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Biomedical subjects

L Xie

Publications and source records attributed to L Xie.

At least 127 records · Page 7Linked to original sources
PubMed1997

[In vitro stimulation of HTC hepatoma cell growth by recombinant human augmenter of liver regeneration (ALR)].

It was demonstrated that biologically active ALR could be expressed from its cDNA in transient expression experiments in cos-7 cells. The results showed that the cytosolic fraction from the transfected cells with constructed plasmids DNA stimulated of DNA synthesis of in vitro HTC cells in a dose dependent manner. This finding suggests that the HTC hepatoma cell line may be used as a target for bioassay of human ALR in vitro.

Carcinoma, Hepatocellular↗
PubMed1997

[Increase in the level of augmenter of liver regeneration mRNA in the rat regenerating liver after partial hepatectomy].

Augmenter of liver regeneration (ALR) is a novel hepatic stimulator. After 70% of the rat liver was removed, ALR-like activity in the remnant liver began to increase within 24 h. In parallel with the activity, the ALR mRNA level in the remnant liver increased 12 h after the operation and reached a maximum in 24 h. These findings indicate that the liver itself produces ALR, which may be a hepatotropic factor acting as a trigger for liver regeneration.

Animals↗
PubMed1996

Reversible thermal denaturation of staphylococcal nuclease: a Fourier transformed infrared spectrum study.

The secondary structures of staphylococcal nuclease (SNase) have been assigned and semiquantitatively estimated from the deconvoluted Fourier transformed infrared (FTIR) spectrum. The changes in the secondary structures accompanying unfolding and refolding of SNase during reversible thermal denaturation up to 70 degrees C are followed by FTIR measurements. Only slight perturbation was observed up to 35 degrees C. The unfolding transition temperatures of beta-structure and alpha-helix are almost the same at 48.0-48.5 degrees C. During refolding the formation of the beta-structure follows the same pathway but that of the alpha-helix does not, although it recovers its original content almost completely. The final thermally denatured state at high temperature (60-70 degrees C) contains nonrandom structures in the complicated interaction, energetically resembling many kinds of structures. The occurrence of local conformational change before the final cooperative transition to the unfolded state during thermal denaturation as judged by FTIR spectra indicates that the unfolding and refolding of SNase may not follow the typical two-state model.

Bacterial Proteins↗
PubMed1996

Serial measures of plasma homocyst(e)ine after acute myocardial infarction.

To determine whether plasma levels of homocyst(e)ine are affected by the acute phase response, we studied 10 subjects serially after acute myocardial infarction. Our data indicate that measurement of homocyst(e)ine in patients with myocardial infarction should ideally be deferred for 7 days if spuriously low levels are to be averted.

Acute-Phase Reaction↗
PubMed1996

In vitro anticryptosporidial activity of dinitroaniline herbicides.

Despite the evaluation of over 100 antimicrobial drugs, the diarrheal disease cryptosporidiosis has remained refractory to treatment. We report the evaluation of five dinitroaniline herbicides including trifluralin, profluralin, nitralin, pendimethalin, and fluchloralin for anticryptosporidial activity in an in vitro cultivation model of Cryptosporidium parvum. All five compounds exhibited significant anticryptosporidial activities with no corresponding evidence of toxicity. The most active compound was pendimethalin with an IC50 of 0.19 microM while nitralin was the least active with an IC50 of 4.5 microM. These compounds should be evaluated further in an animal model of cryptosporidiosis.

Aniline Compounds↗
PubMed1996

A chemiluminescence immunoassay for evaluation of Cryptosporidium parvum growth in vitro.

A chemiluminescence immunoassay (CLIA) was developed to detect Cryptosporidium parvum growth in Madin-Darby canine kidney (MDCK) cell cultures. Optimal results were obtained when MDCK cells were plated at a density of 1 x 10(4) cells/well (96-well plate) and maintained as a monolayer for 4 days prior to infection with 2 x 10(4) parasites/well. Two compounds (paromomycin and maduramicin) were evaluated and shown to have selective activity against C. parvum in a dose-dependent manner. There was excellent correlation between CLIA and immunofluorescence assay when assessing anti-C. parvum agents in MDCK cells. CLIA offers advantages over conventional enzyme-linked immunosorbent assay and immunofluorescence assay methods in that it is more sensitive and efficient. The combination of CLIA and MDCK culture provides an efficient tool for evaluating potential anti-cryptosporidial compounds prior to testing in animal models.

