Altered thymocyte development resulting from expressing a deleting ligand on selecting thymic epithelium.

The maturation of CD4+8- and CD4-8+ thymocytes from CD4+8+ thymocytes is dependent on the mandatory interaction of their alpha beta TCR with selecting ligands expressed on thymic epithelial cells (TE). This is referred to as positive selection. The deletion of CD4+8+ thymocytes that express autospecific TCR (negative selection) is mediated primarily by bone marrow-derived cells. Previous studies have shown that TE is relatively ineffective in mediating the deletion of CD4+8- thymocytes expressing autospecific TCR but TE can render them anergic, i.e., nonresponsive, to the self Ag. The mechanism by which anergy is induced in these cells is unknown. In this study, we used thymocytes expressing a transgenic TCR specific for the male Ag presented by H-2Db class I MHC molecules to examine how expression of the deleting ligand by TE affects thymocyte development and phenotype. The development of female TCR-transgenic thymocytes was examined in irradiated male hosts or in female hosts that had received male fetal thymic epithelial implants. It was observed that the development of transgenic-TCR+ thymocytes was affected in mice with male TE. CD4+8+ thymocytes with reduced CD8 expression and markedly enhanced transgenic TCR expression accumulated in mice with male TE. Development of CD4-8+ thymocytes was also affected in these mice in that fewer were present and they expressed an intermediate CD8 coreceptor level. These CD4-8+ thymocytes expressed a high level of the transgenic TCR, retained the ability to respond to anti-TCR antibodies, but were nonresponsive to male APC. However, the maturation of CD4+8- thymocytes, which are also derived from CD4+8+ precursor cells, was relatively unaffected. In an in vitro assay for assessing negative selection, male TE failed to delete CD4+8+ thymocytes expressing the transgenic TCR under conditions where they were efficiently deleted by male dendritic cells. Collectively these results support the conclusion that male TE was inefficient in mediating deletion. Furthermore, expression of the deleting ligand on thymic epithelium interferes with the maturation of functional male-specific T cells and results in the accumulation of CD4+8+ and CD4-8+ thymocytes expressing a lower level of the CD8 coreceptor but a high level of the transgenic TCR.     

Peripheral deletion of mature CD8+ antigen-specific T cells after in vivo exposure to male antigen.

It has been well established that T cell tolerance to self Ag occurs primarily via clonal deletion of immature thymocytes in the thymus. Evidence also exists that there are additional mechanisms operative on mature T cells for establishing and maintaining tolerance in the periphery. To follow the fate of mature Ag-specific T cells in vivo, we used female transgenic mice, which contain a large population of male H-Y Ag-specific T cells that can be identified by immunostaining with mAb directed against CD8 and the transgenic TCR. H-Y Ag was introduced into these mice by injecting Ag-bearing male lymphocytes using conditions known to induce CTL precursor response reduction. The number of Ag-reactive CD8+ transgenic T cells in the periphery started to decrease after 2 days of in vivo exposure to male Ag. Decline was maximum (up to 80% of total) by 7 days, and stayed at this level for at least 6 wk. CD4+ cells and those CD8+ cells that did not carry the transgenic TCR were not affected. Most or all of the remaining Ag-reactive CD8+ cells in the periphery were fully responsive when stimulated by male Ag in vitro. Maturation of transgenic T cells in the thymus of injected mice remained the same as that of control animals. Our data provide direct evidence that mature Ag-reactive CD8+ cells are susceptible to clonal deletion in the periphery when exposed to the Ag in vivo. These findings suggest the presence of two types of APC in the periphery: stimulatory APC (e.g., macrophages and dendritic cells) required for initiating an active immune response; and functionally deleting APC (or veto cells) capable of deleting mature T lymphocytes that recognize Ag presented on their surface. Functionally deleting APC that present self Ag to peripheral T cells may provide a fail-safe mechanism against autoreactive cells that escaped deletion during differentiation in the thymus.     

Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

1. Predation‐exclusion experiments have highlighted that top‐down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1‐year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant‐excluded than in control trees, whereas only dermapterans were more abundant in bird‐excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator–prey system.     

早期液体复苏对感染性休克患者血流动力学的影响

目的：早期液体复苏对感染性休克患者血流动力学的影响。方法：选取2012年2月-2013年2月我院ICU收治的26例感染性休克患者作为研究对象,随机分为对照组和试验组,各13例。两组患者均采用PICCO监测,并根据早期复苏目标导向（Earlygoaldirectedtherapy,EGDT）进行早期液体复苏治疗。对照组和试验组复苏液分别为林格液和6％羟乙基淀粉130／0．4氯化钠溶液。分别于复苏开始时（Oh）、8h和24h收集患者的血流动力学参数。结果：两组患者CO及PAWP水平均随着时间的延长下降,而CI、CVP及SVR水平均随着时间的增加上升。除对照组CI外,与开始复苏（oh）相比较试验组和对照组的C0、CI、CVP、SVR及PAWP与开始复苏（O小时）相比较均有显著差异（P值均〈0．05）。经重复测量资料的．方差分析进行比较发现,与对照组相比较,试验组CVP和SVR上升水平及PAWP下降水平明显,差异具有统计学意义（P值均〈0．05）。结论：感染性休克患者使用6％羟乙基淀粉130／0．4氯化钠溶液进行复苏,能更好的改善患者的血流动力学指标。     

