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Biomedical subjects

M Worwood

Publications and source records attributed to M Worwood.

At least 19 recordsLinked to original sources
PubMed1991

Luminol peroxidation catalyzed by human isoferritins.

The role of ferritin in catalyzing the oxidation of luminol with the production of chemiluminescence was investigated. The effect of pH was compared to its effect on K3Fe(CN)6-catalyzed oxidation and different pH optima were recorded for the two catalysts. The ferrous iron chelator, bipyridyl, enhanced the production of chemiluminescence catalyzed by FeSO4 and ferritin but had little effect on the K3Fe(CN)6-catalyzed reaction. Desferal reduced the level of chemiluminescence in the presence of FeSO4 and ferritin but was a much more effective inhibitor of chemiluminescence catalyzed by K3Fe(CN)6. The hydroxyl radical scavenger, mannitol, had little effect upon light production whereas superoxide dismutase inhibited light production. The addition of antihuman spleen ferritin completely inhibited activity. The catalytic activity of both H and L rich ferritins was affected by iron content. Activity increased until the Fe/protein ratio reached 0.04 micrograms Fe/micrograms protein and then decreased with increasing iron content. Thus activity is controlled by the iron content of the molecule and influenced by its subunit composition as is the uptake of iron into ferritin. These findings suggest that ferroxidation by ferritin is associated with the ability to generate radicals of the nitrogenous base luminol with the production of chemiluminescence. Although activity is greatest at alkaline pH there is significant activity at pH 7.4. Ferritin therefore may be able to generate free radical reactions in vivo with the acidic isoferritin being most active.

2,2'-Dipyridyl↗
PubMed1991

Stable lyophilized reagents for the serum ferritin assay.

Two monoclonal antibodies to human ferritin, including one that was coupled to horseradish peroxidase, were lyophilized. These reagents show little loss of activity on reconstitution and demonstrate acceptable stability in the accelerated degradation test. When applied in a simple ELISA for the assay of serum ferritin along with the WHO standard for serum ferritin (80/602) they provide a robust assay with standardized reagents which is potentially suitable for use as a reference assay.

Antibodies, Monoclonal↗
PubMed1991

Immunological properties of ferritin during in vitro maturation of human monocytes.

Ferritin in macrophages from human liver and spleen is rich in L subunits but, in the peripheral blood monocytes from which tissue macrophages are derived, the ferritin contains a high proportion of H subunits. We have studied the maturation of monocytes in vitro and the immunological properties of cellular ferritin during this process. Mononuclear cells were isolated from peripheral blood of normal subjects and patients with idiopathic haemochromatosis. Monocytes were obtained by incubation on plastic. The adherent cells were incubated in medium with or without added iron (ferric ammonium citrate) for 20 hours and harvested. Monocytes were also incubated for 7 days before incubation with iron. Ferritin concentrations were determined using immunoassays specific for H and L rich isoferritins. Freshly isolated monocytes were found to have similar concentrations of H- and L-rich isoferritins. Incubation with iron caused an increase in both H- and L-type ferritins. After incubation for 7 d the ferritin present in the normal cell lysates was L-rich and incubation with iron caused accumulation of L-, but not H-type ferritin. Maturation of monocytes is thus associated with the loss of H-rich isoferritins. There were no differences between normal subjects and patients with idiopathic haemochromatosis in ferritin concentrations. In vitro maturation provides an excellent model for studying the developmental control of ferritin synthesis and breakdown.

Adult↗
PubMed1990

Ferritin.

The iron storage protein ferritin is found in all cells of the body as multiple isoferritins composed of 24 sub units of two types. The structure is well understood from increasingly detailed analysis by X-ray crystallography. Genes for the principal subunits (called H and L) have been cloned and are located on chromosomes 11q and 19q respectively. The production of H24 and L24 recombinant molecules is making it possible to explore the relationship between structure and function. The control of ferritin synthesis by iron at the level of translation is providing a model for understanding the control of protein synthesis. H-rich isoferritins are of considerable interest in haematology as they appear to be implicated in control of haemopoiesis and development of malignancy. Whether or not an abnormality in ferritin is the cause of hereditary haemochromatosis is not yet resolved.

Animals↗
PubMed1979

Binding of human serum ferritin to concanavalin A.

1. A high proportion of the ferritin in normal serum binds to concanavalin A. Binding is prevented by the addition of alpha-D-methylglucoside to the reaction mixture. 2. Ferritin in extracts of normal heart, liver and spleen or serum ferritin from patients with massive hepatic necrosis does not bind to concanavalin A. 3. Isoelectric focusing of preparations of serum ferritin from patients with primary haemochromatosis shows that the ferritin fraction binding to concanavalin A consists, predominantly, of the more acidic isoferritins. 4. These findings suggest that carbohydrate residues may be added to ferritin during its secretion into the plasma. Glycosylation may account for the heterogeneity of serum ferritin on isoelectric focusing. 5. Direct release of intracellular ferritin from damaged tissue may be indicated by an increase in the proportion of circulating ferritin which does not bind to concanavalin A. Such an increase has been found in sera from patients with iron overload.

Concanavalin A↗
PubMed1979

Variability of serum ferritin concentration in normal subjects.

Serum ferritin concentrations were measured in normal subjects over periods of 1 day, 1 week and 7 weeks. The variation of the results was compared with variation of control of control sera. In most of the subjects the variation in the results could be attributed to the variation in the method of measurement. No diurnal variation in serum ferritin concentration was observed.

