bisbenzylisoquinoline) alkaloids on phospholipase A2 activation in the signalling system of stimulated rat peritoneal mast cells was studied. Cepharanthine, berbamine and isotetrandrine inhibited antigen- and compound 48/80-induced arachidonic acid liberation, but not diacylglycerol formation or histamine release. They had no effect on A23187-induced arachidonic acid liberation, which was prevented by p-bromophenacyl bromide, a known phospholipase A2 inhibitor, and also did not affect phospholipase A2 activity in a cell-free system including an exogenous phospholipid substrate. Each alkaloid also inhibited arachidonic acid liberation induced by guanosine 5'-O-(3-thiotriphosphate) in saponin-permeabilized mast cells, and by mastoparan or NaF plus AlCl3 intact cells. Furthermore, each alkaloid abolished the inhibitory effect of islet-activating protein on the compound 48/80-induced arachidonic acid liberation. These data suggest that these alkaloids suppress the receptor-mediated phospholipase A2 activation through, at least in part, uncoupling of a GTP-binding protein from the enzyme, rather than by affecting the enzyme directly.

Alkaloids↗
PubMed1992

Beta 2-microglobulin-, CD8+ T-cell-deficient mice survive inoculation with high doses of vaccinia virus and exhibit altered IgG responses.

Transgenic mice lacking an intact beta 2-microglobulin (beta 2m) gene fail to express major histocompatibility complex (MHC) class I proteins on the cell surface and, as a result, are virtually devoid of CD4- CD8+ lymphocytes. These animals provide a unique model system for directly assessing the role of CD8+ lymphocytes in the modulation of viral infection in vivo. beta 2m- CD8- mice and their normal littermates were inoculated at the base of the tail with the WR strain of vaccinia virus and monitored for serum antibody and lesion formation. Both groups developed similar lesions in response to a broad virus dose range, and all animals had completely recovered by day 28 after inoculation. Isotype-specific immunoglobulin levels were determined for each animal on day 7 and day 14 after primary inoculation, and again 7 days after a virus challenge. The virus-specific IgG1, IgG2a, and IgG2b levels were significantly different in the beta 2m-/- group (20-, 9-, and 30-fold lower, respectively, on day 7 after challenge) compared with the beta 2m+/- group. Virus-specific serum IgM levels for both groups remained similar throughout the experiment. In a separate experiment, beta 2m-/- mice were immunized with a nonviral antigen, 2,4,6-trinitrophenyl-conjugated keyhole limpet hemocyanin, and both total and antigen-specific isotype-specific immunoglobulin titers were determined. Total IgG1, IgG2a, IgG2b, and IgG3 tended to be lower overall in the beta 2m-/- mice compared with beta 2m+/- littermates. In contrast, total and antigen-specific IgE titers were similar in the two groups. These data indicate that CD8+ lymphocytes are not required to clear high doses of vaccinia virus, and they suggest that beta 2m-/- mice are less efficient at antigen-specific IgG production than their beta 2m+/- littermates.

Animals↗
PubMed1992

Interactions between recombinant human erythropoietin and serum factor(s) on murine megakaryocyte colony formation.

We investigated the interactions between human erythropoietin (hEpo) and serum factor(s) on murine megakaryocyte (MK) colony formation. Serum-free cultures supported the growth of a large number of murine MK colonies in the presence of murine interleukin-3 (mIL-3). The addition of fetal calf serum (FCS) to mIL-3-containing cultures resulted in only a minimal increase in the number of murine MK colonies. In contrast, hEpo alone had no murine MK colony-stimulating activities in serum-free cultures. hEpo required the presence of FCS, murine serum, or human serum in cultures to promote murine MK colony growth and synergized with these sera to stimulate murine MK colony formation. Furthermore, sera from patients with aplastic anemia showed higher synergistic activities with hEpo than sera from hematologically normal persons (normal human serum). When normal human serum was fractionated by gel-filtration chromatography, two peaks with the synergistic activity were observed in the eluent. However, serum did not show any synergistic effects with hEpo on the growth of murine GM colonies or murine colony-forming unit-erythroid-derived colonies. Although human serum synergized with hEpo to stimulate murine MK colony formation, human cytokines such as IL-3, IL-4, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) failed to induce murine MK colony formation in Epo-containing cultures. In cultures containing human IL-1 alpha + human IL-6 + hEpo as well as in cultures containing hEpo, human IL-3 and human GM-CSF failed to show stimulatory effects on murine MK colony formation. Moreover, the synergistic activity of human serum with hEpo could not be neutralized by antibodies such as antihuman IL-1 alpha, antihuman IL-3, antihuman IL-4, antihuman IL-6, antihuman G-CSF, and antihuman GM-CSF. Our data show that serum contains a growth factor(s) that synergizes with Epo to stimulate the proliferation and differentiation of MK precursors, and strongly suggest that this factor(s) is an unique growth factor(s) that is distinct from IL-1 alpha, IL-3, IL-4, IL-6, G-CSF, and GM-CSF.

Anemia, Aplastic↗
PubMed1992

Conalbumin-conjugated silica gel, a new chiral stationary phase for high-performance liquid chromatography.

