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Biomedical subjects

S Hamada

Publications and source records attributed to S Hamada.

At least 145 records · Page 8Linked to original sources
PubMed1997

A novel component different from endotoxin extracted from Prevotella intermedia ATCC 25611 activates lymphoid cells from C3H/HeJ mice and gingival fibroblasts from humans.

A novel immunobiologically active fraction was prepared from a phenol-water extract of Prevotella intermedia ATCC 25611 by Sephadex G-100 column chromatography. The fraction consisted mainly of carbohydrate and protein and was devoid of fatty acid. The fraction showed high-molecular-weight bands (10,000 to 12,000) on deoxycholate polyacrylamide gel electrophoresis (DOC-PAGE) and was scarcely active in a Limulus test. We designated the fraction Prevotella glycoprotein (PGP). The PGP fraction showed strong mitogenicity on splenocytes and cytokine-inducing activities on peritoneal macrophages from both C3H/HeJ and C3H/HeN mice, and it stimulated human gingival fibroblasts to produce cytokines. The activities of the PGP fraction were resistant to heat inactivation (100 degrees C for 1 h) and protease treatments and were scarcely inhibited by polymyxin B. In contrast, the purified lipopolysaccharide fraction (LPS-PCP) extracted from the same bacterium with a phenol-chloroform-petroleum ether mixture, which showed strong Limulus activity and a single low-molecular-weight band (approximately 3,000) on DOC-PAGE, lacked the activities on splenocytes and macrophages from C3H/HeJ mice and human gingival fibroblasts. The activities of the LPS-PCP fraction on cells from C3H/HeN mice were completely inhibited by polymyxin B. The LPS extracted from the same bacterium with hot phenol-water (LPS-PW) exhibited the properties of both the PGP fraction and the LPS-PCP fraction. These findings suggest that the unique bioactivities of the LPS-PW fraction of oral black-pigmented bacteria reported to date, which differed from those of the classical endotoxin, were derived from the PGP fraction and not from the LPS itself.

Adjuvants, Immunologic↗
PubMed1997

Prophyromonas gingivalis fimbriae mediate coaggregation with Streptococcus oralis through specific domains.

Fimbriae are major adhesive components on the cell surface of Prophyromonas gingivalis. In this study, we evaluated the role of fimbriae in coaggregation with Streptococcus oralis. Fimbriae purified from P. gingivalis competitively inhibited the coaggregation by 100% at a concentration of 50 micrograms/mL. On the other hand, the same amount of lipopolysaccharide isolated from P. gingivalis was inhibited by only 25% of the level of the fimbriae. A fimA-inactivated mutant of P. gingivalis failed to show distinct coaggregation activity. Fimbriae added to a solution of various strains of streptococci caused their self-aggregation at a concentration of 10 to 30 micrograms/mL. The self-aggregation induced by fimbriae was inhibited by lambda-arginine (20 to 40 mM/L). Iodinated fimbriae reacted with S. oralis cells immobilized on the nitrocellulose membrane, and 100 degrees C heating of the cells diminished the binding abilities. Recombinant fimbrillin (r-Fim, corresponding to whole residues 1 to 337 of native fimbrillin) of P. gingivalis also showed 100% inhibition of the coaggregation. The r-Fim variant (residues 1 to 286) lacking the C-terminal 51 residues was as inhibitory as r-Fim. However, the variant (residues 1 to 265) without the C-terminal 72 residues lost 77% of the inhibitory activity. These findings suggested that residues 266 to 286 contain a domain involved in the coaggregation of P. gingivalis with S. oralis. Inhibition by three polypeptides corresponding to residues 266 to 286, 266 to 337, and 287 to 337 was studied. Peptides 266 to 286 and 266 to 337 inhibited by 96 and 100%, respectively, at a concentration of 1.5 nmol/mL. Peptide 287 to 337 also showed a significant inhibitory effect but to a slightly lesser extent than that of peptide 266 to 286. P. gingivalis fimbriae appear to be involved in coaggregation with streptococci, probably through an adhesive protein molecule(s) of the latter, and the fimbriae possess several domains in the C-terminal residues 266 to 337 for interaction with S. oralis.

