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S Zeng

Publications and source records attributed to S Zeng.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Determination of mephenytoin enantiomers in human urine using chiral capillary chromatography and its application in metabolism polymorphism study].

The determination of mephenytoin enantiomers in human urine using chiral capillary chromatography is described. MP in urine was extracted with using dichloroethane and the organic layer was washed with acidic and basic aqueous solution. The organic phase was evaporated to dryness under nitrogen on water bath (55 degrees C). The residue was dissolved in 10 microL ethyl acetate and 1 microL was injected into the GC. MP enantiomers was separated on a Chirasil-Val SFOT column with nitrogen as carrier gas and FID as detector. The linear relationship was obtained over the concentration range of 115-690 micrograms/L (r = 0.9913 for S-MP and r = 0.9934 for R-MP) with a detection limit of 60 ng MP enantiomers/mL urine. The recoveries were 74.41% for S-MP and 73.78% for R-MP. The relative standard deviation within day and between days were less than 6.5%. The method was used to study the metabolism polymorphism of 32 volunteers. The S/R ratio was calculated to express interindividual variation in metabolism, in which, the S/R ratio of 5 subjects was more than 0.95, as the poor metabolizers and that of the others was less than 0.8, as the extensive metabolizers.

Anticonvulsants↗
PubMed1998

[Interferon-alpha 2b inhibits proliferation of human tenon capsule fibroblasts].

PURPOSE: To evaluate the potential effect of interferon-alpha 2b(IFN alpha-2b) as antifibrotic treatment after glaucoma filtering surgery. METHODS: The MTT method was used to study the inhibitory effect of IFN alpha-2b on human Tenon capsule fibroblasts in vitro. The antimetabolites including 5-fluorouracil (5-FU), homoharringtonine(H.H) and mitomycin C(MMC) were also assessed. RESULTS: The IC50 values of IFN alpha-2b, 5-FU, H.H and MMC on fibroblasts at 48 hours were 60.578 mg/L, 5.447 mg/L, 0.531 mg/L, 1.329 mg/L respectively. CONCLUSION: The effect of IFN alpha-2b to inhibit proliferation of fibroblast was less than that of antimetabolites. Further investigation of other aspects of suppress(suppress) wound healing as a possible antifibrotic agent should be deserved.

Antimetabolites↗
PubMed1998

[Study on human eye ciliary muscule cell culture and biologic characteristics].

PURPOSE: We cultured human ciliary muscle [HCM] cells to study their growth, ultrastructure, immunohistochemistry and functional characters. METHODS: HCM cells from 10 young donor eyes were cultured with collagenase IV digestion procedures in vitro, the cells were identified by eletronmicroscope and immunohistochemistry assay, their function were studied by single-cell-contraction assay. RESULTS: The cells were passed and grew in Hill-Valley pattern after conflunet; abundant filaments were presented under electronmicroscope. In Desmin protein immunohistochemistry study, the cultured cells were stained positive; in tissue sections, HCM cells stained positive, vascular smooth muscle stained positive weakly, but fibroblast cells and endothelial cells stained negative. 10(-3) M Carbachol could induce the cultured cells contract, this effect was antagonized by 10(-3) M Atropine. CONCLUSION: We successfully cultured HCM cells, which were able to contract.

Cells, Cultured↗
PubMed1997

Pilot scale expression and purification of soluble protein A tagged beta 1,6N-acetylglucosaminyltransferase in CHO cells.

Expression of recombinant soluble protein A tagged mouse core 2 beta 6-N-acetylglucosaminyltransferase (E.C. 2.4.1.102) has been scaled-up in CHO cells using a continuously operating fluidized bed system yielding 0.3 U/day. A one step 213 fold purification by affinity chromatography on IgG-Sepharose yielded a stable enzyme preparation with a specific activity of 44 mU/mg. The enzyme was shown to belong to the L-type with a highly restricted specificity for the acceptor substrate Gal beta 1-->3GalNAc alpha 1-->R (core 1). Only little activity towards GlcNAc beta 1-->3Gal-NAc alpha 1-->R (core 3) (< 1%) and no incorporation on unsubstituted benzyl or peptide-bound GalNAc was detected. Zn2+ and to a lesser extent Mn2+ were found to be inhibitory whereas Mg2+ could activate the enzyme. The enzyme preparation proved suitable for in vitro application as a catalyst for the synthesis of core 2 structures.

