Obesity has become a widespread concern to human health largely over the past three decades. It is thought that obesity is associated with the over consumption of calorically dense diets. The rewarding value of food is mediated through the mesolimbic dopamine system, though is less understood how appetitive control circuits relay information to existing reward circuitry. The adiposity signaling hormone, leptin, is a critical mediator of food intake and fat storage. Leptin signaling, via the long form of the leptin receptor (LepRb), is predominantly carried out within the hypothalamus. Leptin action specific to the lateral hypothalamus area (LHA) modulates reward function via direct and indirect inhibition of reward circuitry. Here, I have identified a novel leptin receptor population within the LHA that co-expresses the inhibitory neuropeptide galanin (termed Gal-LepRb neurons). To investigate the physiological function of leptin through Gal-LepRb neurons, we selectively deleted LepRb in galanin neurons (referred to as Gal-LepRbKO mice). In a two-bottle-choice paradigm, I assessed nutrient selection for isocaloric lipid and sucrose solutions. Interestingly, Gal-LepRbKO mice demonstrated a significant preference for the sucrose solution and decreased lipid intake compared to controls. Moreover, Gal-LepRbKO mice displayed stronger motivation to work for a sucrose treat. My data further indicate that Gal-LepRb neurons are inhibitory acting neurons that are stimulated by leptin. Gal-LepRb neurons strongly innervate local orexin neurons and noradrenergic neurons in the locus coeruleus (LC). Intriguingly, orexin neurons also strongly innervate the LC, and activation of orexin neurons correlates with motivational and food-seeking behaviors. My data also show that orexin neurons express the Gi-coupled GPCR galanin 1-receptor (GalR1), validating the cellular ability of orexin neurons to respond to galanin. In summary, we have characterized a novel population of LHA LepRb neurons and propose that leptin-mediated inhibition of orexin neurons, possibly via inhibitory galanin-GalR1 signaling, regulates the reward value of nutrients.

Glacial ice currently occupies roughly 11% of Earths surface and contains approximately 70% of the planets freshwater. Once thought to be inhospitable due to the physiochemical challenges presented by freezing temperatures, the basal zones of glaciers and ice sheets have recently been identified as a potential habitat for psychrophilic microorganisms with the ability to mediate biogeochemical cycles on a global scale. Basal ice is found in the deepest layers of a glacier and has distinct chemical and physical characteristics as a result of its proximity to the glacier bed. Basal ice is generally the warmest ice found in a glacier and often contains entrained debris and sediment from the underlying subglacial substrate which may provide nutrients and redox couples for microorganisms immured in the basal ice matrix. ATP/ADP concentrations and ratios, enrichment culturing, 16S rRNA surveys, and cell counts were combined with nutrient, major ion, and gas chemistry analyses to evaluate the microbial assemblages immured in both sediment-rich and sediment-poor basal ice environments. The primary material for this study was a 4 m profile of basal ice collected from Taylor Glacier (Antarctica) but also included basal ice samples from the Matanuska Glacier (Alaska) and Støre Landgletscher Glacier (Greenland). Microbial community abundance varied significantly between the different basal ice samples and was correlated with the presence of sediment in the ice. Sediment-rich banded basal ice from Taylor Glacier contained elevated concentrations of CO₂ (60,000 to 325,000 ppmv) occurring simultaneously with decreased O₂ concentrations (4 to 18% of total gas volume) suggesting the resident microbial assemblages may be respiring in situ and modifying the gas composition of the basal ice. Molecular surveys of 16S rDNA and rRNA sequences revealed species of the genus Paenisporosarcina to be numerically abundant and active members of the microbial assemblages inhabiting these same basal ice horizons. Members of this genus were readily culturable from the basal ice samples and radiolabeled [³H]-leucine and [³H]-thymidine assays with these isolates revealed their ability to conduct macromolecular synthesis while frozen in basal ice melt-water at -15°C. These results support the hypothesis that basal ice environments are microbial habitats harboring bacteria with the physiological capacity to remain metabolically active and cycle elements within the cryosphere.

