摘要:

Endemic goiter in iodide‐sufficient areas of the United States and Colombia has been linked to watersheds rich in coal and shale, which several reports suggest are the source of water‐borne goitrogens. In this report the potential antithyroid activities of aqueous coal and shale extracts and of compounds identified in aqueous effluents from coal conversion processes were assayed in thyroid peroxidase (TPO) and thyroid slice systems. Aqueous extracts of coal and black shale were potent inhibitors of TPO or125l organification by thyroid slices.

ISSN:0098-4108    

DOI:10.1080/15287399209531686

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Municipal refuse incinerator workers may be exposed to mutagenic compounds from combustion gases and particulates during plant operation, maintenance, and ash removal procedures. The frequency of mutagens was measured by the Ames assay in 3 urine samples collected from each of 37 workers in 4 refuse incinerators and 35 (control) workers from 8 water treatment plants during June‐August 1990. When comparing the first urine samples contributed by workers in each cohort, incinerator workers had a significantly (p < .05) increased risk of both direct‐acting mutagens and promutagens (8/37 or 22% for each mutagen type) compared with water treatment workers (2/35 or 6% for each mutagen type). Smoking within 24 h before urine sampling was not a confounder of these results.

ISSN:0098-4108    

DOI:10.1080/15287399209531687

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Correlations between light intensity of animal room lighting and both cataract and retinopathy of rats were examined, and relationships between the cataract and the retinopathy were further investigated. Seventy‐nine male rats and 106 female rats surviving to the end of a 2‐yr carcinogenicity study of monosodium succinate were used in this investigation. Animals were housed in polycarbonate cages, each containing 4 rats, with wire lids and hardwood chips for bedding and with a 12‐h light/dark cycle. Individual groups comprising 13 cages were inserted into 3 by 5 cage hanging type racks. Light intensity was measured at the bottom (on the bedding) of individual cages. Statistically, both the incidence of cataracts and the severity of retinopathy were closely related to light intensity. The incidence of cataracts in males was significantly higher than that in females, while no sex difference was observed for the severity of retinopathy. Meanwhile, no differences in either the incidence of cataracts or the severity of retinopathy were observed between the monosodium succinate‐treated and control groups and between the right and left eyes. While the occurrences of retinopathy and cataract were strongly associated, our results indicated that retinopathy occurs more frequently than cataracts, and thus the retina appeared to be more sensitive to the effects of lighting.

ISSN:0098-4108    

DOI:10.1080/15287399209531688

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The relative potencies for a series of sensory irritants, with structures based on toluene, were determined by measuring the airborne concentrations that caused a 50% decrease in respiratory rate in Swiss‐Webster mice. This concentration is referred to as the RD50. Toluene, a relatively nonirritating compound, and compounds with chlorine, two chlorines, bromine, and iodine atoms substituted on the alpha carbon of toluene were tested. The RD50s for these compound types were determined to be 4900, 27, 27, 5.2, and 4.3 ppm, respectively. In addition, compounds with chlorine substituted at the ortho, meta, and para positions on the toluene ring were also tested. The RD50s were determined to be 4.9, 13, and 14 ppm, respectively. The structure‐activity relationships of the compounds studied are explained by a model (Abraham et al., 1990; Nielsen and Alarie, 1982) that relates the interaction of sensory irritants with a receptor protein in a lipid bilayer. The trends in the RD50s, and thus sensory irritation, for the compounds studied are related to the development of a partial positive charge on the toluene alpha carbon by the positioning of a ring chlorine and the bond dissociation energies of the alpha carbon‐halogen bond for the iodo, bromo, and chloro isomers of benzyl halide.

ISSN:0098-4108    

DOI:10.1080/15287399209531689

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

To determine whether depleted serum 1α,25‐dihydroxyvitamin D (VD) concentrations are associated with cadmium (Cd)‐induced renal damage, the relationships between four indices of renal function and two indicators of bone metabolism, that is, serum VD and parathyroid hormone (PTH) concentrations, were analyzed in 30 male and 44 female subjects exposed to environmental Cd. Also, these associations were compared in male and female subjects to evaluate sex‐related differences in vulnerability to the bone damage observed in Cd‐exposed persons. Serum VD decreased significantly with declines in creatinine clearance and percentage tubular reabsorption of phosphate, and with increases in serum creatinine and serum β2‐microglobulin (β2m) concentrations in the female subjects exposed to Cd, but not in the male subjects. The correlation between serum VD and PTH levels was also significant only in the females. Correlation coefficients between serum β2m and VD and those between serum PTH and VD in both sexes were significantly different. These results suggest that renal damage due to Cd exposure leads to the decreases in the serum VD level and increases in serum PTH level, and that the more marked changes in serum VD and PTH in the women may play a role in the development of sex‐related differences in Cd‐induced bone injury.

