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Biomedical subjects

Yun Gao

Publications and source records attributed to Yun Gao.

At least 19 recordsLinked to original sources
PubMed2006

Films coated with molecular imprinted polymers for the selective stir bar sorption extraction of monocrotophos.

The flexibility and simplicity of stir bar sorption extraction (SBSE) have been combined with the selectivity of molecularly imprinted polymers (MIP). Stir bars were coated reproducible with a 180 microm film formed from a formic acid solution of nylon-6 polymer either nonimprinted or imprinted with monocrotophos. Time sorption profiles were measured for the extraction of monocrotophos from dichloromethane at the concentration of 10-200 micromol/L levels with both types of films in order to compare extraction characteristics. The results indicated that the MIP coated layer showed remarkable high affinity toward monocrotophos and equilibrium adsorption was attained rapidly (60 min) in contrast to free standing molecularly imprinted polymer in which equilibrium adsorption was normally attained after several hours. The stir bars coated with MIP films were capable of extracting four structural analogues of monocrotophos from dichloromethane solution, which suggests that both the amino group and PO part of these molecules is responsible for interaction with the imprinted polymer. Evidence was also presented by FT-IR analysis that the amide-hydrogen-bonding interaction between the MIP-coated films and monocrotophos was originated for monocrotophos recognition. To achieve selective extraction of monocrotophos from sample, stir bars coated with MIP films were washed with 10% (v/v) acetic acid/methanol and methanol. Clean extracts and yields of 95% were obtained, demonstrating the suitability of stir bar coated with MIP films for the analysis of environmental and biological samples. Compared with traditional MIP and SBSE, the MIP-coated film showed not only the high selectivity but also the rapid equilibrium adsorption.

Caprolactam↗
PubMed2006

Design, synthesis, and biological evaluation of hydroquinone derivatives of 17-amino-17-demethoxygeldanamycin as potent, water-soluble inhibitors of Hsp90.

17-Allylamino-17-demethoxygeldanamycin (17-AAG)1 is a semisynthetic inhibitor of the 90 kDa heat shock protein (Hsp90) currently in clinical trials for the treatment of cancer. However, 17-AAG faces challenging formulation issues due to its poor solubility. Here we report the synthesis and evaluation of a highly soluble hydroquinone hydrochloride derivative of 17-AAG, 1a (IPI-504), and several of the physiological metabolites. These compounds show comparable binding affinity to human Hsp90 and its endoplasmic reticulum (ER) homologue, the 94 kDa glucose regulated protein (Grp94). Furthermore, the compounds inhibit the growth of the human cancer cell lines SKBR3 and SKOV3, which overexpress Hsp90 client protein Her2, and cause down-regulation of Her2 as well as induction of Hsp70 consistent with Hsp90 inhibition. There is a clear correlation between the measured binding affinity of the compounds and their cellular activities. Upon the basis of its potent activity against Hsp90 and a significant improvement in solubility, 1a is currently under evaluation in Phase I clinical trials for cancer.

Animals↗
PubMed2006

Fast spectroscopic imaging using online optimal sparse k-space acquisition and projections onto convex sets reconstruction.

Long acquisition times, low resolution, and voxel contamination are major difficulties in the application of magnetic resonance spectroscopic imaging (MRSI). To overcome these difficulties, an online-optimized acquisition of k-space, termed sequential forward array selection (SFAS), was developed to reduce acquisition time without sacrificing spatial resolution. A 2D proton MRSI region of interest (ROI) was defined from a scout image and used to create a region of support (ROS) image. The ROS was then used to optimize and obtain a subset of k-space (i.e., a subset of nonuniform phase encodings) and hence reduce the acquisition time for MRSI. Reconstruction and processing software was developed in-house to process and reconstruct MRSI using the projections onto convex sets method. Phantom and in vivo studies showed that good-quality MRS images are obtainable with an approximately 80% reduction of data acquisition time. The reduction of the acquisition time depends on the area ratio of ROS to FOV (i.e., the smaller the ratio, the greater the time reduction). It is also possible to obtain higher-resolution MRS images within a reasonable time using this approach. MRSI with a resolution of 64 x 64 is possible with the acquisition time of the same as 24 x 24 using the traditional full k-space method.

