Biomedical subjects

C F Chen

Publications and source records attributed to C F Chen.

At least 127 records · Page 7Linked to original sources

PubMed1999

Preliminary validation of tumor cell attachment inhibition assay for developmental toxicants with mouse S180 cells.

This study was designed to explore the possibility of using ascitic mouse sarcoma cell line (S180) to validate the mouse tumor cell attachment assay for developmental toxicants, and to test the inhibitory effects of various developmental toxicants. The results showed that 2 of 3 developmental toxicants under consideration, sodium pentobarbital and ethanol, significantly inhibited S180 cells attachment to Concanavalin A-coated surfaces. Inhibition was dependent on concentration, and the IC50 (the concentration that reduced attachment by 50%), of these 2 chemicals was 1.2 x 10(-3) mol/L and 1.0 mol/L, respectively. Another developmental toxicant, hydrocortisone, did not show inhibitory activity. Two non-developmental toxicants, sodium chloride and glycine were also tested and these did not decrease attachment rates. The main results reported here were generally similar to those obtained with ascitic mouse ovarian tumor cells as a model. Therefore, this study added further evidence to the conclusion that cell specificity does not limit attachment inhibition to Con A-coated surfaces, so S180 cell may serve as an alternative cell model, especially when other cell lines are unavailable. Furthermore, after optimal validation, it can be suggested that an S180 cell attachment assay may be a candidate for a series of assays to detect developmental toxicants.

Animals↗

PubMed1998

On-line microdialysis coupled with microbore liquid chromatography for the determination of unbound chloramphenicol and its glucuronide in rat blood.

On-line microdialysis coupled with microbore liquid chromatography was used to investigate the pharmacokinetics of chloramphenicol and its glucuronide in rat blood. A microdialysis probe was inserted into a jugular vein of male Sprague-Dawley rats. Chloramphenicol succinate (20 mg/kg, intravenously) was then administered via a femoral vein. Dialysates were automatically injected onto a LC system, via an on-line injector. Samples were eluted with a mobile phase containing acetonitrile-10 mM monochloroacetic acid (30:70, v/v, pH 3.0). The UV detector wavelength was set at 278 nm. The limit of quantitation for chloramphenicol was 10 ng/ml. The in vitro recoveries of chloramphenicol and chloramphenicol glucuronide at 500 ng/ml were 32.2+/-0.3% and 11.4+/-0.7%, respectively (n = 6). Intra- and inter-assay accuracy and precision of the analyses were < or =10% in the range of 0.01 to 5.0 microg/ml.

Animals↗

PubMed1998

Simultaneous measurement of blood and brain microdialysates of granisetron in rat by high-performance liquid chromatography with fluorescence detection.

Simultaneous microdialysis probes in the blood and brain and sensitive high-performance liquid chromatography with fluorescence detection were used to examine the granisetron concentration in the jugular vein and frontal cortex of rats after drug administration. Two microdialysis probes were inserted into the right jugular vein and frontal cortex of male Sprague-Dawley rats to which granisetron (6 mg/kg, i.v.) had been administered. Dialysates were automatically collected using a microfraction collector. Samples were eluted with a mobile phase containing 25 mM acetate buffer (pH 4.8)-acetonitrile (72:28, v/v). Excitation and emission wavelengths were set at 305 and 360 nm, respectively, on a scanning fluorescence detector. The limit of quantification for granisetron was 0.5 ng/ml. The in vitro recovery of granisetron was 29.7+/-1.2% (n=6) for the jugular vein microdialysis probe and 6.1+/-0.5% (n=6) for the frontal cortex microdialysis probe. The increasing brain/blood concentration ratio of granisetron suggests that granisetron penetrates the blood-brain barrier.

Animals↗

PubMed1998

Determination of naringenin and its glucuronide conjugate in rat plasma and brain tissue by high-performance liquid chromatography.

