Lipoprotein-derived lysophosphatidic acid promotes atherosclerosis by releasing CXCL1 from the endothelium

Oxidatively modified low-density lipoprotein (oxLDL) plays a key role in the initiation of atherosclerosis by increasing monocyte adhesion. The mechanism that is responsible for the oxLDL-induced atherogenic monocyte recruitment in vivo, however, still remains unknown. Oxidation of LDL generates lysophosphatidylcholine, which is the main substrate for the lysophosphatidic acid (LPA) generating enzyme autotaxin. We show that oxLDL requires endothelial LPA receptors and autotaxin to elicit CXCL1-dependent arterial monocyte adhesion. Unsaturated LPA releases endothelial CXCL1, which is subsequently immobilized on the cell surface and mediates LPA-induced monocyte adhesion. Local and systemic application of LPA accelerates the progression of atherosclerosis in mice. Blocking the LPA receptors LPA(1) and LPA(3) reduced hyperlipidemia-induced arterial leukocyte arrest and atherosclerosis in the presence of functional CXCL1. Thus, atherogenic monocyte recruitment mediated by hyperlipidemia and modified LDL crucially depends on LPA, which triggers endothelial deposition of CXCL1, revealing LPA signaling as a target for cardiovascular disease treatments.     

Site‐specific dynamics in remnant populations of Northern Wheatears Oenanthe oenanthe in the Netherlands

Dynamics of populations may be synchronized at large spatial scales, indicating driving forces acting beyond local scales, but may also vary locally as a result of site‐specific conditions. Conservation measures for fragmented and declining populations may need to address such local effects to avoid local extinction before measures at large spatial scales become effective. To assess differences in local population dynamics, we aimed to determine the demographic drivers controlling population trends in three remaining populations of the Northern Wheatear Oenanthe oenanthe in the Netherlands, as a basis for conservation actions. An integrated population model (IPM) was fitted to field data collected in each site in 2007–2011 to estimate fecundity, survival and immigration. Sites were 40–120 km apart, yet first‐year recruits were observed to move between some of the sites, albeit rarely. All three populations were equally sensitive to changes in fecundity and first‐year survival. One population was less sensitive to adult survival but more sensitive to immigration. A life table response experiment suggested that differences in immigration were important determinants of differences in population growth between sites. Given the importance of immigration for local dynamics along with high philopatry, resulting in low exchange between sites, creating a metapopulation structure by improving connectivity and the protection of local populations are important for the conservation of these populations. Site‐specific conservation actions will therefore be efficient and, for the short term, we propose different site‐specific conservation actions.     

Essential oil constituents derived from different organs of a relictual conifer Wollemia nobilis

The chemical composition of the essential oil of leaves (0.9%, w/v) and twigs (0.33%, w/v) of Wollemia nobilis (Araucariaceae) – a remnant species thought to have been extinct for 65 million years – was investigated by GC/MS. The main constituents of both leaf- and twig-derived oil samples were 16-kaurene (61.8% and 38.2%, respectively) and germacrene D (9.9% and 22%). The principal difference was a considerably more pronounced sesquiterpene presence in the twig-oil, amounting to 33.5%, than in its folial counterpart (23.4%). On the contrary, while remaining the dominant group in both oil samples under investigation, diterpenoids were relatively more abundant in leaf-derived oil constituting 65.3%, versus 41.7% detected in twigs. To our knowledge, this is the first report dealing with the essential oil composition of Wollemi pine twigs, as opposed to the leaf-derived volatiles.     

Glutamate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima: molecular characterization and phylogenetic implications

The hyperthermophilic bacterium Thermotoga maritima, which grows at up to 90°C, contains an L-glutamate dehydrogenase (GDH). Activity of this enzyme could be detected in T. maritima crude extracts, and appeared to be associated with a 47-kDa protein which cross-reacted with antibodies against purified GDH from the hyperthermophilic archaeon Pyrococcus woesei. The single-copy T. maritima gdh gene was cloned by complementation in a glutamate auxotrophic Escherichia coli strain. The nucleotide sequence of the gdh gene predicts a 416-residue protein with a calculated molecular weight of 45852. The gdh gene was inserted in an expression vector and expressed in E. coli as an active enzyme. The T. maritima GDH was purified to homogeneity. The NH₂-terminal sequence of the purified enzyme was PEKSLYEMAVEQ, which is identical to positions 2–13 of the peptide sequence derived from the gdh gene. The purified native enzyme has a size of 265 kDa and a subunit size of 47 kDa, indicating that GDH is a homohexamer. Maximum activity of the enzyme was measured at 75°C and the pH optima are 8.3 and 8.8 for the anabolic and catabolic reaction, respectively. The enzyme was found to be very stable at 80°C, but appeared to lose activity quickly at higher temperatures. The T. maritima GDH shows the highest rate of activity with NADH (V _max of 172U/mg protein), but also utilizes NADPH (V _max of 12U/mg protein). Sequence comparisons showed that the T. maritima GDH is a member of the family II of hexameric GDHs which includes all the GDHs isolated so far from hyperthermophiles. Remarkably, phylogenetic analysis positions all these hyperthermophilic GDHs in the middle of the GDH family II tree, with the bacterial T. maritima GDH located between that of halophilic and thermophilic euryarchaeota. Received: 15 July 1996 / Accepted: 12 October 1996     

Endothelial monocyte-activating polypeptide-II and its functions in (patho)physiological processes

Endothelial monocyte-activating polypeptide-II (EMAP-II) is a pro-inflammatory cytokine with anti-angiogenic properties. Its precursor, proEMAP, is identical to the p43 auxiliary component of the tRNA multisynthetase complex and therefore involved in protein translation. Although most of the activities have been ascribed to the active form EMAP-II, also p43 has reported cytokine properties. ProEMAP/p43 and EMAP-II act on many levels and on many cell types including endothelial cells, immune cells and fibroblasts. In this review we summarize all available data on isolation, expression and functions of EMAP-II both in physiological processes as well as in pathological settings, like cancer. We also discuss the different reported mechanisms for processing of proEMAP/p43 into EMAP-II. Finally, we speculate on the possible applications of this cytokine for (cancer) therapy.     

