入侵种喜旱莲子草和莲子草的营养生长和光合作用对温度的响应

比较温度对入侵种喜旱莲子草(Alternantheraphiloxeroides(Mart.)Griseb.)和其本土近缘种莲子草(A.sessilis(L.)DC.)的营养生长、叶片光合作用及叶绿素荧光的影响。实验将生长均衡的这两种植物放在不同温度(10℃、15℃、20℃、25℃、30℃)的光照培养箱中处理28d。结果表明,喜旱莲子草营养生长的速率和对温度的响应明显不同于莲子草:前者主茎生长的有效积温明显低于后者,分别是11.6d℃和27.0d℃;而新叶萌发的有效积温高于后者,分别是12.1d℃和6.7d℃。入侵种主茎和叶的发育起点温度都比本土种低,分别是10.4℃、11.0℃和12.8℃、14.9℃,表明喜旱莲子草的发育对低温反应不及莲子草敏感。对两种植物叶片的光合作用和叶绿素荧光的测定结果还表明:入侵种比本土种有较高的最大净光合速率和光饱和点,尤其在25℃时;10-30℃的温度范围内喜旱莲子草的最大光化学效率Fv/Fm没有显著变化,而莲子草在10℃低温条件下Fv/Fm值显著降低。较快的主茎生长速率、较宽的温度适应范围以及较高的光合能力可能使喜旱莲子草比本地种具有更强的竞争力,从而在其入侵过程中起了重要作用。     

核心组蛋白的融合表达和纯化

目的:克隆核心组蛋白H2A、H2B、H3和H4的基因,表达并纯化组蛋白与谷胱甘肽S-转移酶(GST)的融合蛋白。方法:用PCR方法从乳腺文库中扩增核心组蛋白H2A、H2B、H3和H4的编码序列,分别将其以正确相位与pGEX-KG载体中的GST编码序列融合,得到重组质粒pGST-H2A、pGST-H2B、pGST-H3和pGST-H4,分别转化大肠杆菌BL21,表达融合蛋白GST-H2A、GST-H2B、GST-H3和GST-H4;用谷胱甘肽-Sepharose 4B亲和纯化融合蛋白;用Western印迹检测融合蛋白的表达及纯化。结果:分别构建了核心组蛋白H2A、H2B、H3和H4的融合表达载体;Western印迹检测表明,融合蛋白GST-H2A、GST-H2B、GST-H3和GST-H4获得表达及纯化。结论:表达并纯化了H2A、H2B、H3和H4的融合蛋白,为进一步研究核心组蛋白的功能奠定了基础。     

Clinical outcome following acute ischaemic stroke relates to both activation and autoregulatory inhibition of cytokine production

Background

As critical mediators of local and systemic inflammatory responses, cytokines are produced in the brain following ischaemic stroke. Some have been detected in the circulation of stroke patients, but their role and source is unclear. Focusing primarily on interleukin(IL)-1-related mechanisms, we serially measured plasma inflammatory markers, and the production of cytokines by whole blood, from 36 patients recruited within 12 h and followed up to 1 year after acute ischaemic stroke (AIS).

Results

Admission plasma IL-1 receptor antagonist (IL-1ra) concentration was elevated, relative to age-, sex-, and atherosclerosis-matched controls. IL-1β, soluble IL-1 receptor type II, tumour necrosis factor (TNF)-α, TNF-RII, IL-10 and leptin concentrations did not significantly differ from controls, but peak soluble TNF receptor type I (sTNF-RI) in the first week correlated strongly with computed tomography infarct volume at 5–7 days, mRS and BI at 3 and 12 months. Neopterin was raised in patients at 5–7 d, relative to controls, and in subjects with significant atherosclerosis. Spontaneous IL-1β, TNF-α and IL-6 gene and protein expression by blood cells was minimal, and induction of these cytokines by lipopolysaccharide (LPS) was significantly lower in patients than in controls during the first week. Minimum LPS-induced cytokine production correlated strongly with mRS and BI, and also with plasma cortisol.

