Implications of rising costs of registering agrochemicals     

A.C.I. Samuel  B.W. Cox  H-H. Cramer 《Crop Protection》1983,2(2):131-141

The increased number and complexity of the requirements for registration of agrochemicals are causing a steep rise in the costs of research and development and therefore in the price of agrochemicals. It now takes about 8–9 years for an agrochemical to be developed and marketed, at a probable cost of 10–20 million US dollars, and each of the individual tests required may cost up to US$ 500 000. A continuation of these trends would have serious consequences for industry, farmers, consumers and the developing countries. So far, the agrochemical industry has been able to continue to produce the new and improved materials necessary to combat changing pest attack: whether it can continue to do so may depend upon whether or not registration requirements are increased. Unnecessary requirements must be identified and eliminated, and any new demands must be fully justified in terms of the cost involved and of the ensuing benefits. However, if the search for greater safety were to be pushed to even greater lengths, so that costs exceed what the market will bear, the extra costs would have to be borne by the authorities and, ultimately, by the taxpayer.  相似文献   

Characterization of Mannheimia (Pasteurella) haemolytica leukotoxin interaction with bovine alveolar macrophage beta2 integrins     

Thumbikat P  Dileepan T  Kannan MS  Maheswaran SK 《Veterinary research》2005,36(5-6):771-786

Mannheimia (Pasteurella) haemolytica, the etiologic agent of bovine pneumonic mannheimiosis, produces an exotoxic leukotoxin. The leukotoxin (LktA) is a member of the RTX (repeats in toxin) family of bacterial cytolysins and is distinguished from other toxins by its unique target cell specificity to ruminant leukocytes occurring through binding to a specific receptor. We have demonstrated previously that the beta2 integrin LFA-1 is a receptor for LktA in bovine leukocytes and is involved in leukotoxin-induced biological effects. However the subunits within LFA-1 involved in binding to LktA, and post-binding signaling leading to cellular activation have not been well characterized. The purpose of our study was to pinpoint these precise subunits on bovine alveolar macrophages and to characterize their interaction with LktA. The results in this study indicate that although LktA can efficiently bind to the CD18 subunit of both LFA-1 and Mac-1, post-binding signaling events including elevation of intracellular calcium and CD18 tail phosphorylation are only observed through LFA-1. Furthermore, LktA also binds to the CD11a subunit of LFA-1. LktA binding to CD11a could be inhibited by a small molecule inhibitor of the I(inserted)-domain, the major ligand binding interface on CD11a. I-domain inhibition significantly blunts LktA-induced intracellular calcium elevation and tyrosine phosphorylation of the CD18 tail. Based on our results we suggest that LFA-1 serves as the functional leukotoxin receptor on bovine alveolar macrophages.  相似文献   

One-step fabrication of supramolecular microcapsules from microfluidic droplets     

Zhang J  Coulston RJ  Jones ST  Geng J  Scherman OA  Abell C 《Science (New York, N.Y.)》2012,335(6069):690-694

Although many techniques exist for preparing microcapsules, it is still challenging to fabricate them in an efficient and scalable process without compromising functionality and encapsulation efficiency. We demonstrated a simple one-step approach that exploits a versatile host-guest system and uses microfluidic droplets to generate porous microcapsules with easily customizable functionality. The capsules comprise a polymer-gold nanoparticle composite held together by cucurbit[8]uril ternary complexes. The dynamic yet highly stable micrometer-sized structures can be loaded in one step during capsule formation and are amenable to on-demand encapsulant release. The internal chemical environment can be probed with surface enhanced Raman spectroscopy.  相似文献   

A description of local pig feeding systems in village smallholder farms of Western Kenya   总被引：3，自引：3，他引：0  

Mutua FK  Dewey C  Arimi S  Ogara W  Levy M  Schelling E 《Tropical animal health and production》2012,44(6):1157-1162

We used face-to-face interviews to gather data on pig feeding practices in rural Busia District, Kenya. We visited 164 pig farms three times in the course of the study period. The pigs were weighed in kilograms during the visits. Feeds offered to pigs were described during the interviews. The most frequently fed feedstuffs were; ground maize or "ugali" (88%), kitchen leftovers (83%) and dried fish locally called "omena" (78%). Farmers provided pigs with water separately from the feeds. Sweet potatoes, "ugali" and cassava were available and could serve as good sources of energy for pigs in the district. Fruits and vegetables were also available and could potentially act as good sources of vitamins. Sweet potato vines, "omena" fish and slaughter blood were available and could provide pigs with proteins. The average daily gain (ADG) for pigs ≤ 5 months of age, pigs of 5.1-9.9 months of age and pigs of ≥ 10 months old was 94.5 (± 43), 127 (± 49.8) and 99 (± 92) g, respectively (p = 0.000). This study has outlined the different local pig feeds available in Busia district. We recommend two things: first, additional research on nutrient composition for the identified local feeds, and second, developing and validating simple local feed combinations that would achieve balanced local pig rations.  相似文献   

