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Biomedical subjects

A Kettrup

Publications and source records attributed to A Kettrup.

At least 37 records · Page 2Linked to original sources
PubMed2002

Quantitative relationships between molecular structures, environmental temperatures and octanol-air partition coefficients of PCDD/Fs.

A concise quantitative model that incorporates information on both environmental temperature (T) and molecular structures, for logarithm of octanol-air partition coefficient (K(OA)) to base 10 (logK(OA)) of PCDDs, was developed. Partial least squares (PLS) analysis together with 14 quantum chemical descriptors were used to develop the quantitative relationships between structures, environmental temperatures and properties (QRSETP) model. It has been validated that the obtained QRSETP model can be used to predict logK(OA) of other PCDDs. Molecular size, environmental temperature (T), q+ (the most positive net atomic charge on hydrogen or chlorine atoms in PCDD molecules) and E(LUMO) (the energy of the lowest unoccupied molecular orbital) are main factors governing logK(OA) of PCDD/Fs under study. The intermolecular dispersive interactions and thus the size of the molecules play a leading role in governing logK(OA). The more chlorines in PCDD molecules, the greater the logK(OA) values. Increasing E(LUMO) values of the molecules leads to decreasing logK(OA) values, implying possible intermolecular interactions between the molecules under study and octanol molecules. Greater q+ values results in greater intermolecular electrostatic repulsive interactions between PCDD and octanol molecules and smaller logK(OA) values.

Journal Article↗
PubMed2002

Identification and quantification of metallothionein isoforms and superoxide dismutase in spiked liver extracts using HPLC-ESI-MS offline coupling and HPLC-ICP-MS online coupling.

A two-dimensional chromatographic method for the characterization of metallothionein isoforms (MT) and superoxide dismutase (SOD) in spiked liver extracts was developed for the optimization of extraction procedures from liver samples. Element-specific detection (ICP-MS) and molecule-specific detection (ESI-MS) were applied for maximum species information. A special focus was laid on the quantitative data evaluation (species stoichiometry, calibration with and without matrix, recovery), which is neglected in most MT/SOD publications with hyphenated techniques. Linearity, precision (residual standard deviation of calibration curves <10%), and detection limits (<0.6 mg L(-1) for MT isoforms and 13 mg L(-1) for SOD) prove the suitability of the method for quantification. An alternative quantification is proposed for the extension towards other lesser or even unknown trace element species, especially the native porcine MT and SOD.

Animals↗
PubMed2002

Correct identification of polychlorinated biphenyls in temperature-programmed GC with ECD detection.

A method has been developed for peak identification of PCBs in GC with ECD detection under different temperature programs and isothermal conditions on two commonly used columns (DB-5 and DB-1701). This was achieved by means of accurate calibration of retention times based on the concept of the relative retention index P (i) and retention times of the selected PCB internal standards. The P (i) was calculated from the predicted retention times with the database of the retention parameters (A, B) and the migration equations. Through comparison of the calibrated and experimental retention times of PCBs in technical samples, it was shown that the developed method was effective for correct PCB comprehensive, quantitative, congener-specific (CQCS) analyses.

Journal Article↗
PubMed2002

Computer-assisted automatic peak recognition and result evaluation for analysis of chlorinated hydrocarbons in environmental samples.

A data manipulation method has been developed for automatic peak recognition and result evaluation in the analysis of organic chlorinated hydrocarbons with dual-column gas chromatography. Based on the retention times of two internal standards, pentachlorotoluene and decachlorobiphenyl, the retention times of chlorinated hydrocarbons can be calibrated automatically and accurately. It is very convenient to identify the peaks by comparing the retention times of samples with the calibrated retention times calculated from the relative retention indices of standards. Meanwhile, with a suggested two-step evaluation method the evaluation coefficients and the suitable quantitative results of each component can be automatically achieved for practical samples in an analytical system using two columns with different polarities and two internal standards.

Automation↗
PubMed2002

Study on the multiple sites binding of human serum albumin and porphyrin by affinity capillary electrophoresis.

Equations to describe the two sites binding between proteins and ligands were deduced. According to these equations, not only the binding constants, but also the mole fraction of proteins in different forms could be obtained. Using the published data on the interaction between human serum albumin (HSA) and three kinds of porphyrin (coproporphyrin (CP), uroporphyrin I (UP) and protoporphyrin (PP)), a further study on their binding was carried out. It was concluded that there may exist two binding sites with the binding constants at the first site, proved to be the preferential one, being 6.50 x l0(5), 1.94 x 10(6) and 8.94 x 10(5), respectively. In addition, it was also demonstrated that the two binding sites of HSA with CP and UP might be of different kinds, though those of HSA and PP were of the same kind but at different positions.

