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971.
Michel Riksen Rita Ketner-Oostra Chris van Turnhout Marijn Nijssen Dirk Goossens Pim D. Jungerius Wim Spaan 《Landscape Ecology》2006,21(3):431-447
In the Netherlands the total active inland drift-sand area has been declining rapidly during the last 50 years. To preserve
the inland drift sands, it is necessary to understand its origin and development and the role of human activity in this semi-natural
ecotype. The objective of this literature review is to describe the development of the drift-sand ecotopes, to explain the
rapid decline of the active drift sands, and to develop a management strategy for the remaining active drift sands. Inland
drift-sand landscapes are relatively young landscapes of Holocene age. They often occur as oval-shaped cells with a length
of 1.5 to over 6 km in the direction of the prevailing wind. These cells presumably represent reactivated deposits of Younger
Cover Sands. Large-scale erosion events in combination with human activity suppressed the development of vegetation. After
the change in land use in the first half of the 20th century in which most of the drift sands were re-afforested, the vegetation
succession started to show a progressive development. In this stage inland drift-sand ecotopes developed in most of the remaining
drift sands with all forms of the typical succession stages from bare sand to forest. The rate at which this development took
place mainly depended on the geomorphological development stage of the area, the area size and human activity. Since the 1960s
the increased nitrogen deposition has accelerated the vegetation succession, not only resulting in a further decline of the
drift sands, but also in a loss of the fragile balance between the different ecotopes and loss of its typical habitants like
the Tree Grayling and Tawny Pipit. Most drift-sand vegetation and fauna need the presence of bare sand nearby and a certain
level of erosion activity to survive. To preserve the drift-sand ecotype, it is therefore recommended to keep the area affected
by erosion sufficiently large (process management). In the meantime one should also ‘maintain’ or increase the wind force
in the drift-sand area by suppressing the growth of high vegetation and removing trees, which form a wind barrier. In areas
which are less suitable for reactivation, one could restore the mosaic vegetation by removing the vegetation on a limited
scale (pattern management). More research is needed to develop a more balanced management strategy and to develop a management
tool for the managers of inland drift sands. Also the role of the increased nitrogen deposition in the regeneration process
needs further investigation in order to find an effective way to suppress its effect. The development of management strategies
for the Dutch inland drift sands might be of great value to drift-sand areas in Western Europe where nature conservationists
start to show more interest in the restoration of former drift-sand areas. 相似文献
972.
Wm Kirk Suedmeyer Chris Ludlow Candace Layton Jeff Dennis Margaret Miller 《Journal of zoo and wildlife medicine》2004,35(4):572-575
A 3-yr-old intact male dingo (Canis familiaris dingo) presented with a 3-mo history of diarrhea. The diarrhea did not resolve with antibiotics or intestinal protectants. Fecal examination for parasites, fecal cultures, physical examination, and radiographs were unremarkable. Enteroscopic duodenal biopsies showed dilated lacteals without inflammation. Results of serum folate, cobalamin, and trypsin-like immunoreactivity were normal. Low serum total protein and albumin combined with increased fecal levels of alpha-1 protease inhibitor suggested the diagnosis of lymphangiectasia. Full-thickness intestinal biopsies of the duodenum, jejunum, and ileum revealed dilated mucosal and submucosal lacteals without associated inflammation, confirming the diagnosis of primary lymphangiectasia. Currently, the dingo is being maintained with nutritional management. 相似文献
973.
Low Temperature–Short Duration Steaming of Soil Kills Soil-Borne Pathogens, Nematode Pests and Weeds
Mariska C.A. van Loenen Yzanne Turbett Chris E. Mullins Nigel E.H. Feilden Michael J. Wilson Carlo Leifert Wendy E. Seel 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(9):993-1002
Agricultural soil samples containing survival structures of the fungal crop pathogens Verticillium dahliae, Sclerotinia sclerotiorum, Sclerotium cepivorum, Pythium ultimum, potato cyst nematodes Globodera rostochiensis and G. pallida and weeds Chenopodium album and Agropyron repens [Elymus repens] were treated in the laboratory with aerated steam at temperatures ranging from 40 to 80°C in a specially constructed apparatus. Steaming at 50 or 60°C for 3min, followed by an 8-min resting period in the steamed soil and immediate removal from the soil thereafter, resulted in 100% kill of all weeds, diseases and nematodes. When steamed at 45°C, there was a small but significant reduction in the survival of V. dahliae microsclerotia but no reduction in survival of S. cepivorum. 相似文献
974.
975.
Schlafer S Nordhoff M Wyss C Strub S Hübner J Gescher DM Petrich A Göbel UB Moter A 《Veterinary microbiology》2008,128(1-2):118-125
Digital dermatitis (DD) of cattle leads to lameness and a decrease of milk production and is responsible for major economic losses worldwide. Although a bacterial aetiology is generally accepted, it still is unclear which microorganisms cause and/or maintain the disease. Recently, a previously undiscovered bacterial species, Guggenheimella bovis, has been isolated from the front of two DD lesions in Swiss cattle and suggested as a potential pathogen. The aims of the present study were to determine the prevalence of G. bovis in 58 German cows suffering from DD via dot blot hybridization, and to analyse the spatial distribution of G. bovis within the affected tissue by fluorescence in situ hybridization (FISH). A species-specific probe, GUBO1, was designed and evaluated. In none of the 58 samples Guggenheimella could be detected, while cultured G. bovis was reliably identified by GUBO1. Further FISH experiments were carried out on two additional biopsies of Swiss cattle tested positive for G. bovis by quantitative PCR and permitted visualization of the newly discovered bacteria in situ. In these biopsies G. bovis proved to be tissue invasive forming characteristic spherical microcolonies not only within the bacterial biofilm but also in seemingly unaffected parts of the tissue not yet reached by the advancing bacterial front. Although the presence of G. bovis does not constitute an essential premise for DD, it seems likely that the bacterial species involved in DD vary, and that in some cases G. bovis is crucial for the development of DD lesions. 相似文献
976.