Bacterial Adhesion↗
PubMed1997

Immunosuppressive effects of gallic acid and chebulagic acid on CTL-mediated cytotoxicity.

Gallic acid (GA) and chebulagic acid (CA) were isolated from the extract of a herbal medicine, kashi (myrobalans: the fruit of Terminalia chebula) as active principles that blocked the cytotoxic T lymphocyte (CTL)-mediated cytotoxicity. GA and CA inhibited the killing activity of CD8+ CTL clone at IC50 values of 30 microM and 50 microM, respectively. Granule exocytosis in response to anti-CD3 stimulation was also blocked by GA and CA at the equivalent concentrations.

Animals↗
PubMed1997

Effect of gemfibrozil on centrifugal behavior of rat peroxisomes and activities of peroxisomal enzymes involved in lipid metabolism.

The effect of gemfibrozil, and analogue of clofibric acid, on the centrifugal behavior of peroxisomes and activity of peroxisomal enzymes involved in lipid metabolism was studied. Rats were fed chow containing 0.2% gemfibrozil for 2 weeks. Nycodenz gradient centrifugation of the light mitochondrial fraction revealed that peroxisomes of gemfibrozil-treated rats were concentrated in fractions of higher density compared with control rats. The activity of fatty acyl-CoA oxidase, crotonase, beta-hydroxybutyryl-CoA dehydrogenase, and thiolase (individual enzymes of the peroxisomal fatty acid beta-oxidation system) were enhanced 9.6, 2.3, 3.4 and 9.1 times respectively compared with controls, by treatment. The hydroxymethylglutaryl-CoA (HMG-CoA) reductase (rate-limiting enzyme of cholesterol synthesis) activity of peroxisomes and microsomes was greatly increased by in vivo treatment with gemfibrozil, but was decreased by addition of the agent to the assay mixture of the enzyme. Gemfibrozil directly inhibited the reductase activity and did so at a lower concentration than clofibric acid. Peroxisomal reductase was more resistant to damage by the agent than the microsomal enzyme. The HMG-CoA reductase activity of peroxisomes and microsomes of hyperlipidemic rats was also increased by in vivo treatment with gemfibrozil, whereas the serum cholesterol level was hardly changed. These results indicate that the effect of gemfibrozil differs from that of clofibric acid, the main difference being the effect on HMG-CoA reductase. Gemfibrozil increased reductase activity in vivo, unlike clofibric acid, but inhibited the enzyme in vitro to a greater extent than clofibric acid.

Animals↗
PubMed1997

Relationship between histological type and endosonographic detection of regional lymph node metastases in gastric cancer.

The aim of the study was to compare the ability of endoscopic ultrasonography (EUS) in detecting lymph node metastases in differentiated and undifferentiated gastric adenocarcinoma. EUS was performed in 149 patients with differentiated or undifferentiated gastric cancer. Histopathological findings were compared with pre-operative EUS findings in a total of 2961 resected lymph nodes. The EUS detection rates of metastasis to individual nodes in relation to node size, the ratio of the metastasized area to the cross-sectional area of the node and to the depth of primary tumour invasion, were also investigated. The accuracy and negative predictive values of EUS for detecting metastatic lymphadenopathy in each patient were significantly higher for differentiated (87%, 94%) than for undifferentiated (71%, 71%) tumours. The detection rate of individual node metastasis was higher for differentiated (31%) than for undifferentiated (21%) tumours. For differentiated lesions, EUS detected more small nodal metastases (< 5 mm in diameter) (p < 0.01) and more nodes involved with a relatively small proportion of the metastasized area to the cross-sectional area of the node (< 1/3 involvement) (p < 0.05). In relatively superficial lesions, such as pT1 and pT2, the pre-operative EUS detection rate of metastatic nodes was higher for differentiated than for undifferentiated tumours. In conclusion, the ability of EUS to detect nodal metastases is related to the histological type of gastric cancer.

