Boats, Pathways, and Aquatic Biological Invasions: Estimating Dispersal Potential with Gravity Models

Biological invaders can have dramatic effects on the environment and the economy. To most effectively manage these invaders, we should consider entire pathways, because multiple species are dispersed through the same vectors. In this paper, we use production-constrained gravity models to describe movement of recreational boaters between lakes – potentially the most important pathway of overland dispersal for many aquatic organisms. These models are advantageous because they require relatively easily acquired data, hence are relatively easy to build. We compare linear and non-linear gravity models and show that, despite their simplicity, they are able to capture important characteristics of the recreational boater pathway. To assess our model, we compared observed data based on creel surveys and mailed surveys of recreation boaters to the model output. Specifically, we evaluate four metrics of pathway characteristics: boater traffic to individual lakes, distances traveled to reach these lakes, Great Lakes usage and movement from the Great Lakes to inland waters. These factors will influence the propagule pressure (hence the probability of establishment of invasive populations) and the rate of spread across a landscape. The Great Lakes are of particular importance because they are a major entry point of non-indigenous species from other continents, hence will act as the origin for further spread across states. The non-linear model had the best fit between model output and empirical observations with r² =0.80, r² =0.35, r² =0.57, and r² =0.36 for the four metrics, respectively. For the distances traveled to individual lakes, r² improved from 0.35 to 0.76 after removal of an outlier. Our results suggest that we were able to capture distances traveled to most but not all lakes. Thus, we demonstrate that production-constrained gravity models will be generally useful for modeling invasion pathways between non-contiguous locations.     

Chemical Characteristics of Particulate, Colloidal, and Dissolved Organic Material in Loch Vale Watershed, Rocky Mountain National Park

The chemical relationships among particulate and colloidal organicmaterial and dissolved fulvic acid were examined in an alpine andsubalpine lake and two streams in Loch Vale Watershed, Rocky MountainNational Park. The alpine lake, Sky Pond, had the lowest dissolved organiccarbon (DOC) (0.37 mgC/L), the highest particulate carbon (POC) (0.13mgC/L), and high algal biomass. The watershed of Sky Pond is primarilytalus slope, and DOC and POC may be autochthonous. Both Andrews Creekand Icy Brook gain DOC as they flow through wet sedge meadows. Thesubalpine lake, The Loch, receives additional organic material from thesurrounding forest and had a higher DOC (0.66 mgC/L). Elemental analysis,stable carbon isotopic compositon, and ¹³C-NMR characterizationshowed that: 1) particulate material had relatively high inorganic contentsand was heterogeneous in compositon, 2) colloidal material was primarilycarbohydrate material with a low inorganic content at all sites; and 3)dissolved fulvic acid varied in compositon among sites. The lowconcentration and carbohydrate-rich character of the colloidal materialsuggests that this fraction is labile to microbial degradation and may beturning over more rapidly than particulate fractions or dissolved fulvic acid.Fulvic acid from Andrews Creek had the lowest N content and aromaticity,whereas Sky Pond fulvic acid had a higher N content and lower aromaticitythan fulvic acid from The Loch. The UV-visible spectra of the fulvic acidsdemonstrate that variation in characteristics with sources of organic carboncan explain to some extent the observed non-linear relationship betweenUV-B extinction coefficients and DOC concentrations in lakes.     

Modulation of the K(v)4.3 channel by syntaxin 1A

The SNARE protein syntaxin 1A (Syn1A) is known to inhibit delayed rectifier K(+) channels of the K(v)1 and K(v)2 families with heterogeneous effects on their gating properties. In this study, we explored whether Syn1A could directly modulate K(v)4.3, a rapidly inactivating K(v) channel with important roles in neuroendocrine cells and cardiac myocytes. Immunoprecipitation studies in HEK293 cells coexpressing Syn1A and K(v)4.3 revealed a direct interaction with increased trafficking to the plasma membrane without a change in channel synthesis. Paradoxically, Syn1A inhibited K(v)4.3 current density. In particular, Syn1A produced a left-shift in steady-state inactivation of K(v)4.3 without affecting either voltage dependence of activation or gating kinetics, a pattern distinct from other K(v) channels. Combined with our previous reports, our results further verify the notion that the mechanisms involved in Syn1A-K(v) interactions vary significantly between K(v) channels, thus providing a wide scope for Syn1A modulation of exocytosis and membrane excitability.     

Dexamethasone alters F-actin architecture and promotes cross-linked actin network formation in human trabecular meshwork tissue

Elevated intraocular pressure is an important risk factor for the development of glaucoma, a leading cause of irreversible blindness. This ocular hypertension is due to increased hydrodynamic resistance to the drainage of aqueous humor through specialized outflow tissues, including the trabecular meshwork (TM) and the endothelial lining of Schlemm's canal. We know that glucocorticoid therapy can cause increased outflow resistance and glaucoma in susceptible individuals, that the cytoskeleton helps regulate aqueous outflow resistance, and that glucocorticoid treatment alters the actin cytoskeleton of cultured TM cells. Our purpose was to characterize the actin cytoskeleton of cells in outflow pathway tissues in situ, to characterize changes in the cytoskeleton due to dexamethasone treatment in situ, and to compare these with changes observed in cell culture. Human ocular anterior segments were perfused with or without 10(-7) M dexamethasone, and F-actin architecture was investigated by confocal laser scanning microscopy. We found that outflow pathway cells contained stress fibers, peripheral actin staining, and occasional actin "tangles." Dexamethasone treatment caused elevated IOP in several eyes and increased overall actin staining, with more actin tangles and the formation of cross-linked actin networks (CLANs). The actin architecture in TM tissues was remarkably similar to that seen in cultured TM cells. Although CLANs have been reported previously in cultured cells, this is the first report of CLANs in tissue. These cytoskeletal changes may be associated with increased aqueous humor outflow resistance after ocular glucocorticoid treatment.     

