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In a series of experiments, sporozoite stabilates of a Theileria lestoquardi (Lahr) and a T. annulata (Ankara) stock prepared from Hyalomma anatolicum anatolicum ticks, were used to examine the infectivity of both parasite species for sheep and cattle and to study the development of cross-immunity between these parasite species. In the first experiment sheep and cattle were inoculated with T. lestoquardi sporozoites. Surviving animals and naive sheep and cattle were, in the second experiment, inoculated with T. annulata. In the third experiment, naive sheep and sheep previously infected with T. annulata, were inoculated with T. lestoquardi. The following responses to inoculations were monitored: clinical and haematological signs of infection, appearance of parasitic stages of the parasites in lymph node biopsies and in peripheral blood and serological response to T. lestoquardi and T. annulata schizont antigens. While T. lestoquardi readily infected sheep and caused severe disease, it did not infect cattle. On the other hand, T. annulata infected both cattle and sheep. However, whereas cattle became severely affected, infected sheep showed mild clinical symptoms only and piroplasms did not develop. Despite their different behaviour in the host species examined, cross-immunity studies suggested that the parasite species are very closely related. Experiments in sheep indicated that T. lestoquardi infection protected against subsequent T. annulata infection. On the other hand, recovery from T. annulata infection did not prevent infection by sporozoites of T. lestoquardi, resulting in the establishment of schizonts and their subsequent development into piroplasms, although it protected against the major clinical effects of T. lestoquardi infection. 相似文献
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Hulme M Mahony M Beck S Görg C Hansjürgens B Hauck J Nesshöver C Paulsch A Vandewalle M Wittmer H Böschen S Bridgewater P Diaw MC Fabre P Figueroa A Heong KL Korn H Leemans R Lövbrand E Hamid MN Monfreda C Pielke R Settele J Winter M Vadrot AB van den Hove S van der Sluijs JP 《Science (New York, N.Y.)》2011,333(6043):697-698
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Global biodiversity scenarios for the year 2100 总被引：18，自引：0，他引：18
Sala OE Chapin FS Armesto JJ Berlow E Bloomfield J Dirzo R Huber-Sanwald E Huenneke LF Jackson RB Kinzig A Leemans R Lodge DM Mooney HA Oesterheld M Poff NL Sykes MT Walker BH Walker M Wall DH 《Science (New York, N.Y.)》2000,287(5459):1770-1774
Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change. 相似文献
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Transforming growth factor-beta (TGF-beta) and TGF-beta-related proteins, such as the bone morphogenetic proteins, have emerged as key regulators of stem cell renewal and differentiation. These proteins have disparate roles in regulating the biology of embryonic stem cells and tumor suppression, and they help define the selection of cell fate and the progression of differentiation along a lineage. Here we illustrate their roles in embryonic stem cells and in the differentiation of neural, hematopoietic, mesenchymal, and gastrointestinal epithelial stem cells. 相似文献
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Allen M. Solomon I. Colin Prentice Rik Leemans Wolfgang P. Cramer 《Water, air, and soil pollution》1993,70(1-4):595-614
The processes controlling total carbon (C) storage and release from the terrestrial biosphere are still poorly quantified. We conclude from analysis of paleodata and climate biome model output that terrestrial C exchanges since the last glacial maximum (LGM) were dominated by slow processes of C sequestration in soils, possibly modified by C starvation and reduced water use efficiency of trees during the LGM. Human intrusion into the C cycle was immeasurably small. These processes produced an averaged C sink in the terrestrial biosphere on the order of 0.05 Pg yr?1 during the past 10,000 years. In contrast, future C cycling will be dominated by human activities, not only from increasing C release with burning of fossil fuels, and but also from indirect effects which increase C storage in the terrestrial biosphere (CO2 fertilization; management of C by technology and afforestation; synchronous early forest succession from widespread cropland abandonment) and decrease C storage in the biosphere (synchronous forest dieback from climatic stress; warming-induced oxidation of soil C; slowed forest succession; unfinished tree life cycles; delayed immigration of trees; increasing agricultural land use). Comparison of the positive and negative C flux processes involved suggests that if the C sequestration processes are important, they likely will be so during the next few decades, gradually being counteracted by the C release processes. Based only on tabulating known or predicted C flux effects of these processes, we could not determine if the earth will act as a significant C source from dominance by natural C cycle processes, or as a C sink made possible only by excellent earth stewardship in the next 50 to 100 yrs. Our subsequent analysis concentrated on recent estimates of C release from forest replacement by increased agriculture. Those results suggest that future agriculture may produce an additional 0.6 to 1.2 Pg yr?1 loss during the 50 to 100 years to CO2 doubling if the current ratio of farmed to potentially-farmed land is maintained; or a greater loss, up to a maximum of 1.4 to 2.8 Pg yr?1 if all potential agricultural land is farmed. 相似文献
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Frank?M.?BakkerEmail author Rik?Feije André?J.?Grove Gijs?Hoogendoorn Gerrit?Jacobs Edwin?D.?Loose Pam?van?Stratum 《Journal of Soils and Sediments》2003,3(2):73-77
We provide a test protocol to evaluate the effects of plant protection products on mortality and reproductive performance
ofHypoaspis aculeifer (Acari: Laelapidae). The test design is in compliance with standard characteristics of extended laboratory studies as formulated
by international expert panels dealing with non-target arthropod testing schemes. Potential effects on survival rates are
evaluated by assessing mortality after an exposure period of 14 days that starts with protonymphs. The reproductive performance
of surviving mites is studied by following the egg production of individually isolated females over a 7-day period. The hatching
success of these eggs is assessed subsequently. Using several years’ data obtained from water control treatments, we propose
criteria to evaluate the validity of individual experiments. 相似文献
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