Dielectric relaxation measurements of 12 kbp plasmid DNA

The dielectric properties of 12 kbp plasmid DNA have been measured as a function of temperature in the range 5 degrees C to 40 degrees C. Time domain reflectometry was used to obtain dielectric data over the frequency range from 200 kHz to 3 GHz. Values of the frequency dependent polarisability per DNA macromolecule have been determined from the measurements. Possible mechanisms that could account for the dielectric dispersion are also discussed, in particular the counterion fluctuation model of Manning-Mandel-Oosawa.     

Impact of HIV-1 infection on VH3 gene repertoire of naive human B cells

B cells of the largest Ig variable heavy chain gene (VH) family, VH3, are reportedly decreased in patients with late stage HIV-1 disease. This deficit may contribute to their impaired responses to infections and vaccines. We confirmed that the VH3 family was underrepresented in serum IgM proteins, with a 45% decrease in patients with advanced HIV-1 disease. However, the proportion of VH3 within VH(1-6) IgM mRNA from peripheral B cells did not differ from that of control subjects (mean +/- SD, 57.1 +/- 9.7 vs 61.1 +/- 8. 7%). Similarly, within VH(1-6) IgD mRNA, which even more closely represents the unstimulated naive repertoire, the relative expression of VH3 mRNA was comparable in the two groups. Moreover, the frequency of individual genes within the VH3 family for IgD, particularly genes which encode putative HIV-1 gp120 binding sites, also was normal in HIV-1-infected patients. However, VH3 family expression for IgG mRNA was significantly decreased (17%) and VH4 IgG was increased (33%) relative to other VH families in advanced HIV-1-infected patients. Thus, the changes in VH family expression were more readily apparent in previously activated IgG "memory" B cell populations and, likely, in cells actively producing IgM rather than in resting naive cells. The presence of a relatively normal naive VH3 IgM and IgD mRNA repertoire in resting cells supports the prospect that with proper stimulation, particularly in conjunction with effective antiviral therapy, vigorous humoral immune responses to infections and vaccines may be elicited in this high-risk population.     

Adhesion of Drosophila imaginal disc cells in vitro

Summary We have used our imaginal disc cell lines to carry out in vitro studies on the cell-cell and cell-substrate adhesion of Drosophila leg and wing disc cells. Single cells were allowed to reaggregate in roller culture, and this process was found to be partially dependent on the presence of magnesium and calcium ions in the suspension medium. Varying rates of reaggregation were observed in cells from different stages of a passage, correlating with the pattern of morphogenesis which occurs during the passage. We have demonstrated that cloned cell lines can be produced showing certain selected characteristics, such as reduced cell adhesiveness.     

Cell-cell and cell-substrate adhesion in cultured Drosophila imaginal disc cells

Summary Drosophila imaginal disc cell lines were used to investigate various aspects of cellular adhesion in vitro. The distribution of PS integrins and their involvement in cell-cell and cell-substrate adhesion were assessed with the monoclonal antibody aBG-1 against the βPS subunit, and both forms of adhesion were found to be impeded by the presence of the antibody. Adhesion to a number of extracellular matrix components was investigated, and the cells were found to adhere to human fibronectin. This adhesion was inhibited by aBG-1. The adhesion molecule fasciclin III was also found in these cells. Given that the cells are competent to perform cell-cell and cell-substrate adhesion, it was thought that apical basal polarity might be restored when other suitable conditions were provided, i.e., an artificial basement layer with feeder cells to provide nutrients basally to the cells, and some features of apical-basal morphology were seen in cells cultured under these conditions.     

Desmin knockout muscles generate lower stress and are less vulnerable to injury compared with wild-type muscles

The functional roleof the skeletal muscle intermediate filament system was investigated bymeasuring the magnitude of muscle force loss after cyclic eccentriccontraction (EC) in normal and desmin null mouse extensor digitorumlongus muscles. Isometric stress generated was significantly greater inwild-type (313 ± 8 kPa) compared with knockout muscles (276 ± 13 kPa) before EC (P < 0.05), but 1 h after 10 ECs, both muscle types generated identical levels of stress (~250kPa), suggesting less injury to the knockout. Differences in injurysusceptibility were not explained by the different absolute stresslevels imposed on wild-type versus knockout muscles (determined bytesting older muscles) or by differences in fiber length or mechanicalenergy absorbed. Morphometric analysis of longitudinal electronmicrographs indicated that Z disks from knockout muscles were morestaggered (0.36 ± 0.03 µm) compared with wild-type muscles(0.22 ± 0.03 µm), which may indicate that the knockoutcytoskeleton is more compliant. These data demonstrate that lack of theintermediate filament system decreases isometric stress production andthat the desmin knockout muscle is less vulnerable to mechanical injury.