Binding Sites↗
PubMed2002

Contamination and distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in agriculture fields in Ya-Er Lake area, China.

The contamination and distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from two agricultural fields of a heavily polluted lake area in China (Ya-Er Lake) are presented. The vertical distribution pattern of total PCDD/Fs in soil cores reveals that the maximum concentration was in the layer of 20-30 cm. The concentrations in the top layer of soil at the two sites were similar (17.48 ng/kg at Site 1 and 18.10 ng/kg at Site 2), but the maximum concentration of Site 1 (120.8 ng/kg) was two times higher than that of Site 2 (64.39 ng/kg). The maximum concentration of PCDD/Fs in mud cores in rice fields (0-50 cm) at Sites 1 and 2 was in the layer of 0-10 cm. The maximum PCDD/F concentration in the top layer in mud at Site 1 (203.1 ng/kg) was higher than that at Site 2 (143.3 ng/kg). Significant correlations were found between the mud PCDD/Fs and the organic carbon content (R = 0.9743, P < 0.05 at Site 1; R = 0.9821, P < 0.05 at Site 2), the two variables being highly correlated (R = 0.9049, P < 0.05, at Site 1; R = 0.9916, P < 0.05 at Site 2). All correlation coefficients were significant at the 95% level. Concentrations were highly correlated with organic carbon, indicating that sorption to organic carbon was the dominant mechanism. Using principal component analysis, the homologue profiles of soil, mud, and plants (rice and radish) were compared. The PCDD/F patterns in plants were found not to be correlated to those in soil and mud. This suggests that atmospheric deposition may be the main source of PCDD/Fs in rice grain. However, mixed exposure involving uptake mechanisms and atmospheric deposition is considered main the source of PCDD/F pollution in radishes.

Agriculture↗
PubMed2002

Ozonation of hydrolyzed azo dye reactive yellow 84 (CI).

The combination of chemical and biological water treatment processes is a promising technique to reduce recalcitrant wastewater loads. The key to the efficiency of such a system is a better understanding of the mechanisms involved during the degradation processes. Ozonation has been applied to many fields in water and wastewater treatment. Especially for textile mill effluents ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the chemical oxygen demand (COD). However, little is known about the reaction intermediates and products formed during ozonation. This work deals with the degradation of hydrolyzed Reactive Yellow 84 (Color Index), a widely used azo dye in textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the hydrolyzed dye in ultra pure water was performed in a laboratory scale cylindric batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (400 nm), was almost complete after 60 and 90 min with an ozone concentration of 18.5 and 9.1 mg/l, respectively. The TOC/TOC0 ratio after ozonation was about 30%, the COD was diminished to 50% of the initial value. The BOD5/COD ratio increased from 0.01 to about 0.8. Oxidation and cleavage of the azo group yield nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused increases in the amount of sulfate. Formic acid and oxalic acid were identified as main oxidation products by high performance ion chromatography (HPIC). The concentrations of these major products were monitored at defined time intervals during ozonation.

Azo Compounds↗
PubMed2002

Reproduction disturbances of Brachionus calyciflorus (rotifer) for the screening of environmental endocrine disrupters.

Rotifers and especially the Brachionus calyciflorus species have already shown advantages (e.g. good sensitivity, simplicity, ecological relevance, short generation time) for the chronic toxicity assessment of water pollutants. In this study, the B. calyciflorus three-day test was evaluated on ethinylestradiol, nonylphenol and testosterone for the determination of endocrine disrupting (reproductive) effects. Reproduction (intrinsic rate of population increase) and sex ratio (males/females and mictic females/amictic females) were explored and discussed as suitable endpoints. B. calyciflorus has shown a fair sensitivity to detect reproductive disrupting effects after exposure to ethinylestradiol, nonylphenol and testosterone. Population growth (intrinsic rate of population increase, r) and the ratio ovigerous females/ non-ovigerous females are both suitable endpoints, whereas the occurrence of males was not frequent enough to be used as endpoint.

Animals↗
PubMed2002

Endocrine effects of sublethal exposure to persistent organic pollutants (POPs) on silver carp (Hypophthalmichthys molitrix).

