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21.
22.
Motivated by investigating the relationship between progesterone and the days in a menstrual cycle in a longitudinal study, we propose a multikink quantile regression model for longitudinal data analysis. It relaxes the linearity condition and assumes different regression forms in different regions of the domain of the threshold covariate. In this paper, we first propose a multikink quantile regression for longitudinal data. Two estimation procedures are proposed to estimate the regression coefficients and the kink points locations: one is a computationally efficient profile estimator under the working independence framework while the other one considers the within-subject correlations by using the unbiased generalized estimation equation approach. The selection consistency of the number of kink points and the asymptotic normality of two proposed estimators are established. Second, we construct a rank score test based on partial subgradients for the existence of the kink effect in longitudinal studies. Both the null distribution and the local alternative distribution of the test statistic have been derived. Simulation studies show that the proposed methods have excellent finite sample performance. In the application to the longitudinal progesterone data, we identify two kink points in the progesterone curves over different quantiles and observe that the progesterone level remains stable before the day of ovulation, then increases quickly in 5 to 6 days after ovulation and then changes to stable again or drops slightly. 相似文献
23.
胀果甘草化学成分的研究(Ⅲ) 总被引:5,自引:0,他引:5
继前文工作,本文报道从胀果甘草(Glycyrrhiza inflata Bat)根及根茎用95%乙醇渗滤后的提取部分中获得的另外五个化合物的结构鉴定。经理化性质及波谱分析,分别鉴定为胡萝卜甙(Daucosterol)、甘草查尔酮甲(Licochalcone A)、β-谷甾醇(β-Sitosterol),异芒柄花甙(Isoononin)和4',7一二羟基黄酮(4',7-Dihydroxy-flavone)。其中胡萝卜甙和异芒柄花甙为首次从该植物中获得。药理实验表明,甘草查尔酮甲对H_2O_2诱异的溶血有极好的抑制作用(97.3%),但甘草甙在三个体外氧化体系中都没有明显的活性。 相似文献
24.
细胞核移植技术已被证明是研究发育中核质相互关系的非常重要的手段之一,电融合技术也是近十年发展起来的新型细胞融合技术。本实验运用这两项技术,进行了鼠、兔目间核质杂交实验,小鼠8-细胞核在激活的兔去核卵母细胞中,发生了染色体超前凝聚及核膨胀,融合卵移植到小鼠输卵管4.5天后,冲洗出,有5.4%的重构卵发育到囊胚期,通过染色体检查,囊胚细胞中均为小鼠染色体,其中一个囊胚为正常小鼠核型(2 n=40,XX)。通过本实验,我们认为:鼠兔远缘核质杂交胚胎的早期发育是可能的。 相似文献
25.
Shumin Guo Jie Wu Zhaoqiang Han Zhutao Li Pinshang Xu Shuwei Liu Jinyang Wang Jianwen Zou 《Global Change Biology Bioenergy》2023,15(4):478-493
Existing studies suggest that biochar application can reduce soil nitrous oxide (N2O) emissions, mainly based on short-term results. However, it remains unclear what the effects (i.e., legacy effects) and underlying mechanisms are on N2O emissions after many years of a single application of biochar. Here, we collected intact soil columns from plots without and with biochar application in a subtropical tea plantation 7 years ago for an incubation experiment. We used the N2O isotopocule analysis combined with ammonia oxidizer-specific inhibitors and molecular biology approaches to investigate how the legacy effect of biochar affected soil N2O emissions. Results showed that the soil in the presence of biochar had lower N2O emissions than the control albeit statistically insignificant. The legacy effect of biochar in decreasing N2O emissions may be attributed to the reduced effectiveness of the soil substrate, nitrification and denitrification activities, and the promotion of the further reduction of N2O. The legacy effect of biochar reduced the relative contribution of nitrifier denitrification/bacterial denitrification, nitrification-related N2O production, and the relative abundance of several microorganisms involved in the nitrogen cycle. Our global meta-analysis also showed that the reduction of N2O by biochar increased with increasing application rate but diminished and possibly even reversed with increasing experimental time. In conclusion, our findings suggest that the abatement capacity of biochar on soil N2O emissions may weaken over time after biochar application, but this remains under further investigation. 相似文献
26.
异色瓢虫若虫对麦三叉蚜的捕食作用 总被引:5,自引:4,他引:1
研究表明,异色瓢虫高龄若虫捕食麦二叉蚜的功能反应为HollingⅡ型反应,喜好捕食低龄若蚜;在40℃下捕食率最低,10℃次之,25℃最高.在10~25℃内捕食率y与温度x的关系为y=28.1303+2.6665x,在25~40℃内为y=199.9275-3.642x;在种内干扰条件下,其捕食作用率E与开敌密度P的关系为E=0.6897P-0.7930,搜索常数Q为0.6897,干扰系数m为0.7930;其分摊竞争强度I与异色瓢虫密度P的关系为I=0.0400+1.0383logP. 相似文献
27.
Alteration of seed fatty acid composition by an ethyl methanesulfonate-induced mutation in Arabidopsis thaliana affecting diacylglycerol acyltransferase activity. 总被引:7,自引:3,他引:4
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V Katavic D W Reed D C Taylor E M Giblin D L Barton J Zou S L Mackenzie P S Covello L Kunst 《Plant physiology》1995,108(1):399-409
In characterizing the enzymes involved in the formation of very long-chain fatty acids (VLCFAs) in the Brassicaceae, we have generated a series of mutants of Arabidopsis thaliana that have reduced VLCFA content. Here we report the characterization of a seed lipid mutant, AS11, which, in comparison to wild type (WT), has reduced levels of 20:1 and 18:1 and accumulates 18:3 as the major fatty acid in triacylglycerols. Proportions of 18:2 remain similar to WT. Genetic analyses indicate that the fatty acid phenotype is caused by a semidominant mutation in a single nuclear gene, designated TAG1, located on chromosome 2. Biochemical analyses have shown that the AS11 phenotype is not due to a deficiency in the capacity to elongate 18:1 or to an increase in the relative delta 15 or delta 12 desaturase activities. Indeed, the ratio of desaturase/elongase activities measured in vitro is virtually identical in developing WT and AS11 seed homogenates. Rather, the fatty acid phenotype of AS11 is the result of reduced diacylglycerol acyltransferase activity throughout development, such that triacylglycerol biosynthesis is reduced. This leads to a reduction in 20:1 biosynthesis during seed development, leaving more 18:1 available for desaturation. Thus, we have demonstrated that changes to triacylglycerol biosynthesis can result in dramatic changes in fatty acid composition and, in particular, in the accumulation of VLCFAs in seed storage lipids. 相似文献
28.
Early cytokine and chemokine gene expression in lymph nodes of macaques infected with simian immunodeficiency virus is predictive of disease outcome and vaccine efficacy. 总被引:4,自引:4,他引:0
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W Zou A A Lackner M Simon I Durand-Gasselin P Galanaud R C Desrosiers D Emilie 《Journal of virology》1997,71(2):1227-1236
Competitive PCR was used to evaluate the expression of cytokine, granzyme B, and chemokine genes in lymph nodes of macaques recently infected with the simian immunodeficiency virus (SIV) pathogenic molecular clone SIVmac239 (n = 16), the nonpathogenic vaccine strain SIVmac239 delta nef (n = 8), and the nonpathogenic molecular clone SIVmac1A11 (n = 8). For both SIVmac239 and its nef-deleted derivative, strong expression was observed as early as 7 days postinfection for interleukin 1beta (IL-1beta), IL-6, tumor necrosis factor alpha, gamma interferon, and IL-13. The levels of gene induction were equally intense for both viruses despite a lower viral load for SIVmac239 deltanef compared with that for SIVmac239. However, the nature of the cytokine network activation varied with the viral inocula. Primary infection with SIVmac239 was characterized by a higher level of IL-4, IL-10, MIP-1alpha, MIP-1beta, MCP-1, and RANTES gene expression and a lower level of IL-12 and granzyme B gene expression compared with infection with SIVmac239 delta nef. Thus, infection with nef-deleted SIV was associated with a preferential Th1 versus Th2 pattern of cytokine production. Infection with SIVmac1A11 was characterized by a delayed immune response for all markers tested. The unique patterns of cytokine and chemokine gene expression in lymph nodes correlated nicely with the pathogenic potential of the SIV strains used as well as with differences in their ability to serve as protective vaccines. 相似文献
29.
The athermal bioeffects caused by nanosecond electromagnetic pulses with body cells was studied by using a broad band transverse EM-wave cell (BTEM CELL). The experimental system and preliminary mechanism analysis were presented. 相似文献
30.
Regulation of GABAB receptors by histamine and neuronal activity in the isolated spinal cord of neonatal opossum in culture. 总被引:1,自引:0,他引:1
D J Zou J M Treherne R R Stewart N R Saunders J G Nicholls 《Proceedings. Biological sciences / The Royal Society》1991,246(1315):77-82
The aim of these experiments has been to analyse the properties of receptors for the transmitter gamma-aminobutyric acid (GABA) in developing mammalian nervous system. Changes in responses of GABAB receptors have been measured after alterations of the chemical environment and the level of electrical activity. We have previously shown that when the central nervous system (CNS) of the new-born opossum, Monodelphis domestica, is cultured for three to five days in the presence of histidine, inhibition by baclofen, a GABAB agonist, disappears (Stewart et al. 1991). We have now investigated whether histidine acts indirectly by way of conversion to histamine. As with histidine, culture with 150 microM histamine for five days virtually abolished the inhibition by baclofen. The effects of histidine, as well as histamine, were blocked by mepyramine, a histamine H1-receptor antagonist, and by ranitidine, an H2-antagonist. Tetrodotoxin (TTX), which blocks all electrical activity, protected preparations from the action of histidine but not histamine. Our results suggest that histidine is converted to histamine, which reduces the efficacy of GABAB agonists. We conclude that, in the developing mammalian CNS, transmitter levels and electrical activity can selectively influence the properties of receptors. 相似文献