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Results for “TOXINS AND ANTITOXINS”

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At least 109 records · Page 6Linked to original sources
PubMed2005

Characterization of ChpBK, an mRNA interferase from Escherichia coli.

Escherichia coli contains a number of antitoxin-toxin modules on its chromosome, which are responsible for cell growth arrest and possible cell death. ChpBK is a toxin encoded by the ChpBIK antitoxin-toxin module. This module consists of a pair of genes, chpBI and chpBK encoding antitoxin ChpBI and toxin ChpBK, respectively. ChpBK consists of 116 amino acid residues, and its sequence shows 35% identity and 52% similarity to MazF, another E. coli toxin. MazF has been shown to be a sequence-specific (ACA) endoribonuclease that cleaves cellular mRNAs and effectively blocks protein synthesis and is thus termed as an mRNA interferase. Here we demonstrate that ChpBK is another mRNA interferase in E. coli whose induction effectively blocks cell growth in a manner similar to that of MazF. The protein synthesis as judged by incorporation of [35S]methionine was, however, reduced by only 60% upon ChpBK induction. We demonstrate that ChpBK is a new sequence-specific endoribonuclease that cleaves mRNAs both in vivo and in vitro at the 5'-or3'-side of the A residue in ACY sequences (Y is U, A, or G). The ChpBK cleavage of a synthetic RNA substrate generated a 2',3'-cyclic phosphate group at the 3'-end of the 5'-end product and a 5'-OH group at the 5'-end of the 3'-end product in a manner identical to that of MazF.

Amino Acid Sequence↗
PubMed1990

Attempts to quantity Clostridium botulinum type A toxin and antitoxin in serum of two cases of infant botulism in Japan.

Serum samples taken from two infant botulism cases during hospitalization were titrated for botulinum toxin by both the intraperitoneal (ip) injection method and the score method in mice. By the ip method, in which death is the only parameter, such low levels of toxin as lower than 4 ip LD50/ml may not be titrated even though the surviving mice show abdominal palsy. By the score method based on the degree of abdominal palsy, such low levels of toxin as 1.1 and 0.8 ip LD50/ml were detected in specimens of one of the patient's serum. No antitoxin was demonstrated in either case of infant botulism by applying the score method. It is not known whether spontaneous recovery from infant botulism is due to the antitoxin production.

Botulinum Antitoxin↗
PubMed1959

The relationship of toxin and antitoxin injection site to tetanus development in the rat.

The pattern of development of symptoms was studied following injection of 3 MLD (minimum lethal dose) of tetanus toxin in each of the following sites in the rat: vein, muscle, endoneurium, epineurium, spinal cord, subarachnoid space, and subdural space. Similar observations were made when 3 MPD (minimum protective dose) of antitoxin were injected into each of the above sites a few minutes after the intramuscular injection of toxin. Local tetanus followed intramuscular, endoneurial, and epineurial injection of the toxin; blood-borne tetanus also appeared in the latter instance. Tetanus dolorosus followed intraspinal injection of toxin. Both dorsal tetanus and blood-borne tetanus developed after subdural administration of toxin. Blood-borne tetanus, alone, appeared following intravenous and subarachnoid injection of toxin. In no case did injection of antitoxin at the various sites listed above prevent local tetanus from developing after intramuscular injection of toxin. Of the various sites injected with antitoxin, the intramuscular, intraspinal, and intravenous were the most effective. It is suggested that the endoneurial tissue spaces serve as a conduit for tetanus toxin from the muscle to the CNS. The perilemma of the peripheral nerve trunk may act as a selectively permeable membrane which permits tetanus toxin to pass from the epineurium to the endoneurium. Outward diffusion of toxin from the endoneurial spaces is apparently markedly reduced. The antitoxin probably is prevented from permeating this barrier in either direction. The importance of absorption of tetanus toxin by the lymphatic and blood circulation is discussed.

Animals↗
PubMed1985

The standardization of an assay for pertussis toxin and antitoxin in microplate culture of Chinese hamster ovary cells.

A microplate assay, based on the clustering effect induced by pertussis toxin (PT) in Chinese hamster ovary (CHO) cells, has been developed and standardized. Toxin titration is done directly in the culture microplate by twofold dilutions of 25 microliters of test material to which are added 10 000 freshly trypsinized cells in 200 microliters of culture medium per well. The dilution causing the clustering effect is determined by direct microscopic observation after 48 h of incubation. The method allows detection of 50-100 pg toxin per millilitre. For determination of neutralizing antibodies (antitoxin), twofold dilutions of 25 microliters of antiserum are first made directly in the culture microplate. Thereafter 25 microliters of toxin, containing four times the minimal clustering concentration, is added to each well. After three hours for neutralization at +37 degrees C, cells are added, incubated and examined as above. The assay has been found to be simple and reproducible for measuring the antibody response to PT in human and different animal sera. For titration of bacteria associated toxin, the CHO cells are seeded and incubated for 24 h before the addition of bacteria. Incubation and examination are done as described for toxin titration.

Animals↗
PubMed1977

The pathogenesis of Shigella diarrhea. VI. Toxin and antitoxin in Shigella flexneri and Shigella sonnei infections in humans.

Two strains of Shigella flexneri and one of Shigella sonnei were studied for toxin production in vitro. All of the three strains produced a cell-free cytotoxin that showed marked similarity to that produced by Shigella dysenteriae 1. Each toxin eluted in two distinct peaks on chromatography with Sephadex G-150, was destroyed by heating at 90 C for 30 min, and was neutralized by S. dysenteriae 1 antitoxin. Patients with infections due to S. flexneri and S. sonnei developed antibody that neutralized S. dysenteriae 1 toxin in vitro. In three of seven positive sera studied by sucrose density-gradient ultracentrifugation, antibody activity was associated only with the IgM fraction. The time course of the antibody response resembled that found in infections due to S. dysenteriae 1, in which an IgM antitoxin antibody has also been described. Since three species of Shigella have now been shown to be toxigenic, it is possible that bacterial toxin may play a role, along with bacterial invasion, in the pathogenesis of infections due to S. flexneri and S. sonnei, as well as those due to S. dysenteriae 1.

Antibody Formation↗