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Biomedical subjects

Feng Chen

Publications and source records attributed to Feng Chen.

At least 199 records · Page 11Linked to original sources
PubMed2003

Separation and determination of the antitumor drug piritrexim by molecularly imprinted microspheres in high-performance liquid chromatography.

Molecularly imprinted microspheres were synthesised using the antitumor drug piritrexim (PTX) as a template molecule by aqueous microsuspension polymerisation and were used as a high-performance liquid chromatographic stationary phase. The molecularly imprinted column exhibited strong retention behaviour to the template molecule. The influences of pH of the buffer and the ratio of methanol to buffer on the retention behaviour were investigated in detail. Results indicated that the baseline separation of PTX, trimetrexate (TMX), trimethoprim (TMP) and sulfamethazine (SMZ) was achieved when the pH value of the acetate buffer was above pH 3.5 and the ratio of methanol to the buffer was 6:4 (v/v). A gradient elution programme was employed to enhance the separation, which led to an improvement in sensitivity and a reduction in determination errors. The method developed was used to analyse urine samples supplemented with PTX. The recoveries of 5 microg mL(-1) PTX in the urine sample were 99.1+/-3.0% and 93.3+/-2.8% at the beginning and 24 h later, respectively.

Animals↗
PubMed2003

The effects of antidepressant treatment on serotonergic and dopaminergic systems in Fawn-Hooded rats: a quantitative autoradiography study.

Fawn-Hooded (FH) rats exhibit a phenotype including depressive behaviour and high alcohol preference, and as such tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs) reduce alcohol consumption in this rat strain [Psychiatr. Genet. 12 (2002) 1-16]. However, the neurochemical effects of these antidepressants on monoamine systems in the brain, especially in mesolimbic areas have not been studied in FH rats. Therefore, the present study investigated neurochemical effects of subchronic treatment (10 days) with desipramine (DMI) and sertraline on several neurochemical markers of serotonin and dopamine systems. Binding to these markers including dopamine transporters (DATs), 5-HT transporters (SERTs), 5-HT(1A)- and 5-HT(2A)-receptors in rat brain sections was performed by quantitative autoradiography. The findings from the present study revealed that DMI and sertraline exhibited differential effects on SERTs and DATs in FH rat brain. For example, DMI caused a dramatic up-regulation of DATs whereas sertraline had no effect on DAT binding. In addition, both antidepressants showed some common and some differential effects on the binding to 5-HT(1A)- and 5-HT(2A)-receptors dependent upon region. These data demonstrate that DMI and sertraline differentially effect serotonergic and dopaminergic systems in mesolimbic regions in FH rats, suggesting that there may be different neurochemical mechanisms underlying their efficacy to reduce ethanol consumption in this animal model.

Animals↗
PubMed2003

Aggregate manganese Schiff base moieties by terephthalate or acetate: dinuclear manganese and trinuclear mixed metal Mn2/Na complexes.

A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(H(2)O) (3), and (salen)(2)Mn(2)(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH(3)OH)(NO(3)) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H[Mn(2)Na(salpn)(2)(mu-OAc)(2)(H(2)O)(2)](OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. (1)H NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/-0.12V has been assigned to the redox of Mn(2)(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.

Journal Article↗
PubMed2003

Preparative separation and purification of squalene from the microalga Thraustochytrium ATCC 26185 by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) was successfully applied to the preparative separation and purification of squalene from microalgae. Crude squalene was obtained from the microalga Thraustochytrium ATCC 26185 by extraction with organic solvents. The crude squalene was further separated using a waterless two-phase solvent system composed of n-hexane-methanol (2:1, v/v). The upper phase as the mobile phase was pumped into the column at a flow-rate of 2.0 ml min(-1) in the tail-to-head elution mode. The fractions purified and collected were analyzed by high-performance liquid chromatography. The method yielded 0.2 mg squalene at 96% purity from 150 mg of the crude squalene (0.14% squalene) with 95% recovery. The separation of squalene by HSCCC was completed in 90 min.

Countercurrent Distribution↗
PubMed2003

Seasonal variations of bromophenols in brown algae (Padina arborescens, Sargassum siliquastrum, and Lobophora variegata) collected in Hong Kong.

