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PubMed1987

Blocking of iron absorption by a preliminary oral dose of iron.

Using a small-dose iron tolerance test (ITT) in mildly iron-deficient healthy adults, we have examined the phenomenon of mucosal block. First proposed and demonstrated by Hahn et al with radioiron, "mucosal block" describes diminished avidity for iron of the intestinal mucosa following an orally administered blocking dose. In the ITT, the index of absorption is an increase in plasma iron concentration, rather than retained radioactivity. The absorption of a blocked 10-mg test dose of iron was compared with that of a 10-mg control dose given to the same subject. Both 60- and 30-mg blocking doses of iron resulted in diminished absorption of the test dose. The refractory state of the intestine lasted as long as 24 hours.

Administration, Oral↗
PubMed2000

Iron absorption from ferrous bisglycinate and ferric trisglycinate in whole maize is regulated by iron status.

BACKGROUND: There is a need to determine whether iron absorption from iron amino acid chelates is protected from inhibition by dietary phytate and regulated normally by iron status. OBJECTIVE: The objective of this study was to compare iron absorption from ferrous sulfate, ferrous bisglycinate, and ferric trisglycinate in whole-maize meal; to determine whether iron from ferrous bisglycinate and ferrous sulfate exchanges in the intestinal pool; and to assess iron absorption from ferrous bisglycinate and ferric trisglycinate over a range of iron statuses. DESIGN: In study 1A, 10 iron-sufficient men consumed ferrous sulfate-fortified whole-maize meal porridge equilibrated with (59)Fe-sulfate on day 1 and (55)Fe-bisglycinate on day 2. In study 1B, these volunteers consumed ferrous sulfate-fortified porridge equilibrated with (59)Fe-sulfate and (55)Fe-bisglycinate simultaneously. In studies 2A and 2B, iron absorption from 3 mg Fe as (59)Fe-ascorbate, (55)Fe-bisglycinate, or (59)Fe-trisglycinate in water and in porridge was compared in 23 subjects with a range of iron statuses. Iron absorption was determined from blood radioactivity on day 16. RESULTS: In study 1A, geometric mean iron absorption from ferrous bisglycinate was 6.0% (range: 2.6-13.6%), 4 times higher than that from ferrous sulfate (1. 7%; range: 1.0-3.3%; P < 0.05). In study 1B, absorption from neither source was different from that in study 1A. In studies 2A and 2B, absorption from all sources was strongly inversely related to serum ferritin, with geometric means of 32.5% (iron ascorbate), 9.1% (bisglycinate), and 15.3% (trisglycinate). Iron from ferric trisglycinate was poorly absorbed (2.3%; range: 0.5-9.2%) from maize. CONCLUSION: In whole-maize meal, iron from ferrous bisglycinate is better absorbed than is iron from ferrous sulfate and does not exchange with iron from maize or ferrous sulfate in the intestinal pool. Absorption of iron from bisglycinate and trisglycinate is regulated normally by iron status.

Absorption↗
PubMed1994

Biliary excretion of plasma non-transferrin-bound iron in rats: pathogenetic importance in iron-overload disorders.

Plasma non-transferrin-bound iron (NTB-iron) is a potentially toxic form of iron, which is efficiently taken up by the normal, as well as the chronically iron-overloaded liver. In fact, NTB-iron may represent the major source of iron gaining access to hepatocytes in the iron-loaded state. We postulated that efficient biliary excretion of this form of iron could protect against iron-related hepatocellular injury. To characterize the biliary excretion of NTB-iron in intact normal and iron-loaded rats, the plasma disappearance and biliary excretion kinetics of plasma 55Fe-labeled NTB-iron were determined. In normal rats, prompt biliary excretion of plasma NTB-iron was evident, with peak radioactivity approximately 10 min after 55Fe injection (4.1% mean recovery at 3 h). In contrast, biliary iron excretion in iron-loaded rats was minimal (0.1%). In normal rats, a marked increase in biliary excretion of plasma NTB-iron was observed after intravenous desferrioxamine (mean recovery 20.9%) and the new oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one administered intravenously (mean recovery 16.1%) or orally (11.4%). In iron-loaded rats, the cumulative recoveries of 55Fe in bile achieved by chelators were lower than in controls (7.6, 3.9, and 3.7%, respectively). Collectively, these findings demonstrate that 1) the normal liver rapidly excretes significant amounts of plasma NTB-iron in bile; 2) the iron-loaded liver exhibits a marked decrease in the capacity to excrete plasma NTB-iron into bile; and 3) chelating agents greatly enhance the biliary excretion of plasma NTB-iron, although the response in terms of cumulative recoveries is less pronounced in the iron-loaded state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Absorption of iron from grape-molasses and ferrous sulfate: a comparative study in normal subjects and subjects with iron deficiency anemia.

We compared the absorption of iron from grape molasses (GM) and ferrous sulfate (FS) using the post-absorptive serum iron increase method (non-radioactive). The study involved 56 subjects, aged 6-36 months. Group I consisted of 30 subjects with iron deficiency anemia (IDA) and group II, 26 non-anemic subjects. Each group was subdivided randomly into two equal subgroups to be given either GM or FS. The absorption of the iron from GM was monitored in 15 infants with IDA and in 13 non-anemic infants, and the absorption of iron from FS was tested in the rest of the subjects in each group. In those infants in each group given GM or FS, there was no significant difference in before-test values for serum iron (SI) and total iron binding capacity (TIBC) (p > 0.05). In the group with IDA, the mean after-test SI value in FS-given infants was higher and the mean TIBC value lower than those of GM-given infants (p < 0.05). However, in the non-anemic group, there was no significant difference in the mean after-test SI and TIBC values in either GM- or FS-given infants (p > 0.05). The mean increase of serum iron in GM-given infants with IDA was 27.0 +/- 13.4 micrograms/ dl and in FS-given infants, 60.6 +/- 17.0 micrograms/dl (p < 0.05). In the non-anemic group, the mean increase of serum iron of GM-given infants was 23.0 +/- 4.3 micrograms/dl, and that of FS-given infants, 23.8 +/- 10.0 micrograms/dl (p > 0.05). We determined that in non-anemic subjects, the absorption of iron from GM was comparable to that from FS. Furthermore, we believe that grape molasses is an effective iron source in preventing iron deficiency anemia in infancy.

Absorption↗
PubMed2001

Ferrate treatment for removing chromium from high-level radioactive tank waste.

A method has been developed for removing chromium from alkaline high-level radioactive tank waste. Removing chromium from these wastes is critical in reducing the volume of waste requiring expensive immobilization and deep geologic disposition. The method developed is based on the oxidation of insoluble chromium(III) compounds to soluble chromate using ferrate. This method could be generally applicable to removing chromium from chromium-contaminated solids, when coupled with a subsequent reduction of the separated chromate back to chromium(III). The tests conducted with a simulated Hanford tank sludge indicate that the chromium removal with ferrate is more efficient at 5 M NaOH than at 3 M NaOH. Chromium removal increases with increasing Fe(VI)/Cr(II) molar ratio, but the chromium removal tends to level out for Fe(VI)/ Cr(III) greaterthan 10. Increasingtemperature leadsto better chromium removal, but higher temperatures also led to more rapid ferrate decomposition. Tests with radioactive Hanford tank waste generally confirmed the simulant results. In all cases examined, ferrate enhanced the chromium removal, with a typical removal of around 60-70% of the total chromium present in the washed sludge solids. The ferrate leachate solutions did not contain significant concentrations of transuranic elements, so these solutions could be disposed as low-activity waste.

Chromium↗
PubMed1970

Studies on iron metabolism in sickle cell anaemia, sickle cell haemoglobin C disease, and haemoglobin C disease using a large volume liquid scintillation counter.

Iron absorption as measured by a faecal recovery method in young adult males living in a tropical zone was high, even in the absence of anaemia. There was an inverse relation between the iron absorption and the packed cell volume. The highest absorption was found in sickle cell anaemia patients, where the packed cell volume is the lowest. The incorporation of iron was also the fastest and greatest in this group. In the controls the iron absorbed accumulated in the marrow and the spleen on the first day; in the sickle cell anaemia group the spleen has an insignificant role in iron storage. The growing radioactivity in the liver parallels that of the heart in the group of sickle cell anaemia patients; however, it remains low in the spleen in the same group, implying a diminution of splenic blood flow. In the sickle cell haemoglobin C and the haemoglobin C patients, the liver and spleen have an intermediate position between that of the sickle cell anaemia group and the control group.

Adolescent↗
PubMed1975

Ferromagnetic silicone necrosis of hypernephromas by selective vascular occlusion to the tumor: a new technique.

Arterial vascular occlusion of hypernephromas may be performed by obstructiing the tumor vascular tree with the injection of ferromagnetic silicone microspheres. The powerful superconducting electromagnet confines the embolized iron-silicone compound to the neoplastic target organ. Radioactive material may or may not be added to the iron-silicone compound to give local direct radioactive radiation therapy to the tumor area. In experimental dogs up to 70,000 rad of beta radiation from the P32 source had been delivered homogeneously within the kidney when mixed with the ferrosilicone. This technique may well be used in cases in which a major operation is contraindicated or when preoperative necrosis of the tumor is advisable. Since the entire procedure can be done with the patient under local anesthesia in a radiology department it may be a valuable new technique in the future management of urological tumors, unilateral renal hypertension, solitary kidney pathology and so forth. Ferrosilicone material has not been found to be toxic. The application of a powerful superconducting electromagnet to the technique provides a means of confining the embolized iron-silicone compound to the target organ.

Adenocarcinoma↗
PubMed2002

Protein transduction technology.

Intracellular delivery of macromolecules remains problematic because of the bioavailability restriction imposed by the cell membrane. Recent studies on protein transduction domains have circumvented this barrier, however, and have resulted in the delivery of peptides, full-length proteins, iron beads, liposomes, and radioactive isotopes into cells in culture and animal models in vivo.

Animals↗
PubMed2003

Performance evaluation of a permeable reactive barrier using reaction products as tracers.

A method incorporating laboratory analysis of constituents that formed as reaction products was developed and used to determine the flux of groundwater through a zerovalent iron-based permeable reactive barrier (PRB) installed to treat U-contaminated groundwater. Concentrations of three nonvolatile constituents (Ca, U, and V) that formed as reaction products in the PRB were analyzed in 279 samples. Areal distributions of the reaction products indicate that groundwater flowed through all portions of the PRB and that nearly the entire volume of reactive material is treating the groundwater. Almost 9 t of calcium carbonate precipitated in the PRB during the first 2.7 yr of operation, but only 24 kg of combined U- and V-bearing minerals precipitated during the same period. Concentration gradients of Ca, U, and V dissolved in the groundwater indicate that a hydraulically upgradient portion of the PRB lost some reactivity during the first 2.7 yr of operation. Calculations that partially couple porosity changes to ZVI reactivity suggest that loss of reactivity may be more limiting than porosity reduction for long-term performance of the PRB. Calculations using groundwater concentration gradients and solid-phase concentrations indicate that the mean groundwater flux ranged from 11 to 24 L/min, considerably less than the design flux of 185 L/min. Flux values calculated with all three constituents were in good agreement. This method provides a more accurate determination of groundwater flux than is possible with flow sensor measurements, dissolved tracers, or Darcy's law computations.

Calcium↗