bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of Distinct Neurologic Disease Manifestations during Relapsing Fever Requires T Lymphocytes
Authors: Liu Hongqi , Fitzgerald Denise , Gran Bruno , Leong John M. , Alugupalli Kishore R. 
Published: April 2010

AbstractRelapsing fever borreliosis is a multisystemic infection characterized primarily by bacteremia but can extend to the CNS. The incidence of CNS disease manifestations in humans depends on the infecting relapsing fever Borrelia species. In the murine model of Borrelia hermsii infection we found high incidence of distinct signs of CNS disease that ranged from a flaccid tail to complete paralysis of hind limbs. Infiltration of large number of T cells into the spinal cord of B. hermsii-infected mice and the upregulation of MHC class II and CD80 on infiltrating macrophages and on microglial cells suggested a role for T cell and Ag-presenting cell interactions in this pathogenesis. Indeed, B. hermsii infection did not induce CNS disease manifestations in T cell-deficient mice (TCR-β × δ−/−), although it resulted in bacteremia comparable to wild-type (Wt) level. Moreover, the infiltration of immune cells into the spinal cord of TCR-β × δ−/− mice was reduced and the resident microglial cells were not activated. Histopathological analysis of lumbar sections of the spinal cord confirmed severe inflammation in Wt but not in TCR-β × δ−/− mice. Induction of CNS disease was dependent on the B. hermsii strain as well as on the ability of the host to control bacteremia. Mice that are impaired in controlling B. hermsii, such as CD14−/− mice, exhibited more severe CNS disease than Wt mice. This study demonstrates that distinct neurologic disease manifestations develop during relapsing fever and that T cells play a critical role in the induction of neuropathogenesis.
miR-146a Is Differentially Expressed by Myeloid Dendritic Cell Subsets and Desensitizes Cells to TLR2-Dependent Activation
Authors: Jurkin Jennifer , Schichl Yvonne M. , Koeffel Rene , Bauer Thomas , Richter Susanne , Konradi Sabine , Gesslbauer Bernhard , Strobl Herbert 
Published: April 2010

Abstract
Langerhans cells (LCs) in epithelia and interstitial dendritic cells (intDCs) in adjacent connective tissues represent two closely related myeloid-derived DC subsets that exert specialized functions in the immune system and are of clinical relevance for cell therapy. Both subsets arise from monocyte-committed intermediates in response to tissue-associated microenvironmental signals; however, molecular mechanisms underlying myeloid DC subset specification and function remain poorly defined. Using microarray profiling, we identified microRNA (miRNA) miR-146a to be constitutively expressed at higher levels in human LCs compared with intDCs. Moreover, miR-146a levels were low in monocytes and nondetectable in neutrophil granulocytes. Interestingly, constitutive high miR-146a expression in LCs is induced by the transcription factor PU.1 in response to TGF-β1, a key microenvironmental signal for epidermal LC differentiation. We identified miR-146a as a regulator of monocyte and DC activation but not myeloid/DC subset differentiation. Ectopic miR-146a in monocytes and intDCs interfered with TLR2 downstream signaling and cytokine production, without affecting phenotypic DC maturation. Inversely, silencing of miR-146a in LCs enhanced TLR2-dependent NF-κB signaling. We therefore conclude that high constitutive miR-146a levels are induced by microenvironmental signals in the epidermis and might render LCs less susceptible to inappropriate activation by commensal bacterial TLR2 triggers at body surfaces.
Mesenchymal Stem Cells Protect Breast Cancer Cells through Regulatory T Cells: Role of Mesenchymal Stem Cell-Derived TGF-β
Authors: Patel Shyam A. , Meyer Justin R. , Greco Steven J. , Corcoran Kelly E. , Bryan Margarette , Rameshwar Pranela 
Published: April 2010

Abstract
Mesenchymal stem cells (MSCs) have been shown to support breast cancer growth. Because MSCs also increase the frequency of regulatory T cells (Tregs), this study tested the hypothesis that human MSCs, via Tregs, protect breast cancer cells (BCCs) from immune clearance MSCs suppressed the proliferation of PBMCs when the latter were exposed to gamma-irradiated BCCs. Similarly, MSCs showed significant inhibition of PBMC migration toward BCCs and a corresponding decrease in CXCL12. MSCs also inhibited NK cell and CTL functions, which correlated with reduced numbers of CD8+ and CD56+ cells compared with parallel cultures without MSCs. The reduced NK and CTL activities correlated with a decrease in intracellular and secreted granzyme B. To explain these immunosuppressive findings, we compared Treg levels after coculture with MSCs and found an ∼2-fold increase in Tregs, with associated decreases in antitumor Th1 cytokines and increases in Th2 cytokines. MSC-derived TGF-β1 was largely responsible for the increase in Tregs based on knockdown studies. In the presence of Treg depletion, PBMC proliferation and effector functions were partially restored. Together, these studies show an MSC-mediated increase in Tregs in cocultures of PBMCs and BCCs. The results could be explained, in part, by the increase in Th2-type cytokines and MSC-generated TGF-β1. These findings demonstrate immune protection by MSCs to BCCs. The reduction in immune cell proliferation and recruitment mediated by MSCs has implications for treatment of breast cancer with chemotherapy.
B7-H1 Expression on Old CD8+ T Cells Negatively Regulates the Activation of Immune Responses in Aged Animals
Authors: Mirza Noweeda , Duque Maria Adelaida , Dominguez Ana Lucia , Schrum Adam G. , Dong Haidong , Lustgarten Joseph 
Published: April 2010

Abstract
T cell responses are compromised in the elderly. The B7-CD28 family receptors are critical in the regulation of immune responses. We evaluated whether the B7-family and CD28-family receptors were differentially expressed in dendritic cells, macrophages, and CD4+ and CD8+ T cells from young and old mice, which could contribute to the immune dysfunction in the old. Although most of the receptors were equally expressed in all cells, &gt;85% of the old naive CD8+ T cells expressed B7-H1 compared with 25% in the young. Considering that B7-H1 negatively regulates immune responses, we hypothesized that expression of B7-H1 would downregulate the function of old CD8+ T cells. Old CD8+ T cells showed reduced ability to proliferate, but blockade of B7-H1 restored the proliferative capacity of old CD8+ T cells to a level similar to young CD8+ T cells. In vivo blockade of B7-H1 restored antitumor responses against the B7-H1− BM-185–enhanced GFP tumor, such that old animals responded with the same efficiency as young mice. Our data also indicate that old CD8+ T cells express lower levels of TCR compared with young CD8+ T cells. However, following antigenic stimulation in the presence of B7-H1 blockade, the levels of TCR expression were restored in old CD8+ T cells, which correlated with stronger T cell activation. These studies demonstrated that expression of B7-H1 in old CD8+ T cells impairs the proper activation of these cells and that blockade of B7-H1 could be critical to optimally stimulate a CD8 T cell response in the old.
A steady state description ofgrowth and light absorption in the marine planktonic diatom Skeletonema costatum
Authors: Sakshaug Egil , Andresen Kjersti , Kiefer Dale A. 
Published: April 2010

Studies of the marine diatom Skeletonema costatum indicate that for a given irradiance and day length, increases in the rate of supply of a limiting nutrient cause linearly proportional increases in the growth rate and the Chl : C ratio. For a given irradiance, increases in day length cause decreases in the Chl : C ratio, and the growth rate is linearly proportional to the product of day length and the Chl : C ratio. For a given day length, increases in irradiance cause decreases in the Chl : C ratio and quantum yield, and the growth rate and irradiance are curvilinearly related.These observations are incorporated into a formulation of steady state growth, which includes day length, irradiance, and the Chl : C ratio, and two coefficients, which are the product of the maximal quantum yield and the specific absorption coefficient and the product of the average absorption cross section of the photosynthetic unit and the minimal rate of turnover of the unit. The photosynthetic quantum yield is represented by a Poisson distribution and is a function of irradiance alone.
The role of endosymbiotic bacteria in the nutrition of Solemya velum: Evidence from a stable isotope analysis of endosymbionts and host
Authors: Conway Noellette , Capuzzo Judith McDowell , Fry Brian 
Published: April 2010

C, N, and S stable isotope compositions were investigated in tissues of the protobranch bivalve Solemya velum. This species is known to harbor endosymbiotic chemoautotrophic bacteria. C and N isotope values were also examined in an enriched bacterial fraction, separated from intact gills by differential centrifugation.The bacterial fraction and host tissues had similar δ13C values, suggesting that endosymbiotic bacteria provide as much as 98% of the carbon requirements of S. velum. The δ15N values of both S. velum and the endosymbionts were comparable and considerably lower than those of bivalve controls that do not harbor endosymbionts. Uptake of pore‐water ammonium by the endosymbionts and subsequent translocation of nitrogenous compounds to the host may account for the low δ15N of S. velum. In this context, the symbionts may provide 100% of the host nitrogen. The δ34S values of S. velum suggest the use of biogenically produced H2S as a source of S. The stable isotope ratios of sulfur and nitrogen are among the lowest reported for animal tissues. This study attempts to estimate the nutritional significance of bacterial endosymbionts by analyzing the stable isotope ratios of both bacteria and host tissue.
Effects of Si : P supply ratio, supply variability, and selective grazing in the plankton: An experiment with a natural algal and protistan assemblage.
Authors: Grover James P. 
Published: April 2010

Semicontinuous cultures were used to examine the effects of Si and P supply on a natural algal community. Three Si : P supply ratios were used, with different patterns of supply variability imposed by various schedules of Si and P pulses delivered 1, 4, or 10 d apart. All cultures with a given Si: P supply ratio received the same time‐averaged supply of Si and P. The Si: P supply ratio had a strong effect on the species composition of the algae. Chlorophytes were most abundant at the low Si: P supply ratio (20 : 1), diatoms were most abundant at the intermediate Si : P supply ratio (80 : 1), and the siliceous chrysophyte Mallomonas sp. was most abundant at the high Si : P supply ratio (160 : 1). Diatom species showed differentiation in their ability to compete for Si and P. On average, algal cells became smaller as the Si: P supply ratio decreased. Higher algal species richness was associated with increased variability in P supply. Competitive ability of some algae was increased by variability in P supply, but that of others was decreased.A flagellated protist grazed selectively on two Nitzschia spp., and thereby altered their competitive dynamics. The biovolume of this protist, and that of other heterotrophic flagellates, decreased with increasing variability in P supply. Despite selective grazing and nutrient supply variability, patterns in the algal communities were generally consistent with expectations based on resource competition theory and previous experience with algal competition in cultures.
Multivariate statistical analysis of the factors controlling the distribution of scaled chrysophytes
Authors: Siver Peter A. , Hamer Josephine S. 
Published: April 2010

A total of 332 collections from 62 water bodies was analyzed for scaled chrysophytes with electron microscopy and correlated with limnological characteristics. The pH and specific conductance were the most important factors controlling the distribution of scaled chrysophytes; temperature and total phosphorus were of lesser importance.A mean of nine and seven taxa per collection were recorded at a pH of 5.5–6.0 and a specific conductance <40 µS, respectively. Significantly fewer taxa per collection were found as the pH lowered below 5.5 or raised above 6.0 or as the specific conductance increased above 40 S. Similar distributional patterns were found for the genera Mallomonas, Synura, and Spiniferomonas.A two‐factor principal component model explained 70% of the total variance within the data set (n = 1,355). The first principal component explained 80 and 83% of the total variance within the pH and specific conductance variables. The pH and specific conductance also dominated the first principal component for each genus and for 23 of the 25 species tested. A cluster analysis, using within‐group linkages, produced five groups of organisms that differed primarily with respect to their distribution along a pH gradient.
Simulation of bacterial attraction and adhesion to falling particles in an aquatic environment
Authors: Jackson George A. 
Published: April 2010

Chemosensory movement of bacteria toward the cloud of leaked material around planktonic algae has been suggested as an important aspect of bacterial nutrition in aquatic ecosystems. Inability of bacteria to keep pace with falling algae has been suggested as inhibiting such interactions. The interaction between bacteria and falling particles, including microalgae, is explored with a simulation model of bacterial chemotaxis that incorporates low Reynolds number fluid flow and resulting substrate spatial distributions. Results show that although bacteria cannot maintain a position relative to a falling particle unless the particle is extremely large, such as a marine snow aggregate, chemosensory response does allow them to stay in the high substrate environment of the leaky particle longer than if they did not have it. The ecological significance for bacterial metabolism depends on several factors, including the frequency of contact between algae and bacteria and the relative concentrations of substrate at the cell surface and in the background. Optimal enhancement should occur in eutrophic conditions of large algal cells present in high abundances. Presently available values for the ratio of substrate concentration next to the algal cell relative to that in solution are not large enough to suggest that the microzones around algal cells provide significant enhancement of bacterial nutrition.Chemotaxis should enhance interactions with large marine snow aggregates, both by allowing bacteria to stay for significant periods around them and by enhancing the rates at which bacteria attach to the aggregate surfaces. This enhancement is greater for surfaces in which there is a lower probability of sticking.
Whole‐lake experiments: The annual record of fossil pigments and zooplankton
Authors: Leavitt P. R. , Carpenter S. R. , Kitchell J. F. 
Published: April 2010

The annual record of fossil pigments and zooplankton was compared with detailed contemporaneous records from two manipulated lakes from 1940 to 1986. Annually resolved sedimentary records accurately monitored known changes inplankton communities, identified periods of trophic change, and proved a powerful tool for examining long‐term, complex interactions. Both Paul and Peter Lakes underwent the same three complete changes in their fish assemblages (trout, cyprinid, bass), and Peter Lake received repeated inputs of lime. Alterations in fish community composition produced long‐lived changes in zooplankton communities that cascaded to the microbial level of the food web. Liming, in concert with trophic changes, caused distinctive phytoplankton dynamics in Peter Lake.Paleolimnological data recorded all major plankton dynamics known from coeval limnological data. Specifically, the sediment record showed transitions in cladoceran size structure and species composition, changes in water clarity resulting from both food web and chemical manipulations that affected vertical zonation of primary producers, and changes in absolute abundance of all algal divisions except dinoflagellates. Undegraded Chl a indicated deep blooms and, in conjunction with Chl c, fucoxanthin and β‐carotene, indicated metalimnetic chrysophytes. Transient (2–3 yr) nonselective increases in sedimentation corresponded with increases in grazing rates. Isorenieratene indicated overlap of photic and anoxic zones, revealing changes in transparency and conditions for pigment preservation.
Gas transport from methane‐saturated, tidal freshwater and wetland sediments
Authors: Chanton Jeffrey P. , Martens Christopher S. , Kelley Cheryl A. 
Published: April 2010

Variations in hydrostatic pressure controlled by diurnal tides triggered ebullition from subtidal freshwater sediments dominated by methanogenesis in the White Oak River estuary, North Carolina. Pulses of gas consisting of 50–80% methane were released when the tidal cycle reached its nadir. In August, site‐to‐site variations in these fluxes ranged from 60 to 650 ml (39–425 mg) CH4 m−2 d−1. At a single site, ebullition made up 50% of the total CH4 flux out of the sediments; the remainder was transported across the sediment‐water interface by molecular diffusion.The sedimentary gas bubble reservoir varied seasonally between 2.6 and 14.8 liters m−3 at two White Oak sites. These quantities represented 10–30% of the total sedimentary CH4 inventory, the balance of which was dissolved in pore waters. Methane shifted between the two pools with seasonal changes in temperature as bubble methane partial pressure maintained equilibrium with dissolved CH4.Factors controlling the composition of sedimentary gas bubbles were investigated by collecting samples from several environments. These bubbles consisted primarily of CH4, N2, and CO2. The ratio of CH4 to N2 was found to be a useful indicator of mechanisms transporting gases from sediments and was controlled by both the ebullition rate and the presence of rooted emergent macrophytes.
Florida diatom assemblages as indicators of trophic state and pH
Authors: Whitmore Thomas J. 
Published: April 2010

Predictive models were developed that relate lake trophic state to diatom assemblages in surface sediments. These models can be used to assess quantitatively the historical impact of cultural activities on lake productivity. One set of models relates trophic state index (TSI) values to a new diatom index based on autecological nutrient categories. A second set uses nutrient categories in multiple regression equations to predict TSI. Both types of models explain ~80% of the variance in total phosphorus TSI and averaged TSI values. Diatom‐pH transfer functions were also developed to assess the influence of eutrophication on lake pH.Because trophic state and pH are positively correlated in Florida lakes, statistical confounding might result when predictive models for pH and trophic state are calibrated. Long‐term changes in pH might lead to errors when inferring historical TSI values, while changes in trophic state could similarly influence historical pH inferences. Partial correlations showed that two multiple regression models were statistically confounded by the nontarget variable, though predictive models based on diatom indices were free from such effects.
Light‐limited growth on ammonium vs. nitrate: What is the advantage for marine phytoplankton?
Authors: Thompson Peter A. , Levasseur Maurice E. , Harrison Paul J. 
Published: April 2010

Thalassiosira pseudonana (3H) was grown in semicontinuous culture on either NO3− or NH4+ at nine different photon flux densities (PFDs). At PFDs >29 µEinst m−2 s−1, growth rates (µ) were 8% lower for cells growing on NO3− compared to cells growing on NH4+. At high PFDs NO3−‐grown cells had 21% lower carbon quotas than NH4+‐grown cells. At high PFDs the possibility exists that competition for reductant may reduce µ and carbon quotas for NO3−‐grown cells.At PFDs ≤29 µEinst m−2 s−1 NO3−‐grown cells had equal growth rates, nitrogen quotas, Chl a cell−1, and equal or greater carbon quotas compared to NH4+‐grown cells. At these light‐limited growth rates NO3−‐grown cells used more reductant overall and up to 51% more reductant per unit Chl a than NH4+‐grown cells to store carbon and nitrogen. These results suggest that use of NO3− rather than NH4+ is of little energetic importance in terms of growth rate at low PFDs.
Metalimnetic cyanobacteria in hard‐water lakes: Buoyancy regulation and physiological state
Authors: Konopka Allan 
Published: April 2010

During summer stratification, Crooked and Little Crooked Lakes, Indiana, contained phytoplankton dominated by populations of Aphanizomenonflos‐aquae that stratified in the metalimnion where photon irradiance was 6% of that at the surface. The gas vacuolate Aphanizomenon filaments from Little Crooked Lake lost buoyancy when exposed to irradiances >100 µmol photons m−2 s−1. If 2 µM KH2PO4 was added to the water samples, however, exposure to irradiances >200 µmol photons m−2 s−1 was necessary to obtain buoyancy losses. Phosphate also affected the recovery of buoyancy by sinking filaments. Filaments that had lost buoyancy due to incubation in the light recovered it when incubated for 5 h in the dark. Addition of phosphate increased the rate of buoyancy recovery by 50%.The metalimnetic populations had stratified in a zone of relatively low irradiance and inorganic nutrient concentration. The physiological state of the populations was evaluated by determining the kinetic characteristics for phosphate, nitrate, and ammonia uptake and the cellular contents of surplus phosphate and chlorophyll a. On the basis of the premise that cells limited by a particular element will express a high uptake potential for that element, the metalimnetic populations showed characteristics of organisms not limited by the availability of light, phosphorus, or nitrogen.
The geochemical evolution of halite structures in hypersaline lakes: The Dead Sea, Israel
Authors: Ganor Jiwchar , Katz Amitai 
Published: April 2010

Depressions in the floor of the southern basin of the Dead Sea contain dense (1.26–1.29 g cm−3) brines which formed by evaporation at the lake’s surface. Absorbance of solar radiation heats these brines by about 2.4°C d−1, as long as the density gradient of the lake prevents overturn. As a result, bottom halite is dissolved in the warmer brines at about 0.4 g NaCl liter−1 °C−1. Continuous heating of the brine of these holes and cooling of the overlying liquids at night causes frequent overturns of the brine column, followed by mixing and cooling of the NaCl‐rich brine. The extra load of halite is precipitated near the holes in the form of halite cones and mushroomlike structures. Whereas the initial NaCl supply to the growing halite structures comes from the floor of the lake, the later growth stage is supported by NaCl supplied from the upper (evaporating) brine layer.Crude mass and heat balances show that the proposed model may well explain the occurrence and distribution of halite islands in the Dead Sea. The model may be applicable to any shallow enough (a few meters) hypersaline lake that is saturated with respect to halite.