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R Freter

Publications and source records attributed to R Freter.

At least 37 records · Page 2Linked to original sources
PubMed1981

Role of chemotaxis in the association of motile bacteria with intestinal mucosa: in vitro studies.

Various Sephadex G-15 fractions of pepsin-digested mucosal extract inhibited the in vitro association of cholera vibrios with mucosal slices. Inhibitory activity paralleled the taxin activity of the fractions for these bacteria. This supports the theory that inhibition of mucosal association by pepsin-digested mucosal scrapings was due to the blocking of taxin receptors on the bacterial surface. Nonchemotactic mutants were significantly less efficient than the chemotactic parent or revertant strains in associating with mucosal slices in vitro. Control experiments in which filter paper disks replaced the mucosal slices showed a comparable extent of association of chemotactic and nonchemotactic vibrios with this material. Histological studies indicated that vibrios associated predominantly with the mucus gel of the intestinal slices rather than with the mucosal epithelium or the serosal surface. Intestinal slices attracted chemotactic vibrios even after prolonged washing, suggesting continuous production of the taxin by the tissue. Inert polystyrene particles 1.1 micrometers in diameter penetrated the mucus gel of intestinal slices very poorly, but nevertheless could be detected in low numbers in the deep intervillous spaces within 15 min. In contrast, chemotactic vibrios reached the deep intervillous spaces in significantly higher numbers, whereas motile, non-chemotactic vibrios reacted like the inert particles. It is concluded that mucus gel represents a partial barrier to the penetration of particles of bacterial size and that this barrier can be invaded efficiently by motile bacteria, but only when their locomotion is guided by chemotactic stimuli.

Animals↗
PubMed1979

Effect of chemotaxis on the interaction of cholera vibrios with intestinal mucosa.

Earlier reports from this laboratory have shown that chemotaxis is an important mechanism that expedites the in vitro association of cholera vibrios with intestinal slices and that affects the in vivo colonization and virulence of these bacteria to a significant degree. The data reported in the present communication indicate that there appears to be a chemotatic gradient attracting cholera vibrios not only to the surface of the mucus gel, but that this gradient continues for at least a considerable distance toward the base of the villi. It is shown further that a strain of Vibrio cholerae was attracted by all 20 amino acids tested, in contrast to Escherichia coli AW405 which is repelled by several of these. Finally, experiments are described that show that superior in vivo colonization of chemotatic vibrios (compared to nonchemotactic mutants) was correlated with a significantly higher degree of mucosal association. Such increased mucosal association of chemotatic vibrios has previously been shown only with mucosal slices in vitro.

Adhesiveness↗
PubMed1978

Adhesion and chemotaxis as determinants of bacterial association with mucosal surfaces.

1) Chemotaxis of cholera vibrios facilitates the association of these bacteria with the mucosal surface. 2) Mucosal extracts can block the chemotactic receptors on the bacterial surface and thereby retard the association of chemotactic bacteria with the mucosal surface. 3) Chemotactic cholera vibrios grow more efficiently than non-chemotactic mutants in germfree mice and in isolated intestinal loops of rabbits. Conversely, non-chemotactic mutants grow more efficiently in infant mice. 4) Chemotaxis is therefore of considerable importance to the in vivo growth of cholera vibrios. The various mechanisms, including those of local immunity, by which bacterial chemotaxis can be exploited for the benefit of the host deserve further exploration.

Animals↗
PubMed1976

Adhesive properties of Vibrio cholerae: adhesion to isolated rabbit brush border membranes and hemagglutinating activity.

Adhesion of vibrios to the small intestine may occur (i) by association of the bacteria with secreted mucus gel or (ii) by adherence of the bacteria to the surface of epithelial cells. In the present study, vibrios readily adhered to isolated brush border membranes obtained from rabbit intestinal epithelial cells. Adhesion was temperature dependent and required the presence of divalent cations such as calcium. The agglutination of human O erythrocytes by Vibrio cholerae was observed also, and the hemagglutination test appeared to detect the same mechanism that was involved in the adhesion of vibrios to brush borders. When the bacteria were grown in broth they were adhesive and hemagglutinating, but vibrios grown on agar plates or suspended in buffer for 15 min at 37 C lacked these abilities, even though they retained undiminished motility. These two model systems differed, however, in that strontium promoted only adhesion to brush borders. The significance of this difference remains to be determined. Vibrios were observed to penetrate intestinal mucus gel and occasionally to become entrapped in it. However, there was no evidence that vibrios attached to mucus gel.

