火烧对黔中喀斯特山地马尾松林土壤理化性质的影响

在黔中喀斯特山地马尾松人工次生林内取样分析火烧和对照样地间土壤理化指标的变化,研究了火烧对林地土壤理化性质的影响。结果表明马尾松火烧林地表层土壤毛管孔隙度和总孔隙度升高、最大持水量和最小持水量增加,土壤密度和非毛管孔隙度降低、土壤质量含水量和体积含水量减少;土壤有机质、全N量、全P量、全K量,水解N量、有效P量、速效K量、交换性盐基量和pH值增大,阳离子交换量降低。林火对马尾松林地土壤主要理化指标影响的趋势为或表层土壤影响率大于剖面影响率、或表层土壤影响率小于剖面影响率,不同指标在土壤剖面的变化趋势或增加、或降低,对数或幂函数拟合曲线均达相关显著性水平。火烧和对照样地间的表层土壤理化指标变化主要反映了林火影响,近岩层土壤理化指标变化主要是成土母质在空间上的分异,也受生物的影响。乔木层植株死亡率同表层土壤最大持水量、最小持水量、有机质量和全N量的正相关性显著,同土壤密度的负相关性显著;灌木层植株死亡率同表层土壤密度正相关性显著,同毛管孔隙度、总孔隙度、质量含水量、最大持水量、最小持水量、有机质量、全N量、全P量和速效K量的负相关性达显著或极显著水平;灌木层生物损失量同表层土壤密度和有机质量正相关显著,同速效K量的负相关性显著,枯物层生物损失量同pH值的正相关性显著。火烧马尾松林分平均胸径同表层土壤密度正相关性显著,同毛管孔隙度、总孔隙度、质量含水量、最大持水量、最小持水量和有机质量的负相关性显著。     

Structural change in β-sheet A of Z α(1)-antitrypsin is responsible for accelerated polymerization and disease

The presence of the Z mutation (Glu342Lys) is responsible for more than 95% of α₁-antitrypsin (α₁AT) deficiency cases. It leads to increased polymerization of the serpin α₁AT during its synthesis and in circulation. It has been proposed that the Z mutation results in a conformational change within the folded state of antitrypsin that enhances its polymerization. In order to localize the conformational change, we have created two single tryptophan mutants of Z α₁AT and analyzed their fluorescence properties. α₁AT contains two tryptophan residues that are located in distinct regions of the molecule: Trp194 at the top of β-sheet A and Trp238 on β-sheet B. We have replaced each tryptophan residue individually with a phenylalanine in order to study the local environment of the remaining tryptophan residue in both M and Z α₁AT. A detailed fluorescence spectroscopic analysis of each mutant was carried out, and we detected differences in the emission spectrum, the Stern-Volmer constant for potassium iodide quenching and the anisotropy of only Trp194 in Z α₁AT compared to M α₁AT. Our data reveal that the Z mutation results in a conformational change at the top of β-sheet A but does not affect the structural integrity of β-sheet B.     

Studies on the Nucleic Acid and Protein Content in the Cotyledon Cells of Lotus Using Fluorescent Imaging System with a Scientific grade Charge Coupled Device

Enzyme dissociated cotyledon cells were obtained from red lotus ( Nelumbo sp. ) on the 5th day and 20th day after fertilization respectively. DNA, RNA and total protein content of individual 5 d and 20 d cell were measured correlatively by microfiuorescent imaging system with a cooled scientific-grade Charge coupled deviced (CCD) camera. The results showed that DNA content of the 20 day cell has become polyploidized from 4C to 8C approximately. The window analysis indicated that relative content of RNA and total protein of the 20 day cell was more than 11 times that of the 5 day cell in the same 4C DNA window respectively. The multiple in-creased of RNA and total protein content was about the same as that of DNA in 2 DNA windows (4C and 8C) of the 20 day cell. These data showed that the enormous accumulation of storage proteins in the cotyledon cells of red lotus depends on both DNA ploidy and selective expression of the subunit genes of the storage proteins during the developmental process.     

