榛子种质资源、育种及栽培技术研究进展

榛子是一种重要的经济植物资源,其果实营养及经济价值高,是世界四大干果之一,市场需求量大,国内供不应求。本文综述了国内外榛子种质资源分布现状、引种、品种选育及栽培技术等方面的研究进展,简要评述了中国榛子种质资源利用与规模化种植中存在的问题,展望了相关研究的发展方向,以期为我国榛树良种选育、规范栽培技术及开发研究等提供参考。     

Evidence for ecological release over a fine spatial scale in a lizard from the White Sands formation

When a population experiences relaxation of selective pressures due to reduced predation or competition, it may undergo ecological release. Ecological release often manifests as increased niche breadth and trait variation, as individuals have the opportunity to exploit a wider variety of resources. At the recently‐colonized White Sands dune formation in New Mexico, lizards from white sand habitat have fewer predators and competitors than their dark soil counterparts, and show evidence of ecological release compared to dark soil lizards. To determine whether the dynamics of ecological release also play out over an even finer habitat gradient, we studied southwestern fence lizards in the center of the White Sands dune formation and the narrow ecotone between White Sands and the surrounding dark soil habitats. We predicted that lizards from the central dunes would exhibit ecological release in terms of broadened resource use compared to lizards from the ecotone. We first conducted avian surveys in both the central dunes and ecotone habitats to measure abundance, richness and diversity of avian species that could act as lizard predators. Next, we measured microhabitat‐scale resource use by comparing perch selection of lizards in both habitats. Finally, we measured landscape‐scale resource use by quantifying home range sizes and daily distances traveled by lizards in both habitats. We found that central dunes lizards used a greater diversity of perch types, and had greater variation in both home range size and daily distances traveled, than ecotone lizards. There were fewer predatory bird species in the central dunes than on the ecotone, and there was a tendency for fewer predation events in the central dunes than on the ecotone. Our results demonstrate that ecological release is detectable over a fine habitat gradient, such as between the center of a recently‐colonized habitat and its ecotone with the surrounding ecosystem.     

Market Incorporation, Agricultural Change, and Sustainability Among the Machiguenga Indians of the Peruvian Amazon

By marshaling empirical data from five Machiguenga communities studied over 20 years, this paper disputes two common assumptions about the behavior of indigenous peoples in the face of increasing commercialization. First, many Amazonian researchers suggest that the social and ecological deterioration confronting native populations results from externally-imposed political, legal and market structures that compel local groups to pursue short-term, unstable economic strategies. Second, these structural explanations are combined with the increasing recognition that indigenous peoples possess a substantial agroecological knowledge to suggest that, if indigenous people receive control of adequate land and resources, they will implement their traditional knowledge in conservative resource management practices. In contrast to these assumptions, this analysis shows that the Machiguenga are not compelled by external forces (such as land tenure, migration policies or economic trends), but instead are active enthusiastic participants seeking to engage the market in order to acquire western goods. Further, despite highly adaptive traditional subsistence patterns and a vast agroecological knowledge, households and communities facing increasing degrees of market integration are progressively altering their traditional cropping strategies, planting practices, labor allocation and land use patterns toward a greater emphasis on commodity crop production and domesticated animal breeding. This increasing concentration on income generating activities subverts the environmentally-friendly nature of traditional productive practices and creates a socially, economically, and ecologically unsustainable system.     

Oligonucleotides: Current Trends and Innovative Applications in the Synthesis,Characterization, and Purification

Oligonucleotides (ONs) are gaining increasing importance as a promising novel class of biopharmaceuticals. Thanks to their fundamental role in gene regulation, they can be used to develop custom‐made drugs (also called N‐to‐1) able to act on the gene expression at pre‐translational level. With recent approvals of ON‐based therapeutics by the Food and Drug Administration (FDA), a growing demand for high‐quality chemically modified ONs is emerging and their market is expected to impressively prosper in the near future. To satisfy this growing market demand, a scalable and economically sustainable ON production is needed. In this paper, the state of the art of the whole ON production process is illustrated with the aim of highlighting the most promising routes toward the auspicated market‐size production. In particular, the most recent advancements in both the upstream stage, mainly based on solid‐phase synthesis and recombinant technology, and the downstream one, focusing on chromatographic techniques, are reviewed. Since ON production is projected to expand to the large scale, automatized multicolumn countercurrent technologies will reasonably be required soon to replace the current ones based on batch single‐column operations. This consideration is supported by a recent cutting‐edge application of continuous chromatography for the ON purification.     

Relation between the O2 supply:demand ratio, MVO2, and adenosine formation in hearts stimulated with inotropic agents

Mooted controllers of adenosine formation in heart are the oxygen supply:demand ratio, myocardial oxygen consumption (MVO2), the cytosolic phosphorylation potential (log[ATP]/[ADP][Pi]). The relationship between these parameters and purine release (adenosine + inosine) into the venous effluent was examined in isovolumic rat hearts perfused at 20 and 12 mL.min-1.g-1 with a glucose containing crystalloid buffer and stimulated with inotropic agents (isoproterenol, norepinephrine, 3-isobutyl-1-methylxanthine, and ouabain). The oxygen supply:demand ratio and MVO2 were continuously determined using an oxygen electrode to monitor oxygen supply and consumption. The phosphorylation potential was calculated from phosphorus metabolite levels determined by 31P-NMR spectroscopy and HPLC analysis. Left ventricular function was assessed as the rate-pressure product. All inotropic agents increased the rate-pressure product, with increases in function being greater in the hearts perfused at 20 mL.min-1.g-1. MVO2 was linearly related to the rate-pressure product at each flow rate; however, the hearts perfused at 20 mL.min-1.g-1 exhibited approximately twofold greater MVO2 values for similar rate-pressure product values. All inotropic agents increased adenosine release into the venous effluent. While there was a significant linear relation between adenosine formation and MVO2 in hearts perfused at both flow rates and stimulated with drugs, the relations differed with adenosine release being approximately fourfold greater in hearts perfused at 12 mL.min-1.g-1 under similar conditions of MVO2. Adenosine formation correlated exponentially with the ratio of oxygen supply:demand under all conditions (r = 0.97) and the relation did not differ significantly between hearts perfused at different rates.(ABSTRACT TRUNCATED AT 250 WORDS)     

The ribosomal peptidyl transferase center: structure, function, evolution, inhibition

The ribosomal peptidyl transferase center (PTC) resides in the large ribosomal subunit and catalyzes the two principal chemical reactions of protein synthesis: peptide bond formation and peptide release. The catalytic mechanisms employed and their inhibition by antibiotics have been in the focus of molecular and structural biologists for decades. With the elucidation of atomic structures of the large ribosomal subunit at the dawn of the new millennium, these questions gained a new level of molecular significance. The crystallographic structures compellingly confirmed that peptidyl transferase is an RNA enzyme. This places the ribosome on the list of naturally occurring ribozymes that outlived the transition from the pre-biotic RNA World to contemporary biology. Biochemical, genetic and structural evidence highlight the role of the ribosome as an entropic catalyst that accelerates peptide bond formation primarily by substrate positioning. At the same time, peptide release should more strongly depend on chemical catalysis likely involving an rRNA group of the PTC. The PTC is characterized by the most pronounced accumulation of universally conserved rRNA nucleotides in the entire ribosome. Thus, it came as a surprise that recent findings revealed an unexpected high level of variation in the mode of antibiotic binding to the PTC of ribosomes from different organisms.     

Micro-economics based resource allocation in Grid-Federation environment

A Grid-Federation environment is composed of a collection of autonomous and selfish distributed cluster resource managers. These selfish managers participate in Grid-Federation to share their resources. Market models could be used to motivate the self-interested participants to share their resources. In this paper, firstly, a market for resource exchange in grid federation environment is established. Then, in order that the market reaches a Walrasian equilibrium, a computationally tractable mechanism is proposed. A Walrasian equilibrium problem consists of finding a set of prices and allocations of resources in such a way that the cluster resource managers could maximize their utilities and the market clears. Market clears when the resource supply equals to the demand. We show that in a Walrasian equilibrium, the Grid Federation market reaches an efficient resource allocation.     

Offspring dynamics affect food provisioning,growth and mortality in a brood-caring spider

In brood-caring species, family members are faced with a conflict over resource distribution. While parents are selected to adapt the amount of care according to their offspring''s needs, offspring might be selected to demand more care than optimal for parents. Recent studies on birds have shown that the social network structure of offspring affects the amount of care and thus the fitness of families. Such a network structure of repeated interactions is probably influenced by within-brood relatedness. We experimentally manipulated the group composition in a brood-caring spider to test how the presence of unrelated spiderlings affects the dynamics between female and brood as well as within broods. Broods consisting of siblings grew better and had a lower mortality compared with mixed broods, no matter whether the caring female was a genetic or foster mother. Interestingly, we found that foster mothers lost weight when caring for sibling broods, whereas females caring for mixed broods gained weight. This indicates that females may be willing to share more prey when the brood contains exclusively siblings even if the entire brood is unrelated to the female. Resource distribution may thus be negotiated by offspring dynamics that could have a signalling function to females.     

Centralization,resource depletion,and coercive conservation among the Tyua of the Northeastern Kalahari

The colonial and post-colonial governments of Botswana and Zimbabwe pursued policies toward their indigenous minority populations which included the establishment of settlement schemes, removals of people from national parks and game reserves, and the imposition of restrictions on hunting by local people. These polices had the effect of dispossessing indigenous groups and reducing their access to resources crucial to their adaptive success. The impacts of these polices are examined using data on Tyua Bushmen in the Nata river region of northern Botswana and western Zimbabwe. It demonstrates that the kinds of conservation and development programs employed resulted in greater resource depletion, increased poverty, and social stratification. There is evidence that resource conservation programs can sometimes do more harm than good.     

Disruptive selection in a bimodal population of Darwin's finches

A key part of the ecological theory of adaptive radiation is disruptive selection during periods of sympatry. Some insight into this process might be gained by studying populations that are bimodal for dual-context traits, i.e. those showing adaptive divergence and also contributing to reproductive isolation. A population meeting these criteria is the medium ground finch (Geospiza fortis) of El Garrapatero, Santa Cruz Island, Galápagos. We examined patterns of selection in this population by relating individual beak sizes to interannual recaptures during a prolonged drought. Supporting the theory, disruptive selection was strong between the two beak size modes. We also found some evidence of selection against individuals with the largest and smallest beak sizes, perhaps owing to competition with other species or to gaps in the underlying resource distribution. Selection may thus simultaneously maintain the current bimodality while also constraining further divergence. Spatial and temporal variation in G. fortis bimodality suggests a dynamic tug of war among factors such as selection and assortative mating, which may alternatively promote or constrain divergence during adaptive radiation.     

Hypoxia alters the release and size distribution of extracellular vesicles in pancreatic cancer cells to support their adaptive survival

Pancreatic tumors are highly desmoplastic and poorly-vascularized, and therefore must develop adaptive mechanisms to sustain their survival under hypoxic condition. Extracellular vesicles (EV) play vital roles in pancreatic tumor pathobiology by facilitating intercellular communication. Here we studied the effect of hypoxia on the release of EVs and examined their role in adaptive survival of pancreatic cancer (PC) cells. Hypoxia promoted the release of EV in PC cell lines, MiaPaCa and AsPC1, wherein former exhibited a far greater induction. Moreover, a time-dependent, measurable and significant increase was recorded for small EV (SEV) in both the cell lines with only minimal induction observed for medium (MEV) and large EVs (LEV). Similarly, noticeable changes in size distribution of SEV were also recorded with a shift toward smaller average size under extreme hypoxia. Thrombospondin (apoptotic bodies marker) was exclusively detected on LEVs, while Arf6 (microvesicles marker) was mostly present on MEV with some expression in LEV as well. However, CD9 and CD63 (exosome markers) were expressed in both SEV and MEVs with a decreased expression recorded under hypoxia. Among all subfractions, SEV was the most bioactive in promoting the survival of hypoxic PC cells and hypoxia-inducible factor-1α stabilization was involved in heightened EV release under hypoxia and for their potency to promote hypoxic cell survival. Altogether, our findings provide a novel mechanism for the adaptive hypoxic survival of PC cells and should serve as the basis for future investigations on broader functional implications of EV.     

Centripetal myosin redistribution in thrombin-stimulated platelets. Relationship to platelet Factor 4 secretion

