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The pathological changes caused by Eimeria falciformis var pragensis in mice. 总被引：2，自引：0，他引：2 
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下载免费PDF全文 Groups of Swiss white mice weighing 25-28 grams were infected orally with 500, 2,000, 5,000 or 20,000 oocysts of Eimeria falciformis var pragensis. Depression, anorexia, weight loss, diarrhea or dysentery, and dehydration were most pronounced at eight to ten days postinfection. The highest mortality, 31%, occurred in mice infected with 20,000 oocysts. None of the mice infected with 500 oocysts died. The pathological findings were equally severe in mice infected with 5,000 and 20,000 oocysts. The enteric lesions, most pronounced at eight to ten days postinfection, were restricted mainly to the large intestine and consisted initially of both cryptal and absorptive epithelial cell destruction and submucosal edema. These changes were followed in 12 to 24 hours by a transient influx of neutrophils into the lamina propria followed by mononuclear cell infiltration which lasted for five to ten days. As the infective dose decreased, the inflammatory response occurred later and was less extensive. When seen, hemorrhage occurred seven to 11 days postinfection. In 50% of the mice infected with 5,000 and 20,000 oocysts, varying degrees of a nonselective mucosal necrosis were seen at eight to 12 days postinfection. In mice infected with 500 oocysts, mucosal destruction was restricted to the epithelium. Neutrophils predominated when necrosis was extensive, otherwise, mononuclear cells were the main inflammatory cells. Two to three days following necrosis, crypt hyperplasia was marked and mucosal integrity was restored. Ulcers, some of which extended into the submucosa, healed by days 14 to 20. Localized granulomatous colitis, induced by trapped oocysts within the lamina propria, was seen until the experiment was terminated at 25 days postinfection. Infection was followed by lymphoid hyperplasia in the lymph nodes and the spleen. 相似文献
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Hiwet Gebremedhin Girmay Gebresamual Nigussie Abadi Kassa Teka Shimbahri Mesfin 《Arid Land Research and Management》2018,32(2):236-252
With rapid population growth and absence of agricultural intensification, smallholders need more land to grow crops. This resulted in communal grazing land conversion to cultivated land. This study, therefore, aimed at exploring the magnitude of communal grazing land conversion and its influence on soil properties and vegetation cover change. Ecological time line approach was used to measure the magnitude of change. Plants and soil samples were taken from open grazing land, seasonal grazing land, 6 years old cultivated land, 16 years old cultivated land and 20 years old cultivated land. Moreover, 95 respondents were selected to assess their perception on the subject. Data were analyzed using statistical analysis system software. Results showed that grazing land declined by 41.88%, while cultivated land increased by 56.80% in the years between 1992 and 2012. Plant attributes showed significant (P?P?相似文献
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Jones Yengwe Mesfin Tsegaye Gebremikael David Buchan Obed Lungu Stefaan De Neve 《Agroforestry Systems》2018,92(2):349-363
The nitrogen status of most Zambian soils is inherently low. Nitrogen-fixing trees such as Faidherbia albida (F. albida) could have the potential to restore soil fertility. We conducted a study to examine the role of mature F. albida trees on the soil microbial communities and overall N fertility status in Zambia. Soil samples were collected under and outside the canopies of F. albida trees in representative fields from two sites namely; Chongwe (loamy sand) and Monze (sandy loam). To assess the long term canopy effects; total N, mineral N and soil organic carbon (Corg) content were directly measured from soils collected under and outside the canopy. Short term litter effects were assessed by subtracting concentrations of biochemical properties of non-amended controls from amended soils with F. albida litter during an 8 week incubation experiment. We also determined N mineralization rates, microbial community structure—Phospholipid fatty acids, microbial biomass carbon, and labile organic carbon (\({\text{C}}_{{{\text{org[K}}_{ 2} {\text{SO}}_{ 4} ]}}\)) during incubation. For the long term canopy effect, average N mineralization rate, Corg, total N and mineral N content of non-amended soils under the canopy were (all significant at p < 0.05) greater than soils outside the canopy on both sites. In the short term, amending soils with litter significantly increased N mineralization rates by an average of 0.52 mg N kg?1 soil day?1 on soil from Monze. Microbial biomass carbon measured after 4 weeks of incubation was on average significantly higher on amended soils by 193 and 334 mg C kg?1 soil compared with non-amended soils in Chongwe and Monze soils, respectively. After 6 weeks of incubation, the concentration of all selected biomarkers for major microbial groups concentrations in non-amended soils were significantly higher (all p < 0.05) under the canopy than outside in Monze soil. Using principal component analysis, we found that the segregation of the samples under and outside the canopy by the first principal component (PC1) could be attributed to a proportional increase in abundances of all microbial groups. Uniform loadings on PC1 indicated that no single microbial group dominated the microbial community. The second principal component separated samples based on incubation time and location. It was mainly loaded with G-positive bacteria, and partly with G-negative bacteria, indicating that microbial composition was dominated by these bacterial groups probably at the beginning of the incubation on Monze soils. Our results show that the improvement of soil fertility status by F. albida could be attributed to a combination of both long term modifications of the soil biological and chemical properties under the canopy as well as short term litter fall addition. 相似文献
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Mesfin Tesfaye Nicholas S DufaultMelinda R Dornbusch Deborah L AllanCarroll P Vance Deborah A Samac 《Soil biology & biochemistry》2003,35(8):1103-1113
Transgenic alfalfa over-expressing a nodule-enhanced malate dehydrogenase (neMDH) cDNA and untransformed alfalfa plants were grown at the same field site and rhizosphere soils collected after 53 weeks of plant growth. These alfalfa lines differ in the amount and composition of root organic acids produced and exuded into the rhizosphere. Nucleotide sequencing of PCR-based 16S ribosomal DNA (rDNA) clone libraries and Biolog™ GN microtiter plates were employed to assess the activity of naturally occurring rhizobacteria in the two alfalfa rhizospheres. Selected macro- and micro-elements in the two alfalfa rhizosphere soils were also measured. Analysis of 240 16S rDNA clone sequences indicated the existence of about 11 bacterial phyla and their major subdivisions in the two alfalfa rhizosphere samples. There were qualitative changes in the abundance of bacterial phylogenetic groups between rhizosphere soils of transgenic and untransformed alfalfa. Carbon substrate utilization profiles suggested that rhizosphere samples from transgenic alfalfa had significantly greater microbial functional diversity compared with rhizosphere samples from untransformed alfalfa. The concentrations of nitric acid extractable P, K, Mn, Zn and Cu increased significantly in the transgenic alfalfa rhizosphere compared with the untransformed alfalfa rhizosphere. These observations indicate that organic acids produced by plant roots significantly influence rhizosphere microbial diversity and availability of macro- and micro-nutrients and demonstrate the utility of such trangenic plants as tools for studying the potential impact of plant root exudates on soil microbial ecosystems. 相似文献
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In this study, 151 households were randomly drawn from three randomly selected Kebele in probability proportional to size method. The demographic and socio-economic factors that determine the participation in improved varieties were household labor availability, education level of the household head, land holdings, distance to the nearest village market, proximity to the main market, and distance to access agricultural extension and access to the source of rice seeds. However, determinants of choice decision varied from cultivar to cultivar. The evidence of the study from the interdependence among the decision of adoption of improved rice varieties suggested that technology adoption will be accelerated by launching a progressively developing package and scheme of rice technology generation, and points to the importance of mobilising additional resources to augment households’ efforts at popularization and promotion of improved rice cultivars. The findings from Linearized Almost Ideal Demand Systems (LA/AIDS) model showed that compelling evidence for small proportion changes in own prices and cross price of improved rice varieties led to greater than unitary proportionate changes in their purchases. The results generally showed that farmers were very sensitive to changes in improved rice seed prices and incomes. The major implication of the findings was that any intervention to improve farmers’ seed purchases should take into account efforts to increase farmers’ purchasing power of agricultural inputs like improved seeds and fertilizers. 相似文献
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Mesfin Kassa Wassie Haile Fassil Kebede 《Communications in Soil Science and Plant Analysis》2019,50(4):388-401
