| 18271. |
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| 18272. |
- Zhao, Guohua, et al.
(författare)
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Determination of short-chain fatty acids in serum by hollow fiber supported liquid membrane extraction coupled with gas chromatography
- 2007
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Ingår i: Journal of Chromatography. B. - : Elsevier BV. - 1873-376X .- 1570-0232. ; 846:1-2, s. 202-208
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Tidskriftsartikel (refereegranskat)abstract
- A method based on hollow fiber supported liquid membrane extraction coupled with a gas chromatograph equipped with flame ionization detector (GC-FID) was developed for the determination of six short-chain fatty acids including acetic acid, propionic acid, i-butyric acid, n-butyric acid, i-valeric acid and n-valeric acid in serum. Hollow fiber supported liquid membrane extraction was employed for preconcentration and clean-up of the samples. The fatty acids were extracted from the acidic donor (diluted serum) into a liquid membrane formed in the wall of the hollow fiber with 10% tri-n-octylphoshphine oxide (TOPO) in di-n-hexyl ether, and then extracted back into a basic acceptor solution filled in the lumen of the hollow fiber. After being acidified with HCl, the acceptor was directly analyzed by GC-FID. The acceptor concentration, donor pH, membrane liquid and extracting time were optimized giving an enrichment factor up to 155 times. The good linearity (r2 > 0.980), reasonable recovery (87.2-121%), and satisfactory intra-assay (8.2-11.5%) and inter-assay (6.1-11.6%) precision illustrated the good performance of the present method. Limits of detection (LOD) ranged from 0.04 to 0.24 μM and limits of quantification (LOQ) varied from 0.13 to 0.80 μM.
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| 18273. |
- Zhao, Guohua, et al.
(författare)
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Rapid determination of short-chain fatty acids in colonic contents and faeces of humans and rats by acidified water-extraction and direct-injection gas chromatography
- 2006
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Ingår i: Biomedical Chromatography. - : Wiley. - 0269-3879 .- 1099-0801. ; 20:8, s. 674-682
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Tidskriftsartikel (refereegranskat)abstract
- Short-chain fatty acids (SCFAs) have attracted much attention recently because of their positive physiological effects. In this work, a rapid and reliable gas chromatographic method for determination of eight SCFAs, in colonic and faecal samples from rats and humans has been developed and validated. The methodology involves extraction of the SCFAs in water before a direct injection procedure on a FFAP capillary column. A stock standard solution containing acetic acid, propionic acid, n-butyric acid, i-butyric acid, n-valeric acid, i-valeric acid, n-caproic acid and n-heptanoic acid was prepared and used. A high linearity (r(2) > 0.9990), low quantification limit (2.38-30.14 mu M) and high recovery for most acids were obtained. Acidification of faecal samples was found to be crucial for quantitative determination of the SCFAs, and adjustment of pH to 2-3 was regarded as necessary. Glass wool inserted in the glass liner of the injection port proved effective in preventing the contamination of the column by non-volatiles, and 12% formic acid reduced the ghost peak that appeared gradually after several injections. After validation, the methodology was applied on two faecal samples from rats fed diets containing different amount of dietary fibre and one faecal sample from human fed a normal diet to test the accuracy of the developed method. Copyright (c) 2005 John Wiley & Sons, Ltd.
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| 18274. |
- Zhao, Ke, et al.
(författare)
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One-dimensional arrays of nanoshell dimers for single molecule spectroscopy via surface-enhanced raman scattering
- 2006
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 125:8
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of one-dimensional arrays of metal nanoshell dimers are studied systematically using the T-matrix method based on Mie theory, within the context of surface enhanced Raman scattering (SERS). It is shown that the local electromagnetic enhancement can be as high as similar to 4.5x10(13) for nanoshell dimer arrays with optimal geometry, and sensitive tunability in the resonant frequency can be gained by varying the geometrical parameters, making such structures appealing templates for SERS measurements with single molecule sensitivity. The extraordinarily high enhancement is attributed to a collective photonic effect constructively superposed onto the intrinsic enhancement associated with an isolated nanoshell dimer. (c) 2006 American Institute of Physics.
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| 18275. |
- Zhao, Peng, et al.
(författare)
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Lentiviral vector mediated siRNA knock-down of hTERT results in diminished capacity in invasiveness and in vivo growth of human glioma cells in a telomere length-independent manner
- 2007
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Ingår i: International Journal of Oncology. - 1019-6439. ; 31:2, s. 361-368
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Tidskriftsartikel (refereegranskat)abstract
- Glioma cells are characterized by their invasiveness and resistance against conventional therapeutics. Telomerase activity has been suggested to be an important target for glioma treatment. Here we assessed the anticancer effects and its potential mechanisms of lentiviral vector mediated siRNA knock-down of the human telomerase reverse transcriptase (hTERT) in U87MG human glioblastoma cells. Stable expression of anti-hTERT siRNA reduced the hTERT expression and TRAP assay telomerase activity to barely detectable levels. Injection of lentiviral vectors encoding anti-hTERT siRNA significantly inhibited the growth of preestablished macroscopic xenograft tumors, which was in contrast to the finding that no obvious effects on cell growth, cell cycle progression and telomere length were observed in anti-hTERT siRNA expressing U87MG cells during short-term in vitro cultures. The in vivo glioma growth inhibition effect was already evident in the period coincided with no detectable telomere length changes, suggesting that hTERT inhibition may hinder glioma cell growth in a telomere length-independent manner. Importantly, transwell migration assay showed profound inhibitory effect on the invasive capacity of U87MG cells following short-term anti-hTERT siRNA expression. Thus, efficient knock-down of hTERT can inhibit glioma cell proliferation and migration prior to its effect on telomere length.
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| 18276. |
- Zhao, Shiwei, et al.
(författare)
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Hybrid ultrawideband modulations compatible for both coherent and transmit-reference receivers
- 2007
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 6:7, s. 2551-2559
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers signaling schemes for heterogeneous ultrawideband communications networks that contain both coherent (rake) and transmitted-reference (TR) receivers. While coherent receivers are capable of receiving TR signals, they do so with a 3 dB penalty, because they cannot make use of the energy invested into the reference pulse. We propose a new signaling scheme that avoids this drawback, by encoding redundant information on the reference pulse. The resulting scheme does not affect the operation of a TR receiver, while recovering the 3 dB penalty and furthermore providing an additional 1.7 dB coding gain to a coherent uncoded binary scheme. This can be explained by interpreting the scheme as a trellis-coded modulation. We also provide an alternative implementation that can be viewed as a recursive systematic convolutional encoder. Combining this version further with a simple forward error correction encoder results in a concatenated code that can be decoded iteratively, providing a bit-error rate of 10(-3) at 2.8 dB signal-to-noise ratio in additive white Gaussian noise. The convergence behavior of this iterative code is analyzed by using extrinsic information transfer charts.
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| 18277. |
- Zhao, Song, et al.
(författare)
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Organ bath in detecting the effect of one-hour warm ischemia on pulmonic arteries and bronchi from non-heart-beating donor lungs
- 2009
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Ingår i: Chinese Medical Journal. - 0366-6999. ; 122:23, s. 2903-2906
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Tidskriftsartikel (refereegranskat)abstract
- Background Non-heart-beating donor lung has been a promising source of lung transplantation. Many studies on non-heart-beating donor lungs are based on animal lung transplantation. In this study, we assessed by organ bath the effect of one-hour warm ischemia on the non-heart-beating donor lung in terms of the integrity of contractile and relaxant functions and tissue structures of pulmonic arteries and bronchi. Methods Sixteen Swedish pigs were randomly classified into two groups: heart-beating donor group and 1-hour warm ischemia non-heart-beating donor group. Pulmonic and bronchial rings were taken from the isolated left lungs of the pigs. The pulmonic rings were stimulated by U-46619 (5.7 mol/L) and acetylcholine (10(-4) mmol/L) to assess the contractile abilities of smooth muscle and the endothelium-dependent relaxation response, respectively. As such, acetylcholine (10(-5) mmol/L) and natrium arachidonic acid (0.01%) were used to detect the contraction of bronchial smooth muscle and epithelium-dependent relaxation response. Meanwhile, the variances of precontraction tension of control groups were recorded to measure whether there was spontaneous relaxation during endothelium/epithelium-dependent relaxation course. Finally, papaverine solution (10(-4) mmol/L) was used to detect the non-endothelium/epithelium-dependent relaxant abilities of pulmonic and bronchial smooth muscles. Results There was no significant difference in the tension values of precontraction of pulmonic rings (P >0.05), endothelium-dependent relaxation (P >0.05), precontraction of bronchial rings (P >0.05) and epithelium-dependent relaxation (P >0.05) between the heart-beating donor group and the 1-hour warm ischemia non-heart-beating donor group. And the pulmonic and bronchial rings of each subgroup B had no spontaneous relaxation. Finally, papaverine solution relaxed the smooth muscle of all the rings completely. Conclusions The results of this experiment suggest that the contractile and relaxant functions and tissue structures of pulmonic arteries and bronchi are not damaged after warm ischemia for 1 hour, and support the further study of ;non-heart-beating donor lung.
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| 18278. |
- Zhao, Xia, et al.
(författare)
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A new understanding of pancreatitis-associated pulmonary injury
- 2006
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Ingår i: Journal of Organ Dysfuntion. - : Informa UK Limited. - 1747-1060 .- 1747-1079. ; 2:3, s. 156-165
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Tidskriftsartikel (refereegranskat)abstract
- Pancreatitis-associated lung injury (PALI) is one of the earliest organ dysfunctions occurring in patients with severe acute pancreatitis. In this review we explore potential mechanisms of endothelial barrier dysfunction, neutrophil and monocyte/macrophage activation, adhesion molecule expression, initial factors, mast cell involvement and intracellular signaling in PALI. Different regulatory mechanisms exist in PALI and sepsis-induced lung injury. Endothelial barrier dysfunction occurs early on in acute pancreatitis and tumor necrosis factor (TNF)-agr and monocyte chemoattractive protein-1 levels in the circulation gradually increase in acute pancreatitis. Leukocytes from the circulation, lung tissue and bronchoalveolar fluid exhibit different expression and activation patterns in the development of PALI. Mast cells seem to be involved in the initiation of leukocyte activation during the initial phase of PALI. Activation of the protein kinase C (PKC) signaling pathway could play an important role in the pathogenesis of PALI. Inhibition of PKC may be one candidate to prevent and treat the development of PALI.
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| 18279. |
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| 18280. |
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