Search PubMed⌕ Search

Biomedical subjects

S Hamada

Publications and source records attributed to S Hamada.

At least 397 records · Page 22Linked to original sources
PubMed1984

Ability of various oral bacteria to bind human plasma fibronectin.

The present study describes the ability of various oral bacteria to bind human plasma fibronectin (PFN). Avid binding of 125I-PFN was found for Streptococcus mutans (serotypes a to h), Streptococcus sanguis, group A Streptococcus pyogenes and Staphylococcus aureus, while other gram-positive bacterial species tested demonstrated only weak or negligible PFN binding ability. Two gram-negative bacterial species, Bacteroides gingivalis and Escherichia coli, did not significantly bind PFN. 125I-PFN binding to S. mutans 6715 cells was decreased by pretreatment with unlabeled PFN, and the radiolabeled PFN bound to the cell surface was released on addition of unlabeled PFN. Strong inhibition of 125I-PFN binding to S. mutans 6715 cells was obtained by protease pretreatment, while partial inhibition was also observed following treatment with acid, alkali, lipase, and monoclonal anti-polyglycerophosphate. These results suggest that PFN binding to S. mutans cells is reversible and that PFN receptors on the cell surface appear to be heat-stable multiple proteins.

Bacteria↗
PubMed1984

Characterization of a monoclonal antibody specific for lipoteichoic acid from various gram-positive bacteria.

A hybrid cell line, 3G6, producing monoclonal antibody (mAb) against the polyglycerophosphate (PGP) backbone of lipoteichoic acids has been derived by the polyethylene glycol-induced fusion of mouse myeloma cells and spleen cells from mice immunized with partially purified glucosyltransferase from culture supernatant of Streptococcus mutans strain 6715. Immunodiffusion tests and ELISA revealed that the antibody reacted with purified PGP from group A Streptococcus pyogenes strain Sv as well as crude phenol-water and saline extracts of various gram-positive bacteria except for a few species such as biotype B S. sanguis, Micrococcus sp., and Actinomyces viscosus. Whole cells of serotype b S. mutans and Staphylococcus epidermidis were agglutinated upon addition of 3G6 mAb, while those of most other species were not significantly affected by this procedure. A hapten inhibition study showed that glycerophosphate was only a potent inhibitor of passive hemagglutination reactions between LTA coated sheep erythrocytes and 3G6 mAb.

Animals↗
PubMed1984

Clinical isolates of Streptococcus mutans serotype c with altered colony morphology due to fructan synthesis.

Streptococcus mutans MT6801 , MT6861 , and MT6879 , which form large mucoid colonies on mitis salivarius agar, were isolated from a mother and her two daughters. These isolates were identified as serotype c by immunodiffusion with serotype-specific antisera. The large colonies formed on sucrose-containing agar were found to contain water-soluble fructan . The cell-free fructosyltransferase ( FTase ) activity of the strains which formed large colonies was five to eight times higher than that of serotype c S. mutans which produced small, rough colonies typical of this serotype. Furthermore, greater quantities of fructan were synthesized from sucrose by growing cells of MT6801 when compared with MT8148 , a typical serotype c S. mutans. Glucosyltransferase and FTase could be isolated by chromatofocusing from culture supernatants of MT6801 and MT8148 . The FTase activity of both strains was eluted at pH 4.5, and glucosyltransferase was released by elution with an NaCl linear gradient. The eluted FTase activity of MT6801 was significantly higher than that of MT8148 . Strains MT6861 and MT6879 were also found to possess a similar property in terms of FTase activity. These results suggest that formation of large mucoid colonies by these strains is a consequence of high FTase activity.

Adult↗
PubMed1984

Virulence factors of Streptococcus mutans and dental caries prevention.

Streptococcus mutans possesses the abilities to adhere to pellicle-coated tooth surfaces and to form acids - two characteristics associated with the cariogenicity of this micro-organism. De novo synthesis of insoluble glucan by S. mutans glucosyltransferase from sucrose is essential in the adherence process. Therefore, agents which interfere with the adherence ability of S. mutans would be useful for controlling dental caries. In the present report, we have summarized our recent findings concerning virulence factors of S. mutans and means for prevention of S. mutans-induced dental caries.

Adhesiveness↗
PubMed1984

Studies on rabbit corneal permeability of local anesthetics (I).

To elucidate the pharmacokinetics of local anesthetics with respect to corneal permeability in the rabbit, we examined the relationship between the corneal permeability velocities of three agents, cocaine X HCl, procaine X HCl and tetracaine X HCl and corneal hydration. The corneal permeability velocity constants (k) of these three ester-type local anesthetics were approximately 0.5-6.0 X 10(-6) cm/sec and the membrane permeability constants of these agents were approximately 0.5-4.0 X 10(-7) cm2/sec, whereas the rabbit corneal hydration values were 3.2-4.2. Tetracaine X HCl with the strongest topical anesthetic action showed the greatest corneal hydration and the smallest corneal permeability velocity constant among these local anesthetics. Rabbit corneal permeability decreased with increasing molecular length of the agents. Permeability of these local anesthetics in the rabbit cornea appears to result from passive transport. As corneal hydration values and the corneal permeability constant increased with greater topical anesthetic activity, it appears that the degree of inhibition of Na+-K+ ATPase activity is associated with the order of topical anesthetic activity in a similar manner as general anesthetics.

Anesthetics, Local↗
PubMed1984

Demonstration and characterization of immunoreactive methionine-enkephalin, leucine-enkephalin, methionine-enkephalin-Arg6-Gly7-Leu8 and methionine-enkephalin-Arg6-Phe7 in human phaeochromocytoma.

To elucidate whether or not human phaeochromocytoma contains methionine-enkephalin-Arg6-Gly7-Leu8 (Met-enkephalin-Arg-Gly-Leu) and methionine-enkephalin-Arg6-Phe7 (Met-enkephalin-Arg-Phe) together with methionine-enkephalin (Met-enkephalin) and leucine-enkephalin (Leu-enkephalin), all of which are known to exist in the same precursor molecule (preproenkephalin A), we examined extracts from 16 phaeochromocytomas using high performance liquid chromatography (HPLC) and gel exclusion chromatography coupled with radioimmunoassays (RIAs) for these four opioid peptides. Met-enkephalin-Arg-Gly-Leu-like immunoreactivity (-LI) and Met-enkephalin-Arg-Phe-LI existed together with Met-enkephalin-LI and Leu-enkephalin-LI in 16 phaeochromocytomas. There was a wide variation in contents of Met-enkephalin-LI, Leu-enkephalin-LI, Met-enkephalin-Arg-Gly-Leu-LI and Met-enkephalin-Arg-Phe-LI. Significant positive correlations were observed among the contents of these four opioid peptides in 16 phaeochromocytomas. HPLC and gel exclusion chromatography followed by the RIAs showed the presence of Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Gly-Leu and Met-enkephalin-Arg-Phe together with their high molecular weight forms, which existed in variable amounts. Molar ratios of the contents of these four opioid peptides determined after HPLC varies from case to case. These results indicate the co-existence of Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Gly-Leu and Met-enkephalin-Arg-Phe in human phaeochromocytomas, suggesting the preservation of amino acid sequences of these four opioid peptides even in neoplastic tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

[Maximum tolerated dose of tegafur in rats].

Maximum Tolerated Dose of Tegafur was estimated by per-oral administration in male Donryu rats. Tegafur was administered for 24 weeks at respective doses of 90 mg, 120 mg and 150 mg/kg/day. Six of 10 (60%) died during the treatment in those groups administered with 120 mg and 150 mg/kg/day, respectively. The cause of death of these rats was severe pneumonia. All 10 of the group given 60 mg/kg/day survived until end of the administration and were sacrificed for histological examination of organs. These rats showed apparent suppression of body weight gain compared with controls (p less than 0.001). Slight inflammation of the lungs was observed in all rats, congestion of the liver and local degeneration and necrosis of the liver cells in a few rats and cellular degeneration of bone marrow in one rat. There was no remarkable change in the digestive tract, kidney, thymus or reproductive organs. Accordingly, the Maximum Tolerated Dose of Tegafur was determined to be 90 mg/kg/day.

Administration, Oral↗
PubMed1984

Continuous culture of human melanoma cells in protein-free medium: establishment and partial characterization.

Human melanoma cells (MEC) continuously grown in protein-free RPMI-1640 medium were established. These cultured cells, designated "sf-MEC," grow well in suspension and have been successfully subcultured more than 100 passages for 30 months with complete loss of serum requirement for their growth. Although sf-MEC as well as MEC had a moderate number of mature melanosomes in the cytoplasm, the tumorigenicity in nude mice was lower in sf-MEC than in MEC. In the tumor tissue formed by sf-MEC but not by MEC, a few immature melanosomes and an increased C-type-like virus production were detected. Furthermore, conditioned medium of sf-MEC stimulated DNA synthesis in both normal and transformed cells, including MEC and sf-MEC. Addition of the conditioned medium of sf-MEC in its cell growth assay caused a twofold to eighteenfold increase in cell number as compared to that for the control.

Animals↗