Assessment of heat resistance of bacterial spores from food product isolates by fluorescence monitoring of dipicolinic acid release

This study is aimed at the development and application of a convenient and rapid optical assay to monitor the wet-heat resistance of bacterial endospores occurring in food samples. We tested the feasibility of measuring the release of the abundant spore component dipicolinic acid (DPA) as a probe for heat inactivation. Spores were isolated from the laboratory type strain Bacillus subtilis 168 and from two food product isolates, Bacillus subtilis A163 and Bacillus sporothermodurans IC4. Spores from the lab strain appeared much less heat resistant than those from the two food product isolates. The decimal reduction times (D values) for spores from strains 168, A163, and IC4 recovered on Trypticase soy agar were 1.4, 0.7, and 0.3 min at 105 degrees C, 120 degrees C, and 131 degrees C, respectively. The estimated Z values were 6.3 degrees C, 6.1 degrees C, and 9.7 degrees C, respectively. The extent of DPA release from the three spore crops was monitored as a function of incubation time and temperature. DPA concentrations were determined by measuring the emission at 545 nm of the fluorescent terbium-DPA complex in a microtiter plate fluorometer. We defined spore heat resistance as the critical DPA release temperature (Tc), the temperature at which half the DPA content has been released within a fixed incubation time. We found Tc values for spores from Bacillus strains 168, A163, and IC4 of 108 degrees C, 121 degrees C, and 131 degrees C, respectively. On the basis of these observations, we developed a quantitative model that describes the time and temperature dependence of the experimentally determined extent of DPA release and spore inactivation. The model predicts a DPA release rate profile for each inactivated spore. In addition, it uncovers remarkable differences in the values for the temperature dependence parameters for the rate of spore inactivation, DPA release duration, and DPA release delay.     

Modification of a Phosphorothioate Oligonucleotide with Cholesterol Induces Association of the Oligonucleotide to Serum Lipoproteins and Affects Its Biological Fate

Abstract

A cholesterol-conjugated phosphorothioate ICAM-1 antisense oligo-nucleotide was evaluated for its binding to lipoproteins and its biodistribution. Our study indicates that the conjugate behaves differently from the parent compound.     

Quality control in LC-MS/MS

In the last 15 years, MS-based protein characterization has expanded at a rapid rate. This success is built upon constantly improving instrumentation and a variety of ingenious methods applied to numerous biological questions. However, the reproducibility of mass spectrometric results is considered by many as insufficient. In part, inadequate quality control might be responsible for the lack of reproducibility. Quality control is rarely discussed in scientific publications. Here, we briefly present measures undertaken in our laboratory to foster a general discussion of the subject.     

Evaluating Contextual Processing in Diffusion MRI: Application to Optic Radiation Reconstruction for Epilepsy Surgery

Diffusion MRI and tractography allow for investigation of the architectural configuration of white matter in vivo, offering new avenues for applications like presurgical planning. Despite the promising outlook, there are many pitfalls that complicate its use for (clinical) application. Amongst these are inaccuracies in the geometry of the diffusion profiles on which tractography is based, and poor alignment with neighboring profiles. Recently developed contextual processing techniques, including enhancement and well-posed geometric sharpening, have shown to result in sharper and better aligned diffusion profiles. However, the research that has been conducted up to now is mainly of theoretical nature, and so far these techniques have only been evaluated by visual inspection of the diffusion profiles. In this work, the method is evaluated in a clinically relevant application: the reconstruction of the optic radiation for epilepsy surgery. For this evaluation we have developed a framework in which we incorporate a novel scoring procedure for individual pathways. We demonstrate that, using enhancement and sharpening, the extraction of an anatomically plausible reconstruction of the optic radiation from a large amount of probabilistic pathways is greatly improved in three healthy controls, where currently used methods fail to do so. Furthermore, challenging reconstructions of the optic radiation in three epilepsy surgery candidates with extensive brain lesions demonstrate that it is beneficial to integrate these methods in surgical planning.     

Quantitative resistance differences between and within natural populations of Solanum chilense against the oomycete pathogen Phytophthora infestans

The wild tomato species Solanum chilense is divided into geographically and genetically distinct populations that show signs of defense gene selection and differential phenotypes when challenged with several phytopathogens, including the oomycete causal agent of late blight Phytophthora infestans. To better understand the phenotypic diversity of this disease resistance in S. chilense and to assess the effect of plant genotype versus pathogen isolate, respectively, we evaluated infection frequency in a systematic approach and with large sample sizes. We studied 85 genetically distinct individuals representing nine geographically separated populations of S. chilense. This showed that differences in quantitative resistance can be observed between but also within populations at the level of individual plants. Our data also did not reveal complete immunity in any of the genotypes. We further evaluated the resistance of a subset of the plants against P. infestans isolates with diverse virulence properties. This confirmed that the relative differences in resistance phenotypes between individuals were mainly determined by the plant genotype under consideration with modest effects of pathogen isolate used in the study. Thus, our report suggests that the observed quantitative resistance against P. infestans in natural populations of a wild tomato species S. chilense is the result of basal defense responses that depend on the host genotype and are pathogen isolate‐unspecific.