Two novel dermonecrotic toxins LiRecDT4 and LiRecDT5 from brown spider (Loxosceles intermedia) venom: from cloning to functional characterization

Loxoscelism (the condition produced by the bite of brown spiders) has been reported worldwide, but especially in warmer regions. Clinical manifestations include skin necrosis with gravitational spreading while systemic loxoscelism may include renal failure, hemolysis and thrombocytopenia. The venom contains several toxins, of which the best biochemically and biologically studied is the dermonecrotic toxin, a phospholipase-D. Purified toxin induces cutaneous and systemic loxoscelism, especially necrotic lesions, hematological disturbances and renal failure. Herein, we describe cloning, heterologous expression and purification of two novel dermonecrotic toxins: LiRecDT4 and LiRecDT5. The recombinant proteins stably expressed in Escherichia coli cells were purified from culture supernatants in a single step using Ni(2+)-chelating chromatography producing soluble proteins of 34 kDa (LiRecDT4) and 37 kDa (LiRecDT5). Circular dichroism analysis evidenced correctly folding for toxins but differences in secondary structures. Both proteins were recognized by whole venom serum antibodies and by a specific antibody to dermonecrotic toxin. Also, recombinant toxins with phospholipase activity induced experimental skin lesions and caused a massive inflammatory response in rabbit skin dermis. Nevertheless, toxins displayed different effects upon platelet aggregation, increase in vascular permeability and not caused death in mice. These characteristics in combination with functional studies illustrates that a family of dermonecrotic toxins exists, and includes two novel members that are useful for future structural and functional studies. They will also be useful in biotechnological ends, for example, as inflammatory and platelet aggregating studies, as antigens for serum therapy source and for lipids biochemical research.     

Antidepressant-like profile of action of two 4-amine derivatives of 10,11-dihydro-5H-dibenzo [a,d] cycloheptane in mice evaluated in the forced swimming test

This study investigated the antidepressant-like effect of 4-amine derivatives of 10,11-dihydro-5H-dibenzo-alkylamine-cycloheptane, 4-amine (3-N,N-dimethylpropylamine)-10,11-dihydro-5H-dibenzo[a,d]cycloheptane-5-one (ADDCH1) and 1,2,3,4,8,9-hexahydro-dibenzocyclohepta[4,4a,5-ef]1,4-diazepin (ADDCH2), in a validated experimental model of depression, the forced swimming test (FST) in mice. Female adult mice were sub-chronically (three doses in 24 h) or repeatedly (once a day for 10 days) treated with either of the compounds and evaluated in the FST. The sub-chronic treatment promoted a dose-dependent reduction in the immobility time in the FST with the doses of 50 mg/kg (ADDCH1) and 30 mg/kg (ADDCH2) ip being the most effective (33% and 37% of reduction, respectively). A similar profile of action was observed in the animals repeatedly treated with ADDCH1 50 mg/kg or ADDCH2 30 mg/kg ip (for 10 days) and there was no sign of motor impairment or locomotor activation as evaluated in the rota-rod and open-field tests, respectively. These findings suggest that these amine derivatives of the system dibenzocycloheptane have an antidepressant-like action which could be of clinical interest and, therefore, deserves further investigation. In addition, putative underlying mechanisms of action are discussed.     

Competition between Hardwood Hammocks and Mangroves

A bstract The boundaries between mangroves and freshwater hammocks in coastal ecotones of South Florida are sharp. Further, previous studies indicate that there is a discontinuity in plant predawn water potentials, with woody plants either showing predawn water potentials reflecting exposure to saline water or exposure to freshwater. This abrupt concurrent change in community type and plant water status suggests that there might be feedback dynamics between vegetation and salinity. A model examining the salinity of the aerated zone of soil overlying a saline body of water, known as the vadose layer, as a function of precipitation, evaporation and plant water uptake is presented here. The model predicts that mixtures of saline and freshwater vegetative species represent unstable states. Depending on the initial vegetation composition, subsequent vegetative change will lead either to patches of mangrove coverage having a high salinity vadose zone or to freshwater hammock coverage having a low salinity vadose zone. Complete or nearly complete coverage by either freshwater or saltwater vegetation represents two stable steady-state points. This model can explain many of the previous observations of vegetation patterns in coastal South Florida as well as observations on the dynamics of vegetation shifts caused by sea level rise and climate change.     

Single crystals of V-amylose complexed with alpha-naphthol

Lamellar square single crystals of V-amylose were obtained by adding alpha-naphthol to metastable dilute aqueous solutions of synthetic amylose chains with an average degree of polymerization of 100. The morphology and structure of the crystals were studied using low-dose transmission electron microscopy including high-resolution imaging, as well as electron and X-ray diffraction. The crystals are crystallized in a tetragonal P4(1)2(1)2 or P4(3)2(1)2 space group with unit cell parameters, calculated from X-ray diffraction data, a = b = 2.2844 nm (+/-0.0005) and c = 0.7806 nm (+/-0.001), implying the presence of two amylose chains per unit cell. High-resolution lattice images of the crystals confirmed that the amylose chains were crystallized as 8-fold helices corresponding to the repeat of four maltosyl units.     

Functional diversification of the dehydrin gene family in apple and its contribution to cold acclimation during dormancy

Dehydrins (DHN) are proteins involved in plant adaptive responses to abiotic stresses, mainly dehydration. Several studies in perennial crops have linked bud dormancy progression, a process characterized by the inability to initiate growth from meristems under favorable conditions, with DHN gene expression. However, an in‐depth characterization of DHNs during bud dormancy progression is still missing. An extensive in silico characterization of the apple DHN gene family was performed. Additionally, we used five different experiments that generated samples with different dormancy status, including genotypes with contrasting dormancy traits, to analyze how DHN genes are being regulated during bud dormancy progression in apple by real‐time quantitative polymerase chain reaction (RT‐qPCR). Duplication events took place in the diversification of apple DHN family. Additionally, MdDHN genes presented tissue‐ and bud dormant‐specific expression patterns. Our results indicate that MdDHN genes are highly divergent in function, with overlapping levels, and that their expressions are fine‐tuned by the environment during the dormancy process in apple.     

Mitochondrial and Oxidative Stress Aspects in Hippocampus of Rats Submitted to Dietary n-3 Polyunsaturated Fatty Acid Deficiency After Exposure to Early Stress

Neurochemical Research - Chronic dietary long-chain polyunsaturated fatty acids (PUFAs) deficiency may lead to changes in cortex and hippocampus neuronal membrane phospholipids, and may be linked...     

Distinguishing noise from signal in patterns of genomic divergence in a highly polymorphic avian radiation

Recently diverged taxa provide the opportunity to search for the genetic basis of the phenotypes that distinguish them. Genomic scans aim to identify loci that are diverged with respect to an otherwise weakly differentiated genetic background. These loci are candidates for being past targets of selection because they behave differently from the rest of the genome that has either not yet differentiated or that may cross species barriers through introgressive hybridization. Here we use a reduced‐representation genomic approach to explore divergence among six species of southern capuchino seedeaters, a group of recently radiated sympatric passerine birds in the genus Sporophila. For the first time in these taxa, we discovered a small proportion of markers that appeared differentiated among species. However, when assessing the significance of these signatures of divergence, we found that similar patterns can also be recovered from random grouping of individuals representing different species. A detailed demographic inference indicates that genetic differences among Sporophila species could be the consequence of neutral processes, which include a very large ancestral effective population size that accentuates the effects of incomplete lineage sorting. As these neutral phenomena can generate genomic scan patterns that mimic those of markers involved in speciation and phenotypic differentiation, they highlight the need for caution when ascertaining and interpreting differentiated markers between species, especially when large numbers of markers are surveyed. Our study provides new insights into the demography of the southern capuchino radiation and proposes controls to distinguish signal from noise in similar genomic scans.     

Dusky damselfish Stegastes fuscus relational learning: evidences from associative and spatial tasks

This study investigated the ability of the dusky damselfish Stegastes fuscus to associate conditioned and unconditioned stimuli (single CS–US) and to find a specific place in a clueless ambiece (spatial learning). After tested for colour preference and showing no specific colour attractively, the fish were trained to associate a colour cue with a stimulus fish (conspecific). Fish were then challenged to locate the exact place where the stimulus fish was presented. Stegastes fuscus spent most time close to the zone where stimulus was presented, even without obvious marks for orientation. The results confirm that S. fuscus show single CS–US learning and suggest the fish ability for spatial orientation. Stegastes fuscus appears to use multiple senses (sight and lateral line) for cues association and recall, and appear to perform relational learning similar to mammals. These data suggest the importance of cognitive skill for reef fishes that may have contributed to their establishment and evolutionary success in such complex environment.