Evaluation of capillary electrophoresis for determining the concentration of dissolved silica in geothermal brines.

The determination of silica concentrations in geothermal brines is widely recognized as a difficult analytical task due to its complex chemical polymerization kinetics that occurs during sample collection and chemical analysis. Capillary electrophoresis (CE) has been evaluated as a new reliable analytical method to measure silica (as silicates) in geothermal brines. Synthetic and geothermal brine samples were used to evaluate CE methodology. A capillary electrophoresis instrument, Quanta 4000 (Waters-Millipore) coupled with a Waters 820 workstation was used to carry out the experimental work. The separation of silicates was completed in approximately 5.5 min using a conventional fused-silica capillary (75 microm i.d. x 375 microm o.d. x 60 cm total length). A hydrostatic injection (10 cm for 20 s at 25 degrees C) was employed for introducing the samples. The carrier electrolyte consisted of 10 mM sodium chromate, 3 mM tetradecyltrimethyl-ammonium hydroxide (TTAOH), 2 mM sodium carbonate, and 1 mM sodium hydroxide, adjusted to a pH 11.0 +/- 0.1. Silicates were determined using an indirect UV detection at a wavelength of 254 nm with a mercury lamp and with a negative power supply (-15 kV). A good reproducibility in the migration times (%R.S.D. approximately 1.6%) based on six non-consecutive injections of synthetic brine solutions was obtained. A linear response between silica concentration and corrected peak area was observed. Ordinary (OLR) and weighted (WLR) linear regression models were used for calculating silica concentrations in all samples using the corresponding fitted calibration curves. The analytical results of CE were finally compared with the most probable values of synthetic reference standards of silica using the Student's t-test. No significant differences were found between them at P = 0.01. Similarly, the atomic absorption spectrometry (AAS) results were also compared with the most probable concentrations of the same reference standards, finding significant differences at P = 0.01.

Macromolecular interactions with cadmium and the effects of zinc, copper, lead, and mercury ions.

Interactions of cadmium (Cd) ions with bovine serum albumin (BSA), bovine hepatic metallothionein (MT), calf thymus histone and deoxyribonucleic acid (DNA), and bovine hepatic chromatins were studied in the presence and absence of divalent zinc (Zn), copper (Cu), mercury (Hg), or lead (Pb) ions, using equilibrium dialysis at pH 7 and at 37°C. The BSA had 3.5 Cd-binding sites with an apparent affinity constant of 1×10(5). The other metal ions inhibited the binding by reducing the affinity constant and the number of Cd-binding sites in BSA. There were 6 high affinity and 13 low affinity Cd-binding sites in the MT. Zinc ions had poor efficacy in reducing the binding of Cd to the MT. However, the Cu(2+) and Hg(2+) ions inhibited the Cd binding to a considerable extent, the former ions being more potent in this respect. Histone did not bind Cd. There were two kinds of Cd-binding sites in DNA: One mole of Cd per four moles DNA-phosphorus at low affinity sites, and one mole of Cd per 6.7 moles DNA-phosphorus at high affinity sites. Their apparent association constants were 8.3×10(5) and 4.4×10(6) M, respectively. The other metal ions had inhibitory effects on the binding of Cd to DNA. Histone reduced the Cd-DNA interactions to only a minor extent. The other metal ions reduced the binding of Cd to DNA-histone complex to a small extent. Cadmium binds to the euchromatin (Euch), heterochromatin (Het), and Euch-Het mixture almost equally. The other metal ions reduced the binding maximally in Euch-Het followed next in order by Het and Euch. Cupric ions were the most potent inhibitors of the interactions of Cd with the nuclear materials.

Metal-binding proteins in bovine and porcine hepatic and renal tissues: isolation and characterization.

Cadmium-binding proteins of single band electrophoretic purity were obtained from the hepatic and renal tissues of cows and pigs fed 2 and 10 mg of cadmium/kg of feed. Zinc, cadmium, and copper constituted a total of 4 to 5 gatom/mole of protein. Zinc and cadmium were the major metal ions of the hepatic and renal proteins, respectively. Amino acid analysis of the proteins revealed the presence of 26.1% to 28.4% cysteine and 4.3% to 5.7% histidine residues. Small amounts of hexose also were in the proteins. Molecular weights (mol wt) of the bovine and porcine hepatic proteins were 15,200 and 14,400, respectively, whereas the mol wt of their renal proteins were 7,900. Hepatic proteins seem to be in the form of two monomers chemically bound together. Large metal and cysteine concentrations and low mol wt indicated that the proteins were metallothioneins.

