Find research datasets worth reusing

Data from: The secret life of ground squirrels: accelerometry reveals sex-dependent plasticity in above-ground activity

The sexes differ in how and when they allocate energy towards reproduction, but how this influences phenotypic plasticity in daily activity patterns is unclear. Here, we use collar-mounted light loggers and triaxial accelerometers to examine factors that affect time spent above ground and overall dynamic body acceleration (ODBA), an index of activity-specific energy expenditure, across the active season of free-living, semi-fossorial arctic ground squirrels (Urocitellus parryii). We found high day-to-day variability in time spent above ground and ODBA with most of the variance explained by environmental conditions known to affect thermal exchange. In both years, females spent more time below ground compared with males during parturition and early lactation; however, this difference was fourfold larger in the second year, possibly, because females were in better body condition. Daily ODBA positively correlated with time spent above ground in both sexes, but females were more active per unit time above ground. Consequently, daily ODBA did not differ between the sexes when females were early in lactation, even though females were above ground three to six fewer hours each day. Further, on top of having the additional burden of milk production, ODBA data indicate females also had fragmented rest patterns and were more active during late lactation. Our results indicate that sex differences in reproductive requirements can have a substantial influence on activity patterns, but the size of this effect may be dependent on capital resources accrued during gestation.

opencc-zeroDec 2016View details →

Data from: 8-year trends in physical activity, nutrition, TV viewing time, smoking, alcohol and BMI: a comparison of younger and older Queensland adults

Lifestyle behaviours significantly contribute to high levels of chronic disease in older adults. The aims of the study were to compare the prevalence and the prevalence trends of health behaviours (physical activity, fruit and vegetable consumption, fast food consumption, TV viewing, smoking and alcohol consumption), BMI and a summary health behaviour indicator score in older (65+ years) versus younger adults (18-65 years). The self-report outcomes were assessed through the Queensland Social Survey annually between 2007-2014 (n=12,552). Regression analyses were conducted to compare the proportion of older versus younger adults engaging in health behaviours and of healthy weight in all years combined and examine trends in the proportion of younger and older adults engaging in health behaviours and of healthy weight over time. Older adults were more likely to meet recommended intakes of fruit and vegetable (OR=1.43, 95%CI=1.23-1.67), not consume fast food (OR=2.54, 95%CI=2.25-2.86) and be non-smokers (OR=3.02, 95%CI=2.53-3.60) in comparison to younger adults. Conversely, older adults were less likely to meet the physical activity recommendations (OR=0.86, 95%CI= 0.78-0.95) and watch less than 14 hours of TV per week (OR=0.65, 95%CI=0.58-0.74). Overall, older adults were more likely to report engaging in 3, or at least 4 out of 5 healthy behaviours. The proportion of both older and younger adults meeting the physical activity recommendations (OR=0.97, 95%CI=0.95-0.98 and OR=0.94, 95%CI=0.91-0.97 respectively), watching less than 14 hours of TV per week (OR=0.96, 95%CI=0.94-0.99 and OR=0.94, 95%CI=0.90-0.99 respectively) and who were a healthy weight (OR=0.95, 95%CI=0.92-0.99 and OR=0.96, 95%CI=0.94-0.98 respectively) decreased over time. The proportion of older adults meeting the fruit and vegetable recommendations (OR=0.90, 95%CI=0.84-0.96) and not consuming fast food (OR=0.94, 95%CI=0.88-0.99) decreased over time. Although older adults meet more health behaviours than younger adults, the decreasing prevalence of healthy nutrition behaviours in this age group needs to be addressed.

opencc-zeroDec 2018View details →

Data from: Wildfire activity and land use drove 20th-century changes in forest cover in the Colorado front range

