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Effect of sucrose reinforcement on operant wheel running on a fixed ratio schedule
Full text linkIn the current study, I investigated the effect of sucrose reinforcement on operant wheel running
on a fixed ratio (FR) schedule. Rats responded on a FR-40 schedule in which wheel-running produced the opportunity to consume sucrose solution. Sucrose reinforcement was removed after 25 sessions and rats were returned to baseline (water). Based on the traditional concept of reinforcement, wheel-running rates were expected to increase close in time before sucrose reinforcement was delivered. Alternatively, there
could be a marked increase in running at the beginning due to a schedule-induced effect of sucrose presentation. Results were not consistent with either prediction. Sucrose reinforcement systematically increased running over the entire 40 revolutions. Possible explanations for this extended reinforcement effect are that wheel running, unlike other operant behaviors, such as lever pressing, generates its own automatic reinforcement effect and is a continuous, rather than a discrete, behavior. Further research is required to explore these aspects of wheel running
The short-term cold storage of blue tilapie (Oreochromis aureus) spermatozoa in HBSS
Full text linkSpermatozoa are an essential part of fertilization in sexual reproduction. Sperm are commonly collected for in vitro fertilization, quality assessment, and research purposes. Sperm cells have incredibly short lifespans which make it difficult for use in aquaculture management and in research. For that reason, it is essential to develop methods for optimal short-term storage of semen. Short-term storage of semen involves temporary cooling of sperm cells (>0 oC), which reduces the metabolic rate and thus extends the lifespan of the cell. That being said, sperm are vulnerable to desiccation as they are highly packed in seminal plasma. Diluents function to reduce the potential for dehydration and decrease sperm density while preventing activation. Extenders are added to semen to mitigate sperm cell damage when stored in cooler temperatures while supplying nutrients to the cells. This is particularly important for work on external fertilizing freshwater fish. Fortunately, there are a variety of diluents and extenders that have already been developed and tested on a variety of freshwater fish species. There has been no work currently done on Blue Tilapia (Oreochromis aureus) in this area. Blue Tilapia are a very important fish for aquaculture and in our lab. The goal of my honours research is to fill this gap and determine if we can successfully store Blue Tilapia semen. I collected semen samples from Blue Tilapia males, diluted it with HBSS, and left samples in the fridge for varying amounts of time. I then examined the effects of the length time in the fridge on sperm percent motility, and swimming velocity. I found that the velocity of spermatozoa of Tilapia in HBSS is not impacted by time in the fridge up to 18 hours. This work opens the door for further research on reproductive biology of Blue Tilapia and improved use for aquaculture and conservation purposes
Induced gold nanoparticle adsorption to oil/water interfaces
Full text linkThe formation of AuNP monolayers and the self-assembly of functionalized AuNPs are important fields of study in multiple disciplines. Using thermodynamic models for the prediction of whether adsorption will occur is a potential path to identifying favourable systems quickly; however, these models require testing to determine whether they have applicability beyond the scope of the study for which they were created. A thermodynamic model is identified and used to screen oils for use in PEGylated-AuNP adsorption experiments. 1-Butanol was selected as the best candidate because of its good modelling results and positive initial performance, attributed to its low interfacial tension with water. Carboxylic acid-functionalized PEGylated AuNPs with 5 nm and 13 nm core sizes were synthesized and tested with different concentrations of NaCl at different pHs to determine where adsorption to the interface was possible. AuNP films from systems comprised of NaCl concentrations of 0.1 M and 0.5 M at pH values of 4 and 8 were selected for study using atomic force microscopy. The results showed that the pH 8 systems at both NaCl concentrations formed monolayers at the interface. To determine whether the packing density of these monolayers could be manipulated, compression using a Langmuir-Blodgett balance was performed, which indicated Gibbs monolayers were being formed and the packing density could not be manipulated through compression
Measuring the binding constant for gold nanospheres to synthetic phospholipid membranes
Full text linkAge-related differences in spatial processing
Full text linkAssociative memory, especially episodic memory, declines in old age—an effect ascribed to age-related decline in the hippocampus. The hippocampus also supports some form of spatial processing, and some have suggested that the decline of spatial processing as early as perception could underly episodic memory deficits. However, to date, no one has investigated spatial processing in older adulthood without the confound of long-term memory demands. I therefore examined age-related differences in spatial perception by having 29 participants complete a novel spatial task that minimized memory demands. The sample comprised 15 younger adults (Mage = 25; SD = 5.75) and 14 older adults (Mage = 64; SD = 3.77). Participants compared screenshots of 3D virtual rooms to simultaneously presented 2D room layouts and indicated whether the rooms were identical or not. My results indicated no age-related difference in accuracy scores on either location or object-based trials. However, older adults spent significantly longer on location-based trials than younger adults did. These results suggest that healthy older adults exhibit subtle age-related deficits in spatial processing, even at perception. My findings support theories proposing that an age-related deficit in spatial processing may cause episodic memory problems in older adults
Intracellular taurine deficiency impairs cardiac contractility in rainbow trout (Oncorhynchus mykiss) without affecting aerobic performance
Full text linkTaurine is a non-proteinogenic sulfonic acid found in high concentrations inside vertebrate cardiomyocytes and its movement across the sarcolemmal membrane is critical for cell volume regulation. Taurine deficiency is rare in mammals, where it impairs cardiac contractility and leads to congestive heart failure. In fish, cardiac taurine levels vary substantially between species and can decrease by up to 60% in response to environmental change but its contribution to cardiac function is understudied. We addressed this gap in knowledge by generating a taurine-deficient rainbow trout (Oncorhynchus mykiss) model using a feed enriched with 3% β-alanine to inhibit cellular taurine uptake. Cardiac taurine was reduced by 17% after 4 weeks with no effect on growth or condition factor. Taurine deficiency did not affect routine or maximum rates of O2 consumption, aerobic scope, or critical swimming speed in whole animals but cardiac contractility was significantly impaired. In isometrically contracting ventricular strip preparations, the force–frequency and extracellular Ca2+-sensitivity relationships were both shifted downward and maximum pacing frequency was significantly lower in β-alanine fed trout. Cardiac taurine deficiency reduces sarcoplasmic reticular Ca2+-ATPase activity in mammals and our results are consistent with such an effect in rainbow trout. Our data indicate that intracellular taurine contributes to the regulation of cardiac contractility in rainbow trout. Aerobic performance was unaffected in β-alanine-fed animals, but further study is needed to determine if more significant natural reductions in taurine may constrain performance under certain environmental conditions.type of work: Research Articlepublication status: Accepted for PublicationThis version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s00360-021-01407-
Connecting antioxidant depletion and reactive oxygen species production by aerosol-borne quinones
Full text linkExposure to particulate matter (PM) is known to induce oxidative stress. In particular, quinones, a class of chemical compounds found in PM, are known to induce oxidative stress via redox cycling where the quinone can catalyze reactions that deplete antioxidants and produce oxidants. The first objective of this study is to determine if the rate of antioxidant depletion and oxidant production correspond for a number of quinones. Given that quinones can have different numbers of benzene rings and hydroxyl (OH) groups (due to atmospheric oxidation), the second objective of the study is to determine the effect of functional groups on the ability of quinones to deplete antioxidants and produce oxidants. To answer these questions, the dithiothreitol (DTT) assay and 2’-7’-dichlorofluorescein. (DCFH) assay were performed on three series of homologous quinones (1, 2, and 3 benzene rings) with increasing OH functionality. The DTT and DCFH assays measure the rate of antioxidant decay (represented by DTT decay) and rate of oxidant production (specifically H2O2 production), respectively. Out of all the quinones tested, HNQ had the fastest second order DTT decay rate constant, followed by 5,8-HNQ, NQ and BQ, respectively. Where 5,8-HNQ had the fastest second order H2O2 production rate constant followed by HNQ, NQ and lastly, BQ did not significantly produce any H2O2. Overall, it was found that the rate of DTT decay and H2O2 production do not correspond for all quinones, and that characterizing both the potential to deplete antioxidant and produce oxidants are required towards accurately representing the potential toxicity of aerosol due to induction of oxidative stress. Using Density Function Theory (DFT) it was found that semiquinone radicals can also undergo subsequent protonation and reduction reactions. These reactions are predicted to affect the overall observed rates of both DTT decay and H2O2 production based on calculated ΔGred values. It has also been predicted that BQ undergoes a reductive addition reaction with DTT instead of forming a semiquinone. This mechanism could explain the significant reduction of DTT but no production of H2O2
