Saccharin inhibits tooth decay in laboratory models.
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Animals↗
Biomedical subjects
A M Slee
Publications and source records attributed to A M Slee.
Sucrose transport by Streptococcus mutans. Evidence for multiple transport systems.
The transport of sucrose by selected mutant and wild-type cells of Streptococcus mutans was studied using washed cocci harvested at appropriate phases of growth, incubated in the presence of fluoride and appropriately labelled substrates. The rapid sucrose uptake observed cannot be ascribed to possible extracellular formation of hexoses from sucrose and their subsequent transport, formation of intracellular glycogen-like polysaccharide, or binding of sucrose or extracellular glucans to the cocci. Rather, there are at least three discrete transport systems for sucrose, two of which are phosphoenolpyruvate-dependent phosphotransferases with relatively low apparent Km values and the other a non-phosphotransferase (non-PTS) third transport system (termed TTS) with a relatively high apparent Km. For strain 6715-13 mutant 33, the Km values are 6.25 X 10(-5) M, 2.4 X 10(-4) M, and 3.0 X 10(-3) M, respectively: strain NCTC-10449, the Km values are 7.1 X 10(-5) M, 2.5 X 10(-4) M and 3.3 X 10(-3) M, respectively. The two lower Km systems could not be demonstrated in mid-log phase glucose-adapted cocci, a condition known to repress sucrose-specific phosphotransferase activity, but under these conditions the highest Km system persists. Also, a mutant devoid of sucrose-specific phosphotransferase activity fails to evidence the two high affinity (low apparent Km) systems, but still has the lowest affinity (highest Km) system. There was essentially no uptake at 4 degrees C indicating these processes are energy dependent. The third transport system, whose nature is unknown, appears to function under conditions of sucrose abundance and rapid growth which are known to repress phosphoenolpyruvate-dependent sucrose-specific phosphotransferase activity in S. mutans. These multiple transport systems seem well-adapted to S. mutans which is faced with fluctuating supplies of sucrose in its natural habitat on the surfaces of teeth.
Biological Transport↗
Predominant microflora associated with human dental periapical abscesses.
The microflora of periapical abscesses of teeth free of periodontal disease was studied. Permucosal aspiration of abscess contents and anaerobic cultural, microscopic, and biochemical techniques indicated a mixed but somewhat specific and relatively limited facultative and obligate anaerobic flora with Fusobacterium nucleatum and Streptococcus mitis as a frequent pair.
Adult↗
Effect of growth conditions on sucrose phosphotransferase activity of Streptococcus mutans.
Sucrose and glucose phosphoenolpyruvate-dependent phosphotransferase (PTS) activities were studied in growing cultures of Streptococcus mutans serotype c and d/g cells adapted to either glucose or sucrose. Both acid production and optical absorbance were used to monitor growth in pH-controlled defined growth medium. The sucrose PTS activity appeared to be significant only under conditions of substrate limitation or slow growth as a result of low environmental pH. However, under environmental conditions which permitted rapid growth sucrose PTS activity appeared to be repressed, and only when the cells approached substrate-limited stationary phase after growth on high sucrose-supplemented medium was significant sucrose PTS activity again observed. A mutant apparently defective in sucrose PTS activity grew rapidly and produced acid under conditions of high environmental sucrose level but showed no sucrose PTS activity when the culture approached stationary phase. The mutant, however, after adaptation to glucose, demonstrated significant glucose PTS once the culture had attained the stationary growth phase. During diauxie growth in the presence of glucose and sucrose, there were sequential apparent inductions and repressions of glucose and sucrose PTS activities corresponding to decreases and increases of growth rate on the two substrates. Thus, S. mutans possesses at least two transport mechanisms for each substrate studied. One system (PTS) functions under conditions permitting slow growth and another functions under conditions permitting rapid growth.
Enzyme Induction↗
Studies on the relative binding affinities of chlorhexidine analogs to cation exchange surfaces.
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Binding Sites↗
In vitro evaluation of seven cationic detergents as antiplaque agents.
The bactericidal efficacy of seven cationic detergents was studied in vitro against intact performed plaques of representative strains of four oral dental plaque-forming microorganisms: Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Actinomyces naeslundii. Both absolute (plaque bactericidal index) and relative (chlorhexidine coefficient) indexes of antiplaque activity were established. Only cetyltrimethylammonium bromide was more efficacious than the reference agent, the bisbiguanide chlorhexidine, for the apparently more potent tooth-adherent cariogenic and periodontopathic elements, respectively, of the in vivo plaque microflora, S. mutans and A. viscosus.
Actinomyces↗
Phosphoenolpyruvate-dependent sucrose phosphotransferase activity in Streptococcus mutans NCTC 10449.
A phosphoenolpyruvate-dependent sucrose phosphotransferase system (PTS) has been demonstrated, by an enzyme-coupled reaction and product isolation, in decryptified cell suspensions of the cariogenic microorganism Streptococcus mutans NCTC 10449. The apparent sucrose PTS reaction for sucrose-adapted, sucrose-challenged cells displayed saturation kinetics with an apparent Km of 7.14 x 10(-5) M, which was distinct from the Km of the glucose PTS activity of glucose-adapted, glucose-challenged cells. Both the sucrose and the glucose PTS activities appear to be inducible and under separate genetic control. The sucrose PTS reaction demonstrated in decryptified cells had an absolute requirement for phosphoenolpyruvate. Only 2-phosphoglycerate, the immediate glycolytic precursor of phosphoenolpyruvate, was found to substitute for phosphoenolpyruvate in this reaction in the absence of fluoride. The sucrose PTS activity of sucrose-adapted cells was competitively inhibited by raffinose and lactose; these same sugars had no effect on the apparent glucose PTS activity. Fructose was the only carbohydrate tested other than sucrose which elicited an apparent PTS reaction in sucrose-adapted cells. The product of the sucrose PTS reaction was isolated and behaved chromatographically on a Dowex-1-X8 column like a monophosphate ester. Alkaline phosphatase treatment of the presumptive sucrose monophosphate liberated a component which behaved chromatographically like free sucrose. Subsequent acid hydrolysis of this component produced moieties which behaved chromatographically like glucose and fructose.
Enzyme Induction↗
Phosphoenolpyruvate-dependent sucrose phosphotransferase activity in five serotypes of Streptococcus mutans.
An inducible phosphoenolpyruvate-dependent sucrose phosphotransferase system has been demonstrated in decryptified cell suspensions of the various common serotypes of the cariogenic microorganism Streptococcus mutans.
Carbohydrate Metabolism↗
Activity of three 8-hydroxyquinoline derivatives against in vitro dental plaque.
Three 8-hydroxyquinoline derivatives, assessed using an in vitro preformed dental plaque model system, were differentially inhibitory for four plaque-forming microorganisms.
Actinomyces↗
Selective medium for isolation of Eikenella corrodens from periodontal lesions.
The addition of 5 microgram of clindamycin per ml to a modified Todd-Hewitt growth medium permitted the ready enumeration of Eikenella corrodens from deep periodontal lesions because it allowed differential growth amongst the periodontal pocket gram-negative microaerophilic-anaerobic flora, maximized the numbers of E. corrodens in such culture, and inhibited the growth of most of the other confounding microorganisms.
Bacteroides↗
In vitro evaluation of three iodine-containing compounds as antiplaque agents.
The antibacterial activity of three iodine-containing compounds was determined for strains of four dental plaque-forming microorganisms, using an in vitro preclinical plaque model system. Solutions of inorganic iodine, povidone-iodine, and Wescodyne were tested for antiplaque activity against preformed plaques of a number of strains of Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Actinomyces naeslundii. Solutions of inorganic iodine were more effective as antiplaque agents, with respect to minimal bactericidal concentration and time and frequency of treatments, than solutions of Wescodyne and povidone-iodine. Inorganic iodine appeared to be particularly effective against the most cariogenic (S. mutans) and periodontopathic (A. viscosus) organisms while allowing survival of the least orally pathogenic plaque-forming microorganism (S. sanguis). It is suggested that topical application of solutions of inorganic iodine may be useful in controlling dental caries and actinomyces-associated periodontal disease.
Actinomyces↗
Structural requirements of guanide, biguanide, and bisbiguanide agents for antiplaque activity.
The bactericidal efficacy of 16 guanide, biguanide, and bisbiguanide agents was studied in vitro against intact preformed plaques of four oral (plaque-forming) microorganisms: Streptococcus mutans, S. sanguis, Actinomyces viscosus, and A. naeslundii. The activities of these agents were examined in relation to their molecular configurations. These studies indicated that the bis- and biguanide configurations are important for efficacy, as is the length of the alkyl side chain. No structural moiety determined efficacy by itself. Furthermore, the activities of these agents were studied to determine the minimal conditions (concentration, duration, and frequency) of treatment required for likely clinical efficacy. At least six agents were judged to have equal or greater efficacy than the reference agent, chlorhexidine digluconate. A plaque bactericidal index was derived for the most potent agents, and comparison to the bactericidal properties of chlorhexidine was expressed as a chlorhexidine coefficient.
Actinomyces↗
Novel small molecule alpha v integrin antagonists: comparative anti-cancer efficacy with known angiogenesis inhibitors.
