Allozymic differentiation of Tunisian populations of Androctonus species and Buthus occitanus (Scorpiones: Buthidae)

We examined the population structure and phylogeny of Buthus occitanus (Amoreux, 1789), Androctonus amoreuxi (Audouin & Savigny 1812) and Androctonus australis (Linnaeus, 1758) in Tunisia, using horizontal starch gel and polyacrylamide gel electrophoresis to resolve allozymes at 18 loci. Populations of B. occitanus and A. amoreuxi showed little genetic variation, whereas A. australis populations showed moderate genetic variation. Moreover, despite the restricted dispersal abilities of these species, the allozyme analysis indicated very low levels of intraspecific population differentiation. The Island model of population differentiation best fitted the intraspecific variation, both for mainland populations and for the slightly more differentiated populations from two Mediterranean islands. No diagnostic, fixed alleles were observed between the species of Androctonus , which concurs with the results of nuclear ribosomal DNA analysis. Two subspecies of A. australis , A. a. garzonii Goyffon & Lamy, 1973 and A. a. hector Vachon, 1948, were not resolved by a phylogenetic analysis of the allozyme data. The most likely reasons for the slight population differentiation are either low mutation rates or recent range extensions promoted by human activities. The possibility of indirect gene flow between Androctonus species should also be explored.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 255–265.     

Drought effects on the dynamics of leaf production and senescence in field-grown Medicago arborea and Medicago citrina

Forage shrub production in the Mediterranean region is frequently limited by soil water availability. To study plant responses to water deficit under such conditions is important for improving crop management and for selecting better yielding forage shrub species. Pre-dawn leaf water potential (Ψ_pd), plant leaf area (PLA), leaf area per stem (LA_s), leaf appearance rate (LAR₁;), leaf senescence rate (LSR), individual leaf area (LA) and maximal leaf elongation rate (LER) were studied throughout the year for Medicago arborea (MA) and Medicago citrina (MC) under irrigated (control) and low rainfall field conditions, at the experimental field site of the University of the Balearic Islands in Spain. With irrigation, the highest LA and LER were observed in autumn and spring and the lowest in winter and summer. LAR; was similar for both species in autumn and winter. Throughout the spring, LAR₁ was higher for MC compared to MA. PLA was similar for both species during the autumn, winter and spring seasons; however, during the summer PLA of MA was significantly reduced by 53%. This decline was attributed to higher leaf senescence during seed maturity. As a consequence, MC maintained higher leaf area (∼ 5 m² plant⁻¹) than MA (3 m² plant⁻¹). Under natural field conditions, soil water deficit increased from February to late August. The main effect of water stress was a marked reduction in LAR₁, LA and LER reflected in lower LA_s and PLA. Leaf area was severely reduced for both species during the summer, but much more intensively in MA, which developed full leaf senescence. Thus, MC maintained higher PLA than MA (0.5 m² compared to 0.0 m²). Throughout the year, but especially in the driest months, MC was superior to MA in leaf growth parameters and PLA.     

不同海拔地区紫外线B辐射状况及植物叶片紫外线吸收物质含量的分析

对不同海拔地区的太阳ＵＶ－Ｂ辐射和植物叶片的光学特性进行了比较研究。结果表明：位于高海拔地区的海北高寒草甸生态系统定位站，太阳ＵＶ－Ｂ辐射明显高于相近纬度的西宁、兰州和南京地区。ＵＶ－Ｂ辐射与总辐射和ＰＡＲ的日变化规律相似，都受太阳高度角的直接影响，在当地太阳正午时最高。ＵＶ－Ｂ／Ｑ的日变化也为单峰曲线，海北部地区的ＵＶ－Ｂ／Ｑ高于西宁的同期测定结果。对蛛芽蓼等植物的研究表明，生长于海北部地区的蛛     

Spatial scaling of ecosystem C and N in a subtropical savanna landscape

Widely occurred woody encroachment in grass‐dominated ecosystems has the potential to influence soil organic carbon (SOC) and total nitrogen (TN) pools at local, regional, and global scales. Evaluation of this potential requires assessment of both pool sizes and their spatial patterns. We quantified SOC and TN, their relationships with soil and vegetation attributes, and their spatial scaling along a catena (hill‐slope) gradient in the southern Great Plains, USA where woody cover has increased substantially over the past 100 years. Quadrat variance analysis revealed spatial variation in SOC and TN at two scales. The larger scale variation (40–45 m) was approximately the distance between centers of woody plant communities and their adjoining herbaceous patches. The smaller scale variation (10 m) appeared to reflect the local influence of shrubs on SOC and TN. Litter, root biomass, shrub, and tree basal area (a proxy for plant age) exhibited not only similar spatial scales, but also strong correlations with SOC and TN, suggesting invasive woody plants alter both the storage and spatial scaling of SOC and TN through ecological processes related primarily to root turnover and, to a lesser extent litter production, as mediated by time of occupancy. Forb and grass biomass were not significantly correlated with SOC and TN suggesting that changes in herbaceous vegetation have not been the driving force for the observed changes in SOC and TN. Because SOC and TN varied at two scales, it would be inappropriate to estimate SOC and TN pools at broad scales by extrapolating from point sampling at fine scales. Sampling designs that capture variation at multiple scales are required to estimate SOC and TN pools at broader scales. Knowledge of spatial scaling and correlations will be necessary to design field sampling protocols to quantify the biogeochemical consequences of woody plant encroachment at broad scales.     

