Modification of the action of pentagastrin on acid secretion by botulinum toxin

Summary I.v. botulinum toxin after 60–90 min abolished the dose-response relationship between pentagastrin and gastric acid secretion in anesthetized rats and guinea-pigs. The toxin reduced but did not abolish the acid stimulatory effect of histamine. As expected, the acid response to vagal stimulation was abolished and that to methacholine in rats was unaltered by the toxin.Acknowledgment. We are grateful to the generosity of Dr Edward J. Schantz, Food Research Institute, University of Wisconsin, for the botulinum toxin used. — This research was supported by NIH grant 1 RO1 AM 17125, The Secretion of Pepsin.     

Modification of the action of pentagastrin on acid secretion by botulinum toxin.

I.v botulinum toxin after 60-90 min abolished the dose-response relationship between pentagastrin and gastric acid secretion in anesthetized rats and guinea-pigs. The toxin reduced but did not abolish the acid stimulatory effect of histamine. As expected, the acid response to vagal stimulation was abolished and that to methacholine in rats was unaltered by the toxin.     

Purification of diphtheria toxin by chromatography on Cibacron Blue-Sepharose

Diphtheria toxin binds to Cibacron Blue-Agarose and may be eluted by increasing the ionic strength of the elution buffer. Experiments using difference spectroscopy showed that the interaction between toxin and dye is ionic rather than hydrophobic, and therefore it is of a different nature with respect to that usually found in nucleotide-requiring enzymes.     

Genetic and molecular approaches to synthesis and action of the yeast killer toxin

Summary The K1 killer toxin ofSaccharomyces cerevisiae is a secreted, virally-coded protein lethal to sensitive yeasts. Killer yeasts are immune to the toxin they produce. This killer system has been extensively examined from genetic and molecular perspectives. Here we review the biology of killer yeasts, and examine the synthesis and action of the protein toxin and the immunity component. We summarise the structure of the toxin precursor gene and its protein products, outline the proteolytic processing of the toxin subunits from the precursor, and their passage through the yeast secretory pathway. We then discuss the mode of action of the toxin, its lectin-like interaction with a cell wall glucan, and its probable role in forming channels in the yeast plasma membrane. In addition we describe models of how a toxin precursor species functions as the immunity component, probably by interfering with channel formation. We conclude with a review of the functional domains of the toxin structural gene as determined by site-directed mutagenesis. This work has identified regions associated with glucan binding, toxin activity, and immunity.     

Botulinum toxin as a carrier for oral vaccines

Botulinum toxin is an unusually potent substance that acts on the nervous system to produce the clinical outcome of flaccid paralysis. To produce this effect, the toxin ordinarily proceeds through two separate but essential sequences of events. During the first, the toxin is ingested, it traverses a portion of the gastrointestinal system and then it is transcytosed from the lumen of the gut to the general circulation. During the second, circulating toxin binds to peripheral cholinergic nerve endings, it is endocytosed and then it acts as a metalloendoprotease to cleave polypeptides that are essential for exocytosis. Although botulinum toxin is antigenic, it ordinarily does not evoke an immune response during or after cases of oral poisoning. This is due to the fact that the dose of toxin that produces flaccid paralysis—and potentially death—is less than the dose needed to evoke an antibody response. In the recent past, the techniques of molecular biology have been used to generate an expression product of botulinum toxin that retains the ability to escape the gut and reach the general circulation, retains the ability to evoke an immune response, but has lost the ability to produce neurotoxicity. This modified toxin may have two clinical applications. The expression product itself may have utility as an oral vaccine against botulism. Beyond this, the modified toxin, or a truncation mutant of the toxin, may have utility as a carrier in the construction of other oral vaccines. Both potential applications could lead to the expression of oral vaccines in common foods. Received 29 December 1998; received after revision 22 March 1999; accepted 24 March 1999     

Bacillus thuringiensis delta-endotoxin: evidence that toxin acts at the surface of susceptible cells

Enzymically activated delta-endotoxin of Bacillus thuringiensis covalently bound to Sephadex beads, has the same effect on insect cells in tissue culture as free toxin. The effect is prevented by antitoxin antibody and heat denaturation and is not due to a nonspecific protein effect, the beads, or toxin released from the beads. The toxin, therefore, probably acts at the cell surface.     

