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PubMed1991

Analysis of the molecular mass heterogeneity of the transferrin receptor in Neisseria meningitidis and commensal Neisseria.

Peroxidase-conjugated transferrin was used to detect transferrin receptors both in intact outer membrane vesicles (OMVs) from Neisseria species in a dot blot assay, and in SDS-PAGE-separated OMV proteins after transferring to nitrocellulose membranes. All N. meningitidis strains produced transferrin receptors after culturing in either iron sufficiency or iron restriction although expression was higher in the latter case, whereas only six N. lactamica and two N. sicca (among 20 commensal species) were able to bind transferrin. Molecular mass (MM) of the receptors were mainly between 78 kDa and 85 kDa (87.5% of strains), 12.5% had receptors with MM close to 70 kDa, and 5% showed receptors with MM over 85 kDa. Our results confirm the molecular mass heterogeneity of the transferrin receptors in N. meningitidis, completely disagree with the 'universal' 98 kDa receptor proposed by some authors, and show a low expression of the receptor in commensal Neisseria.

Densitometry↗
PubMed1984

Interaction of human serum transferrin with Neisseria gonorrhoeae, demonstrated by agglutination and precipitation.

Human sera show non-immune precipitation with ultrasonically disrupted bacteria of the N. gonorrhoeae strain 8551. A human serum was resolved by DEAE cellulose chromatography and immune absorption to isolate the serum component involved in the precipitation. Testing of the final product against antisera to various serum proteins and analysis by SDS-PAGE revealed only serum transferrin. This preparation and transferrin obtained commercially produced precipitation in agar gel against the gonococcal extract. The bacterium was agglutinated by transferrin in solution or when carried by latex particles, and particles sensitized with the bacterial extract were agglutinated by transferrin. Four out of 26 gonococcal strains examined showed reactivity with transferrin in the precipitation and agglutination tests.

Agglutination Tests↗
PubMed1977

Inducibility of transferrin receptors on friend erythroleukemic cells.

The ability of Friend erythroleukemic cells to bind transferrin and take up its iron increases substantially as a result of dimethyl sulfoxide-stimulated differentiation. Although transferrin-binding activity is also demonstrable in another mouse cell line of hematopoietic origin, the lymphoma cell, it does not increase on exposure to dimethyl sulfoxide. Gel filtration studies corroborate that the binding of transferrin to the erythroleukemic cells is due to the formation of a specific complex of transferrin and a membrane receptor. Thus, the specific interaction of transferrin with its receptor is another expression of dimethyl sulfoxide-induced differentiation in the Friend cell.

Cell Line↗
PubMed1982

Expression of a high-affinity mechanism for acquisition of transferrin iron by Neisseria meningitidis.

Iron-starved meningococci grown at either pH 7.2 or 6.6 were capable of removing and incorporating iron from human transferrin by a saturable, cell surface mechanism that specifically recognized transferrin rather than iron. The maximum expression of the iron uptake system occurred after 4 h of iron starvation. The uptake of the iron was dependent upon a functioning electron transport chain and was sensitive to 60 degrees C and trypsin. Cells grown under iron-sufficient conditions were incapable of accumulating iron from transferrin. No evidence was found for a primary role for cell-free soluble siderophores in the removal of iron from transferrin. The nonpathogenic neisseriae, Neisseria flava and N. sicca, were unable to utilize iron on transferrin.

Biological Transport↗
PubMed1986

Diltiazem inhibits transferrin receptor expression and causes G1 arrest in normal and neoplastic T cells.

Transferrin receptor expression is essential for the proliferation of both normal and malignant T cells. While transferrin receptor expression in normal T cells is tightly coupled to interleukin-2 receptor expression, transferrin receptor expression in malignant cells is usually constitutive and is released from this constraint. Temporally, the appearance of these membrane receptors is preceded by changes in the expression of the proto-oncogenes c-myc and c-myb. In addition, although an increase in the level of intracellular free calcium occurs early in the sequence of T-cell activation, the activation events dependent on this calcium flux have not been resolved. In the present study we report that diltiazem, an ion channel-blocking agent that inhibits calcium influx, arrested the growth in vitro of both normal and malignant human T cells in the G1 phase of the cell cycle. However, diltiazem did not inhibit the expression of c-myc or interleukin-2 receptor mRNA and protein in normal mitogen-activated T cells or the constitutive expression of c-myc and c-myb mRNA in malignant T cells (T acute lymphoblastic leukemia cells). In contrast, diltiazem prevented the induction of transferrin receptor (mRNA and protein) in normal T cells and caused a progressive loss of transferrin receptor (mRNA and protein) in malignant T cells. These data demonstrate that diltiazem can dissociate several growth-related processes normally occurring in G1 and thereby disrupt the biochemical cascade leading to cell proliferation.

Cell Cycle↗
PubMed1989

Carbohydrate deficient transferrin: a marker for alcohol abuse.

OBJECTIVE: To assess the value of serum carbohydrate deficient transferrin as detected by isoelectric focusing on agarose as an indicator of alcohol abuse. DESIGN: Coded analysis of serum samples taken from patients with carefully defined alcohol intake both with and without liver disease. Comparison of carbohydrate deficient transferrin with standard laboratory tests for alcohol abuse. SETTING: A teaching hospital unit with an interest in general medicine and liver disease. PATIENTS: 22 "Self confessed" alcoholics admitting to a daily alcohol intake of at least 80 g for a minimum of three weeks; 15 of the 22 self confessed alcoholics admitted to hospital for alcohol withdrawal; 68 patients with alcoholic liver disease confirmed by biopsy attending outpatient clinics and claiming to be drinking less than 50 g alcohol daily; 47 patients with non-alcoholic liver disorders confirmed by biopsy; and 38 patients with disorders other than of the liver and no evidence of excessive alcohol consumption. INTERVENTION: Serial studies performed on the 15 patients undergoing alcohol withdrawal in hospital. MAIN OUTCOME measure--Determination of relative value of techniques for detecting alcohol abuse. RESULTS: Carbohydrate deficient transferrin was detected in 19 of the 22 (86%) self confessed alcohol abusers, none of the 47 patients with non-alcoholic liver disease, and one of the 38 (3%) controls. Withdrawal of alcohol led to the disappearance of carbohydrate deficient transferrin at a variable rate, though in some subjects it remained detectable for up to 15 days. Carbohydrate deficient transferrin was considerably superior to the currently available conventional markers for alcohol abuse. CONCLUSION: As the technique is fairly simple, sensitive, and inexpensive we suggest that it may be valuable in detecting alcohol abuse.

Alcoholism↗
PubMed1975

The measurement of iron-binding capacity in serum and purified transferrin with the aid of chemical affinity chromatography.

In a mew method for the estimation of transferrin by iron-binding capacity iron is added as the tartrate in NaCl with about 10 mM bicarbonate. The excess iron is removed by passage through DEAE-Sephadex A-50 previously treated with the iron chelator disodium catechol-3,5-disulphonate. The iron remaining bound to transferrin is measured without protein precipitation by the use of ferrozine. The method is applicable to fresh, frozen, or lyophilized serum, purified transferrin, and some quality control preparations. Validation experiments confirm that transferrin in serum and in pure solution is saturated with iron and give some evidence of specificity. The possible use of commercially available transferrin preparations as analytical reference standards is discussed.

Chromatography, Affinity↗
PubMed1991

Serum iron and transferrin in acute neuroleptic induced akathisia.

Thirty acute psychiatric patients were examined prospectively at the beginning of neuroleptic treatment for acute psychotic symptoms and on average 16 days later. Two alternative hypotheses were examined: 1) neuroleptic treatment affects the levels of serum iron and transferrin; 2) acute akathisia developing during the initial few weeks of treatment is associated with low levels of serum iron and transferrin, either initially or at follow up or both. Serum iron levels did not change on repeat measurement, while there was a small, but significant decrease of serum transferrin. There was a significantly greater decrease in iron and transferrin levels in patients with akathisia on follow up compared with non-akathisics. In addition, akathisia ratings were highly correlated with serum transferrin levels on follow up.

