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Biomedical subjects

C B Walker

Publications and source records attributed to C B Walker.

At least 55 records · Page 3Linked to original sources
PubMed1981

Tetracycline: levels of achievable in gingival crevice fluid and in vitro effect on subgingival organisms. Part II. Susceptibilities of periodontal bacteria.

The sensitivity to tetracycline of 345 bacterial isolates from periodontal lesions was determined. Most species of bacteria, including those thought to be involved in the initiation and progress of destructive periodontal disease, were inhibited in vitro by tetracycline concentrations of 4 to 8 micrograms/ml. This concentration is equivalent to crevicular fluid levels of tetracycline at dosages of 1 gm/day. These data indicate that tetracycline is inhibitory at levels achieved in crevicular fluid for bacteria currently implicated in destructive periodontal disease.

Bacteria↗
PubMed1980

Sensitive assay for measuring tetracycline levels in gingival crevice fluid.

An increased interest in the clinical use of antibiotics as an adjunct to periodontal therapy has created a need to determine antibiotic concentrations in fluid obtained from the gingival crevice. For this purpose, an increase in sensitivity beyond that possible with current tetracycline assays is essential because sample volumes of gingival fluid typically obtained are less than 0.5 microliter. This report describes the development of an agar-diffusion assay technique capable of measuring the concentration of tetracycline in samples of gingival crevice fluid in the range of 0.1 to 4.0 microgram/ml. The assay will detect amounts of tetracycline in gingival crevice fluid samples as low as 50 pg. The high sensitivity of this assay was achieved by optimizing the medium depth, inoculum density, agar concentration, pH, period of prediffusion, and selection of basal medium. Use of this assay indicated that the concentration of tetracylcine in gingival crevice fluid was greater than that found in blood and persisted at elevated levels for longer periods.

Biological Assay↗
PubMed1979

Agar medium for use in susceptibility testing of bacteria from human periodontal pockets.

An agar medium (medium V) was formulated to determine the minimal inhibitory concentrations (MICs) of antimicrobial agents for bacteria encountered in human periodontal pockets. The medium contained (per liter) Trypticase, 15 g; yeast extract, 5 g; sodium chloride, 5 g; glucose, 2 g; sodium pyruvate, 2 g; sodium formate, 1 g; sodium fumarate, 1.5 g; sodium succinate, 0.1 g; Tween 80, 0.25 ml; agar, 15 g; hemin, 5 mg; and menadione, 0.5 mg. The growth of 50 oral strains was compared on this and six other media which included: Wilkins-Chalgren agar, Schaedler agar, Brucella agar, Trypticase-soy blood agar, and Schaedler and Brucella agars supplemented with whole blood. Growth, for most strains, was greatest on medium V. Medium V was also compared with Wilkins-Chalgren agar, using the same oral strains, to determine the MICs of the following antibiotics: penicillin, tetracycline, chloramphenicol, clindamycin, and erythromycin. The MICs of these antibiotics were essentially the same on both media when growth was quantitatively similar.

Agar↗
PubMed1979

Medium for selective isolation of Fusobacterium nucleatum from human periodontal pockets.

A selective medium, CVE agar, was developed for the isolation of Fusobacterium nucleatum from subgingival plaque of periodontally diseased patients. The medium contained 1.0% Trypticase (BBL Microbiology Systems), 0.5% yeast extract, 0.5% NaCl, 0.2% glucose, 0.02% L-tryptophan, 1.5% agar, and 5% defibrinated whole sheep blood. Erythromycin and crystal violet were added as the selective inhibitory agents at concentrations of 4 and 5 micrograms/ml, respectively. The medium permitted almost total recovery of F. nucleatum when compared with a nonselective medium and suppressed the recovery of most remaining species by nonselective medium and suppressed the recovery of most remaining species by 6 to 8 orders of magnitude. Microorganisms suppressed to a lesser degree included Selenomonas sputigena, Actinobacillus actinomycetemcomitans, Eikenella corrodens, and some strains of Peptostreptococcus. The distinct colonial morphology of F. nucleatum on CVE agar made differentiation relatively easy when contaminants were present. With this medium, F. nucleatum was enumerated from 278 subgingival plaque samples and accounted for less than 1.0 to greater than 25% of the cultivatable microbiota.

Adolescent↗
PubMed1979

Ocular complications in craniofacial fibrous dysplasia.

Three cases of craniofacial fibrous dysplasia are reported, all presenting to the ophthalmologist first. They all had ocular complications due either to direct involvement of the orbital bones or to secondary complications. Sphenoidal mucocele is added to the other complications previously reported, and accordingly a classification of the various ways that fibrous dysplasia can affect the ocular structures is proposed.

Adult↗
PubMed1977

Experimental infections with anaerobic bacteria in mice.

Experimental anaerobic infections in mice are reviewed with a description of a model of pure Bacteroides fragilis infection. In this experimental situation, B. fragilis produces large subcutaneous abscesses in the groins of mice that can be diagnosed without autopsy. This infection was treated effectively with clindamycin in doses that produced levels of drug in blood similar to those attainable in humans.

Anaerobiosis↗
PubMed1977

Chemotherapy of an experimental Bacteroides fragilis infection in mice.

The efficacies of five common antimicrobial agents were determined for a pure Bacteroides fragilis infection in mice. Therapy was begun 4 h after bacterial injection and given every 8 h thereafter for 5 days. Blood levels were determined over an 8-h period for each concentration of antibiotic tested. Clindamycin and tetracycline were the most effective in preventing the formation of abscesses. Chloramphenicol, penicillin G, and cephalothin were not effective in protecting the mice from infection.

Abscess↗
PubMed1976

Use of semisolid agar from initiation of pure Bacteroides fragilis infection in mice.

The development of a pure Bacteroides fragilis infection in mice is described. The infection produces large subcutaneous abscesses at the site of injection which can be observed grossly within 7 days after injection. The infection was initiated by infection of pure cultures grown in semisolid agar medium. Similar infections were also produced with pure cultures of B. distasonis, B. ovatus, B. thetaiotaomicron, and B. vulgatus. However, a distinct deoxyribonucleic acid homology group, formerly classified as B. thetaiotaomicron, did not produce abscesses in any of the mice tested.

Agar↗
PubMed1975

Development of a micromethod for identification of anaerobic bacteria.

A microprocedure was described for determining the carbohydrate fermentation patterns of 48 anaerobic bacteria at one time in microtiter plates. The cultures were transferred into agar-filled wells of microtiter plates with a replicator inside an anaerobic glove box. Fermentation was measured both with a colorimetric indicator and with a small pH electrode. The method was approximately 97% accurate. It would be most useful for laboratories that need to identify large numbers of anaerobes at one time.

Anaerobiosis↗
PubMed1970

A survey of hemoglobin values in Canada.

A compilation of hemoglobin values has been made from submissions from laboratories in Canada using the cyanmethemoglobin standard prepared and distributed by the Canadian Communicable Disease Centre (formerly the Laboratory of Hygiene). From 84 participating laboratories 21,580 values were analyzed statistically by age and sex. "Medical referrals", exclusive of blood dyscrasias, were included but were documented separately from "well persons". In most age groupings no significant difference in these two categories was found.Values for boys and girls were similar up to 12 years of age. For adult women from 18 to 84 years the mean value was 13.0 g. per 100 ml. (95% confidence limits 10.8-15.2 g.); for pregnant women 19 to 44 years the mean value was 12.2 g. per 100 ml. (9.7-14.6 g.). For men aged 17 to 24 years the mean value was 15.0 g. per 100 ml. (12.8-17.3 g.); 25-49 years 14.6 g. per 100 ml. (12.4-16.9 g.); 50-69 years 14.3 g. per 100 ml. (11.8-16.8 g.). It is noteworthy that for the most part the mean values were slightly lower than those frequently quoted as "normal" and that the mean values, particularly for the male, were lower with increasing age.

Adolescent↗
PubMed1967

Summary of a Canadian study of smoking and health.

The object of this study was to investigate the relationship between residence, occupation and smoking habits, and mortality from chronic diseases, particularly lung cancer. It was a prospective study, initiated by a questionnaire sent to Canadian veteran pension recipients. The study was based on the replies of 78,000 males and 14,000 females, together with data on the deaths occurring among these respondents over a six-year follow-up period-July 1, 1956 to January 30, 1962.The outstanding finding of this study was that cigarette smokers compared to non-smokers had excessive mortality, particularly from heart and circulatory diseases, lung cancer, and bronchitis and emphysema. The mortality ratios for heart and circulatory diseases were elevated even for those who smoked cigarettes less than five years, and remained relatively constant as the duration of smoking increased. The mortality ratios for lung cancer increased markedly as the duration of smoking increased. A small excess in mortality was noted among urban residents. An association between cause of death and occupation was not evident in this study.Findings based on the data on smoking collected in this study were incorporated into the Report of the U.S. Surgeon-General's Advisory Committee on Smoking and Health.

Adult↗