Phenotypic characterization of the population of creole wool ewes in the highlands of Puebla State, Mexico     

Samuel Vargas-López  Juan de Dios Guerrero-Rodríguez  Joel Rojas-álvarez  ángel Bustamante-González 《Tropical animal health and production》2012,44(8):1833-1839

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Risk factors associated with occurrence of nematodes in free range pigs in Busia District,Kenya   总被引：1，自引：1，他引：0  

Kagira JM  Kanyari PN  Githigia SM  Maingi N  Ng'ang'a JC  Gachohi JM 《Tropical animal health and production》2012,44(3):657-664

Nematode infections are a serious constraint to pig production, especially where free range pig keeping is practiced. This study investigated the epidemiology of nematodes in free range pigs in Busia District, Kenya. Three hundred and six pigs from 135 farms were sampled for faeces that were analysed for nematode eggs per gram (EPG) of faeces using the McMaster technique. The nematode eggs were also identified to genus and species based on morphology. A questionnaire on risk factors was also administered to the pig owners. The overall prevalence and mean nematode EPG were 84.2% and 2,355, respectively. The nematode eggs were identified as those belonging to Oesophagostomum spp. (75%), Strongyloides ransomi (37%), Ascaris suum (18%), Metastrongylus spp. (11%), Trichuris suis (7%) and Physocephalus sexalatus (3%). The prevalence of nematodes was positively correlated (p < 0.05) with the amount of rainfall in the division of the pigs' origin (all nematodes except S. ransomi). The prevalence of nematodes was also associated with the age of the pigs. A lower burden of nematodes was associated (p < 0.05) with a history of deworming (A. suum) and the provision of night housing (S. ransomi and Metastrongylus spp.). In conclusion, this study has provided information on nematode infections and the associated risk factors for free range pigs in Busia District, which can be used when implementing integrated control measures.  相似文献   

Integrative approach for landscape-based graph connectivity analysis: a case study with the common frog (Rana temporaria) in human-dominated landscapes     

Samuel Decout  Stéphanie Manel  Claude Miaud  Sandra Luque 《Landscape Ecology》2012,27(2):267-279

Graph-based analysis is a promising approach for analyzing the functional and structural connectivity of landscapes. In human-shaped landscapes, species have become vulnerable to land degradation and connectivity loss between habitat patches. Movement across the landscape is a key process for species survival that needs to be further investigated for heterogeneous human-dominated landscapes. The common frog (Rana temporaria) was used as a case study to explore and provide a graph connectivity analysis framework that integrates habitat suitability and dispersal responses to landscape permeability. The main habitat patches influencing habitat availability and connectivity were highlighted by using the software Conefor Sensinode 2.2. One of the main advantages of the presented graph-theoretical approach is its ability to provide a large choice of variables to be used based on the study’s assumptions and knowledge about target species. Based on dispersal simulation modelling in potential suitable habitat corridors, three distinct patterns of nodes connections of differing importance were revealed. These patterns are locally influenced by anthropogenic barriers, landscape permeability, and habitat suitability. And they are affected by different suitability and availability gradients to maximize the best possible settlement by the common frog within a terrestrial habitat continuum. The study determined the key role of landscape-based approaches for identifying the “availability-suitability-connectivity” patterns from a local to regional approach to provide an operational tool for landscape planning.  相似文献   

Conservation of Pattern and Process: Developing an Alternative Paradigm of Rangeland Management     

Samuel D. Fuhlendorf  David M. Engle  R. Dwayne Elmore  Ryan F. Limb  Terrence G. Bidwell 《Strength and Conditioning Journal》2012,65(6):579-589

