RNAA as compared to ICP-MS for the analysis of normal human serum

The merits of radiochemical neutron activation analysis (RNAA) and inductively coupled plasma mass spectrometry (ICP-MS) are critically discussed for the determination of trace and ultratrace elements in normal human serum. For RNAA, two semiautomated procedures, allowing the determination of up to 18 elements, are briefly described. ICP-MS has a series of interesting features for the determination of trace elements. Matrix and spectral interferences can mostly be avoided or corrected for. After a simple 5- or 10-fold dilution and addition of an internal standard, more than 20 elements can be measured precisely and accurately.     

Determination of trace elements in human serum by inductively coupled plasma-mass spectrometry

The determination of trace and ultratrace elements in human serum by ICP-MS is described. The accuracy of the method is tested using a “second generation” human serum reference material. Elements determined include Fe, Co, Cu, Zn, Br, Rb, Sr, Mo, and Cs. The method is compared to nuclear analytical methods (NAA, PIXE). Perspectives for the future are also discussed.     

Factors affecting the selenium intake of people in transbaikalian Russia

The selenium concentration in foods grown and consumed and in plasma, red blood cells, and toenails of people living in the district of Chita in the transbaikalian part of Russia were studied in August 1991. Preliminary results from the area have suggested low selenium intakes and the possible occurrence of cardiomyopathy (Keshan disease) in the population. A low selenium concentration in foods grown locally was found: mean selenium concentration in wheat grains was 1, 5, and 28 μg/kg, respectively, in three villages studied, that of oats was beween 3–6 μg/kg, and of cow's milk 10–27 μg/kg dry matter. The selenium concentration of bread was considerably higher, between 87–337 μg/kg dry wt, presumably because wheat imported from the US had been used for baking. Occasional samples of pork, beef, and mutton contained between 32–318 μg selenium/kg dry wt. Low selenium concentrations were observed in samples of soil and river water. The mean plasma selenium concentration of 52 persons was 1.02 μmol/L, including 33 children and 19 adult subjects. The selenium concentrations in red blood cells and toenails were 1.95 μmol/L and 0.61 mg/kg, respectively. No symptoms of heart disease caused by selenium deficiency were observed. It is concluded that the selenium status of people was fairly good thanks to the contribution to dietary intake of imported wheat with a high selenium content. As the selenium concentration was very low in foods grown in the area, the selenium intake of the population will be reduced to a very low level if only locally produced foods are consumed.     

Vanadium determination at the ultra-trace level in biological reference materials and serum by radiochemical neutron activation analysis

In order to help resolve present inconsistencies of two orders of magnitude or more in reported levels of vanadium in human serum and blood, a totally postirradiation radiochemical neutron activation analysis (NAA) method was further developed and applied to some pertinent nanogram and subnanogram reference materials. In particular, the second generation human serum reference material of Versieck was found to contain a value of 0.67±0.05 ng/g dry wt., corresponding to 0.061±0.005/4/ (see Table 1) ng/mL original fresh serum. Results are also reported for some other appropriate CRMs. Additionally, a small-scale study in 10 normal subjects (5 m, 5 f) revealed levels similar to those in the serum reference material and in agreement with the lowest data reported in the literature. Discussion of pitfalls of vanadium determination and the use of reference materials is included.     

Dietary calcium and blood lead levels in women

Nutritional factors are known to influence metabolism and toxicity of several metals in animal experiments, but relevant human data are scarce and inconclusive. In this work, we tested the hypothesis that dietary calcium influences lead metabolism in humans. Blood lead concentrations were used as indicators of lead exposure and metabolism. Two groups of peasant women living in similar conditions in two different regions in Yugoslavia (100 in each) were chosen as subjects for this purpose. In region A, the dietary calcium intake was about 940 mg, and in region B about two times lower, i.e., 450 mg/day. The average blood lead concentration was significantly lower in women from region A (69 micrograms/L) than from region B (83 micrograms/L). Our results support the assumption that adequate calcium intake might be one of the preventive measures for decreasing lead absorption. This new evidence, sought for some time by nutritionists and toxicologists, needs further international confirmation.     

The distribution of cadmium within the human prostate

Five normal prostates from autopsies of humans aged 61-76 yr were divided into 2 x 24 topographically well-defined pairs of slices that were analyzed for cadmium (Cd) and examined histologically. The corresponding kidney cortex concentrations were also determined. The concentrations in ng Cd/g wet wt were in the range of 50-500 in the prostates and 8,000-39,000 in the kidneys with good mutual correlation. Large variations in Cd concentrations within the prostates were found. The concentrations were highest at the base (near the bladder) and lowest at the apex of the gland. Furthermore, large variations within horizontal layers were found, and this variation was not correlated to the histological amount of stroma or glands.     

Mercury and selenium distribution in human kidney cortex

Concentration of mercury and selenium were analyzed in tissue fractions of human kidney cortex samples from seven autopsy cases. Total mercury content ranged between 0.3–9.0 nmol Hg/g wet wt. Between 27–61% of the total mercury was found in the 105,000g supernatant of the tissue homogenate from six cases. In kidney cortex from the seventh case, a deceased dentist with the highest concentration of mercury, only 3% of the total mercury was found in the 105,000g supernatant and about 88% in a SDS-insoluble fraction. In this fraction the molar ratio between mercury and selenium was close to 1∶1. This study supports results from previous animal studies and indicates that mercury in human kidney cortex could be deposited in forms with different solubility. It could be of importance to speciate different forms of mercury in tissues according to solubility and association to selenium when interpretations of mercury concentrations are made.     

A new technique for the study of erythrocyte survival by double labeling and use of a well-type Ge detector

A double label procedure with⁵⁷Co and⁵⁸Co has been developed for detailed in vivo studies of erythrocyte survival. A well-type Ge detector is used in the measurements. The activities necessary for these experiments are very low, and the associated dose received by the test persons can be neglected.     

The effect of silicon (Si) on lipid parameters in blood serum and arterial wall

The influence of silicon treatment on the levels of lipid parameters of blood serum and aortic wall was studied in rats. The concentrations of total cholesterol, phospholipids, triglycerides, HDL-cholesterol, LDL-cholesterol, and HDL-phospholipids were measured in sera of rats receiving per os a soluble, inorganic silicon compound--sodium metasilicate nonahydrate (Na2SiO3.9H2O)--dissolved in the drinking water. In the aortic tissue levels of total cholesterol, triglycerides and phospholipids were estimated. An increase in HDL-cholesterol and HDL-phospholipid concentrations, with a simultaneous decrease of LDL-cholesterol and triglyceride levels, was observed in the sera of the tested group. The levels of total cholesterol and phospholipids in the sera, as well as the concentrations of lipids in the aortic walls, showed no significant differences. The results obtained could provide evidence for the existence of an additional mechanism of silicon antiatheromatous action, concerning the modification of activity of enzymatic systems involved in lipids metabolism.     

Determination of selenium in duplicate diets of residents of Pinhel,Portugal, by neutron activation

A rapid cyclic instrumental neutron activation analysis (CINAA) method has been used to determine the selenium content of 27 duplicate diet samples from each of the 27 districts surrounding Pinhel, Portugal. The accuracy and precision of the CINAA method have been evaluated by analyzing certified reference materials and observed to be within ±5–10% for samples containing at least 40 ppb of selenium. The detection limit has been found to vary between 26–42 ppb selenium depending on the sample composition. The average daily dietary intake has been calculated as 37 μg of selenium per day.     

The distribution and half-life for retention of vanadium in the organs of normal and diabetic rats orally fed vanadium(IV) and vanadium(V)

The concentration of vanadium in organs of diabetic rats that had been fed vanadium, either as V(IV) or V(V), in their drinking water has been determined. The kidney was found to have the highest concentration, about 185 nmol/g wet tissue. This averages about three times higher than for the liver or spleen, for which concentrations were comparable. The lung, blood plasma, and blood cells tended to have the lowest accumulations of vanadium. A time-course study indicated that the half-life for elimination of vanadium from the bodies of vanadium-fed rats is about 12 d.     

Suboptimal levels of dietary copper vary immunoresponsiveness in rats

The effects of severe, moderate, and mild copper deficiencies on cellular and humoral immunity were studied. Fifty male Sprague-Dawley rats, 5 wk of age, were fed diets containing 0.5, 2.0, 3.5, or 5.0 micrograms Cu/g for either 4 or 8 wk. Ten of the rats were fed the control diet, but were pair-fed with the 0.5-micrograms/g treatment group. All rats were immunized once with sheep red blood cells. Mean plasma-copper concentration reflected the dietary levels of copper, and ceruloplasmin activity correlated highly to plasma copper. Rats consuming suboptimal levels of copper responded differently to the deficiencies, so copper status varied among those animals. After 8 wk, cell proliferation, when stimulated by phytohemagglutinin, was dependent on the copper status of the animal. Severely deficient rats had consistently lower lymphocyte stimulation indexes for phytohemagglutinin and concanavalin A, but specific antibody response was not reduced. Immunoglobulin G (IgG) concentrations were variable for all rats, and immunoglobulin M (IgM) concentrations were lower for the severely deficient rats. Suboptimal dietary copper may alter immune function in rats, depending on the ensuing effect on copper status.     

Zinc,copper, and sexual maturation in 9-18-year-old girls and boys

The relationships between serum levels of zinc and copper and sexual maturation were analyzed in 2291 9-18-yr-old Finnish girls and boys. Development of public hair, breasts, and genitalia were used to grade maturation according to Tanner's classification. Serum zinc and sexual maturation were not related. However, 15- and 18-yr-old girls who had matured most slowly had low serum levels of zinc compared with their age mates. Thus, sexual maturation seems not to be affected by zinc deficiency in Finland; effects of zinc status on maturation in some minor groups cannot, however, be excluded. Serum copper levels were associated with age and sexual maturation, which complicates the drawing of conclusions about possible deficiencies.     

Transformation of human kidney epithelial cells to tumorigenicity by nickel(II) and V-HA-RAS oncogene

Nickel is a toxic metal of environmental concern that has been found to be carcinogenic in man and animals. Primary human kidney (NHKE) cells were immortalized or rescued from senescence after exposure to NiSO₄. The cell lines (IHKE) displayed abnormal karyotype and anchorage independent growth was observed. However, none of the IHKE cells produced tumor upon injection into athymic nude mice. Transfer of the v-Ha-ras oncogene into IHKE cells induced conversion of the immortalized cells into cell lines (THKE) that were tumorigenic when transplanted into athymic nude mice. Ha-ras DNA was present in the transformed cell lines and expressed at high level.     

A review of protein engineering for the food industry

In this review I briefly describe the technique of protein engineering and indicate how the present state of knowledge allows proteins to be mutated to increase or decrease stability. I discuss experiments on both model proteins and those of relevance to the food industry and show how hydrophobic forces are a major driving force for folding as well as having a major role in thermostability, I also indicate the large contribution that hydrogen bonding, electrostatic interactions and, in a less well predicted way, disulfide bridges make to thermostability.     

Effects of etretinate on the distribution of elements in rats

We studied in the rat the effects of the drug etretinate (Tigason), given at three doses 3, 10, and 30 mg/kg body wt for 1 mo, on the concentrations of Na, K, Ca, Mg, Fe, S, P, Cu, and Zn in the plasma, brain, thymus, heart, liver, lung, kidney, testicle, muscle, and bone. The elements were simultaneously determined in tissues after nitric acid dissolution by inductively coupled plasma emission spectrometry using a JY 48 instrument. At the dose of 3 mg/kg, etretinate did not induce any statistically significant modifications of the element distribution. At the dose of 10 mg/kg, the main observed modifications were in plasma an increase of copper (+38%) and a decrease of zinc (-25%). At the highest dose of 30 mg/kg, some variations of the concentrations of elements in tissues were observed. But, on no account did retinoids induce an alteration of the mineral composition of bone, despite obvious macroscopic bone alterations.     

Effects of doxorubicin on the sensitivity of L1210 leukemia cells to deformation-associated trauma

Most of the cancer cells arrested in the microcirculation during hematogenous metastasis are rapidly killed; one major mechanism is surface-membrane rupture, associated with the mechanical deformation of cancer cells in capillaries. The feasibility of increasing the susceptibility of cancer cells to lethal, deformation-associated trauma by doxorubicin, was tested in an in vitro mechanical model system, by filtering suspensions of L1210 leukemia cells through 8-μm pore-size Nuclepore® membranes, with or without prior incubation with 10^-7M doxorubicin. The results showed that mechanically-induced loss of cancer cells immediately after filtration was increased from 18 to 55% in cells previously exposed to doxorubicin for 48 h. The results indicate the feasibility of chemotherapeutic enhancement of the mechanical killing-action of the microvasculature as a potential rate-regulator of hematogenous metastasis.     

Levels of some trace elements in selected autopsy organs,and in hair and blood samples from adult subjects of the Italian population

This study, which is part of a research program for the determination of trace element reference levels in various human tissues for the Italian population, presents the concentrations of Se, Hg, Cr, Cs, Sc, Rb, Zn, Fe, Co, and Sb in lung, liver, spleen, and kidney autopsy samples taken from 14 adult subjects of the Italian population who died from accidental causes. Concentrations of the same trace elements are given also for blood and hair samples taken from subjects of the general Italian population and of a population group living in a small coastal town that has an average annual fish consumption well above the national average. The analytical method used was Instrumental Neutron Activation Analysis. The levels and distribution of the trace elements in the various human organs examined are analyzed and discussed.     

Study of correlation of se content in human hair and internal organs by INAA

The correlations of essential element Se between human hair and kidney-cortex, liver, and lung from the same subjects were investigated by instrumental neutron activation analysis, using the reaction⁷⁶Se (n, γ)^77mSe, for 24 Chinese autopsies. The concentration of Se is higher in kidney-cortex (2.04–5.36 mg/kg) than in liver (0.73–2.29), lung (0.50–1.85), and hair (0.37–1.43). It is important to know that there are significant relationships of Se concentration between hair and the other three internal organs. The correlation coefficient by linear regression analysis are 0.639, 0.570, and 0.635 for liver, lung, and kidney-cortex, respectively; and theP values are all less than 0.01 for the three tissues.