Distributions and seasonal variations of the key seafood flavor compounds including 2-bromophenol, 4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,6-tribromophenol in three species of brown algae (Padina arborescens, Sargassum siliquastrum, and Lobophora variegata) found in Hong Kong waters were investigated. Bromophenols were extracted by simultaneous steam distillation and solvent extraction apparatus and analyzed by gas chromatography-mass spectrometry. On a dried weight basis, the total bromophenol content (TBC) determined varied widely with seasons (from 40.9 to 7030 ng/g). The TBCs detected were higher in winter and lower in summer. Except for 2-bromophenol, the rest of the bromophenols were detected in all of the algal samples. The TBC of L. variegata was generally the highest among all of the algae collected. Relatively high concentrations of bromophenols in algae supported the fact that marine algae were major producers of bromophenols in the marine environment.

Flavoring Agents↗
PubMed2003

Increased anxiety 3 months after brief exposure to MDMA ("Ecstasy") in rats: association with altered 5-HT transporter and receptor density.

Male Wistar rats were treated with 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy") using either a high dose (4 x 5 mg/kg over 4 h) or low dose (1 x 5 mg/kg over 4 h) regimen on each of 2 consecutive days. After 10 weeks, rats were tested in the social interaction and emergence tests of anxiety. Rats previously given either of the MDMA dose regimens were significantly more anxious on both tests. After behavioral testing, and 3 months after the MDMA treatment, the rats were killed and their brains examined. Rats given the high-, but not the low-, dose MDMA treatment regimen exhibited significant loss of 5-hydroxytryptamine (5-HT) and 5-HIAA in the amygdala, hippocampus, striatum, and cortex. Quantitative autoradiography showed loss of SERT binding in cortical, hippocampal, thalamic, and hypothalamic sites with the high-dose MDMA regime, while low-dose MDMA only produced significant loss in the medial hypothalamus. Neither high- nor low-dose MDMA affected 5HT(1A) receptor density. High-dose MDMA increased 5HT(1B) receptor density in the nucleus accumbens and lateral septum but decreased binding in the globus pallidus, insular cortex and medial thalamus. Low-dose MDMA decreased 5HT(1B) receptor density in the hippocampus, globus pallidus, and medial thalamus. High-dose MDMA caused dramatic decreases in cortical, striatal, thalamic, and hypothalamic 5HT(2A)/(2C) receptor density, while low-dose MDMA tended to produce similar effects but only significantly in the piriform cortex. These data suggest that even brief, relatively low-dose MDMA exposure can produce significant, long-term changes in 5-HT receptor and transporter function and associated emotional behavior. Interestingly, long-term 5-HT depletion may not be necessary to produce lasting effects on anxiety-like behavior after low-dose MDMA.

Animals↗
PubMed2003

Autoradiographic quantification of neurochemical markers of serotonin, dopamine and opioid systems in rat brain mesolimbic regions following chronic St John's wort treatment.

Effects of chronic treatment with St John's wort (SJW, Hypericum perforatum) on neurochemical markers of serotonin, dopamine and opioid systems in mesolimbic regions of the fawn-hooded rat were investigated by quantitative autoradiography. After 10 days' treatment, SJW significantly increased [(3)H]citalopram binding to 5-HT transporters in multiple mesolimbic regions. In contrast, SJW resulted in a region-specific alteration of [(3)H]mazindol binding to dopamine transporters, such as increased binding of [(3)H]mazindol in the olfactory tubercle and decreased binding in the ventral tegmental area. In addition, SJW also resulted in differential modulation of the binding properties of 5-HT(1A)-, 5-HT(2A)- and mu-opioid receptors in a region-specific manner. The ability of SJW to affect 5-HT, dopamine and opioid systems in mesolimbic regions in the CNS, either by a direct or by indirect (adaptation) mechanism, may help to explain the efficacy of SJW in the treatment of depression clinically and in some of the behavioural effects observed in experimental rodents.

Animals↗
PubMed2003

Differentiation of Nostoc flagelliforme and its neighboring species using fatty-acid profiling as a chemotaxonomic tool.