Conclusion

Absence of spontaneous whole blood gene activation or cytokine production suggests that peripheral blood cells are not the source of cytokines measured in plasma after AIS. Increased plasma IL-1ra within 12 h of AIS onset, the relationship between sTNF-RI and stroke severity, and suppressed cytokine induction suggests early activation of endogenous immunosuppressive mechanisms after AIS.     

Two soluble glycosyltransferases glycosylate less efficiently in vivo than their membrane bound counterparts

Many Golgi glycosyltransferases are type II membrane proteins which are cleaved to produce soluble forms that are released from cells. Cho and Cummings recently reported that a soluble form of alpha1, 3- galactosyltransferase was comparable to its membrane bound counterpart in its ability to galactosylate newly synthesized glycoproteins (Cho,S.K. and Cummings,R.D. (1997) J. Biol. Chem., 272, 13622-13628). To test the generality of their findings, we compared the activities of the full length and soluble forms of two such glycosyltransferases, ss1,4 N-Acetylgalactosaminyltransferase (GM2/GD2/ GA2 synthase; GalNAcT) and beta galactoside alpha2,6 sialyltransferase (alpha2,6-ST; ST6Gal I), for production of their glycoconjugate products in vivo . Unlike the full length form of GalNAcT which produced ganglioside GM2 in transfected cells, soluble GalNAcT did not produce detectable GM2 in vivo even though it possessed in vitro GalNAcT activity comparable to that of full length GalNAcT. When compared with cells expressing full length alpha2,6-ST, cells expressing a soluble form of alpha2,6-ST contained 3-fold higher alpha2,6-ST mRNA levels and secreted 7-fold greater alpha2,6-ST activity as measured in vitro , but in striking contrast contained 2- to 4-fold less of the alpha2,6-linked sialic acid moiety in cellular glycoproteins in vivo . In summary these results suggest that unlike alpha1,3-galactosyltransferase the soluble forms of these two glycosyltransferases are less efficient at glycosylation of membrane proteins and lipids in vivo than their membrane bound counterparts.      

Effects of grazing on plant species diversity and carbon partitioning in semiarid rangelands of northeastern China

Grasslands are one of the most widespread landscapes worldwide, covering approximately one-fifth of the world’s land surface, where grazing is a common practice. How carbon storage responds to grazing in steppes remains poorly understood. We quantified the effects of grazing on community composition and species diversity, and carbon storage in two typical grasslands of northeastern China, one in Horqin and the other one in Hulunbeier. In both grasslands, grazing did not influence plant species diversity. However, it substantially decreased aboveground carbon by 31% and 54% in Horqin and Hulunbeier, respectively. Fenced and grazing treatments showed a similar belowground carbon at both locations. The predominant carbon pool in the study grassland ecosystem was found in the upper 100 cm soil depth, from 98.2 to 99.1% of the total carbon storage. There were no significant effects of grazing on soil carbon neither in the whole profile nor in the uppermost 20 cm soil depth in the two study grasslands. Studies on the effects of varying rangeland management, such as region disparity and grazing systems, may have important consequences on species diversity and carbon partitioning, and thus on rangeland stability and ecosystem functioning.     

The co-distribution of Plasmodium falciparum and hookworm among African schoolchildren

Background

On the island of Bioko (Equatorial Guinea), insecticide-treated nets (ITNs) have been the main tool used to control malaria over the last 13 years. In 2004, started an indoor residual spraying (IRS) campaign to control malaria. The purpose of this study is to asses the impact of the two control strategies on the island of Bioko (Equatorial Guinea), with regards to Plasmodium infection and anaemia in the children under five years of age.

