Resistance of Gram-positive bacteria to nisin is not determined by Lipid II levels

Lipid II is essential for nisin-mediated pore formation at nano-molar concentrations. We tested whether nisin resistance could result from different Lipid II levels, by comparing the maximal Lipid II pool in Micrococcus flavus (sensitive) and Listeria monocytogenes (relatively insensitive) and their nisin-resistant variants, with a newly developed method. No correlation was observed between the maximal Lipid II pool and nisin sensitivity, as was further corroborated by using spheroplasts of nisin-resistant and wild-type strains of M. flavus, which were equally sensitive to nisin. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved

Comparison of quenching and extraction methodologies for metabolome analysis of Lactobacillus plantarum

<p>Abstract</p> <p>Background</p> <p>A reliable quenching and metabolite extraction method has been developed for <it>Lactobacillus plantarum</it>. The energy charge value was used as a critical indicator for fixation of metabolism.</p> <p>Results</p> <p>Four different aqueous quenching solutions, all containing 60% of methanol, were compared for their efficiency. Only the solutions containing either 70 mM HEPES or 0.85% (w/v) ammonium carbonate (pH 5.5) caused less than 10% cell leakage and the energy charge of the quenched cells was high, indicating rapid inactivation of the metabolism.</p> <p>The efficiency of extraction of intracellular metabolites from cell cultures depends on the extraction methods, and is expected to vary between micro-organisms. For <it>L. plantarum</it>, we have compared five different extraction methodologies based on (i) cold methanol, (ii) perchloric acid, (iii) boiling ethanol, (iv) chloroform/methanol (1:1) and (v) chloroform/water (1:1). Quantification of representative intracellular metabolites showed that the best extraction efficiencies were achieved with cold methanol, boiling ethanol and perchloric acid.</p> <p>Conclusion</p> <p>The ammonium carbonate solution was selected as the most suitable quenching buffer for metabolomics studies in <it>L. plantarum </it>because (i) leakage is minimal, (ii) the energy charge indicates good fixation of metabolism, and (iii) all components are easily removed during freeze-drying. A modified procedure based on cold methanol extraction combined good extractability with mild extraction conditions and high enzymatic inactivation. These features make the combination of these quenching and extraction protocols very suitable for metabolomics studies with <it>L. plantarum</it>.</p

Computing a largest empty anchored cylinder, and related problems

Let $S$ be a set of $n$ points in $R^d$, and let each point $p$ of $S$ have a positive weight $w(p)$. We consider the problem of computing a ray $R$ emanating from the origin (resp.\ a line $l$ through the origin) such that $\min_{p\in S} w(p) \cdot d(p,R)$ (resp. $\min_{p\in S} w(p) \cdot d(p,l)$) is maximal. If all weights are one, this corresponds to computing a silo emanating from the origin (resp.\ a cylinder whose axis contains the origin) that does not contain any point of $S$ and whose radius is maximal. For $d=2$, we show how to solve these problems in $O(n \log n)$ time, which is optimal in the algebraic computation tree model. For $d=3$, we give algorithms that are based on the parametric search technique and run in $O(n \log^5 n)$ time. The previous best known algorithms for these three-dimensional problems had almost quadratic running time. In the final part of the paper, we consider some related problem

Valid measurement of DSM-5 persistent complex bereavement disorder and DSM-5-TR and ICD-11 prolonged grief disorder:The Traumatic Grief Inventory-Self Report Plus (TGI-SR+)

Introduction: When grief reactions after bereavement are so intense that they impair daily functioning, a diagnosis of disturbed grief may apply. Slightly differing criteria-sets for disturbed grief are included in the ICD-11, the DSM-5, and its forthcoming text revision, DSM-5-TR. We examined psychometric properties of a new self-report measure, the 22-item Traumatic Grief Inventory-Self Report Plus (TGI-SR+), that assesses these criteria sets for Persistent Complex Bereavement Disorder (PCBD) as per DSM-5, and Prolonged Grief Disorder (PGD) as defined in ICD-11 and DSM-5-TR. Material and methods: We examined the: i) factor structure, ii) internal consistency, iii) temporal stability, iv) convergent validity, v) known-groups validity, vi) probable caseness, and vii) optimal clinical cut-off scores in two Dutch bereaved samples. Sample 1 consisted of 278 adults, bereaved by various causes. Sample 2 included 270 adults who lost loved ones in a traffic accident. Results: We found support for a 3-factor PCBD model, 1-factor DSM-5-TR model, and 1-factor ICD-11 PGD model. The DSM-5 PCBD, DSM-5-TR PGD, and ICD-11 PGD items demonstrated good internal consistency and temporal stability. Associations between disturbed grief symptoms and posttraumatic stress and depression levels supported convergent validity. Associations between demographic/loss-related variables and disturbed grief symptoms supported known-groups validity. Optimal clinical cut-offs for the TGI-SR+ total score were ≥ 75, ≥71, and ≥ 75 for probable caseness of DSM-5 PCBD, DSM-5-TR PGD, and ICD-11 PGD, respectively. Discussion: While replication of our findings in diverse bereaved samples is needed, we conclude that the TGI-SR+ is a reliable and valid measure to assess symptoms of DSM-5 PCBD, DSM-5-TR PGD, and ICD-11 PGD

