Modeling the succession of barnacles and mussels on a sandstone reef in Pernambuco State, Brazil

Settlement and recruitment rates, biological interactions, environmental parameters, and larval supply are factors that influence community structure in areas where barnacles and mussels are the dominant fauna. This study modeled the succession populations of two barnacle species, Tetraclita stalactifera (Lamarck, 1818) and Chthamalus bisinuatus (Pilsbry, 1916), and a bivalve, Brachidontes solisianus (d’Orbigny, 1846), on a sandstone reef at Piedade Beach, Pernambuco State, Brazil. The different stages of the life cycles of these invertebrates are represented by adult and immature forms in this model and are simulated as numbers of individuals per 100 cm². Recruitment rates are represented as forcing functions based on field recruitment experiments with time-steps of 1 day. In addition to intraspecific competition, the model takes into account interspecific competition based on reciprocal effects and carrying capacities. Field data from field succession experiments were used to calibrate the model. Recruitment and succession data were collected from random 10 × 10-cm plots within a 1-m transect on a Brachidontes bed from April to December 2007. Correlation coefficients between field data and simulation results were statistically significant for both populations; sensitivity analysis showed that increases and decreases in invertebrate population densities were always smaller than 10% compared to baseline model values. Patch closure by mussels population growth was one of the main succession processes observed during the rainy season. However, barnacles were the dominant species at the end of both field and simulation succession experiments, with an average density of close to 100 individuals per 100 cm². Cirripedia individuals may inhibit bivalve re-colonization by settling over shells and more efficiently occupying free space in addition to having higher recruitment rates than bivalves during the dry season.     

Non-peptidic Cruzain Inhibitors with Trypanocidal Activity Discovered by Virtual Screening and In Vitro Assay

A multi-step cascade strategy using integrated ligand- and target-based virtual screening methods was developed to select a small number of compounds from the ZINC database to be evaluated for trypanocidal activity. Winnowing the database to 23 selected compounds, 12 non-covalent binding cruzain inhibitors with affinity values (K _i) in the low micromolar range (3–60 µM) acting through a competitive inhibition mechanism were identified. This mechanism has been confirmed by determining the binding mode of the cruzain inhibitor Nequimed176 through X-ray crystallographic studies. Cruzain, a validated therapeutic target for new chemotherapy for Chagas disease, also shares high similarity with the mammalian homolog cathepsin L. Because increased activity of cathepsin L is related to invasive properties and has been linked to metastatic cancer cells, cruzain inhibitors from the same library were assayed against it. Affinity values were in a similar range (4–80 µM), yielding poor selectivity towards cruzain but raising the possibility of investigating such inhibitors for their effect on cell proliferation. In order to select the most promising enzyme inhibitors retaining trypanocidal activity for structure-activity relationship (SAR) studies, the most potent cruzain inhibitors were assayed against T. cruzi-infected cells. Two compounds were found to have trypanocidal activity. Using compound Nequimed42 as precursor, an SAR was established in which the 2-acetamidothiophene-3-carboxamide group was identified as essential for enzyme and parasite inhibition activities. The IC₅₀ value for compound Nequimed42 acting against the trypomastigote form of the Tulahuen lacZ strain was found to be 10.6±0.1 µM, tenfold lower than that obtained for benznidazole, which was taken as positive control. In addition, by employing the strategy of molecular simplification, a smaller compound derived from Nequimed42 with a ligand efficiency (LE) of 0.33 kcal mol⁻¹ atom⁻¹ (compound Nequimed176) is highlighted as a novel non-peptidic, non-covalent cruzain inhibitor as a trypanocidal agent candidate for optimization.     

Occult hepatitis B virus infection among injecting drug users in the Central-West Region of Brazil

The prevalence of occult hepatitis B virus (HBV) infection was investigated in 149 hepatitis B surface antigen (HBsAg) negative injecting drug users (IDUs) in the Central-West Region of Brazil. Of these individuals, 19 were positive for HBV DNA, resulting in an occult HBV infection prevalence of 12.7% (19/149); six of these 19 individuals had anti-HBV core and/or anti-HBV surface antibodies and 13 were negative for HBV markers. All IDUs with occult hepatitis B reported sexual and/or parenteral risk behaviours. All HBV DNA-positive samples were successfully genotyped. Genotype D was the most common (17/19), followed by genotype A (2/19). These findings reveal a high prevalence of occult HBV infection and the predominance of genotype D among IDUs in Brazil''s Central-West Region.     

