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Biomedical subjects

R M Smibert

Publications and source records attributed to R M Smibert.

At least 37 records · Page 2Linked to original sources
PubMed1982

Bacteriology of experimental gingivitis in young adult humans.

From replicate trials of experimental gingivitis in four periodontally healthy subjects, 166 bacterial species and subspecies were detected among 3,034 randomly selected isolates from 96 samples. Of these bacteria, Actinomyces naeslundii (serotype III and phenotypically similar strains that were unreactive with available antisera), Actinomyces odontolyticus (serotype I and phenotypically similar strains that were unreactive with available antisera), Fusobacterium nucleatum, Lactobacillus species D-2, Streptococcus anginosus, Veillonella parvula, and Treponema species A appeared to be the most likely etiological agents of gingivitis. Statistical interpretations indicated that the greatest source of microbiological variation of the total flora observed was person-to-person differences in the floras. The next greatest source of variation was the inflammatory status of the sample sites. Person-to-person differences were smallest at experimental day 4. The floras became more diverse with time and as gingivitis developed and progressed. Analyses indicated that sequential colonization by certain species was repeatable and therefore probably predictable. Variation was relatively small between replicate trials, between two sites on the same teeth sampled on the same day, and between the same sites sampled at the same relative time in a replicate trial.

Actinomyces↗
PubMed1982

Bacteriology of severe periodontitis in young adult humans.

A total of 78 bacteriological samples were taken from the supragingival tooth surface after superficial cleaning with toothpicks or from the periodontal sulci of 42 affected sites in 21 adolescents or young adults with severe generalized periodontitis. Of 190 bacterial species, subspecies, or serotypes detected among 2,723 isolates, 11 species exceeded 1% of the subgingival flora and were most closely associated with the diseased sulci. Eleven others were also sufficiently frequent to be suspect agents of tissue destruction. Many of these species are known pathogens of other body sites. In addition, 10 species of Treponema were isolated. One of these and the "large treponeme" were also more closely associated with severe periodontitis than they were with healthy sites or gingivitis. There were highly significant differences between the composition of the flora of the affected sulci and the flora of (i) the adjacent supragingival tooth surface, (ii) the gingival crevice of periodontally healthy people, and (iii) sites with a gingival index score of 0 or 2 in experimental gingivitis studies. The floras of different individuals were also significantly different. There was no statistically detectable effect of sampling per se upon the composition of the flora of subsequent samples from the same sites. The composition of the supragingival flora of the patients with severe generalized periodontitis that had serum antibody to Actinobacillus actinomycetemcomitans was significantly different from the supragingival flora of patients without this serum antibody. However, there was no statistically significant difference in the composition of their subgingival floras.

Actinobacillus↗
PubMed1982

Fumarate reduction and product formation by the Reiter strain of Treponema phagedenis.

The catabolic pathways for butyrate, acetate, succinate, and ethanol formation by the Reiter strain of Treponema phagedenis were investigated. Enzyme activities were demonstrated for glucose catabolism to pyruvate by the Embden-Meyerhof-Parnas pathway. Butyrate formation from acetyl-coenzyme A (acetyl-CoA) does not generate ATP by substrate level phosphorylation and involves NAD+-dependent 3-hydroxybutyryl-CoA dehydrogenase and NAD(P)+-independent butyryl-CoA dehydrogenase activities. Butyrate is formed from butyryl-CoA in a CoA transphorase reaction. Phosphate acetyltransferase and acetate kinase activities convert acetyl-CoA to acetate. An NADP+-dependent alcohol dehydrogenase participates in ethanol formation; however, the manner in which acetyl-CoA is reduced to acetaldehyde is unclear. A membrane-associated fumarate reductase was found which utilized reduced ferredoxin or flavin nucleotides as physiological electron donors. Additional electron carriers may also be involved in electron transfer for fumarate reduction. Strains of Treponema denticola, T. vincentii, and T. minutum utilized fumarate without succinate formation, whereas strains of T. phagedenis and T. refringens formed succinate from exogenously supplied fumarate.

Acetates↗
PubMed1982

Pyruvate oxidation by the Reiter strain of Treponema phagedenis.

Spectrophotometric assays of pyruvate oxidation catalyzed by extracts of the Reiter strain of Treponema phagedenis indicated that viologen dyes, flavin nucleotides, and a ferric iron chelate, but not pyridine nucleotides, were utilized as electron acceptors. Benzyl viologen-linked activity partially sedimented during ultracentrifugation and appeared similar to clostridial pyruvate:ferredoxin oxidoreductase with respect to the spectral properties of the enzyme chromophore. Electron carrier activity in treponemal extracts was quantitated by a metronidazole-linked assay in which the oxidation of pyruvate by carrier-depleted extracts led to the reduction of electron carrier in the crude extracts which then reduced metronidazole. The rate of metronidazole reduction was proportional to the amount of electron carrier present in the assay. Electron carrier activity in Triton X-100-solubilized, crude extracts partially purified by DEAE-cellulose chromatography and gel filtration was attributed to a protein possessing the spectral and physical properties of a ferredoxin. A similar protein appeared to be present in extracts of Treponema denticola ST10.

Electron Transport↗
PubMed1982

Fatty acid requirement of Treponema denticola and Treponema vincentii.

Treponema denticola and Treponema vincentii were cultured in a medium supplemented with either 0.2 or 0.4% (w/v) alpha globulin in place of serum. The active factor(s) in alpha globulin was stable at pH 7.0 to autoclaving and was nondialyzable. Extraction of lipids from alpha globulin showed that both protein and lipid, supplied by the alpha globulin, were required for maximal growth of these two oral treponemes. The lipid component was investigated by adding sodium salts of long-chain fatty acids to the basal medium supplemented with 0.4% delipified alpha globulin. The lipid component of alpha globulin was replaced by either oleic acid (cis-18:1(9)) or by elaidic acid (trans- 18:1 (9)0. No other saturated or unsaturated fatty acid tested could support good growth. Tween 80 (polysorbitan monooleate) was the only Tween compound able to support maximal growth of T. denticola. The cellular lipids of T. denticola, grown with oleate in broth supplemented with 0.4% delipified alpha globulin, were extracted and analyzed by gas chromatography. The principle fatty acids were myristic, pentadecanoic, and palmitic acids. Lesser amounts of oleic acid, eicosadienoic acid, and an unidentified fatty acid (retention time, 88 min) were also detected. Treponema denticola appears to be capable of limited synthesis of cellular fatty acids such as myristic, pentadecanoic, and palmitic acids from oleic acid.

Alpha-Globulins↗
PubMed1982

Lipid catabolism of cultivated treponemes.

Treponema require long-chain fatty acids for growth in vitro. Serum, added to culture media, provides a source of long-chain fatty acids. These fatty acids, however, are esterified to triglycerides, phospholipids, and cholesterol. In this study, the major pathways of complex lipid catabolism in T. phagedenis, T. denticola, T. refringens, T. minutum, and T. vincentii were investigated. Lipase activity was demonstrated in five Treponema species using four lipid substrates. Chromatographic data demonstrated that, during growth, treponemes completely utilized lysophosphatidylcholine, present in serum-supplemented culture media, while phosphatidylcholine and phosphatidylinositol were not utilized. Phospholipase B and glycerophosphorylcholine diesterase activities were demonstrated in the five species of Treponema studied. Treponema phagedenis and T. denticola had phosphatase activity, while T. refringens, T. minutum, and T. vincentii did not have an acid phosphatase activity. Phospholipase A, C, and D and alkaline phosphatase activities were not found in five species of Treponema. Based on the enzymes demonstrated in this study, two pathways of phospholipid catabolism are proposed.

Acid Phosphatase↗
PubMed1979

Studies of the microaerophilic nature of Campylobacter fetus subsp. jejuni. II. Role of exogenous superoxide anions and hydrogen peroxide.

The addition of bovine superoxide dismutase to Brucella broth or Brucellar agar greatly echanced the oxygen tolerance of Campylobacter fetus subsp. jejuni strain H840 (ATCC 29428). Catalase also enhanced oxygen tolerance, but to a lesser extent. These enzymes must act externally to the bacteria. All of the diverse compounds which enhance oxygen tolerance of C. fetus, including nor-epinephrine and a combination of ferrous sulfate, sodium metabisulfite, and sodium pyruvate, share the ability to quench either superoxide anions or hydrogen peroxide. On the basis of these and other data, we propose that C. fetus is more sensitive to exogenous superoxide anions and hydrogen peroxide than are aerotolerant bacteria, despite the occurrence of superoxide dismutase and catalse activities in C. fetus. Compounds that enhance oxygen tolerance in C. fetus appear to act by quenching superoxide anions and hydrogen peroxide which occur spontaneously in the culture medium.

Campylobacter↗
PubMed1978

Improved media for growth and aerotolerance of Campylobacter fetus.

The microaerophilic nature of Campylobacter fetus has complicated its recovery from human and animal sources. In this study, modifications of brucella agar and broth were tested for enhancement of growth and aerotolerance of 64 strains of C. fetus, representing each subspecies. Brucella agar supplemented with 0.025% each FeSO4 7H2O, sodium metabisulfite, and sodium pyruvate, supported growth of 98, 77, and 63% of the strains at 6% O2, 17% O2, and 21% O2, respectively. Unsupplemented brucella agar supported growth of 94, 48, and 20% of the strains. Brucella broth supplemented with 0.2% FeSO4.7H2O, 0.025% sodium metabisulfite, and 0.05% sodium pyruvate supported growth of 98% of the strains at 21% O2, compared to 75% with unsupplemented brucella broth. With both the supplemented agar and broth, growth responses occurred 1 to 2 days earlier than usual. Growth and aerotolerance of three strains of Campylobacter sputorum subsp. bubulus were not enhanced by the supplements.

Campylobacter↗
PubMed1976

Stimulatory effect of dihydroxyphenyl compounds on the aerotolerance of Spirillum volutans and Campylobacter fetus subspecies jejuni.

The aerotolerance of the microaerophilic bacterium Spirillum volutans was greatly stimulated in a defined medium by the presence of dihydroxyphenyl ferric iron-binding compounds such as nor-epinephrine at 10(-5) to 10(-6) M. Dihydroxyphenyl compounds at 2 X 10(-4) M, or iron salts (ferrous or ferric) at high concentration, greatly increased the aerotolerance of a strain of Campylobacter fetus subsp. jejuni when grown on streak plates of Brucella agar. The results suggest that the microaerophilism of these organisms might in part be caused by a failure to synthesize microbial ferric iron-binding compounds at sufficient levels to support aerobic growth.

Aerobiosis↗
PubMed1976

Clinical isolates of anaerobic gram-negative rods with a formate-fumarate energy metabolism: Bacteroides corrodens, Vibrio succionogenes, and unidentified strains.

Strains of anaerobic, gram-negative bacteria, isolated from human clinical specimens and from studies of human normal flora, that have energy metabolism similar to Vibrio succinogenes are described. Included are four human isolates of V. succinogenes, five similar strains of motile straight rods, three strains of Bacteroides corrodens, and two unidentified strains. All strains studied grew poorly in usual anaerobic broth media but produced good turbidity in overnight broth cultures in media containing fromate and fumarate, indicating that all have an energy metabolism similar to V. succinogenes: they gain energy by the transfer of electrons from formate or hydrogen to fumarate.

Asparagine↗