Prey Selection by the Water Bug Aphelocheirus aestivalis Fabr. (Heteroptera: Aphelocheiridae)

Feeding experiments were conducted in situ in flow through boxes to determine the vulnerability of different prey types (the mayfly larvae Baetis, Ephemerella and Ecdyonurus spp., the caddisfly larva Hydropsyche spp. and the crustacean Gammarus spp.) to the predaceous water bug Aphelocheirus aestivalis and to estimate the predation impact of Aphelocheirus on prey populations. Experiments with equal densities of mixed prey and experiments where each prey was tested individually revealed that Baetis and Ephemerella were most vulnerable to Aphelocheirus predation: Hydropsyche, Ecdyonurus and Gammarus were little/not preyed upon. The present results suggest that vulnerability of prey depends mainly upon prey mobility and microhabitat overlap between predator and prey and that feeding behaviour of Aphelocheirus resembles more that of megalopterans than of stoneflies. Experiments with different prey densities (120–720 prey m⁻²) showed that the predation rate of Aphelocheirus increased with increasing prey density. Experiments with different substrates documented that mortality rates of prey decreased with increasing substrate complexity. When substrate conditions were complex mortality rates in the control and in the experimental boxes were the same which suggest little importance of Aphelocheirus predation on mayflies in the study site.     

Applicability of various brands of mixed-phase extraction columns for opiate extraction from blood and serum

Four commercially available types of mixed-phase solid-phase extraction (SPE) columns (Bond Elut Certify, Isolute Confirm HCX, Chromabond Drug and Bakerbond Narc-2) were examined in order to compare the extraction efficiencies and chromatographic purity of extracts. The absolute recovery of morphine, 6-monoacetylmorphine and codeine was examined in blood and serum (ten samples each at two concentration levels), using SPE columns of the same batch. GC-MS (ion trap) and HPLC with amperometric detection were used for quantitation. A distinct variability in extraction recovery was observed among the same batches of all brands of SPE columns. All extracts were chromatographically pure and no interfering peaks were observed, neither in GC-MS nor in HPLC examinations, but in some extracts large peaks of plasticizers were identified. The measurements of flow velocities of the same samples of blood or serum through the SPE columns of the same batch showed very large variability of random charactere. The morphometric analysis of particles was performed for two batches of each sort of SPE columns by means of an image analysing system. Symmetrical distribution of particle size was observed only in Chromabond MN Drug packing, while in other cartridges large fractions of fine particles and nonhomogenous distribution were found. Only in one case the morphometric findings were pretty concordant with the data available from the manufacturer; in two cases, observed data varied considerably from the expected, and in one case no information was available at all. The study showed generally that there was room for improvement in the quality of mixed-phase SPE columns.     

Rapid divergence in the course of Drosophila evolution reveals structural important domains of the Notch antagonist Hairless

 Hairless is a member of the Notch signalling pathway, where it acts as antagonist by binding to Suppressor of Hairless [Su(H)], thereby inhibiting Notch target gene activation. The pathway and its members are highly conserved in metazoans from worms to humans. However, a Hairless orthologue from another species has not yet been identified. The identification of Hairless in largely diverged species by cross-hybridization has failed so far probably due to a low degree of conservation. Therefore, we turned to D. hydei where a Hairless mutation has been described before. The D. hydei Hairless orthologue is reasonably well conserved with regard to gene structure and expression. The prospective Hairless protein orthologues share several highly conserved regions which are separated by quite diverged stretches. As to be expected, the largest region of high conservation corresponds to the Su(H) binding domain. This region is also functionally conserved, since this D. hydei protein domain binds very strongly to the D. melanogaster Su(H) protein. The other conserved regions support our earlier structure-function analysis since they nicely correspond to previously defined, functionally important protein domains. Most notably, the very C-terminal domain which is very sensitive to structural alterations, is nearly identical between the two species. In summary, this evolutionary study improves the knowledge on functionally significant domains of the Hairless protein, and may be helpful for the future identification of homologues in other animals, especially in vertebrates. Received: 26 August 1998 / Accepted: 9 November 1998     

Effect of viscoelastic relaxation on moisture transport in foods. Part I: Solution of general transport equation

Within the framework of continuum mechanics, Singh et al. [1] developed an integro-differential equation, which applies to both Darcian (Fickian) and non-Darcian (non-Fickian) modes of fluid transport in swelling biological systems. A dimensionless form of the equation was obtained and transformed from moving Eulerian to the stationary Lagrangian coordinates. Here a solution scheme for the transport equation is developed to predict moisture transport and viscoelastic stresses in spheroidal biopolymeric materials. The equation was solved numerically and results used for predicting drying and sorption curves, moisture profiles, and viscoelastic stresses in soybeans. The Lagrangian solution was obtained by assembling together several schemes: the finite element method was used to discretize the equation in space; non-linearity was addressed using the Newton-Raphson method; the Volterra term was handled via a time integration scheme of Patlashenko et al. [2] and the Galerkin rule was used to solve the time-differential term. The solution obtained in Lagrangian coordinates was transformed back to the Eulerian coordinates. In part II of this sequence we present the numerical results.Revised version: 5 October 2003     

Neuroprotective effects and intracellular signaling pathways of erythropoietin in a rat model of multiple sclerosis

In multiple sclerosis (MS), long-term disability is primarily caused by axonal and neuronal damage. We demonstrated in a previous study that neuronal apoptosis occurs early during experimental autoimmune encephalomyelitis, a common animal model of MS. In the present study, we show that, in rats suffering from myelin oligodendrocyte glycoprotein (MOG)-induced optic neuritis, systemic application of erythropoietin (Epo) significantly increased survival and function of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve. We identified three independent intracellular signaling pathways involved in Epo-induced neuroprotection in vivo: Protein levels of phospho-Akt, phospho-MAPK 1 and 2, and Bcl-2 were increased under Epo application. Using a combined treatment of Epo together with a selective inhibitor of phosphatidylinositol 3-kinase (PI3-K) prevented upregulation of phospho-Akt and consecutive RGC rescue. We conclude that in MOG-EAE the PI3-K/Akt pathway has an important influence on RGC survival under systemic treatment with Epo.     

Simultaneous quantitative and allele-specific expression analysis with real competitive PCR

Background  

For a diploid organism such as human, the two alleles of a particular gene can be expressed at different levels due to X chromosome inactivation, gene imprinting, different local promoter activity, or mRNA stability. Recently, imbalanced allelic expression was found to be common in human and can follow Mendelian inheritance. Here we present a method that employs real competitive PCR for allele-specific expression analysis.     

Evaluation of hyaluronan from different sources: Streptococcus zooepidemicus, rooster comb, bovine vitreous, and human umbilical cord

Sodium hyaluronate (HA) is widely distributed in extracellular matrixes and can play a role in orchestrating cell function. Consequently, many investigators have looked at the effect of exogenous HA on cell behavior in vitro. HA can be isolated from several sources (e.g., bacterial, rooster comb, umbilical cord) and therefore can possess diverse impurities. This current study compares the measured impurities and the differences in biological activity between HA preparations from these sources. It was demonstrated that nucleic acid and protein content was highest in human umbilical cord and bovine vitreous HA and was low in bacterial and rooster comb HA. Macrophages exposed to human umbilical cord HA produced significantly higher amounts of TNF-alpha relative to control or bacterial-derived HA. These results indicate that the source of HA should be considered due to differences in the amounts and types of contaminants that could lead to widely different behaviors in vitro and in vivo.