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At least 1,495 records · Page 83Linked to original sources
PubMed1998

Mutagenesis of human Mel1a melatonin receptor expressed in yeast reveals domains important for receptor function.

A yeast functional colorimetric assay was employed to test the effects of site-directed point mutations on the function of the human Mel1a melatonin receptor. Seven mutants were created in transmembrane domains III, V, and VII of the receptor to test the rhodopsin-based model of melatonin recognition. Two mutants in transmembrane domains III and VI were created to investigate the mechanisms of G protein activation in the melatonin receptor. Mutations in transmembrane domain V either potentiated agonist efficiencies (H195A) or totally abolished all responses to tested compounds (V192T+H195A). Mutation N124A in the conserved NRY motif in the end of transmembrane domain III seriously impaired receptor activation. Several mutants were found to have decreased ability to activate functional responses, reflecting the importance of these residues for receptor function. These data also suggest that activation of the receptor involves interaction of the 5-methoxy group of melatonin with the conserved histidine H195 in transmembrane domain V.

Binding Sites↗
PubMed1997

Cationic phosphonolipids as non viral vectors for DNA transfection in hematopoietic cell lines and CD34+ cells.

The ability to transfer genes into a hematopoietic stem cell and to achieve regulation of their expression in lymphoid or myeloid lineages should open many new therapeutic opportunities. Besides gene transfer mediated by virus vectors like retrovirus or adenovirus, non viral systems have the theoretical advantage of being safe and easy to manage. We developed a new family of cationic lipids called phosphonolipids, synthesized 24 new molecules, and then in a first step we tested their potential to transfer genes in human hematopoietic cell lines (K562 and TF1). A LacZ plasmid under the control of a strong viral promoter was used as a reporter gene and a FACS-Gal assay and a quantitative test CPRG assay evaluated the beta gal expression. The targeted cells were analyzed 48 hours after transfection. The present work shows that seven novel molecules display a high transfer efficiency. One of them is nine-fold more efficient than the commercially available cationic lipids. The results obtained ex vivo on CD34 cells with the FACS-Gal assay show that at day 10 after transfection, 45 percent of cells are expressing gal.

Antigens, CD34↗
PubMed1993

Comparison of bacterial toxicity tests based on growth, dehydrogenase activity, and esterase activity of Pseudomonas fluorescens.

Bacterial test systems that are used to assess the environmental risk of chemicals show considerable differences in sensitivity to toxic chemicals. This variation may be caused by differences in sensitivity between species and test parameters of the test systems. In this study, the differences in sensitivity of three test parameters, growth, esterase activity, and dehydrogenase activity, using Pseudomonas fluorescens as the test organism, were studied. The effect of eight substances was tested: pentachlorophenol, 2,4-dichlorophenol, aniline, trichloroethylene, nonylphenolethoxylate, tetrapropylene benzene sulphonate, copper, and nickel. None of the three test parameters was the most sensitive to all substances, although dehydrogenase activity showed a high sensitivity in most cases. The observed differences in sensitivity among the three test parameters were of the same order of magnitude as those previously observed for different strains of bacteria. It was concluded that the choice of test parameter is just as important as the choice of test species to the sensitivity of a test system. The differences in sensitivity between test parameters and between species may account for a great deal of the observed variation between test results obtained with different methods.

Bacteriological Techniques↗
PubMed1993

The dehydrogenase assay with resazurin: practical performance as a monitoring system and Ph-dependent toxicity of phenolic compounds.

The dehydrogenase assay with resazurin as an oxidoreduction dye was used for monitoring the performance of six laboratory-scale sewage treatment plants. The dehydrogenase activity measured proved to be a reliable monitoring parameter, although it did not always positively correlate with the simultaneously estimated respiration activity. With the help of the dehydrogenase assay, the toxicity of different phenolic compounds was determined. It was found that the toxicity of 2.4-dichlorophenol, 3.5-dichlorophenol, and 2.4-dinitrophenol was clearly dependent on the pH. These data were supported by shock loading experiments in laboratory-scale sewage treatment plants.

Biological Assay↗
PubMed1997

Effects of hypoxia on valve-closure time and bioaccumulation of 2,4,5-trichlorophenol by the freshwater clam Sphaerium corneum [L].