Recent shifts in global forest area highlight the importance of understanding the causes and consequences of forest change. To examine the influence of several potential drivers of forest cover change, we used supervised classifications of historical (1938–1940) and contemporary (2015) aerial imagery covering a 2932‐km2 study area in the northern Front Range (NFR) of Colorado and we linked observed changes in forest cover with abiotic factors, land use, and fire history. Forest cover in the NFR demonstrated broad‐scale changes 1938–2015 and overall cover increased 7.8%, but there was notable spatial variability and many sites also experienced Forest Loss. Recent (1978–2015) wildfire was the largest single driver of Forest Loss, with fires burning 14.3% of the total study area. Recently burned areas showed net losses of 36.9% forest cover. Reasons for Forest Gain were more complex, with elevation, past mining density, fire history, and topographic heat load index being the strongest predictors of increases in forest cover. Historical mining activity is one of the dominant anthropogenic impacts in ecosystems in the NFR and it had a complex, non‐linear relationship with 20th‐century changes in forest cover. Subalpine stands originating after stand‐replacing fires circa mid‐1800s to early 1900s showed some of the greatest gains in forest cover, indicative of slow and continuous post‐fire recovery through the 20th century. We also investigated factors such as land ownership, road density, forest management activities, and development intensity, which played detectable, but more minor roles in observed change. Twentieth‐century changes in forest cover throughout the NFR are a result of ecological disturbances and anthropogenic influences operating at varying timescales and overlaid upon variability in the abiotic environment.

opencc-zeroDec 2018View details →

Data from: Earthworm activity and availability for meadow birds is restricted in intensively managed grasslands

1. Earthworms are an important prey for the endangered meadow birds of north-west Europe. Although intensive grassland management with high manure inputs generally promotes earthworm abundance, it may reduce the effective food availability for meadow birds through desiccation of the topsoil, which causes earthworms to remain deeper in the soil. 2. We studied the response of Red Worm Lumbricus rubellus, a detritivore, and Grey Worm Aporrectodea caliginosa, a geophage, to soil moisture profiles in the field and under experimental conditions. Surfacing earthworms were counted weekly in eight intensively managed grasslands (treated with high inputs of slurry by slit injection) with variable groundwater tables in the Netherlands. At each count, soil penetration resistance, soil moisture tension and groundwater level were measured, while air temperature and humidity were obtained from a nearby weather station. The response to variation in the vertical distribution of soil moisture was also experimentally studied in the two earthworm species. 3. In the field, earthworms' surfacing activity at night was negatively associated with soil moisture tension and positively by relative air humidity. Surprisingly, there was no effect of groundwater level; an important management variable in meadow bird conservation. Under experimental conditions, both L. rubellus and A. caliginosa moved to deeper soil layers (>20 cm) in drier soil moisture treatments, avoiding the upper layer when moisture levels dropped below 30%. 4. Synthesis and applications. We propose that in intensively managed grasslands with slurry application, topsoil desiccation reduces earthworm availability for meadow birds. This can be counteracted by keeping soil moisture tensions of the top soil above -15 kPa. We suggest that the late raising of groundwater tables in spring and the disturbance of the soil by slit injection of slurry increase topsoil desiccation. This decreases earthworm availability when it matters most for breeding meadow birds. Meadow bird conservation will benefit from revised manure application strategies that promote earthworm activity near or at the soil surface.

opencc-zeroDec 2014View details →

Data from: Cruzipain activates latent TGF-β from host cells during T. cruzi invasion

Several studies indicate that the activity of cruzipain, the main lysosomal cysteine peptidase of Trypanosoma cruzi, contributes to parasite infectivity. In addition, the parasitic invasion process of mammalian host cells is described to be dependent on the activation of the host TGF-β signaling pathway by T. cruzi. Here, we tested the hypothesis that cruzipain could be an important activator of latent TGF-β and thereby trigger TGF-β-mediated events crucial for the development of Chagas disease. We found that live epimastigotes of T. cruzi, parasite lysates and purified cruzipain were able to activate latent TGF-β in vitro. This activation could be inhibited by the cysteine peptidase inhibitor Z-Phe-Ala-FMK. Moreover, transfected parasites overexpressing chagasin, a potent endogenous cruzipain inhibitor, prevented latent TGF-β activation. We also observed that T. cruzi invasion, as well as parasite intracellular growth, were inhibited by the administration of Z-Phe-Ala-FMK or anti-TGF-β neutralizing antibody to Vero cell cultures. We further demonstrated that addition of purified cruzipain enhanced the invasive activity of trypomastigotes and that this effect could be completely inhibited by addition of a neutralizing anti-TGF-β antibody. Taken together, these results demonstrate that the activities of cruzipain and TGF-β in the process of cell invasion are functionally linked. Our data suggest that cruzipain inhibition is an interesting chemotherapeutic approach for Chagas disease not only because of its trypanocidal activity, but also due to the inhibitory effect on TGF-β activation.

Data from: Density-dependent diel activity in stream-dwelling Arctic charr Salvelinus alpinus

Intraspecific competition plays a significant role in shaping how animals use and share habitats in space and time. However, the way individuals may modify their diel activity in response to increased competition has received limited attention. We used juvenile (age 1+) Arctic charr Salvelinus alpinus to test the prediction that individuals at high population density are more active and distribute their foraging activity over a greater portion of the 24-h cycle than individuals at low population density. Individually tagged fish were stocked in seminatural stream enclosures at low (2 fish/m2) and high (6 fish/m2) density. During each of two 2-week experimental rounds, activity of all fish within each enclosure was recorded every 3 h over seven 24-h cycles. At high density, fish were more active and distributed their activity over a greater portion of the 24-h cycle, with increased activity particularly at crepuscular times. Fluctuations in ecological conditions (e.g., water temperature and light intensity) also affected activity. Fish at high density grew as fast as fish at low density. This study demonstrates that individuals exhibit a degree of behavioral flexibility in their response to changes in ecological conditions and suggests that intraspecific competition can cause animals to modify temporal aspects of their activity to gain access to resources and maintain growth.

opencc-zeroDec 2016View details →

Data from: Salinity-induced phenotypic plasticity in threespine stickleback sperm activation

Phenotypic expression may be and often is influenced by an organism's developmental environment, referred to as phenotypic plasticity. The sperm cells of teleosts have been found to be inactive in the seminal plasma and are activated by osmotic shock for most fish species, through release in either hypertonic (for marine fish) or hypotonic (for freshwater fish) water. If this is the case, the regulatory system of sperm mobility should be reversed in salt and freshwater fish. We tested this hypothesis by first activating sperm of saltwater and freshwater populations of threespine stickleback in salt- and fresh water. The sperm from saltwater stickleback could be activated in either salinity, which matches the freshwater colonization history of the species, whereas the sperm from the freshwater population acted as predicted by the osmotic shock theory and was activated in freshwater only. As the freshwater population used here was calculated to be thousands of years old, we went on to test whether the trait(s) were plastic and sperm from freshwater males still could be activated in saltwater after individuals were exposed to saltwater. After raising freshwater stickleback in saltwater we found the mature males to have active sperm in both salt and freshwater. Further, we also found the sperm of wild-caught freshwater stickleback to be active in saltwater after exposing those mature males to saltwater for only two days. This illustrates that the ability for stickleback sperm to be activated in a range of water qualities is an environmentally induced plastic trait.

opencc-zeroOct 2019View details →

Data from: Modelling misclassification in multi-species acoustic data when estimating occupancy and relative activity

<p>1. Surveying wildlife communities provides data for informing conservation and management decisions that affect multiple species. Autonomous recording units (ARUs) can efficiently gather community data for a variety of taxa, but generally require software algorithms to classify each recorded call to a species. Species classification errors are possible during this process and result in both false negative and false positive detections. Available approaches for analysing ARU data do not model the species classification probabilities, meaning erroneous detections are attributed to an omnibus source instead of the presence of another species. Additionally, counts of call recordings for each species are often summarized to binary detection data for analyses. Expanding statistical models to capture these nuances of ARU data would allow for improved inferences about occupancy and relative activity. 2. Motivated by bat acoustic surveys, we developed a model to analyse counts of call recordings from multiple species simultaneously while accounting for species classification errors. Our model expands on previously developed false positive occupancy models to better describe acoustic data. We used simulations to compare our model to other false positive occupancy models for an example scenario with ARU data from two species. We also analyse acoustic data for eight bat species in Montana using our model. 3. In simulations, single-species models resulted in biased estimates of occupancy and relative activity because they failed to associate false positives with the presence of the second species. Models analysing binary observations ignored available information on relative activity and led to less precise estimates. Applying our model to bat acoustic data from Montana allowed for species-specific estimates of occupancy and relative activity. This analysis illustrates the flexibility in our model framework while also highlighting the assumptions and data requirements for implementation. Specifically, additional information on the species classification probabilities is needed and we discuss considerations for reliably estimating these parameters. 4. Directly modelling the species classification probabilities allows for improved ecological inferences for both occupancy and relative activity using community ARU data. Our statistical framework helps address the challenges posed by acoustic data, allowing ecologists to better utilize this technology to monitor wildlife communities.</p>

opencc-zeroDec 2018View details →

Data from: Local and landscape-scale heterogeneity shape spotted wing drosophila (Drosophila suzukii) activity and natural enemy abundance: implications for trophic interactions

Like natural enemies, invasive polyphagous pests may respond positively to local and landscape-scale diversity, making them more serious challenges to sustainable management than specialists. Yet the current view of landscape effects on pests rarely considers perennial systems or polyphagous pests. We investigated Drosophila suzukii (SWD) and natural enemy distributions and trophic interactions in blueberry systems of the southeast US in relation to local management and landscape structure. Fields were nested in 1-km landscapes along gradients of crop and forest heterogeneity (landscape compositional diversity) and field border and crop border lengths (landscape configurational diversity). Yeast-sugar bait traps were used to collect SWD and canopy suction sampling for natural enemies. Management practices at the local scale did not influence SWD abundance, but natural enemy abundance was higher in organic systems and fields with vegetation present between rows. Landscape configurational diversity and greater proportion of non-cropping habitat promoted higher SWD populations. Natural enemy communities were composed of highly generalized species, and contrary to our predictions, we observed lower abundances in landscapes with higher proportion of non-cropping area. Few predators were detected to have fed on SWD, and communities were dominated by predators with low specialization on prey in blueberry. Our results indicate that local and landscape features in blueberry landscapes have differential effects on a polyphagous pest and generalist natural enemies. Our initial analysis of predator diets, using a metabarcoding approach, suggests spatial structure in specialization on prey with high diversity of prey in predators collected in forested margins.

Data from: Human activities and landscape features interact to closely define the distribution and dispersal of an urban commensal.

The rock pigeon, Columba livia, is a cosmopolitan human commensal, domesticated thousands of years ago. However, the human-mediated factors governing its distribution and dispersal are not well understood. In this study, we performed (1) hierarchical distance sampling on ~400 island-wide point transects, (2) a population genomic inquiry based on ~7000 SNPs from almost 150 individuals, and (3) landscape-genomic analyses on the basis of extensive ecological and social-economic databases to characterize the distribution and dispersal patterns of rock pigeons across Singapore. Our distance sampling results indicated that the volume of intentional 'mercy feeding' and availability of high-rise buildings are the most reliable predictors of high pigeon densities in Singapore. Genomic analyses demonstrated that rock pigeons in Singapore form a single population possibly derived from rapid expansion from a genetically homogenous group of founder individuals. Specifically, rock pigeons in Singapore lack sex-biased dispersal and are clustered with a genetic patch size of ~3km. Landscape genomic analyses of great precision pointed to the presence of dense trees as agents of resistance to dispersal whereas a high road density reduces this resistance. By pinpointing a range of ecological and socio-economic variables determining the distribution and dispersal of pigeons, our study provides urban planners with the tools for optimal management of this human commensal, such as a curtailment of the practice of mercy feeding and modifications to the urban landscape to reduce pigeon density and to lower the likelihood of repopulation by dispersal.

Data from: How to quantify animal activity from radio-frequency identification (RFID) recordings

Automated animal monitoring via radio-frequency identification (RFID) technology allows efficient and extensive data sampling of individual activity levels, and is therefore commonly used for ecological research. However, processing RFID data is still a largely unresolved problem, which potentially leads to inaccurate estimates for behavioural activity. One of the major challenges during data processing is to isolate independent behavioural actions from a set of superfluous, non-independent detections. As a case study, individual blue tits (Cyanistes caeruleus) were simultaneously monitored during reproduction with both video recordings and RFID technology. We demonstrated how RFID data can be processed based on the time spent in- and outside a nest box. We then validated the number and timing of nest visits obtained from the processed RFID dataset by calibration against video recordings. The video observations revealed a limited overlap between the time spent in- and outside the nest box, with the least overlap at 23 seconds for both sexes. We then isolated exact arrival times from redundant RFID registrations by erasing all successive registrations within 23 seconds after the preceding registration. After aligning the processed RFID data with the corresponding video recordings, we observed a high accuracy in three behavioural estimates of parental care (individual nest visit rates, within-pair alternation and synchronization of nest visits). We provide a clear guideline for future studies that aim to implement RFID technology in their research. We argue that our suggested RFID data processing procedure improves the precision of behavioural estimates, despite some inevitable drawbacks inherent to the technology. Our method is useful, not only for other cavity breeding birds, but for a wide range of (in)vertebrate species that are large enough to be fitted with a tag and that regularly pass near or through a fixed antenna.

Data from: Social facilitation is a better predictor of frog reproductive activity than environmental factors

Anuran breeding activity is frequently linked to environmental factors, mainly temperature and rainfall. However, a key feature of anuran reproductive behavior—gathering in choruses and producing loud advertisement calls to attract females—generates a conspicuous social cue that may also facilitate reproductive behavior. Here, I examine the relative importance of environmental and social factors in explaining the intensity of reproductive activity in the Neotropical treefrog Hypsiboas rosenbergi. I show that social cues generally play an important role, but that there are sex differences: male behavior is associated with a combination of environmental and social factors, while female behavior is associated almost exclusively with social cues. I discuss the potential benefits of using social cues in regulating breeding activity, and suggest that conservation efforts may take advantage of the apparently widespread pattern of social facilitation in anuran reproductive ecology.

Data from: Accelerometers can measure total and activity-specific energy expenditure in free-ranging marine mammals only if linked to time-activity budgets

Energy expenditure is an important component of foraging ecology, but is extremely difficult to estimate in free-ranging animals and depends on how animals partition their time between different activities during foraging. Acceleration data have emerged as a new way to determine energy expenditure at a fine scale but this needs to be tested and validated in wild animals. This study investigated whether vectorial dynamic body acceleration (VeDBA) could accurately predict the energy expended by marine predators during a full foraging trip. We also aimed to determine whether the accuracy of predictions of energy expenditure derived from acceleration increased when partitioned by different types of at-sea activities (i.e. diving, transiting, resting and surface activities). To do so, we equipped 20 lactating northern (Callorhinus ursinus) and 20 lactating Antarctic fur seals (Arctocephalus gazella) with GPS, time-depth recorders and tri-axial accelerometers and obtained estimates of field metabolic rates using the doubly labelled water (DLW) method. VeDBA was derived from tri-axial acceleration, and at-sea activities (diving, transiting, resting and surface activities) were determined using dive depth, tri-axial acceleration and travelling speed. We found that VeDBA did not accurately predict the total energy expended by fur seals during their full foraging trips (R2 = 0·36). However, the accuracy of VeDBA as a predictor of total energy expenditure increased significantly when foraging trips were partitioned by activity and when activity-specific VeDBA was paired with time-activity budgets (R2 = 0·70). Activity-specific VeDBA also accurately predicted the energy expenditures of each activity independent of each other (R2 > 0·85). Our study confirms that acceleration is a promising way to estimate energy expenditures of free-ranging marine mammals at a fine scale never attained before. However, it shows that it needs to be based on the time-activity budgets that make up foraging trips rather than being derived as a single measure of VeDBA applied to entire foraging trips. Our activity-based method provides a cost-effective means to accurately calculate energy expenditures of fur seals using acceleration and time-activity budgets, that can be transfered to studies on other species.