树鼩CXCR4 cDNA的克隆和序列分析

目的　获得树CXCR4的cDNA序列 ,探讨其是否可以支持HIV_1病毒和细胞的结合。方法　设计相应的引物 ,用RT_PCR ,基因克隆 ,DNA序列分析技术。结果　获得了全长为 10 59bp树CXCR4(tsCXCR4)基因的cDNA。发现其核苷酸序列与人的CXCR4(hCXCR4)基因的cDNA有 92 8%的相似性 ,由此推导出的氨基酸序列有 96 9%相似性。与hCXCR4功能相关的关键位点完全相同 ,tsCXCR4的N端第 7和 12位点为酪氨酸 ,第 14、15和3 2位点为谷氨酸 ,胞外环第 183 ,188为精氨酸 ,第 193、2 62位点以及跨膜区 97位点为天冬氨酸。结论　树的CX CR4很可能会作为HIV_1的辅助受体     

不同海拔地区紫外线B辐射状况及植物叶片紫外线吸收物质含量的分析

对不同海拔地区的太阳 UV- B辐射和植物叶片的光学特性进行了比较研究。结果表明 :位于高海拔地区的海北高寒草甸生态系统定位站 ,太阳 UV- B辐射明显高于相近纬度的西宁、兰州和南京地区。UV- B辐射与总辐射和 PAR的日变化规律相似 ,都受太阳高度角的直接影响 ,在当地太阳正午时最高。UV- B/Q的日变化也为单峰曲线 ,海北站地区的 UV- B/Q高于西宁的同期测定结果。对珠芽蓼等植物的研究表明 ,生长于海北站地区的珠芽蓼 ,其叶片中紫外线吸收物质的含量明显高于西宁的同种植物 ,也略高于海拔较高的达坂山和小达坂山山顶的同种植物。叶绿素含量以海北站珠芽蓼最低 ,达坂山和小达坂山的同种植物最高。珠芽蓼叶片中类胡萝卜素的含量以西宁最低 ,海北站、达坂山和小达坂山依次升高。海北站矮嵩草与从海北站移植到西宁生长 4年的同种植物相比 ,叶片中紫外线吸收物质、叶绿素、类胡萝卜素的变化与生长于两地区的珠芽蓼相同     

The Fine Structure of the Cortex of the Protist Protoopalina australis (Slopalinida, Opalinidae) from Litoria nasuta and Litoria inermis (Amphibia: Anura: Hylidae) in Queensland, Australia

ABSTRACT. The ultrastructural appearance of cortical structures of Protoopilina australis is described. With respect to kinetosomal architecture and the supports of the surface folds, Protoopalina australis has an ultrastructural identity similar to other opalines. However, microfibrillar tracts and regular arrays of cortical vesicles—evident in Opalina and Cepedea —are absent from the binucleate genera. This new insight, combined with the recent discovery of a new genus ( Protozelleriella ) is used to revise our understanding of the evolution of slopalines and we favour a common origin for the multinucleate genera Opalina and Cepedea.     

罗米地辛与阿糖胞苷联合用药在肺腺癌细胞中介导组蛋白H3K14乙酰化提高CASP3转录活性

肺癌发病率和病死率均居全球恶性肿瘤首位,有效的药物是治疗肺癌的关键。罗米地辛和阿糖胞苷是已经批准上市并应用于临床治疗的癌症化疗药物。这两种药物的联合用药是否在肺腺癌的治疗中发挥作用及其相关分子机制尚不明确。本研究通过MTT和克隆形成实验证实,罗米地辛和阿糖胞苷联合用药可以显著抑制肺腺癌细胞A549的生长(P<0.05)。体外Transwell细胞侵袭实验和划痕实验表明,联合用药可有效降低肺腺癌细胞的侵袭和转移能力(P<0.05)。同时,流式细胞分析显示,联合用药可以显著诱导肺腺癌细胞的凋亡(P<0.05),并且实时PCR和Western印迹结果提示,肺腺癌细胞A549在联合用药处理后,凋亡相关蛋白质CASP3的mRNA和蛋白质表达水平均明显升高。另外,通过检测联合用药后,A549细胞的组蛋白乙酰化修饰情况发现,H3K14位点乙酰化水平被明显上调,并且ChIP分析进一步显示,CASP3启动子区域组蛋白H3K14乙酰化水平在联合用药后明显增加(P<0.05)。本研究揭示了罗米地辛与阿糖胞苷联合用药能通过增强CASP3启动子区组蛋白H3K14乙酰化水平进而促进CASP3的转录和蛋白质表达,从而抑制肺腺癌细胞的生长、增殖、迁移和侵袭,促进其凋亡的分子机制。在分子和细胞水平上为罗米地辛和阿糖胞苷联合用药治疗肺腺癌提供依据,并为肺腺癌的临床治疗提供切实参考。     

The role of olfaction in aphid host location

Aphids are major economic pests of many of the worlds' crops, causing damage directly by feeding and by acting as vectors for plant viruses. By understanding how aphids locate their host plants, it may become possible to develop new means of controlling populations by taking advantage of these natural host location/nonhost avoidance behaviours. Aphids have also become important model organisms in the study of insect–plant interactions and an improved understanding of host location in aphids could yield insights into the behaviour and ecology of other insect orders. The use of olfaction by host‐seeking aphids is well documented and, in recent years, considerable information has been gained on how volatiles can encode host identity and suitability, as well as the specific behaviours they elicit from aphids. The purpose of this review is to highlight the major findings on how aphids respond behaviourally to volatile compounds and how they can use them to locate their host plants and avoid unsuitable hosts.