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Biomedical subjects

X Chen

Publications and source records attributed to X Chen.

At least 1,009 records · Page 56Linked to original sources
PubMed1998

[A study on lens epithelial cell ultrastructure in rhesus monkey cataract].

OBJECTIVE: To investigate the ultrastructure of lens epithelial cells of normal eyes and cataractous eyes in rhesus monkeys. METHODS: Anterior capsules were taken from 4 normal lenses and 4 cataractous lenses of rhesus monkey eyes, and the samples were observed under transmission electron microscope. RESULTS: The ultrastructure of the cataractous lens epithelial cells changed obviously. Mitochondria with disappearance of crista were swollen, and vacuolar. Hollow cell with a single large vacuole in the cytoplasm could be seen. The cytoplasm presented dissolution. Cells were swollen and damaged, even cell membrane disruption could be seen. Karyopyknosis, nuclear deformity, disappearance of perinuclear cistern and nuclear pores could be found. The heterochromatin was concentrated and aggregated at the nuclear periphery. CONCLUSIONS: The ultrastructural changes of the lens epithelial cells in monkey cataractous lens are similar to that in human cataractous lens. Rhesus monkey cataract may be a suitable experimental model to investigate the formation of human cataract.

Animals↗
PubMed1998

[Quantitative real time measurement of iris configuration in living human eyes].

OBJECTIVE: To evaluate the intraobserver and interobserver reproducibility of real time measurement of iris morphology in living human eyes. METHODS: Based on the platform of software (Autocad, version 12), we developed an ultrasound biomicroscopy (UBM) image assistant measuring system. Using the system, we can perform the iris configuration quantitative measurement in living eyes. The measuring parameters include: iris rest length, radius of iris curvature and the thickness of different part of iris. Ten anterior segment images of one normal individual were obtained by a single operator to evaluate the intraobserver reproducibility of image capture, and ten times of measurement of one image were performed by a single operator to assess the reproducibility of image measurement. The measurements of three independent observers were compared to investigate interobserver reproducibility in quantitative measurement. Intraobserver and interobserver reproducibility of measurement were assessed by calculating the coefficient of variation for each individual observer and by using F test to detect a difference among the observers. The iris configurations of 96 subjects (192 eyes) were measured. RESULTS: Intraobserver reproducibility ranged from 0.9 - 4.9% in all measured parameters. Interobserver reproducibility for some of the measured parameters varied considerably and was affect by subjective interpretation of visualized anatomic landmarks. The preliminary measured parameters in Chinese show that iris rest length is 3.699 +/- 0.397 mm, radius of iris curvature is 9.101 plus minus 1.408 mm, the average thickness of iris is 0.406 +/- 0.042 mm. CONCLUSIONS: The intraobserver reproducibility and the measured accuracy can fit the requisition of the ocular biometry, physiology and pharmacology studies. The method supplies a new assistance for UBM image measurement.

Female↗
PubMed1998

[Endoscopic nasal surgery in treatment of nasopharyngeal angiofibroma].

OBJECTIVE: To avoid complications of the routine surgeries for nasopharyngeal angiofibroma. METHODS: Endoscopic nasal surgery and other new techniques including controlled-hypotension anesthesia and preoperative feeding artery embolism had been used. From April 1996 to September 1997 eight young male patients with diagnosis of nasopharyngeal angiofibroma were treated by endoscopic sinus surgery. The average age was 16.6 years old. Six accepted preoperative embolism, seven accepted hypotension anesthesia. RESULTS: No complications had occurred. Average intraoperative blood loss was 900 ml. All cases were followed for 1 to 20 months(mean 8 months). Recurrence was found in only one patient three months after operation. The recurrent rate was 12.5%. CONCLUSION: The lesions limited to nasal and nasopharyngeal cavities and with sphnoid and ethmoid invasions can be removed by endoscopic nasal surgery. Endoscopic surgery has advantages in reducing complications and obtaining better post operative functions. Transnasal endoscopic examination is also necessary in the follow-up period. Other techniques such as CT, digital subtract angiography, preoperative feeding artery embolism and controlled-hypotension technique during anesthesia are beneficial.

Adolescent↗
PubMed1998

[Synthesis of baicalin derivatives and evaluation of their anti-human immunodeficiency virus (HIV-1) activity].