In this study, fatty-acid content and patterns were analyzed in order to distinguish Nostoc flagelliforme, an edible terrestrial cyanobacterium, from other Nostoc species and representatives typical of its close neighbors (genera Anabaena, Microcystis, and Synechococcus). According to the Kenyon-Murata classification system, all the Nostoc species were assigned to Group II due to the presence of C18:2n3 and C18:3n3, and the absence of C18:3n6. Hierarchical cluster analysis was also employed to separate N. flagelliforme and other Nostoc species or strains. A dendrogram calculation of all fatty-acid components manifested phenetic characteristics, showing that the degree of relatedness of two strains of N. flagelliforme aggregated them within a small subgroup. Another dendrogram, calculated from seven comprehensive parameters (including ratios of different fatty-acid categories, degree of fatty-acid unsaturation, etc.), also clearly delimited the minute difference in fatty-acid profiles between the tested organisms. Our results suggest that profiling fatty acids could be a useful approach in the taxonomic or phylogenetic study of the genus Nostoc and might serve as a valuable supplement to the current morphology-based classification system.

Anabaena↗
PubMed2003

Mutational analysis of the transforming growth factor beta receptor type I gene in primary non-small cell lung cancer.

Transforming growth factor-beta receptor-dependent signals are critical for cell growth and differentiation and are often disrupted during tumorigenesis. The entire coding region of TGFbetaRI and flanking intron sequences from 53 primary non-small cell lung cancer (NSCLC) tissues were examined for alterations using SSCP and direct sequencing. No somatic point mutations other than two silent mutations and a polymorphism were found in the TGFbetaRI gene. The two silent mutations located at codon 344 (AAT to AAC) and codon 406 (TTA to CTA), respectively, and the polymorphism was at the 24th base of intron 7 (G to A). To investigate whether the presence of this polymorphism is associated with NSCLC, we determined its allele distribution in all the 53 carcinomas and 89 normal controls. Interestingly, we found that the subjects with homozygous genotype A/A displayed more than 3-fold increased risk of developing NSCLC than the common wild genotype G/G. As the first report, the present study showed that TGFbetaRI gene is not a frequent site of spontaneous mutational inactivation while the detected polymorphism is frequent in the pathogenesis of NSCLC.

Activin Receptors, Type I↗
PubMed2003

Impact of flexor digitorum superficialis on gliding function of the flexor digitorum profundus according to regions in zone II.

PURPOSE: Structures and gliding characteristics of the flexor tendons vary remarkably according to regions of zone II in the hand. We studied the impact of the flexor digitorum superficialis (FDS) on the work of flexion and excursion efficiency of the flexor digitorum profundus (FDP) tendon in different regions of zone II. METHODS: Twenty-one fresh-frozen human fingers were used as an experimental model. The FDP was pulled to flex the finger with a tensile machine. The work of flexion of the finger and gliding excursion of the tendon were recorded in the fingers with the FDS intact, after excision of the FDS proximal to, under, or distal to the A2 pulley. RESULTS: The FDS tendon exerts notably different effects on the work of flexion and excursion efficiency of the FDP in subregions of zone II. Removal of the FDS under the A2 pulley affected the FDP most manifestly, causing a 12% decrease in the work of flexion and a loss of the excursion efficiency at the metacarpophalangeal joint. Removal of the FDS proximal to the A2 pulley had a less notable effect on the work of flexion. Removal of the FDS distal to the pulley did not markedly alter the biomechanics of the FDP. CONCLUSIONS: Removal of the FDS tendon in the area of the A2 pulley reduces the work of flexion most notably and causes a loss of excursion efficiency. Removal of the FDS tendon distal to the A2 pulley does not change the work of flexion, and removal of the FDS tendon proximal to the A2 pulley has a notable but less pronounced effect on the FDP tendon.

Aged↗
PubMed2003

Heterotrophic production of eicosapentaenoic acid by microalgae.

