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A Michel

Publications and source records attributed to A Michel.

255 records · Page 15Linked to original sources
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Dose-response analysis of acute hypotensive and renal effects of atrial natriuretic peptide in the rat.

Acute treatments with synthetic atrial natriuretic peptides induce hypotension, in which several mechanisms, including renal effects, are involved. The implication of the renal vasculature and the excretory capacities in the hypotensive action of atrial natriuretic peptides are not ascertained as yet. To address this issue, the rapid time sequence of the acute effects of atrial natriuretic peptides upon renal blood flow, mean arterial pressure, heart rate, and salt and water excretion, as well as a dose-response analysis, were investigated in 38 anesthetized euvolemic rats. Doses varying from 0.25 to 2.50 micrograms of atrial natriuretic peptide were injected i.v. in 30 sec. Each dose induced a brisk and transient increase in renal blood flow, which was maximal (13%) above 1 microgram of atrial natriuretic peptide. A small reduction in mean arterial pressure, timely related to renal vasodilation, occurred at first. It was followed by a second reduction in mean arterial pressure, which was concomitant to the maximal increases in diuresis and natriuresis. It persisted over a longer period of time. The maximal hypotensive effect (-15 mmHg) was observed above 1.5 micrograms of atrial natriuretic peptide. All effects were dose-dependent. There were no changes in heart rate. In conclusion, atrial natriuretic peptides transiently induced dose-dependent increases in renal blood flow and salt and water excretion, while the mean arterial pressure decreased stepwisely. The biphasic hypotensive effect was time-related to the renal vasodilator and diuretic effects, respectively.

Animals↗
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[Toxic food infection caused by Shigella flexneri in a military unit].

Food borne disease outbreaks have increased in France, but outbreaks caused by Shigella are rare, accounting for only 73 cases (1.62%) in 1993. We report a food borne outbreak of Shigella flexneri strain 3 infection in a fire fighting unit in Paris between July 13th and 17th 1995. Forty of the 127 firemen suffered symptoms including acute diarrhea (80%), fever (50%) and blood and mucus in stools (1 case, 2.5%). Epidemiological investigation generated an unimodal epidemic curve suggesting a single source of contamination with no secondary cases. The median incubation period was between 43 hours 30 minutes and 51 hours 30 minutes. This is consistent with food borne Shigella infection. Statistical analysis of a case-control study implicated a mixed salad containing frozen shellfish from Asia (shrimps and mussels), served at lunch and dinner on July 13th 1995. Shigella was not detected in this salad by microbiological methods. However, inoculation with as little as 100 organisms can cause symptoms. There was low-level contamination with Escherichia coli (940 cfu/g) due to cross-contamination. Shigella flexneri strain 3 was isolated from 11 of 18 stool cultures, but was never isolated from cultures of stools provided by the cooks. All isolates had identical antibiotic resistance profiles. They were resistant to ampicillin and ticarcillin, moderately sensitive to amoxicillin-clavulanic acid, highly sensitive to aminosides, erythromycin and quinolones. This identical pattern in all isolates suggests a common source of contamination. Plasmid-based multiple resistance is common in this organism. Therefore, antibiotics should only be given to patients with evident clinical signs of infection. Treatment was symptom-based in all but 4 patients, who had acute diarrhea and were treated with ciprofloxacin. This antibiotic is well tolerated, has rapid bactericidal action and significantly reduces the duration of the symptoms and excretion of Shigella, thus preventing secondary contamination with this highly infectious bacterium. Thus, food borne outbreaks of Shigella can occur in countries with a high standard of living because of the increase in mass catering (e.g. fast food restaurants) and importation of foodstuffs from developing countries with endemic shigellosis. This is a public health problem because of the morbidity and absenteeism due to illness, particularly when the patients are firemen responsible for emergency management.

Amoxicillin↗