PubMed · 8213307
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P Mishra, A Singh. 1993. Microbial pentose utilization.. https://doi.org/10.1016/s0065-2164(08)70594-x
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Concerning speed, cost and on-line capabilities, biosensors offer attractive alternatives to existing methods for food analysis. They make monitoring and control of manufacturing processes possible. Furthermore, portable biosensors could be used for monitoring in manufacturing, retail and distribution of foods. An overview is given about existing biosensors for foodstuffs that could find applications in food industry.
In the present investigation, brain stem spinal cord preparations of 0-4-day-old rats were used to determine whether inspiratory-related discharges were modulated by a central pattern generator either during baseline conditions or during conditions of increased chemical drive. Spectral analyses were carried out on pairs of nerve activities during superfusion with normal solutions (pH = 7.4) and during superfusion with acidic solutions (pH = 6.8-7.0). Autopower spectra of nerve discharges in normal pH solution revealed the presence of two peaks: one in the 2-6 Hz band and the other in the 20-39 Hz band. Peaks occurring over both frequency ranges were highly correlated as revealed by coherence spectral analysis. Acidic stimulation produced no systematic changes in spectral features, for example, shifting peaks to other frequency regions, or increasing the values of coherence. The 2-6 Hz peak is most likely due to the arrival of depolarizing inputs from the brain stem that generate a ramp of activity at recording sites. On the other hand, activity in the 20-39 Hz region represents the discharge frequency of inspiratory motoneurons. The fact that coherence is present in this latter band provides evidence for short-time scale (ms) synchronization of functionally and anatomically distinct inspiratory motoneurons by a central pattern generator.
Virulent Salmonella typhimurium strains differ from the attenuated laboratory strain LT2 at the rpoS locus. It was previously shown that the rpoS gene in strain LT2 contains a rare UUG start codon (I. S. Lee, J. Lin, H. K. Hall, B. Bearson, and J. W. Foster, Mol. Microbiol. 17:155-167, 1995). This difference is responsible for the inability of LT2 to display a sustained log-phase acid tolerance response. We show that the altered rpoS allele (rpoS(LT2)) also affects the stationary-phase acid tolerance response in Salmonella. By transducing the rpoS(LT2) allele into virulent strain backgrounds and crossing wild-type rpoS allele into strain LT2, we demonstrate that the rpoS(LT2) allele contributes to the attenuation of strain LT2. We examined the effect of the rpoS allele on invasion and found that the rpoS status of the cell had no effect on the ability of the strains to invade intestinal epithelial cells in tissue culture. Enumeration of bacteria from tissues of infected mice indicated that the presence of the rpoS(LT2) allele affected the ability of S. typhimurium to reach the liver and spleen and to persist in several tissues at 6 days postinfection. This is likely due, at least in part, to a decrease in spv gene expression in these mutants. We demonstrate that strains containing the rpoS(LT2) allele are not only sensitive to pH 3.0 (acid stress) but are also sensitive to the DNA-damaging agent methyl methanesulfonate. However, these strains appear to survive stationary-phase and oxidative stresses as well as strains containing a wild-type rpoS allele. Despite an increased sensitivity to acid stress and DNA damage, strains containing either an rpoS-null mutation or the rpoS(LT2) allele survived in J774 cells and bone marrow-derived macrophages as well as did otherwise isogenic strains with a wild-type rpoS allele.