PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Essential elements”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1996

[Effects of essential trace elements on bone turnover--in relation to the osteoporosis].

Trace Elements are essential for normal growth and development of skeletons in humans and animals. Although they are minor building components in teeth and bone, they play important functional roles in bone metabolism and bone turnover. Fluoride accumulates in new bone formation sites and results in a net gain in bone mass. Aluminum induces impairment of bone formation by the inhibition of osteoblastic function. Magnesium enhances bone turnover by through the stimulation of osteoclastic function. Zinc regulates secretion of calcitonin from thyroid grand and influences on bone turnover. Gallium suppresses bone turnover in humoral hypercalcemia of malignancy in a similar mechanism as aluminum and cadmium. Copper induces low bone turnover by both suppressions of osteoblastic and osteoclastic functions. Iodine as the hormonal forms of thyroxine and triiodothyronine enhances bone turnover. Among the trace elements in bone and hair, significant differences were found in the contents of zinc, copper and manganese between normal subjects and osteoporotic patients. However, exact involvements of the trace elements in osteoporosis have not yet been clarified.

Animals↗
PubMed1999

Functional dissection of the promoter of the interphotoreceptor retinoid-binding protein gene: the cone-rod-homeobox element is essential for photoreceptor-specific expression in vivo.

The essential control elements in the interphotoreceptor retinoid-binding protein gene (IRBP) promoter are located between -156 and +19. The -156/-109 sequence contains a retina-specific DNAse I footprint and shows a positive regulatory activity in transiently transfected retinoblastoma cells. The -105/-85 sequence is G/C rich, shows a non-tissue specific DNAse I hypersensitivity, and a negative regulatory activity in retinoblastoma cells. The -76/-42 sequence shows a retinal-specific footprint and contains a "cone-rod-homeobox element" (CRXE) and a "photoreceptor conserved element" (PCE). IRBP promoter fragments with mutations in either CRXE, PCE or in both were linked to reporter genes and analyzed both by transient transfection and in transgenic mice. In retinoblastoma cells, the mutated CRXE-containing promoter shows a 60% repression of the CAT activity whereas the mutated PCE-containing promoter shows a 30% repression. In HeLa cells transfected with these promoters, co-transfection of a Crx expression vector with wild-type, but not with CRXE mutant promoter, activates CAT activity 20-fold over the background activity. Mutation of PCE alone or conversion of CRXE to PCE reduces this Crx-activated CAT activity to only 4-fold over the background activity. In the transgenic mouse experiments, none of the 12 lines with CRXE mutant promoter show significant expression of lacZ in the retina. In contrast, 9 of the 17 transgenic lines with PCE mutant promoter show photoreceptor-specific lacZ expression. Thus the Crx interaction with CRXE is essential for the photoreceptor-specific activity of the IRBP promoter in vivo. This interaction does not appear to require PCE, but is enhanced when PCE is present.

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↗
PubMed2001

Effects of oral aluminum on essential trace elements metabolism during pregnancy.

The present study was conducted to assess in rats the effects of oral aluminum (Al) exposure on calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn), and iron (Fe) accumulation and urinary excretion. Three groups of plug-positive Sprague-Dawley (SD) rats were given by gavage 0, 200, and 400 mg/kg/d of Al(OH)3 on gestational days 1-20. Three groups of nonpregnant female SD rats of the same age received Al(OH)3 by gavage at the same doses for 20 consecutive days. At the end of the treatment period, 24-h urine samples were collected for analysis of Al and essential elements. Subsequently, all animals were sacrificed and samples of liver, bone, spleen, kidneys, and brain were removed for metal analyses. With some exceptions, the urinary amounts of Al, Mn, and Cu excreted by pregnant animals as well as the urinary levels of Al excreted by nonpregnant rats were higher in the Al-treated groups than in the respective control groups. Although higher Al levels were found in the liver of pregnant rats, the concentrations of Al in the brain of these animals were lower than those found in the same tissues of nonpregnant rats. With regard to the essential elements, tissue accumulation was most affected in pregnant than in nonpregnant animals. In pregnant rats, the hepatic and renal concentrations of Ca, Mg, Mn, Cu, Zn, and Fe, as well as the levels of Ca in bone, and the concentrations of Cu in brain were significantly higher in the Al-exposed groups than in the control group. According to the current results, oral Al exposure during pregnancy can produce significant changes in the tissue distribution of a number of essential elements.

