Defining Benthic Organism Exposure: Bioavailability and Effects of Non-Polar Organics

Laboratory and field tests were conducted to evaluate the hypothesis that factors such as the total organic carbon (TOC) contents and groundwater-surface water interactions (GSI) in the sediments can affect chemical desorption, bioavailability and benthic organism exposure. Laboratory studies were conducted with the polycyclic aromatic hydrocarbon fluoranthene (FLU) and the herbicide trifluralin (TF). Toxicokinetic parameters were determined for Lumbriculus variegatus and Hyalella azteca in water-only exposures to 0, 5, 20 and 50 µg/L of the compounds and bioaccumulation was measured during exposures to 0, 100 and 200 mg/kg of FLU and TF spiked onto sediments from Lakes Erie and Huron. Mean uptake clearance rates ranged from 150-180 mL/g wet animal/h for FLU and 84-120 mL/g/h for TF, and elimination rates were 0.12-0.18 and 0.067-0.10/h for FLU and TF, respectively. The uptake clearances in sediments (ks) ranged from 0.021 to 0.070 g dry sed/g wet animal/h for FLU and 0.013 to 0.041 g/g/h for TF. The desorption kinetics of FLU and TF from spiked sediments were measured over 34 d by extraction with Tenax®. The rapidly desorbing fraction for FLU and TF ranged from 31.3 to 54.9% of the initial concentrations and rates of the rapidly (krap), slowly (kslow) and very slowly (kvs) desorbing fractions were on the order of 10-1/h, 10-2–3/h and 10-4/h, respectively. The influence of GSI on contaminant bioavailability was demonstrated with in situ exposures of benthic invertebrates to river sediments that were contaminated primarily with chlorobenzenes (CBs). Hydrologic and chemistry data from nested mini-piezometers explained the exposure-effects relationships. Overall, downwelling conditions reduced the in situ exposure of organisms in surficial sediments, and hence, the toxicity and bioaccumulation of CBs. Data from these field and laboratory investigations were combined with literature values of contaminant partitioning (i.e., Koc values), and L. variegatus feeding rates and chemical assimilation efficiencies to parameterize a bioaccumulation model. Simulated tissue concentrations at sites containing contaminated sediments were compared to the body burdens measured in the field. The model predicted field observations within an order of magnitude and indicated that TOC, GSI and organism feeding behavior were sensitive parameters. The bioaccumulation model represents a useful tool that can reduce resource expenditures associated with site assessments and provide more accurate risk characterizations

Defining Benthic Organism Exposure: Bioavailability and Effects of Non-Polar Organics

Laboratory and field tests were conducted to evaluate the hypothesis that factors such as the total organic carbon (TOC) contents and groundwater-surface water interactions (GSI) in the sediments can affect chemical desorption, bioavailability and benthic organism exposure. Laboratory studies were conducted with the polycyclic aromatic hydrocarbon fluoranthene (FLU) and the herbicide trifluralin (TF). Toxicokinetic parameters were determined for Lumbriculus variegatus and Hyalella azteca in water-only exposures to 0, 5, 20 and 50 µg/L of the compounds and bioaccumulation was measured during exposures to 0, 100 and 200 mg/kg of FLU and TF spiked onto sediments from Lakes Erie and Huron. Mean uptake clearance rates ranged from 150-180 mL/g wet animal/h for FLU and 84-120 mL/g/h for TF, and elimination rates were 0.12-0.18 and 0.067-0.10/h for FLU and TF, respectively. The uptake clearances in sediments (ks) ranged from 0.021 to 0.070 g dry sed/g wet animal/h for FLU and 0.013 to 0.041 g/g/h for TF. The desorption kinetics of FLU and TF from spiked sediments were measured over 34 d by extraction with Tenax®. The rapidly desorbing fraction for FLU and TF ranged from 31.3 to 54.9% of the initial concentrations and rates of the rapidly (krap), slowly (kslow) and very slowly (kvs) desorbing fractions were on the order of 10-1/h, 10-2–3/h and 10-4/h, respectively. The influence of GSI on contaminant bioavailability was demonstrated with in situ exposures of benthic invertebrates to river sediments that were contaminated primarily with chlorobenzenes (CBs). Hydrologic and chemistry data from nested mini-piezometers explained the exposure-effects relationships. Overall, downwelling conditions reduced the in situ exposure of organisms in surficial sediments, and hence, the toxicity and bioaccumulation of CBs. Data from these field and laboratory investigations were combined with literature values of contaminant partitioning (i.e., Koc values), and L. variegatus feeding rates and chemical assimilation efficiencies to parameterize a bioaccumulation model. Simulated tissue concentrations at sites containing contaminated sediments were compared to the body burdens measured in the field. The model predicted field observations within an order of magnitude and indicated that TOC, GSI and organism feeding behavior were sensitive parameters. The bioaccumulation model represents a useful tool that can reduce resource expenditures associated with site assessments and provide more accurate risk characterizations

