Showing papers on "Zinc toxicity published in 1988"

Zinc: biochemistry, physiology, toxicology and clinical pathology.

Abstract: Among the transition and group II elements the abundance of zinc in biology is second only to that of iron. It is present in and indispensable to all forms of life. Knowledge regarding the biological occurrence and function of zinc, the development of methods that permit its detection and those aspects of biochemistry which have allowed an appreciation of the manner in which it participates in generating biological specificity have grown exponentially in the last two decades. The recognition that zinc is an essential, coenzyme-like component of many enzymes, indispensable to their function, is reminiscent of the role of some vitamins. Technical advances in the isolation and characterization of enzymes in general and metalloenzymes in particular were basic to the rapid growth of zinc metallobiochemistry during the last two decades. Zinc is now known to be an integral component of a large variety of proteins and enzymes and, hence, the total zinc content of tissues cannot serve as a guide to the multiple functions of the metal. Zinc participates in a wide variety of metabolic processes including carbohydrate, lipid, protein and nucleic acid synthesis or degradation. Most recently, zinc proteins have been shown to be involved in the transcription and translation of the genetic material, perhaps accounting for its essentiality to all forms of life. A number of zinc proteins have been described whose function is not known as yet. Among these, the metallothioneins are prominent. They are widely distributed, of low molecular weight (approximately 6700), and their content of cadmium and/or zinc as well as sulfur is exceptionally high.(ABSTRACT TRUNCATED AT 250 WORDS)

Subchronic oral toxicity of zinc in rats.

Abstract: It is well known that zinc has important biological functions. Clinical manifestations in zinc-deficient animals include growth retardation, testicular atrophy, skin changes, and poor appetite. On the other hand, high levels of dietary zinc have been shown to induce copper deficiency in rats and to interfere with the metabolism of calcium and iron. Little is known on the oral toxicity of zinc in mammals. However, some toxic effects in human subjects, rodents, and sheep have been reported. In order to extend the information about the oral toxicity of zinc, a semichronic toxicity study of zinc acetate in rats has been carried out in this paper.

Effects of Glucose Concentrations on Cadmium, Copper, Mercury, and Zinc Toxicity to a Klebsiella sp.

Abstract: The influence of glucose concentration on Cd, Cu, Hg, and Zn toxicity to a Klebsiella sp. was studied by following the degradation of 14C-labeled glucose at pH 6.0. Uptake of 14C into the cells was also determined. The carbon concentrations ranged from 0.01 to 40 mg liter−1, which are equivalent to soluble C concentrations in natural environments. The toxicity of Cu, Cd, and Zn to a Klebsiella sp. was affected considerably by the C concentration. Copper at 10−5 M was toxic when the carbon concentration was 10 or 40 mg liter−1, while at 0.01 to 1.0 mg liter−1 no toxicity was observed. Cadmium and zinc were toxic at 10−2 M in media containing 0.01 to 1.0 mg of C liter−1. At C concentrations greater than 1.0 mg liter−1, the inhibition of glucose degradation and carbon assimilation was observed at 10−3 M Cd and Zn. The toxicity of mercury seemed to be independent of the C concentration. Results of this study showed that the nutritional state of an organism may have a profound effect on its sensitivity to metals. Metals taken up by an energy-driven transport system may be less toxic under conditions of C starvation. The C concentration should be taken into account when evaluating results from toxicity studies, especially as most microorganisms in nature live under energy-limited conditions.

Indicators of lead, zinc and cadmium exposure in cattle. I. Results in a polluted area.

Abstract: Dairy cattle on a farm located in the vicinity of a lead and zinc-ore processing factory were studied over 21 mo and compared with cattle on a control farm. Mean daily intakes of lead from the diet were 4.3 mg/kg body weight, with great variations; mean daily zinc intakes were 5.6 mg/kg body weight; and mean daily cadmium intakes were 0.064 mg/kg body weight. The 3 major indicators of contamination were blood lead concentrations, with mean values of 50 micrograms/100 ml of blood, zinc protoporphyrin with mean values of 165 micrograms/100 ml blood, and lead concentrations in hair which averaged 10 micrograms/g. Blood zinc concentrations and zinc concentrations were not significantly increased. One cow developed fatal post-partum paralysis. Liver, kidney and bone lead concentrations and kidney cadmium concentrations were good "post-mortem" indicators of exposure.

Damage to the forest ecosystem on Blue Mountain from zinc smelting

Abstract: Two zinc smelters in Palmerton, Pennsylvania, emitted large amounts of zinc, cadmium, lead, and sulfur dioxide for more than 80 years. A review of the ecological studies done at Lehigh Gap on Blue Mountain yields a comprehensive picture of damage that may result from metal emissions. The most obvious effect has been the destruction of trees, caused by a combination of zinc toxicity and natural stresses. High zinc concentrations in soil inhibited seedling root growth, reducing the number of young trees and hindering regeneration. Effects on the vegetation include stunting, susceptibility to drought, and changes in species and age structure. Communities of lower plants have also been affected. Populations of bacteria, actinomycetes, fungi, and arthropods in soil and litter were reduced. This has led to a reduced rate of litter decomposition and an increased thickness of the horizon. Some strains of microorganisms were tolerant to very high zinc concentrations. Some wild vertebrates, such as amphibians, were virtually absent from sites near to Lehigh Gap. Zinc poisoning was diagnosed in a white-tailed deer with an abnormally high renal zinc concentration and an articular lesion in a hind leg. There was some evidence of lead poisoning of wildlife; a short-tailed shrew hadmore » high tissue concentrations, depressed red blood cell delta-aminolevulinic acid dehydratase activity, and renal nuclear inclusion bodies. Some songbirds had highly elevated hepatic lead concentrations. Although Lehigh Gap is extremely contaminated with cadmium, there was no evidence of pathological lesions that could be attributed to cadmium in any of the wild animals examined.« less

Indicators of lead, zinc and cadmium exposure in cattle: II. Controlled feeding and recovery.

