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Biomedical subjects

B H Chen

Publications and source records attributed to B H Chen.

At least 19 recordsLinked to original sources
PubMed2006

Effect of pH on binding of mutagenic heterocyclic amines by the natural biopolymer poly(gamma-glutamic acid).

Poly(gamma-glutamic acid) (gamma-PGA), a nontoxic and biodegradable macropolymer, was evaluated for its efficiency in binding three mutagenic heterocyclic amines (HAs), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-p-2), as affected by pH in a batch mode. The maximum HA sorption was attained for pH 3-7 and decreased sharply for pH less than 3. Binding isotherms obtained at pH 2.5 and 5.5 showed different isotherm shapes that belong to S and L types, respectively. The isotherm data at pH 2.5 were well described by a linear form of the Langmuir equation, while at pH 5.5 it showed two distinct curves, which were precisely fitted as multiple Langmuir curves. The deviation of linearity in Scatchard plot proved the multisite HA sorption. The Brunauer-Emmett-Teller equation also fitted better to isotherm data at pH 5.5, suggesting a multisite sorption caused by multimolecular HA layers on gamma-PGA. High HA sorption levels of 1250, 667, and 1429 mg/g at pH 2.5 and 1429, 909, and 1667 mg/g at pH 5.5 were observed for MeIQ, 4,8-DiMeIQx, and Trp-p-2, respectively. Among the HAs studied, the sorption capacity correlated directly with hydrophobicity of HAs and inversely with the number of methyl groups in HA molecules. The plausible binding mechanism of HAs on gamma-PGA may include a combination of hydrophobic, hydrogen-bonding, ionic, and dipole-dipole interactions.

Adsorption↗
PubMed2006

Removal of cationic dyes from aqueous solution using an anionic poly-gamma-glutamic acid-based adsorbent.

Natural polymeric materials are gaining interest for application as adsorbents in wastewater treatment due to their biodegradable and non-toxic nature. In this study, a biopolymer, poly-gamma-glutamic acid (gamma-PGA) derived from bacterial sources (Bacillus species) was evaluated for its efficiency in removing basic dyes from aqueous solution. Sorption studies under batch mode were conducted using C.I. Basic blue 9 (BB9) and C.I. Basic green 4 (BG4) as test dyes. Equilibrium process conformed well with the Redlich-Peterson isotherm equation and the monolayer sorption capacity obtained from the Langmuir model was 352.76 and 293.32mg/g for BB9 and BG4 dyes, respectively. The kinetic studies of dye sorption on gamma-PGA gave high coefficients of determination (>0.98) for a pseudo second-order equation. An ion-exchange model, which assumes adsorption as a chemical phenomenon, was also found to fit the kinetic data precisely. The dye sorption largely depended on the initial pH of the solution with maximum uptake occurring at pH above 5. About 98% of the dye adsorbed on gamma-PGA could be recovered at pH 1, which facilitates the reuse of spent gamma-PGA.

Adsorption↗
PubMed2006

Lack of formation of heterocyclic amines in fumes from frying French fries.

The formation of heterocyclic amines (HAs) in the fumes from frying French fries in soybean oil or lard was studied. A high-pressure liquid chromatography method was used to determine the various HAs in fumes. Results showed that the yields of fumes produced from soybean oil when heated alone for 2 or 4 h were higher than from lard; however, a reversed trend was found when frying French fries in soybean oil and lard. Most fumes from soybean oil and lard while frying French fries were adsorbed onto the condensation apparatus, while the other portions were adsorbed onto the wool and glass beads, which were incorporated in our experimental design for collecting the fumes. The fumes from soybean oil when heated alone were found to contain three HAs, namely, 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQx), 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ), and 1-methyl-9H-pyrido[4,3-b ]indole (Harman), whereas two more HAs, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b ]indole (Trp-P-1), were generated in lard. Lard was more susceptible to the formation of HAs than soybean oil when both were heated alone. No HAs were detected in the fumes from French fries fried in soybean oil and lard.

Amines↗
PubMed2005

Improved high performance liquid chromatographic method for determination of carotenoids in the microalga Chlorella pyrenoidosa.

