Crotoxin, the major toxin from the rattlesnake Crotalus durissus terrificus, inhibits ³H-choline uptake in guinea pig ileum

We examined the effect of crotoxin, the neurotoxic complex from the venom of the South American rattlesnake Crotalus durissus terrificus, on the uptake of ³H-choline in minces of smooth muscle myenteric plexus from guinea pig ileum. In the concentration range used (0.03-1 µM) and up to 10 min of treatment, crotoxin decreased ³H-choline uptake by 50-75% compared to control. This inhibition was time dependent and did not seem to be associated with the disruption of the neuronal membrane, because at least for the first 20 min of tissue exposure to the toxin (up to 1 µM) the levels of lactate dehydrogenase (LDH) released into the supernatant were similar to those of controls. Higher concentrations of crotoxin or more extensive incubation times with this toxin resulted in elevation of LDH activity detected in the assay supernatant. The inhibitory effect of crotoxin on ³H-choline uptake seems to be associated with its phospholipase activity since the equimolar substitution of Sr2+ for Ca2+ in the incubation medium or the modification of the toxin with p-bromophenacyl bromide substantially decreased this effect. Our results show that crotoxin inhibits ³H-choline uptake with high affinity (EC25 = 10 ± 5 nM). We suggest that this inhibition could explain, at least in part, the blocking effect of crotoxin on neurotransmission

Avaliação da vigilância de contatos de casos novos de tuberculose no Estado de Mato Grosso - Brasil Evaluation of surveillance of contacts of new tuberculosis cases in the state of Mato Grosso - Brazil

OBJETIVO: Avaliar as ações de vigilância de contatos de casos novos de tuberculose em Mato Grosso no período de 1999 a 2004. MÉTODOS: Estudo epidemiológico descritivo baseado em dados do Sistema de Informação de Agravos de Notificação-Tuberculose. O número de casos novos de tuberculose, o número de contatos (estimados, examinados e não examinados) e a taxa de incidência de tuberculose foram analisados segundo a faixa etária. Calculou-se, por ano de estudo, a média de contatos examinados para cada caso de tuberculose segundo a faixa etária. Os casos de tuberculose pulmonar com e sem contatos examinados foram analisados segundo o resultado da baciloscopia. RESULTADOS: Em 2004, Mato Grosso apresentou 41,3 casos de tuberculose por 100 mil habitantes. A mesorregião centro-sul apresentou a maior taxa de incidência (57 casos/100 mil habitantes) e uma taxa de 15% de contatos examinados. Entre os menores de 15 anos, examinaram-se 63 contatos (60,5%), enquanto entre aqueles com 15 anos ou mais, examinaram-se 389 contatos (8,9%). Em 1999, a média de contatos examinados em Mato Grosso foi de 0,02 (0,5%), e, em 2004, ela alcançou 0,42 (10,5%). O percentual de contatos examinados foi 40,0% maior entre os contatos de casos bacilíferos (OR = 1,4; IC95%: 1,08-1,83). CONCLUSÕES: O percentual de contatos examinados é muito baixo, principalmente entre os adultos. A normatização do exame de contatos de tuberculose pela Secretaria de Vigilância em Saúde do Ministério da Saúde não tem sido suficiente para garantir que esse grupo de maior risco de adoecimento seja priorizado pelos serviços de saúde de Mato Grosso.<br>OBJECTIVE: To evaluate surveillance of contacts of new tuberculosis cases in the state of Mato Grosso from 1999 to 2004. METHODS: This was a descriptive epidemiological study based on data from the Tuberculosis Case Registry Database. The number of new tuberculosis cases, the number of contacts (estimated, investigated, and uninvestigated), and the tuberculosis incidence rate were analyzed by age bracket. The mean rate of contacts investigated for each case of tuberculosis by age bracket was calculated per year of study. The cases of pulmonary tuberculosis with and without contacts investigated were analyzed by sputum smear microscopy results. RESULTS: In 2004, there were 41.3 cases of tuberculosis per 100,000 inhabitants in the state of Mato Grosso. The south-central region presented the highest incidence rate (57 cases/100,000 inhabitants) and a 15% rate of contacts investigated. Among those younger than 15 years, 63 contacts (60.5%) were investigated, whereas among those aged 15 or older, 389 (8.9%) were investigated. In 1999, the mean rate of contacts investigated statewide was 0.02 (0.5%), and, in 2004, it reached 0.42 (10.5%). The percentage of contacts investigated was 40% higher among the contacts of contagious cases (OR = 1.4; 95% CI: 1.08-1.83). CONCLUSIONS: The percentage of contacts investigated is very low, principally among adults. The adoption of the standards for investigation of tuberculosis contacts proposed by the Brazilian National Ministry of Health Department of Health Surveillance has not ensured that this group at highest risk of developing active tuberculosis be given priority at health care facilities in the state of Mato Grosso