Functional analysis of sigma-70 consensus promoters in Pseudomonas aeruginosa and Escherichia coli.

A series of synthetic promoters, based upon the Escherichia coli sigma 70 consensus promoter sequence, was constructed upstream of the lacZ reporter gene in the modified broad-host-range vector pQF52. The role of the intervening spacer region in gene expression in Pseudomonas aeruginosa and E. coli was studied by insertions and deletions within this region. In P. aeruginosa and E. coli the patterns of gene expression were identical with maximum beta-galactosidase activity being measured from promoters possessing 19 bp in their intervening regions, presumably as a result of impeded promoter clearance with the consensus 17-bp promoter. In P. aeruginosa a second occurrence of enhanced activity, which could not be attributed to the involvement of the alternative sigma factor RpoN (sigma 54), was evident with the promoter having a 16-bp spacer.

Hypertension without cardiac hypertrophy does not induce a cardiac baroreflex deficit.

OBJECTIVE: To investigate the effects of prolonged hypertension in the absence of cardiac hypertrophy on the blood pressure-heart rate reflex during acute and chronic NO synthase blockade. METHODS: Male Wistar rats were treated acutely with N omega-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg intraperitoneally) or chronically with L-NAME (2.5-3 weeks, 50 mg/kg per day orally). The cardiac baroreceptor reflex was assessed in previously instrumented conscious rats by using a 'steady-state' method that involved alternating vasoactive drug-induced stepwise increases and decreases in mean arterial pressure with methoxamine and sodium nitroprusside. Following baroreflex assessment, the rats were killed by an overdose of anaesthetic, their hearts were removed and the left ventricle plus septum separated from the heart and weighed. RESULTS: The arterial pressure at one-half of the heart rate range was shifted to higher arterial pressures, consistent with the increase in the operating point of mean arterial pressure following NO synthase blockade. No change in any of the baroreflex parameters could be detected despite prolonged L-NAME-induced hypertension. On the basis of the study criteria, the data from one rat were not included in the group analysis because of the presence of cardiac hypertrophy. CONCLUSIONS: The results of the present study indicate that increased blood pressure alone, either acutely or chronically, is not a sufficient stimulus to induce a baroreflex deficit.

Aeromonas hydrophila bacteremia in ambulatory immunocompromised hosts.

We observed seven episodes of Aeromonas hydrophila septicemia in five patients. All but one patient had an underlying disease resulting in immunosuppression. All episodes occurred in ambulatory patients whose vocation or avocation had recently caused them to contact water or fish. We hypothesize that infection with this gram-negative bacterium is acquired more frequently from the natural habitat of the organism than from nosocomial sources.