Biomedical subjects

Jun Chen

Publications and source records attributed to Jun Chen.

At least 397 records · Page 22Linked to original sources

PubMed2002

[Studies on DNA damage and apoptosis in rat brain induced by fluoride].

OBJECTIVE: To explore the DNA damage effects and apoptosis in brain cells of rats induced by sodium fluoride. METHODS: SD rats were divided into two groups, i.e. control group and fluoride treated group, which were injected intraperitoneally with distilled water and sodium fluoride (20 mg.kg(-1).d(-1)) respectively. On the hand, 5 mmol/L NaF were used in in vitro study. Single Cell Gel Electrophosis (SCGE or Comet Assay) was utilized to measured DNA damage and apoptosis was detected by the TUNEL method and Flow Cytometry (FCM). RESULTS: The DNA damage in pallium neurons in rats of the fluoride group was much more serious compared with those of the control group, with the Ridit value being 0.351 and 0.639 respectively (P < 0.01) in vivo, and 0.384 4 and 0.650 1 respectively (P < 0.01) in vitro. TUNEL positive cells were found in pallium, hippocampus and cerebellar granule cells in rats of fluoride group, whereas those in the control group were rare. It was demonstrated by FCM results that the percentages of apoptotic cells both in pallium and hippocampus were significantly higher (P < 0.01) in rats of fluoride group (27.12 +/- 3.08, 34.97 +/- 5.46) than those in control group (4.63 +/- 0.98, 5.35 +/- 0.79), (P < 0.01). CONCLUSION: Sodium fluoride could induce DNA damage and apoptosis in rats brain.

Animals↗

PubMed2002

[Quality evaluation of seed of Scutellaria baicalensis from different habitats].

OBJECTIVE: To study the seed quality of Scutellaria baicalensis Georgi. METHOD: Collecting seeds from different habitats and studying the thousand-seeds weight, plumpness rate and germination percentage. RESULT: The seeds from Ningxia and Juxian (Shandong province) are better than those from other habitats. Its plumpness rate is above 95%, thousand-seeds weight is 2.2 g and germination percentage is above 90%. CONCLUSION: There are obvious differences in quality of seeds of Scutellaria baicalensis from different habitats.

Climate↗

PubMed2002

[Study on the antibacterial activity of ginkgolic acids].

In this article we studied the anti-bacterial activity of the extract from testa of Ginkgo biloba and ginkgolic acids. They can inhibit the growth of Staphylocococus aureus, Escherichia coli, Bacillus subtilis, B. cereus and MRSA. Ginkgolic acids combined with peniciline can enhance their inhibitory activity to MRSA.

Anti-Bacterial Agents↗

PubMed2002

[Study on hydrolysis conditions of Dioscorea nipponica with uniform design method].

OBJECTIVE: To optimize hydrolysis conditions of Dioscorea nipponica so as to provide parameters for extracting diosgenin in industry. METHODS: The optimum hydrolysis conditions were investigated using diosgenin as an index with uniform design and high performance liquid chromatography method. RESULTS: The optimum conditions were as follows: the hydrochloric acid concentration was 2.5 mol/L, solid-liquid rate was 1:5, the reaction temperature was 140 degrees C, the reaction time was 4.0 h, the mix round speed was 120 r/min. CONCLUSION: The content of diosgenin under the optimum hydrolysis conditions is raised, and the hydrochloric acid concentration should be strictly controlled because of its large influences on the results.

Dioscorea↗

PubMed2002

[A preliminary study of the postburn intestinal biological barrier injury in severely burned rats].

OBJECTIVE: To investigate the postburn change in the intestinal biological barrier in severely burned rats. METHODS: Wistar rats inflicted by 30% TBSA III degree scalding on the back were employed as the model. The samples were harvested at 24, 48, 72 and 96 postburn hours (PBHs), respectively with the employment of microorganism analysis, biochemical and radio-immune methods for the study. The membranous flora in cecum, the mucin and sIgA in intestinal content, the intestinal endotoxin and bacterial translocation rate and quantification analysis and the endotoxin content in cava vein were observed. RESULTS: The total intestinal membranous flora amount decreased, especially and obviously did the anaerobic bacteria such as bifidobacteria. But aerobic ones increased. In addition, The fungus and enterobacteria exhibited rapid overgrowth. This lead to evident imbalance between anaerobic and aerobic bacteria and to the destruction of intestinal biological barrier and the decrease of colonization resistance. As a result, the intestinal bacterial translocation rate increased markedly. The endotoxin content in the cava and intestinal containing increased, while the mucin and sIgA contents decreased. CONCLUSION: Intestinal biological barrier could be severely damaged after major burn, which might be one of the causes of postburn intestinal infection.

Animals↗

PubMed2002

The apoptotic effect of HA14-1, a Bcl-2-interacting small molecular compound, requires Bax translocation and is enhanced by PK11195.

