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J L McDonel

Publications and source records attributed to J L McDonel.

At least 19 recordsLinked to original sources
PubMed1985

Bacterial toxin vaccines.

A rebirth of interest and activity in vaccine development has occurred in recent years which is probably due to the persistence of threat to health by infectious diseases, as well as technological advances which have made possible new approaches to solve old problems. Most work being done today with vaccine development against diseases caused entirely or in part by bacterial toxins falls into the categories of, attenuated organisms (whether by classical means or application of newly developed genetic technologies), and/or toxin subunits (derived by genetic manipulations, peptide synthesis, or chemical modification of toxins). This review discusses some of these new approaches in general as well as specific examples of their application to several bacterial diseases whose pathologies involve toxins.

Animals↗
PubMed1982

In vivo effects of enterotoxin from Clostridium perfringens type A in the rabbit colon: binding vs. biologic activity.

Rabbit colonic loops were exposed to purified enterotoxin from Clostridium perfringens type A and perfused for analysis of the effects of the enterotoxin on transport and surface structure of the colon. The colon showed no apparent response to the enterotoxin in the transport of fluid and electrolytes as compared with untreated animals. There was a significant increase in levels of luminal fluid protein, corresponding to an observed increase in secretion of mucus. Histologic sections showed no epithelial damage, but scanning electron microscopy showed an increase in the number of mucous fields over the value in control animals. The colon showed little or no overt response to enterotoxin treatment, but isolated colonic epithelial cells bound 125I-labeled enterotoxin at levels even greater than those observed in cells from the ileum, where the enterotoxin has considerable biologic activity. Thus, although binding of enterotoxin is necessary for its biologic activity, biologic activity does not necessarily follow binding to specific receptors.

Absorption↗
PubMed1982

Clostridium perfringens type A enterotoxin: characterization of the amino-terminal region.

The amino-terminal region of the enterotoxin of Clostridium perfringens was investigated by automated sequence analysis. The primary structure results revealed that the enterotoxin is composed of a single polypeptide amino acid sequence. Computer comparison of a 20-residue sequence with a sequence library of reported proteins revealed no significant chemical similarities, indicating that the enterotoxin represents a unique polypeptide primary structure.

Amino Acid Sequence↗
PubMed1981

Protective effects of osmotic stabilizers on morphological and permeability alterations induced in Vero cells by Clostridium perfringens enterotoxin.

Culture medium made hypertonic by the addition of osmotic stabilizers such as sucrose, poly(ethylene glycol), dextran and bovine serum albumin protected against changes in morphology and plasma membrane permeability induced by Clostridium perfringes enterotoxin. The protection did not appear to be due to binding inhibition. Results of these studies support an osmotic disruption mechanism for the action of the enterotoxin. A comprehensive model of the enterotoxin's action based on an osmotic disruption mechanism is proposed.

Animals↗
PubMed1981

Relationship of sporulation, enterotoxin formation, and spoilage during growth of Clostridium perfringens type A in cooked chicken.

Sporulation and enterotoxin formation were determined for 17 strains of Clostridium perfringens type A in autoclaved chicken dark meat and in Duncan-Strong sporulation medium. The mean numbers of heat-resistant spores detected after 24 h at 37 degrees C were log10 1.13 to log10 7.64/ml in Duncan-Strong medium and log10 4.93 to log10 6.59/g in chicken. Of 17 strains, 7 formed enterotoxin in Duncan-Strong culture supernatant (1.0 to 60 microgram/ml) and 8 produced enterotoxin in chicken (0.21 to 24 microgram/g). Additional studies with chicken were conducted with C. perfringens NCTC 8239. With an inoculum of 10(6) cells per g, greater than log10 7.99 vegetative cells per g were detected by 4 h in chicken at 37 degrees C. Heat-resistant spores occurred by 4 and 6 h and enterotoxin occurred by 8 and 6 h in autoclaved chicken dark meat and barbecued chicken drumsticks, respectively. Enterotoxin was detected in autoclaved dark meat after incubation at 45 degrees C for 1.5 h followed by 37 degrees C for 4.5 h, but not after incubation at 45 degrees C for 1.5 to 8 h. With an inoculum of 10(2) cells per g in oven-cooked or autoclaved chicken, greater than log10 8.00 vegetative cells per g were detected by 6 to 8 h at 37 degrees C, heat-resistant spores were detected by 8 h, and enterotoxin was detected by 12 h. A statistical analysis of odor determinants of chicken after growth of C. perfringens indicated that, at the 95% confidence level, the product was considered spoiled (off or unwholesome odor) by the time spores or enterotoxin were formed.