Many of the most notorious biological invasions occur at continent-wide or global scales but studies investigating mechanisms enhancing species invasions are often conducted at small spatial scales. Moreover, the contribution of mechanisms facilitating invasion might also vary across a geographical space. I used biogeographical approaches to explore the mechanisms enhancing invasion of introduced genotypes of Phragmites australis along the coastal wetlands of North America. I tested the hypotheses that large-scale disturbance events, such as hurricanes and tropical storms, enhance the invasion success of introduced P. australis in North America. The growth rate of P. australis patches was strongly and positively related to the frequency of hurricane events along the coastal wetlands of the United States. Hurricane frequency alone explained 81% of the variation in the growth rate of P. australis patches over this broad geographical range. I also examined the evolution of latitudinal gradients in native and invasive genotypes of P. australis in relation to plant-herbivore interactions in North America. Common garden experiments revealed that the native and invasive genotypes of P. australis have evolved latitudinal clines on traits associated with herbivory, specifically for aphid Hyalopterus pruni. For a chewing herbivore, Spodoptera frugiperda, only native genotypes exhibited latitudinal clines. The existence of non-parallel latitudinal gradients between native and invasive genotypes creates spatial heterogeneity in the importance of herbivory on P. australis invasion and suggests the greater susceptibility of high-latitude communities. These latitudinal and genotypic variations on plant defenses, palatability, and herbivory suggest a possibility of an asymmetric apparent competition between native and invasive genotypes. A replicated field study in four sites along the Atlantic Coast showed that invasive genotypes could suppress the fitness of native genotypes by herbivore-mediated apparent competition. Moreover, the intensity of apparent competition declined with increasing latitude. These biogeographical studies suggest that multiple processes might be contributing to the spread of the introduced genotypes of P. australis in North America and that the importance of these processes might vary along an environmental gradient. These studies have broader implications for understanding species invasions at the continental scale and for managing natural habitats that are threatened by plant invasions.

microRNAs (miRNAs) are small noncoding RNAs that bind the 3 untranslated regions (UTRs) of mRNA targets and, acting with associated proteins, facilitate translation repression and degradation of target mRNAs. Since their discovery in C. elegans, miRNAs and their accessory proteins have been shown to be conserved throughout phylogeny. miRNAs exert their regulatory functions in myriad biological settings, from development and growth to disease. What follows is a general overview of miRNA discovery, organization, and function, and of the use of the powerful vertebrate developmental biology model organism, zebrafish (Danio rerio), zebrafish retinal development, and an overview of Notch-Delta signaling. The purpose of this dissertation is to examine the role of a specific miRNA, miR-216a, in regulation of the Notch-Delta signaling pathway during zebrafish retinal development.

Vibrio vulnificus, a Gram-negative halophile which is ubiquitously present in the marine environments, can cause diseases like gastroenteritis, septicemia and wound infections in susceptible human beings. Production of capsular polysaccharide results in an opaque phenotype, which is pathogenic to humans. Loss or reduction of capsule results in translucent colonies composed of cells that are nonpathogenic or have diminished virulence, respectively. The opaque and the translucent phenotypes, upon production of an exopolysaccharide, give rise to a dry, wrinkled rugose form that can form copious biofilms. These three phenotypes can spontaneously switch from one form to another in a process known as phase variation. In this study, we have sought to identify environmental factors and genetic mechanisms that affect phase variation and biofilm formation in V. vulnificus. Elements such as Ba2+, Mn2+, and Sr2+, were tested to determine their effect on V. vulnificus phase variation and we found that manganese at micromolar to millimolar concentrations, induces V.vulnificus polysaccharide phase variation from opaque to translucent or rugose forms in this species. Since calcium was previously shown to induce significant phase variation in different V.vulnificus strains, we have also attempted to compare the effects of equimolar addition of manganese and calcium on phase variation of different V.vulnificus strains. Here, we have also attempted to better understand the process of V. vulnificus rugose colony formation. Our study has identified 28 proteins that include translational elongation factors, various metabolic enzymes, proteases, sugar binding proteins, amino acid transporters, polar flagellins and an uncharacterized protein that are differentially expressed in the biofilm proficient rugose phase variant compared to the parent isogenic opaque phase variant. One protein of particular interest, MalE (VVA0397 gene product), a maltose binding periplasmic protein, was identified as being expressed at higher amounts, and concomitantly showed higher transcript levels in the rugose variant compared to the opaque variant. Interestingly, generation of a targeted mutant of the malE gene did not knock out rugosity, indicating that the malE (VVA0397) gene is not required for rugosity in V.vulnificus. However, its up-regulation at both the transcriptional and translational levels suggests that MalE protein is involved in rugose colony formation in a way that remains to be determined.