Animals↗
PubMed1996

Cataract extraction and intraocular lens implantation with anterior vitrectomy in children.

OBJECTIVE: Extracapsular cataract extraction (ECCE) with selective intraocular lens (IOL) implantation has been the choice of the treatment for children with cataracts. With regard to surgical technique, ECCE with anterior segment vitrectomy has shown some success in reducing complications. Formation of a secondary membrane and opacity of the posterior capsule, however, are still major postoperative complications. To reduce these complications, we modified current surgical procedures with minimal incisions and manipulations. PATIENTS AND METHODS: ECCE with anterior segment vitrectomy was performed using Storz Protage's system in 84 eyes of 58 children ranging in age from 14 months to 14 years. Of 70 eyes of children aged above 3 years, IOLs were implanted simultaneously. Vision improvement and incidence of postoperative complications were compared with other standard procedures to determine the benefits of the operation for children with cataracts. After the anterior capsule was opened by continuous circular capsulorhexis or envelope-form capsulectomy, the lens cortex was excised. Subsequently, the IOL was implanted into the bag. RESULTS: Nine-30 months follow-up showed that all of the central area of the posterior capsule remained clear except one eye in which a secondary membrane was partially formed on the anterior surface of vitreous. No other operative or postoperative complications occurred. CONCLUSIONS: The results indicate that the modified procedure is beneficial in the prevention of secondary cataract formation and other postoperative complications in a short term follow-up, however, a long-term follow-up is warranted to evaluate its role in pediatric cataract surgery.

Adolescent↗
PubMed1996

[Penetrating keratoplasty in children].

OBJECTIVE: The study was designed to approach the operative techniques of penetrating keratoplasty (PKP) in children and the influential factors on the rate of graft clarity. METHODS: PKP was performed on 33 eyes of 30 children whose corneal opacities resulted from various causes and they were followed for 6 months to 3 years. RESULTS: The rate of graft clarity was 66.7% and 44.8% of these eyes were relieved from blindness. The poorest results achieved were in cases with congenital corneal opacity and the main cause of graft failure is endothelial immune rejection. CONCLUSION: Although the surgical results in children are poorer than that in adults, from the concern of prevention of amblyopia and cosmetic problem, it is necessary to perform the operation earlier.

Adolescent↗
PubMed1996

Effect of captopril on intracellular free calcium ([Ca2+]i) of thymocytes in spontaneously hypertensive rats.

Hypertension is associated with dysfunction of the immune system. Intracellular free calcium ([Ca2+]i) was reportedly increased in immune cells, such as lymphocytes and thymocytes, both in hypertensive patients and in animals. To evaluate if captopril has an effect on the immune system, [Ca2+]i in thymocytes was monitored during the development of hypertension from 4-24 weeks, and after treatment with captopril for 4 and 12 weeks in spontaneously hypertensive rats (SHR). SHR (n = 24) were treated with captopril at a dose of 20 mg/kg/day at 12 weeks of age after establishment of hypertension. Untreated SHR (n = 17) and normotensive Wistar Kyoto (WKY n = 14) served as control. [Ca2+]i of thymocytes was measured using Fura-2. It was found that [Ca2+]i of thymocytes decreased both in SHR and WKY from 4-12 weeks of age. From 12-24 weeks, [Ca2+]i in thymocytes remained at a constant level in WKY. However, [Ca2+]i in thymocytes increased significantly in SHR after 12 weeks. Captopril (CAP) treatment significantly lowered [Ca2+]i in thymocytes derived from SHR at 24 weeks. This treatment was associated with a moderate reduction in systolic blood pressure. Established hypertension in SHR is associated with increased [Ca2+]i in thymocytes. This may be indicative of immunological dysfunction. Captopril inhibits the increase in [Ca2+]i of thymocytes in SHR.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Assay of plasma homocysteine: light sensitivity of the fluorescent 7-benzo-2-oxa-1, 3-diazole-4-sulfonic acid derivative, and use of appropriate calibrators.

