An Experimental Release of Elk into Great Smoky Mountains National Park

I conducted 6 years of field work to evaluate the habitat use and population dynamics of an experimental release of elk (Cervus elaphus) into Great Smoky Mountains National Park (Park). Elk exhibited relatively small home ranges (female: 10.4 km2 and males: 22.4 km2) and movement distances decreased over time. I calculated survival rates (x = 0.73–0.93) and litter production rates (x = 0.73) for the population. To assess the potential for a long-term elk population, I incorporated those vital rates into the population modeling software Riskman and tested its sensitivity to any given vital rate. The projected population growth was positive (1.03, SD = 0.001) and the probability of extinction in 100 years was minimal (1%, SD = 0.001). However, the model was sensitive to adult female survival, and the simulated annual deaths of only 4 adult females increased the probability of extinction to 45% (SD = 0.021). Compositional analysis detected a strong preference for grassland areas by elk in the Park. I used spatial data to identify potential habitat for elk on a multivariate level by calculating the Mahalanobis distance (D2) statistic based on the relationship between elk locations and 7 landscape variables. The D2 model indicated that the best elk habitat primarily occurred in areas of moderate landscape complexity and edge denisty and gentle slope, and was limited in the Park. At the current small population density, elk had minimal impact on vegetation inside the Park and their diet consisted primarily of graminoids. The elk population at Great Smoky Mountains National Park will likely remain small and vulnerable to extinction for some time due to low growth rates, high environmental stochasticity, and limited habitat. Active management (e.g. predator management, prescribed burning, and mowing) will be required to maintain this population until the population grows to more sustainable levels

Lower low-density lipoprotein cholesterol levels are associated with Parkinson's disease

The apolipoprotein E (APOE) ε2 allele has been associated with both Parkinson’s disease (PD) and lower low density lipoprotein cholesterol (LDL-C). The study is to test the hypothesis that lower LDL-C may be associated with PD. This case-control study used fasting lipid profiles obtained from 124 PD cases and 110 controls, the PD cases recruited from consecutive cases presenting at our tertiary Movement Disorder Clinic, and controls recruited from the spouse populations of the same clinic. Multivariate odds ratios (OR) and 95% confidence intervals (CI) were calculated from unconditional logistic regressions, adjusting for age, gender, smoking status, and use of cholesterol-lowering agents. Lower LDL-C concentrations were associated with a higher prevalence of PD. Compared with participants with the highest LDL-C (≥139 mg/dL), the OR was 2.2 (95% CI 0.9–5.1) for participants with LDL-C of 115–138, 3.5 (95% CI 1.6–8.1) for LDL-C of 93–114, and 2.6 (95% CI 1.1 – 5.9) for LDL-C ≤ 92. Interestingly, use of cholesterol lowering drugs or just statins was related to lower PD prevalence. Our data provide preliminary evidence that low LDL-C may be associated with higher occurrence of PD, and/or that statin use may lower PD occurrence; either of which findings warrant further investigations

Opportunities for organoids as new models of aging.

The biology of aging is challenging to study, particularly in humans. As a result, model organisms are used to approximate the physiological context of aging in humans. However, the best model organisms remain expensive and time-consuming to use. More importantly, they may not reflect directly on the process of aging in people. Human cell culture provides an alternative, but many functional signs of aging occur at the level of tissues rather than cells and are therefore not readily apparent in traditional cell culture models. Organoids have the potential to effectively balance between the strengths and weaknesses of traditional models of aging. They have sufficient complexity to capture relevant signs of aging at the molecular, cellular, and tissue levels, while presenting an experimentally tractable alternative to animal studies. Organoid systems have been developed to model many human tissues and diseases. Here we provide a perspective on the potential for organoids to serve as models for aging and describe how current organoid techniques could be applied to aging research

Attentional Dynamics Explain the Elusive Nature of Context Effects

Context effects in multi-alternative, multi-attribute choice are pervasive and yet, paradoxically, elusive at the same time. For example, simple changes to the spatial layout of alternatives on the screen can nullify or reverse the effects. Despite the success of dynamic decision models in explaining the occurrence of context effects, a coherent theory for understanding their elusiveness is currently lacking. We introduce a novel theoretical framework that relies on attention modulated comparisons to explain the elusive nature of context effects. We show via simulation that our model produces the attraction, compromise, and similarity effects simply by assuming that more time is spent comparing alternatives that are more similar. However, when more time is spent comparing dissimilar alternatives, model simulations reveal a reversal of the attraction and compromise effects. The empirical support for this model-based prediction is assessed by manipulating similarity-based attention in separate experiments for the three context effects (total N = 317). Further, by allowing the spatial organization of information to constrain the attention process, the model can explain changes in context effects induced by display layout. We show that the model's spatial attention mechanism allows it to capture presentation order effects in a reanalysis of previously published data. Finally, we develop a continuous approximation of the full model that permits fitting of choices and response times. In summary, the proposed framework provides a new tool for understanding not only the existence of context effects in choice, but also the attentional factors that lead to null or reversed context effects

MULTI-seq: sample multiplexing for single-cell RNA sequencing using lipid-tagged indices.

Sample multiplexing facilitates scRNA-seq by reducing costs and identifying artifacts such as cell doublets. However, universal and scalable sample barcoding strategies have not been described. We therefore developed MULTI-seq: multiplexing using lipid-tagged indices for single-cell and single-nucleus RNA sequencing. MULTI-seq reagents can barcode any cell type or nucleus from any species with an accessible plasma membrane. The method involves minimal sample processing, thereby preserving cell viability and endogenous gene expression patterns. When cells are classified into sample groups using MULTI-seq barcode abundances, data quality is improved through doublet identification and recovery of cells with low RNA content that would otherwise be discarded by standard quality-control workflows. We use MULTI-seq to track the dynamics of T-cell activation, perform a 96-plex perturbation experiment with primary human mammary epithelial cells and multiplex cryopreserved tumors and metastatic sites isolated from a patient-derived xenograft mouse model of triple-negative breast cancer

A Data-Based Conservation Planning Tool for Florida Panthers

Habitat loss and fragmentation are the greatest threats to the endangered Florida panther (Puma concolor coryi). We developed a data-based habitat model and userfriendly interface so that land managers can objectively evaluate Florida panther habitat. We used a geographic information system (GIS) and the Mahalanobis distance statistic (D2) to develop a model based on broad-scale landscape characteristics associated with panther home ranges. Variables in our model were Euclidean distance to natural land cover, road density, distance to major roads, human density, amount of natural land cover, amount of semi-natural land cover, amount of permanent or semipermanent flooded area–open water, and a cost–distance variable. We then developed a Florida Panther Habitat Estimator tool, which automates and replicates the GIS processes used to apply the statistical habitat model. The estimator can be used by persons with moderate GIS skills to quantify effects of land-use changes on panther habitat at local and landscape scales. Example applications of the tool are presented