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Biomedical subjects

Feng Qiu

Publications and source records attributed to Feng Qiu.

At least 37 records · Page 2Linked to original sources
PubMed2005

Impact of pharmaceutical dosage forms on the pharmacokinetics of roxithromycin in healthy human volunteers.

OBJECTIVES: The impact of two different pharmaceutical preparations on the pharmacokinetics of roxithromycin was investigated in healthy human volunteers. METHODS: The degradation kinetics and products of roxithromycin were investigated in simulated gastric fluid and simulated intestinal fluid. Two oral dosage forms of roxithromycin were employed: enteric-coated pellets and dispersible tablets. RESULTS: The degradation half-time of roxithromycin in simulated gastric fluid was 0.23 h, and three main degradation products were characterized. In contrast, roxithromycin was stable in simulated intestinal fluid and remained unchanged after a 1.00 h incubation. The roxithromycin enteric-coated pellets exhibited higher bioavailability and a more potent serum antibacterial activity than the dispersible tablets. CONCLUSIONS: The type of oral dosage forms of roxithromycin altered its pharmacokinetics. Whether or not this affects the in vivo antibacterial efficacy requires further study.

Adult↗
PubMed2005

Threading-unthreading equilibrium in solution of molecular nanotubes and linear flexible polymer chains.

Using the Flory-Huggins lattice model, we investigate the threading-unthreading equilibrium in a solution of linear flexible polymer chains and molecular nanotubes formed by covalently bonding the ringlike molecules, such as cyclodextrins (CDs). It is found that the threading-unthreading equilibrium depends on the temperature and the molar concentrations of the ringlike molecules and polymer chain segments but is independent of the polymer chain length, which agrees with the experimental observations. By fitting the experimental data of alpha-CD and poly(ethylene glycol) (PEG), the inclusion energy between alpha-CD and PEG, which includes the conformation energy loss of PEG resulted from the inclusion, is calculated to be approximately -20.45 kJ/mol per PEG unit.

Journal Article↗
PubMed2005

Isolation and identification of seven glucuronide conjugates of andrographolide in human urine.

Andrographolide is one of the principal components of a famous traditional Chinese herbal medicine, Andrographis paniculate (Burm) Nees, and has been widely used in the clinic for the treatment of infectious diseases. In this paper, metabolites of andrographolide in the urine of eight healthy volunteers after oral administration were further investigated. Building on previous findings, an additional seven phase II metabolites were isolated by liquid-liquid extraction, open-column chromatography, medium-pressure liquid chromatography, and, finally, preparative high-performance liquid chromatography. Structural elucidation was carried out by mass spectra and NMR spectroscopy including 1H NMR, 13C NMR and two-dimensional NMR (distortionless enhancement by polarization transfer, heteronuclear multiple-quantum correlation, heteronuclear multiple-bond correlation, 1H-1H correlated spectroscopy, and nuclear Overhauser enhancement spectroscopy). All of the metabolites were characterized as glucuronide conjugates, and the structures were determined to be andrographolide-19-O-beta-D-glucuronide (M-1), isoandrographolide-19-O-beta-D-glucuronide (M-2), 14-deoxy-12-hydroxy-andrographolide-19-O-beta-D-glucuronide (M-3), andrographolide-19-O-[6'-methyl-beta-D-glucuronide] (M-4), 14-deoxy-12(13)-en-andrographolide-19-O-beta-D-glucuronide (M-5), 14-deoxyandrographolide-19-O-beta-D-glucuronide (M-6), and 3-oxoandrographolide-19-O-beta-D-glucuronide (M-7), respectively.

Adult↗
PubMed2005

Influence of dosage forms on pharmacokinetics of daidzein and its main metabolite daidzein-7-O-glucuronide in rats.

