Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Confluent monolayers of cultured microvascular endothelial cells from goat brain were used as an in vitro model system of the blood-brain barrier to study the effect of aluminum on the anionic sites located on the cell surface. Four experimental groups were used: (1) untreated (control 1) cells growing in normal medium; (2) cells growing in a medium containing 50 microM maltol (control 2); (3) cells growing in a medium containing 50 microM aluminum maltolate; and (4) cells growing in a medium containing 6 microM cadmium chloride as a known cytotoxic substance. The cell cultures were exposed to the substances listed above for 4 days. The anionic sites were detected at the ultrastructural level with cationic colloidal gold and cationized ferritin in non-fixed and fixed cells (prefixation and postfixation procedures). In the applied experimental conditions, aluminum maltolate was found to affect the surface density of anionic sites, as manifested by their redistribution and segmental disappearance from the apical plasmalemma of the endothelial cells. These changes were more pronounced in the non-fixed than the fixed cells and are reversible. Most probably, aluminum, because of its unique properties as a cross-linker, facilitates the lateral migration of anionic sites induced by cationic probes. Whether these alterations contribute to in vivo aluminum-induced blood-brain barrier dysfunction requires further elucidation.
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PMID:Aluminum-induced alteration of surface anionic sites in cultured brain microvascular endothelial cells. 825 88

The present study characterizes the transport of nontransferrin (non-Tf) iron by K562 cells. Accumulation of radiolabel by cells incubated with 55Fe-nitrilotriacetate (NTA) is a saturable process that is time and temperature dependent (Ea approximately 20 kcal/mol). Initial rate analysis of iron influx yields values of Vmax = 855 fmol/min/10(6) cells and apparent Km = 0.54 microM. NHCL4 and chloroquine, agents that block cellular acquisition of iron from Tf, do not interfere with assimilation from FeNTA, demonstrating that uptake is truly independent of the Tf-mediated pathway. Furthermore, the inactivation of this transport mechanism by limited proteolytic digestion on ice indicates that specific cell surface proteins are involved. The extent of radiolabel incorporation into heme and ferritin is the same regardless of whether K562 cells acquire iron from 55FeNTA via the cell surface mechanism or from 55Fe-Tf via receptor-mediated endocytosis. Unlike other Tf-independent iron transport pathways that have been described, the K562 cell transport mechanism is not inhibited by divalent cations such as Ni2+, Co2+, or Mn2+. Uptake from 55FeNTA can be blocked by Cu2+ but at concentrations > 1500-fold molar excess. However, Cd2+ is a fairly specific inhibitor of 55Fe uptake by K562 cells (IC50 approximately 50 microM). Additionally, the K562 cell transport mechanism is not Ca2+ dependent and does not appear to be regulated by extracellular iron salts, in contrast to features noted for non-Tf iron uptake by fibroblasts (Sturrock, A., Alexander, J., Lamb, J., Craven, C. M., and Kaplan, J. (1991) J. Biol. Chem. 265, 3139-3145; Kaplan, J., Jordan, I., and Sturrock, A. (1991) J. Biol. Chem. 266, 2997-3004). These unique characteristics of the K562 cell uptake mechanism suggest that multiple transport systems function in Tf-independent iron assimilation.
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PMID:Characterization of transferrin-independent iron transport in K562 cells. Unique properties provide evidence for multiple pathways of iron uptake. 847 96

Dietary intake and uptake of cadmium (Cd) were studied in nonsmoking women, 20-50 years of age, consuming a mixed diet low in shellfish (N = 34) or with shellfish once a week or more (N = 17). Duplicate diets were collected during 4 consecutive days for the determination of Cd content. The women kept detailed dietary records, and the intake of energy and various nutrients was calculated. The shellfish diets (median 22.3 micrograms Cd/day) contained twice as much Cd as the mixed diets (median 10.5 micrograms Cd/day; p < 0.0001). Cadmium in feces corresponded to 100 and 99% of that in duplicates of shellfish diets and mixed diets, respectively, indicating a low average absorption of the dietary Cd. In spite of the differences in the daily intake of Cd, there was no statistically significant difference in the concentrations of Cd in blood (B-Cd, shellfish group 0.25 micrograms/liter, mixed diet group 0.23 micrograms/liter) or urine (U-Cd, 0.10 micrograms Cd/liter in both groups). This indicates a lower absorption of Cd in the shellfish group than in the mixed diet group or a difference in the kinetics. A higher gastrointestinal absorption of Cd in the mixed diet group could partly be explained by lower body iron stores as measured by the concentrations of serum ferritin (S-fer, median 18 micrograms/liter, compared to 31 micrograms/liter in the shellfish group). In the mixed diet group, S-fer was negatively correlated with B-Cd and the main determining for B-Cd besides U-Cd in the multiple regression analysis, indicating an increased absorption of Cd at low body iron stores. When women with S-fer exceeding 20 micrograms/liter were compared, the higher dietary intake of Cd in the shellfish group compared to the mixed diet group (24 versus 10 micrograms/day) resulted in higher B-Cd (0.26 versus 0.16 micrograms/liter), although not in proportion to the difference in Cd intake. Thus, there seems to be differences in the bioavailability and/or kinetics of dietary Cd related to the type of diet. This is, to our knowledge, the first study where the influence of various types of diets and nutritional factors on the intake and uptake of cadmium in human subjects has been studied.
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PMID:Bioavailability of cadmium from shellfish and mixed diet in women. 861 41

Surface charges of protein molecules are not only important to biological functions but also crucial to the molecular assembly responsible for crystallization. Appropriate alteration in the surface charge distribution of a protein molecule induces new molecular alignment in the proper direction in the crystal and, hence, controls the crystal form. Apoferritin molecules are known to crystallize in two- and three-dimensional forms in the presence of cadmium ions, which bridge neighboring protein molecules. Here we report a controlled transformation of the apoferritin 2-D crystal by site-directed mutagenesis. In mutant apoferritin, two amino acid residues binding a cadmium-ion through their negative charge, were replaced by one type of nonionic amino acid residues. The amino acid residues, Asp-84 and Gln-86 in the sequence of recombinant (i.e., wild-type) horse L-apoferritin, were replaced by Ser. The wild-type apoferritin yielded a hexagonal lattice 2-D crystal in the presence of cadmium ions. In contrast, the mutant apoferritin yielded two types of oblique crystals independent of the presence of cadmium ions. Image reconstruction of electron micrographs of the mutant crystals made clear that the mutant apoferritin molecules oriented themselves with the 2-fold symmetry axis perpendicular to the crystal plane in both crystals, while the wild-type apoferritin molecules oriented themselves with the 3-fold symmetry axis perpendicular to the crystal plane. The changes of crystal forms and molecular orientation in the 2-D crystals were well explained by a change of the electrostatic interactions induced by the mutagenesis.
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PMID:Control of crystal forms of apoferritin by site-directed mutagenesis. 874 50

This study evaluated the effect of dietary cadmium (Cd) on atherosclerosis in the rabbit. Cholesterol was added to the diet to initiate and/or accelerate atherogenesis. Cd was added to the diet at two dose levels. Uptake of Cd was 55 micro gram/kg body weight (BW)/day at the low dose level and 1350 micrograms/ kg BW/day at the high dose level. Five groups of rabbits were fed five different diets for 9 months: (1) basal diet without additional constituents; (2) background diet, which was basal diet to which cholesterol had been added; (3) the low-dose level Cd diet, which was background diet to which 2 mg Cd/kg had been added; (4) high-dose level Cd diet, which was background diet to which 50 mg Cd/kg had been added; and (5) basal diet to which 50 mg Cd/kg had been added. Dietary cholesterol increased blood total leucocyte count, serum and liver total cholesterol concentrations, serum total bilirubin concentration, low-density lipoprotein vitamin E concentration and induction of atherosclerotic plaques in the aorta and coronary arteries. Cd in the diet increased liver and kidney Cd concentrations in a dose-dependent way, decreased prothrombin time and temporarily increased urea and creatinine clearances. Slight kidney damage was induced by Cd only in animals fed the high-dose level Cd diet (with or without cholesterol). Dietary Cd partly counteracted the dietary cholesterol-induced increases of serum and liver total cholesterol concentrations, and tended to reduce plaque formation in the aorta. Dietary Cd in rabbits fed cholesterol-containing diets influenced cholesterol metabolism and tended to decrease atherosclerosis in a dose-related fashion. This is in contrast with limited epidemiological human data. Dietary Cd also decreased serum ferritin concentration and increased serum transferrin concentration. Free iron concentration is associated with myocardial infarction in man and augments the development of atherosclerosis in rabbits. It is concluded that the observed reduction in atherogenesis is related to dietary Cd-induced changes in cholesterol metabolism, increased rheology of blood and/or, most likely, reduced free iron concentration.
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PMID:Cadmium and atherosclerosis in the rabbit: reduced atherogenesis by superseding of iron? 876 54

This report provides a review of the cadmium exposure situation in Sweden and updates the information on health risk assessment according to recent studies on the health effects of cadmium. The report focuses on the health effects of low cadmium doses and the identification of high-risk groups. The diet is the main source of cadmium exposure in the Swedish nonsmoking general population. The average daily dietary intake is about 15 micrograms/day, but there are great individual variations due to differences in energy intake and dietary habits. It has been shown that a high fiber diet and a diet rich in shellfish increase the dietary cadmium intake substantially. Cadmium concentrations in agricultural soil and wheat have increased continuously during the last century. At present, soil cadmium concentrations increase by about 0.2% per year. Cadmium accumulates in the kidneys. Human kidney concentrations of cadmium have increased several fold during the last century. Cadmium in pig kidney has been shown to have increased by about 2% per year from 1984-1992. There is no tendency towards decreasing cadmium exposure among the general nonsmoking population. The absorption of cadmium in the lungs is 10-50%, while the absorption in the gastrointestinal tract is only a few percent. Smokers have about 4-5 times higher blood cadmium concentrations (about 1.5 micrograms/l), and twice as high kidney cortex cadmium concentrations (about 20-30 micrograms/g wet weight) as nonsmokers. Similarly, the blood cadmium concentrations are substantially elevated in persons with low body iron stores, indicating increased gastrointestinal absorption. About 10-40% of Swedish women of child-bearing age are reported to have empty iron stores (S-ferritin < 12 micrograms/l). In general, women have higher concentrations of cadmium in blood, urine, and kidney than men. The population groups at highest risk are probably smokers, women with low body iron stores, and people habitually eating a diet rich in cadmium. According to current knowledge, renal tubular damage is probably the critical health effect of cadmium exposure, both in the general population and in occupationally exposed workers. Tubular damage may develop at much lower levels than previously estimated, as shown in this report. Data from several recent reports from different countries indicate that an average urinary cadmium excretion of 2.5 micrograms/g creatinine is related to an excess prevalence of renal tubular damage of 4%. An average urinary excretion of 2.5 micrograms/g creatinine corresponds to an average concentration of cadmium in renal cortex of 50 micrograms/g, which would be the result of long-term (decades) intake of 50 micrograms per day. When the critical concentrations for adverse effects due to cadmium accumulation are being evaluated, it is crucial to consider both the individual variation in kidney cadmium concentrations and the variations in sensitivity within the general population. Even if the population average kidney concentration is relatively low for the general population, a certain proportion will have values exceeding the concentration where renal tubular damage can occur. It can be estimated that, at the present average daily intake of cadmium in Sweden, about 1% of women with low body iron stores and smokers may experience adverse renal effects related to cadmium. If the average daily intake of cadmium would increase to 30 micrograms/day, about 1% of the entire population would have cadmium-induced tubular damage. In risk groups, for example, women with low iron stores, the percentage would be higher, up to 5%. Both human and animal studies indicate that skeletal damage (osteoporosis) may be a critical effect of cadmium exposure. We conclude, however, that the present evidence is not sufficient to permit such a conclusion for humans. We would like to stress, however, that osteoporosis is a very important public health problem worldwide, but especially in the Scandinav
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PMID:Health effects of cadmium exposure--a review of the literature and a risk estimate. 956 44

We refined the structure of the tetragonal form of recombinant horse L-chain apoferritin to 2.0 A and we compared it with that of the cubic form previously refined to the same resolution. The major differences between the two structures concern the cadmium ions bound to the residues E130 at the threefold axes of the molecule. Taking advantage of the significant anomalous signal (f" = 3.6 e-) of cadmium at 1.375 A, the wavelength used here, we performed anomalous Fourier difference maps with the refined model phases. These maps reveal the positions of anomalous scatterers at different locations in the structure. Among these, some are found near residues that were known previously to bind metal ions, C48, E57, C126, D127, E130, and H132. But new cadmium binding sites are evidenced near residues E53, E56, E57, E60, and H114, which were suggested to be involved in the iron loading process. The quality of the anomalous Fourier difference map increases significantly with noncrystallographic symmetry map averaging. Such maps reveal density peaks that fit the positions of Met and Cys sulfur atoms, which are weak anomalous scatterers (f" = 0.44 e-).
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PMID:Evidence of new cadmium binding sites in recombinant horse L-chain ferritin by anomalous Fourier difference map calculation. 962 6

