Age-related change in breeding performance in early life is associated with an increase in competence in the migratory barn swallow Hirundo rustica

1. We investigated age-related changes in two reproductive traits (laying date and annual fecundity) in barn swallows Hirundo rustica L. using a mixed model approach to di-stinguish among between- and within-individual changes in breeding performance with age. 2. We tested predictions of age-related improvements of competence (i.e. constraint hypothesis) and age-related progressive disappearance of poor-quality breeders (i.e. selection hypothesis) to explain age-related increase in breeding performance in early life. 3. Reproductive success increased in early life, reaching a plateau at middle age (e.g. at 3 years of age) and decreasing at older age (> 4 years). Age-related changes in breeding success were due mainly to an effect of female age. 4. Age of both female and male affected timing of reproduction. Final linear mixed effect models (LME) for laying date included main and quadratic terms for female and male age, suggesting a deterioration in reproductive performance at older age for both males and females. 5. We found evidence supporting the constraints hypothesis that increases in competence within individuals, with ageing being the most probable cause of the observed increase in breeding performance with age in early life. Two mechanisms were implicated: (1) advance in male arrival date with age provided middle-aged males with better access to mates. Yearling males arrived later to the breeding grounds and therefore had limited access to high-quality mates. (2) Breeding pairs maintaining bonds for 2 consecutive years (experienced pairs) had higher fecundity than newly formed inexperienced breeding pairs. 6. There was no support for the selection hypothesis because breeding performance was not correlated with life span. 7. We found a within-individual deterioration in breeding and migratory performance (arrival date) in the oldest age-classes consistent with senescence in these reproductive and migratory traits.     

Mechanism of Action and Epitopes of Clostridium difficile Toxin B-neutralizing Antibody Bezlotoxumab Revealed by X-ray Crystallography

The symptoms of Clostridium difficile infections are caused by two exotoxins, TcdA and TcdB, which target host colonocytes by binding to unknown cell surface receptors, at least in part via their combined repetitive oligopeptide (CROP) domains. A combination of the anti-TcdA antibody actoxumab and the anti-TcdB antibody bezlotoxumab is currently under development for the prevention of recurrent C. difficile infections. We demonstrate here through various biophysical approaches that bezlotoxumab binds to specific regions within the N-terminal half of the TcdB CROP domain. Based on this information, we solved the x-ray structure of the N-terminal half of the TcdB CROP domain bound to Fab fragments of bezlotoxumab. The structure reveals that the TcdB CROP domain adopts a β-solenoid fold consisting of long and short repeats and that bezlotoxumab binds to two homologous sites within the CROP domain, partially occluding two of the four putative carbohydrate binding pockets located in TcdB. We also show that bezlotoxumab neutralizes TcdB by blocking binding of TcdB to mammalian cells. Overall, our data are consistent with a model wherein a single molecule of bezlotoxumab neutralizes TcdB by binding via its two Fab regions to two epitopes within the N-terminal half of the TcdB CROP domain, partially blocking the carbohydrate binding pockets of the toxin and preventing toxin binding to host cells.     

Antitumor efficacy,pharmacokinetic and biodistribution studies of the anticancer peptide CIGB‐552 in mouse models

Accumulation of the COMMD1 protein as a druggable pharmacology event to target cancer cells has not been evaluated so far in cancer animal models. We have previously demonstrated that a second‐generation peptide, with cell‐penetrating capacity, termed CIGB‐552, was able to induce apoptosis mediated by stabilization of COMMD1. Here, we explore the antitumor effect by subcutaneous administration of CIGB‐552 in a therapeutic schedule. Outstandingly, a significant delay of tumor growth was observed at 0.2 and 0.7 mg/kg (p < 0.01) or 1.4 mg/kg (p < 0.001) after CIGB‐552 administration in both syngeneic murine tumors and patient‐derived xenograft models. Furthermore, we evidenced that ¹³¹I‐CIGB‐552 peptide was actually accumulated in the tumors after administration by subcutaneous route. A typical serine‐proteases degradation pattern for CIGB‐552 in BALB/c mice serum was identified. Further, biological characterization of the main metabolites of the peptide CIGB‐552 suggests that the cell‐penetrating capacity plays an important role in the cytotoxic activity. This report is the first in describing the antitumor effect induced by systemic administration of a peptide that targets COMMD1 for stabilization. Moreover, our data reinforce the perspectives of CIGB‐552 for cancer targeted therapy. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Symbiotic Association Between Symbiodinium and the Gastropod Strombus gigas: Larval Acquisition of Symbionts

The importance of the dinoflagellate Symbiodinium sp. was studied in the early life stages of the gastropod Strombus gigas. This dinoflagellate was not found in the eggs or the gelatinous mass surrounding the eggs of the mollusk; therefore, Symbiodinium is not inherited directly. To determine whether the planktonic veligers can acquire these algae from the environment, they were exposed to freshly isolated Symbiodinium from adult S. gigas (homologous). The optimal stage for Symbiodinium inoculation was found at 48 h post-hatching. Survival and growth rates of veligers and juveniles were higher when inoculated with freshly isolated Symbiodinium in conjunction with daily feeding of Isochrysis spp. Veligers inoculated with Symbiodinium freshly isolated from three host species elicited distinct responses: (1) veligers did not take up Symbiodinium isolated from the hydrozoan Millepora alcicornis suggesting that there is discrimination on contact prior to ingestion, (2) veligers did take up Symbiodinium isolated from the anemone Bartholomea annulata, but the algae did not persist in the host tissue suggesting that selection against this type took place after ingestion or that the algae did not divide in the host, and (3) veligers did take up Symbiodinium isolated from Pterogorgia anceps where it persisted and was associated with metamorphosis of the larvae. In contrast, the Symbiodinium freshly isolated from S. gigas were not associated with metamorphosis and required an inducer such as the red alga Laurencia poitei. These data present a significant advancement for the establishment of a new approach in the aquaculture of this important but declining Caribbean species.     

