Interaction of Cytotoxic and Cytoprotective Bile Acids with Model Membranes: Influence of the Membrane Composition.

To understand the role of bile acids (BAs) in cell function, many authors have investigated their effect on biomembrane models which are less complex systems, but there are still many open questions. The present study aims to contribute for the deepening of the knowledge of the interaction between BAs and model membranes, in particular, focusing on the effect of BA mixtures. The cytotoxic deoxycholic acid (DCA), the cytoprotective ursodeoxycholic acid (UDCA), and the equimolar mixture (DCA + UDCA) were investigated. Monolayers and liposomes were taken as model membranes with two lipid compositions: an equimolar mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), sphingomyelin (SM), and cholesterol (Chol)) traditionally associated with the formation of lipid rafts and an equimolar POPC/SM binary mixture. The obtained results showed that DCA causes the fluidization of monolayers and bilayers, leading to the eventual rupture of POPC/SM liposomes at high concentration. UDCA may provide a stabilization of POPC/SM membranes but has a negligible effect on the Chol-containing liposomes. In the case of equimolar mixture DCA/UDCA, the interactions depend not only on the lipid composition but also on the design of the experiment. The BA mixture has a greater impact on the monolayers than do pure BAs, suggesting a cooperative DCA-UDCA interaction that enhances the penetration of UDCA in both POPC/SM and POPC/SM/Chol monolayers. For the bilayers, the presence of UDCA in the mixture decreases the disturbing effect of DCA.

Discovery of Streptococcus pneumoniae serogroup 35 variants in Australian patients.

OBJECTIVES: Streptococcus pneumoniae isolates from Australian invasive pneumococcal disease cases displaying an atypical 35B phenotype. Whole genome sequencing was used to analyse these strains and identify changes to the capsule gene regions. METHODS: Four atypical serogroup 35 isolates from Australian reference laboratories were unable to be assigned to one of the four known group 35 serotypes by the Quellung serotyping method. Genetic characterization of the capsule locus was performed by bioinformatic analysis of whole genome sequencing data for all isolates. RESULTS: Genetic analysis identified four independent disruptions to the wciG gene, which encodes an O-acetyltransferase responsible for the O-acetylation of the 6Galß1 residue in the capsular polysaccharide repeat unit of serotype 35B. CONCLUSIONS: This is the first published report on the incidence and capsular gene characteristics of a S. pneumoniae 35B variant.

Phase behaviour of stearic acid-stearonitrile mixtures. A thermodynamic study in bulk and at the air-water interface.

The solid-liquid phase behaviour of stearic acid (SA) and stearonitrile (SN) in binary mixtures was investigated by differential scanning calorimetry (DSC), and the formation of SA-SN mixed monolayers at the air-water interface was followed by surface pressure-area (pi-A) measurements and by Brewster angle microscope (BAM) observation. The solid-liquid phase diagram is a eutectic type phase diagram, with the eutectic composition 0.90

Thin films of hydrophobically modified poly(N,N-dimethylacrylamide).

The behavior of a poly(N,N-dimethylacrylamide) hydrophobically modified by incorporating 0.33 mol % of a pyrenyl derivative, [4-(1-pyrenyl)butyl]amine hydrochloride (PY) and 3.56 mol % of dodecylamine (DO) has been studied at the air/water interface. Surface pressure-area isotherm measurements show that the film is initially anchored by the hydrophobic groups at the air-water interface with a pancake-like structure and, with increasing surface pressure, evolves to a quasi mushroom structure, finally reaching a brush configuration at high pressures. Monolayers of this polymer were transferred to silica substrates using the Langmuir-Blodgett (LB) technique at 5, 15, and 25 mN.m(-1). The properties of the LB films were studied by steady-state and time-resolved fluorescence as well as by atomic force microscopy. The results show that the aggregates formed at low pressures are disrupted by pressure increase, while the water-soluble poly(N,N-dimethylacrylamide) becomes dissolved in the water subphase.

Herpes simplex virus type 2 in Brazil: seroepidemiologic survey.

BACKGROUND: The incidence of genital herpes is increasing worldwide. Herpes simplex virus type 2 (HSV-2) is the most common cause of genital ulcerations among the sexually transmitted diseases (STDS). In order to investigate the sexual transmission of genital herpes infection in Brazil, the prevalence of specific antibodies to HSV-2, in populations of high and low risk for STDS was evaluated. METHODS: The population at low risk for STDS was composed of 155 voluntary blood donors at the University Hospitals between February and August, 1994. The population at high risk for STDS was composed of 85 HIV-seropositive persons, consisting of homosexual and promiscuous heterosexual men. A group of 20 highly active prostitutes was also studied between May and July, 1994. All blood samples were screened using an enzyme-linked immunosorbent assay (ELISA) that detects type-specific antibodies to HSV-2 glycoprotein G. Before donating blood, all persons in the study group were given a questionnaire concerning risk factors for acquisition of STDS and suitable to show the socioepidemiologic characteristics of the subjects. RESULTS: The prevalence of ELISA showing HSV-2 infections among HIV-seroposite persons, was 73% (P < 0.01). In the whole group at high risk for STDS, the prevalence was 72% (P < 0.05). Infection with HSV-2, as determined by seroprevalence, was significantly and independently associated with years of sexual activity, history of previous STDS, number of sexual partners in the previous month, number of pregnancies, and previous induced abortions, as well as the percentage of sexual acts involving receptive anal intercourse. CONCLUSIONS: The current strategy for diagnosing genital HSV-2 infection misses many cases. Newly developed type-specific serologic methods can identify cases of unrecognized or subclinical infection. With the high seroprevalence rates detected, routine screening for HSV-2-specific antibodies should be considered in populations at high risk for STDS.

PIP: The incidence of genital herpes is increasing worldwide and herpes simplex virus type 2 (HSV-2) is the most common cause of genital ulcerations among sexually transmitted diseases (STDs). Findings are reported from an assessment of the prevalence of antibodies to HSV-2 in low- and high-risk populations in Brazil. 155 voluntary blood donors and 85 HIV-seropositive homosexual and promiscuous heterosexual men were screened with ELISA for infection with HSV-2 during February-August 1994. 20 highly active prostitutes were also studied during May-July 1994. The subjects were of mean age 30 years, 70% were sexually active at the time of the study, and 6.55% used condoms. Antibodies to HSV-2 were detected in 29.1% of the blood donors, 73% of the HIV-seropositive men, and 72% of the overall high-risk group. Only 10%, however, admitted to ever having episodes of genital herpes. HSV-2 infection was significantly and independently associated with years of sexual activity, history of previous STDs, number of sex partners in the previous month, number of pregnancies, number of induced abortions, and the percentage of sex acts involving receptive anal intercourse. Routine screening for HSV-2 infection should be considered in populations at high risk for STDs.