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PubMed1984

What is a biological oscillator?

Biological oscillators are amenable to qualitative analysis even before they have been described exhaustively in quantitative terms. Qualitative analysis can identify the elements essential for generating the oscillations and can enhance our understanding of underlying oscillator mechanisms. Two essential elements of a biological oscillator are 1) an inhibitory feedback loop, which includes one or more oscillating variables, and 2) a source of delay in this feedback loop, which allows an oscillating variable to overshoot a steady-state value before the feedback inhibition is fully effective. The analysis of the patterns of interactions and delays observed in biological oscillators is simplified by the translation of variables, interactions, and delays into schematic representations. To illustrate how such translations can be implemented, three biological oscillators are described schematically: 1) the glycolytic oscillator, 2) the bursting of the molluscan neuron, R15, and 3) the oscillations underlying smooth muscle contractions.

Animals↗
PubMed1989

Selenium intake with diet in Italy: a pilot study.

Selenium is an element essential to man. The main environmental pathway of Se-exposure for the general population is through food. As is true for all essential elements, not only deficient but also excessive exposure results in adverse health effects. Between these extremes there is a range of safe and adequate Se intakes. In 1980 the Italian National Research Council recommended 50-200 micrograms/day as an interval adequate to meet nutritional requirements, being at the same time below the threshold of toxic effects. Therefore the evaluation of dietary Se intake has become very important. The purpose of this work is the estimation of dietary intakes of Se using data on the amount and composition of an average Italian diet. Complete meals from a factory canteen were analyzed and calculations of weekly intake of Se carried out. Analyses were performed by means of Inductively-coupled Plasma Atomic Emission Spectrometry. The results obtained, related to the average and indicative food consumption of Italian people, showed that the daily intake is well within the recommended range.

Diet↗
PubMed1990

[An insufficiency of essential trace elements and its manifestations in pathology].

There exist 11 essential elements (iron, copper, iodine, zinc, chromium, cobalt, molybdenum, manganese, nickel, selenium and fluorine) vitally important for human health. The deficiency of these trace elements results in many pathological processes, including such world-wide human diseases, as iron-deficient anemias and other forms of hyposiderosis, endemic hypothyroid goiter, endemic fluorine deficiency states, particularly manifested by dental caries in children and osteoporosis of the advanced age. Selenium deficiency causes endemic cardiopathy in China, is a risk factor for the development and severe course of congestive cardiopathies, as well as myocardial infarction in a number of European countries. Correction of selenium deficiency with sodium selenite reduced to the minimum the mortality rate from endemic cardiopathy in China (Keshan disease) and had a favourable effect on other forms of cardiovascular pathology. Essential trace element deficiency results in many forms of embryonal and fetal pathology and decreases the antitumour resistance in man. New essential trace elements are still being identified and their number reached 19 at present. Development of pathological anatomy of essential trace element deficiency is an important task of modern medicine.

Animals↗
PubMed1989

Patient classification system evaluation. Part 1: Essential system elements.

How can nurse executives assure optimum patient classification system performance? This two-part series advances a framework for patient classification system (PCS) evaluation. Using an expanded definition of a PCS, part one presents a discussion of the six system elements considered essential to a fully operational PCS. Part Two offers a description of PCS selection criteria as well as keys to successful system implementation. Application of this evaluation framework allows for rapid problem identification and remediation, assists with PCS selection, and enhances overall system performance.

Evaluation Studies as Topic↗
PubMedDate not supplied

PIXE determination of essential trace elements in some traditional Chinese medicines.

The essential trace elements in 30 traditional Chinese medicines, (24 tonics and 6 nontonics) were determined by proton-induced X-ray emission. The authors' previous suggestion that traditional Chinese medicines may be classified by the order of magnitude of their essential trace elements, thus indicating their pharmacological effects, is not justified. The pharmacological effect of a trace element or its essentiality may be dependent on some ligand that can be chelated with it. A nonlinear mapping algorithm, however, shows that the 30 traditional Chinese medicines are nearly separated into two groups, indicating their tonic or nontonic pharmacological effects.

Drugs, Chinese Herbal↗
PubMed1987

Biological and health implications of toxic heavy metal and essential trace element interactions.

