A defining characteristic of superantigens is their ability to stimulate T cells based predominantly on the type of variable segment of the T cell receptor (TCR) beta chain (V beta). The V beta specificity of these toxins most likely results from direct contact between the toxin and the TCR, although the low affinity nature of this binding has prevented direct assessment of this interaction. To...

background and objectives: clostridium perfringens, a gram-positive obligate anaerobic bacterium, is able to form resistant spores which are widely distributed in the environment. c. perfringens is subdivided into five types a to e based on its four major alpha, beta, epsilon and iota toxins. the aim of the present study was cloning and expression of c. perfringens type d vaccine strain epsilon...

BACKGROUND Aging decreases cardiac beta-adrenergic responsiveness in model systems and in humans in vivo. The purpose of this study was to comprehensively evaluate the age-related changes in the beta-receptor-G protein-adenylyl cyclase complex in nonfailing human hearts. METHODS AND RESULTS Twenty-six nonfailing explanted human hearts aged 1 to 71 years were obtained from organ donors and sub...

Clostridium difficile is a major nosocomial pathogen that produces two large protein toxins [toxin A (TcdA) and toxin B (TcdB)] capable of disrupting intestinal epithelial cells. Both belong to the family of large clostridial cytotoxins, which are characterized by the presence of a repetitive C-terminal repetitive domain (CRD). In TcdA, the CRD is composed of 39 repeats that are responsible for...

the aim of this study was to determine the presence of toxin genes in clostridium perfringens isolated from 200minced meat samples using molecular typing. for this purpose, after isolation of clostridium perfringens using conventional culture method and confirmation by specific 16srd na gene pcr, alpha (cpa), beta (cpb), beta 2 (cpb2),epsilon (etx), iota (ia) and enterotoxin (cpe) genes were in...

Infection with Staphylococcus aureus and the production of toxic shock syndrome toxin-1 (TSST-1) have been implicated in the pathogenesis of toxic shock syndrome. Previous in vitro studies have demonstrated that TSST-1 is a powerful but selective stimulator of human T cells, and that the majority of activated cells express the TCR V beta 2 gene segment. We therefore studied patients with toxic ...

T-2 toxin was rapidly converted in the 9,000 X g supernatant fraction of rat liver homogenate into HT-2 toxin, T-2 tetraol, and two unknown metabolites designated as TMR-1 and TMR-2. TMR-1 was characterized as 4-deacetylneosolaniol (15-acetoxy-3 alpha, 4 beta, 8 alpha-trihydroxy-12,13-epoxytrichothec-9-ene) by spectroscopic analyses. Since the same metabolites were also obtained from HT-2 toxin...

Chinese hamster ovary (CHO) cell cultures in microtiter wells are sensitive to growth inhibition and killing by picogram quantities of diphtheria toxin. In the absence of biologically active toxin, the CHO cell culture produces sufficient acidic metabolites to change the phenol red pH indicator from pink to yellow within 56 h. In the presence of 10 pg of toxin per well, growth inhibition can be...

Several naturally occurring polypeptide neurotoxins target specific sites on the voltage-gated sodium channels. Of these, the gating modifier toxins alter the behavior of the sodium channels by stabilizing transient intermediate states in the channel gating pathway. Here we have used an integrated approach that combines electrophysiological and spectroscopic measurements to determine the struct...

Scorpion beta and alpha-toxins modify the activation and inactivation of voltage-gated sodium channels. Although the two types of toxin bind at two distinct receptor sites on the same sodium channel, they exhibit synergic effects when coinjected into insects. To clarify the basis of this synergism we examined the mutual effects of alpha and beta toxin representatives in radio-ligand binding ass...