Genetic variation in the efficiency of nitrogen utilization and photosynthetic activity of flag leaves among the old and modern germplasm of winter wheat

Genotypic variation in major components of the efficiency of nitrogen utilization and photosynthetic activity of flag leaves among old (released 1881-1963) and modern (released 1969-2003) cultivars of winter wheat was studied in field conditions under varied N fertilization levels (110, 90 and 80 kg N ha-1). Significant genotypic differences were observed for all characters. Their heritabilities ranged from 0.37 to 0.93 and were the lowest for the leaf efficiency of gas exchange, photosynthetic rate, straw N content and the economic index of N utilization efficiency (NUE). Some modern cultivars exhibited an enhanced tolerance to N shortage and several attributes of efficient N utilization (e.g. later senescing and more photosynthetically active flag leaves, increased ability to redistribute N into grains). The genotypes may serve as donors of appropriate characteristics for breeding. The observed cultivar-by-fertilization interactions suggest, however, that evaluations under diverse fertilization regimes may be necessary when searching for improved wheat efficiency and adaptation to less favourable environments.     

Clinical characteristics of tumors derived from colorectal cancer patients who harbor the Tumor Necrosis Factor α-1031T/T and NOD2 3020insC polymorphism

Background: Genetic predispositions to disease have focused on highly penetrant causative changes in tumor suppressor genes or genes associated with DNA mismatch repair. New investigations are revealing new genetic associations with disease that are more subtle in their association with disease and require characterization. Methods: In this report we have examined the tumor characteristics in a group of patients who have been shown to harbor two polymorphisms in two genes that are associated with the immune system NOD2 and TNFα. Results: Colorectal cancers from patients with NOD2 3020insC and TNFα-1031T/T constitutional changes are mostly right-sided disease (OR = 2.21, p = 0.03) with a tendency to higher stages (OR = 2.41, p = 0.06), increased number of associated polyps (OR = 1.77, p = 0.16) and later age of average age of disease onset (p = 0.039). Conclusion: The results reveal that there appear to be specific characteristics associated with the tumors that may aid in determining management strategies to reduce the risk of disease.     

Molecular genetics of mutants of Rhizobium leguminosarum which fail to fix nitrogen

Summary Mutants of Rhizobium leguminosarum which failed to fix nitrogen within nodules on peas were isolated following the insertion of the transposon Tn5 into pRL1JI, a Rhizobium plasmid known to carry the genes for nitrogenase. The sites of the Tn5 insertions were identified by restriction endonuclease mapping of cloned fragments of DNA from the mutant strains. One group of mutants was located within 4 kilobases of the structural genes for nitrogenase and another was located about 30 kilobases from this region. Two mutants from the first group, one of which appeared to be affected in a nitrogenase gene, induced nodules that contained bacterioids, but the number of plant cells containing bacteroids was less than in a normal nodule. Another group of mutants, which was located about 30 kilobases from the nitrogenase genes failed to form bacterioids. Electron microscopy of the nodules induced by these mutants indicated that there was a defect in their release from infection threads.     

大豆异黄酮对大鼠乳腺癌细胞内cAMP/PKA信号途径的影响

本实验研究了大豆异黄酮对SHZ-88大鼠乳腺癌细胞内cAMP／PKA信号途径的影响。实验设3组：空白对照组、50μg／ml大豆黄酮及15μg／ml染料木素组。采用放射免疫测定法（RIA）检测了胞内cAMP的浓度、腺苷酸环化酶（adenylate cyclase,AC）和磷酸二酯酶（phosphodiesterase,PDE）的活性,用（γ-^32P）ATP掺入法测定cAMP依赖性PKA的活性,半定量RT-PCR法分析cAMP反应元件结合蛋白（cAMP response element binding protein,CREB）mRNA表达的变化。结果表明：在处理后5min,大豆黄酮组和染料木素组细胞的cAMP浓度分别比对照组升高了9．5％和11．0％（P〈0．05）：10min时,分别比对照组升高31．0％和40.3％（P〈0．01）。3组细胞的AC活性在处理时间内没有明显变化。但在处理后5min,大豆黄酮组和染料木素组细胞的PDE活性分别降至对照组的71．8％和71．6％（P〈0．05）。处理后20min,大豆黄酮组和染料木素组细胞PKA活性分别上升到对照组的125．8％和122．3％（P〈0．05）;到40min时仍维持在高水平。大豆黄酮组和染料木素组细胞CREB mRNA的表达量在处理后3h分别比对照组增加31．6％和51．1％（P〈0．05）;6h后开始下降。这些结果提示,大豆异黄酮能够激活大鼠乳腺癌细胞内cAMP／PKA信号途径;而且是通过抑制磷酸二酯酶的活性,导致胞内cAMP浓度升高而实现的。     

Caspase-3在roscovitine诱发PC12细胞凋亡中发挥重要作用

我们已证实周期蛋白激酶（cyclin-dependent kinases）cdk2、cdc2和cdk5抑制剂roscovitine诱导PC12细胞凋亡。本实验应用caspase-3免疫细胞化学与hoechst 33342荧光化学双标、MTT比色法细胞活性测定和Western blot方法,研究了caspase-3在roscovitine所致PC12细胞凋亡中的作用。结果显示,roscovitine（50μmol／L）处理PC12细胞12h,细胞核染色质凝缩及核碎片形成,同时胞浆中出现caspase-3阳性标志,caspase-3阳性细胞占细胞总数的42％。非特异性caspases抑制剂Z-VAD-FMK（50μmol／L）和caspase-3特异性抑制剂Z-DEVD-FMK（100μmol／L）可部分降低roscovitine所致的细胞死亡,使细胞存活率分别由29．03％（roscovitine）增至58．06％（Z-VAD-FMK＋roscovitine）和45．16％（Z-DEVD-FMK＋roscovitine）：用单克隆non-erythroid α-spectrin抗体检测roscovitine处理组细胞匀浆提取液,表明caspase-3裂解的特异性spectfin 120kDa蛋白产物较对照组显著增加。提示细胞凋亡成分caspases参与roscovitine所敛的细胞凋亡,其中caspase-3发挥重要作用。     

Folding thermodynamics and kinetics of YNMG RNA hairpins: specific incorporation of 8-bromoguanosine leads to stabilization by enhancement of the folding rate

Modified nucleotides allow fundamental energetic and kinetic properties of nucleic acids to be probed. Here, we demonstrate that an RNA hairpin containing the nucleotide analogue 8-bromoguanosine (8BrG or G), gcUUCGgc, has enhanced stability relative to the unmodified hairpin, with DeltaDeltaG(37)(degrees)= -0.69 +/- 0.15 kcal mol(-1) and DeltaT(M) = +6.8 +/- 1.4 degrees C. NMR spectroscopic data suggest that the enhanced stability of gcUUCGgc does not arise from the native state; laser temperature-jump experiments support this notion, as gcUUCGgc and gcUUCGgc have similar unfolding rate constants, but the folding rate constant of gcUUCGgc is 4.1-fold faster at 37.5 degrees C and 2.8-fold faster under isoenergetic conditions. On the basis of these findings, we propose that 8BrG reduces the conformational entropy of the denatured state, resulting in an accelerated conformational search for the native state and enhanced stability.