Scorpion sting epidemiology in Montes municipality of the State of Sucre, Venezuela: geographic distribution Epidemiología do escorpionismo no Município Montes, Estado Sucre, Venezuela: distribuição geográfica

Scorpion stings were surveyed in the Montes Municipality of the State of Sucre, Venezuela, aiming to extend the information on these poisonous accidents by characterizing their geographic distribution. From 1980 to 1990, 184 cases of scorpion stings were recorded with an incidence rate of 38.6 cases per 10,000 inhabitants. The locality of San Fernando presented the highest incidence (68.3(0)/000) of poisonous accidents. The highest percentages of severe cases were recorded in the towns of Arenas (27%), San Lorenzo (21%), and Cocollar (19%), which are located at the foot of the Turimiquire Mountains. This region is a dispersion area of scorpions of the Tityus genus. Our results show that this region of the State of Sucre is endemic for scorpion stings which are an important public health problem.<br>Os autores estudam o escorpionismo no Município Montes, Estado Sucre, Venezuela. Durante o período 1980 a 1990, foi registrado um total de 184 acidentes causados por escorpiões, com índice de incidência de 38,6 casos por 10.000 habitantes. A localidade de São Fernando apresentou a maior probabilidade para o acidente com incidência de 68.3(0)/000. A maioria dos casos graves foi observada nas populações de Arenas (27%), São Lorenzo (21%) e Cocollar (19%), localizadas no pé da montanha da sub-região geográfica do maciço montanhoso do Turimiquire, áreas de dispersão definidas para espécies do gênero Tityus. Os resultados obtidos evidenciam que esta região do Estado Sucre é endêmica para o acidente peçonhento causado por escorpiões que assumem importância como problema de saúde pública

Scorpion toxins specific for Na+-channels.

International audienceNa+-channel specific scorpion toxins are peptides of 60-76 amino acid residues in length, tightly bound by four disulfide bridges. The complete amino acid sequence of 85 distinct peptides are presently known. For some toxins, the three-dimensional structure has been solved by X-ray diffraction and NMR spectroscopy. A constant structural motif has been found in all of them, consisting of one or two short segments of alpha-helix plus a triple-stranded beta-sheet, connected by variable regions forming loops (turns). Physiological experiments have shown that these toxins are modifiers of the gating mechanism of the Na+-channel function, affecting either the inactivation (alpha-toxins) or the activation (beta-toxins) kinetics of the channels. Many functional variations of these peptides have been demonstrated, which include not only the classical alpha- and beta-types, but also the species specificity of their action. There are peptides that bind or affect the function of Na+-channels from different species (mammals, insects or crustaceans) or are toxic to more than one group of animals. Based on functional and structural features of the known toxins, a classification containing 10 different groups of toxins is proposed in this review. Attempts have been made to correlate the presence of certain amino acid residues or 'active sites' of these peptides with Na+-channel functions. Segments containing positively charged residues in special locations, such as the five-residue turn, the turn between the second and the third beta-strands, the C-terminal residues and a segment of the N-terminal region from residues 2-11, seems to be implicated in the activity of these toxins. However, the uncertainty, and the limited success obtained in the search for the site through which these peptides bind to the channels, are mainly due to the lack of an easy method for expression of cloned genes to produce a well-folded, active peptide. Many scorpion toxin coding genes have been obtained from cDNA libraries and from polymerase chain reactions using fragments of scorpion DNAs, as templates. The presence of an intron at the DNA level, situated in the middle of the signal peptide, has been demonstrated