Eicosapentaenoic acid (EPA) is an omega-3 polyunsaturated fatty acid that plays an important role in the regulation of biological functions and prevention and treatment of a number of human diseases such as heart and inflammatory diseases. As fish oil fails to meet the increasing demand for purified EPA, alternative sources are being sought. Microalgae contain large quantities of high-quality EPA and they are considered a potential source of this important fatty acid. Some microalgae can be grown heterotrophically on cheap organic substrate without light. This mode of cultivation can be well controlled and provides the possibility to maximize EPA production on a large scale. Numerous strategies have been investigated for commercial production of EPA by microalgae. These include screening of high EPA-yielding microalgal strains, improvement of strains by genetic manipulation, optimization of culture conditions, and development of efficient cultivation systems. This paper reviews recent advances in heterotrophic production of EPA by microalgae with an emphasis on the use of diatoms as producing organisms.

Bioreactors↗
PubMed2003

An Arabidopsis thaliana gene for methylsalicylate biosynthesis, identified by a biochemical genomics approach, has a role in defense.

Emission of methylsalicylate (MeSA), and occasionally of methylbenzoate (MeBA), from Arabidopsis thaliana leaves was detected following the application of some forms of both biotic and abiotic stresses to the plant. Maximal emission of MeSA was observed following alamethicin treatment of leaves. A gene (AtBSMT1) encoding a protein with both benzoic acid (BA) and salicylic acid (SA) carboxyl methyltransferase activities was identified using a biochemical genomics approach. Its ortholog (AlBSMT1) in A. lyrata, a close relative of A. thaliana, was also isolated. The AtBSMT1 protein utilizes SA more efficiently than BA, whereas AlBSMT1 catalyzes the methylation of SA less effectively than that of BA. The AtBSMT1 and AlBSMT1 genes showed expression in leaves under normal growth conditions and were more highly expressed in the flowers. In A. thaliana leaves, the expression of AtBSMT1 was induced by alamethicin, Plutella xylostella herbivory, uprooting, physical wounding, and methyl jasmonate. SA was not an effective inducer. Using a beta-glucuronidase (GUS) reporter approach, the promoter activity of AtBSMT1 was localized to the sepals of flowers, and also to leaf trichomes and hydathodes. Upon thrip damage to leaves, AtBSMT1 promoter activity was induced specifically around the lesions.

Amino Acid Sequence↗
PubMed2003

Biosynthesis and emission of terpenoid volatiles from Arabidopsis flowers.

Arabidopsis is believed to be mostly self-pollinated, although several lines of genetic and morphological evidence indicate that insect-mediated outcrossing occurs with at least a low frequency in wild populations. Here, we show that Arabidopsis flowers emit both monoterpenes and sesquiterpenes, potential olfactory cues for pollinating insects. Of the 32 terpene synthase genes in the Arabidopsis genome, 20 were found to be expressed in flowers, 6 of these exclusively or almost exclusively so. Two terpene synthase genes expressed exclusively in the flowers and one terpene synthase gene expressed almost exclusively in the flowers were characterized and found to encode proteins that catalyze the formation of major floral volatiles. A beta-glucuronidase fusion construct with a promoter of one of these genes demonstrated that gene expression was restricted to the sepals, stigmas, anther filaments, and receptacles, reaching a peak when the stigma was receptive to cross pollen. The observation that Arabidopsis flowers synthesize and emit volatiles raises intriguing questions about the reproductive behavior of Arabidopsis in the wild and allows detailed investigations of floral volatile biosynthesis and its regulation to be performed with this model plant system.

Alkyl and Aryl Transferases↗
PubMed2003

[Influence of cervical curvature change on the nerve root and vertebral artery of patients with cervical spondylosis and clinical observation of manipulation treatment].

OBJECTIVE: To observe the influence of the change of cervical curvature on the nerve root and the vertebral artery of the patients with cervical spondylosis and the curative effect of therapeutic manipulations. METHODS: Sixty cases of cervical spondylosis with the change of cervical curvature, 60 cases of cervical spondylosis without the change of cervical curvature and 60 normal people were chosen. They were clinically observed and the cervical spondylosis was treated by manipulations and the data was processed according to the principle of statistics. RESULTS: The change of cervical curvature affected the nerve root and the vertebral artery and therapeutic manipulations produced a satisfactory curative effect. CONCLUSION: Cervical spondylosis with change of cervical curvature has special characteristics in the etiology, course and state of the disease. The change of cervical curvature produces an effect on the nerve root and the vertebral artery. Selected therapeutic manipulations produce a better curative effect.

