Testing the short-term effects of a fish invader on the trophic ecology of a closely related species

The effects of invaders on native species are usually tested using species mean trait values over long time scales. However, considering individual variation over short timescales can help us better understand the interaction between invaders and native species. We compared trophic traits of the non-native guppy (Poecilia reticulata) and the native Brazilian poeciliid Phalloceros harpagos using experiments simulating the early stages of an invasive process. We used short-term mesocosms to simulate an early invasion scenario, where the two species were placed together, and a pre-invasion scenario, where species were kept separated, and analyzed interspecific and intraspecific trophic variability. We also compared the foraging efficiency of species in laboratory experiments. We found no differences on the mean diet of both species between pre and early invasion treatments. At the individual level, in the early invasion scenario, individuals of both species reduced their trophic niche as a probable effect of the presence of the heterospecific. Phalloceros harpagos had higher consumption rates than guppies indicating greater efficiency in feeding on invertebrates. Our results suggest that non-native species were not intrinsically better consumers of high-quality resources. Instead, intraspecific variation might be playing an overlooked role in shaping interactions between species during the early stages of invasion.

     

Gardnerella vaginalis Vaginolysin (VLY)-Derived MAP8 Peptide (VLY-MAP8) Induced the Production of Egg Yolk IgY Antibodies that Inhibit Erythrocytes Lysis

International Journal of Peptide Research and Therapeutics - Gardnerella vaginalis produces vaginolysin (VLY), a cholesterol-dependent cytolysin, responsible of the cellular lysis and epithelial...     

Role of particle coating in controlling skin damage photoinduced by titania nanoparticles

TiO₂ nanoparticles hazard is associated to their photocatalytic activity causing release of DNA damaging ROS (Reactive Oxygen Species), lipid peroxidation and skin damage. Various coatings have been proposed to minimize photocatalysis, while keeping the potential to block UV radiations. Uncoated and variously coated commercial nano-titania have been classified on the basis of UVB-induced lipoperoxidation of linoleic acid. A selection of the most and the least protective specimens was then examined by ESR (Electron Spin Resonance) to evidence the presence of surface paramagnetic centres and the release of ROS in aqueous suspensions (spin trapping). Paramagnetic centres and ROS were correlated with the extent of lipid peroxidation. When tested on porcine skin (mimicking the human one), titania acted as on linoleic acid. The combined use of lipid peroxidation of simple fatty acids with ESR analysis is here proposed as a possible screening tool for the evaluation of the potential toxicity of nano-titania in sunscreen preparations.     

Synergistic antifungal activity of statin–azole associations as witnessed by Saccharomyces cerevisiae- and Candida utilis-bioassays and ergosterol quantification

BackgroundFrequent opportunist fungal infections and the resistance to available antifungal drugs promoted the development of new alternatives for treatment, like antifungal drug combinations.AimsThis work aimed to detect the antifungal synergism between statins and azoles by means of an agar-well diffusion bioassay with Saccharomyces cerevisiae ATCC 32051 and Candida utilis Pr_1–2 as test strains.MethodsSynergistic antifungal effects were tested by simultaneously adding a sub inhibitory concentration (SIC) of statin (atorvastatin, lovastatin, pravastatin, rosuvastatin or simvastatin) plus a minimal inhibitory concentration (MIC) of azole (clotrimazole, fluconazole, itraconazole, ketoconazole or miconazole) to yeast-embedded YNB agar plates, and a positive result corresponded to a yeast growth inhibition halo higher than that produced by the MIC of the azole alone. Yeast cell ergosterol quantification by RP-HPLC was used to confirm statin–azole synergism, and ergosterol rescue bioassays were performed for evaluating statin-induced ergosterol synthesis blockage.ResultsGrowth inhibition was significantly increased when clotrimazole, fluconazole, itraconazole, ketoconazole and miconazole were combined with atorvastatin, lovastatin, rosuvastatin and simvastatin. Highest growth inhibition increments were observed on S. cerevisiae (77.5%) and C. utilis (43.2%) with a SIC of simvastatin plus a MIC of miconazole, i.e. 4 + 2.4 μg/ml or 20 + 4.8 μg/ml, respectively. Pravastatin showed almost no significant effects (0–7.6% inhibition increase). Highest interaction ratios between antifungal agents corresponded to simvastatin–miconazole combinations and were indicative of synergism. Synergism was also confirmed by the increased reduction in cellular ergosterol levels (S. cerevisiae, 40% and C. utilis, 22%). Statin-induced ergosterol synthesis blockage was corroborated by means of ergosterol rescue bioassays, pravastatin being the most easily abolished inhibition whilst rosuvastatin being the most ergosterol-refractory.ConclusionsSelected statin–azole combinations might be viable alternatives for the therapeutic management of mycosis at lower administration doses or with a higher efficiency.     

