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排序方式: 共有223条查询结果,搜索用时 375 毫秒
81.
The observer effect in plant science 总被引:1,自引:0,他引:1
82.
Does a warmer climate with frequent mild water shortages protect grassland communities against a prolonged drought? 总被引:1,自引:0,他引:1
C. Zavalloni B. Gielen C. M. H. M. Lemmens H. J. De Boeck S. Blasi S. Van den Bergh I. Nijs R. Ceulemans 《Plant and Soil》2008,309(1-2):119-130
While irrigation of farm dairy effluent (FDE) to land is becoming popular in New Zealand, it can lead to increased emissions of the greenhouse gas nitrous oxide (N2O). This paper reports the results from trials on N2O emissions from irrigation of FDE to two dairy-grazed pastures on two poorly drained silt-loam soils located at Waikato and Manawatu, New Zealand. These pasture soils were periodically irrigated with FDE under contrasting soil moisture conditions with water-filled pore-space (WFPS) ranging between 26% and 94%. Nitrous oxide emissions were measured from the FDE irrigated and unirrigated sites using large numbers of static chambers (12–20). Irrigation of FDE generally increased N2O emissions compared to the control. N2O emissions varied with changes in climatic conditions and soil WFPS. Overall N2O emissions from effluent-derived N ranged between 0.01% and 4.93% depending on irrigation time and soil WFPS. Lower N2O emissions from FDE were attributable to very low soil WFPS conditions during the dry seasons. Higher N2O emissions were measured from application of FDE to a recently grazed pasture on wet soil. Our results suggest strategic application of FDE during dry summer and autumn seasons can reduce N2O emissions from application of FDE. Delaying effluent-irrigation after grazing events could further reduce N2O emissions by reducing the levels of surplus mineral-N. 相似文献
83.
Steven De Decker Richard Lam Rowena M. A. Packer Ingrid M. V. L. Gielen Holger A. Volk 《PloS one》2015,10(4)
Ankylosing spinal disorders can be associated with alterations in vertebral bone mineral density (BMD). There is however controversy about vertebral BMD in patients wuse idiopathic skeletal hyperostosis (DISH). DISH in Boxer dogs has been considered a natural occurring disease model for DISH in people. The purpose of this study was to compare vertebral BMD between Boxers with and without DISH. Fifty-nine Boxers with (n=30) or without (n=29) DISH that underwent computed tomography were included. Vertebral BMD was calculated for each thoracic and lumbar vertebra by using an earlier reported and validated protocol. For each vertebral body, a region of interest was drawn on the axial computed tomographic images at three separate locations: immediately inferior to the superior end plate, in the middle of the vertebral body, and superior to the inferior end plate. Values from the three axial slices were averaged to give a mean Hounsfield Unit value for each vertebral body. Univariate statistical analysis was performed to identify factors to be included in a multivariate model. The multivariate model including all dogs demonstrated that vertebral DISH status (Coefficient 24.63; 95% CI 16.07 to 33.19; p <0.001), lumbar vertebrae (Coefficient -17.25; 95% CI -23.42 to -11.09; p < 0.01), and to a lesser extent higher age (Coefficient -0.56; 95% CI -1.07 to -0.05; p = 0.03) were significant predictors for vertebral BMD. When the multivariate model was repeated using only dogs with DISH, vertebral DISH status (Coefficient 20.67; 95% CI, 10.98 to 30.37; p < 0.001) and lumbar anatomical region (Coefficient -38.24; 95% CI, -47.75 to -28.73; p < 0.001) were again predictors for vertebral BMD but age was not. The results of this study indicate that DISH can be associated with decreased vertebral BMD. Further studies are necessary to evaluate the clinical importance and pathophysiology of this finding. 相似文献
84.
85.
Summary Effects of steroids on the accumulation of glycoprotein gonadotropin (GTH) in pituitaries of juvenile trout were investigated by means of scanning cytophotometry applied to immunocytochemical preparations, and with the use of a radioimmunoassay. Effects on other aspects of GTH-cell activity were analyzed by measuring the size of the gonadotrops and their nuclei.Progesterone added to aquarium water and methyltestosterone incorporated into the food showed a pronounced stimulatory effect on the accumulation of GTH. To a lesser extent, treatment with cortisol, cortisone, and desoxycorticosterone acetate administered to aquarium water, and 11-hydroxy-androstenedione added to the food resulted in an increase of the hypophysial content of GTH. Steroids stimulating the accumulation of GTH in the pituitary also exhibited a positive effect on GTH-cell activity as indicated by an increase in the size of gonadotropic cells. Progesterone incorporated into the food did not influence the GTH-content and the GTH-cell activity. It is suggested that the route of administration of an exogenous steroid is essential for its effect on GTH cells in trout.Comparison of GTH values reveals an excellent correlation between the data from the radioimmunoassay and those from the corresponding densitometric measurements. No correlation was observed between values of morphometrically determined GTH-cell activity and the densitometric values reflecting hypophysial GTH content. 相似文献
86.
Hepatocytes in culture are presently considered as an interesting model for pharmacological and toxicological investigations. The study of their cytochrome P-450-linked monooxygenases requires sophisticated methodologies to detect the usual very low enzymatic activities. In this paper, we describe a new, rapid, sensitive, and specific technique for the measurement of 7-ethoxycoumarin deethylase. This assay is based on the multiple-ion detection of the trimethylsilyl ether of 7-hydroxycoumarin. This method, developed for the study of cytochrome P-450-dependent monooxygenases in cultured fetal rat liver cells, allows the detection of activities as low as 0.2 pmol/min. 相似文献
87.
Joseph Duvivier Jacques Van Cantfort Jacques E. Gielen 《Biochemical and biophysical research communications》1981,99(1):252-258
The intraperitoneal injection of the well known monooxygenase inducers (phenobarbital, β-naphtoflavone, pregnenolone-16α-carbonitrile, benzo(a)-pyrene, methylcholanthrene) elicits a net decrease in the specific binding of estradiol to its cytosol receptor in female rat livers. Amongst the five chemicals tested, only phenobarbital did not exhibit such a phenomenon, but caused a slight increase. This observation was neither due to a competitive inhibition by these compounds, nor to an enhanced metabolism of [3H]-estradiol. Moreover, when this effect was produced by polycyclic hydrocarbons, it was inversely correlated to the activity of aryl hydrocarbon hydroxylase, induced by these same chemicals. 相似文献
88.
Globin gene expression in cultured erythroleukemic cells 总被引:25,自引:0,他引:25
89.
90.