Development of Stresses in Cohesionless Poured Sand

The pressure distribution beneath a conical sandpile, created by pouring sand from a point source onto a rough rigid support, shows a pronounced minimum below the apex (`the dip'). Recent work of the authors has attempted to explain this phenomenon by invoking local rules for stress propagation that depend on the local geometry, and hence on the construction history, of the medium. We discuss the fundamental difference between such approaches, which lead to hyperbolic differential equations, and elastoplastic models, for which the equations are elliptic within any elastic zones present .... This displacement field appears to be either ill-defined, or defined relative to a reference state whose physical existence is in doubt. Insofar as their predictions depend on physical factors unknown and outside experimental control, such elastoplastic models predict that the observations should be intrinsically irreproducible .... Our hyperbolic models are based instead on a physical picture of the material, in which (a) the load is supported by a skeletal network of force chains ("stress paths") whose geometry depends on construction history; (b) this network is `fragile' or marginally stable, in a sense that we define. .... We point out that our hyperbolic models can nonetheless be reconciled with elastoplastic ideas by taking the limit of an extremely anisotropic yield condition.Comment: 25 pages, latex RS.tex with rspublic.sty, 7 figures in Rsfig.ps. Philosophical Transactions A, Royal Society, submitted 02/9

Gene expression profiles of human endometrial cancer samples using a cDNA-expression array technique: assessment of an analysis method

The recently developed cDNA expression array technique can be used to generate gene-expression fingerprints of tumour specimens. To gain insight into molecular mechanisms involved in the development and progression of cancer, this cDNA expression array technique could be a useful tool, however, no established methods for interpreting the results are yet available. We used the Atlas cancer cDNA expression array (Clontech, USA) for analysing total RNA isolated from four human endometrial carcinoma samples (two cell-lines and two tissue samples), one benign endometrial tissue sample and a human breast cancer cell-line, in order to develop a method for analysing the array data. The obtained gene-expression profiles were highly reproducible. XY-scatterplots and regression analysis of the logarithmic transformed data provided a practical method to analyse the data without the need of preceding normalization. Three genes (Decorin, TIMP3 and Cyclin D1) were identified to be differentially expressed between the benign endometrial tissue sample and the endometrial carcinoma samples (tissue and cell-lines). These three genes may potentially be involved in cancer progression. A higher degree of similarity in gene-expression profile was found between the endometrial samples (tissue and cell-lines) than between the endometrial samples and the breast cancer cell-line, which is indicative for an endometrial tissue-specific gene-expression profile. © 2000 Cancer Research Campaig

Assessment and treatment of distorted schemas in sexual offenders

The aim of this review is to examine the literature related to the assessment and treatment of sex offenders’ distorted schemas. Where appropriate, the review draws upon current insights from the field of social cognition to aid in the critical evaluation of the findings. First, the review considers the various different methodologies for assessing distorted schemas, discussing their strengths and limitations. Second, the review examines the work related to the treatment of sex offenders’ schemas. Suggestions for future research, and the implications for clinical practice, are highlighted in the article

From casein to cheese: The role of Lactococcus lactis

Lactococci have limited biosynthetic abilities. In addition to the energy sources many solutes have to be taken up. Essential and non-essential amino acids are accumulated via specific transport systems. The concentration of these solutes in milk is insufficient to support optimal growth. Cells secrete proteinases and peptidases to hydrolyse casein. During milk fermentation, the growth requirements of lactococci are satisfied by the peptides and amino acids released upon casein degradation. When present in limiting amounts. amino acids are acquired by uptake and subsequent hydrolysis of peptides. The effects of an imbalance of the supply of amino acids on the growth and metsbolic activities of these bacteria are discussed

Stress Propagation through Frictionless Granular Material

We examine the network of forces to be expected in a static assembly of hard, frictionless spherical beads of random sizes, such as a colloidal glass. Such an assembly is minimally connected: the ratio of constraint equations to contact forces approaches unity for a large assembly. However, the bead positions in a finite subregion of the assembly are underdetermined. Thus to maintain equilibrium, half of the exterior contact forces are determined by the other half. We argue that the transmission of force may be regarded as unidirectional, in contrast to the transmission of force in an elastic material. Specializing to sequentially deposited beads, we show that forces on a given buried bead can be uniquely specified in terms of forces involving more recently added beads. We derive equations for the transmission of stress averaged over scales much larger than a single bead. This derivation requires the Ansatz that statistical fluctuations of the forces are independent of fluctuations of the contact geometry. Under this Ansatz, the $d(d+1)/2$-component stress field can be expressed in terms of a d-component vector field. The procedure may be generalized to non-sequential packings. In two dimensions, the stress propagates according to a wave equation, as postulated in recent work elsewhere. We demonstrate similar wave-like propagation in higher dimensions, assuming that the packing geometry has uniaxial symmetry. In macroscopic granular materials we argue that our approach may be useful even though grains have friction and are not packed sequentially.=17Comment: 15 pages, 4 figures, revised vertion for Phys. Rev.