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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have compared the plasma clearance rate of radioactive iron in cows both as ferric chloride and as iron specifically bound to transferrin. We have also repeated the transfusion experiment of Dern et al. (Dern, R.J., Monti A. and Glynn, M.F. (1963) J. Lab. Clin. Med. 61,280-291) using goats. The results show that neither non-specificity bound iron (Bates, F.W. and Schlabach, M.R. (1973) J. Biol. Chem. 248, 3228-3232) nor the iron bound to the two different sites in transferrin (Awai, M., Chipman, B. and Brown, E.B. (1975) J. Lab. Clin. Med. 85,769-784) can be identified as distinguishable iron pools by this technique.
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PMID:Iron dynamics in the ruminant. 94 8

Lactoferrin content of colostrum obtained from cows within 24 h after parturition was measured using a single radial immunodiffusion test and was compared among cows of two dairy breeds (Holstein-Friesian, Jersey) and two beef breeds (Japanese Black and Japanese Brown). Average lactoferrin content in colostrum of dairy breeds was 2 mg/ml and in colostrum of beef breeds was .5 mg/ml. Lactoferrin content of colostrum due to lactation number was also different among breeds. In dairy breeds, multiparous cows had lactoferrin content two to three times higher than that of primiparous cows; beef breeds showed no obvious differences between lactation years. Lactoferrin content also varied considerably within breed. In beef breeds, half the cows had values of nearly zero. Transferrin content in colostrum was fairly constant (.9 mg/ml) and was not as variable among and within breeds. There was no correlation between lactoferrin and transferrin contents in colostrum. Examination of cows lacking lactoferrin suggested that transferrin plays an important role as an iron carrier from a cow to her newborn calf.
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PMID:Comparison of lactoferrin content in colostrum between different cattle breeds. 210 29

The distribution of transferrin receptors (Tf-R) was determined in Clone 9 hepatocytes and compared to that of 215 kDa, cation-independent mannose-6-phosphate receptors (M6P-R) by double labeling. Cells were allowed to take up exogenous human transferrin (Tf) for 5 to 30 min, after which Tf, Tf-R, and M6P-R were localized by immunofluorescence using specific antibodies. All these proteins were found to be concentrated in the juxtanuclear or Golgi region. When Clone 9 cells were treated with NH4Cl to trap M6P-R in endosomes (Brown, W. J., J. Goodhouse, M. G. Farquhar: J. Cell Biol. 103, 1235-1247 (1986)), the distribution of the two receptors differed: Tf-R remained the same as in controls, but M6P-R were localized in large vacuolated endosomes. To carry out double labeling experiments at the electron microscope level, transferrin gold conjugates (Tf-Au) were prepared, and M6P-R were detected by immunoperoxidase labeling. Tf-Au binding to the cell surface was specific as it was reduced approximately 70 to 79% in the presence of excess native Tf. When Clone 9 cells were incubated with Tf-Au at 37 degrees C for 5 to 30 min, or binding of Tf-Au was carried out at 4 degrees C followed by warming to 37 degrees C, Tf-Au was found within a peripheral tubulovesicular network and within multivesicular endosomes that were not labeled with anti-M6P-R. Other multivesicular endosomes of similar size and morphology were heavily labeled for M6P-R but contained little or no Tf-Au. Tf-Au and M6P-R were also found in separate endosomes in cells treated with NH4Cl. Native Tf was localized in the same compartments as Tf-Au by immunoperoxidase labeling of both Clone 9 cells and mouse myeloma cells. We conclude that in Clone 9 hepatocytes, Tf/Tf-R internalized from the cell surface and M6P-R bearing newly synthesized lysosomal enzymes from the Golgi deliver their ligands to two different subpopulations of multivesicular endosomes. The endosomal subpopulation visited by Tf/Tf-R is known to correspond kinetically to early endosomes. The endosomal subpopulation heavily labeled for M6P-R presumably represent a later endosomal compartment which serves as the junction point where endocytosed ligands and newly synthesized lysosomal enzymes enroute to lysosomes meet.
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PMID:Transferrin receptors and cation-independent mannose-6-phosphate receptors deliver their ligands to two distinct subpopulations of multivesicular endosomes. 255 86

It has been recently shown (Larkin, J. M., M. S. Brown, J. L. Goldstein, and R. G. W. Anderson, 1983, Cell, 33:273-285) that after a hypotonic shock followed by incubation in a K+-free medium, human fibroblasts arrest their coated pit formation and therefore arrest receptor-mediated endocytosis of low density lipoprotein. We have used this technique to study the endocytosis of transferrin, diphtheria toxin, and ricin toxin by three cell lines (Vero, Wi38/SV40, and Hep2 cells). Only Hep2 cells totally arrested internalization of [125I]transferrin, a ligand transported by coated pits and coated vesicles, after intracellular K+ depletion. Immunofluorescence studies using anti-clathrin antibodies showed that clathrin associated with the plasma membrane disappeared in Hep2 cells when the level of intracellular K+ was low. In the absence of functional coated pits, diphtheria toxin was unable to intoxicate Hep2 cells but the activity of ricin toxin was unaffected by this treatment. By measuring the rate of internalization of [125I]ricin toxin by Hep2 cells, with and without functional coated pits, we have shown that this labeled ligand was transported in both cases inside the cells. Hep2 cells with active coated pits internalized twice as much [125I]ricin toxin as Hep2 cells without coated pits. Entry of ricin toxin inside the cells was a slow process (8% of the bound toxin per 10 min at 37 degrees C) when compared to transferrin internalization (50% of the bound transferrin per 10 min at 37 degrees C). Using the indirect immunofluorescence technique on permeabilized cells, we have shown that Hep2 cells depleted in intracellular K+ accumulated ricin toxin in compartments that were predominantly localized around the cell nucleus. Our study indicates that in addition to the pathway of coated pits and coated vesicles used by diphtheria toxin and transferrin, another system of endocytosis for receptor-bound molecules takes place at the level of the cell membrane and is used by ricin toxin to enter the cytosol.
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PMID:Inhibition of coated pit formation in Hep2 cells blocks the cytotoxicity of diphtheria toxin but not that of ricin toxin. 286 51

Measurements of the magnetic field dependence of the longitudinal nuclear magnetic relaxation rates of solvent protons (NMRD profiles) in solutions of paramagnetic proteins have contributed significantly to the elucidation of the physical biochemistry of a number of metalloprotein systems. In many cases, NMRD profiles were used as indicators of chemical state, both static and dynamic [cf. Brewer, C. F., Brown, R. D., III, & Koenig, S. H. (1983) J. Biomol. Struct. Dyn. 1, 961-997], in part because a proper theoretical description of the data, with realistic assumptions for a model system, was computationally intractable. This has been particularly true for Cu2+-protein complexes, attributable in part to the S = 1/2 ground-state configuration of the Cu2+ ions; significant progress in interpreting such data has been made only recently [Bertini, I., Briganti, F., Luchinat, C., Mancini, M., & Spina, G. (1985) J. Magn. Reson. 63, 41-55]. We report NMRD profiles for solutions of Cu2+ - and VO2+-substituted human transferrin, both S = 1/2 ions, as well as computations that include the effects of the anisotropic hyperfine interactions of the paramagnetic ions with their respective nuclei. The description of the data that results from these computations is quite good, sufficiently so that one can say with confidence that the protons that contribute to the relaxation are rather distant (approximately 3.5 A) from the ions and in rapid exchange (approximately 10(8) s-1) with solvent. A possible view, consistent with what is known of the biochemistry of these substituted transferrins, is that relaxation occurs in the second coordination sphere: the exchanging entity is a water molecule hydrogen bonded to a donor atom of the metal ion complex.
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PMID:Magnetic relaxation of solvent protons by Cu2+- and VO2+-substituted transferrin: theoretical analysis and biochemical implications. 387 26

Phenotypic and genotypic characteristics of groups of Pinzgauer cattle bred at lowland, highland, and alpine farms in the Carpathian Mountains were studied. A high variation of the cattle with respect to blood groups was revealed. It was found that the genetic structure of the highland group of Pinzagauer cattle was somewhat similar to that of Brown Carpathian cattle with respect to biochemical genetic systems, mainly transferrin and amylase-I loci. It is thought that the similarity found may be accounted for by close ecological and geographical breeding conditions of the groups of cattle studied.
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PMID:[Genetic structure of the Pinzgauer breed in the Carpathian region]. 875 40

The binding of iron by transferrin leads to a significant conformational change in each lobe of the protein. Numerous studies have shown that the transferrin receptor discriminates between iron-saturated and iron-free transferrin and that it modulates the release of iron. Given these observations, it seems likely that there is contact between each lobe of transferrin and the receptor. This is the case with chicken transferrin, in which it has been demonstrated unambiguously that both lobes are required for binding and iron donation to occur [Brown-Mason and Woodworth (1984) J. Biol. Chem. 259, 1866-1873]. Further support to this contention is added by the ability of both N- and C-domain-specific monoclonal antibodies to block the binding of a solution containing both lobes [Mason, Brown and Church (1987) J. Biol. Chem. 262, 9011-9015]. In the present study a similar conclusion is reached for the binding of human serum transferrin to the transferrin receptor. With the use of recombinant N- and C-lobes of human transferrin produced in a mammalian expression system, we show that both lobes are required to achieve full binding. (Production of recombinant C-lobe in the baby hamster kidney cell system is reported here for the first time.) Each lobe is able to donate iron to transferrin receptors on HeLa S3 cells in the presence of the contralateral lobe. The results are not identical with the chicken system, because the C-lobe alone shows a limited ability to bind to receptors and to donate iron. Further complications arise from the relatively weak re-association between the two lobes of human transferrin compared with the re-association of the ovotransferrin lobes. However, domain-specific monoclonal antibodies to either lobe block the binding of N- and C-lobe mixtures in the human system, thus substantiating the need for both.
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PMID:Receptor recognition sites reside in both lobes of human serum transferrin. 933 53