An isocratic high-performance liquid chromatographic method with ultraviolet detection was utilized for the investigation of the pharmacokinetics of naringenin and its glucuronide conjugate in rat plasma and brain tissue. Plasma and brain tissue were deproteinized by acetonitrile, then centrifuged for sample clean-up. The drugs were separated by a reversed-phase C18 column with a mobile phase consisting of acetonitrile-orthophosphoric acid solution (pH 2.5-2.8) (36:64, v/v). The detection limits of naringenin in rat plasma and brain tissue were 50 ng/ml and 0.4 microg/g, respectively. The glucuronide conjugate of naringenin was evaluated by the deconjugated enzyme beta-glucuronidase. The naringenin conjugation ratios in rat plasma and brain tissue were 0.86 and 0.22, respectively, 10 min after naringenin (20 mg/kg, i.v.) administration. The mean naringenin conjugation ratio in plasma was approximately four fold that in brain tissue.

Animals↗

PubMed1998

Tyrosine kinase inhibitors, emodin and its derivative repress HER-2/neu-induced cellular transformation and metastasis-associated properties.

We have previously shown that emodin suppresses tyrosine kinase activity of HER-2/neu-encoded p185neu receptor tyrosine kinase. In this study, we examine the relationship between the chemical structure and the activity of emodin and nine derivatives, and identified that one methyl, one hydroxy, and one carbonyl functional groups are critical for the biological activities of emodin. We also found that one of the derivatives 10-(4-acetamidobenzylidene)-9-anthrone (DK-V-47) is more effective than emodin in repressing the tyrosine phosphorylation of p185neu and in inhibiting the proliferation and transformation of HER-2/neu-overexpressing human breast cancer cells. Using mutation-activated HER-2/neu transformed 3T3 cells, we also investigated whether emodin and DK-V-47 can inhibit malignant transformation induced solely by the HER-2/neu oncogene. We found that DK-V-47 is more potent than emodin in suppressing transformation phenotypes of activated HER-2/neu transformed 3T3 cells including anchorage-dependent and -independent growth, metastasis-associated properties. These results clearly indicate that the inhibition of p185neu tyrosine kinase by both emodin and DK-V-47 is capable of suppressing the HER-2/neu associated transformed phenotypes including the ability to induce metastatic potential. Our results also support the chemotherapeutic implications of the use of either emodin or DK-V-47 to target HER-2/neu-overexpressing cancer cells.

3T3 Cells↗

PubMed1998

Low and high frequency electroacupuncture at Hoku elicits a distinct mechanism to activate sympathetic nervous system in anesthetized rats.

To address the effect of electroacupuncture (Ea) on autonomic nerve activity, the responses of rhythmic micturition contraction (RMC), urine excretion (UE), blood pressure (BP), renal sympathetic nerve activity (RNA) and pelvic parasympathetic nerve activity (PNA) to Ea were investigated in urethane-anesthetized rats. The acupoint Hoku (Li-4) was tested with two different stimulation frequencies (2 Hz and 20 Hz). Elongation of the RMC cycle and an increase in UE associated with the elevation of BP and RNA was elicited during Ea at Hoku. However, the pressor response induced by low frequency Ea (LFEa) was different from that by high frequency Ea (HFEa), i.e. a tonic effect was elicited by LFEa, while a phasic one was induced by HFEa. These results imply that: (1) Ea at Hoku may selectively activate the sympathetic, but not the parasympathetic nervous system, (2) Ea at Hoku with a different stimulation frequency may elicit a distinct mechanism to activate the sympathetic nervous system and (3) Ea at Hoku may ameliorate the hyperactive bladder in clinical therapy.

Acupuncture Points↗

PubMed1998

The BRC repeats in BRCA2 are critical for RAD51 binding and resistance to methyl methanesulfonate treatment.

The BRCA2 gene was identified based on its involvement in familial breast cancer. The analysis of its sequence predicts that the gene encodes a protein with 3,418 amino acids but provides very few clues pointing to its biological function. In an attempt to address this question, specific antibodies were prepared that identified the gene product of BRCA2 as a 390-kDa nuclear protein. Furthermore, direct binding of human RAD51 to each of the four single 30-amino acid BRC repeats located at the 5' portion of exon 11 of BRCA2 was demonstrated. Such an interaction is significant, as BRCA2 and RAD51 can be reciprocally coimmunoprecipitated by each of the individual, specific antibodies and form complexes in vivo. Inferring from the function of RAD51 in DNA repair, human pancreatic cancer cells, Capan-1, expressing truncated BRCA2 were shown to be hypersensitive to methyl methanesulfonate (MMS) treatment. Exogenous expression of wild-type BRCA2, but not BRC-deleted mutants, in Capan-1 cells confers resistance to MMS treatment. These results suggest that the interaction between the BRC repeats of BRCA2 and RAD51 is critical for cellular response to DNA damage caused by MMS.