ISSN:0098-4108    

DOI:10.1080/15287399209531690

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Iodine (I2) has been proposed to be used as a water disinfectant on the manned space station. Previous work has shown that subchronic administration of I2to Sprague‐Dawley rats in drinking water significantly increases plasma thyroxine/triiodothy‐ronine (T4/T3) levels. This is not observed with iodide (I−) treatment. The present study addresses the possibility that I2reacts with deiodinated T4metabolites in the gastrointestinal tract to resynthesize T4. Incubation of diiodothyronine (T2), T3, or reverse T3with I2in phosphate‐buffered saline resulted in the formation of T4as measured by radioimmunoassay. Washes from the initial segments of the small intestine of the rat show that substrates are present that react with I2to produce T4. Single oral doses of I2to rats produced significant dose‐related increases in serum T4and decreases in T3concentrations after 2 h. Administration of an equivalent dose of I−did not alter significantly plasma T4concentrations. Higher concentrations of a radioactive substance that bound a T4‐specific antibody are present in plasma of animals treated with125I2compared to125I−. These data support the hypothesis that I2reacts with metabolites of thyroid hormone in the gastrointestinal tract to resynthesize T4and elevate its levels in blood.

ISSN:0098-4108    

DOI:10.1080/15287399209531691

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this project, a total of 60 adult Fischer 344 male rats were exposed to dimethylselenide (DMSe) vapor at 1607, 4499, or 8034 ppm for 1 h (20 rats/group). In addition, 26 unexposed rats were used as controls. The exposed rats were observed frequently during the 7 d following exposure and appeared normal. The animals were sacrificed at either 7 or 7 d after inhalation and the major tissues were grossly examined and weighed. Selenium levels were found to be elevated only in the lung at d 1. At d 1, significant changes in organ weights were an increase in the lung weight at exposure levels of 1607 and 8034 ppm of DMSe and in liver weight at 4499 and 8034 ppm. At d 1, significant changes in the lung were an increase in protein at 1607 and 8034 ppm of DMSe, and an increase in RNA and a reduction in DNA at 4499 ppm DMSe. The only change in the liver was a reduction in DNA at 4499 ppm. At 7 d, the protein content and RNA content of spleen were increased. Lung, liver, kidney, spleen, thymus, lymph nodes, pancreas, and adrenal gland were examined microscopically and found to be normal. All of these observed responses were minor and did not severely impact the health of the rats. Overall, the data indicate that the inhalation of DMSe for 1 h has relatively low toxicity in rats even at high concentrations.

ISSN:0098-4108    

DOI:10.1080/15287399209531692

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Recent studies indicate that sodium methyldithiocarbamate is immunotoxic. Major effects of this compound in female B6C3F1 mice include decreased thymus weight, increased spleen weight, and decreased natural killer (NK) cell activity. The effects of other dithiocarbamates on these parameters are not known, and the immunotoxic potential of this important class of compounds is uncertain. In the present study, the effects of sodium methyldithiocarbamate (SMD), sodium diethyldithiocarbamate (DEDTC), and disodium ethylene‐bis(dithiocarbamate)(EBD) on thymus weight, spleen weight, and NK cell activity were compared in female B6C3F1 mice. SMD caused significant loss of thymic weight following oral administration at 200, 225, or 300 mg/kg/d for 7 d and caused significant suppression of splenic NK cell activity at doses of 150, 225, or 300 mg/kg/d for 7 d. In contrast, a dose of 1000 mg/kg/d of DEDTC was required to decrease significantly thymus weight or increase spleen weight, and the only significant change produced by EBD was a slight increase in spleen weight at a dose of 675 mg/kg/d. EBD and DEDTC did not affect NK cell activity at any dose tested. Dithiocarbamates are known to be cytotoxic for a variety of cell types, and it seemed possible that SMD might be more potent in vivo than EBD or DEDTC because it was more cytotoxic than these compounds. However, direct measurement of the cytotoxicity of all three compounds toward splenocytes and thymocytes in vitro demonstrated that SMD and EBD are approximately equally potent (EC50from 6.1 to 10.5 μM), whereas DEDTC is much more potent (EC50from 0.13 to 0.15 μM). Of the three compounds examined in this study, only SMD affected thymus weight, spleen weight, and splenic NK cell activity in vivo. Thus, this pattern of immunological effects is not produced by all dithiocarbamates. In addition, the data demonstrate that differences in the potency of SMD, DEDTC, and EBD in vivo do not correlate with their relative cytotoxic potencies in vitro.

ISSN:0098-4108    

DOI:10.1080/15287399209531693

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0098-4108    

DOI:10.1080/15287399209531685

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor