Anthropogenic disturbance and streams: land use and land‐use change affect stream ecosystems via multiple pathways

1. Ecosystems are strongly influenced by land use practices. However, identifying the mechanisms behind these influences is complicated by the many potential pathways (often indirect) between land use and ecosystems and by the long‐lasting effects of past land use. To support ecosystem restoration and conservation efforts, we need to better understand these indirect and lasting effects. 2. We constructed structural equation models (SEM) to evaluate the direct and indirect effects of contemporary (2002) land use (agriculture and development) and change in land use from 1952 to 2002 on present‐day streams (n = 190) in Maryland, U.S.A. Additional variables examined included site location, system size, altitude, per cent sand in soils, riparian condition, habitat quality, stream water NO₃‐N and benthic macroinvertebrate and fish measures of stream condition. Our first SEM (2002 Land Use) included the proportions of contemporary agriculture and development in catchments in the model. The second SEM (Land Use Change) included five measures of land use change (proportion agricultural in both times, developed in both times, agricultural in 1952 and developed in 2002, forested in 1952 and developed in 2002 and agricultural in 1952 and forested in 2002). 3. The data set fit both SEMs well. The 2002 Land Use model explained 71% of variation in NO₃‐N and 55%, 42% and 38% of variation in riffle quality, macroinvertebrate condition and fish condition, respectively. The Land Use Change model explained similar amounts of variation in NO₃‐N (R² = 0.72), riffle quality (R² = 0.57) and macroinvertebrate condition (R² = 0.44) but slightly more variation in fish condition (R² = 0.43). 4. Both models identified pathways through which landscape variables affect stream responses, including negative direct effects of latitude on macroinvertebrate and fish conditions and positive direct and indirect effects of altitude on NO₃‐N, riffle quality and macroinvertebrate and fish conditions. The 2002 Land Use model showed contemporary development and agriculture had positive total effects on NO₃‐N (both through direct pathways); contemporary development had negative effects on macroinvertebrate condition. The Land Use Change model showed that contemporary developed land that was forested in 1952 had no effects on NO₃‐N; current developed land that was developed or agricultural in 1952 showed positive effects on NO₃‐N. Forests that were agricultural in 1952 had negative effects on NO₃‐N, suggesting reduced NO₃‐N export with reforestation. The Land Use Change model also showed negative total effects of all types of contemporary developed land (developed, agricultural or forested in 1952) on benthic condition. Developed land that was forested in 1952 had negative effects on fish condition. Forest sites that were agricultural in 1952 had negative effects on fish and macroinvertebrate conditions, suggesting a long‐term imprint of abandoned agriculture in stream communities. 5. Our analyses (i) identified multiple indirect effects of contemporary land use on streams, (ii) showed that current land uses with different land use histories can exhibit different effects on streams and (iii) demonstrated an imprint of land use lasting >50 years. Knowledge of these indirect and long‐term effects of land use will help to conserve and restore streams.     

益生菌混合发酵条件及其对发酵胡萝卜汁色泽及风味的影响

目的 研究3株益生菌混合发酵胡萝卜汁的发酵条件对色泽、风味的影响及其贮藏特性等.方法 通过菌种配比、单因素试验及正交试验优化了胡萝卜汁的发酵条件,并利用分光测色计和气质联用仪分别研究了发酵前后胡萝卜汁的风味成分和色泽变化.结果 添加30％ (m/m)的新鲜胡萝卜汁(原液),接种3％的以1∶1∶1(v/v/v)混合的嗜热...     

The effective population size of Anopheles gambiae in Kenya: implications for population structure

We estimated current and long-term effective population size (Ne) of two Anopheles gambiae (savanna cytotype) populations in Kenya. Temporal variation at nine microsatellite loci in each population sampled 7 and 9 years apart and genetic diversity in each sample were analyzed to answer the following questions. (1) Do bottlenecks occur in Kenyan populations of A. gambiae? (2) How variable are different populations with respect to their current and long-term Ne values? (3) What are the implications of these results on population structure and history? The estimates of Ne of Asembo and Jego were 6,359 and 4,258, respectively, and the lower 95% limits were 2,455 and 1,669, respectively. Thus, despite the typical observation of low density at the village level during the dry season, large populations are maintained annually. Large current Ne is consistent with previous studies showing low differentiation across the continent, especially under Wright's isolation-by-distance model. Current Ne in Asembo was 1.5-fold higher than in Jego, but this difference was not significant. Long-term Ne in Asembo (22,667) was 2.9-fold higher than that in Jego (7,855) based on the stepwise mutation model. The difference between populations was significant at both time points regardless of whether long-term Ne values were calculated based on the stepwise mutation model or the infinite-alleles model. Heterozygosity in Jego declined significantly between 1987 (59%) and 1996 (54%), whereas heterozygosity in Asembo was stable (66%-65%). Despite the relatively high and significant differentiation between Asembo and Jego (FST = 0.072-0.10, RST = 0.037- 0.038), all alleles in Jego were found in Asembo but not vice versa. All of these findings suggest that lower Ne in Jego magnifies differentiation between the two populations. The long-term Ne was biased downward, because its calculation was based on an upper bound estimate of microsatellite mutation rate. Ne values based on mtDNA and allozymes were an order of magnitude higher. Long-term Ne therefore, is probably measured in hundreds of thousands and hence does not support a recent expansion of this species from a small population.      

Peripheral hyaline blebs (podosomes) of macrophages

The plasmalemma and hyaline ectoplasm together constitute the sensory and motor organ of macrophages. The purpose of this study was to isolate this cell fraction in order to analyze it biochemically and functionally. Brief sonification of warmed rabbit lung macrophages caused release of heterodisperse hyaline blebs and filopodia, which were easily collected by differential centrifugation. Viewed in the electron microscope, these structures consisted of membrane-bounded sacs principally containing actin filaments. Some contained secondary lysosomes. They were enriched threefold over whole cell homogenates in specific adenylate cyclase activity and in trichloroacetic-acid-precipitable (125)I when derived from cells labeled with 125(I) by means of a lactoperoxidase-catalyzed reaction. These markers were found to have identical isopycnic densitites when macrophage homogenates were subjected to sedimentation in a focusing sucrose density gradient system, and these markers had densities distinct from those of other cytoplasmic organelles. These markers were therefore assumed to be associated with macrophage plasma membranes. The specific β- glucuronidase activity of the bleb fraction was similar to that of homogenates, but the blebs had considerably lower specific succinic dehydrogenase activity and RNA content, and DNA was undetectable. Electrophoresis of blebs solubilized in sodium dodecyl sulfate on polyacrylamide gels revealed polypeptides co-migrating with macrophage actin-binding protein, myosin, and actin; blebs also had EDTA-activated adenosine triphosphatase activity characteristic of myosin. The concentrations of actin-binding protein and myosin were higher in blebs than in cells or cytoplasmic extracts, whereas actin concentrations were similar (relative to extracts) or only slightly greater (than in cells). Blebs and intact cells had high lactate dehydrogenase activities in the presence but not the absence of Triton X-100. Blebs and cells oxidased 1-[(14)C]glucose, and the rate of glucose oxidation was increased substantially in the presence of latex beads. We conclude that intact sacs of plasmalemma encasing contractile proteins and cytoplasmic enzymes can be isolated from macrophages. They are enriched in myosin and actin-binding protein, indicating that the contractile apparatus is regulated in the cell periphery. These structures have the capacity to respond to environmental signals. We suggest the name "podosomes" for them because of their resemblance to macrophage pseudopodia. We propose that podosome formation results from rapid dissolution of the cortical gel when the membrane is in an actively extended configuration.     

Role of macrophage colony-stimulating factor in the differentiation and expansion of monocytes and dendritic cells from CD34+ progenitor cells

The present study focused on whether it is possible to expand monocytic cells from CD34⁺ progenitor cells by using macrophage colony-stimulating factor (M-CSF) in the absence and presence of mast cell growth factor (MGF) and IL-6. It was demonstrated that CD34⁺ cells differentiate without expansion to functional mature monocytic cells in the presence of M-CSF or combinations of M-CSF plus IL-6 and MGF. A different response pattern was observed for the number of clonogenic cells. The addition of IL-6 or both IL-6 and MGF to M-CSF containing cultures resulted in significant higher numbers of colony-forming unit-macrophage (CFU-M) as tested in clonogenic and³H-thymidine assays. Furthermore, M-CSF plus both IL-6 and MGF appeared to be the most potent combination to preserve the monocytic precursor in cell suspension culture assays. These results indicate that IL-6 and MGF in conjunction with M-CSF affect CD34⁺ cells especially at precursor level without distinct effect on the more mature stages. Secondly we studied whether M-CSF is only critical for the monocytic lineage or also affects dendritic cell (DC) development. Indeed, we were able to culture CD83⁺ DC from CD34⁺ progenitor cells in the presence of M-CSF in conjunction with TNF-α, IL-4, and MGF although their absolute number is almost threefold lower than the number of CD83⁺ cells yielded from GM-CSF plus TNF-α, IL-4, and MGF stimulated CD34⁺ cells.     

A study of the suitability of gas chromatography-electron capture detection for the analysis of deoxynivalenol in cereals

A gas chromatographic-electron capture detection (GC-ECD) method for the analysis of deoxynivalenol (DON) in cereals was investigated. The sample was extracted with a mixture of acetonitrile-water and purified with a MycoSep #225 column. The silylation was performed with Tri-Sil-TBT reagent, followed by dilution with hexane and a washing step with buffer. By using Tri-Sil-TBT reagent no double peaks were observed for DON in the gas chromatograms, in comparison with two other silylation reagents TMSI and Tri-Sil-Z. The use of trichothecolone (TRI) as an internal standard for DON was studied in order to indicate possible problems in the derivatisation reaction. TRI proved to be a relatively good internal standard for DON in cereal samples, as well as 1,1-bis-(4-chlorophenyl)-2,2-dichloroethylene (DDE), which was used as a GC standard for ensuring the function of GC-ECD. During the study, a matrix effect was clearly observed between the cereal matrix-assisted calibration curve and the calibration curve prepared without cereal matrix. The results of spiked and reference material samples, quantified with the calibration curve prepared without and with matrix, demonstrated that the matrix affects the results. However, after recovery correction the results were comparable. The validation results demonstrated that the GC-ECD method for DON analysis in cereals is sufficiently reliable.     

Heme oxygenase-1 prevents smoke induced B-cell infiltrates: a role for regulatory T cells?

Background

Smoking is the most important cause for the development of COPD. Since not all smokers develop COPD, it is obvious that other factors must be involved in disease development. We hypothesize that heme oxygenase-1 (HO-1), a protective enzyme against oxidative stress and inflammation, is insufficiently upregulated in COPD.The effects of HO-1 modulation on cigarette smoke induced inflammation and emphysema were tested in a smoking mouse model.

Methods

Mice were either exposed or sham exposed to cigarette smoke exposure for 20 weeks. Cobalt protoporphyrin or tin protoporphyrin was injected during this period to induce or inhibit HO-1 activity, respectively. Afterwards, emphysema development, levels of inflammatory cells and cytokines, and the presence of B-cell infiltrates in lung tissue were analyzed.

Results

Smoke exposure induced emphysema and increased the numbers of inflammatory cells and numbers of B-cell infiltrates, as well as the levels of inflammatory cytokines in lung tissue. HO-1 modulation had no effects on smoke induced emphysema development, or the increases in neutrophils and macrophages and inflammatory cytokines. Interestingly, HO-1 induction prevented the development of smoke induced B-cell infiltrates and increased the levels of CD4⁺CD25⁺ T cells and Foxp3 positive cells in the lungs. Additionally, the CD4⁺CD25⁺ T cells correlated positively with the number of Foxp3 positive cells in lung tissue, indicating that these cells were regulatory T cells.

Conclusion

These results support the concept that HO-1 expression influences regulatory T cells and indicates that this mechanism is involved in the suppression of smoke induced B-cell infiltrates. The translation of this interaction to human COPD should now be pursued.