Identification of naphthalene metabolism by white rot fungus Pleurotus eryngii

The use of biomaterials or microorganisms in PAHs degradation had presented an eye-catching performance. Pleurotus eryngii is a white rot fungus, which is easily isolated from the decayed woods in the tropical rain forest, used to determine the capability to utilize naphthalene, a two-ring polycyclic aromatic hydrocarbon as source of carbon and energy. In the meantime, biotransformation of naphthalene to intermediates and other by-products during degradation was investigated in this study. Pleurotus eryngii had been incubated in liquid medium formulated with naphthalene for 14 days. The presence of metabolites of naphthalene suggests that Pleurotus eryngii begin the ring cleavage by dioxygenation on C1 and C4 position to give 1,4-naphthaquinone. 1,4-Naphthaquinone was further degraded to benzoic acid, where the proposed terepthalic acid is absent in the cultured extract. Further degradation of benzoic acid by Pleurotus eryngii shows the existence of catechol as a result of the combination of decarboxylation and hydroxylation process. Unfortunately, phthalic acid was not detected in this study. Several enzymes, including manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase and 2,3-dioxygenase are enzymes responsible for naphthalene degradation. Reduction of naphthalene and the presence of metabolites in liquid medium showed the ability of Pleurotus eryngii to utilize naphthalene as carbon source instead of a limited glucose amount.     

Long-term trends and causal factors associated with Microcystis abundance and toxicity in San Francisco Estuary and implications for climate change impacts

The impacts of climate change on Microcystis blooms in San Francisco Estuary are uncertain because factors associated with the abundance and distribution of Microcystis blooms since their inception in 1999 are poorly understood. Discrete and continuous data collected between 2004 and 2008 were used to assess what factors controlled bloom initiation and persistence, if there was an impact of the bloom on mesozooplankton abundance and toxicity or dissolved organic carbon concentration, and how these might vary with climate change. Microcystis abundance was greater in dry years than wet years and both total microcystins concentration and the microcystins content of mesozooplankton tissue increased with abundance. The bloom began in the upstream portions of the estuary and spread farther west during dry years. Bloom initiation required water temperature above 19°C and surface irradiance in the visible range above 100 W m^?2. The bloom persisted during a wide range of water quality conditions but was closely correlated with low turbidity. The intensity of Microcystis blooms will likely increase with climate change due to increased water temperature and low streamflow during droughts. Elevated water temperature earlier in the spring could also extend the duration of Microcystis blooms by up to 3 months.     

Metabotropic Glutamate Receptor 1 Expression and Its Polymorphic Variants Associate with Breast Cancer Phenotypes

Several epidemiological studies have suggested a link between melanoma and breast cancer. Metabotropic glutamate receptor 1 (GRM1), which is involved in many cellular processes including proliferation and differentiation, has been implicated in melanomagenesis, with ectopic expression of GRM1 causing malignant transformation of melanocytes. This study was undertaken to evaluate GRM1 expression and polymorphic variants in GRM1 for associations with breast cancer phenotypes. Three single nucleotide polymorphisms (SNPs) in GRM1 were evaluated for associations with breast cancer clinicopathologic variables. GRM1 expression was evaluated in human normal and cancerous breast tissue and for in vitro response to hormonal manipulation. Genotyping was performed on genomic DNA from over 1,000 breast cancer patients. Rs6923492 and rs362962 genotypes associated with age at diagnosis that was highly dependent upon the breast cancer molecular phenotype. The rs362962 TT genotype also associated with risk of estrogen receptor or progesterone receptor positive breast cancer. In vitro analysis showed increased GRM1 expression in breast cancer cells treated with estrogen or the combination of estrogen and progesterone, but reduced GRM1 expression with tamoxifen treatment. Evaluation of GRM1 expression in human breast tumor specimens demonstrated significant correlations between GRM1 staining with tissue type and molecular features. Furthermore, analysis of gene expression data from primary breast tumors showed that high GRM1 expression correlated with a shorter distant metastasis-free survival as compared to low GRM1 expression in tamoxifen-treated patients. Additionally, induced knockdown of GRM1 in an estrogen receptor positive breast cancer cell line correlated with reduced cell proliferation. Taken together, these findings suggest a functional role for GRM1 in breast cancer.     

Linking leaf veins to growth and mortality rates: an example from a subtropical tree community

A fundamental goal in ecology is to link variation in species function to performance, but functional trait–performance investigations have had mixed success. This indicates that less commonly measured functional traits may more clearly elucidate trait–performance relationships. Despite the potential importance of leaf vein traits, which are expected to be related to resource delivery rates and photosynthetic capacity, there are few studies, which examine associations between these traits and demographic performance in communities. Here, we examined the associations between species traits including leaf venation traits and demographic rates (Relative Growth Rate, RGR and mortality) as well as the spatial distributions of traits along soil environment for 54 co‐occurring species in a subtropical forest. Size‐related changes in demographic rates were estimated using a hierarchical Bayesian approach. Next, Kendall's rank correlations were quantified between traits and estimated demographic rates at a given size and between traits and species‐average soil environment. Species with denser venation, smaller areoles, less succulent, or thinner leaves showed higher RGR for a wide range of size classes. Species with leaves of denser veins, larger area, cheaper construction costs or thinner, or low‐density wood were associated with high mortality rates only in small size classes. Lastly, contrary to our expectations, acquisitive traits were not related to resource‐rich edaphic conditions. This study shows that leaf vein traits are weakly, but significantly related to tree demographic performance together with other species traits. Because leaf traits associated with an acquisitive strategy such as denser venation, less succulence, and thinner leaves showed higher growth rate, but similar leaf traits were not associated with mortality, different pathways may shape species growth and survival. This study suggests that we are still not measuring some of key traits related to resource‐use strategies, which dictate the demography and distributions of species.