Phosphohydrolase activity of the isolated, brush-border membrane of Hymenolepis diminuta (Cestoda) following sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis

Following electrophoresis of isolated, brush-border membranes of Hymenolepis diminuta on SDS-polyacrylamide gels, three distinct areas of alpha-naphthyl phosphate (NP) hydrolysis were detected; these corresponded to proteins with molecular weights of 106,800, 172,700, and greater than 340,000 Daltons. Hydrolysis of NP was inhibited by adenosine triphosphate, adenosine;5'-monophosphate, p-nitrophenyl-phosphate, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, molybdate, ethylenediaminetetraacetate (EDTA), and ethyleneglycol-bis-(beta-amino-ethyl)-N,N'-tetraacetate (EGTA), but not by fluoride. Inhibition of NP hydrolysis by EDTA was relieved in the presence of Mg++ or Ca++. Heating the isolated, brush-border membrane in the presence of SDS for 5 min at 95 C destroyed all enzymatic activity. These characteristics indicated that the enzyme(s) responsible for NP hydrolysis (following separation of membrane proteins by SDS-polyacrylamide gel electrophoresis) were the same enzymes responsible for the phosphohydrolase activity associated with intact and solubilized, brush-border membrane preparations of H. diminuta.     

Incidence of resistance to neonicotinoid insecticides in greenhouse populations of the whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) from Greece

The greenhouse whitefly, Trialeurodes vaporariorum Westwood, is an important pest of field and greenhouse crops of horticultural and ornamental plants. In integrated pest management programs its control is mainly based on the release of biological control agents and application of chemical insecticides. Neonicotinoids are relatively new chemicals currently applied for the chemical control of T. vaporariorum. However, cases of development of insecticide resistance to neonicotinoids have already been reported. The state of resistance to neonicotinoid insecticides for populations of the greenhouse whitefly in Greece is currently unknown. The objective of our study was to screen a number of whitefly populations for resistance to the neonicotinoids imidacloprid and thiacloprid. Seven whitefly populations were collected from tomato greenhouse crops from different areas of central and northern Greece. LC₅₀ values were estimated for all populations following the method proposed by the Insecticide Resistance Action Committee (IRAC). The development of resistance to both neonicotinoids was confirmed for all tested populations with resistance ratios ranging from 1.5 to 4.4-fold and from 1.4 to 12.2-fold for imidacloprid and thiacloprid, respectively. We discuss our results with regard to the development of neonicotinoid resistance in T. vaporariorum populations and its implications for whitefly control.     

Linking variability of tree water use and growth with species resilience to environmental changes

Tree growth is an indicator of tree vitality and its temporal variability is linked to species resilience to environmental changes. Second-order statistics that quantify the cross-scale temporal variability of ecophysiological time series (statistical memory) could provide novel insights into species resilience. Species with high statistical memory in their tree growth may be more affected by disturbances, resulting in lower overall resilience and higher vulnerability to environmental changes. Here, we assessed the statistical memory, as quantified with the decay in standard deviation with increasing time scale, in tree water use and growth of co-occurring European larch Larix decidua and Norway spruce Picea abies along an elevational gradient in the Swiss Alps using measurements of stem radius changes, sap flow and tree-ring widths. Local-scale interspecific differences between the two conifers were further explored at the European scale using data from the International Tree-Ring Data Bank. Across the analysed elevational gradient, tree water use showed steeper variability decay with increasing time scale than tree growth, with no significant interspecific differences, highlighting stronger statistical memory in tree growth processes. Moreover, Norway spruce displayed slower decay in growth variability with increasing time scale (higher statistical memory) than European larch; a pattern that was also consistent at the European scale. The higher statistical memory in tree growth of Norway spruce in comparison to European larch is indicative of lower resilience of the former in comparison to the latter, and could potentially explain the occurrence of European larch at higher elevations at the Alpine treeline. Single metrics of resilience cannot often summarize the multifaceted aspects of ecosystem functioning, thus, second-order statistics that quantify the strength of statistical memory in ecophysiological time series could complement existing resilience indicators, facilitating the assessment of how environmental changes impact forest growth trajectories and ecosystem services.     

In vitro and in vivo assessment of vitamin A encapsulation in a liposome–protein delivery system

Vitamin A (VA) is an essential nutrient needed in small amounts by humans and supports a wide range of biological actions. Retinol, the most common and most biologically active form of VA has also been found to inhibit peroxidation processes in membranes and it has been widely used as an ingredient with pharmaceutical and nutritional applications. VA is a lipophilic molecule, sensitive to air, oxidizing agents, ultraviolet light and low pH levels. For these reasons, it is necessary for VA to be protected against oxidation. Another disadvantage in the application of VA is its low solubility in aqueous media. Both issues (sensitivity and solubility) can be solved by employing encapsulation techniques. Liposomes can efficiently encapsulate lipid-soluble materials, such as VA. The encapsulated materials are protected from environmental and chemical changes. A new liposome/β-lactoglobulin formulation has been developed as a stable delivery system for VA. The aim of this study was the encapsulation of VA into β-lactoglobulin–liposome complexes, recently developed in our laboratory. The in vivo bioavailability characterization of VA was tested after administration in laboratory animals (mice). In this report, we demonstrate that VA could be efficiently entrapped and delivered in a phospholipid–sterol–protein membrane resembling system, a newly synthesized promising carrier. Based on this finding, the phospholipid–sterol–protein membrane resembling system may be one of the promising approaches to enhance VA absorption and to overcome the formulation difficulties associated with lipophilic means. The carrier system described here has huge potential in food fortification applications to treat VA deficiency.     

The canonical NF-κB pathway differentially protects normal and human tumor cells from ROS-induced DNA damage

DNA damage responses (DDR) invoke senescence or apoptosis depending on stimulus intensity and the degree of activation of the p53-p21(Cip1/Waf1) axis; but the functional impact of NF-κB signaling on these different outcomes in normal vs. human cancer cells remains poorly understood. We investigated the NF-κB-dependent effects and mechanism underlying reactive oxygen species (ROS)-mediated DDR outcomes of normal human lung fibroblasts (HDFs) and A549 human lung cancer epithelial cells. To activate DDR, ROS accumulation was induced by different doses of H(2)O(2). The effect of ROS induction caused a G2 or G2-M phase cell cycle arrest of both human cell types. However, ROS-mediated DDR eventually culminated in different end points with HDFs undergoing premature senescence and A549 cancer cells succumbing to apoptosis. NF-κB p65/RelA nuclear translocation and Ser536 phosphorylation were induced in response to H(2)O(2)-mediated ROS accumulation. Importantly, blocking the activities of canonical NF-κB subunits with an IκBα super-repressor or suppressing canonical NF-κB signaling by IKKβ knock-down accelerated HDF premature senescence by up-regulating the p53-p21(Cip1/Waf1) axis; but inhibiting the canonical NF-κB pathway exacerbated H(2)O(2)-induced A549 cell apoptosis. HDF premature aging occurred in conjunction with γ-H2AX chromatin deposition, senescence-associated heterochromatic foci and beta-galactosidase staining. p53 knock-down abrogated H(2)O(2)-induced premature senescence of vector control- and IκBαSR-expressing HDFs functionally linking canonical NF-κB-dependent control of p53 levels to ROS-induced HDF senescence. We conclude that IKKβ-driven canonical NF-κB signaling has different functional roles for the outcome of ROS responses in the contexts of normal vs. human tumor cells by respectively protecting them against DDR-dependent premature senescence and apoptosis.     

Nonuniform shortening in the biceps brachii during elbow flexion.

This study tested the common assumption that skeletal muscle shortens uniformly in the direction of its fascicles during low-load contraction. Cine phase contrast magnetic resonance imaging was used to characterize shortening of the biceps brachii muscle in 12 subjects during repeated elbow flexion against 5 and 15% maximum voluntary contraction (MVC) loads. Mean shortening was relatively constant along the anterior boundary of the muscle and averaged 21% for both loading conditions. In contrast, mean shortening was nonuniform along the centerline of the muscle during active elbow flexion. Centerline shortening in the distal region of the biceps brachii (7.3% for 5% MVC and 3.7% for 15% MVC) was significantly less (P < 0.001) than shortening in the muscle midportion (26.3% for 5% MVC and 28.2% for 15% MVC). Nonuniform shortening along the centerline was likely due to the presence of an internal aponeurosis that spanned the distal third of the longitudinal axis of the biceps brachii. However, muscle shortening was also nonuniform proximal to the centerline aponeurosis. Because muscle fascicles follow the anterior contour and centerline of the biceps brachii, our results suggest that shortening is uniform along anterior muscle fascicles and nonuniform along centerline fascicles.     

Hymenolepis diminuta: Action of worm RNase against RNA

Hymenolepis diminuta possesses a tegumental ribonuclease (RNase) which hydrolyzes rat liver and degraded yeast RNA. Polyacrylamide gel electrophoresis and gel chromatography of rat liver RNA after incubation with intact worms demonstrated significant hydrolysis of the high molecular weight RNA fractions (28 S and 18 S), with the appearance of fractions of intermediate molecular weight (i.e., between 18 S and 4 S), as well as ethanol-soluble fractions. Hydrolysis of degraded yeast RNA (with a molecular weight of approximately 25,000) yielded a single ethanol-precipitable hydrolysis product, as well as ethanol-soluble hydrolysis products.