Search PubMed⌕ Search

Biomedical subjects

Y C Ling

Publications and source records attributed to Y C Ling.

18 recordsLinked to original sources
PubMed1999

Supercritical fluid extraction and clean-up of organochlorine pesticides in Chinese herbal medicine.

A method involving the simultaneous extraction and clean-up of 13 organochlorine pesticides (OCPs) from Chinese herbal medicines (CHMs) was developed using supercritical fluid extraction (SFE) followed by gas chromatography-electron capture detection and mass spectrometric confirmation. The pesticides in the study consisted of alpha-, beta-, gamma-, and delta-benzene hexachloride, heptachlor, aldrin, heptachlor epoxide, endosulfan I, 4,4'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethene), dieldrin, endrin, 4,4'-DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane), endosulfan II, 4,4'-DDT (2,2-bis(p-chlorophenyl)1,1,1-trichloroethane), endrin aldehyde, and endosulfan sulfate. A series of experiments was conducted to optimize the final extraction conditions [pure CO2, 250 atm extraction pressure (1 atm = 101,325 Pa), 50 degrees C extraction temperature, 5 min static extraction time, 20 min dynamic extraction time, 2.0-g Florisil sorbent on top of 0.1-g samples, 12-ml n-hexane eluting at 1 ml/min, and a 10-ml extraction vessel]. Florisil sorbent was placed with the sample in the SFE vessel to provide a facile and effective clean-up approach. Mean recoveries of 78-121% with reproducibilities of 5-31% were obtained for the pesticides except for endosulfan II, endosulfan sulfate and endrin aldehyde. The simple and rapid method may be used to determine OCPs in CHMs routinely, and in fact, was used to analyze CHMs sold in Taiwan.

Chemical Phenomena↗
PubMed1998

Quantitative analysis of antibiotics by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Comparative studies of the matrix-assisted laser desorption/ionization (MALDI) of 30 antibiotics were made using alpha-cyano-4-hydroxycinnamic acid (HCCA), 2,5-dihydroxybenzoic acid (DHB), 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin and meso-tetra(N-methyl-4-pyridyl)porphyrin matrices. Most antibiotics generated intense protonated molecules in HCCA and DHB matrices, and sodium or potassium adduct ions in porphyrin matrices. Using sulfonamide antibiotics as model compounds, DHB was found to be the most suitable matrix for quantitative analysis. Detection limits were about 1 picomole. Linear correlation (R2 > 0.97), between the sample quantity over the range 1 to 100 picomole and the signal response, was obtained when ratios of the sum of peak areas of protonated molecules and sodium adduct ions, with reference to that of a structurally analogous internal standard (acetaminophen), were measured. The precision was found to be in the range of 4 to 32% relative standard deviation, dependent on the type and concentration of the analyte. A simple acylation derivatization process was developed to confirm the presence of suspected antibiotic residues. It is demonstrated that MALDI is a viable technique for the quantitative analysis of low molecular weight antibiotics.

Anti-Bacterial Agents↗
PubMed1997

Supercritical fluid extraction and clean-up of organochlorine pesticides and polychlorinated biphenyls in mussels.

The simultaneous extraction and clean-up of mussel samples followed by gas chromatography with electron-capture detection and mass spectrometric confirmation of 15 organochlorine pesticides (OCPs) and 11 polychlorinated biphenyls (PCBs) is developed using Florisil sorbent in the supercritical fluid extraction cell. The method detection limits vary from 1 to 10 ng/g for OCPs and from 2 to 15 ng/g for PCBs. Mean reproducibilities of 11% and 10% and mean recoveries of 80% and 53%, respectively, for OCPs and PCBs are obtained. The feasibility of the proposed supercritical fluid extraction method was confirmed by analyzing a certified reference material and mussels collected from Taiwan region. The method is simple, rapid and requires only small amounts of samples and solvents. It may serve as a screening protocol for the determination of OCPs and PCBs in mussels on a routine basis.

Animals↗
PubMed1996

Application of hemodilution in microsurgical free flap transplantation.

The intra-operative hemodilution and blood auto-transfusion is a blood-saving technique that can be performed when major blood loss is expected. The effects of this technique were studied in 30 microsurgical free flap transplantation patients. Between 400-600 ml blood was collected from the patients before surgery. The patients received dextran, a balanced salt solution, and glucose with the ratio of 3:1 to the collected blood volume, bleeding, and urine before the blood auto-transfusion. There were no significant changes in RBC, HCT, MCV, blood pressure, or heart rate. Of the 30 free flaps, 28 were successful with a 93.3% survival rate. The safety of intra-operative hemodilution and autologous blood transfusion in microsurgery as well as the effect of hemodilution on transplanted flap survival are discussed in this study.

Adult↗
PubMed1995

Multi-residue matrix solid-phase dispersion method for the determination of six synthetic pyrethroids in vegetables followed by gas chromatography with electron capture detection.

An effective multi-residue matrix solid-phase dispersion (MSPD) extraction and gas chromatographic-electron-capture detection method for the determination of six synthetic pyrethroids (fenpropathrin, cyhalothrin, permethrin, cypermethrin, fenvalerate and deltamethrin) in 5 g of vegetables (West Indian gherkin, eggplant, pak-choi, cabbage and garden peas) is described. The method uses a Florisil-based MSPD column for direct in-line clean-up with n-hexane-acetone (9:1). Recoveries calculated at 0.1 and 0.5 micrograms/g fortification levels were between 92 and 113%. The method detection limits were between 5.1 and 91.5 ng/g. The method compared favourably with the traditional method in terms of the sample size, analysis time and overall cost. The method may serve as a screening protocol for the determination of pyrethroids in vegetables.

Chromatography, Gas↗
PubMed1995

PCDD/DFs and coplanar PCBs in sediment and fish samples from the Er-Jen river in Taiwan.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) and coplanar polychlorinated biphenyls (Co-PCBs) have been determined in sediment and fish samples from the Er-Jen river in Taiwan. Sediment samples collected near the incineration site show TEQ of PCDD/DFs ranging from 14 pg/g to 14200 pg/g and 2,3,7,8-tetrachlorodibenzo-p-dioxins equivalents (TCDD-EQ) of Co-PCBs ranging from 9 pg/g to 1030 pg/g. The fish samples show TEQ of PCDD/DFs ranging from 37 pg/g to 2084 pg/g and TCDD-EQ of Co-PCBs ranging from 12 pg/g to 120 pg/g. Possible PCDD/DFs sources are discharged PCBs, open-air incineration activities, and pentachlorophenol. PCB#126 was found to degrade more readily than PCB#77. TCDD-EQ of Co-PCBs could be estimated from the total concentration of PCBs. A daily intake value of 28 pg/kg/day to 450 pg/kg/day was estimated when consuming fish caught from the Er-Jen river.

Animals↗
PubMed1994

Matrix solid-phase dispersion extraction and gas chromatographic screening of polychlorinated biphenyls in fish.

A matrix solid-phase extraction (MSPD) and gas chromatographic-electron-capture detection method for determining polychlorinated biphenyls (PCBs) in fish (grass carp) is described. The method uses an octadecylsilyl-derivatized silica and acidic silica gel-based MSPD co-column for direct in-line clean-up. The performance of the method compares favourably with that of the traditional approach but the sample size, analysis time and overall cost are lower. The method may serve as a screening protocol for the isolation and determination of PCBs in fish.

Animals↗
PubMed1989

Quantitative imaging of boron, calcium, magnesium, potassium, and sodium distributions in cultured cells with ion microscopy.

A method for the conversion of intensity information in ion micrographs of freeze-fractured, freeze-dried cultured cells to local dry weight elemental concentrations is presented. Homogenates generated from cultured cells are used as calibration standards. Ion microscope (IM) relative sensitivity factors for B, Ca, K, Mg, and Na with respect to the matrix element C are determined by the correlation of IM and inductively coupled plasma atomic emission spectrometry analyses of the cellular homogenates. After calibration of the IM imaging system, the relative sensitivity factors are used to determine local intracellular concentrations of B, Ca, K, Mg, and Na in cultured Swiss 3T3 fibroblasts. Intracellular B was introduced through cellular uptake of Na2B12H11SH, a candidate therapeutic agent for boron neutron capture cancer therapy. The IM intracellular concentration results show good agreement with published electron probe X-ray microanalysis results. Estimated detection limits are in the low- to subparts-per-million dry weight concentration range.

