Biomedical subjects

Yong Chen

Publications and source records attributed to Yong Chen.

At least 181 records · Page 10Linked to original sources

PubMed2004

[Preliminary study on RT-PCR-ELISA method for virus titer testing of live attenuated hepatitis A vaccine].

OBJECTIVE: To evaluate the RT-PCR-ELISA method applied for testing live attenuated hepatitis A vaccine titer. METHODS: A solid phase hybridization-enzyme colorimetric detection method was used for detecting specific nucleic acid. Primer labeled with biotin was used to amplify viral gene fragment, then the product was quickly hybridized with the specific probe covalently coupled on DNA-binding microplate wells. Finally, peroxidase-labeled streptavidin was used in colorimetric detection. The results were judged by reading A value. Eleven batches of live attenuated hepatitis A vaccine titer were tested by this method. The results were compared with that of routine cell culture method (CCID50). RESULTS: The sensitivity was similar to routine cell culture method (P>0.05). This method was convenient, fast and specific. CONCLUSION: CCID50 method may be replaced by the RT-PCR-ELISA method in evaluating the titer of live attenuated hepatitis A vaccine.

Base Sequence↗

PubMed2004

[Study on quality analysis of essential oil from twig and leaf of Baeckea frutescens].

OBJECTIVE: To provide scientific methods for quality criterion by studying the chemical components of essential oil from Baeckea frutescens. METHOD: The chemical components of essential oil from B. frutescens were identified by GC-MS-DS, TLC and capillary GC. The relative contents of main components were determined by area normalization. RESULT: More than 50 peaks were separated, and 38 components were identified, which accounted for over 94% of the total GC peaks areas of the essential oil. The methods for quality evaluation of essential oil from B. frutescens by TLC and capillary GC were established. CONCLUSION: The chemical components of essential oil from B. frutescens collected from different habitats and collecting periods have common characteristics as well as differences. Some components, such as linalool, can be used as a standard and chromatography fingerprint to analyze the quality of essential oil from B. frutescens.

Acyclic Monoterpenes↗

PubMed2004

[A new method for small displacement test and measurement based on the light reflection theory].

A new idea for small displacement test and measurement system based on light reflection is presented in this paper. Some theoretical researches using the method and experiments in practice were carried out. The results proved that the theory is feasible and efficient. Compared with the traditional small displacement test and measurement system, such as mechanical displacement magnifier; resistance strain test and measurement method; piezoelectric material strain test and measurement system and so on, this method has the following advantages: it creates little disturbance of the test and measurement system; the displacement magnification coefficient is high and is convenient for user to adjust; the test and measurement precision is high and is very easy for its realization; and the cost is low. It fits a lot of test and measurement situations.

Biomechanical Phenomena↗

PubMed2004

[Cloning, expression of human keratinocyte growth factor and its purification and identification].

To clone KGF-2 gene, get hKGF-2 protein and detemine its activity. The cNDA of human KGF-2 was isolated from fetal lung by RT-PCR and cloned into pBV220 plasmid. The recombinant pBV220-hKGF-2 plasmid was transformed into E. coli (BL21), induced at 42 degrees C for the expression of hKGF-2. Recombinant human KGF-2 was purified from the ultrasonic-treated BL21 by heparin-Sepharose CL-6B treated column chromatography and cation exchange column chromatography. MTT method was used for the determination of its biological activity. SDS-PAGE showed that rhKGF-2 was expressed in E. coli BL21 as soluble protein of approximately 20kD. The rhKGF-2 protein can stimulate the proliferation of NIH3T3 cells significantly from 1 ng/mL to 10 ng/mL. HKGF-2 cDNA wasclned and highly expressed in E. coli BL21 and the purified rhKGF-2 showed the mitogenic activity on NIH3T3 cells.

Cloning, Molecular↗

PubMed2004

[Laparoscopic suture uterosacral ligament hysteropexy for uterine prolapse].

OBJECTIVE: To investigate possibility and effect of laparoscopic suture uterosacral ligament hysteropexy or colpopexy for women with uterine prolapse. METHODS: Thirty-two women with symptomatic uterine prolapse underwent laparoscopic suture uterosacral ligament hysteropexy. At the laparoscopic suture hysteropexy or colpopexy, the pouch of Douglas was closed and the uterosacral ligaments were plicated and reattached to the cervix. All patients were multipara and menopausal with prolapse of anterior wall of vagina. Additionally, 4 patients were with prolapse of posterior wall of vagina, 15 with stress urinary incontinence, and 4 with myomas. RESULTS: All procedures were successfully completed laparoscopically. The mean operating time for the laparoscopic suture hysteropexy or colpopexy alone was (32 +/- 11) min (range 20 approximately 80 min), and the mean blood loss was less than 50 ml. After a mean follow-up of (12 +/- 6) months (range 4 approximately 28 months), 23 women had no symptoms of uterine prolapse and seven had no objective evidence of uterine prolapse. Two women presented recurrence of uterine prolapse 3 months after operation. CONCLUSIONS: The laparoscopy suture hysteropexy or colpopexy is effective and safe in the management of symptomatic uterine prolapse. It may be an appropriate procedure for women with uterine prolapse hoping for uterine preservation.

Aged↗

PubMed2003

Microwave-assisted headspace solid-phase microextraction for the analysis of bioemissions from Eucalyptus citriodora leaves.

Microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) was developed as a simple and effective method for fast sampling of volatile organic compounds (VOCs) from Eucalyptus citriodora Hook (E. citriodora) leaves. During microwave heating, a simple shielding device made of aluminum foil was used to protect the SPME fiber from microwave irradiation while allowing the sample to be heated. A room temperature water bath was also used to allow microwave heating to be conducted in a more controlled manner. The inner heating caused by microwave irradiation dramatically accelerated the emission of VOCs from the sample, but no marked change in headspace temperature in the sample vial was found. Under optimum conditions, the extraction efficiencies obtained with microwave heating were much higher than those obtained without microwave heating for all fibers used, namely, 7-microm polydimethylsiloxane (PDMS), 100-microm polydimethylsiloxane (PDMS), 65-microm polydimethylsiloxane/divinylbenzene (PDMS/DVB), and 75-microm carboxen/polydimethylsiloxane (CAR/PDMS). The improvement of extraction efficiency using MA-HS-SPME allowed more VOC events to be detected, with more balanced extraction of VOCs of lower and higher molecular masses. Moreover, a good linear relationship was found between sample size and GC-FID response (total peak area of VOCs), indicating the usefulness of MA-HS-SPME for quantitative analysis of individual volatile compounds in E. citriodora leaves.

Chromatography, Gas↗

PubMed2003

Studies of electron-transfer and charge-transfer coupling processes at a liquid/liquid interface by double-barrel micropipet technique.

Investigation of a heterogeneous electron-transfer (ET) reaction at the water/1,2-dichloroethane interface employing a double-barrel micropipet technique is reported. The chosen system was the reaction between Fe(CN)63- in the aqueous phase (W) and ferrocene in 1,2-dichloroethane (DCE). According to the generation and the collection currents as well as collection efficiency, the ET-ion-transfer (IT) coupling process at such an interface and competing reactions with the organic supporting electrolyte in the organic phase can be studied. In addition, this technique has been found to be an efficient method to distinguish and measure the charge-transfer coupling reaction between two ions (IT-IT) processes occurring simultaneously at a liquid/liquid interface. On this basis, the formal Gibbs energies of transfer of some ions across the W/DCE interface, such as NO3-, NO2-, Cl-, COO-, TBA+, TPAs+, Cs+, Rb+, K+, Na+, and Li+, for which their direct transfers are usually difficult to obtain because of the IT-IT coupling processes, were quantitatively evaluated.

Journal Article↗

PubMed2003

Calibration for on-site analysis of hydrocarbons in aqueous and gaseous samples using solid-phase microextraction.

Rapid sampling and sample preparation methodology was investigated using adsorptive poly(dimethylsiloxane)/divinylbenzene and Carboxen/poly(dimethylsiloxane) solid-phase microextraction (SPME) fiber coatings and volatile aromatic hydrocarbons (BTEX: benzene, toluene, ethylbenzene, and o-xylene). A flow-through system was used to generate a standard aqueous solution of BTEX as model sample with known linear velocity. Parameters that affect the extraction process, including sampling time, concentration, water velocity, and temperature, were investigated. Very short sampling times from 10 s and sorbents with strong affinity and large capacity were used to ensure the effect of '"zero sink" and to calibrate the extraction process in the initial linear extraction region. Several different concentrations were investigated, and it was found that mass uptake changes with concentration linearly. The increase of water velocity increases mass uptake, though the increase is not linear. Temperature does not affect mass uptake significantly under typical field sampling conditions. To further accurately describe rapid SPME analysis of aqueous samples, a new model translated from heat transfer to a circular cylinder in cross-flow was used. An empirical correlation to this model was used to predict the mass-transfer coefficient. Findings indicate that predicted mass uptake compares well with experimental mass uptake. The new model was tested for rapid air sampling, and it was found that this new model also predicted rapid air sampling accurately. Findings presented in this study extend the existing fundamental knowledge related to rapid sampling/sample preparation with SPME.

Journal Article↗

PubMed2003

Resiniferatoxin reversibly blocks adjuvant-induced thermal hyperalgesia in the rat.

The role of capsaicin-sensitive sensory afferents and mast cells in complete Freund's adjuvant (CFA)-induced thermal hyperalgesia and edema was investigated in rats. A single systemic injection of resiniferatoxin produced a reversible prevention of adjuvant-induced thermal hyperalgesia which lasted several days. In addition, resiniferatoxin markedly reduced the early edema. Chronic degranulation of mast cells with compound 48/80 also reduced the thermal hyperalgesia and edema, especially in the early phase of inflammation. Co-pretreatment with resiniferatoxin and compound 48/80 induced effects similar to those of resiniferatoxin alone. The data support the involvement of capsaicin-sensitive fibers in the adjuvant-induced inflammation.

Animals↗

PubMed2003

Mucosal tolerance to E-selectin provides cell-mediated protection against ischemic brain injury.

We have demonstrated that induction of mucosal tolerance to E-selectin, a cytokine-inducible adhesion molecule restricted to activating blood vessels, prevents ischemic and hemorrhagic stroke in spontaneously hypertensive, genetically stroke-prone (SHR-SP) rats. We now examine whether mucosal tolerance to E-selectin has protective effects in ischemic brain damage after permanent middle cerebral artery occlusion (MCAO) in SHR-SP rats and whether these effects are related to generation of regulatory T cells. Rats were exposed to intranasal administration of E-selectin every other day for 10 days (single tolerization group) or on two tolerization schedules separated by 11 days (booster tolerization group). Control groups received PBS on corresponding schedules. MCAO was performed 48 h after the last dose of E-selectin or PBS. There were 45.8% and 37.9% (P < 0.05) decreases of infarction volume in the E-selectin booster group compared with the PBS group at 6 and 48 h, respectively. Single tolerization with E-selectin had only a slight trend toward a decrease in infarction volume (6.3%). CD8-positive cells were decreased in brains of E-selectin booster animals (46.6%, P < 0.01) compared with controls; splenocyte-culture supernatant levels of IL-10 were increased (59.3%, P < 0.05) in E-selectin booster animals. A decrease of infarction volume (34%, P < 0.05) was also observed in SHR-SP rats subjected to MCAO after adoptive transfer of splenocytes from E-selectin-tolerized compared with PBS-tolerized donors. The results indicate that, in addition to preventing stroke, mucosal tolerance to E-selectin is cytoprotective. Thus, immunomodulation targeted to activated blood vessel segments can both reduce stroke occurrence and attenuate brain damage if a stroke supervenes.

Animals↗

PubMed2003

Two-dimensional crystallization of a small heat shock protein HSP16.3 on lipid layer.

As a member of small heat shock proteins, HSP16.3 was identified as the major membrane-bound protein of Mycobacterium tuberculosis during stationary phase. Previous studies revealed that HSP16.3 was in a nonameric form in solution. Here, two-dimensional crystal of HSP16.3 molecules on lipid monolayer was obtained for the first time. The crystal exhibited p422 symmetry with lattice parameters a=b=90A, gamma=90 degrees. The projection map of untilted crystals showed that the basic unit of the crystal was a rod-like structure with two high-density regions. The three-dimensional map at 2.2 nm resolution revealed a rod-like structure with a dimension of 56A x 32A x 25A, similar to the dimeric forms of M. jannaschii HSP16.5 and wheat HSP16.9. Cross-linking experiments confirmed that HSP16.3 nonamers dissociated into dimers upon interaction with the positively charged lipid layer. Surface plasmon resonance measurements revealed that both electrostatic and hydrophobic forces involved in the formation of the 2D crystal on the lipid monolayer. These results provide a basis for further investigation on the unique dimeric structure of HSP16.3 and its functions in vivo.

