First Record of Rosellinia desmazieresii on Scots Pine and its Association with Disease in Poland

Rosellinia desmazieresii was found for the first time on a tree of Scots pine. It occurred on a dying tree in a mixed Scots pine-oak plantation in Poland. The fungus girdled the base of the trunk, where perithecia were produced abundantly. The fungus was evidently the cause of the tree's poor growth and ultimate death.     

Population genetics of rhizobia: construction and analysis of an "Infection and Release" model

A mathematical model is created to assess the inputs of sym gene transfer of in planta multiplication and of interstrain competition into dynamics of the rhizobia populations. Their microevolution is presented as a series of the "infection and release" cycles; each cycle includes transfer of sym genes from virulent initial symbionts to avirulent local bacteria yielding the virulent novel symbionts; competition between initial symbionts and novel symbionts for the host nodulation; multiplication of initial symbionts and novel symbionts in planta and their release into soil; competition between the released novel symbionts and resident local bacteria for ex planta survival. A recurrent equation is created to determine the number of novel symbionts at each cycle of evolution of the closed bacteria-plant system. Its analysis demonstrates that under certain, really allowable values of the introduced parameters two major effects may occur: (a) rapid multiplication of novel symbionts arisen from sym gene transfer; and (b) increase of frequency of rare local bacteria genotypes after acquisition of virulence. Multiplication of very rare strains (p<10(-19)) in the plant-associated bacteria population is possible at certain parameters of the system. Variation of the sizes of bacteria populations and of the parameters for interstrain competition may influence the evolutionary rate of the bacteria population. The "infection and release" model represents a selective mechanism which may be responsible for a high taxonomic diversity of rhizobia and for a panmictic structure of their populations.     

Association of common variation in the <Emphasis Type="Italic">PPARA</Emphasis>gene with incident myocardial infarction in individuals with type 2 diabetes: A Go-DARTS study

Background

Common variants of the PPARA gene have been found to associate with ischaemic heart disease in non diabetic men. The L162V variant was found to be protective while the C2528G variant increased risk. L162V has also been associated with altered lipid measures. We therefore sought to determine the effect of PPARA gene variation on susceptibility to myocardial infarction in patients with type 2 diabetes. 1810 subjects with type 2 diabetes from the prospective Go-DARTS study were genotyped for the L162V and C2528G variants in the PPARA gene and the association of the variants with incident non-fatal myocardial infarction was examined. Cox's proportional hazards was used to interrogate time to event from recruitment, and linear regression for analysing association of genotype with quantitative clinical traits.

Results

The V162 allele was associated with decreased risk of non-fatal myocardial infarction (HR = 0.31, 95%CI 0.10–0.93 p = 0.037) whereas the C2528 allele was associated with increased risk (HR = 2.77 95%CI 1.34–5.75 p = 0.006). Similarly V162 was associated with a later mean age of diagnosis with type 2 diabetes and C2582 an earlier age of diagnosis. C2528 was also associated with increased total cholesterol and LDL cholesterol, which did not account for the observed increased risk. Haplotype analysis demonstrated that when both rare variants occurred on the same haplotype the effect of each was abrogated.

Conclusion

Genetic variation at the PPARA locus is important in determining cardiovascular risk in both male and female patients with diabetes. This genotype associated risk appears to be independent of the effect of these genotypes on lipid profiles and age of diagnosis with diabetes.

     

Plasmid pSym1-32 from Rhizobium leguminosarum bv. viceae, controlling nitrogen-fixing activity, effectiveness of symbiosis, competitiveness, and acid tolerance

The symbiotic plasmid (pSym1-32) of the highly effective Rhizobium leguminosarum bv. viceae 1-32 strain was identified after the conjugal transfer of replicons carrying Tn5-mob into the plasmidless Agrobacterium tumefaciens Gm1-9023 strain. Plasmid pSym1-32 was transferred into R. leguminosarum bv. viceae strains Y14 (showing low effectiveness of symbiosis with Vicia villosa) and Y57 (unable to fix nitrogen). Transconjugants formed Fix+ nodules on roots of V. villosa and had a highly enhanced nitrogen fixing ability, increased plant weight, and increased nitrogen accumulation compared to the recipient strains. Variation of transconjugants in symbiotic properties (accompanied by alterations in plasmid composition in some of the conjugants) was detected. Moreover, the donor strain R. leguminosarum bv. viceae 1-32 was shown to be more efficient in the competitiveness and acid tolerance than the recipient Y14 strain. Both these properties were transmitted upon transfer of pSym1-32 into the recipient. Thus, plasmid pSym1-32 was shown to carry genes involved in the control of the nitrogen fixing ability, symbiotic effectiveness, competitiveness, and acid tolerance in R. leguminosarum bv. viceae.     