This article examines the question of how well the rangeland management profession has served conservation of patterns and processes that support multiple ecosystem services. We examine the paradigms under which rangeland management operates and argue that our profession developed under the utilitarian paradigm with the primary goals of sustainable forage for livestock production. While optimization of multiple rangeland products and services has always been a consideration, a comprehensive set of principles have not be been developed to advance this concept. We argue that fire and grazing, often viewed as mere tools used for production goals, should rather be viewed as essential ecosystem processes. Rangeland management continues to operate under the utilitarian paradigm appropriate to societal values of the 20th century and by and large has failed to provide management guidance to reverse degradation of several highly valued ecosystem services. We support this argument with evidence that biodiversity has declined on rangelands in the past half century and that much of this decline is due to management goals that favor a narrow suite of species. The full suite of ecosystem services valued by society will only benefit by management for heterogeneity, which implies that there is no one goal for management and that landscape-level planning is crucial. Explicitly incorporating heterogeneity into state-and-transition models is an important advancement not yet achieved by our profession. We present new principles for rangeland management formed on the basis of conservation of pattern and process. While recognizing that many rangelands have significant deviations from historic plant communities and disturbance regimes, we suggest that management for conservation of pattern and process should focus on fire and grazing to the extent possible to promote a shifting mosaic across large landscapes that include patches that are highly variable in the amount of disturbance rather than the current goal of uniform moderate disturbance.  相似文献   

Sprout development and processing quality changes in potato tubers stored under ethylene: 1. Effects of ethylene concentration     

Barbara J. Daniels-Lake  Robert K. Prange  Jerzy Nowak  Samuel K. Asiedu  John R. Walsh 《American Journal of Potato Research》2005,82(5):389-397

Ethylene effectively inhibits sprouting of potatoes (Solanum tuberosum L.) during storage, but it often darkens fry color. The objective of the work described here was to determine if altering the concentration of ethylene applied would reduce the darkening while retaining adequate sprout inhibition. Trials were conducted over three consecutive years (1991–1992, 1992–1993, and 1993–1994). Tubers of cv Russet Burbank (ca 150–300 g) were stored at 9 C for 25 wk in closed chambers in a refrigerated room under continuous exposure to 0.4, 4, 40, or 400 µL L^?1 ethylene gas delivered with the ventilation airstream (ca 0.5 air exchanges per h, for 6 h each day). Untreated control and chlorpropham-treated (CIPC) check tubers were stored under the same conditions but without ethylene supplementation. Sprout number, length, and biomass, fry color, loss of tuber mass, disease, and dry matter content were evaluated at 5-wk intervals. Dose-dependent effects (400>40>4>0.4 µL L^?1) of ethylene on sprout growth and fry color were observed. The 400, 40, and 4 µL L^?1 ethylene treatments inhibited sprout growth as effectively as CIPC, whereas in 0.4 µL L^?1 ethylene sprouting was midway between CIPC and the untreated control. Sprout mass and maximum sprout length in all ethylene treatments were significantly lower (P<0.05) than in the untreated control. Compared with the initial value (57.3 Agtron reflectance units [ARu]), after 5 wk of storage fry color was up to 5 ARu darker in the ethylene treatments, but recovered steadily at the subsequent evaluation dates. At 25 wk of storage the fry color of tubers from the 40 and 4 µL L^?1 ethylene treatments were, however, still darker than tubers stored with CIPC. Inhibition of sprout growth was slightly more effective in the 400 and 40 µL L^?1 ethylene treatments than in 4 µL L^?1, although there were no significant differences (P<0.01) in fry color between these treatments. In comparison with the other ethylene treatments, fry color in 0.4 µL L^?1 ethylene was lighter, but inhibition of sprout growth was significantly (P<0.05) poorer. There were no differences in tuber disease incidence or dry matter content between the treatments. At 25 wk, the untreated tubers had ca 50% greater loss of tuber mass than any other treatment, attributable to their heavy sprouting. Loss of tuber mass in the ethylene treatments was not significantly different (P<0.001) from that in the CIPC treatment.  相似文献   

Contrasting Preference for Grassland Landscapes Among Population Groups in the Central and Southern Great Plains     

Terrie A. Becerra  David M. Engle  R. Dwayne Elmore  Samuel D. Fuhlendorf 《Strength and Conditioning Journal》2013,66(5):529-538

Recent opposition to the rangeland management paradigm of achieving uniform, moderate grazing across entire landscapes has emerged because heterogeneity is recognized as the foundation of biodiversity, ecosystem resilience, and multifunctionality of agricultural landscapes. Agriculture production goals appear to drive the traditional rangeland management focus on homogeneity and uniformity. To determine if preference for homogeneity is a broadly applicable social construct or one limited to agricultural producers, we determined preferences for heterogeneous grassland landscapes expressed by three study populations—managers of working lands (ranchers), natural resource professionals (grassland/rangeland specialists), and the general population living in rangeland regions within the US Great Plains. We distributed surveys that included photographs of landscapes and patterned images to assess preference. Preference for heterogeneous landscapes among ranchers, natural resource professionals, and the general population in our study area were generally consistent with the central paradigm of managing rangeland for homogeneity. However, we discovered that people, across geographic location and population group, clearly prefer heterogeneous patterned images to homogeneous patterned images. This suggests that preference for homogeneity is acquired.  相似文献