phnE and glpT genes enhance utilization of organophosphates in Escherichia coli K-12

Wild-type Escherichia coli K-12 strain JA221 grows poorly on low concentrations (< or = 1 mM) of diisopropyl fluorophosphate and its hydrolysis product, diisopropyl phosphate (DIPP), as sole phosphorus sources. Spontaneous organophosphate utilization (OPU) mutants were isolated that efficiently utilized these alternate sources of phosphate. A genomic library was constructed from one such OPU mutant, and two genes were isolated that conferred the OPU phenotype to strain JA221 upon transformation. These genes were identified as phnE and glpT. The original OPU mutation represented phnE gene activation and corresponded to the same 8-bp unit deletion from the cryptic wild-type E. coli K-12 phnE gene that has been shown previously to result in phnE activation. In comparison, sequence analysis revealed that the observed OPU phenotype conferred by the glpT gene was not the result of a mutation. PCR clones of glpT from both the mutant and the wild type were found to confer the OPU phenotype to JA221 when they were present on the high-copy-number pUC19 plasmid but not when they were present on the low-copy-number pWSK29 plasmid. This suggests that the OPU phenotype associated with the glpT gene is the result of amplification and overproduction of the glpT gene product. Both the active phnE and multicopy glpT genes facilitated effective metabolism of low concentrations of DIPP, whereas only the active phnE gene could confer the ability to break down a chromogenic substrate, 5-bromo-4-chloro-3-indoxyl phosphate-p-toluidine (X-Pi). This result indicates that in E. coli, X-Pi is transported exclusively by the Phn system, whereas DIPP (or its metabolite) may be transported by both Phn and Glp systems.     

Effects of channel dispersion and path correlations on system-wide throughput in MIMO-based cellular systems

We compute cell-wide mean throughputs for a wide range of multiple-input-multiple-output (MIMO) system design parameters, in both single- and multi-cell scenarios, using realistic models for channel dispersion, path correlations, and cochannel interference. We assume the use of single-carrier modulation, and quantify the degradation in downlink throughput as the channel dispersion increases. Our results highlight the potential harm even from mild dispersion in MIMO links. In studying path correlations, we assume linear arrays at each end of the link, and quantify the interplay among device size, number of antenna elements, path correlation, and carrier frequency. We show that, under practical size constraints, the use of additional antenna elements can be counterproductive.     

Motor and sensory fibres of neck muscle nerves in the cat

The numbers and sizes of nerve fibres to the dorsal neck muscles, splenius, complexus and biventer cervicis have been examined in the cat. The total number of fibres is unusually high as is the content of sensory fibres (estimated as the loss of fibres after ganglionectomy). The fibre spectra of these sensory nerves has an unusually large number of fibres in the group II and III range (3-7 mum) and differs markedly in this way from other muscle nerves. The motor fibres contain a high proportion (64-99%) in the gamma fibre size range. Large motor fibres are absent in the nerves to biventer cervicis (a slow muscle). The ratio of unmyelinated to myelinated fibres in neck muscle nerves is similar to that in hind legs at about 2.5:1.     

Oestrogenic, anti-oestrogenic and fertility effects of some triphenylethanes and triphenylethylenes related to ethamoxytriphetol (MER 25)

The myocardial content of digoxin 60 min after intravenous administration in open-chest dogs correlated with heart rate controlled in individual dogs between 64 and 215 beats/min. In other dogs, increasing right ventricular mechanical work by constriction of the pulmonary artery resulted in greater right ventricular digoxin uptake. Increase in myocardial blood flow per se could not explain these findings since, in further dogs, increasing regional myocardial blood flow by adenosine infusion did not much affect digoxin uptake. Active uptake of cardiac glycosides is probably influenced by myocardial mechanical and metabolic activity.     

规划师与经济师之间有关土地市场政策的争论

为了进一步探讨在经济学家和规划师之间长期以来就对土地市场能否实现广泛的社会目标等问题而存在的争论,林肯学院组织研讨会对相关问题进行讨论和交流,并特别关注了政治在规划和决策中所起到的作用.