We have examined the F-actin and myosin distribution in resting and thrombin-activated platelets by double label immunofluorescence microscopy. In resting, discoid platelets, F-actin and myosin staining was distributed in a diffuse pattern throughout the interior of the cell with slight accentuation at the cell periphery. In contrast, platelet factor 4 antigen (PF4) was more centrally localized in a fine punctate distribution which is consistent with its localization in alpha-granules. Within 5 sec after thrombin stimulation both F-actin and myosin staining were increased at the periphery of the now spherical platelets. Subsequently, a myosin-containing spherical structure decreased in diameter closely surrounding a phase-dense central zone. In contrast, F-actin staining continued to be accentuated at the cell periphery and was prominent in filopodia and blebs. As previously shown, PF4 staining was localized after 30 sec within large intracellular masses that corresponded to closed vacuolar structures at the ultrastructural level. Morphometric analysis of electron micrographs showed that formation of these vacuolar structures kinetically paralleled alpha-granule disappearance and preceded PF4 release. These PF4-containing structures translocated to the cell periphery after 1-3 min, where they appeared to fuse with the plasma membrane. Ultrastructural analysis of thin sections showed that the myosin-rich spherical structure spatially and temporally correlated with a band of microfilaments that closely surrounded the organelle-rich central zone of the cell. Morphometric analysis of these micrographs showed that the absolute volume of this central zone decreased with time after thrombin addition, showing a significant change after 15 sec and reaching a maximum value after 3-5 min. Changes in the volume of this compartment kinetically preceded PF4 release. On the basis of these data, we propose that an actomyosin contractile force is generated which centripetally redistributes the myosinrich structure and organelle zone. Conceivably this inward force may not only accelerate granule-granule fusion to form intracellular secretory vacuoles, but may also provide aid in their extrusion toward the platelet plasma membrane.     

The Ribosomal Peptidyl Transferase Center: Structure,Function, Evolution,Inhibition

ABSTRACT

The ribosomal peptidyl transferase center (PTC) resides in the large ribosomal subunit and catalyzes the two principal chemical reactions of protein synthesis: peptide bond formation and peptide release. The catalytic mechanisms employed and their inhibition by antibiotics have been in the focus of molecular and structural biologists for decades. With the elucidation of atomic structures of the large ribosomal subunit at the dawn of the new millennium, these questions gained a new level of molecular significance. The crystallographic structures compellingly confirmed that peptidyl transferase is an RNA enzyme. This places the ribosome on the list of naturally occurring riboyzmes that outlived the transition from the pre-biotic RNA World to contemporary biology. Biochemical, genetic and structural evidence highlight the role of the ribosome as an entropic catalyst that accelerates peptide bond formation primarily by substrate positioning. At the same time, peptide release should more strongly depend on chemical catalysis likely involving an rRNA group of the PTC. The PTC is characterized by the most pronounced accumulation of universally conserved rRNA nucleotides in the entire ribosome. Thus, it came as a surprise that recent findings revealed an unexpected high level of variation in the mode of antibiotic binding to the PTC of ribosomes from different organisms.     

Biogeographic, environmental, and phylogenetic influences on reproductive traits in subtropical forest trees, South Africa

The distribution of subtropical forests in South Africa is largely a consequence of climatic change during the Quaternary period. We gathered data for 195 canopy tree species from Afrotemperate, scarp, and coastal forests in KwaZulu-Natal, South Africa and assessed patterns in reproductive traits using a comparative phylogenetic approach. The overlap in species composition among the forest types reflected the geographic position and colonisation history of the forests. Despite a high degree of phylogenetic conservatism in reproductive traits, there were differences in their expression among forest types. Afrotemperate forests had a higher incidence of wind pollination, consistent with the steep topography, seasonally dry environment, and limited resource availability in the habitat. Scarp forests had more dry brown fruits with abiotic (explosive and wind) dispersal. Coastal forests had the most species with fleshy fruits, zoochory, and large seeds, all traits that may have facilitated the colonisation or persistence of species in this more recent and dynamic community. Since many suites of traits occur together in diverse phylogenetic lines, they represent adaptive complexes that are influenced by biogeography and environmental conditions. Overall, this study demonstrates that biogeography, environmental factors, and phylogenetic history all influence the distribution of reproductive traits in these forest communities.     

Discrete consumers,small scale resource heterogeneity,and population stability

We present a consumer-resource model in which individual consumers subsist on a continuum of resource distributed over a very large number of small “bite-sized” patches, each patch being sufficiently small that all its resource is eaten whenever a consumer visits. This form of consumer–resource interaction forces a heterogeneous distribution of resource among the patches, and may dampen out the large amplitude, consumer-resource cycles that are predicted by traditional models of well-mixed, spatially homogeneous systems. The resource equilibrium does not increase with enrichment, a prediction that distinguishes this model from models that invoke direct or indirect consumer density dependence as a stabilizing mechanism.     

