131 research outputs found
Climate-Related Variation in Spatial Memory and Hippocampal Morphology in Food-Caching Chickadees.
Harsh environments may lead to increased demands on memory in animals that rely on memory for survival. We previously showed that winter severity is associated with non-experience-based differences in memory and the hippocampus over a large continental scale in food-caching black-capped chickadees (Poecile atricapillus). However, large climatic differences also occur along steep elevational gradients in montane environments over a small geographic scale. Here we demonstrate for the first time that large differences in memory and the hippocampus exist over extremely short distances (10km) along the elevation gradient. We discovered that food-caching mountain chickadees (P. gambeli) from the highest elevations in the Sierra Nevada Mountains exhibited significantly better spatial memory associated with larger hippocampi with almost twice the number of hippocampal neurons compared to individuals only 600m lower in elevation. We found similarly large differences in hippocampal neurogenesis rates as indicated by the total number of immature neurons. Our study therefore suggests that climate-related environmental differences can produce dramatic differences in memory and the hippocampus in animals within close proximity on small spatial scales and that currently observed trends in global climate may have significant effects on cognition and the brain. Additionally, we attempted to integrate a new metric for enhanced spatial memory by looking specifically at the morphology of the neuron. While most comparative studies of cognition have focused on volumetric brain measurements it remains unclear whether neuron morphology, which appears to be directly linked to cognitive functions, may be responsive to differential selection on cognitive ability. We show that neuron soma size in the hippocampus, exhibits significant population variation associated with different environmental pressures on spatial memory related to differences in winter climate harshness in two species of food-caching chickadees. Comparing ten populations of black-capped chickadees and three populations of mountain chickadees along a gradient of winter climate harshness, we found that birds from harsher environments had significantly larger hippocampal neuron soma sizes. Finally, using chickadees from the two most divergent populations reared in a laboratory environment, we showed that these differences appear to be at least partly heritable as significant differences between these populations remained in birds sharing the same laboratory environment. At the same time, laboratory reared birds had significantly smaller neuron soma size compared to the wild-sampled birds, suggesting that at least some variation in neuron soma size may be due to environment-related plasticity. Our data suggests that environment-related selection on memory may generate differences in neuron morphology, which appear to be controlled by some heritable mechanisms and likely underlie population differences in spatial memory
Application of Remote Sensing to the Chesapeake Bay Region. Volume 2: Proceedings
A conference was held on the application of remote sensing to the Chesapeake Bay region. Copies of the papers, resource contributions, panel discussions, and reports of the working groups are presented
Application of Remote Sensing to the Chesapeake Bay Region. Volume 1: Executive summary
The proceedings are presented of a conference, jointly sponsored by the National Aeronautics and Space Administration, the U.S. Environmental Protection Agency, and the University of Maryland. The purpose of the Conference was to assemble representatives of federal and state government agencies engaged in research on the condition and evolution of the Chesapeake Bay to compose a status report, to present current activities and future plans, and to recommend a long-range future course of policies and programs
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Effect of different catalysts and amounts of styrene monomer on strength and durability of glass-cloth plastic laminates
This report is one of a series issued in cooperation with the Air Force-Navy-Civil Subcommittee on Aircraft Design Criteria under the supervision of the Aircraft Committee of the Munitions Board. Information reviewed and reaffirmed 1958. Original report issued March 1952
Risky choice and memory for effort : hard work stands out
When deciding between different courses of action, both the potential outcomes and the costs of making a choice should be considered. These costs include the cognitive and physical effort of the different options. In many decision contexts, the outcome of the choice is guaranteed but the amount of effort required to achieve that outcome is unknown. Here, we studied choices between options that varied in the riskiness of the effort (number of responses) required. People made repeated choices between pairs of options that required them to click different numbers of sequentially presented response circles. Easy-effort options led to small numbers of response circles, whereas hard-effort options led to larger numbers of response circles. For both easy- and hard-effort options, fixed options led to a consistent effort, whereas risky options led to variable effort that, with a 50/50 chance, required either more effort or less effort than the fixed option. Participants who showed a preference for easier over harder options were more risk averse for decisions involving hard options than for decisions involving easy options. On subsequent memory tests, people most readily recalled the hardest outcome, and they overestimated its frequency of occurrence. Memory for the effort associated with each risky option strongly correlated with individual risky preferences for both easy-effort and hard-effort choices. These results suggest a relationship between memory biases and risky choice for effort similar to that found in risky choice for reward. With effort, the hardest work seems to particularly stand out
Effects of separate proteolytic and high-affinity binding activities of human thrombin on rapid platelet activation. A quenched-flow study
The association between clinical integration of care and transfer of veterans with acute coronary syndromes from primary care VHA hospitals
BACKGROUND: Few studies report on the effect of organizational factors facilitating transfer between primary and tertiary care hospitals either within an integrated health care system or outside it. In this paper, we report on the relationship between degree of clinical integration of cardiology services and transfer rates of acute coronary syndrome (ACS) patients from primary to tertiary hospitals within and outside the Veterans Health Administration (VHA) system. METHODS: Prospective cohort study. Transfer rates were obtained for all patients with ACS diagnoses admitted to 12 primary VHA hospitals between 1998 and 1999. Binary variables measuring clinical integration were constructed for each primary VHA hospital reflecting: presence of on-site VHA cardiologist; referral coordinator at the associated tertiary VHA hospital; and/or referral coordinator at the primary VHA hospital. We assessed the association between the integration variables and overall transfer from primary to tertiary hospitals, using random effects logistic regression, controlling for clustering at two levels and adjusting for patient characteristics. RESULTS: Three of twelve hospitals had a VHA cardiologist on site, six had a referral coordinator at the tertiary VHA hospital, and four had a referral coordinator at the primary hospital. Presence of a VHA staff cardiologist on site and a referral coordinator at the tertiary VHA hospital decreased the likelihood of any transfer (OR 0.45, 95% CI 0.27–0.77, and 0.46, p = 0.002, CI 0.27–0.78). Conversely, having a referral coordinator at the primary VHA hospital increased the likelihood of transfer (OR 6.28, CI 2.92–13.48). CONCLUSIONS: Elements of clinical integration are associated with transfer, an important process in the care of ACS patients. In promoting optimal patient care, clinical integration factors should be considered in addition to patient characteristics
Crucial role of ultraviolet light for desert ants in determining direction from the terrestrial panorama
Ants use the panoramic skyline in part to determine a direction of travel. A theoretically elegant way to define where terrestrial objects meet the sky is to use an opponent-process channel contrasting green wavelengths of light with ultraviolet (UV) wavelengths. Compared with the sky, terrestrial objects reflect relatively more green wavelengths. Using such an opponent-process channel gains constancy in the face of changes in overall illumination level. We tested the use of UV wavelengths in desert ants by using a plastic that filtered out most of the energy below 400 nm. Ants, Melophorus bagoti, were trained to home with an artificial skyline provided by an arena (experiment 1) or with the natural panorama (experiment 2). On a test, a homing ant was captured just before she entered her nest, and then brought back to a replicate arena (experiment 1) or the starting point (the feeder, experiment 2) and released. Blocking UV light led to deteriorations in orientation in both experiments. When the artificial skyline was changed from opaque to transparent UV-blocking plastic (experiment 3) on the other hand, the ants were still oriented. We conclude that UV wavelengths play a crucial role in determining direction based on the terrestrial surround.10 page(s
[L’effet de l’affinité pour l’oxygène et du poids moléculaire des TOBH sur l’oxygé-nation et la tension artérielle chez les rats]
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