摘要:

To explore the peripheral nervous system effects of regular agricultural pesticide use, a cross-sectional survey was conducted in highland Ecuador. Participants were 144 occupationally exposed farm members, 30 female farm members with little direct exposure, and 72 unexposed local town residents, frequency matched to the exposed people on age, sex, and education. Organophosphorus and carbamate insecticides and dithiocarbamate fungicides accounted for the majority of pesticide applications, with leaking backpack sprayers, minimal use of personal protective equipment, and frequent dermal contact being the norm. In polytomous logistic regression analyses, applicators had significantly greater odds for more current peripheral nerve symptoms (odds ratio OR = 3.1), signs of poor coordination (OR = 4.3), abnormal deep tendon reflexes (OR = 2.9), and reduced power (OR = 2.1) compared to controls. Mean toe vibration threshold scores, on a logarithmic scale, were significantly higher among applicators (beta= 0.035) and those reporting previous pesticide poisonings (beta= 0.074). Such indicators of peripheral nervous system effects may be due to a variety of factors, including high pesticide exposure conditions.

ISSN:1528-7394    

DOI:10.1080/009841098158520

出版商:Informa UK Ltd    

年代:1998

数据来源: Taylor

摘要:

Concerns have been raised over the use of iodine for disinfecting drinking water on extended space flights. Most fears revolve around effects of iodide on thyroid function. Iodine (I2) is the form used in drinking-water disinfection. Risk assessments have treated the various forms of iodine as if they were toxicologically equivalent. Recent experiments conducted in rats found that administration of iodine as I- (iodide) versus I2 had opposite effects on plasma thyroid hormone levels. I2-treated animals displayed elevated thyroxine (T4) and thyroxine/triiodothyronine (T4/T3) ratios, whereas those treated with I- displayed no change or reduced plasma concentrations of T4 at concentrations in drinking water of 30 or 100 mg/L. The study herein was designed to assess whether similar effects would be seen in humans as were observed in rats. A 14-d repeated-dose study utilizing total doses of iodine in the two forms at either 0.3 or 1 mg/kg body weight was conducted with 33 male volunteers. Thyroid hormones evaluated included T4, T3, and thyroid-stimulating hormone (TSH). TSH was significantly increased by the high dose of both I and I-2, as compared to the control. Decreases in T were observed with dose schedules with I-4 and I2, but none were statistically significant compared to each other, or compared to the control. This human experiment failed to confirm the differential effect of I2 on maintenance of serum T4 concentrations relative to the effect of I- that was observed in prior experiments in rats. However, based on the elevations in TSH, there should be some concern over the potential impacts of chronic consumption of iodine in drinking water.

ISSN:1528-7394    

DOI:10.1080/009841098158539

出版商:Informa UK Ltd    

年代:1998

数据来源: Taylor

摘要:

Numerous immunomodulatory effects are caused by propanil, an extensively used postemergent herbicide. The T-dependent antibody response is suppressed after exposure to propanil, raising the question of propanil's effect on T-helper-cell populations. In the present study, we show that the production of several T-cell cytokines is affected by propanil after in vivo or in vitro exposure. In vivo exposure to propanil caused the reduction of interleukin (IL)-2, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon (IFN)- production in concanavalin A-stimulated spleen cell cultures established 2 d after exposure. IFN- and GM-CSF production had recovered by d 4 postexposure; however, IL-2 and IL-6 levels continued to be depressed through d7 postexposure. Continuous in vitro treatment of normal spleen cells with propanil decreased IL-2, IL-6, GM-CSF, and IFN- production after concanavalin A activation. Pulsing normal spleen cell cultures with propanil for up to 8 h before T-cell activation resulted in reduced IL-6 but not IL-2 or IFN- production. These data indicate that propanil can selectively inhibit spleen cell cytokine production, which could contribute to the immunomodulatory effects previously described.

ISSN:1528-7394    

DOI:10.1080/009841098158548

出版商:Informa UK Ltd    

年代:1998

数据来源: Taylor

摘要:

The effects of two substituted polychlorinated biphenyls, the 3,4,5,3',4',5' (PCB-169) and the 2,3,4,2',4',5' (PCB-138) forms, were examined on the expression of c- myc, cjun, c- ras, and jun -b in 3T3-L1 cells. Northern blot analysis demonstrated that the two PCBs, which exhibit a coplanar and di- ortho -substituted configuration, activated these oncogenes differently. PCB-138 markedly induced overexpression of ras, jun, and myc, whereas PCB-169 led to the overexpression of jun -b. High-performance liquid chromatography analysis of the cell samples treated in medium without serum revealed a higher intracellular concentration of the 2,3,4,2',4',5'-hexachlorobiphenyl (hexaCB), whereas the 3,4,5,3',4',5'-hexaCB reached the same concentration in the sonicated samples of cells with or without serum. These results indicated that there was a relationship between PCB structure, bioavailability, and the capacity to stimulate oncogene expression.

ISSN:1528-7394    

DOI:10.1080/009841098158557

出版商:Informa UK Ltd    

年代:1998

数据来源: Taylor

摘要:

The systemic and neurobehavioral effects of benzo\[b]thiophene (routinely referred to as benzothiophene) were studied in rats following 13-wk oral exposure. Male (170 +/- 16 g) and female (146 +/- 12 g) Sprague-Dawley rats (10 animals per group) were fed diet containing 0.5, 5, 50, or 500 ppm benzothiophene for 13 wk. Control animals were given rat feed plus vehicle ( corn oil) only. No clinical signs of toxicity and neurobehavioral effects were observed using screening tests that included cage-side observations, righting reflex, open field activities, and forelimb and hindlimb grip strength. Elevated serum aspartate aminotransferase activity and bilirubin level were observed in highest dose females. Except for a statistically significant decrease in hematocrit in the highest dose males, benzothiophene exerted no marked effects on hematological parameters. Benzothiophene exposure did not result in alterations in hepatic alkaline phosphatase activity, or the typical hepatic phase I (aniline hydroxylase, ethoxyresorufin O -deethylase, pentoxyresorufin O -dealkylase, aminopyrine N -demethylase) and phase II (UDPglucuronosyltransferase, glutathione S -transferase) drug-metabolizing enzyme activities. No significant elevation in urinary ascorbic acid, protein, and N -acetylglucosaminidase activity was detected in the treated animals. Peribiliary fibrosis was the most significant histological change and occurred in the liver of females in the 50 and 500 ppm groups. Mild epithelial hyperplasia in the renal pelvis was detected in the majority of 5 and 50 ppm females, with epithelial hyperplasia in the urinary bladder observed in the 50 ppm females. In males, increased incidence and severity of mild binucleation of hepatocytes and mild thickening of the basement membrane in kidney cortex were observed at 500 ppm. Benzothiophene was not detected in the urine of high-dose animals at the termination of the experiment. Based on the kidney, hepatic, and hematocrit changes, the no-observed-adverse-effect level (NOAEL) in the diet was determined to be 0.5 ppm (0.04 mg/kg/ d) for females and 50 ppm (3.51 mg/kg/ d) for males.

ISSN:1528-7394    

DOI:10.1080/009841098158566

出版商:Informa UK Ltd    

年代:1998

数据来源: Taylor

摘要:

Nondialyzable Maillard reaction products (MRPs) were recovered from three different coffee brew extracts (i.e., brewed, boiled, instant) to evaluate the efficacy of MRPs in modulating in vitro metal-induced cytotoxicity in C3H/10T1/2 mouse embryo fibroblast cells, cultured in the presence of Fe2+, Fe3+, or Cu2+ ions. Preliminary experiments were performed in an vitro linoleic acid emulsion model system to characterize the anti- or pro-oxidant activity of coffee MRPs. Cytotoxicity experimental protocols involved both the direct application of metal ions and coffee MRPs to fibroblast cells, and the premixing of metal ions with coffee MRPs at room temperature prior to incubating with fibroblast cells. Fe2+ and Cu2+ significantly lowered the colonization efficiency (CE) of cells at all three concentrations (i.e., 0.1, 10, 50 mu M) used. Similar Fe3+ activity was observed only at 50 mu M concentration. None of the coffee MRPs alone or together with 0.1 and 10 mu M of Fe2+ or Fe3+ produced cytotoxic effects during direct application. The premixing step, however, significantly enhanced the CE of cells compared to the control, denoting cytoprotection, only in the presence of Fe2+. In addition, the application of MRPs with 0.1 or 10 mu M of Cu2+ significantly lowered the CE of cells than the control, but enhanced the CE of cells than the Cu2+ added control. These results corresponded directly with the results of model linoleic acid emulsion test, thereby demonstrating that lipid hydroperoxide generation is the source for fibroblast cell toxicity when MRPs are added to cells together with metal ions. These results further indicate that coffee MRPs can suppress in vitro metal-induced cytotoxicity to a certain extent when Fe2+, Cu2+, or Fe3+ ions are present below a concentration of 50 mu M , possibly by chelating the metal ions. Ionic reducing capacity of coffee MRPs, albeit small, may explain the potential for increased cytotoxicity at higher coffee MRP concentrations.

ISSN:1528-7394    

DOI:10.1080/009841098158575

出版商:Informa UK Ltd    

年代:1998

数据来源: Taylor