Amines↗

PubMed2003

Theoretical studies of the conformational behavior of chain molecules containing polar groups: simulations of a poly(vinylidene fluoride) model.

Atomistic Monte Carlo simulations have been conducted to elucidate the conformational behavior of a single chain molecule containing polar functional groups. Here, we resort to an atomistic poly(vinylidene fluoride) (PVDF) chain model as a representative example. The model is modified in such a way that bond lengths and bond angles are fixed, aiming to manifest the role of dipolar interactions. For a given chain length, chain conformation is sensitive to two environmental parameters, temperature and dielectric constant. The mean chain size increases when temperature and/or dielectric constant are increased. The conformational behavior is further characterized by chain size distribution function, and our findings show that temperature induced conformational transition for a chain molecule can be discrete or continuous, depending on its chain length. Also, the dipolar interactions in PVDF are effectively attractive, and enhance chain contraction. As a result, when the strength of dipolar interactions is increased, the discrete conformational transition shifts toward longer chains; and for a given chain length, such a transition occurs at higher temperatures.

Algorithms↗

PubMed2003

[Adenovirus mediate FGF receptor gene transfer inhibits accelerated graft arteriosclerosis in rat aortic transplants].

OBJECTIVE: To evaluate the efficacy of adenovirus mediated fibroblast growth factor (FGF) receptor gene transfer in inhibition of accelerated graft arteriosclerosis (AGA) in rat aorta transplantation model. METHODS: The PCR product of rat sFGFR-1 cDNA was cloned into pCMV1-flag vector, then flag-sFGFR was cloned into pAdvs6a to construct recombinant vector pAv3flag-sFGFR1. The abdominal aorta was injected with buffer containing 5 x 10(9) pfu Adv3-sFGFR-1 and then resected in 30 DA rats. A section of abdominal aorta was resected in 30 PVG rats and the abdominal aorta of DA rats was transplanted. Av3-Nall and normal saline of the same volume were injected into the abdominal aortae of and rats as experimental controls and blank controls. Six rats were killed 5, 30, 60, and 90 days after the operation respectively. The transplanted aorta was harvested. RT-PCR was performed to detect the expression of sFGFR-1 gene with pCMV-Flag-sFGFR1 cDNA as positive control and the abdominal aorta RNA of non-transfected rats as negative control. Immunohistochemistry and HE staning were used to detect the localization and expression of sFGFR-1, and the morphology and cytology of the transplanted vessels. RESULTS: A construct encoding the FGFR1 ectodomain produced secreted sFGFR1 protein, which bound [(125)I]FGF-2 with high affinity and specificity, and inhibited FGF-2 stimulated 3T3 fibroblast proliferation in vitro. Gene transfer of sFGFR1 into rat aortic grafts, using an adenoviral vector, resulted in expression of sFGFR1 protein in endothelium and adventitia. Neointimal formation 60 and 90 days after transplantation was inhibited (P = 0.013) in aortic allograft transduced with sFGFR1, compared to allograft transduced with Null virus and saline. CONCLUSION: FGFs play a causal role in the development of AGA in the rat aortic transplant model and postulate that targeted interruption of FGF function could similarly reduce neointimal formation in transplant setting.

Adenoviridae↗

PubMed2003

Studies of effect of phase volume ratio on transfer of ionizable species across the water/ 1,2-dichloroethane interface by a three-electrode setup.

The electrochemical behavior of pyridine distribution at the water/1,2-dichloroethane interface with variable phase volume ratios (r = Vo/Vw) was investigated by cyclic voltammetry. The system was composed of an aqueous droplet supported on a Ag/AgCl disk electrode covered with an organic solution or an organic droplet supported on a Ag/AgTPBCl disk electrode covered with an aqueous solution. In this way, a conventional three-electrode potentiostat can be used to study an ionizable compound transfer process at a liquid/liquid interface with a wide range of phase volume ratios (from 0.0004 to 1 and from 1 to 2500). Using this special cell we designed, only very small volumes of both phase were needed for r equal to unity, which is very useful for the investigation of the distribution of ionizable species at a biphasic system when the available amount of species is limited. The ionic partition diagrams were obtained for different phase volume ratios.

Journal Article↗

PubMed2003

Observation of the marcus inverted region of electron transfer reactions at a liquid/liquid interface.

Scanning electrochemical microscopy was used to probe the influence of a driving force on the heterogeneous electron transfer (ET) processes at the externally polarized water/1,2-dichloroethane interface. Being a part of the driving force, the Galvani potential difference at the interface, Deltaowphi, can be quantitatively controlled in a wide range, allowing the precise measurements of the rate constants of the ET reactions. Two opposite systems were chosen in this work. One was 5,10,15,20-tetraphenyl 21H,23H-porphyrin zinc (ZnPor, O)/Fe(CN)64- (W), and the other was TCNQ (O)/Fe(CN)63- (W). For both systems studied, the relations between the rate constant and the Deltaowphi were of parabolic shape; that is, the rate constants increased initially with the Deltaowphi until reaching a maximum and then decreased steadily as the Deltaowphi increased further. This is in accordance with the prediction of the Marcus theory. To our knowledge, this is the first report that the Marcus inverted region can be observed electrochemically at an unmodified liquid/liquid interface with only one redox couple at each phase. The effect of the concentrations of the organic supporting electrolyte has also been discussed in detail.

Journal Article↗

PubMed2003

[Fasting plasma insulin and insulin sensitivity in the offspring of parents with a family hypertensive history].

OBJECTIVE: To investigate the plasma insulin levels and insulin sensitivity in the offspring of parents with family hypertensive history in Tibetan population. METHODS: Tibetan hypertensive pedigrees and normotensive pedigrees based on a door-to-door cross section study performed from 1997 to 1998 in stable communities in the ruban district of Lhasa city were set up, 47 offsprings from hypertensive pedigrees (group I) and 21 offsprings from normotensive pedigrees (group II) were enrolled into this study. Plasma insulin levels using by radioimmunoassay and insulin sensitivity with the formulae insulin sensitivity = 1/(fasting plasma glucose x fasting plasma insulin) were compared between two groups. RESULTS: There were no statistically significant differences in fasting blood glucose levels between group I and group II. But fasting plasma insulin level was 10.20 +/- 6.95 m IU/L in group I and 6.56 +/- 2.81 m IU/L in group II, respectively, and there were statistically significant differences between these two groups. The insulin sensitivity index in group I was significantly lower than that in group II (0.036 +/- 0.024 and 0.046 +/- 0.022, respectively). CONCLUSION: Offspring of Tibetan hypertensive pedigrees were observed to be hyperinsulinemia and reduced insulin sensitivity. These metabolic abnormalities may be associated with hypertension and dyslipidemia in adulthood.

Blood Glucose↗

PubMed2003

Microwave resonance of the 2D Wigner crystal around integer Landau fillings.

We have observed a resonance in the real part of the finite frequency diagonal conductivity using microwave absorption measurements in high quality 2D electron systems near integer fillings. The resonance exists in some neighborhood of filling factor around corresponding integers and is qualitatively similar to previously observed resonance of weakly pinned Wigner crystal in high B and very small filling factor regime. Data measured around both nu=1 and nu=2 are presented. We interpret the resonance as the signature of the Wigner crystal state around integer Landau levels.

Journal Article↗

PubMed2003

On-site calibration method based on stepwise solid-phase microextraction.

A stepwise solid-phase microextraction (SPME) method was developed for on-site calibration of SPME for volatile organic compounds analysis. In this approach, a 75-microm Carboxen-polydimethylsiloxane coated fibre was loaded with a prior to exposure to samples of interest Extraction time for the target analytes can be controlled independently from that of the standard, and the response factors for the target analytes can be adjusted accordingly. A good reproducibility of the response factors for BTEXs (benzene, toluene, ethylbenzene and xylenes) was obtained with stepwise SPME. Satisfactory results were obtained by using this method for quantitative analysis of BTEXs in the air of a gas station when tetrachloroethylene was used as a standard. The introduction of standard via the stepwise SPME procedure makes SPME more useful in field applications. It can be used to detect leaks, contaminations and losses from loading of a standard onto a fibre to introduction of the fibre to an analytical instrument. However, this method cannot be used for compensation of sample matrix effects.

Benzene↗