兴安落叶松老龄林落叶松林木死亡格局以及倒木对更新的影响

对兴安落叶松老龄林落叶松林木死亡格局和死亡木对更新的影响进行了研究 .结果表明 ,丛桦落叶松林和杜香落叶松林的枯立木以中径木占多数 ,赤杨落叶松林主要为中、大径木 ,草类落叶松林主要是中、小径木 .落叶松枯立木主要因火烧、受压和老死而形成 .丛桦落叶松林和赤杨落叶松林掘根倒木较多 .杜香落叶松林和草类落叶松林的倒木以风折为主 .地形、山体走向和盛行风向对树倒方向影响很大 .丛桦落叶松林倒木方向杂乱 ,赤杨落叶松林林木均向东倒下 ,杜香落叶松林和草类落叶松林的掘根木分别向南、东北方倒下 ,两者的风折木倒向随机性较大 .草类落叶松和赤杨落叶松老龄林内 ,倒木更新为 1 8和 40株·m- 2 ,远远高于矿物土基质上 2株·m- 2 的水平 .丛桦落叶松林内倒木和林地上更新均相当好 ,约为 2 8株·m- 2 .杜香落叶松林倒木更新效果不突出 .     

Deletion of dop in Mycobacterium smegmatis abolishes pupylation of protein substrates in vivo

Proteasome‐bearing bacteria make use of a ubiquitin‐like modification pathway to target proteins for proteasomal turnover. In a process termed pupylation, proteasomal substrates are covalently modified with the small protein Pup that serves as a degradation signal. Pup is attached to substrate proteins by action of PafA. Prior to its attachment, Pup needs to undergo deamidation at its C‐terminal residue, converting glutamine to glutamate. This step is catalysed in vitro by Dop. In order to characterize Dop activity in vivo, we generated a dop deletion mutant in Mycobacterium smegmatis. In the Δdop strain, pupylation is severely impaired and the steady‐state levels of two known proteasomal substrates are drastically increased. Pupylation can be re‐established by complementing the mutant with either DopWt or a Pup variant carrying a glutamate at its ultimate C‐terminal position (PupGGE). Our data show that Pup is deamidated by Dop in vivo and that likely Dop alone is responsible for this activity. Furthermore, we demonstrate that a putative N‐terminal ATP‐binding motif is crucial for catalysis, as a single point mutation (E10A) in this motif abolishes Dop activity both in vivo and in vitro.     

Recombinant Sendai virus vectors deleted in both the matrix and the fusion genes: efficient gene transfer with preferable properties

BACKGROUND: Sendai virus (SeV) is a new type of cytoplasmic RNA vector, which infects and replicates in most mammalian cells, directs high-level expression of the genes on its genome and is free from genotoxicity. In order to improve this vector, both the matrix (M) and fusion (F) genes were deleted from its genome. METHODS: For the recovery of the M and F genes-deleted SeV (SeV/DeltaMDeltaF), the packaging cell line was established by using a Cre/loxP induction system. SeV/DeltaMDeltaF was characterized and compared with wild-type and F or M gene-deleted SeV vectors in terms of transduction ability, particle formation, transmissible property and cytotoxicity. RESULTS: SeV/DeltaMDeltaF was propagated in high titers from the packaging cell line. When this vector was administered into the lateral ventricle and the respiratory tissue, many of the ependymal and epithelial cells were transduced, respectively, as in the case of wild-type SeV. F gene-deletion made the SeV vector non-transmissible, and M gene-deletion worked well to inhibit formation of the particles from infected cells. Simultaneous deletions of these two genes in the same genome resulted in combining both advantages. That is, both virus maturation into particles and transmissible property were almost completely abolished in cells infected with SeV/DeltaMDeltaF. Further, the cytopathic effect of SeV/DeltaMDeltaF was significantly attenuated rather than that of wild type in vitro and in vivo. CONCLUSIONS: SeV/DeltaMDeltaF is an advanced type of cytoplasmic RNA vector, which retains efficient gene transfer, gains non-transmissible properties and loses particle formation with less cytopathic effect.     

Handling specimens in liquid preservative: adding and removing the liquid paraffin overlayer

Adding a overlayer of liquid paraffin to formalin and subsequently removing it with oil-absorbent sheets in order to observe the specimen are very useful procedures when handling specimens preserved in formalin.     

Synthesis and structure–activity relationships of N-(4-amino-2,6-diisopropylphenyl)-N’-(1,4-diarylpiperidine-4-yl)methylureas as anti-hyperlipidemic agents

Based on 1,4-diarylpiperidine-4-methylureas, a new class of ACAT inhibitors, we examined in the study the SAR of a series of compounds prepared by replacing the substituent at the three aromatic parts. Introduction of long alkoxy group onto the phenyl moiety at the B-part was effective in improving both the inhibitory activity for ACAT and the up-regulatory activity for LDL-R expression. Particularly, 3-hydroxypropoxy group (43) on the phenyl moiety of B-part led to improved solubility, while keeping both biological activities. Compound 43 inhibited ACAT activity with an IC₅₀ value of 18 nM, which is superior to that of a known ACAT inhibitor, CI-1011. In addition, compound 43 revealed an LDL-R up-regulatory activity comparable to that of SMP-797. We therefore expect this compound to be a novel ACAT inhibitor.     

Global gradients in moss and vascular plant diversity

Knowledge on the distribution and hotspots of different taxon groups is indispensable for improving the state of biodiversity protection. Our aim was to determine if the relations between major environmental factors and species richness of two plant groups, mosses and vascular plants differ on a global scale. The dependence of species richness on environmental factors in 50 regions, covering 17 % of the global terrestrial territory, was analysed with SAS statistical software. Species richness of vascular plants increases significantly towards the equator, but for mosses the increase is not significant. Species richness of mosses and vascular plants are significantly positively correlated only in the near equator zone. Although there were similarities in the trends of mosses and vascular plant diversities at a global scale, their relations with some factors differ with distance from the equator. The effect of precipitation on species richness is similar for both plant groups, but coastline length has a significant positive influence only on moss richness, whereas species richness of vascular plants was related strongly to area and energy input. Therefore, effective conservation policy at both local and global scale demands consideration of all diversity drivers of different taxon groups.     

Changes in spatial distribution of phosphorus and nitrogen in the large north-temperate lowland Lake Peipsi (Estonia/Russia)

We investigated changes in the spatial distribution of nitrogen (N) and phosphorus (P) in Lake Peipsi using limnological data from 1970 to 2005. The results show differences in nutrient content between the northern and southern parts of the lake (polarity) and indicate possible causes of eutrophication of this large international lake. The results show a steady gradient in total P (TP) and total N (TN) content along the lake: the northern and deepest part, Lake Peipsi s.s., is significantly less loaded with nutrients than the southern and very shallow part, Lake Pihkva, into which the main inflow, the Velikaya River, discharges. However, the long-term temporal patterns of N and P polarity are different. Statistical analysis, using a parametric functions technique in the framework of general linear analysis provided by the SAS procedures GLM and MIXED, revealed that the polarity of N compounds has been relatively stable over the years and can be related to differences in natural conditions between different parts of the lake. Our study indicates that Lake Peipsi is quite resistant to year-to-year changes in N load, and the in-lake N concentrations are quite stable on a long-term scale. In contrast, the increasing difference in P concentrations between the northern and southern parts of the lake clearly shows that the input of P from the south is increasing. Our results confirm that the anthropogenic input of P is the main reason for the deterioration of the Lake Peipsi ecosystem.     

濒危植物独花兰的形态变异及其适应意义

采用ANOVA和UPGMA等方法对濒危植物独花兰(Changnieniaamoena)分布于庐山、新宁和神农架3个地点的12个自然居群的形态变异进行了研究,探讨其形态多样性水平和地理变异式样及其可能的适应机制。结果表明,庐山居群13个性状的平均观测值均高于新宁和神农架居群。在物种水平上各个性状存在较丰富的变异,变异系数(CV值)为0.02–0.30。尽管同一性状在不同居群中的变异程度较大,但总体而言,花部器官的变异性比营养器官低。单因素方差分析显示3个地区间多个形态性状存在极显著差异(P<0.01);UPGMA聚类分析也表明这3个地区分别形成明显不同的分支。值得注意的是,神农架地区龙门河和关门山两个地点间存在明显的形态分化,而这种形态分化是以传粉者为媒介自然选择的结果。相关性分析显示,营养器官之间、花部器官之间,以及营养器官与花部器官之间均存在较高的相关性。上述结果对进一步了解独花兰的适应机制以及制定科学的保护策略提供了有益的资料。     

Platelet-activating factor metabolism in human amnion and the responses of this tissue to extracellular platelet-activating factor

It was found previously that platelet-activating factor (PAF, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is undetectable in human amniotic fluid obtained before labor but is present in the majority of samples of amniotic fluid obtained after labor. In the present investigation, the amount of PAF in amnion tissue and the ability of this tissue to produce PAF and respond to PAF were investigated. Amounts of PAF in amnion obtained either during the second trimester of gestation or at term (before labor) were similar. After labor, however, the amount of PAF in amnion increased to 2.5-times that in amnion before labor without any discernible changes in the amounts of two related glycerophospholipids viz., 1-0-alkyl-sn-glycero-3-phosphocholine and 1-0-alkyl-2-acyl-sn-glycero-3-phosphocholine. The Ca2+-ionophore A23187, in the presence of Ca2+, caused an increase in the amount of PAF in amnion tissue disks but PAF did not appear to be released into the incubation medium. The stimulation of PAF formation by A23187 and Ca2+ was not affected by the addition of indomethacin. Addition of PAF to disks of amnion tissue resulted in an increase in the concentration of prostaglandin E2 in the incubation medium. An increase in prostaglandin E2 formation of similar magnitude was induced by A23187. Based on these results it is concluded that PAF can be synthesized in amnion tissue and net production is stimulated by Ca2+. In addition, amnion is receptive to extracellular PAF and exhibits, as one response, an increased production of prostaglandin E2.