Open Access Research and Scholarship Fund (OARS)

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Since 2013, the Colorado State University Libraries, under the guidance of the CSU Faculty Council Committee on Libraries, has allocated funds to support the Open Access Research and Scholarship (OARS) Fund. The fund is open to CSU tenured/tenure track faculty and full-time research scientists. This digital collection contains articles that received OARS funding between 2011 and 2020.

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Open Access
Will elephants soon disappear from West African savannahs?
(Colorado State University. Libraries, 2011) Bouché, Philippe, author; Douglas-Hamilton, Iain, author; Wittemyer, George, author; Nianogo, Aimé J., author; Doucet, Jean-Louis, author; Lejeune, Philippe, author; Vermeulen, Cédric, author; Public Library of Science, publisher
Precipitous declines in Africa's native fauna and flora are recognized, but few comprehensive records of these changes have been compiled. Here, we present population trends for African elephants in the 6,213,000 km2 Sudano-Sahelian range of West and Central Africa assessed through the analysis of aerial and ground surveys conducted over the past 4 decades. These surveys are focused on the best protected areas in the region, and therefore represent the best case scenario for the northern savanna elephants. A minimum of 7,745 elephants currently inhabit the entire region, representing a minimum decline of 50% from estimates four decades ago for these protected areas. Most of the historic range is now devoid of elephants and, therefore, was not surveyed. Of the 23 surveyed elephant populations, half are estimated to number less than 200 individuals. Historically, most populations numbering less than 200 individuals in the region were extirpated within a few decades. Declines differed by region, with Central African populations experiencing much higher declines (-76%) than those in West Africa (-33%). As a result, elephants in West Africa now account for 86% of the total surveyed. Range wide, two refuge zones retain elephants, one in West and the other in Central Africa. These zones are separated by a large distance (~900 km) of high density human land use, suggesting connectivity between the regions is permanently cut. Within each zone, however, sporadic contacts between populations remain. Retaining such connectivity should be a high priority for conservation of elephants in this region. Specific corridors designed to reduce the isolation of the surveyed populations are proposed. The strong commitment of governments, effective law enforcement to control the illegal ivory trade and the involvement of local communities and private partners are all critical to securing the future of elephants inhabiting Africa's northern savannas.
Open Access
Characterising the impacts of emerging energy development on wildlife, with an eye towards mitigation
(Colorado State University. Libraries, 2012) Northrup, Joseph M., author; Wittemyer, George, author; Blackwell Publishing Ltd., publisher
Global demand for energy is projected to increase by 40% in the next 20 years, and largely will be met with alternative and unconventional sources. Development of these resources causes novel disturbances that strongly impact terrestrial ecosystems and wildlife. To effectively position ecologists to address this prevalent conservation challenge, we reviewed the literature on the ecological ramifications of this dominant driver of global land-use change, consolidated results for its mitigation and highlighted knowledge gaps. Impacts varied widely, underscoring the importance of area and species-specific studies. The most commonly reported impacts included behavioural responses and direct mortality. Examinations of mitigation were limited, but common easements included (1) reduction of the development footprint and human activity, (2) maintenance of undeveloped, 'refuge' habitat and (3) alteration of activity during sensitive periods. Problematically, the literature was primarily retrospective, focused on few species, countries, and ecoregions, and fraught with generalisations from weak inference. We advocate future studies take a comprehensive approach incorporating a mechanistic understanding of the interplay between development caused impacts and species ecology that will enable effective mitigation. Key areas for future research vital to securing a sustainable energy future in the face of development-related global change are outlined.
Open Access
Infrared thermometry to estimate crop water stress index and water use of irrigated maize in northeastern Colorado
(Colorado State University. Libraries, 2012) Taghvaeian, Saleh, author; Chávez, José L., author; Hansen, Neil C., author; Molecular Diversity Preservation International, publisher
With an increasing demand of fresh water resources in arid/semi-arid parts of the world, researchers and practitioners are relying more than ever on remote sensing techniques for monitoring and evaluating crop water status and for estimating crop water use or crop actual evapotranspiration (ETa). In this present study, infrared thermometry was used in conjunction with a few weather parameters to develop non-water-stressed and non-transpiring baselines for irrigated maize in a semi-arid region of Colorado in the western USA. A remote sensing-based Crop Water Stress Index (CWSI) was then estimated for four hourly periods each day during 5 August to 2 September 2011 (29 days). The estimated CWSI was smallest during the 10:00-11:00 a.m. and largest during the 12:00-13:00 p.m. hours. Plotting volumetric water content of the topsoil vs CWSI revealed that there is a high correlation between the two parameters during the analyzed period. CWSI values were also used to estimate maize actual transpiration (Ta). Ta estimates were more influenced by crop biomass rather than irrigation depths alone, mainly due to the fact that the effects of deficit irrigation were largely masked by the significant precipitation during the growing season. During the study period, applying an independent remotely sensed energy balance model showed that maize ETa was 159 mm, 30% larger than CWSI-Ta (122 mm) and 9% smaller than standard-condition maize ET (174 mm).
