Epidemiological study of bovine respiratory syncytial virus infections in calves: influence of maternal antibodies on the outcome of disease   总被引：7，自引：0，他引：7  

T G Kimman  G M Zimmer  F Westenbrink  J Mars  E van Leeuwen 《The Veterinary record》1988,123(4):104-109

A prospective epidemiological survey on bovine respiratory syncytial virus (BRSV) infections in calves was carried out on 21 dairy farms during one BRSV epidemic season. Special attention was paid to the role of maternal antibodies. On 15 farms the spread of the virus was demonstrated during the investigation period and on eight farms this was accompanied by an outbreak of acute respiratory disease. Disease seldom occurred in calves younger than two weeks old and the most severe disease was observed in calves from one to three months old. Although maternal antibodies did not effectively prevent the disease, both the incidence and severity of disease were inversely related to the level of specific maternal antibodies. Two serodiagnostic techniques were compared. In calves older than three months from herds with disease outbreaks associated with bovine respiratory syncytial virus the diagnosis was established in 80 per cent of the animals by an increase in IgG titre against BRSV and in 77 per cent by the detection of BRSV specific IgM. In comparison, only 10 per cent of the calves younger than three months were positive by IgG serodiagnosis, and 51 per cent by IgM serodiagnosis. On farms where the spread of the virus was accompanied by an outbreak of clinical disease more calves were present, a higher proportion of the calves was younger than three months, and calves of all ages were more often housed together.  相似文献   

The selenium status of dairy herds in Prince Edward Island          下载免费PDF全文

Wichtel JJ  Keefe GP  Van Leeuwen JA  Spangler E  McNiven MA  Ogilvie TH 《The Canadian veterinary journal. La revue veterinaire canadienne》2004,45(2):124-132

Bulk tank milk selenium (Se) concentration was compared with mean serum Se concentration in 15 herds and was found to be an accurate reflection of the herd Se status. The Se status of 109 Prince Edward Island (PEI) dairy herds was monitored for 1 year using bulk tank milk Se concentration. Fifty-nine percent of the herds surveyed were, at some point, found to be marginal or deficient in Se, putting them at risk of disease and suboptimal production. The periods of greatest risk of deficiency were fall and winter, at which time 5% and 4%, respectively, of herds sampled fell in the range considered truly deficient in Se. Herds in which Se supplementation was provided in the form of a commercial dairy concentrate were over 4 times more likely to be Se-adequate than herds not using this method, and adjusted average daily milk yield was 7.6% greater in herds determined to be Se-adequate when compared with Se-marginal herds. We conclude that many dairy producers in PEI are providing insufficient supplementary Se in the ration to meet the recommended Se intake for lactating cows.  相似文献   

Cytosolic streaming in vegetative mycelium and aerial structures of Aspergillus niger     

R. Bleichrodt  A. Vinck  P. Krijgsheld  M.R. van Leeuwen  J. Dijksterhuis  H.A.B. W?sten 《Studies in Mycology》2013,74(1):31-46

Aspergillus niger forms aerial hyphae and conidiophores after a period of vegetative growth. The hyphae within the mycelium of A. niger are divided by septa. The central pore in these septa allows for cytoplasmic streaming. Here, we studied inter- and intra-compartmental streaming of the reporter protein GFP in A. niger. Expression of the gene encoding nuclear targeted GFP from the gpdA or glaA promoter resulted in strong fluorescence of nuclei within the vegetative hyphae and weak fluorescence in nuclei within the aerial structures. These data and nuclear run on experiments showed that gpdA and glaA are higher expressed in the vegetative mycelium when compared to aerial hyphae, conidiophores and conidia. Notably, gpdA or glaA driven expression of the gene encoding cytosolic GFP resulted in strongly fluorescent vegetative hyphae and aerial structures. Apparently, GFP streams from vegetative hyphae into aerial structures. This was confirmed by monitoring fluorescence of photo-activatable GFP (PA-GFP). In contrast, PA-GFP did not stream from aerial structures to vegetative hyphae. Streaming of PA-GFP within vegetative hyphae or within aerial structures of A. niger occurred at a rate of 10–15 μm s^-1. Taken together, these results not only show that GFP streams from the vegetative mycelium to aerial structures but it also indicates that its encoding RNA is not streaming. Absence of RNA streaming would explain why distinct RNA profiles were found in aerial structures and the vegetative mycelium by nuclear run on analysis and micro-array analysis.Key words: aerial hypha, Aspergillus, conidia, conidiophore, cytoplasmic streaming, development, fungus, vegetative mycelium  相似文献   

Germination of conidia of Aspergillus niger is accompanied by major changes in RNA profiles     

M.R. van Leeuwen  P. Krijgsheld  R. Bleichrodt  H. Menke  H. Stam  J. Stark  H.A.B. W?sten  J. Dijksterhuis 《Studies in Mycology》2013,74(1):59-70

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Differences in early developmental rate and yolk conversion efficiency in offspring of trout with alternative life histories          下载免费PDF全文

Travis E. Van Leeuwen  Shaun S. Killen  Neil B. Metcalfe  Colin E. Adams 《Ecology of Freshwater Fish》2017,26(3):371-382

Partial migration, in which some individuals of a population migrate while other individuals remain resident, is generally associated with ontogenetic shifts to better feeding areas or as a response to environmental instability, but its underlying mechanisms remain relatively unknown. Brown trout (Salmo trutta) exhibit partial migration, with some individuals remaining in freshwater (freshwater resident) while others undertake an anadromous migration, where they spend time at sea before returning to breed in freshwater (migrant). We reared full‐sibling groups of offspring from freshwater‐resident and anadromous brown trout from the same catchment in the laboratory under common garden conditions to examine potential differences in their early development. Freshwater‐resident parents produced eggs that were slower to hatch than those of anadromous parents, but freshwater‐resident offspring were quicker to absorb their yolk and reach the stage of exogenous feeding. Their offspring also had a higher conversion efficiency from the egg stage to the start of exogenous feeding (so were larger by the start of the fry stage) than did offspring from anadromous parents despite no difference in standard metabolic rate, maximal metabolic rate or aerobic scope. Given these differences in early development, we discuss how the migration history of the parents might influence the migration probability of the offspring.  相似文献   

A novel attempt at artificial spawning of captive bonefish (Albula spp.)     

Sahar Mejri  William R. Halstead  Cameron A. Luck  Christopher Robinson  Travis E. Van Leeuwen  Aaron J. Adams  Jon Shenker  Matthew J. Ajemian  Paul S. Wills 《Aquaculture Research》2019,50(9):2718-2723

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Interlaboratory tests for resistance to Synchytrium endobioticum in potato by the Glynne‐Lemmerzahl method     

K. Flath  J. Przetakiewicz  P. C. J. van Rijswick  V. Ristau  G. C. M. van Leeuwen 《EPPO Bulletin》2014,44(3):510-517

Synchytrium endobioticum is a major quarantine pathogen of potato causing potato wart disease. In Europe, the pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) are the most widespread and occur locally in almost all countries. Resistance to this disease in potato cultivars is tested for in the majority of the EU countries by the Glynne‐Lemmerzahl method. This paper describes the results of testing two different protocols of this method in five laboratories of three different countries (Germany, Poland, and the Netherlands). The four pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) were tested mainly on the cultivars described in the EPPO Standard PM 7/28 Synchytrium endobioticum. For pathotype 1(D1) and in most cases also for pathotype 18(T1), the results of the cultivars tested were identical to the rating in the EPPO Standard for both protocols. For pathotypes 2(G1) and 6(O1), the cultivars Désirée, Delcora and Miriam showed different results between laboratories as well as between the two protocols. In conclusion, further research is needed to develop one harmonised methodology for resistance testing of potato cultivars to the pathotypes 2(G1), 6(O1) and 18(T1) and to develop a new differential set of potato cultivars for the identification of pathotypes of S. endobioticum.  相似文献   

Cross‐resistance risk of the novel complex II inhibitors cyenopyrafen and cyflumetofen in resistant strains of the two‐spotted spider mite Tetranychus urticae     

Mousaalreza Khalighi  Luc Tirry  Thomas Van Leeuwen 《Pest management science》2014,70(3):365-368

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Acetylcholinesterase point mutations in European strains of Tetranychus urticae (Acari: Tetranychidae) resistant to organophosphates     

Jahangir Khajehali  Thomas Van Leeuwen  Maria Grispou  Evangelia Morou  Haoués Alout  Mylène Weill  Luc Tirry  John Vontas  Anastasia Tsagkarakou 《Pest management science》2010,66(2):220-228

BACKROUND: In Tetranychus urticae Koch, acetylcholinesterase insensitivity is often involved in organophosphate (OP) and carbamate (CARB) resistance. By combining toxicological, biochemical and molecular data from three reference laboratory and three OP selected strains (OP strains), the AChE1 mutations associated with resistance in T. urticae were characterised. RESULTS: The resistance ratios of the OP strains varied from 9 to 43 for pirimiphos‐methyl, from 78 to 586 for chlorpyrifos, from 8 to 333 for methomyl and from 137 to 4164 for dimethoate. The insecticide concentration needed to inhibit 50% of the AChE1 activity was, in the OP strains, at least 2.7, 55, 58 and 31 times higher for the OP pirimiphos‐methyl, chlorpyrifos oxon, paraoxon and omethoate respectively, and 87 times higher for the CARB carbaryl. By comparing the AChE1 sequence, four amino acid substitutions were detected in the OP strains: (1) F331W (Torpedo numbering) in all the three OP strains; (2) T280A found in the three OP strains but not in all clones; (3) G328A, found in two OP strains; (4) A201S found in only one OP strain. CONCLUSIONS: Four AChE1 mutations were found in resistant strains of T. urticae, and three of them, F331W, G328A and A201S, are possibly involved in resistance to OP and CARB insecticides. Among them, F331W is probably the most important and the most common in T. urticae. It can be easily detected by the diagnostic PCR‐RLFP assay developed in this study. Copyright © 2009 Society of Chemical Industry  相似文献   

Retrieval of forest structural parameters using LiDAR remote sensing   总被引：1，自引：0，他引：1  

Martin van Leeuwen  Maarten Nieuwenhuis 《European Journal of Forest Research》2010,129(4):749-770

In this paper, a literature overview is presented on the use of laser rangefinder techniques for the retrieval of forest inventory parameters and structural characteristics. The existing techniques are ordered with respect to their scale of application (i.e. spaceborne, airborne, and terrestrial laser scanning) and a discussion is provided on the efficiency, precision, and accuracy with which the retrieval of structural parameters at the respective scales has been attained. The paper further elaborates on the potential of LiDAR (Light Detection and Ranging) data to be fused with other types of remote sensing data and it concludes with recommendations for future research and potential gains in the application of LiDAR for the characterization of forests.  相似文献