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Biomedical subjects

D C Alexander

Publications and source records attributed to D C Alexander.

50 records · Page 3Linked to original sources
PubMed1975

Biological characterization of Fusobacterium necrophorum. Cell fractions in preparation for toxin and immunization studies.

Fusobacterium necrophorum isolated from bovine liver abscesses was grown in bulk at 37 C for 24 h under a strict anaerobic atmosphere. Harvested washed cells were disrupted ultrasonically and fractionated by differential centrifugation into the intracellular (cytoplasm) and cell wall fractions. Both intact cells and cell fractions induced generalized cytopathic effect on primary pig kidney cultures and caused a variety of signs of illness and/or death of intraperitoneally injected mice. The intact cells, disrupted cells, and cell walls produced necrotic lesions and erythema on intradermally injected guinea pigs and rabbits, whereas the cytoplasm mainly erythema. By contrast, the used culture medium (culture filtrate) of F. necrophorum did not show any detectable toxicity. The toxic component of the cytoplasm appears to be associated with nondialyzable, hemolytic, high-molecular-weight proteins and its toxicity is reduced by trypsin and pronase. Heating at 60 C for 10 min decreased markedly its erythemal and cytotoxic ability, wheras the toxicity of the cell walls appeared to be only slightly affected even when heated at 100 C for 1 h. These results suggest that at leasttwo distinct cell-bound toxic factors are present in F. necrophorum cells.

Amino Acids↗
PubMed1974

Results of a preliminary trial with Sphaerophorus necrophorus toxoids to control liver abscesses in feedlot cattle.

A preliminary field experiment was undertaken to evaluate the efficacy of alum precipitated toxoids of Sphaerophorus necrophorus prepared from sonicated whole cells and cell fractions to reduce the incidence of bovine abscesses. A total of 108 calves were divided into five groups and treated as follows: I. uninoculated control, II. adjuvant inoculated control, III. 15.5 mg protein of sonicated (fragmented cells) toxoid, IV. 10.5 mg protein of cytoplasmic toxoid. V. 15.5 mg protein of cytoplasmic toxoid. All animals were maintained under similar conditions to those prevailing in feedlots in Alberta. Livers were examined at slaughter. The most promising result was achieved with the injection of 15.5 mg protein of cytoplasmic toxoid. In this treatment group, no scars (healed lesions) were found in the liver and the incidence of liver abscesses was reduced to 10% from the average 35% liver abscesses and scars found in the uninoculated and adjuvant inoculated groups. The toxoid from sonicated whole cells did not reduce liver abscess incidence. These data suggest that the incidence of liver abscesses in cattle fattened in feedlots may be reduced by immunization.

Adjuvants, Immunologic↗
PubMed1971

Bacteriological studies on meat pies and frozen prepared dinners.

A bacteriological survey of meat pies, frozen prepared dinners and entrees indicated that their bacterial populations were related to the components, the environment and handling in manufacture. Results were correlated with microbiological examinations of ingredients, line samples and plant environmental samples. Total bacterial counts, coliform counts and Staphylococcus counts of the finished product were low. Coliform organisms found were primarily Aerobacter spp. originating with the frozen vegetables. Enterococci were also found in the frozen vegetables and finished product. Both enterococci and Aerobacter organisms were recovered from the plant environment where they appeared to multiply. Many of the plant personnel carried coagulase-positive staphylococci in the throat or nasal cavity, and this was indicated as a possible source for these organisms found in low numbers in the finished product. Cooking of the products produced sterility except for the survival of some spore forming Bacillus spp. The presence of a poultry slaughtering operation adjacent to the manufacturing area was considered to contribute to microbial contamination of the air in the plant.

Air Microbiology↗
PubMed1971

Studies on the bacterial floral of condemmed portions from arthritic hogs.

Studies were conducted on the bacterial floral of 122 excised joints and related iliac and inguinal lymph nodes, 118 whole hams and 42 shoulders from condemned arthritic hog carcasses. Erysipelothrix insidiosa was isolated from 15% of the joints and lymph nodes, 20% of the hams, and 33% of the shoulders. Beta-hemolytic streptococci were recovered from 12% of the joints and lymph nodes, 49% of the hams, and 54% of the shoulders. Staphylococcus aureus was found in 3% of the joints and lymph nodes, 16% of the hams and 14% of the shoulders. Gross tissue changes were not pathognomonic for any causative organism.

Animals↗
PubMed1967

Chromatographic studies of sera from calves vaccinated with brucella abortus, strain 19.

The presence of antibody was detected by agglutination tests in the serum of calves four days after vaccination with Brucella abortus strain 19. Titres had reached a maximum by seven to ten days post-vaccination. Sucrose density-gradient ultracentrifugation demonstrated that the earliest antibodies were macroglobulins, IgM (19Sgamma; gammaM)-globulins. Lighter antibodies, IgG (7Sgamma(2); gammaG)-globulins, appeared a few days later. With time, antibody titres fell, IgM declining somewhat more quickly than IgG. After revaccination some seven months later, there was a rapid rise in both IgM and IgG.Anion-exchange column chromatography (DEAE-cellulose) and gel filtration (Sephadex G-200) were applied in separating the two forms of antibody. The former method, in which a gradient buffer system was used, proved to be the more efficient; the IgG antibodies apeared in early eluates at pH 7.8 to 8.0 and low ionic strength, 0.03M, whereas IgM was eluted late when the pH had fallen below 6.0 and the molarity had increased to beyond 0.2. DEAE cellulose chromatography detected IgG as well as IgM sera collected as early as five days after vaccination.

Agglutination Tests↗