AIM: To investigate the influence of dosage forms on the pharmacokinetics of daidzein and its main metabolite daidzein-7-O-glucuronide in Wistar rats. METHODS: After administration of two typical dosage forms (daidzein solution and suspension), the concentrations of daidzein and daidzein-7-O-glucuronide were determined by an LC-MS-MS method. The pharmacokinetic parameters were calculated and analyzed statistically using the Student's t-test. RESULTS: Absorption of daidzein after administration of daidzein solution (tmax=0.46 h) was more rapid than that of the suspension (tmax=5.00 h). The peak plasma concentrations of daidzein after administration of daidzein solution and suspension were 601.1 microg/L and 127.3 microg/L, respectively, and those of daidzein-7-O-glucuronide were 3000 microg/L and 192.6 microg/L, respectively. The absolute bioavailabilities of free daidzein in rats after administration of daidzein solution and suspension were 12.8% and 6.1%, respectively, which were calculated to be 47.0% and 12.2%, respectively, in the form of total daidzein (free plus conjugated daidzein). CONCLUSION: Absorption of daidzein solution was better than absorption of suspension (P<0.05).

Animals↗
PubMed2005

[Two-dimensional gel electrophoresis of subcellular fractions of hepatoma cells].

OBJECTIVES: To seek a better profiling of proteins of hepatoma cells. METHODS: The homogenate of hepatoma cells QGY-7703 was fractionated into four parts by differential centrifugation: the nuclei, the pellet by 20,000 x g, the pellet by 100,000 x g and the cytosolic supernatant. The four fractions were submitted to two-dimensional gel electrophoresis and their electrophoretic patterns were analyzed. RESULTS: In comparison with the protein pattern of hepatoma cells not fractionated, the patterns of the four fractions display many more protein spots, and a large number of proteins present in the nuclei and cytosolic supernatant were not shown in the not-fractionated samples. CONCLUSION: Preparation of subcellular fractions before electrophoretic procedures proves to be very useful; not only can it improve the results of two-dimensional gel electrophoresis, but also can lead to research into the subcellular level.

Carcinoma, Hepatocellular↗
PubMed2005

Validated liquid chromatography-tandem mass spectrometric method for the quantitative determination of daidzein and its main metabolite daidzein glucuronide in rat plasma.

A highly selective and sensitive liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed and validated to determine daidzein and its main metabolite daidzein glucuronide in rat plasma. The analytes and internal standard genistein were extracted from plasma samples by n-hexane-diethyl ether (1:4, v/v), and separated on a C18 column. The mobile phase consisted of acetonitrile-water-formic acid (80 : 20: 1, v/v/v). Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI) source. The method has a limit of quantification of 0.24 ng/ml. The linear calibration curves were obtained in the concentration range of 0.24-1000 ng/ml. The intra- and inter-day precisions were lower than 13.2% in terms of % RSD. The accuracy ranged from -0.5% to 2.4% in terms of % RE (relative error). This method was successfully applied to the determination of plasma concentration of daidzein and its main metabolite daidzein glucuronide in rats after an oral administration of 20 mg/kg daidzein.

Animals↗
PubMed2005

[Differential expression of mitochondrial proteins in hepatoma cells analyzed using two-dimensional electrophoresis].

BACKGROUND & OBJECTIVE: Mitochondria play a key role in cell apoptosis. Proteomic analysis of mitochondria will contribute to the discovery of tumorigenic mechanism, early detection of cancer, and findings of anticarcinogens. This study was to identify the differentially expressed mitochondrial proteins in hepatoma cells using two-dimensional gel electrophoresis (2-DE). METHODS: Mitochondria were isolated from normal hepatocytes L02, and hepatoma QGY-7703 cells before and after treatment of epirubicin by density gradient centrifugation; the proteins of mitochondrial samples were analyzed with 2-DE. RESULTS: After density gradient centrifugation, the mitochondrial marker enzyme activities were increased by 11.8, 13.8, and 10.2 times, respectively, for L02 cells, untreated QGY-7703 cells, and epirubicin-treated QGY-7703 cells, and the 2-DE profiles identified 206, 217, and 214 protein spots, respectively, from the 3 samples. Compared L02 cells and QGY-7703 cells, 49 differentially expressed protein spots were identified; compared QGY-7703 cells before and after treatment of epirubicin, 29 differentially expressed protein spots were identified. CONCLUSION: A set of differentially expressed protein spots are detected in mitochondria of QGY-7703 cells with density gradient centrifugation and 2-DE.