Proteomic techniques were used to identify cardiac proteins from whole heart homogenate and heart mitochondria of Fisher 344/Brown Norway F1 rats, which suffer protein nitration as a consequence of biological aging. Soluble proteins from young (5 mo old) and old (26 mo old) animals were separated by one- and two-dimensional gel electrophoresis. One- and two-dimensional Western blots with an anti-nitrotyrosine antibody show an age-related increase in the immunoresponse of a few specific proteins, which were identified by nanoelectrospray ionization-tandem mass spectrometry (NSI-MS/MS). Complementary proteins were immunoprecipitated with an immobilized anti-nitrotyrosine antibody followed by NSI-MS/MS analysis. A total of 48 proteins were putatively identified. Among the identified proteins were alpha-enolase, alpha-aldolase, desmin, aconitate hydratase, methylmalonate semialdehyde dehydrogenase, 3-ketoacyl-CoA thiolase, acetyl-CoA acetyltransferase, GAPDH, malate dehydrogenase, creatine kinase, electron-transfer flavoprotein, manganese-superoxide dismutase, F1-ATPase, and the voltage-dependent anion channel. Some contaminating blood proteins including transferrin and fibrinogen beta-chain precursor showed increased levels of nitration as well. MS/MS analysis located nitration at Y105 of the electron-transfer flavoprotein. Among the identified proteins, there are important enzymes responsible for energy production and metabolism as well as proteins involved in the structural integrity of the cells. Our results are consistent with age-dependent increased oxidative stress and with free radical-dependent damage of proteins. Possibly the oxidative modifications of the identified proteins contribute to the age-dependent degeneration and functional decline of heart proteins.
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PMID:Proteomic identification of 3-nitrotyrosine-containing rat cardiac proteins: effects of biological aging. 1534 82

Choroidal neovascularization (CNV) leads to loss of vision in age-related macular degeneration (AMD), the leading cause of blindness in adult population over 50 years old. In this study, we developed intravenously administered, nanoparticulate, targeted nonviral retinal gene delivery systems for the management of CNV. CNV was induced in Brown Norway rats using a 532 nm laser. We engineered transferrin, arginine-glycine-aspartic acid (RGD) peptide or dual-functionalized poly-(lactide-co-glycolide) nanoparticles to target delivery of anti-vascular endothelial growth factor (VEGF) intraceptor plasmid to CNV lesions. Anti-VEGF intraceptor is the only intracellularly acting VEGF inhibitory modality. The results of the study show that nanoparticles allow targeted delivery to the neovascular eye but not the control eye on intravenous administration. Functionalizing the nanoparticle surface with transferrin, a linear RGD peptide or both increased the retinal delivery of nanoparticles and subsequently the intraceptor gene expression in retinal vascular endothelial cells, photoreceptor outer segments and retinal pigment epithelial cells when compared to nonfunctionalized nanoparticles. Most significantly, the CNV areas were significantly smaller in rats treated with functionalized nanoparticles as compared to the ones treated with vehicle or nonfunctionalized nanoparticles. Thus, surface-functionalized nanoparticles allow targeted gene delivery to the neovascular eye on intravenous administration and inhibit the progression of laser-induced CNV in a rodent model.
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PMID:Intravenous transferrin, RGD peptide and dual-targeted nanoparticles enhance anti-VEGF intraceptor gene delivery to laser-induced CNV. 1919 80

A 39-year-old woman was admitted to our hospital with an eight-month history of dyspnea on exertion, weakness and increasing fatigue. She reported repeated episodes of menometrorrhagia and underwent a myomectomy. She is not a vegetarian. Her menstrual bleeding: 3-5 days per month. Two months ago, she complained of burning sensation of the tongue upon swallowing food and noted brittle nails. She tolerated soft foods. On physical examination, she was pale; her nails were very thin, fragile and somewhat concave. Her oral examination showed angular stomatitis, depapillated tongue and glossitis. The clinical diagnosis was anemia and dysphagia. Laboratory tests were: Hb: 7.0g/dL, MCV: 57.42fL, MCH: 15.82 pg; leukocytes: 4,980; reticulocytes: 2.18%, reticulocyte index: 0.1%, serum iron: 21ug/dl, total iron binding capacity (TIBC): 286, transferrin saturation: 7% and serum ferritin: 27ng/ml. The peripheral blood smear showed anisocytosis and hypochromic microcytic cells. Thevenon test was negative. Abdominal ultrasound: uterine myoma. A barium swallow X-ray showed a 2-mm linear filling defect between the 4th and 5th cervical vertebrae in the anteroposterior and lateral view; it protruded from the anterior wall and reduced esophageal lumen by 60%. In the endoscopy, we found a fibrous web in the cricopharyngeal area. Serial dilatations were performed over a guidewire using Savary-Gilliard dilators with diameter up to 14 mm, improving dysphagia. She was treated with transfusional therapy and parenteral iron. She was discharged with ferrous sulfate and folic acid. The Plummer-Vinson syndrome, Paterson-Brown-Kelly or sideropenic dysphagia is characterized by dysphagia, irondeficiency anemia and upper esophageal web. The syndrome is described as very rare.
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PMID:[Plummer-Vinson syndrome: report of a case and review of literature]. 2302 85


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