The aglycone baicalien(1) and the key intermediate 5,6-O-dibenzyl-baicalien(3) were prepared from baicalin in order to evaluate the influence of different glycosyloxies linked to baicalien on anti-HIV activity. Four new flavone-glycosides namely 5-hydroxyl-6-O-benzyl-flavone-7-beta-D-glucoside(12), 5-hydroxyl-6-O-benzyl-flavone-7-beta-D-galactoside(13), 5-hydroxyl-6-O-benzyl-flavone-7-alpha-D-mannoside(14) and 5-hydroxyl-6-O-benzyl-flavone-7-alpha-D-arabinoside (15) were synthesized by condensation of the corresponding protected glycosyl bromides with (3). Biological activity test showed that (a) both baicalin and baicalien inhibited HIV-1 RT; (b) the 6-hydroxyl substitution of baicalin and baicalien is necessary for their inhibitory activity on HIV-1 RT; (c) the HIV-1 inhibitory activity and cytotoxicity of baicalien were higher than those of baicalin, the two compounds were found to have almost identical therapeutic index.

Antiviral Agents↗
PubMed1998

[Studies on synthesis and anti-HIV RT activity of hypericin and ethylhypericin].

Condensed polycyclic anthraquinone hypericin and its analogues showed activity against several retroviruses, including human immunodeficiency virus (HIV). Another condensed polycyclic anthraquinone ethylhypericin was synthesized from butanone in order to compare its biological activity with hypericin. Biological activity showed that ethylhypericin was slightly more effective than hypericin in HIV-RT inhibitory test.

Anthracenes↗
PubMed1998

[A new method for study of the effect of drugs on cancer cells--31PNMR with perfused cell system].

31P NMR was performed for the studies on the metabolic changes of endogenous phosphorus-containing molecules in KB and HCT-8 cells exposed to taxol at a concentration of 10(-6) mol.L-1. Using the perfusion method, the cells can be detected for a longer time by NMR, so as to give continuous spectra of the two cell-lines during the perfusion with and without the drug. The spectra showed that the levels of ATP peaks for both cells enhanced during the perfusion with the drug, but the change of the level is more prominent in KB cells than in HCT-8 cells. This shows that KB cells are more sensitive to taxol than HCT-8 cells. This is in coincident with the result in the cytotoxicity studies. However, the experiment using vincristine at the same concentrations demonstrated that the level of the ATP peak was not changed significantly.

Adenosine Triphosphate↗
PubMed1998

[Determination of captopril plus its disulfide metabolites in human plasma].

A new and sensitive HPLC method has been developed for the determination of captopril plus its disulfide metabolites (total captopril) in human plasma. Captopril disulfides and the drug covalently bound to protein were reduced with sodium borohydride to captopril. After liquid-liquid extraction, captopril was treated with o-phthalaldehyde in the presence of D-phenylalanine. The fluorescent derivative of captopril was measured by HPLC using a C-18 reversed phase column with fluorescence detection at the excitation and emission wavelengths of 235 nm and 440 nm, respectively. The mobile phase consisted of a methanol-acetonitrile-phosphate buffer (0.02 mol.L-1, pH 6.4) mixture (30:30:135, v/v), and was set at a flow rate of 1 ml.min-1. The linear range of the assay was between 5 ng.ml-1 (lower limit of quantitation) and 300 ng.ml-1 for total captopril in plasma. The method was successfully applied to determine plasma concentrations of captopril plus its disulfide metabolites in hypertensive patients and was demonstrated to be suitable for the therapeutic drug monitoring.

Antihypertensive Agents↗
PubMed1998

[Effect of d-limonene, Salvia miltiorrhiza and turmeric derivatives on membrane association of Ras gene product and gap junction intercellular communication].

Gap junction intercellular communication (GJIC), H-ras oncogene expression and Ras oncogene product(P21ras protein) expression were studied in four human solid tumor cell lines, W1-38, CACO2, A549 and PaCa (with the different Ras gene mutation rate), and the effects of four compounds, Salvia miltiorrhiza derivative (SMD), d-limonene, turmeric derivative I(TD-I) and turmeric derivative II(TD-II), on them. The abilities of the four solid tumor cell lines to transfer dye to adjacent cells were examined using the scrape-loading/dye transfer technique, and the H-ras oncogene expression by Northern blotting and P21ras protein expression by Western blotting. The results showed the loss of intercellular coupling in PaCa cells, slight GJIC in A549 and CACO2 cells, and good GJIC in W1-38 cells. The four compounds used was shown to improve the GJIC of PaCa to different extents. The amount of total and membrane associated P21ras in PaCa cells were decreased after treatment with SMD, d-limonene and TD-I(2.5 micrograms.ml-1) for 48 h. Concomitantly, the growth of PaCa cells decreased in soft agar and GJIC was enhanced. The relative potency was found to be: d-limonene > SMD > TD-I = TD-II. No significant effect of the four compounds on H-ras oncogene expression was observed. These results suggest that 1. there was an excellent correlation between loss of Lucifer Yellow dye transfer and ras gene mutation rate in the four solid tumor cell lines used (ras gene mutation rate inversely correlated with average cell number couplied, r = 0.98) i.e., showing that high ras gene mutation is closely correlated with loss of GJIC in these malignant human tumor cells; 2. the antitumor effect of the monoterpene d-limonene and the phenol compound, SMD, might be related to the inhibition of P21ras membrane association and enhancement of GJIC, whilst that of the others may be by a different mechanism; 3. the inhibition of P21ras membrane association is directly related to the enhancement of gap junction intercellular communication.

