β-(1,3)-Glucan Exposure Assessment by Passive Airborne Dust Sampling and New Sensitive Immunoassays

Associations between house dust-associated β-(1,3)-glucan exposure and airway inflammatory reactions have been reported, while such exposures in early childhood have been suggested to protect against asthma and wheezing. Most epidemiological studies have used reservoir dust samples and an inhibition enzyme immunoassay (EIA) for β-(1,3)-glucan exposure assessment. The objective of this study was to develop inexpensive but highly sensitive enzyme immunoassays to measure airborne β-(1,3)-glucans in low-exposure environments, like homes. Specificities of available anti-β-(1,3)-glucan antibodies were defined by direct and inhibition experiments. Three suitable antibody combinations were selected for sandwich EIAs. β-(1,3)-Glucans in passive airborne dust collected with an electrostatic dust fall collector (EDC) and floor dust from seven homes were measured with the three EIAs. Floor dust samples were additionally analyzed in the inhibition EIA. The sandwich EIAs were sensitive enough for airborne glucan measurement and showed different specificities for commercial glucans, while the β-(1,3)-glucan levels in house dust samples correlated strongly. The feasibility of measuring glucans in airborne dust with the recently introduced EDC method was further investigated by selecting the most suitable of the three EIAs to measure and compare β-(1,3)-glucan levels in the EDC and in floor and actively collected airborne dust samples of the previously performed EDC validation study. The EDC β-(1,3)-glucan levels correlated moderately with β-(1,3)-glucans in actively collected airborne dust and floor dust samples, while the glucan levels in the airborne dust and floor dust samples did not correlate. The combination of the newly developed β-(1,3)-glucan sandwich EIA with EDC sampling now allows assessment in large-scale population studies of exposure to airborne β-(1,3)-glucans in homes or other low-exposure environments.β-(1,3)-Glucans are polysaccharides produced by plants, bacteria, and fungi. Their chain lengths, their degrees of branching, and the numbers and positions of their other glycosidic linkages, like β-(1,4)- and/or β-(1,6)-linkages, may vary largely. While β-(1,3)-(1,4)-glucan structures are typically found in plant material, β-(1,3)-(1,6)-chains are more prevalent in fungi and bacteria (31). Because they are typical microbe-associated molecular patterns (MAMPs), β-(1,3)-glucans activate cells of the innate immune system by binding to glucan-specific receptors like dectin-1 (1, 4, 6) and other cellular membrane receptors (5, 21). Associations between indoor β-(1,3)-glucan exposure and inflammatory reactions of the respiratory system have been reported (3, 10, 25, 33, 34, 40), but protective effects of glucan exposure in early childhood against the development of asthma and allergy have also been suggested (9, 13, 15, 29). β-(1,3)-Glucans are less potent inducers of inflammatory reactions than bacterial endotoxins (16, 30, 35), but since their total amounts in our environment may be much higher—glucans are measured in micrograms per milligram of house dust, whereas endotoxins are measured in nanograms per milligram of house dust (10, 14, 29, 37)—their proinflammatory impact may be similar to that of endotoxin exposure.An inexpensive and relatively simple β-(1,3)-glucan-specific inhibition immunoassay was introduced in the mid-1990s by Douwes et al. (8). This assay has found wide application in large-scale population studies in which glucans have been routinely measured in dust from mattresses and living room and/or bedroom floors (9, 10, 12, 13, 29). However, while useful for quantification of β-(1,3)-glucans in extracts with >1 to 2% (wt/vol) floor or mattress dust, the sensitivity of the assay is usually too low for airborne measurements. Even in environments with high microbial contaminations, like the household waste recycling industry (36), β-(1,3)-glucan levels in airborne dust samples may often remain under the limit of detection. Until recently, the only published methods sensitive enough to measure β-(1,3)-glucans in airborne dust samples were the modified Limulus amebocyte lysate (LAL) assay (a modification of the endotoxin assay with which glucans can be specifically detected [11]) and two sandwich enzyme immunoassays (EIAs) (2, 23, 27). Due to its high cost, which is at least 5-fold higher than that of the inhibition EIA, the LAL assay has thus far hardly been used in epidemiological studies. The assay developed by Sander et al. (27) has been applied to only a limited number of samples from the work environment, and the EIA described by Blanc et al. (2) and Rao et al. (23) has been used only to analyze reservoir and airborne dust samples from heavily mold-contaminated houses in New Orleans after the hurricanes Katrina and Rita. A third sensitive EIA makes use of galactosyl ceramide, a receptor specific for β-(1,3)-glucans (41), as the capture reagent and of a monoclonal antibody specific for β-(1,3)-(1,6)-glucans as the detecting antibody (20). Application of this EIA in population studies has, however, not yet been reported.Apart from the low sensitivity of the inhibition EIA and/or high cost of the modified LAL assay, the time, equipment, and budget needed for active sampling of airborne dust are reasons why epidemiological studies have relied mainly on β-(1,3)-glucan analyses of reservoir dust samples from floors or mattresses. β-(1,3)-Glucan levels in airborne dust samples may, however, be more representative of real inhalatory exposures.The aim of this study was to develop new sensitive but inexpensive assays for β-(1,3)-glucans in airborne dust from homes or other locations with low exposure levels. We combined methods and reagents from three laboratories that previously developed and applied β-glucan EIAs (2, 8, 23, 27). The specificities of available antibodies to a panel of 13 different glucans were determined to assess whether it is possible to develop sandwich assays that would show clear differences in specificities toward glucans from different taxonomic sources—bacterial, fungal, or plant derived—and/or between glucans with different chemical structures.Another objective of the present study was to explore the feasibility of using our recently developed passive airborne dust sampling method, the electrostatic dust fall collector (EDC) (22), for assessing exposure to glucans in airborne dust in the home environment, when combined with the new sensitive immunoassays.     