Evolutionary Genetics of Nodule Bacteria: Molecular and Population Aspects

The molecular analysis of the genetic systems controlling the main stages of nodule bacteria (rhizobia) interaction with a legume host (signaling at early stages and symbiotic nitrogen fixation) has shown that the widespread recombination of genetic material in free-living ancestors of rhizobia was an important factor in the evolution of these systems. These recombinations could be conditioned by a high content of repeated DNA sequences and the IS elements in the rhizobial genome. A high recombination activity of rhizobia is manifested in the panmictic structure of their populations, which is associated with frequency-dependent selection favoring rare recombinants. This selection is realized through the competition of virulent strains for the nodule formation and can be controlled by the genes whose expression depends on population density (via the quorum sensing mechanism). A high degree of panmixia in rhizobial populations is associated with their ecotypic polymorphism, manifested as the coexistence of symbiotic and nonsymbiotic strains. This type of polymorphism is caused by individual selection during the periodic changes of ecological niches (soil–plant host) in the rhizobia life cycle. The rhizobia–plant interaction stimulates selection in bacterial populations, which results in the increased levels of their heterogeneity and panmixia. The combination of individual and frequency-dependent selection types resulted in the high rates of symbiosis evolution and polyphyletic origin of diverse rhizobial species.     

白音华矿区土壤重金属含量的空间异质性

为探讨开矿对白音华矿区土壤重金属空间分布的影响, 本研究以内蒙古西乌珠穆沁旗白音华煤矿区周边土壤为对象,分析了距离矿区8 km内的重金属Cu、Cr、Pb和Mn含量的空间异质性。结果表明: 土壤重金属Cu、Cr、Pb和Mn的平均含量分别为12.7、32.6、29.9和201.3 mg·kg^-1,其变异系数分别为26.8%、33.9%、27.1%和45.7%。采用半方差函数进行模型拟合, Cu、Cr、Pb和Mn空间分布分别符合高斯模型、高斯模型、高斯模型和线性模型。对其空间分布格局分析发现,Mn、Cr 和 Cu的空间自相关水平较高,主要受结构性因素影响,受随机性因素影响很小,Pb的空间相关性水平适中,同时受结构性因素和随机性因素影响。分形维数分析表明,4种土壤重金属含量空间分布简单,结合2D及3D图看,4种土壤重金属均呈现梯度分布,随着距离增加其含量逐步降低,Cu和Mn主要集中分布在距离矿区1.5 km内,Cr与Pb则分别集中分布在距离矿区2.0与3.0 km内。     

复方环丙酮胺治疗浅部真菌病的疗效观察

观察复方环丙酮胺喷剂治疗浅部真菌病的疗效。第Ⅰ批给予复方环丙酮胺喷剂,1次/d喷于患处,用药4周后观察疗效;第Ⅱ批随机入A、B组,A组给予复方环丙酮胺喷剂+曲安奈德喷剂,B组给予复方环丙酮胺喷剂,均1次/d喷于患处,用药2周、4周后观察疗效。第Ⅰ批治疗4周总有效率为80%;第Ⅱ批A、B组治疗2周总有效率分别为75%及82.35%,治疗4周总有效率分别为94.74%及100%。复方环丙酮胺喷剂和复方环丙酮胺喷剂+曲安奈德喷剂治疗浅部真菌病的疗效相似(P>0.05),且疗效显著、局部刺激小、瘙痒缓解明显、安全性较高。     

大鼠脑缺血再灌注后血清中血管内皮生长因子与神经元凋亡的研究

目的:通过检测SD大鼠脑缺血再灌注模型血清中血管内皮生长因子(VEGF)与神经元凋亡动态表达变化的关系,以探讨两者之间的相关性。方法:将40只大鼠随机分为8组:对照组、假手术组和脑缺血30min再灌注12h组、1d组、3d组、5d组、7d组、及14d组,每组5只。采用ELISA双抗夹心法检测大鼠血清中血管内皮生长因子、原位细胞凋亡TUNEL法检测脑组织中的凋亡神经细胞数。结果:再灌注12h、1d、3d、5d、7d及14d大鼠血清VEGF表达和凋亡神经元百分比的变化均为负相关性(均为P<0.05)。结论:在脑缺血再灌注大鼠模型中,缺血诱导使VEGF的表达发生变化,VEGF通过直接或间接的途径抑制神经元凋亡。     

不同密度樟子松人工林土壤碳氮磷化学计量特征

以科尔沁沙地不同密度(490、750、1550、1930、2560株·hm^-2)樟子松人工林(栽植于1980年)为研究对象,分析林分密度对土壤碳、氮、磷浓度及其计量比的影响,研究林分密度与土壤养分状况的关系。结果表明:随着樟子松林密度增加,各土层(0~10、10~20和20~40 cm)土壤有机碳、全氮、全磷浓度和C∶N呈先增加后降低趋势,而土壤有效磷浓度呈先降低后增加趋势。土壤有机碳浓度在490株·hm^-2密度小于其他密度,而有效磷浓度大于其他密度;土壤C∶P和N∶P在2560株·hm^-2密度显著大于其他密度。各密度樟子松林土壤有机碳、全氮、全磷和有效磷浓度在0~10 cm土层显著大于10~20和20~40cm土层,樟子松人工林土壤养分具有表聚性。通过典范对应分析发现,密度对樟子松林土壤养分影响的主要因子是土壤有机碳、全氮和全磷,且密度为1550株·hm^-2时土壤有机碳、全氮、全磷和碱解氮浓度较高,而C∶P和N∶P较低。因此,当樟子松人工林密度为1550株·hm^-2时,土壤养分浓度较高,林木生长较好,为最佳经营密度。