Cloning, characterization, and structural analysis of a C-type lectin from Bothrops insularis (BiL) venom

Lectins are carbohydrate-binding molecules that mediate a variety of biological processes. In this work, we identify and characterize a lectin from Bothrops insularis venom, with respect to its biochemical properties and theoretical structure. Initially, from a venom gland cDNA library, we cloned and sequenced a cDNA encoding a protein with high identity to snake venom lectins. A lectin molecule was purified to homogeneity from the venom by affinity column and gel filtration. This protein named BiL displayed hemagglutinating activity that was inhibited by galactose, lactose, and EDTA. Mass spectrometry analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that BiL is a disulfide-linked dimeric protein consisting of monomers with 16,206 m/z. The amino acid sequence, deduced from its cDNA sequence, was confirmed by Edman sequencing and by peptide mass fingerprint analysis. BiL shows similarity to other C-type lectin family members. Modeling studies provide insights into BiL dimeric structure and its structural determinants for carbohydrate and calcium binding.     

Grazing without grasses: Effects of introduced livestock on plant community composition in an arid environment in northern Patagonia

Question: How does grazing intensity affect plant density, cover and species richness in an Patagonian arid ecosystem? Location: Monte steppe ecoregion, SW Argentina. Methods: I analysed the effect of grazing on plant density, cover and species richness using a stocking rate gradient within the same habitat. Six paddocks were used with stocking rates ranging between 0.002 – 0.038 livestock/ha. Plant density, species richness, plant cover and percentage of grazed branches were determined by sampling plots within each paddock. The percentage of grazed branches was used as an independent measurement of grazing intensity. Results: Higher stocking rates were related to lower plant density, species richness and plant cover. The paddock with the lowest grazing intensity had 86% more plants per unit area, 63% more plant cover and 48% higher species richness. The percentage of grazed branches and the quantity of dung increased with stocking rate. Conclusions: Introduced livestock seriously affect native vegetation in the Patagonian Monte. The damage observed in this xerophytic plant community suggests that plant adaptations to aridity do not provide an advantage to tolerate or avoid grazing by vertebrate herbivores in this region. Plant degradation in this arid environment is comparable to the degradation found in more humid ecosystems.     

SPARC downregulation attenuates the profibrogenic response of hepatic stellate cells induced by TGF-β1 and PDGF

Liver fibrosis is an active process that involves changes in cell-cell and cell-extracellular matrix (ECM) interaction. Secreted protein, acidic and rich in cysteine (SPARC) is an ECM protein with many biological functions that is overexpressed in cirrhotic livers and upregulated in activated hepatic stellate cells (aHSCs). We have recently shown that SPARC downregulation ameliorates liver fibrosis in vivo. To uncover the cellular mechanisms involved, we have specifically knocked down SPARC in two aHSC lines [the CFSC-2G (rat) and the LX-2 (human)] and in primary cultured rat aHSCs. Transient downregulation of SPARC in hepatic stellate cells (HSCs) did not affect their proliferation and had only minor effects on apoptosis. However, SPARC knockdown increased HSC adhesion to fibronectin and significantly decreased their migration toward PDFG-BB and TGF-β(1). Interestingly, TGF-β(1) secretion by HSCs was reduced following SPARC small interfering RNA (siRNA) treatment, and preincubation with TGF-β(1) restored the migratory capacity of SPARC siRNA-treated cells through mechanisms partially independent from TGF-β(1)-mediated induction of SPARC expression; thus SPARC knockdown seems to exert its effects on HSCs partially through modulation of TGF-β(1) expression levels. Importantly, collagen-I mRNA expression was reduced in SPARC siRNA-transfected HSCs. Consistent with previous results, SPARC knockdown in aHSCs was associated with altered F-actin expression patterns and deregulation of key ECM and cell adhesion molecules, i.e., downregulation of N-cadherin and upregulation of E-cadherin. Our data together suggest that the upregulation of SPARC previously reported for aHSCs partially mediates profibrogenic activities of TGF-β(1) and PDGF-BB and identify SPARC as a potential therapeutic target for liver fibrosis.     

From the saltpan to the plate: An evaluation of the use of the edible halophyte Salicornia ramosissima in catering

The halophyte species Salicornia ramosissima has long been consumed as food and is currently regarded as a high-value gourmet item. However, given that these plants grow in estuarine areas, often impacted by pollution, and are prone to the accumulation of ions, the risks associated with food borne pathogens or toxic metals has to be carefully considered. The objective of this work was to gather evidence that S. ramossissima harvested locally in an estuarine system (Ria de Aveiro, Portugal) can be safely consumed as a healthy and catering-amenable food. Fresh shoots, taken as green vegetables, and dried powdered shoots (green salt) intended as seasoning, were analysed for total aerobic bacteria, total coliforms, Escherichia coli, Bacillus cereus and fungi (yeasts and moulds). The nutritional profile and the concentration of macro and micro elements, including potential toxic elements, was also established. Fresh shoots and green salt were incorporated in catering meals (soup and a meat dish) and subjected to sensory analyses. The microbiological quality of fresh shoots and green salt was compliant with the guidelines for salad greens and herbs and spices, respectively. The nutritional and elemental profile revealed that fresh shoots have a high content in fibre and NaCl. From the concentration of Na determined in green salt, a daily dose of 7 g was estimated as corresponding to the recommended daily dietary intake Na. None of the other elements was present in concentrations that could exceed the dietary intake limits. In the sensory tests, fresh shoots were well accepted as salad greens but green salt, used as seasoning, was considered as insufficient in terms of saltiness and does not completely substitute cooking salt. The results confirm the nutritional and sensory value of S. ramossisima and represent a promising prospect for the incorporation of locally harvested or crop cultivated plants in catering meals.     