A new chiral stationary phase using conalbumin (from chicken egg white) was developed for high-performance liquid chromatography. Chiral resolution of racemic azelastine, an antiallergic drug, was achieved on a conalbumin-conjugated silica gel column. The effects of the pH, the concentration of organic solvents and salts in the mobile phase, and the temperature on the capacity factor and resolution of racemic azelastine were examined. This column shows good stability and can separate optical isomers with an aqueous mobile phase. It should be very useful in studies on pharmacokinetics and in clinical chemistry.

Chromatography, High Pressure Liquid↗
PubMed1992

Mutagenicity from ozonation of humic substances.

Eight structural components of humic substances were ozonated. Mutagenic activity was found using TA100 with and without S9 mix for all ozonated components. p-Hydroxybenzaldehyde was chosen as an important component and ozonation products were determined by gas chromatography-mass spectrometry (GC-MS). Aldehydes, ketones and carboxylic acids were identified as the ozonation products. Among these products, acetaldehyde, formaldehyde, glyoxal, methylglyoxal and glyoxylic acid were recognized to be mutagenic. Furthermore, p-hydroxybenzaldehyde was first ozonated and then chlorinated. A great variety of chlorinated organic compounds, many of which are known mutagens, have been identified by GC-MS in the ether extract. The same compounds have previously been reported as chlorination products of humic substances. Aldehydic products by ozonation were identified from ozonation followed by chlorination of humic substances and p-hydroxybenzaldehyde.

Animals↗
PubMed1992

Kinetic studies on CO binding to reconstituted myoglobins with four synthetic hemes; structural control in ligand binding to myoglobin.

Examination was made of CO binding reactions to four kinds of modified sperm whale myoglobin (Mb), whose heme was reconstituted by iron complexes of synthetic porphyrins such as porphine (Por), meso-tetramethylporphyrin (TMeP), meso-tetraethylporphyrin (TEtP) and meso-tetra(n-propyl)porphyrin (TnPrP), using flash photolysis and stopped-flow methods. The CO association rate was found to be 5- to 20-times and dissociation rate 10- to 36-times accelerated by replacement with synthetic hemes. These features could be explained based on characteristic structures of modified Mbs indicated by X-ray crystallography. The side chain of Arg-45 protruded from the heme vicinity into the solvent region and heme was tilted by interactions of meso-alkyl side chains with surrounding peptides, resulting in the formation of widely opened channels and pockets for ligand passage. These structural features indicate the CO ligand to more easily enter or exit from heme pockets of reconstituted myoglobins, compared to native Mb.

Animals↗
PubMed1992

Detection of citrulline residues in deiminated proteins on polyvinylidene difluoride membrane.

We have developed a new detection method of deiminated proteins on polyvinylidene difluoride membranes. Citrulline residues in enzymatically deiminated histones were modified by incubating with diacetyl monoxime and antipyrine in a strong acid mixture. The products were injected to rabbits, and the antibodies obtained were affinity-purified using a modified citrulline column. Sample proteins blotted to the membrane were modified in a similar manner and incubated successively with the purified antibody and an alkaline phosphatase-conjugated second antibody. Detection was performed using a chemiluminescent substrate. The method enabled detection of 3-10 fmol of citrulline residues dot blotted as deiminated model proteins. It visualized numerous rat pituitary soluble proteins that had been enzymatically deiminated and Western blotted to the membrane. The data suggest usefulness of the method for detecting deiminated proteins regardless of the backbone protein molecules. Search for deiminated proteins on the Western blots of various rat tissue homogenates detected a single band on that of spinal cord, another band on that of uterus, and multiple bands on those of skin and hair root. The bands in the former two tissue homogenates comigrated with glial fibrillary acidic protein and vimentin, respectively.

Animals↗
PubMed1992

Immunochemical characterization of rat testicular asparagine synthetase.

We studied immunochemical properties of rat testicular asparagine synthetase. Western blot analysis of testis extract with polyclonal antibody raised against purified asparagine synthetase revealed an immunoreactive band at 62 kDa. The pancreas, brain, thymus, and spleen also showed 62-kDa bands. The intensities of these bands were roughly proportional to the specific activities of the enzyme in these tissues. The antibody showed some degree of cross-reactivity to asparagine synthetases from human, beef, pig, mouse, guinea pig, chicken, and frog, but not carp. But the enzyme from human HL-60 cells and lower vertebrates reacted with the antibody less strongly than enzyme from rats. The N-terminal amino acid sequence of the enzyme, determined by the Edman degradation method, in 10 recovered residues was identical to that of human asparagine synthetase deduced from corresponding cDNA (I.L. Andrulis et al., 1987, Mol. Cell. Biol. 7, 2435-2443). Immunohistochemical staining of the testis showed the presence of asparagine synthetase mainly in Sertoli cells in the seminiferous tubules.

Amino Acid Sequence↗
PubMed1992

Generation of mutagenicity by ozonation of humic substances' components.

Components of humic substances, such as vanillin, syringaldehyde, vanillic acid and di-n-butylphtalate, were ozonated and subjected to the mutagenicity assay using Salmonella typhimurium TA 98 and 100 with and without S9 mix. The strong mutagenic activity was found on all components except di-n-butylphtalate by strain TA 100 with and without S9 mix. Substances with strong mutagenic activity in ozonated vanillin were water-soluble and were slightly extracted with benzene, dichloromethane and ethyl acetate. Following gel chromatography on Sephadex G-10, the strong mutagens generated by ozonation were found with molecular weights greater than 300.

Animals↗