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Biomedical subjects

T H Sun

Publications and source records attributed to T H Sun.

At least 19 recordsLinked to original sources
PubMed2006

Earthworm cytochrome P450 determination and application as a biomarker for diagnosing PAH exposure.

We developed a new microsome purification method and used the Omura and Sato method to measure the total content of cytochrome (Cyt) P450 in earthworm (Eisenia fetida) microsomes. In method development, two different pretreatments, i.e. solubilization or manual separation were used to purify worm microsomes. Solubilization was more effective than manual separation and difference spectra showed a peak at 450 +/- 1 nm in microsomes received solubilization pretreatment. We conducted a 48 h contact test by exposing worms on pyrene (Py) and benzo[a]pyrene (BaP) spiked filter paper. A dose-response relationship was established between total P450 content and the concentration of Py or BaP ranging from 10(-6) mg mL(-1) to 10(-2) mg mL(-1). Results show that total Cyt P450 content in earthworms is a promising biomarker for diagnosing PAHs exposure at sublethal dose ranges.

Animals↗
PubMed2006

Surface flow constructed wetland for heavy oil-produced water treatment.

Heavy oil-produced water from China' Liaohe Oilfield was purified in a surface flow constructed wetland (SFCW) during a 3-yr field experiment. Treatment showed high mean removal efficiencies of 80%, 93%, 88% and 86% for COD, oil, BOD and TKN, respectively for reed bed #1 and 71%, 92%, 77%, and 81% for COD, oil, BOD and TKN, respectively for reed bed #2. The results also showed that in the third year of the system's operation, the oil-produced water had mainly positive impacts on the reed's health parameters. Thus, reed can be used as a feasible wetland macrophyte for treating such wastewater, and this SFCW system can operate for a long time.

Petroleum↗
PubMed2005

DNA changes in barley (Hordeum vulgare) seedlings induced by cadmium pollution using RAPD analysis.

In recent years, several plant species have been used as bioindicators, and several tests have been developed to evaluate the toxicity of environmental contaminants on vegetal organisms. In this study, barley (Hordeum vulgare L) seedling was used as bioindicator of cadmium (Cd) pollution in the range of 30-120 mgl(-1). Inhibition of root growth and reduction of total soluble protein content in root tips of barley seedlings were observed with the increase of Cd concentrations. The changes occurring in random amplified polymorphic DNA (RAPD) profiles of root tips following Cd treatment included variation in band intensity, loss of normal bands and appearance of new bands compared with the normal seedlings. Additionally, we found that the effect of changes was dose-dependent. These results indicated that genomic template stability (a qualitative measure reflecting changes in RAPD profiles) was significantly affected at the above Cd concentration. Thus, DNA polymorphisms detected by RAPD analysis could be used as an investigation tool for environmental toxicology and as a useful biomarker assay for the detection of genotoxic effects of Cd pollution on plants.

Biomarkers↗
PubMed2001

[Molecular coherent radiation in VUV/XUV regions and the determination of rotational temperature of molecule].

The investigation of spectroscopy of vacuum ultraviolet (VUV, 100-200 nm) and extreme ultraviolet (XUV, 10-100 nm) regions has attracted the attention of many researchers in recent years because of its promising applications in such areas as spectroscopy of highly excited states of atoms and molecules, life science, plasma physics and material science. In this paper we report the study of molecular coherent spectrum in the VUV and XUV regions through nonlinear optical processes and the determination of the rotational temperature of molecules. Because molecular gases have abundant energy levels, it can provide resonant levels to enhance the generated radiation and a wide tunibility of the spectrum in VUV and XUV regions. The determination of the rotational temperature of molecules will be very useful for the study of molecular spectroscopy and the nonlinear optical process in VUV/XUV regions.

Chemical Phenomena↗
PubMed1998

Loading of doxorubicin into liposomes by forming Mn2+-drug complexes.

A new procedure for loading doxorubicin into large unilamellar vesicles (LUVs) is characterized. It is shown that doxorubicin can be loaded into LUVs composed of sphingomyelin/cholesterol (55:45 mole/mole) in response to a transmembrane MnSO4 gradient in the absence of a transmembrane pH gradient. Complex formation between doxorubicin and Mn2+ is found to be a driving force for doxorubicin uptake. Uptake levels approaching 100% can be achieved up to a drug-to-lipid molar ratio of 0.5 utilizing an encapsulated MnSO4 concentration of 0.30 M. In vitro leakage assays show excellent retention properties over a 24 h period. The possible advantages of a liposomal formulation of doxorubicin loaded in response to entrapped MnSO4 are discussed.

Cholesterol↗
PubMed1998

A highly active microsomal glutathione transferase from frog (Xenopus laevis) liver that is not activated by N-ethylmaleimide.

Microsomal glutathione transferase has hitherto only been purified from mammalian species. N-ethylmaleimide and trypsin activation (discriminating features of this enzyme) has only been observed in microsomes from mammals. In this paper we describe the first isolation and characterization of a non-mammalian microsomal glutathione transferase from frog (Xenopus laevis) liver. This protein has a molecular weight similar to that of the mammalian enzyme (approximately 17 kDa), but cannot be activated by N-ethylmaleimide or trypsin. In fact the enzyme is rapidly inactivated by this sulfhydryl reagent and protease. It thus appears that N-ethylmaleimide activation is not an obligatory property of microsomal glutathione transferase. The frog liver microsomal glutathione transferase has one of the highest specific activities towards the second substrate 1-chloro-2,4-dinitrobenzene (CDNB) (200 mumol/min mg) obtained with any glutathione transferase and accounts for the high activity found in frog liver microsomes. The kcat/K(m) for glutathione and CDNB are 0.017 and 1.1 x 10(6) M-1 s-1, respectively. The enzyme also functions as a glutathione peroxidase (dilinoleoyl phosphatidylcholine hydroperoxide is reduced (5.2 mumol/min mg)). It is now evident that a highly active microsomal glutathione transferase, with a molecular weight similar to that of the mammalian enzymes also exists in a non-mammal species.

Animals↗
PubMed1997

Binding of glutathione and an inhibitor to microsomal glutathione transferase.

Microsomal glutathione transferase is an abundant liver protein that can be activated by thiol reagents. It is not known whether the activation is associated with changed binding properties of the enzyme. Therefore the binding of GSH and an inhibitor to rat liver microsomal glutathione transferase was studied by use of equilibrium dialysis and equilibrium partition in a two-phase system. The radioactive substrate glutathione and an inhibitor (glutathione sulphonate) give hyperbolic binding isotherms with a stoichiometry of 1 mol per mol of enzyme (i.e. 1 molecule per homotrimer). Glutathione had an equilibrium binding constant of 18 microM. Competition experiments involving glutathione sulphonate showed that it could effectively displace GSH. These and kinetic studies showed that the Kd and Ki for glutathione sulphonic acid are close to 10 microM. No change in these parameters was obtained after N-ethylmaleimide activation of the enzyme. Thus activation does not result from changes in binding affinity to GSH.

Animals↗
PubMed1995

Kinetic studies on rat liver microsomal glutathione transferase: consequences of activation.

Rat liver microsomal glutathione transferase is activated by sulfhydryl reagents and proteolysis. This property varies, however, depending on the combination, concentration and reactivity of the substrates. Thus, a multi-dimensional diagram can be envisioned in which the parameters affecting enzyme activity and activation are visualized. In principle activation could stem from an alteration in enzyme mechanism, transition-state complementarity, product release rate or pH-rate behaviour. These studies appear to rule out these possibilities and an alternate hypothesis is suggested based on the following experiments: (i) alternate substrate diagnosis of the kinetic mechanism of microsomal glutathione transferase indicates a random sequential mechanism. Non-activated and activated enzyme follow the same mechanism by these criteria. (ii) The microsomal glutathione transferase stabilizes a Meisenheimer complex between 1,3,5-trinitrobenzene and glutathione. The formation constants were similar for the unactivated and activated enzyme ((15 +/- 1).10(3) and (14 +/- 1).10(3) M-1, respectively, at pH 8). Inasmuch as the Meisenheimer complex resembles the transition state there is no evidence for an increased stabilization upon activation. (iii) The catalytic rate constant kcat does not vary with the viscosity in the assay medium. Thus, product release is not rate limiting for the unactivated and activated microsomal glutathione transferase (with saturating 1-chloro-2,4-dinitrobenzene and varying GSH). (iv) The pH dependence of the Kf-values for Meisenheimer complex formation exhibited pKa values close to 6 for both the activated and unactivated microsomal glutathione transferase. The pH profile of kcat (with saturating 1-chloro-2,4-dinitrobenzene and variable GSH concentrations) showed apparent pKa values of 5.7 +/- 0.5 and 6.3 +/- 0.4 for the unactivated and activated enzyme, respectively, indicative of a very similar requirement for deprotonation of the enzyme-GSH-1-chloro-2,4-dinitrobenzene complex. (v) Examination of the kinetic parameters (obtained with GSH as the variable substrate against increasingly reactive electrophilic substrates) in Hammett plots shows that the activation mechanism entails a more efficient utilization of GSH. It is suggested that a higher rate of formation of the glutathione thiolate anion occurs in the activated enzyme.