The recognition of homocysteine as a vascular risk factor has led to increased clinical interest in assaying plasma homocysteine concentrations. Our aim was to improve the reliability of a widely used assay based on HPLC of the fluorescent 7-benzo-2-oxa-1, 3-diazole-4-sulfonic acid (SBD) derivative. We found that SBD derivatives of homocysteine, cysteine, and N-acetylhomocysteine were highly unstable in light but essentially stable in the dark for several hours at either 0 degree C or 25 degrees C. As our primary calibrator, we chose homocystine added to human serum for more consistent results than homocysteine or homocystine in an aqueous buffer. N-acetylcysteine was effective as an internal recovery standard. We observed a previously unreported peak with a prolonged elution time in some plasma samples from subjects who had ingested methionine. Our findings suggest improvements in this and other assay procedures for plasma homocysteine.

Calibration↗
PubMed1996

[An experimental study on epikeratophakia].

OBJECTIVE: The study was designed to investigate the corneal changes at various times after epikeratophakia performed on rabbit cornea. METHODS: The process of epithelial repair, or interlayer healing, the changes of endothelial cells and Langerhans cells (LC) in corneal epithelium were observed at different intervals after surgery by using histochemistry technique. RESULTS: The epithelial repair of the graft was completed by 4-12 postoperative days. The repopulation of keratocytes was seen firstly at peripheral and superior part of the lenticule at 7-14 postoperative days and completed to normal by postoperative 2 months. No changes were observed in the endothelial cells. The proliferation of LC was observed in the limbal epithelium at day 3, reached the peak by day 14 and recovered to normal at month 2 postoperatively. CONCLUSION: Epikeratophakia is available and safe, The proliferation of LC might result from wound healing not from immune rejection.

Animals↗
PubMed1996

[Pharmacokinetic and electocardiographic study of oral verapamil sustained-release tablet in 10 Chinese volunteers].

Both verapamil pharmacokinetics and electrocardio graphic changes in 10 Chinese volunteers were studied after po 240 mg of verapamil sustained release tablet. A one-compartment model with zero-order absorption gave a better fitting to concentration--time data with values of r2 > 0.96. The main pharmacokinetic parameters obtained were: Tmax, 5.9 +/- 1.6 h; Cmax, 118.9 +/- 37.2 micrograms.L-1; T1, 5.4 +/- 1.5 h; k0, 30.5 +/- 17.5 micrograms.L-1.h-1; T1/2, 10.8 +/- 4.9 h; MRT, 15.4 +/- 3.2 h and AUC. 1.96 +/- 0.82 mg.h.L-1. There were significant prolongations of PR intervals after dose. Relationships between PR interval changes and plasma concentrations of verapamil were better fitted to sigmoidal model, with r2 > 0.98. The corresponding pharmacodynamic parameters were estimated. EC50, 64.6 +/- 16.9 micrograms.L-1, Emax, 54 +/- 11 ms and s, 1.68 +/- 0.66.

Adult↗
PubMed1996

Diltiazem concentrations in plasma vs PR intervals on electrocardiogram in 8 men.

AIM: To develop an acute tolerant model in describing relationship between diltiazem (Dil) concentrations in plasma and PR intervals on ECG in men. METHOD: Both plasma concentrations of Dil and changes of ECG were simultaneously determined after po Dil 90 mg in 8 men. RESULTS: A two-compartmental pharmacokinetic model with first-order input gave a good fitting for the plasma concentration of Dil. Corresponding pharmacokinetic parameters were estimated: t1/2 beta, 5.9 +/- 1.0 h; MRT, 15.9 +/- 1.0 h; t0, 0.38 +/- 0.07 h; tmax, 2.7 +/- 0.4 h, and Cmax, 161 +/- 60 micrograms.L-1. The good fittings for plasma concentration-effect data were obtained with tolerant model E = S x C/(1 + T/T50). The pharmacodynamic parameters were given as follows: S, 829 +/- 293 s.g-1.L; Kt0, 0.037 +/- 0.024 h-1 and T50, 10 +/- 4 micrograms.L-1. CONCLUSION: Relationship between Dil concentrations in plasma and PR interval changes in men after po 90 mg was described using an acute tolerant model.

Adult↗
PubMed1996

[Two-site absorption model fits to pharmacokinetic data of gemfibrozil in man].

The plasma concentration-time data of gemfibrozil in 8 male subjects were determined after an oral dose of 600 mg. Two-peak concentrations in plasma were observed. A kind of one-compartment model with two-sites of drug absorption was proposed and used to fit these data. A good agreement between observed and predicted data was found in all subjects with correlation indexes (gamma 2) > 0.99. The corresponding pharmacokinetic parameters were estimated as follows: Tmax1, 1.10 +/- 0.46 h; Tmax2, 2.60 +/- 0.73 h; Cmax1, 13.62 +/- 4.30 micrograms.ml-1; Cmax2, 17.22 +/- 3.83 micrograms.ml-1; T1, 0.06 +/- 0.06 h; T2, 1.42 +/- 0.57 h and T3, 1.79 +/- 0.60 h.

Adult↗
PubMed1995

Anti-AIDS (acquired immune deficiency syndrome) agents. 17. New brominated hexahydroxybiphenyl derivatives as potent anti-HIV agents.

Sixteen biphenyl derivatives were synthesized and evaluated for their inhibitory activity against HIV-1 replication in acutely infected H9 cells. 3-Bromo- (4) and 3,3'-dibromo-4,4'-dimethoxy-5,6,5',6'-bis(methylenedioxy)-2,2'- bis(methoxycarbonyl)biphenyl (5) demonstrated potent anti-HIV activity with EC50 values of 0.52 and 0.23 micrograms/mL and therapeutic index values of > 190 and > 480, respectively. A comparison of the anti-HIV activity of these biphenyl derivatives suggested that the types of substituents on the phenolic hydroxy groups rather than the number of bromine(s) on the aromatic rings are important to the enhanced anti-HIV activity. Compounds 4 and 5 also showed potent inhibitory activity against HIV-1 reverse transcriptase in a template-primer dependent manner. The site of inhibition of HIV could be related to inhibition of this enzyme. Compounds 4 and 5 did not induce virus expression from the chronic HIV-1-infected cell lines ACH-2 and U1. Furthermore, these two agents did not inhibit an increase in virus production from the chronic HIV-1-infected cell lines when the phorbol ester PMA was present.

Antiviral Agents↗
PubMed1995

Comparative studies of the conformation of the N-terminal fragments of staphylococcal nuclease R in solution.

In order to elucidate the folding of nascent peptide, five peptide fragments of staphylococcal nuclease R starting from N-terminal end and of different chain lengths are made by deletion of 47, 39, 28, 14 and 8 amino-acid residues from its C-terminal end, respectively. Changes in conformation of the N-terminal fragments have been compared by using Fourier-transform infrared spectra, far-ultraviolet circular dichroism spectra and analysis of surface hydrophobicity. The experiments indicate that all the five fragments have certain amounts of residual structure; in general, with increasing the peptide chain, the contents of secondary structure and the enzyme's activity of the peptide increase, and the exposed hydrophobic side chains brought about by the deletion of C-terminal residues are gradually buried in the interior of the nuclease. However, the ordered secondary structures do not always increase with increasing the peptide chain. Further growth of the length of the peptide chain could have an important effect on the conformation of the peptide fragment already synthesized, suggesting some structural adjustments should be necessary in order for the newly synthesized polypeptide to attain its final native conformation. These results support Tsou's nascent peptide folding hypothesis (Tsou, C.-L. (1988) Biochemistry 27, 1809-1812).

Circular Dichroism↗
PubMed1995

A molecular-based magnet test for malaria.

The molecular-based magnet test for malaria is shown to be more sensitive than the thin blood film test. The globally used thin blood film test is less sensitive because it uses preparation steps that result in the reduction of the absolute number of diagnostically pertinent erythrocytes. Several reports of diagnostic error with the thin film test and the thick film test have appeared in the literature. In marked contrast to the commonly accepted tests, the magnet test concurrently partitions and concentrates the infected erythrocytes present in the initial sample. The magnetic test permits a brief and sensitive microscopic-based enumeration of the malaria-infected erythrocytes in the enriched sample. Diagnostically pertinent hemozoin is simply identified through two of its specific molecular properties: paramagnetism and birefringence. The former property mediates the capture and enrichment of malaria-infected erythrocytes within the magnetic flux and the latter property manifests the characteristic birefringence demonstrated by polarized light.

Animals↗