太湖湖滨生态修复区大型底栖动物群落结构及梯度分布

2010—2011年对太湖贡湖湾湖滨带生态修复区滨岸挺水植物带(Ⅰ)、湾相沉水植物带(Ⅱ)和堰外开敞水体(Ⅲ)3个滨岸生境梯度带的水质状况和底栖动物群落特征进行了研究。结果表明:调查共发现底栖动物13科18种,其中仅出现于1个生境梯度带的物种7个;在其余的11个物种中,有5个种群的密度在生境梯度带间存在显著差异;比较发现,按底栖动物摄食功能类群的相对比例,刮食者相对丰度在带Ⅰ最高,收集者在带Ⅱ最高,滤食者在带Ⅲ最高,不同生境梯度带间底栖动物的摄食功能类群构成存在显著差异。对底栖动物相对丰度和水环境参数的冗余分析显示,环节动物和昆虫与DO、NO3--N和PO43--P浓度正相关,软体动物则与NO3--N和PO43--P负相关,一些腹足类对低DO耐受能力较强,与NH4+-N和COD正相关。修复区3个梯度带水动力条件、水质状况和底质类型的差异性对底栖动物的分布有重要影响,形成了生活习性、摄食特征等显著不同的3个底栖动物群落。     

Hybrid Oligomer of Cyclonucleotides and Deoxynucleotides. A High Anti Left-handed Double Helical DNA Structure

Abstract

It has been shown by us that oligonucleotides containing cyclonucleosides with a high anti glycosidic conformation take left-handed, single and double helical structures (S. Uesugi, J. Yano, E. Yano and M. Ikehara, J. Am. Chem. Soc. 99, 2313 (1977) and references therein). In order to see whether DNA can adopt the high anti left-handed double helical structure or not, a self-complementary hexanucleotide containing 6,2′-O-cyclocytidine (C^○), 8,2′-O-cyclo- guanosine (G^○), deoxycytidine and deoxyguanosine, C^○G^{○dCdGC ○}G^○, was synthesized. Corresponding hexanucleotide containing only cyclonucleosides, C^○G^○C^○G^○C^○G^○, was also synthesized. Their conformation was examined by UV, CD and ¹H NMR spectroscopy. C^○G^○C^○G^○C^○G^○ forms an unusually stable, left-handed duplex. Imino proton NMR spectra and the results of nuclear Overhauser effect experiments strongly suggest that C^○G^○dCdGC^○G^○ take a left-handed double helical structure where the deoxynucleoside residues are involved in hydrogen bonding and take a high anti glycosidic conformation. Thus it is revealed that DNA could form a high anti, left-handed double helix which is different from that of Z-DNA under some constrained conditions.     

Cationic interactions with Na+-H+ exchange and passive Na+ flux in cardiac sarcolemmal vesicles

Na⁺-H⁺ exchange and passive Na⁺ flux were investigated in cardiac sarcolemmal vesicles as a function of changing the ionic composition of the reaction media. The inclusion of EGTA in the reaction medium resulted in a potent stumulation of Na⁺ uptake by Na⁺-H⁺ exchange. It was found that millimolar concentrations of Mg²⁺ and Li⁺ were capable of inhibiting Na⁺-H⁺ exchange by 80%. One mechanism by which these ions may inhibit intravesicular Na⁺ accumulation by Na⁺-H⁺ exchange is via an increase in Na⁺ efflux. An examination of Na⁺ efflux kinetics from vesicles pre-loaded with Na⁺ revealed that Na⁺, Ca²⁺, Mg²⁺ and Li⁺ could stimulate Na⁺ efflux. Na⁺-H⁺ exchange was potently inhibited by an organic divalent cation, dimenthonium, which screens membrane surface charge. This would suggest that Na⁺-H⁺ exchange occurs in the diffuse double layer region of cardiac sarcolemma and this phenomenon is distinctly different from other Na⁺ transport processes. The results in this study indicate that in addition to a stimulation of Na⁺ efflux, the inhibitory effects of Mg²⁺, Ca²⁺ and Li⁺ on Na⁺-H⁺ exchange may also involve a charge dependent screening of Na⁺ interactions with the membrane.     

Biology, herbivory, and host specificity of Antiblemma leucocyma (Lepidoptera: Noctuidae) on Miconia calvescens DC. (Melastomataceae) in Brazil

Miconia calvescens DC. (Melastomataceae) is an invasive tree considered one of the greatest threats to natural ecosystems of Hawaii and other Pacific islands. The potential for using the defoliator Antiblemma leucocyma (Lepidoptera: Noctuidae) as a biological control agent of M. calvescens was evaluated in the native habitat of the insect in Brazil. Impact assessment in the field showed that 37.2% of leaves presented damage by A. leucocyma, and among damaged leaves, 1.5-51.9% of the leaf area (16.3% on average) was affected. Damage was found in young to fully expanded leaves (28-915 cm² in area). Individual A. leucocyma developing as third through sixth instars in the laboratory consumed an average of 1348 cm² of M. calvescens leaf material in about 11 days. Populations of A. leucocyma in the field were heavily impacted (up to 83% parasitism) by a braconid parasitoid. Observations in the field and single- and two-host choice tests in the laboratory indicated that A. leucocyma has a narrow host range restricted to M. calvescens. Usefulness of this herbivore for biological control in Hawaii appears low, however, because of its probable susceptibility to generalist parasitoids.     

东北山地灌木沼泽植物铜、锌分布特征及季节动态

研究了东北山地灌木沼泽主要植物--细叶沼柳、五蕊柳、丛苔草和修氏苔草中Cu、Zn分布、积累及其季节动态.结果表明:Cu含量变动范围为6～12 mg·kg-1,细叶沼柳和五蕊柳各器官Cu含量为根》枝》叶;丛苔草和修氏苔草为茎》叶》根,Cu主要积累在灌木的根系和苔草的茎叶中,灌木和苔草中Cu含量相差较小.Zn含量变动在30～250 mg·kg-1之间,细叶沼柳和五蕊柳各器官Zn含量为叶》枝》根,尤其是叶和枝中都在150 mg·kg-1以上;丛苔草和修氏苔草各器官Zn含量为根》茎》叶.Zn多积累在灌木的叶和苔草的根中,且灌木各器官Zn含量明显高于苔草.细叶沼柳和五蕊柳各器官对Zn的富集系数均大于1.45,显示出较强的Zn富集能力.4种供试植物在生长初期地上部分Cu、Zn含量较高,且随着季节变化呈波动式降低趋势,而根中则表现出生长初期和末期Cu、Zn含量较高的特点.     

Leaf trait variation captures climate differences but differs with species irrespective of functional group

Aims To clarify whether variation in leaf traits with climate differs with scale, i.e. across species and within a species, and to detect whether plant functional group affects species-specific response.Methods Leaf dry matter content (LDMC), specific leaf area (SLA), mass- and area-based leaf N (N mass, N area) and leaf P concentrations (P mass, P area) and leaf chlorophyll concentration (SPAD) were measured for 92 woody plant species in two botanical gardens in China. The two gardens share plant species in common but differ in climate. Leaf trait variation between the two gardens was examined via mean comparison at three scales: all species together, species grouped into plant functional groups and within a species. A meta-analysis was performed to summarize the species-specific responses.Important findings At the scale of all species together, LDMC, SLA, P mass and N mass were significantly lower in the dry-cold habitat than in the wet-warm one, whereas N area and SPAD showed an inverse pattern, indicating a significant environmental effect. The meta-analysis showed that the above-mentioned patterns persisted for SLA, N area and SPAD but not for the other variables at the species-specific scale, indicating that intraspecific variation affects the overall pattern of LDMC, P mass and N mass and P area. In terms of species-specific response, positive, negative or nonsignificant patterns were observed among the 92 species. Contrary to our prediction, species-specific responses within a functional group were not statistically more similar than those among functional groups. Our results indicated that leaf trait variation captured climatic difference yet species-specific responses were quite diverse irrespective of plant functional group, providing new insights for interpreting trait variability with climate.     

热带季节雨林林窗边缘不同热力作用面热力效应的季节变化特征

通过对热带季节雨林雾凉季和湿热季昼间林窗区域不同热力作用面的热力效应初步分析,指出在西双版纳,不论是雾凉季还是湿热季,热带季节雨林林窗边缘壁面均具有不可忽视的热力作用,且由于受林缘树木的影响,热力效应较强的东侧,北侧林缘壁面最大区域出现位置高于次生林林窗,而强度小于次生林林窗,显示了林窗边缘壁面的热力效应除与太阳高度角,太阳辐射的时间长短和强度有关之外,林窗边缘树木高度也是不可忽视的因子,其结果可为进一步研究林窗小气候形成机制提供研究基础,为研究林窗更新及生物多样性问题提供科学参考。     

Auricular surface aging: Worse than expected? A test of the revised method on a documented historic skeletal assemblage

