Purification, structure and activity of three insect toxins from Buthus occitanus tunetanus venom.
ABSTRACT One contractive and two depressant toxins active on insect were purified by high-performance liquid chromatography from the venom of Buthus occitanus tunetanus (Bot). The two depressant toxins, BotIT4 and BotIT5, differ only at position 6 (Arg for Lys) and are equally toxic to insects (LD50 to Blatella germanica = 110 ng/100 mg body weight). They show a strong antigenic cross-reaction with a depressive toxin from Leiurus quinquestriatus quinquestriatus (LqqIT2). The two toxins are able to inhibit with high affinity (K0.5 between 2 and 3 nM) the specific binding of the radioiodinated excitatory insect toxin (125I-AaHIT) on its receptor site on Periplaneta americana synaptosomal membranes. These toxins depolarize the cockroach axon, irreversibly block the action potential, and slow down and very progressively block the transmembrane transient Na+ current. The contracturant toxin BotIT1 is highly toxic to B. germanica (LD50 = 60 ng/ 100 mg body weight) and barely toxic to mice (LD50 = 1 microgram/20 g body weight) when injected intracerebroventricularly. It does not compete with 125I-AaHIT for its receptor site on P. americana synaptosomal membranes. On cockroach axon, BotIT1 develops plateau potentials and slows down the inactivation mechanism of the Na+ channels. Thus, BotIT1 belongs to the group of alpha insect-selective toxins and shows a strong sequence identity (> 90%) with Lqh alpha IT and LqqIII, two insect alpha-toxins previously purified from the venom of L. q. hebraeus and L. q. quinquestriatus. respectively.
- SourceAvailable from: Juliana Félix-SilvaAn Integrated View of the Molecular Recognition and Toxinology - From Analytical Procedures to Biomedical Applications, 01/2012: chapter 2: pages 23 - 72;
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ABSTRACT: The number and types of venom components that affect ion-channel function are reviewed. These are the most important venom components responsible for human intoxication, deserving medical attention, often requiring the use of specific anti-venoms. Special emphasis is given to peptides that recognize Na(+)-, K(+)- and Ca(++)-channels of excitable cells. Knowledge generated by direct isolation of peptides from venom and components deduced from cloned genes, whose amino acid sequences are deposited into databanks are now adays in the order of 1.5 thousands, out of an estimate biodiversity closed to 300,000. Here the diversity of components is briefly reviewed with mention to specific references. Structural characteristic are discussed with examples taken from published work. The principal mechanisms of action of the three different types of peptides are also reviewed. Na(+)-channel specific venom components usually are modifier of the open and closing kinetic mechanisms of the ion-channels, whereas peptides affecting K(+)-channels are normally pore blocking agents. The Ryanodine Ca(++)-channel specific peptides are known for causing sub-conducting stages of the channels conductance and some were shown to be able to internalize penetrating inside the muscle cells.Toxicon 07/2013; · 2.92 Impact Factor
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ABSTRACT: LIWC is, originally, a text analysis program that counts words of English texts in psychologically meaningful categories. It provides an analysis (in percentage) for 80 dimensions of language (functional words, topics, punctuation). The goal of this methodological note is to present the French LIWC. This version respects the structure of the categories of the English version of the software and gives explanations about the user guide such the preparation of the to be analyzed texts. Then, we explain the decisions for translating the English dictionary into French. We emphasize the constraints imposed by the morphology of written French language and the difficulties encountered (elision of the article, elision of negation and of verbs’ tense). Presenting the translation problems allows understanding the modalities of construction of the dictionary and allows for a LIWC user to build a personalized dictionary in order to analyze contents more suited to the research needs. A qualitative comparison of dimensions obtained with both the French and English versions for 66 bilingual texts of various types and contents provides satisfactory results. A statistical comparison of 119 expressive writings produced by students from three university courses (Humanities, Sciences and Psychology) about a given event (success or failure to an exam) shows the validity of the French version for identifying the expressed contents. Thus, this tool should be efficient for undertaking research in different fields of psychology (health, work and education) concerning oral and written language produced in different contexts.Psychologie Francaise - PSYCHOL FR. 01/2011; 56(3):145-159.