HCVE2／NS1相对保守区多肽体外诱导慢丙肝患者PBMC增殖反应的研究

为了解ＨＣＶ感染后细胞免疫在其中的作用,对３１例慢丙肝及２０例正常献血员以ＭＴＴ法检测外周血单核细胞（ＰＢＭＣ）对ＨＣＶＥ２／ＮＳ１相对保守区多肽抗原及Ｃ２２、ＮＳ５的增殖反应。结果表明与正常人相比,慢性丙型肝炎患者ＰＢＭＣ对ＨＣＶＣ２２、Ｅ２／ＮＳ１抗原有明显的增殖反应（Ｐ＜００５）,而对ＮＳ５无明显增殖,其中以Ｃ２２抗原性最强。作者认为慢性丙型肝炎患者存在针对与ＨＣＶ相关抗原的细胞免疫,这种细胞免疫不能消除ＨＣＶ感染,而且与疾病的状态无关。     

因子与巢式交配设计群体近交率的比较研究

探讨了因子和巢式交配设计群体近交率的形成机理,结果表明,这两种交配设计群体结构本身并不导致基近交率累积的差异。在育种选择情况下因子交配设计比巢式设计群体的近交率上升慢,而在完全随机留种和限制随机种情形这两种酱地群体近交率的影响没有差异,但在交配设计情况下,限制随机留种比完全随机留有有交地控制群体近交率的提高。这一结果显示,在动物的家畜遗传留种比完全随机留各 效地控制群体近交率的提高。这一结果显示,     

Protein kinase CK2 links polyamine metabolism to MAPK signalling in Drosophila

MAPK signalling is a complex process not only requiring the core components Raf, MEK and Erk, but also many proteins like the scaffold protein KSR and several kinases to specifically localize, modulate and fine-tune the outcome of the pathway in a cell context specific manner. In mammals, protein kinase CK2 was shown to bind to the scaffold protein KSR and to phosphorylate Raf proteins at a conserved serine residue in the negative-charge regulatory (N−) region, thereby facilitating maximal activity of the MAPK signalling pathway. In this work we show that in Drosophila CK2 is also bound to KSR. However, despite the presence of a corresponding serine residue in the N-region of DRaf, CK2-mediated phosphorylation of DRaf takes place on a serine residue at the N-terminus and is required for Erk activation. Previous work identified polyamines as regulators of CK2 kinase activity. The main cellular source of polyamines is the catabolism of amino acids. Evidence is provided that phosphorylation of DRaf by CK2 is modulated by polyamines, with spermine being the most potent inhibitor of the reaction. We suggest that CK2 is able to monitor intracellular polyamine levels and translates this information to modulate MAPK signalling.     

A conserved aspartate residue located at the extracellular end of the binding pocket controls cation interactions in brain glutamate transporters

In the brain, transporters of the major excitatory neurotransmitter glutamate remove their substrate from the synaptic cleft to allow optimal glutamatergic neurotransmission. Their transport cycle consists of two sequential translocation steps, namely cotransport of glutamic acid with three Na(+) ions, followed by countertransport of K(+). Recent studies, based on several crystal structures of the archeal homologue Glt(Ph), indicate that glutamate translocation occurs by an elevator-like mechanism. The resolution of these structures was not sufficiently high to unambiguously identify the sites of Na(+) binding, but functional and computational studies suggest some candidate sites. In the Glt(Ph) structure, a conserved aspartate residue (Asp-390) is located adjacent to a conserved tyrosine residue, previously shown to be a molecular determinant of ion selectivity in the brain glutamate transporter GLT-1. In this study, we characterize mutants of Asp-440 of the neuronal transporter EAAC1, which is the counterpart of Asp-390 of Glt(Ph). Except for substitution by glutamate, this residue is functionally irreplaceable. Using biochemical and electrophysiological approaches, we conclude that although D440E is intrinsically capable of net flux, this mutant behaves as an exchanger under physiological conditions, due to increased and decreased apparent affinities for Na(+) and K(+), respectively. Our present and previous data are compatible with the idea that the conserved tyrosine and aspartate residues, located at the external end of the binding pocket, may serve as a transient or stable cation binding site in the glutamate transporters.     

Effects of Rhinoncomimus latipes on the growth and reproduction of Persicaria perfoliata,an invasive plant in North America

Native to Asia, mile-a-minute Persicaria perfoliata, is an invasive weed in North America, and the weevil Rhinoncomimus latipes is a host-specific insect agent which occurs widely in China. We conducted a common garden experiment to compare P. perfoliata plant responses of native and invasive populations to herbivory by the weevils from different origins. We found weevils from Hunan, Hubei and Heilongjiang Provinces had strong, moderate and weak ability to suppress host plant, respectively. Weevils from Hunan and Hubei Provinces had stronger impact on the growth of both native and invasive plant populations than the weevil from Heilongjiang Province. The losses in seed output of invasive plants were also significantly greater than natives in the weevil treatments. Our results suggested that the weevil population from Hunan Province may be the most suitable for the control of mile-a-minute, while the population from Heilongjiang Province may be the least suitable due to climate matching.