民勤红砂岗地区绵刺分布和繁殖方式及濒危原因调查

本文调查了民勤红砂岗地区绵刺的分布现状和面积,初步观测了它的生活习性和繁殖方式,发现枝条生根是它的重要繁殖方式,并对绵刺濒危的原因和保护措施进行了讨论。     

The antimutagenic effect of selenium on 7,12-dimethylbenz(a)anthracene and metabolites in the amesSalmonella/microsome system

The antimutagenic effect of selenium as sodium selenite, sodium selenate, selenium dioxide, and seleno-methionine was studied in the AmesSalmonella/microsome mutagenicity test using 7,12-dimethylbenz(a)anthracene (DMBA) and some of its metabolites. Selenium (20 ppm) as sodium selenite reduced the number of histidine revertants on plates containing up to 100 μg DMBA/plate. Increasing concentrations of selenium as sodium selenite, sodium selenate, and selenium dioxide up to 40 ppm Se progressively decreased the number of revertants caused by 50 μg DMBA. DMBA and its metabolites 7-hydroxymethyl-12-methylbenz(a)anthracene, 12-hydroxymethyl-7-methylbenz(a)anthracene, and 3-hydroxy-7,12-dimethylbenz(a)anthracene were mutagenic forSalmonella typhimurium TA100 in the presence of an S-9 mixture. Selenium supplementation as Na₂SeO₃ reduced the number of revertants induced by these metabolites to background levels. The antimutagenic effect of inorganic selenium compounds cannot be explained by toxicity of selenium as determined by viability tests withSalmonella typhimurium TA100. Selenium supplementation in all forms examined, except sodium selenate, decreased the rate of spontaneous reversion. Selenium as sodium selenate was slightly mutagenic at concentrations of 4 ppm or less. Higher concentration of Na₂SeO₄ inhibited the mutagenicity of DMBA. The present studies support the anticarcinogenic potential of selenium and indicate that form and concentration are important factors in this trace element's efficacy.     

Delayed fluorescence from Rhodopseudomonas viridis following single flashes

Delayed fluorescence from Rhodopseudomonas viridis membrane fragments has been studied using a phosphoroscope employing single, short actinic flashes, under conditions of controlled redox potential and temperature. The emission spectrum shows that delayed fluorescence is emitted by the bulk, antenna bacteriochlorophyll. The energy for delayed fluorescence, however, must be stored in a reaction-center complex including the photooxidized form (P⁺) of the primary electron-donor (P) and the photoreduced form (X^?) of the primary electron-acceptor. This is shown by the following observations: (1) Delayed luminescence is quenched (a) at low redox potentials which allow cytochromes to reduce P⁺ rapidly after the flash, (b) at higher redox potentials which, by oxidizing P chemically, prevent the photochemical formation of P⁺X^?, and (c) upon transfer of an electron from X^? to a secondary acceptor, Y. (2) Under conditions that prevent the reduction of P⁺ by cytochromes and the oxidation of X^? by Y, the decay kinetics of delayed fluorescence are identical with those of P⁺X^?, as measured from optical absorbance changes.The main decay route for P⁺X^? under these conditions has a rate-constant of approximately 10³ s^?1. In contrast, a comparison of the intensities of delayed and prompt fluorescence indicates that the process in which P⁺X^? returns energy to the bulk bacteriochlorophyll has a rate-constant of 3.7 s^?1, at 295 °K and pH 7.8. The decay kinetics of P⁺X^? and delayed fluorescence change little with temperature, whereas the intensity of delayed fluorescence increases with increasing temperature, having an activation energy of 12.5 kcal · mol^?1. We conclude that the main decay route involves tunneling of an electron from X^? to P⁺, without the promotion of P to an excited state. Delayed fluorescence requires such a promotion, followed by transfer of energy to the bulk bacteriochlorophyll, and this combination of events is rare. The activation energy, taken with potentiometric data, indicates that the photochemical conversion of PX to P⁺X^? results in increases of both the energy and the entropy of the system, by 16.6 kcal · mol^?1 and 8.8 cal · mol^?1 · deg^?1. The intensity of delayed fluorescence depends strongly on the pH; the origin of this effect remains unclear.     

云南及周边地区野菜和野果资源

本文是根据“云南及周边地区生物资源调查”项目的系统调查结果汇总的。云南及周边地区野菜和野果资源,指的是该地区栽培蔬菜、果树及其野生近缘植物之外的可食的野菜和野果。云南及周边地区是多个少数民族聚居区,各少数民族都有采食野菜和野果的习俗,并且在长期采食野菜和野果中,积累了丰富的食用方法。本文介绍云南及周边地区的野菜和野果,旨在为深入研究和开发利用这些资源,并为国家制定野生植物保护有关政策提供基础数据和信息。     

云南及周边地区农作物野生近缘植物

"云南及周边地区生物资源调查"项目是国家科技部基础性工作专项,现已通过国家验收。云南及周边地区是低纬度高海拔地区,也是我国少数民族聚居区,农作物的种类和物种多样性及遗传多样性都十分丰富,并且孕育了丰富的农作物野生近缘植物。本文仅介绍云南及周边地区粮食作物、经济作物、蔬菜作物、果树作物的野生近缘植物,旨在为这些野生近缘植物的研究和开发,制定国家野生植物多样性保护政策提供基础数据和相关信息。     

