Showing papers on "Zinc toxicity published in 1992"

Zinc toxicity in ectomycorrhizal Pinus sylvestris

Abstract: Six strains of ectomycorrhizal fungi were compared for their ability to increase zinc tolerance in Pinus sylvestris L. seedlings. Pioneer and ‘late-stage’ fungi as well as one strain collected from a Zn-polluted site were included in the study. The accumulation of zinc in the host plants was determined at two different sublethal substrate Zn concentrations. The mycobionts varied considerably in their protection of the autobionts against zinc toxicity. Several fungal species reduced zinc accumulation in the pine seedlings. A Thelephora terrestris (Ehrh.) Fr. Strain, however, increased the Zn concentration in its host plants. Specific zinc-retaining capacity of the mycelium and density of the extramatrical mycelium were important features determining the effectiveness of the zinc retention in the fungal symbiont.

Morphologic Findings in Bone Marrow Precursor Cells in Zinc-Induced Copper Deficiency Anemia

Abstract: Damage to the bone marrow elements, as shown by cytoplasmic vacuolization, has been reported in patients with acute alcohol intoxication, drug reactions, nutritional deficiencies, myeloproliferative syndromes, malignant hematologic conditions, some metabolic conditions, and in those treated with chemotherapeutic agents. A case of zinc toxicity with anemia, leukopenia, and cytoplasmic vacuolization of both myeloid and erythroid precursors is described. The patient described was a 30-year-old quadriplegic man who was receiving oral zinc to promote the healing of and prevention of decubitus ulcers. In the gut, dietary zinc interacts with copper in a competitive manner, and high levels of zinc can lead to copper deficiency. Zinc-induced copper deficiency anemia can be morphologically identified in the bone marrow preparations by cytoplasmic vacuolization of both myeloid and erythroid precursor elements.

Zinc toxicity and induction of the 72 kD heat shock protein in primary astrocyte culture.

Abstract: Zinc is a potent inducer of the 72 kD heat shock protein (HSP72). In brain, pathological conditions such as ischemia and seizures increase extracellular zinc. The present study examines the effect of zinc on HSP72 expression in rat primary cortical astrocyte culture. Astrocytes were grown to confluence and exposed to zinc chloride in CO2-equilibrated Earle's buffered salt solution. Expression of HSP72 was examined using immunocytochemistry. HSP72 was induced with zinc concentrations of 5 to 100 μM after 4 h exposures, or 200 to 300 μM after 15 min exposures. At the lower concentrations expression occurred in small clusters of contiguous cells. At concentrations high enough to cause cell death, HSP72-positive astrocytes formed a continuous margin around patches of dead cells. These patterns of HSP72 expression are similar to the patterns seen after cerebral ischemia in vivo. Exposure to zinc at 100 μM for 4 h or 400 μM for 15 min caused greater than 90% cell death. Increases in extracellular zinc may contribute to HSP72 induction and astrocyte death under ischemia and other pathological conditions in brain. © 1992 Wiley-Liss, Inc.

The effect of heavy metal salts on the embryonic development of the common frog

Abstract: To elaborate methods of biological testing during monitoring of the environment, a study was made of the effect of heavy metal salts on frog embryos and of the influence of temperature on the extent of toxicity of these substances. It was shown that the early stages of embryogenesis were more sensitive to this toxic effect. The differences in the effect of heavy metals are expressed not only in the extent of toxicity, but also in the pattern of change in toxicity as related to concentration. A rise in temperature of the solution containing heavy metals results in a relative increase in the number of abnormal larvae, whereas a decrease in temperature of the solution leads to a higher mortality at the earliest stages of embryogenesis. The latter, apparently, is due to a longer duration of development at low temperature, and thus, to a longer exposure of embryos to toxic effect. This is more pronounced at earlier stages of development, more vulnerable (sensitive) to toxicants. The estimation of toxicity of a substance by the pathological changes induced in embryos and larvae is one of the most sensitive methods, which allows not only to determine the extent of toxicity, but also to give prognosis of its possible effect on the population.