1,568 research outputs found
Viral Infection Results in Massive CD8+ T Cell Expansion and Mortality in Vaccinated Perforin-Deficient Mice
AbstractPerforin-mediated cytotoxicity is essential for clearance of primary LCMV infection. BALB/c-perforin-deficient (PKO) mice survived LCMV infection by deleting NP118-specific CD8+ T cells whereas vaccination of PKO mice with Listeria expressing NP118 generated a stable memory CD8+ T cell population. However, >85% of vaccinated BALB/c-PKO mice died after LCMV infection. Mortality was associated with enormous expansion of NP118-specific CD8+ T cells in both lymphoid and nonlymphoid tissues and aberrant CD8+ T cell cytokine production. Depletion of CD8+ T cells or treatment with anti-IFNγ antibody rescued vaccinated mice from mortality. Thus, perforin was essential for resistance to secondary LCMV infection, and, in the absence of perforin, vaccination resulted in lethal disease mediated by dysregulated CD8+ T cell expansion and cytokine production
Does the Density of Invasive Rusty Crayfish Affect Stream Macroinvertebrates?
Rusty crayfish (_Orconectes rusticus_) have invaded streams of the upper Susquehanna River catchment (New York, USA), replacing native crayfish and probably increasing overall crayfish density. Crayfish are important consumers and agents of disturbance in aquatic communities, so the introduction and expansion of rusty crayfish could affect the invaded community through the change in crayfish species composition, the increase in crayfish density, or some combination of the two. Other macroinvertebrates are prey of, competitors with, or subject to disturbance by crayfish and so are likely to be affected by changes in the crayfish assemblage. We conducted correlative field sampling and an enclosure experiment to investigate the effects of invading _O. rusticus_ on the abundance, diversity, and composition of the stream macroinvertebrate assemblage. We sampled crayfish and macroinvertebrates at 13 sites on 4 streams in the upper Susquehanna River catchment that varied in crayfish species composition and density. Total macroinvertebrate abundance, taxon richness, diversity, and density of individual taxa were not significantly correlated to either total crayfish density or the relative abundance of _O. rusticus_. We also conducted an experiment in stream enclosures to test the effects of _O. rusticus_ density on the macroinvertebrate assemblage. Increasing crayfish density caused a significant decrease in total macroinvertebrate density but did not significantly affect macroinvertebrate taxon richness or diversity. The density of some individual taxa were also significantly affected by crayfish density. Our experiment shows that rusty crayfish density can affect the stream community; the mechanism of these effects, and whether they differ from those of native species, remain to be determined
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Drivers of Kelp Forest Responses to Global Change: From Populations to Policies
Kelps are large brown algae in the order Laminariales and are foundation species that form the basis of kelp forests. Present across a quarter of the world’s coastlines, kelp forests provide diverse services to coastal communities, as habitat for commercially and culturally important species, as a food source for humans as well as myriad animals, as raw material used in the pharmaceutical and cosmetics industries, as a place of recreation and tourism, and as a potential source of carbon sequestration. Like all ecosystems on the planet, kelp forests are deeply impacted by human-derived global change. The most comprehensive meta-analysis of global trends in kelp forest cover found that on average kelp forest cover has been declining globally over the past two decades. This negative trend is underlaid by various human impacts. For instance, kelp harvesting is thought to be the primary driver of kelp forest decline in northern Chile, invasive bryozoans in parts of Nova Scotia, and climate-change induced changes in water temperature in western Australia. Furthermore, human impacts can intersect to create cumulative impacts on kelp forests that prevent attribution of kelp forest decline to any one factor. For instance, in Northern California, a marine heat wave, loss of an urchin-eating predator, and unusually high urchin recruitment all contributed to the collapse of Nereocystis forests in 2015.
While some kelp forests in North America are rigorously studied, covered by long-term monitoring, and relatively well-understood (such as Monterey Bay and Point Loma in California), the vast majority are not. In this dissertation, I utilize broad approaches to overcome these data limitations and provide insights into the drivers of kelp forest responses to global change that are relevant to decision-makers. In Chapter 2 I created a 35-year time series of Nereocystis canopy area in Oregon using remote sensing analysis of Landsat satellite data. This dataset showed that multiple-endmember spectral mixing analysis techniques previously utilized to track changes in Macrocystis pyrifera canopy in California can be used with different species and in different regions. Additionally, it retroactively provided rich insights into trends in kelp forest cover across the state and identified novel environmental correlates of kelp forest cover, such as a positive association with winter wave height that have deepened our understanding of the population biology and ecology of Nereocystis. Insights from this work has been shared with the Oregon Department of Fish and Wildlife, the Oregon Kelp Alliance, the Elakha Alliance, the Coquille Tribe, Senator Jeff Merkley and others in order to support policy-making, restoration, and science funding efforts related to kelp in Oregon.
In Chapter 3, I used the contributed data of over 30 collaborators to provide range-wide insights into the impacts of disease on a Pycnopodia helianthoides, a urchin-eating predator whose loss has been tied to kelp forest overgrazing. This work found that disease-driven mortality had been so severe (~99%) in the southern half of the species range that recovery to ecologically-relevant population levels was unlikely to happen in a time frame relevant for kelp forests. In the northern half of the range however, populations were impacted less dramatically and could still be found in relatively high densities, although densities were patchy. Additionally, we found that the importance of temperature in predicting Pycnopodia distributions rose dramatically after the disease event, indicating that temperature-disease interactions were related to the latitudinal pattern in disease severity. Furthermore, through a partnership with The Nature Conservancy, this work has influenced global Pycnopodia conservation efforts through the successful listing of the species as Critically Endangered on the IUCN Red List, the formation of a Pycnopodia Recovery Working group, and incorporation into a Pycnopodia Recovery Roadmap.
Finally, in Chapter 4, I brought together insights from the scholarly literature on kelp forest ecology, the framework of Ecosystem Based Management (EBM), and regional case studies of ongoing management to synthesize cross-regional principles for managing kelp forests sustainably. Our case studies focused on three regions, each with unique socioecological contexts around kelp forests: northern Chile, California (USA), and British Columbia (Canada). Drawing lessons from across disciplines and regions, we identified six principles for kelp forest EBM: 1) monitoring at biologically relevant temporal and spatial scales, 2) assessing and addressing cumulative impacts, 3) managing across spatial scales, 4) co-management with users, 5) employing rapid adaptive management and/or the precautionary principle, and 6) managing food web connections. We explore and illustrate these concepts using examples from multiple regions to provide concrete guidance on EBM-inspired strategies that are likely to improve kelp forest management outcomes. We hope this work can be a starting place for further discussion around and development of best practices in kelp forest management
Design, assembly, and validation of a nose-only inhalation exposure system for studies of aerosolized viable influenza H5N1 virus in ferrets
<p>Abstract</p> <p>Background</p> <p>The routes by which humans acquire influenza H5N1 infections have not been fully elucidated. Based on the known biology of influenza viruses, four modes of transmission are most likely in humans: aerosol transmission, ingestion of undercooked contaminated infected poultry, transmission by large droplets and self-inoculation of the nasal mucosa by contaminated hands. In preparation of a study to resolve whether H5N1 viruses are transmissible by aerosol in an animal model that is a surrogate for humans, an inhalation exposure system for studies of aerosolized H5N1 viruses in ferrets was designed, assembled, and validated. Particular attention was paid towards system safety, efficacy of dissemination, the viability of aerosolized virus, and sampling methodology.</p> <p>Results</p> <p>An aerosol generation and delivery system, referred to as a Nose-Only Bioaerosol Exposure System (NBIES), was assembled and function tested. The NBIES passed all safety tests, met expected engineering parameters, required relatively small quantities of material to obtain the desired aerosol concentrations of influenza virus, and delivered doses with high-efficacy. Ferrets withstood a mock exposure trial without signs of stress.</p> <p>Conclusions</p> <p>The NBIES delivers doses of aerosolized influenza viruses with high efficacy, and uses less starting material than other similar designs. Influenza H5N1 and H3N2 viruses remain stable under the conditions used for aerosol generation and sample collection. The NBIES is qualified for studies of aerosolized H5N1 virus.</p