Antineoplastic Agents, Phytogenic↗
PubMed1998

[Characterization of some glucuronide conjugates by electrospray ion trap mass spectrometry].

To investigate the characteristics of mass spectra of some drug metabolites, solutions of glucuronide conjugates of N-(4-ethoxyphenyl)-2-hydroxyl-benzamide (etofesalamide), 4-(3H-1, 2-dihydro-1-pyrrolizinone-2-methylamino)-benzoic acid, 5-hydroxypropafenone and propafenone were analyzed using electrospray ion trap mass spectrometry in a multi-stage full scan mode performed on a Finnigan LCQ instrument. Sample solutions were directly introduced into the ESI source at a flow rate of 15-30 microliters.min-1 by a syringe pump. The mass spectrometer was operated in the negative ion mode. A full scan mass spectra of each analyte provided quasimolecular ion m/z M-1, and full scan MS2 and MS3 spectra gave characteristic fragment ions m/z 175 and m/z 113, respectively, which were derived from the glucuronate moiety of each analyte. The proposed interpretation of m/z 175 is the negative ion of glucuronic acid with a loss of 18 u (H2O), which produces m/z 113 after further losing 18 u (H2O) and 44 u (CO2). Fragmentation pathway has been established for each analyte. The results show that quasimolecular ion m/z M-1 and the characteristic fragment ions m/z 175 and m/z 113 in the multi-stage full scan mass analysis of each analyte can be predicted for future structure elucidation or quantitative determination of glucuronide conjugates by LC/MS.

Animals↗
PubMed1998

[Influence of smear layer and adhesive resin on the retentive force of amalgam restoration in vitro study].

UNLABELLED: The purposes of this in vitro study were to determine whether removing of smear layer and using of self-cured adhesive can increase retentive strength of amalgam restoration and to understand the adhesive mechanism between amalgam and adhesive. Class I cavities without mechanical retention were prepared in the occlusal surfaces of 45 extracted molars which were randomly divided into 3 groups. Group 1: 10%EDTA(pH 7.4) was applied to cavity walls for 1 minute prior to amalgam condensation. Group 2: 10%EDTA was applied in the same manner as in group 1, then the walls were water-sprayed and dried. Miradapt adhesive was applied, and amalgam must be packed into cavity before the adhesive cures. CONTROL GROUP: no special treatment before amalgam condensation. The tensile strength of the restorations were measured. The adhesive interface of two samples from group 2 were evaluated by SEM and EDS. As a result, removing smear layer had little effect on retentive force of amalgam (P > 0.05), while removing smear layer and applying adhesive improved the retentive strength of amalgam fillings significantly (P < 0.05), and there were micromechanical interlock between amalgam and adhesive according to SEM and EDS observation.

Adhesives↗
PubMed1998

[Studies on dynamic changes of SOD and MDA in cultured cells from Schistosoma japonicum schistosomula].

AIM: To observe the dynamic changes of superoxide dismutase(SOD) and maldondialdehyde(MDA) in cultured cells from Schistosoma japonicum schistosomula and to explore the degeneration process of cultured cells. METHODS: Pyrogallol method and thiobarbituric acid method were used to determinate the levels of SOD and MDA, respectively, in the cells cultured for 0-54 days. RESULTS: SOD in the cells reached a peak level on d12 of the early stage of culture and then decreased. The MDA levels in the cultures cells ascended gradually, and had two peaks on d18 and d48, during the period of culture. CONCLUSION: The cultured cells from S. japonicum schistosomula degenerated progressively.

Animals↗
PubMed1998

[The transfection and morphological changes of human embryonic nasopharyngeal epithelia infected by Epstein-Barr virus cooperated with promoter in vitro and in vivo].