Aluminum↗
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↗
PubMed1996

Location of essential sequence elements at the Escherichia coli melAB promoter.

The Escherichia coli melAB promoter has been cloned on a short DNA fragment and subjected to deletion mutagenesis, random mutagenesis and site-directed mutagenesis. In previous work we had shown that expression from the melAB promoter is triggered by melibiose and that this requires the MelR transcription activator. Melibiose-dependent expression is suppressed by deletions that remove both DNA-binding sites for MelR and by point mutations in the -10 hexamer, the -35 hexamer and the region just upstream of the -35 hexamer. The point mutations identify promoter elements that are essential for triggering the melAB promoter. The importance of these elements was confirmed by site-directed mutagenesis. The results show that the organization of the melAB promoter is fundamentally different from the organization of other bacterial promoters controlled by homologues of MelR.

Base Sequence↗
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↗
PubMed1996

[Zinc--update of an essential trace element].

Since the recognition of zinc as an essential trace element in man and animals there has been a remarkable progress in our knowledge of the role of zinc in nutritional physiology, biology and medicine during the last few decades. Highlights in zinc research, mechanisms and homeostatic regulation of zinc absorption, sources of zinc intake, dietary factors and mineral interactions affecting zinc bioavailability are reviewed in the present paper. This is followed by an overview of the biochemical functions of zinc in enzymes, gene expression, endocrinology, immunology and oxidative stress. General signs and metabolic consequences of zinc deficiency as well as excessive intake and toxicity of zinc are summarized. Furthermore, national and international dietary zinc recommendations and different methods to determine the zinc status are discussed.

Animal Nutritional Physiological Phenomena↗
PubMed1996

[Essential trace elements and immunity].

The effects of zinc, iron, copper and selenium on the immune system are reviewed. Among the essential trace elements in humans, zinc, iron, copper and selenium are essential for the integrity and optimum function of the immunity. Although each element has different functions in the immune system, the deficiencies in each of these elements mainly causes the dysfunction of cell-mediated immunity. Deficiencies do not significantly effect the B cell function. These immunological abnormalities can be improved by supplementation of deficient elements. However, excess supplementation also impairs the immune system. Therefore, a proper balance of these elements is essential for maintenance of immunocompetence.

Animals↗
PubMed1994

A conserved helical element is essential for internal initiation of translation of hepatitis C virus RNA.

Translation of hepatitis C virus (HCV) RNA is initiated by cap-independent internal ribosome binding to the 5' noncoding region (NCR). To identify the sequences and structural elements within the 5' NCR of HCV RNA that contribute to the initiation of translation, a series of point mutations was introduced within this sequence. Since the pyrimidine-rich tract is considered a characteristic feature of picornavirus internal ribosome entry site (IRES) elements, our mutational analysis focused on two putative pyrimidine tracts (Py-I and Py-II) within the HCV 5' NCR. Translational efficiency of these mutant RNAs was examined by in vitro translation and after RNA transfection into liver-derived cells. Mutational analysis of Py-I (nucleotides 120 to 130), supported by compensatory mutants, demonstrates that the primary sequence of this motif is not important but that a helical structural element associated with this region is critical for HCV IRES function. Mutations in Py-II (nucleotides 191 to 199) show that this motif is dispensable for IRES function as well. Thus, the pyrimidine-rich tract motif, which is considered as an essential element of the picornavirus IRES elements, does not appear to be a functional component of the HCV IRES. Further, the insertional mutagenesis study suggests a requirement for proper spacing between the initiator AUG and the upstream structures of the HCV IRES element for internal initiation of translation.

Base Sequence↗