Novel locus required for expression of high-level macrolide-lincosamide-streptogramin B resistance in Staphylococcus aureus

The yycF1(Ts) mutation in Staphylococcus aureus conferred hypersensitivity to macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics on strains either containing or lacking ermB. The overexpression of the S. aureus Ssa protein restored the yycF1 mutant to wild-type levels of susceptibility. Inactivation of ssa in an unmutagenized strain dramatically reduced ermB-based resistance. Conditional loss of function or expression of ssa in the yycF1 mutant is proposed to result in the observed hypersensitivity to MLS(B) antibiotics.     

Parasitic infection and the polarized Th2 immune response can alter a vaccine-induced immune response

The AIDS epidemic in the Developing World represents a major global crisis. It is imperative that we develop an effective vaccine. Vaccines are economically the most efficient means of controlling viral infections. However, the development of a vaccine against HIV-1 has been a formidable task, and in developing countries chronic parasitic infection adds another level of complexity to AIDS vaccine development. Helminthic and protozoan infections, common in developing countries, can result in a constant state of immune activation that is characterized by a dominant Th2 type of cytokine profile, high IgE levels, and eosinophilia. Such an immune profile may have an adverse impact on the efficacy of vaccines, in particular, an HIV-1 vaccine. Indeed, the CD8 cellular immune response and the corresponding Th1 type cytokines that enhance the CD8 cellular immune response are important for clearing many viral infections. It is believed that an antigen specific CD8 cellular immune response will be an important component of an HIV-1 vaccine.     

Quantitative characterization of the interaction between purified human estrogen receptor alpha and DNA using fluorescence anisotropy

In an effort to better define the molecular mechanisms of the functional specificity of human estrogen receptor α, we have carried out equilibrium binding assays to study the interaction of the receptor with a palindromic estrogen response element derived from the vitellogenin ERE. These assays are based on the observation of the fluorescence anisotropy of a fluorescein moiety covalently bound to the target oligonucleotide. The low anisotropy value due to the fast tumbling of the free oligonucleotide in solution increases substantially upon binding the receptor to the labeled ERE. The quality of our data are sufficient to ascertain that the binding is clearly cooperative in nature, ruling out a simple monomer interaction and implicating a dimerization energetically coupled to DNA binding in the nanomolar range. The salt concentration dependence of the affinity reveals formation of high stoichiometry, low specificity complexes at low salt concentration. Increasing the KCl concentration above 200 mM leads to specific binding of ER dimer. We interpret the lack of temperature dependence of the apparent affinity as indicative of an entropy driven interaction. Finally, binding assays using fluorescent target EREs bearing mutations of each of the base pairs in the palindromic ERE half-site indicate that the energy of interaction between ER and its target is relatively evenly distributed throughout the site.     

A colorimetric assay for rapid screening of antimicrobial peptides

The increased resistance of various bacteria toward available antibiotic drugs has initiated intensive research efforts into identifying new sources of antimicrobial substances. Short antibiotic peptides (10-30 residues) are prevalent in nature as part of the intrinsic defense mechanisms of most organisms and have been proposed as a blueprint for the design of novel antimicrobial agents. Antimicrobial peptides are generally believed to kill bacteria through membrane permeabilization and extensive pore-formation. Assays providing rapid and easy evaluation of interactions between antimicrobial membrane peptides and lipid bilayers could significantly improve screening for substances with effective antibacterial properties, as well as contribute to the elucidation of structural and functional properties of antimicrobial peptides. Here we describe a colorimetric sensor in which particles composed of phospholipids and polymerized polydiacetylene (PDA) lipids were shown to exhibit striking color changes upon interactions with antimicrobial membrane peptides. The color changes in the system occur because of the structural perturbation of the lipids following their interactions with antimicrobial peptides. The assay was also sensitive to the antibacterial properties of structurally and functionally related peptide analogs.     

Passive nitrate transport by root plasma membrane vesicles exhibits an acidic optimal pH like the H(+)-ATPase

Previous work has indicated that sugar sensing may be important in the regulation of fructan biosynthesis in grasses. We used primary leaves of barley (Hordeum vulgare cv Baraka) to study the mechanisms involved. Excised leaf blades were supplied in the dark with various carbohydrates. Fructan pool sizes and two key enzymes of fructan biosynthesis, sucrose (Suc):Suc-1-fructosyltransferase (1-SST; EC 2. 4.1.99) and Suc:fructan-6-fructosyltransferase (6-SFT; EC 2.4.1.10) were analyzed. Upon supply of Suc, fructan pool sizes increased markedly. Within 24 h, 1-SST activity was stimulated by a factor of three and 6-SFT-activity by a factor of more than 20, compared with control leaves supplemented with mannitol (Mit). At the same time, the level of mRNA encoding 6-SFT increased conspicuously. These effects were increased in the presence of the invertase inhibitor 2, 5-dideoxy-2,5-imino-D-mannitol. Compared with equimolar solutions of Suc, glucose (Glu) and fructose stimulated 6-SFT activity to a lesser extent. Remarkably, trehalose (Tre; Glc-alpha-1 and 1-alpha-Glc) had stimulatory effects on 6-SFT activity and, to a somewhat lesser extent, on 6-SFT mRNA, even in the presence of validoxylamine A, a potent trehalase inhibitor. Tre by itself, however, in the presence or absence of validoxylamine A, did not stimulate fructan accumulation. Monosaccharides phosphorylated by hexokinase but not or weakly metabolized, such as mannose (Man) or 2-deoxy-Glc, had no stimulatory effects on fructan synthesis. When fructose or Man were supplied together with Tre, fructan and starch biosynthesis were strongly stimulated. Concomitantly, phospho-Man isomerase (EC 5.3.1.8) activity was detected. These results indicate that the regulation of fructan synthesis in barley leaves occurs independently of hexokinase and is probably based on the sensing of Suc, and also that the structurally related disaccharide Tre can replace Suc as a regulatory compound.     