Adsorption isotherm is essential for predicting its mechanisms, which are important for potassium (K) fertilizer application and to recommendation appropriate rates for acidic soils. Thus, the objective of this study was to evaluate K adsorption characteristic of the selected soils by comparing different adsorption models with soil properties of the soil in different districts (Sodo Zurie, Damot Gale, Damot Sore and Boloso Sore) in the Wolaita Zone of Southern Ethiopia. Four adsorption isotherms are: Langmuir, Freundlich, Temkin, and Van Huay were used to describe adsorption processes. Composite surface (0-20 cm) depth soil samples from four districts sites were collected. The results revealed that the K adsorption data coincide with both models with (r2 = 0.99). However, Freundlich model was better in describing K adsorption than the other model. The adsorption maxima(ad(max), distribution coefficient, buffer capacity (BC), and adsorption capacity(a(capacity) values of soils ranged from -333 to334.5,0.54 to78.7,159.9 to 389.3, and 327 to 417mg Kkg-1 respectively, these results showed that Sodo Zurie, Bolos Sore and Demote Sore were effective model parameters. Van Huay a(capacity) 417mg Kkg-1 while the bonding energy constant Langmuir is -0.075mg Kkg-1 in Bolos Sore soil compared to other soils, which were found to be more valuable in discriminating between high K adsorption soils. Correlation between some soil properties with ad(max) were positively a highly correlated with clay, pH, organic carbon (OC) and exchangeable potassium with r2 = 0.92**, 0.93**, 0.95** and 0.96 ** respectively, but negatively correlated with bonding energy with r2= -0.79, -0.80,-0.77 and -0.72 respectively, while calcium carbonate (CaCO3) was very highly correlated with ad(max) r2= 0.99***). The Freundlich constant, Temkin BC, and Van Hauy a(capacity) were correlated with CaCO3 content soils with r2=0.12,-0.01,and 0.12,respectively, while slope (1/n) was significantly negatively correlated with soil cation exchange capacity (CEC), CaCO3, clay contents and exchangeable K and Mg2+ with r2= 0.04, -0.67, -0.78, -0.69, and –0.69, respectively. These findings reveal the extent of K depletion in the soils of Wolaita providing a baseline for K rates required for crop production and validation of all models through real-time experiments in the field; this is recommended before the models are used on a large scale basis. 相似文献
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The immunogenicity of the different stages of E. falciformis var. pragensis was evaluated with the indirect fluorescent antibody reaction. Sporozoites, mature asexual stages and merozoites treated with sera from immune mice and with fluorescein-conjugated goat antimouse gammaglobulin showed the most intence specific fluoresence. The immature asexual stages and the sexual stages fluoresced weakly, whereas the sporocysts and oocysts did not specifically fluoresce. On the basis of the intensity of the immunofluorescence, the sporoziotes and mature asexual generations (merozoites) were considered to be more immunogenic than that immature asexual and the sexual stages. Antibodies against sporocysts and oocysts could not be demonstrated. 相似文献
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Sara De Bolle Mesfin T. Gebremikael Veerle Maervoet Stefaan De Neve 《Biology and Fertility of Soils》2013,49(6):705-714
A way to bring phosphate-saturated soils back to an environmentally safe P level is by P mining through plants. Phosphate-solubilizing bacteria (PSB) could be very useful for increasing mining efficiency over time. The goal of this research was to investigate the adaptation and performance of PSB in conditions of high total P content in soil. In the first experiment, the P-solubilizing capacity of five PSB species (three Bacillus spp. and two Pseudomonas spp.) were tested under fully controlled conditions on several growth media with different forms of insoluble phosphate (FePO4, AlPO4, or (Ca)3(PO4)2) added at different rates. The colony growth after 14 days of inoculation demonstrated that all five bacteria were able to proliferate and solubilize P on each of the tested growth media, in contradiction with the normally used technique of halo determination. In the second experiment, the same bacterial species were inoculated in pure quartz sand amended with a nutrient solution and P was added separately in an insoluble form, as Fe–P, Al–P, or Ca–P. The extractable ammonium lactate ranged from 3.2 to 6.9 and 29.0 to 40.7 mg?kg?1 sand for the insoluble Al–P and Fe–P treatments, respectively. Pseudomonas putida and Bacillus brevis performed best as PSB at high P concentration where the P is fixed with Al or Fe. In the third experiment, P. putida and B. brevis were inoculated in an acidic sandy, P-saturated soil for 4 weeks. The inoculation of the PSB gave promising results in solubilizing P. 相似文献