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排序方式: 共有151条查询结果,搜索用时 15 毫秒
91.
The evolution of resistance to plant protection products (PPPs) is an increasing management challenge that relates to both an increasing number of species and a limited number of active substances. The number of available active substances (a.s.) has decreased considerably over the past two decades, increasing the gravity of the resistance problem. Managing the threat of resistance is based on a reasoned choice of a.s., their sequence and combination. No quantitative information is available on how many different PPPs are needed for a sustainable control system of a given pest. This paper provides a first expert judgement‐based attempt at estimating the number of different a.s. necessary for sustainable control of a pest in which the evolution of resistance is prevented. 相似文献
92.
Schulz HN Brinkhoff T Ferdelman TG Mariné MH Teske A Jorgensen BB 《Science (New York, N.Y.)》1999,284(5413):493-495
A previously unknown giant sulfur bacterium is abundant in sediments underlying the oxygen minimum zone of the Benguela Current upwelling system. The bacterium has a spherical cell that exceeds by up to 100-fold the biovolume of the largest known prokaryotes. On the basis of 16S ribosomal DNA sequence data, these bacteria are closely related to the marine filamentous sulfur bacteria Thioploca, abundant in the upwelling area off Chile and Peru. Similar to Thioploca, the giant bacteria oxidize sulfide with nitrate that is accumulated to =800 millimolar in a central vacuole. 相似文献
93.
Lynch-Stieglitz J Adkins JF Curry WB Dokken T Hall IR Herguera JC Hirschi JJ Ivanova EV Kissel C Marchal O Marchitto TM McCave IN McManus JF Mulitza S Ninnemann U Peeters F Yu EF Zahn R 《Science (New York, N.Y.)》2007,316(5821):66-69
The circulation of the deep Atlantic Ocean during the height of the last ice age appears to have been quite different from today. We review observations implying that Atlantic meridional overturning circulation during the Last Glacial Maximum was neither extremely sluggish nor an enhanced version of present-day circulation. The distribution of the decay products of uranium in sediments is consistent with a residence time for deep waters in the Atlantic only slightly greater than today. However, evidence from multiple water-mass tracers supports a different distribution of deep-water properties, including density, which is dynamically linked to circulation. 相似文献
94.
Liver is the main catabolic tissue for low density lipoprotein in rainbow trout (Gjøen and Berg 1992). We have investigated the interaction of LDL with isolated trout liver cells and liver membranes. 125I-TC labelled trout LDL bound to isolated trout liver cells in a time dependent and saturable manner with an apparant Kd of 20.1 g/ml, suggesting the existence of a specific binding site on the surface of these cells. The binding was Ca2+ dependent assessed by the 50% reduction obtained by 5 mM EDTA. Saturable binding to isolated trout liver membranes could also be demonstrated, but with lower affinity as compared to intact cells. Degradation of 125I-TC-LDL in hepatocytes was also saturable as degradation could be inhibited about 60% by a 100 fold surplus of unlabelled LDL. The rate of degradation increased with temperature up to 20°C. Both cell association (binding + uptake) and degradation were reduced down to 20% of control in the presence of microtubular and lysosomal inhibitors. Hepatic catabolism of trout LDL therefore seems to depend on receptormediated endocytosis, followed by lysosomal degradation.Abbreviations TC
tyramine cellobiose
- LDL
low density lipoproteins
- MeLDL
methylated low density lipoproteins
- VLDL
very low density lipoproteins
- HDL
high density lipoproteins
- VTG
vitellogenin
- EDTA
ethylenediamine tetraacetic acid
- PBS
phospate buffered saline
- SDS-PAGE
sodium dodecyl sulphatepolyacrylamide gel electrophoresis
- DMPC
L--phosphatidylcholine-dimyristoyl 相似文献
95.
