Screening of natural products extracts for the presence of phosphodiesterase inhibitors using liquid chromatography coupled online to parallel biochemical detection and chemical characterization

The ability to rapidly identify active compounds in a complex mixture (e.g., natural products extract) is still one of the major problems in natural products screening programs. An elegant way to overcome this problem is to separate the complex mixture by gradient liquid chromatography followed by online biochemical detection parallel with chemical characterization, referred to as high-resolution screening (HRS). To find and identify phosphodiesterase (PDE) inhibitors in natural products extracts using the HRS technology, the authors developed a continuous-flow PDE enzymatic assay. The suitability of the continuous-flow PDE enzymatic assay for natural products screening was demonstrated. After optimization of the continuous-flow PDE assay, the limit of detection for 3-isobutyl-1-methyl-xanthine (IBMX) was 1 muM, with a dynamic range from 1 to 100 muM IBMX. The applicability of the HRS technology for the detection of PDE inhibitors in natural products extracts was demonstrated by the analysis of a plant extract spiked with 2 naturally occurring PDE inhibitors. The plant extract was analyzed with 2 assay lines in parallel, enabling background fluorescence correction of the sample. The simultaneous quantification of the active compounds using evaporative light-scattering detection allowed the estimation of the IC(50) value of the active compounds directly in the crude extract.     

Presentation of alpha B-crystallin to T cells in active multiple sclerosis lesions: an early event following inflammatory demyelination

In the development of multiple sclerosis (MS), (re)activation of infiltrating T cells by myelin-derived Ags is considered to be a crucial step. Previously, alpha B-crystallin has been shown to be an important myelin Ag to human T cells. Since alpha B-crystallin is an intracellular heat shock protein, the question arises at what stage, if any, during lesional development in MS this Ag becomes available for CD4+ T cells. In 3 of 10 active MS lesions, alpha B-crystallin could be detected inside phagocytic vesicles of perivascular macrophages, colocalizing with myelin basic protein and myelin oligodendrocyte glycoprotein (MOG). Although the detectability of MOG in phagosomes is considered as a marker for very recent demyelination, MOG was detected in more macrophages and in more lesions than alpha B-crystallin. The disappearance of alpha B-crystallin from macrophages even before MOG was confirmed by in vitro studies; within 6 h after myelin-uptake alpha B-crystallin disappears from the phagosomes. Alpha B-crystallin-containing macrophages colocalized with infiltrating T cells and they were characterized by expression of MHC class II, CD40, and CD80. To examine functional presentation of myelin Ags to T cells, purified macrophages were pulsed in vitro with whole myelin membranes. These macrophages activated both myelin-primed and alpha B-crystallin-primed T cells in terms of proliferation and IFN-gamma secretion. In addition, alpha B-crystallin-pulsed macrophages activated myelin-primed T cells to the same extent as myelin-pulsed macrophages, whereas myelin basic protein-pulsed macrophages triggered no response at all. These data indicate that, in active MS lesions, alpha B-crystallin is available for functional presentation to T cells early during inflammatory demyelination.     

Genetic structure of natural Nasonia vitripennis populations: validating assumptions of sex-ratio theory

The parasitic wasp Nasonia vitripennis has been used extensively in sex allocation research. Although laboratory experiments have largely confirmed predictions of local mate competition (LMC) theory, the underlying assumptions of LMC models have hardly been explored in nature. We genotyped over 3500 individuals from two distant locations (in the Netherlands and Germany) at four polymorphic microsatellite loci to validate key assumptions of LMC theory, in terms of both the original models and more recent extensions to them. We estimated the number of females contributing eggs to patches of hosts and the clutch sizes as well as sex ratios produced by individual foundresses. In addition, we evaluated the level of inbreeding and population differentiation. Foundress numbers ranged from 1 to 7 (average 3.0 ± 0.46 SE). Foundresses were randomly distributed across the patches and across hosts within patches, with few parasitizing more than one patch. Of the hosts, 40% were parasitized by more than one foundress. Clutch sizes of individual foundresses (average 9.99 ± 0.51 SE) varied considerably between hosts. The time period during which offspring continued to emerge from a patch or host correlated strongly with foundress number, indicating that sequential rather than simultaneous parasitism is the more common. Genetic differentiation at the regional level between Germany and the Netherlands, as estimated by Slatkin's private allele method (0.11) and Hedrick's corrected G' _LT (0.23), indicates significant substructuring between regions. The level of population inbreeding for the two localities ( F _IL = 0.168) fitted the expectation based on the average foundress number per patch.     

The influence of fixatives and other variations in tissue processing on nuclear morphometric features

The influence on the area and numerical density of nuclei was investigated in 5-mm-thick slices of guinea pig liver for different fixatives and variations in tissue processing: delay in fixation, air drying, degree of acidity of 10% formalin (= 4% formaldehyde), Bouin and mercury-formalin fixatives, acetone and ethanol dehydration and understretching and overstretching of the paraffin-embedded sections. Air drying (either forced or as a result of delayed fixation), the type of fixative and the degree of acidity affected the nuclear area. Regarding the latter, nuclear area was approximately 25% lower for pH less than or equal to 3 as compared with pH greater than 5. In comparison with the standard tissue processing used, the nuclear density was higher after all of the variations studied (air drying, acetone dehydration and fixation). These findings indicate that nuclear area, in contrast to other tissue components, is relatively insensitive to variations in tissue processing. However, it is essential to regularly measure the pH of the fixative: deviations from pH = 7 should be carefully avoided in order to keep nuclear area variations as a result of tissue processing within acceptable limits.     

Temperature stress increases hybrid incompatibilities in the parasitic wasp genus Nasonia

Hybrid incompatibilities, measured as mortality and sterility, are caused by the disruption of gene interactions. They are important post-zygotic isolation barriers to species hybridization, and much effort is put into the discovery of the genes underlying these incompatibilities. In hybridization studies of the haplodiploid parasitic wasp genus Nasonia, genic incompatibilities have been shown to affect mortality and sterility. The genomic regions associated with mortality have been found to depend on the cytotype of the hybrids and thus suggest cytonuclear incompatibilities. As environmental conditions can affect gene expression and gene interaction, we here investigate the effect of developmental temperature on sterility and mortality in Nasonia hybrids. Results show that extreme temperatures strongly affect both hybrid sterility (mainly spermatogenic failure) and mortality. Molecular mapping revealed that extreme temperatures increase transmission ratio distortion of parental alleles at incompatible loci, and thus, cryptic incompatible loci surface under temperature stress that remain undiscovered under standard temperatures. Our results underline the sensitivity of hybrid incompatibilities to environmental factors and the effects of unstable epistasis.     

Recombination and Its Impact on the Genome of the Haplodiploid Parasitoid Wasp Nasonia

Homologous meiotic recombination occurs in most sexually reproducing organisms, yet its evolutionary advantages are elusive. Previous research explored recombination in the honeybee, a eusocial hymenopteran with an exceptionally high genome-wide recombination rate. A comparable study in a non-social member of the Hymenoptera that would disentangle the impact of sociality from Hymenoptera-specific features such as haplodiploidy on the evolution of the high genome-wide recombination rate in social Hymenoptera is missing. Utilizing single-nucleotide polymorphisms (SNPs) between two Nasonia parasitoid wasp genomes, we developed a SNP genotyping microarray to infer a high-density linkage map for Nasonia. The map comprises 1,255 markers with an average distance of 0.3 cM. The mapped markers enabled us to arrange 265 scaffolds of the Nasonia genome assembly 1.0 on the linkage map, representing 63.6% of the assembled N. vitripennis genome. We estimated a genome-wide recombination rate of 1.4–1.5 cM/Mb for Nasonia, which is less than one tenth of the rate reported for the honeybee. The local recombination rate in Nasonia is positively correlated with the distance to the center of the linkage groups, GC content, and the proportion of simple repeats. In contrast to the honeybee genome, gene density in the parasitoid wasp genome is positively associated with the recombination rate; regions of low recombination are characterized by fewer genes with larger introns and by a greater distance between genes. Finally, we found that genes in regions of the genome with a low recombination frequency tend to have a higher ratio of non-synonymous to synonymous substitutions, likely due to the accumulation of slightly deleterious non-synonymous substitutions. These findings are consistent with the hypothesis that recombination reduces interference between linked sites and thereby facilitates adaptive evolution and the purging of deleterious mutations. Our results imply that the genomes of haplodiploid and of diploid higher eukaryotes do not differ systematically in their recombination rates and associated parameters.     

