Reduced conception rates associated with bovine mastitis during a 'window of opportunity'     

Perrin L  Bostelmann RW  Sheldon IM 《The Veterinary record》2007,161(2):61-62

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Mercury antagonists: protection of plants against vapor injury by thiamine and other compounds     

S. M. Siegel  B. Z. Siegel  Leeann Sheldon  Elizabeth Yaeger  Darwin Chang 《Water, air, and soil pollution》1986,27(3-4):243-246

Mercury vapor-induced abscission ofColeus cuttings was prevented by Thiamine, other organo-S (Se) compounds and selenite, but not by common sugar metabolites, amino acids, non-auxin growth regulators and selenate. Protection was also afforded to other plants including ferns and gymnosperms. Thus the compounds that protect plants against Hg intoxication correspond to the Hg antagonists known in animals including man.  相似文献   

Adaptive phenotypic plasticity in response to climate change in a wild bird population     

Charmantier A  McCleery RH  Cole LR  Perrins C  Kruuk LE  Sheldon BC 《Science (New York, N.Y.)》2008,320(5877):800-803

Rapid climate change has been implicated as a cause of evolution in poorly adapted populations. However, phenotypic plasticity provides the potential for organisms to respond rapidly and effectively to environmental change. Using a 47-year population study of the great tit (Parus major) in the United Kingdom, we show that individual adjustment of behavior in response to the environment has enabled the population to track a rapidly changing environment very closely. Individuals were markedly invariant in their response to environmental variation, suggesting that the current response may be fixed in this population. Phenotypic plasticity can thus play a central role in tracking environmental change; understanding the limits of plasticity is an important goal for future research.  相似文献   

Conservation value of variable connectivity: aquatic invertebrate assemblages of channel and floodplain habitats of a central Australian arid-zone river, Cooper Creek     

Fran Sheldon  Andrew J. BoultonJim T. Puckridge 《Biological conservation》2002,103(1):13-31

Rapidly expanding water resource development in arid and semi-arid zones of Australia threatens the flow regime and ecological integrity of the few large dryland rivers and their immense floodplains. Efforts to manage and conserve the surface waters of these rivers are hampered by limited scientific data on the ecology of their flora and fauna and on their responses to the high natural variability of flow regime that typifies dryland rivers. Irregular floods connect channel and floodplain wetlands to differing degrees and for varying periods of time but the ecological significance of this connectivity is poorly understood. On Cooper Creek, a large dryland river in central Australia, we explored the degree to which assemblage composition varied with connectivity and hydrological regime. Shortly after protracted regional flooding, we sampled aquatic macroinvertebrate assemblages from the principal microhabitats in 12 channel and floodplain wetlands. Ephemeral and temporary lakes tended to have fewer taxa than semi-permanent channel or terminal lake habitats. Although hydrological connection had only recently been lost for some wetlands, there was already evidence of divergence in aquatic macroinvertebrate assemblage composition. Disruption of the natural variability in connectivity and hydrological regime by excessive water abstraction or river-flow regulation threatens the ecological integrity and aquatic macroinvertebrate biodiversity of dryland rivers. Preservation of the irregular flow regime and sporadic connectivity underpins conservation of the mosaic of floodplain wetlands that play such a crucial role in the ecosystem functioning of rivers such as Cooper Creek.  相似文献   

Space,Time, and Local Employment Growth: An Application of Spatial Regression Analysis     

RICHARD SHEARMUR  PHILIPPE APPARICIO  PAULINE LIZION  MARIO POLSE 《Growth and change》2007,38(4):696-722

ABSTRACT Local and regional employment growth is generally studied either by searching for local qualitative explanatory factors such as governance, synergy between firms, and milieu effects, or by searching for general growth factors using statistical techniques. The body of work that relies on this approach has tended, in keeping with economics’ nomothetic tradition, to assume that local and regional growth factors are constant over space. The focus of this paper is on exploring the spatial stationarity of employment growth factors in Canada, but it also seeks to clarify some of the broad principles behind spatial regression techniques in order to provide a point of entry and a conceptual framework for empirical researchers. To do so, we apply a recently developed technique, Geographically Weighted Regression (GWR), and we explore the method's advantages and limits for answering our research question. We find evidence that growth factors differ across Canada, but we also conclude that the GWR technique, given the number and shape of regions available for our analysis and given certain limitations that are currently inherent to the method, can only provide tentative and exploratory results.  相似文献   

Cross‐breeding performance of white leghorn and Australorp lines selected under continuous light for short interval between eggs: Full‐year egg production and efficiency of food utilisation     

B. H. Yoo  B. L. Sheldon  R. N. Podger 《British poultry science》1984,25(2):233-243

1. White Leghorn (LS) and Australorp (AS) lines selected for short oviposition interval and their control lines (LC and AC), together with three strains of Australian commercial layers, were evaluated for crossbreeding performance.

2. The estimates of selection effect on crossbreeding performance in lines LS and AS respectively were 3·5% and 15·2% for survivors’ egg number, ‐3·3% and ‐2·0% for average egg weight, and 4·3% and 7·4% for efficiency of food utilisation.

3. Compared to the commercial strains, the LS × AS cross was 13 to 15% higher for egg number, 7 to 10% lower for egg weight and 2 to 7% better for efficiency of food utilisation.

4. The LC × AC cross laid more but smaller eggs than the commerical strains. This raised the question of how effective conventional selection in the commercial nucleus flocks had been in improving egg number in the previous 10 years, a period when the control lines had been bred without deliberate selection.

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Pathogenesis of experimentally produced mouse adenovirus infection in mice   总被引：4，自引：0，他引：4  

F C Heck  W G Sheldon  C A Gleiser 《American journal of veterinary research》1972,33(4):841-846

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Congenital hypothyroidism in Scottish Deerhound puppies     

WF ROBINSON  SE SHAW  B. STANLEY  RS WYBURN 《Australian veterinary journal》1988,65(12):386-389

Two Scottish Deerhound puppies had clinical and pathological features consistent with the diagnosis of congenital non-goitrous hypothyroidism. They were from separate litters, but were the progeny of the same sire and dam. The puppies were smaller, had shorter limbs and shorter, broader heads than their littermates. They also had histories of weakness, difficulty in walking and somnolence. A characteristic radiographic feature was the absence of epiphyseal growth centres. Both had depressed serum thyroxine (T4) levels and one did not respond to exogenous thyroid stimulating hormone. On necropsy, the thyroid glands were small, the follicles varied in size and contained little or no colloid. The adenohypophysis contained many cells with markedly vacuolated cytoplasm. It is suggested that the clinicopathological pattern is the result of a primary thyroid abnormality. Possible mechanisms include either primary thyroid hypoplasia or an unresponsiveness to thyroid stimulating hormone.  相似文献   

Association between clinical hypocalcaemia and postpartum endometritis     

Whiteford LC  Sheldon IM 《The Veterinary record》2005,157(7):202-203

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2005 Guidelines for the diagnosis, prevention and management of heartworm (Dirofilaria immitis) infection in dogs   总被引：2，自引：0，他引：2  

Nelson CT  McCall JW  Rubin SB  Buzhardt LF  Dorion DW  Graham W  Longhofer SL  Guerrero J  Robertson-Plouch C  Paul A;Executive Board of the American Heartworm Society 《Veterinary parasitology》2005,133(2-3):255-266

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