Complex predictive eye pursuit in monkey: a model system for cerebellar studies of skilled movement

Smooth pursuit eye movements provide a good model system for cerebellar studies of complex motor control in monkeys. First, the pursuit system exhibits predictive control along complex trajectories and this control improves with training. Second, the flocculus/paraflocculus region of the cerebellum appears to generate this control. Lesions impair pursuit and neural activity patterns are closely related to eye motion during complex pursuit. Importantly, neural responses lead eye motion during predictive pursuit and lag eye motion during non-predictable target motions that require visual control. The idea that flocculus/paraflocculus predictive control is non-visual is also supported by a lack of correlation between neural activity and retinal image motion during pursuit. Third, biologically accurate neural network models of the flocculus/paraflocculus allow the exploration and testing of pursuit mechanisms. Our current model can generate predictive control without visual input in a manner that is compatible with the extensive experimental data available for this cerebellar system. Similar types of non-visual cerebellar control are likely to facilitate the wide range of other skilled movements that are observed.     

Intracellular trafficking of polyamidoamine-poly(ethylene glycol) block copolymers in DNA delivery

The delivery of nucleic acids has the potential to revolutionize medicine by allowing previously untreatable diseases to be clinically addressed. Viral delivery systems have shown immunogenicity and toxicity dangers, but synthetic vectors have lagged in transfection efficiency. Previously, we developed a modular, linear-dendritic block copolymer architecture with high gene transfection efficiency compared to commercial standards. This rationally designed system makes use of a cationic dendritic block to condense the anionic DNA and forms complexes with favorable endosomal escape properties. The linear block provides biocompatibility and protection from serum proteins, and can be functionalized with a targeting ligand. In this work, we quantitate performance of this system with respect to intracellular barriers to gene delivery using both high-throughput and traditional approaches. An image-based, high-throughput assay for endosomal escape is described and applied to the block copolymer system. Nuclear entry is demonstrated to be the most significant barrier to more efficient delivery and will be addressed in future versions of the system.     

Ubiquitin‐Activated Interaction Traps (UBAITs) identify E3 ligase binding partners

We describe a new class of reagents for identifying substrates, adaptors, and regulators of HECT and RING E3s. UBAITs (Ub iquitin‐A ctivated I nteraction T raps) are E3‐ubiquitin fusion proteins and, in an E1‐ and E2‐dependent manner, the C‐terminal ubiquitin moiety forms an amide linkage to proteins that interact with the E3, enabling covalent co‐purification of the E3 with partner proteins. We designed UBAITs for both HECT (Rsp5, Itch) and RING (Psh1, RNF126, RNF168) E3s. For HECT E3s, trapping of interacting proteins occurred in vitro either through an E3 thioester‐linked lariat intermediate or through an E2 thioester intermediate, and both WT and active‐site mutant UBAITs trapped known interacting proteins in yeast and human cells. Yeast Psh1 and human RNF126 and RNF168 UBAITs also trapped known interacting proteins when expressed in cells. Human RNF168 is a key mediator of ubiquitin signaling that promotes DNA double‐strand break repair. Using the RNF168 UBAIT, we identify H2AZ—a histone protein involved in DNA repair—as a new target of this E3 ligase. These results demonstrate that UBAITs represent powerful tools for profiling a wide range of ubiquitin ligases.     

Structural and electronic properties of the liver fluke hemoglobin heme cavity by nuclear magnetic resonance: hemin isotope labeling

Reconstitution of liver fluke (Dicrocoelium dendriticum) apo-hemoglobin with hemins selectively deuterated at specific positions has permitted the assignment of several heme resonances in the proton nuclear magnetic resonance spectrum of the Met-aquo and Met-cyano forms of the holoprotein. It was established that in the Met-aquo form the meso protons resonate at positions characteristic of a six-co-ordinated in-plane iron. From this, we deduced that the Met-aquo species retains a bound water molecule at pH values as low as 4.5. The orientation of the proximal histidine imidazole ring with respect to the heme group in the cavity was determined through the identification of the heme methyl signals and the analysis of the hyperfine shift pattern in the Met-cyano hemoglobin proton nuclear magnetic resonance spectrum. Compared to sperm whale myoglobin, the heme appears to be rotated by 180 degrees about the alpha, gamma meso-axis. Protein isomers with the heme group in a reversed orientation were not detected, even shortly after reconstitution. In the Met-cyano form, the resonances most affected by the Bohr transition were shown to arise from the heme propionates.     

Neuroleptic-induced oral movements in rats: methodological issues

In three separate experiments groups of rats were chronically administered neuroleptics in a variety of ways (chronic injections, subcutaneous implants, and decanoate injections) and examined for oral movements (OMs) in two different tests: in an open cage using a human observer, or in a plexiglas tube enclosure, where OMs were monitored both by a human observer and computerized video analysis system. These two testing methods showed different effects of neuroleptic administration. In the open cage, OMs tended to be enhanced during chronic neuroleptic exposure and to rapidly subside upon drug withdrawal. The enhanced OMs were especially present just after drug injections, when activity levels were low. In the observation tube environment, however, OMs tended to be low soon after drug treatments, and elevated upon withdrawal. Thus, the type of behavioral test used determines how neuroleptic-induced increases in oral activity should be interpreted.