A study of the basis of virulence variation of bovine rotaviruses.   总被引：3，自引：0，他引：3  

J C Bridger  G A Hall  K R Parsons 《Veterinary microbiology》1992,33(1-4):169-174

Rotaviruses are enteric pathogens of cattle but sub-clinical infections are common. Virulence variation has been identified with bovine rotaviruses and some rotaviruses replicated without clinical signs in non-immune calves. The rotavirus genome is composed of eleven segments of double-stranded RNA and the fourth largest segment codes for a non-glycosylated surface protein, VP4, which has been linked with virulence. In the present study the biological basis of rotavirus virulence variation was studied in vivo and compared with the known properties of the fourth gene. Calves were inoculated orally with a virulent rotavirus or a rotavirus of low virulence which multiplied but failed to cause diarrhoea. They were taken for necropsy at intervals of 2 days after inoculation. Clinical signs, virus in faeces and the percentage of infected small intestinal epithelium were determined. Damage to the small intestine was assessed by measurement of villus heights and crypt-cell production rates. Virulence was associated with a greater level of colonization of the small intestinal epithelium, greater enterocyte damage and preferential infection of the upper small intestine. The fourth gene determines the ability of rotaviruses to spread in vitro and the finding that virulence was associated with greater colonization in vivo raises the possibility that this gene may have an important role in rotavirus virulence.  相似文献   

Relationship of some blood components to morbidity and mortality in auction calves     

G E Staples  M F Andrews  R M Parsons  P McIlwain 《The Cornell veterinarian》1969,59(2):313-325

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A comparison of single and multiple stressor protocols to assess acute stress in a coastal shark species,Rhizoprionodon terraenovae     

Eric R. Hoffmayer  Jill M. Hendon  Glenn R. Parsons  William B. Driggers III  Matthew D. Campbell 《Fish physiology and biochemistry》2015,41(5):1253-1260

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Humeral condylar fractures and fissures in the French bulldog     

Oliver J. Anderson BVetMed  Sorrel J. Langley-Hobbs MA  BVetMed  DSAS  DECVS  FHEA  Kevin J. Parsons BVSc  PhD  Cert SAS  Diplomate ECVS 《Veterinary surgery : VS》2023,52(1):134-145

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Simulation of drainage water quality with DRAINMOD     

R. W. Skaggs  M. A. Brevé  A. T. Mohammad  J. E. Parsons  J. W. Gilliam 《Irrigation and Drainage Systems》1995,9(3):259-277

The design and management of drainage systems should consider impacts on drainage water quality and receiving streams, as well as on agricultural productivity. Two simulation models that are being developed to predict these impacts are briefly described. DRAINMOD-N uses hydrologic predictions by DRAINMOD, including daily soil water fluxes, in numerical solutions to the advective-dispersive-reactive (ADR) equation to describe movement and fate of NO₃-N in shallow water table soils. DRAINMOD- CREAMS links DRAINMOD hydrology with submodels in CREAMS to predict effects of drainage treatment and controlled drainage losses of sediment and agricultural chemicals via surface runoff. The models were applied to analyze effects of drainage intensity on a Portsmouth sandy loam in eastern North Carolina. Depending on surface depressional storage, agricultural production objectives could be satisfied with drain spacings of 40 m or less. Predicted effects of drainage design and management on NO₃-N losses were substantial. Increasing drain spacing from 20 m to 40 m reduced predicted NO₃-N losses by over 45% for both good and poor surface drainage. Controlled drainage further decreases NO₃-N losses. For example, predicted average annual NO₃-N losses for a 30 m spacing were reduced 50% by controlled drainage. Splitting the application of nitrogen fertilizer, so that 100 kg/ha is applied at planting and 50 kg/ha is applied 37 days later, reduced average predicted NO₃-N losses but by only 5 to 6%. This practice was more effective in years when heavy rainfall occurred directly after planting. In contrast to effects on NO₃-N losses, reducing drainage intensity by increasing drain spacing or use of controlled drainage increased predicted losses of sediment and phosphorus (P). These losses were small for relatively flat conditions (0.2% slope), but may be large for even moderate slopes. For example, predicted sediment losses for a 2% slope exceeded 8000 kg/ha for a poorly drained condition (drain spacing of 100 m), but were reduced to 2100 kg/ha for a 20 m spacing. Agricultural production and water quality goals are sometimes in conflict. Our results indicate that simulation modeling can be used to examine the benefits of alternative designs and management strategies, from both production and environmental points-of-view. The utility of this methodology places additional emphasis on the need for field experiments to test the validity of the models over a range of soil, site and climatological conditions.  相似文献   

Stratigraphy and land use of the Post-Diamond Hill Paleosol,western Oregon     

Rog B. Parsons 《Geoderma》1979,22(1):67-70

The Post-Diamond Hill Paleosol generally underlies Late Pleistocene sediments of the Willamette Formation. However, in numerous localities in the Willamette Valley, reddish gray clay paleosols either outcrop at the surface or occur within soil profile depth. Then they are part of soils of the modern landscape. Where the paleosols outcrop, the soils are mostly Typic Pelloxererts in the fine, montmorillonitic, mesic family. Because of the nature of the paleosols, these soils are poorly suited for nearly all intensive uses; the dominant use is hay and pasture.  相似文献   

Thermal decomposition of protein in soil organic matter     

J.D. Russell  A.R. Fraser  J.R. Watson  J.W. Parsons 《Geoderma》1974,11(1):63-66

Infrared spectroscopy and nitrogen analyses suggest that secondary amide groups in protein-like components of soil clay-organic complexes and extracted organic matter decompose above 100°C to yield ammonia which is retained as NH₄⁺ by acid-washed clay-organic complexes. Above about 400°C, other volatile nitrogenous decomposition products are released. Clay surfaces in the clay-organic complexes may catalyse the decomposition.  相似文献   

Seasonal Effect on Zebu Embryo Quality as Determined by Their Degree of Apoptosis and Resistance to Cryopreservation     

YC Marquez  CS Galina  N Moreno  H Ruiz  A Ruiz  H Merchant 《Reproduction in domestic animals》2005,40(6):553-558

In order to optimize the production of embryos under tropical conditions and to test a possible seasonal effect on embryo quality, 40 Zebu cows were superovulated during the dry season (April to May) and during the rainy season (July to August). A total of 116 (average 2.7/cow) and 83 embryos (3.5 average/cow) were obtained during the respective seasons. After classification as good, fair or poor quality, embryos were tested based on their ultrastructural differences (n = 53 dry season 16 good, 20 fair and 17 poor and n = 61 rainy season 21 good, 20 fair and 20 poor) and their degree of apoptosis using the TUNEL technique (n = 30 during the dry season and n = 55 in the rainy season). Structural characteristics determining embryo quality varied between good and fair quality embryos. No difference, however, was observed between good, fair and poor quality embryos from the two seasons. The number of TUNEL-positive cells was different among embryos (p < 0.001), being lower in labelled cells of good quality embryos regardless of the season. Fewer apoptotic cells were observed in embryos assigned in all three quality levels during the rainy season (p < 0.001). Ultrastructural evaluations confirmed the results obtained by TUNEL. Cryopreserved embryos of good (n = 25 in each season) and fair quality (n = 11 dry season; n = 17 rainy season) showed a significant decrease of TUNEL-positive cells during the rainy season (p < 0.05). Results suggest that embryos collected in the dry season have more cellular damage in contrast; embryos cryopreserved in the rainy season appeared morphologically better equipped to result in a pregnancy following transfer.  相似文献   

Dendritic cells in cattle: phenotype and function     

Howard CJ  Brooke GP  Werling D  Sopp P  Hope JC  Parsons KR  Collins RA 《Veterinary immunology and immunopathology》1999,72(1-2):119-124

Dendritic cells are professional antigen presenting cells derived from the bone marrow and distributed throughout body tissues where they are located in sites that are suitable for antigen uptake. They are central to the induction of immune responses in naive animals and thus have become targets in strategies that are aimed at modulating resistance to infection. Studies in cattle have shown that the dendritic cells are phenotypically heterogeneous and that the different phenotypes have different biological properties. The molecular basis for this variation has begun to be investigated and has led to the identification of a member of the SIRPalpha family of signal regulatory proteins (MyD1) on a subset of dendritic cells in afferent lymph. Uptake of antigen by cattle dendritic cells is by a number of mechanisms that can involve endocytosis via clathrin coated pits or via caveolae as well as macropinocytosis.  相似文献   

Effects of dietary change and rotavirus infection on small intestinal structure and function in gnotobiotic piglets   总被引：1，自引：0，他引：1  

G A Hall  K R Parsons  G L Waxler  K J Bunch  R M Batt 《Research in veterinary science》1989,47(2):219-224

The combined effects of weaning and rotavirus infection on small intestinal structure and function and on growth rate were studied in 28 gnotobiotic piglets. There was little damage by rotavirus to the proximal small intestine, some damage to the mid small intestine and relatively severe damage to the distal small intestine; villi were stunted, crypts lengthened and activities of all brush border enzymes decreased. The damage was short-lived despite the synchronisation of rotavirus infection with simulated weaning. There was no evidence of persistent damage to the small intestine and growth rate was unaffected.  相似文献