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

Chelating agents disrupted the superficial layers on Spirillum putridiconchylium and adsorption of cationized ferritin indicated that both upper and lower surfaces of superficial layer fragments, as well as the outer membrane surface, possessed areas which were negatively charged. Growth of the bacterium in 1% casamino acids (vitamin free) resulted in cells which were devoid of the superficial layers, and negative staining of these cells revealed in amorphous precipitate together with a vesicular outer membrane component extruding from their surfaces into the medium. Addition of either 1 mM Ca2+ or 1 mM Sr2+ to the growth medium produced the typical regularly structured cell surface, whereas addition of equal concentrations of Li+, Na+, K+, Mg2+, Ba2+, Mn2+, Fe3+, or three polyamines produced the structureless surface.
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PMID:Dependence of the superficial layers of Spirillum putridiconchylium on Ca2+ or Sr2+. 1 67

We have used ferritin-conjugated divalent and monovalent anti-Ig antibodies to study simultaneously, histamine secretion and the ultrastructural distribution and redistribution of Ig receptors on rat peritoneal mast cells. We conclude that (a) divalent anti-Ig is required for both receptor redistribution and for calcium-dependent degranulation and histamine release, (b) divalent anti-Ig induces patching and pinocytosis but not capping of Ig molecules, (c) neither capping nor pinocytosis are required for triggering and if clustering is necessary, then less than 10 Ig molecules are required per cluster, and (d) degranulation (and histamine release) is not an all or none response of the mast cell.
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PMID:Anti-immunoglobulin-induced histamine secretion by rat peritoneal mast cells studied by immunoferritin electron microscopy. 4 87

Chicken erythrocytes were fused either by Sendai virus or by the combination of Ca2+ and ionophore A23187. Intramembrane particles and external anionic sites of cells undergoing fusion were found to acquire the ability to undergo a process of cold-induced clustering (thermotropic separation). Cationized ferritin (200 microgram/ml 5% (v/v) cell suspension) inhibited both the fusion process and the thermotropic separation of intramembrane particles and external anionic sites. The correlation between the mobility of membrane proteins and the fusion process is discussed. It is suggest that an increase in the lateral mobility of membrane proteins is a prerequisite for initiation of membrane fusion.
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PMID:Inhibition of membrane fusion by suppression of lateral movement of membrane proteins. 21 87

Polycationic ferritin, a multivalent ligand, was used as a visual probe to determine the distribution and density of anionic sites on the surfaces of rat liver mitochondrial membranes. Both the distribution of bound polycationic ferritin and the topography of the outer surface of the inner mitochondrial membrane were studied in depth by utilizing thin sections and critical-point dried, whole mount preparations for transmission electron microscopy and by scanning electron microscopy. Based on its relative affinity for polycationic ferritin, the surface of the inner membrane contains discrete regions of high density and low density anionic sites. Whereas the surface of the cristal membrane contains a low density of anionic sites, the surface of the inner boundary membrane contains patches of high density anionic sites. The high density anionic sites on the inner boundary membrane were found to persist as stable patches and did not dissociate or randomize freely when the membrane was converted osmotically to a spherical configuration. The observations suggest that the inner mitochondrial membrane is composed of two major regions of anionic macromolecular distinction. It is well-known that an intermembrane space exists between the two membranes of the intact mitochondrion; however, a number of contact sites occur between the two membranes. We determined that the outer membrane, partially disrupted by treatment with digitonin, remains attached to the inner membrane at these contact sites as inverted vesicles. Such attached vesicles show that the inner surface of the outer membrane contains anionic sites, but of decreased density, surrounding the contact sites. Thus, the intermembrane space in the intact mitochondrion may be maintained by electronegative surfaces of the two mitochondrial membranes. The distribution of anionic sites on the outer surface of the outer membrane is random. The nature and function of fixed anionic surface charges and membrane contact sites are discussed with regard to recent reports relating to calcium transport, protein assembly into mitochondrial membranes, and membrane fluidity.
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PMID:The distribution of anionic sites on the surfaces of mitochondrial membranes. Visual probing with polycationic ferritin. 23 6

A23187 and certain other carboxylate ionophores are capable of transferring Fe(II) but not Fe(III) across phospholipid bilayers (liposomes) and red cell membranes. A23187 is able to transfer Fe(II) from ferritin loaded liposomes when allied with a suitable redox couple and sink. The affinity of A23187 for Fe(II) is approximately five orders of magnitude greater than for Ca2+, as judged by two phase extraction techniques.
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PMID:Mobile carrier ionophores for Fe(II). 33 29

The distribution of anionic sites on the membranes of rat pancreatic B cells and of their storage granules has been studied by the use of a visual probe of cationic ferritin. Membranes of isolated storage granules possessed a net negative charge which was apparently evenly distributed; the number of anionic sites was not markedly altered by prior incubation of the granules with neuraminidase or with 10(-5) to 2 X 10(-3) M calcium chloride. Distribution of charges along B cell plasma membranes was less uniform but was similarly unaffected by alterations of calcium concentration, or by neuraminidase treatment. However, during the fusion of plasma membrane and granule membrane which occurs in exocytosis, the emerging granule membrane was found to be devoid of anionic sites. The implications of these findings for the regulation of insulin secretion by exocytosis are discussed.
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PMID:Distribution of anionic sites on surface of B cell granule and plasma membranes: a study using cationic ferritin. 33 20

Renal bone disease is an important cause of morbidity in patients on dialysis. The prevalence of renal bone disease, especially aluminium related bone disease, has not been studied in the Singapore dialysis population. As such, we studied 45 haemodialysis patients for renal bone disease using biochemical and radiological parameters. Selected patients underwent a renal biopsy. There were 29 males and 16 females, mean (+/- SEM) age, 44.6 +/- 13.4 years. The duration of haemodialysis ranged from two months to ten years, mean 18.5 months. 75.4% of patients had hyperphosphatasemia, 24.4% had hypocalcemia and two patients had hypercalcemia. There was a wide range in the serum parathyroid hormone levels and 55.4% of patients had serum parathyroid hormone levels > 1000 pmol/L. Patients with symptoms and radiological abnormalities had significantly higher serum parathyroid hormone and alkaline phosphatase levels than those without (P < 0.005). The desferrioxamine infusion test was positive, with an increment in serum aluminium (DL) > 100 mg/L in five patients. Skeletal survey was positive for renal bone disease in 24.4% of patients. There was a significant correlation between the serum parathyroid hormone level, DA1 and the duration of dialysis (r = 0.752, p < 0.001 and r = 0.837, p < 0.001 respectively). There was no correlation between serum parathyroid hormone, calcium, phosphate levels and DA1. The serum haemoglobin concentration and ferritin levels did not show a correlation with DA1. Bone biopsy revealed hyperparathyroid bone disease in two patients, aluminium-related bone disease in one patient and mixed uraemic osteodystrophy in one patient.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Renal bone disease in patients on haemodialysis: biochemical and radiological assessment. 129 14

This study evaluated how different training periods affect dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. Subjects were 17 skiers and 39 controls, ages 18-38 yrs. Dietary data were collected by 7-day food records at 3-month intervals. Coefficient of variation (CV) was used to indicate magnitude of seasonal changes. Energy intake for the year (28 food record days) was 3,802 kcal/day (CV 19.1%) in male skiers, 2,754 kcal/day (CV 3.7%) in male controls, 2,812 kcal/day (CV 9.1%) in female skiers, and 2,013 kcal/day (CV 5.9%) in female controls. CVs for thiamin, riboflavin, vitamin C, calcium, magnesium, iron, and zinc intake were 14.1-23.9% (male skiers), 2.9-15.0% (male controls), 4.8-24.5% (female skiers), and 4.3-11.5% (female controls). Seasonal changes in energy, carbohydrate, and micronutrient intakes reflected energy expenditure in male endurance athletes particularly. Erythrocyte transketolase activation coefficients and serum ferritin and zinc concentrations did not differ between skiers and controls. Seasonal variations in these biochemical indices of nutritional status were of the same magnitude in skiers and controls, despite large changes in skiers' physical activity.
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PMID:Dietary intake and thiamin, iron, and zinc status in elite Nordic skiers during different training periods. 129 5

Atrial distension, which stimulates atrial natriuretic peptide secretion by atrial myocytes, also stretches nonmuscle cells. In a noncontracting in vitro preparation of combined right and left atria we demonstrated by electron microscopy that, at 37 degrees C, transition from zero pressure to a physiological distending pressure of 5.1 mm Hg rapidly rendered atrial endocardial endothelium permeable to the macromolecular probes horseradish peroxidase (HRP; M(r), approximately 40,000) and wheat germ agglutinin-HRP (M(r), approximately 70,000); each probe was introduced at the atrial cavitary endocardial surface. Stretch-dependent permeabilization was also demonstrable in spontaneously contracting atria, was reversed by removing the distending pressure, and was unaffected by varying external Ca2+ concentration from 0.2 to 1.4 mM or by experimental perturbations that markedly decrease ANP secretory rates. Although transendocardial HRP and wheat germ agglutinin-HRP passage required stretch, native ferritin (M(r), = 500,000) could traverse unstretched endocardium. Probes were detected in noncoated endocardial vesicles and intercellular junctions between endocardial cells, but the relative contributions of vesicular transcytosis and paracellular diffusion could not be determined. Although HRP entered plasmalemmal caveolae of myocytes in stretched atria, myocytes did not internalize HRP by fluid-phase endocytosis. Distending pressure also caused apparent flow reversal in thebesian blood vessels, with retrograde transfer of HRP across the endocardium into the myocardium. HRP and ferritin presented at the external surface of the epicardium (visceral pericardium) were endocytosed by mesothelial cells, entered junctions between mesothelial cells, and readily crossed the epicardium of both stretched and unstretched preparations.
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PMID:Permeability of rat atrial endocardium, epicardium, and myocardium to large molecules. Stretch-dependent effects. 137 44

This study examined the effect of diet-induced, marginal zinc deficiency for 7 wks in 15 men (aged 25.3 +/- 3.3 yrs; mean +/- SD) on selected indices of iron and copper status. The regimen involved low-zinc diets based on egg albumin and soy protein with added phytate and calcium such that mean [phytate]/[Zn] and [phytate] X [Ca]/[Zn] molar ratios were 209 and 4116, respectively, for 1 wk, followed by 70 and 2000, respectively, for 6 wks. Subjects were then repleted with 30 mg Zn/d for 2 wks. Plasma copper, Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activity in plasma and red blood cells (RBC), hemoglobin, hematocrit, and serum ferritin were determined weekly on fasting blood samples. Significant reductions (p less than 0.05) after 7 wks in RBC Cu,Zn-superoxide dismutase (49.5 +/- 7.2 vs 33.6 +/- 6.3 U/mg Hb) and serum ferritin (69.2 +/- 38.7 vs 53.8 +/- 33.7 micrograms/L) occurred; no comparable decline was noted for plasma Cu, hemoglobin, or hematocrit. Significant (p less than 0.05) but less consistent changes were also observed in plasma superoxide dismutase activity. None of the changes were associated with the decreases in plasma, urinary and hair zinc concentrations, and alkaline phosphatase activity in RBC membranes. Results indicate that the biochemical iron and copper status of the subjects was marginally impaired, probably from the dietary regimen that induced marginal zinc deficiency.
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PMID:Indices of iron and copper status during experimentally induced, marginal zinc deficiency in humans. 138 39


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