Data from: Active and reactive behaviour in human mobility: the influence of attraction points on pedestrians

Human mobility is becoming an accessible field of study thanks to the progress and availability of tracking technologies as a common feature of smart phones. We describe an example of a scalable experiment exploiting these circumstances at a public, outdoor fair in Barcelona (Spain). Participants were tracked while wandering through an open space with activity stands attracting their attention. We develop a general modeling framework based on Langevin Dynamics, which allows us to test the influence of two distinct types of ingredients on mobility: reactive or context-dependent factors, modelled by means of a force field generated by attraction points in a given spatial configuration, and active or inherent factors, modelled from intrinsic movement patterns of the subjects. The additive and constructive framework model accounts for some observed features. Starting with the simplest model (purely random walkers) as a reference, we progressively introduce different ingredients such as persistence, memory, and perceptual landscape, aiming to untangle active and reactive contributions and quantify their respective relevance. The proposed approach may help in anticipating the spatial distribution of citizens in alternative scenarios and in improving the design of public events based on a facts-based approach.

Data from: Developmental changes in hippocampal CA1 single neuron firing and theta activity during associative learning

Hippocampal development is thought to play a crucial role in the emergence of many forms of learning and memory, but ontogenetic changes in hippocampal activity during learning have not been examined thoroughly. We examined the ontogeny of hippocampal function by recording theta and single neuron activity from the dorsal hippocampal CA1 area while rat pups were trained in associative learning. Three different age groups [postnatal days (P)17-19, P21-23, and P24-26] were trained over six sessions using a tone conditioned stimulus (CS) and a periorbital stimulation unconditioned stimulus (US). Learning increased as a function of age, with the P21-23 and P24-26 groups learning faster than the P17-19 group. Age- and learning-related changes in both theta and single neuron activity were observed. CA1 pyramidal cells in the older age groups showed greater task-related activity than the P17-19 group during CS-US paired sessions. The proportion of trials with a significant theta (4–10 Hz) power change, the theta/delta ratio, and theta peak frequency also increased in an age-dependent manner. Finally, spike/theta phase-locking during the CS showed an age-related increase. The findings indicate substantial developmental changes in dorsal hippocampal function that may play a role in the ontogeny of learning and memory.

Data from: Vegetation connectivity increases ant activity and potential for ant-provided biocontrol services in a tropical agroforest

In natural and managed systems, connections between trees are important structural resources for arboreal ant communities with ecosystem-level effects. However, ongoing agricultural intensification in agroforestry systems, which reduces shade trees and connectivity between trees and crop plants, may hinder ant recruitment rates to resources and pest control services provided by ants. We examined whether increasing connectivity between coffee plants and shade trees in coffee plantations increases ant activity and enhances biological control of the coffee berry borer, the most devastating insect pest of coffee. Further, we examined whether artificial connections buffer against the loss of vegetation connectivity in coffee plants located at larger distances from the nesting tree. We used string to connect Inga micheliana shade trees containing Azteca sericeasur ant nests to coffee plants to compare ant activity before and after placement of the strings, and measured borer removal by ants on coffee plants with and without strings. Ant activity significantly increased after the addition of strings on connected plants, but not on control plants. Borer removal by ants was also three times higher on connected plants after string placement. Greater distance from the nesting tree negatively influenced ant activity on control coffee plants, but not on connected plants, suggesting that connections between coffee plants and nest trees could potentially compensate for the negative effects that larger distances pose on ant activity. Our study shows that favoring connectivity at the local scale, by artificially adding connections, promotes ant activity and may increase pest removal in agroecosystems.

opencc-zeroDec 2014View details →

Data from: Effects of the selective stretch-activated channel blocker GsMtx4 on stretch-induced changes in refractoriness in isolated rat hearts and on ventricular premature beats and arrhythmias after coronary occlusion in swine

Mechanical factors may contribute to ischemic ventricular arrhythmias. GsMtx4 peptide, a selective stretch-activated channel blocker, inhibits stretch-induced atrial arrhythmias. We aimed to assess whether GsMtx4 protects against ventricular ectopy and arrhythmias following coronary occlusion in swine. First, the effects of 170-nM GsMtx4 on the changes in the effective refractory period (ERP) induced by left ventricular (LV) dilatation were assessed in 8 isolated rat hearts. Then, 44 anesthetized, open-chest pigs subjected to 50-min left anterior descending artery occlusion and 2-h reperfusion were blindly allocated to GsMtx4 (57 μg/kg iv. bolus and 3.8 μg/kg/min infusion, calculated to attain the above concentration in plasma) or saline, starting 5-min before occlusion and continuing until after reflow. In rat hearts, LV distension induced progressive reductions in ERP (35±2, 32±2, and 29±2 ms at 0, 20, and 40 mmHg of LV end-diastolic pressure, respectively, P<0.001) that were prevented by GsMTx4 (33±2, 33±2, and 32±2 ms, respectively, P=0.002 for the interaction with LV end-diastolic pressure). Pigs receiving GsMtx4 had similar number of ventricular premature beats during the ischemic period as control pigs (110±28 vs. 103±21, respectively, P=0.842). There were not significant differences among treated and untreated animals in the incidence of ventricular fibrillation (13.6 vs. 22.7%, respectively, P=0.696) or tachycardia (36.4 vs. 50.0%, P=0.361) or in the number of ventricular tachycardia episodes during the occlusion period (1.8±0.7 vs. 5.5±2.6, P=0.323). Thus, GsMtx4 administered under these conditions does not suppress ventricular ectopy following coronary occlusion in swine. Whether it might protect against malignant arrhythmias should be tested in studies powered for these outcomes.

Data from: Deconstruction of an African folk medicine uncovers a novel molecular strategy for therapeutic potassium channel activation

A third of the global population relies heavily upon traditional or folk medicines, such as the African shrub Mallotus oppositifolius. Here, we used pharmacological screening and electrophysiological analysis in combination with in silico docking and site-directed mutagenesis to elucidate the effects of M. oppositifolius constituents on KCNQ1, a ubiquitous and influential cardiac and epithelial voltage-gated potassium (Kv) channel. Two components of the M. oppositifolius leaf extract, mallotoxin (MTX) and 3-ethyl-2-hydroxy-2-cyclopenten-1-one (CPT1), augmented KCNQ1 current by negative shifting its voltage dependence of activation. MTX was also highly effective at augmenting currents generated by KCNQ1 in complexes with native partners KCNE1 or SMIT1; conversely, MTX inhibited KCNQ1-KCNE3 channels. MTX and CPT1 activated KCNQ1 by hydrogen bonding to the foot of the voltage sensor, a previously unidentified drug site which we also find to be essential for MTX activation of the related KCNQ2/3 channel. The findings elucidate the molecular mechanistic basis for modulation by a widely used folk medicine of an important human Kv channel and uncover novel molecular approaches for therapeutic modulation of potassium channel activity.

opencc-zeroDec 2013View details →

Data from: Abiotic constraints on the activity of tropical lizards

Many tropical ectotherms are considered vulnerable to anthropogenic climate change because they have evolved to become thermal specialists. Indeed, several recent studies have suggested that even small increases in mean operative temperature may lead to a reduction in activity and the subsequent extinction of populations. Within the tropics, lizards are considered particularly vulnerable due to the potential for climate change to directly impact physiology and alter community interactions. However, models usually focus on the effects of mean operative temperature at the expense of other climate variables that may also affect lizard physiology. We used daily variation in operative temperature, humidity, and wind speed to examine how changes in climate influence activity in two species of lizards from the island of Cayo Menor, Honduras. Anolis lemurinus is a forest species, whereas A. allisoni is an open-habitat species. We conducted daily surveys for active lizards in habitat typical to each species, while simultaneously measuring operative thermal environments with physical models. The effects of the thermal environment were considered in the context of the thermal sensitivity of sprint speed for each species, and compared with the effects of the hydric (humidity) and convective (wind) environments. When all surveys were combined into a single analysis, the activity of the forest species Anolis lemurinus was positively correlated with wind speed, the spatial heterogeneity of operative temperature, and the mismatch between mean operative temperature and the optimal temperature for sprint performance. Mean operative temperature did significantly effect Anolis lemurinus activity, but only when it was above their thermal optimum. Activity of the open-habitat species A. allisoni was negatively correlated with wind speed, but was not related to any other climate variable. Whereas the mismatch between mean operative temperature and the thermal optimum for performance predicted the activity level of the forest species in ways partially consistent with its use in models for the response of lizards to climate change, the effects of the abiotic environment were habitat-dependent. Our results suggest that successfully predicting the biological impacts of climate change will require holistic models that account for more than changes in mean temperature alone.