Scopolamine Administration Modulates Muscarinic, Nicotinic and NMDA Receptor Systems

Studies on the effect of scopolamine on memory are abundant but so far only regulation of the muscarinic receptor (M1) has been reported. We hypothesized that levels of other cholinergic brain receptors as the nicotinic receptors and the N-methyl-D-aspartate (NMDA) receptor, known to be involved in memory formation, would be modified by scopolamine administration

Methyl methacrylate and respiratory sensitization: A Critical review

Methyl methacrylate (MMA) is a respiratory irritant and dermal sensitizer that has been associated with occupational asthma in a small number of case reports. Those reports have raised concern that it might be a respiratory sensitizer. To better understand that possibility, we reviewed the in silico, in chemico, in vitro, and in vivo toxicology literature, and also epidemiologic and occupational medicine reports related to the respiratory effects of MMA. Numerous in silico and in chemico studies indicate that MMA is unlikely to be a respiratory sensitizer. The few in vitro studies suggest that MMA has generally weak effects. In vivo studies have documented contact skin sensitization, nonspecific cytotoxicity, and weakly positive responses on local lymph node assay; guinea pig and mouse inhalation sensitization tests have not been performed. Cohort and cross-sectional worker studies reported irritation of eyes, nose, and upper respiratory tract associated with short-term peaks exposures, but little evidence for respiratory sensitization or asthma. Nineteen case reports described asthma, laryngitis, or hypersensitivity pneumonitis in MMA-exposed workers; however, exposures were either not well described or involved mixtures containing more reactive respiratory sensitizers and irritants.The weight of evidence, both experimental and observational, argues that MMA is not a respiratory sensitizer

Variabilidade comportamental em humanos: efeitos de regras e contingências

Dois experimentos investigaram, com estudantes universitários, a variabilidade aprendida. No Experimento 1, quatro grupos (n = 5) foram submetidos a dois esquemas de reforçamento para seqüências de respostas de pressão às teclas P e Q do computador. Para o grupo Variabilidade (VAR) o reforçamento era dependente do alto grau de variação entre as seqüências, e para o grupo Acoplado (ACO) o reforçamento independia dessa variabilidade. Foram manipuladas a ordem de apresentação dessas contingências e o intervalo entre elas (0 e 3 meses). No Experimento 2, essas contingências foram combinadas a instruções verbais (regras) que as descreviam correta ou incorretamente (quatro grupos, n = 5). Os resultados mostraram: 1) maior variabilidade em VAR, independente das demais variáveis manipuladas, 2) desempenho em ACO afetado parcialmente pela ordem das contingências, pelo intervalo e pelas regras. Em ambos os estudos, os sujeitos não foram capazes de descrever as contingências em vigor. Esses resultados indicam o controle operante da variabilidade observada