Antibiotics, Antineoplastic↗
PubMed2004

Determination of nimodipine in human plasma by a sensitive and selective liquid chromatography-tandem mass spectrometry method.

A sensitive and highly selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed to determine nimodipine in human plasma. The analyte and internal standard nitrendipine were extracted from plasma samples by n-hexane-dichloromethane-isopropanol (300:150:4, v/v/v), and chromatographed on a C(18) column. The mobile phase consisted of methanol-water-formic acid (80:20:1, v/v/v). Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI) source. The method has a limit of quantification of 0.24 ng/ml. The linear calibration curves were obtained in the concentration range of 0.24-80 ng/ml. The intra- and inter-day precisions were lower than 4.4% in terms of relative standard deviation (R.S.D.), and the accuracy ranged from 0.0 to 5.8% in terms of relative error (RE). This validated method was successfully applied for the evaluation of pharmacokinetic profiles of nimodipine tablets administered to 18 healthy volunteers.

Adult↗
PubMed2004

Rapid determination of metformin in human plasma by liquid chromatography-tandem mass spectrometry method.

A rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method is described for quantitation of metformin in human plasma. After a simple, one-step protein precipitation using acetonitrile, metformin and the internal standard diphenhydramine were chromatographed on a C(8) column and detected by tandem mass spectrometry. An atmospheric pressure chemical ionization interface was chosen to reduce ion suppression from sample matrix components and provide high sensitivity. The method has a chromatographic total run time of 3.4 min and was linear within the range 2-2000 ng/ml. Intra- and inter-day precision, expressed as the relative standard deviation (R.S.D.), ranged from 4.4 to 5.7% and from 1.3 to 2.8%, respectively. Assay accuracy was less than 1% in terms of %RE (relative error). The assay was used to evaluate the pharmacokinetics of metformin after an oral administration of multicomponent formulation containing 500 mg metformin and 2.5 mg glyburide to 20 healthy volunteers.

Gas Chromatography-Mass Spectrometry↗
PubMed2004

Morphology and phase diagram of complex block copolymers: ABC linear triblock copolymers.

Using a real space implementation of the self-consistent field theory for the polymeric system, we explore microphases of ABC linear triblock copolymers. For the sake of numerical tractability, the calculation is carried out in a two-dimensional (2D) space. Seven microphases are found to be stable for the ABC triblock copolymer in 2D, which include lamellae, hexagonal lattice, core-shell hexagonal lattice, tetragonal lattice, lamellae with beads inside, lamellae with beads at the interface, and hexagonal phase with beads at the interface. By systematically varying the composition, triangle phase diagrams are constructed for four classes of typical triblock polymers in terms of the relative strengths of the interaction energies between different species. In general, when both volume fractions and interaction energies of the three species are comparable, lamellar phases are found to be the most stable. While one of the volume fractions is large, core-shell hexagonal or tetragonal phases can be formed, depending on which of the blocks dominates. Furthermore, more complex morphologies, such as lamellae with beads inside, lamellae with beads at the interface, and hexagonal phases with beads at the interface compete for stability with lamellae structures, as the interaction energies between distinct blocks become asymmetric. Our study provides guidance for the design of microstructures in complex block copolymers.

Journal Article↗
PubMed2004

Barhl1 regulates migration and survival of cerebellar granule cells by controlling expression of the neurotrophin-3 gene.