Microalgae have become an important commercial source of carotenoids and microalgae-derived functional foods are consumed by people worldwide. Therefore, an HPLC method was developed to discern the variety and content of carotenoids in the microalga Chlorella pyrenoidosa. The microalga sample was powdered, extracted, saponified and subjected to HPLC analysis. A mobile phase of methanol-acetonitrile-water (84:14:2, v/v/v) (A) and methylene chloride (100%) (B) with the following gradient elution was developed: 100% A and 0% B in the beginning, maintained for 14 min, decreased to 95% A in 25 min, 75% A in 30 min, 74% A in 35 min, 45% A in 50 min and returned to 100% A in 55 min. A total of 32 carotenoids were resolved within 49 min by using a C30 column with flow rate at 1 mL/min and detection at 450 nm. An internal standard beta-apo-8'-carotenal was used to quantify all the carotenoids. All-trans-lutein was present in exceptionally large amount (125034.4 microg/g), followed by cis isomers of lutein (27975.3 microg/g), all-trans-alpha-carotene (2465.8 microg/g), zeaxanthin (2170.3 microg/g), cis isomers of beta-carotene (2159.3 microg/g), all-trans-beta-carotene (2155.0 microg/g), cis isomers of alpha-carotene (1766.7 microg/g), beta-cryptoxanthin (334.9 microg/g), neoxanthin and its cis isomers (199.7 microg/g), neochrome (65.2 microg/g), auroxanthin (38.5 microg/g) and violaxanthin and its cis isomers (38.1 microg/g).

Carotenoids↗
PubMed2005

An improved HPLC method for determination of carotenoids in human serum.

An HPLC method was developed to determine the various carotenoids in human serum. A C-30 column and a mobile phase of 100% methanol (A) and 100% methylene chloride (B) with the following gradient elution were used: 90% A and 10% B in the beginning, maintained for 5 min, decreased to 78% A at 15 min, 62% A at 30 min, 52% A at 40 min, 41% A at 50 min, 38% A at 55 min, maintained for 3 min, and returned to 100% A at 65 min. A total of 21 carotenoids, including all-trans forms of lutein, zeaxanthin, alpha-cryptoxanthin, beta-cryptoxanthin, alpha-carotene, beta-carotene and lycopene, as well as their 14 cis-isomers were resolved within 51 min at a flow rate of 1.0 mL/min and detection at 476 nm. all-trans-beta-Carotene was found to be present in highest amount (256.3-864.2 ng/mL), followed by all-trans-lycopene (64.4-569.2 ng/mL), all-trans-lutein (137.9-450.3 ng/mL), all-trans-alpha-cryptoxanthin (55.7-188.2 ng/mL), all-trans-beta-cryptoxanthin (43.1-134.5 ng/mL), all-trans-alpha-carotene (20.0-122.1 ng/mL) and all-trans-zeaxanthin (9.1-21.3 ng/mL). Similar trend was observed for cis-isomers of carotenoids.

Carotenoids↗
PubMed2004

Improved liquid chromatographic method for determination of carotenoids in Taiwanese mango (Mangifera indica L.).

An HPLC method was developed to determine the various carotenoids in Taiwanese mango (Mangifera indica L.). Initially, the peel and seed of mangoes were removed, the pulps were cut into pieces, freeze-dried, ground into powder, extracted and subjected to HPLC analysis. A mobile phase of methanol-isopropanol (99:1, v/v) (A) and methylene chloride (100%) (B) with the following gradient elution was developed: 100% A and 0% B in the beginning, maintained for 15 min, decreased to 70% A in 45 min, maintained for 15 min and returned to 100% A in 65 min. A total of 25 carotenoids were resolved within 53 min by using a C-30 column with flow rate at 1 mL/min and detection at 450 nm. alpha-Carotene was used as an internal standard to quantify all the carotenoids. All-trans-beta-carotene was present in largest amount (29.34 microg/g), followed by cis isomers of beta-carotene (9.86 microg/g), violaxanthin and its cis isomers (6.40 microg/g), neochrome (5.03 microg/g), luteoxanthin (3.6 microg/g), neoxanthin and its cis isomers (1.88 microg/g), zeaxanthin (1.16 microg/g) and 9- or 9'-cis-lutein (0.78 microg/g).

Carotenoids↗
PubMed2004

Effects of heating time and antioxidants on the formation of heterocyclic amines in marinated foods.

The effect of heating time and antioxidants on the heterocyclic amine (HAs) formation in marinated foods were studied. Food samples were cooked at 98 +/- 2 degrees C for 1, 2, 4, 8, 16 and 32 h in a closed pan in the presence of water, soy sauce and rock candy with or without antioxidants. The various HAs in marinated food samples and juice were analyzed by HPLC with photodiode-array detection. Results showed that the amount of HAs formed during heating followed an increased order for each increasing heating time. A larger variety and higher amount of HAs were generated in marinated pork when compared to marinated eggs and bean cake. In marinated juice, the levels of HAs were present in greater amount than in marinated foods. The incorporation of antioxidants Vitamin C, Vitamin E and BHT were found to be effective towards HAs inhibition, however, the effect was minor.

Amines↗
PubMed2003

Determination of carotenoids in tomato juice by liquid chromatography.

