Antibody dynamics in BRSV-infected Danish dairy herds as determined by isotype-specific immunoglobulins     

Uttenthal A  Larsen LE  Philipsen JS  Tjørnehøj K  Viuff B  Nielsen KH  Nielsen TK 《Veterinary microbiology》2000,76(4):329-341

Using specific ELISAs, antibody levels of four different isotypes to bovine respiratory syncytial virus (BRSV) were determined in calves, following experimental BRSV infection.Most calves experienced an increase in the specific IgM and IgG1 titres about 6-10 days after infection with BRSV. The IgM titre was transient showing positive titres for only 5-10 days, while specific IgG1 was present for a longer time. IgA was detected concomitantly with IgM but at a lower level. Production of IgG2 anti-BRSV antibodies was detected from 3 weeks after infection.In two closed herds, repeated blood samplings were performed on young stock to analyse maternal immunity. The passively transferred antibodies were mainly of the IgG1 isotype and the half-life of IgG1 to BRSV was estimated to be 26.6 days. One of the herds had an outbreak of enzootic pneumonia, diagnosed to be caused by BRSV. Furthermore, another herd with acute BRSV was followed by weekly blood samples in six calves; in both herds IgM and IgG1 was detected shortly after the appearance of clinical signs. Serum samples from 50 Danish dairy herds (453 samples) were tested for immunoglobulins of the isotypes IgG1, IgG2 and IgM. The presence of antibodies to BRSV was widespread and more than 54% of the samples had BRSV antibodies of both the IgG1 and IgG2 isotypes indicating a high herd prevalence to BRSV. Test samples from two herds out of 50 were free from all isotypes to BRSV.  相似文献   

Suppression of Rice Blast by Preinoculation with Avirulent Pyricularia oryzae and the Nonrice Pathogen Bipolaris sorokiniana     

Manandhar HK  Lyngs Jørgensen HJ  Mathur SB  Smedegaard-Petersen V 《Phytopathology》1998,88(7):735-739

ABSTRACT Avirulent isolates of Pyricularia oryzae and isolates of Bipolaris sorokiniana, a nonrice pathogen, were used to suppress rice blast caused by P. oryzae. In greenhouse experiments, both fungi substantially reduced leaf blast when applied 24 h or more before the pathogen. B. sorokiniana, but not avirulent isolates of P. oryzae, systemically reduced disease in leaf 5 when applied to whole plants at the four-leaf stage. In field experiments, both fungi were able to reduce neck blast significantly. No increase in grain yield was obtained by using avirulent isolates of P. oryzae, whereas five sprays with B. sorokiniana from seedling to heading stages increased the grain yield in two of three experiments conducted at two locations in Nepal. The significant increase in yield was observed under high inoculum pressure of P. oryzae. Induced resistance is suggested to be involved in the suppression of disease.  相似文献   

Effects of grazing strategy on limiting nitrate leaching in grazed grass‐clover pastures on coarse sandy soil     

E. M. Hansen  J. Eriksen  K. Søegaard  K. Kristensen 《Soil Use and Management》2012,28(4):478-487

Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long‐term mean. The experiment was initiated in a 4‐yr‐old grass‐clover sward in south Denmark. Three treatments were as follows grazing only (G), spring cut followed by grazing (CG) and both spring and autumn cuts with summer grazing (CGC). Nitrate leaching was calculated by extracting water isolates from 80 cm depth using ceramic suction cups. Because of considerable variation in measured nitrate concentrations, the 32 installed suction cups per treatment were insufficient to reveal differences between treatments. However, weighted nitrate leaching estimations for G, CG and CGC showed estimated mean nitrate N concentrations of 23, 19 and 13 mg/L for an estimated proportion area occupied by urine patches of 0.33, 0.26 and 0.16, respectively. Thus, N concentrations in G and CG exceeded the EU limit of 11.3 mg N/L. Under the prevailing conditions, the time of urination did not appear important. The estimated background leaching calculated from suction cups presumably not situated under urine patches resulted in mean nitrate N concentrations of 2.6 mg/L.  相似文献   