Common evolution of waprin and kunitz-like toxin families in Australian venomous snakes

The venoms of Australian snakes contain a myriad of pharmacologically active toxin components. This study describes the identification and comparative analysis of two distinct toxin families, the kunitztype serine protease inhibitors and waprins, and demonstrates a previously unknown evolutionary link between the two. Multiple cDNA and full-length gene isoforms were cloned and shown to be composed of three exons separated by two introns. A high degree of identity was observed solely within the first exon which coded for the propeptide sequence and its cleavage site, and indicates that each toxin family has arisen from a gene duplication event followed by diversification only within the portion of the gene coding for the functional toxin. It is proposed that while the mechanism of toxin secretion is highly conserved, diversification of mature toxin sequences allows for the existence of multiple protein isoforms in the venom to adapt to variations within the prey environment.     

The effect of lidocaine on the secretion induced by cholera toxin in the cat small intestine

The intraluminal administration of lidocaine, a local anaesthetic agent, inhibits the net loss of fluid into the intestinal lumen produced by cholera toxin in the cat. It is suggested that the activation of a nervous reflex is involved in the pathogenesis of cholera.     

Cholera toxin structure, gene regulation and pathophysiological and immunological aspects

Many notions regarding the function, structure and regulation of cholera toxin expression have remained essentially unaltered in the last 15 years. At the same time, recent findings have generated additional perspectives. For example, the cholera toxin genes are now known to be carried by a non-lytic bacteriophage, a previously unsuspected condition. Understanding of how the expression of cholera toxin genes is controlled by the bacterium at the molecular level has advanced significantly and relationships with cell-density-associated (quorum-sensing) responses have recently been discovered. Regarding the cell intoxication process, the mode of entry and intracellular transport of cholera toxin are becoming clearer. In the immunological field, the strong oral immunogenicity of the non-toxic B subunit of cholera toxin (CTB) has been exploited in the development of a now widely licensed oral cholera vaccine. Additionally, CTB has been shown to induce tolerance against co-administered (linked) foreign antigens in some autoimmune and allergic diseases. Received 25 October 2007; accepted 12 December 2007     

Resistance of purified cholera toxin to enzymatic treatment with pancreatic elastase and papain

Summary Treatment of Cholera toxin with pancreatic elastase and papain in vitro shoed a high resistance of the toxin molecule to these enzymes, under non-denaturing conditions or in the presence of 2M urea. These experiments support the hypothesis of a particularly stable molecular structure of the toxin, as an explanation of its activity in the intestinal lumen where the pancreatic proteases are active.     

Structure of victorin C,the major host-selective toxin fromCochliobolus victoriae

Summary The predominant host-selective toxin fromCochliobolus victoriae, victorin C, is a peptide with an apparent mol. wt of 796, representing a cyclic array of the subunits1–6. The structure of the toxin has now been established as in16 through analysis of the degradation products generated by enzymic and non-enzymic partial hydrolysis. The presence of a hydrated aldehydo group requires for victorin C the composition C₃₁H₄₅O₁₃N₆Cl₃ with an amended mol. wt of 814, for which independent experimental support has been secured.     

Zinc antagonizes the effect of botulinum type A toxin at the mouse neuromuscular junction

Zn2+ (10-100 microM) elevated the frequency of miniature end-plate potentials (MEPPs) in the mouse diaphragm. The effect did not depend on external Ca2+. Botulinum type A toxin (BTXA, 50 ng/ml) abolished MEPPs almost completely within 30 min. Zn2+ (100 microM) restored MEPPs and increased their frequency after they had been abolished by BTXA in Ca2+ -free solutions. The antagonistic effect of Zn2+ in the Ca2+ -free solution was reduced by exposing the diaphragm to the toxin in the Ca2+ -free solutions containing high K+. Thus, the action of BTXA is probably enhanced by depolarization of the motor nerve terminals.     

Amaninamide,a new toxin ofAmanita virosa mushrooms

Summary Amaninamide, a toxin closely related to the family of amatoxins, was found exclusively inAmanita virosa mushrooms. It differs from the well known toxin -amanitin in that it lacks the 6-hydroxyl group of the tryptophan unit, and from the toxin amanin found inAmanita phalloides by the presence of a carboxamide group instead of a carboxylic acid group.Communication No. 57 of the series: Components of the green deathcap toadstool Amanita phalloides. No. 56: E. Munekata, H. Faulstich and Th. Wieland, Liebigs Ann. Chem., in press.     

Genetics of toxin production and resistance in phytopathogenic bacteria

Genes for phytotoxin production have been identified and cloned from several phytopathogenic pseudomonads. These genes comprise physically linked clusters that have been located both on the chromosome and on endogenous plasmids. Contained within these genetic regions are resistance genes specific to those toxins that have a bactericidal component to their activity. DNA sequences required for toxin production are often conserved among bacteria with divergent host specificities, suggesting the ability of toxin genes to be transferred between bacteria. Toxins are usually modulators of plant pathogenicity, their production causing a significant increase in disease severity. In one case, however, toxin production appears to be a major contributor to the basic pathogenicity of a plant pathogenic bacterium.     

Action of serotonin on neuromuscular transmission in normal guinea pigs and those treated with paralyzing doses of botulinum toxin type A]

Serotonin inhibits the muscular contractions elicited by indirect stimulation; injected before Botulinum toxin it prevents the paralysis induced by this toxin.     

Effect of botulinum toxin on the choline acetyltransferase activity in salivary glands of cats

Summary The choline acetyltransferase activity of submandibular glands that had previously received a retrograde injection of botulinum toxin via their ducts was found to be markedly lower than in the untreated contralateral glands. In the parotid glands exposed to the same treatment the activity of this enzyme was less affected.This work was supported by grants from the Wellcome Foundation to S. K. K. and J. R. G., and from the Faculty of Medicine in Lund to J. E.     

Characterization of victorin C,the major host-selective toxin fromCochliobolus victoriae: Structure of degradation products

Summary Several host-selective toxins have been isolated in pure form culture filtrates ofCochliobolus victoriae. Acid hydrolysis of the major toxin, victorin C (apparent mol.wt 796), produced five fragments to which structures1–5 have been assigned. Spectroscopic techniques revealed that the toxin contains an additional subunit corresponding to6; thus all the components of victroin C are accounted for.     

The effect of lidocaine on the secretion induced by cholera toxin in the cat small intestine

Summary The intraluminal administration of lidocaine, a local anaesthetic agent, inhibits the net loss of fluid into the intestinal lumen produced by cholera toxin in the cat. It is suggested that the activation of a nervous reflex is involved in the pathogenesis of cholera.This research was sponsored by grants from the Swedish Medical Research Council (14X-2855), from the Swedish Society for Medical Sciences, from Magnus Bergvalls Stiftelse and from the Medical Faculty, University of Göteborg.     

Effect of scorpion venom (Androctonus australis) on neuromuscular transmission inhibited by botulinum toxin in the frog]

We have shown that Scorpion venom restores the neuro-muscular transmission inhibited by Botulinum toxin in the Frog. The effectiveness of Scorpion venom was antagonized by excess magnesium.     

Effects of pertussis toxin on alpha 1-agonist-mediated phosphatidylinositide turnover and myocardial cell hypertrophy in neonatal rat ventricular myocytes

In neonatal rat ventricular myocytes pretreatment with pertussis toxin did not affect 1 microM (-)-norepinephrine stimulation of inositol phosphates or myocardial cell hypertrophy as measured either by protein radiolabelling or by myocardial cell protein content. Thus guanine nucleotide protein(s) ADP-ribosylated by pertussis toxin do not play a role in two alpha 1-adrenoceptor-mediated processes, phosphatidylinositide turnover and induction of myocardial cell hypertrophy.