     

Evaluating the Use of Blood Cultures in the Management of Children Hospitalized for Community-Acquired Pneumonia

BackgroundBlood cultures are often recommended for the evaluation of community-acquired pneumonia (CAP). However, institutions vary in their use of blood cultures, and blood cultures have unclear utility in CAP management in hospitalized children.ObjectiveTo identify clinical factors associated with obtaining blood cultures in children hospitalized with CAP, and to estimate the association between blood culture obtainment and hospital length of stay (LOS).MethodsWe performed a multicenter retrospective cohort study of children admitted with a diagnosis of CAP to any of four pediatric hospitals in the United States from January 1, 2011-December 31, 2012. Demographics, medical history, diagnostic testing, and clinical outcomes were abstracted via manual chart review. Multivariable logistic regression evaluated patient and clinical factors for associations with obtaining blood cultures. Propensity score-matched Kaplan-Meier analysis compared patients with and without blood cultures for hospital LOS.ResultsSix hundred fourteen charts met inclusion criteria; 390 children had blood cultures obtained. Of children with blood cultures, six (1.5%) were positive for a pathogen and nine (2.3%) grew a contaminant. Factors associated with blood culture obtainment included presenting with symptoms of systemic inflammatory response syndrome (OR 1.78, 95% CI 1.10–2.89), receiving intravenous hydration (OR 3.94, 95% CI 3.22–4.83), receiving antibiotics before admission (OR 1.49, 95% CI 1.17–1.89), hospital admission from the ED (OR 1.65, 95% CI 1.05–2.60), and having health insurance (OR 0.42, 95% CI 0.30–0.60). In propensity score-matched analysis, patients with blood cultures had median 0.8 days longer LOS (2.0 vs 1.2 days, P < .0001) without increased odds of readmission (OR 0.94, 95% CI 0.45–1.97) or death (P = .25).ConclusionsObtaining blood cultures in children hospitalized with CAP rarely identifies a causative pathogen and is associated with increased LOS. Our results highlight the need to refine the role of obtaining blood cultures in children hospitalized with CAP.     

Generalised Sandpile Dynamics on Artificial and Real-World Directed Networks

The main finding of this paper is a novel avalanche-size exponent τ ≈ 1.87 when the generalised sandpile dynamics evolves on the real-world Japanese inter-firm network. The topology of this network is non-layered and directed, displaying the typical bow tie structure found in real-world directed networks, with cycles and triangles. We show that one can move from a strictly layered regular lattice to a more fluid structure of the inter-firm network in a few simple steps. Relaxing the regular lattice structure by introducing an interlayer distribution for the interactions, forces the scaling exponent of the avalanche-size probability density function τ out of the two-dimensional directed sandpile universality class τ = 4/3, into the mean field universality class τ = 3/2. Numerical investigation shows that these two classes are the only that exist on the directed sandpile, regardless of the underlying topology, as long as it is strictly layered. Randomly adding a small proportion of links connecting non adjacent layers in an otherwise layered network takes the system out of the mean field regime to produce non-trivial avalanche-size probability density function. Although these do not display proper scaling, they closely reproduce the behaviour observed on the Japanese inter-firm network.     

Hunting and predation in a fiddler crab

Fiddler crabs are known primarily to be deposit feeders. They eat detritus, bacteria, and other small particles of organic material found in the sandy or muddy substrate on which they live. They have highly specialized mouthparts used to separate edible matter from nondigestable material. Here we provide evidence of cannibalism and predation in a fiddler crab, Uca annulipes. We additionally provide the first evidence of a fiddler crab hunting shrimp and insects. This study is an exemplary reminder that, even though an animal may have evolved highly specialized feeding traits, this need not preclude it from opportunistically acting as a generalist feeder.     

Structure–activity relationships amongst 4-position quinoline methanol antimalarials that inhibit the growth of drug sensitive and resistant strains of Plasmodium falciparum

Utilizing mefloquine as a scaffold, a next generation quinoline methanol (NGQM) library was constructed to identify early lead compounds that possess biological properties consistent with the target product profile for malaria chemoprophylaxis while reducing permeability across the blood–brain barrier. The library of 200 analogs resulted in compounds that inhibit the growth of drug sensitive and resistant strains of Plasmodium falciparum. Herein we report selected chemotypes and the emerging structure–activity relationship for this library of quinoline methanols.