HA14-1 is a small molecular compound that was identified based on the structure of Bcl-2. HA14-1 interacts with Bcl-2 and inhibits the antiapoptotic effect of Bcl-2. We investigated the mechanism of HA14-1-induced apoptosis and found that HA14-1 induces translocation of Bax from cytosols to the mitochondria. Cells deficient in Bax were much more resistant to HA14-1-induced apoptosis, suggesting that Bax is required for this process. A pan-caspase inhibitor failed to inhibit the apoptotic effect of HA14-1, indicating that this is through a caspase-independent pathway. To eliminate the effect of cytosolic Bax, we incubated cell-free mitochondria with HA14-1 to study its effect on cytochrome c release. HA14-1 was ineffective in causing cytochrome c release from the purified mitochondria. However, the combination of HA14-1 and PK11195, an antagonist of peripheral benzodiazepine receptor of the mitochondria, enhanced the cytochrome c release by HA14-1. The combination of PK11195 and HA14-1 could therefore serve as a potentially useful approach to enhance apoptosis in cancer.

Animals↗

PubMed2002

[Determination of moth-proof agent residues in textiles with headspace solid-phase microextraction and gas chromatography-mass spectrometry].

A procedure is described for the identification and determination of volatile moth-proof pesticide residues, dichlorobenzene and naphthalene, in textile products by headspace solid-phase microextraction (HS-SPME) coupled with GC/MS in selective ion monitoring mode (SIM). Several standard fabrics (ISO 105/F01-1982) are used as sample matrices to reduce the target compound-matrix interaction. Prior to SPME, 0.2 g textile sample is immersed in 3 mL boric acid-citric acid-sodium acid phosphate buffer (pH 2.2) solution with 300 g/L sodium chloride and 5% (volume fraction) methanol for supersonic treatment in water bath(50 +/- 1) degrees C. Then an SPME fiber holder is used manually by passing the needle through the septum of the sample vial, depressing the plunger and lowering a fused silica fiber coated with 100 microns polydimethylsiloxane (PDMS) into the headspace right above the sample solution. Adsorption equilibrium is almost established within 5 minutes with magnetic stirring at (40 +/- 1) degrees C. After sample adsorption, draw SPME fiber into the needle, and withdraw the needle from the sample vial and immediately introduce it into the chromatograph injector, where the adsorbed analytes are thermally desorbed for 3 minutes at 230 degrees C and delivered to a capillary GC column for analysis by mass detector. The method provides data of very good linearity with low coefficients of variation for volatile target compounds like p-dichlorobenzene and naphthalene. For all the fabrics tested, typical limits of detection (LOD) were 1 microgram/kg and average recoveries from fortified sample fabrics were between 83.6%-115.2% and the relative standard deviations of the residues were 8.1%-9.8%.

English Abstract↗

PubMed2002

[Method for determining chlorinated solvent residues in dry cleaning fabrics with gas chromatography-mass spectrometry].

An analytical technique was provided for using headspace solid phase microextraction (SPME) with gas chromatography-mass spectrometry (GC-MS) to estimates exposure and emissions of chlorinated hydrocarbon residues in dry cleaning fabrics or garments. Hazardous substances used by chlorinated dry cleaning operation include-perchloroethylene (PEC), trichloroethylene (TCE) and small amounts of trichloroethane, all known as volatile organic compounds (VOCs) listed in many professional testing criteria and limit values of pollutant control index. A standard fabric matrix was spiked with several chlorinated volatile organic compounds to achieve a theoretical concentration based on Oko-Tex Standard 100 levels. Samples were soaked in 5% (volume fraction) methanol saturated NaCl solution with supersonic treatment in a water-bath at (40 +/- 1) degree for 10 min, and then the solution extracted by headspace SPME with a 100 microns PDMS fiber was analyzed by GC-MS. The method gives the applicable range of 0.005 mg/kg-5.000 mg/kg for PCE and TCE, and 0.012 mg/kg-1.200 mg/kg for trichloroethane as the safe assessment of fabrics and garments in dry cleaning. The limits of detection for target compounds PCE, TCE and trichloroethane were 0.005 mg/kg with average recoveries between 90.6%-108.7%.

Clothing↗

PubMed2002

[Investigation on occurrence of lycium pests and their natural enemies].

OBJECTIVE: To Provide the scientific basis for controlling the lycium pests. METHOD: The kinds and number of pests and their natural enemies were investigated at regular intervals and on the fixed trees. RESULT: There are 13 kinds of lycium pests and 17 kinds of natural enemies, the occurrence of which are closely related. CONCLUSION: Natural enemies can control aphids and psyllidae effectively, but ten-spotted lema and Epithrix sp. must be controlled by pesticides.