A high-performance liquid chromatography method was developed to determine the various carotenoids in tomato juice. A C30 column and a mobile phase of acetonitrile-1-butanol (7:3, v/v) (A) and methylene chloride (B) with the following gradient elution were used: 99% A and 1% B intitally, increased to 4% B in 20 min, 10% B in 50 min and returned to 1% B in 55 min. Sixteen carotenoids, including all-trans-lutein, all-trans-beta-carotene, all-trans-lycopene and their 13 cis isomers were identified and resolved within 52 min with flow-rate at 2.0 ml/min and detection at 476 nm. Of the various extraction solvent systems, the best extraction efficiency of carotenoids in tomato juice was achieved by employing ethanol-hexane (4:3, v/v). Lycopene was found to be present in largest amount in tomato juice, followed by beta-carotene and lutein.

Carotenoids↗
PubMed2003

Determination of polycyclic aromatic hydrocarbons in fumes from fried chicken legs.

The amount and variety of polycyclic aromatic hydrocarbons (PAHs) in fumes during frying of chicken legs in edible oils were determined using a modified smoke collection device and a GC-MS technique. Chicken legs were fried in soybean oil, canola oil, or sunflower oil at 163 degrees C for 1-4 h. Results showed that most smoke (99%) was collected in the condensation apparatus, whereas the rest (1%) was adsorbed onto adsorption wool. A large proportion of PAHs in the smoke were detected in adsorption wool, whereas a small portion was found in the condensation apparatus. Canola oil generated the largest content (500.9 g for a frying time of 4 h) of smoke, followed by soybean oil, and sunflower oil. A similar trend was observed for PAH formation in fumes, with the exception that soybean oil produced a higher level than canola oil.

Animals↗
PubMed2003

Mutagenicity of fumes from fried chicken legs.

The mutagenicity of fumes formed during the frying of chicken legs at 163 degrees C for 1 to 4 h in soybean oil, canola oil, or sunflower oil was studied. A modified smoke adsorption device was used to collect fumes, and the mutagenicity of the fumes was determined with the Ames test. The results obtained show that the mutagenicity of the fumes from all three oils increased with an increase in frying time. Under the same heating conditions, the oil showing the most extensive mutagenicity was soybean oil, followed by canola oil and sunflower oil. For the smoke adsorption device, the strongest mutagenicity was exhibited by the adsorptive wool, followed by the condensates and glass bead extracts.

Animals↗
PubMed2002

Creating new supramolecular materials by architecture of three-dimensional nanocrystal fiber networks.

The architecture of three-dimensional interconnecting self-organized nanofiber networks from separate needlelike crystals of L-DHL (lanosta-8,24-dien-3beta-ol:24,25-dihydrolanosterol = 56:44) in di-isooctylphthalate has been achieved for the first time, on the basis of the completely new concept of branching creation by additives (branching promoters). [In this work, an additive, ethylene/vinyl acetate copolymer (EVACP), is used at a concentration of several 10 ppm.] We demonstrate that this novel technique enables us to produce previously unknown self-supporting supramolecular functional materials with tailormade micro- or nanostructures, possessing significantly modified macroscopic properties, by utilizing materials thus far considered to be "useless". In addition, both the self-organized structure and the properties of the new materials can be fine-tuned by altering the processing conditions. Our results show that the formation of the interconnecting 3D self-organized network structure is controlled by a new mechanism, so-called crystallographic mismatch branching mechanism, as opposed to the conventionally adopted molecular self-assembly mechanism. The principles and criteria for the selection of branching promoters are also discussed from the point of view of molecular structures.

Drug Delivery Systems↗
PubMed2002

Collagen metabolism and turnover in women with stress urinary incontinence and pelvic prolapse.

The aim of this study was to investigate quantitative mRNA expression of matrix metalloproteinases MMP-1, MMP-2, MMP-9, and their inhibitors, the tissue inhibitors of metalloproteinases TIMP-1, TIMP-2 and TIMP-3, in vaginal wall tissue from women with stress urinary incontinence compared to continent controls. Vaginal wall tissues were obtained from 7 women with stress urinary incontinence/severe pelvic prolapse and 15 continent controls. RNA was then extracted and quantified. Quantitative competitive reverse transcription (QC-RT-PCR) was carried out with oligonucleotide primers to quantify MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2 and TIMP-3 mRNA expression. Stress continent women demonstrated a significant decrease in TIMP-1 and mRNA expression (P = 0.03). There was no difference in TIMP-2, TIMP-3, MMP-2 or MMP-9 mRNA expression between stress incontinent women and controls. However, MMP-1 mRNA expression was significantly increased (P = 0.05) in the incontinent group and the MMP-1/TIMP-1 ratio (P = 0.04) was consistent with increased collagen degradation in the stress incontinence. Stress incontinent women demonstrated an increase in MMP-1 mRNA expression and a decrease in the inhibitor TIMP-1 mRNA expression. Both these findings are consistent with increased collagen breakdown as a pathologic etiology of incontinence.

