Improved fluorescent probes for the measurement of rapid changes in membrane potential

To improve the quality of fluorescent voltage-sensitive probes twenty new styryl dyes were synthesized. Some of the new probes are significantly better than any used in the past. A signal-to-noise ratio of 90 root mean square (rms) noise was obtained for an optical recording of action potentials from neuroblastoma cells maintained in monolayer culture. The fluorescence fractional change of the optical signal is as large as 14%/100 mV. Photodynamic damage and bleaching are much less significant with the new probes. These fluorescent probes can be used to measure small and rapid changes in membrane potential from single cells maintained in monolayer cultures, from single cells in invertebrate ganglia, from their arborization, and from other preparations. The optical measurement can be made with a standard fluorescent microscope equipped with DC mercury illumination. Guidelines for the design of even better fluorescent probes and more efficient instruments are suggested

Ocorrência de Listeria monocytogenes em queijo artesanal tipo coalho comercializado na cidade de Manaus-AM, Brasil Occurrence of Listeria monocytogenes in handmade type cheese coagulum marketed in the city of Manaus-Amazonas, Brazil

A ocorrência de Listeria sp. em queijo artesanal tipo coalho comercializado na cidade de Manaus foi estudada. No período de março a maio de 1998 foram coletadas 58 amostras do produto em feiras e mercados localizados em seis zonas da cidade de Manaus. Em duas amostras de queijo foram identificadas duas espécies de Listeria: L. monocytogenes e L. innocua. A primeira espécie é reconhecidamente patogênica para o ser humano. Os resultados apresentados demonstraram haver risco de transmissão de enfermidades pelo consumo de queijos processados sem os devidos cuidados de higiene.<br>The occurrence of Listeria sp. in cheese craft type coagulum marketed in the city of Manaus was studied. In the period of March to May of 1998 58 samples of the product were collected at fairs and located markets in six areas of the city. In two cheese samples we identified two species of Listeria: L. monocytogenes and L. innocua. The first species was found fobe pathogenic for the human being. The results demonstrated there to be risk of transmission of illnesses from the consumption of cheeses processed without the due hygiene care