Adenocarcinoma↗
PubMed1997

Pre-operative TN staging of gastric cancer using a 15 MHz ultrasound miniprobe.

The aim of the study was to evaluate the usefulness of and problems associated with a new endoscopically guided ultrasound miniprobe, used for pre-operative staging of gastric cancers. 59 cases of gastric cancer were prospectively examined with a 15 MHz ultrasound miniprobe. The results of the ultrasound imaging were compared with the histological findings of the resected specimens. The accuracy of the miniprobe for depth of invasion (T category) was 61% for all tumours, and 72% and 40%, respectively, for T1 and T2 to T4 lesions. If indeterminate cases due to ultrasound attenuation were excluded, the accuracy was improved to 82% for T1 and 57% for T2 to T4 tumours, respectively. The accuracy of the miniprobe for nodal staging (N category) was 69% overall, and 86%, 25% and 14% for stages N0, N1 and N2, respectively. In tumours classified on the basis of endoscopic types, the miniprobe staged early type gastric cancers (T category = 73%, N category = 80%) significantly (p < 0.01) more accurately than advanced ones (T category = 21%, N category = 36%). This study suggests that the miniprobe is indicated for pre-operative TN staging when endoscopy reveals an early gastric cancer.

Adenocarcinoma↗
PubMed1997

TM rats: a model for platelet storage pool deficiency.

TM rats have a light brown hooded coat pattern resembling that of Fawn hooded (FH) rats which are a model of platelet storage pool deficiency (SPD). We examined whether the TM strain has the same platelet SPD as the FH strain. TM rats had a prolonged bleeding time and a low blood serotonin level, although their blood coagulation time and platelet counts were normal. The light coat color of the TM strain was judged to be associated with the red-eyed dilution gene as in the FH strain, but not pink eye dilution as in the RCS rat strain. Platelet SPD seen in TM rats may be a pleiotropic effect of the red-eyed dilution gene proposed in FH rats. Despite these similarities, the genetic background of the TM strain was obviously different from that of the FH strain. The TM strain, developed independently of the FH strain, will therefore be used as a model of platelet SPD.

Animals↗
PubMed1996

Myocardial infarction as a complication of pheochromocytoma in a pregnant woman.

Pheochromocytoma is an unusual cause of hypertension during pregnancy. We present a 40-year-old woman who had a myocardial infarction during pregnancy in whom pheochromocytoma was subsequently diagnosed. This disorder carries a high risk of maternal and perinatal mortality, if undiagnosed prior to delivery. Therefore, the diagnosis of pheochromocytoma should be considered in pregnant patients who exhibit a marked fluctuation in hypertension. Urinary concentrations of catecholamines and their metabolites should be measured in such cases.

Adrenal Gland Neoplasms↗
PubMed1996

Peroxidase-catalyzed generation of catechin oligomers that inhibit glucosyltransferase from Streptococcus sobrinus.

Oolong tea extract (OTE) and the purified polymeric polyphenols from OTE have been found to inhibit glucosyltransferase (GTase) of mutans streptococci. In view of the partial fermentation characteristic of oolong tea, we describe here an in vitro model reaction system to produce partially fermented products of D-(+)-catechin or green tea extract (GTE) using horseradish peroxidase. A dimeric catechin molecule was identified as dehydro-dicatechin A by instrumental analyses. The molecular size of some oligomeric catechins was estimated by the elution profile with HPLC. These catechin oligomers markedly inhibited GTase from Streptococcus sobrinus 6715. As the degree of polymerization of catechin or GTE increased, GTase was inhibited more effectively. These results suggest that polymeric polyphenols found in OTE are synthesized by partial fermentation due to oxidases/peroxidases present in tea leaves.