Animals↗
PubMed1981

Highly sensitive assay for Clostridium perfringens enterotoxin that uses inhibition of plating efficiency of Vero cells grown in culture.

A highly sensitive and reproducible biological assay for Clostridium perfringens enterotoxin is described that uses Vero (African green monkey kidney) cells grown in tissue cultures. Very small doses of the enterotoxin inhibited the plating efficiency of the cells. This inhibition of plating efficiency could be used to detect as little as 0.1 ng (1 ng/ml) of enterotoxin, and a linear dose-response curve was obtained with 0.5 to 5 ng (5 to 50 ng/ml). A nonlinear, but reproducible, curve was obtained with a dose range from 0.1 to 100 ng (1 to 1,000 ng/ml). A new unit of biological activity, called the plating efficiency unit, was defined as that amount of enterotoxin that caused a 25% inhibition of the plating of 200 cells inoculated into 100 microliters of medium in a microwell culture system. One milligram of highly purified enterotoxin contained about 400,000 plating efficiency units. Additional studies demonstrated that the biological and serological activities of the enterotoxin molecule were not equally labile.

Animals↗
PubMed1980

Binding of Clostridium perfringens [125I]enterotoxin to rabbit intestinal cells.

125I-Labeled enterotoxin from Clostridium perfringens was utilized to characterize the association of the enterotoxin with cells isolated from rabbit intestine and tissue homogenates from liver, kidney, and brain. The enterotoxin was found to bind in a specific and saturable manner to cells from intestine and to tissue homogenates from liver and kidney but not the brain. Detailed studies of the binding were carried out with the ileal epithelial intestinal cells. The rate and amount of binding of enterotoxin to cells appeared to be temperature dependent. Apparent affinity and association and dissociation rate constants were calculated for what appeared to be two classes of saturable binding sites. The amount of enterotoxin molecules that bound per milligram of cell protein was similar in tissue of intestinal, liver, and kidney origin (approximately 10(13) molecules/mg of cell protein). Spontaneous dissociation into the supernatant medium was observed to be much slower than expected from calculations based on the rate of association. Chaotropic ions did not enhance dissociation of the enterotoxin from cells. Enterotoxin binding was demonstrated to be heat labile (binding ability was lost after the enterotoxin was heated for 10 min at 60 degrees C). A mechanism is described whereby the enterotoxin binds and then is inserted into the membrane where it becomes trapped.

Animals↗
PubMed1980

Characterization of membrane permeability alterations induced in Vero cells by Clostridium perfringens enterotoxin.

Alterations in plasma membrane permeability induced by Clostridium perfringens enterotoxin were studied using Vero (African green monkey kidney) cells which were radioactively labeled with four markers of different molecular size. The markers were alpha-amino[14C]isobutyric acid (Mr 103), 3H-labeled nucleotide (Mr approx. 300), 51Cr label (Mr approx. 3000) and [3H]RNA (Mr>25000). Over a 2h period, enterotoxin caused significant release of aminoisobutyric acid, nucleotides and 51Cr label but not RNA. The effects of enterotoxin on label release were dose- and time-dependent. The rate of release of markers was dependent upon their size. Permeability alterations could be detected within 15 min with a high dose of enterotoxin. Gel chromatography of released material was used to determine that markers of Mr 3000 but not 25000 leaked from permeabilized cells. It was concluded that enterotoxin is producing functional 'holes' of limited size in the membrane. Permeability changes due to enterotoxin treatment differed between confluent and nonconfluent (growing) cells. We propose that the primary action of the enterotoxin is to interact with the plasma membrane and produce functional 'holes' of defined size. The resultant alterations in membrane permeability cause the loss of essential cellular substances which inhibits processes such as macromolecular synthesis and eventually leads to cell deterioration and death.

