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PubMedDate not supplied

Seminal plasma transferrin in infertile men.

Seminal plasma transferrin levels were estimated in 51 men with various infertility problems and in 15 fertile subjects. The estimation of transferrin was carried out by using the radial immunodiffusion technique on LC-partigen transferrin plates. The mean value of transferrin decreased (p less than .05) in cases of azoospermia (91 +/- 51 micrograms/ejaculate). No significant difference was found in other sperm quality disorders (asthenoteratospermia = 227 +/- 141, mild OTA = 186 +/- 96, severe OTA = 247 +/- 137 micrograms/ejaculate). The mean value of transferrin decreased (p less than .05) in obstructive azoospermia cases (73 +/- 70 micrograms/ejaculate), whereas in the other causes of infertility no statistical differences were found. Transferrin was correlated with sperm count, sperm volume, and serum LH.

Follicle Stimulating Hormone↗
PubMed1996

Carbohydrate-deficient transferrin for identification of drug overdose patients at risk of an alcohol withdrawal syndrome.

BACKGROUND: Chronic alcohol abuse is frequent in patients admitted to the intensive care unit with acute drug overdose. During detoxification, an alcohol withdrawal syndrome may develop in patients with a history of chronic alcohol abuse. Withdrawal or delirium is associated with serious risks, necessitating early identification of patients at risk. Since the information obtained from the patients or their relatives on alcohol consumption is often unreliable, biochemical markers may be helpful. Carbohydrate deficient transferrin is considered a highly specific marker (reported maximum specificity 97%, sensitivity 40-85%) for identifying alcohol abuse. METHODS: In 20 patients with acute drug overdose and suspected alcohol abuse, carbohydrate deficient transferrin was determined by an immunoturbidimetric assay on admission to the intensive care unit. Eight of the patients had carbohydrate deficient transferrin levels above the "positive" threshold and nine in a suspicious range. A "false" negative carbohydrate deficient transferrin was found in three patients who were thought to have changed their drinking habits prior to hospitalization. A "positive" carbohydrate deficient transferrin test is assumed to be associated with ingestion of more than 60-80 g ethanol/d for a period of more than seven days. RESULTS: In all patients, clonidine (30-210 micrograms/h i.v.) was started. None developed delirium. Since alcohol addiction is frequently denied, determination of carbohydrate deficient transferrin may be useful for its early diagnosis but the sensitivity of this parameter requires further evaluation.

Alcohol Withdrawal Delirium↗
PubMed1991

Characterization of transferrin receptor released by K562 erythroleukemia cells.

A soluble form of transferrin receptor has been detected in human serum and has been shown recently to be a truncated form of the intact membrane bound receptor. Mechanisms governing the release of transferrin receptor by cells are poorly understood and could be better defined by tissue culture. The present investigation was undertaken to characterize the transferrin receptor released by K562 erythroleukemic cells. In contrast with maturing sheep reticulocytes, which have been shown to release transferrin receptor in small vesicles termed exosomes, we demonstrated, with a monoclonal enzyme-linked immunoassay, that less than 30% of the transferrin receptor released by K562 cells in log phase growth was in a particulate form. The relative amounts of soluble and particulate receptor released to the supernatant did not change significantly during 48 hr of incubation. Soluble receptor was purified by immunoaffinity chromatography. On polyacrylamide gel electrophoresis, its mobility was the same (85 kDa) as that of the truncated monomeric form recently identified in human serum. Further evidence that serum and soluble receptors released by K562 cells are identical was provided by amino acid sequence analysis, which demonstrated that 16 of the first 19 residues of the N-terminal sequence of soluble K562 receptor are homologous with the serum receptor. The remaining three were not identifiable. K562 cells provide a useful in vitro model for studying the production of membrane-bound and soluble forms of released transferrin receptor.

Amino Acid Sequence↗
PubMed1999

Beta-2 transferrin assay in the identification of perilymph.

