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451.
Koen C. A. Brker Rikke G. Hansen Kathleen E. Leonard William R. Koski Mads Peter Heide‐Jrgensen 《Marine Mammal Science》2019,35(4):1253-1279
From 25 to 30 August 2014 a double‐observer line‐transect survey was conducted over Melville Bay, home to one of two summering populations of narwhal (Monodon monoceros) off West Greenland. A total of 1,932 linear kilometers was surveyed along 33 transects. In addition to using observers, the aircraft was equipped with two oblique cameras to capture a comparable data set. Analysts reviewed the images for narwhal sightings, which were then matched to the observer sightings. The objectives of the study were to determine advantages and disadvantages of the detection capabilities of both methodologies, and to conduct a comparative analysis of population abundance estimates. Correcting for the truncated detection distance of the images (500 m), the image analysts recorded more sightings (62) and a lower mean group size (2.2) compared to aerial observers (36 and 3.5, respectively), resulting in comparable numbers of individuals detected by both platforms (135 vs. 126). The abundance estimate based on the image sightings was 2,536 (CV = 0.51, 95% CI: 1,003–6,406), which was not significantly different from the aerial observers estimate of 2,596 individuals (CV = 0.51; 95% CI: 961–7,008). This study supports the potential of using UAS for marine mammal abundance studies. 相似文献
452.
Marie-Louise Kampmann Ida Bærholm Schnell Randi Holm Jensen Jan Axtner Adam F. Sander Anders J. Hansen Mads F. Bertelsen Alex D. Greenwood M. Thomas P. Gilbert Andreas Wilting 《European Journal of Wildlife Research》2017,63(2):36
Surveillance of wild vertebrates can be challenging in remote and inaccessible areas such as tropical rainforests. Blood-feeding parasites, such as leeches, can facilitate wild vertebrate monitoring by targeting residual DNA from the animals the leeches feed on. Successes in detecting host DNA from leeches suggest that host viruses may also be detectable. To systematically test this hypothesis, we performed a proof of concept study using quantitative PCR (qPCR) to detect DNA viruses (bovine herpesvirus [BHV], human adenovirus [HAdV]) and RNA viruses (influenza A [InfA] and measles morbillivirus [MeV]) from nucleic acids extracted from medicinal leeches fed with blood spiked with each virus. All viruses except BHV showed a gradual decline in concentration from day 1 to 50, and all except BHV were detectable in at least half of the samples even after 50 days. BHV exhibited a rapid decline at day 27 and was undetectable at day 50. Our findings in medicinal leeches indicate that leeches collected in the wild might be an untapped resource for detecting vertebrate viruses and could provide new opportunities to study wildlife viral diseases of rare species in challenging environments, where capturing and handling of animals is difficult. 相似文献
453.
454.
Unexpected high genetic diversity in small populations suggests maintenance by associative overdominance
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Mads F. Schou Volker Loeschcke Jesper Bechsgaard Christian Schlötterer Torsten N. Kristensen 《Molecular ecology》2017,26(23):6510-6523
The effective population size (Ne) is a central factor in determining maintenance of genetic variation. The neutral theory predicts that loss of variation depends on Ne, with less genetic drift in larger populations. We monitored genetic drift in 42 Drosophila melanogaster populations of different adult census population sizes (10, 50 or 500) using pooled RAD sequencing. In small populations, variation was lost at a substantially lower rate than expected. This observation was consistent across two ecological relevant thermal regimes, one stable and one with a stressful increase in temperature across generations. Estimated ratios between Ne and adult census size were consistently higher in small than in larger populations. The finding provides evidence for a slower than expected loss of genetic diversity and consequently a higher than expected long‐term evolutionary potential in small fragmented populations. More genetic diversity was retained in areas of low recombination, suggesting that associative overdominance, driven by disfavoured homozygosity of recessive deleterious alleles, is responsible for the maintenance of genetic diversity in smaller populations. Consistent with this hypothesis, the X‐chromosome, which is largely free of recessive deleterious alleles due to hemizygosity in males, fits neutral expectations even in small populations. Our experiments provide experimental answers to a range of unexpected patterns in natural populations, ranging from variable diversity on X‐chromosomes and autosomes to surprisingly high levels of nucleotide diversity in small populations. 相似文献
455.
456.
F Ekelund S Christensen R R?nn E Buhl C S Jacobsen 《Journal of microbiological methods》1999,38(3):177-182
An automated modification of the most-probable-number (MPN) technique has been developed for enumeration of phagotrophic protozoa. The method is based on detection of prey depletion in micro titre plates rather than on presence of protozoa. A transconjugant Pseudomonas fluorescens DR54 labelled with a luxAB gene cassette was constructed, and used as growth medium for the protozoa in the micro titre plates. The transconjugant produced high amounts of luciferase which was stable and allowed detection for at least 8 weeks. Dilution series of protozoan cultures and soil suspensions were inoculated into micro titre plates amended with a suspension of the transconjugant. After 45 days measurement of light emission allowed detection of individual wells in the titre plates, where protozoan grazing had removed the inoculated bacteria. 相似文献
457.
