Pasteurella haemolytica A1 and Bovine Respiratory Disease: Pathogenesis     

Laurence O. Whiteley DVM  PhD    Samuel K. Maheswaran BVSc  PhD    Douglas J. Weiss DVM  PhD    Trevor R. Ames DVM  MS  Mathur S. Kannan BVSc  PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):11-22

The severe fibrinonecrotic pneumonia associated with pneumonic pasteurellosis usually results from colonization of the lower respiratory tract by Pasteurella haemolytica biotype A, serotype 1(A1). Despite recent research efforts, the authors lack a detailed understanding of the interactions and host response to P. haemolytica in the respiratory tract. The authors hypothesize that management and environmental stress factors or viral infection alters the upper respiratory tract (URT) epithelium allowing P. haemolytica to colonize the epithelium. Once the URT is colonized, large numbers of organisms enter the lung where they interact with alveolar macrophages. Endotoxin, released from the bacteria, crosses the alveolar wall where it activates pulmonary intravascular macrophages, endothelium, neutrophils, lymphocytes, platelets, complement, and Hageman factor leading to complex interactions of cells and mediators. It is the progression of this inflammatory response with neutrophil influx that is ultimately responsible for the pulmonary injury. Leukotoxin is a major virulence factor of P. haemolytica that allows it to survive by destroying phagocytic cells. At subcytolytic concentrations it may also enhance the inflammatory response by activating cells to produce mediators and release reactive oxygen metabolites and proteases.  相似文献   

An economist's perspective on irrigation performance assessment: With examples from large scale irrigation in Morocco     

Laurence E. D. Smith 《Irrigation and Drainage Systems》1990,4(4):329-343

This paper accepts that assessing the performance of irrigated agriculture is difficult because being multi-dimensional it requires a multi-disciplinary approach. Public irrigation schemes may have a number of often competing objectives and are assessed by interest groups with differing values and perspectives. A wide range of performance indicators are thus required. Some of these and the complex inter-relationships that may exist in the system are illustrated.  相似文献   

The River Wadu role play — ten years experience     

Ian Carruthers  Laurence Smith 《Irrigation and Drainage Systems》1989,3(3):281-308

This paper describes a role playing planning exercise that has been used for training agriculturists, engineers and agricultural economists for more than ten years. It sets out the objectives and key features of the exercise and the experience that has been gained in its use. The exercise has been found to successfully test and integrate subject matter expertise acquired from formal teaching. It also highlights the multiple and often conflicting objectives of irrigation planning, and the need for full evaluation of alternatives and sound technical judgements under conditions of inadequate data and time pressure. The exercise is also successful in developing professional personal skills such as group working, interviewing and presentation, and is recommended as an effective training aid.  相似文献   

Sentinel-2 images reveal functional biophysical heterogeneities in crop mosaics     

Mercier  Audrey  Hubert-Moy  Laurence  Baudry  Jacques 《Landscape Ecology》2021,36(12):3607-3628

Landscape Ecology - Identifying landscape structure and understanding its functions are crucial for biological control. However, the relationship between the crop mosaic phenological heterogeneity...  相似文献   

Molecular analysis of the Arbuscular mycorrhiza symbiosis     

Philipp Franken  Natalia Requena  Britta Bütehorn  Franziska Krajinski  Gerrit Kuhn  Laurence Lapopin 《Archives of Agronomy and Soil Science》2013,59(4):271-286

The molecular analysis of the arbuscular mycorrhizal (AM) symbiosis started at the beginning of this decade. The paper summarises the work of the ‘Laboratorium für Molekulare Genetik arbuskulärer Mykorrhiza’ at the MPI für terrestrische Mikrobiologie in Marburg on three major topics. Firstly, the plant response to the mycorrhizal colonisation was analysed using both, targeted and non‐targeted approaches. As an example, the localisation of the gst1 mRNA in potato mycorrhiza is shown. Second, molecular techniques were established to analyse gene expression of the fungal partner of the symbiosis. We present a differential RNA display analysis of spore germination in two AM fungi and the cloning of a gene from Glomus mosseae that shows expression at all stages of the fungal life cycle. In the last part, we introduce the work we are carrying out with a new root endophytic fungus, Piriformospora indica. Infection experiments on maize showed that despite the fungus performs as a root necrotroph, it has a positive effect on plant growth.  相似文献   

Distribution of glyphosate and of its target enzyme inside wheat plants     

Laurence Arnaud  Franoise Nurit  Patrick Ravanel  Michel Tissut 《Pest management science》1994,40(3):217-223

Enolpyruvylshikimate phosphate (EPSP) synthase activity has been measured in different organs of 1–14-day-old wheat seedlings growing in culture chambers. Enzyme activity was first detected after two days, and reached its maximum value at day 4. It remained almost unchanged for 14 days thereafter. During germination, one of the most important sources of enzyme was the seed scutellum. Later, the developed leaves contained 43% of the whole stock of enzyme. Although the enzyme distribution was not identical under light or in the dark, there was no evident light induction of EPSP synthase. High enzyme activity was found in the coleoptile, continuing for the whole life-time of this organ, and which might be associated with its lignification. Five to 40% of the total enzyme was found in the roots, reaching a maximum at 14 days. At this stage, glyphosate applied to the first grown leaf was phloem-transported to the sink organs, with no clear relationship being shown between EPSP synthase activity and herbicide quantity in each organ. At day 4, glyphosate treatment, by soaking the seedlings in the herbicide solution, was followed by an active phloem transport from the scutellum to the growing parts. The average internal concentration of radiolabelled compounds (glyphosate plus its possible derivatives) which induced wheat seedling growth decrease, was shown to reach 50 to 100 μM under our conditions.  相似文献   

Hunting debate     

Brain LT 《The Veterinary record》2002,151(10):308

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The Use of Green Fluorescent Protein-Tagged Recombinant Viruses to Test Lettuce mosaic virus Resistance in Lettuce     

Candresse T  Le Gall O  Maisonneuve B  German-Retana S  Redondo E 《Phytopathology》2002,92(2):169-176

ABSTRACT Seed certification and the use of cultivars containing one of two, probably allelic, recessive genes, mo1(1) and mo1(2), are the principal control methods for Lettuce mosaic virus (LMV) in lettuce. Although for a few LMV isolates, mo1(2) confers resistance with most isolates, the genes mo1(1) or mo1(2) confer a tolerance, and virus accumulation is readily detected in mo1-carrying plants. This phenotype complicates evaluation of the resistance status, in particular for mo1(1), for which there are no viral strains against which a true resistance is expressed. Two green fluorescent protein (GFP)-tagged viruses were constructed, derived from a non-resistance breaking isolate (LMV-0) and from a resistance-breaking isolate (LMV-E). An evaluation of 101 cultivars of known status was carried out with these recombinant viruses. Using the LMV-0-derived recombinant, identification of mo1-carrying cultivars was simple because, contrary to its wild-type parent, systemic movement of LMV-0-GFP was abolished in resistant plants. This assay detected four cases of misidentification of resistance status. In all these cases, further tests confirmed that the prior resistance status information was incorrect, so that a 100% correlation was observed between LMV-0-GFP behavior and the mo1 resistance status. Similarly, the LMV-E-derived recombinant allowed the identification of mo1(2) lettuce lines because its systemic movement was restricted in mo1(2) lines but not in susceptible or in mo1(1) lines. The tagged viruses were able to systemically invade another host, pea, irrespective of its resistance status against another member of the genus Potyvirus, Pea seed-borne mosaic virus. The use of these recombinant viruses could therefore greatly facilitate LMV resistance evaluation and speed up lettuce breeding programs.  相似文献   

Medical management of a corneal stromal abscess in a female Asian elephant (Elephas maximus).     

Ellen B Wiedner  Ramiro Isaza  Laurence E Galle  Kathleen Barrie  William A Lindsay 《Journal of zoo and wildlife medicine》2006,37(3):397-400

A 47-yr-old female Asian elephant (Elephas maximus) developed a corneal stromal abscess in her right eye. The elephant was trained to open her eye for topical ophthalmic therapy, and was treated six times daily with antibiotics and an antifungal solution for almost 2 mo. Nonsteroidal anti-inflammatory drugs were used to control pain, and atropine was applied topically to dilate the pupil and provide additional comfort. Vascularization of the abscess began shortly after initiating therapy, and complete resolution was obtained by 7 wk.  相似文献   

Ototoxicity of the antiseptic combination chlorhexidine/cetrimide (Savlon): effects on equilibrium and hearing     

H G Gallé  A J Venker-van Haagen 《The Veterinary quarterly》1986,8(1):56-60

Literature concerning the ototoxicity of the antiseptic combination chlorhexidine/cetrimide (Savlon) is reviewed. The ototoxic effects are illustrated by the results of our own experiments in guinea pigs. The impetus for this article was the observation of vestibular dysfunction in 15 clinical cases (12 dogs and 3 cats), in 8 of which it was confirmed that the ear canal had been rinsed with this drug combination in the presence of a ruptured tympanic membrane.  相似文献