Feeding dynamics of Northwest Atlantic small pelagic fishes
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Progress in Oceanography 165 (2018): 52-62, doi:10.1016/j.pocean.2018.04.014.Small pelagic fishes represent a critical link between zooplankton and large predators. Yet, the
taxonomic resolution of the diets of these important fishes is often limited, especially in the Northwest
Atlantic. We examined the diets, along with stable isotope signatures, of five dominant small pelagic
species of the Northeast US continental shelf ecosystem (Atlantic mackerel Scomber scombrus, Atlantic
herring Clupea harengus, alewife Alosa pseudoharengus, blueback herring Alosa aestivalis, and Atlantic
butterfish Peprilus triacanthus). Diet analyses revealed strong seasonal differences in most species. Small
pelagic fishes predominantly consumed Calanus copepods, small copepod genera
(Pseudocalanus/Paracalanus/Clausocalanus), and Centropages copepods in the spring, with
appendicularians also important by number for most species. Krill, primarily Meganyctiphanes norvegica,
and hyperiid amphipods of the genera Hyperia and Parathemisto were common in the stomach contents
of four of the five species in the fall, with hyperiids common in the stomach contents of butterfish in both
seasons and krill common in the stomach contents of alewife in both seasons. Depth and region were also
found to be sources of variability in the diets of Atlantic mackerel, Atlantic herring, and alewife (region
but not depth) with krill being more often in the diet of alewife in more northerly locations, primarily the
Gulf of Maine. Stable isotope data corroborate the seasonal differences in diet but overlap of isotopic
niche space contrasts that of dietary overlap, highlighting the differences in the two methods. Overall, the
seasonal variability and consumer-specific diets of small pelagic fishes are important for understanding
how changes in the zooplankton community could influence higher trophic levels.Funding for this work
was primarily through a US National Science Foundation (NSF) OCE-RIG grant (OCE 1325451) to JKL,
with additional support from NOAA through the Cooperative Institute for the North Atlantic Region
(CINAR) under Cooperative Agreement NA14OAR4320158 in the form a CINAR Fellow Award (JKL),
an NSF Long-term Ecological Research grant for the Northeast US Shelf Ecosystem (OCE 1655686;
JKL), a Hendrix College summer research award (ZRK), and an NSF REU-supported Woods Hole
Oceanographic Institution Summer Student Fellowship (SLH)
IL-4 sensitivity shapes the peripheral CD8\u3csup\u3e+\u3c/sup\u3e T cell pool and response to infection
Previous studies have revealed that a population of innate memory CD8+ T cells is generated in response to IL-4, first appearing in the thymus and bearing high expression levels of Eomesodermin (Eomes) but not T-bet. However, the antigen specificity and functional properties of these cells is poorly defined. In this study, we show that IL-4 regulates not only the frequency and function of innate memory CD8+ T cells, but also regulates Eomes expression levels and functional reactivity of naive CD8+ T cells. Lack of IL-4 responsiveness attenuates the capacity of CD8+ T cells to mount a robust response to lymphocytic choriomeningitis virus infection, with both quantitative and qualitative effects on effector and memory antigen-specific CD8+ T cells. Unexpectedly, we found that, although numerically rare, memory phenotype CD8+ T cells in IL-4Rα–deficient mice exhibited enhanced reactivity after in vitro and in vivo stimulation. Importantly, our data revealed that these effects of IL-4 exposure occur before, not during, infection. Together, these data show that IL-4 influences the entire peripheral CD8+ T cell pool, influencing expression of T-box transcription factors, functional reactivity, and the capacity to respond to infection. These findings indicate that IL-4, a canonical Th2 cell cytokine, can sometimes promote rather than impair Th1 cell–type immune responses
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