HYPOTHESIS: Western blot assay for beta-2 transferrin protein is a clinically useful method for the detection of human perilymph and should be used for the diagnosis of perilymph fistulas (PLFs). BACKGROUND: Considerable controversy exists regarding the diagnosis of PLF. Recent studies suggest that the detection of beta-2 transferrin protein may be useful in the identification of perilymph. METHODS: To evaluate the usefulness of the beta-2 transferrin assay for identifying human perilymph, paired perilymph samples and negative controls were collected on Gelfoam pledgets from 20 patients who had surgery that opened the inner ear. Blinded immunoelectrophoretic assay (Western blot) for beta-2 transferrin was performed on each specimen. RESULTS: Only one (5%) of the known perilymph samples and none of the control specimens were definitely positive for beta-2 transferrin. Combined with historical data, this assay has 29% sensitivity, 100% specificity, 100% positive predictive value, and 31% negative predictive value. CONCLUSIONS: These findings suggest that the beta-2 transferrin protein assay may not be a reliable method for detecting human perilymph when performed using this technique.

Cochlear Aqueduct↗
PubMed1999

Transferrin As A targeting ligand for liposomes and anticancer drugs.

In cancer treatment, one of the approaches is targeting of the drug to tumor cells via receptor specific ligands. Transferrin (molecular weight 80,000) has been used as a ligand for delivering anticancer drugs or drug containing liposomes mostly due to the increased number of transferrin (trf) receptors found on tumor cells as compared to normal cells. Transferrin was linked to methotrexate (MTX) containing small unilamellar liposomes and its activity was compared to antitransferrin receptor antibody (7D-3) linked to MTX liposomes. In each of these conjugates, the method of coupling was the same and a disulphide linkage was formed between the ligand and MTX liposomes. No significant differences in the potency of 7D-3 conjugate or trf conjugate with MTX liposomes were observed in studies performed in vitro against various human tumor cell lines (Hela, KB and Colon). Trf was also linked to adriamycin via a schiff base which was formed by using glutaraldehyde. This conjugate was found to be effective in vitro against various human tumors (Lovo, HL-60, SW 403 and Hep2) and also in vivo against H-mesothelioma tumors. Transferrin receptor has also been used for gene delivery. Gene delivery to K562 haematopoietic leukaemic cells was achieved by using a transferrin-polycation (poly-L-lysine or protamine) conjugate. This review will cover the various important applications of transferrin based drug delivery formulations in the chemotherapy of cancer and the related work performed in our and other laboratories.

Animals↗
PubMed1999

Dried plasma spot measurements of ferritin and transferrin receptor for assessing iron status.

BACKGROUND: Efforts to reduce the high global prevalence of nutritional anemia require the use of both reliable laboratory assays to distinguish iron deficiency from other causes of anemia and cost-effective methods for collection of blood specimens under field conditions. The suitability of using small plasma samples spotted and dried on filter paper for measurements of plasma ferritin and transferrin receptor was evaluated in the present study. METHODS: Blood specimens obtained from 73 male and 83 female subjects (19-40 years) representing a wide range of iron status were used to perform parallel measurements of plasma ferritin and transferrin receptor on whole plasma and spotted plasma samples. RESULTS: Ratio plots, evaluating the acceptability and precision of the spot method in ferritin and transferrin receptor assays, showed the expected proportion of data points within the 95% prediction interval. In the composite group of 156 subjects, both the whole plasma and plasma spot methods gave a geometric mean transferrin receptor/ferritin ratio of 18. The regression equation for the ratio was logy = 1.045 logx - 0.05126; r = 0.986; P <0.0001. The ratio of transferrin receptor/ferritin determined from plasma spots correctly identified all 12 subjects with iron deficiency anemia compared with 11 of the 12 for whole plasma measurements. CONCLUSIONS: Measurements of ferritin and transferrin receptor on plasma spotted and dried on filter paper are comparable to whole plasma values for the identification of iron deficiency anemia. The use of dried plasma spots will facilitate the collection, storage, and transport of samples in epidemiological studies of anemia prevalence.

Adult↗
PubMed2000

Effect of varicocelectomy on seminal plasma transferrin values: a comparative clinical trial.