The responsiveness of TrkB to BDNF and antidepressant drugs is differentially regulated during mouse development

Background

Previous studies suggest that the responsiveness of TrkB receptor to BDNF is developmentally regulated in rats. Antidepressant drugs (AD) have been shown to increase TrkB signalling in the adult rodent brain, and recent findings implicate a BDNF-independent mechanism behind this phenomenon. When administered during early postnatal life, ADs produce long-lasting biochemical and behavioural alterations that are observed in adult animals.

Methodology

We have here examined the responsiveness of brain TrkB receptors to BDNF and ADs during early postnatal life of mouse, measured as autophosphorylation of TrkB (pTrkB).

Principal Findings

We found that ADs fail to induce TrkB signalling before postnatal day 12 (P12) after which an adult response of TrkB to ADs was observed. Interestingly, there was a temporally inverse correlation between the appearance of the responsiveness of TrkB to systemic ADs and the marked developmental reduction of BDNF-induced TrkB in brain microslices ex vivo. Basal p-TrkB status in the brain of BDNF deficient mice was significantly reduced only during early postnatal period. Enhancing cAMP (cyclic adenosine monophosphate) signalling failed to facilitate TrkB responsiveness to BDNF. Reduced responsiveness of TrkB to BDNF was not produced by the developmental increase in the expression of dominant-negative truncated TrkB.T1 because this reduction was similarly observed in the brain microslices of trkB.T1 ^−/− mice. Moreover, postnatal AD administration produced long-lasting behavioural alterations observable in adult mice, but the responses were different when mice were treated during the time when ADs did not (P4-9) or did (P16-21) activate TrkB.

Conclusions

We have found that ADs induce the activation of TrkB only in mice older than 2 weeks and that responsiveness of brain microslices to BDNF is reduced during the same time period. Exposure to ADs before and after the age when ADs activate TrkB produces differential long-term behavioural responses in adult mice.     

Inferring the skeleton cell cycle regulatory network of malaria parasite using comparative genomic and variational Bayesian approaches

The development of new antimalarial drugs is urgently needed due to elevated drug resistance in the causative agents Plasmodium parasites. An intervention strategy based on the interruption of the parasite cell cycle could be undertaken using a systems-biology aided drug discovery approach. However, little is known about the components or the mechanism of parasite cell cycle control to date. In this proof of concept study, we attempted to infer the skeleton components using comparative genomic analysis and to uncover the genetic regulatory network (GRN) ab initio using a Variational Bayesian expectation maximization (VBEM) approach.     

Anthraquinones from in vitro root culture of <Emphasis Type="Italic">Morinda royoc</Emphasis> L.

Morinda royoc L. (Rubiaceae) root cultures were established for the production of anthraquinones (AQs). Three independent experiments were performed to evaluate the effects of different levels of indole-3-acetic acid (0–22.8 μM), culture duration (15–75 days) and subculture number (0–4). The following indicators were recorded: root fresh weight per Erlenmeyer and intracellular and extracellular AQ production. The experiments performed in this study allowed an increase of intracellular AQ content up to a maximum of 4.5 mg g⁻¹ of fresh mass, after 30 days of culture in a medium 5.7 μM of IAA. In addition, isolation and identification of seven AQs from M. royoc L. roots is described, one of them being reported for the first time for this species. The structures of isolated compounds were determined from ¹H-NMR data. To the best of our knowledge, this is the first report on AQ production from root culture of this plant.     

Severe deficits in 5-HT2A -mediated neurotransmission in BDNF conditional mutant mice

BDNF is thought to provide critical trophic support for serotonin neurons. In order to determine postnatal effects of BDNF on the serotonin system, we examined a line of conditional mutant mice that have normal brain content of BDNF during prenatal development but later depletion of this neurotrophin in the postnatal period. These mice show a behavioral phenotype that suggests serotonin dysregulation. However, as shown here, the presynaptic serotonin system in the adult conditional mutant mice appeared surprisingly normal from histological, biochemical, and electrophysiological perspectives. By contrast, a dramatic and unexpected postsynaptic 5-HT2A deficit in the mutant mice was found. Electrophysiologically, serotonin neurons appeared near normal except, most notably, for an almost complete absence of expected 5-HT2A -mediated glutamate and GABA postsynaptic potentials normally displayed by these neurons. Further analysis showed that BDNF mutants had much reduced 5-HT2A receptor protein in dorsal raphe nucleus and a similar deficit in prefrontal cortex, a region that normally shows a high level of 5-HT2A receptor expression. Recordings in prefrontal slice showed a marked deficit in 5-HT2A -mediated excitatory postsynaptic currents, similar to that seen in the dorsal raphe. These findings suggest that postnatal levels of BDNF play a relatively limited role in maintaining presynaptic aspects of the serotonin system and a much greater role in maintaining postsynaptic 5-HT2A and possibly other receptors than previously suspected.