摘要:

Kashin‐Beck disease (KBD) is a chronic osteoarthritic disease, endemic in parts of China. Its etiology is unknown. Selenium deficiency, high concentration of organic matter (mainly fulvic acid) in drinking water, and severe contamination of grain by fungi have been proposed environmental causes. Free radicals, possible mediators between the environmental factors and origin of KBD, have been studied in this work. Drinking water from KBD‐affected areas contains a higher level of semiquinone radicals than that from disease‐free areas. In animal experiments, fulvic acid (FA) accumulated in the skeletal system as semiquinone radicals. Contamination of grain by Fusar‐ium oxysporum or Alternaria alternata significantly increased the content of semiquinone radicals. Furthermore, corn grown in endemic areas had a higher content of radicals than that from disease‐free areas. The g factor values for these radicals from contaminated corn were about 2.0040, in the range of semiquinone radical. In monolayer culture of human embryonic chondrocytes, FA and aqueous extracts of grain contaminated by Fusarium injured the chondrocytes and enhanced lipid peroxi‐dation. Selenite and superoxide dismutase (SOD) protected the cells from injury by these toxins and reduced lipid peroxide. Lower glutathione peroxidase activities and higher levels of lipid peroxidation were also found in the children living in KBD‐affected regions. Thus, FA and the mycotoxin, which are seen as exogeneous free‐radical carriers, are important environmental factors in the pathogenesis of Kashin‐Beck disease; and selenium, vitamin C, and vitamin E, which inhibit free‐radical formation, are considered to be protective.

ISSN:0098-4108    

DOI:10.1080/15287399209531597

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Permethrin is an agricultural insecticide of great interest to the military because of its repellency toward disease‐bearing insects when impregnated into uniforms. However, migration of the substance from clothing to the skin surface is of toxicological importance. To quantitate leaching from treated clothing, studies were performed in which swatches of fabric impregnated with14C‐labeled permethrin were applied to the backs of rabbits for 1 wk. Permethrin migration was quantitated by measuring the fate of the14C label. Conditions that could affect leaching and/or absorption were also evaluated, that is, varying environments, the presence of sweat, different fabric types, and the effects of prelaundering. Results showed that fabric treated with permethrin at a rate of 0.125 mg/cm2lost the substance to the skin surface at an average rate of 0.49%/d. At the end of the 7‐d exposures in rabbits, about 3.2% of the available permethrin had reached the skin, 2% having been recovered from excreta (absorbed) and 1.2% remaining on the skin surface. Prelaundering the treated fabric had little effect on migration rate, nor did the other variables tested. Exposure dose to humans from wearing permethrin‐treated (0.125 mg/cm2) military clothing is predicted to be 6 × 10−4mg/kg/d.

ISSN:0098-4108    

DOI:10.1080/15287399209531598

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The aim of this experiment was to test the modulation of genotoxicity produced by vitamin C (V‐C) challenged against mitomycin C (MMQ in vivo, by analyzing the sister chromatid exchanges (SCE) and cell proliferation kinetics. We used the mouse bone marrow cytogenetic method, and tested three dosages of V‐C (3, 5, and 7 g/kg of body weight), along with the appropriate positive (2 mg MMC/kg body weight) and negative V‐C controls. The results showed that V‐C caused a strong inhibition of SCEs induced by MMC in the three dosages administered. The highest dose (7 glkg) caused an SCE inhibition of 70.02%, while the lower ones caused an inhibition of 54.61% and 52.30%, respectively. It was also clear that V‐C per se does not increase the level of SCEs in mouse bone marrow cells. On the other hand, V‐C induced a slight decrease in cell proliferation that was stronger when combined with MMC. Our data suggest that V‐C effectively inhibit the SCE damage in vivo, but caution must be taken because of the observed cytotoxicity.

ISSN:0098-4108    

DOI:10.1080/15287399209531599

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Genetic differences in the acute hepatic and testicular toxicity of Cd occur among different strains of mice. However, it is not known whether genetic variation to the renal damage caused by Cd‐metallothionein (CdMT) exists. Therefore, male mice of the C3H/HeJ, C57/B/10, CBA/CA, and DBA/2] strains, previously shown to differ in hepatic and testicular injury due to Cd, were treated with CdMT at dosages of 0.2, 0.4, 0.8, and 1.6 mg/kg (sc). For all strains of mice, tissue accumulation of Cd occurred predominantly in kidney, which had two to three times as much Cd as liver, while testes had no measurable amounts of Cd. Hepatic and renal metallothionein (MT) concentrations were increased with increasing dosage of CdMT, and no differences between strains were demonstrated. Urinary glucose was increased significantly at the three highest dosages of CdMT, with no differences between strains. At each dose level, light microscopic manifestations of CdMT nephropathy did not differ between strains. In summary, all CdMT‐treated strains of mice responded similarly with respect to all measured renal parameters (accumulation of Cd and MT and nephrotoxicity). Unlike the strain differences in hepatic and testicular injury from Cd in these strains of mice, CdMT nephrotoxicity shows no such genetic variation.

ISSN:0098-4108    

DOI:10.1080/15287399209531600

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The effects of carbon monoxide (CO) on blood carboxyhemoglobin (COHb) levels, though well studied at sea level, have not been investigated in populations at altitude. COHb levels were measured in laboratory rats following 6 wk exposure to either clean air or air containing 9 ppm CO at ambient altitude (3300 ft), 10,000 ft, or 15,000 ft simulated high altitude. In animals breathing clean air, COHb levels increased with increasing altitude from 0.68 ± 0.09% at 3300 ft to 1.16 ± 0.28% and 1.68 ± 0.14%, respectively, at 10,000 and 15,000 ft. The relationship between COHb levels and increasing altitude is linear with a correlation coefficient of 0.90 (p < .001). In animals breathing 9 ppm CO, COHb levels also increased with increasing altitude from 0.99 ± 0.06% at 3300 ft to 1.77 ± 0.17% and 2.10 + 0.08%, respectively, at 10,000 and 15,000 ft. The relationship between COHb levels and increasing altitude in animals breathing CO is also linear with a correlation coefficient of .92 (p < .001). These data indicate that, compared with animals at sea level, animals at altitude have an increased body burden of COHb and will attain the COHb level associated with the National Ambient Air Quality Standard for CO more quickly when breathing CO.

ISSN:0098-4108    

DOI:10.1080/15287399209531601

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Exposure to an exogenous chemical via milk causes superimposition on the body burden that might have already existed in the neonatal organism due to in utero exposure. Such exposure via breast milk is avoidable, although transplacental exposure cannot be avoided at present. In this paper, mercury exposure via breast milk was examined in an animal model. Maternal guinea pigs were shortly exposed to mercury vapor at the mean concentrations of 6–70 mg/m3immediately after parturition. Newborn guinea pigs were then nursed by the natural mothers. Mercury concentrations in breast milk and tissue samples were determined on d 3, 5, and 10 postpartum. Mercury concentrations in breast milk were slightly lower than plasma mercury concentrations of the maternal guinea pigs over the observation period. However, the decrease in the mercury concentration in breast milk with time was slower than that in maternal plasma. Mercury concentrations in major organs of the neonates were highest in kidney, followed by liver and lung. In brain and whole blood, mercury concentrations were slightly elevated compared with the nonexposed control. Organ distribution of mercury in the suckling neonates indicated that they were exposed via breast milk to inorganic, not elemental, mercury.

ISSN:0098-4108    

DOI:10.1080/15287399209531602

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0098-4108    

DOI:10.1080/15287399209531596

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor