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Yan Yao

Publications and source records attributed to Yan Yao.

17 recordsLinked to original sources
PubMed2007

Time-resolved fluoroimmunoassay for ractopamine in swine tissue.

This study describes the development and validation of a time-resolved fluoroimmunoassay (TR-FIA) for screening ractopamine (RAC) in swine tissue. The method is based on the direct competitive-type immunoassay using europium-labeled anti-RAC monoclonal antibody as a tracer and RAC-ovalbumin as a solid-phase antigen. When RAC was spiked at levels of 1-10 microg kg(-1), recoveries ranged from 88.2 to 118.5% for swine liver and muscle with coefficients of variation from 7.1 to 20.5%. The detection limit was 0.1 microg kg(-1). The proposed TR-FIA method was applied to the determination of RAC in an actual residue study and the applicability was confirmed by liquid chromatography-tandem mass spectrometry.

Animals↗
PubMed2006

Three-dimensional pore structure of chromatographic adsorbents from electron tomography.

The pore structure of chromatographic adsorbents directly influences macromolecular partitioning and transport in chromatography. Quantitative structural characterization of chromatographic media has generally been performed in terms of the mean pore size or, at best, the pore size distribution (PSD), but more detailed information on, e.g., connectivity has been lacking. We have applied electron tomography, a 3D TEM technique that views a sample from multiple perspectives and allows reconstruction of the volumetric structure, to capture the internal details of microporous chromatographic media with nanometer-scale resolution. Visualization of reconstructions of three adsorbents, Toyopearl SP-650 C, SP-550 C, and CM Sepharose FF, provides thorough and direct information on the geometry and the interconnectivity of the pore network. The structures are qualitatively consistent with in situ AFM images, and quantitative data for the porosities and PSDs from the analysis of tomographic data agree reasonably well with inverse size-exclusion chromatography results. For a more straightforward representation of the networking and size features of the disordered pore space, a 3D thinning algorithm was used to derive pore skeletons and consequently quantitative data on distributions of local path lengths, widths, tortuosities, and connectivities. Such enriched structural information can be instrumental in more discriminate structural evaluation and construction of engineered pore models for the study of solute intraparticle transport.

Algorithms↗
PubMed2006

Pore size distributions of ion exchangers and relation to protein binding capacity.

The pore structure of chromatographic media directly influences macromolecular transport and adsorption, and consequently separation resolution and loading capacity in chromatographic separations. The pore size distribution (PSD) is therefore a central structural characteristic of chromatographic materials and a critical determinant of chromatographic behavior. In this work the PSDs of a set of commercial anion exchangers were determined by inverse size-exclusion chromatography (ISEC). The PSDs were further utilized to develop relations to functional properties of adsorbents, such as intraparticle diffusivity, and static and dynamic binding capacities. We find that the detailed PSD is useful in semi-quantitative understanding of chromatographic behavior. However, more accurate prediction of column behavior requires more thorough knowledge of the pore structure, specifically the connectivity of the pore network, as well as improved understanding of the function of grafted resins.

Chromatography, Gel↗
PubMed2006

Regioregular copolymers of 3-alkoxythiophene and their photovoltaic application.

Low band gap conjugated polymers with proper energy levels for charge transfer are required to achieve high-efficiency polymer solar cells. We report the synthesis and characterization of two new regioregular copolymers that are based on 3-alkoxythiophene monomers: poly(3-octylthiophene-2,5-diyl-co-3-decyloxythiophene-2,5-diyl) (POT-co-DOT) and poly{(9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-decyloxythien-2-yl)-2,1,3-benzothiadiazole]-5',5' '-diyl} (PF-co-DTB). Compared to the alkyl substituents, the alkoxy side chains on the thiophene units can effectively lower the band gap of copolymers and enhance the charge transfer to electron acceptors such as (6,6)-phenyl C(61)-butyric acid methyl ester (PCBM). The chemical structure and regioregularity of the copolymers were confirmed by NMR. Both copolymers are readily soluble in organic solvents and form high-quality thin films. Electrochemical and photophysical studies reveal band gaps of 1.64 eV for POT-co-DOT and 1.78 eV for PF-co-DTB. Bulk heterojunction photovoltaic devices were fabricated using blends of these copolymers with PCBM as the active layer, ITO-glass as the anode, and aluminum as the cathode. Power conversion efficiency of 1.6% was obtained under simulated solar light AM 1.5 G (100 mW/cm(2)) from a solar cell with an active layer containing 20 wt % PF-co-DTB and 80 wt % PCBM. Regioregular poly(3-decyloxythiophene-2,5-diyl) (P3DOT) was also studied for comparison purposes.

Journal Article↗
PubMed2006

Inhibitory effects of blocking voltage-dependent potassium channel 1.3 on human monocyte-derived macrophage differentiation into foam cells.

OBJECTIVE: To investigate the expression of voltage-dependent potassium channel 1.3 (Kv1.3) mRNA and protein during human monocyte-derived macrophage differentiation into foam cells and its function in foam cell formation. METHODS: Human peripheral blood monocytes were isolated from healthy male volunteers by density gradient centrifugation and then by adherent method. The obtained monocytes were cultured for 5 days to differentiate into macrophages. Based on establishment of the human macrophage-derived foam cell model, the expression of Kv1.3 channel was investigated by immunocytochemical staining, reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Furthermore, the effects of rMargatoxin, a Kv 1.3 channel-specific inhibitor, on cholesterol metabolism in macrophages incepting oxidized low density lipoprotein (OxLDL) were studied. RESULTS: After the macrophages co-incubated with 30 mg/L OxLDL at 37 degrees C for 60 hours, the cellular volume obviously enlarged and many red lipid granules were deposited in cytoplasm. The total amount of cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) in cells markedly increased and the ratio of CE/TC rose from (14.4+/-6.8)% to (57.9+/-3.5)% (n=7, P<0.05). However, the expression of Kv1.3 channel had no significant change. rMargatoxin (0.1 nmol/L and 10 nmol/L) markedly reduced the contents of TC, FC and CE in macrophages and the ratios of CE/TC decreased to (42.8+/-11.6)% and (22.6+/-8.0)%, respectively (n=7, P<0.05). Meanwhile, the red lipid granules deposited in the cytoplasm of macrophages also decreased. CONCLUSION: These data clearly show that the expression of Kv1.3 channel does not change obviously during human monocyte-derived macrophage differentiation into foam cells and the blocking of it would prevent foam cell formation.

Adult↗
PubMed2006

Mutation Glu82Lys in lamin A/C gene is associated with cardiomyopathy and conduction defect.

Dilated cardiomyopathy is a form of heart muscle disease characterized by impaired systolic function and ventricular dilation. The mutations in lamin A/C gene have been linked to dilated cardiomyopathy. We screened genetic mutations in a large Chinese family of 50 members including members with dilated cardiomyopathy and found a Glu82Lys substitution mutation in the rod domain of the lamin A/C protein in eight family members, three of them have been diagnosed as dilated cardiomyopathy, one presented with heart dilation. The pathogenic mechanism of lamin A/C gene defect is poorly understood. Glu82Lys mutated lamin A/C and wild type protein was transfected into HEK293 cells. The mutated protein was not properly localized at the inner nuclear membrane and the emerin protein, which interacts with lamin A/C, was also aberrantly distributed. The nuclear membrane structure was disrupted and heterochromatin was aggregated aberrantly in the nucleus of the HEK293 cells stably transfected with mutated lamin A/C gene as determined by transmission electron microscopy.

Adult↗
PubMed2006

Potassium magnesium supplementation for four weeks improves small distal artery compliance and reduces blood pressure in patients with essential hypertension.

It has been postulated that the loss of arterial compliance may precede cardiovascular diseases, and that arterial compliance is an important parameter to consider when evaluating arterial diseases such as essential hypertension (EH) and the effects of antihypertensive treatment. In all, 133 EH patients and 147 healthy subjects were enrolled in this study. Large arterial compliance (C1) and small arterial compliance (C2) were measured by the CVProfilor DO-2020 CardioVascular Profiling System. Thirty-five patients randomly received magnesium potassium supplementation (magnesium, 70.8 mg/d; potassium, 217.2 mg/d) for four weeks, and 32 patients received lacidipin (4 mg/d) as a control. Before and after the four weeks, blood pressure, C1, and C2 were measured. It was found that arterial compliance was significantly lower in EH patients compared with healthy subjects (C1: 12.53 +/- 0.33 vs. 15.63 +/- 0.30 ml/mmHg x 10, p < 0.01;C2: 3.79 +/- 0.17 vs. 5.69 +/- 0.25 ml/mmHg x 100, p < 0.01). On lacidipine, systolic and diastolic BP decreased 13.27 +/- 1.76 mm Hg and 6.33 +/- 1.55 mm Hg, and C1 and C2 compliance values increased 25.05% +/- 4.49% and 34.50% +/- 7.40%, respectively. On K+ and Mg2+ supplementation, systolic and diastolic BP decreased 7.83 +/- 1.87 mm Hg and 3.67 +/- 1.03 mm Hg, and C1 and C2 compliance values increased 12.44% +/- 4.43% and 45.25% +/- 6.67%, respectively. Decreases in systemic vascular resistance (mean arterial pressure divided by cardiac output) by 11.9% and 16.6 % (p < 0.01) were seen between the drug-induced changes, respectively. Both large arterial compliance and small arterial compliance were decreased in essential hypertension patients. In essential hypertension patients, magnesium and potassium supplementation could improve small arterial compliance, while lacidipine improved large arterial compliance significantly.

Adult↗
PubMed2006

The expression of maxiK channel alpha--subunit during human macrophages differentiating into foam cells.

OBJECTIVE: To investigate the expression of MaxiK channel alpha-subunit during human monocyte-derived macrophages differentiating into foam cells. METHODS: Human peripheral blood monocytes were isolated from male healthy volunteers by density gradient centrifugation, which, by culture, differentiated further into macrophages as a homogeneous monocyte population. The foam cell model originated from human macrophage was established by incubating macrophages with oxidized low density lipoprotein (OxLDL). The expression of MaxiK channel alpha-subunit was investigated by RT-PCR techniques, Western blotting and immunocytochemistry. RESULTS: After incubating macrophages with 30 mg/L OxLDL for 60 hours, the cellular contents of total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were markedly increased and the ratio of CE/TC was further raised from (14.437 +/- 6.781) % to (57.946 +/- 3.507) %. Although the expression of MaxiK channel alpha-subunit was downregulated during human monocyte-derived macrophages differentiating into foam cells, there was no significant difference between macrophages and foam cells (P > 0.05). CONCLUSION: That 30 mg/L OxLDL can lead the monocyte-derived macrophage cultured for 60 hours to differentiate into foam cell, but the expression of MaxiK channel alpha-subunit does not change obviously.

Adult↗
PubMed2006

[Inhibitory effect of blocking MaxiK channel on human monocyte-derived macrophages differentiation into foam cells].

AIM: To investigate the expression of high-conductance Ca2+-activated potassium channel (MaxiK channel) mRNA and protein during human monocyte-derived macrophage differentiation into foam cells and to study its function in foam cell formation. METHODS: Human peripheral blood monocytes were isolated from healthy male volunteers by density gradient centrifugation and then by adherent method. The obtained monocytes were cultured for 5 days to differentiate into macrophages. Based on establishment of human macrophage-derived foam cells model, the expression of MaxiK channel alpha-subunit was investigated by immunocytochemical staining, RT-PCR and Western blot. Furthermore, the effect of Paxilline, a MaxiK channel-specific inhibitor, on cholesterol metabolism in macrophages incepting oxidized low density lipoprotein (OxLDL) was studied. RESULTS: After the macrophages were co-incubated with 30 mg/L OxLDL at 37 degrees C for 60 hours, the cellular volume obviously enlarged and many red lipid granules were deposited in cytoplasm. The total amount of cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) in cells markedly increased and the ratio of CE/TC rose from (14.437+/-6.781)% to (57.946+/-3.507)% (n=7, P<0.05). However, the expression of MaxiK channel alpha-subunit had no significant change (P<0.05). Paxilline (5 micromol/L and 10 micromol/L) markedly reduced the content of TC, FC and CE in macrophages and the ratio of CE/TC decreased to (41.217+/-5.584)% (5 micromol/L Paxilline) and (18.017+/-11.559)% (10 micromol/L Paxilline), respectively (n=7, P<0.05). Meanwhile, the red lipid granules deposited in the cytoplasm of macrophages also decreased. CONCLUSION: Blocking MaxiK channel can inhibit human monocyte-derived macrophage to be differentiated into foam cells.

Animals↗
PubMed2006

[The reflection spectrometer and quantitative analysis design].

The reflection spectrometer with optical fibre transmission was designed and used in quantitative analysis. The reflection spectrometry was applied to the determination of reducing sugar in samples based on the reduction reaction of the reducing sugar with Fehling's reagent. The reduction reaction was carried out in a micro-reaction cell, and the reddish colored Cu2O produced was settled at the bottom of the reaction cell. The reflectance R(infinity), which is directly proportional to the amount of Cu2O produced, was measured by the reflection spectrometer. The fundamental principle, effect factors, and experimental conditions of the method were discussed. Linear relationship was obtained in the range of 20-120 microg of reducing sugar. The special features of this method were its simplicity in operation, relatively high sensitivity of determination, and the use of small amount of reagent. Satisfactory results were obtained in its application to the analysis of wine and honey samples.

English Abstract↗
PubMed2006

[Inhibition of human macrophage-derived foam cell differentiation by blocking Kv1.3 and Kir2.1 channels].

OBJECTIVE: To investigate the expression of Kv1.3 and Kir2.1 during human monocyte-derived macrophages differentiation into foam cells and their function in foam cells formation. METHODS: The human macrophage-derived foam cells were obtained by incubating macrophages with ox-LDL (30 mg/L) for 60 h. The expression of Kv1.3 and Kir2.1 channels were examined by immunocytochemistry, RT-PCR and Western blot. Effects of channel blockers (rMargatoxin and BaCl2) on the cellular cholesterol metabolism were studied by measuring the cellular contents of total cholesterol (TC), free cholesterol (FC), and cholesterol ester (CE) in the presence or absence of the channel blockers. RESULTS: After incubating macrophages with 30 mg/L ox-LDL for 60 h, the cellular contents of TC, FC and CE were markedly increased and the ratio of CE/TC was raised from (14.4+/-6.8)% to (57.9+/-3.5)% (P<0.05), which indicated that the cells had differentiated into foam cells. The expression of Kv1.3 and Kir2.1 channels appeared no obvious difference when differentiating into foam cells (P>0.05); After being blocked specifically (rMargatoxin: 0.1, 10 nmol/L; BaC(12): 75, 125 micromol/L), the cellular contents of TC and CE were markedly reduced without exception and the ratios of CE/TC were all less than 50% (P<0.05). CONCLUSION: Both Kv1.3 and Kir2.1 channels play a critical role in differentiation of macrophages into foam cells and blockage of corresponding potassium channels would prevent the formation of the foam cells.

Barium Compounds↗
PubMed2006

[Effect of losartan on sarcoplasmic reticulum Ca2+ handing proteins in heart failure rabbit].

OBJECTIVE: To investigate the effects of losartan on mRNA expression of myocardial sarcoplasmic reticulum calcium handling proteins (SERCA2, RyR2 and PLB) and the role of which in prevention of chronic heart failure in rabbit. METHODS: After chronic heart failure was induced by ligation of the left anterior descending artery in rabbits, the animals were treated with losartan. At 8 weeks after ligation, left ventricular function, hemodynamic parameters, and SERCA2, RyR2, PLB mRNA expressions were observed. RESULTS: Compared with the control group (group C), LVEDP in the infarcted group (group I) increased (P < 0.01), while +dp/dt(max) and -dp/dt(max) decreased significantly (P < 0.01). LVEDP was lower but +dp/dt(max) and -dp/dt(max) significantly higher in the losartan treated group (group L) than those in group I (P < 0.05). SERCA2, RyR2, and PLB mRNA expressions in group I were remarkably lower than those in group L (P < 0.01) and group C (P < 0.01), respectively. CONCLUSION: Losartan can improve cardiac function, probably owing to its upregulating mRNA expressions of myocardial sarcoplasmic reticulum Ca(2+) handling proteins (RyR2, SERCA2 and PLB) in the prevention of heart failure.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2005

Electrostatic contributions to protein retention in ion-exchange chromatography. 2. Proteins with various degrees of structural differences.

The relation of protein structure to retention provides a framework within which to investigate chromatographic adsorption mechanisms. Protein sets with varying degrees of structural differences were studied to relate variations in protein properties to retention behavior. To explore molecular contributions to protein adsorption in ion-exchange chromatography, protein-adsorbent electrostatic interactions were modeled using a continuum approach. The calculations qualitatively capture the chromatographic differentiation of closely related subtilisin variants. Descriptions of the electrostatic interactions of FGF-1 vs FGF-2 with cation exchangers were obtained, and aid in rationalizing differences in experimental retention trends across a set of adsorbents based on different adsorption mechanisms linked to the adsorbent structure. Comparative calculations for proteins with differences in local or overall arginine-lysine composition, including subtilisin variants G166R/G166K and lysozyme/cytochrome c, suggest that continuum electrostatics is not adequate to capture the full quantitative characteristics of the chromatographic retention of proteins. To allow more accurate description of retention, additional molecular interactions, specifically hydration effects, must be incorporated in the model.

Arginine↗
PubMed2005

Expression of Kir2.1 channel during differentiation of human macrophages into foam cells.

OBJECTIVE: Detected in non-transformed bone marrow-derived macrophages (BMDM) and identified as one of the key channels in modulating macrophage proliferation, activation and apoptosis, Kir2.1 channel is also characterized to play a crucial role in cell differentiation. The purpose of this study was to investigate the expression of Kir2.1 channel mRNA and protein during human monocyte-derived macrophage differentiation into foam cells. METHODS: Human peripheral blood monocytes were isolated from healthy male volunteers by density gradient centrifugation and then by adherence method. The macrophages identified as a homogeneous population of adherent cells were obtained after 5 days of culture. Expression of Kir2.1 channel during human macrophage differentiation into foam cells was investigated by RT-PCR, Western blotting and immunocytochemistry, respectively. RESULTS: After incubation of the macrophages with 30 mg/L OxLDL at 37 degrees C for 60 h, the cells were obviously enlarged in size and numerous red lipid granules observed under optical microscope. The cellular contents of the total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were markedly increased from 54.79+/-28.304 mg/g, 47.968+/-26.787 mg/g and 6.822+/-3.437 mg/g to 229.775+/-57.453 mg/g, 96.241+/-24.003 mg/g and 133.535+/-36.292 mg/g, respectively; the CE/TC ratio rose from (14.437+/-6.781)% to (57.946+/-3.507)% (n=7, P<0.05), suggesting the phenotype of foam cells. However, there was no significant difference in the relative expression of Kir2.1 channel mRNA between the macrophages and foam cells [(59.074+/-10.566)% vs (46.98+/-12.527)%, n=5, P>0.05], nor was there significant difference in the relative expression of Kir2.1 channel protein between them [(60.527+/-18.621)% vs (50.243+/-11.583)%, n=6, P>0.05]. CONCLUSION: Incubation of human monocyte-derived macrophages with 30 mg/L OxLDL for 60 h induces the differentiation of the cells into foam cells, but the expression of Kir2.1 channel does not change obviously.

Adult↗
PubMed2004

Electrostatic contributions to protein retention in ion-exchange chromatography. 1. Cytochrome C variants.

Among the factors that modulate protein interactions, several protein structural properties, such as size, shape, and charge distribution, may play significant roles. In this work, we investigate the influence of protein structure on binding in ion-exchange chromatography, in which electrostatic interactions are dominant. Chromatographic experiments show separation of cytochrome c variants with a limited number of sequence differences to be feasible. To probe the molecular basis for this behavior, protein-adsorbent electrostatic interactions were modeled in the context of continuum electrostatics accounting for the full 3D protein structure. Protein retention was modeled by averaging over all protein-adsorbent configurations using the full accessible surface of the protein. The electrostatic interaction free energy distribution shows that configurations in which numerous positive protein charges are close to the cation exchanger functional groups produce the most favorable binding. The calculated binding equilibrium constant, found by averaging over the full 3D configurational space, captures the chromatographic differentiation of closely related cytochrome c variants. To obviate the need for full sampling of protein configurations, calculations of interaction free energies at short protein-adsorbent separation distances or of protein surface potentials were found to yield reasonable semiquantitative descriptions of the retention trends.

Adsorption↗
PubMed2004

Determination of pore size distributions of porous chromatographic adsorbents by inverse size-exclusion chromatography.

The macroscopic properties of porous chromatographic adsorbents are directly influenced by the pore structure, with the pore size distribution (PSD) playing a major role beyond simply the mean pore size. Inverse size-exclusion chromatography (ISEC), a widely used chromatographic method for determining the PSD of porous media, provides more relevant information on liquid chromatographic materials in situ than traditional methods, such as gas sorption and mercury intrusion. The fundamentals and applications of ISEC in the characterization of the pore structure are reviewed. The description of the probe solutes and the pore space, as well as theoretical models for deriving the PSD from solute partitioning behavior, are discussed. Precautions to ensure integrity of the experiments are also outlined, including accounting for probe polydispersity and minimization of solute-adsorbent interactions. The results that emerge are necessarily model-dependent, but ISEC nonetheless represents a powerful and non-destructive source of quantitative pore structure information that can help to elucidate chromatographic performance observations covering both retention and rate aspects.

Adsorption↗