A model for resource management in computational grid using sequential auction and bargaining procurement

Resources in a computational grid system fall under the purview of different administrative domains of varying policies for their usages. Commercial grid offers their services (resources) on use-and-pay basis. Resource management in computational grid, offers a market place for the two prominent grid market players i.e. resource provider and resource consumer. It has been observed that, in the grid, the request for the resources may not be uniform throughout. It fluctuates from very high demand at peak time to low or negligible at off-peak time. This information may be used to fetch the resource utilization and cost benefits out of the grid. The provider would prefer to charge extra for its resources at peak time, whereas users may shift their resources usage preference to off-peak time. This work proposes a model in which the resource provider and consumer play a non-cooperative game at different time-zones and act independently to choose their actions. Some characteristic parameters such as cost, execution time and reliability have been considered to facilitate the job execution. Based on the outcome of the game, the grid cluster offering maximum reliability within the desired execution time and/or cost for the job execution. The model has been simulated for performance evaluation with quite encouraging results.     

Inhibition of a mitotic motor protein: where, how, and conformational consequences

We report here the first inhibitor-bound structure of a mitotic motor protein. The 1.9 A resolution structure of the motor domain of KSP, bound with the small molecule monastrol and Mg2+ x ADP, reveals that monastrol confers inhibition by "induced-fitting" onto the protein some 12 A away from the catalytic center of the enzyme, resulting in the creation of a previously non-existing binding pocket. The structure provides new insights into the biochemical and mechanical mechanisms of the mitotic motor domain. Inhibition of KSP provides a novel mechanism to arrest mitotic spindle formation, a target of several approved and investigative anti-cancer agents. The structural information gleaned from this novel pocket offers a new angle for the design of anti-mitotic agents.     

Adaptive and non‐adaptive evolution of trait means and genetic trait correlations for herbivory resistance and performance in an invasive plant

The EICA‐hypothesis predicts that invading plants adapt to their novel environment by evolving increased performance and reduced resistance in response to the release from natural enemies, and assumes a resource allocation tradeoff among both trait groups as mechanistic basis of this evolutionary change. Using the plant Silene latifolia as a study system, we tested these predictions by investigating whether 1) invasive populations evolved lower resistance and higher performance, 2) this evolutionary change is indeed adaptive, and 3) there is a negative genetic correlation between performance and resistance (i.e. a tradeoff) in native and introduced individuals. Moreover, we sampled eight native and eight invasive populations and determined their population co‐ancestry based on neutral SSR‐markers. We performed controlled crossings to produce five sib‐groups per population and exposed them to increased and reduced levels of enemy attack in a full‐factorial experiment to estimate performance and resistance. With these data, we performed trait‐by‐trait comparisons between ranges with ‘animal models’ that account for population co‐ancestry to quantify the amount of variance in traits explained by non‐adaptive versus adaptive evolution. Moreover, we tested for genetic correlations among performance and resistance traits within sib‐groups. We found significant reductions in resistance and increases in performance in invasive versus native populations, which could largely be attributed to adaptive evolution. While we detected a non‐significant trend towards negative genetic performance × resistance correlations in native populations, invasive populations exhibited both significant and non‐significant positive correlations. In summary, these results do not support a shift of performance and resistance trait values along a tradeoff line in response to enemy release, as predicted by EICA. They rather suggest that the independent evolution of both traits is not constrained by a tradeoff, and that various selective agents (including resource availability) interact in shaping both traits and in weakening negative genetic correlations in the invaded habitat.     

Solventless photocurable film coating: Evaluation of drug release,mechanical strength,and photostability

A new solventless photocurable film-coating system was investigated in which nonpareil beads were coated in a minicoating pan with liquid prepolymer (L) and powdered solid pore-forming agents (S) and cured by UV light. Release from the coating could by altered by changing the material, the number of layers, and the coating thickness. Immediate release of a blue dye contained in the nonpareils was obtained with sodium starch glycolate as a pore former that swelled the coating and yielded large pores; through these pores the dye quickly released while leaving behind the scaffold provided by the photocured prepolymer. Simple pore formers (lactose and sodium chloride) dissolved away without swelling and provided a more sustained release. The nature of the scaffold and pore structure of the coating were determined by simultaneously monitoring the release of sodium chloride from the coating and blue dye from the beads. At least 50% of the sodium chloride that was incorporated into the coating released before the dye released through the coating, except at an S/L ratio (ratio of the amount of solid pore-forming agent to the volume of liquid prepolymer) of 2.4, where 40% of the sodium chloride was released before the release of dye. The coupling between dye release and pore formation was found to be dependent on the S/L ratio of the coating. Simulation based on percolation theory showed that the coupling of pore formation and dye release was higher when the variance in tortuosity was lower. The coating was photostable and could withstand normal handling stress. Published: July 13, 2007