ABO Blood-Group System↗
PubMed1976

Adhesive properties of Vibrio cholerae: nature of the interaction with isolated rabbit brush border membranes and human erythrocytes.

Nonmotile vibrio mutants lacked the ability to adhere to rabbit intestinal brush border membranes and to agglutinate human group O erythrocytes, but motile revertant vibrios isolated from such strains expressed adhesiveness equivalent to that of the original parent. Two possible explanations for the relation between vibrio motility and adhesion in these assays systems are (i) that the rate of adhesion depends on the rate of chance contact brought about by motility, and (ii) that the flagellum either acts as a carrier for the bacterial adhesin or may itself be the adhesin. The present study indicates, however, that the lack of adhesion by nonmotile vibrios did not depend on motility as such and did not involve greater rates of elution. Increasing the rate of contact between nonmotile vibrio mutants and brush border membranes by compaction did not restore the adhesive properties of the defective strains. Accordingly, we speculate that the flagellum may function in some indirect way that allows the expression of the adhesive properties, such as by acting as a carrier for a specific vibrio adhesin. Adhesion to brush borders and agglutination of human group O erythrocytes was specifically inhibited by L-fucose and various glycosides of L-fucose and to a lesser extent by D-mannose. Vibrios adhered specifically to agarose beads that carried covalently linked L-fucose on their surfaces. The results suggest that L-fucose-containing structures of eukaryotic cell surfaces may function as receptors for the vibrio adhesin and may therefore be an important determinant of host susceptibility.

Animals↗
PubMed1976

Adhesive properties of Vibrio cholerae: nature of the interaction with intact mucosal surfaces.

Two companion papers in this series have characterized the interaction between Vibrio cholerae and the surfaces of eukaryotic cells. The present paper reports studies of the association between vibrios or Salmonella enteritidis and intact slices of intestinal tissue. A significant number of differences were noted in the characteristics of bacterial adhesion in these systems. The results are interpreted to indicate the presence of at least two receptors for vibrio adhesion on the mucosal surface of the rabbit small intestine. The receptor mediating the adhesion of salmonella appeared to be distinct from these. A primary role for bacterial motility in the process of adhesion of vibrios to mucosal surfaces could not be demonstrated in the assay systems studied. Rather, loss of motility in mutant vibrios appeared to be correlated with the simultaneous loss of adhesive factors (adhesins) from the bacterial surface. The inhibition of vibrio adhesion to slices of intestinal tissues by antibody to the heat-stable antigens of V. cholerae occurred in the absence of bacterial agglutination. Agglutination in this assay system appeared to be an artifact in that it could be observed only in experiments where extremely high concentrations of vibrios were used. We speculate that such high vibrio concentrations are not likely to be present in humans at the time of infection and that agglutination in the lumen of the intestine might therefore play only a minor role in prophylactic immunity against natural cholera and other enteric infections of humans.

Agglutination↗
PubMed1972

Function of various intestinal bacteria in converting germfree mice to the normal state.

Earlier work had shown that a collection of anaerobic bacteria, in conjunction with facultative anaerobes, may be implanted into germfree mice, thereby rendering the animals "normal" with respect to a variety of parameters tested. The present experiments indicate that a different collection of anaerobic bacteria, isolated from the cecum of normal mice, was necessary to convert germfree mice to the "normal" state when the animals were fed a crude diet, rather than the refined food which had been used in the earlier work. The nature and level of short-chain fatty acids associated with various natural or synthetic "normal" floras in the ceca of mice did not always correlate with the Escherichia coli population present, indicating that fatty acids were not the sole agents inhibiting bacterial populations in the intestine. Experiments are reported which indicate that intestinal anaerobes may under certain circumstances be sufficient to control the populations of other intestinal bacteria such as E. coli. In other instances, such as control of Shigella populations in the mouse intestine, intestinal anaerobes appeared to act synergistically with an E. coli strain, in spite of the fact that the population of the latter was itself suppressed by the anaerobes.