Amino Acids↗
PubMed2002

Effects of soy sauce and sugar on the formation of heterocyclic amines in marinated foods.

The effects of soy sauce and sugar on the formation of heterocyclic amines (HAs) in marinated pork, eggs, and bean cakes were studied. Food samples were immersed in water in the presence of various levels of soy sauce and sugar, and the mixtures were subjected to simmering at 98+/-2 degrees C for 1 h in a closed saucepan. The various HAs in marinated food samples were analyzed by HPLC with photodiode-array detection. Results showed that seven HAs: 2-amino-3-methylimidazo[4,5-f]quinoline (IQ); 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx); 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ); 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx); 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1); 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine (PhIP); and 2-amino-9H-pyrido[2,3,-b]indole (AalphaC) were detected in marinated pork, while five HAs: IQ, MeIQx; 4,8-DiMeIQx; PhIP; and AalphaC in bean cakes, as well as four HAs, MeIQx, 4,8-DiMeIQx, Trp-P-1 and PhIP in eggs. In most samples PhIP was formed in largest amount, followed by MeIQx, 4,8-DiMeIQx, IQ, AalphaC, Trp-P-1 and MeIQ. The amounts of HAs produced in marinated food samples followed an increased order for each increasing level of soy sauce or sugar. Marinated juice was found to contain a higher content of HAs than marinated foods.

Amines↗
PubMed2001

A novel cloud-point extraction process for preconcentrating selected polycyclic aromatic hydrocarbons in aqueous solution.

A novel but simple cloud-point extraction (CPE) process is developed to preconcentrate the trace of selected polycyclic aromatic hydrocarbons (PAHs) with the use of the readily biodegradable nonionic surfactant Tergitol 15-S-7 as extractant. The concentrations of PAHs, mixtures of naphthalene and phenanthrene as well as pyrene, in the spiked samples were determined with the new CPE process at ambient temperature (23 degrees C) followed by high performance liquid chromatography(HPLC) with fluorescence detection. More than 80% of phenanthrene and pyrene, respectively, and 96% of naphthalene initially present in the aqueous solutions with concentrations near or below their aqueous solubilities were recovered using this new CPE process. Importantly Tergitol 15-S-7 does not give any fluorometric signal to interfere with fluorescence detection of PAHs in the UV range. No special washing step is, thus, required to remove surfactant before HPLC analyses. Different experimental conditions were studied. The optimum conditions for the preconcentration and determination of these selected PAHs at ambient temperature have been established as the following: (1) 3 wt% surfactant; (2) addition of 0.5 M Na2SO4; (3) 10 min for equilibration time; and (4) 3000 rpm for centrifugal speed with duration of 10 min.

Chromatography, High Pressure Liquid↗
PubMed2001

Turbidity and critical behavior of a colloid-polymer system.

The osmotic compressibility and correlation length of a colloid-polymer system, consisting of grafted silica particles in cyclohexane in the presence of the soluble polymer polydimethylsiloxane, are determined by turbidity measurements in the entire one-phase liquid region, with emphasis on the critical region. The renormalized critical exponents of the osmotic compressibility and the correlation length are found to be respectively gamma(*)=1.39+/-0.01 and nu(*)=0.71+/-0.01, while the amplitude of the correlation length is 16.0+/-0.3 nm. Comparison is made with theoretical predictions.

Journal Article↗
PubMed2001

Slow release of drug through deformed coating film: effects of morphology and drug diffusivity in the coating film.

The effects of the morphology and drug diffusivity in the coating film on the slow release characteristics have been analyzed numerically under the constraint that the volume of the coating film and the drug matrix is maintained constant. Two different systems of coated particles with deformed coating films were studied and their release characteristics compared with those of the coated particles having spherical coating films. The average release rate, fractional release, drug concentration profiles, and the initial burst of drug were found to be strongly influenced by the ratio of drug diffusivity in the coating film to that in the drug matrix D(r) (i.e., dimensionless drug diffusivity in the coating film). Increasing D(r) always increased the release rate, the fractional release, and the initial burst of drug, but reduced the initial lag times of drug release. The effect of shape deformation was very significant in the drug concentration profiles and the initial lag times; in contrast, it was not so substantial on the fractional release and the average release rates. The morphology difference in the deformed systems was also found to affect the release characteristics to different extents. Increasing the degree of the shape deformation, represented by the perturbation parameter epsilon, always reduced the effective surface area for the controlled release of drug. Because of the compensation effects between decreasing surface area and the non-uniform mass flux distribution, even though the heterogeneity of surface mass flux distribution would become more considerable, the effects of increasing shape deformation to the overall release rate would be less than expected unless the coating film was deformed significantly enough. The effect of the shape deformation and the morphology difference become less effective to differentiate the release characteristics with increasing D(r).

Delayed-Action Preparations↗