Animals↗
PubMed1997

Particle Aggregation due to Combined Gravitational and Electrophoretic Motion

The stability and pairwise aggregation rates of small spherical particles in a heterogeneous suspension under the collective effects of gravitational motion and electrophoretic migration are analyzed. The particles are assumed to be non-Brownian, with thin, unpolarized double layers and different zeta potentials. The gravity vector and the electric field are assumed to be oriented in either the same direction or opposite directions. The particle aggregation rates are always enhanced by the presence of an electric field for parallel alignment of the gravitational and electrophoretic velocities. For antiparallel alignment with the magnitude of the gravitational relative velocity exceeding the magnitude of the electrophoretic relative velocity between two widely separated particles, the particle aggregation rates are reduced by the presence of the electric field, and there is a "collision-forbidden" region in parameter space due to stronger hydrodynamic interactions of the particles for gravitational motion than for electrophoretic motion. For antiparallel alignment with the magnitude of the electrophoretic relative velocity exceeding the magnitude of the gravitational relative velocity between two widely separated particles, the particle aggregation rates are enhanced by the presence of the electric field.

Journal Article↗
PubMed1997

Functional domains of the nuclear receptor hepatocyte nuclear factor 4.

The hepatocyte nuclear factor 4 (HNF-4) is a member of the nuclear receptor superfamily and participates in the regulation of several genes involved in diverse metabolic pathways and developmental processes. To date, the functional domains of this nuclear receptor have not been identified, and it is not known whether its transcriptional activity is regulated by a ligand or other signals. In this report, we show that HNF-4 contains two transactivation domains, designated AF-1 and AF-2, which activate transcription in a cell type-independent manner. AF-1 consists of the extreme N-terminal 24 amino acids and functions as a constitutive autonomous activator of transcription. This short transactivator belongs to the class of acidic activators, and it is predicted to adopt an amphipathic alpha-helical structure. In contrast, the AF-2 transactivator is complex, spanning the 128-366 region of HNF-4, and it cannot be further dissected without impairing activity. The 360-366 region of HNF-4 contains a motif that is highly conserved among transcriptionally active nuclear receptors, and it is essential for AF-2 activity, but it is not necessary for dimerization and DNA binding of HNF-4. Thus, HNF-4 deletion mutants lacking the 361-465 region bind efficiently to DNA as homo- and heterodimers and behave as dominant negative mutants. Remarkably, the full transactivation potential of AF-2 is inhibited by the region spanning residues 371-465 (region F). The inhibitory effect of region F on the HNF-4 AF-2 activity is a unique feature among members of the nuclear receptor superfamily, and we propose that it defines a distinct regulatory mechanism of transcriptional activation by HNF-4.

Amino Acid Sequence↗
PubMed1997

Mepyramine inhibits platelet activating factor-induced rabbit platelet aggregation: role of intracellular histamine.

AIM: To study the possible role of intracellular histamine (HA) in platelet activating factor (PAF)-induced platelet activation. METHODS: Washed rabbit platelet suspension was used to test the inhibitory effect of mepyramine (Mep, an H1 receptor antagonist) on PAF-induced platelet aggregation. The thromboxane B2 (TXB2) generation was measured by radioimmunoassay and the intracellular calcium ([Ca2+]i) concentration was determined by the specific fluorescence indicator Fura-2. RESULTS: Mep > 100 mumol.L-1 generated a concentration-dependent inhibition on PAF-induced aggregation, with an IC50 value of 162 (95% confidence limits: 114-232 mumol.L-1). Cimetidine, an H2 receptor antagonist, even up to 400 mumol.L-1 had no effect on it. Exogenous HA (10 mumol.L-1) and H1 receptor agonist, 2-thiazolylethylamine had no energetic effect. alpha-Fluoromethylhistidine, an inhibitor of histidine decarboxylase, did not inhibit platelet responses. However, in platelets permeabilized with saponin (8-10 mg.L-1), exogenous HA attenuated the inhibitory effect of Mep to about 50% at a concentration of 50 mumol.L-1. Preincubation of platelets with Mep (100 or 200 mumol.L-1) resulted in an inhibition on TXB2 generation and [Ca2+]i elevation induced by PAF. CONCLUSION: Platelets activated by PAF is associated with an intracellular HA synthesis and release via a common pathway of TXB2 generation and the rise of [Ca2+]i.