The neurons generated at the germinal rhombic lip undergo long distance migration along divergent pathways to settle in widely dispersed locations within the hindbrain, giving rise to cerebellar granule cells and precerebellar nuclei. Neurotrophin-3 (NT-3) signaling has been shown to be required for proper migration and survival of cerebellar granule cells. The molecular bases that govern NT-3 expression within the cerebellum, however, remain unknown at present. Here we report that, during early mouse neurogenesis, the Barhl1 homeobox gene is highly expressed by the rhombic lip and rhombic lip-derived migratory neurons. Its expression is later restricted to cerebellar granule cells and precerebellar neurons extending mossy fibers, two groups of neurons that synaptically connect in the adult cerebellar system. Loss of Barhl1 function causes cerebellar phenotypes with a striking similarity to those of NT-3 conditional null mice, which include attenuated cerebellar foliation as well as defective radial migration and increased apoptotic death of granule cells. Correlating with these defects, we find that NT-3 expression is dramatically downregulated in granule cells of the posterior lobe of Barhl1(-)/- cerebella. Moreover, in the precerebellar system of Barhl1(-/-) mice, all five nuclei that project mossy fibers fail to form correctly because of aberrant neuronal migration and elevated apoptosis. These results suggest that Barhl1 plays an essential role in the migration and survival of cerebellar granule cells and precerebellar neurons and functionally link Barhl1 to the NT-3 signaling pathway during cerebellar development.

Animals↗
PubMed2004

A troponin switch that regulates muscle contraction by stretch instead of calcium.

The flight muscles of many insects have a form of regulation enabling them to contract at high frequencies. The muscles are activated by periodic stretches at low Ca2+ levels. The same muscles also give isometric contractions in response to higher Ca2+. We show that the two activities are controlled by different isoforms of TnC (F1 and F2) within single myofibrils. F1 binds one Ca2+ with high affinity in the C-terminal domain and F2 binds one Ca2+ in the C-terminal domain and one exchangeable Ca2+ in the N-terminal domain. We have characterised the isoforms and determined their effect on the development of stretch-activated and Ca2+-activated tension by replacing endogenous TnC in Lethocerus flight muscle fibres with recombinant isoforms. Fibres with F1 gave stretch-activated tension and minimal isometric tension; those with F2 gave Ca2+-dependent isometric tension and minimal stretch-activated tension. Regulation by a TnC responding to stretch rather than Ca2+ is unprecedented and has resulted in the ability of insect flight muscle to perform oscillatory work at low Ca2+ concentrations, a property to which a large number of flying insects owe their evolutionary success.

Actomyosin↗
PubMed2004

Structure of a hydroxyproline (Hyp)-arabinogalactan polysaccharide from repetitive Ala-Hyp expressed in transgenic Nicotiana tabacum.

A synthetic gene encoding the fusion protein (Ala-Hyp)(51)-enhanced green fluorescent protein expressed in Nicotiana tabacum cells produced a fusion glycoprotein with all proline residues hydroxylated and substituted with an arabinogalactan polysaccharide. Alkaline hydrolysis of the fusion glycoprotein yielded a population of hydroxyproline (Hyp)-arabinogalactan polysaccharides ranging in size from 13 to 26 saccharide residues/Hyp, with a median size of 15-17 residues. We isolated a 15-residue Hyp-arabinogalactan for structure determination by sugar analyses and one- and two-dimensional nuclear magnetic resonance techniques that provided the assignment of proton and carbon signals of a small polysaccharide O-linked to the hydroxyl group of Hyp. The polysaccharide consisted of a 1,3-linked beta-D-Galp backbone with a single 1,6-linked beta-D-Galp "kink." The backbone had two side chains of Galp substituted at position 3 with an arabinose di- or trisaccharide and at position 6 with glucuronic acid or rhamnosyl glucuronic acid. Energy-minimized space-filling molecular models showed hydrogen bonding within polysaccharides attached to repetitive Ala-Hyp and also between polysaccharides and the peptide backbone. Polysaccharides distorted the peptide Ramachandran angles consistent with the circular dichroic spectra of isolated (Ala-Hyp)(51) and its reversion to a polyproline II-like helix after deglycosylation. This first complete structure of a Hyp-arabinogalactan polysaccharide shows that computer-based molecular modeling of Hyp-rich glycoproteins is now feasible and supports the suggestion that small repetitive subunits comprise larger arabinogalactan polysaccharides.

Carbon↗
PubMed2004

Four new andrographolide metabolites in human urine.