Camilla Røsjø Trond Berg Ketil Manum Tor Gjøen Sigurdur Magnusson Magny S. Thomassen 《Fish physiology and biochemistry》1994,13(2):119-132
Effects of different incubation temperatures (2, 8, 14 and 20°C) and hepatocyte membrane fatty acid composition on the rate
of internalization and lysosomal degradation of the ligand, mannosylated albumin, that is taken up by receptor-mediated endocytosis,
were investigated in rainbow trout (Oncorhynchus mykiss, Walbaum). The fish were kept at a water temperature ranging from 9 to 14°C and fed pelleted diets coated with either capelin
oil (control), EPA/DHA-concentrate (rich in n-3 polyunsaturated fatty acids) or soybean oil (rich in n-6 unsaturated fatty
acids) for at least 3 months prior to sampling. The endocytic uptake mediated by the mannose receptor was very efficient at
all temperatures studied. Lysosomal degradation, on the other hand, came to a halt below 8°C. The activation energies for
uptake and degradation were 54.6 and 164.2 kJ/mol respectively. No negative effects of increased amounts of either n-3 or
n-6 fatty acids were observed on the endocytic parameters studied. On the contrary, multivariate analysis indicated a positive
relationship between high levels of n-6 fatty acids and low unsaturation index in the phosphatidylcholine (PC) fraction of
the hepatocytes and the internalization rate of 2°C, meaning that the rate of receptor-mediated endocytosis may be affected
by membrane fatty acid composition. 相似文献
96.
Lars Olav Brandsæter Kjell Mangerud Lars Andersson Trond Børresen Guro Brodal Bo Melander 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2020,70(4):318-332
ABSTRACTThere is a need both in organic farming and on farms using integrated pest management for non-chemical measures that control the perennial weed flora. The effect of mechanical weeding and fertilisation on perennial weeds, fungal diseases and soil structure were evaluated in two different experiments in spring cereals. Experiment I included six strategies. The first strategy was (1) without specific measures against perennial weeds. The other strategies encompassed one or two seasonal control measures; (2) rhizome/root cutting with minimal soil disturbance in autumn, (3) hoeing with 24?cm row spacing, (4) combined hoeing and disc harrowing in autumn, (5) ‘KvikUp’ harrowing in spring, and (6) ‘KvikUp’ harrowing in spring and autumn. Experiment II included factor (i) inter-row hoeing and (ii) fertilisation level. This experiment included the comparison between normal row spacing (12?cm) with weed harrowing versus double row spacing (=24?cm) in combination with inter-row hoeing and 4 fertilisation levels (50–200?kg N ha?1). In experiment I the strategies consisting of no or one direct weed control measure (1, 2, 3 and 5) clearly did not control the perennial weeds. The two seasonal control measures (4 and 6) gave a satisfactory weed control and highest crop yield. The combination of best weed control and no measured harmful effects on soil structure or increase of fungal diseases may explain the highest yields for these strategies. In Experiment II, hoeing and 24?cm spacing gave less perennial biomass compared to 12?cm spacing. Grain yields increased linearly with increasing nitrogen input. The study shows that both inter-row hoeing and weed harrows, are important elements in integrated pest management practice and organic farming. In addition, our results indicate that efficient mechanical weeding is possible without harmful effects in crop rotation consisting of various spring cereals as regards soil structure and plant health. 相似文献
97.
Proanthocyanidin isolates from grape (Vitis vinifera L. cv. Pinot noir) skin and seed underwent oxidative degradation in solution (10 g/L) under basic conditions while exposed to atmospheric oxygen. Degradation was monitored by reversed-phase HPLC following acid-catalyzed cleavage in the presence of excess phloroglucinol (phloroglucinolysis) and by high-performance gel permeation chromatography. All isolates degraded under these conditions and followed second-order kinetics for over 1 half-life, consistent with an oxidation reaction. The conversion of proanthocyanidins to known subunits (conversion yield) when measured by phloroglucinolysis showed a dramatic decline over the course of the reaction. With the exception of (+)-catechin extension subunits, all individual subunits decreased in concentration during the oxidation process, also following second-order kinetics for over 1 half-life. Skin proanthocyanidins degraded the fastest due to the presence of (-)-epigallocatechin extension subunits. Seed procyanidins were degraded with and without flavan-3-ol monomers. Flavan-3-ol monomers slowed the rate of seed procyanidin degradation. The mean degree of polymerization (mDP) determined by phloroglucinolysis indicated a large decrease in mDP as the reaction progressed; yet, by GPC, the size distribution of all proanthocyanidins changed little in comparison. The conversion yield could be an important parameter to follow when using phloroglucinolysis as a means for determining proanthocyanidin mDP, and when monitoring the oxidative degradation of proanthocyanidins. 相似文献
98.
