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At least 127 records · Page 7Linked to original sources
PubMed1979

Determination of chlorinated pesticide residues in foods. I. Rapid screening method for chlorinated pesticides in milk.

A rapid analytical method for determining chlorinated pesticide residues in milk was developed. Thirteen pesticides were almost completely extracted. Ten mL samples of fortified milk were extracted 3 times with 20 mL portions of n-hexane as follows: (A) in the absence of water-soluble solvent; in the presence of (B) 1 mL acetonitrile; (C) 3 mL acetonitrile; (D) 5 mL acetonitrile; (E) 5 mL ethanol; (F) 5 mL acetonitrile and 1 mL ethanol. System F produced the highest pesticide recoveries but the lowest fat extraction, thus eliminating the necessity for liquid-liquid partitioning and minimizing Florisil column cleanup. Pesticide recoveries throughout the procedure were 94--103%. It was noticed, however, that the fat in high fat-containing raw milk is more readily extracted than that in commercial milk.

Animals↗
PubMed2003

Theoretical study of chlorine nitrates: implications for stratospheric chlorine chemistry.

Reported here is a theoretical study of possible stratospheric chlorine reservoir species including isomers of chemical formula ClNO(4) and ClNO(5), in addition to the well-known ClONO(2) reservoir species. Density functional theory (DFT) in conjunction with large one-particle basis sets has been used to determine equilibrium structures, dipole moments, rotational constants, harmonic vibrational frequencies, and infrared intensities. The B3LYP functional was used since it has previously been shown to perform well for similar compounds. The equilibrium geometry and vibrational spectra of ClONO(2) are shown to be in good agreement with the experimental data and also with high-level coupled-cluster calculations reported previously. Three stable isomers have been identified for each ClNO(4) and ClNO(5). The vibrational spectrum of O(2)ClONO(2) has been compared with the available experimental data and found to be in good agreement. The relative energetics of the ClNO(4) and ClNO(5) isomers have been determined using large atomic natural orbital (ANO) basis sets in conjunction with the singles and doubles coupled-cluster method that includes a perturbational correction for triple excitations, denoted CCSD(T). Accurate heats of formation have been evaluated by computing energies for isodesmic reactions involving the ClNO(4) and ClNO(5) isomers. The stability of these molecules with respect to thermal dissociation is examined. The present study suggests that isomers of ClNO(4) and ClNO(5) may have no atmospheric chemical relevance because the atmospheric concentrations of the necessary reactants are insufficient, but it is also found that under laboratory conditions the formation of O(2)ClONO(2) cannot be ignored.

Journal Article↗
PubMed1983

Bacterial methylation of chlorinated phenols and guaiacols: formation of veratroles from guaiacols and high-molecular-weight chlorinated lignin.

Two strains of bacteria, provisionally assigned to the genus Arthrobacter, were shown to metabolize mono-, di-, tri-, and tetrachloroguaiacols and pentachlorophenol to the corresponding O-methyl compounds. Hydroxylated intermediates were formed only transiently, except for the synthesis by one strain of 3,4,5-trichlorosyringol from 3,4,5-trichloroguaiacol. Two isomeric trichloroveratroles and tetrachloroveratrole were formed by three of the strains from a high-molecular-weight chlorinated lignin isolated from kraft pulp mill bleach plant. The concentrations of methylated metabolites varied widely and did not appear to be correlated with degradation. The possible environmental consequences resulting from synthesis of these highly lipophilic substances are discussed briefly.

Journal Article↗
PubMed1998

Photocytotoxic action of EGF-PVA-Sn(IV)chlorin e6 and EGF-dextran-Sn(IV)chlorin e6 internalizable conjugates on A431 cells.

Certain tumour cells, such as squamous carcinoma cells, express an increased number of epidermal growth factor (EGF) receptors. The goal of this study was the targeted delivery of Sn(IV)chlorin e6 (SnCe6) to tumours that overexpress the EGF receptor. Therefore EGF was conjugated to the photosensitizer through a carrier, such as dextran (Dex) and polyvinylalcohol (PVA). These conjugates were then compared to a conjugate of the photosensitizer to dextran or PVA alone. The EGF-Dex-SnCe6 conjugates bound specifically to the EGF receptors of the human squamous carcinoma cell line A431 in contrast to EGF-PVA-SnCe6. However, EGF-PVA-SnCe6 exhibited a higher photocytotoxicity (CC50, 2.8 microM) than EGF-Dex-SnCe6 (CC50, >10 microM) and SnCe6 (CC50, >10 microM). PVA-SnCe6 had a similar photocytotoxicity (CC50, 3.5 microM) to EGF-PVA-SnCe6, indicating that PVA, more than EGF, plays a determinant role in the uptake of the conjugates by A431 cells. Together with the improved affinity of EGF-Dex-SnCe6 over EGF-PVA-SnCe6 for the EGF receptor, the former displayed a small increased photocytotoxicity over Dex-SnCe6, reflecting a limited EGF receptor mediated uptake effect. It was concluded that the photodynamic activity of the EGF-conjugate turns out to be strongly dependent on the carrier used.

