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Selected AbstractsThe workload of riding-school horses during jumpingEQUINE VETERINARY JOURNAL, Issue S36 2006M. M. SLOET Van OLDRUITENBORGH-OOSTERBAAN Summary Reasons for performing the study: As there are no reports on the real workload of horses that jump fences, this study was undertaken in riding-school horses. Objective: To compare the workload of horses jumping a course of fences with that of horses cantering over the same course at the same average speed without jumping fences. The workload variables included heart rate (HR), packed cell volume (PCV), acid-base balance (venous pH, pCO2, HCO3,) and blood lactate (LA), glucose, total protein and electrolyte concentrations. Methods: Eight healthy riding-school horses performed test A (a course of approximately 700 m with 12 jumps from 0.8-1.0 m high at an average speed of approximately 350 m/min) and test B (same course at the same speed, but without the rails) in a crossover study with at least 4 h between the 2 tests. Before each test the horses were fitted with a heart rate meter (Polar Electro)1. Blood samples were taken from the jugular vein at rest prior to the test, after warm-up before starting the course, immediately after the course and after recovery. All samples were analysed immediately. Results: The mean ± s.d maximal HR (beats/min) during the course (184 ± 17 and 156 ± 21, respectively) and the mean HR after recovery (75 ± 6 and 63 ± 7, respectively) were significantly higher in test A compared to test B (P=0.001 and P=0.007 respectively). The mean LA concentrations after the course and after recovery (mmol/1) were significantly higher in test A (3.6 ± 2.7 and 1.0 ± 0.9, respectively) compared to test B (0.9 ± 0.5 and 0.3 ± 0.1, respectively), (P=0.016 and P = 0.048 respectively). The mean PCV (1/1) after the course and after recovery was also significantly different between tests A (0.48 ± 0.04 and 0.39 ± 0.03, respectively) and B (0.42 ± 0.04 and 0.36 ± 0.03, respectively) (P<0.01). The mean pH and the mean HCO3, (mmol/1) after the course were significantly lower in test A (7.40 ± 0.04 and 28.9 ± 1.4, respectively) compared to test B (7.45 ± 0.03 and 30.4 ± 2.3, respectively) (P<0.05). Conclusions: This study indicates that in riding-school horses jumping fences, even at a low level competition, provokes a significant workload compared to cantering the same distance and speed without fences. Potential relevance: This study makes it clear that the extra workload of jumping fences should be taken into account in the training programmes of jumping horses. Further research with more experienced horses jumping higher fences will reveal the workload for top-level jumping horses. [source] Detection and Avoidance of Predators in White-Tailed Deer (Odocoileus virginianus) and Mule Deer (O. hemionus)ETHOLOGY, Issue 2 2001Susan Lingle In this paper, we investigate the relationship between early detection of predators and predator avoidance in white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus), two closely related species that differ in their habitat preferences and in their anti-predator behavior. We used observations of coyotes (Canis latrans) hunting deer to test whether the distance at which white-tails and mule deer alerted to coyotes was related to their vulnerability to predation. Coyote encounters with both species were more likely to escalate when deer alerted at shorter distances. However, coyote encounters with mule deer progressed further than encounters with white-tails that alerted at the same distance, and this was not due to species differences in group size or habitat. We then conducted an experiment in which a person approached groups of deer to compare the detection abilities and the form of alert response for white-tails and mule deer, and for age groups within each species. Mule deer alerted to the approacher at longer distances than white-tails, even after controlling for variables that were potentially confounding. Adult females of both species alerted sooner than conspecific juveniles. Mule deer almost always looked directly at the approacher as their initial response, whereas white-tails were more likely to flee or to look in another direction with no indication that they pinpointed the approacher during the trial. Mule deer may have evolved the ability to detect predators earlier than white-tails as an adaptation to their more open habitats, or because they need more time to coordinate subsequent anti-predator defenses. [source] Synthesis and structural characterization of a mimetic membrane-anchored prion proteinFEBS JOURNAL, Issue 6 2006Matthew R. Hicks During pathogenesis of transmissible spongiform encephalopathies (TSEs) an abnormal form (PrPSc) of the host encoded prion protein (PrPC) accumulates in insoluble fibrils and plaques. The two forms of PrP appear to have identical covalent structures, but differ in secondary and tertiary structure. Both PrPC and PrPSc have glycosylphospatidylinositol (GPI) anchors through which the protein is tethered to cell membranes. Membrane attachment has been suggested to play a role in the conversion of PrPC to PrPSc, but the majority of in vitro studies of the function, structure, folding and stability of PrP use recombinant protein lacking the GPI anchor. In order to study the effects of membranes on the structure of PrP, we synthesized a GPI anchor mimetic (GPIm), which we have covalently coupled to a genetically engineered cysteine residue at the C-terminus of recombinant PrP. The lipid anchor places the protein at the same distance from the membrane as does the naturally occurring GPI anchor. We demonstrate that PrP coupled to GPIm (PrP,GPIm) inserts into model lipid membranes and that structural information can be obtained from this membrane-anchored PrP. We show that the structure of PrP,GPIm reconstituted in phosphatidylcholine and raft membranes resembles that of PrP, without a GPI anchor, in solution. The results provide experimental evidence in support of previous suggestions that NMR structures of soluble, anchor-free forms of PrP represent the structure of cellular, membrane-anchored PrP. The availability of a lipid-anchored construct of PrP provides a unique model to investigate the effects of different lipid environments on the structure and conversion mechanisms of PrP. [source] Naive Analysis of Food Web Dynamics: A Study of Causal Judgment About Complex Physical SystemsCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 4 2000Peter A. White When people make judgments about the effects of a perturbation on populations of species in a food web, their judgments exhibit the dissipation effect: a tendency to judge that effects of the perturbation weaken or dissipate as they spread out through the food web from the locus of the perturbation. In the present research evidence for two more phenomena is reported. Terminal locations are points in the food web with just a single connection to the rest of the web. Judged changes tended to be higher for species at terminal locations than for species the same distance from the perturbation but at nonterminal locations. Branches are points in the web where a route splits into two or more routes. Judged changes tended to be lower for species following branching points than for species the same distance from the perturbation but not following branching points. It is proposed that the findings can be explained as effects of a mental model employing concepts of influence and resistance. Under this model a perturbation is a change in energy level at a point in the system that acts as an influence affecting the rest of the system. The basic concepts in this model are domain-general and on that basis it is predicted that the dissipation effect should be found in judgments of any physical system to which notions of influence and resistance can be applied. [source] Evaluation of biological and chemical insecticide mixture against Aedes aegypti larvae and adults by thermal fogging in SingaporeMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2001Y. K. Chung Abstract. To improve the operational efficiency of dengue vector control in Singapore, larvicide and adulticide were applied together by thermal fog generator (Agrofog® AF40). The mixture consisted of Bacillus thuringiensis var. israelensis (Vectobac® 12 AS) as biological larvicide at 1.5 L/ha and pirimiphos-methyl (Actellic® 50 EC) as adulticide at 100 g ai/ha, diluted 10-fold with water. Aerosol of this mixture was evaluated against the mosquito Aedes aegypti (L.) (Diptera: Culicidae) in bioassays using cages of 10 adult females exposed at heights of 0.3,2.4 m and distances of 3,12 m from the hand-held generator. Cups containing 200 mL water were treated at ground level by exposure to the aerosol application at the same distances from the generator. Subsequent larval bioassays on days 1, 7, 14, 21 and 28 post-spray involved exposing 20 larvae/cup for 48 h. Droplets had VMD 57 µm and female mosquitoes were killed by 2 s exposure to the aerosol at 3 m. We obtained 92,100% mortality of the adult mosquitoes and 100% control of larvae at 3 m distance, but only 10,13% mortality at 12 m from the fogger. In treated cups, larvae showed high mortality (92%) when exposed for 48 h even 1 month post-treatment. Results demonstrate the practical advantage of using this mixture of Vectobac® 12AS and Actellic® 50 EC for simultaneous control of Aedes adults and larvae, with prolonged larvicidal efficacy in treated containers. [source] Determination of intermolecular distance for a model peptide of Bombyx mori silk fibroin, GAGAG, with rotational echo double resonanceBIOPOLYMERS, Issue 2 2002Tsunenori Kameda Abstract Rotational echo double resonance NMR spectroscopy is applied for the determination of the distance of intermolecular chains of pentapeptide, GAGAG (G: Gly, A: Ala), a model typical of the crystalline domain in Bombyx mori silk fibroin. 1:4 mixture of G[1- 13C]AGAG and GAG[15N]AG with antiparallel ,-sheet structure was used to determine the distance of intermolecular hydrogen bonding between adjacent molecules within pleated sheet and the 13C,15N interatomic distance was determined to be 4.3 Å. On the other hand, 1:4 mixture of GAG[1- 13C]AG and GAG[15N]AG gave information on the interpleated sheet arrangement. When we assumed the same distances between two interpleated sheets, the distance was calculated to be 5.3 Å and the angle 15N,13C,15N was 180°. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 80,85, 2002 [source] | |||||||||||||