Size-dependent mortality in a Neotropical savanna tree: the role of height-related adjustments in hydraulic architecture and carbon allocation

Size-related changes in hydraulic architecture, carbon allocation and gas exchange of Sclerolobium paniculatum (Leguminosae), a dominant tree species in Neotropical savannas of central Brazil (Cerrado), were investigated to assess their potential role in the dieback of tall individuals. Trees greater than ∼6-m-tall exhibited more branch damage, larger numbers of dead individuals, higher wood density, greater leaf mass per area, lower leaf area to sapwood area ratio (LA/SA), lower stomatal conductance and lower net CO₂ assimilation than small trees. Stem-specific hydraulic conductivity decreased, while leaf-specific hydraulic conductivity remained nearly constant, with increasing tree size because of lower LA/SA in larger trees. Leaves were substantially more vulnerable to embolism than stems. Large trees had lower maximum leaf hydraulic conductance ( K _leaf) than small trees and all tree sizes exhibited lower K _leaf at midday than at dawn. These size-related adjustments in hydraulic architecture and carbon allocation apparently incurred a large physiological cost: large trees received a lower return in carbon gain from their investment in stem and leaf biomass compared with small trees. Additionally, large trees may experience more severe water deficits in dry years due to lower capacity for buffering the effects of hydraulic path-length and soil water deficits.     

Effect of glucose on protein phosphorylation in rat pancreatic islets

Isolated rat pancreatic islets, incubated in the presence of extracellular ³²Pi to steady state ³²P incorporation into cellular phosphopeptides, were exposed to glucose for 10 min. Glucose (16.7 mM) significantly stimulated the phosphorylation of six phosphoproteins with molecular weights of 15,000, 35,000, 49,000, 64,000, 93,000 and 138,000. Mannoheptulose (16.7 mM) markedly inhibited glucose-stimulated phosphorylation of these six phosphoproteins. This protein phosphorylation might be important in mediating glucose-stimulated insulin release.     

细菌萜类合成酶的生物信息学分析

【目的】目前对于萜类合成酶(Terpenoid synthase,TPS)的研究主要集中在植物和真菌中,而对细菌TPS的系统研究尚少。建立在大量已经被测序的细菌基因组基础上,利用生物信息学方法,对细菌TPS在全基因组范围内进行识别、分类和功能分析。【方法】利用TPS的隐马尔科夫模型(Pfam编号为PF03936)搜索自建的细菌蛋白质组数据库,预测出细菌TPS。对这些候选TPS的蛋白序列用MAFFT 7.130b进行多序列比对,并利用MEGA 6.0对多序列比对结果进行进化分析。利用MEME和PredictProtein分别进行细菌TPS的基序(Motifs)和点突变分析。【结果】建立在生物信息学分析的基础上,1 423条细菌TPS被识别,它们分布在8个门中,即放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、蓝藻门(Cyanobacteria)、拟杆菌门(Bacteroidetes)、厚壁菌门(Firmicutes)、绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteria)和衣原体门(Chlamydiae)。进化分析表明细菌TPS可分为4大类,Motifs分析表明除了各类之间保守的基序(Motifs)外,还有特异的Motifs,这暗示着细菌TPS在不同类别之间的功能分化。点突变分析表明,细菌TPS不同位点的氨基酸突变对TPS功能的影响不同。【结论】细菌TPS主要分布于8个门中,其中在2个门中细菌TPS尚未见报道,即厚壁菌门(Firmicutes)与酸杆菌门(Acidobacteria)。基于进化分析,可以把细菌TPS分为4类,各类之间的差异可能是由类特异的Motifs决定的,另外细菌TPS不同氨基酸位点的突变分析为今后验证TPS的功能提供了很好的理论基础。     

330例2型糖尿病患者死因分析

目的:通过对80年代、90年代及近6年(2000-2006)我院2型糖尿病患者死因的比较,探讨分析糖尿病患者的死亡原因及其变迁,为提高糖尿病防治水平,减少糖尿病死亡率提供科学依据。方法:采用回顾性调查方法对我院1983-2006年住院2型糖尿病患者死因进行分析,并分三阶段进行比较。共调查2型糖尿病死亡病例330例。结果:不同年代心脑血管疾病均是导致2型糖尿病患者死亡的主要原因,位居死因第一,占总死亡人数的38.2%。肿瘤作为2型糖尿病患者的死因所占比例明显增加,占总死亡人数的19.4%。以感染为直接死因逐渐下降,但仍为重要死因,占14.2%。而糖尿病酮症酸中毒、高渗昏迷和低血糖昏迷等急性并发症所占比例显著减少,占8.8%。结论:糖尿病慢性并发症尤其是心脑血管病变是2型糖尿病的主要死因,近年来肿瘤已经成为2型糖尿病患者的重要死因,以感染为直接死因逐渐下降,但仍为重要死因,而糖尿病酮症酸中毒、高渗昏迷和低血糖昏迷等急性并发症所占比例显著减少。     

黄瓜抗白粉病分子育种研究现状与展望

对黄瓜白粉病病原菌的种类及生理小种分化、抗性遗传规律、分子标记及QTL定位等方面的研究进展进行了综述。对黄瓜白粉病抗病遗传规律的研究结果进行了对比分析,指出了现阶段研究中存在的问题,并提出相应的解决方案和建议,对今后的研究方向进行了展望。     

报春花属的保育遗传学及亲缘地理学研究进展

现存物种的分布格局、遗传结构是当前因素和历史因素共同作用的结果。人类的过度开发、全球变暖等当前因素造成的生境片段化是目前许多报春花属植物濒危的一大原因。该文总结了近年来报春花属内的保育遗传学研究进展,期望以此为更好地保护报春花属植物提供一定的理论基础。应用亲缘地理学研究方法可以弥补古生物学难以研究报春花植物历史成因的不足,因此也总结该方法在报春花属内的研究进展,并初步整理不同地区间的报春花属植物的分化式样,同时期望这些研究成果能为为研究报春花属植物在应对全球气候变化的响应机制方面提供一些参考。     

Following the recovery of naso-pharyngeal cancer patients by trace elements in hair using statistical pattern recognition methods

This article describes a study where the recovery of nasopharyngeal cancer (NPC) patients was traced by trace elements (TEs) in hair of these patients. These patients whose concentrations of TEs in hair were studied are volunteers who were divided into three groups B, C, and D. Group B was made up of volunteers who had just been diagnosed as having NPC, group C and group D were made up of volunteers who had been diagnosed as having NPC after 3 and 6 mo, respectively, of treatment. For comparison, a control group, namely group A, which was made up of volunteers from healthy persons was added to this study. By implementation of statistic pattern recognition methods, it has been found that the concentrations of TEs in hair can remarkably reflect different recovery phases of NPC patients.     

水稻无侧根突变体RM109的显微结构及其根毛形态观察

水稻原品种"大力"以NaN3诱变方法获得了稳定突变体RM109.显微结构观察表明,RM109种子根外表根毛稀少且短小,无侧根发生,而"大力"品种则有侧根发生,且密生根毛.根毛观察比较显示,距种子根根端1 cm处的RM109根毛数是"大力"品种的19%,差异极显著,根直径与"大力"品种差异不显著;距根端8 cm处的RM109根毛数和根直径分别是"大力"品种的45%和79%,二者差异极显著;距根端3 cm处,RM109最大根毛长是"大力"品种的33%,差异极显著;RM109种子根根端到根毛发生区的长度,与"大力"品种的差异不显著.