Bacterial Adhesion↗
PubMed1996

Usefulness of electron-beam computed tomography in arrhythmogenic right ventricular dysplasia. Relationship to electrophysiological abnormalities and left ventricular involvement.

BACKGROUND: Electron-beam computed tomography (CT) may be useful for detecting myocardial fat infiltration and diagnosing arrhythmogenic right ventricular dysplasia (ARVD). There are several characteristic electron-beam CT findings of ARVD. However, the incidence, their relation to electrophysiological abnormalities, and the usefulness of electron-beam CT for evaluating left ventricular involvement are unknown. This study aimed to clarify these issues. METHODS AND RESULTS: Electron-beam CT was performed in 14 patients with ARVD (ARVD group), 16 age- and sex-matched patients with right ventricular enlargement and/or dysfunction without ARVD (RV enlargement group), and 13 control subjects (control group). The incidences of abnormal electron-beam CT findings in the three groups were examined. Furthermore, we examined the endocardial fat-infiltrated areas detected by electron-beam CT (CT-A) and electrophysiologically abnormal areas detected in the mapping electrophysiology study (EPS-A) and compared the relationship between them in the ARVD group. (1) The frequencies of abundant epicardial adipose tissue, low-attenuation trabeculations, scalloping of the right ventricular free wall, and intramyocardial fat deposits were 86%, 71%, 79%, and 50%, respectively, in the ARVD group, whereas these findings were not observed in the RV enlargement and control groups. (2) Three ARVD patients (21%) had adipose tissue involvement of the left ventricle. (3) The relationship between CT-A and EPS-A was as follows: CT-A > EPS-A, 71%; CT-A = EPS-A, 14%; and EPS-A only, 14%. CONCLUSIONS: Characteristic electron-beam CT findings are frequently observed only in patients with ARVD. Electron-beam CT is useful for evaluating for left ventricular involvement and can estimate EPS-A.

Adult↗
PubMed1996

Deletion and reintroduction of glucosyltransferase genes of Streptococcus mutans and role of their gene products in sucrose dependent cellular adherence.

Streptococcus mutans has three kinds of glucosyltransferases (GTases), i.e. GTase-I, GTase-SI and GTase-S. These enzymes co-operatively synthesize adhesive glucan from sucrose, which contributes to firm adherence of growing organisms to solid surfaces. In this study, the genes encoding GTase-I (gtfB) and GTase-SI (gtfC) of S. mutans MT8148 (serotype c) were inactivated by the insertion mutagenesis by allelic exchange. Three types of isogenic mutants lacking either GTase-I, GTase-SI or both, respectively were isolated. Sucrose dependent cellular adherence of these mutants were significantly lower than that of the parent. Adherence of GTase-SI deficient mutant was lower than that of GTase-I deficient mutant. We then generated Escherichia coli-Streptococcus shuttle vectors carrying the gtfB and gtfC gene. The shuttle vector containing the gtfB gene was transformed into the GTase-I deficient mutant. Western blot analysis of the transformant revealed that GTase-I protein was fully expressed. Sucrose dependent adherence of the transformant increased but did not reach that of the parent. Similarly, the shuttle vector containing the gtfC gene was transformed into the GTase-SI deficient mutant. The expression of GTase-SI and sucrose dependent adherence of the transformant was revealed to be at a level similar to those by the parent. These results indicated that GTase-SI does play an essential role in the production of adhesive glucan that can lead to firm cellular adherence to solid surfaces.

Bacterial Adhesion↗
PubMed1996

Mechanisms for mucosal immunogenicity and adjuvancy of Escherichia coli labile enterotoxin.

