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Biomedical subjects

E C Chan

Publications and source records attributed to E C Chan.

At least 127 records · Page 7Linked to original sources
PubMed1983

In vitro activity of rodogyl against putative periodontopathic bacteria.

The minimal inhibitory concentrations of Rodogyl (composite tablet of metronidazole and spiramycin), metronidazole-spiramycin mixture, spiramycin, metronidazole, and tetracycline were determined for selected putative periodontopathic microorganisms. Rodogyl was active against almost all strains, including Bacteroides species and the anaerobic spirochetes. Synergism of the component drugs in the Rodogyl combination was noted against Propionibacterium species. Spiramycin activity against Actinomyces species was enhanced in the presence of metronidazole.

Bacteria↗
PubMed1983

Phase variation of hyaluronidase-producing peptostreptococci associated with periodontal disease.

Peptostreptococci isolated from diseased periodontal pockets produced large amounts of extracellular hyaluronidase throughout their growth cycle. Phase variants, obtained by re-streaking aged colonies of the wild types, had different colonial morphology and shorter generation times. These variants produced less hyaluronidase, and enzyme production occurred only during the early stationary phase.

Humans↗
PubMed1981

Use of fluorescence microscopy for monitoring periodontal disease state.

Samples of subgingival plaque from patients with periodontal disease and control subjects were stained with the Fluoretec Fluorescent test kits (Pfizer Inc., New York) developed for the rapid detection of members of the Bacteroides fragilis and B. melaninogenicus groups of anaerobes. The same fluorescent fields were also examined by dark-field microscopy for the total count of bacteria. Bacteroides fragilis and B. melaninogenicus were found in plaque samples of healthy subjects and periodontally diseased patients with no significant difference in percent of total flora. Oral spirochetes also fluoresced with the antisera used. Samples from healthy sites showed virtually no spirochetes; spirochetes were present in diseased sites. Tests with other antisera also showed that fluorescein-labelled antibodies can be adsorbed nonspecifically to the surface of spirochetes. Such a phenomenon can be used to monitor an individual's periodontal disease state.

Bacteroides↗
PubMed1978

Preparation of prereduced anaerobically sterilized media and their use in cultivation of anaerobic bacteria.

Several modifications of the roll-tube method have made it simpler for routine use in the isolation and growth of anaerobic bacteria. These include use of a check valve for the production of prereduced anaerobically sterilized media; a Salvarsan tube under oxygen-free gas pressure for the dispensing of molten prereduced anaerobically sterilized agar medium; a Kelly infusion bottle with a graduated pipette side arm (also under gas pressure) for quantitative delivery of fluid prereduced anaerobically sterilized media; and screw-capped prescription bottles for the cultivation of anaerobes. Colonies of Bacteroides melaninogenicus were easily identified and counted by this method. Other anaerobic bacteria have also been cultivated successfully.

Anaerobiosis↗
PubMed1978

Morphogenetic expression of Arthrobacter globiformis 425 in continuous culture with carbon or biotin limitation.

When deprived of biotin, Arthrobacter globiformis 425 exhibits abnormal morphology (large, branched forms of variable size) and a retardation of its normal growth rate. In chemostat cultures, when cells were grown under glucose limitation, the morphology was normal (coccoids or rods) at specific growth rates between 0.05 and 0.125 h-1 (doubling times between 14 and 5.5 h, respectively) at 25 degrees C. The coccoid-to-rod morphogenesis occurs at a specific growth rate of 0.11 h-1. At the same specific growth rates and temperature, but under biotin limitation, abnormal morphology was observed.

Arthrobacter↗
PubMed1973

Biotin deficiency in Arthrobactger globiformis: comparative cell ultrastructure and nonreplacement of the vitamin by structurally unrelated compounds.

The development of aberrant cell forms of Arthrobacter globiformis 425 due to biotin deficiency was followed by electron microscopy of ultrathin sections. Upon comparison with normal cell growth, aberrant cells developed in the early logarithmic growth phase. Several membrane-bound bodies were embedded in a thick matrix, showing that cell division was impaired. Mesosomes and cytoplasmic membranes were still present in the abnormal cell although the normal cell wall was absent. This condition persisted throughout the growth cycle. This pattern of morphological development was correlated with changes in macromolecular composition of the cells. Various structurally unrelated compounds were tested for their ability to replace biotin. These included aspartic acid, oxalacetic acid, coenzyme A, oleic acid, linoleic acid, linolenic acid, and Tween 80. Only Tween 80 was able to spare biotin to a limited degree. However, this sparing action was eliminated in the presence of avidin.

Arthrobacter↗