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41.
Agrobacterium and plant genetic engineering 总被引:27,自引:0,他引:27
Erratum
Agrobacterium and plant genetic engineering 相似文献42.
Knowiedge on community structure of North Sea meiofauna has greatly increased recently. A quasisynoptic picture of meiofauna
densities and copepod community structure from 171 stations of the southern North Sea, sampled in April–May 1986, has been
obtained during the North Sea Benthos Survey. Latitudinal patterns in meiofauna abundance and copepod weight, abundance and
diversity exist in an area between 51°30′N and 58°30′N. Using TWINSPAN-classification five major groups of copepod species
can be recognized which are related to sediment type, latitude and depth. The part of the meiofauna in total benthic energy
flow, their role in the benthic food web and in biogeochemical cycles is discussed based on existing literature. There are
still considerable gaps in knowledge and the field is not progressing rapidly.
Publication no. 599 Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands. 相似文献
43.
Dr. Martin P. Schreibman Ellen J. Berkowitz Rob van den Hurk 《Cell and tissue research》1982,224(1):81-87
Summary The gonads of 3-day- to 7-month-old male and female platyfish (Xiphophorus maculatus) were examined for the presence of 5-3-hydroxysteroid dehydrogenase (3-HSD) and glucose-6-phosphate dehydrogenase (G6PD) by histochemical means. In 3-day-old males a positive response for both enzymes is localized in the Leydig cells. With subsequent testicular development, these cells increase in number and display greater activity at the periphery of the testis and around the efferent ducts. In 3-day-old females 3-HSD and G6PD are localized in the stromal cells of the ovary. These cells increase in number and activity as the animals become sexually mature. Sertoli cells, efferent duct epithelium, and ovarian granulosa cells are negative at all stages of development examined. Our findings suggest that the gonads of neonatal fish possess the potential for steroidogenesis. The role played by sexsteroid hormones in the maturation of the brain-pituitary-gonad axis is discussed. 相似文献
44.
Shutoff on Neuroblastoma Cell Protein Synthesis by Semliki Forest Virus: Loss of Ability of Crude Initiation Factors to Recognize Early Semliki Forest Virus and Host mRNA's 下载免费PDF全文
Harry van Steeg Adri Thomas Sjef Verbeek Marcelle Kasperaitis Harry O. Voorma Rob Benne 《Journal of virology》1981,38(2):728-736
A crude ribosomal wash containing the initiation factors of protein synthesis was isolated from mouse neuroblastoma cells 8 h after infection with Semliki Forest virus (SFV). The activity of this wash was compared with that of a wash from control cells in a cell-free protein-synthesizing “pH5” system, with early SFV mRNA (42S), late SFV mRNA (26S), encephalomyocarditis virus (EMC) mRNA, or neuroblastoma polyadenylated mRNA templates. A pronounced loss of activity (±80%) of the crude ribosomal wash from infected cells was observed with host mRNA (neuroblastoma polyadenylated mRNA) and early SFV mRNA, messengers which contain a cap structure at the 5′ terminus. However, these washes were only slightly less active in systems programmed with (noncapped) EMC mRNA and late SFV mRNA. Although late SFV mRNA (26S) is capped, the synthesis of late (= structural) proteins in infected lysates was insensitive to inhibition by cap analogs. Purified initiation factors eIF-4B (Mr, 80,000) and cap-binding protein (Mr, 24,000) from reticulocytes (but none of the others) were able to restore the activity of infected factors to about 90% of control levels in systems programmed with early SFV mRNA and host mRNA. These observations indicate that infection-exposed crude initiation factors have a decreased level of eIF-4B and cap-binding protein activity. However, after partial purification of these and other initiation factors from infected and control cells, we found no significant difference in activity when model assay systems were used. Furthermore, both eIF-4B and cap-binding protein from infected cells were able to restore the activity of these infection-exposed factors to the same level obtained when these factors isolated from control cells or reticulocytes were added. A possible mechanism for the shutoff of host cell protein synthesis is discussed. 相似文献
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47.
Marcello De Vitis Fiona R. Hay John B. Dickie Clare Trivedi Jaeyong Choi Rob Fiegener 《Restoration Ecology》2020,28(Z3):S249-S255
Effective seed storage after sourcing (harvesting or purchasing) is critical to restoration practitioners and native seed producers, as it is key to maintaining seed viability. Inadequate seed storage can lead to a waste of both natural and economic resources when seeds of poor quality are sown. When working with native species with unknown storage behavior, general assumptions can be made based on studies on related species, and standard practices may be applied with caution; however, an investigation should be conducted to understand if specific storage requirements are needed and for how long seeds can be stored before they lose significant viability. In this paper of the Special Issue Standards for Native Seeds in Ecological Restoration, we provide an overview of the key concepts in seed storage and the steps to take for effective storage of native seeds for restoration use. 相似文献
48.