Animals↗

PubMed2002

[Determination of ginkgolic acids by high performance liquid chromatography].

AIM: To establish a simple pre-treated method and high performance liquid chromatographic method for separation and determination of ginkgolic acids in Ginkgo biloba leaves. METHODS: The ginkgolic acids in the German standard sample were identified by LC/DAD/ESI/MS. The methods for pre-treatment and high performance liquid chromatography determination of ginkgolic acids were studied. Ginkgo biloba leaves were extracted with n-hexane in Soxhlet apparatus, then concentrated under vacuum. The ginkgolic acids can be determined directly by HPLC after one-pre-purified-step by silica gel column chromatography. The eluant was petroleum ether-diethyl ether-formic acid (89:11:1). The chromatographic column was Inertsil ODS-2; the mobile phase was methanol-3% acetic acid (92:8); the flow rate was 1.0 mL.min-1; the column temperature was 40 degrees C; the detection wavelength was at 310 nm. RESULTS: There were five kinds of ginkgolic acid (C13:0, C15:1, C17:2, C15:0 and C17:1) in ginkgo biloba leaves. The relative percentage content of ginkgolic acids C15:1 and C17:1 was about 85%. Ginkgolic acid C17:2 had not been reported in China. The HPLC indicates that there was nearly no impurities except ginkgolic acids after treated by column chromatography. The results showed that the content of ginkgolic acids in the leaves of Ginkgo biloba collected in April, May and June was 1.48%, 1.19% and 1.11% respectively. The average recovery of Ginkgo biloba leaves collected in June was 97.0%, RSD was 1.7% (n = 6). CONCLUSION: The method is accurate, simple and reliable, and can be used for determination of ginkgolic acids in Ginkgo biloba leaves.

Chromatography, High Pressure Liquid↗

PubMed2001

Pivotal role of capsaicin-sensitive primary afferents in development of both heat and mechanical hyperalgesia induced by intraplantar bee venom injection.

To investigate the roles of primary afferent fibers in development of the bee venom (BV)-induced persistent spontaneous nociception (PSN) and hyperalgesia (HA), the sciatic nerve or both the sciatic and saphenous nerves of rats were topically treated with capsaicin respectively under pentobarbital anesthesia to destroy the capsaicin-sensitive primary afferent (CSPA) fibers. Effect of the sciatic nerve capsaicin on the formalin-induced PSN was also evaluated. Destruction of the CSPA fibers of the sciatic nerve or both the sciatic and saphenous nerves only produced 34 or 69% inhibition of the mean total number of 1 h BV-induced paw flinches. However, the total number of 1 h formalin-induced paw flinches was inhibited by 90% (85% for phase 1 and 91% for phase 2). In naïve rats, destruction of the CSPA fibers of the sciatic nerve caused 237 and 60% increase in paw withdrawal thermal latency (PWTL) to radiant heat in the injection site (paw pad) and at the heel of the treated hind paw compared to the baseline values. However, it was without significant influence upon the PWTL in the non-treated side or the paw withdrawal mechanical threshold (PWMT) to von Frey filament stimuli in both hind paws. In the BV-treated rats, the CSPA fiber destruction of the sciatic nerve completely blocked development of the heat and mechanical HA in the BV injection site. However, the reduction in either PWTL (drop to baseline level) or PWMT (drop by 56% from the baseline level) at the heel of the BV-treated side was not affected by this treatment. However, destruction of the CSPA fibers of both the sciatic and saphenous nerves was able to block development of both heat and mechanical HA in the whole BV-treated hind paw and heat hyperalgesia in the non-injected hind paw. Taken together, we conclude that: (1) the CSPA (C- and A delta-) fibers play a pivotal role in mediation of either the heat or the mechanical hyperalgesia induced by s.c. BV; (2) the CSPA fibers may play a crucial role in mediation of the formalin-induced PSN, but play a partial role in the BV-induced nociceptive process; (3) in addition to the sciatic nerve, the saphenous nerve is also involved in mediation of the BV-induced PSN as well as heat and mechanical hyperalgesia, while it is not likely to be involved in the formalin-induced nociception.

Administration, Topical↗

PubMed1999

Study of angiogenesis induced by metastatic and non-metastatic liver cancer by corneal micropocket model in nude mice.

AIM:To study the angiogenesis induced by liver cancer with different metastatic potentials using corneal micropocket model in nude mice.METHODS: Corneal micropockets were created in nude mice. Tumor tissues and liver tissues were implanted into the corneal micropockets. Angiogenesis was observed usinga digital camera under slit-lamp biomicroscope,and compared among different grafts and incision alone. Vascular responses were recorded in regard to the range, number and length of new blood vessels toward the grafts or incisions.RESULTS:Vascular responses induced by tumor tissues were greater than those by incision alone and liver tissue grafts. LCI-D20 induced more intensive angiogenesis than LCI-D35.CONCLUSION:Highly metastatic liver cancer LCI D20 was more angiogenic than low metastatic cancer LCI D35 and liver tissue. Micropocket was a useful model to study dynamic process of angiogenesis in vivo.

Journal Article↗

PubMedDate not supplied

Bioequivalence evaluation of two rabeprazole enteric coated formulations in healthy Chinese volunteers.

A bioequivalence study of two rabeprazole enteric-coated formulations was carried out in 20 healthy Chinese volunteers according to a single dose, two-sequence, crossover randomized design. The two formulations were administered in two treatment days, separated by a washout period of 7 days. Blood samples were collected at specified time intervals over 10 hours post-dosing. Plasma samples were separated and assayed for rabeprazole using a selective and sensitive HPLC method with UV detection. The pharmacokinetic parameters AUC(0-T), AUCmax, Cmax, tmax, t(1/2) and MRT were determined from plasma concentration-time profile of both formulations. ANOVA and two one-sided t test procedures showed no significant difference in log-transformed Cmax, AUC(0-T) AUC(0-infinity) while the 90% confidence interval (CI) of the ratio of the geometric means of their values were also used to assess bioequivalence between the two formulations. The results of this study indicated that the two rabeprazole formulations can be considered to be bioequivalent.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMedDate not supplied

Nanomaterials for field electron emission: preparation, characterization and application.

We review the current development in synthesis and deposition techniques of quasi-one-dimensional nanomaterials and recent achievements in the study of the field electron emission properties of these materials. Major findings are given from our recent experimental study of the field electron emission characteristics of carbon nanotubes, copper sulfide and silicon carbide nanorods. The study reveals that the above nanomaterials are promising candidates as cold cathode electron emitters. Furthermore, we review the recent development of techniques for growing and depositing the above nanomaterials in device structures. Typical device structures and their performance are also shown.

Journal Article↗

PubMedDate not supplied

Resonant field emission through amorphous diamond thin films (a model study).

A model for field emission through an amorphous diamond thin film with defects is constructed. Theoretical study shows that the emission is enhanced by attractive defects which would make the resonant emission observable for films with thickness of about 10nm. The emitted current density in typical parameters is calculated as functions of thickness, field strength and defect density. The energy distribution of emitted electrons is attained.

Journal Article↗

PubMedDate not supplied

A cold cathode lighting element prototype.

In this study, we present a prototype of lighting element in which a carbon-containing field emission material is used as the cathode. The operating characteristics, i.e. current-voltage characteristics, current stability, luminance and lifetime of the lighting element are tested. By applying high-voltage phosphor, a maximum brightness of 10000cd/m(2) has been recorded and a lighting element under lifetime test has been operating in DC driving mode for over 2500h without decay in emission current and brightness. These results imply that the prototype lighting element is suitable for commercial application.

Journal Article↗

PubMedDate not supplied

The application of carbon nanotubes in high-efficiency low power consumption field-emission luminescent tube.

In this report, details are given of our recent experimental study of using carbon nanotubes (CNTs) as cathode of the luminescent tubes. The CNT film is synthesized by thermal chemical vapor deposition. Two kinds of luminescent tubes that have different gaps have been fabricated. The luminescent tube with 0.1mm gap has a low threshold voltage of about 780V and high emission current of 300 microA when the gate voltage is 970V. The DC power consumption of the luminescent tube with a 0.1mm gap is approximately 1.12W. The results show that the CNTs are very good emission sources and suitable for application in the luminescent tube.

Journal Article↗

PubMedDate not supplied

Detection of deterministic behavior within the tissue injury-induced persistent firing of nociceptive neurons in the dorsal horn of the rat spinal cord.

To unravel the temporal features of the peripheral tissue injury induced persistent nociceptive discharge, single wide dynamic range (WDR) unit activity was recorded extracellularly in lumbar dorsal horn of anesthetized rats and interspike interval (ISI) series were obtained. Subcutaneous (s.c.) bee venom (BV) injection induced persistent discharge of spinal WDR neurons and has been well established to be a good model in evaluation of tissue injury induced pain. By applying a more novel approach, i.e., the unstable periodic orbit (UPO) identification method, we detected a family of significant separate UPOs (period-1, 2 and 3 orbits) within the ISI series of BV-induced nociceptive discharge, but not spontaneous background activity of spinal WDR neuron. Furthermore, temporally dynamic changes of UPOs at lower period-1, 2 and 3 for 4 successive time segments within 1 h time course of WDR unit firing showed temporally dynamic changes, i.e., new orbits with longer ISIs emerged and those with shorter ISIs vanished with time change. By using this method we suggest that BV-induced nociceptive discharge of spinal WDR neuron be a kind of deterministic activity and various UPOs may play some role in temporal coding of sensory information.

Action Potentials↗