In order to detect the ability of EBV on transfecting and transforming human nasopharyngeal epithelia(HNE) isolated from human embryo, the HNE was cultured in vitro and then transplanted into nude mice. HNEs were treated by EBV, EBV + TPA and TPA in vitro, respectively. The mice transplanted with HNE tissues were injected subdermally by EBV, EBV + TPA and distilled water several times, respectively. The morphological changes indicated that EBV induced not only enhancement of foci and N/C ratio in cultured HNE which are important characteristics of malignant transformation, but also carcinogenesis of transplanted HNE, all of the carcinoma were EBV positive. TPA seems to increase EBV transfection rate (EBV PCR positive rate) in vitro, especially in the early stage. TPA alone did not exert effect on malignant transformation Cooperating with TPA, EBV induced early invasive carcinoma in vivo.

Animals↗
PubMed1998

[Oxygen free radical scavening activity and anti-lipid peroxidation of tea polyphenol].

The oxygen free radical scavenging activity and anti-lipid peroxidation of tea polyshenol were studied in vitro. Tea polyphenol possessed significantly scavening effect on hydorxyl radical produced by Fenton recation and superoxide anion produced by xanthine-xanthine oxidase system (IC50 were 919.6 mg/L and 836 mg/L espectively). Tea polyphenol could significantly inhibit the lipid peroxidation of brain omogenate and cerbral mitochondrial membrane induced by hyderxyl radical. The results suggest that the anti-lipid peroxidation of tea polyphenol may be related to its scavenging effects on oxygen free radicals.

Animals↗
PubMed1998

[Effects of herba Pogostemonis on gastrointestinal tract].

The effects of the three extracts (Decoction, oil-free decoction and volatile oil) of Herba Pogostemonis on gastrointestinal tract were studied. The results showed that all the three extracts inhibited the automatic contraction and Ach, BaCl2-induced spasmodic contraction of isolated rabbit intestine, among the three extracts the volatile oil was the most potent. In vivo the decoction and the oil-free decoction could depress gastric evacuation and inhibit the normal and neostigmine-induced intestinal propellent movement in mice, but the volatile oil could not. The decoction and the oil-free decoction also increased gastric secretion of acid and activity of pepsin and amylase. Furthermore, the decoction and the oil-free decoction reduced the incidence of diarrhea induced by senna but volatile oil enhanced cooperatively. All the three extracts relieved the gripping pain induced by abdominal administration of acetic acid, and the effect of decoction was more potent that the others. The above results revealed that the effective components of Herba Pogostemonis may be mainly water-solube.

Animals↗
PubMed1998

[Study on the dynamic examination of anterior chamber angle by ultrasound biomicroscopy].

PURPOSE: To study the factors that influence ultrasound biomicroscopy(UBM) examination on anterior chamber angle, and explore a dynamic differentiating method. METHOD: To compare the UBM morphologic characters of the anterior chamber angle of the high-risk chamber angle and adhered angle groups under different illumination. RESULT: Under routine working condition, some eyes of the high-risk-group (9/12) displayed bombing iris with extremely narrowly-opened angle; but 3/12 cases and the control group showed bombing iris and closed angle. Under bright circumstances, all angles of the high-risk group showed widely-opened, but the control group remained closed. CONCLUSION: Different illumination influences the UBM examination of the anterior chamber angle significantly, we should differentiate the angle morphologic characters under different illumination if it seems to be closed. Factors that affect the UBM examination were also discussed.

Anterior Chamber↗
PubMed1998

[Three-dimensional volumetric display--a new application of frequency up-conversion].

This paper discusses the present research situation and the application prospect of 3-D volumetric display technology. The possible usability and science significance of frequency up-conversion in 3-D volumetric display field are also demonstrated systematically. In ZBLAN: Pr, Yb glasses, we primarily demonstrated and achieved a new application of frequency up-conversion three dimensional volumetric display, using the two-frequency up-conversion of the rare earth ions. The efficiency of luminescence of Pr was enhanced much by the energy transfer between Pr and Yb ions.

English Abstract↗
PubMed1998

[Study of photoreflectance in Cd1-xMnxTe/Cd1-yMnyTe superlattices of II - VI diluted magnetic semiconductors].

The observation of photoreflectance spectra of Cd1-xMnxTe/Cd1-yMnyTe superlattices was carried out at temperature T = 80K. The samples were grown by molecular beam epitaxy (MBE) technique. The heavy-and light-hole excitonic transition structures 11H, 22H, 33H and 11L were observed and the theoretical calculations, including the strain effects, were performed. By comparison, both agree well.

English Abstract↗