Recent evidence supports the involvement of integrins in angiogenesis: blockade of alpha v beta 3 and alpha v beta 5 integrins disrupts angiogenesis leading to decreased blood vessel formation and hence decreased tumor growth. We hypothesized that av antagonists could inhibit tumor growth in tumor cells devoid of alpha v beta 3 integrins. We evaluated SM256 and SD983, novel small molecules that are specific av antagonists in mouse models of angiogenesis and tumorigenesis, and compared them with standards: TNP470, a fumagillin analog in the clinic, and flavopiridol, a cell cycle kinase inhibitor. In vitro SM256 was a selective alpha v beta 3 inhibitor with an IC50 = 4nM, and the affinity of SD983 against the mouse endothelial alpha v beta 3 integrin yielded an IC50 = 2nM and an IC50 = 54nM against alpha v beta 5. In the mouse Matrigel model of angiogenesis SM256 decreased blood vessel formation (hemoglobin content) with an ED50 = 0.055 ug/kg/day, tenfold more potent than TNP470. SG545, an ester of SD983, decreased blood vessel formation with an ED50 = 6 ug/kg/day, while flavopiridol ED50 = 18 ug/kg/day. In the mouse xenograft model, using human colon carcinoma RKO cells that do not express alpha v beta 3 but express alpha v beta 5, tumor growth was inhibited by SG545 (10 mg/kg/day) and flavopiridol (5 mg/kg/every other day) 40% and 70%, respectively (p < 0.05). Although the proliferative index (measured by BrdU incorporation) was not significantly changed with SM256, SG545 or flavopiridol (29-32%), the apoptotic index increased significantly (p < 0.05) in the SM256 and SG545-treated groups (2.3-2.7%) compared with controls (1.1%), suggesting increased cell death contributed to decreased tumor volumes. Neovascularization decreased with SM256 and SG545 treatment. The data demonstrate that potent selective av antagonist can target endothelial cells, tumor cells, inhibit angiogenesis and inhibit tumor growth.
Animals↗
The hollow fiber assay: continued characterization with novel approaches.
The hollow fiber assay, a unique in vivo model, permits the simultaneous evaluation of compound efficacy against multiple cell lines in two physiological compartments. This assay has been used to characterize in vivo activity of cytotoxic compounds. The purpose of the present study was to characterize and optimize this assay for compounds with a defined mechanism of action, specifically cell cycle inhibition. Two human tumor cell lines and one normal human cell line were loaded into polyvinylidene fluoride hollow fibers at two or more cell concentrations and grown in mice for 3-10 days. The data demonstrate the importance of characterizing the initial loading density of various cell lines in the evaluation of compounds. All studies were performed with cells in the linear part of the cell growth curves. Initial loading densities of 1-2 x 10(4) cells/fiber gave the greatest opportunity for growth in the three human cell lines tested (HCT116 colon carcinoma, NCI-H460 non-small cell carcinoma, and AG 1523 normal fibroblast). Utilizing the MTT assay, standard curves were constructed to correlate the final number of cells with optical density (OD) readings at 540 nm in order to calculate cell numbers in the fibers. Insights into the mechanism of action of cisplatin have been gained using Western blot analysis of the cell cycle markers PCNA (a protein present throughout the cell cycle) and Rb (a protein that acts as a tumor suppressor gene product) from the hollow fiber cells. In cisplatin-treated NCI-H460 cells both PCNA and Rb phosphorylation decreased, suggesting the arrest of the cells prior to the S phase. Standard therapeutic agents, cisplatin, racemic flavopiridol, cyclophosphamide and mitomycin C, were evaluated independently in the hollow fiber assay and the xenograft model. The data demonstrate that compounds active in the hollow fiber assay are also active in the xenograft.
Animals↗
Regulation of gene expression and cell growth in vivo by tetracycline using the hollow fiber assay.
The hollow fiber assay presents a potentially unique tool to study the effects of regulated gene expression in cell lines that do not form tumors in vivo. The hollow fibers allow small molecules to pass freely through while keeping the cells within the fibers and segregated from host cells. OSp16.1 cells, derived from the U24 clone of the U2-OS osteogenic sarcoma tumor line, express the p16INK4a tumor suppressor under the regulation of tetracycline (tet) (Mitra J et al. Mol Cell Bio 19:3916, 1999). The in vitro induction of p16 in the OSp16.1 cell line is regulated by tet. The hollow fiber assay was used to determine whether the regulation of the p16 gene could be achieved in vivo, since these cells did not grow in the xenograft model. There were no differences in the in vivo growth pattern of U24 cells loaded into the hollow fibers with and without tet: 807% and 839% net growth, respectively. OSp16.1 cells in fibers in mice receiving 3.33 mg/kg/day tet had a 644% net growth after 21 days. There was a 194% net growth without tet. Immunoblotting of extracts prepared from the hollow fibers confirmed that p16 was induced in the absence of tet. These data demonstrate this assay is a useful tool for studying the effects of regulated gene expression in vivo.
Animals↗