BRCA2 Protein↗

PubMed1998

Characterization of the antiplatelet effects of (2S)-5-methoxy-6-methylflavan-7-ol from Draconis Resina.

(2S)-5-methoxy-6-methylflavan-7-ol (MMF) was purified from Draconis Resina and its in vitro effects on various aspects of platelet reactivity were examined. Results indicated that MMF dose dependently inhibited aggregation of washed rabbit platelets induced by collagen, arachidonic acid, ADP, U46619 or platelet-activating factor (PAF), with IC50) values of 17.2, 49.8, 179.8, 109.6, and 189.2 microM, respectively. Concomitantly, MMF also dose dependently suppressed ATP release by platelets activated by these stimulants. The increase in intracellular free calcium ([Ca2+]i), elicited by these activating agents, was inhibited by MMF as reflected by fura-2 fluorescence measurements. However, MMF had no effects on the cyclic AMP level of platelets. In addition, MMF inhibited the arachidonic acid-induced thromboxane B2 and prostaglandin D2 formation in intact platelet suspensions or homogenized platelet lysates. This study provided evidence that MMF is an antiplatelet agent whose activity is likely related to cyclooxygenase inhibition and suppression of [Ca2+]i increase.

Adenosine Triphosphate↗

PubMed1998

Identification of a novel cytoplasmic protein that specifically binds to nuclear localization signal motifs.

Active transport of proteins into the nucleus is mediated by interaction between the classical nuclear localization signals (NLSs) of the targeted proteins and the NLS receptor (importin) complex. This nuclear transport system is highly regulated and conserved in eukaryotes and is essential for cell survival. Using a fragment of BRCA1 containing the two NLS motifs as a bait for yeast two-hybrid screening, we have isolated four clones, one of which is importin alpha. Here we characterize one of the other clones identified, BRAP2, which is a novel gene and expressed as a 2-kilobase mRNA in human mammary epithelial cells and some but not all tissues of mice. The isolated full-length cDNA encodes a novel protein containing 600 amino acid residues with pI 6.04. Characteristic motifs of C2H2 zinc fingers and leucine heptad repeats are present in the middle and C-terminal regions of the protein, respectively. BRAP2 also shares significant homology with a hypothetical protein from yeast Saccharomyces cerevisiae, especially in the zinc finger region. Antibodies prepared against the C-terminal region of BRAP2 fused to glutathione S-transferase specifically recognize a cellular protein with a molecular size of 68 kDa, consistent with the size of the in vitro translated protein. Cellular BRAP2 is mainly cytoplasmic and binds to the NLS motifs of BRCA1 with similar specificity to that of importin alpha in both two-hybrid assays in yeast and glutathione S-transferase pull-down assays in vitro. Other motifs such as the SV40 large T antigen NLS motif and the bipartite NLS motif found in mitosin are also recognized by BRAP2. Similarly, the yeast homolog of BRAP2 also binds to these NLS motifs in vitro. These results imply that BRAP2 may function as a cytoplasmic retention protein and play a role in regulating transport of nuclear proteins.

Amino Acid Sequence↗

PubMed1998

Magnolol inhibits Mac-1 (CD11b/CD18)-dependent neutrophil adhesion: relationship with its antioxidant effect.

Magnolol, a phenolic compound isolated from a Chinese herbal drug, Magnolia officinalis, has been shown to protect rat heart from ischemia/reperfusion injury. Neutrophil adhesion plays a crucial process during this inflammatory response. To evaluate whether magnolol prevents ischemia/reperfusion injury by inhibiting neutrophil adhesion, we determined whether magnolol can inhibit adhesion of phorbol-12-myristate-13-acetate (PMA)-activated human neutrophils to a fibrinogen-coated surface in a dose-dependent manner. Using flow cytometric analysis, we observed that magnolol pretreatment (10 min at 37 degrees C) diminished PMA (100 ng/ml)-induced Mac-1 upregulation. PMA also induced rapid intracellular accumulation of superoxide (O2-.) and hydrogen peroxide (H2O2) in neutrophils; magnolol pretreatment attenuated the accumulation of these two substances. Inhibition of reactive oxygen species by superoxide dismutase and/or catalase, which decompose O2-. and H2O2, respectively, also abolished Mac-1 upregulation and neutrophil adhesion. We conclude that magnolol inhibits neutrophil adhesion and that this can account for its anti-ischemia/reperfusion injury effect. We propose that the inhibitory effect of magnolol on neutrophil adhesion to the extracellular matrix is mediated, at least in part, by inhibition of the accumulation of reactive oxygen species, which in turn suppresses the upregulation of Mac-1 that is essential for neutrophil adhesion.

Adult↗

PubMed1998

Effects of methanol extract of Chansu on hypothalamic-pituitary-testis function in rats.

Chansu, a galenical preparation of the dried white venom of Chinese Bufo bufo gargarizans, is one of the major components of Kyushin, a traditional Chinese medicine. Kyushin is reported to have a cardiotonic effect that has been suggested to be due to the action of bufadienolides such as bufalin and cinobufagin. Recently, we found that administration of bufalin in male rats diminished the luteinizing hormone (LH) response to gonadotropin-releasing hormone (GnRH) and the secretion of testosterone both in vivo and in vitro. These observations suggest that Chansu may possess hypogonadal effects in male rats. In the present study, the effects of the methanol extract of Chansu on hypothalamic-pituitary-testicular function in male rats were examined. Crude Chansu was extracted by methanol and purified by a Sep-Pak C18 column. No activity of bufalin, cinobufagin, estradiol, or digoxin in purified methanol extract was detected; all Chansu used in this study was the purified methanol extract. A single intravenous injection of Chansu resulted in a decrease of the basal (20% to 55%) and human chorionic gonadotropin (hCG)-induced (35% to 40%) levels of plasma testosterone and the GnRH-induced level of plasma LH (25% to 30%). Administration of Chansu in vitro decreased basal and hCG-stimulated testosterone production by 60% to 70% and 40% to 60%, respectively, as well as spontaneous and forskolin- or 3-isobutyl-1-methylxanthine (IBMX)-induced accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) by 30% to 45% in rat testicular interstitial cells. Although LH release by rat anterior pituitary glands was diminished, GnRH release by the rat mediobasal hypothalamus was enhanced by administration of Chansu in vitro. These results suggest that the bufalin-free extracts of Chansu inhibit testosterone secretion in rats, in part, due to (1) a decreased production of testicular cAMP, (2) a decreased response of testosterone to gonadotropin, and (3) a reduction of the LH response to GnRH.

Animals↗

PubMed1998

Central inhibitory effects of water extract of Acori graminei rhizoma in mice.

The present study evaluated in mice the central inhibitory effects of a water extract of shichangpu (Acori graminei rhizoma (AGR), the dry rhizome of Acorus gramineus Soland. (Araceae)). AGR (0.5-5.0 g/kg) dose-dependently decreased the locomotor activity and increased the pentobarbital-induced sleeping time, but had no significant effect on the treadmill performance. AGR also dose-dependently inhibited the intensity of apomorphine-induced stereotypic behavior. At the highest dose (5.0 g/kg), AGR had a weak anticonvulsant effect on the pentylenetetrazol-induced seizures. Receptor binding assays showed that AGR competed with [3H]SCH-23390 and [3H]YM-09151-2 for specific binding to striatal dopamine D1 and D2 receptors with Ki values of 5.6 and 4.2 mg/ml, respectively. AGR also competed with [3H]muscimol for specific binding to the gamma-aminobutyric acid (GABA) binding site of cortex GABA(A) receptors with a Ki value of 0.31 mg/ml. It also increased the specific binding of [3H]flunitrazepam to the benzodiazepine binding site of the GABA(A) receptors, suggesting a GABA agonist-like action. These results suggested that the central inhibitory effects of AGR were probably effected through an action on the central dopamine receptors and GABA(A) receptors. The principle of AGR acting at these ligand binding sites was not alpha-asarone, one of the important principles of AGR, since that alpha-asarone (10(-6)-10(-4) M) had no significant interactions with these binding sites.