Escherichia coli labile toxin (LT) was assessed as mucosal immunogen and as adjuvant for tetanus toxoid (TT) in mice. After oral administration of LT, C57BL/6 (H-2b) and BALB/c(H-2d) mice were high mucosal and serum antibody responders, while C3H/HeN (H-2k) mice were low responders. High responders exhibited mainly serum IgG (including IgG1, IgG2a, and IgG2b), as well as IgM and IgA, while mucosal responses were IgA. Analysis of LT-B-specific CD4+ T helper (Th) cells from Peyer's patches (PP) or from spleen revealed a mixed Th1 (interferon-gamma) and Th2 (interleukin-4 and -5) cell pattern. Oral LT given with TT induced TT-specific response patterns identical to LT-B. Analysis of mRNA from TT-specific PP CD4+ Th cells also revealed a mixed Th1- and Th2- type response. Thus, antibody response profiles induced by LT are regulated by both CD4+ Th1 and Th2 cell types.

Adjuvants, Immunologic↗
PubMed1996

Oral immunization with the B subunit of the heat-labile enterotoxin of Escherichia coli induces early Th1 and late Th2 cytokine expression in Peyer's patches.

The B subunit of heat-labile toxin (LT-B) from enterotoxigenic Escherichia coli has been shown to be a powerful mucosal immunogen. Oral immunization of mice with LT-B revealed that BALB/c (H-2d) and C57BL/6 (H-2b) mice gave high serum IgG and mucosal IgA responses specific for LT-B. However, ALY (H-2b) mice lacking intestinal Peyer's patches (PP) did not respond to oral LT-B with either serum or mucosal antibodies. These results indicate that PP lymphocytes supported both systemic and mucosal immune responses when the antigen was administered orally. Reverse transcription polymerase chain reaction analyses revealed that PP CD4 T cells expressed early Th1-type (interferon-gamma and interleukin [IL]-2) and late Th2-type (IL-4, -5, and -6) cytokine mRNA. These results suggest that the systemic and mucosal antibody responses induced by LT-B are regulated by a cooperation of PP Th1 and Th2 cells.

Animals↗
PubMed1996

Role of alpha beta T cells and gamma delta T cells in protective immunity to Actinobacillus actinomycetemcomitans in mutant mice by targeted gene disruption.

The relative roles of alpha beta or gamma delta T cells in protection against Actinobacillus actinomycetemcomitans were analysed by using mutant mice deficient in alpha beta or gamma delta T cell receptor (TCR). The dose of A. actinomycetemcomitans producing lethality for the TCR-alpha deficient mice was 25% of that for control C57BL/6 mice, while that of TCR-delta deficient mice was similar to that of C57BL/6 mice. Reverse transcription (RT)-PCR revealed that gamma delta T cells from the A. actinomycetemcomitans-infected alpha beta TCR deficient mice expressed significant levels of interferon (IFN)-gamma, interleukin (IL)-5 and IL-6 mRNA, whereas alpha beta T cells from A. actinomycetemcomitans-infected gamma delta TCR deficient mice exhibited significant levels of IFN-gamma and IL-2 mRNA. Delayed-type hypersensitivity (DTH) reactions against heat shock protein (HSP) 60 were prominently observed in A. actinomycetemcomitans-infected TCR-delta mutant and C57BL/6 mice, but were absent in TCR-alpha mutant mice, suggesting that the DTH response is exclusively dependent on HSP60-specific alpha beta T cells producing IFN-gamma and IL-2 mRNA. It was found that all the mice used exhibited similar levels of serum IgG and IgM responses against A. actinomycetemcomitans-specific antigens (whole cells and HSP60), suggesting that alpha beta as well as gamma delta T cells participate in the serum immune responses. In addition, the humoral antibody responses displayed in the TCR-alpha deficient mice implies resistance to A. actinomycetemcomitans infection. Thus, the resistance to A. actinomycetemcomitans infection may be ascribed mainly to alpha beta T cells, while gamma delta T cells can partially compensate for the alpha beta T cell defect.

Aggregatibacter actinomycetemcomitans↗