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1.
Braz. j. med. biol. res ; 35(4): 485-491, Apr. 2002. ilus
Artigo em Inglês | LILACS | ID: lil-309199

RESUMO

Trimethylsulfonium, a compound present in the midgut gland of the sea hare Aplysia brasiliana, negatively modulates vagal response, indicating a probable ability to inhibit cholinergic responses. In the present study, the pharmacological profile of trimethylsulfonium was characterized on muscarinic and nicotinic acetylcholine receptors. In rat jejunum the contractile response induced by trimethylsulfonium (pD2 = 2.46 + or - 0.12 and maximal response = 2.14 + or - 0.32 g) was not antagonized competitively by atropine. The maximal response (Emax) to trimethylsulfonium was diminished in the presence of increasing doses of atropine (P<0.05), suggesting that trimethylsulfonium-induced contraction was not related to muscarinic stimulation, but might be caused by acetylcholine release due to presynaptic stimulation. Trimethylsulfonium displaced [³H]-quinuclidinyl benzilate from rat cortex membranes with a low affinity (Ki = 0.5 mM). Furthermore, it caused contraction of frog rectus abdominis muscles (pD2 = 2.70 + or - 0.06 and Emax = 4.16 + or - 0.9 g), which was competitively antagonized by d-tubocurarine (1, 3 or 10 æM) with a pA2 of 5.79, suggesting a positive interaction with nicotinic receptors. In fact, trimethylsulfonium displaced [³H]-nicotine from rat diaphragm muscle membranes with a Ki of 27.1 æM. These results suggest that trimethylsulfonium acts as an agonist on nicotinic receptors, and thus contracts frog skeletal rectus abdominis muscle and rat jejunum smooth muscle via stimulation of postjunctional and neuronal prejunctional nicotinic cholinoreceptors, respectively


Assuntos
Animais , Masculino , Ratos , Aplysia , Colinérgicos , Agonistas Nicotínicos , Receptores Muscarínicos , Receptores Nicotínicos , Atropina , Relação Dose-Resposta a Droga , Contração Muscular , Ratos Wistar
2.
Braz. j. med. biol. res ; 31(6): 785-91, jun. 1998. ilus, tab
Artigo em Inglês | LILACS | ID: lil-210967

RESUMO

The antimicrobial, hemagglutinating and toxic activities of the purple fluid of the sea hare Aplysia dactylomela are described. Intact or dialyzed purple fluid inhibited the growth of species of Gram-positive and Gram-negative bacteria and the action was not bactericidal but bacteriostatic. The active factor or factors were heat labile and sensitive to extreme pH values. The fluid preferentially agglutinated rabbit erythrocytes and, to a lesser extent, human blood cells, and this activity was inhibited by the glycoprotein fetuin, a fact suggesting the presence of a lectin. The fluid was also toxic to brine shrimp nauplii (LD 50 141.25 µg protein/ml) and to mice injected intraperitoneally (LD 50 201.8 ñ 8.6 mg protein/kg), in a dose-dependent fashion. These toxic activities were abolished when the fluid was heated. Taken together, the data suggest that the activities of the purple fluid are due primarily to substance(s) of a protein nature which may be involved in the chemical defense mechanism of this sea hare


Assuntos
Animais , Coelhos , Camundongos , Aplysia , Bactérias/efeitos dos fármacos , Líquidos Corporais , Hemaglutinação/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Eletroforese em Gel de Poliacrilamida , Inibidores do Crescimento , Testes de Sensibilidade Microbiana
3.
Psicol. teor. pesqui ; 7(3): 303-10, set.-dez. 1991.
Artigo em Português | LILACS | ID: lil-123714

RESUMO

O estudo dos mecanismos neurais da aprendizagem revelou considerável progresso nos últimos vinte anos. A possibilidade de experimentaçäo com invertebrados tem levado a descobertas importantes sobre as mudanças funcionais e estruturais, a nível celular, que acompanham processos simples de aprendizagem como a habituaçäo e a sensitizaçäo


Assuntos
Habituação Psicofisiológica , Aprendizagem , Neurônios , Aplysia
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