Differences in plant function in phosphorus- and nitrogen-limited mangrove ecosystems

Mangrove ecosystems can be either nitrogen (N) or phosphorus (P) limited and are therefore vulnerable to nutrient pollution. Nutrient enrichment with either N or P may have differing effects on ecosystems because of underlying differences in plant physiological responses to these nutrients in either N- or P-limited settings. Using a common mangrove species, Avicennia germinans, in sites where growth was either N or P limited, we investigated differing physiological responses to N and P limitation and fertilization. We tested the hypothesis that water uptake and transport, and hydraulic architecture, were the main processes limiting productivity at the P-limited site, but that this was not the case at the N-limited site. We found that plants at the P-deficient site had lower leaf water potential, stomatal conductance and photosynthetic carbon-assimilation rates, and less conductive xylem, than those at the N-limited site. These differences were greatly reduced with P fertilization at the P-limited site. By contrast, fertilization with N at the N-limited site had little effect on either photosynthetic or hydraulic traits. We conclude that growth in N- and P-limited sites differentially affect the hydraulic pathways of mangroves. Plants experiencing P limitation appear to be water deficient and undergo more pronounced changes in structure and function with relief of nutrient deficiency than those in N-limited ecosystems.     

Primary Herbivory by Wood-Boring Insects along an Architectural Gradient of Rhizophora mangle

We investigated the distribution of primary xylovores in Rhizophora mangle (red mangrove) first-order branches, i.e., “twigs”, along an architectural gradient on Belizean mangrove cays. Greater structural diversity in R. mangle architecture, xylovore availability, occurrence of natural enemies, and habitat do not result in variable xylovore species richness. Despite large differences in architectural complexity, tall, fringe, dwarf, and sapling trees host the same set of primary wig borers. However, tall trees support greater diversity and abundance of twig inquilines than other tree forms. Primary twig borers have a key role in structuring these mangrove communities because their galleries and pupal chambers provide habitats for numerous species of secondary xylovores and inquilines. We also measured the amount of leaf area removed from R. mangle's canopy by wood- and leaf-feeding herbivores. Vigorously growing tall and sapling trees sustain greater losses because of twig borers than dwarf trees. However, xylovory in fringe trees was not different from any of the other categories. Cumulative herbivory was greatest in the tall trees. In most cases, leaf-area loss as an indirect or collateral result of primary xylovory equaled or exceeded leaf-area loss as a direct result of folivory.     

A Role for Tissue Factor in Cell Adhesion and Migration Mediated by Interaction with Actin-binding Protein 280

Tissue factor (TF), the protease receptor initiating the coagulation system, functions in vascular development, angiogenesis, and tumor cell metastasis by poorly defined molecular mechanisms. We demonstrate that immobilized ligands for TF specifically support cell adhesion, migration, spreading, and intracellular signaling, which are not inhibited by RGD peptides. Two-hybrid screening identified actin-binding protein 280 (ABP-280) as ligand for the TF cytoplasmic domain. Extracellular ligation of TF is necessary for ABP-280 binding. ABP-280 recruitment to TF adhesion contacts is associated with reorganization of actin filaments, but cytoskeletal adaptor molecules typically found in integrin-mediated focal contacts are not associated with TF. Chimeric molecules of the TF cytoplasmic domain and an unrelated extracellular domain support cell spreading and migration, demonstrating that the extracellular domain of TF is not involved in the recruitment of accessory molecules that influence adhesive functions. Replacement of TF's cytoplasmic Ser residues with Asp to mimic phosphorylation enhances the interaction with ABP-280, whereas Ala mutations abolish coprecipitation of ABP-280 with immobilized TF cytoplasmic domain, and severely reduce cell spreading. The specific interaction of the TF cytoplasmic domain with ABP-280 provides a molecular pathway by which TF supports tumor cell metastasis and vascular remodeling.     

RELATIONSHIPS BETWEEN LITTORAL DIATOMS AND THEIR CHEMICAL ENVIRONMENT IN NORTHEASTERN GERMAN LAKES AND RIVERS1

We explored statistical relationships between the composition of littoral diatom assemblages and 21 chemical and physical environmental variables in 69 lakes and 15 river sites in the lowland of northeastern Germany. Canonical correspondence analysis with single treatment and with forward selection of environmental variables was used to detect 11 important ecological variables (dissolved inorganic carbon [DIC], Na ⁺ , total phosphorus [TP], dissolved organic carbon [DOC], total nitrogen [TN], pH, oxygen saturation, dissolved iron, SO₄^{2 ?} , NH₄ ⁺ , soluble reactive silicium) and maximum water depth or Ca^{2 +} or soluble reactive phosphorus that most independently explain major proportions of the total diatom variance among the habitats. Monte Carlo permutation tests showed that each contributed a significant additional proportion (P < 0.05) of the variance in species composition. Together, these 11 most important environmental variables explained 34% of the total variance in species composition among the sites and captured 73% of the explained variance from the full 21 parameters model. Weighted‐averaging regression and calibration of 304 indicator taxa with tolerance down‐weighting and classic deshrinking was used to develop transfer functions between littoral diatoms and DIC, pH, TP, TN, and Cl ^? . The DOC:TP ratio was introduced and a weighted‐averaging model was developed to infer allochthonous DOC effects in freshwater ecosystems. This diatom‐DOC/TP model was significant (P < 0.001) and explained 7.6% of the total diatom variance among the sites, surpassing the inferential power of the diatom‐TP‐transfer function (7.3% explained variance). The root‐mean‐square errors of prediction of the models were estimated by jack‐knifing and were comparable with published data sets from surface sediment diatom samples. The data set of littoral diatoms and environmental variables allows use of the diatom‐environmental transfer functions in biomonitoring and paleolimnological approaches across a broad array of natural water resources (such as floodplains, flushed lakes, estuaries, shallow lakes) in the central European lowland ecoregion.     

Seasonal and spatial variation of reduced sulphur compounds in mistletoes (Viscum album) and the xylem sap of its hosts (Populus × euramericana and Abies alba)

In the present field study with adult trees inhabited by Viscum album , the question was addressed as to whether European mistletoes are able to remove reduced sulphur from the xylem sap of its hosts. For this purpose the reduced sulphur composition and content of the xylem sap of Viscum album and the corresponding hosts Populus  ×  euramericana and Abies alba were analysed. The xylem sap of Viscum was enriched in reduced sulphur compared to the hosts but still reflected the higher reduced sulphur content of Populus compared to Abies . Despite similar xylem sap composition of the hosts with glutathione as the dominating thiol, Viscum on Populus contained predominantly cysteine, Viscum on Abies predominantly glutathione in its xylem sap. These findings suggest selective and different removal of reduced sulphur from these hosts. Still the amount of reduced sulphur removed was too small to result in changes of the concentration of thiols in the xylem sap of the hosts that are statistically significant, probably due to the high variability encountered under field conditions. Despite the differences in the reduced sulphur composition and contents of the xylem sap between Viscum on Populus and Viscum on Abies , total thiol content as well as thiol composition of Viscum leaves on the two hosts were similar throughout the seasons. The seasonal pattern in the thiol composition and contents of Viscum leaves showed high levels in spring and autumn and low levels in summer. The significance of these seasonal changes is discussed.     

