摘要:

The half‐life of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (2,3,7,8‐TCDD; commonly known as dioxin) in serum has been measured in 36 Air Force Vietnam veterans of Operation Ranch Hand, which was the operation that aerially sprayed the herbicide Agent Orange in Vietnam. From serum specimens taken in 1982 and 1987, the median half‐life of 2,3,7,8‐TCDD in these Ranch Hand veterans was found to be 7.1 yr (95% confidence interval about the median of 5.8–9.6 yr). These veterans reported no civilian exposure to dioxin or herbicides. Concentrations of 2,3,7,8‐TCDD in the 1982 serum specimens from these veterans ranged from 16.9 to 423 parts per trillion on a lipid weight basis. The half‐life estimates were not associated with the concentration of 2,3,7,8‐TCDD in the 1982 serum specimens. This half‐life of 7.1 yr is much longer than the half‐life of 2,3,7,8‐TCDD reported in animals but is consistent with recent evidence from other human exposures to 2,3,7,8‐TCDD.

ISSN:0098-4108    

DOI:10.1080/15287398909531288

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Male Syrian golden hamsters were used for an initiation‐promotion study of respiratory tract carcinogenesis. Hamsters were given a single subcutaneous dose of 0 or 80 mgN‐nitrosodiethylamine (NDEA)/kg body weight and were fed diets containing 0 or 100 mg polybrominated biphenyls (PBB)/kg diet for 140 d. Basal diet was fed from d 140 until the end of the experiment on d 273. The number of tracheal papillomas was significantly increased in hamsters given NDEA and PBB as compared to those in hamsters given only NDEA. Tracheal papillomas were not seen in untreated hamsters or in those not given NDEA and fed diets containing PBB. Nasal tumors occurred at approximately the same incidence in hamsters given NDEA as in those given NDEA and PBB. Results indicate that PBB may promote the development of tracheal papillomas in the hamster.

ISSN:0098-4108    

DOI:10.1080/15287398909531289

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Estimated half‐lives of mercury following methylmercury exposure in humans are 52–93 d for whole body and 49–164 d for blood. In its most recent 1980 review, the World Health Organization concluded that there was no evidence to suggest that brain half‐life differed from whole‐body half‐life. In the present study, female monkeys (Macaca fascicularis) were dosed for at least 1.7 yr with 10, 25, or 50 μg/kg·d of mercury as methylmercuric chloride. Dosing was discontinued, and blood half‐life was determined to be about 14 d. Approximately 230 d after cessation of dosing, monkeys were sacrificed and organ and regional brain total mercury levels determined. One monkey that died while still being dosed had brain mercury levels three times higher than levels in blood. Theoretical calculations were performed assuming steady‐state brain : blood ratios of 3, 5, or 10. Brain mercury levels were at least three orders of magnitude higher than those predicted by assuming the half‐life in brain to be the same as that in blood. Estimated half‐lives in brain were between 56 (brain : blood ratio of 3) and 38 (brain : blood ratio of 10) d. In addition, there was a dose‐dependent difference in half‐lives for some brain regions. These data clearly indicate that brain half‐life is considerably longer than blood half‐life in the monkey under conditions of chronic dosing.

ISSN:0098-4108    

DOI:10.1080/15287398909531290

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Chlordecone was reported to produce neurotoxicity by modulating the Na+pump in adult rat brain. The present in vitro and in vivo studies were initiated to investigate its effect on maturing rat brain ATPases. Neonates were exposed to chlordecone for 20 d indirectly through lactation by treating the mothers po and from 21 to 50 d as adults. Brain P2fractions were prepared from treated and control rats. Na+, K+, oligomycin‐sensitive (O.S.) and oligomycin‐insensitive (O.I.) Mg2+‐ATPase activities were increased with age up to d 20. Na+, K+‐ and O.S. Mg2+‐ATPases were inhibited in both in vitro and in vivo treatment with chlordecone. Both these enzymes were more sensitive to chlordecone in the neonatal brains as compared to adult rats (20–50 d). The activity of Mg2+‐ATPase but not of Na+, K+‐ATPase was restored to normal activity after 20 d of withdrawal of chlordecone treatment. O.I. Mg2+‐ATPase was insensitive to chlordecone treatment in all age groups. Ca2+‐ATPase activity was not increased with age; however, it was more sensitive to chlordecone in neonates as compared to adults. These results suggest that the Na+pump, Ca2+‐ATPase, and ATP synthesizing enzymes are highly sensitive to chlordecone during early postnatal development.

ISSN:0098-4108    

DOI:10.1080/15287398909531291

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Organophosphates (OP) comprise one of the major classes of pesticides in use today. It is well accepted that the primary site of action of the OPs is at cholinergic synapses. However, it has been suggested that OPs may have direct neural effects as well. In this study, cultured chick dorsal root ganglia (DRC) were used to study the effect of fenthion (FEN), an OP pesticide, on isolated nerve cell growth and ultrastructure. Light microscopic evaluation revealed a dose‐response relationship between the concentration of FEN (10−2Mto 10−5M) and severity of morphologic changes. Cultured ex‐plants were treated with a lower concentration of FEN (10−6M) and morphologic alterations were compared to those observed in explants treated with 10−6Mparaoxon, a more acutely toxic OP, or 10−6Mneostigmine, a non‐OP inhibitor of acetyl‐cholinesterase. Based on both light and electron microscopy, neostigmine had no observed effect on cell morphology except for an inhibition of the extension of neurites by DRG cells. In contrast, explants treated with OPs exhibited a significant alteration in cell morphology. Initial lesions were observed first in the neurites and pseudo‐podia and consisted of vacuolization, loss of tubular structures, retraction of pseudopodia, and cell membrane disruption at the growth cone. Lipid accumulations were observed within the cytoplasm of treated cells. The effects of paraoxon on DRG cell morphology were significantly more severe than the effects of FEN, and lipid vacuoles observed in paraoxon‐treated cells were several times larger than those observed in FEN‐treated cells (5–10 μm in diameter vs. 0.5–1.0 μm in diameter). Results show that OPs have a direct effect on DRG nerve cells in culture, consistent with an alteration in cell membrane integrity. Cultured DRG cells can be useful in the evaluation of toxicologic effects.