Amino Acid Sequence↗
PubMed1995

Harmful effects of MSG on function of hypothalamus-pituitary-target gland system.

It has been demonstrated that neonatal administration of monosodium glutamate (MSG) results in a clearly defined lesion of the arcuate nucleus (AN) of the hypothalamus. The present study shows that fat was accumulated in the abdomen of male rats treated with MSG; weights of the body, pituitary and testis were lower; beta-EP content in hypothalamus decreased while L.EnK content increased; serum LH, FSH, TSH, GH and TS levels all decreased in varying degrees while serum PRL level significantly increased. The cAMP content lowered in pituitary, but nor in testes; clear histological changes occurred in testicular tissue; Se-GSH-Px activity in both testis and adrenal gland lowered while LPO level significantly increased. Both Se-GSH-Px activity and LPO level in liver increased. These results indicate that MSG is harmful to the function of the hypothalamus-pituitary-target system of neonatal rats.

Adrenal Glands↗
PubMed1987

Clinical acceptability, use-patterns and use-effectiveness of the vaginal contraceptive sponge and Neo Sampoon tablets--an international multi-center randomized clinical trial.

This paper describes the results from a randomized clinical trial comparing the Collatex vaginal contraceptive sponge (a predecessor of the Today sponge) and Neo Sampoon foaming vaginal contraceptive tablets; the trial was conducted from 1979 to 1983 in four centers located in three countries (two in Yugoslavia and one each in Taiwan and Bangladesh). The sponge was associated with more insertion and retention problems than the tablet, especially in the two Asian centers. More Neo Sampoon users complained of a burning or stinging sensation. This complaint, however, seemed to be well-tolerated and was not a frequent reason for irregular use and/or discontinuation of use of the tablets. Clinically significant medical complications were rarely reported for either method. Sponge users were more likely to report irregular use than tablet users, primarily due to inconvenience of use. Rates of discontinuation at six months of use were also consistently higher among sponge users than Neo Sampoon users in the four centers. Life-table pregnancy rates at 12 months of use ranged from 3.8 to 18.2 per 100 sponge users and 6.2 to 29.9 per 100 Neo Sampoon users, based on data from the two Yugoslavian centers and the Taiwan center (data from the Bangladesh center were excluded from analysis of pregnancy rates). Practical implications of these findings are discussed.

Adolescent↗
PubMed1984

Social and economic change, intergenerational relationships, and family formation in Taiwan.

This paper examines the influence of social change and economic growth on intergenerational relationships and the formation of families in Taiwan. Using data from two island-wide surveys in 1973 and 1980, the analysis shows that, as expected, social change has been accompanied by rapid changes in family structure and relationships, including the spread of schooling, the employment of young people outside the family, increasing separation of the residences of parents and children before and after marriage, growing independence of young people, and increases in premarital sex and pregnancies. The position of a family in the social structure also influences the way young people interact with their parents and form their own families: women with educated fathers have more nonfamilial experiences than others, and farm origins tend to exert a traditional influence on the life course. Finally, experiences early in the life course have important ramifications for later behavior and transitions.

Adult↗
PubMed1982

Valproic acid analysis in saliva and serum using selected ion monitoring (electron ionization) of the tert.-butyldimethylsilyl derivatives.

A highly sensitive ion monitoring method for the determination of valproic acid in saliva and in serum has been developed based on the gas chromatographic--mass spectrometric analysis of the tert.-butyldimethylsilyl derivatives. Extraction methods are simple and the techniques for derivatization are rapid and convenient. Selected ion monitoring was carried out using electron ionization conditions and a common ion m/z 201 (M+--57) present in valproic acid and the internal standard octanoic acid. The lower limit of sensitivity that has acceptable precision for assay purposes is 0.1 mg/l based on a 200-microliter sample size. The ion monitoring method (derivatized) was compared to a gas chromatographic method (underivatized) for serum valproate assays and found to be essentially identical. The assay methodology was used in a kinetic study of valproic acid in two normal subjects. Saliva levels of drug were found to give reasonably good correlations with serum total and with serum free concentrations of drug in both individuals.U

Administration, Oral↗