David Sumpter Jerome Buhl Dora Biro Iain Couzin 《Theorie in den Biowissenschaften》2008,127(2):177-186
Moving animal groups provide some of the most intriguing and difficult to characterise examples of collective behaviour. We
review some recent (and not so recent) empirical research on the motion of animal groups, including fish, locusts and homing
pigeons. An important concept which unifies our understanding of these groups is that of transfer of directional information.
Individuals which change their direction of travel in response to the direction taken by their near neighbours can quickly
transfer information about the presence of a predatory threat or food source. We show that such information transfer is optimised
when the density of individuals in a group is close to that at which a phase transition occurs between random and ordered
motion. Similarly, we show that even relatively small differences in information possessed by group members can lead to strong
collective-level decisions for one of two options. By combining the use of self-propelled particle and social force models
of collective motion with thinking about the evolution of flocking we aim to better understand how complexity arises within
these groups.
相似文献
David SumpterEmail: |
458.
Mads Skak Jensen Barbara Ahlemeyer Alexander Ravati Pratima Thakur Hans Dieter Mennel Josef Krieglstein 《Neurochemistry international》2002,40(4):285-293
The central nervous system is one of the main target organs in cyanide toxicity. In this study, primary cultures of chick embryonic neurons were used to characterize sodium cyanide (NaCN)-induced cell death and to investigate the mechanism of NaCN-mediated preconditioning. After treatment of the cells with 1mM NaCN for 1h followed by a NaCN-free incubation period of 23 h, we observed features of apoptosis such as a reduction in nuclear size, chromatin condensation and nuclear fragmentation as evaluated by nuclear staining with Hoechst 33258 and electron microscopy. In addition, NaCN-induced neurotoxicity was reduced by the protein synthesis inhibitor cycloheximide (CHX) suggesting an active type of cell death. Most of the neurons with condensed chromatin and a shrunken nuclei also showed membrane damage at a late stage. Mitochondrial membrane potential as well as the protein levels of Bcl-2 and Bcl-x(L) decreased 15-60 min and 1-3 h after the exposure to NaCN (1mM, 1h), respectively. Preconditioning caused by incubating chick neurons with 100 microM NaCN for 30 min followed by a NaCN-free interval of 24h significantly protected the neurons against subsequent NaCN (1mM, 1h)-induced damage. Preconditioning prevented NaCN-induced decrease in the mitochondrial membrane potential as well as in the protein levels of Bcl-2 and Bcl-x(L) suggesting that preconditioning-induced neuroprotection is mediated by preserving mitochondrial function. 相似文献
459.
Wolf-Juergen Buhl Liisa M. Eisenlohr Ulrich Gehring 《Prostaglandins & other lipid mediators》1997,53(3):139-152
Intervillous blood was collected from term placentae at delivery, and sera were tested for phospholipase A2 under various experimental conditions. Enzyme activity was found to develop upon extended storage in the cold or at 37°C. The enzyme is reversibly inhibited by dithiothreitol, requires Ca++ ions for activity, and tolerates various detergents. The apparent molecular weight is 42 kDa. In all these parameters the serum enzyme behaves similar to the 42 kDa phospholipase A2 which we recently purified to homogeneity from thoroughly washed placental tissue. Serum phospholipase A2 appears to be generated by proteolytic processing from a slightly larger inactive precursor which was detected immunochemically. Most likely this protein originates from fetal cells and may be released by membrane damage. We conclude that both placental serum and tissue harbour a novel type of phospholipase A2 which is distinct from cytosolic and secretory phospholipases A2. Preference for arachidonate containing substrate suggests a role in eicosanoid production within gestational tissues. 相似文献
460.
Overton HA Babbs AJ Doel SM Fyfe MC Gardner LS Griffin G Jackson HC Procter MJ Rasamison CM Tang-Christensen M Widdowson PS Williams GM Reynet C 《Cell metabolism》2006,3(3):167-175
The endogenous lipid signaling agent oleoylethanolamide (OEA) has recently been described as a peripherally acting agent that reduces food intake and body weight gain in rat feeding models. This paper presents evidence that OEA is an endogenous ligand of the orphan receptor GPR119, a G protein-coupled receptor (GPCR) expressed predominantly in the human and rodent pancreas and gastrointestinal tract and also in rodent brain, suggesting that the reported effects of OEA on food intake may be mediated, at least in part, via the GPR119 receptor. Furthermore, we have used the recombinant receptor to discover novel selective small-molecule GPR119 agonists, typified by PSN632408, which suppress food intake in rats and reduce body weight gain and white adipose tissue deposition upon subchronic oral administration to high-fat-fed rats. GPR119 therefore represents a novel and attractive potential target for the therapy of obesity and related metabolic disorders. 相似文献