Animals↗
PubMed1997

[Prediction of RP-HPLC retention index for hydroxyl-containing compounds and their glucuronides].

The quantitative relationships between the structure of solutes and their chromatographic retention behaviors have been widely studied. A lot of compounds have been investigated, but drug metabolites have not been involved. Determination of glucuronic acid conjugation is the most important route for investigations of metabolism of drug, while the glucuronide samples are rarely obtained. In this paper the glucuronides have been obtained with the method of biosynthesis in vitro. The peaks of glucuronides were identified by several means including diode-array spectrophotometer detection, beta-D-glucuronidase hydrolysis, glucuronide references and chromatogram comparison of the incubation samples at different times. Two systems have been developed to predict retention index in reversed-phase high performance liquid chromatography based on the molecular structure of the analytes and on the behavior of the parent compounds. We observed a good correlation between retention index of hydroxyl-containing compounds of glucuronides and hydrophobility based on Hansh pi value: I=383.4+136.0pi, n=10, r=0.9912. A good correlation between hydroxyl-containing compounds and their glucuronides was also observed: Y=-471.1+1.4430X, n=11, r=0.9600. The errors in this experiment are less than 12%.

Animals↗
PubMed1997

[Chiral separation of racemic 5-(p-hydroxyphenyl)-5-phenylhydantoin by RP-HPLC using eluents containing beta-cyclodextrin].

A chiral RP-HPLC method was developed to assay the 5-(p-hydroxyphenyl)-5-Phenylhydantoin (p-HPPH) enantiomers, the major metabolite of antiepileptic drug phenytoin, in rat hepatic microsomes. A 50 mm FLC-C8 column was used as the analytical column, beta-cyclodextrin (beta-CD) as chiral mobile phase additive and phenobarbital as the internal standard. The detection wavelength was 250 nm. The linear range of p-HPPH enantiomers was 0.5-110 mg/L. The detection limit was 5 ng (S/N = 3). The recoveries of S- and R-p-HPPH were 93.6% +/- 2.8% and 94.7% +/- 1.8% respectively. The RSD within day and between days were less than 2%. The concentration of beta-CD played an important role in separating chiral enantiomers. When the concentration of beta-CD was between 8.8 and 13.2 mmol/L the resolution of p-HPPH enantiomers had the largest value Rs = -1.1. In this work, 8.8 mmol/L beta-CD solution (4 g beta-CD, 6 g urea, and 1.5 g ammonium acetate in 400 mL water) was selected in considering some factors such as column efficiency, solubility of beta-CD etc. Urea can increase the solubility of beta-CD. When urea: beta-CD = 1:1-1.5:1 (g/g), the solubilization of beta-CD was significant. Methanol concentration in mobile phase affected retention time, resolution of p-HPPH enantiomers and solubility of beta-CD.

Animals↗
PubMed1997

[Improvement of technigue in restoration of stability of thoracolumbal spine].

A new fixator for spine was designed to restore the stability of spine in improving the treatment of thoraco-lumbar dislocation. This instrument was composed of six nails, two longitudinal connecting rods and two transverse connecting rods. On the surface of the nails, there were furrows engraved, instead of screw thread. It fixed the spine through pedicle of vertebra from the posterior approach. The fixed vertebrae were limited between two vertebrae. From 1989 th 1995, twelve patients with fracture-dislocation of thoraco-lumbar spine were reduced with this instrument. After four years follow-up, it showed that the deformity was corrected and the spine firmly fixed. Compared with Dick's screws, it had the following advantages such as simple manipulation, increased strergth of nails and minimal damage to tissue during operation.