Open Access
Slow DNA loss in the gigantic genomes of salamanders
(Colorado State University. Libraries, 2012) Sun, Cheng, author; Arriaza, José R. López, author; Mueller, Rachel Lockridge, author; Oxford University Press, publisher
Evolutionary changes in genome size result from the combined effects of mutation, natural selection, and genetic drift. Insertion and deletion mutations (indels) directly impact genome size by adding or removing sequences. Most species lose more DNA through small indels (i.e., ~1-30 bp) than they gain, which can result in genome reduction over time. Because this rate of DNA loss varies across species, small indel dynamics have been suggested to contribute to genome size evolution. Species with extremely large genomes provide interesting test cases for exploring the link between small indels and genome size; however, most large genomes remain relatively unexplored. Here, we examine rates of DNA loss in the tetrapods with the largest genomes - the salamanders. We used low-coverage genomic shotgun sequence data from four salamander species to examine patterns of insertion, deletion, and substitution in neutrally evolving non-long terminal repeat (LTR) retrotransposon sequences. For comparison, we estimated genome-wide DNA loss rates in non-LTR retrotransposon sequences from five other vertebrate genomes: Anolis carolinensis, Danio rerio, Gallus gallus, Homo sapiens, and Xenopus tropicalis. Our results show that salamanders have significantly lower rates of DNA loss than do other vertebrates. More specifically, salamanders experience lower numbers of deletions relative to insertions, and both deletions and insertions are skewed toward smaller sizes. On the basis of these patterns, we conclude that slow DNA loss contributes to genomic gigantism in salamanders. We also identify candidate molecular mechanisms underlying these differences and suggest that natural variation in indel dynamics provides a unique opportunity to study the basis of genome stability.
Open Access
Devastating decline of forest elephants in Central Africa
(Colorado State University. Libraries, 2013) Maisels, Fiona, author; Strindberg, Samantha, author; Blake, Stephen, author; Wittemyer, George, author; Hart, John, author; Williamson, Elizabeth A., author; Aba'a, Rostand, author; Abitsi, Gaspard, author; Ambahe, Ruffin D., author; Amsini, Fidèl, author; Bakabana, Parfait C., author; Hicks, Thurston Cleveland, author; Bayogo, Rosine E., author; Bechem, Martha, author; Beyers, Rene L., author; Bezangoye, Anicet N., author; Boundja, Patrick, author; Bout, Nicolas, author; Akou, Marc Ella, author; Bene, Lambert Bene, author; Fosso, Bernard, author; Greengrass, Elizabeth, author; Grossmann, Falk, author; Ikamba-Nkulu, Clement, author; Ilambu, Omari, author; Inogwabini, Bila-Isia, author; Iyenguet, Fortune, author; Kiminou, Franck, author; Kokangoye, Max, author; Kujirakwinja, Deo, author; Latour, Stephanie, author; Liengola, Innocent, author; Mackaya, Quevain, author; Madidi, Jacob, author; Madzoke, Bola, author; Makoumbou, Calixte, author; Malanda, Guy-Aimé, author; Malonga, Richard, author; Mbani, Olivier, author; Mbendzo, Valentin A., author; Ambassa, Edgar, author; Ekinde, Albert, author; Mihindou, Yves, author; Morgan, Bethan J., author; Motsaba, Prosper, author; Moukala, Gabin, author; Mounguengui, Anselme, author; Mowawa, Brice S., author; Ndzai, Christian, author; Nixon, Stuart, author; Nkumu, Pele, author; Nzolani, Fabian, author; Pintea, Lilian, author; Plumptre, Andrew, author; Rainey, Hugo, author; De Semboli, Bruno Bokoto, author; Serckx, Adeline, author; Stokes, Emma, author; Turkalo, Andrea, author; Vanleeuwe, Hilde, author; Vosper, Ashley, author; Warren, Ymke, author; Public Library of Science, publisher
African forest elephants - taxonomically and functionally unique - are being poached at accelerating rates, but we lack range-wide information on the repercussions. Analysis of the largest survey dataset ever assembled for forest elephants (80 foot-surveys; covering 13,000 km; 91,600 person-days of fieldwork) revealed that population size declined by ca. 62% between 2002-2011, and the taxon lost 30% of its geographical range. The population is now less than 10% of its potential size, occupying less than 25% of its potential range. High human population density, hunting intensity, absence of law enforcement, poor governance, and proximity to expanding infrastructure are the strongest predictors of decline. To save the remaining African forest elephants, illegal poaching for ivory and encroachment into core elephant habitat must be stopped. In addition, the international demand for ivory, which fuels illegal trade, must be dramatically reduced.
Open Access
Comparative demography of an at-risk African elephant population
(Colorado State University. Libraries, 2013) Wittemyer, George, author; Daballen, David, author; Douglas-Hamilton, Iain, author; Public Library of Science, publisher
Knowledge of population processes across various ecological and management settings offers important insights for species conservation and life history. In regard to its ecological role, charisma and threats from human impacts, African elephants are of high conservation concern and, as a result, are the focus of numerous studies across various contexts. Here, demographic data from an individually based study of 934 African elephants in Samburu, Kenya were summarized, providing detailed inspection of the population processes experienced by the population over a fourteen year period (including the repercussions of recent increases in illegal killing). These data were compared with those from populations inhabiting a spectrum of xeric to mesic ecosystems with variable human impacts. In relation to variability in climate and human impacts (causing up to 50% of recorded deaths among adults), annual mortality in Samburu fluctuated between 1 and 14% and, unrelatedly, natality between 2 and 14% driving annual population increases and decreases. Survivorship in Samburu was significantly lower than other populations with age-specific data even during periods of low illegal killing by humans, resulting in relatively low life expectancy of males (18.9 years) and females (21.8 years). Fecundity (primiparous age and inter-calf interval) were similar to those reported in other human impacted or recovering populations, and significantly greater than that of comparable stable populations. This suggests reproductive effort of African savanna elephants increases in relation to increased mortality (and resulting ecological ramifications) as predicted by life history theory. Further comparison across populations indicated that elongated inter-calf intervals and older ages of reproductive onset were related to age structure and density, and likely influenced by ecological conditions. This study provides detailed empirical data on elephant population dynamics strongly influenced by human impacts (laying the foundation for modeling approaches), supporting predictions of evolutionary theory regarding demographic responses to ecological processes.
Open Access
Arabidopsis thaliana VOZ (Vascular plant One-Zinc finger) transcription factors are required for proper regulation of flowering time
(Colorado State University. Libraries, 2013-04-15) Celesnik, Helena, author; Ali, Gul S., author; Robison, Faith M., author; Reddy, Anireddy S. N., author; The Company of Biologists Ltd., publisher
Transition to flowering in plants is tightly controlled by environmental cues, which regulate the photoperiod and vernalization pathways, and endogenous signals, which mediate the autonomous and gibberellin pathways. In this work, we investigated the role of two Zn2+-finger transcription factors, the paralogues AtVOZ1 and AtVOZ2, in Arabidopsis thaliana flowering. Single atvoz1-1 and atvoz2-1 mutants showed no significant phenotypes as compared to wild type. However, atvoz1-1 atvoz2-1 double mutant plants exhibited several phenotypes characteristic of flowering-time mutants. The double mutant displayed a severe delay in flowering, together with additional pleiotropic phenotypes. Late flowering correlated with elevated expression of FLOWERING LOCUS C (FLC), which encodes a potent floral repressor, and decreased expression of its target, the floral promoter FD. Vernalization rescued delayed flowering of atvoz1-1 atvoz2-1 and reversed elevated FLC levels. Accumulation of FLC transcripts in atvoz1-1 atvoz2-1 correlated with increased expression of several FLC activators, including components of the PAF1 and SWR1 chromatin-modifying complexes. Additionally, AtVOZs were shown to bind the promoter of MOS3/SAR3 and directly regulate expression of this nuclear pore protein, which is known to participate in the regulation of flowering time, suggesting that AtVOZs exert at least some of their flowering regulation by influencing the nuclear pore function. Complementation of atvoz1-1 atvoz2-1 with AtVOZ2 reversed all double mutant phenotypes, confirming that the observed morphological and molecular changes arise from the absence of functional AtVOZ proteins, and validating the functional redundancy between AtVOZ1 and AtVOZ2.
Open Access
Microbial responses to multi-factor climate change: effects on soil enzymes
(Colorado State University. Libraries, 2013-06) Steinweg, J. Megan, author; Dukes, Jeffrey S., author; Paul, Eldor A., author; Wallenstein, Matthew D., author; Frontiers Research Foundation, publisher
The activities of extracellular enzymes, the proximate agents of decomposition in soils, are known to depend strongly on temperature, but less is known about how they respond to changes in precipitation patterns, and the interaction of these two components of climate change. Both enzyme production and turnover can be affected by changes in temperature and soil moisture, thus it is difficult to predict how enzyme pool size may respond to altered climate. Soils from the Boston-Area Climate Experiment (BACE), which is located in an old field (on abandoned farmland), were used to examine how climate variables affect enzyme activities and microbial biomass carbon (MBC) in different seasons and in soils exposed to a combination of three levels of precipitation treatments (ambient, 150% of ambient during growing season, and 50% of ambient year-round) and four levels of warming treatments (unwarmed to ∼4° C above ambient) over the course of a year. Warming, precipitation and season had very little effect on potential enzyme activity. Most models assume that enzyme dynamics follow microbial biomass, because enzyme production should be directly controlled by the size and activity of microbial biomass. We observed differences among seasons and treatments in mass-specific potential enzyme activity, suggesting that this assumption is invalid. In June 2009, mass-specific potential enzyme activity, using chloroform fumigation-extraction MBC, increased with temperature, peaking under medium warming and then declining under the highest warming. This finding suggests that either enzyme production increased with temperature or turnover rates decreased. Increased maintenance costs associated with warming may have resulted in increased mass-specific enzyme activities due to increased nutrient demand. Our research suggests that allocation of resources to enzyme production could be affected by climate-induced changes in microbial efficiency and maintenance costs.
Open Access
Biomass for thermochemical conversion: targets and challenges
(Colorado State University. Libraries, 2013-07) Tanger, Paul, author; Field, John L., author; Jahn, Courtney E., author; DeFoort, Morgan W., author; Leach, Jan E., author; Frontiers Research Foundation, publisher
Bioenergy will be one component of a suite of alternatives to fossil fuels. Effective conversion of biomass to energy will require the careful pairing of advanced conversion technologies with biomass feedstocks optimized for the purpose. Lignocellulosic biomass can be converted to useful energy products via two distinct pathways: enzymatic or thermochemical conversion. The thermochemical pathways are reviewed and potential biotechnology or breeding targets to improve feedstocks for pyrolysis, gasification, and combustion are identified. Biomass traits influencing the effectiveness of the thermochemical process (cell wall composition, mineral and moisture content) differ from those important for enzymatic conversion and so properties are discussed in the language of biologists (biochemical analysis) as well as that of engineers (proximate and ultimate analysis). We discuss the genetic control, potential environmental influence, and consequences of modification of these traits. Improving feedstocks for thermochemical conversion can be accomplished by the optimization of lignin levels, and the reduction of ash and moisture content. We suggest that ultimate analysis and associated properties such as H:C, O:C, and heating value might be more amenable than traditional biochemical analysis to the high-throughput necessary for the phenotyping of large plant populations. Expanding our knowledge of these biomass traits will play a critical role in the utilization of biomass for energy production globally, and add to our understanding of how plants tailor their composition with their environment.
Open Access
The use of on-animal acoustical recording devices for studying animal behavior
(Colorado State University. Libraries, 2013-07) Lynch, Emma, author; Angeloni, Lisa, author; Fristrup, Kurt, author; Joyce, Damon, author; Wittemyer, George, author; John Wiley and Sons, publisher
Audio recordings made from free-ranging animals can be used to investigate aspects of physiology, behavior, and ecology through acoustic signal processing. On-animal acoustical monitoring applications allow continuous remote data collection, and can serve to address questions across temporal and spatial scales. We report on the design of an inexpensive collar-mounted recording device and present data on the activity budget of wild mule deer (Odocoileus hemionus) derived from these devices applied for a 2-week period. Over 3300 h of acoustical recordings were collected from 10 deer on their winter range in a natural gas extraction field in northwestern Colorado. Analysis of a subset of the data indicated deer spent approximately 33.5% of their time browsing, 20.8% of their time processing food through mastication, and nearly 38.3% of their time digesting through rumination, with marked differences in diel patterning of these activities. Systematic auditory vigilance was a salient activity when masticating, and these data offer options for quantifying wildlife responses to varying listening conditions and predation risk. These results (validated using direct observation) demonstrate that acoustical monitoring is a viable and accurate method for characterizing individual time budgets and behaviors of ungulates, and may provide new insight into the ways external forces affect wildlife behavior.
Open Access
Pulmonary arterial pressures, arterial blood-gas tensions, and serum biochemistry of beef calves born and raised at high altitude
(Colorado State University. Libraries, 2013-07-15) Neary, Joseph M., author; Garry, Franklyn B., author; Holt, Timothy N., author; Knight, Anthony P., author; Gould, Daniel H., author; Dargatz, David A., author; Dove Medical Press Ltd., publisher
High-altitude exposure is physiologically challenging. This is particularly true for animals native to low-altitude environments, such as British breeds of cattle. The objective of this study was to document the effect of high altitude on select physiological parameters of healthy beef calves (Bos taurus) born and raised on a high-altitude ranch typical of the Rocky Mountain region. Pulmonary arterial pressures, arterial blood-gas tensions, serum biochemistry, and hematocrit were evaluated. The calves studied were a composite of British (50%-75%) and Continental (25-50%) breeds born on one ranch at an altitude of 2410 m. Calves were sampled at an altitude of 2410 m when 1 month old and again at an altitude of 2730 m when 3 and 6 months old. Between 3 and 6 months of age, calves had access to grazing from 2730 m to approximately 3500 m above sea level. On each occasion, 16 to 50 calves were sampled. Only calves that remained healthy throughout all three testing periods were included in the dataset. Calves with the highest pulmonary arterial pressures at 1 month of age tended to have the highest pressures at 6 months of age (r = 0.43, P = 0.16, n = 12). Respiratory alkalosis was greatest at 6 months of age (pH 7.48 ± 0.06). Mean alveolar-arterial oxygen pressure gradients were 11.7and 11.6 mmHg at 3 and 6 months of age, indicating poor transfer of oxygen from the alveoli into the pulmonary blood. Median values for blood lactate ranged from 1.4 to 3.4 mmol/L indicating substantial anaerobic respiration at all ages. Mean hematocrits were ≤ 35.7%, only slightly higher than values obtained from age-matched calves at sea level. These results suggest that the provision of oxygen to the peripheral tissues of beef calves may be compromised at altitudes over 2410 m. This may have implications for diseases of the cardiopulmonary system.
Open Access
Carbon-degrading enzyme activities stimulated by increased nutrient availability in Arctic tundra soils
(Colorado State University. Libraries, 2013-10) Koyama, Akihiro, author; Wallenstein, Matthw D., author; Simpson, Rodney T., author; Moore, John C., author; Public Library of Science, publisher
Climate-induced warming of the Arctic tundra is expected to increase nutrient availability to soil microbes, which in turn may accelerate soil organic matter (SOM) decomposition. We increased nutrient availability via fertilization to investigate the microbial response via soil enzyme activities. Specifically, we measured potential activities of seven enzymes at four temperatures in three soil profiles (organic, organic/mineral interface, and mineral) from untreated native soils and from soils which had been fertilized with nitrogen (N) and phosphorus (P) since 1989 (23 years) and 2006 (six years). Fertilized plots within the 1989 site received annual additions of 10 g N⋅m-2⋅year-1 and 5 g P⋅m-2⋅year-1. Within the 2006 site, two fertilizer regimes were established - one in which plots received 5 g N⋅m-2⋅year-1 and 2.5 g P⋅m-2⋅year-1 and one in which plots received 10 g N⋅m-2⋅year-1 and 5 g P⋅m-2⋅year-1. The fertilization treatments increased activities of enzymes hydrolyzing carbon (C)-rich compounds but decreased phosphatase activities, especially in the organic soils. Activities of two enzymes that degrade N-rich compounds were not affected by the fertilization treatments. The fertilization treatments increased ratios of enzyme activities degrading C-rich compounds to those for N-rich compounds or phosphate, which could lead to changes in SOM chemistry over the long term and to losses of soil C. Accelerated SOM decomposition caused by increased nutrient availability could significantly offset predicted increased C fixation via stimulated net primary productivity in Arctic tundra ecosystems.
Open Access
Metabolic engineering of Arabidopsis for butanetriol production using bacterial genes
(Colorado State University. Libraries, 2013-11) Abdel-Ghany, Salah E., author; Day, Irene, author; Heuberger, Adam L., author; Broeckling, Corey D., author; Reddy, Anireddy S. N., author; Elsevier Inc., publisher
1,2,4-butanetriol (butanetriol) is a useful precursor for the synthesis of the energetic material butanetriol trinitrate and several pharmaceutical compounds. Bacterial synthesis of butanetriol from xylose or arabinose takes place in a pathway that requires four enzymes. To produce butanetriol in plants by expressing bacterial enzymes, we cloned native bacterial or codon optimized synthetic genes under different promoters into a binary vector and stably transformed Arabidopsis plants. Transgenic lines expressing introduced genes were analyzed for the production of butanetriol using gas chromatography coupled to mass spectrometry (GC-MS). Soil-grown transgenic plants expressing these genes produced up to 20 µg/g of butanetriol. To test if an exogenous supply of pentose sugar precursors would enhance the butanetriol level, transgenic plants were grown in a medium supplemented with either xylose or arabinose and the amount of butanetriol was quantified. Plants expressing synthetic genes in the arabinose pathway showed up to a forty-fold increase in butanetriol levels after arabinose was added to the medium. Transgenic plants expressing either bacterial or synthetic xylose pathways, or the arabinose pathway showed toxicity symptoms when xylose or arabinose was added to the medium, suggesting that a by-product in the pathway or butanetriol affected plant growth. Furthermore, the metabolite profile of plants expressing arabinose and xylose pathways was altered. Our results demonstrate that bacterial pathways that produce butanetriol can be engineered into plants to produce this chemical. This proof-of-concept study for phytoproduction of butanetriol paves the way to further manipulate metabolic pathways in plants to enhance the level of butanetriol production.
Open Access
The challenges of maintaining indigenous ecological knowledge
(Colorado State University. Libraries, 2014) McCarter, Joe, author; Gavin, Michael C., author; Baereleo, Sue, author; Love, Mark, author; Resilience Alliance, publisher
Increased interest in indigenous ecological knowledge (IEK) has led to concern that it is vulnerable amidst social and ecological change. In response, multiple authors have recommended the establishment of programs for the maintenance and revitalization of IEK systems. However, few studies have analyzed the methods, opportunities, and challenges of these programs. This is a critical gap, as IEK maintenance is challenging and will require layered and evidence-based solutions. We seek to build a foundation for future approaches to IEK maintenance. First, we present a systematic literature review of IEK maintenance programs (n = 39) and discuss the opportunities and challenges inherent in five broad groups of published approaches. Second, we use two case studies from the Republic of Vanuatu to illustrate these challenges in more depth. The first case study takes a community-based approach, which has inherent strengths (e.g., localized organization). It has, however, faced practical (e.g., funding) and epistemological (changing modes of knowledge transmission) challenges. The second case study seeks to facilitate IEK transmission within the formal school system. Although this model has potential, it has faced significant challenges (e.g., lack of institutional linkages). We conclude that supporting and strengthening IEK is important but that serious attention is needed to account for the social, situated, and dynamic nature of IEK. In closing, we use the review and case studies to propose four principles that may guide adaptive and flexible approaches for the future maintenance of IEK systems.
Open Access
Regulators of human white adipose browning: evidence for sympathetic control and sexual dimorphic responses to sprint interval training
(Colorado State University. Libraries, 2014-03) Scalzo, Rebecca L., author; Peltonen, Garrett L., author; Giordano, Gregory R., author; Binns, Scott E., author; Klochak, Anna L., author; Paris, Hunter L. R., author; Schweder, Melani M., author; Szallar, Steve E., author; Wood, Lacey M., author; Larson, Dennis G., author; Luckasen, Gary J., author; Hickey, Matthew S., author; Bell, Christopher, author; Public Library of Science, publisher
The conversion of white adipose to the highly thermogenic beige adipose tissue has been proposed as a potential strategy to counter the unfavorable consequences of obesity. Three regulators of this conversion have recently emerged but information regarding their control is limited, and contradictory. We present two studies examining the control of these regulators. Study 1: In 10 young men, the plasma concentrations of irisin and fibroblast growth factor 21 (FGF21) were determined prior to and during activation of the sympathetic nervous system via hypoxic gas breathing (FIO2 = 0.11). The measurements were performed twice, once with and once without prior/concurrent sympathetic inhibition via transdermal clonidine administration. FGF21 was unaffected by basal sympathetic inhibition (338±113 vs. 295±80 pg/mL; P = 0.43; mean±SE), but was increased during hypoxia mediated sympathetic activation (368±135); this response was abrogated (P = 0.035) with clonidine (269±93). Irisin was unaffected by sympathetic inhibition and/or hypoxia (P>0.21). Study 2: The plasma concentration of irisin and FGF21, and the skeletal muscle protein content of fibronectin type III domain containing 5 (FNDC5) was determined in 19 young adults prior to and following three weeks of sprint interval training (SIT). SIT decreased FGF21 (338±78 vs. 251±36; P = 0.046) but did not affect FNDC5 (P = 0.79). Irisin was decreased in males (127±18 vs. 90±23 ng/mL; P = 0.045) and increased in females (139±14 vs. 170±18). Collectively, these data suggest a potential regulatory role of acute sympathetic activation pertaining to the browning of white adipose; further, there appears to be a sexual dimorphic response of irisin to SIT.
Open Access
Behavioral responses associated with a human-mediated predator shelter
(Colorado State University. Libraries, 2014-04) Graeme, Shannon, author; Cordes, Line S., author; Hardy, Amanda R., author; Angeloni, Lisa M., author; Crooks, Kevin R., author; Public Library of Science, publisher
Human activities in protected areas can affect wildlife populations in a similar manner to predation risk, causing increases in movement and vigilance, shifts in habitat use and changes in group size. Nevertheless, recent evidence indicates that in certain situations ungulate species may actually utilize areas associated with higher levels of human presence as a potential refuge from disturbance-sensitive predators. We now use four-years of behavioral activity budget data collected from pronghorn (Antilocapra americana) and elk (Cervus elephus) in Grand Teton National Park, USA to test whether predictable patterns of human presence can provide a shelter from predatory risk. Daily behavioral scans were conducted along two parallel sections of road that differed in traffic volume - with the main Teton Park Road experiencing vehicle use that was approximately thirty-fold greater than the River Road. At the busier Teton Park Road, both species of ungulate engaged in higher levels of feeding (27% increase in the proportion of pronghorn feeding and 21% increase for elk), lower levels of alert behavior (18% decrease for pronghorn and 9% decrease for elk) and formed smaller groups. These responses are commonly associated with reduced predatory threat. Pronghorn also exhibited a 30% increase in the proportion of individuals moving at the River Road as would be expected under greater exposure to predation risk. Our findings concur with the 'predator shelter hypothesis', suggesting that ungulates in GTNP use human presence as a potential refuge from predation risk, adjusting their behavior accordingly. Human activity has the potential to alter predator-prey interactions and drive trophic-mediated effects that could ultimately impact ecosystem function and biodiversity.
Open Access
Greater glucose uptake heterogeneity in knee muscles of old compared to young men during isometric contractions detected by [18F]-FDG PET/CT
(Colorado State University. Libraries, 2014-05) Rudroff, Thorsten, author; Kindred, John H., author; Benson, John-Michael, author; Tracy, Brian L., author; Kalliokoski, Kari K., author; Frontiers Media S. A., publisher
We used positron emission tomography/computed tomography (PET/CT) and [18F]-FDG to test the hypothesis that glucose uptake (GU) heterogeneity in skeletal muscles as a measure of heterogeneity in muscle activity is greater in old than young men when they perform isometric contractions. Six young (26 ± 6 years) and six old (77 ± 6 years) men performed two types of submaximal isometric contractions that required either force or position control. [18F]-FDG was injected during the task and PET/CT scans were performed immediately after the task. Within-muscle heterogeneity of knee muscles was determined by calculating the coefficient of variation (CV) of GU in PET image voxels within the muscles of interest. The average GU heterogeneity (mean ± SD) for knee extensors and flexors was greater for the old (35.3 ± 3.3%) than the young (28.6 ± 2.4%) (P = 0.006). Muscle volume of the knee extensors were greater for the young compared to the old men (1016 ± 163 vs. 598 ± 70 cm3, P = 0.004). In a multiple regression model, knee extensor muscle volume was a predictor (partial r = −0.87; P = 0.001) of GU heterogeneity for old men (R2 = 0.78; P < 0.001), and MVC force predicted GU heterogeneity for young men (partial r = −0.95, P < 0.001). The findings demonstrate that GU is more spatially variable for old than young men and especially so for old men who exhibit greater muscle atrophy.
Open Access
Age-related changes in arterial blood-gas variables in Holstein calves at moderate altitude
(Colorado State University. Libraries, 2014-05-15) Neary, Joseph M., author; Garry, Franklyn B., author; Raabis, Sarah M., author; Dove Medical Press Ltd., publisher
The goal of this study was to determine whether peripheral oxygen delivery and efficacy of alveolar-arterial oxygen (A-a O2) transfer, as estimated from the A-a O2 pressure gradient, are compromised in Holstein calves at moderate altitude. The primary objective was to evaluate age-related changes in arterial blood-gas variables, L-lactate, and hematocrit in healthy calves. The secondary objective was to determine if coughing and nasal discharge, commonly used indicators of respiratory disease, are associated with A-a O2 gradient. Arterial blood-gas tensions were evaluated in a cohort of 61 dairy calves on one farm at moderate altitude (1,601 m to 1,696 m). Sampling was performed on four occasions at approximately 10, 38, 150, and 261 days of age. Hyperventilation, as indicated by hypocapnia, was evident in calves of all ages. Increasing age was associated with a nonlinear increase in arterial oxygen tension (P<0.001) and a nonlinear decrease in A-a O2 gradient (P<0.001). The mean A-a O2 gradient at 10 and 38 days of age was over 18 mmHg, indicating poor efficacy of oxygen transfer. Cough score (P=0.02) but not nasal score (P=0.32) was associated with an in increase in A-a O2 pressure gradient. Mean hematocrit remained low (<27%) despite hypoxemia. From 38 days of age, median L-lactate concentration remained over 1.5 mmol/L, indicating substantial anaerobic respiration due to inadequate oxygen delivery. Twenty-five percent of calves were treated for respiratory disease. The maximum age at first treatment was 102 days. In conclusion, there was a nonlinear improvement in A-a O2 transfer efficacy with increasing age, but peripheral oxygen delivery remained compromised. Hyperventilation and impaired A-a O2 transfer due to functional immaturity of the pulmonary system may be risk factors for respiratory disease in dairy calves at moderate altitude.
Open Access
Chemical and mechanical defenses vary among maternal lines and leaf ages in Verbascum thapsus L. (Scrophulariaceae) and reduce palatability to a generalist insect
(Colorado State University. Libraries, 2014-08) Alba, Christina, author; Bowers, M. Deane, author; Blumenthal, Dana, author; Hufbauer, Ruth A., author; Public Library of Science, publisher
Intra-specific variation in host-plant quality affects herbivore foraging decisions and, in turn, herbivore foraging decisions mediate plant fitness. In particular, variation in defenses against herbivores, both among and within plants, shapes herbivore behavior. If variation in defenses is genetically based, it can respond to natural selection by herbivores. We quantified intra-specific variation in iridoid glycosides, trichome length, and leaf strength in common mullein (Verbascum thapsus L, Scrophulariaceae) among maternal lines within a population and among leaves within plants, and related this variation to feeding preferences of a generalist herbivore, Trichopulsia ni Hübner. We found significant variation in all three defenses among maternal lines, with T. ni preferring plants with lower investment in chemical, but not mechanical, defense. Within plants, old leaves had lower levels of all defenses than young leaves, and were strongly preferred by T. ni. Caterpillars also preferred leaves with trichomes removed to leaves with trichomes intact. Differences among maternal lines indicate that phenotypic variation in defenses likely has a genetic basis. Furthermore, these results reveal that the feeding behaviors of T. ni map onto variation in plant defense in a predictable way. This work highlights the importance of variation in host-plant quality in driving interactions between plants and their herbivores.
Open Access
Effects of 28Si ions, 56Fe ions, and protons on the induction of murine acute myeloid leukemia and hepatocellular carcinoma
(Colorado State University. Libraries, 2014-08) Weil, Michael M., author; Ullrich, Robert L., author; Fallgren, Christina M., author; McCarthy, Maureen, author; Yu, Yongjia, author; Genik, Paula C., author; Ray, F. Andrew, author; Public Library of Science, publisher
Estimates of cancer risks posed to space-flight crews by exposure to high atomic number, high-energy (HZE) ions are subject to considerable uncertainty because epidemiological data do not exist for human populations exposed to similar radiation qualities. We assessed the carcinogenic effects of 300 MeV/n 28Si or 600 MeV/n 56Fe ions in a mouse model for radiation-induced acute myeloid leukemia and hepatocellular carcinoma. C3H/HeNCrl mice were irradiated with 0.1, 0.2, 0.4, or 1 Gy of 300 MeV/n 28Si ions, 600 MeV/n 56Fe ions or 1 or 2 Gy of protons simulating the 1972 solar particle event (1972SPE) at the NASA Space Radiation Laboratory. Additional mice were irradiated with 137Cs gamma rays at doses of 1, 2, or 3 Gy. All groups were followed until they were moribund or reached 800 days of age. We found that 28Si or 56Fe ions do not appear to be substantially more effective than gamma rays for the induction of acute myeloid leukemia. However, 28Si or 56Fe ion irradiated mice had a much higher incidence of hepatocellular carcinoma than gamma ray irradiated or proton irradiated mice. These data demonstrate a clear difference in the effects of these HZE ions on the induction of leukemia compared to solid tumors, suggesting potentially different mechanisms of tumorigenesis. Also seen in this study was an increase in metastatic hepatocellular carcinoma in the 28Si and 56Fe ion irradiated mice compared with those exposed to gamma rays or 1972SPE protons, a finding with important implications for setting radiation exposure limits for space-flight crew members.