Blume,H.-P. und U. Schleuß (Hrsg.): Bewertung anthropogener Stadtböden, 1997, Band 38, Schriftenreihe Institut für Pflanzenernährung und Bodenkunde der Universität Kiel (Hrsg.: Blume,H.-P./Horn,R./Sattelmacher,B.) ISSN 0933–680 x. Paperback, 346 Seiten,DM 30,-     

Jrg Bachmann 《植物养料与土壤学杂志》1998,161(6):699-699

  相似文献   

Apoplastic Peroxidases in Needles of Norway Spruce (Picea abies) Progenies from Different Crossing Environments     

T. Zöller  T. Skrøppa  Ø. Johnsen  Andrea Polle 《European Journal of Forest Research》2003,122(3):153-159

  相似文献   

Grundflächenzuwachs und Massenzuwachs mit verschiedenen Definitionen     

Carl Mar Møller 《European Journal of Forest Research》1954,73(11-12):350-354

  相似文献   

Lignicole Pilze an Schwarz-Erle )Alnus glutinosa [L.] Gaertn.) — welche Arten sind bedeutsame Fäuleerreger?     

Jörg Schumacher  Paul Heydeck  Andreas Roloff 《European Journal of Forest Research》2001,120(1-6):8-17

  相似文献   

Comparing the performance of generalized diameter-height equations for Maritime pine in Northwestern Spain     

Jörg Schröder  Juan Gabriel Álvarez González 《European Journal of Forest Research》2001,120(1-6):18-23

  相似文献   

Modeling spatial variability in the life-cycle costs of low-volume forest roads     

Jürg Andreas Stückelberger  Hans Rudolf Heinimann  Edouard Charles Burlet 《European Journal of Forest Research》2006,125(4):377-390

Cost estimation is probably the most decisive factor in the process of computer-aided, preliminary planning for low-volume road networks. However, the cost of construction is normally assumed to be route-independent for a specific project area, resulting in sub-optimal layouts. This is especially true for mountainous terrain and in areas with unstable subsoil. Here, we present a model for more accurately estimating spatial variability in road life-cycle costs, based on terrain surface properties as well as geological properties of the subsoil. This parametric model incorporates four structural components: embankment, retaining structures, pavement, and drainage and stream-crossing structures. It is linked to a geo-database that allows users to derive location-specific parameter values as input. In applying this model, we have demonstrated that variability in costs ranges widely for mountainous areas, with the most expensive construction being approximately five times greater there than on more favorable sites. This variability strongly affects the optimal layout of a road network. First, when location-specific slope gradients are considered, costs are reduced by about 17% from those calculated via currently available engineering practices; when both slope gradient and geotechnical formations are included, those costs are decreased by about 20%. Second, the length of the road network is increased by about 4% and 10% respectively, compared with current practices.  相似文献   

The role of land tenure in conservation of tree and shrub species diversity in miombo woodlands of southern Malawi     

Weston F. Mwase  Åsmund Bjørnstad  James M. Bokosi  Moses B. Kwapata  Brita Stedje 《New Forests》2007,33(3):297-307

Biodiversity is declining throughout southern African miombo woodlands due to poor land use practices that are detrimental to soil, vegetation and habitat. We aimed at examining tree and shrub species diversity and distribution in Uapaca kirkiana-dominated woodlands under three land tenure types; forest reserves, customary and leasehold land. The study was conducted at different forest sites within similar agroecological zone in southern Malawi. Study sites were located at a range of altitudes between 900 and 1,200 m a.s.l. Three circular plots each with 32.60 m radius were established at each study site to sample tree and shrub species composition, structure and distribution under three land tenure types. We found that forest reserves had higher species diversity with an average of 16 tree families, 27 genera and 34 species as compared to only 10 tree families, 6 genera and 6 species on customary forest lands. Comparisons of diameter at breast height size class distributions showed that customary land had significantly low numbers of small (5.0–10.0 cm) and very large (≥30 cm) diameter classes suggesting lower levels of regeneration and high rate of anthropogenic activities. The high species diversity and richness in forest reserves and leasehold land indicate high potential for protected lands to restore tree species diversity. It is concluded that levels of human activities as influenced by land tenure type reduce tree species diversity, composition and distribution at the different sites, and this confirms the hypothesis that open access lands are not compatible with conservation of tree and shrub species diversity because of high anthropogenic activities.  相似文献