Animals↗
PubMed1989

Quantitative imaging of free and total intracellular calcium in cultured cells.

Techniques of fluorescence and ion microscopies were combined to study the free [Ca2+] and total Ca in NIH 3T3 fibroblast and L6 rat myoblast cells. Free Ca2+ measurements with the Ca2+ indicator fura-2 and digital imaging reveal an inhomogeneous distribution of free cytoplasmic Ca2+ in both cell lines. Fura-2 also reveals a difference in free Ca2+ activity between the nucleus and cytoplasm of cells. Ion microscopic observations on sister cells show that total Ca in the cytoplasm is also inhomogeneously distributed and that mean cytoplasmic levels of total Ca are higher than levels in the nuclei. In the nuclei of NIH 3T3 cells, the mean free [Ca2+] and total [Ca] were 110 +/- 30 nM and 225 +/- 43 microM, respectively, while regions in the cell cytoplasm contained up to 490 +/- 270 nM free [Ca2+] and 559 +/- 184 microM mean total [Ca]. Intracellular total Ca was greater than 3 orders of magnitude higher than intracellular free Ca2+ in either nuclear or cytoplasmic compartments. Perinuclear cytoplasmic regions in 3T3 cells contained higher free and total Ca than the cell nucleus. Loading of cells with fura-2 did not modify the subcellular distribution of total K, Na, Ca, or Mg. This combination of two powerful ion imaging techniques provides a comparison between free and total calcium in cells and introduces a different approach for examining the role of this important element in cell physiology.

Animals↗
PubMed1989

Experience using microvascular anastomotic rings for the transplantation of 20 free flaps.

A new microvascular anastomosis technique was employed with success in 1985-1986 with the result of 18 free-flap survivals and 2 failures. The rate of success in microvascular anastomoses was 90.5 percent (38 of 42). The advantages of this technique are its simplicity, convenience, and safety, and it may shorten the duration of the operation. Our experience in using vascular anastomotic rings is presented.

Adult↗
PubMed1987

SIMIPS: secondary ion mass image processing system.

A secondary ion mass image processing system (SIMIPS) is presented as a quantitative image analysis tool, with emphasis on an efficient man-machine interface. The combined applications of digital image processing and pattern recognition ensure an intelligent problem-resolving scheme and optimal extraction of information. The system performance is evaluated, and typical applications are presented to illustrate the versatility and usefulness of SIMIPS in analyzing digital images.

Colon↗
PubMedDate not supplied

Clinical experience and surgical anatomy of 32 free anterolateral thigh flap transplantations.

The anterolateral thigh flap, first described by Song, is one of the septocutaneous flaps in the thigh. Since November 1985 we have transferred 32 anterolateral thigh flaps successfully without any loss. Six of these flaps were performed in Australia. The vascular pedicles are divided into three types: fasciocutaneous perforator (37.5%-12/32), vertical musculocutaneous perforator (56.2%-18/32) and horizontal musculocutaneous perforator (6.6%-2/32). This paper presents the surgical anatomy of the flap and clinical experience.

Adolescent↗
PubMedDate not supplied

Reassessment of PCDD/DFs and Co-PCBs toxicity in contaminated rice-bran oil responsible for the disease "Yu-Cheng".

Reassessment of dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) and coplanar polychlorinated biphenyls (Co-PCBs) in toxic Yu-Cheng rice-bran oil was carried out. The contaminating source appears to be a mixture of KC-400 and KC-500. The oil contains 176 micrograms/g PCBs and 37.194 ng/g 2,3,7,8,-TCDD toxicity equivalency (TEQ). The TEQ contributions from the PCDDs (4.472 ng/g), PCDFs (19.568 ng/g), and Co-PCBs (13.154 ng/g) are 12% 53% and 35%, respectively. Complete identification and quantitation suggests that 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, 2,3,7,8,-TCDF. 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD and PCB# 77 are candidates for the primary causal agents of Yu-Cheng disease.

Benzofurans↗