The role of regulatory mechanisms for control of plant diseases and food security — case studies from potato production in Britain

Being aware of the potentially devastating impacts of plant diseases on food security, governments have designed and employ plant health legislation to prevent or inhibit the worst impacts. The development of such policies in Britain, and latterly in Europe, can be closely linked to disease events that have occurred in the potato sector. We analyse early and current examples of policies governing potato diseases in Britain to identify the decision processes leading to the implementation of such phytosanitary policies and how they have evolved over time and in response to different disease threats. Reasons for developing and implementing phytosanitary policies include the desire to prevent pathogens being introduced (entering and establishing in a new area), the protection of export markets, and the lack of effective control measures. Circumstances in which regulatory policies would not be appropriate could include situations where a disease is already widely distributed, unacceptable costs, lack of exclusion measures, or difficulties of disease diagnosis. We conclude that in general, government policies have worked well in protecting British potato growing over the last one hundred years, despite of the failures of some of the policies discussed here. They have also contributed much to the development of plant health policies for other crops. Voluntary grower initiatives are a new mechanism complementing existing formal policies with an additional level of security that allows individual growers to take on additional responsibility rather than relying entirely on government legislation

Tree Species Control Rates of Free-Living Nitrogen Fixation in a Tropical Rain Forest

Tropical rain forests represent some of the most diverse ecosystems on earth, yet mechanistic links between tree species identity and ecosystem function in these forests remains poorly understood. Here, using free-living nitrogen (N) fixation as a model, we explore the idea that interspecies variation in canopy nutrient concentrations may drive significant local-scale variation in biogeochemical processes. Biological N fixation is the largest “natural” source of newly available N to terrestrial ecosystems, and estimates suggest the highest such inputs occur in tropical ecosystems. While patterns of and controls over N fixation in these systems remain poorly known, the data we do have suggest that chemical differences among tree species canopies could affect free-living N fixation rates. In a diverse lowland rain forest in Costa Rica, we established a series of vertical, canopy-to-soil profiles for six common canopy tree species, and we measured free-living N fixation rates and multiple aspects of chemistry of live canopy leaves, senesced canopy leaves, bulk leaf litter, and soil for eight individuals of each tree species. Free-living N fixation rates varied significantly among tree species for all four components, and independent of species identity, rates of N fixation ranged by orders of magnitude along the vertical profile. Our data suggest that variations in phosphorus (P) concentration drove a significant fraction of the observed species-specific variation in free-living N fixation rates within each layer of the vertical profile. Furthermore, our data suggest significant links between canopy and forest floor nutrient concentrations; canopy P was correlated with bulk leaf litter P below individual tree crowns. Thus, canopy chemistry may affect a suite of ecosystem processes not only within the canopy itself, but at and beneath the forest floor as well

Nutrient Regulation of Organic Matter Decomposition in a Tropical Rain Forest

errestrial biosphere–atmosphere CO2 exchange is dominated by tropical forests, so understanding how nutrient availability affects carbon (C) decomposition in these ecosystems is central to predicting the global C cycle\u27s response to environmental change. In tropical rain forests, phosphorus (P) limitation of primary production and decomposition is believed to be widespread, but direct evidence is rare. We assessed the effects of nitrogen (N) and P fertilization on litter-layer organic matter decomposition in two neighboring tropical rain forests in southwest Costa Rica that are similar in most ways, but that differ in soil P availability. The sites contain 100–200 tree species per hectare and between species foliar nutrient content is variable. To control for this heterogeneity, we decomposed leaves collected from a widespread neotropical species, Brosimum utile. Mass loss during decomposition was rapid in both forests, with B. utile leaves losing \u3e80% of their initial mass in (DOM) rather than direct CO2 mineralization. While P fertilization did not significantly affect mass loss in the litter layer, it did stimulate P immobilization in decomposing material, leading to increased P content and a lower C:P ratio in soluble DOM. In turn, increased P content of leached DOM stimulated significant increases in microbial mineralization of DOM in P-fertilized soil. These results show that, while nutrients may not affect mass loss during decomposition in nutrient-poor, wet ecosystems, they may ultimately regulate CO2 losses (and hence C storage) by limiting microbial mineralization of DOM leached from the litter layer to soil

Experimental Drought in a Tropical Rain Forest Increases Soil Carbon Dioxide Losses to the Atmosphere