Narrative analysis of experiences accessing care for long COVID in Canada
Full text linkThis study explored experiences seeking care for long COVID in the Canadian healthcare system. We randomly sampled participants who completed a Canada-wide survey study on long COVID and conducted eight interviews. Participants varied broadly in age, were mostly female (75%), and lived in five different provinces. Through narrative analysis of these interviews, we identified five narratives: (1)situation: this has…, (2) identity: I am…, (3) personal capacity: I can…, (4) system capacity: I think the system…, and (5) work: (when) I tried… Collectively these narratives describe the complex care seeking experience of participants in this study. To make system-level improvements to a healthcare system built for acute illnesses, it is pivotal that we understand the care seeking experiences of chronic illness patients, including the unique experiences of those with long COVID
Exploring the effects of size and age on vulnerability to predation of larval zebrafish (Danio rerio)
Full text linkPredation is a leading cause of mortality in the yolk sac larval stage of teleost fish. Size and age are known to impact larval vulnerability to predation, but how they do so have been debated. The bigger-is-better hypothesis that proposed large larvae have fitness advantages over their smaller counterparts has come under scrutiny as most studies that support this hypothesis only consider proxies for probability of capture. A less explored hypothesis suggests that the benefits of size vary with each day, where it could be beneficial to be small or large depending on external conditions. This study seeks to expand on this hypothesis by exploring the effects of size and age on proxies of probability of encounter and probability of capture during the yolk sac stage of zebrafish larvae (Danio rerio). Direct yolk sac manipulation attempted to create larvae of distinct size groups at hatch, but it was found unsuccessful as the control and reduction groups were not significantly different at hatch (p = 0.878). Instead, larvae were split into large and small groups from the top and bottom 25% from standard length that varied in size from 8 to 22. Probability of encounter was estimated from free swimming trials which measured distance travelled (mm) and mean velocity (mm/s). Probability of encounter was estimated from escape response experiments, where larvae experienced a tactile stimulation. It was found that large larvae moved significantly further distances on day 4 (p = 0.00835), and significantly faster on day 3 (p = 0.00813). Escape response was measured as distance travelled (mm), mean velocity (mm/s), max acceleration (mm2/s), and latency to respond. It was found that small larvae travelled significantly further on day 2 (p = 0.00216), but large larvae responded quicker to a threat than small larvae on day 2 (p = 0.00399). The estimates of probability of encounter and probability of capture in this study do not indicate that age or size effect the vulnerability to predation of yolk sac zebrafish larvae. This suggests small larvae are not at a fitness disadvantage to large cohort members, potentially providing the beginning steps to a counter argument of the bigger-is-better hypothesis
Individual and organizational predictors of employee well-being during the fourth wave of the COVID-19 pandemic
Full text linkThe COVID-19 pandemic introduced work-from-home mandates that sent many employees into remote work environments for the first time (Richter, 2020). This transition was suggested to impact the psychological well-being of employees. (Villani et al., 2021). Thus, appropriate organizational features must be implemented as a means of maintaining employee well-being (Azizi et al., 2021). The present study examined the impact of organizational variables including Perceived Organizational Support, Perceived Job Insecurity, and individual variables including Locus of Control on the psychological well-being of employees working from home during the COVID-19 pandemic. A sample of 165 remote employees from the Canadian labour force participated, in which the participants’ mean age was 44.40 (SD = 13.34). Participation occurred online through the LimeSurvey platform. The results indicated that perceived organizational support, perceived job insecurity, and locus of control were significant predictors of employee well-being. In addition, the amount of time spent working from home and aspects of the work-from-home environment were also found to influence well-being. As such, organizational features surrounding increased support and security, individual features such as locus of control, and situational features including work area should be considered in the development of organizational resources for employee well-being, especially within the context of the COVID-19 pandemic