Andrographolide is one of principal components of a famous traditional Chinese herbal medicine Andrographis paniculate (BURM) NEES. Four new metabolites of andrographolide were isolated from human urine. All of them were characterized as sulfate and one of them also as a cysteine S-conjugate. The structures were determined to be andrographolide-3-O-sulfate (M-1), isoandrographolide-3-O-sulfate (M-2), 14-deoxyandrographolide-3-O-sulfate (M-3), 14-deoxy-12-(cysteine-S-yl)-andrographolide-3-O-sulfate (M-4), respectively, based on chemical evidence and spectroscopic analyses.

Adult↗
PubMed2004

[Constriction effect of daidzein on guinea pig's gall bladder].

OBJECTIVE: To study the effect of daidzein on gall bladder constriction. METHODS: To study daidzein how to antagonize the gall bladder constriction of guinea pig induced by acitylcholine, histamine, excessive K+ or Ca2+. RESULTS: It has been found that daidzein could remarkedly antagonize the gall bladder constriction of guinea pig induced by acitylcholine, histamine, excessive K+, cumulation Ca2+. CONCLUSION: Daidzein could obviously antagonize gall bladder constriction in guinea pig.

Acetylcholine↗
PubMed2004

[Determination of levodropropizine and its pharmacokinetics in human plasma using LC/MS/MS].

AIM: To develop a rapid and sensitive LC/MS/MS method for the analysis of levodropropizine in plasma and study the pharmacokinetics of levodropropizine in healthy Chinese volunteers. METHODS: Levodropropizine and zolmitriptan (internal standard, IS) were extracted from plasma samples and chromatographed on a C18 column and detected using a tandem mass spectrometer with a TurboIon Spray ionization interface. Quantitation was performed using multiple reaction monitoring (MRM) of the transitions of the m/z 237 --> m/z 120 for levodropropizine and m/z 288 --> m/z 58 for the IS. RESULTS: The limit of quantification of the method for levodropropizine was 0.25 microg x L(-1). The assay was linear over the concentration range from 0.25 to 500.0 microg x L(-1) and intra- and inter-day precision over this range were < 11.4% with good accuracy. CONCLUSION: The method is shown to be accurate, and suitable for clinical pharmacokinetic study of levodropropizine.

Administration, Oral↗
PubMed2003

Troponin C in different insect muscle types: identification of two isoforms in Lethocerus, Drosophila and Anopheles that are specific to asynchronous flight muscle in the adult insect.

The indirect flight muscles (IFMs) of Lethocerus (giant water bug) and Drosophila (fruitfly) are asynchronous: oscillatory contractions are produced by periodic stretches in the presence of a Ca(2+) concentration that does not fully activate the muscle. The troponin complex on thin filaments regulates contraction in striated muscle. The complex in IFM has subunits that are specific to this muscle type, and stretch activation may act through troponin. Lethocerus and Drosophila have an unusual isoform of the Ca(2+)-binding subunit of troponin, troponin C (TnC), with a single Ca(2+)-binding site near the C-terminus (domain IV); this isoform is only in IFMs, together with a minor isoform with an additional Ca(2+)-binding site in the N-terminal region (domain II). Lethocerus has another TnC isoform in leg muscle which also has two Ca(2+)-binding sites. Ca(2+) binds more strongly to domain IV than to domain II in two-site isoforms. There are four isoforms in Drosophila and Anopheles (malarial mosquito), three of which are also in adult Lethocerus. A larval isoform has not been identified in Lethocerus. Different TnC isoforms are expressed in the embryonic, larval, pupal and adult stages of Drosophila; the expression of the two IFM isoforms is increased in the pupal stage. Immunoelectron microscopy shows the distribution of the major IFM isoform with one Ca(2+)-binding site is uniform along Lethocerus thin filaments. We suggest that initial activation of IFM is by Ca(2+) binding to troponin with the two-site TnC, and full activation is through the action of stretch on the complex with the one-site isoform.

Amino Acid Sequence↗