Climate models predict precipitation changes for much of the humid tropics, yet few studies have investigated the potential consequences of drought on soil carbon (C) cycling in this important biome. In wet tropical forests, drought could stimulate soil respiration via overall reductions in soil anoxia, but previous research suggests that litter decomposition is positively correlated with high rainfall fluxes that move large quantities of dissolved organic matter (DOM) from the litter layer to the soil surface. Thus, reduced rainfall could also limit C delivery to the soil surface, reducing respiration rates. We conducted a throughfall manipulation experiment to investigate how 25% and 50% reductions in rainfall altered both C movement into soils and the effects of those DOM fluxes on soil respiration rates. In response to the experimental drought, soil respiration rates increased in both the −25% and −50% treatments. Throughfall fluxes were reduced by 26% and 55% in the −25% and −50% treatments, respectively. However, total DOM fluxes leached from the litter did not vary between treatments, because the concentrations of leached DOM reaching the soil surface increased in response to the simulated drought. Annual DOM concentrations averaged 7.7 ± 0.8, 11.2 ± 0.9, and 15.8 ± 1.2 mg C/L in the control, −25%, and −50% plots, respectively, and DOM concentrations were positively correlated with soil respiration rates. A laboratory incubation experiment confirmed the potential importance of DOM concentration on soil respiration rates, suggesting that this mechanism could contribute to the increase in CO2 fluxes observed in the reduced rainfall plots. Across all plots, the data suggested that soil CO2 fluxes were partially regulated by the magnitude and concentration of soluble C delivered to the soil, but also by soil moisture and soil oxygen availability. Together, our data suggest that declines in precipitation in tropical rain forests could drive higher CO2 fluxes to the atmosphere both via increased soil O2 availability and through responses to elevated DOM concentrations

Knowledge and attitudes of men to prostate cancer

Objective: To ascertain the current level of understanding about prostate cancer (PCa), including treatment options and potential side effects of treatment, among older men. Design and Setting: Questionnaires administered by general practitioners (GPs) in 5 general practices in the Perth metropolitan and regional areas of Western Australia. Participants: Convenience sample of men aged 40-80 years (n=503) with or without prostate cancer presenting for routine consultations. Main outcome measures: Knowledge and attitudes of men to prostate cancer Results: Eighty percent of men did not know the function of the prostate and 48% failed to identify PCa as the most common internal cancer in men. Thirty-five percent had no knowledge of the treatments for PCa and 53% had no knowledge of the side effects of treatments. Asked how they would arrive at a decision about treatment, 70% stated they would ask the GP/specialist for all their options and then decide themselves. Conclusion: This study confirms a deficit in knowledge of the disease among men in the at risk age group. Lack of knowledge encompassed areas which could delay diagnosis and hence treatment. Overall the population preferred some GP/specialist involvement in treatment decision making

PPARδ status and mismatch repair mediated neoplasia in the mouse intestine

BACKGROUND: Therapeutic regulation of PPARδ activity using selective agonists has been proposed for various disorders. However, the consequences of altered peroxisome proliferator-activated receptor delta (PPARδ) activity in the context of intestinal tumourigenesis remain somewhat unclear. Contradictory evidence suggesting PPARδ either attenuates or potentiates intestinal neoplasia. To further investigate the PPARδ dependency of intestinal tumourigenesis, we have analysed the consequences of PPARδ deficiency upon intestinal neoplasia occurring in mice with impaired mismatch DNA repair. METHODS: Mice deficient for both PPARδ and the mismatch repair gene Mlh1 were produced and the incidence and severity of intestinal neoplasia recorded. RESULTS: No significant differences between the control genotypes and the double mutant genotypes were recorded indicating that deficiency of PPARδ does not modify impaired mismatch repair induced neoplasia. CONCLUSION: In contrast with the previously observed acceleration of intestinal neoplasia in the context of the Apc(Min/+ )mouse, PPARδ deficiency does not alter the phenotype of mismatch repair deficiency. This data supports the notion that PPARδ is not required for adenoma formation and indicate that any pro-tumourigenic effect of PPARδ inactivation may be highly context dependent

Spatiotemporal regulation of liver development by the Wnt/β- catenin pathway

While the Wnt/β-catenin pathway plays a critical role in the maintenance of the zonation of ammonia metabolizing enzymes in the adult liver, the mechanisms responsible for inducing zonation in the embryo are not well understood. Herein we address the spatiotemporal role of the Wnt/β-catenin pathway in the development of zonation in embryonic mouse liver by conditional deletion of Apc and β-catenin at different stages of mouse liver development. In normal development, the ammonia metabolising enzymes carbamoylphosphate synthetase I (CPSI) and Glutamine synthetase (GS) begin to be expressed in separate hepatoblasts from E13.5 and E15.5 respectively and gradually increase in number thereafter. Restriction of GS expression occurs at E18 and becomes increasingly limited to the terminal perivenous hepatocytes postnatally. Expression of nuclear β-catenin coincides with the restriction of GS expression to the terminal perivenous hepatocytes. Conditional loss of Apc resulted in the expression of nuclear β-catenin throughout the developing liver and increased number of cells expressing GS. Conversely, conditional loss of β-catenin resulted in loss of GS expression. These data suggest that the Wnt pathway is critical to the development of zonation as well as maintaining the zonation in the adult liver