Cadmium uptake from feed and its distribution to food products of livestock.

Distribution of cadmium (Cd) into the edible products of three species of food-producing animals was investigated during long-term dietary administration of supplemental cadmium chloride. Cows were exposed to 0.2 (control), 2.4, and 11.3 ppm Cd on whole ration basis for a period of three months followed by a three-month period on control ration. No accumulation of Cd occurred in milk, muscle, or bone at any of the time periods. A dose-related increase of Cd was observed in liver and kidney. The Cd concentration in these organs showed a gradual rise even when the animals were given control ration for three months after an initial three-month exposure to Cd; this observation suggests a mobilization and redistribution of this metal from other tissues. Dietary Cd levels in swine rations were 0.2, 2.4, and 10.1 ppm. The highest level of Cd produced a slightly reduced growth rate in swine. No accumulation of Cd was observed in muscle, bone, or brain. Liver and kidney showed a treatment and time-related increase in cadmium values at 6 and 12 weeks on experiment. During a three-month depletion phase after an initial three months of Cd administration, no further change in liver and kidney Cd levels was observed. White Leghorn chickens were treated by administering 0.3, 1.9, and 13.1 ppm Cd in their diets for up to 6 months. No accumulation of Cd occurred in eggs or bones. A slight increase of Cd level was observed in chicken muscle after six months of exposure. Liver and kidney had the highest levels of Cd, which showed a dose and time-related increase in these organs. No depletion of liver and kidney Cd was seen during seven weeks following a six-week treatment period. In all three species, the kidney Cd levels were severalfold higher than those of liver at all dietary levels. In swine, the renal cortex and medulla had similar Cd concentration in control animals but in all animals exposed to supplemental Cd, a dramatic rise in Cd levels in renal cortex was observed. Medullary Cd did not show a proportional time and dose-related increase in Cd levels, although the levels showed some increase. In kidney and liver of all three species the Cd levels showed a positive correlation with the amount of Cd-binding protein in these tissues. Induced levels of this metal-binding protein may explain accumulation and persistence of Cd-residues in these organs. In all three species, the concentrations of renal Cd-binding protein increased at a rate greater than those in liver. Although the food-producing animals may act as an effective filter of Cd in the case of an environmental increase of this metal, consumption of visceral organs from such animals may pose a hazard. This is particularly critical since the daily intake of Cd in human diet is already estimated to exceed the tolerance limits suggested by WHO/FAO.

Hepatic and renal metallothionein concentrations in cows, swine, and chickens given cadmium and lead in feed.

Dairy cows, growing swine, and laying chickens were given supplemental cadmium (Cd) at concentrations of approximately 2 and 10 ppm in feed as cadmium chloride and were given lead at concentrations of 5 and 25 ppm in feed as lead acetate for 12 to 24 weeks. Metallothionein (MT) and Cd concentrations increased more in renal than in hepatic tissues of the Cd-treated animals. The hepatic MT values in pigs and chickens and the renal MT values in all species continued to increase for several weeks after Cd feeding was stopped. A significant correlation between Cd and MT concentrations of the hepatic and the renal tissues was observed, except in bovine liver. The feeding of lead did not have any effect on the hepatic or the renal MT concentrations in cows, pigs, and chickens. Dietary Cd and possibly some other metals, but not lead, may be determinants of concentration of metal binding protein in tissues.

Relationship of pulmonary dysfunction to respiratory infection. A study of New York City office workers.

Pulmonary function tests were administered to 1,573 male and female office workers 30 years of age or older during their annual periodic health examinations. The frequency of respiratory infections was established from the workers' medical records. Fourteen percent had pulmonary function abnormalities; the men and women were equally abnormal. A comparison of the frequency of respiratory infections in subjects with normal and abnormal pulmonary function, matched according to age, sex and smoking history, showed no significant differences. Two subsequent years of retesting produced similar data for pulmonary function as well as for the occurrence of respiratory infections.