Human civilization and a concomitant increase in industrial activity has gradually redistributed many toxic metals from the earth's crust to the environment and increased the possibility of human exposure. Among the various toxic elements, heavy metals cadmium, lead, and mercury are specially prevalent in nature due to their high industrial use. These metals serve no biological function and their presence in tissues reflects contact of the organism with its environment. They are cumulative poison, and are toxic even at low dose. Studies of metabolism and toxicity of these elements have revealed important interactions between them and some essential dietary elements like calcium, zinc, iron, selenium, copper, chromium, and manganese. In general, a deficiency of these essential elements increases toxicity of heavy metals, whereas an excess appears to be protective. While most of the observations are on laboratory animals, limited human data are in agreement with the results of animal experiments. These suggest that the dietary presence of the essential elements may contribute to the protection of man and animal from the effects of heavy metal exposure, while their deficiency may increase toxicity. Appropriate dietary manipulation thus may be valuable in the prevention and treatment of heavy metal toxicity.

Animals↗
PubMedDate not supplied

New aspects on the distribution and metabolism of essential trace elements after dietary exposure to toxic metals.

Under present environmental conditions, an increase in pollution owing to metals such as cadmium (Cd), lead (Pb), and methylmercury (MeHg) must be expected. The resulting effects would be seen particularly in the food chain. The daily intake of toxic metals in various parts of the world is different and depends on both the dietary habits and the concentration in foodstuffs. Oral ingestion of these toxic metals perturbs the metabolism of essential elements, especially zinc (Zn), copper (Cu), iron (Fe), and selenium (Se). The elemental composition of body tissues and fluids is an indicator of the nutritional and pathological status of humans. This review will describe the dietary intake and gut absorption of essential and toxic elements. Furthermore, it will discuss threshold values, toxic effects in relation to body burden of toxic metals, the biological indices of exposure, and the interaction between toxic and essential elements. The overall ratio of Cu, Zn, Fe, and Se concentration to Cd in the human kidney is the lowest in comparison to Hg and Pb. Increased kidney copper and urinary losses may be common denominators in the manifestation of renal toxicity induced by heavy metals. Factors affecting availability and loss of copper should be identified and measured. The critical kidney concentration for Cd, Pb, and MeHg should be revised in relation to essential elements.

Animals↗
PubMed1995

Cadmium-induced alterations in essential trace element homeostasis in the tissues of scallop Mizuhopecten yessoensis.

Studies were performed regarding the effect of cadmium accumulation on the levels of essential elements (copper, zinc and iron) in the tissues of a marine bivalve mollusc, Mizuhopecten yessoensis, exposed to cadmium at 250 ppb during 2 weeks. It was found that the concentration of cadmium in the tissues increased in the order gonads < gills < hepatopancreas < kidney during exposure time. However, the highest value of concentration factor was recorded in the gills. Our data demonstrate that cadmium accumulation in all mollusc tissues is followed by the alterations in copper, zinc and iron concentration, but that the pattern of these changes varies with each tissue. Cadmium had the most pronounced effects on essential trace element homeostasis in the kidney. The present study suggests that levels of the essential metals in a particular tissue can be modified depending on the level of cadmium accumulation. The possible mechanisms of the effects of cadmium on the essential trace elements are discussed.

Analysis of Variance↗
PubMed1981

Absorption, transport and tissue storage of essential trace elements.

Intestinal absorption of many essential trace elements probably occurs by saturable and carrier-mediated processes. The nature and efficiency of these are influenced by a range of physiological, nutritional and genetic variables. Special emphasis is given to the influence of exogenous and endogenous ligands of small molecular mass in the intestinal lumen on absorptive efficiency. The effect of enterocyte proteins such as metallothionein which, by sequestering metals, influence their fate during absorption is also considered. Changes in the metabolic activity of the intestinal mucosa induced by copper or zinc deficiencies influence the fate of other nutrients, either by inhibiting intracellular transport or by preventing the degradation of potential antagonists of absorption. Conflicting evidence of roles for plasma albumin, transferrin and caeruloplasmin in the transport of zinc and copper is considered. The extent, location and form in which trace elements are stored in tissues differs between elements and between species. Retention and utilization are also influenced by pregnancy, lactation, stage of foetal development and by genetic variables. Better definition of the effects of these variables would improve the validity of estimates of the trace element requirements of man and other animals.

Animals↗
PubMed1988

Organization of multiple regulatory elements in the control region of the adenovirus type 2-specific VARNA1 gene: fine mapping with linker-scanning mutants.

The adenovirus type 2-specific virus-associated RNA 1 (VARNA1) gene is transcribed by eucaryotic RNA polymerase III. Previous studies using deletion mutants for transcription have shown that the VARNA1 gene has a large control region which is composed of several regulatory elements. Twenty-five exact linker-scanning mutations in the control region, from -33 to +77, of this gene were used for definition of the number and boundaries of these elements. The effects of these mutations on transcription and competition for transcription factors in human KB cell extracts revealed five positive regulatory elements. The essential element, which coincided with the B block, was absolutely required for both transcription and formation of stable complexes. A second element, which included the A block, was also required for both transcription and formation of stable complexes. Although this element is not as essential as the B-block element, together with the B-block element it may be necessary for formation of the most basal form of transcription machinery. Therefore, these two elements are the promoter elements in this gene. In addition, one possible element in the interblock region and two elements in the 5' flanking region were also required for efficient transcription, but they were moderately required for formation of stable complexes. Transcription of these mutants and the wild-type gene using an extract of 293 cells was stimulated at least threefold over that with the KB cell extract, as expected. Similar regulatory elements of this gene were revealed, however, when the 293 cell extract was used for transcription of these mutants, suggesting that the E1A-mediated specific transcription factors act on the transcription machinery in a sequence-nonspecific manner.

Adenoviruses, Human↗
PubMed1990

Cadmium-induced route-specific alterations in essential trace element homeostasis.

To determine if route-specific differences in essential trace element homeostasis occur after cadmium (Cd) exposure, selected metals (Zn, Fe, Ca, K, Cu, Mg, and Cd) were determined in testis, liver and lung after subcutaneous and intravenous Cd treatment. Cd by the subcutaneous route had the most pronounced effects on essential trace element homeostasis in the testes, increasing the concentration of Zn (51%), Fe (242%), Ca (95%), K (93%), and Cu (345%) in conjunction with a decrease of testicular Mg (46%), while few changes occurred with intravenous Cd. In the lung, modest changes of all elements except Ca and Cu were observed with Cd. However, alterations in Fe and Zn concentration were seen only in the liver. The present study suggests that levels of the essential metals in a particular tissue can be modified depending on the route of Cd administration.

Animals↗
PubMedDate not supplied

[Intake of essential trace elements (selenium, copper and iron) in the nutrition of patients hospitalized with liver cirrhosis].

Dietary intake for three essential trace elements: selenium, copper and iron was studied in hospitalized patients receiving either ordinary meals or regimens adapted for liver cirrhosis. The aim of the study was to assess the effects of dietary manipulations: reduction in sodium intake for uncomplicated disease and protein restriction to 40 g per day in patients with hepatic encephalopathy. The meals proposed to these three groups were collected during fourteen days and daily intake for three elements was estimated by direct analysis of the assembled meals of the day. Dietary selenium was greatly affected by the restriction in protein intake contrary to copper and iron which were not significantly reduced. Moreover, overall daily trace element intake was rather low and clearly less than the most recent recommended allowances for these essential elements. Relationships between deficiency in some of these trace elements and worsening of the liver disease have been partly documented. They should encourage studies on the correction of dietary intake.

Copper↗
PubMed1992

[Effects of an essential trace element agent (TE-5) for total parenteral nutrition on the mineral nutrition in rats fed a trace element-deficient diet].

TE-5 is an essential trace element agent containing iron, zinc, copper, manganese and iodine for total parenteral nutrition (TPN). We have already reported that TE-5 improved the reduction of trace element concentrations induced by TPN. However, effects of TE-5 on the changes in biological function relating to trace elements are poorly understood. The present study was designed to clarify the effects of TE-5 on these functions. Rats fed a trace element (iron, zinc, copper, manganese and iodine)-deficient diet for 7 weeks showed reductions in the following parameters: plasma and various tissue concentrations of iron, zinc, copper, manganese and iodine, growth rate, erythrocyte (iron), hemoglobin (iron), hematocrit (iron), mean corpuscular constants (iron), plasma alkaline phosphatase activity (zinc), serum ceruloplasmin concentration (copper), liver pyruvate carboxylase activity (manganese) and serum thyroxine concentration (iodine). On the other hand, when TE-5 (0.008, 0.04 and 0.2ml/kg: x 0.2, x 1 and x 5 the usual clinical dose, respectively) was intravenously administered once a day for 7 weeks under the conditions described above, there was a tendency to prevent the reductions of plasma and various tissue concentrations of iron, zinc and manganese. In addition, TE-5 prevented the reductions of growth rate, iron metabolism functions, plasma alkaline phosphatase activity, serum ceruloplasmin concentration and liver pyruvate carboxylase activity. The present study shows that TE-5 prevents both reductions of trace element contents and trace element-related functions, and suggests that TE-5 is useful for treatment of trace element deficiency in TPN.