Theodorus J. Meuleman Vanessa M. Cowton Arvind H. Patel Rob M.J. Liskamp 《Journal of peptide science》2020,26(1)
In this research we describe the improvement of the water‐solubility of cyclic epitope mimics based on the HCV E2 glycoprotein by incorporation of suitable polar hinges. The poor solubility of epitope mimics based on peptide sequences in the envelope (E2) protein hampered their synthesis and purification and made it very difficult to prepare the molecular constructs for evaluation of their bioactivity. Since changes in the amino acid composition are hardly possible in these epitope mimics in order to increase water‐solubility, a polar cyclization hinge may offer a remedy leading to a significant increase of polarity and therefore water solubility. These polar hinges were applied in the synthesis of better water‐soluble HCV‐E2 epitopes. An azide functionality in the polar hinges allowed attachment of a tetraethylene glycol linker by Cu‐catalyzed azide‐alkyne cyclo‐addition (CuAAC) for a convenient conjugation to ELISA plates in order to evaluate the bio‐activity of the epitope mimics. The immunoassays showed that the use of more polar cyclization hinges still supported anti‐HCV antibody recognition and did not negatively influence their binding. This significantly increased solubility induced by polar hinges should therefore allow for the molecular construction and ultimate evaluation of synthetic vaccine molecules. 相似文献
49.
Aafke M. Schipper Jelle P. Hilbers Johan R. Meijer Laura H. Anto Ana Benítez‐Lpez Melinda M. J. de Jonge Luuk H. Leemans Eddy Scheper Rob Alkemade Jonathan C. Doelman Sido Mylius Elke Stehfest Detlef P. van Vuuren Willem‐Jan van Zeist Mark A. J. Huijbregts 《Global Change Biology》2020,26(2):760-771
Scenario‐based biodiversity modelling is a powerful approach to evaluate how possible future socio‐economic developments may affect biodiversity. Here, we evaluated the changes in terrestrial biodiversity intactness, expressed by the mean species abundance (MSA) metric, resulting from three of the shared socio‐economic pathways (SSPs) combined with different levels of climate change (according to representative concentration pathways [RCPs]): a future oriented towards sustainability (SSP1xRCP2.6), a future determined by a politically divided world (SSP3xRCP6.0) and a future with continued global dependency on fossil fuels (SSP5xRCP8.5). To this end, we first updated the GLOBIO model, which now runs at a spatial resolution of 10 arc‐seconds (~300 m), contains new modules for downscaling land use and for quantifying impacts of hunting in the tropics, and updated modules to quantify impacts of climate change, land use, habitat fragmentation and nitrogen pollution. We then used the updated model to project terrestrial biodiversity intactness from 2015 to 2050 as a function of land use and climate changes corresponding with the selected scenarios. We estimated a global area‐weighted mean MSA of 0.56 for 2015. Biodiversity intactness declined in all three scenarios, yet the decline was smaller in the sustainability scenario (?0.02) than the regional rivalry and fossil‐fuelled development scenarios (?0.06 and ?0.05 respectively). We further found considerable variation in projected biodiversity change among different world regions, with large future losses particularly for sub‐Saharan Africa. In some scenario‐region combinations, we projected future biodiversity recovery due to reduced demands for agricultural land, yet this recovery was counteracted by increased impacts of other pressures (notably climate change and road disturbance). Effective measures to halt or reverse the decline of terrestrial biodiversity should not only reduce land demand (e.g. by increasing agricultural productivity and dietary changes) but also focus on reducing or mitigating the impacts of other pressures. 相似文献
50.
The process of adaptation can be highly dependent upon historical and contemporary factors, especially in environmentally and topographically complex regions affected by Pleistocene glaciations. Here, we investigate Hilaria jamesii (Poaceae), a dryland C4 graminoid, to test how patterns of adaptive genetic variation are linked to its glacial and post-glacial history. We show that the species persisted in a single, southern refugium during the last glacial period and subsequently migrated throughout its current distribution concurrent with post-glacial warming. The species’ putative adaptive genetic variation correlates with climatic gradients (e.g. monsoon precipitation and mean diurnal temperature range) that covary with the species’ probable route of demographic expansion. The short timescale and multiple climatic dimensions of adaptation imply that natural selection acted primarily upon standing genetic variation. These findings suggest that restoration and conservation practices should prioritize the maintenance of standing genetic variation to ensure that species have the capacity to respond to future environmental changes. 相似文献