This study presents results and recommendations arising from a blind test of the revised age estimation method for the auricular surface as proposed by Buckberry and Chamberlain ([2002] Am. J. Phys. Anthropol. 119:321-329). Auricular surfaces of 167 individuals from St. Bride's, London, a documented skeletal assemblage spanning the late 17th to early 19th century, were analyzed for the following traits: transverse organization, surface texture appearance, macroporosity, microporosity, and morphological changes to the apex. Composite scores of trait expressions were found to generally correlate with age and to show a positive association with known chronological age (P < 0.01). However, when composite scores were combined to define auricular surface phases, which ultimately assign age estimations, only three distinct developmental stages, compared with seven suggested by Buckberry and Chamberlain ([2002] Am. J. Phys. Anthropol. 119:321-329), could be identified and statistically supported, all showing a considerable degree of individual variation in age. The most well-defined stage in the St. Bride's assemblage was the new stage III, where the majority of individuals were older than 60 years, whereas middle-aged adults displayed a large variation in composite scores. These results provide little hope for a promising application of age-at-death estimation of auricular surface morphology traits with higher resolution, but rather suggest indications of broad stages of life.     

Directed movements of ciliary and flagellar membrane components: a review.

The ability to rapidly translocate polystyrene microspheres attached to the surface of a plasma membrane domain reflects a unique form of cellular force transduction occurring in association with the plasma membrane of microtubule based cell extensions. This unusual form of cell motility can be utilized by protistan organisms for whole cell locomotion, the early events in mating, and transport of food organisms along the cell surface, and possibly intracellular transport of certain organelles. Since surface motility is observed in association with cilia and flagella of algae, sea urchin embryos and cultured mammalian cells, it is likely that it serves an additional role beyond those already cited; this is likely to be the transport of precursors for the assembly and turnover of ciliary and flagellar membranes and axonemes. In the case of the Chlamydomonas flagellum, where surface motility has been most extensively studied, it appears that cross-linking of flagellar surface exposed proteins induces a transmembrane signaling pathway that activates machinery for moving flagellar membrane proteins in the plane of the flagellar membrane. This signaling pathway in vegetative Chlamydomonas reinhardtii appears to involve an influx of calcium, a rise in intraflagellar free calcium concentration and a change in the level of phosphorylation of specific membrane-matrix proteins. It is hypothesized that flagellar surface contact with a solid substrate (during gliding), a polystyrene microsphere or another flagellum (during mating) will all activate a signaling pathway similar to the one artificially activated by the use of monoclonal antibodies to flagellar membrane glycoproteins. A somewhat different signaling pathway, involving a transient rise in intracellular cAMP level, may be associated with the mating of Chlamydomonas gametes, which is initiated by flagellum-flagellum contact. The hypothesis that the widespread observation of microsphere movements on various ciliary and flagellar surfaces may reflect a mechanism normally utilized to transport axonemal and membrane subunits along the internal surface of the organelle membrane presents a paradox in that one would expect this to be a constitutive mechanism, not one necessarily activated by a signaling pathway.     

Structure and Disorder in an Unfolded State under Nondenaturing Conditions from Ensemble Models Consistent with a Large Number of Experimental Restraints

Obtaining detailed structural models of disordered states of proteins under nondenaturing conditions is important for a better understanding of both functional intrinsically disordered proteins and unfolded states of folded proteins. Extensive experimental characterization of the drk N-terminal SH3 domain unfolded state has shown that, although it appears to be highly disordered, it possesses significant nonrandom secondary and tertiary structure. In our previous attempts to generate structural models of the unfolded state using the program ENSEMBLE, we were limited by insufficient experimental restraints and conformational sampling. In this study, we have vastly expanded our experimental restraint set to include ¹H-¹⁵N residual dipolar couplings, small-angle X-ray scattering measurements, nitroxide paramagnetic relaxation enhancements, O₂-induced ¹³C paramagnetic shifts, hydrogen-exchange protection factors, and ¹⁵N R₂ data, in addition to the previously used nuclear Overhauser effects, amino terminal Cu²⁺-Ni²⁺ binding paramagnetic relaxation enhancements, J-couplings, chemical shifts, hydrodynamic radius, and solvent accessibility restraints. We have also implemented a new ensemble calculation methodology that uses iterative conformational sampling and seeks to calculate the simplest possible ensemble models. As a result, we can now generate ensembles that are consistent with much larger experimental data sets than was previously possible. Although highly heterogeneous and having broad molecular size distributions, the calculated drk N-terminal SH3 domain unfolded-state ensembles have very different properties than expected for random or statistical coils and possess significant nonnative α-helical structure and both native-like and nonnative tertiary structure.