Large scale plant biodiversity bioinformatics projects are now making taxonomic datasets available at a frenetic pace via the World Wide Web (WWW). While these new resources provide the fundamental textual and visual backbone of expert level knowledge, their information structure often impedes the development of derivative works for identification. But when this information is rearranged from a traditional format, questions can be asked of the data that were previously thought to be unanswerable. The difficulty in transforming this big-data is manifold: how to deliver it rapidly to researchers across the world while providing visualizations of data that encompass these large data sets. Interactive Visual Identification Keys (VIK) are introduced here to help manage this magnitude of image data, using both analytic and gestalt methods, (Chapter 2) here via the Carex Interactive Visual Identification Key (CIVIK). Through matrix preparation utilizing ontological methods only, and brute force data-mining, Flora of North America is leveraged to develop and provide a novel identification system for the largest vascular plant genus of North America, Carex. The third chapter focuses on pollination syndromes found within the graminoids, or the grasses and sedges of which Carex is a member. The graminoid pollination syndrome is known as anemophily, or wind pollination. During preparation of CIVIK it was noted repeatedly while taking the photos required for its generation, that small solitary bees and flies will often visit graminoids to collect pollen during anthesis. Yet, traditional botanical literature often neglects to mention this fact, or it is described as being inadvertent or mistaken. This chapter presents solid evidence that even common honey bees, Apis mellifera, will exclusively visit a common turf grass to collect pollen. Then, Chapter 4 examines and analyzes these plant biodiversity websites for use. Are they being used? With what technology? Are trends present to be considered for future development? With answers to these questions, curators of museum quality data, in conjunction with web developers may be able to provide a richer user experience in a shorter amount of time.

The objective of this thesis was not only to contribute to our understanding of batfishes but to also show interesting and educational ways research can be presented to the general public. The first part of this project examines the evolutionary history of batfishes. Batfishes (Ogcocephalidae) are an understudied, group of marine anglerfishes that are dorsoventrally flattened and have an illicium and esca used to attract prey. Relationships among these taxa, as well as the position of Ogcocephalidae within Lophiiformes, remain poorly understood, with previous studies showing conflicting, and poorly resolved results. The timing of divergence and depth of origination in the water column have also not been explored in any detail. In this study, a concatenated nuclear and mitochondrial dataset was constructed across several anglerfish families to elucidate phylogenetic relationships among all batfish genera, to clarify the placement of Ogcocephaloidei within Lophiiformes, and to estimate divergence times using fossil calibrations. An ancestral state reconstruction was also conducted to examine the history of shifts in preferred habitat depths within batfishes. Phylogenetic analyses supported monophyly of each sub-order within Lophiiformes, and placed Ogcocephaloidei as the sister group to Antennarioidei. Batfish genera were divided into an Eastern Pacific/Western Atlantic clade and an Indo-Pacific clade; Halieutaea was recovered as the sister group to all other batfishes. Based on divergence time estimations and ancestral state reconstructions, Ogcocephalidae is Eocene/Paleocene in age and likely originated on the lower continental shelf/upper continental slope. To bring elements of the batfish research into public outreach, I contributed to the LSU Museum of Natural Sciences stand alone fish exhibit book, Making a Big Splash with Louisiana Fishes, which aimed to complement the concepts discussed in the exhibit in an engaging way. In addition to the text included in the exhibit, the book also incorporates ten kids activities, a short story for kids, ABCs of Louisiana, and a short guide to Louisiana fishes. Museum exhibits are a great way to incorporate research into public outreach. They not only enrich the surrounding community, but also contribute to an overall understanding of the importance and nature of scientific research.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 4 uppsatser.

The adaptor protein 4 (AP4) heterotetrameric complex helps form vesicles and traffic cargo from the trans-Golgi Network. Tepsin, a member of the epsin family of trafficking proteins, is the only known accessory protein of AP4. My research focuses on understanding the interaction between AP4 and tepsin, and the function of tepsin. Through analysis of the largely unstructured C-terminus of tepsin, I identified a conserved motif that interacts specifically with AP4 β4. Mutagenesis of the motif affected binding in vitro and lead to loss of tepsin at the membrane in cells. I also showed tepsin binds a surface on β4 conserved across AP β subunits. Slight differences in the surfaces give rise to specific epsin family binding interactions. These data provided the first molecular description of the AP4-tepsin interaction. Unlike other epsins, tepsin contains a unique internal domain named VHS/ENTH-like (tVHS). I determined a high-resolution (1.85Ã) structure of the tVHS domain and found it is smaller than other VHS domains. The structure explains negative binding data between tVHS and typical VHS interactors such as ubiquitin and acidic dileucine motifs. The first structure of an internal VHS domain, it raised interesting questions about the evolution of the ENTH/ANTH/VHS domain family. We showed through phylogenetic analyses that tVHS clusters with VHS domains, but tepsin diverges early from other epsins, in line with my functional data. Commercial Y2H screens have revealed potential binding partners for tVHS and the N-terminal ENTH domain (tENTH). I have shown direct interactions between the tVHS domain and ISCA1, an iron-sulfur cluster assembly protein, as well as tENTH and c16orf62, a newly discovered retromer-like subunit, and we are validating the interactions in cells.