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Biomedical subjects

R Osawa

Publications and source records attributed to R Osawa.

33 records · Page 2Linked to original sources
PubMed1994

Differences related to the production of arachidonic acid between collagen- and thrombin-stimulated human platelets.

The effects of collagen and thrombin on the liberation of free arachidonic acid were investigated in human platelets by fluorometric high-performance liquid chromatography. Collagen induced a concentration-dependent increase in the extent of platelet aggregation, as well as an accumulation of arachidonic acid in human platelets. By contrast, thrombin effectively provoked a potent aggregation at relatively low concentration without any accumulation of free arachidonic acid, although the accumulation of arachidonic acid was detected at a high concentration of thrombin (> 0.1 U/ml) that induced full aggregation. The selective liberation of arachidonic acid was found in thrombin-stimulated platelets. Non-selective liberation of fatty acids occurred in platelets that had been stimulated with a high concentration of collagen (10 micrograms/ml), as well as in platelets stimulated with A23187. The net amount of free arachidonic acid in collagen-stimulated platelets was estimated by use of eicosatetraenoic acid (ETYA), which is an inhibitor of both cyclooxygenase and lipoxygenase. ETYA markedly potentiated the accumulation of free arachidonic acid in collagen-stimulated platelets without changing the amounts of other fatty acids in the cell.

Arachidonic Acid↗
PubMed1993

Visual reading method for detection of bacterial tannase.

Tannase activity of bacteria capable of degrading tannin-protein complexes was determined by a newly developed visual reading method. The method is based on two phenomena: (i) the ability of tannase to hydrolyze methyl gallate to release free gallic acid and (ii) the green to brown coloration of gallic acid after prolonged exposure to oxygen in an alkaline condition. The method has been successfully used to detect the presence of tannase in the cultures of bacteria capable of degrading tannin-protein complexes.

Journal Article↗
PubMed1992

Tannin-protein complex-degrading enterobacteria isolated from the alimentary tracts of koalas and a selective medium for their enumeration.

Tannin-protein complex (T-PC)-degrading enterobacteria (T-PCDE) were isolated from the feces and from a layer of bacteria attached to the cecal wall of koalas. The T-PCDE were facultatively anaerobic, gram-negative, pleomorphic, nonmotile bacilli. The bacteria were also oxidase and catalase negative and resistant to vancomycin, reduced nitrates to nitrites, and grew on MacConkey agar. Growth on tannin-treated agar media showed a distinctive clear zone around the colony. From these observations, a selective agar plate medium (vancomycin- and tannin-treated Wilkins-Chalgren anaerobe agar) was developed to enumerate T-PCDE isolated from the feces of koalas. This medium was highly selective in the enumeration of the fecal T-PCDE and inhibited the growth of concomitant T-PC-degrading Streptococcus bovis. The T-PCDE were isolated from 10 of the 12 captive koalas studied; in 8 of these 10 koalas, the facultatively anaerobic bacterial flora was dominated (more than 60%) by T-PCDE. Viable numbers of T-PCDE were, in most of the animals, much larger (more than 100 times) than the numbers of T-PC-degrading S. bovis, suggesting that T-PCDE played a more active role in digesting T-PC in the alimentary tracts of koalas.

Animals↗
PubMed1992

Microflora of the pouch of the koala (Phascolarctos cinereus).

Microflora of the pouch epithelium of 17 female koalas (Phascolarctos cinereus) were examined in relation to their current reproductive status and recent reproductive history. No microbial growth was observed in pouch swabs from 13 of 17 (76%) koalas, including four females without young, seven with pouch young and two with back young (i.e. permanently emerged from the pouch). Growth of bacteria or yeasts was observed in pouch swabs from four koalas, each of which had experienced mortality of its pouch young during the current breeding season. Seven species of microorganisms were isolated, including Pseudomonas aeruginosa, Serratia marcescens and Enterococcus faecalis. Based on the absence of microflora in the majority of females examined, we propose that the pouch epithelium normally provides a hostile environment for microbial colonization.

Acinetobacter↗
PubMed1991

DNA damage in forestomach epithelium from male F344 rats following oral administration of tert-butylquinone, one of the forestomach metabolites of 3-BHA.