Aminoisobutyric Acids↗
PubMed1980

Clostridium perfringens type A: in vitro system for sporulation and enterotoxin synthesis.

Polysomes were isolated from an enterotoxigenic strain of Clostridium perfringens during vegetative growth and at 1-h intervals after transfer into Duncan-Strong sporulation medium. During vegetative growth, about 67% of the ribosomes were in polysomal complexes. This proportion decreased to about 20% during the first 2 h in sporulation medium and then gradually increased to a maximum of 45% at 6 h. Ribosomes isolated from cells in vegetative or in sporulation phase could equally translate vegetative, sporulation, and natural viral R17 messenger ribonucleic acid with either vegetative or sporulation initiation factors. When polysomes were allowed to complete their nascent chains with labeled amino acids in vitro, most of the polypeptides synthesized by the vegetative phase and by the sporulation phase polysomes appeared to be identical. There were, however, notable differences upon further investigation. Specifically, when antiserum against the enterotoxin was reacted with the completed polypeptides, no counts were precipitated from the vegetative products. On the other hand, up to 12% of the total labeled protein was precipitated from the products obtained with the sporulation phase polysomes. Upon electrophoresis on sodium dodecyl sulfate, the putative enterotoxin synthesized in vitro ran as a major band with a molecular weight of 35,000, and as two minor bands with molecular weights of 17,000 and 52,000, respectively.

Bacterial Proteins↗
PubMed1979

The effects of Clostridium perfringens enterotoxin on morphology, viability, and macromolecular synthesis in Vero cells.

Vero (African green monkey kidney) cells grown in tissue culture monolayer were sensitive to Clostridium perfringens enterotoxin. Within 30 minutes of exposure to the enterotoxin gross morphological damage was observed and within 40 minutes approximately 75% of the cells had detached. Nearly half of the cells were nonviable following 35 to 40 minutes incubation with the enterotoxin. Doses as low as 0.1 ng caused small but detectable inhibition of plating efficiency of the cells while more than 100 ng caused the inhibition to approach 100%. Total inhibition of DNA, RNA, and protein synthesis occurred within 30 minutes exposure to enterotoxin. Heat inactivated enterotoxin had no apparent effects upon cellular morphology, detachment, viability, plating efficiency, or incorporation. We propose that the enterotoxin induces structural damage to the cytoplasmic membrane which results in loss of electrolytes and other essential substances from the cells. The outcome of this process is shut down of macromolecular synthesis, gross morphological damage, and eventual death of the cell.

Animals↗
PubMed1979

The molecular mode of action of Clostridium perfringens enterotoxin.

While certain strains of Clostridium perfringens have been associated with food poisoning outbreaks for the past 30 years, it has been only during the past 10 years that progress has been made in describing the disease process. And only within the past 5 years has meaningful progress been made in understanding the mechanism by which the disease is caused. Early observations, that the protein enterotoxin can cause erythema, increase capillary permeability, and exhibit parasympathomimetic properties, have been greatly added to in more recent studies. It is now believed tht the enterotoxin can alter intestinal transport of fluid, ions, and glucose, cause tissue damage in the gut and inhibit metabolic processes in intestinal tissue. Furthermore, the enterotoxin is thought to act very quickly (in a matter of minutes, compared to hours for other known enteropathogenic factors) and to affect basic function (macromolecular synthesis) and structure (membrane damage to microvillus brush borders) of individual cells. These findings have opened up many new questions that hopefully, when answered, will further the understanding of how this enterotoxin acts, as well as other enterotoxins being studied today.

Animals↗