Biomedical subjects

T Koga

Publications and source records attributed to T Koga.

At least 487 records · Page 27Linked to original sources

PubMed1989

Development of a rapid chemosensitivity test for anticancer drugs with contact-sensitive monolayers of Balb/3T3 cells.

We investigated whether lethally irradiated, contact-sensitive Balb/3T3 cell confluent monolayers, termed "cell mats," could be used for the screening of human tumors for sensitivity to anticancer drugs. Cell mats greatly inhibited the growth of normal Balb/3T3 cells and normal human fibroblasts but did not inhibit the growth of human tumor cells. To assess chemosensitivity of tumor cells, we measured the [14C]thymidine (dThd) incorporation by tumor cells that had been plated and then treated with various anticancer drugs on the cell mats. Although the [14C]dThd incorporation assay, when compared with the colony-formation assay, underestimated the toxicity of certain drugs, the assays gave similar results with regard to the degree of colony inhibition and to the decrease in [14C]dThd incorporation when various anticancer drugs were used at the same concentration ranges. Therefore, the method we used for measuring the isotope uptake in the cell mats could also be used to test for tumor-specific chemosensitivity. Because our results from this assay on various human tumor cells, including those from primary human tumors, can be obtained within 5 days, we believe that the system is potentially useful for testing anticancer drugs against human tumors in vitro.

Cell Division↗

PubMed1989

Cell-mediated immunity to mycobacteria: a double-sided sword?

Mycobacteria are intracellular pathogens capable of replicating in resting macrophages. Specific helper T lymphocytes which activate antimycobacterial capacities in infected macrophages represent an important constituent of acquired resistance. In addition, cytolytic T lymphocytes may contribute to resistance. On the other hand, lysis of infected host cells may also comprise autoaggressive consequences. Recent evidence suggest that T cells with specificity for mycobacterial heat shock proteins are involved in the antimycobacterial immune response. Heat shock proteins are evolutionarily highly conserved and cross-reactivity between microbial and mammalian molecules may occur on the B-cell and T-cell level. Thus, T cells directed against shared epitopes of mycobacterial and autologous origin could initiate autoimmune reactions.

Animals↗

PubMed1989

T cell line specific for bacterial peptidoglycan subunit: possible role of the COOH-terminal amino acid of the disaccharide tetrapeptide in binding to the T cell receptor.

The T cell line specific for a bacterial cell wall peptidoglycan subunit, disaccharide tetrapeptide of diaminopimelic acid type, was examined for epitope specificity in elicitation of delayed-type hypersensitivity (DTH) in X-irradiated Lewis rats, using pairs of analogs different in optical configuration of the COOH-terminal amino acid. The test cell line induced DTH against analogs with the COOH-terminal D-amino acid but not against those with the L-amino acid at the COOH terminus. A close correlation was found between the T cell line-induced DTH reaction in vivo and the proliferative response in vitro, in terms of clear discrimination of the optical configuration of COOH-terminal amino acid of disaccharide tetrapeptide. The L-isomers (non-stimulatory analogs of T cell proliferation) competitively inhibited the proliferation of the T cell line by the corresponding D-isomers. Thus the L-isomers appear to interact with Ia molecules on antigen-presenting cells. We conclude that COOH-terminal D-amino acid of the disaccharide tetrapeptide could be involved in binding to the T cell receptor, induction of T cell proliferation, and elicitation of DTH.

Amino Acids↗

PubMed1989

Protective role of potentially lethal damage repair in the neoplastic transformation of Balb/c 3T3 cells treated with N-methyl-N'-nitro-N-nitrosoguanidine.

To determine the role of repair of potentially lethal damage (PLD) in the initiation process of neoplastic transformation, Balb/c 3T3 cells treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were temporarily exposed to conditioned medium obtained from density-inhibited Chinese hamster cell cultures, as a post-treatment for the induction of PLD repair. With or without this exposure, cell survival and transformation frequencies were simultaneously determined by colony-formation and focus-formation assays, respectively. Temporary exposure to conditioned medium resulted in a 20-30% increase in cell survival compared with no exposure. Post-treatment with conditioned medium resulted in a 60-65% reduction in transformation frequencies. At the molecular level, the repair of MNNG-induced single-strand breaks of DNA occurred much more rapidly in conditioned medium. These data suggest that PLD repair reduces the in vitro neoplastic transformation through excision repair operative during the cessation of DNA replication. Thus, PLD repair appears to be preventive against neoplastic fixation in initiation of neoplastic development.

Animals↗

PubMed1989

Effect of subculturing on expression of a cell-surface protein antigen by Streptococcus mutans.

Two freshly isolated strains, Xc and Yc, of Streptococcus mutans serotype c from human dental plaque were subcultured 100 times in Brain Heart Infusion broth. The cell-surface hydrophobicity of strain Xc markedly decreased after subculturing 60 times, but that of strain Yc remained unaltered. Radioimmunoassay showed a close correlation between surface hydrophobicity and the amount of a cell-surface protein antigen (PAc) of Mr 190,000. One hydrophilic variant (strain Xc100L), one relatively hydrophobic variant (strain Xc100H), and two hydrophobic variants (strains Yc100H1 and Yc100H2) were isolated from the 100-fold subcultures of hydrophobic strains Xc and Yc, respectively. SDS-PAGE showed that the amount of cell-associated and cell-free PAc of strain Xc100L was smaller than that of strains Xc and Xc100H. Strain Yc100H2 produced larger amounts of cell-associated PAc than strains Yc and Yc100H1. Resting cells of hydrophilic strain Xc100L attached in smaller numbers to saliva-coated hydroxyapatite than did other hydrophobic strains. RNA dot-blot analysis demonstrated a significant decrease in PAc-specific mRNA in strain Xc100L, as compared with strains Xc and Xc100H. Neither rearrangement nor deletion in the structural gene (pac) for PAc of these strains was observed by Southern blot analysis. These findings suggest that a mechanism which regulates the transcription of the pac gene participates in the quantitative variation of PAc after repeated subculturing.

Antigens, Bacterial↗

PubMed1989

Purification and characterization of cell-associated glucosyltransferase synthesizing water-insoluble glucan from serotype c Streptococcus mutans.

Strains of Streptococcus mutans (serotypes c, e and f) were found to possess high levels of glucosyltransferase (GTase) activity, both cell-associated and in the culture medium, when grown in either sucrose-free or sucrose-containing broth media. The cell-associated GTase of S. mutans MT8148 (serotype c) was effectively extracted by treatment with 8 M-urea at 25 degrees C for 1 h. Approximately 95% of the GTase activity was solubilized by this treatment. The crude extract was purified by DEAE-Sephacel and hydroxylapatite column chromatography. For comparison, extracellular GTase was also purified from the culture supernatant of the same strain by ammonium sulphate precipitation, chromatofocusing and hydroxylapatite chromatography. The molecular masses of the cell-associated and extracellular GTase proteins were similar (156 kDa) as determined by SDS-PAGE. However, the pH optima for maximum GTase activity were different: pH 6.7 to 7.0 for the cell-associated enzyme and pH 5.5 to 6.5 for the extracellular enzyme. The product of cell-associated GTase from sucrose was almost exclusively water-insoluble glucan. On the other hand, extracellular GTase produced mainly water-soluble glucan from sucrose. This indicates that GTase synthesizing water-insoluble glucan is present primarily in a cell-associated form in serotype c S. mutans. Insoluble glucan synthesis by the cell-associated GTase from sucrose was not enhanced by addition of primer dextran T10 to the reaction mixture. The extracellular and cell-associated GTases were immunologically unrelated as determined by ELISA using monoclonal antibodies.

Chromatography↗

PubMed1989

Characterization of a cell-surface protein antigen of hydrophilic Streptococcus mutans strain GS-5.

Fourteen strains of Streptococcus mutans serotype c were examined for their cell-surface protein antigens in terms of hydrophobicity, Mr and immunochemical specificities. Thirteen strains were hydrophobic, while strain GS-5 was markedly hydrophilic as compared to the other strains tested. Cell-surface protein antigens were then analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western immunoblotting. A protein antigen of Mr 190,000 (PAc) was found in cell extracts and culture supernatants of all the hydrophobic strains. Neither culture supernatant nor cell extract of strain GS-5 contained PAc. Strain GS-5, however, produced extracellularly a large amount of a protein of Mr 155,000 (PAGS-5) which reacted with rabbit anti-PAc serum. Immunodiffusion analysis showed that PAGS-5 lacked a part of the antigenic moieties in the PAc molecule. SDS-PAGE and radioimmunoassay showed a small amount of PAGS-5 on the cell surface of strain GS-5. These findings suggest that PAGS-5 may correspond to PAc which lacks a region participating in binding of PAc to the streptococcal cell.

Antigens, Bacterial↗

PubMed1989

Role of antibodies against outer-membrane proteins in murine resistance to infection with encapsulated Klebsiella pneumoniae.

In the assessment of immunity to the encapsulated virulent strain of Klebsiella pneumoniae and its avirulent mutant defective for capsular polysaccharide (CPS), killed bacterial vaccine of both strains could protect mice equally against challenge with 100 x LD50 of encapsulated wild strain. Antisera to each strain conferred the same level of protection on naive mice upon transfer; the protective anti-mutant serum was highly capable of opsonizing the encapsulated bacteria. In addition to the common antigenic components shared by both strains, the wild strain had antigen(s) unrelated to the mutant since the protective capacity of the anti-wild serum was not affected by preabsorption with the mutant strain; the protection conferred by the anti-mutant serum was mediated by antibodies against non-capsular antigens since the antiserum did not contain antibodies against purified CPS detectable by ELISA. As possible candidates among the non-capsular antigens, outer-membrane proteins (OMPs) extracted from the mutant strain were examined for their immunogenicity. Immunoblotting of the protein-containing fraction and ELISA using LPS-free OMP suggested that a number of proteins were involved in the immune response evoked by K. pneumoniae. Furthermore, mice immunized with OMP or anti-OMP serum could overcome a lethal challenge with the wild strain. These results indicated that OMPs of K. pneumoniae are implicated as the protective antigens and may pave the way for the development of non-capsular, proteinaceous vaccines.

Animals↗

PubMed1989

Molecular characterization of a surface protein antigen gene from serotype c Streptococcus mutans, implicated in dental caries.

The complete nucleotide sequence of the gene for a cell-surface protein antigen (PAc) of Streptococcus mutans MT8148 (serotype c) was determined. The pac gene consisted of 4695 bp and coded for a 170773D protein. The pac gene product contained a putative 38 amino acid signal peptide, resulting in a 166817D mature protein. A potential promoter sequence and a putative Shine-Dalgarno sequence preceded the open reading frame. Two internal repeating amino acid sequences were present in the PAc. One repeating region located in the N-terminal region was rich in alanine, and the other located in the central region was rich in proline. Southern blot analysis under the less stringent condition (allowing up to 35% base mismatch) revealed that the probe covering the proline-rich region hybridized to DNA preparations from strains of Streptococcus cricetus, Streptococcus sobrinus and Streptococcus downei as well as Streptococcus mutans.

Amino Acid Sequence↗

PubMed1989

Cloning of a surface protein antigen gene from serotype c Streptococcus mutans.

The structural gene for a 190 kD protein antigen (PAc) of Streptococcus mutans MT8148 (serotype c) was cloned into the plasmid vector pUC118. SDS-polyacrylamide gel electrophoresis and Western immunoblotting showed that the Escherichia coli harbouring the chimaeric plasmid produced multiple polypeptides of 190-210 kD. Immunodiffusion analysis revealed that the cloned PAc had the same specific determinants as S. mutans PAc. The cloned pac gene was mapped, and its transcriptional orientation was determined by characterizing deletion mutants of the chimaeric plasmid. Southern blot analysis with the cloned gene sequence as a probe revealed the presence of a homologous sequence in DNAs from serotypes e and f S. mutans. PAc-defective mutants were constructed by inserting an erythromycin-resistance gene into the pac gene. The cell-surface hydrophobicity of the mutants was lower than that of the parent strain.

Antibodies, Bacterial↗

PubMed1989

Demonstration in Tupaia papillary muscle preparations of alpha-adrenoceptors mediating positive inotropic effects: comparison with guinea-pigs.

1. Positive inotropic responses to alpha- and beta-adrenoceptor agonists of isolated papillary muscles from the tree shrew (Tupaia), were compared with those from guinea-pigs. 2. In Tupaia, the concentration-response curve for phenylephrine, unlike that for isoprenaline, was not affected by pindolol in a concentration (10(-8) M) sufficient to block beta-adrenoceptor-mediated responses, but it was significantly shifted to the right by phentolamine (10(-6) M). In guinea-pig papillary muscles, however, the concentration-response curve for phenylephrine, like that for isoprenaline, was shifted to the right by pindolol (10(-8) M) but was unaltered by phentolamine (10(-6) M). Furthermore, when the mean concentrations of agonists inducing maximal positive inotropic responses were compared (relative to that of isoprenaline = 1.0), phenylephrine was found to be only slightly less potent (0.84 +/- 0.04; n = 5) in Tupaia and much less potent (0.33 +/- 0.06; n = 5) in the guinea-pig. 3. Although in Tupaia papillary muscles the increase in developed tension induced by a combination of phenylephrine and isoprenaline did not significantly differ from that by phenylephrine alone, it was approximately 3 times larger than that produced by phenylephrine alone in guinea-pigs. 4. These results indicate that in papillary muscles from Tupaia, unlike the guinea-pig, the positive inotropic effects of phenylephrine can be mediated by alpha-adrenoceptors.

