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At least 937 records · Page 52Linked to original sources

PubMed1985

Enteropathogenicity of purified Clostridium perfringens enterotoxin in the pig.

In an assay procedure, purified Clostridium perfringens enterotoxin induced the accumulation of fluid in the ileal loop of the axenic pig. The smallest amount of enterotoxin causing a positive response was 25 micrograms (1:32 titer by counterimmunoelectrophoresis [CIEP] ), and 100 micrograms (1:128 CIEP titer) caused a marked response. Possibly, diarrhea in pigs with 1:32 CIEP titer or more of enterotoxin in the feces may be associated with enterotoxigenic C perfringens.

Animals↗

PubMed1987

[Effect of cholera enterotoxin on carbohydrate metabolism of the liver and small intestine mucosa in the rabbit].

Changes in carbohydrate metabolism were studied in the isolated intestinal loops of rabbits during secretory diarrhea, induced by cholera enterotoxin. Glucose synthesis level in the small intestinal mucosa and liver was measured by isotope technique, using L-alanine as a precursor. Intestinal gluconeogenesis, calculated per mg of protein, appeared to be twice higher than in the liver of fasting rabbits. Cholera enterotoxin administration enhanced gluconeogenesis in the liver by 60%, as compared to the control. The rate of glucose synthesis and glucose-6-phosphatase activity in the intestinal mucosa remained unchanged, whereas glucose-6-phosphatase in the liver was slightly inhibited. It is suggested that gluconeogenesis in the liver supplies glucose as a convenient energy source for the secretory process induced by cholera enterotoxin in the rabbit small intestine.

Animals↗

PubMed1987

Role of Ca2+/calmodulin in the regulation of sugar uptake in Escherichia coli heat-stable enterotoxin induced diarrhoea in mice.

The mucosal-to-serosal fluxes of 3-O-methyl-D-glucose, a non-metabolizable analogue of D-glucose, were carried out in control and heat-stable enterotoxin treated mice in the presence or absence of Ca2+-ionophore, Ca2+-channel blocker, calmodulin inhibitor and Na+-K+-ATPase inhibitor. The transport of the sugar was significantly decreased (p less than 0.01) in the experimental animals. In the presence of Ca2+-ionophore, the uptake of the sugar decreased significantly (p less than 0.01) only in the control group while experimental group remained unaffected. Ca2+ channel blocker and calmodulin inhibitor significantly increased (p less than 0.01) the uptake of sugar in both the groups, however, the changes were more pronounced in the experimental group. Ouabain blocked the uptake of the sugar in both the groups. These studies indicated that heat-stable enterotoxin inhibit Na+-K+-ATPase by increasing Ca2+ uptake and calmodulin activity, thus resulting in decreased uptake of 3-O-methyl-D-glucose in heat-stable enterotoxin treated mice.

3-O-Methylglucose↗

PubMed1977

Effect of heat stable and heat labile Escherichia coli enterotoxins, cholera toxin and theophylline on unidirectional sodium and chloride fluxes in the proximal and distal jejunum of weanling swine.

Acute, isolated loops of proximal and distal jejunum of weanling swine were exposed to either heat stable porcine Escherichia coli enterotoxin, heat labile porcine Escherichia coli enterotoxin, cholera toxin or theophylline. Unidirectional sodium fluxes in response to heat stable in the proximal jejunum were dependent on the length of time that the intestinal mucosae was exposed to the enterotoxin. Net water, sodium and chloride and unidirectional sodium and chloride flux measurements in the proximal jejunum in response to each agent uniformly indicated that net secretion of fluid and electrolytes was the result of increased unidirectional sodium secretion or blood-to-lumen flux and decreased unidirectional chloride absorption or lumen-to-blood flux. In addition heat stable cholera toxin and theophylline but not heat labile decreased unidirectional chloride secretion a small but significant amount in the proximal jejunum. Sodium and chloride flux measurements in the distal jejunum demonstrated that all four secretory agents could stimulate net secretion of water, sodium and chloride in that region. The response to these secretory agents as measured by sodium and chloride unidirectional flux rates was not similar to changes observed in the proximal jejunum. In the distal small intestine, whereas heat labile cholera toxin and theophylline induced similar qualitative changes in unidirectional sodium and chloride fluxes, that induced by heat stable differed.

Animals↗

PubMed1977

Detecting enteropathogenic Escherichia coli strains of porcine origin. 1. Correlations between O and K antigens and the enterotoxin production in strains isolated from the newborn piglet.

A study of enterotoxin production by means of biological tests (Y1 adrenal cells and suckling mice) using 67 Escherichia coli strains responsible for diarrhea in newborn piglets, confirmed the advantages of these methods and demonstrated the correlation between antigenic specificity and enterotoxin production. In particular the presence of capsular antigen K 88 is related to the thermolabile (LT) fraction of the enterotoxin in 73.9 % of the enteropathogenic strains studied.

