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Biomedical subjects

K W Knox

Publications and source records attributed to K W Knox.

At least 19 recordsLinked to original sources
PubMed1979

Erythrocyte binding properties of streptococcal lipoteichoic acids.

The lipoteichoic acids (LTA) of gram-positive bacteria are known to bind spontaneously to a variety of animal cell membranes. We investigated the biological and biochemical characteristics of the binding of LTA of Streptococcus pyogenes and S. faecalis to human and sheep erythrocytes. The kinetics of the binding of the radiolabeled LTA ([(3)H]LTA) from each of these organisms to erythrocytes was similar. The dissociation constants for sheep and adult human erythrocytes were 1.6 muM and 4.5 muM, respectively, whereas that of human cord blood erythrocytes was approximately 10-fold higher, 31 muM. The number of binding sites for sheep erythrocytes was calculated to be 7.2 x x 10(6) per cell, and that of human erythrocytes, 29 x 10(6) per cell. Binding was reversible. More than 50% of bound [(3)H]LTA was displaced from erythrocytes by a 50-fold excess of unlabeled LTA. LTA prepared from heterologous species of gram-positive bacteria were all inhibitory to the binding of [(3)H]LTA whether derived from S. pyogenes or from S. faecalis. Among a number of potential receptor analogues and other inhibitors tested, including serum albumin, gangliosides Gm(2) and Gm(3), lipopolysaccharide of gram-negative bacteria, and various sugars, only albumin and the gangliosides significantly inhibited LTA binding. Trypsin or neuraminidase treatment of erythrocytes had no effect on LTA binding. Deacylation of [(3)H]LTA abolished binding ability and binding was restored by esterification of the deacylated material with stearoyl chloride, indicating that ester-linked lipids are necessary for membrane binding.

ABO Blood-Group System↗
PubMed1979

Serological studies on chemostat-grown cultures of Lactobacillus fermentum and Lactobacillus plantarum.

Lactobacillus fermentum NCTC 6991 and Lactobacillus plantarum NCIB 7220 were grown in a chemostat in the diffusible fraction of complex medium at pH 6.0 with glucose limitation. Organisms grown at different dilution rates (D) were injected into rabbits, and the resultant antisera were examined for reactivity with antigens previously isolated from batch-grown organisms. For L. fermentum, antisera obtained on injecting cells grown at D = 0.5 h-1 contained a significantly higher level of antibody reacting with lipoteichoic acid and a lower level of antibody reacting with wall polysaccharide than did antisera obtained with slower-growing cells (D = 0.05 and 0.033). Antibodies to the cell wall polysaccharide were alpha-D-glucosyl specific and cross-reacted with dextran and alpha-D-glucosyl ribitol teichoic acid from L. plantarum. The immunogenicity of the ribitol teichoic acid and lipoteichoic acid components of L. plantarum was not influenced by injecting organisms grown at different rates. However, chemical and serological studies indicate that growth of L. plantarum in the diffusible fraction of complex medium results in a wall teichoic acid of lower glucose substitution. This apparently influences the specificity of the resultant antibodies so that some sera react much less with glucosyl-substituted lipoteichoic acid and dextran.

Antibody Specificity↗
PubMed1979

Effect of growth conditions on the formation of extracellular lipoteichoic acid by Streptococcus mutans BHT.

Streptococcus mutans BHT was grown in a chemostat with glucose limitation and at defined dilution rates and pH values. Lipoteichoic acid was estimated by determining the ability of dilutions of culture fluid to sensitize erythrocytes. The greatest amounts of extracellular lipoteichoic acid were produced by organisms growing at a low dilution rate and at pH 6.0 or 6.5. To enable a more accurate estimation of the total amount of extracellular material, rocket immunoelectrophoresis was employed. These results confirmed that the greatest amounts of reactive material were produced by slow-growing organisms, although there were discrepancies between these results and those obtained by hemagglutination. The extracellular material was fractionated by column chromatography and membrane ultrafiltration to yield a lipoteichoic acid-containing fraction and a presumptive deacylated lipoteichoic acid fraction. The relative proportions detected by rocket immunoelectrophoresis differed with the growth conditions, particularly the dilution rate. Analysis of the phenol-extracted cellular material also indicated the presence of deacylated lipoteichoic acid, although less than in the culture fluid.

Glucose↗
PubMed1979

Phenotypic stability of the cell wall of Streptococcus mutans Ingbritt grown under various conditions.