Palladium (II)-catalyzed alternating copolymerization of alkenes with sulfur dioxide

Cationic palladium(II) complexes of the type [L₂Pd(CH₃)(CH₃CN)]BF₄ (L₂ = 1,3-bis(diphenylphosphino)propane (Dppp) or 1,2-bis(2,5-dimethylphospholano)benzene (Me-Duphos)) were found to catalyze the alternating copolymerization of ethene, propene and cyclopentene with sulfur dioxide, as well as the terpolymerization of ethene, propene and sulfur dioxide. The resultant materials are high melting solids with an alternating alkene-SO₂ structure and an exclusive head-to-tail enchainment for propene.     

An Augmented SMS Intervention to Improve Access to Antenatal CD4 Testing and ART Initiation in HIV-Infected Pregnant Women: A Cluster Randomized Trial

BackgroundLess than one-third of HIV-infected pregnant women eligible for combination antiretroviral therapy (ART) globally initiate treatment prior to delivery, with lack of access to timely CD₄ results being a principal barrier. We evaluated the effectiveness of an SMS-based intervention to improve access to timely antenatal ART.MethodsWe conducted a stepped-wedge cluster randomized trial of a low-cost programmatic intervention in 20 antenatal clinics in Gaborone, Botswana. From July 2011-April 2012, 2 clinics were randomly selected every 4 weeks to receive an ongoing clinic-based educational intervention to improve CD₄ collection and to receive CD₄ results via an automated SMS platform with active patient tracing. CD₄ testing before 26 weeks gestation and ART initiation before 30 weeks gestation were assessed.ResultsThree-hundred-sixty-six ART-naïve women were included, 189 registering for antenatal care under Intervention and 177 under Usual Care periods. Of CD₄-eligible women, 100 (59.2%) women under Intervention and 79 (50.6%) women under Usual Care completed CD₄ phlebotomy before 26 weeks gestation, adjusted odds ratio (aOR, adjusted for time that a clinic initiated Intervention) 0.87 (95% confidence interval [CI]0.47–1.63, P = 0.67). The SMS-based platform reduced time to clinic receipt of CD₄ test result from median of 16 to 6 days (P<0.001), was appreciated by clinic staff, and was associated with reduced operational cost. However, rates of ART initiation remained low, with 56 (36.4%) women registering under Intervention versus 37 (24.2%) women under Usual Care initiating ART prior to 30 weeks gestation, aOR 1.06 (95%CI 0.53–2.13, P = 0.87).ConclusionsThe augmented SMS-based intervention delivered CD₄ results more rapidly and efficiently, and this type of SMS-based results delivery platform may be useful for a variety of tests and settings. However, the intervention did not appear to improve access to timely antenatal CD₄ testing or ART initiation, as obstacles other than CD₄ impeded ART initiation during pregnancy.     

Combining the Sterile Insect Technique with Wolbachia-Based Approaches: II- A Safer Approach to Aedes albopictus Population Suppression Programmes,Designed to Minimize the Consequences of Inadvertent Female Release

Due to the absence of a perfect method for mosquito sex separation, the combination of the sterile insect technique and the incompatible insect technique is now being considered as a potentially effective method to control Aedes albopictus. In this present study first we examine the minimum pupal irradiation dose required to induce complete sterility in Wolbachia triple-infected (HC), double-infected (GUA) and uninfected (GT) female Ae. albopictus. The HC line is a candidate for Ae. albopictus population suppression programmes, but due to the risk of population replacement which characterizes this triple infected line, the individuals to be released need to be additionally irradiated. After determining the minimum irradiation dose required for complete female sterility, we test whether sterilization is sufficient to prevent invasion of the triple infection from the HC females into double-infected (GUA) populations. Our results indicate that irradiated Ae. albopictus HC, GUA and GT strain females have decreased fecundity and egg hatch rate when irradiated, inversely proportional to the dose, and the complete sterilization of females can be acquired by pupal irradiation with doses above 28 Gy. PCR-based analysis of F₁ and F₂ progeny indicate that the irradiated HC females, cannot spread the new Wolbachia wPip strain into a small cage GUA population, released at a 1:5 ratio. Considering the above results, we conclude that irradiation can be used to reduce the risk of population replacement caused by an unintentional release of Wolbachia triple-infected Ae. albopictus HC strain females during male release for population suppression.