Showing papers on "Zinc toxicity published in 1994"

Textile wastewater effluent toxicity identification evaluation

Abstract: The need to control toxic substances in industrial and municipal wastewater effluents has led to the inclusion in National Pollutant Discharge Elimination System (NPDES) permits of requirements for testing toxicity to aquatic species. Recently, permitted wastewater effluents from particular textile dyeing and finishing operations exhibited a low degree of toxicity to the freshwater Cladoceran Daphnia pulex in acute, static, 48-h testing. An extensive effort was launched to determine components contributing to effluent toxicity. The toxicity identification evaluation combined three elements: fractionation of wastewater effluents, testing for aquatic toxicity, and analyses for specific chemicals. An anionic, speciated form of zinc was implicated as a major contributor to the toxicity. Water hardness was a principal determinant of zinc toxicity to Daphnia pulex.

Sensitivity of Trichomonas vaginalis, Tritrichomonas foetus and Giardia intestinalis to bacitracin and its zinc salt in vitro

Abstract: The activity of bacitracin in vitro against Giardia intestinalis, Trichomonas vaginalis and Tritrichomonas foetus was enhanced 5–10 times by equimolar concentrations of zinc. Bacitracin and bacitracin zinc activity was tolerant to either aerobic or anaerobic culture conditions and equally effective against T. vaginalis isolates sensitive or insensitive to metronidazole. This enhancement was not due to zinc toxicity and was zinc dose dependent.

Effect of pharmacologic doses of zinc on the therapeutic index of brain tumor chemotherapy with carmustine

Abstract: To evaluate the potential differential effect of pretreatment with pharmacologic doses of the trace element zinc on the chemosensitivity of glioma cells and bone marrow cells for carmustine (BCNU), we performed in vitro and in vivo studies of zinc toxicity as well as of the combined treatment with zinc and the anticancer drug. We studied the in vitro effects on established human and rat glioma cell lines using a microcolorimetric growth assay and on murine bone marrow using a clonogenic assay for committed progenitor cells of the granulocyte-monocyte lineage. Zinc exposures of up to 100 μM for 120 h did not influence the growth of six of seven human glioma cell lines. Only U87MG demonstrated statistically significant toxicity during high zinc exposure (100 μM over 120 h). Dose-response growth curves generated for BCNU did not show protection against the anticancer agents by a 48-h pretreatment with different zinc concentrations. The clonogenic capacity of bone marrow cells was slightly reduced by in vitro culture for 24 and 48 h. Although this effect appeared to be more prominent in the presence of zinc supplementation, overall a statistically significant inhibition was seen only after exposure to a concentration of 100 μM zinc over 48 h. As compared with chemotherapy alone, in vitro pretreatment with 50 μM zinc over 48 h followed by chemotherapy resulted in an increased number of colony-forming unit-granulocyte monocyte (CFU-GM): CFU-GM increased by a factor of 2 for BCNU (60 μM×2 h). This statistically significant in vitro chemoprotection would translate into a dose-protection factor of 1.5, i.e., for the same level of myelosuppression, zinc pretreatment would allow administration of a 50% increased dose of BCNU. The in vivo studies were performed in an s.c. xenograft model of the human glioma cell line U87MG in athymic mice. The maximal tolerable pretreatment with zinc was determined to be a 10-day course of daily i.p. injections of 10 mg/kg ZnCl2. The subsequent i.p. administration of the dose lethal to 10% of the mice (LD10) and of a 1.5×LD10 dose of BCNU resulted in less bone marrow toxicity in pretreated animals than in non-zinc-pretreated mice as determined in a CFU-GM assay. Glioma colony-forming efficiency (CFE) assays, on the other hand, did not show any zinc-related difference in the BCNU sensitivity of U87MG. Our in vitro and in vivo results suggest the potential usefulness of high-zinc pretreatment for improving the therapeutic index of BCNU chemotherapy for gliomas.

Impact of acute zinc sulphate toxicity and salinity stress on the carbohydrate metabolism in Oreochromis mossambicus during different exposure periods

Abstract: Zinc is an important trace element involved in enzymatic functions like protein synthesis and carbohydrate metabolism (Hammond and Beliles 1980). However, it becomes toxic when exceeds the critical level. Acccffding to Hodson (1976), the effect of toxicity of heavy metals increases with increase in concentration and exposure time. This study has been done to understand the degree of adaptability of fish Oreochromis mossambicus in different exposure periods to zinc toxicity. The ameliorating effect of salinity on acute zinc toxicity to the fish has also been studied during different exposure periods.

Comparative effects of copper and zinc toxicity and tolerance of Hyptis suaveolens (L.) Poit. and Helianthus annuus L.

Abstract: Soil application of copper and zinc to the plants Hyptis suaveolens (L) Poit and Helianthus annuus L caused phytotoxic symptoms and decreased growth in terms of dry weight and chlorophyll content Copper was found to be more toxic to sunflower than to Hyptis In Hyptis, much of the absorbed copper was retained in the roots Imbalances, in the levels of Fe, Mn, Cu and Zn were greater for sunflower which exhibited severe phytotoxicity Zinc treatment caused a greater reduction in the biological yield of Hyptis At the highest level of 1200 ppm Zn, dry weight yield of Hyptis was only 573% as against 664% in sunflower The content of K and Mg in leaves and Ca levels in roots of Zn‐treated sunflower markedly increased In general, the phytotoxic effects of Zn were found to be less severe than those of Cu, at the concentrations employed in this experiment