There is still debate in the literature on whether or not endurance athletes tend to have low iron stores. In this article, we propose that endurance athletes really are at risk of becoming iron deficient due to an imbalance between absorption of dietary iron and exercise-induced iron loss. The purpose of this article is to present a critical review of the literature on iron supplementation in sport. The effect of iron deficiency on performance, its diagnosis and suggestions for treatment are also discussed. Studies of the nutritional status of athletes in various disciplines have shown that male, but not female, athletes clearly achieve the recommended dietary intake of iron (10 to 15 mg/day). This reflects the situation in the general population, with menstruating women being the main risk group for mild iron deficiency, even in developed countries. Whereas the benefit of iron supplementation in athletes with iron deficiency anaemia is well established, this is apparently not true for non-anaemic athletes who have exhausted iron stores alone (prelatent iron deficiency); most of the studies in the literature show no significant changes due to supplementation in the physical capacity of athletes with prelatent iron deficiency. However, the treatment protocols used in some of these studies do not meet the general recommendations for the optimal clinical management of iron deficiency, that is, with respect to adequate daily dosage, mode of administration and treatment period. For future studies, we recommend a prolonged treatment period (> or = 3 months) with standardised conditions of administration (use of a pharmaceutical iron preparation with known high bioavailability and a dosage of ferrous (Fe++) iron 100 mg/day, taken on an empty stomach). Currently, decisions regarding iron supplementation are best made on the basis of taking care of individual athletes. We believe that there are sufficient arguments to support controlled iron supplementation in all athletes with low serum ferritin levels. Firstly, the development of iron deficiency is prevented. Secondly, the nonspecific upregulation of intestinal metal ion absorption is reverted to normal, thus limiting the hyperabsorption of potentially toxic lead and cadmium even in individuals with mild iron deficiency.
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PMID:Iron supplementation in athletes. Current recommendations. 982 Sep 21

The results of studies of biochemical redox reactions photosensitized by inorganic semiconductor particles are reviewed. The mechanisms of hydrogen photoproduction, NAD+ or NADP+ photoreduction, CO2 photofixation and photosynthesis of organic and amino acids under the coupled action of TiO2, ZnO, CdS, ZnS and enzymes or bacterial cells are considered. Studies on the photocatalytic activity of ferritin, a protein containing microcrystals of hydrous ferric oxide, are described. The data on biosynthesis of cadmium sulfide by microorganisms and plants are analyzed. The possibility of the participation of inorganic semiconductors in photoprocesses in vivo is discussed.
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PMID:Inorganic semiconductors as photosensitizers in biochemical redox reactions. 1037 51

Iron loading in hemochromatosis attains extremely high levels and is accompanied by many signs (ferritin >300 microg/l, hematocrit >50%, transferrin saturation >70%, etc.). Nevertheless, the disease is often overlooked by physicians, until several organs have been damaged permanently (heart, liver, brain, pancreas, kidneys, spleen, etc.). Therefore, severe oxidative damage catalyzed by Fe could occur, without the extremely high ferritin, hematocrit and transferrin saturation levels of hemochromatosis, and it is unlikely that it would ever be detected or even suspected. I postulate a mechanism, by which a cell can continue to express transferrin receptors, without producing ferritin, even when it is saturated with iron. Furthermore, I suggest that this silent iron loading, induced by cadmium and other metals, plays an important role in many degenerative diseases involving free radicals, DNA damage and peroxynitrite, all of which are intimately linked to iron.Moreover, since ferritin, transferrin saturation and hematocrit levels are not directly related to cellular iron levels, and since excess iron can wreak havoc in the cell, we can conclude that there is a need for a better way to evaluate intracellular iron levels and especially the intracellular free iron levels by a non-invasive technique.Finally, phlebotomy is suggested as the best way to reduce Fe and Mo stores, and chelation with succimer is recommended in order to eliminate Cd.
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PMID:Iron catalyzed oxidative damage, in spite of normal ferritin and transferrin saturation levels and its possible role in Werner's syndrome, Parkinson's disease, cancer, gout, rheumatoid arthritis, etc. 1098 17


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