Analysis of the role of the p47 GTPase IIGP1 in Resistance against Intracellular Pathogens

IIGP1 is a member of the p47 GTPase family of IFNγ-induced proteins, which are among the most potent presently known mediators of cell-autonomous resistance against intracellular bacterial and protozoan pathogens in the mouse. From all studied members of this family IIGP1 is the best characterized with respect to biochemical characteristics and enzymatic activity in vitro, as well as membrane binding properties and dynamic behavior in cells. The role of the protein in intracellular defense was however, unknown and this study was set as an initial attempt to reveal it. This thesis describes the generation of an IIGP1 deficient mouse and analysis of the susceptibility of this animal to pathogens from protozoan and bacterial origin, which employ diverse strategies for host cell invasion and intracellular survival and replication. Despite having intact adaptive immune system, the IIGP1 deficient mice showed higher incidence of development of cerebral malaria after infection with Plasmodium berghei sporozoites. In addition, IIGP1 deficient astrocytes exhibited a partial loss of IFNγ-induced inhibition of Toxoplasma gondii growth. IIGP1 deficient animals were not susceptible to infection with Leishmania major, Listeria monocytogenes, Chlamydia trachomatis and Anaplasma phagocytophilum. From the analysis of the obtained data in the context of the intracellular lifestyle of the pathogens involved in this study, we concluded that IIGP1 seems to be specifically involved in defense against protozoan parasites, which like Pl. berghei and T. gondii reside in non-fusigenic parasitophorous vacuoles after entering cells. The mechanisms of IIGP1-dependent protection of cells against these pathogens remain to be studied

Food webs in the lower Waikato River and the role of hydrogeomorphic complexity

Large rivers are fundamental to human societies and consequently their ecosystems have come under increasing pressure from a range of developments and uses. Despite this, there is still a major knowledge gap understanding food webs supporting fisheries of large river ecosystems. Quantifying the contributions of carbon sources that support food webs is an important and growing field of ecological research, with implications for future management and rehabilitation of large rivers. I reviewed theoretical concepts addressing carbon flow in large river food webs where organic matter from floodplains (Flood Pulse Concept), local aquatic sources (Riverine Productivity Model), or leakage from upstream processing of terrestrial organic matter (River Continuum Concept) can fuel secondary production. Recent empirical evidence highlights the importance of autochthonous carbon, especially in the form of benthic algae and phytoplankton, to food webs in a variety of large rivers along with a range of secondary carbon sources that can assume importance depending on temporal and spatial variation in hydrogeomorphic conditions. The geographic spread of studies addressing carbon flow in large river food webs is steadily increasing, although information remains sparse on temperate Southern Hemisphere rivers and long-term data sets on carbon flow are generally lacking. I measured natural abundances of stable carbon (δ13C) and nitrogen (δ15N) isotopes to quantify spatial and temporal patterns of carbon flow through aquatic food webs in the lowland section of New Zealand’s longest river, the Waikato River. Zones of potential ecological importance influencing carbon transfer along the lower Waikato River were identified using a combination of (i) high-frequency, along-river water quality measurements collected during four seasons and (ii) river channel morphology data derived from aerial photos. A multivariate statistical approach was developed to identify three hydrogeomorphic zones shaped by the physical complexity and channel character of constituent river reaches, and characterised by shifts, sometimes transitional, of physico-chemical variables. Changes in water clarity, chlorophyll fluorescence and specific conductance were driven by tributary inflows and tidal influence. Carbon flow estimated using the mixing model IsoSource supported predictions of the Riverine Productivity Model, with autochthonous algae and biofilms (phytomicrobenthos) the most important basal carbon sources contributing to consumer biomass in all three zones. These sources were often supported by C3 aquatic macrophytes and allochthonous C3 riparian plants. However, the relative importance of organic carbon sources appeared to change depending on season and zone, likely in response to variations in water temperature and flow, particularly in the unconstrained zone of the lower river. It was also demonstrated that to draw robust conclusions, consideration must be given to quantifying the isotopic signatures of organisms lower in the food web, as these can change significantly between sampling times and hydrogeomorphic zones. Tributary confluences can be hotspots for biological production and provide novel carbon sources from donor sub-catchments in large river systems. Littoral food webs and water quality were compared between two main stem habitats (constrained and unconstrained hydrogeomorphic zones) and tributary junctions representing those fed by streams, lakes and wetlands during seasonal low flows when these habitats were likely to be most different. δ13C and δ15N isotopes were then employed using the Bayesian statistics R package Stable Isotope Analysis in R (SIAR) to estimate carbon flow through food webs and also to estimate measures of trophic structure. Pathways were also tested using analysis of fish stomach contents. SIAR mixing models confirmed that autochthonous benthic carbon was the most important carbon source to littoral food webs in all habitats. Riparian carbon appeared to be the most important secondary carbon source to fish consumers, and estimates of its contribution were often greater in tributary junctions compared to fish of the same species in the main stem. Trophic patterns of fish species collected in both the main stem and tributary junctions were similar amongst habitats, as were community metrics estimated using stable isotope signatures and SIAR. This study demonstrates that, while they may add to the lateral complexity of the riverscape, permanently connected habitats such as tributary junctions do not necessarily contribute to overall food web complexity. In this study tributary junctions tended to be steep-sided, and complex littoral habitats containing woody debris and macrophytes were typically rare, potentially limiting the development of more complex food webs. These results contribute to the ever-improving data regarding food web ecology in large rivers, particularly with regard to carbon flow, and the role played by lateral habitats and hydrogeomorphic zones in shaping these processes. This study also provides information and recommendations that provide direction for future research and management actions aimed at aiding the rehabilitation of the lower Waikato River, its riverscape and biological communities