Glacial cycles promote greater dispersal, which can help explain larger clutch sizes, in north temperate birds

Earth’s glacial history and patterns in the life history traits of the planet’s avifauna suggest the following interpretations of how recent geological history has affected these key characteristics of the biota: 1) Increased colonizing ability has been an important advantage of increased dispersal, and life history strategies are better categorized by dispersive colonizing ability than by their intrinsic growth rates; 2) Birds of the North Temperate Zone show a greater tendency to disperse, and they disperse farther, than tropical or south temperate birds; 3) Habitat changes associated with glacial advance and retreat selected for high dispersal ability, particularly in the North; and 4) Selection for greater dispersal throughout the unstable Pleistocene has also resulted in other well-recognized life history contrasts, especially larger clutch sizes in birds of North Temperate areas

Common Garden Experiment Reveals Genetic Control of Phenotypic Divergence between Swamp Sparrow Subspecies That Lack Divergence in Neutral Genotypes

Adaptive divergence between populations in the face of strong selection on key traits can lead to morphological divergence between populations without concomitant divergence in neutral DNA. Thus, the practice of identifying genetically distinct populations based on divergence in neutral DNA may lead to a taxonomy that ignores evolutionarily important, rapidly evolving, locally-adapted populations. Providing evidence for a genetic basis of morphological divergence between rapidly evolving populations that lack divergence in selectively neutral DNA will not only inform conservation efforts but also provide insight into the mechanisms of the early processes of speciation. The coastal plain swamp sparrow, a recent colonist of tidal marsh habitat, differs from conspecific populations in a variety of phenotypic traits yet remains undifferentiated in neutral DNA.Here we use an experimental approach to demonstrate that phenotypic divergence between ecologically separated populations of swamp sparrows is the result of local adaptation despite the lack of divergence in neutral DNA. We find that morphological (bill size and plumage coloration) and life history (reproductive effort) differences observed between wild populations were maintained in laboratory raised individuals suggesting genetic divergence of fitness related traits.Our results support the hypothesis that phenotypic divergence in swamps sparrows is the result of genetic differentiation, and demonstrate that adaptive traits have evolved more rapidly than neutral DNA in these ecologically divergent populations that may be in the early stages of speciation. Thus, identifying evolutionarily important populations based on divergence in selectively neutral DNA could miss an important level of biodiversity and mislead conservation efforts

Colocalization of F-actin and talin during Fc receptor-mediated phagocytosis in mouse macrophages

We have studied the distribution of talin in J774 cells and mouse peritoneal macrophages undergoing Fc receptor-mediated phagocytosis. At early stages of phagocytosis, talin accumulates in the cells' cortical cytoplasm adjacent to the forming phagosome and extends into pseudopods that are encircling the particle. Talin colocalizes with F-actin at these sites. After particle ingestion is completed, F-actin and talin are no longer concentrated adjacent to phagosomes. Thus, talin and F-actin undergo dynamic and coordinate changes in their cytoplasmic location during Fc receptor-mediated phagocytosis

Tyrosine phosphorylation is required for Fc receptor-mediated phagocytosis in mouse macrophages

Although Fc receptor-mediated phagocytosis is accompanied by a variety of transmembrane signaling events, not all signaling events are required for particle ingestion. For example, Fc receptor-mediated phagocytosis in mouse inflammatory macrophages (Di Virgilio, F., B. C. Meyer, S. Greenberg, and S. C. Silverstein. 1988. J. Cell Biol. 106:657; Greenberg, S., J. El Khoury, F. Di Virgilio, and S. C. Silverstein. 1991. J. Cell Biol. 113:757) and neutrophils (Della Bianca, V., M. Grzeskowiak, and F. Rossi. 1990. J. Immunol. 144:1411) occurs in the absence of cytosolic calcium transients. We sought to identify transmembrane signaling events that are essential for phagocytosis. Here we show that tyrosine phosphorylation is an early event after Fc receptor ligation in mouse inflammatory macrophages, and that the formation of tyrosine phosphoproteins coincides temporally with the appearance of F-actin beneath phagocytic cups. The distribution of tyrosine phosphoproteins that accumulated beneath phagocytic cups was punctate and corresponded to areas of high ligand density on the surface of the antibody-coated red blood cells, which provided the phagocytic stimulus. A tyrosine kinase inhibitor, genistein, but not several inhibitors of protein kinase C, blocked the appearance of tyrosine phosphoproteins as assessed by immunofluorescence, the focal accumulation of F-actin beneath immunoglobulin G-opsonized particles, and the ingestion of these particles as well. We suggest that tyrosine phosphorylation is a critical signaling event that underlies Fc receptor-mediated phagocytosis in mouse macrophages, and is necessary for the engulfment per se

Impact of Massachusetts Health Care Reform on Asthma Mortality

Thesis advisor: Marvin KrausThesis advisor: Matt RutledgeThe state of Massachusetts implemented a health care reform in 2006 that induced a number of changes to its health care system. Studies regarding this reform bear a certain degree of predictive power on the national scale because the reform was used as a model for the Affordable Care Act, the highly controversial national health care reform law passed in 2010. Most of the research on health care reform focuses on the costs, not the quality, of health care. I utilized a difference-in-differences statistical design to isolate the impact of the Massachusetts reform on the state's asthma mortality rate, a health care quality indicator. Given certain assumptions, my empirical results indicate that the reform led to a 45.38% reduction in asthma mortality in Massachusetts. Due to the similarity between the Massachusetts and the national health care reform laws, I drew the conclusion that national asthma mortality rates will decrease after 2014 when certain key provisions of the national reform come into play.Thesis (BA) — Boston College, 2013.Submitted to: Boston College. College of Arts and Sciences.Discipline: Economics Honors Program.Discipline: Economics

Fc receptor-mediated phagocytosis occurs in macrophages at exceedingly low cytosolic Ca2+ levels.

Cytosolic free Ca2+ ([Ca2+]i) homeostasis was investigated in mouse peritoneal macrophages and in the macrophage-like cell line J774. [Ca2+]i measurements were performed in both cells in suspension and cells in monolayers loaded with either quin2 or fura-2. Resting [Ca2+]i was 110-140 and 85-120 nM for cell suspensions and monolayers, respectively. There were no significant differences in [Ca2+]i between the two macrophage populations whether quin2 or fura-2 were used as Ca2+ indicators. Addition of heat-aggregated IgG, IgG-coated erythrocyte ghosts, or a rat monoclonal antibody (2.4G2) directed against mouse Fc receptor II induced a rise in [Ca2+]i. This [Ca2+]i increase was consistently observed in J774 and peritoneal macrophage suspensions and in J774 macrophage monolayers; in contrast it was observed inconsistently in peritoneal macrophages in monolayer cultures. The increase in [Ca2+]i induced by ligation of Fc receptors was inhibited totally in macrophages in suspension and by 80% in macrophages in monolayers by a short preincubation of macrophages with PMA; however, phagocytosis itself was unaffected. The effect of reducing cytosolic Ca2+ to very low concentrations on Fc receptor-mediated phagocytosis was also investigated. By incubating macrophages with high concentrations of quin2/AM in the absence of extracellular Ca2+, or by loading EGTA into the cytoplasm, the [Ca2+]i was buffered and clamped to 1-10 nM. Despite this, the phagocytosis of IgG-coated erythrocytes proceeded normally. These observations confirm the report of Young et al. (Young, J. D., S. S. Ko, and Z. A. Cohn. 1984. Proc. Natl. Acad. Sci. USA. 81:5430-5434) that ligation of Fc receptors causes Ca2+ mobilization in macrophages. However, these results confirm and extend the findings of McNeil et al. (McNeil, P. L., J. A. Swanson, S. D. Wright, S. C. Silverstein, and D. L. Taylor. 1986. J. Cell Biol. 102:1586-1592) that a rise in [Ca2+]i is not required for Fc receptor-mediated phagocytosis; and they provide direct evidence that Fc receptor-mediated phagocytosis occurs normally even at exceedingly low [Ca2+]i