Non-Hebbian Learning Implementation in Light-Controlled Resistive Memory Devices

Non-Hebbian learning is often encountered in different bio-organisms. In these processes, the strength of a synapse connecting two neurons is controlled not only by the signals exchanged between the neurons, but also by an additional factor external to the synaptic structure. Here we show the implementation of non-Hebbian learning in a single solid-state resistive memory device. The output of our device is controlled not only by the applied voltages, but also by the illumination conditions under which it operates. We demonstrate that our metal/oxide/semiconductor device learns more efficiently at higher applied voltages but also when light, an external parameter, is present during the information writing steps. Conversely, memory erasing is more efficiently at higher applied voltages and in the dark. Translating neuronal activity into simple solid-state devices could provide a deeper understanding of complex brain processes and give insight into non-binary computing possibilities.     

A role for tRNA modifications in genome structure and codon usage

Transfer RNA (tRNA) gene content is a differentiating feature of genomes that contributes to the efficiency of the translational apparatus, but the principles shaping tRNA gene copy number and codon composition are poorly understood. Here, we report that the emergence of two specific tRNA modifications shaped the structure and composition of all extant genomes. Through the analysis of more than 500 genomes, we identify two kingdom-specific tRNA modifications as major contributors that separated archaeal, bacterial, and eukaryal genomes in terms of their tRNA gene composition. We show that, contrary to prior observations, genomic codon usage and tRNA gene frequencies correlate in all kingdoms if these two modifications are taken into account and that presence or absence of these modifications explains patterns of gene expression observed in previous studies. Finally, we experimentally demonstrate that human gene expression levels correlate well with genomic codon composition if these identified modifications are considered.     

Frequency of the hypervariable DNA loci D18S849, D3S1744, D12S1090 and D1S80 in a mixed ancestry population of Chilean blood donors

Blood donors (N = 150) at San José Hospital (Santiago, Chile) were typed for one VNTR locus (D1S80) and three STR loci (D18S849, D3S1744, D12S1090). A questionnaire was used to determine the socioeconomic level of the donors, because it is known that some genetic markers (e.g., the ABO and Rh groups) are differentially distributed between different socioeconomic strata. This methodology revealed that two of the three socioeconomic strata distinguishable in Santiago were present in our sample of blood donors, with stratum II representing the middle strata and stratum III the low strata. Allele frequency was determined for each locus and socioeconomic stratum, and it was found that the allele distributions of each locus in socioeconomic strata II and III were statistically similar. All loci conformed to the Hardy-Weinberg law and there was no evidence for association between the alleles of the four loci, allelic frequencies being similar to those found in North American Hispanic populations. The results support the view that the analysis of these loci may have useful applications in population genetics as well as in identity tests.     

Characterization and daily variation of nitrate reductase in Gracilaria tenuistipitata (Rhodophyta)

The chemosensory protein CSP-sg4 of the desert locust Schistocerca gregaria binds reversibly N-phenyl-1-naphthylamine in fluorescent-binding assays, with a dissociation constant of 4 microM. Upon binding to the protein, the emission peaks of the fluorescent probe undergo a marked blue shift, accompanied by an order of magnitude increase of the maximum intensity. The assay has also allowed the measurement of the affinity of CSP to other aromatic and aliphatic compounds. The binding capacity of this protein is unaffected by thermal treatments up to 100 degrees C for 20 min. The ligand-binding characteristics of chemosensory proteins may help in clarifying the role of this recently discovered class of soluble proteins in chemoreception.     

Ancient versus reticulate origin of a hemiclonal lineage

Crossing experiments revealed that a diploid hybridogenetic fish (genus Poeciliopsis) from the Río Mocorito (Sinaloa, Mexico) is trihybrid. Its haploid maternal genome is inherited clonally (i.e., hemiclonally), and it expresses a mixture of morphological traits found in the closely related species P. monacha and P. viriosa. Its haploid paternal genome is replaced in each generation by mating with males of a more distantly related sexual species, P. lucida. However, expression of mixed (monacha X viriosa) traits by this hemiclone is also consistent with retention of shared ancestral polymorphisms. If true, this hemiclonal lineage would be one of the few examples of an ancient asexual taxon. We used mitochondrial DNA and allozymes to test whether the maternal progenitor of the Mocorito hybridogen was a recent P. monacha X P. viriosa hybrid or a remnant of their most recent common ancestor. Our results clearly link the hemiclonal genome to contemporary P. monacha and therefore support the hypothesis of a recent origin. Additionally, our findings suggest that this unisexual fish may serve as a vehicle for introgression between two allopatric sexual species.