Biomedical subjects

P Lancy

Publications and source records attributed to P Lancy.

5 recordsLinked to original sources

PubMed1986

Identification of a Streptococcus sanguis receptor for salivary agglutinins.

The objective of this study was to characterize a fraction from oral streptococci containing receptor activity for salivary agglutinin molecules. Several species and strains of streptococci were disrupted in a Ribi press. The supernatant was nuclease-treated and subjected to differential centrifugation. Receptor activity in the fractions was measured by the inhibition of saliva-mediated bacterial aggregation. In addition, bacterial strains were tested for their ability to aggregate and to deplete saliva of agglutinin activity. Three patterns of activity were observed: Streptococcus sanguis M5 depleted saliva of agglutinin activity and aggregated well; Streptococcus sanguis CC5A depleted saliva of agglutinin but did not aggregate well; and Streptococcus faecalis S-161 neither depleted saliva of agglutinin nor did it aggregate. The 105,000 g supernatant fractions derived from Ribi-disrupted Streptococcus sanguis M5 and CC5A, but not from Streptococcus faecalis, showed dose-dependent inhibition of saliva-mediated aggregation. This inhibitory activity was non-dialyzable, had the same heat and trypsin sensitivity as that seen with intact bacteria, and was not due to enzymatic digestion of the salivary agglutinin. Iso-electric focusing revealed a single active region with a pI of 5.5 which was clearly separated from the bulk of the bacterial proteins.

Agglutination↗

PubMed1983

Corncob formation between Fusobacterium nucleatum and Streptococcus sanguis.

Corncob formation in dental plaque was believed to be limited to strains of Bacterionema matruchotii and Streptococcus sanguis. We observed recently that strains of Fusobacterium nucleatum also interacted with S. sanguis to form corncobs. Since the fusobacteria are among the first anaerobic filaments to colonize subgingival plaque, these interactions could serve as a connecting link between the transformation of supra- to subgingival plaque. To further characterize these interactions, quantitative in vitro studies of the kinetics of corncob formation of the fusobacteria were undertaken. These studies indicated that fewer streptococci were needed to saturate F. nucleatum strain 364 compared to strain 10953. Corncob formation with both strains was enhanced with increasing pH up to pH 8, at which point autoaggregation of the streptococci occurred. Variation in ionic strength and divalent cations had little effect on the interaction, and EDTA suppressed aggregate formation only slightly. Detergents at concentrations above 0.05% also inhibited corncob formation. Electron micrographs suggested that attachment of the cocci to the fusiforms was mediated through localized tufts of fimbriae, as they are in the Bacterionema system. However, although both trypsin and heat treatment of the streptococci inhibited corncob formation with fusobacteria, the effects were not as complete as those seen in Bacterionema species. Unlike the Bacterionema model, trypsin and heat treatment of the fusobacteria resulted in inhibition of corncob formation. These results suggest that several different receptors may be involved in corncob formation.

Adhesiveness↗

PubMed1980

Quantitative in vitro assay for "corncob" formation.

The interaction of Bacterionema matruchotii with strains of Streptococcus sanguis produces a structure which morphologically resembles a corncob. To determine the specific bacterial surface receptors involved in the interaction, we developed a quantitative assay. The assay consisted of mixing saline suspensions of [CH(3)-(3)H]thymidine-labeled streptococci and B. matruchotii, incubating at 37 degrees C for 2 h, and filtering the mixture through a 5-mum polycarbonate membrane filter. The free cocci and filaments passed through the filter, but the corncobs were retained. Estimates of the number of corncobs formed were obtained by quantitating the radioactivity retained on the membranes relative to that of controls of streptococci alone. Although saturation of the Bacterionema occurred at a ratio of streptococci to Bacterionema of 10:1 (Klett units), a 2:1 ratio was chosen because of the increased sensitivity of the assay at this ratio. The percentage of streptococci binding at this ratio was 18.6 +/- 8.1 (standard deviation). All five Bacterionema strains tested formed corncobs; in contrast, only three strains of S. sanguis were positive. These were serotype 1 strains which had localized surface "fuzz." Although scanning electron microscopic observations revealed an almost random distribution of cocci along the filament surface, transmission electron microscopy revealed that the streptococci were attached to the Bacterionema by the surface fuzz. No differences in corncob formation were observed in sodium phosphate buffer, pH 6 to 8, at phosphate concentrations ranging from 0.005 to 0.05 M. Concentrations of NaCl or KCl up to 0.25 M did not affect corncob formation, and low concentrations of CaCl(2) increased corncob formation slightly, whereas MgCl(2), ethylenediaminetetraacetic acid, and citrate buffers reduced the number of streptococci binding to the filaments. These results suggest that divalent cations may play a role in this process.

Actinomycetaceae↗

PubMed1979

Effects of some platinum IV complexes on cell division of Escherichia coli.

A comparison was made of the effects of cis-tetrachlorodiaminoplatinum (IV) (cis-TCDPt), rans-TCDPt), and hexachloroplatinum (HCP) on growth and cell division of Escherichia coli strains D21 and D22. At or below 40 microgram/mL, cis-TCDPt inhibited cell division but not growth, DNA, or protein synthesis, although areas of increased electron density could be demonstrated in treated cells. In contrast, 40 microgram/mL of trans-TCDPt or HCP inhibited growth. Trans-TCDPt-treated cells developed condensed nucleoids; HCP-treated cells showed no obvious cytological changes to correlate with growth inhibition. Combination of cis-TCDPt with nalidixic acid, both at one-half the lowest filament-forming concentrations, resulted in formation of filaments, suggesting an additive effect. Combination of cis-TCDPt followed by ampicillin on E. coli B/r resulted in single bulges near the center of the filaments. Cis-TCDPt could therefore inhibit an initial step in the septation sequence, possibly at the level of the regulation of the hydrolytic enzymes. Whether cis-TCDPt exerts its effect by interreaction with DNA or with a membrane target is still uncertain.

Ampicillin↗

PubMed1978

The envelope of Micrococcus radiodurans: isolation, purification, and preliminary analysis of the wall layers.

Two methods are presented that separate the complex envelope of Micrococcus radiodurans, strain Sark, into its constituent layers. The first involved treating whole cells with 0.025 M Tris buffer (pH 7.5) containing 2 mM of calcium and 3 mM of magnesium, resulting in the degradation of an intermediate ('compartmentalized') layer and consequent sloughing of the outer subunit and interior layers to form vesicles. This treatment also appears to show that the interior layer may be connected with the peptidoglycan-containing 'holey' layer. The second method involves treating whole cells with benzene followed by sonication; the results suggested that this treatment only released the outer layers from the 'compartmentalized' layer and did not degrade layers. Following benzene treatment, digestion of the 'compartmentalized' layer with cold sodium dodecyl sulfate (SDS) released the 'holey' layer. Electrophoretic analysis of some of the isolated layer preparations suggested that the subunit layer consisted of three major proteins of 90 000, 92 000, and 94 000 molecular weight, one minor protein of 100 000, a small amount of carbohydrate associated with the 94 000 protein, and a small amount of a 55 000 lipoprotein. The interior layer contained at least 10 proteins and may be attached to the peptidoglycan-containing 'holey' layer by means of the 55 000 lipoprotein.

Cell Fractionation↗