The possible effects of varicocele and of the varicocelectomy procedure on Sertoli cell function were investigated. Transferrin concentrations in seminal plasma in men with varicocele before and 3 months after the operation were evaluated. Concentrations were measured in 10 normozoospermic fertile men as a control group and 32 oligozoospermic men with varicocele. Also, sperm analysis before and 3 months after the operation was performed. The mean transferrin level in seminal plasma was 108.4 +/- 17.5 micrograms ml-1 in normoozoospermic men and 58.1 +/- 14.4 micrograms ml-1 in patients with varicocele before the operation (P < 0.0001). Mean sperm concentration, motility and normal morphology ratio showed significant improvement 3 months after the operation (P < 0.0001). Although the mean transferrin level increased slightly (to 60.8 +/- 16.2 micrograms ml-1; P = 0.2), there was a statistically significant correlation between the change in transferrin concentration and the change in sperm concentration after the operation (r = 0.56, P = 0.0008). These results showed that elevated transferrin secretion after the treatment seems to be associated with an increase in sperm concentration after varicocelectomy. The finding of improvements in seminal parameters after the operation but insignificant changes in seminal transferrin levels indicates that varicocelectomy results in a greater improvement in sperm quality than in Sertoli cell function.

Adult↗
PubMed2000

The use of transferrin for enrichment of fetal cells from maternal blood.

Iron loaded transferrin (holotransferrin) was used for enrichment of fetal cells from peripheral blood of pregnant women. Cord blood samples were used to evaluate enrichment efficacy of single and double MACS separations. Blood samples were obtained from 10 pregnant women prior to chorion villus sampling (CVS). Erythroblasts and other mononuclear cells were isolated by triple-density gradient centrifugation. Fetal cells were further enriched by positive magnetic sorting (VarioMACS) using biotinylated transferrin and streptavidin conjugated to magnetic microbeads. The isolated cells were analysed with dual-colour in situ hybridization (FISH) with X- and Y-chromosome specific probes. Male fetuses were correctly identified in three out of four (75%) pregnancies and female fetuses in six out of six (100%) pregnancies. By using transferrin instead of antibodies to the transferrin receptor to label and enrich fetal cells, we believe that unspecific binding attributed to immunological labelling can be minimized. The results indicate that transferrin may be an alternative to antibodies to transferrin receptor for separation of fetal cells from maternal blood.

Biotinylation↗
PubMed1975

In vivo evidence for the functional heterogeneity of transferrin-bound iron. I. Studies in normal rats.

Functional heterogeneity of iron atoms bound to transferrin as postulated by Fletcher and Huehns was demonstrated by in vivo studies in rats. Serum transferrin was selectively double-labeled by adding 59Fe to 90 per cent saturation of iron binding capacity, incubation with rat reticulocytes to reduce the saturation to 50 per cent or less, and then adding back 55Fe. Rats were killed at various times after intravenous injection of this double-labeled transferrin, and the ratios of 55Fe to 59Fe were measured in plasma, circulating erythrocytes, bone marrow and spleen heme, whole liver and isolated hepatic Kupffer and parenchymal cells, and in small intestinal segments. Selective uptake of erythroblast-oriented 55Fe was observed in red cells and heme from marrow and spleen; storage-oriented 59Fe was selectively removed by liver cells and small intestine. Greater polarization was achieved by using Fe3+-nitrilotriacetic acid instead of ferrous ammonium sulfate and by injecting transferrin selectively double-labeled at less than 50 per cent saturation. These studies confirm the hypothesis of Fletcher and Huehns that the iron atoms of transferrin are functionally different and support the concept that transferrin plays a selective role in the distribution of iron to tissues in the rat.

Animals↗
PubMed1995

Alfa-inhibin and transferrin in human fetal testis.

Aim of this research was to investigate the immunohistochemical localization of alfa-inhibin and transferrin in the human fetal testis. In addition, an attempt was made to identify the Sertoli cells in primary cell cultures of fetal testes by the demonstration of the mRNA for transferrin and the presence of the FSH receptor. 15 fetal testes (8-12 weeks) were utilized. The results of this study show: 1. In sections, immunoreactivity for alfa-inhibin was present in the interstitial cells, whereas transferrin was localized in Sertoli cells; 2. After 20 days of primary culture: a) the percentage of immunoreactive cells for both the substances was about 15%; b) the presence of FSH receptor and the expression of transferrin mRNA were observed in 12-15% of cells. These findings suggest: 1. alfa-inhibin and transferrin are present in the human fetal testis; 2. the expression of transferrin mRNA and the presence of the FSH receptor permit the identification of the Sertoli cells in primary cultures of fetal testes (8-12 weeks).

Cells, Cultured↗
PubMed2002

Bleomycin-detectable iron assay for non-transferrin-bound iron in hematologic malignancies.

BACKGROUND: A microwell modification of the bleomycin assay for determining non-transferrin-bound iron (NTBI) was evaluated and compared with a chelation method. METHODS: The bleomycin assay reagent and sample volumes were halved, and measurements were done in microwell plates. Samples from patients treated for hematologic malignancies were studied. The chelation method was based on mobilization of NTBI with a chelator and measurement of the ultrafiltered iron-chelator complex. NTBI results were also compared with transferrin saturation and the distribution of transferrin iron forms by urea-polyacrylamide gel electrophoresis. RESULTS: The bleomycin assay intraassay imprecision (CV) was 7.7% and 8.2% and the interassay imprecision was 18% and 9.8% for a low (0.2 micromol/L) and a high (1.5 micromol/L) contrtrol, respectively. Hemolysis increased measured NTBI. A detection limit of 0.1 micromol/L was established based on the interference of nonvisible hemolysis and on accuracy studies. In patient samples, NTBI exceeded the detection limits only when transferrin saturation was >80%. Compared with the chelation method, the bleomycin assay gave clearly lower NTBI concentrations. The chelation method also gave positive results at <80% transferrin saturation. The recovery of iron added as ferric nitrilotriacetate to serum was 33% by the bleomycin assay and 64% by the chelation assay. CONCLUSIONS: The microwell version of the bleomycin assay is reproducible. When hemolyzed samples were excluded, bleomycin-detectable iron was found only when the transferrin saturation was >80%, suggesting high specificity. Bleomycin-detectable iron constitutes only a portion of the NTBI measured by the chelation method.

Antineoplastic Agents, Alkylating↗
PubMed1999

[Influence of cell growth factors on transferrin gene expression of human lens epithelial cells in culture].

OBJECTIVE: To assess the influence of transforming growth factor-beta(1) (TGF-beta(1)) and basic fibroblast growth factor (bFGF) on the transferrin mRNA levels of cultured human lens epithelial cells. METHODS: Lens anterior capsules were collected from 40 eyeballs of 20 human donors under 3 years of age within 24 hours after death. Lens epithelial cells were primarily cultured and subcultured. TGF-beta(1) (1 microg/L) and bFGF (250 microg/L) were added to the 3rd passage cells when they became confluent after their growth for 2 weeks. The total cellular RNA was extracted from cultured cells by guanidine isothiocyanate, etc. after the growth factors acting for 3 days. Transferrin mRNA levels were determined by a Northern blot analysis with a probe. RESULTS: In comparison with the control group, the expressions of transferrin in the growth factor treatment groups were obviously increased. In comparison with bFGF group, transferrin mRNA level in TGF-beta(1) group was obviously increased. CONCLUSIONS: TGF-beta(1) and bFGF upregulate transferrin gene expression of cultured lens epithelial cells remarkably, can reduce lenticular oxidative damaging process in which transferrin participates and play an important role in the pathological mechanism of cataract formation after extracapsular cataract extraction.

Cells, Cultured↗
PubMed1992

[Preparation of human placenta microvillous membrane and the study of its transferrin receptor].

Human placenta microvillous membrane (PMM) was prepared by differential centrifugation and by sucrose gradient centrifugation, and the transferrin receptor (TfR) was studied using the receptor radioassay with 125I-transferrin as a radioligand. The factors affecting ligand-receptor binding reaction and the characteristics of TfR were also studied. The result showed that there was no significant differences (P > 0.1) in specific binding rates of 125I-transferrin to its receptor between the two membrane preparations, indicating that both of them could be used for TfR analysis, but the method of differential centrifugation was more simple and less time consuming. The study of TfR in sixty cases showed that the TfR binding sites on PMM and Bmax were 3.53 +/- 1.98 x 10(12) sites/mg membrane protein and 6.33 +/- 4.21 x 10(-12) mol/mg membrane protein, respectively. The Kd was 4.95 +/- 3.39 x 10(-9) mol/L, and the highest specific binding was 26% with nonspecific binding less than 3%. The conditions for ligand-receptor binding reaction were optimized when the concentrations of membrane protein and the 125I-transferrin in each test tube were 50 micrograms and 50,000 cpm (specific radioactivity being 2109 kBq/micrograms transferrin) respectively the incubation time was 30 min, and the concentration of polyethylene glycol added for separating B/F was 12% (W/V). transferrin binding to its receptor was characterized by high affinity, high specificity and being saturated.

Cell Membrane↗
PubMed1992

[Effect of placental transferrin receptors on iron nutritional state of normal full-term gravidas and their newborns].

Sixty full-term gravidas were divided into four groups, normal insidious iron deficiency, mild iron deficient anemia and moderate iron deficient anemia, according to their iron nutritional state determined by the measurement of hematologic and iron biochemical indexes. The iron nutritional state of newborns in each group and the level and the affinity of transferrin receptor in placenta were also studied. The iron nutritional state of newborns was found to decrease mildly along with the decrease of their mothers' iron nutritional state, especially the decrease of serum ferritin, but the differences were not statistically significant. It was suggested that the iron nutritional state of newborns was relatively normal although their mothers were in severe iron deficiency. The differences of transferrin receptor levels were significant among the four groups, the mild IDA group had the highest level of transferrin receptor, which was 1.68 times of normal group and 1.77 times of moderate IDA group. The differences between each two groups were significant. The differences of dissociate constant (Kd) of transferrin receptor were not significant among the four groups, indicating that the iron metabolism between mothers and their babies was regulated not by changing the affinity of transferrin binding to its receptor but by changing the numbers of transferrin receptor to maintain the relative stableness of newborns iron nutritional state.

Anemia, Hypochromic↗
PubMed1992

Transferrin receptor expression by retinal pigment epithelial cells in proliferative vitreoretinopathy.

Immunotoxins directed against a membrane marker of cell proliferation, transferrin receptor, were investigated to inhibit the growth of retinal pigment epithelial (RPE) cells in proliferative vitreoretinopathy (PVR). We undertook an immunocytological study in specimens of vitreous, subretinal fluid, and epiretinal membranes from patients with PVR to address the expression of transferrin receptor by proliferating pigment epithelial cells during the course of PVR and in normal human ocular structures. Thirty four specimens of vitreous and subretinal fluid, as well as seven epiretinal membranes, were immunocytologically examined using monoclonal antibodies to transferrin receptor. They showed a strong expression of this marker by a large majority of the cells in these two periretinal fluids (mean percentages 80 and 91% in vitreous and subretinal fluid, respectively). In contrast, only a few cells within epiretinal membranes were found to express transferrin receptor. In normal human eye sections conjunctival and corneal epithelial cells, subcapsular epithelium of the lens strongly expressed transferrin receptor, whereas RPE cells remained negative to antitransferrin receptor antibodies. A few iris or ciliary pigment epithelial cells reacted weakly. Thus, this study shows that most intravitreal and subretinal fluid proliferating cells strongly express transferrin receptor on their surface. Also confirmed is that immunotoxins to this membrane antigen could constitute potentially useful therapeutic agents in PVR.

Adult↗
PubMed1992

Endocytosed transferrin in African trypanosomes is delivered to lysosomes and may not be recycled.

