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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two different procedures were employed for the isolation of sarcolemma from the rat heart and the membranes were studied with respect to the presence of cell surface material as well as their functional characteristics. Both hypotonic shock-LiBr treatment method (fraction HL) and sucrose density gradient method (fraction S) yielded membranes enriched 8 to 13 fold with respect to Na+-K+ ATPase and adenylate cyclase activities in comparison to heart homogenate. Cell surface material was demonstrated on the outer surface of the vesicles only in fraction HL with cationic dyes, lanthanum and ferritin, applied either to the isolated fractions or perfused in the heart through coronaries. Fraction HL also had high sialic acid content. ATP independent Ca2+ binding in fraction HL was about 6 times more than that in fraction S which had little sialic acid and showed no cell surface staining with cationic dyes. On the other hand, ATP-dependent Ca2+ binding and Ca2+-stimulated Mg2+ dependent ATPase activities in fraction S were 4 to 6 times higher than those in fraction HL. Epinephrine stimulated adenylate cyclase in fractions HL and S by 24 and 3% whereas ouabain was found to inhibit Na+-K+ ATPase in these fractions by 80 and 10% respectively. A mild treatment of the membranes with deoxycholate to eliminate the semipermeable characteristics or effects of sidedness of the vesicles resulted in an almost complete ouabain inhibition of Na+-K+ ATPase in both fractions. These data suggest that presence of cell surface material as well as membrane sidedness has an important role in in vitro expression of functional characteristics of sarcolemma. It is emphasized that sarcolemmal preparations containing cell surface material will provide information more realistic to the native conditions in situ.
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PMID:Differences in sarcolemmal preparations: cell surface material and membrane sidedness. 619 85

This study systematically examined the characteristics of specific binding of adult diferric transferrin to its receptor using a Triton X-100 solubilized preparation from human placentas as the receptor source. The following information was obtained. The ionic strength for maximal binding is in the range of 0.1-0.3 M NaCl. The pH optimum for specific binding extends over the range, from pH 6.0-10.0. Specific binding of diferric transferrin is not affected by 2.5 approximately 50 mM CaCl2 or by 10 mM EDTA. Triton X-100 in the concentration range of 0.02-3.0% does not affect specific binding. Specific binding is saturated within 10 min at 25 or 37 degrees C in the presence of excess amounts of diferric transferrin. The binding is reversible and the dissociation of diferric transferrin from the transferrin receptor is complete within 40 min at 25 degrees C. Apotransferrin, both adult and fetal, showed less binding than the holotransferrin species by competitive binding assay in the presence of 10 mM EDTA independent of up to 20 mM CaCl2. A 1500-fold molar excess of adult and fetal apotransferrin is required to give 40% inhibition for 125I-labeled diferric transferrin binding. Since calcium ion is not a factor, and since apotransferrin has such high binding affinity for iron (Ka = 1 X 10(24], this experiment suggests that the EDTA was necessary to prevent conversion of apotransferrin to holotransferrin from available iron in the reaction system. The specificity of the transferrin receptor for transferrin was examined by competitive binding studies in which 125I-diferric transferrin binding was measured in the presence of a series of other proteins. The proteins tested in the competitive binding studies were classified into three groups; in the first group were human serum albumin and ovalbumin; in the second group were proteins containing iron ions, such as hemoglobin, hemoglobin-haptoglobin complex, heme-hemopexin complex, ferritin, and diferric lactoferrin; in the third group were the metal-binding serum proteins, ceruloplasmin and metallothionein. None of these proteins except ferritin showed inhibition of diferric transferrin binding to the receptor. The effect of ferritin was small since a 700- to 1500-fold molar excess of ferritin is required for 50% inhibition of binding of diferric transferrin to the receptor.
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PMID:Characterization of transferrin binding and specificity of the placental transferrin receptor. 631 Nov 10

The ultrastructural localization of the Ca2+ + Mg2+-dependent ATPase of sarcoplasmic reticulum in rat gracilis muscle was determined by indirect immunoferritin labeling of ultrathin frozen sections. Simultaneous visualization of ferritin particles and of adsorption-stained cellular membranes showed that the Ca2+ + Mg2+-ATPase was concentrated in the longitudinal sarcoplasmic reticulum and in the nonjunctional regions of the terminal cisternae membrane but was virtually absent from mitochondria, plasma membranes, transverse tubules, and junctional sarcoplasmic reticulum. Ferritin particles were found preponderantly on the cytoplasmic surface of the membrane, in agreement with published data showing an asymmetry of the Ca2+ + Mg2+-ATPase within the sarcoplasmic reticulum membrane. Comparison of the density of ferritin particles in fast and slow myofibers suggested that the density of the Ca2+ + Mg2+-ATPase in the sarcoplasmic reticulum membrane in a fast myofiber is approximately two times higher than in a slow myofiber.
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PMID:Ultrastructural localization of the Ca2+ + Mg2+-dependent ATPase of sarcoplasmic reticulum in rat skeletal muscle by immunoferritin labeling of ultrathin frozen sections. 646 Jul 75

Zinc levels in plasma and whole blood were investigated in 2 groups of blood donors. The first group consisted of 19 men and 11 women who donated blood for the first time and were followed during 3 phlebotomies. The second group comprised 44 men with 9 or more previous blood donations, their blood being analysed on a single occasion. Plasma concentrations of copper, magnesium, calcium and ferritin were also analysed. The zinc levels in whole blood and plasma in the second group were significantly lower as compared to the first group (P less than 0.001). Furthermore, the second group had significantly higher levels of copper and copper:zinc quotient in plasma as compared to those of the new blood donors (P less than 0.001). Our results indicate that besides the earlier known effect of blood donation on iron stores, there are also signs of zinc depletion when judged from the zinc levels in plasma and in erythrocytes. No significant changes in calcium and magnesium concentrations were seen during phlebotomy.
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PMID:Zinc, copper, magnesium, and calcium in blood and plasma after phlebotomy. 661 29

We describe the use of a magnetic sector spectrometer positioned below the projection chamber of an electron microscope for energy filtered transmission imaging. The spectrometer used has circular pole face edges and is corrected for second order aberrations. A round EM lens is placed after the sector to form a real image of the virtual achromatic image produced by the spectrometer. A slit placed in the dispersion plane allows the passage of electrons in a selected energy range. The filtered image is projected onto a transmission phosphor and acquired with a silicon intensified TV camera and stored in digital form on computer disk. Filtered images are taken at two energies, one immediately preceding (pre-edge) and one on the characteristic energy loss (edge). To obtain images showing the distribution of elements, background subtraction is performed by either subtraction or division of edge and pre-edge images. The optical properties of the imaging system are described and the results are illustrated by energy filtered images of single ferritin molecules (Fe M2,3 and C k), the phosphorus distribution in ribosomes (PL2,3) and the localization of calcium in muscle (Ca L2, 3). The major advantage of the system, compared to other energy filtered imaging methods, is that it can be readily adapted to existing high vacuum microscopes without the necessity of modifying the column to insert a spectrometer.
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PMID:Applications of energy filtered imaging in biology. 663 70

Metabolic balance for lead and cadmium were carried out in 23 healthy elderly people aged 69.7 to 85.5 yr while living in their own homes and eating self-selected diets. Mean intakes of lead and cadmium were 54.6 and 8.6 micrograms/day, with mean retentions of -8.7 and -1.7 micrograms/day, respectively. Daily dietary lead correlated (p less than 0.05) with the intake of energy, nitrogen, calcium, iron, and zinc but not with manganese or copper. Dietary intake of cadmium correlated (p less than 0.05) only with that of zinc and manganese. There was a highly significant (p less than 0.001) inverse correlation between the percentage cadmium absorbed and body iron stores measured as serum iron, percentage iron saturation, and ferritin. Mean whole blood concentrations were 138 micrograms/l for lead and 0.79 microgram/l for cadmium. The negative balances observed in these elderly people were very different from the positive balances found in a previous similar study in children.
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PMID:The intake and excretion of lead and cadmium by the elderly. 671 83