Binding, Competitive↗
PubMed1989

The effect of chlorinated chemicals on porphyrin metabolism--the synergistic effect with chlorinated chemicals and low concentrations of griseofulvin.

The synergistic effect of chlorinated chemicals and 0.1% griseofulvin on porphyrin metabolism was investigated. Feeds containing 0.1% 4-chloro-m-cresol, 0.1% cumarone or 0.25% trichloroacetic acid with or without 0.1% griseofulvin were given to dd-y strain mice respectively. The treatments were continued for 10 to 450 days, after which coproporphyrin and protoporphyrin in the erythrocytes and liver were analyzed. In the 0.1% griseofulvin alone group, protoporphyria was induced in 6 of 55 dd-y strain mice, although the other 49 mice did not show any abnormal porphyrin metabolism and the severity of the protoporphyria was mild in the 6 mice. In the 4-chloro-m-cresol group, a slight elevation of erythrocytic porphyrins was seen, but the difference was not statistically significant. Elevation of the hepatic porphyrins was not seen. Trichloroacetic acid and cumarone did not influence porphyrin metabolism, and also there was no synergistic effect of griseofulvin on porphyrinopathy. These results suggest that the three chemicals selected in this study are not capable of inducing porphyrinopathy.

Animals↗
PubMed1979

Determination of chlorinated pesticide residues in foods. II. Simultaneous analysis of chlorinated pesticide and phthalate ester residues by using AgNO3-coated Florisil column chromatography for cleanup of various samples.

A simplified method suitable for simultaneous analysis of chlorinated pesticide and phthalate ester residues in various foods was developed. Chemical residues were quantitatively extracted from fatty and vegetable samples with acetonitrile as follows: Chemical standard in 0.5 mL ethanol solution was added to 10 g homogenized sample. After 3 hr, pork and beef were extracted 3 times with 20 mL portions of acetonitrile. The acetonitrile layers were diluted with water and extracted with n-hexane. Rice samples were combined with 10 mL water, 5 mL acetonitrile and 1 mL ethanol and extracted 3 times with 20 mL portions of n-hexane. The n-hexane concentrate from each sample was submitted to AgNO3-coated Florisil column chromatography. The AgNO3 coating adequately adsorbed interfering coextractives. Extracts of fish and vegetable samples were separated into 2 fractions by the above column chromatography. Supplemental cleanup procedures were also developed to accurately determine phthalate esters eluted in the second fraction. Satisfactory gas chromatograms were obtained for most samples.

Animals↗
PubMed1992

Analysis of DNA strand breaks induced in rodent liver in vivo, hepatocytes in primary culture, and a human cell line by chlorinated acetic acids and chlorinated acetaldehydes.

An alkaline unwinding assay was used to quantitate the induction of DNA strand breaks (DNA SB) in the livers of rats and mice treated in vivo, in rodent hepatocytes in primary culture, and in CCRF-CEM cells, a human lymphoblastic leukemia cell line, following treatment with tri- (TCA), di- (DCA), and mono- (MCA) chloroacetic acid and their corresponding aldehydes, tri- (chloral hydrate, CH), di- (DCAA) and mono- (CAA) chloroacetaldehyde. None of the chloroacetic acids induced DNA SB in the livers of rats at 4 hr following a single administration of 1-10 mmole/kg. TCA (10 mmole/kg) and DCA (5 and 10 mmole/kg) did produce a small amount of strand breakage in mice (7% at 4 hr) but not at 1 hr. N-nitrosodiethylamine (DENA), an established alkylating agent and a rodent hepatocarcinogen, produced DNA SB in the livers of both species. TCA, DCA, and MCA also failed to induce DNA strand breaks in splenocytes and epithelial cells derived from the stomach and duodenum of mice treated in vivo. None of the three chloroacetaldehydes induced DNA SB in either mouse or rat liver. The continuous exposure of mice to 5 g/L DCA in the drinking water for 7 and 14 days did not induce appreciable hepatic DNA SB (< 10% at 14 days), although peroxisome proliferation, as evidenced by an increased cyanide-insensitive palmitoyl CoA oxidase (PCO) activity, was stimulated to 490% (7 days) and 652% (14 days) of control. Under this protocol, DENA (0.1 g/L) produced DNA damage after both 7 days (73% of control) and 14 days (57% of control). Similarly, long-term exposure of rats (30 weeks) to 2 g/L DCA in the drinking water, a level that increased PCO activity to 364% of the control value, exhibited no DNA damage. Both the chloroacetic acids and the chloroacetaldehydes were ineffective in inducing DNA SB in cultured rat and mouse hepatocytes at concentrations below those that yielded cytotoxicity. The chloroacetic acids were also ineffective in the CCRF-CEM cells. However, two of the chloroaldehydes, DCAA and CAA, did induce DNA SB in the CCRF-CEM cells at concentrations that did not decrease the cell viability after 2 hr of treatment. Prior incubation of DCAA and CAA with a rat S9 liver homogenate eliminated much of the DNA damaging activity. These studies provide further evidence that the chloroacetic acids lack genotoxic activity not only in rodent liver, a tissue in that they induce tumors, but in a variety of other roden tissues and cultured cell types.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetaldehyde↗