Recombinase-mediated cassette exchange (RMCE) — A rapidly-expanding toolbox for targeted genomic modifications

Starting in 1991, the advance of Tyr-recombinases Flp and Cre enabled superior strategies for the predictable insertion of transgenes into compatible target sites of mammalian cells. Early approaches suffered from the reversibility of integration routes and the fact that co-introduction of prokaryotic vector parts triggered uncontrolled heterochromatization. Shortcomings of this kind were overcome when Flp-Recombinase Mediated Cassette Exchange entered the field in 1994. RMCE enables enhanced tag-and-exchange strategies by precisely replacing a genomic target cassette by a compatible donor construct. After “gene swapping” the donor cassette is safely locked in, but can nevertheless be re-mobilized in case other compatible donor cassettes are provided (“serial RMCE”). These features considerably expand the options for systematic, stepwise genome modifications. The first decade was dominated by the systematic generation of cell lines for biotechnological purposes. Based on the reproducible expression capacity of the resulting strains, a comprehensive toolbox emerged to serve a multitude of purposes, which constitute the first part of this review. The concept per se did not, however, provide access to high-producer strains able to outcompete industrial multiple-copy cell lines. This fact gave rise to systematic improvements, among these certain accumulative site-specific integration pathways. The exceptional value of RMCE emerged after its entry into the stem cell field, where it started to contribute to the generation of induced pluripotent stem (iPS-) cells and their subsequent differentiation yielding a variety of cell types for diagnostic and therapeutic purposes. This topic firmly relies on the strategies developed in the first decade and can be seen as the major ambition of the present article. In this context an unanticipated, potent property of serial Flp-RMCE setups concerns the potential to re-open loci that have served to establish the iPS status before the site underwent the obligatory silencing process. Other relevant options relate to the introduction of composite Flp-recognition target sites (“heterospecific FRT-doublets”), into the LTRs of lentiviral vectors. These “twin sites” enhance the safety of iPS re-programming and -differentiation as they enable the subsequent quantitative excision of a transgene, leaving behind a single “FRT-twin”. Such a strategy combines the established expression potential of the common retro- and lentiviral systems with options to terminate the process at will. The remaining genomic tag serves to identify and characterize the insertion site with the goal to identify genomic “safe harbors” (GOIs) for re-use. This is enabled by the capacity of “FRT-twins” to accommodate any incoming RMCE-donor cassette with a compatible design.     

Philosophy,politics and extralegal action: Native Indian leaders in Canada*

Immigration and asylum are key political issues in Britain and the European Union. Yet the policies of states and supranational bodies seem to have had little success in preventing unwanted flows and effectively managing immigration and integration. This article examines three types of reasons for policy failure: factors arising from the social dynamics of the migratory process; factors linked to globalization and the North-South divide; and factors arising within political systems. Key issues include the role of migrant agency, the way the North-South divide encourages flows, and hidden agendas in national policies. EU efforts attempts to address the root causes of migration in countries of origin are discussed. The article concludes that migration policies might be more successful if they were explicitly linked to long-term political agendas concerned with trade, development and conflict prevention. Reducing North-South inequality is the real key to effective migration management.     

Trend (1999–2009) in U.S. death rates from myelodysplastic syndromes: Utility of multiple causes of death in surveillance

BackgroundFor myelodysplastic syndromes (MDS) (formerly known as preleukemia), a diverse group of myeloid neoplasms usually involving anemia in elderly persons, trends in U.S. death rates apparently have not been reported.MethodsTrends in annual age-standardized rates per 100,000 from 1999 to 2009 were examined for MDS using multiple causes vs. underlying cause alone, coded on death certificates for U.S. residents.ResultsThe death rate (all ages combined) for MDS increased from 1999 to 2009, from 1.62 to 1.84 using underlying cause alone and from 2.89 to 3.27 using multiple causes. Rates using multiple causes were about 80% higher than those based on underlying cause alone. From 2001 to 2004 the rate for MDS using underlying cause alone (but not using multiple causes) declined, accompanied by an increase in the rate for deaths from leukemia as underlying cause with mention of MDS; this trend coincided with the advent of the 2001 World Health Organization's reclassification of certain MDS as leukemia. The MDS rate for age 65+ years increased after 2005, whereas the rate for age 25–64 years was low but declined from 2001 to 2003 and then stabilized. For deaths with MDS coded as other than underlying cause, rates did not decline for deaths from each of the two most common causes (i.e., cardiovascular diseases and leukemia).ConclusionsEvidence for decreases in MDS-related mortality rates was limited; the increase at age 65+ years is consistent with increases in incidence rates reported from cancer registries. Using multiple causes of death vs. only the underlying cause results in substantially higher MDS-related death rates, shows the impact of changes in the classification of myeloid neoplasms and emphasizes the importance of reducing cardiovascular disease mortality in MDS patients.