Anaerobiosis↗
PubMed1972

Parameters affecting the association of vibrios with the intestinal surface in experimental cholera.

Intestinal antibody (coproantibody) significantly reduced the adsorption of heat-killed Vibrio cholerae to the mucosa of in vivo isolated ileal loops of adult rabbits. This suggests a direct effect of coproantibody on adsorption, which appears to function in addition to the antibacterial mechanism described earlier. When antivibrio serum was administered passively into intestinal loops, it showed a predilection for the intestinal mucosa. In vivo adsorption of vibrios appeared to parallel their viability, i.e., vibrios killed by heat or in the presence of neomycin adsorbed significantly less than live vibrios. In contrast, in vivo adsorption was only slightly affected in the presence of bacteriostatic concentrations of tetracycline. Adsorption of Salmonella senftenberg and V. cholerae to slices of rabbit ileum in Krebs-Ringer solution appeared to involve different mechanisms, in that the former was strongly removed from the intestinal tissues by sodium lauryl sulfate, whereas vibrios were not affected by this agent. Triton X-100 increased the adsorption of vibrios, whereas rabbit bile and changes in pH had no effect.

Adsorption↗
PubMed1972

Availability of locally synthesized and systemic antibodies in the intestine.

The present studies are concerned with the parameters which control the appearance of locally synthesized or serum-derived antibodies in the intestine. The data show that intestinal antibody may be found in rabbits as well as in conventional or germfree mice after active immunization with Vibrio cholerae. However, a large fraction of the intestinal antibody in rabbits and conventional mice originated from the serum as indicated by (i) analysis of correlation between serum and intestinal antibody titers, and (ii) the occurrence of intestinal antibody after parenteral administration of antiserum. In contrast, only locally synthesized 11S immunoglobulin A antibody was detected in the intestine of actively immunized germfree mice. No intestinal antibody was demonstrable in germfree mice after parenteral injection of V. cholerae antiserum. With respect to the appearance of serum antibody in the intestine, the response of conventionalized (ex-germfree) mice was intermediate between that of rabbits or conventional mice and germfree mice. The availability of serum-derived coproantibody in germfree and conventional mice was related to the rates of intestinal degradation of serum antibody. When enzymes were removed by prior washing of intestinal segments, serum antibodies entered the intestine of germfree or conventional mice at similar rates. Rates of entry of serum antibodies into the lumen were comparable at different levels of the small intestine. The presence of a normal enteric flora appeared to protect intestinal antibody from degradation by lowering the concentration or activity of intestinal enzymes. The results are discussed in relation to the question of whether antibacterial immunity to cholera involves local or systemic mechanisms.

Administration, Oral↗
PubMed1970

Efficiency of various intestinal bacteria in assuming normal functions of enteric flora after association with germ-free mice.

Strictly anaerobic and facultatively anaerobic bacteria were isolated from the intestinal tract of normal mice. Germ-free mice were associated with mixtures of varying complexity of pure cultures of these bacteria. The development of normal features in these animals was then determined on the basis of the following criteria: (i) size of the cecum, (ii) size of the Escherichia coli population in the cecum, (iii) histology of the intestinal tract, and (iv) development of a mucosa-associated flora in stomach and large intestine. Germ-free mice contaminated with cecal contents from conventional mice were used as controls to establish normal values for these parameters. Some strictly anaerobic bacteria could be implanted into germ-free mice only after prior implantation of an E. coli strain. E. coli was found in large numbers in stomach and cecum of mice monocontaminated with this organism. Use of restraining devices indicated that the E. coli population in the stomach was maintained by coprophagy and did not contribute significantly to the size of the cecal population. A mixture of 50 strictly anaerobic bacteria plus 80 facultative anaerobes rendered recipient animals normal with respect to the criteria tested. Other, less complex bacterial mixtures reduced the cecal size and the intestinal E. coli population to levels intermediate between those found in normal and germ-free mice. With all bacterial mixtures tested, the intestinal E. coli population decreased, if at all, within a period of about 10 days after introduction of other bacteria, and remained stable thereafter. This suggests that the intestinal E. coli population is controlled by a mechanism which reduces population size without affecting the growth rate.

Journal Article↗