Mode of action of methoprene in affecting female reproduction in the African malaria mosquito,Anopheles gambiae     

Hua Bai  Dale B Gelman  Subba R Palli 《Pest management science》2010,66(9):936-943

BACKGROUND: One of the most studied actions of juvenile hormone (JH) is its ability to modulate ecdysteroid signaling during insect development and metamorphosis. Previous studies in mosquitoes showed that 20‐hydroxyecdysone (20E) regulates vitellogenin synthesis. However, the action of JH and its mimics, e.g. methoprene, on female reproduction of mosquitoes remains unknown. RESULTS: Here, a major malaria vector, Anopheles gambiae Giles, was used as a model insect to study the action of methoprene on female reproduction. Ecdysteroid titers and expression profiles of ecdysone‐regulated genes were determined before and after a blood meal. An ecdysteroid peak was detected at 12 h post blood meal (PBM). The maximum expression of ecdysone‐regulated genes, such as ecdysone receptor (EcR), hormone receptor 3 (HR3) and vitellogenin (Vg) gene, coincided with the ecdysteroid peak. Interestingly, topical application of methoprene at 6 h PBM delayed ovarian development and egg maturation by suppressing the expression of ecdysone‐regulated genes in female mosquitoes. CONCLUSION: The data suggest that ecdysteroid titers are correlated with Vg synthesis, and methoprene affects vitellogenesis by modulating ecdysteroid action in A. gambiae. Copyright © 2010 Society of Chemical Industry  相似文献   

Improving the yield, processing quality and disease and pest resistance of potatoes by genotypic recurrent selection     

John E. Bradshaw  M. Finlay B. Dale  George R. Mackay 《Euphytica》2009,170(1-2):215-227

A potato (Solanum tuberosum Gp Tuberosum) breeding programme is described and analysed in which resistances to late blight [Phytophthora infestans (Mont.) de Bary] and the white potato cyst nematode (Globodera pallida) have been combined with a modest increase in yield and acceptable fry colour for processing. It began in 1991 and has involved cycles of crossing, selection between from 120 to 145 progenies (full-sib families), and clonal selection within the selected progenies. We have shown that the breeding scheme can operate on a 3-year cycle with limited within progeny selection, and on a 5- or 6-year cycle with more extensive within progeny selection. Six years are required when resistance to late blight is assessed in the tubers as well as the foliage. The more extensive within progeny selection is recommended once genes have been combined from sufficient parents to achieve one’s objectives. The yield increase after three cycles of indirect selection through breeders’ visual preference was only modest because it was operating against a decrease which would occur in the absence of selection. A practical improvement in the scheme would be to increase the number of progenies assessed to over 200, given the moderate to high heritabilities of the progeny and clonal tests. But this would require a considerable effort because the success rate achieved with the potato pollinations was typical at just over 30%. In the fourth cycle we showed how new breeding objectives and germplasm could be accommodated whilst continuing to maintain progress, something that is important in any long term breeding strategy.  相似文献   

Feedbacks and synergism among biogeochemistry,basic ecology,and forest soil science     

Helga Van Miegroet  Dale W. Johnson 《Forest Ecology and Management》2009

Sustainable natural resource use is only possible when management practices are grounded in the basics of soil science and ecology, and reflect a sound understanding of the interaction between soil–plant processes and nutrient cycling pathways. History has yielded numerous examples where an incomplete understanding of biogeochemistry has resulted in unexpected and sometimes undesirable management outcomes. In this paper we explore, using nitrogen biogeochemistry as our working model, how the boundaries between basic science and management-driven research have become increasingly blurred over time. The mutual feedbacks and synergisms between basic and applied sciences have been key in solving many environmental problems and have increased our ability to predict ecosystem responses to natural and anthropogenic disturbances. Projects with a distinct management focus have also provided a fertile ground for cutting-edge and theoretical studies, and have greatly improved our understanding of the relationship between ecosystem structure and function. Periodically, scientists are faced with unexpected results or oddities that force us to question the veracity of long-held notions and lead us to revise conceptual models.  相似文献   

High resolution temporal variation in wood properties in irrigated and nonirrigated Eucalyptus globulus     

David M. Drew  Geoffrey M. Downes  Anthony P. O’Grady  Jennifer Read  Dale Worledge 《Annals of Forest Science》2009,66(4):406-406

? Environmental determinants of wood properties variation were examined in Eucalyptus globulus, a globally important hardwood plantation species, in southern Tasmania, Australia.

? Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees.

? Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees.

? Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated.

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Enteritis of Early Weaned Pigs: I. Enteropathogenic Escherichia coli   总被引：7，自引：0，他引：7       下载免费PDF全文

S. L. Chopra  A. C. Blackwood    D. G. Dale 《Canadian journal of veterinary research》1964,28(10):239-242,243-247

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Rice (Oryza sativa) response to drift rates of glyphosate     

Koger CH  Shaner DL  Krutz LJ  Walker TW  Buehring N  Henry WB  Thomas WE  Wilcut JW 《Pest management science》2005,61(12):1161-1167

Greenhouse and field studies were conducted to investigate response of two rice varieties, Priscilla and Cocodrie, to sub-lethal rates of glyphosate in terms of injury, shikimate accumulation and yield. In the greenhouse, more shikimate accumulated in Cocodrie than Priscilla at comparable glyphosate rates applied to plants at the three-leaf stage. In field studies, glyphosate was applied to both varieties when they were 74-cm tall and in the internode separation growth stage. Visual injury, plant height, and leaf-tissue samples for shikimate analysis were collected at 3, 7, 14, 21 and 28 days after treatment (DAT). Rice yield was also determined. Noticeable visual injury and height reduction to both varieties was observed as early as 7 and 3 DAT in Cocodrie and Priscilla, respectively. Shikimate levels in leaves began to increase in both varieties by 3 DAT in a dose-dependent manner and reached a peak between 7 and 14 DAT. Elevated shikimate levels were still detectable by 28 DAT. Similar levels of shikimate accumulated in both varieties at comparable glyphosate rates. However, glyphosate treatment at comparable rates reduced rice yields more in Cocodrie than in Priscilla. The highest rate of glyphosate reduced yield in Cocodrie by 92% whereas there was only a 60% yield reduction in Priscilla. Shikimate levels in glyphosate-treated rice were strongly correlated to yield reductions across both varieties and appeared to be a better predictor of yield reduction than was visual injury. Visual injury coupled with measured shikimate levels can be used collaboratively to identify glyphosate exposure and estimate subsequent rice yield reductions.  相似文献   

Exploring student attitudes to directed self-learning online through evaluation of an Internet-based biomolecular sciences resource     

Dale VH  Nasir L  Sullivan M 《Journal of veterinary medical education》2005,32(1):129-137

RATIONALE FOR THE STUDY: In 2000, funding was awarded by the University of Glasgow's Learning and Teaching Development Fund (L&TDF) for the authors to develop an interactive, online learning resource for veterinary biomolecular sciences teaching. This course is a core component of the veterinary undergraduate curriculum at the university. Evaluations were carried out to gauge students' experiences of using the resource as a basis for exploring students' attitudes toward online, independent learning. METHODOLOGY: Peers were asked to review the design and content of four modules, also evaluated by students using questionnaires and focus group discussions. Additionally, students were observed using the modules. Both first-year students and second-year direct-entry students (i.e., students entering the veterinary program with advanced training) participated in the evaluation, which allowed for some comparison between the groups. One cohort used the modules independently, and their responses were compared with the cohorts that used the modules in scheduled classes. RESULTS AND CONCLUSIONS: The evaluations indicate that this is a useful resource that could act as a template for other courses within the veterinary undergraduate curriculum, particularly for learning of basic sciences. On average, first-year and timetabled students rated the program more highly overall, rated the program more highly in relation to previous instruction, and rated tutor presence as more important than second-year direct-entry and independent students did. The lower rating given to tutor presence by second-year direct-entry and independent students indicates that they are more confident using the modules without tutor supervision.  相似文献   

Ten years of CLIVE (Computer-Aided Learning in Veterinary Education) in the United Kingdom     

Dale VH  McConnell G  Short A  Sullivan M 《Journal of veterinary medical education》2005,32(1):47-50

This paper outlines the work of the CLIVE (Computer-Aided Learning in Veterinary Education) project over a 10-year period, set against the backdrop of changes in education policy and learning technology developments. The consortium of six UK veterinary schools and 14 international Associate Member Schools has been very successful. Sustaining these partnerships requires that the project redefine itself and adapt to cater to the diverse learning needs of today's students and to changing professional and societal needs on an international scale.  相似文献   

Survival time, lifespan, and quality of life in dogs with idiopathic Fanconi syndrome     

Yearley JH  Hancock DD  Mealey KL 《Journal of the American Veterinary Medical Association》2004,225(3):377-383

OBJECTIVE: To evaluate survival time of dogs with idiopathic Fanconi syndrome. DESIGN: Case series. ANIMALS: 60 dogs with idiopathic Fanconi syndrome. PROCEDURE: Data were collected by means of questionnaires distributed to owners and veterinarians of dogs with idiopathic Fanconi syndrome and by examination of medical records when accessible. Questionnaires and records were reviewed for criteria used in diagnosis, treatments administered, survival time, and subjective owner perceptions regarding their dogs' general condition. RESULTS: 58 of the dogs were Basenjis. Fifty-seven dogs (95%) were reportedly managed by use of a single therapeutic regimen. Median survival time after diagnosis of Fanconi syndrome was 5.25 years; median estimated lifespan was calculated to be between 11.3 and 12.1 years. Owners of 28 of 29 (97%) dogs still alive at the time of the study subjectively assessed their dogs' general condition as good to excellent. Seizures or other neurologic dysfunction was reported for 11 dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that expected lifespan for dogs with idiopathic Fanconi syndrome was not substantially reduced, compared with expected lifespan for unaffected dogs, and that affected dogs generally had a good to excellent quality of life, as subjectively assessed by their owners. What effect the treatment regimen had on survival time or lifespan could not be determined, given the small number of dogs managed with other methods. The high percentage of dogs with neurologic abnormalities was a concern, but whether this was related to Fanconi syndrome or represented a breed-related predisposition to neurologic disease could not be determined.  相似文献   

Introducing the theme--continuing veterinary medical education: where are we?     

Moore DA 《Journal of veterinary medical education》2003,30(1):12

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