Algorithms↗
PubMed2006

Bayesian population decoding of motor cortical activity using a Kalman filter.

Effective neural motor prostheses require a method for decoding neural activity representing desired movement. In particular, the accurate reconstruction of a continuous motion signal is necessary for the control of devices such as computer cursors, robots, or a patient's own paralyzed limbs. For such applications, we developed a real-time system that uses Bayesian inference techniques to estimate hand motion from the firing rates of multiple neurons. In this study, we used recordings that were previously made in the arm area of primary motor cortex in awake behaving monkeys using a chronically implanted multielectrode microarray. Bayesian inference involves computing the posterior probability of the hand motion conditioned on a sequence of observed firing rates; this is formulated in terms of the product of a likelihood and a prior. The likelihood term models the probability of firing rates given a particular hand motion. We found that a linear gaussian model could be used to approximate this likelihood and could be readily learned from a small amount of training data. The prior term defines a probabilistic model of hand kinematics and was also taken to be a linear gaussian model. Decoding was performed using a Kalman filter, which gives an efficient recursive method for Bayesian inference when the likelihood and prior are linear and gaussian. In off-line experiments, the Kalman filter reconstructions of hand trajectory were more accurate than previously reported results. The resulting decoding algorithm provides a principled probabilistic model of motor-cortical coding, decodes hand motion in real time, provides an estimate of uncertainty, and is straightforward to implement. Additionally the formulation unifies and extends previous models of neural coding while providing insights into the motor-cortical code.

Action Potentials↗
PubMed2006

Generation of a constitutively active mutant of human GPR48/LGR4, a G-protein-coupled receptor.

GPR48, also known as leucine-rich repeat (LRR)-containing G-protein-coupled receptor 4 (LGR4), is a member of the G-protein-coupled receptor (GPCR) family of proteins. However, its biological functions remain unclear, since neither its ligand nor signal transduction pathway have been identified, and it is usually difficult to solve the function of such orphan receptors. The aim of this study was to generate a constitutively active form of human GPR48, that would form a ligand-independent active conformation and may function in a similar manner to activated GPR48 following ligand binding. We introduced four independent mutations into transmembrane domains V and VI of a human GPR48 cDNA. The wild-type and mutant GPR48s were expressed in HEK293 cells by transient transfection of appropriate expression plasmids. Since ligand-activated receptors for gonadotropins, which are structurally similar to GPR48, stimulate adenylate cyclase and increase cellular cyclic AMP, we investigated, whether the GPR48-transfected cells showed altered cyclic AMP levels. The cellular cyclic AMP level in HEK293 cells was increased following transfection of wild-type GPR48 in a dose-dependent manner. Moreover, transfection of a GPR48-T7551 mutant, in which threonine-755 was replaced with isoleucine, dramatically increased the cyclic AMP level. Stable transformants derived from HCT116 cells that constitutively expressed the GPR48-T7551 mutant also showed high cyclic AMP levels. These results indicate that the GPR48-T7551 mutant is a constitutively active mutant. This mutant may be useful for studying the biological functions of GPR48 and GPR48-mediated signal transduction, even if the specific ligand remains unknown in the future.

Amino Acid Sequence↗
PubMed2005

Effect of the combination of fibrin glue and growth hormone on incomplete intestinal anastomoses in a rat model of intra-abdominal sepsis.

BACKGROUND: The presence of established intra-abdominal sepsis has been considered a contraindication to primary anastomoses. Our hypothesis was that fibrin glue (FG), growth hormone (rhGH), and combination of them synergistically improve intestinal primary anastomotic healing in a rat model of intestinal fistulae with peritonitis. MATERIALS AND METHODS: Male Wistar rats, induced intestinal fistulae with peritonitis after 24 h, were performed an enterectomy and intestinal anastomoses. Group A, rats (n = 60) had a complete anastomoses (end-to-end single layer anastomoses using 12 inverted interrupted 6-0 sutures) without peritonitis, group B, rats (n = 60) had a complete anastomoses after 24 h of peritonitis, group C rats had an incomplete anastomoses (four inverted interrupted sutures), groups D, E, F rats (n = 60) received FG, rhGH, or both of them, respectively. rhGH was given daily for 5 days. Anastomoses indicated the anastomotic bursting pressure (ABP), tensile strength, and hydroxyproline content, were determined. RESULTS: On POD 1, ABP of group C and group D was significantly lower than that of other groups (P < 0.01); On POD 3, ABP could not be determined because of intestinal dehiscence in groups C and E, ABP was significantly higher in groups D and F than that of groups A and B (P < 0.01); the ABP increased after 5 days of operation in groups A, B, and F. At the same time, that of group D decreased (P < 0.01). On POD 5, the tensile strength was significantly higher in groups A, D, and F than that in groups C, and E. On POD 5, hydroxyproline content was higher in groups D and F compared to that in group C (P < 0.05). CONCLUSIONS: These data suggested that FG improve intestinal primary anastomotic healing within post-operative 5 days in a rat model of intestinal fistulae with peritonitis. RhGH alone fails to improve intestinal anastomotic healing, and the combination of FG and rhGH have no synergistic effect to improves intestinal anastomotic healing.

Anastomosis, Surgical↗
PubMed2005

Thoron levels in traditional Chinese residential dwellings.

A survey on radon (222Rn), thoron (220Rn) and its decay products (220RnD) was conducted in Chinese traditional residential dwellings constructed with loam bricks or soil wall. The activity concentrations in 164 dwellings under investigation were 72.4+/-59.2 (arithmetic mean, AM) and 57.5+/-2.0 Bq m-3 (geometric mean, GM) for 222Rn, and 318+/-368 and 162+/-3.7 Bq m-3 for 220Rn, respectively. For 220RnD, 67 dwellings were studied. The AM of the 220RnD equilibrium equivalent concentration was 3.8+/-3.3 Bq m-3 with a maximum value of 15.8 Bq m-3. On the basis of these results, the average annual effective doses to the local residents due to radon and thoron exposure were 1.44-4.62 mSv. Thoron contributes 12.9-56.6% to the total doses. Preliminary results show that there is a relation between 220RnD in air and 232Th in soil. The correlation factors of outdoor and indoor were 0.88 and 0.40. The 232Th activity content of Chinese soil is estimated to be about two times the world average. The traditional residential dwellings with soil construction are still common in China. Further investigations on the 220Rn level in these dwelling with the aim of dose reduction are proposed.

Air Pollution, Indoor↗
PubMed2005

Matrix solid phase dispersion-Soxhlet simultaneous extraction clean-up for determination of organochlorine pesticide residues in tobacco.

A novel method combining matrix solid phase dispersion (MSPD) with Soxhlet simultaneous extraction clean-up (SSEC) was developed. Being a single-step extraction and clean-up procedure, it could be used instead of multistep solvent extraction and Florisol column clean-up. It not only reduces sample contamination during the procedure, but it also decreases the amount of organic solvent needed. The retention times of standards were used to qualitatively assess the method, and the external standard method was used to quantitatively assess it. Residues of organochlorine pesticides (OCP) in tobaccos were determined by gas chromatography-electron capture detection (GC-ECD), and their identities were confirmed by the standard addition method (SAM). The performance of the method was evaluated and validated: the detection limit was 0.01-0.02 microg g(-1), relative standard deviations were 5-26%, and recoveries were 72-99% at fortification levels of 0.10, 1.00 and 10.0 microg g(-1). The analytical characteristics of MSPD-SSEC compared very favorably with the results from the classical multistep solvent extraction and Florisol column clean-up method.

Chemical Fractionation↗
PubMed2005

Selective solid-phase extraction using molecularly imprinted polymer for the analysis of polar organophosphorus pesticides in water and soil samples.

An analytical methodology for the analysis of four polar organophophorus pesticides (monocrotophos, mevinphos, phosphamidon, omethoate) in water and soil samples incorporating a molecularly imprinted solid-phase extraction (MISPE) process using a monocrotophos-imprinted polymer was developed. Binding study demonstrated that the polymer showed excellent affinity and high selectivity to monocrotophos. The MISPE procedure including the clean-up step to remove any interferences was optimized. The accuracy and selectivity of the MISPE process developed were verified using a non-imprinted (blank) polymer and a classical ENVI-18 cartridge as the SPE matrix during control experiments. The use of MISPE improved the accuracy and precision of the GC method and lowered the limit of detection. The recoveries of four polar organophosphorus pesticides (OPPs) extracted from 1 L of river water at a 100 ng/L spike level were in the range of 77.5-99.1%. The recoveries of organophosphorus pesticides extracted from a 5-g soil sample at the 100 microg/kg level were in the range of 79.3-93.5%. The limit of detection varied from 10 to 32 ng/L in water and from 12 to 34 microg/kg in soil samples. The molecularly imprinted polymer (MIP) enabled the selective extraction of four organophosphorus pesticides successfully from water and soil samples, demonstrating the potential of molecularly imprinted solid-phase extraction for rapid, selective, and cost-effective sample pretreatment.

Chromatography, Gas↗
PubMed2005

[Inhibition of acetamide-45 on airway smooth muscle contraction induced by electric field stimulation and methacholine in vitro].

OBJECTIVE: To investigate the effects of the new antiallergic agent N-(pyridin-4-yl)-(indol-3-yl) acetamide-45 (acetamide-45) on electric field stimulation (EFS)-and methacholine-induced contraction of airway smooth muscle in vitro. METHODS: Contractions were induced by EFS in isolated trachea and bronchus of rats or by cumulative methacholine concentrations in isolated trachea of guinea pigs. Changes in isometric force of isolated airway smooth muscle were measured by force transducers and recorded on a multi-channel polygraph recorder. RESULTS: Acetamide-45 inhibited the contraction induced by EFS in isolated rat airway. The IC50 was 10.74 (95% CI 8.87-13.00) micromol.L(-1) and 18.83 (95% CI 14.57-24.33) micromol.L(-1) in tracheae and bronchi, respectively. Acetamide-45 also inhibited methacholine-induced contractile response of isolated guinea pig trachea in a concentration-dependent manner. At concentrations of 3, 10, 30 micromol.L(-1) acetamide-45 significantly decreased maximal contractile response of methacholine by 24.6%-43.2% and increased EC50 of methacholine by 3.1-to 21.4-fold. CONCLUSION: Acetamide-45 inhibits EFS-or methacholine-induced contraction of isolated airway smooth muscle, and these effects might be non-specific inhibition on cholinergic receptor.

Acetamides↗
PubMed2005

[Construction of an adeno-associated virus vector expressing CTLA-4Ig and its expression in the transplanted liver allografts].