Methylation patterns revealed by MSAP profiling in genetically stable somatic embryogenic cultures of <Emphasis Type="Italic">Ocotea catharinensis</Emphasis> (Lauraceae)

Ocotea catharinensis is a rare tree species indigenous to the Atlantic rainforest of South America. In spite of its value as a hardwood species, it is in danger of extinction. The species erratically produces seeds showing irregular flowering and slow growth. Therefore, plants are not easily replaced. Tissue culture-based techniques are commonly used for obtaining living material for tree propagation and in vitro preservation. Therefore, a high-frequency somatic embryogenic system was developed for the species. In the present work, the genetic fidelity of cell aggregates and somatic embryos at various stages of in vitro development of O. catharinensis was investigated using RAPD and AFLP markers. Both analyses confirmed the absence of genetic variation in all developmental stages of O. catharinensis embryogenic cultures, verifying that the in vitro system is genetically stable. The cultures were also analyzed for their methylation profiles at 5′-CCGG-3′ sites by identifying methylation-sensitive amplification polymorphisms. Some of these markers differentiated cell aggregates from embryo bodies. The sequencing of ten MSAP markers revealed that four sequences showed significant similarity to genes encoding plant proteins. Particularly, the predicted amino acid sequence of the fragment designated as OcEaggHMttc155 was similar to the enzyme 1–aminocyclopropane-1-carboxylate oxidase (ACO), which is involved in the biosynthesis of ethylene, and its expression was reported to occur from the beginning to the intermediate stages of plant embryo development. Here, we suggest that this enzyme is possibly involved in the control of the earliest stages of somatic embryogenesis of O. catharinensis, and an approach to study ACO expression during somatic embryogenesis is proposed.     

Functional implications of the microbial community structure of undefined mesophilic starter cultures

This review describes the recent advances made in the studies of the microbial community of complex and undefined cheese starter cultures. We report on work related to the composition of the cultures at the level of genetic lineages, on the presence and activity of bacteriophages and on the population dynamics during cheese making and during starter culture propagation. Furthermore, the link between starter composition and starter functionality will be discussed. Finally, recent advances in predictive metabolic modelling of the multi-strain cultures will be discussed in the context of microbe-microbe interactions.

     

Schistosoma mansoni in a low-prevalence area in Brazil: the importance of additional methods for the diagnosis of hard-to-detect individual carriers by low-cost immunological assays

Schistosomiasis diagnosis is based on the detection of eggs in the faeces, which is laborious and lacks sensitivity, especially for patients with a low parasite burden. Immunological assays for specific antibody detection are available, but they usually demonstrate low sensitivity and/or specificity. In this study, two simple immunological assays were evaluated for the detection of soluble Schistosoma mansoni adult worm preparation (SWAP) and egg-specific IgGs. These studies have not yet been evaluated for patients with low parasite burdens. Residents of an endemic area in Brazil donated sera and faecal samples for our study. The patients were initially diagnosed by a rigorous Kato-Katz analysis of 18 thick smears from four different stool samples. The ELISA-SWAP was successful for human diagnosis with 90% sensitivity and specificity, confirming the Kato-Katz diagnosis with nearly perfect agreement, as seen by the Kappa index (0.85). Although the ELISA-soluble S. mansoni egg antigen was 85% sensitive, it exhibited low specificity (80%; Kappa index: 0.75) and was more susceptible to cross-reactivity. We believe that immunological assays should be used in conjunction with Kato-Katz analysis as a supplementary tool for the diagnosis of schistosomiasis for patients with low infection burdens, which are usually hard to detect.     

Evaluation of heritable determinants of blood and brain serotonin homeostasis using recombinant inbred mice

The biogenic amine serotonin (5‐HT, 5‐hydroxytryptamine) exerts powerful, modulatory control over multiple physiological functions in the brain and periphery, ranging from mood and appetite to vasoconstriction and gastrointestinal motility. In order to gain insight into shared and distinct molecular and phenotypic networks linked to variations in 5‐HT homeostasis, we capitalized on the stable genetic variation present in recombinant inbred mouse strains. This family of strains, all derived from crosses between C57BL/6J and DBA/2J (BXD) parents, represents a unique, community resource with approximately 40 years of assembled phenotype data that can be exploited to explore and test causal relationships in silico. We determined levels of 5‐HT and 5‐hydroxyindoleacetic acid from whole blood, midbrain and thalamus/hypothalamus (diencephalon) of 38 BXD lines and both sexes. All 5‐HT measures proved highly heritable in each region, although both gender and region significantly impacted between‐strain correlations. Our studies identified both expected and novel biochemical, anatomical and behavioral phenotypes linked to 5‐HT traits, as well as distinct quantitative trait loci. Analyses of these loci nominate a group of genes likely to contribute to gender‐ and region‐specific capacities for 5‐HT signaling. Analysis of midbrain mRNA variations across strains revealed overlapping gene expression networks linked to 5‐HT synthesis and metabolism. Altogether, our studies provide a rich profile of genomic, molecular and phenotypic networks that can be queried for novel relationships contributing risk for disorders linked to perturbed 5‐HT signaling .