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Biomedical subjects

R R Russell

Publications and source records attributed to R R Russell.

At least 109 records · Page 6Linked to original sources
PubMed1985

Cloning and expression of two Streptococcus mutans glucosyltransferases in Escherichia coli K-12.

Chromosomal DNA from Streptococcus mutans strain MFe28 (serotype h) was cloned in the bacteriophage vector lambda L47.1. Two classes of recombinants were found which expressed glucosyltransferase activity in phage plaques: (i) gtfS, which expressed a glucosyltransferase synthesizing a water-soluble, dextranase-sensitive glucan, and (ii) gtfI, which expressed a primer-dependent glucosyltransferase synthesizing an insoluble glucan.

Bacteriophage lambda↗
PubMed1984

Prediction of abuse liability of drugs using IV self-administration by rats.

A total 31 psychoactive drugs were offered to groups of naive rats for IV self-administration and an injection rate greater than that for rats offered only saline indicated reinforcement. Two protocols were used: in the first, rats were offered drug at a selected dose for 5 days, then the dose was reduced by 1 log unit (to 0.1 the original dose) for an additional 4 days; in the second, rats were offered saline for 3 days as a "prescreen' to eliminate rats with high or low operant-injection rates. Drug was offered to acceptable rats for 5 days, then the dose was reduced 0.5 log unit (to 0.32 the original dose) for 5 more days. A scoring system, based upon the injection rates during the last 3 days of each period, describes the reinforcing action. Scores were dose-related. Tests on both protocols gave similar results. Data from monkey studies have been reported for 27 of the drugs tested. Of these drugs, 18 were reinforcers and six were nonreinforcers in both species, nalorphine and ethylketazocine were reinforcers only in rats, and ethanol was a reinforcer only in monkeys.

Animals↗
PubMed1984

The adsorption of human salivary components to strains of the bacterium Streptococcus mutans.

Using strains of Streptococcus mutans suspended in human saliva, the salivary proteins capable of binding to the surface of the bacteria were identified by immunological and electrophoretic techniques. Six binding components were recognized: IgA, lysozyme, some high molecular weight material (greater than 400,000), probably a glycoprotein, a low molecular weight component (11-13,000), a 150,000 mol. wt protein, and one major component, mol. wt 20-25,000 which did not resolve fully on SDS-polyacrylamide electrophoresis. All these salivary components could be desorbed from the bacteria with 1 M NaCl, and subsequent extraction of the same cells with 6 M guanidine-HCl did not release any more salivary material. The significance of the binding of these salivary components is unknown but some may modify the behaviour of the organisms in vivo.

Adsorption↗
PubMed1984

Evolution and resolution of oedema following severe temporary cerebral ischaemia in the gerbil.

Regional cerebral blood flow (rCBF) and oedema following profound temporary ischaemia were studied in the gerbil. Ninety-four per cent of animals died within 24 hours of reperfusion; 50% by 4 hours. Regional differences in oedema (specific gravity method), Evans blue (EB) staining and rCBF (hydrogen clearance technique) occurred. Oedema developed during arterial occlusion, being inversely proportional to residual flow and was markedly exacerbated during reperfusion. Reperfusion hyperaemia was maximal in the parietal and hippocampal regions (ischaemic rCBF 4 ml 100 g-1 min-1). Oedema was disappearing in all areas by 3 hours of reperfusion and autoregulation returned in the occipital region (mean ischaemia rCBF 8 ml 100 g-1 min-1). EB staining and haemorrhage appeared in the thalamus (rCBF 10 ml 100 g-1 min-1) as oedema was decreasing. It is suggested that the amount of oedema and hyperaemia during reperfusion are dependent on the severity of the ischaemia. Areas of moderate ischaemia (8-10 ml 100 g-1 min-1) show little hyperaemia and greater oedema resolution during reperfusion as compared to areas of severe ischaemia (circa 4 ml 100 g-1 min-1) where there is marked hyperaemia with less oedema resolution. Early in the reperfusion period, oedema is not associated with EB staining and indicates a cytotoxic mechanism. The vasogenic component, with macroscopic haemorrhages and leakage of EB occurs later. In this model it is concluded that the early cytotoxic oedema formation and hyperaemia are phenomena with little bearing on mortality, which correlates better with later vasogenic changes.

Animals↗
PubMed1983

Fructosyltransferase activity of a glucan-binding protein from Streptococcus mutans.

Streptococcus mutans serotype c produces several extracellular proteins which bind to affinity columns of immobilized glucans. The proteins are three distinct glucosyltransferases and another glucan-binding protein (molecular weight 74000) which is now shown to be a fructosyltransferase. This enzyme is antigenically distinct and genetically independent of two other fructosyltransferases produced by the same organism. A mutant is described which lacks the glucan binding fructosyltransferase and has defective ability to form adherent colonies in the presence of sucrose. Although the production of glucans from sucrose results in the glucan binding protein becoming bound to the bacterial surface, and hence perhaps contributing to adherence, the fructans synthesized by the enzyme do not appear to contribute to this phenomenon.

Carrier Proteins↗
PubMed1983

Antibody responses to antigens of Streptococcus mutans in monkeys (Macaca fascicularis) immunized against dental caries.

Immunization of rabbits or monkeys with walls prepared from Streptococcus mutans by a procedure including extraction with SDS at room-temperature induced antibodies to three antigens (A, B and C) detectable by crossed immunoelectrophoresis. Antigens A and B have previously been characterized as proteins of molecular weight 29 000 and 190 000, respectively. Antigen C was characterized as having a molecular weight of 70 000 and was purified by immunosorbent affinity chromatography and hydrophobic interaction chromatography. Another wall protein, antigen D, of molecular weight 13 000, was extracted from walls with Triton X-100. Immunization of monkeys with walls prepared from cultures of S. mutans grown at a high (D = 0.5 h-1) or low (D = 0.05 h-1) dilution rate in a chemostat showed that only the latter induced protection against dental caries. There was a positive correlation between levels of antibody to antigens A and C and induction of protection and a negative correlation between protection and the level of antibody to antigen B. No antibody to antigen D was detected in protected monkeys and an experiment in which monkeys were immunized with pure antigen D confirmed that it does not induce protection.

Animals↗
PubMed1982

Effect of specific antisera on adherence properties of the oral bacterium Streptococcus mutans.

Antisera to Strep. mutans antigens B, glucosyltransferase (GTF) and a glucan-binding protein (GBP) reduced the build-up of this bacterium on glass surfaces in vitro; antiserum to antigen A and a control non-immune serum were without significant effect. The same sera were used to study the involvement of these antigens in cell-cell aggregation mediated by sucrose or water-soluble Dextran 2000. Antiserum to GTF and antigen B inhibited sucrose-dependent cell-cell aggregation of the organism by approximately 50 per cent; none of the antisera tested had any effect upon dextran-mediated aggregation. In the presence of sucrose, GTF and GBP became cell associated while the distribution of antigens A and B between culture supernatant and cell surface remained unchanged. Cells incubated in the presence of Dextran 2000 showed no change in the distribution of any of these antigens. It is concluded that the aggregation of Strep. mutans induced by sucrose or by dextran involves different cellular components. Consideration of these in-vitro results in relation to data from experiments in which macaque monkeys were immunized with purified Strep. mutans antigens suggests that inhibition of sucrose-dependent adherence is not the basis for protection against dental caries.

Adhesiveness↗
PubMed1982

Evaluation of a commercial latex particle agglutination test for rapid diagnosis of Haemophilus influenzae type b infection.

The effectiveness of a commercially available latex particle agglutination test (Bactogen) in the diagnosis of invasive Haemophilus influenzae type b infection was evaluated. Bactogen correctly diagnosed all 27 patients with bacteriologically proven H influenzae type b infection (sensitivity 100%). Two of 39 patients with proven, non-H influenzae type b infections had false-positive tests (specificity 95%). One of 103 sera and 0 of 55 urine specimens from hospitalized adults contained detectable H influenzae type b antigen. Bactogen is a sensitive, specific, commercially available test for rapid diagnosis of H influenzae type b infection.

Evaluation Studies as Topic↗
PubMed1981

The isolation of characterization of Streptococcus mutans serotype h from dental plaque of monkeys (Macaca fascicularis).

A new serotype (h) of Streptococcus mutans was isolated from the dental plaque of monkeys (Macaca fascicularis). Serotype h strains fermented mannitol and melibiose but not sorbitol or raffinose, failed to hydrolyse aesculin and arginine, did not produce hydrogen peroxide and were unable to grow in the presence of bacitracin at 2 units ml-1. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of whole-cell proteins showed serotype h strains to be closely related to strains of genetic group III (i.e. serotypes d and g). The serotype-specific antigen of serotype h contained glucose and galactose but was antigenically distinct from the polysaccharide antigens of serotypes a, d and g. Serotype h strains preferentially colonized developmental grooves of teeth and the proportion of serotype h in the plaque flora was greater in monkeys fed a sucrose-rich diet than in monkeys fed a starch-based diet. A serotype h strain was cariogenic for germ-free rats fed a high-sucrose diet, and serotype h strains appear to be implicated in the caries process in monkeys.

Animals↗
PubMed1980

Distribution of cross-reactive antigens A and B in Streptococcus mutans and other oral streptococci.

A collection of strains representing the various common species of oral streptococci was examined for the presence of antigens cross-reacting with A and B from Streptococcus mutans serotype c. Antigens cross-reacting with A were found only in S. mutans serotype b. Antigens cross-reacting with B were found in S. mutans serotypes a, c, d, e, f and g and also in strains of S. sanguis. All antigens cross-reacting with B were precipitated by antiserum to human heart tissue.

Antibodies, Bacterial↗