ISSN:0098-4108    

DOI:10.1080/15287398909531292

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Pitch and bitumen, two complex petroleum derivative mixtures, were studied for both their chemical composition and their mutagenic/DNA damaging activity. While bitumen revealed no genotoxic effect and low polycyclic aromatic hydrocarbons (PAHs) concentration, petroleum pitch showed a high concentration of mutagenic/carcinogenic PAHs, and also an elevated mutagenic activity when assayed by the Ames test, in the presence of postmitochondrial rat liver fractions. The in vitro mutagenic activity was detectable as frameshift mutation by assaying the pitch both as an in toto mixture and after HPLC fractionation, the most polar fractions being the most active. In contrast, both derivatives showed no in vivo DNA damage in rat liver, using the DNA alkaline elution technique and the fluorometric assay of DNA unwinding.

ISSN:0098-4108    

DOI:10.1080/15287398909531293

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Adult rats were exposed to 1 ppm (1.96 mg/m3) ozone or air for 2 wk. Animals were sacrificed at 3, 5, 7, or 14 d after the onset of exposure, and samples of plasma and lung lavage were obtained. Heat‐inactivated plasma, from animals exposed to ozone for 7 or 14 d, significantly increased DNA synthesis by lung fibroblasts compared with plasma from air‐exposed animals. Fractionation of plasma and lavage samples indicated that the factor responsible had an isoelectric point of 6.45–6.75 and a molecular weight of 32 ± 2 kDa. This factor has a dose‐dependent effect on lung fibroblast DNA synthesis in culture, but no significant effect on cultured pneumocyte DNA synthesis. The factor is detectable within 72 h of exposure, and may hold some promise as a marker of early oxidant lung injury.

ISSN:0098-4108    

DOI:10.1080/15287398909531294

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The ability of the rat liver to oxidize 2‐butanol via a cytochrome P‐450‐mediated mixed‐function oxidase reaction is well known. The purpose of this study was to examine this microsomal alcohol oxidizing system in rat lung and determine if it could be altered by treatments that inhibit or induce this activity. 2‐Butanol was incubated with microsomal preparations from male rats, and methyl ethyl ketone production was measured by gas chromatography. The rate was six to eight times lower in lung than in liver. Administration of low doses of ethanol (0.5 ml/kg and 1.0 ml/kg) ip for 7 d did not alter activity in the liver but was inhibitory in the lung, as was a high dose of 3.0 ml/kg in the liver. Carbon tetrachloride (1.0 ml/kg, ip) decreased activity in both tissues, especially the lung. The effects of the two inhibitors were not additive. Methyl ethyl ketone induced 2‐butanol oxidation in both tissues. The lung possesses butanol oxidase activity that is alterable by both inhibitors and inducers.

ISSN:0098-4108    

DOI:10.1080/15287398909531295

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Studies were conducted with mallard (Anas platyrhynchos) ducklings to determine the effects of excess dietary selenium (Se) on hepatic glutathione concentration and associated enzymes, and lipid peroxidation. Day‐old ducklings were fed 0.1, 10, 20, or 40 ppm Se as seleno‐DL‐methionine or sodium selenite for 6 wk. Selenium from selenomethionine accumulated in a dose‐dependent manner in the liver, resulting in a decrease in the concentration of hepatic‐reduced glutathione (GSH) and total hepatic thiols (SH). These effects were accompanied by a dose‐dependent increase in the ratio of oxidized glutathione (GSSG) to GSH, and an increase in malondialdehyde concentration as evidence of lipid peroxidation. Hepatic and plasma GSH peroxidase activity was initially elevated at 70 ppm Se as selenomethionine, whereas GSSG reductase activity was elevated at higher dietary concentrations of Se. Selenium from sodium selenite accumulated in the liver to an apparent maximum at 10 ppm in the diet, resulting in an increase in hepatic GSH and GSSG accompanied by a small decrease in total hepatic SH. Sodium selenite resulted in an increase in hepatic GSSG reductase activity at 10 ppm and in plasma GSSG reductase activity at 40 ppm. A small increase in lipid peroxidation occurred at 40 ppm. These findings indicate that excess dietary Se as selenomethionine has a more pronounced effect on hepatic glutathione metabolism and lipid peroxidation in ducklings than does selenite, which may be related to the pattern of accumulation. Effects of Se as selenite appear to be less pronounced in ducklings than reported in laboratory rodents. The effects of selenomethionine, which occurs in vegetation, are of particular interest with respect to the health of wild aquatic birds in seleniferous locations.

ISSN:0098-4108    

DOI:10.1080/15287398909531296

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

FOOD TOXICOLOGY. Part A: Principles and Concepts. Part B: Contaminants and Additives. Edited byJosé M. Concon, Marcel Dekker, New York, 1988, 1440 pp., $250.00.

ISSN:0098-4108    

DOI:10.1080/15287398909531297

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor