Publications by authors named "Barbara Zimmermann"

39 Publications

Age at first reproduction in wolves: different patterns of density dependence for females and males.

Proc Biol Sci 2021 Apr 7;288(1948):20210207. Epub 2021 Apr 7.

Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 73993 Riddarhyttan, Sweden.

Age at first reproduction constitutes a key life-history trait in animals and is evolutionarily shaped by fitness benefits and costs of delayed versus early reproduction. The understanding of how intrinsic and extrinsic changes affects age at first reproduction is crucial for conservation and management of threatened species because of its demographic effects on population growth and generation time. For a period of 40 years in the Scandinavian wolf () population, including the recolonization phase, we estimated age at first successful reproduction (pup survival to at least three weeks of age) and examined how the variation among individuals was explained by sex, population size (from 1 to 74 packs), primiparous or multiparous origin, reproductive experience of the partner and inbreeding. Median age at first reproduction was 3 years for females ( = 60) and 2 years for males ( = 74), and ranged between 1 and 8-10 years of age ( = 297). Female age at first reproduction decreased with increasing population size, and increased with higher levels of inbreeding. The probability for males to reproduce later first decreased, reaching its minimum when the number of territories approached 40-60, and then increased with increasing population size. Inbreeding for males and reproductive experience of parents and partners for both sexes had overall weak effects on age at first reproduction. These results allow for more accurate parameter estimates when modelling population dynamics for management and conservation of small and vulnerable wolf populations, and show how humans through legal harvest and illegal hunting influence an important life-history trait like age at first reproduction.
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http://dx.doi.org/10.1098/rspb.2021.0207DOI Listing
April 2021

Control of endothelial quiescence by FOXO-regulated metabolites.

Nat Cell Biol 2021 Apr 1;23(4):413-423. Epub 2021 Apr 1.

Angiogenesis and Metabolism Laboratory, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.

Endothelial cells (ECs) adapt their metabolism to enable the growth of new blood vessels, but little is known how ECs regulate metabolism to adopt a quiescent state. Here, we show that the metabolite S-2-hydroxyglutarate (S-2HG) plays a crucial role in the regulation of endothelial quiescence. We find that S-2HG is produced in ECs after activation of the transcription factor forkhead box O1 (FOXO1), where it limits cell cycle progression, metabolic activity and vascular expansion. FOXO1 stimulates S-2HG production by inhibiting the mitochondrial enzyme 2-oxoglutarate dehydrogenase. This inhibition relies on branched-chain amino acid catabolites such as 3-methyl-2-oxovalerate, which increase in ECs with activated FOXO1. Treatment of ECs with 3-methyl-2-oxovalerate elicits S-2HG production and suppresses proliferation, causing vascular rarefaction in mice. Our findings identify a metabolic programme that promotes the acquisition of a quiescent endothelial state and highlight the role of metabolites as signalling molecules in the endothelium.
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http://dx.doi.org/10.1038/s41556-021-00637-6DOI Listing
April 2021

Impact of a recolonizing, cross-border carnivore population on ungulate harvest in Scandinavia.

Sci Rep 2020 12 10;10(1):21670. Epub 2020 Dec 10.

Faculty of Applied Ecology, Agricultural Sciences and Biotechnology, Campus Evenstad, Inland Norway University of Applied Sciences, 2480, Koppang, Norway.

Predation from large carnivores and human harvest are the two main mortality factors affecting the dynamics of many ungulate populations. We examined long-term moose (Alces alces) harvest data from two countries that share cross-border populations of wolves (Canis lupus) and their main prey moose. We tested how a spatial gradient of increasing wolf territory density affected moose harvest density and age and sex composition of the harvested animals (n = 549,310), along a latitudinal gradient during 1995-2017. In areas containing average-sized wolf territories, harvest density was on average 37% (Norway) and 51% (Sweden) lower than in areas without wolves. In Sweden, calves made up a higher proportion of the moose harvest than in Norway, and this proportion was reduced with increased wolf territory density, while it increased in Norway. The proportion of females in the adult harvest was more strongly reduced in Sweden than in Norway as a response to increased wolf territory density. Moose management in both countries performed actions aimed to increase productivity in the moose population, in order to compensate for the increased mortality caused by wolves. These management actions are empirical examples of an adaptive management in response to the return of large carnivores.
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http://dx.doi.org/10.1038/s41598-020-78585-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7730186PMC
December 2020

Heart rate sensor validation and seasonal and diurnal variation of body temperature and heart rate in domestic sheep.

Vet Anim Sci 2019 Dec 1;8:100075. Epub 2019 Oct 1.

Norwegian Institute of Bioeconomy Research (NIBIO), Division of Forestry and Forest Resources, Gunnars veg 6, NO-6630 Tingvoll, Norway.

Advantages of low input livestock production on large pastures, including animal welfare, biodiversity and low production costs are challenged by losses due to undetected disease, accidents and predation. Precision livestock farming (PLF) enables remote monitoring on individual level with potential for predictive warning. Body temperature (Tb) and heart rate (HR) could be used for early detection of diseases, stress or death. We tested physiological sensors in free-grazing Norwegian white sheep in Norway. Forty Tb sensors and thirty HR sensors were surgically implanted in 40 lambs and 10 ewes. Eight (27%) of the HR and eight (20%) of the Tb sensors were lost during the study period. Two Tb sensors migrated from the abdominal cavity in to the digestive system. ECG based validation of the HR sensors revealed a measurement error of 0.2 bpm (SD 5.2 bpm) and correct measurement quality was assigned in 90% of the measurements. Maximum and minimum HR confirmed by ECG was 197 bpm and 68 bpm respectively. Mean passive HR was 90 bpm (SD = 13 bpm) for ewes and 112 bpm (SD = 13 bpm) for lambs. Mean Tb for all animals was 39.6°C (range 36.9 to 41.8°C). Tb displayed 24-hour circadian rhythms during 80.7 % but HR only during 41.0 % of the studied period. We established baseline values and conclude that these sensors deliver good quality. For a wide agricultural use, the sensor implantation method has to be further developed and real-time communication technology added.
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http://dx.doi.org/10.1016/j.vas.2019.100075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7386703PMC
December 2019

Wolf habitat selection when sympatric or allopatric with brown bears in Scandinavia.

Sci Rep 2020 06 18;10(1):9941. Epub 2020 Jun 18.

Grimsӧ Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, SE-730 91, Riddarhyttan, Sweden.

Habitat selection of animals depends on factors such as food availability, landscape features, and intra- and interspecific interactions. Individuals can show several behavioral responses to reduce competition for habitat, yet the mechanisms that drive them are poorly understood. This is particularly true for large carnivores, whose fine-scale monitoring is logistically complex and expensive. In Scandinavia, the home-range establishment and kill rates of gray wolves (Canis lupus) are affected by the coexistence with brown bears (Ursus arctos). Here, we applied resource selection functions and a multivariate approach to compare wolf habitat selection within home ranges of wolves that were either sympatric or allopatric with bears. Wolves selected for lower altitudes in winter, particularly in the area where bears and wolves are sympatric, where altitude is generally higher than where they are allopatric. Wolves may follow the winter migration of their staple prey, moose (Alces alces), to lower altitudes. Otherwise, we did not find any effect of bear presence on wolf habitat selection, in contrast with our previous studies. Our new results indicate that the manifestation of a specific driver of habitat selection, namely interspecific competition, can vary at different spatial-temporal scales. This is important to understand the structure of ecological communities and the varying mechanisms underlying interspecific interactions.
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http://dx.doi.org/10.1038/s41598-020-66626-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303184PMC
June 2020

Hydrophilic Interaction Liquid Chromatography Coupled to Mass Spectrometry and Multivariate Analysis of the Pyrimidine Pathway Metabolites.

Biomolecules 2019 07 31;9(8). Epub 2019 Jul 31.

Laboratory of Advanced Analytical Techniques in Natural Products, Universidad de los Andes, Bogotá 111711, Colombia.

In this study, we describe the optimization of a Hydrophilic Interaction Liquid Chromatography coupled to mass spectrometry (HILIC-MS) method for the evaluation of 14 metabolites related to the de novo synthesis of pyrimidines (dnSP) while using multivariate analysis, which is the metabolic pathway for pyrimidine nucleotide production. A multivariate design was used to set the conditions of the column temperature, flow of the mobile phase, additive concentration, gradient rate, and pH of the mobile phase in order to attain higher peak resolution and ionization efficiency in shorter analysis times. The optimization process was carried out while using factorial fractional designs, Box-Behnken design and central composite design while using two zwitterionic columns, ZIC-p-HILIC and ZIC-HILIC, polymeric, and silica-based columns, respectively. The factors were evaluated while using resolution (R), retention factor (), efficiency of the column (N), and peak height (h) as the response variables. The best optimized conditions were found with the ZIC-p-HILIC column: elution gradient rate 2 min., pH 7.0, temperature 45 °C, mobile phase flow of 0.35 mL min, and additive (ammonium acetate) concentration of 6 mM. The total analysis time was 28 min. The ZIC-p-HILIC LC-MS method yielded satisfactory results for linearity of calibration curves, limit of detection (LOD), and limit of quantification (LOQ). The method has been shown to be appropriate for the analysis of dnSP on samples of tomato plants that were infected with Phytophthora infestans.
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http://dx.doi.org/10.3390/biom9080328DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6722987PMC
July 2019

Dihydroorotate Dehydrogenase Is a Potential Target for Chemical Control - A Comparison With the Enzyme From .

Front Microbiol 2019 28;10:1479. Epub 2019 Jun 28.

Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá, Colombia.

The oomycete is the causal agent of tomato and potato late blight, a disease that causes tremendous economic losses in the production of solanaceous crops. The similarities between oomycetes and the apicomplexa led us to hypothesize that dihydroorotate dehydrogenase (DHODH), the enzyme catalyzing the fourth step in pyrimidine biosynthetic pathway, and a validated drug target in treatment of malaria, could be a potential target for controlling growth. In eukaryotes, class 2 DHODHs are mitochondrially associated ubiquinone-linked enzymes that catalyze the fourth, and only redox step of pyrimidine biosynthesis. We characterized the enzymes from both the pathogen and a host, . Plant DHODHs are known to be class 2 enzymes. Sequence analysis suggested that the pathogen enzyme (PiDHODHs) also belongs to this class. We confirmed the mitochondrial localization of GFP-PiDHODH showing colocalization with mCherry-labeled ATPase in a transgenic pathogen. N-terminally truncated versions of the two DHODHs were overproduced in , purified, and kinetically characterized. StDHODH exhibited a apparent specific activity of 41 ± 1 μmol min mg, a k of 30 ± 1 s, and a K of 20 ± 1 μM for L-dihydroorotate, and a K= 30 ± 3 μM for decylubiquinone (Qd). PiDHODH exhibited an apparent specific activity of 104 ± 1 μmol min mg, a k of 75 ± 1 s, and a K of 57 ± 3 μM for L-dihydroorotate, and a K of 15 ± 1 μM for Qd. The two enzymes exhibited different activities with different quinones and napthoquinone derivatives, and different sensitivities to compounds known to cause inhibition of DHODHs from other organisms. The IC for A77 1726, a nanomolar inhibitor of human DHODH, was 2.9 ± 0.6 mM for StDHODH, and 79 ± 1 μM for PiDHODH. , 0.5 mM A77 1726 decreased mycelial growth by approximately 50%, after 92 h. Collectively, our findings suggest that the DHODH could be a target for selective inhibitors and we provide a biochemical background for the development of compounds that could be helpful for the control of the pathogen, opening the way to protein crystallization.
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http://dx.doi.org/10.3389/fmicb.2019.01479DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6611227PMC
June 2019

Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale.

Glob Chang Biol 2019 09 24;25(9):3005-3017. Epub 2019 Jun 24.

Departamento de Biología Aplicada, Universidad Miguel Hernández, Elche, Spain.

Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large-scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion-consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species-poor to species rich assemblages (4-30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human-impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As species-rich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human-dominated landscapes in the Anthropocene.
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http://dx.doi.org/10.1111/gcb.14708DOI Listing
September 2019

Testing the influence of habitat experienced during the natal phase on habitat selection later in life in Scandinavian wolves.

Sci Rep 2019 04 25;9(1):6526. Epub 2019 Apr 25.

Faculty of Applied Ecology, Agricultural Sciences and Biotechnology, Inland Norway University of Applied Sciences, Evenstad, NO-2480, Koppang, Norway.

Natal habitat preference induction (NHPI) occurs when characteristics of the natal habitat influence the future habitat selection of an animal. However, the influence of NHPI after the dispersal phase has received remarkably little attention. We tested whether exposure to humans in the natal habitat helps understand why some adult wolves Canis lupus may approach human settlements more than other conspecifics, a question of both ecological and management interest. We quantified habitat selection patterns within home ranges using resource selection functions and GPS data from 21 wolf pairs in Scandinavia. We identified the natal territory of each wolf with genetic parental assignment, and we used human-related characteristics within the natal territory to estimate the degree of anthropogenic influence in the early life of each wolf. When the female of the adult wolf pair was born in an area with a high degree of anthropogenic influence, the wolf pair tended to select areas further away from humans, compared to wolf pairs from natal territories with a low degree of anthropogenic influence. Yet the pattern was statistically weak, we suggest that our methodological approach can be useful in other systems to better understand NHPI and to inform management  about human-wildlife interactions.
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http://dx.doi.org/10.1038/s41598-019-42835-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6484024PMC
April 2019

No place like home? A test of the natal habitat-biased dispersal hypothesis in Scandinavian wolves.

R Soc Open Sci 2018 Dec 12;5(12):181379. Epub 2018 Dec 12.

Faculty of Applied Ecology and Agricultural Sciences, Inland Norway University of Applied Sciences, Evenstad, 2480 Koppang, Norway.

Natal dispersal is an important mechanism for the viability of populations. The influence of local conditions or experience gained in the natal habitat could improve fitness if dispersing individuals settle in an area with similar habitat characteristics. This process, defined as 'natal habitat-biased dispersal' (NHBD), has been used to explain distribution patterns in large carnivores, but actual studies evaluating it are rare. We tested whether grey wolf territory establishment was influenced by the habitat characteristics of the natal territory using the long-term monitoring of the Scandinavian wolf population. We paired the locations of natal and established territories, accounted for available habitats along the dispersing route, and compared their habitat characteristics for 271 wolves during 1998-2012. Wolves with the shortest dispersal distances established in natal-like habitat types more than expected by chance, whereas wolves that dispersed longer distances did not show NHBD. The pattern was consistent for male and female wolves, with females showing more NHBD than males. Chances to detect NHBD increased with the size of habitat defined as available. This highlights the importance of considering the biological characteristics of the studied species when defining habitat availability. Our methodological approach can prove useful to inform conservation and management to identify habitats to be selected by reintroduced or naturally expanding populations.
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http://dx.doi.org/10.1098/rsos.181379DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6304128PMC
December 2018

Habitat segregation between brown bears and gray wolves in a human-dominated landscape.

Ecol Evol 2018 Dec 11;8(23):11450-11466. Epub 2018 Nov 11.

Grimsӧ Wildlife Research Station Department of Ecology Swedish University of Agricultural Sciences Riddarhyttan Sweden.

Identifying how sympatric species belonging to the same guild coexist is a major question of community ecology and conservation. Habitat segregation between two species might help reduce the effects of interspecific competition and apex predators are of special interest in this context, because their interactions can have consequences for lower trophic levels. However, habitat segregation between sympatric large carnivores has seldom been studied. Based on monitoring of 53 brown bears () and seven sympatric adult gray wolves () equipped with GPS collars in Sweden, we analyzed the degree of interspecific segregation in habitat selection within their home ranges in both late winter and spring, when their diets overlap the most. We used the K-select method, a multivariate approach that relies on the concept of ecological niche, and randomization methods to quantify habitat segregation between bears and wolves. Habitat segregation between bears and wolves was greater than expected by chance. Wolves tended to select for moose occurrence, young forests, and rugged terrain more than bears, which likely reflects the different requirements of an omnivore (bear) and an obligate carnivore (wolf). However, both species generally avoided human-related habitats during daytime. Disentangling the mechanisms that can drive interspecific interactions at different spatial scales is essential for understanding how sympatric large carnivores occur and coexist in human-dominated landscapes, and how coexistence may affect lower trophic levels. The individual variation in habitat selection detected in our study may be a relevant mechanism to overcome intraguild competition and facilitate coexistence.
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http://dx.doi.org/10.1002/ece3.4572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6303696PMC
December 2018

Data to model risks for recolonizing wolves in Scandinavia through the integration of territory presence and human-driven mortalities.

Data Brief 2018 Oct 28;20:686-690. Epub 2018 Aug 28.

Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, SE-73091 Riddarhyttan, Sweden.

This dataset article describes the data and sources used to model risks for the recolonizing wolf () in Sweden and Norway in the article "Integrated spatially-explicit models predict pervasive risks to recolonizing wolves in Scandinavia from human-driven mortality" (Recio et al., 2018). Presences on wolf territories were used to model the potential distribution of the species. Presences of human-driven mortalities including traffic collisions, culling (protective/defensive, and licensed hunting), and illegal killing (i.e. poaching) were used to model predictions on the distribution of these mortalities. Sources for the independent variables used for the models are also described.
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http://dx.doi.org/10.1016/j.dib.2018.08.060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6129723PMC
October 2018

Den site selection by male brown bears at the population's expansion front.

PLoS One 2018 30;13(8):e0202653. Epub 2018 Aug 30.

Department of Forestry and Wildlife Management, Inland Norway University of Applied Sciences, Evenstad, Norway.

Brown bears (Ursus arctos) spend about half of the year in winter dens. In order to preserve energy, bears may select denning locations that minimize temperature loss and human disturbance. In expanding animal populations, demographic structure and individual behavior at the expansion front can differ from core areas. We conducted a non-invasive study of male brown bear den sites at the male-biased, low-density western expansion front of the Scandinavian brown bear population, comparing den locations to the available habitat. Compared to the higher-density population core in which intraspecific avoidance may affect den site selection of subordinate bears, we expected resource competition in the periphery to be low, and all bears to be able to select optimal den sites. In addition, bears in the periphery had access to free-ranging domestic sheep during summer. We found that males in the periphery denned on high-elevation slopes, probably providing good drainage, longer periods of consistent, insulating snow cover and fewer melting-freezing events. Forests were the principal denning habitat and no dens were found in alpine areas. The Scandinavian brown bears have a history of intense harvest, including culling at the den. This may have exerted a selection pressure to avoid denning in open alpine habitat which compared to forests provide little cover. The bears denned away from main roads and in steep, rugged terrain, probably limiting human access. The odds for finding a bear den decreased with increasing distance to the population core where females could be found. Previous studies have documented directed movement of male brown bears from the male-biased population periphery toward the core areas during the mating season. In this way, denning males may be trading off between low resource competition and access to sheep in the low-density periphery, and mating opportunities in the higher-density population core.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0202653PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6116945PMC
February 2019

The alternative prey hypothesis revisited: Still valid for willow ptarmigan population dynamics.

PLoS One 2018 6;13(6):e0197289. Epub 2018 Jun 6.

Faculty of Applied Ecology and Agricultural Sciences, Inland Norway University of Applied Sciences, Campus Evenstad, Koppang, Norway.

The alternative prey hypothesis predicts that the interaction between generalist predators and their main prey is a major driver of population dynamics of alternative prey species. In Fennoscandia, changes in climate and human land use are assumed to alter the dynamics of cyclic small rodents (main prey) and lead to increased densities and range expansion of an important generalist predator, the red fox Vulpes vulpes. In order to better understand the role of these potential changes in community structure on an alternative prey species, willow ptarmigan Lagopus lagopus, we analyzed nine years of population census data from SE Norway to investigate how community interactions affected their population dynamics. The ptarmigan populations showed no declining trend during the study period, and annual variations corresponded with marked periodic small rodent peaks and declines. Population growth and breeding success were highly correlated, and both demographic variables were influenced by an interaction between red fox and small rodents. Red foxes affected ptarmigan negatively only when small rodent abundance was low, which is in accordance with the alternative prey hypothesis. Our results confirm the important role of red fox predation in ptarmigan dynamics, and indicate that if small rodent cycles are disrupted, this may lead to decline in ptarmigan and other alternative prey species due to elevated predation pressure.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0197289PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5991367PMC
November 2018

A CTP Synthase Undergoing Stage-Specific Spatial Expression Is Essential for the Survival of the Intracellular Parasite .

Front Cell Infect Microbiol 2018 22;8:83. Epub 2018 Mar 22.

Departamento de Ciencias Biologicas, Universidad de los Andes, Bogota, Colombia.

Cytidine triphosphate synthase catalyzes the synthesis of cytidine 5'-triphosphate (CTP) from uridine 5'-triphosphate (UTP), the final step in the production of cytidine nucleotides. CTP synthases also form filamentous structures of different morphologies known as , whose functions in most organisms are unknown. Here, we identified and characterized a novel CTP synthase (CTPS) from . We show that CTPS is capable of substituting for its counterparts in the otherwise lethal double mutant (Δ Δ) of . Equally, recombinant CTPS purified from encodes for a functional protein in enzyme assays. The epitope-tagged CTPS under the control of its endogenous promoter displays a punctate cytosolic distribution, which undergoes spatial reorganization to form foci or filament-like structures when the parasite switches from a nutrient-replete (intracellular) to a nutrient-scarce (extracellular) condition. An analogous phenotype is observed upon nutrient stress or after treatment with a glutamine analog, 6-diazo-5-oxo-L-norleucine (DON). The exposure of parasites to DON disrupts the lytic cycle, and the CTPS is refractory to a genetic deletion, suggesting an essential requirement of this enzyme for . Not least, this study, together with previous studies, supports that CTP synthase can serve as a potent drug target, because the parasite, unlike human host cells, cannot compensate for the lack of CTP synthase activity.
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http://dx.doi.org/10.3389/fcimb.2018.00083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874296PMC
April 2019

Prey Selection of Scandinavian Wolves: Single Large or Several Small?

PLoS One 2016 28;11(12):e0168062. Epub 2016 Dec 28.

Faculty of Applied Ecology and Agricultural Sciences, Hedmark University of Applied Sciences, Evenstad, Koppang, Norway.

Research on large predator-prey interactions are often limited to the predators' primary prey, with the potential for prey switching in systems with multiple ungulate species rarely investigated. We evaluated wolf (Canis lupus) prey selection at two different spatial scales, i.e., inter- and intra-territorial, using data from 409 ungulate wolf-kills in an expanding wolf population in Scandinavia. This expansion includes a change from a one-prey into a two-prey system with variable densities of one large-sized ungulate; moose (Alces alces) and one small-sized ungulate; roe deer (Capreolus capreolus). Among wolf territories, the proportion of roe deer in wolf kills was related to both pack size and roe deer density, but not to moose density. Pairs of wolves killed a higher proportion of roe deer than did packs, and wolves switched to kill more roe deer as their density increased above a 1:1 ratio in relation to the availability of the two species. At the intra-territorial level, wolves again responded to changes in roe deer density in their prey selection whereas we found no effect of snow depth, time during winter, or other predator-related factors on the wolves' choice to kill moose or roe deer. Moose population density was only weakly related to intra-territorial prey selection. Our results show that the functional response of wolves on moose, the species hitherto considered as the main prey, was strongly dependent on the density of a smaller, alternative, ungulate prey. The impact of wolf predation on the prey species community is therefore likely to change with the composition of the multi-prey species community along with the geographical expansion of the wolf population.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0168062PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5193335PMC
July 2017

Pyrimidine Pathway-Dependent and -Independent Functions of the Toxoplasma gondii Mitochondrial Dihydroorotate Dehydrogenase.

Infect Immun 2016 10 19;84(10):2974-81. Epub 2016 Sep 19.

Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA

Dihydroorotate dehydrogenase (DHODH) mediates the fourth step of de novo pyrimidine biosynthesis and is a proven drug target for inducing immunosuppression in therapy of human disease as well as a rapidly emerging drug target for treatment of malaria. In Toxoplasma gondii, disruption of the first, fifth, or sixth step of de novo pyrimidine biosynthesis induced uracil auxotrophy. However, previous attempts to generate uracil auxotrophy by genetically deleting the mitochondrion-associated DHODH of T. gondii (TgDHODH) failed. To further address the essentiality of TgDHODH, mutant gene alleles deficient in TgDHODH activity were designed to ablate the enzyme activity. Replacement of the endogenous DHODH gene with catalytically deficient DHODH gene alleles induced uracil auxotrophy. Catalytically deficient TgDHODH localized to the mitochondria, and parasites retained mitochondrial membrane potential. These results show that TgDHODH is essential for the synthesis of pyrimidines and suggest that TgDHODH is required for a second essential function independent of its role in pyrimidine biosynthesis.
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http://dx.doi.org/10.1128/IAI.00187-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5038078PMC
October 2016

Sarcoptic mange in the Scandinavian wolf Canis lupus population.

BMC Vet Res 2016 Jul 27;12(1):156. Epub 2016 Jul 27.

Faculty of Applied Ecology and Agricultural Sciences, Hedmark University College, Campus Evenstad, N-2480, Koppang, Norway.

Background: Sarcoptic mange, a parasitic disease caused by the mite Sarcoptes scabiei, is regularly reported on wolves Canis lupus in Scandinavia. We describe the distribution and transmission of this parasite within the small but recovering wolf population by analysing 269 necropsy reports and performing a serological survey on 198 serum samples collected from free-ranging wolves between 1998 and 2013.

Results: The serological survey among 145 individual captured Scandinavian wolves (53 recaptures) shows a consistent presence of antibodies against sarcoptic mange. Seropositivity among all captured wolves was 10.1 % (CI. 6.4 %-15.1 %). Sarcoptic mange-related mortality reported at necropsy was 5.6 % and due to secondary causes, predominantly starvation. In the southern range of the population, seroprevalence was higher, consistent with higher red fox densities. Female wolves had a lower probability of being seropositive than males, but for both sexes the probability increased with pack size. Recaptured individuals changing from seropositive to seronegative suggest recovery from sarcoptic mange. The lack of seropositive pups (8-10 months, N = 56) and the occurrence of seropositive and seronegative individuals in the same pack indicates interspecific transmission of S. scabiei into this wolf population.

Conclusions: We consider sarcoptic mange to have little effect on the recovery of the Scandinavian wolf population. Heterogenic infection patterns on the pack level in combination with the importance of individual-based factors (sex, pack size) and the north-south gradient for seroprevalence suggests low probability of wolf-to-wolf transmission of S. scabiei in Scandinavia.
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http://dx.doi.org/10.1186/s12917-016-0780-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4962404PMC
July 2016

Leave before it's too late: anthropogenic and environmental triggers of autumn migration in a hunted ungulate population.

Ecology 2016 Apr;97(4):1058-68

Autumn has to a large extent been neglected in the climate effect literature, yet autumn events, e.g., plant senescence and animal migration, affect fitness of animals differently than spring events. Understanding how variables including plant phenology influence timing of autumn migrations is important to gain a comprehensive understanding of the full annual cycle of migratory species. Here we use 13 yr of data from 60 male and 168 female red deer (Cervus elaphus) to identify triggers of autumn migration. We relate the timing of autumn migration to environmental variables like snow fall, temperature, and plant phenology (NDVI), and to onset of hunting, sex, and migration distance. Severe weather has been suggested as the main trigger of autumn migration, but we found that the majority of the individuals had left the summer range well before snow fall (80.3%) and frost (70.5%), and also before the peak deterioration in forage quality (71.9%). Declining temperatures were associated with a higher daily migration potential. Onset of hunting showed the largest effect on migration potential, with a marked increase during the first days of hunting. Individuals still present in the summer range when snow fall, frost, or peak forage deterioration occurred showed a significantly higher migration potential around these events. Males were less responsive to environmental cues, suggesting rutting activity, starting earlier in males, initiate movement prior to such conditions. Also, individuals with longer migration distances had a higher migration potential late in the season than individuals with shorter migration distances. Our study shows that factors beyond weather and plant phenology, such as onset of hunting, may be important triggers of autumn migration. Severe weather and forage deterioration were important triggers for the individuals experiencing this, which suggests a hierarchical response to environmental cues. The trade-off between staying longer in the summer range and increased energy expenditures if surprised by severe weather is asymmetric, and leaving well in advance can be seen as a risk-averse tactic.
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April 2016

Leave before it's too late: anthropogenic and environmental triggers of autumn migration in a hunted ungulate population.

Ecology 2016 Apr;97(4):1058-1068

Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, NO-0316, Oslo, Norway.

Autumn has to a large extent been neglected in the climate effect literature, yet autumn events, e.g., plant senescence and animal migration, affect fitness of animals differently than spring events. Understanding how variables including plant phenology influence timing of autumn migrations is important to gain a comprehensive understanding of the full annual cycle of migratory species. Here we use 13 yr of data from 60 male and 168 female red deer (Cervus elaphus) to identify triggers of autumn migration. We relate the timing of autumn migration to environmental variables like snow fall, temperature, and plant phenology (NDVI), and to onset of hunting, sex, and migration distance. Severe weather has been suggested as the main trigger of autumn migration, but we found that the majority of the individuals had left the summer range well before snow fall (80.3%) and frost (70.5%), and also before the peak deterioration in forage quality (71.9%). Declining temperatures were associated with a higher daily migration potential. Onset of hunting showed the largest effect on migration potential, with a marked increase during the first days of hunting. Individuals still present in the summer range when snow fall, frost, or peak forage deterioration occurred showed a significantly higher migration potential around these events. Males were less responsive to environmental cues, suggesting rutting activity, starting earlier in males, initiate movement prior to such conditions. Also, individuals with longer migration distances had a higher migration potential late in the season than individuals with shorter migration distances. Our study shows that factors beyond weather and plant phenology, such as onset of hunting, may be important triggers of autumn migration. Severe weather and forage deterioration were important triggers for the individuals experiencing this, which suggests a hierarchical response to environmental cues. The trade-off between staying longer in the summer range and increased energy expenditures if surprised by severe weather is asymmetric, and leaving well in advance can be seen as a risk-averse tactic.
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http://dx.doi.org/10.1890/15-1191.1DOI Listing
April 2016

FOXO1 couples metabolic activity and growth state in the vascular endothelium.

Nature 2016 Jan 6;529(7585):216-20. Epub 2016 Jan 6.

Angiogenesis &Metabolism Laboratory, Max Planck Institute for Heart and Lung Research, D-61231 Bad Nauheim, Germany.

Endothelial cells (ECs) are plastic cells that can switch between growth states with different bioenergetic and biosynthetic requirements. Although quiescent in most healthy tissues, ECs divide and migrate rapidly upon proangiogenic stimulation. Adjusting endothelial metabolism to the growth state is central to normal vessel growth and function, yet it is poorly understood at the molecular level. Here we report that the forkhead box O (FOXO) transcription factor FOXO1 is an essential regulator of vascular growth that couples metabolic and proliferative activities in ECs. Endothelial-restricted deletion of FOXO1 in mice induces a profound increase in EC proliferation that interferes with coordinated sprouting, thereby causing hyperplasia and vessel enlargement. Conversely, forced expression of FOXO1 restricts vascular expansion and leads to vessel thinning and hypobranching. We find that FOXO1 acts as a gatekeeper of endothelial quiescence, which decelerates metabolic activity by reducing glycolysis and mitochondrial respiration. Mechanistically, FOXO1 suppresses signalling by MYC (also known as c-MYC), a powerful driver of anabolic metabolism and growth. MYC ablation impairs glycolysis, mitochondrial function and proliferation of ECs while its EC-specific overexpression fuels these processes. Moreover, restoration of MYC signalling in FOXO1-overexpressing endothelium normalizes metabolic activity and branching behaviour. Our findings identify FOXO1 as a critical rheostat of vascular expansion and define the FOXO1-MYC transcriptional network as a novel metabolic checkpoint during endothelial growth and proliferation.
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http://dx.doi.org/10.1038/nature16498DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5380221PMC
January 2016

Pyrimidine Metabolism: Dynamic and Versatile Pathways in Pathogens and Cellular Development.

J Genet Genomics 2015 May 8;42(5):195-205. Epub 2015 May 8.

Department of Biological Sciences, Los Andes University, Bogota, Colombia. Electronic address:

The importance of pyrimidines lies in the fact that they are structural components of a broad spectrum of key molecules that participate in diverse cellular functions, such as synthesis of DNA, RNA, lipids, and carbohydrates. Pyrimidine metabolism encompasses all enzymes involved in the synthesis, degradation, salvage, interconversion and transport of these molecules. In this review, we summarize recent publications that document how pyrimidine metabolism changes under a variety of conditions, including, when possible, those studies based on techniques of genomics, transcriptomics, proteomics, and metabolomics. First, we briefly look at the dynamics of pyrimidine metabolism during nonpathogenic cellular events. We then focus on changes that pathogen infections cause in the pyrimidine metabolism of their host. Next, we discuss the effects of antimetabolites and inhibitors, and finally we consider the consequences of genetic manipulations, such as knock-downs, knock-outs, and knock-ins, of pyrimidine enzymes on pyrimidine metabolism in the cell.
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http://dx.doi.org/10.1016/j.jgg.2015.04.004DOI Listing
May 2015

Behavioral responses of wolves to roads: scale-dependent ambivalence.

Behav Ecol 2014 Nov 20;25(6):1353-1364. Epub 2014 Aug 20.

Department of Ecology, Grimsö Wildlife Research Station, Swedish University of Agricultural Science , SE-73091 Riddarhyttan , Sweden.

Throughout their recent recovery in several industrialized countries, large carnivores have had to cope with a changed landscape dominated by human infrastructure. Population growth depends on the ability of individuals to adapt to these changes by making use of new habitat features and at the same time to avoid increased risks of mortality associated with human infrastructure. We analyzed the summer movements of 19 GPS-collared resident wolves ( L.) from 14 territories in Scandinavia in relation to roads. We used resource and step selection functions, including >12000 field-checked GPS-positions and 315 kill sites. Wolves displayed ambivalent responses to roads depending on the spatial scale, road type, time of day, behavioral state, and reproductive status. At the site scale (approximately 0.1 km), they selected for roads when traveling, nearly doubling their travel speed. Breeding wolves moved the fastest. At the patch scale (10 km), house density rather than road density was a significant negative predictor of wolf patch selection. At the home range scale (approximately 1000 km), breeding wolves increased gravel road use with increasing road availability, although at a lower rate than expected. Wolves have adapted to use roads for ease of travel, but at the same time developed a cryptic behavior to avoid human encounters. This behavioral plasticity may have been important in allowing the successful recovery of wolf populations in industrialized countries. However, we emphasize the role of roads as a potential cause of increased human-caused mortality.
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http://dx.doi.org/10.1093/beheco/aru134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4235582PMC
November 2014

Predator-dependent functional response in wolves: from food limitation to surplus killing.

J Anim Ecol 2015 Jan 6;84(1):102-12. Epub 2014 Sep 6.

Faculty of Applied Ecology and Agricultural Sciences, Hedmark University College, Campus Evenstad, N-2480 Koppang, Norway.

The functional response of a predator describes the change in per capita kill rate to changes in prey density. This response can be influenced by predator densities, giving a predator-dependent functional response. In social carnivores which defend a territory, kill rates also depend on the individual energetic requirements of group members and their contribution to the kill rate. This study aims to provide empirical data for the functional response of wolves Canis lupus to the highly managed moose Alces alces population in Scandinavia. We explored prey and predator dependence, and how the functional response relates to the energetic requirements of wolf packs. Winter kill rates of GPS-collared wolves and densities of cervids were estimated for a total of 22 study periods in 15 wolf territories. The adult wolves were identified as the individuals responsible for providing kills to the wolf pack, while pups could be described as inept hunters. The predator-dependent, asymptotic functional response models (i.e. Hassell-Varley type II and Crowley-Martin) performed best among a set of 23 competing linear, asymptotic and sigmoid models. Small wolf packs acquired >3 times as much moose biomass as required to sustain their field metabolic rate (FMR), even at relatively low moose abundances. Large packs (6-9 wolves) acquired less biomass than required in territories with low moose abundance. We suggest the surplus killing by small packs is a result of an optimal foraging strategy to consume only the most nutritious parts of easy accessible prey while avoiding the risk of being detected by humans. Food limitation may have a stabilizing effect on pack size in wolves, as supported by the observed negative relationship between body weight of pups and pack size.
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http://dx.doi.org/10.1111/1365-2656.12280DOI Listing
January 2015

Reversible immobilization of free-ranging red deer (Cervus elaphus) with xylazine-tiletamine-zolazepam and atipamezole.

J Wildl Dis 2014 Apr 7;50(2):359-63. Epub 2014 Feb 7.

1  Norwegian Institute for Agricultural and Environmental Research, Organic Food and Farming Division, NO-6630 Tingvoll, Norway.

Forty-eight free-ranging red deer (Cervus elaphus) were immobilized with xylazine (X) and tiletamine-zolazepam (TZ) by dart injection during winter 2008 in Norway. A follow-up study in five animals during winter 2010 included arterial blood samples analyzed with a portable clinical analyzer in the field. Thirty-five of 48 animals were effectively immobilized and 13 required a second dart. Mean ± SD doses were 2.89 ± 0.45 mg X/kg and 2.89 ± 0.45 mg TZ/kg in calves and 2.97 ± 0.66 mg X/kg and 1.91 ± 0.43 mg TZ/kg in adults. Mean induction times for calves and adults were 8.5 ± 5 min and 11.6 ± 5.5 min, respectively. The main physiologic side effect during immobilization was hypoxemia (pulse oximetry, SpO2<85%). All five animals evaluated with arterial blood gas samples were hypoxemic (PaO2<10 kPa). Xylazine was antagonized with 0.43 ± 0.19 mg/kg and 0.27 ± 0.05 mg/kg of atipamezole in calves and adults, respectively. Time to standing/walking in calves and adults was 12 ± 7 min and 12 ± 11 min, respectively. Two capture mortalities occurred.
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http://dx.doi.org/10.7589/2012-10-267DOI Listing
April 2014

De novo pyrimidine biosynthesis in the oomycete plant pathogen Phytophthora infestans.

Gene 2014 Mar 18;537(2):312-21. Epub 2013 Dec 18.

Laboratory of Mycology and Plant Pathology, Universidad de los Andes, Carrera 1 # 18-10, Edificio J-205, Bogotá DC, Colombia. Electronic address:

The oomycete Phytophthora infestans, causal agent of the tomato and potato late blight, generates important economic and environmental losses worldwide. As current control strategies are becoming less effective, there is a need for studies on oomycete metabolism to help identify promising and more effective targets for chemical control. The pyrimidine pathways are attractive metabolic targets to combat tumors, virus and parasitic diseases but have not yet been studied in Phytophthora. Pyrimidines are involved in several critical cellular processes and play structural, metabolic and regulatory functions. Here, we used genomic and transcriptomic information to survey the pyrimidine metabolism during the P. infestans life cycle. After assessing the putative gene machinery for pyrimidine salvage and de novo synthesis, we inferred genealogies for each enzymatic domain in the latter pathway, which displayed a mosaic origin. The last two enzymes of the pathway, orotate phosphoribosyltransferase and orotidine-5-monophosphate decarboxylase, are fused in a multi-domain enzyme and are duplicated in some P. infestans strains. Two splice variants of the third gene (dihydroorotase) were identified, one of them encoding a premature stop codon generating a non-functional truncated protein. Relative expression profiles of pyrimidine biosynthesis genes were evaluated by qRT-PCR during infection in Solanum phureja. The third and fifth genes involved in this pathway showed high up-regulation during biotrophic stages and down-regulation during necrotrophy, whereas the uracil phosphoribosyl transferase gene involved in pyrimidine salvage showed the inverse behavior. These findings suggest the importance of de novo pyrimidine biosynthesis during the fast replicative early infection stages and highlight the dynamics of the metabolism associated with the hemibiotrophic life style of pathogen.
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http://dx.doi.org/10.1016/j.gene.2013.12.009DOI Listing
March 2014

Decomposing risk: landscape structure and wolf behavior generate different predation patterns in two sympatric ungulates.

Ecol Appl 2013 Oct;23(7):1722-34

Norwegian Institute for Nature Research, P.O. Box 5685 Sluppen, NO-7485 Trondheim, Norway.

Recolonizing carnivores can have a large impact on the status of wild ungulates, which have often modified their behavior in the absence of predation. Therefore, understanding the dynamics of reestablished predator-prey systems is crucial to predict their potential ecosystem effects. We decomposed the spatial structure of predation by recolonizing wolves (Canis lupus) on two sympatric ungulates, moose (Alces alces) and roe deer (Capreolus capreolus), in Scandinavia during a 10-year study. We monitored 18 wolves with GPS collars, distributed over 12 territories, and collected records from predation events. By using conditional logistic regression, we assessed the contributions of three main factors, the utilization patterns of each wolf territory, the spatial distribution of both prey species, and fine-scale landscape structure, in determining the spatial structure of moose and roe deer predation risk. The reestablished predator-prey system showed a remarkable spatial variation in kill occurrence at the intra-territorial level, with kill probabilities varying by several orders of magnitude inside the same territory. Variation in predation risk was evident also when a spatially homogeneous probability for a wolf to encounter a prey was simulated. Even inside the same territory, with the same landscape structure, and when exposed to predation by the same wolves, the two prey species experienced an opposite spatial distribution of predation risk. In particular, increased predation risk for moose was associated with open areas, especially clearcuts and young forest stands, whereas risk was lowered for roe deer in the same habitat types. Thus, fine-scale landscape structure can generate contrasting predation risk patterns in sympatric ungulates, so that they can experience large differences in the spatial distribution of risk and refuge areas when exposed to predation by a recolonizing predator. Territories with an earlier recolonization were not associated with a lower hunting success for wolves. Such constant efficiency in wolf predation during the recolonization process is in line with previous findings about the naive nature of Scandinavian moose to wolf predation. This, together with the human-dominated nature of the Scandinavian ecosystem, seems to limit the possibility for wolves to have large ecosystem effects and to establish a behaviorally mediated trophic cascade in Scandinavia.
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http://dx.doi.org/10.1890/12-1615.1DOI Listing
October 2013

A migratory northern ungulate in the pursuit of spring: jumping or surfing the green wave?

Am Nat 2012 Oct 23;180(4):407-24. Epub 2012 Aug 23.

Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Aas, Norway.

The forage-maturation hypothesis (FMH) states that herbivores migrate along a phenological gradient of plant development in order to maximize energy intake. Despite strong support for the FMH, the actual relationship between plant phenology and ungulate movement has remained enigmatic. We linked plant phenology (MODIS-normalized difference vegetation index [NDVI] data) and space use of 167 migratory and 78 resident red deer (Cervus elaphus), using a space-time-time matrix of "springness," defined as the instantaneous rate of green-up. Consistent with the FMH, migrants experienced substantially greater access to early plant phenology than did residents. Deer were also more likely to migrate in areas where migration led to greater gains in springness. Rather than "surfing the green wave" during migration, migratory red deer moved rapidly from the winter to the summer range, thereby "jumping the green wave." However, migrants and, to a lesser degree, residents did track phenological green-up through parts of the growing season by making smaller-scale adjustments in habitat use. Despite pronounced differences in their life histories, we found only marginal differences between male and female red deer in this study. Those differences that we did detect pointed toward additional constraints on female space-use tactics, such as those posed by calving and caring for dependent offspring. We conclude that whereas in some systems migration itself is a way to surf the green wave, in others it may simply be a means to reconnect with phenological spring at the summer range. In the light of ubiquitous anthropogenic environmental change, understanding the relationship between the green wave and ungulate space use has important consequences for the management and conservation of migratory ungulates and the phenomenon of migration itself.
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http://dx.doi.org/10.1086/667590DOI Listing
October 2012

Biochemical and molecular characterization of the pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase from Toxoplasma gondii.

Mol Biochem Parasitol 2012 Aug 8;184(2):71-81. Epub 2012 May 8.

Departamento de Ciencias Biologicas, Universidad de los Andes, Carrera 1, No. 18A-10, Bogotá, Colombia.

The pyrimidine biosynthesis pathway in the protozoan pathogen Toxoplasma gondii is essential for parasite growth during infection. To investigate the properties of dihydroorotate dehydrogenase (TgDHOD), the fourth enzyme in the T. gondii pyrimidine pathway, we expressed and purified recombinant TgDHOD. TgDHOD exhibited a specific activity of 84U/mg, a k(cat) of 89s(-1), a K(m)=60μM for l-dihydroorotate, and a K(m)=29μM for decylubiquinone (Q(D)). Quinones lacking or having short isoprenoid side chains yielded lower k(cat)s than Q(D). As expected, fumarate was a poor electron acceptor for this family 2 DHOD. The IC(50)s determined for A77-1726, the active derivative of the human DHOD inhibitor leflunomide, and related compounds MD249 and MD209 were, 91μM, 96μM, and 60μM, respectively. The enzyme was not significantly affected by brequinar or TTFA, known inhibitors of human DHOD, or by atovaquone. DSM190, a known inhibitor of Plasmodium falciparum DHOD, was a poor inhibitor of TgDHOD. TgDHOD exhibits a lengthy 157-residue N-terminal extension, consistent with a potential organellar targeting signal. We constructed C-terminally c-myc tagged TgDHODs to examine subcellular localization of TgDHOD in transgenic parasites expressing the tagged protein. Using both exogenous and endogenous expression strategies, anti-myc fluorescence signal colocalized with antibodies against the mitochondrial marker ATPase. These findings demonstrate that TgDHOD is associated with the parasite's mitochondrion, revealing this organelle as the site of orotate production in T. gondii. The TgDHOD gene appears to be essential because while gene tagging was successful at the TgDHOD gene locus, attempts to delete the TgDHOD gene were not successful in the KU80 background. Collectively, our study suggests that TgDHOD is an excellent target for the development of anti-Toxoplasma drugs.
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http://dx.doi.org/10.1016/j.molbiopara.2012.04.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3855825PMC
August 2012

Predicting the potential demographic impact of predators on their prey: a comparative analysis of two carnivore-ungulate systems in Scandinavia.

J Anim Ecol 2012 Mar 11;81(2):443-54. Epub 2011 Nov 11.

Norwegian Institute for Nature Research, PO Box 5685, Sluppen, NO-7485 Trondheim, Norway.

1. Understanding the role of predation in shaping the dynamics of animal communities is a fundamental issue in ecological research. Nevertheless, the complex nature of predator-prey interactions often prevents researchers from modelling them explicitly. 2. By using periodic Leslie-Usher matrices and a simulation approach together with parameters obtained from long-term field projects, we reconstructed the underlying mechanisms of predator-prey demographic interactions and compared the dynamics of the roe deer-red fox-Eurasian lynx-human harvest system with those of the moose-brown bear-gray wolf-human harvest system in the boreal forest ecosystem of the southern Scandinavian Peninsula. 3. The functional relationship of both roe deer and moose λ to changes in predation rates from the four predators was remarkably different. Lynx had the strongest impact among the four predators, whereas predation rates by wolves, red foxes, or brown bears generated minor variations in prey population λ. Elasticity values of lynx, wolf, fox and bear predation rates were -0·157, -0·056, -0·031 and -0·006, respectively, but varied with both predator and prey densities. 4. Differences in predation impact were only partially related to differences in kill or predation rates, but were rather a result of different distribution of predation events among prey age classes. Therefore, the age composition of killed individuals emerged as the main underlying factor determining the overall per capita impact of predation. 5. Our results confirm the complex nature of predator-prey interactions in large terrestrial mammals, by showing that different carnivores preying on the same prey species can exert a dramatically different demographic impact, even in the same ecological context, as a direct consequence of their predation patterns. Similar applications of this analytical framework in other geographical and ecological contexts are needed, but a more general evaluation of the subject is also required, aimed to assess, on a broader systematic and ecological range, what specific traits of a carnivore are most related to its potential impact on prey species.
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http://dx.doi.org/10.1111/j.1365-2656.2011.01928.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440569PMC
March 2012