It has been shown in mammalian systems that the passage of transferrin-colloidal gold (Tf-Au) through the endocytic system is influenced by the size of the gold colloid (Neutra, M. R. et al., J. Histochem. Cytochem. 33, 1134-1144 (1985); Woods, J. W. et al., Eur. J. Cell Biol. 50, 132-143 (1989)). However, in both Trypanosoma brucei brucei and Trypanosoma congolense, widely varying sizes of Tf-Au (Tf-Au5 and Tf-Au15) have been shown to proceed to lysosomes (Webster, P., Eur. J. Cell Biol. 49, 295-302 (1989); Webster, P., D. Grab, J. Cell Biol. 106, 279-288 (1988)). Using an affinity-purified anti-bovine transferrin IgG we have demonstrated that, in both T. brucei and T. congolense, native transferrin, like Tf-Au, is found in the flagellar pocket, coated vesicles, tubular structures, and lysosome-like organelles where it appears to be concentrated. The presence of Tf in the lysosomes was confirmed in colocalization experiments using T. congolense, where native bovine transferrin colocalized with a trypanosome lysosomal marker, a cysteine protease. The data suggest that, unlike the situation in mammalian cells where most transferrin is recycled to the cell surface, in African trypanosomes transferrin is routed into lysosomes and may not, therefore, be recycled.

Animals↗
PubMed1992

Non-transferrin dependent 59Fe uptake in phytohemagglutinin-stimulated human peripheral lymphocytes.

Human peripheral lymphocytes stimulated by phytohemagglutinin (PHA) have been used to demonstrate the characteristics of iron uptake from non-transferrin iron donors. When incubated with 59Fe(II)-ascorbate or 59Fe(III)-nitrilotriacetate (Fe-NTA), stimulated lymphocytes (2 micrograms/ml PHA) showed a tenfold increase in uptake of 59Fe as compared with the resting cells. The uptake of 59Fe from these iron donors was time and concentration dependent, showed saturation kinetics, and was not influenced by the addition of a tenfold excess of unlabeled Fe(III)2-transferrin (Fe-Tf). The amount of 59Fe accumulated from 59Fe-NTA was about one-third of that from 59Fe2-Tf, whereas the uptake of 59Fe from 59Fe-ascorbate was about tenfold higher. When stimulated with varying doses of PHA, lymphocytes showed maximal uptake of 59Fe from 59Fe2-Tf at the concentration of PHA (1 microgram/ml) optimal for 3H-thymidine incorporation. Lymphocytes stimulated with supraoptimal concentrations (5-20 micrograms/ml) of PHA showed slightly less iron uptake from 59Fe-Tf and had a longer transferrin cycle time, as compared with the cells under optimal stimulation. In contrast, the uptake of 59Fe from non-transferrin 59Fe donors in cells stimulated with 5-20 micrograms/ml PHA was greater than that in cells grown with 1 or 2 micrograms/ml PHA. It is suggested that lymphocytes take up iron from non-transferrin iron donors by processes different from the iron uptake pathway used by transferrin.

Biological Transport↗
PubMed1991

Cyclosporin A inhibits an initial step in folding of transferrin within the endoplasmic reticulum.

As resolved by electrophoresis in non-reducing SDS gels, transferrin newly made in Hep G2 cells migrates as a very diffuse set of species. During a subsequent 1-h chase all transferrin polypeptides are converted to a single, rapidly migrating species. These changes in gel mobility are due to alterations in the pattern of disulfide bonding, are not caused by carbohydrate processing, and occur while the protein is in the rough endoplasmic reticulum. Cyclosporin A causes an approximately 10-min lag in transferrin folding, after which folding resumes at the normal rate. Cyclosporin A also retards transferrin maturation from the endoplasmic reticulum and its secretion, at concentrations that do not affect secretion of other hepatoma proteins. Neither FK506 nor rapamycin affect transferrin folding. We conclude that an initial stage in transferrin folding is accelerated by an endoplasmic reticulum peptidyl-proline isomerase that is inhibited by cyclosporin A.

Animals↗