The ultrastructure of low temperature stimulated rubber-producing cortical parenchyma in guayule     

C.R. BenedictRachel Goss  Paul J. Greer  M.A. Foster 《Industrial Crops and Products》2011,33(1):89-93

The low temperatures of the Chihuahuan Desert stimulate rubber biosynthesis in guayule plants, primarily by promoting rubber-producing cortical parenchyma cells and inducing the activity of enzymes in the pathway of rubber biosynthesis. Further progress in increasing rubber production in guayule requires a better understanding of the ultrastructure of the organelles in the rubber producing cortical parenchyma. The objective of this study was to investigate the ultrastructure of the organelles in the rubber producing cortical parenchyma. The electron photomicrographs show that the rubber-producing cortical parenchyma, in contrast to mature cortical parenchyma in stems not exposed to the low temperatures, contain a high population of rubber particles, an abundant number of mitochondria, chloroplasts, a well-structured nucleus, rough endoplasmic reticulum and Golgi apparati. The double membrane nucleus is important in the low temperature induction of rubber-forming enzymes: rubber transferase and 3-hydroxy-3-methylglutaryl coenzyme A reductase. Photographic enlargements of the population of mitochondria show well-developed inner membrane folding that functions in ATP production to support the energy requirements of rubber biosynthesis. Electron photomicrographs show dividing chloroplasts that increase the number of plastids in the rubber-producing parenchyma. The well-structured grana and stroma lamellae may produce energy for the stroma production of carbon precursors of rubber. Photographic enlargements show a cortical parenchyma with an active Golgi apparatus, producing an abundant number of vesicles. Features of this electron photomicrograph is the fusion of a Golgi vesicle with a rubber particle, suggesting the transport of Golgi-processed glycolipids and glycoproteins to the rubber particles, and the rubber particles extending into the central cytosol still attached to the RER indicating an earlier origin of the rubber particle from the RER. The electron photomicrographs of the ultrastructure of rubber-producing cortical parenchyma in guayule stems support the conclusion that these cells contain an abundant number of organelles relating to the low temperature stimulated rubber synthesis.  相似文献   

English field samples of Thrips tabaci show strong and ubiquitous resistance to deltamethrin     

Stephen P Foster  Kevin Gorman  Ian Denholm 《Pest management science》2010,66(8):861-864

BACKGROUND: Onion thrips, Thrips tabaci Lindeman, is a prevalent pest of glasshouse and field vegetables, such as leeks and salad onions. Pesticides are the main option for control, but this approach risks the evolution and spread of insecticide resistance. In the light of anecdotal reports in the United Kingdom of poor efficacy of pyrethroids against T. tabaci, thought to be primarily a consequence of resistance, the responses to deltamethrin of ten English samples of T. tabaci, collected from field leeks and salad onions in 2006, were measured to establish the level and prevalence of potential resistance to this compound. RESULTS: All the samples showed significant deltamethrin resistance that was comparable or slightly lower than the maximum level reported previously for T. tabaci from New Zealand. CONCLUSION: The mechanism(s) conferring deltamethrin resistance remain unknown at present but are likely to extend to other synthetic pyrethroids approved for use against this species. The findings suggest that these compounds are unlikely to give satisfactory control of T. tabaci in England and have stimulated the recommendation to use alternatives. Copyright © 2010 Society of Chemical Industry  相似文献   

Estimation of bioenergy crop yield and N status by hyperspectral canopy reflectance and partial least square regression     

A. J. Foster  V. G. Kakani  J. Mosali 《Precision Agriculture》2017,18(2):192-209

The objective of this study was to compare performance of partial least square regression (PLSR) and best narrowband normalize nitrogen vegetation index (NNVI) linear regression models for predicting N concentration and best narrowband normalize different vegetation index (NDVI) for end of season biomass yield in bioenergy crop production systems. Canopy hyperspectral data was collected using an ASD FieldSpec FR spectroradiometer (350–2500 nm) at monthly intervals in 2012 and 2013. The cropping systems evaluated in the study were perennial grass {mixed grass [50 % switchgrass (Panicum virgatum L.), 25 % Indian grass “Cheyenne” (Sorghastrum nutans (L.) Nash) and 25 % big bluestem “Kaw” (Andropogon gerardii Vitman)] and switchgrass “Alamo”} and high biomass sorghum “Blade 5200” (Sorghum bicolor (L.) Moench) grown under variable N applications rates to estimate biomass yield and quality. The NNVI was computed with the wavebands pair of 400 and 510 nm for the high biomass sorghum and 1500 and 2260 nm for the perennial grass that were strongly correlated to N concentration for both years. Wavebands used in computing best narrowband NDVI were highly variable, but the wavebands from the red edge region (710–740 nm) provided the best correlation. Narrowband NDVI was weakly correlated with final biomass yield of perennial grass (r² = 0.30 and RMSE = 1.6 Mg ha^?1 in 2012 and r² = 0.37 and RMSE = 4.0 Mg ha^?1, but was strongly correlated for the high biomass sorghum in 2013 (r² = 0.72 and RMSE = 4.6 Mg ha^?1). Compared to the best narrowband VI, the RMSE of the PLSR model was 19–41 % lower for estimating N concentration and 4.2–100 % lower for final biomass. These results indicates that PLSR might be best for predicting the final biomass yield using spectral sample obtained in June to July, but narrowband NNVI was more robust and useful in predicting N concentration.  相似文献   

Comparison of direct sampling and brochoalveolar lavage for determining active drug concentrations in the pulmonary epithelial lining fluid of calves injected with enrofloxacin or tilmicosin          下载免费PDF全文

D. M. Foster  H. J. Sylvester  M. G. Papich 《Journal of veterinary pharmacology and therapeutics》2017,40(6):e45-e53

Antibiotic distribution to interstitial fluid (ISF) and pulmonary epithelial fluid (PELF) was measured and compared to plasma drug concentrations in eight healthy calves. Enrofloxacin (Baytril^® 100) was administered at a dose of 12.5 mg/kg subcutaneously (SC), and tilmicosin (Micotil^® 300) was administered at a dose of 20 mg/kg SC. PELF, sampled by two different methods—bronchoalveolar lavage (BAL) and direct sampling (DS)—plasma, and ISF were collected from each calf and measured for tilmicosin, enrofloxacin and its metabolite ciprofloxacin by HPLC. Pharmacokinetic analysis was performed on the concentrations in each fluid, for each drug. The enrofloxacin/ciprofloxacin concentration as measured by AUC in DS samples was 137 ± 72% higher than in plasma, but in BAL samples, this value was 535 ± 403% (p < .05). The concentrations of tilmicosin in DS and BAL samples exceeded plasma drug concentrations by 567 ± 189% and 776 ± 1138%, respectively. The enrofloxacin/ciprofloxacin concentrations collected by DS were significantly different than those collected by BAL, but the tilmicosin concentrations were not significantly different between the two methods. Concentrations of enrofloxacin/ciprofloxacin exceeded the MIC values for bovine respiratory disease pathogens but tilmicosin did not reach MIC levels for these pathogens in any fluids.  相似文献   

Interventions for atopic dermatitis in dogs: a systematic review of randomized controlled trials     

Thierry Olivry  Aiden P. Foster  Ralf S. Mueller  Neil A. McEwan  Christopher Chesney  Hywel C. Williams 《Veterinary dermatology》2010,21(1):4-22

The objective of this systematic review, which was performed following the guidelines of the Cochrane collaboration, was to assess the effects of interventions for treatment of atopic dermatitis (AD) in dogs. Citations identified from three databases (MEDLINE, Thomson's Science Citation Index Expanded and CAB Abstracts) and trials published by December 2007 were selected. Proceedings books from the major veterinary dermatology international congresses were hand searched for relevant citations. The authors selected randomized controlled trials (RCTs), published from January 1980 to December 2007, which reported the efficacy of topical or systemic interventions for treatment or prevention of canine AD. Studies had to report assessments of either pruritus or skin lesions, or both. Studies were selected and data extracted by two reviewers, with discrepancies resolved by a third arbitrator. Missing data were requested from study authors of recently published trials. Pooling of results and meta-analyses were performed for studies reporting similar interventions and outcome measures. A total of 49 RCTs were selected, which had enrolled 2126 dogs. This review found some evidence of efficacy of topical tacrolimus (3 RCTs), topical triamcinolone (1), oral glucocorticoids (5), oral ciclosporin (6), subcutaneous recombinant γ-interferon (1) and subcutaneous allergen-specific immunotherapy (3) to decrease pruritus and/or skin lesions of AD in dogs. One high-quality RCT showed that an oral essential fatty acid supplement could reduce prednisolone consumption by approximately half. Additional RCTs of high design quality must be performed to remedy previous flaws and to test interventions for prevention of flares of this disease.  相似文献   

Molecular diagnostics for fungal plant pathogens     

McCartney HA  Foster SJ  Fraaije BA  Ward E 《Pest management science》2003,59(2):129-142

Accurate identification of fungal phytopathogens is essential for virtually all aspects of plant pathology, from fundamental research on the biology of pathogens to the control of the diseases they cause. Although molecular methods, such as polymerase chain reaction (PCR), are routinely used in the diagnosis of human diseases, they are not yet widely used to detect and identify plant pathogens. Here we review some of the diagnostic tools currently used for fungal plant pathogens and describe some novel applications. Technological advances in PCR-based methods, such as real-time PCR, allow fast, accurate detection and quantification of plant pathogens and are now being applied to practical problems. Molecular methods have been used to detect several pathogens simultaneously in wheat, and to study the development of fungicide resistance in wheat pathogens. Information resulting from such work could be used to improve disease control by allowing more rational decisions to be made about the choice and use of fungicides and resistant cultivars. Molecular methods have also been applied to the study of variation in plant pathogen populations, for example detection of different mating types or virulence types. PCR-based methods can provide new tools to monitor the exposure of a crop to pathogen inoculum that are more reliable and faster than conventional methods. This information can be used to improve disease control decision making. The development and application of molecular diagnostic methods in the future is discussed and we expect that new developments will increase the adoption of these new technologies for the diagnosis and study of plant disease.  相似文献   

Amplified esterase genes and their relationship with other insecticide resistance mechanisms in English field populations of the aphid,Myzus persicae (Sulzer)     

Field LM  Foster SP 《Pest management science》2002,58(9):889-894

Myzus persicae samples were collected from populations present on a range of field crops between 1997 and 2000. A combination of biochemical, DNA-based diagnostics and bioassays was used to assess the presence of three insecticide resistance mechanisms: elevated carboxylesterase (E4 or FE4), insensitive acetylcholinesterase and insensitive sodium channels (knockdown resistance, kdr). For the carboxylesterases, both the levels of enzyme and the type of gene present (E4 or FE4) were determined. The results showed that during the time period studied there was a dramatic reduction in the proportion of aphids with very high levels of E4 and an increase in those with lower levels of FE4. There was also a slightly different E4 gene present in a limited number of samples. The change in esterase genes was accompanied by a virtual loss of the insensitive AChE variant and a maintenance of aphids with kdr. The selection pressures and other factors leading to these changes in field populations of M persicae are discussed.  相似文献   

Effects of lysostaphin on Staphylococcus aureus infections of the mouse mammary gland   总被引：5，自引：0，他引：5  

A J Bramley  R Foster 《Research in veterinary science》1990,49(1):120-121

A 5 to 6 log10 reduction in the viable count of Staphylococcus aureus was produced in vitro with 10 micrograms lysostaphin ml-1 milk. Infusion of the lactating murine mammary gland with 10 micrograms lysostaphin, immediately following inoculation with 10(8) colony forming units of S aureus, resulted in a significant 2 to 3 log10 reduction in viable S aureus (P less than 0.02) within 30 minutes. Pre-infusion with 10 micrograms lysostaphin either immediately before or one hour before staphylococcal challenge reduced the recovery of S aureus by more than 6 log10 and greatly reduced pathological changes typical of S aureus mastitis. This clearly demonstrates that lysostaphin has considerable potential for the therapeutic or prophylactic control of staphylococcal mastitis.  相似文献   

Bacterial pathogens in dry dog foods   总被引：1，自引：0，他引：1  

W C Ladiges  J F Foster 《Journal of the American Veterinary Medical Association》1974,165(2):181-182

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Temporal relationships of viremia, interferon activity, and antibody responses of sheep infected with several bluetongue virus strains.     

N M Foster  A J Luedke  I M Parsonson  T E Walton 《American journal of veterinary research》1991,52(2):192-196

Sheep had viremias that were first detected on day 3 (+/- 1) after infection with several strains of bluetongue virus (BTV) representing United States serotypes 10, 11, 13, and 17. Diphasic peaks of infectivity were attained on days 6 and 10 (+/- 2). Interferon (IFN) was first detected in serum samples on day 5 (+/- 1), and reached greatest concentrations on day 6 (+/- 2), which coincided with the first viremic peak; IFN concentrations then decreased toward zero by day 10 (+/- 2). Interferon peak concentrations induced approximately a 90% decrease in virus titer. The decrease in IFN concentrations by day 9 (+/- 2) corresponded with the second viremic peak on day 10 (+/- 2). Onset of the decrease in detectable concentrations of virus after the second peak of viremia corresponded to the initial detection of serum antibody to BTV by day 10 (+/- 2). Virus titer decreased and antibody production increased until approximately days 21 to 28, when the titers plateaued and virus was not detected. Febrile responses peaked on day 7 (+/- 1) during the peak viremic period. The WBC count was depressed at the time the virus titer increased, but returned to normal values while the sheep were still viremic. Diphasic viremias in BTV-infected sheep were attributed to induction of high concentrations of IFN concurrent with the first virus titer peak, followed by production of antibody to specific BTV strains and a subsequent reduction in viremia at the second virus titer peak.  相似文献