The effects of hypoxia and 2,4,5-trichlorophenol (TCP) on the behavior of the freshwater clam Sphaerium corneum (L.) and the accumulation and elimination rates of 2,4,5-trichlorophenol were studied in the laboratory at 20 degrees C. After an initial high activity period, the shell valves were held closed for significantly longer periods in hypoxia than in normoxia. At the end of the 36-hr exposure period, the number of individuals with closed valves increased under normoxic conditions as well. The accumulation of TCP into clam tissues in normoxia was rapid and an uptake rate constant of 27.97 (+/-6.64) ml/g/hr was measured. An apparent steady state was achieved within 12 to 24 hr and the bioconcentration factors varied between 115 and 139. The depuration rate constant (kd) based on the accumulation data was 0.2717 (+/-0.07) hr-1. However, the much lower kd of 0.0137 (+/-0.0019) hr-1 measured over the depuration period from 24 to 120 hr suggests biphasic depuration kinetics. After a 6-hr exposure to TCP in both hypoxia and normoxia, the highest body burdens were found in clams exposed under normoxic conditions. A significant correlation was found between body burden and length of time the valves were open during the exposure. Results suggest that in short-term experiments, S. corneum can reduce the bioaccumulation of TCP by closing their shell valves.

Anaerobiosis↗
PubMed1998

Light and scanning electron microscopic cytopathology of 3, 5-dichlorophenol in the permanent fish cell line RTG-2.

The permanent fibrocyte-like fish cell line RTG-2 from rainbow trout (Oncorhynchus mykiss) gonads was investigated by means of light and scanning electron microscopy with respect to alterations as a consequence of sublethal exposure to 0, 1, 10, 16, 25, and 50 mg/liter 3,5-dichlorophenol (3,5-DCP) for 24 h. Control RTG-2 cells were spindle-like in shape and almost three times longer than wide. In subconfluent cultures, they displayed widely spread, flat leading lamellae and formed small groups. Along the edges of the cell protrusions, numerous retraction fibrils could be identified. Except for shallow ridges and small folds, the surface of untreated cells was completely smooth. Following exposure to 3,5-DCP, distinct dose-dependent alterations in cell shape, the appearance of surface blebs and invaginations, as well as progressive retraction of cell extensions could be observed from the lowest test concentration. Morphological changes could be correlated to suppression of lactate dehydrogenase and reduced neutral red retention capacity.

Animals↗
PubMed2000

Effects of 2,4-dichlorophenol on the net-spinning behavior of hydropsyche slossonae larvae (Trichoptera; Hydropsychidae), an early warning signal of chronic toxicity.

In order to assess the potential of hydropsychid capture net anomalies as a bioindicator of chronic toxicity in streams and rivers, the effects of 2,4-dichlorophenol (2,4-DCP) exposure on the net-spinning behavior of Hydropsyche slossonae were examined for anomalies after 0, 5, 10, 15, and 20 exposure days to gradient concentration of 2,4-dichlorophenol. The net-spinning behavior was significantly affected when larvae were exposed to 1.0, 10, 25, and 50 microg small middle dotL(-1), as expressed by the occurrence of two distinct abnormalities. The first one was a distortion of the midline meshes, where the normal diamond-shape structure is disrupted and the meshes are separated by extra strands (called "midline anomaly). The second aberration observed was called "chaotic net, where the nets are highly irregular without any real structure or well-defined areas. A good correlation was found between the chaotic net frequencies and the reduction of ATP concentrations in the larvae, indicating possible uncoupling effects of 2,4-DCP on the oxidative phosphorylation process. Toxicity curves demonstrate that the sensitivity threshold of chaotic net frequencies ranged from 3.5 to 7 microg small middle dotL(-1), which is highly sensitive compared with other sublethal effects of 2,4-DCP on other aquatic species.

Abnormalities, Drug-Induced↗
PubMed1995

Pesticide residues in urine of adults living in the United States: reference range concentrations.

We measured 12 analytes in urine of 1000 adults living in the United States to establish reference range concentrations for pesticide residues. We frequently found six of these analytes: 2,5-dichlorophenol (in 98% of adults); 2,4-dichlorophenol (in 64%); 1-naphthol (in 86%); 2-naphthol (in 81%); 3,5,6- trichloro-2-pyridinol (in 82%); and pentachlorophenol (in 64%). The 95th percentile concentration (95th PC) for 2,5-dichlorophenol (indicative of p-dichlorobenzene exposure) was 790 micrograms/liter; concentrations ranged up to 8700 micrograms/liter. 2,4-Dichlorophenol concentrations ranged up to 450 micrograms/ liter, and the 95thPC was 64 micrograms/liter. 1-Naphthol and 2-naphthol (indicative of naphthalene exposure) had 95thPCs of 43 and 30 micrograms/liter, respectively; concentrations of 1-naphthol ranged up to 2500 micrograms/liter. Chlorpyrifos exposure was indicated by 3,5,6-tricholoro-2-pyridinol concentrations of 13 (95thPC) and 77 micrograms/liter (maximum observed). Pentachlorophenol had a 95thPC of 8.2 micrograms/liter. Other analytes measured included 4-nitrophenol (in 41%); 2,4,5-trichlorophenol (in 20%); 2,4,6-trichlorophenol (in 9.5%); 2,4-dichlorophenoxyacetic acid (in 12%); 2-isopropoxyphenol (in 6.8%); and 7-carbofuranphenol (in 1.5%). The 95thPCs of these analytes were < 6 micrograms/liter. p-Dichlorobenzene exposure is ubiquitous; naphthalene and chlorpyrifos are also major sources of pesticide exposure. Exposure to chlorpyrifos appears to be increasing. Although pentachlorophenol exposure is frequent, exposure appears to be decreasing. These reference range concentrations provide information about pesticide exposure and serve as a basis against which to compare concentrations in subjects who may have been exposed to pesticides.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1997

Role of 3,4-dichlorophenyl methyl sulfone, a metabolite of o-dichlorobenzene, in the changes in hepatic microsomal drug-metabolizing enzymes caused by o-dichlorobenzene administration in rats.

2,3- and 3,4-Dichlorophenyl methyl sulfoxides and 2,3- and 3,4-dichlorophenyl methyl sulfones (2,3- and 3,4-DCPSO2Mes) were detected in the urine of rats administered o-dichlorobenzene (o-DCB). After administration of o-DCB to rats, swift decreases were observed in the concentrations of o-DCB in blood, liver, and kidneys, whereas 3,4-DCPSO2Me appeared in blood, liver, kidneys, and adipose tissue. The concentrations of 3,4-DCPSO2Me in the blood and three tissues reached maxima at 24 hr. Both aminopyrine N-demethylase and aniline hydroxylase activities and cytochrome P450 content of hepatic microsomes decreased 24 hr after administration of o-DCB. In contrast, 3,4-DCPSO2Me increased the activities of these enzymes and cytochrome P450 and b5 contents in rat liver microsomes. In both antibiotic-pretreated and bile duct-cannulated rats dosed with o-DCB, the concentrations of 2,3- and 3,4-DCPSO2Mes in blood, liver, kidneys, and adipose tissue were dramatically reduced. These findings suggest that the process of formation of methylsulfonyl metabolites of o-DCB involves biliary secretion of DCPSO2Mes and/or their precursors which will be subjected to metabolism by intestinal microflora. In antibiotic-pretreated rats, the inhibitory effects of o-DCB administration on the activities of aminopyrine- and aniline-metabolizing enzymes and the contents of cytochromes P450 and b5 in hepatic microsomes were greater than those observed in the intact rats. In bile duct-cannulated rats, the decrease in aminopyrine N-demethylase activity after administration of o-DCB was greater than that observed in the intact rats. These findings suggest that the apparent inhibition of drug-metabolizing enzymes by o-DCB is the result of simultaneous contrary effects, namely, the inductive effect of 3,4-DCPSO2Me and the stronger inhibitory effect of an unknown factor(s) on drug-metabolizing enzymes.

Aminopyrine N-Demethylase↗
PubMed1997

4-Amino-2,6-dichlorophenol nephrotoxicity in the Fischer 344 rat: protection by ascorbic acid, AT-125, and aminooxyacetic acid.

