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51.
Chun Wang Derrick Y. F. Lai Chuan Tong Weiqi Wang Jiafang Huang Chongsheng Zeng 《PloS one》2015,10(5)
Understanding the functional relationship between greenhouse gas fluxes and environmental variables is crucial for predicting the impacts of wetlands on future climate change in response to various perturbations. We examined the relationships between methane (CH4) emission and temperature in two marsh stands dominated by the Phragmites australis and Cyperus malaccensis, respectively, in a subtropical estuarine wetland in southeast China based on three years of measurement data (2007–2009). We found that the Q10 coefficient of CH4 emission to soil temperature (Qs10) from the two marsh stands varied slightly over the three years (P > 0.05), with a mean value of 3.38 ± 0.46 and 3.89 ± 0.41 for the P. australis and C. malaccensis stands, respectively. On the other hand, the three-year mean Qa10 values (Q10 coefficients of CH4 emission to air temperature) were 3.39 ± 0.59 and 4.68 ± 1.10 for the P. australis and C. malaccensis stands, respectively, with a significantly higher Qa10 value for the C. malaccensis stand in 2008 (P < 0.05). The seasonal variations of Q10 (Qs10 and Qa10) differed among years, with generally higher values in the cold months than those in the warm months in 2007 and 2009. We found that the Qs10 values of both stands were negatively correlated with soil conductivity, but did not obtain any conclusive results about the difference in Q10 of CH4 emission between the two tidal stages (before flooding and after ebbing). There were no significant differences in both Qs10 and Qa10 values of CH4 emission between the P. australis stand and the C. malaccensis stands (P > 0.05). Our results show that the Q10 values of CH4 emission in this estuarine marsh are highly variable across space and time. Given that the overall CH4 flux is governed by a suite of environmental factors, the Q10 values derived from field measurements should only be considered as a semi-empirical parameter for simulating CH4 emissions. 相似文献
52.
J. A. M. van Eekelen N. Y. Rots W. Sutanto M. S. Oitzl E. R. de Kloet 《The Journal of steroid biochemistry and molecular biology》1991,40(4-6):679-683
The present study examined the stress responsiveness of the hypothalamic-pituitary-adrenal axis in relation to the properties of corticosteroid receptors in the brain and pituitary in old (30 months) and young (3 months) male Brown Norway rats. The data demonstrate that circulating ACTH rather than the corticosteroid plasma level was elevated under basal conditions and following stress. Furthermore, a reduction of mineralocorticoid receptor (MR) number in the hippocampus and of glucocorticoid receptor (GR) number in the hypothalamus and the pituitary correspond to increased neuroendocrine responsiveness and negative feedback following stress. The changes in receptor binding do not parallel the changes in the amount of MR and GR mRNA measured with in situ hybridization. This suggests that the processing rather than the receptor gene expression is affected in senescence. 相似文献
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54.
J Lubínski K Ptaszynski Y Tsujimoto K Huebner C Croce 《Analytical and quantitative cytology and histology / the International Academy of Cytology [and] American Society of Cytology》1991,13(6):425-428
The configuration of the BCL-2 major breakpoint region was analyzed by Southern blot hybridization and polymerase chain reaction amplification in DNA derived from 44 benign hyperplastic lymph nodes with follicular overgrowth. None of the cases exhibited translocation of the BCL-2 gene at the major breakpoint region of chromosome 18. The potential usefulness of molecular genetic detection of BCL-2 translocation in the differential diagnosis between hyperplastic lymph nodes and lymphomas is suggested. 相似文献
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57.
Typical Huntington's disease (HD) was studied in a 40-year-old Sudanese man from Khartoum. He had 51 CAG repeats in the Huntington's gene. It is suspected that his mother and his 16-year-old son (both deceased) were also affected. Up to now, there had only been anecdotal evidence of HD in the Sudanese. 相似文献
58.
Analysis of several key active site residues of ricin A chain by mutagenesis and X-ray crystallography. 总被引:6,自引:0,他引:6
Active site residues of ricin A chain were analyzed by site-directed mutagenesis and X-ray diffraction to help assess their roles in the mechanism of action of this toxic N-glycosidase enzyme. Arg180 is thought, from X-ray studies, to protonate the adenine substrate at N3; this facilitates bond cleavage and is crucial to the mechanisms of action. The residue was converted to Gln and initial rate data measured. Km for the mutant is not significantly affected, increasing only 2-fold. The kcat, however, is decreased approximately 1000-fold. This is consistent with a simple interpretation that Arg180 is involved more in transition state stabilization than in substrate binding. Tyrosines 80 and 123 are known from X-ray models to stack on either side of the substrate adenine ring. When they were each converted to serine overall activity was reduced 160- and 70-fold respectively against ribosomes from Artemia salina. These effects are each approximately 10 times greater than when the residues were previously converted to phenylalanines. Sufficient protein for the Tyr80 to Phe mutant was obtained to carry out an X-ray analysis. Together with mutagenesis data, the structure suggests that the invariance of the two active site Tyr residues is largely caused by structural stability. 相似文献
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60.
A Y Kwong P C Wong R C Ko 《Comparative biochemistry and physiology. B, Comparative biochemistry》1990,95(1):193-197
1. All major classes of lipids were found in the young adults in brain (22 days post-infection) and gravid Angiostrongylus cantonensis in lung of rats (34 days post-infection) comprising approximately 60% of phospholipids, 30% of neutral lipids and the rest, glycolipids. 2. The relative composition of phospholipids were quite similar between worms from the two different habitats, with phosphatidylcholine predominating. The glycolipid profiles were also similar. 3. More neutral lipids in the worms from brain existed as cholesterol and cholesterol esters than those from the lung. More than 20% of the fatty acids in these lipids of the brain were found as C10-C14 acids while oleic acid was the main component in the lung worm. 相似文献