Animals↗

PubMed1998

Andrographolide suppresses the expression of inducible nitric oxide synthase in macrophage and restores the vasoconstriction in rat aorta treated with lipopolysaccharide.

1. We investigated whether andrographolide, a diterpenoid lactone found at Andrographis paniculata, influences the induction of the inducible nitric oxide synthase (iNOS) in RAW264.7 cells activated by bacterial endotoxin (LPS), as well as in the rats with endotoxic shock and in aortic rings treated with LPS. 2. Incubation of RAW264.7 cells with andrographolide (1 to 50 microM) inhibited the LPS (1 microg ml(-1))-induced nitrite accumulation in concentration- and time-dependent manners. Maximum inhibition was observed when andrographolide was added together with LPS and decreased progressively as the interval between andrographolide and LPS was increased to 20 h. 3. Western blot analysis demonstrated that iNOS expression was markedly attenuated in the presence of andrographolide for 6-24 h, suggesting that andrographolide inhibited iNOS protein induction. 4. Thoracic aorta incubation with LPS (300 ng ml(-1)) for 5 h in vitro exhibited a significant decrease in the maximal contractile response to phenylephrine (10(-9)-10(-5) M). Andrographolide (30 microM) restored the contractile response to control level. 5. In anaesthetized rats, LPS (10 mg kg(-1), i.v.) caused a fall in mean arterial blood pressure (MAP) from 116+/-4 to 77+/-5mmHg. The pressor effect of phenylephrine (10 microg ml(-1), i.v.) was also significantly reduced at 30, 60, 120 and 180 min after LPS injection. In contrast, animals pretreated with andrographolide (1 mg kg(-1), i.v., 20 min prior to LPS) maintained a significantly higher MAP when compared to LPS-rats given with vehicle. Administration of andrographolide 60 min after LPS caused a increase in MAP and significantly reversed the reduction of the pressor response to phenylephrine. 6. Our results indicated that andrographolide inhibits nitrite synthesis by suppressing expression of iNOS protein in vitro. And, this inhibition of iNOS synthesis may contribute to the beneficial haemodynamic effects of andrographolide in endotoxic shock.

Animals↗

PubMed1998

Inhibitory effect of digoxin on testosterone secretion through mechanisms involving decreases of cyclic AMP production and cytochrome P450scc activity in rat testicular interstitial cells.

1. In vivo and in vitro experiments were performed to examine inhibitory effects of digoxin on testosterone secretion and to determine possible underlying mechanisms. 2. A single intravenous injection of digoxin (1 microg kg(-1)) decreased the basal and human chorionic gonadotropin (hCG)-stimulated plasma testosterone concentrations in adult male rats. 3. Digoxin (10(-7) - 10(-4) M) decreased the basal and hCG-stimulated release of testosterone from rat testicular interstitial cells in vitro. 4. Digoxin (10(-7) - 10(-4) M) also diminished the basal and hCG-stimulated production of cyclic 3':5'-adenosine monophosphate (AMP) and attenuated the stimulatory effects of forskolin and 8-Br-cyclic AMP on testosterone production by rat testicular interstitial cells. 5. Digoxin (10(-4) M) inhibited cytochrome P450 side chain cleavage enzyme (cytochrome P450sec) activity (conversion of 25-hydroxy cholesterol to pregnenolone) in the testicular interstitial cells but did not influence the activity of other steroidogenic enzymes. 6. These results suggest that digoxin inhibits the production of testosterone in rat testicular interstitial cells, at least in part, via attenuation of the activities of adenylyl cyclase and cytochrome P450sec.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1998

Relaxation of corpus cavernosum and raised intracavernous pressure by berberine in rabbit.