Abstract: Two pre-exposed and 2 normal heifers were fed lead (Pb), zinc (Zn), and cadmium (Cd) polluted hay (500 g/100 kg body weight) over a 17-week period. They were then examined over a 10-month period (42 or 38 weeks) to study the decay of the indicators of exposure. The elimination pattern of blood Pb and Zn protoporphyrin concentrations displayed a very slow decay. A bi-exponential equation, with the half-times of the fast component set at approximately 1 week, and the half-times of the slow component set from 3 mo to 2 years, was fitted to blood Pb levels. In man, the half-life of the slow component is still longer (2 to 15 years). This slow elimination rate represents release of Pb from skeleton, which in bovines, may accumulate up to 100 ppm Pb/dry or more. Lead concentrations in the hair were not proportionate to the areas under the curves of blood Pb levels; there was the same lack of correlation concerning skeleton and viscerae Pb levels. The withdrawal of contaminated hay from the diet resulted in a significant increase in blood copper. This is in accordance with the depressive effect of Pb and Zn on the bioavailability of this metal.

Studies on the role of iron in zinc toxicity in chicks.

Abstract: The interaction of dietary iron and zinc was studied in chicks. Zinc was found to be more toxic in iron-deficient animals than iron-supplemented animals as measured by hemoglobin concentrations and growth. Analyses of the kidney and liver for iron and zinc were carried out. As the level of iron was increased from 0-1000 ppm supplementation, the concentration of liver zinc increased. The organ levels of iron were decreased as the dietary zinc levels were increased from 0-5000 ppm. Radioisotope studies using 65Zn revealed that the iron content of the diet did not affect absorption of zinc. Administration of the isotope, either in an intestinal segment or intravenously, resulted in more zinc being taken up by the liver in the iron supplemented animals. This was especially noted when the ratio of the isotope in liver to that in the blood was compared. Gel chromatography of kidney and liver homogenates revealed that iron deficiency resulted in less zinc being eluted in a volume characteristic of metallothionein compared to homogenates of organs from iron supplemented animals. The results indicate that iron-supplemented animals have a greater capacity for sequestering zinc on metallothionein than do iron-deficient animals. Conversely, iron-deficient chicks were more susceptible to the effects of zinc toxicity than are iron-adequate chicks.

Effect of heavy metals on the growth of tissue cultures (II).

Abstract: The effect of toxic concentrations of three heavy metal compounds on the growth of the secondary callus tissue of Nicotiana tabacum L. and Ruta graveolens L. was studied. The metal compounds examined were ZnSO4, NiSO4, CuSO4. The metal compounds used were placed in Murashige, Skoog (1962) and White (1943) culture medium at 10(-6) and 10(-4) M concentration, respectively, before autoclaving. The culture media containing macro- and microelements and vitamins were completed with carbon source and regulators (IAA, GA, kinetin for Nicotiana and IAA, 2, 4-D for Ruta). The cultures were kept for 4 weeks at 25 (+2) degrees C under 16/8 n light/dark conditions. The value of pH was 5.6 before the autoclave treatment. The increase in fresh weight of the secondary callus tissue was inhibited by the metal compounds applied with both plant species (to 75-87% by zinc, 7-97% by nickel, 5-98% by copper with tobacco; to 47-69% by zinc, 5-88% by nickel, 57-90% by copper with rue). The cell number and dry weight per g of callus tissue partly increased, partly decreased compared to the control in response to the heavy metal treatment. The growth values obtained with various concentrations of the heavy metals were different in the two plant species due to differences in metabolism and organization potential between them.

Toxicity and character of the effect of some zinc compounds.

Abstract: Investigation of the parameters of toxicity of 8 zinc compounds revealed some differences in the degree of their risk for persons working with them. The following TSELs (tentative safe exposure levels of harmful substances) have been determined: 0.5 mg/m3 for zinc nitrate and hydrogen and dihydrogen zinc phosphates, 2 mg/m3 for zinc carbonate and zinc selenide, as well as MAC (maximum allowable concentration) for zinc sulphide equal to 5 mg/m3. No TSEL have been set for zinc caprylate and zinc stearate, but intratracheal administration of 50 mg caprylate caused 100%, of stearate 50% death of experimental animals due to pulmonary edema. Maximum tolerable doses were 10 and 1 mg, respectively. Zinc nitrate shows an expressed irritative effect on the skin and a highly expressed effect on the conjunctiva. Zinc phosphates, zinc caprylate and zinc stearate are resorbed by the skin. In all cases, working persons must be protected from the effect of the compounds under study because even though the toxicity of a compound may be rather low, highly noxious compounds may develop in the course of the technological process, e.g., in mechanical treatment of zinc selenide and zinc sulphide monocrystals, hydrogen selenide and hydrogen sulphide, respectively, can be isolated.

Retinal toxicity of intravitreal ethyldeoxyuridine and zinc.

Abstract: We investigated the toxicity of intravitreal zinc sulfate, zinc gluconate, and ethyldeoxyuridine (EDU) in albino rabbits. Various concentrations of EDU were added to the infusion solution during pars plana vitrectomy. Retinal changes were observed by light microscopy after intravitreal injections containing 20 micrograms of zinc gluconate, all concentrations of zinc sulfate, and 400 micrograms of EDU. No histologic or electroretinographic alterations occurred with doses of 15 micrograms or less of zinc gluconate or 200 micrograms or less of EDU. When added to the vitrectomy solution, concentrations of 20 micrograms/mL or less of EDU appeared nontoxic to the rabbit retina.