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Androgen synthesis inhibition increases behavioural flexibility and mPFC tyrosine hydroxylase in gonadectomized male rats
No full textBehavioural flexibility is essential to adapt to a changing environment and depends on the medial prefrontal cortex (mPFC). Testosterone administration decreases behavioural flexibility. It is well known that testosterone is produced in the gonads, but testosterone is also produced in the brain, including the mPFC and other nodes of the mesocorticolimbic system. It is unclear how testosterone produced in the brain versus the gonads influences behavioural flexibility. Here, in adult male rats, we assessed the effects of the androgen synthesis inhibitor abiraterone acetate (ABI) and long-term gonadectomy (GDX) on behavioural flexibility in two paradigms. In Experiment 1, ABI but not GDX reduced the number of errors to criterion and perseverative errors in a strategy set-shifting task. In Experiment 2, with a separate cohort of rats, ABI but not GDX reduced perseverative errors in a reversal learning task. In Experiment 1, we also examined tyrosine hydroxylase immunoreactivity (TH-ir), and ABI but not GDX increased TH-ir in the mPFC. Our findings suggest that neurally-produced androgens modulate behavioural flexibility via modification of dopamine signalling in the mesocorticolimbic system. These results indicate that neurosteroids regulate executive functions and that ABI treatment for prostate cancer might affect cognition
Hippocampal neurogenesis promotes effortful responding but does not regulate effort‐based choice
No full textA fundamental trait of depression is low motivation. Hippocampal neurogenesis has been associated with motivational deficits but detailed evidence on how it regulates human-relevant behavioral traits is still missing. We used the hGFAP-TK rat model to deplete actively dividing neural stem cells in the rat hippocampus. Use of the effort-discounting operant task allowed us to identify specific and detailed deficits in motivation behavior. In this task, rats are given a choice between small and large food rewards, where 2–20 lever presses are required to obtain the large reward (four sugar pellets) versus one press to receive the smaller reward (two sugar pellets). We found that depleting adult neurogenesis did not affect effort-based choice or general motivation to complete the task. However, lack of adult neurogenesis reduced the pressing rate and thus increased time to complete the required presses to obtain a reward. In summary, the present study finds that adult hippocampal neurogenesis specifically reduces response vigor to obtain rewards and thus deepens our understanding in how neurogenesis shapes depression
Ocean acidification alters anti-predator responses in a competitive dominant intertidal mussel
No full textWidespread intertidal mussels are exposed to a variety of natural and anthropogenic stressors. Even so, our understanding of the combined influence of stressors such as predation risk and ocean acidification (OA) on these species remains limited. This study examined the response of the purple mussel (Perumytilus purpuratus), a species distributed along Pacific southeastern rocky shores, to the effects of predation risk and OA. Using a laboratory 2 × 2 cross design, purple mussels were either devoid or exposed to predator cues from the muricid snail Acanthina monodon, while simultaneously exposing them to current (500 ppm) or projected OA conditions (1500 ppm). The response of purple mussels to these factors was assessed using growth, calcification, clearance, and metabolic rates, in addition to byssus production. After 60 d, the presence of predator cues reduced mussel growth in width and length, and in the latter case, OA enhanced this response making the effects of predator cues more severe. Calcification rates were driven by the interaction between the two stressors, whereas clearance rates increased only in response to OA, likely explaining some of the growth results. Mussel byssus production also increased with pCO2 but interacted with predation risk: in the absence of predator cues, byssus production increased with OA. These results suggest that projected levels of OA may alter and in some cases prevail over the natural response of purple mussels to predation risk. Considering the role played by this mussel as a dominant competitor and ecosystem engineer in rocky shores, these results have community-wide implications
Density topologies and the marginal strong lifting problem for hyperstonian spaces
No full textWe investigate properties of density topologies and of topological measure spaces whose topologies are density topologies, motivated by the search for necessary as well as sufficient conditions for the canonical strong lifting of a hyperstonian space to be a marginal. For topological probability spaces we establish relations between the existence of strong liftings and the marginal property of the canonical strong lifting of their hyperstonian space, building on earlier work
Colostrum management practices that improve the transfer of passive immunity in neonatal dairy calves: A scoping review
No full textThe objective of this scoping review was to describe the literature on the characteristics and management practices of colostrum feeding and their associations with the level of transfer of passive immunity (TPI) in dairy calves. Observational and experimental studies were searched in 5 electronic databases and 3 conference proceedings. Two reviewers independently screened primary studies, either analytic observational or experimental studies written in English. Studies on dairy or dual-purpose calves with passive immunity analyzed by blood sampling between 1 to 9 days of age were included. All studies had to compare at least one colostrum intervention or risk factor and their association with passive immunity. Of the 3,675 initially identified studies, 256 were included in this synthesis. One hundred and ninety-five were controlled trials, 57 were cohort studies, and 4 were cross-sectional studies. The effect of colostral quantity at first feeding was investigated in 30 controlled studies including studies that were comparable to each other. The effect of colostral quality was explored in 24 controlled studies with inconsistent criteria used to define the quality. The effect of the timing of first feeding of colostrum was investigated in 21 controlled studies, where the timing of feeding ranged widely from immediately after birth to 60 h of age. Only 4 controlled studies evaluated the relationship between bacterial load in the colostrum and TPI in dairy calves. Of the 256 total studies, 222 assessed blood IgG concentration while 107 measured blood total protein concentration. We identified a gap in knowledge on the association between passive immunity in dairy calves and the bacterial load in colostrum, or the timing of harvesting colostrum from the dam. A possible quantitative synthesis could be conducted among the studies that evaluated colostral quantity at the first feeding in relation to TPI in dairy calves
Recent advances in algae-derived biofuels and bioactive compounds
No full textOwing to the declining reserve of fossil resources as well as more concerns on climate change, and essential energy security, and especially the broad consensus on carbon neutralization, it is significantly critical to develop renewable and sustainable energy and chemicals. Algae as alternative resources can be applied to produce biofuels and biochemicals. Among them, algae-derived natural pigments exhibit high market value due to their uses in pharmaceutical and food industries. As a result of the developments of engineering tools, it is feasible to scale up algal processing and applications. Prior to the industrial implementation, life cycle assessment is required to ensure the environmental feasibility of algae-based biofuels and biochemicals. In this article, recent advances in processing algae for liquid, gas, and solid fuels are reviewed. New approaches for enhancing the natural pigment accumulation are also discussed. Recent studies on life cycle assessment of algae-based biofuels and biochemicals, as well as the main challenges faced by the algal biorefinery, are discussed in this manuscript.Natural Sciences and Engineering Research Council of Canada (NSERC)University of Prince Edward Island (UPEI
Portfolio optimization under multivariate affine generalized hyperbolic distributions
No full textThis paper focuses on capturing the impacts of leptokurtic phenomenon and heterogeneous preferences in higher moments on asset allocation. To achieve this, we propose a utility maximization asset allocation framework under the multivariate affine generalized hyperbolic (MAGH) asset prices dynamics. With the investor’s preference given by the exponential utility, we derive the closed-form optimal asset allocations for mixed multivariate affine normal inverse Gaussian-normal model and mixed multivariate affine variance gamma-normal model, which covers Markowitz’s mean–variance model as our special case. Extensive empirical studies are conducted to assess the effectiveness of the proposed asset allocation models relative to other portfolio strategies based on the Markowitz’s mean–variance theory and the equally weighted rule. Using the out-of-sample Sharpe ratio, the certainty-equivalent return, quantile and tail metrics as the performance measures, the proposed methods are found to be very effective and robust.