Adult↗
PubMed1988

Affinities of Treponema pallidum for human lactoferrin and transferrin.

The acquisition of lactoferrin and transferrin by live Treponema pallidum organisms was examined. Saturation binding kinetics were obtained for virulent treponemes with increasing amounts of radioiodinated lactoferrin but not with transferrin. Furthermore, lactoferrin bound up to 100 times more effectively than transferrin. Only unlabelled lactoferrin stoichiometrically completed with iodinated lactoferrin binding. Time course kinetics showed maximum lactoferrin acquisition within the first five minutes at 34 degrees C. Optimum iron accumulation, however, was achieved by T pallidum in 30 minutes at 34 degrees C, and amounts of iron were six times greater than the equivalent amount of lactoferrin bound. Interestingly, iron uptake was also detected in the presence of transferrin, despite the minimal amounts of transferrin acquired by live treponemes. These observations reinforce the possibility that the associations of T pallidum with host molecules, such as plasma proteins, are essential for survival of the parasite within host environments.

Humans↗
PubMed1980

Reticulocyte membrane transferrin receptors.

A membrane protein with specific transferrin binding activity has been isolated from rabbit reticulocytes. The isolation procedure involved the immunoprecipitation by antibody to transferrin of transferrin-receptor complexes from reticulocyte membrane proteins which had been solubilized with nonionic detergent. Receptor dissociated from the antibody-transferrin-receptor complexes could bind transferrin saturably and reversibly. It migrated electrophoretically as a single band of glycoprotein with an estimated molecular weight of approximately 180 000 which was reduced to around 93 000 following complete dissociation with dithiothreitol.

Animals↗
PubMed1991

Insulin and transferrin restore important cellular functions of human fetal kidney in serum-free organ culture.

A model previously developed in our laboratory to culture human fetal kidneys in serum-free chemically defined medium was used to evaluate the direct influence of potential regulators on nephrogenesis. The aim of the present work was to verify the effects of insulin and transferrin, two hormones considered as essential in other serum-free culture systems. Explants of renal cortex from human fetuses (15-21 weeks) were cultured for 2 and 5 days in serum-free Leibovitz's L-15 medium (37 degrees C, 95% air - 5% CO2). The addition of transferrin (5 micrograms/mL) had no effect, but insulin (30, 60, and 125 mU/mL) increased DNA and protein syntheses in a dose-dependent manner. The influence of insulin (125 mU/mL) was potentiated by the addition of transferrin and the combination of the two stimulated DNA synthesis by threefold on day 2 when compared with controls and by sixfold on day 5 of culture. After 5 days, synthesis was restored to values observed at day 0. Transferrin did not modify the insulin effect on protein synthesis, since the latter was already maximally stimulated as early as day 2 of culture and at levels well above that of uncultured explants (day 0). The activities of four hydrolases considered as markers of brush border differentiation were not importantly changed by any of the hormones, supplemented alone or in combination. The results indicate that proliferation rather than differentiation is the parameter mostly influenced by these two hormones. The combination of insulin plus transferrin restores cellular functions of human fetal kidney explants cultured in serum-free medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

Transferrin delays oxygen radical induced cardiac-contractile failure.

The role of iron-loaded transferrin in xanthine-xanthine oxidase (X-XO) induced cardiac injury in isolated perfused rat hearts was examined. X (2 mM) - XO (10 U/L) perfusion resulted in contractile failure, a rise in resting tension, an increase in lipid peroxidation, and myocardial cell damage. The addition of transferrin (2.4 microM) into the X-XO medium had a protective effect, as indicated by an increase in time to contractile failure, a lesser rise in resting tension, a decrease in MDA values, and lesser damage compared with the X-XO perfused controls. Ultrastructural studies revealed localization of transferrin along the capillary basement membrane. In contrast, addition of transferrin and Desferal (desferrioxamine mesylate, 3 mM, an iron chelator) into X-XO medium caused a rapid contractile failure as well as a rise in resting tension, and in these hearts transferrin was localized inside the myocytes. These findings suggest that a vascular supply of iron protein chelators may have a beneficial effect against myocardial cell injury caused by a vascular source of oxygen radicals.

Animals↗
PubMed2002

The transcytosis of divalent metal transporter 1 and apo-transferrin during iron uptake in intestinal epithelium.

Caco-2 cells grown in bicameral chambers are a model system to study intestinal iron absorption. Caco-2 cells exhibit constitutive transport of iron from the apical (luminal) chamber to the basal (serosal) chamber that is enhanced by apo-transferrin in the basal chamber, with the apo-transferrin undergoing endocytosis to the apical portion of the cell. With the addition of iron to the apical surface, divalent metal transporter 1 (DMT1) on the brush-border membrane (BBM) undergoes endocytosis. These findings suggest that in Caco-2 cells DMT1 and apo-transferrin may cooperate in iron transport through transcytosis. To prove this hypothesis, we determined by confocal microscopy that, after addition of iron to the apical chamber, DMT1 from the BBM and Texas red apo-transferrin from the basal chamber colocalized in a perinuclear compartment. Colocalization was also observed by isolating endosomes from Caco-2 cells after ingestion of ultra-small paramagnetic particles from either the basal or apical chamber. The isolated endosomes contained both transferrin and DMT1 independent of the chamber from which the paramagnetic particles were endocytosed. These findings suggest that iron transport across intestinal epithelia may be mediated by transcytosis.

Apoproteins↗
PubMed1993

Lactoferrin interferes with uptake of iron from transferrin and asialotransferrin by the rat liver.

Intravenous injection of bovine or human lactoferrin (6.25 x 10(-2) mumol/100 g body wt) in rats resulted in marked reduction of hepatic iron uptake from transferrin and asialotransferrin. The effect was dose dependent, saturable at approximately 5 mg/100 g body wt, and independent of lactoferrin's iron content. At this dose level, iron uptake from transferrin was reduced by 28% and from asialotransferrin by 43% in experiments lasting 90 min. Bovine lactoperoxidase, another basic protein, was similarly effective. The clearance of asialofetuin and pinocytosis of polyvinylpyrrolidone remained unaffected. Perfusion of isolated rat livers at 4 degrees C showed a strong reduction in asialotransferrin binding in the presence of lactoferrin. Chromatography of hepatic heparan sulfate proteoglycan on immobilized lactoferrin, lactoperoxidase, asialotransferrin, and transferrin showed that it possessed affinity for each of these proteins, more for the first two than the latter two. Heparan sulfate proteoglycan binding and efficacy in reducing hepatic iron uptake were also studied after selective modifications of positively charged amino acids in these proteins. The data obtained are compatible with the hypothesis that lactoferrin and other proteins with similarly high affinity for hepatic heparan sulfate exert their negative effect on iron uptake by preventing transferrin binding to the proteoglycan. The possibility is thus raised that the large number of low-affinity transferrin binding sites reported by earlier investigators for the liver may be heparan sulfate molecules.

Animals↗
PubMed1980

Transferrin C subtypes in US blacks and whites.

Transferrin C is genetically heterogeneous. Isoelectric focusing in a pH gradient of 4.0-6.5 reveals two subtypes of transferrin C, TfC1 and TfC2, that differ slightly in their isoelectric point. The three transferrin bands seen in homozygotes (double bands for heterozygotes) probably represent different degrees of iron saturation. The most cathodal band consists of apotransferrin and the anodal band is fully saturated diferric transferrin. Family data are consistent with a codominant allelic mode of inheritance. The allele frequencies in US whites were 0.8 for TfC1 and 0.19 for TfC2; in US blacks the frequencies were 0.84 and 0.11, respectively. The concentrations of transferrin are probably the same for the three common phenotypes.

Black People↗
PubMed1997

The expression of transferrin receptors on erythroblasts in anaemia of chronic disease, myelodysplastic syndromes and iron deficiency.

The presence of transferrin receptors on erythroblasts in patients with iron deficiency, anaemia of chronic disease (ACD) and myelodysplastic syndrome (MDS) was studied by two-colour analysis on a flow cytometer. CD 71 was used to quantify the number of transferrin receptors and GLY-A to identify erythroblasts. In cases of iron deficiency, the number of transferrin receptors was increased on part of the erythroblasts thus facilitating iron uptake by the cells. In patients with ACD or MDS, a decrease of the number of transferrin receptors on erythroblasts was found. This leads to the conclusion that the ineffective response to iron therapy in cases of ACD and MSD can be explained by a decline of transferrin receptors on the red cells.

Anemia↗
PubMed1986

Effects of transferrin genetic phenotypes on total iron-binding capacity.

Serum transferrin level and total iron-binding capacity (TIBC) were studied in a group of 297 healthy adult male subjects having HbAA and G6PDB+ phenotypes by standard chemical and immunoelectrophoretic techniques to examine the influence of different transferrin variants on these parameters. TIBC (67.1 +/- 13.4 mumol/l) and transferrin concentrations (27.0 +/- 3.95 mumol/l) for the whole group were found to be within reported normal values. Serum transferrin concentrations of the subjects having different electrophoretic variants and TfC subtypes of transferrin were not significantly different from each other. There was no significant difference of TIBC in relation to different electrophoretic variants of Tf. However, the TIBC of the subjects of the 1-1 subtype of TfC (70.4 +/- 13.6 mumol/l) was significantly higher than that of the 2-1 subtype (65.0 +/- 12.8 mumol/l; p less than 0.05) as well as that of the 2-2 subtype (60.4 +/- 11.4 mumol/l; p less than 0.01).

Adult↗
PubMed1992

Ceruloplasmin and transferrin levels are altered in serum and bronchoalveolar lavage fluid of patients with the adult respiratory distress syndrome.

The respiratory burst of neutrophils generates oxygen radicals that can result in lipid peroxidation and may contribute to acute lung injury in the adult respiratory distress syndrome (ARDS). Because ceruloplasmin and transferrin are inhibitors of lipid peroxidation and may play a role in regulating tissue injury, antigen levels of ceruloplasmin and transferrin and ceruloplasmin oxidase levels were measured in the serum and bronchoalveolar lavage fluid (BALF) of ARDS patients (n = 28), patients at risk for ARDS (n = 22), and normal control subjects (n = 45). Serum ceruloplasmin levels were similar in ARDS (mean +/- SEM) (3.8 +/- 0.3 microM) and at-risk (3.3 +/- 0.4 microM) patients compared with control subjects (3.2 +/- 0.2 microM). Serum transferrin levels were decreased in ARDS (14.9 +/- 1.7 microM) and at-risk (20.4 +/- 1.7 microM) patients compared with normal control subjects (32.9 +/- 1.2 microM), and serum transferrin levels correlated with serum unsaturated iron binding capacity (UIBC). Ceruloplasmin was detected in only one of 38 normal BALF samples (0.002 +/- 0.002 microM) and two of 13 at-risk BALF samples (0.15 +/- 0.1 microM), yet it was present in 17 of 23 ARDS BALF samples (0.9 +/- 0.2 microM). Transferrin was also increased in ARDS BALF (5.4 +/- 1.1 microM) compared with at-risk (0.7 +/- 0.5 microM) and normal (0.4 +/- 0.1 microM) samples. Ceruloplasmin that was present in the BALF and serum samples had functional oxidase activity, and purified human ceruloplasmin inhibited hydroxyl radical formation by phorbol myristate acetate (PMA)-stimulated neutrophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchoalveolar Lavage Fluid↗