Animals↗

PubMed1978

[Edema of the paws of white mice--test for assessing the activity of E. coli enterotoxins].

The authors studied the paw edema test in mice for detection of the E. coli (strain P-99) enterotoxins activity. This test proved to be simple, sensitive and reproducible; it permitted to determine the activity of thermostable and thermolabile enterotoxins and endotoxin; the mentioned test was particularly useful in testing various preparations of enterotoxins obtained during their extraction and purification.

Animals↗

PubMed1987

[Staphylococcal enterotoxin type D: isolation, purification, identification].

The three step scheme of isolation and purification of staphylococcal type D enterotoxin was elaborated to obtain the homogeneous protein. The scheme includes protein concentration by (NH4)2SO4 saturation and subsequent fractionation on DEAE-cellulose and Sephacryl S-200. The yield of homogeneous protein is 25.5%. The molecular mass of the 29,600 D protein was identified by electrophoresis in polyacrylamide gel in the presence of SDS. The enterotoxic dose for staphylococcal type D enterotoxin is 5 mkg per kg of body mass as identified in experiments with cats. Immunological identity of the obtained protein was established to the commercial preparation of staphylococcal enterotoxin D produced by "Serva".

Chromatography, Gel↗

PubMed1987

[Structural similarity and functional activity of molecular fragments of staphylococcal enterotoxin B and thymopoietin II].

Structural similarity between Staphylococcus enterotoxin B and a thymus hormone, thymopoietin, has been revealed concerning thymopentin, one of active centres of thymopoietin. Fragments of enterotoxin B homologous to thymopoietin and their analogues were synthesized their immunological activity studied. Acetyl derivative of the fragment 225-229 of enterotoxin B increased infectional resistance and stimulated delayed type of hypersensitivity reaction.

Amino Acid Sequence↗

PubMed1978

[Dynamics of biologically active enterotoxin release by E. coli].

Accumulation of E. coli enterotoxin in the Finkelshtein's culture medium in growing the cells in a 30-litre reactor was studied. Accumulation of active highly molecular enterotoxin occurred in the course of a 6-hour cultivation of E. coli, strain P-99 (O141: K85ab; K88ab: H4) in the fluid medium under aeration. Oxygen utilization, synthesis and release into the nutrient medium of pyruvic acid, and protein accumulation were observed. The preparation obtained was stable to the lyophylic drying, contained thermolabile and thermostable toxins and marked edema of mouse limbs. The data obtained were of significance for the industrial production of active enterotoxin preparations.

Bacterial Proteins↗

PubMed1979

Permeability properties of swine small intestine: effect of a heat stable Escherichia coli enterotoxin.

The permeability of weanling swine small intestine was estimated using measurements of filtration coefficients and equivalent pore size. Hypertonic solutions of mannitol, erythritol and urea were used to calculate reflection coefficients in the duodenum, mid jejunum and distal jejunum. Estimated effective pore radius was 6.4-7.4, 5.6-7.2 and 4.7-4.9A degrees in the three respective regions. Similarly the filtration coefficient induced by hypertonic solutions of mannitol decreased significantly in the distal jejunal segments. The results show an aboral gradient of decreasing permeability along the small intestine of the weanling pig. In situ incubation of loops in the proximal jejunum with a heat stable Escherichia coli enterotoxin for one hour did not significantly change the effective pore size as calculated from reflection coefficients of hypertonic solutions of erythritol and urea. However, the filtration coefficients of loops exposed to the enterotoxin were significantly greater than control loops with hypertonic solutions of erythritol and urea but not mannitol. This suggests the occurrence of a slight reduction in epithelial porosity. The results support the hypothesis that intestinal secretion induced by heat stable E. coli enterotoxin is not the result of an increased mucosal permeability.

Animals↗

PubMed1986

Monoclonal antibodies to Escherichia coli heat-labile enterotoxins: neutralising activity and differentiation of human and porcine LTs and cholera toxin.

Forty-four monoclonal antibodies (MAbs) prepared against heat-labile enterotoxins (LTs) from human (LTh) or porcine (LTp) E. coli isolates were characterised, especially with regard to their reactivity with epitopes shared with the heterologous LT and/or cholera toxin (CT), and their toxin neutralising activity. Of 24 MAbs against LTh (all directed against the B subunit portion) 12 cross-reacted with LTp and CT, 4 with LTp but not CT, and 1 with CT but not LTp; 7 MAbs reacted with LTh epitope(s) not shared by either LTp or CT. Among 20 MAbs against LTp (9 directed against the B subunits and 11 against the A subunit) 2 cross-reacted with LTh as well as CT, 13 with LTh but not CT, and 5 MAbs were specific for LTp. Irrespective of whether the anti-LT MAbs were directed against shared or unshared epitopes, or against the A or B subunits, they neutralised their homologous toxin in direct proportion to their toxin-binding titre. The results show how minute differences in enterotoxin primary structures e.g., the LTh and LTp B chains differ in only 4 of 103 amino acid residues, are associated with antigenic epitopes against which toxin-differentiating MAbs with neutralising activity can be produced. Such MAbs are promising tools for species-specific diagnostic detection of enterotoxins in clinical specimens.