Adrenergic alpha-Agonists↗

PubMed1989

Inhibitory effects of rabbit antisera on mitogenic activity of Actinobacillus actinomycetemcomitans lipopolysaccharide.

Lipopolysaccharides (LPSs) were isolated from Actinobacillus actinomycetemcomitans strains ATCC 29523 (serotype a), Y4 (b), and NCTC 9710 (c) by the hot phenol-water procedure. Y4 lipid A was obtained by the hydrolysis of Y4 LPS in 1% acetic acid. All the LPS preparations and Y4 lipid A were mitogenic for C3H/HeN mouse spleen cells, but not for C3H/HeJ mouse spleen cells. Immunoglobulin preparations partially purified by ammonium sulfate precipitation at 33% saturation from rabbit antisera against Y4 whole cells inhibited the mitogenic response of C3H/HeN mouse spleen cells to LPSs from all the strains of A. actinomycetemcomitans and Y4 lipid A. Anti-Y4 LPS immunoglobulin preparation inhibited the mitogenic activity of Y4 LPS and Y4 lipid A. Furthermore, anti-Y4 whole cell Fab fragments inhibited the mitogenic activity of both Y4 LPS and Y4 lipid A. These results suggest that antibodies against A. actinomycetemcomitans LPS may modify immune responses of lymphocytes to this organism at periodontal sites.

Actinobacillus↗

PubMed1989

Comparative effects of ouabain on isolated papillary muscle from tree shrews, guinea-pigs and rats.

Inotropic effects of ouabain were investigated in the isolated papillary muscle preparations of the tree shrew (Tupaia glis), guinea-pigs and rats. In the guinea-pig and shrew papillary muscles, ouabain at concentrations of 10(-8) to 3 x 10(-7) M caused a concentration-dependent positive inotropic response in a similar magnitude, while in the rat, ouabain at concentrations of 10(-7) to 3 x 10(-6) M elicited negative inotropic one. Either phentolamine or pindolol in a concentration sufficient to block the alpha- and beta-adrenoceptors did not antagonize the positive inotropic effect of ouabain in the papillary muscle preparation of the shrews.

Animals↗

PubMed1989

Contribution of the tissue angiotensin converting enzyme to the antihypertensive effect of altiopril calcium (MC-838) in spontaneously hypertensive rats.

The effect of a new orally active angiotensin converting enzyme (ACE) inhibitor, calcium (-)-N-[(S)-3-[(N-cyclohexylcarbonyl-D-alanyl)thio]-2-methylpropionyl+ ++]-L- prolinate (MC-838, altiopril calcium), on systemic blood pressure (SBP) and tissue ACE activity has been examined in conscious spontaneously hypertensive rats (SHRs). MC-838 (3 mg kg-1) given orally to SHRs elicited a long-lasting hypotension lasting over 24 h. With the development of the hypotension, MC-838 significantly reduced ACE activity in the lung, kidney and aorta, but not in the brain and heart. Suppression of plasma ACE and rise of plasma renin activity occurred only transiently at an earlier stage.

Animals↗

PubMed1989

[Antibiotic susceptibility and T-serotypes of group A hemolytic streptococci, clinically isolated in 1986 and 1987].

