RESUMO
Salmonellae in chicken carcass rinse water or enrichment broth were detected with a fluorescence concentration immunoassay (FCIA) using intact salmonellae cells as the reacting particles. Sample Solutions and reagents were added to a 96-well fluoricon assay plate and incubated 30 min in the chamber of a fluorescence concentration analyzer at room temperature. The bound and free components were separated by automated vacuum filtration and washings through the membrane filters equipped at the bases of the wells. The fluorescent signals were concentrated through vacuum filtration and were read at a wavelength of 485/535 nm. A cut-off value of the arbitrary fluorescence units was calculated by adding two standard deviations to the mean value of the negative control. When the arbitrary fluorescence units of a sample were above the cut-off value, it was scored positive indicating the presence of salmonellae in the test suspensions. It was found the FCIA method could detect salmonellae at 1.25 × 104 cells per mi in pure culture and was specific enough to screen salmonellae from four types of common chicken carcass contaminating bacteria. By coupling with 18-h direct enrichment in selenite cystine broth of the whole carcass rinse, the detection of salmonellae in chicken carcass rinse water was accomplished in less than 24 h.
RESUMO
Salmonellae attached to artificially contaminated chicken carcasses were identified in less than 24 h using a nitrocellulose membrane lift method. Six pieces of nitrocellulose membrane were pressed onto each chicken carcass at the breast, the thigh, and the back in order to lift the salmonellae from the carcasses. After direct incubation of the membranes on xylose lysine tergitol 4 agar overnight at 37°C, the appearance of black colonies on the white membrane was considered a positive presumptive test for salmonellae. Immunoassay of black colonies on the membrane with Salmonella -specific antiserum confirmed that the black colonies were salmonellae . The nitrocellulose membrane lift technique was shown to be comparable in sensitivity by direct enrichment of whole carcass rinse in selenite cystine broth.
RESUMO
Amphetamine (AMPH) induces behavioral sensitization and neurotoxicity primarily by enhancing the dopamine-mediated neurotransmission. However, the involvement of the N-methyl-D-aspartate (NMDA) receptor in AMPH-induced neuropathology is also known. Recent investigation has found that high concentration of dopamine could inhibit NMDA receptor-mediated responses by blocking the NMDA receptor channel. By virtue of the structure similarity between dopamine and AMPH, we determined whether d-AMPH and its analogs, l-AMPH and methamphetamine (MAMH), could affect the NMDA receptor-mediated [3H]N-[1-(2-thienyl)cyclohexyl] piperidine ([3H]TCP) binding in rat cortical membrane preparations and intracellular 45Ca2+ accumulation and cell death in the rat primary cortical cell cultures. AMPH concentration-dependently inhibited NMDA- and glycine-stimulated [3H]TCP binding and intracellular 45Ca2+ accumulation with two distinct potencies; a minor inhibition with high potency and a major inhibition with low potency. [3H]TCP binding suggested that the high-potency inhibition was produced by decreasing agonist-induced activation of the NMDA receptor channel. On the other hand, the low-potency inhibition was produced by competing with [3H]TCP binding in the NMDA receptor channel, like the action of noncompetitive antagonist of the NMDA receptor. However, AMPH analogs were less potent in inhibiting NMDA- and glycine-induced cultured cell death. Thus, this result indicates that AMPH could antagonize the NMDA receptor-mediated responses in vitro by two different mechanisms, probably, through directly interacting with two distinct sites on this receptor/channel complex.