Enhanced ATP-dependent copper efflux across the root cell plasma membrane in copper-tolerant Silene vulgaris

We studied copper uptake in inside-out plasma membrane vesicles derived from roots of copper-sensitive, moderately copper-tolerant and highly copper-tolerant populations of Silene vulgaris (Amsterdam, Marsberg and Imsbach, respectively). Plasma membrane vesicles were isolated using the two-phase partitioning method and copper efflux was measured using direct filtration experiments. Vesicles derived from Imsbach plants accumulated two and three times more copper than those derived from Marsberg and Amsterdam plants, respectively. This accumulation was ATP-dependent. Also, 9-amino-6-chloro-2-methoxyacridine fluorescence quenching rates upon copper addition decreased in the order Imsbach>Marsberg>Amsterdam. Our results support the hypothesis that efflux of copper across the root plasma membrane plays a role in the copper tolerance mechanism in S. vulgaris .     

Genetics of postzygotic isolation and Haldane's rule in haplodiploids

The process of speciation has puzzled scientists for decades, but only recently they have they been able to reveal the genetic basis of reproductive isolation. Much emphasis has been on Haldane's rule, the observation that the heterogametic sex often suffers more from hybridization than the homogametic sex. Most research on Haldane's rule has focused on diploid organisms with chromosomal sex determination. We argue that species lacking chromosomal sex determination, such as haplodiploids, also follow Haldane's rule and thus should be included in the definition of this rule. We provide evidence for Haldane's rule in Nasonia wasps and describe how haplodiploids can be used to test the different theories that have been proposed to explain Haldane's rule. We discuss how the faster-male and faster-X theories can shape speciation differently in haplodiploids compared to diploids.     

A new electric method for non-invasive continuous monitoring of stroke volume and ventricular volume-time curves

ABSTRACT: BACKGROUND: In this paper a new non-invasive, operator-free, continuous ventricular stroke volume monitoring device (Hemodynamic Cardiac Profiler, HCP) is presented, that measures the average stroke volume (SV) for each period of 20 seconds, as well as ventricular volume-time curves for each cardiac cycle, using a new electric method (Ventricular Field Recognition) with six independent electrode pairs distributed over the frontal thoracic skin. In contrast to existing non-invasive electric methods, our method does not use the algorithms of impedance or bioreactance cardiography. Instead, our method is based on specific 2D spatial patterns on the thoracic skin, representing the distribution, over the thorax, of changes in the applied current field caused by cardiac volume changes during the cardiac cycle. Since total heart volume variation during the cardiac cycle is a poor indicator for ventricular stroke volume, our HCP separates atrial filling effects from ventricular filling effects, and retrieves the volume changes of only the ventricles. METHODS: In-vitro experiments on a post-mortem human heart have been performed to measure the effects of increasing the blood volume inside the ventricles in isolation, leaving the atrial volume invariant (which can not be done in-vivo). These effects have been measured as a specific 2D pattern of voltage changes on the thoracic skin. Furthermore, a working prototype of the HCP has been developed that uses these in-vitro results in an algorithm to decompose voltage changes, that were measured in-vivo by the HCP on the thoracic skin of a human volunteer, into an atrial component and a ventricular component, in almost real-time (with a delay of maximally 39 seconds). The HCP prototype has been tested in-vivo on 7 human volunteers, using G-suit inflation and deflation to provoke stroke volume changes, and LVot Doppler as a reference technique. RESULTS: The in-vitro measurements showed that ventricular filling caused a pattern over the thorax quite distinct from that of atrial filling. The in-vivo tests of the HCP with LVot Doppler resulted in a Pearson's correlation of R = 0.892, and Bland-Altman plotting of SV yielded a mean bias of -1.6 ml and 2SD = 14.8 ml. CONCLUSIONS: The results indicate that the HCP was able to track the changes in ventricular stroke volume reliably. Furthermore, the HCP produced ventricular volume-time curves that were consistent with the literature, and may be a diagnostic tool as well.