OBJECTIVES: To construct a recombinant adeno-associated virus vector pSNAV expressing CTLA-4Ig and to demonstrate its expression in transplanted liver allografts and to see if a long term inhibitive effect of CTLA-4Ig could be obtained though its use. METHODS: After AAVCTLA-4Ig and PUC18 were cut with BamHI, CTLA-4Ig cDNA was inserted into the plasmid PUC18 by T4DNA ligase and PUC18-CTLA-4Ig was constructed. The obtained PUC18-CTLA-4Ig and pSNAV cut with Kpn I and EcoR I, CTLA-4Ig cDNA was inserted into plasmid pSNAV to construct the recombinant vector pSNAV-CTLA-4Ig, which was transfected into BHK-21 packaging cells by lipofectine-mediated transfection. Then the BHK-21 cell line was infected with HSV1-rc to produce a large amount of pSNAV- CTLA-4Ig. The specificity of the expressed product was identified by digestion with BamHI, PCR and sequence determination. The titer of the virus was detected. The product was infused into rats liver allografts via portal vein and its expression in the transplanted livers was detected immunohistochemically. RESULTS: Recombinant adeno-associated virus vector pSNAV-CTLA-4Ig was generated and purified into 8.5 x 10(11)/ml. Agarose gel analysis of PCR products verified the presence of CTLA-4Ig. Digestion with BamHI and sequence determination confirmed that pSNAV-CTLA-4Ig was constructed. Expression of CTLA-4Ig in the transplanted livers was detected successfully. CONCLUSION: Prepared pSNAV-CTLA-4Ig was constructed correctly and can express CTLA-4Ig effectively. Besides this, it can express CTLA-4Ig in rat liver allografts. It may be used in the study of transplant tolerance.

Abatacept↗
PubMed2005

[Detection of DNA damages of peripheral white blood cells in benzene-exposed workers].

OBJECTIVE: To investigate the effect of benzene exposure on DNA damage of the peripheral white blood cells and to assess the possible dose-response relationship between benzene and DNA damage. METHODS: Personal benzene exposure was sampled with 3M organic vapor monitors. The time weighted average concentration (8h-TWA) and the cumulative dose were calculated. Single cell gel electrophoresis assay was used to detect DNA damage in white blood cells of benzene-exposed workers. The Olive tail moment and the grade of DNA breakage were used to measure DNA damage. RESULTS: The Olive tail moment and the grade of DNA breakage in benzene exposure groups were significantly increased in comparison with those in the control group (F = 30.03, P < 0.0001, chi2 = 239.9, P < 0.0001, respectively) and showed a dose-response relationship with benzene concentration. Correlation analysis showed that Olive tail moment was correlated with benzene exposure concentration. CONCLUSIONS: Benzene exposure resulted in an increase of DNA damage of the peripheral white blood cell, which was in a dose-response relationship manner; cumulative dose was better than simply concentration to reflect benzene exposure.

Adult↗
PubMed2004

Effect of tetramethylpyrazine on acute nociception mediated by signaling of P2X receptor activation in rat.

Tetramethylpyrazine (TMP) has been used in traditional Chinese medicine as an analgesic for dysmenorrhea. In the present study, we try to investigate the effects of TMP on acute nociception mediated by P2X receptor activation of rat hindpaw and the membrane depolarization of rat dorsal root ganglion (DRG) neurons induced by P2X receptor agonists. The subcutaneous administration of TMP (0.1-10 mmol) into rat hindpaw in a dose-dependent manner decreased acute paw flinching responses mediated by adenosine 5'-triphosphate (ATP, 1000 nmol) or alpha,beta-methylene ATP (alpha,beta-meATP, 600 nmol). The subcutaneous administration of TMP (5 or 10 mmol) into rat hindpaw inhibited significantly the first phase of nociceptive behaviors induced by 5% formalin and attenuated slightly the second phase of nociceptive behaviors induced by 5% formalin. The subcutaneous administration of TMP (10 mmol) into rat hindpaw reduced the nociceptive responses induced by alpha,beta-meATP (200 nmol) co-injected with Prostaglandin E2 (PGE2), 5 micromol). The membrane depolarization induced by ATP (200 micromol) or alpha,beta-meATP (50 micromol) in DRG neurons was inhibited by TMP (300 micromol). The data suggest that the antinociceptive effect of TMP is involved in blocking the signaling of P2X3 receptor activation in rat.

Adenosine Triphosphate↗
PubMed2004

Modeling and decoding motor cortical activity using a switching Kalman filter.

We present a switching Kalman filter model for the real-time inference of hand kinematics from a population of motor cortical neurons. Firing rates are modeled as a Gaussian mixture where the mean of each Gaussian component is a linear function of hand kinematics. A "hidden state" models the probability of each mixture component and evolves over time in a Markov chain. The model generalizes previous encoding and decoding methods, addresses the non-Gaussian nature of firing rates, and can cope with crudely sorted neural data common in on-line prosthetic applications.

Action Potentials↗
PubMed2004

[Analysis of volatile fragrant components in hawthorn tincture by gas chromatography-mass spectrometry].

The volatile fragrant components in hawthorn tincture were analyzed by GC/MS. 38 components were identified. The relative content of these constituents were determined with area mormalizing method and the identification ratio was 97.19%. The main components were 3-Hexen-1-ol(370.59 micrograms/g), Eugenol(320.95 micrograms/g), Butanedioic acid hydroxy, diethyl ester(191.25 micrograms/g), 2-Methyl-pentenoic acid(164.83 micrograms/g) and citric acid(80.87 micrograms/g) etc. The method is simple, rapid and highly sensitive and suitable for routine analysis and quality control.

Crataegus↗
PubMed2004

[Chromosome aberration analysis of peripheral lymphocytes in workers exposed to benzene].

OBJECTIVE: To study the effects of benzene exposure on chromosome aberration of peripheral lymphocytes in workers. METHODS: Measure the benzene concentration with 3M passive dosimetry badges and analyze chromosome aberrations of peripheral lymphocytes using non-banding method. RESULTS: The numerically aberrated cell rate of the workers exposed by benzene [13.00% (2.50%-21.00%)] was significantly higher than that of the controls [10.50% (3.50%-18.00%)] (P < 0.05), and the aberrated cell rate (excluded gaps) [14.50% (5.00%-23.50%)] was significantly higher than that of the controls [11.75(3.50-18.00)] (P < 0.05), too; the P values of the dose-effect relationships between hyperploidy cell rate, numerically aberrated cell rate and aberrated cell rate (excluded gaps) and 8 h-TWA were 0.0008, 0.3741 and 0.2816, respectively, and the P values of the dose-effect relationships between those and the cumulative exposure were 0.0009, 0.0376 and 0.0486, respectively; the premature centromere division cell rate of the benzene-exposed workers [1.75% (0-19.50%)] was not significantly higher than that of the controls [1.00% (0-15.00%)] (P > 0.05). CONCLUSION: Benzene exposure resulted in an increase of chromosome aberrations of the peripheral lymphocytes, which was in a dose-effect relationship manner; whether benzene exposure could induce premature centromere division deserves further studies.

Adult↗
PubMed2004

[Construction of recombinant expression vector and prokaryotic expression of human epididymal sperm protein P34H].

OBJECTIVE: To acquire purified recombinant human epididymal sperm protein P34H for basic and clinical studies. METHODS: On the basis of cloning of P34H coding region, P34H fragment was subcloned into the pQE-30 expression vector. The recombinant expression vector designated pQE-30/P34H was transformed into E. coli to induce the expression of the recombinant protein P34H on the reduction of IPTG. After sonication, the recombinant protein P34H was purified from the supernatant with Ni-NTA resin under native conditions. It was identified by SDS-PAGE analysis and DNA sequencing. RESULTS: Recombinant expression vector pQE-30/P34H was correctly constructed, identified with PCR and double-enzyme digestion. And the results of SDS-PAGE analysis and DNA sequencing showed that the protein was what we had hoped to acquire. CONCLUSION: Purified recombinant P34H can be acquired successfully with the above mentioned prokaryotic expression method.

Cloning, Molecular↗