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51.
Jie Zhou Jiajia Zhang Alexander C. Mclain Wenbin Lu Xuemei Sui James W. Hardin 《Biometrics》2019,75(3):853-863
Varying‐coefficient models have become a common tool to determine whether and how the association between an exposure and an outcome changes over a continuous measure. These models are complicated when the exposure itself is time‐varying and subjected to measurement error. For example, it is well known that longitudinal physical fitness has an impact on cardiovascular disease (CVD) mortality. It is not known, however, how the effect of longitudinal physical fitness on CVD mortality varies with age. In this paper, we propose a varying‐coefficient generalized odds rate model that allows flexible estimation of age‐modified effects of longitudinal physical fitness on CVD mortality. In our model, the longitudinal physical fitness is measured with error and modeled using a mixed‐effects model, and its associated age‐varying coefficient function is represented by cubic B‐splines. An expectation‐maximization algorithm is developed to estimate the parameters in the joint models of longitudinal physical fitness and CVD mortality. A modified pseudoadaptive Gaussian‐Hermite quadrature method is adopted to compute the integrals with respect to random effects involved in the E‐step. The performance of the proposed method is evaluated through extensive simulation studies and is further illustrated with an application to cohort data from the Aerobic Center Longitudinal Study. 相似文献
52.
Ma Si Li Yaxin Li Xin Sui Xiaolei Zhang Zhenxian 《Journal of Plant Growth Regulation》2019,38(2):494-500
Journal of Plant Growth Regulation - Carbohydrate produced by photosynthesis is loaded into phloem via collection phloem, translocated via the transport phloem, and unloaded by release phloem into... 相似文献
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56.
Numerical simulations of surface plasmon resonance system for monitoring DNA hybridization and detecting protein-lipid film interactions 总被引:1,自引:0,他引:1
This paper presents a simple method to extract information about thin organic films from surface plasmon resonance (SPR)
spectra. From numerical simulations it was found that a shift (Δθ
SPR) of an absorption peak in the SPR spectrum was directly proportional to the product of the thin organic film thickness and
the refractive index difference between the thin organic film and a buffer soaking the sample. It was also found that Δθ
SPR was not sensitive to the thin organic film support of a gold film and a glass cover slip. Relationships between Δθ
SPR and distributions of macromolecule structures, in the thin organic films were theoretically established. Formulae were derived
for a homemade SPR system to calculate length, transverse area, density and surface concentration of macromolecules in the
thin organic film. The validity of these treatments was checked by precisely measuring the size of a single distearoylphosphatidylcholine
molecule on a gold-supported phospholipid film; by quantitatively monitoring hybridization of synthesized oligonucleotides
strands based on a biotin/avidin system; and by quantitatively detecting the steric hindrance of rabbit C-reactive protein
specifically bound to phospholipid monolayers composed of synthesized lipids.
Received: 4 May 1998 / Revised version: 27 July 1998 / Accepted: 27 August 1998 相似文献
57.
急性低压低氧对大鼠空间学习记忆的影响及与海马内孤啡肽的关系 总被引:4,自引:0,他引:4
目的:研究暴露在不同海拔高度的急性低压低氧环境中,大鼠空间学习记忆能力的变化及与海马内孤啡肽的关系.方法:采用低压舱模拟4 500 m(中度)和7 500 m(重度)两种海拨高度,Morris水迷宫训练方法和反转录多聚酶链式反应(RT-PCR)技术.结果:①海马内孤啡肽mRNA表达在急性重度低压低氧(8 h/d,连续6 d)后明显增加,然而在Morris 水迷宫训练(6 counts/d,连续6 d,定位航行潜伏期逐渐缩短)后则显著降低.②急性低压低氧后,定位航行潜伏期明显延长,而海马内孤啡肽mRNA表达较学习记忆训练组明显升高.结论:海马内孤啡肽参与急性低压低氧降低大鼠空间学习记忆的机制. 相似文献
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A novel type of deubiquitinating enzyme 总被引:1,自引:0,他引:1
Evans PC Smith TS Lai MJ Williams MG Burke DF Heyninck K Kreike MM Beyaert R Blundell TL Kilshaw PJ 《The Journal of biological chemistry》2003,278(25):23180-23186
A previous report from this laboratory described two novel proteins that have sequence similarity to A20, a negative regulator of NF-kappaB (Evans, P. C., Taylor, E. R., Coadwell, J., Heyninck, K., Beyaert, R., and Kilshaw, P. J. (2001) Biochem. J. 357, 617-623). One of these molecules, cellular zinc finger anti-NF-kappaB (Cezanne), a 100-kDa cytoplasmic protein, also suppressed NF-kappaB. Here we demonstrate that Cezanne is a novel deubiquitinating enzyme, distinct from the two known families of deubiquitinases, Types I and II. We show that Cezanne contains an N-terminal catalytic domain that belongs to the recently discovered ovarian tumor protein (OTU) superfamily, a group of proteins displaying structural similarity to cysteine proteases but having no previously described function. Recombinant Cezanne cleaved ubiquitin monomers from linear or branched synthetic ubiquitin chains and from ubiquitinated proteins. Mutation of a conserved cysteine residue in the catalytic site of the proteolytic domain caused Cezanne to co-precipitate polyubiquitinated cellular proteins. We also provide evidence for an additional ubiquitin binding site in the C-terminal part of the molecule. Our data provide the first demonstration of functional activity among OTU proteins. 相似文献
60.
PTP-MEG2 is an intracellular protein tyrosine phosphatase with a putative lipid-binding domain at the N-terminus. The present study reports expression, purification, and characterization of the full-length form of the enzyme plus a truncated form containing the catalytic domain alone. Full-length PTP-MEG2 was expressed with an adenovirus system and purified from cytosolic extracts of human 293 cells infected with the recombinant adenovirus. The purification scheme included chromatographic separation of cytosolic extracts on fast flow Q-Sepharose, heparin-agarose, l-histidyldiazobenzylphosphonic acid agarose, and hydroxylapatite. The enrichment of PTP-MEG2 from the cytosol was about 120-fold. The truncated form of PTP-MEG2 was expressed in E. coli cells as a non-fusion protein and purified by using a chromatographic procedure similar to that used for the full-length enzyme. The purified full-length and truncated enzymes showed single polypeptide bands on SDS-polyacrylamide gel electrophoresis under reducing conditions and behaved as monomers on gel exclusion chromatography. With para-nitrophenylphosphate and phosphotyrosine as substrates, both forms of the enzyme exhibited classical Michaelis-Menten kinetics. Their responses to pH, ionic strength, metal ions, and protein phosphatase inhibitors are similar to those observed with other characterized tyrosine phosphatases. Compared with full-length PTP-MEG2, the truncated DeltaPTP-MEG2 displayed significantly higher V(max) and lower K(m) values, suggesting that the N-terminal putative lipid-binding domain may have an inhibitory role. The full-length and truncated forms of PTP-MEG2 were also expressed as GST fusion proteins in E. coli cells and purified to near homogeneity through affinity columns. However, the specific phosphatase activities of the GST fusion proteins were 10-25-fold below those obtained with the correspondent non-fusion proteins. 相似文献