Nitrogen Addition Increases Freeze Resistance in Black Mangrove (Avicennia germinans) Shrubs in a Temperate-Tropical Ecotone

Ecosystems - Low temperature stress is the primary factor determining the latitudinal limits of tropical plants. As the climate warms, tropical species are migrating poleward, displacing native...     

Adaptation of anaerobically grown Thauera aromatica,Geobacter sulfurreducens and Desulfococcus multivorans to organic solvents on the level of membrane fatty acid composition

The effect of different solvents and pollutants on the cellular fatty acid composition of three bacterial strains: Thauera aromatica, Geobacter sulfurreducens and Desulfococcus multivorans, representatives of diverse predominant anaerobic metabolisms was investigated. As the prevailing adaptive mechanism in cells of T. aromatica and G. sulfurreducens whose cellular fatty acids patterns were dominated by palmitic acid (C16:0) and palmitoleic acid (C16:1cis), the cells reacted by an increase in the degree of saturation of their membrane fatty acids when grown in the presence of sublethal concentrations of the chemicals. Next to palmitic acid C16:0, the fatty acid pattern of D. multivorans was dominated by anteiso-branched fatty acids which are characteristic for several sulfate-reducing bacteria. The cells responded to the solvents with an increase in the ratio of straight-chain saturated (C14:0, C16:0, C18:0) to anteiso-branched fatty acids (C15:0anteiso, C17:0anteiso, C17:1anteisoΔ9cis). The results show that anaerobic bacteria react with similar mechanisms like aerobic bacteria in order to adapt their membrane to toxic organic solvents. The observed adaptive modifications on the level of membrane fatty acid composition can only be carried out with de novo synthesis of the fatty acids which is strictly related to cell growth. As the growth rates of anaerobic bacteria are generally much lower than in the so far investigated aerobic bacteria, this adaptive response needs more time in anaerobic bacteria. This might be one explanation for the previously observed higher sensitivity of anaerobic bacteria when compared with aerobic ones.     

The haemodynamic and catecholamine response to xenon/remifentanil anaesthesia in Beagle dogs

The noble gas xenon seems to have minimal cardiovascular side-effects and so may be an ideal anaesthetic agent when investigating cardiovascular physiology. In comparison with standard modern anaesthetics, we investigated the haemodynamic and hormonal effects of xenon in Beagle dogs. After a 30 min baseline period, anaesthesia was induced with propofol and maintained with either (1) 1.2% isoflurane/70% nitrous oxide (N(2)O), (2) 0.8% isoflurane/0.5 microg/kg/min remifentanil or (3) 63% xenon/0.5 microg/kg/min remifentanil (n = 6 per group). Haemodynamics were recorded and blood samples taken before and 60 min after induction. Mean arterial blood pressure (MAP) was higher in conscious dogs than during isoflurane/N(2)O (86 +/- 2 vs. 65 +/- 2 mmHg, mean +/- SEM) and isoflurane/remifentanil anaesthesia (95 +/- 2 vs. 67 +/- 3 mmHg), whereas MAP did not decrease significantly in response to xenon/remifentanil anaesthesia (96 +/- 4 vs. 85 +/- 6 mmHg). Bradycardia was present during isoflurane/remifentanil (54 +/- 2/min) and xenon/remifentanil (40 +/- 3/min), but not during isoflurane/N(2)O anaesthesia (98 +/- 3/min, P < 0.05). Xenon/remifentanil anaesthesia induced the highest reduction in cardiac output (CO) (-61%), and the highest increase in systemic vascular resistance (+120%) among all treatment groups (P < 0.05). A simultaneous increase in endogenous adrenaline and noradrenaline concentrations could only be observed in the xenon/remifentanil group, whereas angiotensin II and vasopressin concentrations increased in all groups. In conclusion, xenon/remifentanil anaesthesia maintains MAP but reduces heart rate and CO and is associated with a considerable stimulation of vasopressor hormones in Beagle dogs. Therefore, xenon/remifentanil exerts a new quality of adverse haemodynamic effects different from volatile anaesthetics and may not perform better during studies of cardiovascular physiology.