Adolescent↗
PubMed1996

Intraoperative use of mitomycin in trabeculectomy.

Mitomycin (0.2 mg/ml) was applied intraoperatively to 26 glaucomatous patients (33 eyes) during conventional trabeculectomy procedure. Most of them were considered to be at high risk of surgical failure. The conjunctival flap was fornix-based in 9 patients (11 eyes). The success rate was 84.8% without any serious side effect.

Female↗
PubMed1995

[Functional analysis of the CPS I upstream sequences with a CAT assay].

Expression plasmids (pKCPSx-CAT) containing carbamyl phosphate synthetase I (CPS I) upstream sequences of different lengths were constructed, and the function and characteristics of the sequences were studied with the CAT assay. The results showed that the CPS I upstream sequences exerted highly tissue-specific control on CPS I gene expression, and the -142- -38bp region relative to the cap site was found to be indispensable for CPS I gene transcription. The -1700- -161bp region contains sequences which confer an enhancing effect on CPS I gene transcription. Dexamethasone and thioproline (a differentiation inducer) showed enhancing effects on CPS I gene transcription in hepatoma cells. These results would have significance in studies on the gene regulation of CPS I associated with the mechanism of hepatocyte differentiation and carcinogenesis.

3T3 Cells↗
PubMed1995

Experimental studies of the effect of Forskolin on the lowering of intraocular pressure.

PURPOSE: To determine the effect of domestic Forskolin on lowering of intraocular pressure (IOP) in rabbits. METHODS: Measure the normal IOP and ocular hypertension by water load in rabbits using Perkins tonometer. Measure the adenylate cyclase (AC) activity by Ho & Sutherland's method. RESULTS: The results show that Forskolin significantly lowered the normal IOP of rabbits and blocked the ocular hypertension induced by water load in rabbits (P < 0.01). The maximum decrease value of 2%, 1% and 0.5% of the Forskolin was 0.59, 0.36 and 0.19 kPa (1kPa = 7.5 mmHg), which showed the noticeable dose-effect relationship. Topical ocular application of Forskolin lowered IOP in half an hour, reached to a peak in 2-3 hours and remained significantly for 10 hours. The pupillary diameter did not change when IOP was reduced. The Forskolin had potent stimulative properties to AC. The greater the ability of the Forskolin to stimulate AC, the stronger the effect of IOP lowering. CONCLUSIONS: The Forskolin had the effect on lowering the IOP of rabbits. The mechanism of IOP reduction by Forskolin is related to its AC activation.

Adenylyl Cyclases↗
PubMed1995

[An experimental study on homoharringtonine and glaucoma surgery].

PURPOSE: To test the inhibiting effect of a Chinese herbal drug. Homoharringtonine (HH) on the wound healing process at the filtering site in an experimental model. METHODS: Posterior sclerectomies were performed in 20 rabbits. Postoperatively one eye of each rabbit received subconjunctival injections of HH and fellow eye received saline injections in a randomized masked fashion. RESULTS: 14 days after operation, intraocular pressure decreased significantly compared with that of control (P < 0.05). The number of filtration blebs was greater than that of control (14/6). On pathological examination, the number of fibroblasts per square measure of cross section of tissue cut from filtration region that was diminished significantly compared with that of control (P < 0.01). There were no serious and permanent ocular toxic and side effects. CONCLUSIONS: The study suggests that the HH can inhibit cicatrization at the glaucoma filtering site, promote the formation of filtering blebs and provide a sufficient evidence for the further clinical use of HH.

Animals↗
PubMed1994

[Quantification of the enantiomers of ofloxacin in human urine by RP-HPLC with chiral mobile phase additive].

The method for determination of S-(-) and R-(+)-ofloxacin (OFLX) in human urine by RP-HPLC with a chiral mobile phase additive is described. L-phenylalanine was used as the chiral additive, Cu2+ as the ligand ion and fluorescence for detection. This chiral ligand exchange chromatography has been applied to reveal the enantioselective disposition of ofloxacin in human volunteers.

Adult↗