Tennessee Wildlife Special Edition, 2023-2024 Fishing Regulations

https://digitalcommons.memphis.edu/govpubs-tn-wra-hunting-fishing-regulations/1000/thumbnail.jp

Seedling Emergence from Seed Banks in Ludwigia hexapetala-Invaded Wetlands: Implications for Restoration

Soil seed banks play a critical role in the maintenance of wetland plant communities and contribute to revegetation following disturbances. Analysis of the seed bank can therefore inform restoration planning and management. Emergence from seed banks may vary in response to hydrologic conditions and sediment disturbances. To assess the community-level impact of exotic Ludwigia hexapetala on soil seed banks, we compared differences in species composition of standing vegetation among invaded and non-invaded wetlands and the degree of similarity between vegetation and soil seed banks in northern California. To determine potential seed bank recruitment of L. hexapetala and associated plant species, we conducted a seedling emergence assay in response to inundation regime (drawdown vs. flooded) and sediment depth (surface vs. buried). Plant species richness, evenness, and Shannon’s H’ diversity were substantially lower in standing vegetation at L. hexapetala invaded sites as compared to non-invaded sites. Over 12 months, 69 plant taxa germinated from the seed banks, including L. hexapetala and several other exotic taxa. Seedling density varied among sites, being the highest (10,500 seedlings m−2) in surface sediments from non-invaded sites subjected to drawdown treatments. These results signal the need for invasive plant management strategies to deplete undesirable seed banks for restoration success

Adolescent Reading Improvement: A Phenomenology of High School Students’ Perspectives

The purpose of this phenomenological study was to explore the experience of improvement in reading comprehension of adolescent readers who have made gains greater than what might be predicted based on previous growth in reading comprehension measures. These research questions guided this study: What influences have impacted the lived experiences of these improving readers? What barriers to reading improvement existed for these students? In addition, what school-related reading experiences, if any, hold meaning for these readers? What characteristics are shared among adolescent readers who have experienced better-than-expected growth? Interviews, story chart artifacts created by participants, and observations of students’ process and self-talk while reading short passages were collected from 12 students at Placid High School (pseudonym). Analysis was conducted using Hycner’s framework and hermeneutic analysis in order to discover the essence of these students’ experiences as improving readers. Methodologically, this study ascertained shared characteristics and experiences that influenced the reading comprehension growth of these adolescents through inductive study of all data. Four themes emerged through the data analysis: Reading as Provocation, Reading as Displacement, Reading as Relationship, and Reading as Confluence