Journal of trace elements and electrolytes in health and disease最新文献

Human serum proteins of blood donors and dialysis patients were separated by means of gel filtration chromatography. The resulting fractions were analyzed for copper and zinc. Separation resulted in 3 zinc peaks with a molecular weight of about 700,000, 300,000, and 75,000 Dalton, with alpha 2-macroglobulin co-eluting in the first and albumin co-eluting in the third zinc peak. The zinc protein(s) of the second peak remained unidentified. The three peaks contained, in succession, 0.72 +/- 0.30 mumol/L (4.8 +/- 1.6%), 1.26 +/- 0.37 mumol/L (8.5 +/- 1.7/1000) and 12.8 +/- 2.1 mumol/L (86.8 +/- 2.8%) of total zinc in the case of blood donors, and 1.19 +/- 1.05 mumol/L (9.2 +/- 7.2%), 0.97 +/- 0.22 mumol/L (8.0 +/- 2.6%), and 10.4 +/- 1.66 mumol/L (82.7 +/- 6.7%) in the case of dialysis patients. Separation followed by copper analysis resulted in the three peaks, as well, with a molecular weight of about 750,000, 140,000, and 75,000 dalton. The copper protein of the first peak remained unidentified, while coeruloplasmin co-eluted in the second and albumin in the third peak. The three peaks contained, in succession, 0.4 +/- 0.16 mumol/L (2.3 +/- 0.95%), 14.6 +/- 0.7 mumol/L (83.9 +/- 4.1%), and 2.4 +/- 0.6 mumol/L (13.7 +/- 3.5%) of total copper in the case of blood donors, and 0.5 +/- 0.73 mumol/L (2.2 +/- 3.2%), 19.5 +/- 1.1 mumol/L (90.5 +/- 4.9%), and 1.6 +/- 0.66 mumol/L (7.3 +/- 3.0/1000) in the case of dialysis patients. Limitation of the method is shown regarding separation of major from minor proteins and albumin from transferrin.

Selenium (Se) has been shown to counteract the toxicity of heavy metals such as cadmium, inorganic mercury, methylmercury, thallium and to a limited extent silver. Although not as effective as Se, vitamin E significantly alters methylmercury toxicity and is more effective than Se against silver toxicity. Vitamin E is very effective against lead toxicity but Se has little effect. The presumed protective effect of Se against cadmium and mercury toxicity is through the diversion in their binding from low molecular weight proteins to higher molecular weight ones. Se appears effective in counteracting the chemical carcinogens (3-methyl-4-dimethyl-aminoazobenzene, 2-acetylaminofluorene, diethylnitrosamine, aflatoxin, 7,12-dimethylben (a) anthracene, benzopyrene and 3-methylcholanthrene) used to induce skin, liver and mammary tumors, but much less effective against those (dimethylhydrazine, azoxymethane, methylazoxymethanol, bis (2-oxopropyl) nitrosamine, benzopyrene, 1 methyl-1-nitrosourea and n-methyl-n-nitro-nitrosoguanidine) used to produce tumors in the colon, lungs, trachea and pancreas in laboratory animals. In contrast, Se many even increase pancreatic carcinomas in animals treated with bis (2-oxopropyl) nitrosamine. The health implications in humans of Se and heavy metal toxicities and in cancer are discussed.

Zinc in plasma and urine and serum albumin and alpha 2-macroglobulin were measured in 48 patients with burns. Mean total burned surface area amounted to 18%, ranging from 2 to 55%, and mean hospitalization time amounted to 35 days, ranging from 10 to 124 days. All parameters showed a decrease during the first two post-burn days. Minimal values were reached on days 2 and 3 for plasma and urine zinc, and between days 5 and 10 for the proteins. Thereafter, values increased, rapidly for both plasma and urinary zinc, more slowly for albumin and alpha 2-macroglobulin. The ratio R of the total plasma zinc minus the alpha 2-macroglobulin concentration to the albumin concentration is postulated as an indicator for zinc deficiency. From values of R and of the urinary zinc excretion, conclusions can be drawn about various processes of the zinc metabolism that may occur during the acute stage following the thermal accident and during the stages of tissue demarcation and of recovery. These processes are discussed in terms of possible temporary and/or local zinc deficiency. Evidence is presented that zinc administration in only indicated during the final stages of recovery in case of inadequate dietary intake.

The concentrations of the trace elements As, Au, Cd, Cs, Cu, Fe, Hg, Mo, Rb, Se and Zn were studied in the serum of 5 patients with end-stage renal failure who were undergoing treatment with hemodiafiltration. The concentrations of the following elements differ significantly from the reference values: As, Cd, Cu, Hg and Mo are higher, while Rb, Se, Zn and some of the Cs values are lower. The observed concentration deviations may be due to the uremic state and/or the dialysis process. To asses the contribution of the latter, the elements were determined in the substitution fluid and in the dialysate before and after blood contact and passage through the artificial kidney. Our findings suggest that the concentration abnormalities could be related to the substitution fluid for Cs, Rb, Se and Zn and to the dialysate for Mo and Rb.

Selenium (Se) is an essential trace element for animals and humans. Its biological role was established following the discovery that Se is a structural component of the active center of the enzyme glutathione peroxidase (GSH-Px). During the last decade remarkable progress has been made in the recognition of the structure and function of several selenoproteins. Cellular GSH-Px was the first enzyme recognized as a selenoprotein. In it Se was found in the form of selenocysteine. The enzyme is a tetrameric protein and is composed of four apparently identical subunits each containing one gram atom of Se. Plasma GSH-Px also has a tetrameric form with identical subunits and with one atom of Se per subunit. It is, however, a glycosylated protein, and is distinct from cellular enzyme. Both enzymes catalyze the reduction of hydrogen peroxide and a variety of organic hydroperoxides by glutathione. A third GSH-Px, called phospholipid hydroperoxide glutathione peroxidase (PHGSH-Px), is a monomeric, membrane-associated enzyme containing one atom of Se per mole of protein. This enzyme destroys esterified lipid hydroperoxides. The fourth known mammalian selenoenzyme is a type I iodothyronine 5'-deiodinase that catalyzes the deiodination of L-thyroxine to the biologically active hormone 3,3',5-triiodothyronine. It is a monomeric enzyme and contains one atom of Se per mole of protein. Selenoprotein P, a fifth known selenoprotein, is a glycosylated, monomeric protein containing ten atoms of Se per molecule. The function of this protein is not known, but it may play a role in Se transport or be connected with a protective activity against free radicals. In all these selenoproteins the Se is incorporated into the protein molecule via the selenocysteinyl-tRNA which recognizes the specific UGA codons in mRNAs to insert selenocysteine into the primary structure of selenoproteins.

Data on Cd sources in food are presented and the effects are discussed of the raised environmental level of Cd concentration in some foods. Information is also presented on normal dietary intakes of this element and how these intakes may be increased by environmental pollution or atypical dietary habits. With reference to the exposure risk, the FAO/WHO has established for adults a Provisional Tolerable Weekly Intake (PTWI) limit of 7 micrograms/kg B.W.. Therefore the evaluation of dietary Cd intake has become very important. The purpose of this work is the estimation of dietary intakes of Cd using data on the composition of an average Italian diet. Complete meals from a factory canteen were analyzed and calculations of weekly intake of Cd carried out. Mean dietary intake was 222 micrograms per week (range 137-326 micrograms per week) or 32 micrograms per day (range 19-46 micrograms per day), with the median intake being 198 micrograms per week or 28 micrograms per day. Analyses were performed by means of Zeeman Electrothermal Atomization Atomic Absorption Spectrometry (ETA-AAS). The results obtained, related to the average and representative food consumption of Italian people, show that the weekly intake is well within the PTWI, but the emission of Cd into the environment is continuing and attention must be paid to population groups at risk due to particular food habits.

In experiments with rats dose-response relationships of alimentary PtCl2 and PtCl4 were investigated. 2 x 81 animals weighing 35 g were randomly distributed among 9 treatment groups which were fed ad libitum with a synthetic diet containing various amounts of Pt during 4 weeks. Pt was added in the form of PtCl2 or PtCl4 in the amounts 0; 0.01; 0.05; 0.10; 0.50; 1.0; 5.0; 10 and 50 mg/kg diet. The Pt supplementation had no influence on life mass gain or food consumption. In the case of 50 mg/kg Pt in the form of PtCl4 the erythrocyte count and hematocrit were reduced by about 13% in comparison with the control group. Dependent on the Pt dose, the application of PtCl4 and PtCl2 induced Pt retention in nearly all tissues especially in kidney. The effects were greater with PtCl4 than with PtCl2. As a result of the higher Pt retention in the kidneys, the serum creatinine was increased for the higher doses of PtCl4.

Six groups of weanling rats were fed a low-selenium based diet containing less than 0.01 mg/kg of Se in the diet or the basal diet supplemented with five levels of selenium as selenite (0.1, 0.2, 0.3, 0.4 and 0.5 mg/kg) for at least 16 to 18 weeks. For determination of the effect of selenium on ribonucleic acid (RNA) synthesis in rat liver, rats of each dietary group were injected with a single dose of (5-3H)-uridine, and 3 hours later their livers were removed and subjected to cell fractionation. The radioactivities in the nuclear and cytoplasmic RNA were taken as a measure of the RNA synthesis rate. With selenium supplementation between 0.2 and 0.5 mg/kg diet, the radioactivities, amounts of RNA, as well as RNA/DNA ratios in both nuclear and cytoplasmic fractions of rat liver all increased significantly. In addition, at similar levels of selenium supplementation, statistically significant increments of glutathione peroxidase (GSH-Px) activity and reductions in lipid peroxide in liver were also observed. For assessment of RNA degradation, activities of ribonucleases (RNase) and RNase inhibitor in rats fed the low-selenium diet or a selenium-supplemented diet were determined. The activities of acid RNase and both free and latent alkaline RNase in liver homogenate were not affected by selenium deficiency; however, the level of RNase inhibitor present in the supernatant fraction increased significantly with selenium supplementation at 0.2 mg/kg diet.(ABSTRACT TRUNCATED AT 250 WORDS)