University of Lethbridge
  • Lethbridge, Alberta, Canada
Recent publications
snR30/U17 is a highly conserved H/ACA RNA that is required for maturation of the small ribosomal subunit in eukaryotes. By base-pairing to the expansion segment 6 (ES6) of 18S ribosomal RNA (rRNA), the snR30 H/ACA Ribonucleoprotein (RNP) indirectly facilitates processing of the precursor rRNA (pre-rRNA) together with other proteins such as Utp23 and other RNAs acting as ribosome assembly factors. However, the details of the molecular interaction network of snR30 and its binding partners and how these interactions contribute to pre-rRNA processing remains unknown. Here, we report the in vitro reconstitution of a Saccharomyces cerevisiae snR30 RNP and quantitative characterization of the interactions of snR30, H/ACA proteins, the Utp23 protein and ES6 of the 18S rRNA. The snR30 RNA is bound tightly by both H/ACA proteins and Utp23. We dissected the importance of different 18S rRNA regions for snR30 RNP binding and demonstrated that the snR30 complex is tightly anchored on the pre-rRNA through base-pairing to ES6 whereas other reported rRNA binding sites do not contribute to the affinity of the snR30 RNP. On its own, the ribosome assembly factor Utp23 binds in a tight, but unspecific manner to RNA. However, in complex with the snR30 RNP, Utp23 increases the affinity of the RNP for rRNA revealing synergies between snR30 RNP and Utp23 which are enhancing specificity and affinity for rRNA, respectively. Together, these findings provide mechanistic insights how the snR30 RNP and Utp23 cooperate to interact tightly and specifically with rRNA during the early stages of ribosome biogenesis.
The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of gravitational waves can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas.
Institutional differences between countries influence strategic choices and performance of international businesses, but the unintended effects of legal institutions on firm legitimacy have received less attention. We argue that, while minority shareholder rights protection in an investment location does not directly protect shareholder interests abroad, the normative and mimetic effects it has on host country managers can mitigate agency problems. Using Japanese FDI established between 1986 and 2013 we find that (a) subsidiaries established in host countries with higher shareholder rights protection employ a smaller proportion of Japanese expatriates, (b) shareholder rights protection enhances a country’s FDI attractiveness, and (c) that the impacts of shareholder rights protection on expatriate ratio and location attractiveness are stronger when firm ownership is concentrated among exchange-listed firms. This research contributes to the literature on institutional difference in international business, in particular by highlighting the value of studying the imprinting effects of regulations.
A weighing matrix W is quasi-balanced if |W||W|⊤=|W|⊤|W| has at most two off-diagonal entries, where |W|ij=|Wij|. A quasi-balanced weighing matrix W signs a strongly regular graph if |W| coincides with its adjacency matrix. Among other things, signed strongly regular graphs and their equivalent association schemes are presented.
Recent reports on tool use in nonforaging contexts have led researchers to reconsider the proximate drivers of instrumental object manipulation. In this study, we explore the physiological and behavioral correlates of two stone‐directed and seemingly playful actions, the repetitive tapping and rubbing of stones onto the genital and inguinal area, respectively, that may have been co‐opted into self‐directed tool‐assisted masturbation in long‐tailed macaques (i.e., “Sex Toy” hypothesis). We predicted that genital and inguinal stone‐tapping and rubbing would be more closely temporally associated with physiological responses (e.g., estrus in females, penile erection in males) and behavior patterns (e.g., sexual mounts and other mating interactions) that are sexually motivated than other stone‐directed play. We also predicted that the stones selected to perform genital and inguinal stone‐tapping and rubbing actions would be less variable in number, size, and texture than the stones typically used during other stone‐directed playful actions. Overall, our data partly supported the “Sex Toy” hypothesis indicating that stone‐directed tapping and rubbing onto the genital and inguinal area are sexually motivated behaviors. Our research suggests that instrumental behaviors of questionably adaptive value may be maintained over evolutionary time through pleasurable/self‐rewarding mechanisms, such as those underlying playful and sexual activities. Genital‐directed stone play actions are sexually motivated in male long‐tailed macaques. Adult females show a higher level of selectivity for the texture of the stones they use to perform genital‐directed stone play. Balinese long‐tailed macaques can use stones as tools to masturbate.
N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone), a rubber tire oxidation product found in road runoff, is highly and acutely toxic to selected salmonids including coho salmon, brook trout, and rainbow trout but not other fish species and invertebrates studied to date. Sensitive species displayed increased ventilation and gasping, suggesting a possible impact on respiration. Here, adherent cell lines RTL-W1 and RTgill-W1 were exposed to 5− 80 μg/L 6PPD-quinone, and cytotoxicity, oxygen consumption rate (OCR), and biotransformation of 6PPD-quinone were measured to assess the ability of 6PPD-quinone to uncouple mitochondrial respiration in vitro. RTL-W1 cells were not sensitive to 6PPD-quinone, and exposure did not result in significant impacts on cytotoxicity or OCR. In contrast, RTgill-W1 cells demonstrated decreased cell viability at 80 μg/L and a 2-fold increase in OCR at 20 μg/L. Effects appear to be partly driven by toxicokinetic differences where incubation of RTL-W1 cells with 6PPD-quinone led to almost quantitative conversion of 6PPD-quinone into a suspected hydroxy-metabolite, which was not observed in RTgill-W1 cells. Exposure studies with primary cultures of rainbow trout gill cells indicated that 6PPD-quinone increased OCR by uncoupling the mitochondrial electron transport chain. Together, these findings suggest that 6PPD-quinone toxicity might be driven by a tissue-specific disruption of mitochondrial respiration.
Inorganic pyrophosphatase (iPPase) is an enzyme that cleaves pyrophosphate into two phosphate molecules. This enzyme is an essential component of in vitro transcription (IVT) reactions for RNA preparation as it prevents pyrophosphate from precipitating with magnesium, ultimately increasing the rate of the IVT reaction. Large-scale RNA production is often required for biochemical and biophysical characterization studies of RNA, therefore requiring large amounts of IVT reagents. Commercially purchased iPPase is often the most expensive component of any IVT reaction. In this paper, we demonstrate that iPPase can be produced in large quantities and of high quality using a reasonably generic laboratory facility and that laboratory-purified iPPase is as effective as commercially available iPPase. Furthermore, using size-exclusion chromatography coupled with multi-angle light scattering and dynamic light scattering (SEC-MALS-DLS), analytical ultracentrifugation (AUC), and small-angle X-ray scattering (SAXS), we demonstrate that yeast iPPase can form tetramers and hexamers in solution as well as the enzymatically active dimer. Our work provides a robust protocol for labs involved with RNA in vitro transcription to efficiently produce active iPPase, significantly reducing the financial strain of large-scale RNA production.
For riparian woodlands, occasional floods provide geomorphic disturbance that creates barren colonization sites, and river stage patterns that enable seedling establishment. To investigate impacts from river damming and instream flow regulation on these processes, we studied the lower Red Deer River in the semi‐arid region of Alberta, Canada. Dickson Dam was implemented in 1983 and although major flood peaks in June 2005 and June 2013 were attenuated by about one‐quarter, substantial seedling establishment of plains cottonwoods (Populus deltoides) was observed. Cross‐sectional transects in 2014 and 2015 revealed the reproductively mature cottonwood band from 2005, while the 2013 colonization was limited to low elevations of 0.3–1.3 m above the base river stage. Seedling numbers and the elevational ranges were probably reduced by abrupt (>4 cm/day) river stage reductions in July 2005 and in July 2013. In addition to direct seedling establishment on barren sandbars, we observed “coupled colonization” with cottonwood recruitment within sparse patches of sandbar willows (Salix exigua). The flood‐tolerant willows stabilize the bars and increase aggradation through sediment trapping. Thus, cottonwood colonization persisted after damming, indicating that the pattern of downstream flow regulation was important, rather than damming per se. To sustain riparian recruitment along regulated rivers in dry regions, we recommend: (1) that floods be allowed as feasible, (2) higher river stages during seed dispersal, (3) flow ramping (gradual summer recession) for seedling survival, (4) sufficient growing season flows to avoid drought‐induced mortality, and (5) that willows be encouraged as well as cottonwoods.
Let k ≥ 2 be an integer and S = {1} ∪ S ′ be a Goldbach-type set such that S ′ ⊆ 2N and {2, 4, 6, 8, 12, 18} ∈ S ′. If a multiplicative function f satisfies f(x_1+x_2+...+x_k)=f(x_1)+f(x_2)+...+f(x_k) for arbitrary x_1,...,x_k∈ S, then f is the identity function f(n)=n for all n∈ N. In particular, the set of practical numbers is a k-additive uniqueness set.
Key message Despite the abundant alluvial groundwater below the floodplain, riparian cottonwoods are limited by water availability during warm and dry periods, as revealed with substantially increased sap flow following flood irrigation. Abstract In dry ecoregions trees are generally restricted to floodplains along perennial streams, where river water recharges the alluvial groundwater, supplementing the sparse local precipitation. Precipitation and river flow often decline through the warm and dry summer and we hypothesized that water availability would become limiting. To test this, we measured sap flow in narrowleaf cottonwoods (Populus angustifolia) along the Oldman River in the semi-arid prairie region of western Canada. After slight rain and river recession through July and August, we provided a flood irrigation treatment to four of eight study trees, which doubled the shallow soil moisture (θg). There were slight increases in dawn (Ψd) and mid-day (Ψmd) leaf water potentials although only temporary differences between the irrigated and non-irrigated trees in Ψd (− 0.4 vs. − 0.6 MPa), Ψmd (− 1.5 vs. − 1.7 MPa) or their difference, ∆Ψ. The daily sap flux density (Fd) was increased by 26% over a 12-day interval after irrigation, revealing increased water use and an upward shift in the association between canopy stomatal conductance (GS) vs. vapour pressure deficit (D). In contrast, Fd in non-irrigated trees declined 15% with the shortening days and aging leaves. The sap flow response contrasts with prior studies, probably due to differences in irrigation volume and timing. Thus, even with abundant groundwater from river infiltration, cottonwood transpiration was limited by water availability in the dry interval of late summer. For the underlying mechanism, we introduce the River Riparian Tree Atmosphere Continuum (RRTAC), which coordinates the system hydrology and water relations.
Early treatment of ischemic stroke is one of the most effective ways to reduce brains’ cell death and promote functional recovery. This study was designed to examine the effect of aerobic exercise on post ischemia/reperfusion injury on concentration and expression of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) after inducing a neuronal loss in CA1 region of hippocampus in Male Wistar rats. Three experimental groups including sham(S), ischemia/reperfusion-control (IRC) and ischemia/reperfusion exercise (IRE) were used for this purpose. The rats in the IRE group received a bilateral carotid artery occlusion treatment. They ran for 45 minutes on a treadmill five days per week for eight consecutive weeks. Cresyl violet (Nissl), Hematoxylin (H & E) and Eosin staining procedure were used to determine the extent of damage. A ladder rung walking task was used to assess the functional impairments and recovery after the ischemic lesion. ELISA and immunohistochemistry method were employed to measure BDNF and VEGF protein expressions. The result showed that the brain ischemia/reperfusion condition increased the cell death in hippocampal CA1 neurons and impaired motor performance on the ladder rung task whereas the aerobic exercise program significantly decreased the brain cell’s death and improved motor skill performance. It was concluded that ischemic brain lesion decreased the BDNF and VEGF expression. It seems that the aerobic exercise following the ischemia/reperfusion potentially promotes neuroprotective mechanisms and neuronal repair and survival mediated partly by BDNF and other pathways.
While the ontogeny of beluga (Delphinapterus leucas) socio-sexual behavior has been documented in animals between 37-and 108-months-old, the first 36 months of life are yet to be examined. This study investigated how socio-sexual behaviors emerge over the first three years of life in a group of belugas in managed care. The emergence of socio-sexual behaviors was relatively consistent among immature animals. More complex behaviors , like s-posture presentations, developed in a piecemeal fashion (i.e., simple components of the behavior sequence emerged before complex components). The presence of an adult male significantly predicted if immature belugas would initiate and participate in socio-sexual behavior. However, partner preferences changed with age. In the first year of life, belugas engaged in sexual behavior with their mother most frequently but preferred to play with older males if given a choice. By the third year of life, belugas engaged in socio-sexual behavior most frequently with other immature animals. These findings enhance our understanding of how be-lugas develop sexually and socially and have implications for social housing practices of immature belugas.
Peatlands have acted as net CO2 sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2 sink function. Here we show that sensitivity of peatland net CO2 exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2 sink responses. We use multiannual net CO2 exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2 uptake, while warmer late summers lead to decreased net CO2 uptake. Thus, net CO2 sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2 uptake over the coming few decades.
Using the theoretical constructs of double instrumental genesis and instrumental distance, in this article, I examine case studies of four primary school teachers (K–5) in British Columbia, Canada, who implemented the multi-touch, iPad application TouchTimes (hereafter, TT) into their mathematics teaching. This novel digital technology provides embodied and relational experiences of multiplication through two different dynamic multiplicative models. In interviews, these teachers shared their personal experiences learning about this relatively new digital application themselves, the obstacles they encountered and their experiences integrating TT into their instructional repertoires as a tool for student learning. My aim was to identify specific episodes in which transitions occurred during the implementation of technology-enhanced mathematics lessons and to highlight how instrumental distance influenced the teachers’ professional instrumental genesis. These episodes focus on (1) the internal shifts in thinking that the teachers experience personally and professionally while undergoing double instrumental genesis; (2) transitions across the two different microworlds that comprise TT, and the different multiplicative models portrayed by each of them; and (3) transitioning beyond the dynamic multiplicative models portrayed by TT towards mathematical activities with a static medium. My analysis indicates that these transitions are multi-faceted and complex, that the personal and professional instrumental geneses that teachers undergo may be closely intertwined and that, when speaking of TT, they clearly differentiate between ways of teaching with it and how students may learn using this technology.
Animals often differ in their responses towards novelty, and sometimes these differences are consistent across individuals. Here, we explored interindividual variation in neophilia towards novel foods by recording whether animals ingested novel food stuffs (Nindividuals = 116; Ntrials = 276) in three troops of wild vervet monkeys. We tested for the effects of individual level variables, between-individual variation (i.e. personality), within-individual variation (i.e. plasticity) and variation in testing conditions (e.g. ecological conditions, proximate social environment). We found that our animals showed consistent differences towards eating novel foods, with lower-ranking animals displaying a more neophilic response than higher-ranking animals, and that neophilia was socially facilitated. Social facilitation did not depend on whether the partner was foraging, the social association between the focal and their partner or relatedness, indicating that the mere presence of another increased the likelihood that animals would eat the novel food. We also found some evidence that animals responded differentially to variation in their proximate social environment, as some, but not all, animals were more likely to eat the novel food as the number of partners increased, whereas others were not. Our results underscore the importance of testing behaviour and cognition under natural conditions rather than always doing so under strictly controlled settings and controlling for possible confounding factors statistically rather than controlling the testing conditions themselves.
Many of the bacterial strains found in the mammalian gut are difficult to culture and isolate due to their various growth and nutrient requirements that are frequently unknown. Here, we assembled strain-level genomes from short metagenomic sequences, so-called metagenome-assembled genomes (MAGs), that were derived from fecal samples collected from pigs at multiple time points.
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2,740 members
Cheryl L Currie
  • Faculty of Health Sciences
Darren R Christensen
  • Faculty of Health Sciences
Narendra Singh Yadav
  • Department of Biological Sciences
Laura Chasmer
  • Department of Geography
John Vokey
  • Department of Psychology
4401 University Drive, T1K 3M4, Lethbridge, Alberta, Canada
Head of institution
Dr. Michael J. Mahon
(403) 329-2111