Glomus cells from carotid bodies of adult rats dissociated by means of collagenase or collagenase + trypsin were used to study by electron microscopy the endocytotic uptake of cationized ferritin (CF) tracer into subcellular compartments. The glomus cells were incubated with the tracer (1) in a basic salt medium (BM), or (2) in the BM into which calcium ionophore A23187 had been added, or (3) in a potassium-rich medium. Incubation of the cells in BM containing CF for 30 min resulted in attachment of the tracer to the cell membrane and uptake of a few solitary tracer particles into small vesicles and multivesicular bodies. No uptake into the cisternae of the Golgi apparatus was observed. Further incubation in BM containing CF for another 30 min resulted in increased uptake of the tracer into small vesicles and multivesicular bodies. A similar pattern of uptake was observed when the dissociated glomus cells were first preincubated in BM with CF for 30 min and then incubated for 1 min or 30 min in the BM solution containing both the ionophore and CF. Upon such incubation, CF particles were seen to penetrate into coated pits and sites of exocytosis at the cell surface. When the 30-min preincubation in BM was followed by incubation in a CF-containing potassium-rich medium for 15-30 min, uptake into vesicles, small lysosomes and occasionally also into profiles of the smooth endoplasmic reticulum was seen. Endocytotic mechanisms of the glomus cells are outlined.
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PMID:Endocytotic uptake of cationized ferritin tracer into glomus cells dissociated from the adult rat carotid body. 681 57

The effects of calcium concentration changes in carotid body cells on the chemoreceptor discharges were studied in vitro on carotid bodies removed from anaesthetized rabbits. Addition of calcium-containing liposomes to the superfusing medium increased the chemoreceptors' discharges. This effect was abolished by hyperoxia or when EGTA-containing liposomes were simultaneously added with the calcium-containing liposomes. A histological control with ferritin-enriched liposomes showed that the liposome content was transferred into the cellular elements of the preparation except the nerve endings. Results suggest a relationship between calcium concentration changes in carotid body cells and chemoafferent activity.
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PMID:Effects of ion-containing liposomes upon the chemoafferent activity of the rabbit carotid body superfused in vitro. 684 3

Energy-dispersive X-ray analysis has been performed on marrow sideroblasts obtained from 10 patients with sideroblastic anaemias or erythroleukaemia (six primary refractory sideroblastic anaemia, two pyridoxine-responsive, one secondary sideroblastic anaemia, two erythroleukaemia). Irrespective of the nature of the disorder associated with the presence of sideroblasts, X-ray analysis of siderotic mitochondria consistently revealed the presence of iron and phosphorus with the average Fe/P intensity ratio measuring 1.4-1.5. Other elements variably detected within siderotic mitochondria included calcium, lead, potassium and zinc. Variation in the presence of these latter elements was detected not only between different patients, but also within different samples taken at different times from a single patient and even among different cells of the same sample. Despite the detection of lead in siderotic mitochondria of a significant number of patients (five out of seven), there was no clinical evidence of lead toxicity. The elemental composition of the intramitochondrial deposits in sideroblasts was distinct from that of ferritin or haemosiderin and probably consists of ferric phosphate, possibly, ferric orthophosphate (FePO4).
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PMID:Energy-dispersive X-ray analysis of the mitochondria of sideroblastic anaemia. 693 57

This article reviews selected nutrition research pertinent to adolescent health care. Protein--calorie malnutrition affects 25% of hospitalized adolescents studied, which correlates, as in adults, with increased morbidity and mortality. Some subgroups of adolescents, notably Asian immigrants, have been shown to be at high risk for developing vitamin D deficient rickets. On the other hand, excessive vitamin D intake has been linked to arteriosclerosis in animal models. Calcium supplementation is not likely to be indicated in U.S. adolescents. Iron deficiency prevalence in adolescence is not well documented, owing to the confusion between anemia and iron deficiency. Serum ferritin and free erythrocyte protoporphyrin measures should help to clarify this issue. Zinc nutrition must be assessed in high-risk groups such as those with short stature or Crohn's disease. Oral contraception effects on vitamin B6 and on serum lipids need to be considered in the risk-benefit equation when prescribing this method of birth control for adolescents.
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PMID:Nutrition and the adolescent: an update. 702 6


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