Application of antimicrobial polypeptide host defenses to aquaculture: Exploitation of downregulation and upregulation responses

Antimicrobial polypeptides (AMPPs), consisting of peptides and small proteins with antimicrobial activity, are an integral component of innate immunity. Their often potent properties and widespread prevalence in fish suggests that designing means of manipulating their levels has considerable potential for maintaining or improving fish health. There is evidence that a number of chronic stresses lead to significant downregulation of AMPPs and thus their monitoring could be a highly sensitive measure of health status and risk of an infectious disease outbreak. Conversely, upregulation of AMPP expression could be used to enhance disease resistance in stressful environments, as well as improve the efficacy of traditional antimicrobial drugs. However, further work is required in linking levels of a number of AMPPs to physiological function since, while a number of studies have documented the down- or upregulation of AMPPs via gene expression, relatively few studies have quantitatively examined changes in protein expression. In addition, not all AMPPs appear to be expressed at microbicidal levels in vivo, suggesting that at least some may have functions other than being directly protective. Nonetheless, in fish, there is evidence that some constitutively expressed AMPPs, such as piscidins and histone-like proteins, are expressed at microbicidal levels and that they decline with stress. Furthermore, certain AMPPs derived from hemoglobin-β are upregulated to microbicidal levels after experimental challenge. The likely widespread distribution of these three AMPP groups in fish provides the opportunity to design strategies to greatly improve the health of cultured fish populations.     

UV photoreceptors and UV-yellow wing pigments in Heliconius butterflies allow a color signal to serve both mimicry and intraspecific communication

Mimetic wing coloration evolves in butterflies in the context of predator confusion. Unless butterfly eyes have adaptations for discriminating mimetic color variation, mimicry also carries a risk of confusion for the butterflies themselves. Heliconius butterfly eyes, which express recently duplicated ultraviolet (UV) opsins, have such an adaptation. To examine bird and butterfly color vision as sources of selection on butterfly coloration, we studied yellow wing pigmentation in the tribe Heliconiini. We confirmed, using reflectance and mass spectrometry, that only Heliconius use 3-hydroxy-DL-kynurenine (3-OHK), which looks yellow to humans but reflects both UV- and long-wavelength light, whereas butterflies in related genera have chemically unknown yellow pigments mostly lacking UV reflectance. Modeling of these color signals reveals that the two UV photoreceptors of Heliconius are better suited to separating 3-OHK from non-3-OHK spectra compared with the photoreceptors of related genera or birds. The co-occurrence of potentially enhanced UV vision and a UV-reflecting yellow wing pigment could allow unpalatable Heliconius private intraspecific communication in the presence of mimics. Our results are the best available evidence for the correlated evolution of a color signal and color vision. They also suggest that predator visual systems are error prone in the context of mimicry.     

��-Amyloid Causes Depletion of Synaptic Vesicles Leading to Neurotransmission Failure

Alzheimer disease is a progressive neurodegenerative brain disorder that leads to major debilitating cognitive deficits. It is believed that the alterations capable of causing brain circuitry dysfunctions have a slow onset and that the full blown disease may take several years to develop. Therefore, it is important to understand the early, asymptomatic, and possible reversible states of the disease with the aim of proposing preventive and disease-modifying therapeutic strategies. It is largely unknown how amyloid β-peptide (Aβ), a principal agent in Alzheimer disease, affects synapses in brain neurons. In this study, we found that similar to other pore-forming neurotoxins, Aβ induced a rapid increase in intracellular calcium and miniature currents, indicating an enhancement in vesicular transmitter release. Significantly, blockade of these effects by low extracellular calcium and a peptide known to act as an inhibitor of the Aβ-induced pore prevented the delayed failure, indicating that Aβ blocks neurotransmission by causing vesicular depletion. This new mechanism for Aβ synaptic toxicity should provide an alternative pathway to search for small molecules that can antagonize these effects of Aβ.     

Biodiversity,dynamics, and impact of chakras on the Ecuadorian Amazon

Aims Deforestation and biodiversity loss are two alarming, closely related problems, and the main factors triggering changes in land use. Indigenous agricultural practices in the western Amazon Basin are known as chakras, and their structure and dynamics are seemingly optimal for forest management. However, the variability in tree species and the degree of forest recovery after abandonment is poorly documented in this agroforestry system (AFS). The goals of this study were: (i) to investigate whether the different AFSs (chakras) preserve similar levels of forest diversity, (ii) to determine the effect of transformation of mature forests (MF) to chakras, in particular, forest alpha and beta diversity levels, and (iii) to investigate whether native tree species recovery leads to the original forest structure following chakra abandonment.     

Effects of salinity on the immune response of an ‘osmotic generalist’ bird

Salt stress can suppress the immune function of fish and other aquatic animals, but such an effect has not yet been examined in air-breathing vertebrates that frequently cope with waters (and prey) of contrasting salinities. We investigated the effects of seawater salinity on the strength and cost of mounting an immune response in the dunlin Calidris alpina, a long-distance migratory shorebird that shifts seasonally from freshwater environments during the breeding season to marine environments during migration and the winter period. Phytohaemagglutinin (PHA)-induced skin swelling, basal metabolic rate (BMR), body mass, fat stores, and plasma ions were measured in dunlins acclimated to either freshwater or seawater (salinity: 0.3 and 35.0 ‰, respectively). Seawater-acclimated dunlins mounted a PHA-induced swelling response that was up to 56 % weaker than those held under freshwater conditions, despite ad libitum access to food. Freshwater-acclimated dunlins significantly increased their relative BMR 48 h after PHA injection, whereas seawater-acclimated dunlins did not. However, this differential immune and metabolic response between freshwater- and seawater-acclimated dunlins was not associated with significant changes in body mass, fat stores or plasma ions. Our results indicate that the strength of the immune response of this small-sized migratory shorebird was negatively influenced by the salinity of marine habitats. Further, these findings suggest that the reduced immune response observed under saline conditions might not be caused by an energy or nutrient limitation, and raise questions about the role of osmoregulatory hormones in the modulation of the immune system.