Adult↗
PubMed2003

Distribution and anti-HBV effects of antisense oligodeoxynucleotides conjugated to galactosylated poly-L-lysine.

AIM: To describe distribution of the phosphorothioated antisense oligodeoxynucleotides (PS-asODNs) conjugated to galactosylated poly-L-lysine (Gal-PLL) in mice, and to observe their effects on expression of HBV gene in the 2.2.15 cells and transgenic mice. METHODS: According to the result of direct sequencing of PCR amplified products, a 16 mer phosphorothioate analogue of the antisense oligodeoxynucleotides (PS-asODNs) directed against the HBV U(5)-like region was conjugated to the hepatotropic Gal-PLL molecules. Its distribution was demonstrated using asODNs labeled with (32)P at the 5' terminus with a T4-polynucleotide Kinase. Its inhibition effect on HBV expression was observed in the transfected 2.2.15 cells and transgenic mice. RESULTS: The Gal-PLL and asODNs could form stable complex at a molar ratio of 2:1. As shown in the HBV-transfected 2.2.15 cells, the inhibition effects of asODNs alone and asODNs conjugated to Gal-PLL, at 10 micromol/L for both, on HBsAg and HBeAg production were different,the former being 70 % and 58 %, respectively, and the latter being 96 % and 82 %, respectively. A more pronounced reduction was also observed in viral DNA load in the culture supernatant for the test with Gal-PLL-asODNs. Among many mouse organs, livers retained more asODNs molecules after administration. The preferential concentration in liver was found to be 52.14 % for Gal-PLL-asODNs, as high as 2.38-fold of that for asODNs (21.9 %). Both elements decreased gradually in liver, with 2.9 % of the former, 5.99 % of the latter retained 24 hours after the administration. The injection interval, therefore, was recommended to be 24 hours. In the transgenic mice, serum HBsAg decreased significantly (P<0.01) at the 12th day after administrating Gal-PLL- asODNs, the serum HBV DNA turned negative in 4 of the 6 mice. CONCLUSION: Antisense oligodeoxynucleotides conjugated to Gal-PLL can be concentrated in liver and intaked by hepatocytic cells. This may result in specific inhibition of expression and replication of HBV in vitro and in vivo.

Animals↗
PubMed2003

Spiral CT in gastric carcinoma: comparison with barium study, fiberoptic gastroscopy and histopathology.

AIM: To evaluate spiral computed tomography (CT) including virtual gastroscopy for diagnosis of gastric carcinoma in comparison with upper gastrointestinal series (UGI), fiberoptic gastroscopy (FG) and histopathology. METHODS: Sixty patients with histologically proven gastric carcinoma (54 advanced and 6 early) were included in this study. The results of spiral CT were compared with those of UGI and FG. Two observers blindly evaluated images of spiral CT and UGI and video recording of FG with consensus in terms of diagnostic confidence with a five-point scale. Sensitivities of lesion detection, Borrmann's classification of spiral CT, UGI and FG, as well as the accuracy of TNM staging of spiral CT were determined by comparing them to surgical and histological findings. RESULTS: The lesion detection rate was 98 % (59/60), 95 % (57/60) and 98 % (59/60) for spiral CT, UGI and FG, respectively. There were no statistical differences in the detection sensitivity among the three techniques (P>0.05). For the sensitivity in Borrmann's classification, spiral CT was higher than that of UGI (P=0.025) and similar to that of FG (P>0.05). The accuracy of spiral CT in staging the gastric carcinoma was 76.7 %. Six cases of early gastric carcinoma were all detected by spiral CT as well as FG. CONCLUSION: Spiral CT is equivalent to UGI and FG in the detection of gastric carcinoma, and superior to UGI but similar to FG in the Borrmann's classification of advanced gastric carcinoma. Spiral CT is more valuable than FG in the staging of gastric carcinoma.

Adult↗