Search

Within a set of 13 induced symbiotic pea (Pisum sativum L.) mutants, two distinct mutated genes sym25 and sym26, selected for ineffective modulation have been counteracted in their effect by Rhizobium strains 254 and 94 respectively, thereby establishing an N2-fixing symbiosis. This suggests that mutagenesis can be a helpful tool in creating specificity systems such as those described in centres of origin and diversification of legume species. [ABSTRACT FROM AUTHOR]

The membrane activity of some saponins, such as digitonin or alpha-hederin, is usually attributed to their interaction with membrane cholesterol (Chol). This contrasts with our recent publication showing that Chol, contrary to sphingomyelin (SM), can delay the cytotoxicity of the saponin ginsenoside Rh2, challenging the usual view that most saponins mediate their membrane effects through interaction with Chol. The aim of the present study was to elucidate the respective importance of Chol and SM as compared to phosphatidylcholine (PC) species in the membrane-related effects of Rh2. On simple lipid monolayers, Rh2 interacted more favorably with eggSM and DOPC than with Chol and eggPC. Using Large Unilamellar Vesicles (LUVs) of binary or ternary lipid compositions, we showed that Rh2 increased vesicle size, decreased membrane fluidity and induced membrane permeability with the following preference: eggSM:eggPC > eggSM:eggPC:Chol > eggPC:Chol. On Giant Unilamellar Vesicles (GUVs), we evidenced that Rh2 generated positive curvatures in eggSM-containing GUVs and small buds followed by intra-luminal vesicles in eggSM-free GUVs. Altogether, our data indicate that eggSM promotes and accelerates membrane-related effects induced by Rh2 whereas Chol slows down and depresses these effects. This study reconsiders the theory that Chol is the only responsible for the activity of saponins.

Under pathological conditions, cholesterol oxidation products (oxysterols) appear in enhanced concentration in blood and cerebrospinal fluid, which leads to cytotoxic effect, especially in central nervous system. However, the mode of action of oxysterols on the membrane level has not been fully resolved. In this paper we have investigated the interaction between 7α- hydroxycholesterol, 7α-OH (one of the most abundant oxysterol in human body) and two major membrane lipids: sphingomyelin, SM (basic component of lipid rafts and nerve membrane) and 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine, POPC (main phospholipid of mammalian cell membranes). 7α-OH/SM mixtures may mimic pathologically changed lipid raft (ordered phase, L O ) while the SM/POPC system can model its surrounding (liquid-disordered phase, L α ). For our study, the Langmuir monolayer technique (based on registration of the surface pressure/area, π/A isotherms), complemented with surface visualization technique (Brewster angle microscopy, BAM) and theoretical calculations, have been employed. The observed affinity of 7α-OH to SM, which appears to be stronger than in cholesterol/SM system, indicates that cholesterol might be partially replaced in lipid rafts by its oxidized derivative. Its incorporation significantly increases rigidity of the system in relation to normal (cholesterol-containing) raft, which can disturb its proper functioning. On the other hand, the poor effect of this oxysterol on the raft's environment was observed., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objectives: First Nations communities in Manitoba were significantly affected by the pandemic H1N1 influenza virus (pH1N1) in 2009. Our objective was to conduct an epidemiologic investigation of a pH1N1 outbreak in one remote First Nations community (population 3,300) in northern Manitoba to inform a timely public health response and provide recommendations for preventing future outbreaks., Methods: Chart reviews were conducted at the nursing station for patients meeting the influenza-like illness (ILI) case definition during the study period (April 20 to June 11, 2009). Descriptive analyses examined age, gender, clinical presentation, management, outcomes and risk factors. Comparisons were made for hospitalized versus non-hospitalized cases and laboratory-confirmed versus possible cases using Pearson's chi-square test for gender and symptoms and using a t-test for age., Results: There were 180 ILI cases, including 23 laboratory-confirmed cases of pH1N1. Forty percent of children < 1 year old in the community and 9.4% of pregnant women presented to the nursing station with ILI. Most ILI cases were managed through the community nursing station, although 18.3% of cases (n = 33) were medically evacuated and 16.1% (n = 29) were hospitalized. There were no differences between hospitalized versus non-hospitalized or laboratory-confirmed versus possible cases. Risk factors identified in a subset of cases included exposure to an individual with ILI prior to illness onset, overcrowding and inadequate access to household water., Conclusions: Early arrival and rapid transmission of pH1N1 rendered usual non-pharmacological control measures largely ineffective. Recommendations for prevention of future outbreaks include an effective communications strategy and daily surveillance for disease detection and monitoring. Key determinants of health should be addressed in remote First Nations communities to prevent disease and protect the health of these populations.