DNA damage in the forestomach epithelium of male F344 rats was tested by alkaline elution assay following oral administration of 3-tert-butyl-4-hydroxyanisole (3-BHA) and its free metabolites. Although 1% 3-BHA and 0.001% tert-butylhydroquinone (BHQ) caused no detectable DNA damage, a tert-butylquinone (BQ) treated group showed a significantly higher elution rate than the corn oil and 3-BHA group. Dose-dependent induction of DNA damage in forestomach epithelium by 3-BHA metabolites was compared. BQ showed DNA damaging activity from 0.0001% (1 microgram/ml). On the other hand, BHQ showed the activity at greater than 100 times higher concentration than that of BQ. Six other quinones related to the BQ have been synthesized and examined in vivo for their activity in single strand breaks in forestomach epithelium DNA. The order of the DNA damage was not always correlated with the order of the first reduction potentials of the quinones. 2-Benzylthio-5-tert-butyl-p-benzoquinone (BQSBn-2), 2-phenyl-1,4-benzoquinone and 2,5-di-tert-butyl-p-benzoquinone had higher DNA damaging activity than BQ. The effects of ethylacrylate (EA) pretreatment on the DNA damage by BQ and BQSBn-2 were compared. The DNA damage by BQ was decreased by increasing the EA concentrations. On the other hand, BQSBn-2 had a DNA damaging activity following the EA pretreatment. In order to examine whether 3-BHA is metabolized in forestomach, 3-BHA and BQ levels in the mucosa of forestomach were measured by HPLC with an electrochemical detector. The concentrations of BQ in mucosa correlated with the 3-BHA dose levels from 0.01% to 0.1% 3-BHA. The concentration of BQ in mucosa was approximately 1/4000 of the concentration of 3-BHA in mucosa at the dose level of 1% 3-BHA. The present results indicate that BQ and its thiol conjugates are the active metabolites from 3-BHA in forestomach and may play an important role in inducing carcinogenicity of 3-BHA in F344 rats.

Acrylates↗
PubMed1991

Serological assessment of chlamydial infection in the koala by a slide EIA technique.

A rapid and simplified slide enzyme immunosorbent assay (EIA) was developed for the diagnosis of chlamydial infection in the koala. HeLa 229 cells infected with koala strain Chlamydia psittaci were fixed on the surface of multiwell slides and used as the antigen. The assay consisted of first reacting koala antiserum with the fixed C psittaci antigen, followed by reaction with biotinylated rabbit anti-koala IgG, ABC reagent and substrate. The chlamydial EIA antibody titres obtained were compared with those of a complement fixation (CF) test using koala strain C psittaci as antigen. Of 35 koala sera tested, 16 CF positive sera (greater than or equal to 1:8) also had a positive titre (greater than or equal to 1:200) in the slide EIA test (sensitivity 93.8%, 15/16). Nineteen CF negative sera were also negative in the slide EIA (specificity 100%, 19/19). Sixty-eight samples of koala blood were collected by ear-prick using a sampling paper method and were assayed by both tests. Sensitivity of the slide EIA was 100% (15/15) and specificity of the test was 96.2% (51/53). To simplify the slide EIA for use as a practical screening test, a 3-point serum dilution series (1:100, 1:200, 1:400) was used. This 3-point slide EIA was compared with the CF test using sheep strain chlamydial antigen. Thirty-nine sera were assayed by both tests. The sensitivity of the 3-point method was 85.7% (6/7) and the specificity was 71.9% (23/32) as compared with the sheep antigen CF test.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Phenotypic characterization of CO2-requiring strains of Streptococcus bovis from koalas.

We examined phenotypic characteristics of six mannitol-fermenting strains of Streptococcus bovis, including two unusual CO2-requiring strains isolated from koala feces. These strains did not grow in air, but grew in air supplemented with CO2 and under reduced oxygen conditions. All six strains had the same biochemical characteristics, except that the CO2-requiring strains did not produce beta-N-acetylglucosaminidase.

Animals↗
PubMed1990

[DNA damage test in forestomach squamous epithelium of F344 rat following oral administration of ethyl acrylate].

The alkaline elution assay were applied for testing DNA damage of forestomach squamous epithelium in male F344 rat after oral administration of ethyl acrylate (EA), a forestomach carcinogen. The animals were starved for 18 hr and then given a single oral dose of EA. No DNA damage were observed by EA at the concentration of 0.1-4.0%. The weights of the forestomach increased with EA dose, reflecting edema and inflammation, but that of glandular stomach did not change with its dose.

Acrylates↗
PubMed1972

[Patient's needs].

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Nursing Care↗