Determination of T-serotype for a total 245 strains (157 strains in 1986, 88 strains in 1987) of Streptococcus pyogenes (Group A hemolytic streptococci) isolated from clinical specimens (throat swab) of pediatric patients in Fukuoka Prefecture from 1986 until 1987 were performed. The susceptibilities of 9 antibiotics against 241 strains were studied. The most dominant strain was T-12 (57 strains, 36.3%) and followed by T-4 (32 strains, 20.4%) and T-28 (30 strains, 19.1%) in 1986. The total of these three strains was 75.8% of all strains. In 1987, T-4 (41 strains, 46.6%) was the dominant strain instead of T-12 (14 strains, 15.9%). T-28 was isolated only 4 strains (4.5%) in 1987, although it was isolated in 30 stains (19.1%) in 1986. In susceptibility-tests, no strains of 1986 and 1987 was resistant to beta-lactams. Resistant strains (MIC greater than or equal to 25 micrograms/ml) to erythromycin (EM), tetracycline (TC) and chloramphenicol (CP) were 4 (2.6%), 51 (33.3%) and 1 (0.7%), respectively in 1986. In 1987, resistant strains to EM and CP were not detected, to TC were 52 strains (59.1%), so there was an increase of susceptibility to EM and CP. As for relationship between T-serotype and antibiotic resistance, only one strain (T-12) showed multiple resistance in 1986, however in 1987, multiple resistant strain was not detected. In 1986 and 1987, 31 of 49 only TC resistant strains (63.3%) and 41 of 52 only TC resistant strains (78.8%) were T-4, respectively.

Anti-Bacterial Agents↗

PubMed1989

Immunochemical and structural characterization of a serotype-specific polysaccharide antigen from Actinobacillus actinomycetemcomitans Y4 (serotype b).

A serotype-specific polysaccharide antigen of Actinobacillus actinomycetemcomitans Y4 (serotype b) was extracted from whole cells by autoclaving. The extract was purified by chromatography on DEAE-Sephadex A-25 and Sephacryl S-300 columns. The purified polysaccharide antigen formed a single precipitin line with anti-type b serum but not with anti-type a serum and anti-type c serum. The antigen was composed of 43.9% L-rhamnose, 49.1% D-fucose, and a trace amount of fatty acid. Methylation analysis, Smith degradation, and optical rotation data showed that the antigen was a polymer consisting of a disaccharide repeating unit, ----3)-alpha-D-fucopyranosyl-(1----2)-beta-L-rhamnopyranosyl-(1----. In quantitative precipitin inhibition tests, D-fucose and L-rhamnose showed very low inhibition, but the partial hydrolysate of the purified antigen was an effective inhibitor, suggesting that the serotype b specific antiserum recognizes the larger oligosaccharide units.

Actinobacillus↗

PubMed1989

Age and hypertension promote endothelium-dependent contractions to acetylcholine in the aorta of the rat.

This study was undertaken to compare age-related changes in endothelium-dependent vascular responses in both hypertensive and normotensive rats. Aorta from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) aged 4-6 weeks (young), 3-6 months (adult), and 12-25 months (old) were examined for relaxation to acetylcholine, adenosine 5'-triphosphate (ATP), and sodium nitroprusside. Rubbed (endothelium denuded) aorta from all groups displayed neither relaxation nor contraction to acetylcholine. Maximal relaxation responses to acetylcholine were reduced progressively with increasing age in unrubbed aorta of both SHR and WKY rats. In addition, acetylcholine caused not only dose-dependent relaxations at lower concentrations but also increases in tension at higher concentrations in unrubbed aorta of old WKY rats as well as adult and old SHR. However, indomethacin completely inhibited the tension development. As a result, aorta treated with indomethacin demonstrated similar acetylcholine-induced, endothelium-dependent relaxations in all groups. The thromboxane A2 synthetase inhibitor (E)-7-phenyl-7-(3-pyridyl)-6-heptanoic acid (CV-4151) partially but significantly depressed the increases in tension in aorta of old WKY rats. The degrees of endothelium-dependent relaxations to ATP and endothelium-independent relaxations to sodium nitroprusside were almost similar in all groups. These findings suggest that the release of or vascular responsiveness to endothelium-derived relaxing factor in the aorta is well maintained through senescence in both strains and that, in the aorta of not only SHR but also old normotensive WKY rats, the endothelium releases contracting factors that may be thromboxane A2 and other vasoconstrictor prostanoids.

Acetylcholine↗

PubMed1989

Hypotensive effects of nifedipine in patients with primary hyperparathyroidism: case reports.

Nifedipine was administered orally to 2 patients with primary hyperparathyroidism before and after parathyroidectomy. The operation lowered serum calcium concentration and parathyroid hormone but did not alter plasma renin activity, plasma aldosterone concentration, and serum magnesium. The hypotensive effects of nifedipine were markedly enhanced with the decrease in serum calcium concentration following parathyroidectomy. Thus, the level of serum calcium concentration may modulate the hypotensive effect of nifedipine in humans.

Aged↗