A halogenated derivative of 4-aminophenol, 4-amino-2, 6-dichlorophenol (ADCP), is a potent nephrotoxicant and a weak hepatotoxicant in Fischer 344 rats. Although the mechanism of ADCP nephrotoxicity is unknown, ADCP could undergo oxidation to a reactive intermediate, such as a 4-amino-2,6-dichlorophenoxy radical or 2,6-dichloro-1,4-benzoquinoneimine, which can generate additional free radicals and/or covalently bind to cellular proteins. The toxic process might also be mediated by glutathione (GSH) conjugates of ADCP, as suggested for the mechanism of 4-aminophenol nephrotoxicity. In this study, the effects of modulators of oxidation and GSH conjugation-related metabolism or transport on ADCP-induced nephrotoxicity were examined. In one set of experiments, male Fischer 344 rats (four/group) were intraperitoneally (ip) administered ADCP (0.38 mmol/kg) only or coadministered an antioxidant, ascorbic acid (1.14 mmol/kg, ip) with ADCP. Administration of ascorbic acid markedly reduced both functional nephrotoxicity and morphological changes induced by ADCP. Administration of a gamma-glutamyltransferase (GGT) inhibitor, l-(alphaS, 5S)-alpha-amino-3-chloro-4,5-dihydroxy-5-isoxazoleacetic acid (10 mg/kg, ip), or a cysteine conjugate beta-lyase inhibitor, aminooxyacetic acid (0.5 mmol/kg, ip), 1 hr before ADCP (0.38 mmol/kg) challenge partially protected rats against ADCP nephrotoxicity. In contrast, administration of an organic anion transport inhibitor, probenecid (140 mg/kg, ip), 30 min before ADCP had little effect on ADCP nephrotoxicity. The GSH depletor, buthionine sulfoximine (890 mg/kg, ip), was given 2 hr prior to ADCP and only minimal protection was noted. In addition, the nonprotein sulfhydryl (NPSH) contents in renal cortex and liver were determined at 2 hr following the administration of ADCP only or ascorbic acid/ADCP. Ascorbic acid afforded complete prevention of the depletion of NPSH in the kidney and liver caused by ADCP administration and also prevented the elevation of renal glutathione disulfide content induced by ADCP. The results indicate that oxidation of ADCP appears to be essential to ADCP nephrotoxicity and that GSH or GSH-derived conjugates of ADCP may be partly responsible for the nephrotoxic effects of ADCP via a GGT-mediated mechanism.

Aminooxyacetic Acid↗
PubMed1993

Cancer in phenoxy herbicide manufacturing workers in Denmark, 1947-87--an update.

This report is an update of a cohort study from the two Danish phenoxy herbicide manufacturing plants. The study originally covered the period 1947-82. Data now have been added for the period 1983-87. In 1943-87, the 940 phenoxy herbicide manufacturing and packaging workers experienced the same overall cancer incidence as the Danish population (observed [Obs] = 66; expected [Exp] = 64.27; standardized incidence ratio [SIR] = 1.0; 95 percent confidence interval [CI] = 0.8-1.3). The same was true for the 1,179 workers employed in manual service functions. The data for 1947-82 included five cases of soft tissue sarcoma (STS). One of these patients had his diagnosis changed when he died in 1985. One new STS case was diagnosed during the period 1983-87. This updated study thus includes a total of five STS cases. Four of the STS cases were observed among persons potentially exposed to phenoxy herbicide (Exp = 1.76; SIR = 2.3; CI = 0.6-5.8). Three of the cases occurred among men employed for at least one year in one factory. In this subgroup, an SIR of 6.4 (CI = 1.3-18.7) was observed when a 10-year latency period was taken into account. Based on small numbers, this Danish study thus continues to add to the evidence for a possible association between phenoxy herbicide exposure and risk of STS. Persons potentially exposed to phenoxy herbicide had an incidence of non-Hodgkin's lymphoma close to that of the Danish population (Obs = 4; Exp = 3.08; SIR = 1.3; CI = 0.4-3.3).

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed1996

Cancer mortality in German male workers exposed to phenoxy herbicides and dioxins.

In an occupational cohort study, the relation between exposure to phenoxy herbicides, and contaminants (dioxins and furans) and cancer mortality was investigated. A total of 2,479 workers from four plants in Germany were included, with a mortality follow-up until the end of 1989 (for one cohort, until the end of 1992). A total of 484 deaths were recorded yielding a standardized mortality ratio (SMR) of 101 (95 percent confidence interval [CI] = 92-111) for total mortality, and an SMR of 119 (CI = 100-141) for all malignant diseases. A variety of herbicides was produced, including those which are known to have been contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). High dioxin and furan exposure (in particular, exposure to TCDD, but also to higher chlorinated dioxins) had occurred in two of the four plants as shown by blood-fat measurements in a sample of workers. Mortality from all neoplasms increased with latency and was highest in the largest plant where the highest TCDD blood levels were recorded. An increased mortality in the total cohort from respiratory cancer (SMR = 154, CI = 115-202), cancer of the buccal cavity and pharynx (SMR = 295, CI = 135-560), and non-Hodgkin's lymphoma (SMR = 326, CI = 119-710) was observed. Our findings are consistent with results from other cohorts which showed an increased overall cancer mortality and mortality of respiratory cancer after long-term exposure to these phenoxy herbicides and dioxins.

Adipose Tissue↗