Methods

Two transversal studies, the first one prior to the start of the IRS campaign and the second one year later. Sampling was carried out by stratified clusters. Malaria infection was measured by means of thick and thin film, and the packed cell volume (PCV) percentage. Data related to ITN use and information regarding IRS were collected. The Pearson's chi-square and logistic regression statistical tests were used to calculate odds ratios (OR)

Results

In the first survey, 168 children were sampled and 433 children in the second one. The prevalence of infection was 40% in 2004, and significantly lower at 21.7% in 2005. PCV was 41% and 39%, respectively. 58% of the children surveyed in 2004 and 44.3% in 2005 had slept under an ITN. 78% of the dwellings studied in 2005 had been sprayed. In the 2005 survey, sleeping without a mosquito net meant a risk of infection 3 times greater than sleeping protected with a net hanged correctly and with no holes (p < 0.05).

Conclusion

IRS and ITNs have proven to be effective control strategies on the island of Bioko. The choice of one or other strategy is, above all, a question of operational feasibility and availability of local resources.     

Bacterial species and evolution: Theoretical and practical perspectives

A discussion of the species problem in modern evolutionary biology serves as the point of departure for an exploration of how the basic science aspects of this problem relate to efforts to map bacterial diversity for practical pursuits—for prospecting among the bacteria for useful genes and gene-products. Out of a confusing array of species concepts, the Cohesion Species Concept seems the most appropriate and useful for analyzing bacterial diversity. Techniques of allozyme analysis and DNA fingerprinting can be used to put this concept into practice to map bacterial genetic diversity, though the concept requires minor modification to encompass cases of complete asexuality. Examples from studies of phenetically definedBacillus species provide very partial maps of genetic population structure. A major conclusion is that such maps frequently reveal deep genetic subdivision within the phenetically defined specles; divisions that in some cases are clearly distinct genetic species. Knowledge of such subdivisions is bound to make prospecting within bacterial diversity more effective. Under the general concept of genetic cohesion a hypothetical framework for thinking about the full range of species conditions that might exist among bacteria is developed and the consequences of each such model for species delineation, and species identification are discussed. Modes of bacterial evolution, and a theory of bacterial speciation with and without genetic recombination, are examined. The essay concludes with thoughts about prospects for very extensive mapping of bacterial diversity in the service of future efforts to find useful products. In this context, evolutionary biology becomes the handmaiden of important industrial activities. A few examples of past success in commercializing bacterial gene-products from species ofBacillus and a few other bacteria are reviewed.     

E. coli chaperones DnaK,Hsp33 and Spy inhibit bacterial functional amyloid assembly

Amyloid formation is an ordered aggregation process, where β-sheet rich polymers are assembled from unstructured or partially folded monomers. We examined how two Escherichia coli cytosolic chaperones, DnaK and Hsp33, and a more recently characterized periplasmic chaperone, Spy, modulate the aggregation of a functional amyloid protein, CsgA. We found that DnaK, the Hsp70 homolog in E. coli, and Hsp33, a redox-regulated holdase, potently inhibited CsgA amyloidogenesis. The Hsp33 anti-amyloidogenesis activity was oxidation dependent, as oxidized Hsp33 was significantly more efficient than reduced Hsp33 at preventing CsgA aggregation. When soluble CsgA was seeded with preformed amyloid fibers, neither Hsp33 nor DnaK were able to efficiently prevent soluble CsgA from adopting the amyloid conformation. Moreover, both DnaK and Hsp33 increased the time that CsgA was reactive with the amyloid oligomer conformation-specific A11 antibody. Since CsgA must also pass through the periplasm during secretion, we assessed the ability of the periplasmic chaperone Spy to inhibit CsgA polymerization. Like DnaK and Hsp33, Spy also inhibited CsgA polymerization in vitro. Overexpression of Spy resulted in increased chaperone activity in periplasmic extracts and in reduced curli biogenesis in vivo. We propose that DnaK, Hsp33 and Spy exert their effects during the nucleation stages of CsgA fibrillation. Thus, both housekeeping and stress induced cytosolic and periplasmic chaperones may be involved in discouraging premature CsgA interactions during curli biogenesis.Key words: chaperone, curli, functional amyloid, CsgA, DnaK, Hsp33, Spy