Sequestration of the Aβ Peptide Prevents Toxicity and Promotes Degradation In Vivo

Protein aggregation, arising from the failure of the cell to regulate the synthesis or degradation of aggregation-prone proteins, underlies many neurodegenerative disorders. However, the balance between the synthesis, clearance, and assembly of misfolded proteins into neurotoxic aggregates remains poorly understood. Here we study the effects of modulating this balance for the amyloid-beta (Aβ) peptide by using a small engineered binding protein (Z_Aβ3) that binds with nanomolar affinity to Aβ, completely sequestering the aggregation-prone regions of the peptide and preventing its aggregation. Co-expression of Z_Aβ3 in the brains of Drosophila melanogaster expressing either Aβ₄₂ or the aggressive familial associated E22G variant of Aβ₄₂ abolishes their neurotoxic effects. Biochemical analysis indicates that monomer Aβ binding results in degradation of the peptide in vivo. Complementary biophysical studies emphasize the dynamic nature of Aβ aggregation and reveal that Z_Aβ3 not only inhibits the initial association of Aβ monomers into oligomers or fibrils, but also dissociates pre-formed oligomeric aggregates and, although very slowly, amyloid fibrils. Toxic effects of peptide aggregation in vivo can therefore be eliminated by sequestration of hydrophobic regions in monomeric peptides, even when these are extremely aggregation prone. Our studies also underline how a combination of in vivo and in vitro experiments provide mechanistic insight with regard to the relationship between protein aggregation and clearance and show that engineered binding proteins may provide powerful tools with which to address the physiological and pathological consequences of protein aggregation.     

Rapid Decision-Making with Side-Specific Perceptual Discrimination in Ants

Background

Timely decision making is crucial for survival and reproduction. Organisms often face a speed-accuracy trade-off, as fully informed, accurate decisions require time-consuming gathering and treatment of information. Optimal strategies for decision-making should therefore vary depending on the context. In mammals, there is mounting evidence that multiple systems of perceptual discrimination based on different neural circuits emphasize either fast responses or accurate treatment of stimuli depending on the context.

Methodology/Principal Findings

We used the ant Camponotus aethiops to test the prediction that fast information processing achieved through direct neural pathways should be favored in situations where quick reactions are adaptive. Social insects discriminate readily between harmless group-members and dangerous strangers using easily accessible cuticular hydrocarbons as nestmate recognition cues. We show that i) tethered ants display rapid aggressive reactions upon presentation of non-nestmate odor (120 to 160 ms); ii) ants'' aggressiveness towards non-nestmates can be specifically reduced by exposure to non-nestmate odor only, showing that social interactions are not required to alter responses towards non-nestmates; iii) decision-making by ants does not require information transfer between brain hemispheres, but relies on side-specific decision rules.

Conclusions/Significance

Our results strongly suggest that first-order olfactory processing centers (up to the antennal lobes) are likely to play a key role in ant nestmate recognition. We hypothesize that the coarse level of discrimination achieved in the antennal lobes early in odor processing provides enough information to determine appropriate behavioral responses towards non-nestmates. This asks for a reappraisal of the mechanisms underlying social recognition in insects.     

Prion‐like Doppel gene polymorphisms and scrapie susceptibility in portuguese sheep breeds

The establishment of an association between prion protein gene (PRNP) polymorphisms and scrapie susceptibility in sheep has enabled the development of breeding programmes to increase scrapie resistance in the European Union. Intense selection for PRNP genotype may lead to correlated selection for genes linked to PRNP. We intended to investigate if any association exists between genetic variation in prion‐like protein Doppel gene (PRND) and scrapie susceptibility, determined through PRNP genotyping. Sampling included 460 sheep from eight Portuguese breeds and the PRND gene coding region was analysed by multiple restriction fragment‐single strand conformation polymorphism (MRF‐SSCP), whereas PRNP genotyping was carried out by primer extension. A synonymous substitution (c.78G>A) was detected in codon 26 of the PRND gene, in all breeds except Churra Mondegueira. Linkage disequilibrium was found between the PRND and PRNP loci (P = 0.000). Specifically, PRND was monomorphic in the 45 animals with the more resistant ARR/ARR PRNP genotype (P = 0.003), whereas a higher frequency of PRND heterozygotes (GA) was associated with ARQ/AHQ (P = 0.029). These results constitute preliminary evidence of an association between a polymorphism in the PRND gene and scrapie susceptibility, and indicate that the possibility of undesirable consequences from widespread selection for PRNP genotype on genetic diversity and reproduction traits needs to be further investigated.     