Amino Acids↗

PubMed1985

[Trial of different nutrient media for the production of an intracellular thermolabile enterotoxin by Escherichia coli strains H74-114 and 86].

The conditions of cultivation, ensuring the maximum accumulation of intracellular thermolabile enterotoxin in the cultures of two E. coli strains of different origin, have been studied. Culture media manufactured in the USSR have been selected and the conditions of cultivation, necessary for obtaining intracellular thermolabile enterotoxin in preparative amounts, have been established. Under these conditions the yield of thermolabile enterotoxin in 1.4 mg per 1 liter of culture medium for strain H74-114 and 1.0 mg per 1 liter of culture medium for strain 86.

Culture Media↗

PubMed1985

[Isolation and characteristics of the thermolabile enterotoxin from Escherichia coli strain H74-114].

The modified method for isolation and purification of LT-enterotoxin from Escherichia coli strain H74-114 has been proposed. Modification is based on exclusion of concentration of bacterial cell lysates by 3-5 fold dilution and changing PH during chromatography. The proposed modification permitted to increase the yield of purified and active product 8-10 fold. The obtained preparations are homogenic due to PAAG-SDS data and immunochemical analysis. B-component of TL-enterotoxin is shown to consist of 4 subunits B in contrast to B-component of choleragen, consisting of 5 subunits. The mol mass of A component of both toxins is identical but in contrast to choleragen the component of LT-enterotoxin is not subject to proteolysis.

Bacterial Toxins↗

PubMed1985

Analysis of receptor-binding site in Escherichia coli enterotoxin.

Heat-labile enterotoxin produced by enterotoxigenic Escherichia coli and cholera enterotoxin are both composed of A and B subunits. The A subunit is an enzymatically active ADP-ribosylating subunit, while the B subunit, consisting of 103 amino acids, binds the toxin to a receptor, GM1-ganglioside, on the cell surface. A mutant isolated after treatment of E. coli producing heat-labile enterotoxin with N-methyl-N'-nitro-N-nitrosoguanidine produces a B subunit that is unable to bind to ganglioside. This subunit was purified and its primary amino acid sequence was determined. It differed from the native B subunit in only one amino acid at position 33; namely it had aspartate instead of glycine at position 33 from the N terminus. Thus glycine at position 33 from the N terminus of the B subunit is important for binding the B subunit to the ganglioside receptor.

Adenosine Diphosphate Ribose↗

PubMed1979

Enterotoxins of enteric bacteria--a review.

A review of the enterotoxins of enteric bacteria was compiled, taking into account recent developments of the field as well as results of the author's own research work. After characterization of enterotoxins of different origin, their pathogenic role is described, with special attention to the genetic background of these agents. The possible use of enterotoxins for active immunization purposes is also discussed.

Adhesiveness↗

PubMed1971

Immunity to Escherichia coli in pigs: anti-enterotoxins in colostrum and serum from vaccinated and non-vaccinated sows.

Colostrum from non-vaccinated sows did not contain naturally occurring antibodies to heat labile Escherichia coli enterotoxin. Vaccination of sows by either the intramuscular or intramammary routes with a live formalinized E. coli vaccine resulted in the production of colostrum capable of neutralizing the heat labile toxin. Intramammary vaccination resulted in the production of colostrum which significantly reduced the enterotoxigenic effects of the vaccine strain of E. coli organisms but not that of a heterologous strain. Vaccination of the sows resulted in the production of serum antibodies to heat labile enterotoxin. Antibodies to heat stable enterotoxin were not demonstrable in the colostrum of either non-vaccinated or vaccinated sows.

Animals↗

PubMed1984

[Enzyme immunoassay in the detection of Clostridium perfringens enterotoxin].

An enzyme-linked immunosorbent assay (ELISA) for C. perfringens enterotoxin detection was evaluated using purified enterotoxin preparations, supernatant fluids of sporulating C. perfringens cultures and other Clostridium species. The assay was found satisfactorily sensitive and specific to detect C. perfringens enterotoxin.

Animals↗

PubMed1982

[Production of a monovalent staphylococcal enterotoxic antiserum type A and its use for typing staphylococcal enterotoxins].

A monovalent specific staphylococcal antiserum, type A, was obtained by means of the isolated and purified preparation of type A staphylococcal enterotoxin. This antiserum was proved to be identical to antiserum of the same type, manufactured by Serva Feinbiochemica GmbH & Co. (West Germany). The titer of the newly obtained antiserum in the precipitation test was 1 : 16, and its use allowed one to detect enterotoxin of the above-mentioned type at a concentration of 0.004 mg/ml. The study of 320 staphylococcal strains with the use of this antiserum revealed that 25 strains (7.8%) produced type A enterotoxin.

Enterotoxins↗