Silver carp (Hypophthalmichthys molitrix) samples were collected from five selected sites that represent diverse levels of downgraded persistent organic pollutants (POPs) contamination in Ya-Er Lake in October 1999. Hepatic ethoxyresorufin-O-deethylase (EROD) and UDP glucuronosyltransferase (UDPGT) activities, hepatosomatic index (HSI), hepatic retinoids, serum thyroid hormones were measured. It was found that hepatic retinol and serum free 3,5,3'- tetraiodothyronine (FT3) significantly increased (P < 0.01) when both hepatic EROD and UDPGT activities significantly declined (P < 0.01) from pond 1 to 5 with decrease in the degree of pollution. This significant negative correlation (P < 0.01) suggests that the persistent organochlorinated contaminants could induce hepatic EROD and UDPGT activities, alter retinoid and thyroid hormone homeostasis, and finally lead to the reduction of retinol and FT3, the two biologically active forms of retinoids and thyroid hormone in silver carp of Ya-Er Lake.

Animals↗
PubMed2002

Linear free energy relationships on rate constants for dechlorination by zero-valent iron.

By correlation analysis, molecular structural factors governing surface area-normalized rate constants (k) for dechlorination by zero-valent iron, were identified. Twenty-nine quantum chemical descriptors computed by MNDO, AM1 and PM3 Hamiltonians for gas-phase and the conductor-like screening model (COSMO) for incorporating solvent (H2O) effects were studied. Besides the energy of the lowest unoccupied molecular orbital (E(LUMO)), the character of carbon-chlorine bonds (C-Cl bonds) and especially the strength of C-Cl bonds was found significant in governing the magnitude of log k. By PLS analysis, six two-parameter linear free energy relationships (LFER) were obtained. The best two-parameter LFER model was the one using E(LUMO) and C (the Coulombic interaction energy of the two-center term for the C-Cl bonds) computed by PM3/H2O method as molecular structural descriptors. Chlorinated compounds with high E(LUMO) and C values tend to have low dechlorination rate constants.

Carbon↗
PubMed2001

Comparison of different extraction techniques for the determination of polychlorinated organic compounds in sediment.

The performance of various enhanced extraction techniques, such as accelerated solvent extraction, microwave-assisted extraction, Soxhlet extraction, ultrasonic extraction and fluidized-bed extraction for the determination of polychlorinated organic compounds in dry sediment was investigated in two laboratories. The results of the two laboratories were in good agreement. The extraction yields from the batch extraction methods were lower than those from the dynamic techniques. Accelerated solvent extraction, especially, exhibited higher extraction efficiency than the standard procedure, Soxhlet extraction, whereas the results of fluidized-bed extraction were comparable.

Journal Article↗
PubMed2001

Monitoring polycyclic aromatic hydrocarbon metabolites in human urine: extraction and purification with a sol-gel glass immunosorbent.

A new, rapid method for selective extraction of hydroxylated polycyclic aromatic hydrocarbons metabolites (OH-PAHs) in human urine was developed using an immunosorbent of anti-pyrene antibodies which were encapsulated in a sol-gel glass (SGG) matrix. Resulting chromatograms after immunoextraction of urine samples and HPLC analysis of the extracts were free from matrix interferences. The LODs for the determination of OH-PAHs in these difficult samples were in the low-ppt range (1-16 ng/L). In addition to its high selectivity, the immunosorbent proved to be robust and reusable. Obtained recoveries in spiked urine samples ranged from 83 to 107% for the hydroxyphenanthrene and hydroxypyrene compounds under investigation, while recovery for 3-hydroxybenzo[a]pyrene was only 45-62%. In a biomonitoring study, the SGG immunosorbent was successfully used for trace-level analysis of OH-PAHs in 20 human urine samples. Results were compared to data obtained by an independent reference analysis method and revealed good correlation between both methods.

Carcinogens↗
PubMed2001

Regioselective synthesis of a branched isomer of nonylphenol, 4-(3',6'-dimethyl-3'-heptyl)phenol, and determination of its important environmental properties.

A method for the synthesis of a pure nonylphenol isomer, 4-(3',6'-dimethyl-3-heptyl)phenol, by Friedel-Crafts reaction between anisole and 3-bromo-3,6-dimethylheptane that gives a 47.3% overall yield is reported. The reactions were followed by GC-MS, and the chemical structures are in agreement with the NMR and IR spectra. The log K(ow) value for this compound, its water solubility, vapor pressure, and Henry's Law constant were also determined. These physicochemical properties were required for prediction of the compound's behavior in aquatic ecosystems.

Journal Article↗