1. In the present study, we have investigated the effect of berberine in rabbit isolated corpus cavernosum and measured the intracavernous pressure (ICP) change after intracavernosal injection of berberine in rabbit. 2. Berberine alone suppressed the basal tone and induced a concentration (0.1-100 microM)-dependent relaxation in phenylephrine (PE)-precontracted corpus cavernosum. 3. Tetrodotoxin (0.1 and 1 microM) treatment had no significant effect on the berberine-induced relaxation. Phentolamine (1 and 10 microM), propranolol (1 and 3 microM) and atropine (1 and 3 microM) were also without effect. These results suggest that berberine might cause relaxation of the cavernosal strip by direct action on the corpus cavernosum, not by a neuronal effect. Furthermore, muscarinic- and beta-adrenoceptors were not involved. 4. Berberine-induced relaxations were significantly reduced by endothelium removal and by exposure to L-NG-nitro arginine methyl ester (0.1 and 0.3 mM), but not indomethacin (30 microM). 5. In endothelium-deprived corpus cavernosal tissues, berberine-induced relaxations were significantly reduced in high K+ medium (KCl = 60 mM), by charybdotoxin (ChTX) and 4-aminopyridine (4-AP) but not by glibenclamide and apamin. 6. After intracavernous injection of berberine (1, 2, 3 and 5 mg kg(-1)), the ICP rose from 12.7+/-3.6 to 13.2+/-5.4, 25.3+/-6.1, 46.5+/-8.2, and 63.4+/-10.2 mmHg, respectively. The duration of tumescence ranged from 11.5 - 43.7 min. 7. The results show that berberine possesses a relaxant effect on rabbit corpus cavernosal tissues which is attributable to both endothelium-dependent and-independent properties. While the former component is apparently due to the release of NO from sinusoidal endothelium, the endothelium-independent mechanism involved in berberine relaxation is probably linked to ChTX- and 4-AP-sensitive K+ channel activation in the cavernosal vasculature.

4-Aminopyridine↗

PubMed1998

Anti-tumor effects of d-dicentrine from the root of Lindera megaphylla.

d-Dicentrine, a naturally occurring aporphine type isoquinoline alkaloid, isolated from the root of Lindera megaphylla Hemsl. (Lauraceae), was evaluated for its potential anti-cancer activity. We found d-dicentrine significantly inhibited the growth of human hepatoma cell line HuH-7 by delaying its doubling time in tissue culture. An in vitro colony forming assay showed that d-dicentrine decreased the colony formation efficiency in both hepatoma cell lines, HuH-7 and MS-G2, used in our study. Biosyntheses of the macromolecules DNA and RNA were also strongly inhibited. An MTT assay in 21 tumor cell lines also revealed that d-dicentrine was most cytotoxic to esophageal carcinoma HCE-6, lymphoma cell lines Molt-4 and CESS, leukemia cell lines HL60 and K562, and hepatoma cell line MS-G2. An in vitro tumor growing assay in the Severe Combined immunodeficiency (SCID) mice showed that intraperitoneal injection of d-dicentrine at the dose of 100 micrograms twice a week for 4 weeks significantly inhibited the tumor incidence of leukemia cell line K562 in SCID mice. All these data indicated that d-dicentrine has potential anti-tumor applications.

Animals↗

PubMed1998

Determination of the components in a Chinese prescription, yu-ping-feng san, by RAPD analysis.

In this study, the RAPD (random amplified polymorphic DNA) technique was employed for the first time to determine the components in a Chinese herbal prescription. Forty decamer oligonucleotide primers were screened in the RAPD analysis to identify three Chinese medicines, the dried root of Astragalus membranaceus (Fisch.) Bge., the dried root of Ledebouriella seseloides Wolff, and the dried rhizome of Atractylodes macrocephala Koidz, in a Chinese prescription. Only primer OPP-10 simultaneously generated three distinct markers were each specific to one component. The marker with 200 bp is specific to Astragalus membranaceus; the 440 bp marker is specific to Atractylodes macrocephala; and the remaining marker with 500 bp was present in Ledebouriella seseloides. The presence of the three herbal medicines in the mixed sample, the Chinese prescription, was determined when the primer OPP-10 RAPD reaction was performed. The technique was proved to contribute to the identification of components in the Chinese medicinal preparations.

Astragalus propinquus↗

PubMed1998

Benzodiazepine binding site-interactive flavones from Scutellaria baicalensis root.

A benzodiazepine binding assay directed separation led to the identification of 3 flavones baicalein (1), oroxylin A (2), and skullcapflavone II (3) from the water extract of Scutellaria baicalensis root. Compounds 1, 2, and 3 interacted with the benzodiazepine binding site of GABAA receptors with a Ki value of 13.1, 14.6 and 0.36 micromol/L, respectively.

Animals↗