Animal Nutritional Physiological Phenomena↗
PubMed1987

Activation of calmodulin by the essential trace element chromium.

Chromium at very low concentrations is an essential trace element--at higher concentrations it is associated with contact dermatitis and other toxicity problems. Its ionic radius is just outside that of other metal cations which have been found to activate calmodulin in vitro. We found that chromium was able to activate calmodulin at two different concentration ranges--over the micromolar range (which would probably never be achieved in man) a small degree of activation was found--but a much greater activation (76% of the maximum possible) was also found at nanomolar concentrations of chromium. In welders, who work with stainless steel and who were not reporting any physical symptoms of chromium toxicity, red cell chromium levels were 28.2 +/- 3.3 nM (n = 22) compared to 7.5 +/- 0.7 nM (n = 11) for normal controls. Thus, the concentration of chromium experienced within the cell can be of the order which will activate calmodulin in vitro. The possibility exists, therefore, that inappropriate activation of calmodulin could be relevant to chromium biology possibly contributing to the symptoms of chromium toxicity.

Animals↗
PubMedDate not supplied

Dietary intakes of some essential and non-essential trace elements, nitrate, nitrite and N-nitrosamines, by Dutch adults: estimated via a 24-hour duplicate portion study.

Duplicate portions of 24-hour diets of 110 adults have been analyzed for aluminium, cadmium, copper, lead, manganese, mercury, zinc, nitrate, nitrite and volatile N-nitrosamines. The mean daily intake of copper (1.2 mg) is only about 50% of recommended values; mean daily intakes for manganese (3.3 mg) and zinc (8.4 mg) are adequate and marginal respectively with respect to recommended amounts. For the non-essential elements Al, Cd, Hg and Pb, mean daily intakes of 3.1 mg, 0.01 mg, 0.002 mg and 0.034 mg were found, respectively. For Cd this amounts to 17% of the acceptable daily amount, for Al, Hg and Pb 5%, 5% and 8%, respectively. Since 1976-1978 the dietary intake of lead has been reduced by a factor three; for the other six elements daily dietary intakes are almost the same as in 1976-1978. Average nitrate intake was 52 mg NO3-/day, about 25% of the ADI. Only 16 diets contained a measurable amount of nitrite. The highest daily intake (0.7 mg NO2-) is less than 10% of the ADI. Volatile N-nitrosamines were detectable in two duplicate diets (NDMA and NPIP). It is estimated that the daily dietary intake of volatile N-nitrosamines is around 0.1 microgram or less.

Adult↗
PubMed1975

Trace element concentration in human brain. Activation analysis of cobalt, iron, rubidium, selenium, zinc, chromium, silver, cesium, antimony and scandium.

Up to 60 tissue samples were dissected from 13 human brains in defined regions and were analysed by means of neutron activation analysis for trace element concentration of cobalt, iron, rubidium, selesium, zinc, chromium, silver, cesium, antimony and scandium. It was shown that the variation in concentration of the non-essential elements in the different brain regions was greater than the corresponding variations in concentration of the essential elements. The mean values of Fe and Rb concentrations were higher in the basal ganglia than in the cortex areas. With increasing age the Fe concentration in the human brain was found to increase and that of Rb to decrease. Comparison of the trace element concentration in corresponding areas of the right and left hemispheres showed highly significant positive correlations for the essential elements. The concentration of each of the essential elements Fe, Rb and Zn was also found to differ significantly between defined functional regions. The characteristic distribution of essential trace elements in different areas is discussed in the light of known metabolic functions of these elements.

Adult↗