Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0014118 (endocarditis)
 15,629 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Actinobacillus actinomycetemcomitans is a fastidious, facultative gram-negative rod associated with endocarditis, certain forms of periodontal disease, and other focal infections. Human neutrophils have demonstrated bactericidal activity against A. actinomycetemcomitans, and much of the oxygen-dependent killing has been attributed to the myeloperoxidase-H2O2-halide system. However, the contribution of other neutrophil components to killing activity is obscure. Lactoferrin, an iron-binding glycoprotein, is a major constituent of neutrophil-specific granules and is also found in mucosal secretions. In this report, we show that human lactoferrin is bactericidal for A. actinomycetemcomitans. Killing activity required an unsaturated (iron- and anion-free) molecule that produced a 2-log decrease in viability within 120 min at 37 degrees C at a concentration of 1.9 microM. Besides exhibiting concentration dependence, killing kinetics were affected by minor variations in temperature and pH. Magnesium, a divalent cation thought to stabilize lipopolysaccharide interactions on the surface of gram-negative organisms, enhanced lactoferrin killing of A. actinomycetemcomitans, while other cations, such as potassium and calcium, had no effect. Our data suggest that lactoferrin contributes to killing of A. actinomycetemcomitans by human neutrophils and that it may also play a significant role in innate secretory defense against this potential periodontopathogen.
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PMID:Killing of Actinobacillus actinomycetemcomitans by human lactoferrin. 341 49

To explore the possibility that Streptococcus sanguis aggregation of platelet-rich plasma (PRP) might be mediated by soluble agents, we tested cell-free S. sanguis supernatant for aggregation activity. The supernatant of untreated S. sanguis was without measurable PRP aggregation activity. In contrast, the cell-free supernatant of ATP-incubated S. sanguis produced an immediate wave of PRP aggregation. The supernatant with PRP aggregating activity contained insufficient protease to produce a response. The response increased with the time of incubation with ATP. Active supernatant was desalted and chromatographed on nucleotide-calibrated columns of Dowex 1-X8. An active ADP function was identified. The activity was insensitive to dicyclohexylcarbodiimide, but was sensitive to both Ca2+ and Ca2+-Mg2+ chelating agents, cold (4 degrees C), heat (80 degrees C), pH (optimum between pH 7 and 8), apyrase, and sodium molybdate. In addition, preincubation of PRP with adenosine inhibited activity. Strains of viridans streptococci were screened for activity. Aggregation-promoting strains showed two times more activity than did other strains. Although it was not vigorously excluded that the ADP was discharged from the microbes, the existence of an exogenous ATPase on S. sanguis was strongly suggested. The expression of the activity was associated with the lag time to onset of PRP aggregation with intact S. sanguis. This activity could, therefore, be a synergistic promoter of PRP aggregation and an additional virulence factor in endocarditis.
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PMID:ADP-like platelet aggregation activity generated by viridans streptococci incubated with exogenous ATP. 621 55

We investigated the mechanisms of platelet aggregation by the type strain of Streptococcus sanguis (NCTC 7863). This species is one of the major aetiological agents of infective endocarditis. S. sanguis NCTC 7863 caused aggregation of normal human platelets in vitro following a lag period that varied between donors (7-19 min). Platelet aggregation was dependent on one or more plasma constituents and all the necessary factors gradually became bound to the bacterial surface during the lag period. The length of the lag period was determined by the plasma of the donor and not by a feature of their platelets. Platelet aggregation by S. sanguis NCTC 7863 could be inhibited by heating plasma at 56 degrees C, by treating plasma with cobra venom factor, or by incubating with soluble Complement Receptor 1, all of which inhibit or deplete complement. Complement activation required Mg2+, but not Ca2+ ions and the the cleavage fragment, Ba, of factor B was produced, indicating that the alternative pathway was operative. Zymosan- and S. sanguis-induced aggregation showed similarities, including the same variability in lag times among donors, and absorption of plasma with zymosan prevented the plasma from supporting platelet aggregation by S. sanguis, C3, C9 and vitronectin were found to bind to S. sanguis NCTC 7863, but the latter two were present at very low levels on a non-aggregating strain of S. sanguis, SK96. The rate of assembly of the C5b-9 complex on the NCTC 7863 bacterial surface correlated with the lag time. These data suggest a role for the complement pathway in platelet aggregation by the type strain of S. sanguis.
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PMID:Evidence for the involvement of complement proteins in platelet aggregation by Streptococcus sanguis NCTC 7863. 882 2