In vitro and in vivo fertility of ram semen cryopreserved in different extenders

Seminal traits of frozen-thawed (FT) ram semen and in vitro and field fertility in native Portuguese breeds were evaluated in 4 experiments. In exp. 1 and 2 the cryopreservation capacity of 2 extenders, E1 (15% egg yolk-EY) and E2 (4.5% EY and trehalose) was compared through morphological evaluation and in vitro fertilizability of FT ram semen. Exp. 3 aimed to determine the usefulness of in vitro homologous/heterologous fertilization tests as tools for predicting ram fertility. Exp. 4 was conducted to verify if the identified differences between the 2 extenders could be confirmed by field fertility. E1 showed a better cryoprotective action expressed by higher in vitro and field fertility results. In conclusion, EY is difficult to be replaced in ram semen extenders. Heterologous fertilization seems to be a useful tool for predicting fertility of FT ram semen.     

Impact of two bacterial biocontrol agents on bacterial and fungal culturable groups associated with the roots of field-grown maize

Aims:  To assess the impact of Bacillus amyloliquefaciens and Microbacterium oleovorans on bacterial and fungal groups associated to the roots of field-grown maize.
Methods and Results:  Identification and count of bacterial and fungal culturable populations associated to the roots of maize seedlings, changes in culturable community structure according to the richness and diversity indexes concept and shifts in microbial activity through analysis of cellulolytic, ammonification and nitrification potentials were determined, in relation to kernel treatment with biological control agents. Following the treatment of maize kernels with B. amyloliquefaciens at 10⁷ CFU ml⁻¹, an increase in bacterial diversity was observed at the rhizoplane of resultant seedlings. Bacterial richness was significantly increased at the root inner tissues of seedlings treated with Mic. oleovorans . Fusarium , Aspergillus , Penicillium and Trichoderma were the main fungal genera isolated and there population sizes were unequally affected by the addition of biocontrol agents.
Conclusions:  Numbers and types of isolated bacteria and fungi changed in response to the addition of biocontrol agents, while microbial activity remained unchanged with respect to control.
Significance and Impact of the Study:  This study provides an insight of the effects of proven biocontrol agents on micro-organisms naturally associated to the target crop.     

Production of reactive oxygen species by hemocytes from the cattle tick Boophilus microplus.

We have investigated the phagocytic activity and the production of reactive oxygen species (ROS) by hemocytes from the cattle tick Boophilus microplus. Two main types of hemocytes were detected in tick hemolymph: plasmatocytes and granulocytes. The plasmocytes were the most abundant cells, being responsible for the in vivo phagocytosis of yeast. ROS production was evaluated by luminol-amplified luminescence and phenol red oxidation. The luminescence increased when hemocytes were incubated with bacteria, zymosan, or phorbol 12-miristate 13-acetate (PMA). The luminescence was inhibited by superoxide dismutase and catalase, which are antioxidant enzymes that remove superoxide and hydrogen peroxide, respectively. The phenol red oxidation assay also showed an increase in the level of hydrogen peroxide produced by hemocytes stimulated with bacteria and PMA. Taken all together, our data indicate that tick hemocytes are able to produce ROS during the phagocytic process similarly to vertebrate phagocytes.     

Deriving ecological relationships from geographical correlations between host and parasitic species: an example with orchid bees

Aim  To investigate biogeographical patterns of cleptoparasitic Exaerete bee species and their orchid bee hosts.
Location  Neotropical region, from Central America to southern Brazil.
Methods  Correlations between relative frequencies of cleptoparasitic Exaerete species and their host Eulaema species were employed to investigate the geographical association between such species pairs.
Results  Our data support the current proposition that the Eulaema meriana / Eulaema flavescens complex is the main host for Exaerete frontalis . Contrary to current belief, however, Eulaema nigrita apparently is not the only and, in some regions, not the most important host for Exaerete smaragdina .
Main conclusions  Current knowledge on cleptoparasite host associations among orchid bees is based on fortuitous observations, and in some instances generalizations from such observations are not corroborated by the frequencies and distributions of the bees involved. Our data suggest that cleptoparasitic pressure, rather than other features of the forest environment, may be responsible for the low abundance of E. nigrita in the Amazonian forests.