Inhibition of the cardiac inward rectifier potassium currents by KB-R7943

KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea) was developed as a specific inhibitor of the sarcolemmal sodium–calcium exchanger (NCX) with potential experimental and therapeutic use. However, KB-R7943 is shown to be a potent blocker of several ion currents including inward and delayed rectifier K⁺ currents of cardiomyocytes. To further characterize KB-R7943 as a blocker of the cardiac inward rectifiers we compared KB-R7943 sensitivity of the background inward rectifier (I_K1) and the carbacholine-induced inward rectifier (I_KACh) currents in mammalian (Rattus norvegicus; rat) and fish (Carassius carassius; crucian carp) cardiac myocytes. The basal I_K1 of ventricular myocytes was blocked with apparent IC50-values of 4.6 × 10^− 6 M and 3.5 × 10^− 6 M for rat and fish, respectively. I_KACh was almost an order of magnitude more sensitive to KB-R7943 than I_K1 with IC₅₀-values of 6.2 × 10^− 7 M for rat and 2.5 × 10^− 7 M for fish. The fish cardiac NCX current was half-maximally blocked at the concentration of 1.9–3 × 10^− 6 M in both forward and reversed mode of operation. Thus, the sensitivity of three cardiac currents to KB-R7943 block increases in the order I_K1 ~ I_NCX < I_KACh. Therefore, the ability of KB-R7943 to block inward rectifier potassium currents, in particular I_KACh, should be taken into account when interpreting the data with this inhibitor from in vivo and in vitro experiments in both mammalian and fish models.     

Proteomic approach of adaptive response to arsenic stress in Exiguobacterium sp. S17, an extremophile strain isolated from a high-altitude Andean Lake stromatolite

The North-Western part of Argentina is particularly rich in wetlands located in the Puna in an altitude between 3,600 and 4,600 m above sea level. Most of these high-altitude Andean lakes are inhospitable areas due to extreme habitat conditions such as high contents of toxic elements, particularly arsenic. Exiguobacterium sp. S17, isolated from stromatolites in Laguna Socompa, exhibited remarkable tolerance to high arsenic concentration, i.e., it tolerated arsenic concentration such as 10 mM of As(III) and 150 mM of As(V). A proteomics approach was conducted to reveal the mechanisms that provide the observed outstanding resistance of Exiguobacterium sp. S17 against arsenic. A comparative analysis of S17, exposed and unexposed to arsenic revealed 25 differentially expressed proteins. Identification of these proteins was performed by MALDI-TOF/MS revealing upregulation of proteins involved in energy metabolism, stress, transport, and in protein synthesis being expressed under arsenic stress. To our knowledge, this work represents the first proteomic study of arsenic tolerance in an Exiguobacterium strain.     

Development of polyploidy of scale-building cells in the wings of Manduca sexta

The developing wings of butterflies and moths are composed of two epithelial monolayers. Each epithelial sheet is made up of two kinds of cells, diploid cells that make up the epidermal surface and body of the wing, and large polyploid cells that become the scale-building cells whose cytoplasmic projections develop into the scales that will cover the adult wing and bear the pigment pattern. We studied the development of polyploidization of the scale-building cells during the pupal stage of the tobacco hornworm moth, Manduca sexta. The endomitotic divisions of the presumptive scale-building cells and the mitotic divisions of the diploid epithelial cells begin on day 3 of the pupal stage and continue until day 7. We show that scales of different colors and positions on the wing differ in size, and that the size of the scale is proportional to the ploidy of the scale-building cell. Scale-building cells are arranged in irregular rows and within each row there is an alternation of ploidy levels, with the lower ploidy cells giving rise to the underscales and the higher ploidy cells giving rise to the cover scales that carry the color pattern. Along the wing there is a proximo-distal decreasing gradient of average ploidy and scale size. Scale-building cells of high ploidy are surrounded by fewer epidermal cells than those of low ploidy. This inverse relationship is known as Henke's compensation principle, which posits that the number of endomitoses of a pre-polyploid cell and the number of mitotic divisions of its diploid daughter cell add up to a constant. We show that the inverse relationship fits the predictions of the compensation principle and does not fit constraints imposed by packing density, and we discuss mechanisms that could give rise to the inverse relationship.     

IL-10 Inhibits the NF-κB and ERK/MAPK-Mediated Production of Pro-Inflammatory Mediators by Up-Regulation of SOCS-3 in Trypanosoma cruzi-Infected Cardiomyocytes

Trypanosoma cruzi (T. cruzi) infection produces an intense inflammatory response which is critical for the control of the evolution of Chagas’ disease. Interleukin (IL)-10 is one of the most important anti-inflammatory cytokines identified as modulator of the inflammatory reaction. This work shows that exogenous addition of IL-10 inhibited ERK1/2 and NF-κB activation and reduced inducible nitric oxide synthase (NOS2), metalloprotease (MMP) -9 and MMP-2 expression and activities, as well as tumour necrosis factor (TNF)-α and interleukin (IL)-6 expression, in T. cruzi-infected cardiomyocytes. We found that T. cruzi and IL-10 promote STAT3 phosphorylation and up-regulate the expression of suppressor of cytokine signalling (SOCS)-3 thereby preventing NF-κB nuclear translocation and ERK1/2 phosphorylation. Specific knockdown of SOCS-3 by small interfering RNA (siRNA) impeded the IL-10-mediated inhibition of NF-κB and ERK1/2 activation. As a result, the levels of studied pro-inflammatory mediators were restored in infected cardiomyocytes. Our study reports the first evidence that T. cruzi up- regulates SOCS-3 expression and highlights the relevance of IL-10 in the modulation of pro-inflammatory response of cardiomyocytes in Chagas’ disease.