977.
Kubota K Yamauchi N Matsumoto K Watanabe R Oozono S Aramaki S Wood C Soh T Hattori MA 《The Journal of reproduction and development》2008,54(5):340-345
Hedgehog (Hh) plays a pivotal role in various tissues during embryonic development, tissue homeostasis and tumorigenesis. In mammals, Hh exists in three homologs: Desert hedgehog (Dhh), Indian hedgehog (Ihh) and Sonic hedgehog (Shh). In this study, we cloned full-length cDNAs encoding Dhh and Ihh from the rat uterus. Their amino acid sequences have a high homology with those of the mouse and human. In addition, the changes of Hh gene expression in the rat uterus during early pregnancy were analyzed. The results showed that all three hedgehog mRNAs were detected in the rat uterus at the proestrus stage and during early pregnancy (1.5, 3.5, 5.5 and 7.5 days post coitus: dpc). Ihh mRNA expression varied and peaked at 3.5 dpc in the luminal and glandular epithelium. Expression was decreased on 5.5 dpc with the exception of sustained expression in the glandular epithelium. Despite such Ihh variability, the expressions of Dhh and Shh mRNA remained unchanged. This indicated that Ihh was mainly expressed in the rat uterus during early pregnancy. Moreover, the Hh target gene (glioma-associated oncogene homolog 1; Gli1) was also highly expressed at 3.5 dpc in the epithelium and periepithelial stroma in a manner similar to the temporal pattern of Ihh expression. This suggests that Ihh signaling axis play a role in the rat uterus during early pregnancy. In summary, our results elucidate that Ihh is a predominant Hh protein in the rat uterus during early pregnancy and that other Hhs have the potential to be expressed. This observation will help to elucidate the basic molecular mechanism of rat uterus during early pregnancy. 相似文献
978.
Target-site resistance to pyrethroids in European populations of pollen beetle, Meligethes aeneus F.
Ralf Nauen Christoph T. Zimmer Melanie AndrewsRussell Slater Chris BassBarbara Ekbom Göran GustafssonLars Monrad Hansen Michael KristensenClaus P.W. Zebitz Martin S. Williamson 《Pesticide biochemistry and physiology》2012,103(3):173-180
Pollen beetle, Meligethes aeneus F. (Coleoptera: Nitidulidae) is a major univoltine pest of oilseed rape in many European countries. Winter oilseed rape is cultivated on several million hectares in Europe and the continuous use of pyrethroid insecticides to control pollen beetle populations has resulted in high selection pressure and subsequent development of resistance. Resistance to pyrethroid insecticides in this pest is now widespread and the levels of resistance are often sufficient to result in field control failures at recommended application rates. Recently, metabolic resistance mediated by cytochrome P450 monooxygenases was implicated in the resistance of several pollen beetle populations from different European regions. Here, we have also investigated the possible occurrence of a target-site mechanism caused by modification of the pollen beetle para-type voltage-gated sodium channel gene. We detected a single nucleotide change that results in an amino acid substitution (L1014F) within the domain IIS6 region of the channel protein. The L1014F mutation, often termed kdr, has been found in several other insect pests and is known to confer moderate levels of resistance to pyrethroids. We developed a pyrosequencing-based diagnostic assay that can detect the L1014F mutation in individual beetles and tested more than 350 populations collected between 2006 and 2010 in 13 European countries. In the majority of populations tested the mutation was absent, and only samples from two countries, Denmark and Sweden, contained pollen beetles heterozygous or homozygous for the L1014F mutation. The mutation was first detected in a sample from Denmark collected in 2007 after reports of field failure using tau-fluvalinate, and has since been detected in 7 out of 11 samples from Denmark and 25 of 33 samples from Sweden. No super-kdr mutations (e.g. M918T) known to cause resistance to pyrethroids were detected. The implications of these results for resistance management strategies of pollen beetle populations in oilseed rape crops are discussed. 相似文献
979.
Biochemical evaluation of interactions between synergistic molecules and phase I enzymes involved in insecticide resistance in B‐ and Q‐type Bemisia tabaci (Hemiptera: Aleyrodidae) 下载免费PDF全文
980.
Barker EN Darby AC Helps CR Peters IR Heesom KJ Arthur CJ Crossett B Hughes MA Radford AD Tasker S 《Veterinary research》2011,42(1):83
ABSTRACT: Mycoplasma haemofelis is a pathogenic feline hemoplasma. Despite its importance, little is known about its metabolic pathways or mechanism of pathogenicity due to it being uncultivatable. The recently sequenced M. haemofelis str. Langford 1 genome was analysed and compared to those of other available hemoplasma genomes.Analysis showed that in hemoplasmas genes involved in carbohydrate metabolism are limited to enzymes of the glycolytic pathway, with glucose appearing to be the sole energy source. The majority of the pentose phosphate pathway enzymes that catalyze the de novo synthesis of ribonucleotides were absent, as were cell division protein FtsZ and chaperonins GroEL/ES. Uncharacterized protein paralogs containing putative surface expression motifs, comprised 62% of M. haemofelis and 19% of Mycoplasma suis genome coverage respectively, the majority of which were present in a small number of unstructured islands. Limited mass spectrometry and immunoblot data matched a number of characterized proteins and uncharacterized paralogs, confirming their expression and immunogenicity in vivo.These data have allowed further characterization of these important pathogens, including their limited metabolic capabilities, which may contribute to their uncultivatable status. A number of immunogenic proteins, and a potential mechanism for host immune system evasion, have been identified. 相似文献