Quantitative analyses of cell walls from Streptococcus mutans Ingbritt grown under carbohydrate limitation in the chemostat showed that growth conditions had no statistically significant effect on the composition of polysaccharide, peptidoglycan, or the proportion of polysaccharide in the cell wall. Lysis of cell wall preparations with a muramidase supported this conclusion and further indicated that there was little difference in their overall structure. In contrast, there was a consistent difference between the rates of lysis by this enzyme of organisms grown in 0.2% glucose and 0.5% glucose. Extremes of pH or dilution rate essentially did not influence the immunogenicity of type c antigen in whole organisms irrespective of whether the carbohydrate source was glucose or sucrose. However, differences were found in the immunogenicity of lipoteichoic acid under similar circumstances. The results indicated there was an inherent phenotypic stability in the cell walls of S. mutans Ingbritt despite changes in pH, generation time, and carbohydrate source, and that any changes that did occur were probably due to associated cell-surface components.

Alanine↗
PubMed1979

Effect of carbohydrate source and growth conditions on the production of lipoteichoic acid by Streptococcus mutans Ingbritt.

Streptococcus mutans Ingbritt was grown in a chemostat at defined dilution rates and pH values and under carbohydrate limitation. At a constant dilution rate of D = 0.1 h-1 and with either 0.5% glucose or 0.5% sucrose, the amounts of both cellular and extracellular lipoteichoic acid increased as the culture pH increased from 5.0 to 7.5. At a constant pH of 6.0, the amount of cellular lipoteichoic acid formed by cultures growing in 0.2% or 0.5% glucose was relatively constant over a range of dilution rates, although the amount of extracellular lipoteichoic acid formed in 0.2% glucose at intermediate dilution rates was less than that formed in 0.5% glucose. Organisms grown in 0.5% sucrose at pH 6.0 contained increasing amounts of cellular lipoteichoic acid as the dilution rate was increased. A comparison of the amounts of cellular lipoteichoic acid formed by organisms growing at D = 0.5 h-1 and pH 6.0 in glucose, sucrose, fructose, or mixtures of glucose and fructose in limiting amounts suggested that the enhanced production of lipoteichoic acic by sucrose-grown organisms was due to the fructose component. The culture fluids from both glucose- and sucrose-grown organisms contained detectable amounts of serotype c antigen, whereas glucose-grown cultures also contained significant amounts of an extracellular hexose-containing polymer.

Animals↗
PubMed1979

Inhibition of complement-mediated lysis of sheep erythrocytes by cell-free preparations from Streptococcus mutans BHT.

A cell-free extract from the spent medium of Streptococcus mutans BHT was tested for anti-complementary activity with sheep erythrocytes (E) as target cells. It was determined that this extract was enriched for extracellular lipoteichoic acid (LTA) and that the LTA bound to the surfaces of sheep E. Furthermore, sheep E, sheep E plus antibodies (EA), and sheep cells in the intermediate stage of complement (C) component fixation EAC14 became refractory to C-mediated lysis after treatment with the LTA-rich extract. Sheep E in the intermediate states EAC142 and EAC1423567 were unaffected despite the fact that LTA could be detected on the surfaces of these cells with the passive hemagglutination procedure. Preliminary results showed that the C inhibitory activity co-purified with LTA, and LTA (both crude and purified) from other bacteria were anticomplementary. Both crude extracellular material from S. mutans BHT and partially purified extracellular LTA from the same bacteria caused consumption of whole human C activity.

Animals↗
PubMed1979

Examination of parotid saliva for antibodies reacting with Streptococcus mutans, lipoteichoic acid and peptidoglycan by the enzyme-linked immunosorbent assay.

Human parotid saliva was investigated for the presence of IgA antibodies reacting with Streptococcus mutans, lipotechoic acid (LTA) and peptidoglycan. By using an enzyme-linked immunosorbent assay, ELISA, it was shown that the salivas of 12 subjects contained antibodies reacting with S. mutans serotype c and d and with LTA. Six salivas were tested against peptidoglycan but these tests indicated only low levels of antibodies. Absorption of saliva with whole cells of S. mutans inhibited the homologous reaction by up to 87% and the reaction with LTA by up to 52%. Also prior treatment of saliva with LTA caused a decrease in the salivary IgA reaction with LTA and with whole cells of S. mutans. Addition of peptidoglycan to saliva did not markedly affect the salivary IgA reaction with S. mutans. The data show that LTA may be responsible for part of the salivary IgA reaction with whole cells of S. mutans. The significance of LTA in this reaction may vary between different subjects and for different serotypes of S. mutans.

Adolescent↗
PubMed1978

Effect of growth conditions on the antigenic components of Streptococcus mutans and lactobacilli.

1) The release of LTA from chemostat-grown cultures of S. mutans and L. fermentum is dependent on the generation time and pH. 2) The growth rate affects the immunogenicity of LTA and the wall polysaccharide of L. fermentum. 3) The growth of L. plantarum under glucose limitation influences the glucose content of the wall teichoic acid. The composition of the wall polysaccharide of S. mutans Ingbritt may also be changed under these conditions. 4) The conditions of autoclaving used to release cell wall antigens can hydrolyse the covalent linkage between polysaccharide and peptidoglycan.

Antigens, Bacterial↗
PubMed1978

Extractability of cell wall polysaccharide from lactobacilli and streptococci by autoclaving and by dilue acid.

