Effects of homocysteine on acetylcholine- and adenosine-induced vasodilatation of pancreatic vascular bed in rats.

1. Epidemiological and experimental data have shown that homocysteine may provoke vascular lesions and that moderate homocysteinaemia may constitute an independent risk factor for vascular disease. It is now documented that homocysteine damages human endothelial cells in culture, possibly by producing hydrogen peroxide in an oxygen-dependent reaction. 2. In this study, we have examined the direct effect of this sulphur amino acid on pancreatic vascular resistance. Experiments were performed on the vascular bed of the rat isolated pancreas perfused at constant pressure; thus, any change in pancreatic vascular resistance resulted in a change in the flow rate. D,L-Homocysteine perfused for one hour at three different concentrations (200 microM, 2 mM, 20 mM) did not induce any significant change in the flow rate per se. Homocysteine infusion for 30 min at a concentration of 200 microM or 2 mM abolished the endothelium-dependent vasodilatation induced by acetylcholine (0.05 microM), but did not modify adenosine (1.5 microM)-induced vasodilatation. 3. The effect of D,L-homocysteine (200 microM or 2 mM) cannot be ascribed to a direct antimuscarinic effect since 30 min pretreatment of rat ileum with these concentrations did not significantly change the contractile effect of increasing concentrations of acetylcholine (0.015-15 microM). 4. Preincubation of human umbilical vein endothelial cells with D,L-homocysteine (0.2-5.0 mM) had no significant effect on overall cell number or viability during 18 h of incubation; the endothelial cells exposed to concentrations up to 5 mM exhibited a spindle-shaped, whirled pattern. This pattern was reversed 48 h after the removal of homocysteine. A cytotoxic effect was seen after 18 h incubation in 10 mM D,L-homocysteine. 5. In conclusion, an acute infusion of homocysteine altered acetylcholine endothelium-induced vasodilation, whereas the adenosine vasodilatator effect was insensitive to the deleterious action of homocysteine in vitro.

[Enzyme determination in vitro of inhibitor activity of beta-lactamase from tazobactam. Comparison with high performance liquid chromatography]. / Dosage enzymatique in vitro de l'activité inhibitrice de beta-lactamase du tazobactam. Comparaison à la chromatographic liquide à haute performance.

We developed an enzymatic method using nitrocefin to assay tazobactam in vitro. Tazobactam was incubated with TEM-1 beta-lactamase. Then, residual beta-lactamase activity was assayed by adding nitrocefin. This activity corresponded indirectly to the initial concentration of tazobactam. Within-assay, between-assay and accuracy coefficients of variation were below 15%. The correlation coefficients between enzymatic method and high performance liquid chromatography (the reference method)was 0.98. The enzymatic method is rapid, easy to perform and should be applied to daily clinical practice.

In-vitro evaluation of beta-lactamase inhibition by latamoxef and imipenem.

The in-vitro 50% inhibitory concentrations (IC50s) of latamoxef and imipenem against a set of plasmid-mediated beta-lactamases including TEM-1, TEM-3, TEM-5 and TEM-10 were determined by an enzymatic method using nitrocefin as substrate. The IC50s of both antibiotics against extended-spectrum beta-lactamases were below 0.2 mg/L. The conventional spectrum beta-lactamase TEM-1 was not inhibited by either antibiotic at the highest concentration tested. Except for TEM-10 for which the IC50s of the two antibiotics were the same, imipenem showed significantly greater activity than latamoxef against TEM-3 and TEM-5. Clavulanic acid taken as a control demonstrated greater and wider inhibitory activity, but on the other hand it has no significant antibiotic activity.

An enzymatic method for assaying sulbactam in human serum: comparison with high performance liquid chromatography.

An enzymatic method using nitrocefin as substrate was developed to assay sulbactam in human serum. Serum containing sulbactam was incubated with purified titrated TEM-1 beta-lactamase and nitrocefin was then added to the mixture to determine the remaining beta-lactamase activity and consequently the concentration of sulbactam. Assays were carried out on five patients with pulmonary infections receiving sulbactam plus amoxycillin iv. The values for serum sulbactam concentrations determined by the enzymatic method were compared with those determined by high performance liquid chromatography (HPLC). The correlation coefficient was 0.990 for serum sulbactam concentrations below 15 mg/L.

Bifocal cervical spondylodiscitis due to Citrobacter diversus.

Spondylodiscitis due to Citrobacter diversus is rare. An unusual case of bifocal cervical spondylodiscitis following transurethral prostatectomy is reported. C. diversus was detected by urinary cultures and locally by intervertebral disc puncture. Satisfactory recovery occurred after treatment with imipenem and amikacin, and then imipenem alone. Citrobacter infections are still rare in adults but are increasing in immunocompromised patients and sometimes occur in healthy subjects following surgery.

Venous occlusion and chronic cigarette smoking: dose-dependent decrease in the measurable release of tissue-type plasminogen activator and von Willebrand factor.

This study was aimed at examining the effect of chronic cigarette smoking on a venous occlusion test. Two groups of young healthy men, a control group of 20 non-smoking subjects and a group of 21 smoking subjects having an average consumption of 17.6 packages.day-1.years (SD 8.6) were studied. Venous occlusion performed in smokers did not induce a significant measurable release of von Willebrand factor (vWF). The release of tissue-type plasminogen activator (t-PA) was significantly weaker for the smokers than for the control group (P less than 0.02). An inverse correlation was found between the cumulative parameter of tobacco consumption and the measurable amount of t-PA Ag or vWF Ag released during venous occlusion (r' = -0.994 and r' = -0.889). Cigarette smoking is thus associated with disturbances of the biological response to this venous occlusion test.

Study of quantitative modifications of the plasma protein S system components in non-acute inflammatory syndromes.

Thrombosis frequently accompanies inflammatory disease. There are numerous and frequent modifications of haemostasis parameters during inflammatory disease. Deficiencies in protein S, a protein C cofactor, are predisposing factors for thromboses. In 43 patients with biological inflammatory syndromes (ESR above 80 mm in the first hour found twice in a three-day period and disturbances of other biological inflammatory markers) we studied the variations of the protein S system: total antigenic protein S, free antigenic protein S, C4b BP, all antigenic fractions being assayed by electro-immuno diffusion. The results show an increase in free protein S (mean 114.3%, range 25%-180%, P less than 0.005), the biologically active fraction of protein S. They also evidence the expected increase in C4b BP (mean 188.3%, range 41%-335%, P less than 10(-5]. There is an increase in total protein S Ag (mean 145.3%, range 56%-220%, P less than 10(-5]. The results show a high positive correlation between the increased free protein S Ag and total protein S Ag (r' = 0.78, P less than 0.01), between total protein S and C4b BP (r' = 0.8, P less than 0.01) and between free protein S and C4b BP (r' = 0.73, P less than 0.01). C4b BP concentrations are correlated with haptoglobin (r' = 0.59, P less than 0.01), orosomucoid (r' = 0.53, P less than 0.01), C3 complement component (r' = 0.80, P less than 0.01), C4 (r' = 0.39, P less than 0.02) and platelet count (r' = 0.51, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)