Carotid thromboendarterectomy for recent total occlusion of the internal carotid artery

AbstractBackground: The efficacy of emergency carotid thromboendarterectomy (CTEA) for acute internal carotid artery (ICA) thrombosis has been questioned. We evaluated the use of CTEA in patients with recent ICA occlusion. Methods: From August 1989 to December 1999 patients who underwent urgent CTEA for recent ICA thrombosis were retrospectively evaluated. Patient data analyzed included age, sex, comorbid risk factors, diagnostic evaluation, operative procedure, and long-term follow-up with clinical assessment and carotid duplex scan. Neurologic status was evaluated with the Modified Rankin Scale (MRS) before the operation, immediately after the operation, and at 3- to 6-months' follow-up. Results: Twenty-nine patients underwent emergency ipsilateral CTEA for acute ICA thrombosis over the last 10 years. The average age of the patients was 69.9 ± 1.7 years, and 66% were men. Patient risk factors included diabetes (7 [24%]), hypertension (21 [72%]), coronary artery disease (8 [29%]), and history of tobacco abuse (20 [69%]). Presenting symptoms included cerebrovascular accident (7 [24%]), transient ischemic attack (nonamaurosis) (10 [34%]), crescendo transient ischemic attack (7 [24%]), stroke in evolution (2 [7%]), and amaurosis fugax (3 [10%]). Diagnostic evaluation included computed tomographic scan (29 [100%]), magnetic resonance imaging/magnetic resonance angiography (4 [14%]), duplex scan evaluation of the carotid arteries (23 [79%]), and cerebral angiography (18 [64%]). Antegrade flow in the ICA was successfully established in 24 (83%) of 29 patients and confirmed with intraoperative angiography or duplex sonography. Postoperative morbidity included 2 hematomas (7%), 4 transient cranial nerve deficits (14%), and 1 conversion to hemorrhagic stroke (3.6%), which resulted in the only death (3.6%). MRS scores averaged 3.4 ± 0.2 preoperatively. Follow-up averaging 74.1 ± 21 months (range, 3-140 months) was obtained in 27 (93%) patients. Improvement or deterioration was defined as a change in MRS ± 1. Immediately postoperatively, 14 (48%) patients were improved, 2 (7%) deteriorated, and 13 (45%) had no change. At 3 to 6 months, 20 (74%) of 27 patients were improved, seven (26%) had no change, and none deteriorated. Of patients with successful CTEA, 23 (96%) of 24 had a patent ICA on follow-up duplex scan evaluation, and there was no evidence of recurrent ipsilateral neurologic events at an average of 49 months. Conclusion: These data support an aggressive early surgical intervention for acute ICA thrombosis in carefully selected patients. In the previous decade we reported a 46% success rate for establishing antegrade flow in the ICA long term. Data from this decade show a 79% (P =.0114) success rate for establishing antegrade flow long term in all patients undergoing emergency CTEA. New and improved imaging modalities have allowed better patient selection, resulting in improved outcomes. (J Vasc Surg 2001;33:242-50.

Dark matter halo concentrations in the Wilkinson Microwave Anisotropy Probe year 5 cosmology

We use a combination of three large N-body simulations to investigate the dependence of dark matter halo concentrations on halo mass and redshift in the WMAP year 5 cosmology. The median relation between concentration and mass is adequately described by a power-law for halo masses in the range 10^11 - 10^15 Msol/h and redshifts z < 2, regardless of whether the halo density profiles are fit using NFW or Einasto profiles. Compared with recent analyses of the Millennium Simulation, which uses a value of sigma_8 that is higher than allowed by WMAP5, z = 0 halo concentrations are reduced by factors ranging from 23 per cent at 10^11 Msol/h to 16 per cent at 10^14 Msol/h. The predicted concentrations are much lower than inferred from X-ray observations of groups and clusters.Comment: 6 pages, 4 figures, Accepted by MNRAS letters. Version 4: Typo fixe