Autoclaving cell wall of Streptococcus mutans Ingbritt for 15 min under the Rantz and Randall conditions released one-tenth of the total cell wall carbohydrate, whereas two-thirds was extracted after autoclaving for 180 min. The extract contained the serotype c-specific antigen but lacked the lipoteichoic acid component extracted when whole cells were autoclaved. Autoclaving cell wall preparations from other strains of S. mutans and also Streptococcus salivarius and Streptococcus mitis in 0.85% NaCl for 180 min released the major proportion of the wall polysaccharide fraction. Approximately 50 to 90% of wall carbohydrate of Lactobacillus fermentum and Lactobacillus casei was released when cell wall preparations were autoclaved in 0.85% NaCl for 180 min. For wall preparations from several strains of S. mutans, autoclaving for 60 min at pH 3.75 released only 39 to 62% of wall carbohydrate, whereas almost total release could be achieved with the lactobacilli. Heating S. mutans Ingbritt cell wall for 24 h at 60 degrees C in 0.1 N H(2)SO(4) released only two-thirds of the wall carbohydrate; by comparison nearly all of the wall carbohydrate was released in 3 h from L. casei and L. fermentum. Autoclaving L. casei cell wall and purified soluble wall fractions hydrolyzed the phosphodiester bond between the polysaccharide and peptidoglycan. This was shown by the release of reactive N-acetylhexosamine in both cases and the presence of a phosphomonoester in the autoclaved soluble wall fractions. The results indicate that autoclaving can hydrolyze covalent linkages, and this must be considered when the Rantz and Randall procedure is used to obtain antigen preparations.

Cell Wall↗
PubMed1976

Fluoride content of prepackaged fruit juices and carbonated soft drinks.

Epidemiological studies have established the beneficial effects of water fluoridation. Present dietary trends, however, indicate that many Australian children may consume more prepackaged fluids than actual tap water. The fluoride concentrations of a selection of carbonated soft drinks and prepackaged fruit juices were investigated. The results indicate that, in an optimal fluoride area such as Sydney, children who consume a consistent and large proportion of their fluids as carbonated soft drinks in cans, fruit juices and fruit drinks may not be receiving the full benefit of the water fluoridation.

Australia↗
PubMed1976

Isolation of lipoteichoic acids from Butyrivibrio fibrisolvens.

Lipoteichoic acid (LTA) and deacylated lipoteichoic acid have been isolated from the bovine-rumen Gram-negative anaerobe Butyrivibrio fibrisolvens by phenol extraction. Lipoteichoic acid (21.8 mumol phosphorus/g cells) consisted of a conventional 1, 3-phosphodiester-linked chain of glycerol phosphate units joined covalently to a glycolipid. It was not substituted with glycosyl or D-alalyl ester groups. Deacylated lipoteichoic acid (57.5 mumol phosphorus/g cells) was similar in constitution but lacked fatty acid esters. Lipoteichoic acid reacted serologically with antisera to the glycerol phosphate backbone of known lipoteichoic acids. The presence of similar teichoic acid polymers has also been demonstrated in some other strains of B. fibrisolvens and this is of significance in demonstrating that teichoic acids can occur in Gram-negative bacteria.

Animals↗
PubMed1976

The potential role of bacteria and their antigens in periodontal disease.

The inflammatory changes typical of periodontal disease are believed to involve immunological reactions, with bacteria being a potential source of the antigens inducing these reactions, with bacteria being a potential source of the antigens inducing these reactions. Various investigators have studied the ability of specific organisms to induce tissue changes in experimental animals, while others have examined human sera and tissues for the presence of antibodies reacting with particular organisms or their isolated antigens. The significance of these results is assessed, particularly with respect to the problem of antibody cross-reactivity. The antigens that could be involved in periodontal disease are discussed in terms of the difference in structure of Gram-positive and Gram-negative bacterial cells, with attention being drawn to those components that could occur extracellularly and thus diffuse into oral tissues. The antigen most studied is the lipopolysaccharide or endotoxin of Gram-negative cells which, through the mediation of complement, is a potential inflammatory agent.

Adhesiveness↗
PubMed1976

Formation of cross-reacting antibodies against cellular and extracellular lipoteichoic acid of Streptococcus mutans BHT.

Antisera prepared against strains of Streptococcus mutans, particularly strain BHT, contain antibodies to the membrane lipoteichoic acid component that will cross-react with lipoteichoic acids from three species of lactobacilli. A more detailed study of the antibodies to strain BHT confirmed that the antibodies are specific for the polyglycerol phosphate component common to the lipoteichoic acids. Sera with a higher hemagglutinating titer could be obtained by injecting disrupted organisms. The partially purified lipoteichoic acid isolated from the culture fluid of S. mutans BHT was also immunogenic antibodies; antibodies were also formed against another unidentified component in this extracellular fraction.

Antibodies↗