Paratuberculosis in pigs. Experimental infection by oral administration of Mycobacterium paratuberculosis 总被引:2,自引:0,他引:2
J B Jorgensen 《Acta veterinaria Scandinavica》1969,10(3):275-287
Oral administration of Mycobacterium paratuberculosis to 61 pigs resulted in the development of caseous lesions of the mesenteric lymph nodes in 27.9 % of the animals. Positive results were found by bacterioscopy in 31.1 %, by culture in 60.7 % and by histological examination in 42.6 % of the animals.Histological changes typical of infection with M. paratuberculosis were found in the ileum in eight pigs. These changes, which consisted of infiltrations with epithelioid cells, were usually limited to the Peyer patches, but in one case such infiltrations were also present in the propria mucosae, similarly as in paratuberculosis in cattle. 相似文献
99.
Ambachew Demessie Rattan Lal Trond Børresen 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(5):455-466
Abstract Plantation establishment using exotic species on disturbed cultivated and undisturbed primary forest soils is common in Gambo district, southern Ethiopia, but their effects on soil properties are not fully known. This study investigated the effects of plantation species on major soil physical and chemical properties and further evaluated the soil quality under different land uses. Soil samples in triplicates, collected under different plantations, were analysed for their physical and chemical properties. Based on these soil properties, an integrated soil quality index was determined. The soil bulk density (BD) varied from 0.72 to 0.80 cm?3 in plantations established on primary forest land and natural forest and from 0.86 to 1.14 g cm?3 in those plantations established on cultivated soils. Also significantly lower pore volume and infiltration rate were observed under plantations established on cultivated lands than those on primary forest soils. Higher water volume (% at ?1500 kPa matric potential) was obtained in soils under Juniperus procera and natural forest compared with that under the rest of the plantations investigated. The concentration of soil organic carbon (SOC) varied from 3.4 to 10.2%, N from 0.3 to 1.0% and Av.P from 1.5 to 7.0% in soils under plantations and natural forest. Exchangeable cations generally showed a decreasing trend with depth in all land use types with minor exceptions. The concentrations of exchangeable Ca+2 varied from 6.5 to 22.7 cmol kg?1 and were significantly higher under Juniperus procera than under Eucalyptus species. The soil under plantations on previously cultivated lands showed soil quality index below 0.5 (the baseline value), while those established on undisturbed forest soil were generally above that value. The study results suggest that selecting species such as Juniperus procera and prolonging the harvesting period would improve and maintain the quality of soil properties. 相似文献
100.
G Laycock L Sait C Inman M Lewis H Smidt P van Diemen F Jorgensen M Stevens M Bailey 《Veterinary immunology and immunopathology》2012,149(3-4):216-224
Maximising the ability of piglets to survive exposure to pathogens is essential to reduce early piglet mortality, an important factor in efficient commercial pig production. Mortality rates can be influenced by many factors, including early colonization by microbial commensals. Here we describe the development of an intestinal microbiota, the Bristol microbiota, for use in gnotobiotic pigs and its influence on synthesis of systemic immunoglobulins. Such a microbiota will be of value in studies of the consequences of early microbial colonization on development of the intestinal immune system and subsequent susceptibility to disease. Gnotobiotic pig studies lack a well-established intestinal microbiota. The use of the Altered Schaedler Flora (ASF), a murine intestinal microbiota, to colonize the intestines of Caesarean-derived, gnotobiotic pigs prior to gut closure, resulted in unreliable colonization with most (but not all) strains of the ASF. Subsequently, a novel, simpler porcine microbiota was developed. The novel microbiota reliably colonized the length of the intestinal tract when administered to gnotobiotic piglets. No health problems were observed, and the novel microbiota induced a systemic increase in serum immunoglobulins, in particular IgA and IgM. The Bristol microbiota will be of value for highly controlled, reproducible experiments of the consequences of early microbial colonization on susceptibility to disease in neonatal piglets, and as a biomedical model for the impact of microbial colonization on development of the intestinal mucosa and immune system in neonates. 相似文献