Cholesterol efflux capacity, carotid atherosclerosis, and cerebrovascular symptomatology.

OBJECTIVE: To investigate the association of cholesterol efflux capacity with carotid atherosclerosis and cerebrovascular disease. APPROACH AND RESULTS: Patients with high-grade carotid stenosis (n=154) were recruited from Vascular Surgery clinics and 9 healthy controls from the McGill University Health Network, Montreal, Canada. Cerebrovascular symptomatology history was obtained. Stenosis was assessed by carotid ultrasound. Fasting blood samples were collected and depleted of apolipoprotein B particles by polyethylene glycol precipitation from serum. Cholesterol efflux was determined by incubating apolipoprotein B-depleted serum in cAMP-stimulated J774 cells for 6 hours. Carotid specimens were classified by 2 vascular pathologists using the American Heart Association atheromatous plaque classification. Differences in efflux were assessed according to (1) stenosis, (2) American Heart Association classification, and (3) cerebrovascular symptomatology. Normalized efflux was significantly lower in patients with carotid atherosclerosis compared with controls (0.97±0.16 versus 1.5±0.46; P<0.0001). Efflux was inversely associated with stenosis; the odds ratio for 80% to 99% versus 50% to 79% stenosis of tertile 1 (lowest) versus tertile 3 (highest) of efflux was 3.78 (95% confidence interval, 1.18-12.06) after adjusting for age, sex, low-density lipoprotein, and high-density lipoprotein. There were significant differences in cholesterol efflux between American Heart Association fibroatheroma (Va, 0.91±0.13), mainly calcific (Vb, 0.97±0.15), and mainly fibrotic (Vc, 1.03±0.21; P=0.05). There were no significant differences in efflux according to symptomatology. CONCLUSIONS: Cholesterol efflux capacity is inversely associated with increasing carotid stenosis and is associated with more advanced carotid plaque morphology, suggesting that cholesterol efflux capacity may be a biomarker for severity of carotid atherosclerotic burden. Whether therapies targeting high-density lipoprotein quality could be useful for stabilizing carotid atherosclerosis needs to be assessed.

Characterization of Pseudomonas aeruginosa strains isolated from cystic fibrosis patients by different typing methods.

Pseudomonas (P.) aeruginosa strains isolated from the sputum of cystic fibrosis patients (CFP) are frequently difficult to type by conventional typing methods. The purpose of this study was to develop a random amplified polymorphic DNA (RAPD) analysis for the routine typing of these strains. Sixty P. aeruginosa non-repetitive strains recovered from CFP in a teaching hospital were typed. Thirty-five non-serotyped strains were studied by RAPD-PCR analysis with primers 272 and 208. RAPD data were performed to establish the relatedness between bioptype, antibiotic susceptibility and genotype. Fifty-five percent of strains are multiresistant, and no relation was found between antibiotype and biotype. A possible correlation between various phenotypes belonging to a single genotype was observed. RAPD typing characterized 30 distinct genotypes and two small clusters of strains were observed among isolates with each primer. Strains belonging to one cluster were present in two (6%) of the 35 strains. Strains belonging to the other cluster were present in three (8%) of the 35 strains. The occurrence of these clusters indicates that cross-infection may occur. The results indicate also that only the RAPD method can establish a clonal relation whereas the other methods may only reflect phenotypical differences, and thus are inadequate to type these strains.

[Various typing methods of Pseudomonas aeruginosa strains isolated from cystic fibrosis patients]. / Différentes méthodes de typage des souches de Pseudomonas aeruginosa isolées des patients atteints de mucoviscidose.

Typing methods are essential to understand the epidemiology of bacterial infections. Strain typing is important for the detection of sources or routes of infections, identification between endemic and epidemic strains and prevention of transmission between patients. Some Pseudomonas aeruginosa cystic-fibrosis strains could not be typed with conventional typing methods. Due to the diverse phenotypic nature of P. aeruginosa, phenotyping methods are not discriminatory enough to identify strains belonging to the same genotype. Thus, molecular typing methods are required. These methods should be applied when data from phenotypic typing analysis becomes ambiguous, such as in cystic fibrosis. Molecular typing methods, developed over the past decade, are highly discriminatory in capacity and reproducibility. However, they are more likely applied in specialized laboratories since they are expensive and increase the workload. A reliable and low-cost typing system is required for better defining the epidemiology of this pathogen and designing more rational policies of infection control. Comparison between typing methods will pinpoint the limits and effectiveness of each method and will improve in turn the choice of a nonspecialized laboratory in terms of simplicity, time and cost.

Surface Activity of n-Alkyltrimethylammonium Bromides in Concentrated Orthophosphoric Acid.

The aggregation and interface behavior of alkyltrimethylammonium bromides (CnH2n+1(CH3)3N+Br-: CnTMA with n = 14, 16, 18) have been investigated in concentrated orthophosphoric acid by means of surface tension measurements. Adsorption of these cationic surfactants at the interface between air and aqueous H3PO4 solutions has been determined at 298 K using the Wilehlmy plate method. Measurements in the most concentrated H3PO4-H2O mixture (95% by weight of acid or 17.5 mol/L) were done at the n-decane/H3PO4 interface using the ring method to avoid any contamination with atmospheric moisture. The critical micelle concentration (CMC), the maximum surface concentration, and surface pressure of C16TMA in water-H3PO4 mixtures and of the homologous series of surfactants, CnTMA, in 95%-H3PO4, were determined at 323 K. Benzene has been used as a test solute for solubilization measurements in 95%-H3PO4 containing C16 TMA micelles. From this experimental work, it can be concluded that micelles are forming even in the most concentrated solutions in acid and that the CMC displays a large depression between 4 and 10 mol/L of H3PO4. The maximum surface concentration increases by steps in the lowest (0 to 1 mol/L) and highest range of concentration (8 to 10 mol/L) in acid. The Klevens equation relating the CMC in relation to the chain length of the surfactants holds in 95%-H3PO4. Values obtained for the parameters of the Klevens equation and for the free energy of micellization in 95%-H3PO4 have been compared to other strongly acidic media like concentrated sulfuric or methanesulfonic acids. Copyright 1998 Academic Press.