Circadian Rhythm↗
PubMed1979

Serum ferritin.

(1) Brief introduction to iron metabolism and the biochemistry of ferritin. (2) Early studies of circulating ferritin. (3) Methods for measuring serum ferritin concentrations -- immunoradiometric, radioimmuno- and enzyme-linked immuno assays based on liver or spleen ferritin -- an evaluation of these techniques. (4) Serum ferritin concentrations in normal subjects -- definition of normality -- relationship between storage iron and serum ferritin concentrations -- changes during development from birth to old age -- iron deficiency -- variability of serum ferritin concentration -- evaluation of use of ferritin assay for assessment of storage iron levels. (5) Serum ferritin concentrations in disease -- hemochromatosis -- secondary iron overload -- liver damage -- infection and chronic disease -- cancer. (6) Assay of serum ferritin with antibodies to ferritins other than liver or spleen -- ferritinemia and cancer. (7) Properties of serum ferritin -- molecular weight -- iron content -- isoelectric focusing patterns -- carbohydrate content -- immunological properties. (8) Physiology of circulating ferritin -- release of ferritin from tissues -- origin of circulating ferritin -- clearance from the plasma -- iron and protein turnover. (9) Summary -- factors influencing serum ferritin concentrations and clinical use of ferritin estimations.

Adolescent↗
PubMed1978

Properties of human tissue isoferritins.

1. Human liver ferritin was separated by preparative isoelectric focusing into six fractions. 2. Except for the least acidic fraction the reactivity with antibody against spleen ferritin increased with rising pI, but with antibody against heart ferritin the reactivity decreased. 3. The highest iron content was found in the most acidic isoferritins and progressively decreased with rising pI. 4. Iron uptake was studied in apoferritin prepared from heart and liver ferritin fractions separated by ion-exchange chromatography. There was good correlation between the rate of iron uptake and pI. The most acidic fractions took up iron more rapidly than did the more basic ones. 5. Ferritin was prepared from heart, liver, spleen and kidney. There was little difference on isoelectric focusing between ferritin obtained from normal tissues and the corresponding iron-loaded tissues from patients who had received multiple blood transfusions. The iron-loaked heart ferritin invariably contained relatively more of the basic isoferritins. Normal and iron-overloaded heart ferritins were separated into isoferritin fractions by ion-exchange chromatography, and in each case there was a fall in iron content as the pI increased. The iron content of ferritin from the iron-overloaded heart was higher throughout than that from normal heart. 6. There is a relationship between the rate of iron uptake by apoferritin and pI, and this probably accounts for the variation in iron content of the isoferritins found in human liver and heart.

Apoferritins↗
PubMed1978

An immunoradiometric assay for the acidic ferritin of human heart: application to human tissues, cells and serum.

Human tissues contain ferritin molecules with a range of isoelectric points but immunoassays for detecting serum ferritin have generally employed antibodies to the more basic liver or spleen proteins. To study the distribution of more acidic ferritins in tissues and serum acidic ferritin has been isolated from normal human heart and a two-site immunoradiometric assay for this protein developed. This assay gives little cross-reaction with spleen ferritin. Tissue ferritins have been fractionated by anion exchange chromatography and assayed with both spleen and heart antibodies. The spleen ferritin assay detects the more basic ferritin and the heart ferritin assay the more acidic ferritin. Acidic ferritins were found in heart, kidney, reticulocytes and HeLa cells. In sera from normal subjects and patients with iron overload, myocardial infarction, leukaemia and carcinoma only low concentrations of heart ferritin were found, although in the pathological sera spleen ferritin concentrations were generally raised. Circulating ferritin contains only a small proportion of molecules with the immunological characteristics of acidic heart ferritin.

Antibody Formation↗
PubMed1978

Lead and iron absorption from rat small intestine: the effect of dietary Fe deficiency.

1. When lead is administered in drinking-water iron-deficient rats retain more Pb than Fe-replete rats (Six & Goyer, 1972; Klauder & Petering, 1975). In the present study the relationship between the absorption of Pb and Fe was investigated. 2. Adult male rats were transfered to a milk-based diet fed with or without supplementary Fe (180 mg Fe/kg as ferrous sulphate). After 7--9 d the absorption of duodenally-administered 203Pb and 59Fe was measured as uptake of radioactivity from the gastrointestinal tract after 90 min. 59Fe absorption was increased in rats given the unsupplemented diet for 7 d and was further increased in rats kept on the diet for up to 7 weeks. 203Pb absorption was not consistently increased by either short- or long-term Fe deprivation. 3. Much of the 203Pb in homogenates of the upper small intestine was bound to soluble protein of which up to 85% was dialysable. In contrast little 59Fe was dialysable. Only a small proportion of the soluble musosal Pb was associated with ferritin during gel-filtration chromatography although 203Pb precipitated together with carrier rat-liver ferritin with an antibody to rat-liver ferritin. 4. There appeared to be no direct relationship between the transfer of Fe and Pb across the small intestine of the adult rat.

Animals↗
PubMed1977

Isoferritins in acute leukaemia.

Leucocytes containing a high proportion of blast cells were obtained from 11 patients with acute myeloid leukaemia, and leucocytes were also obtained from 2 normal subjects. Ferritin was partially purified from leucocyte extracts and subjected to anion-exchange chromatography and isoelectric focusing. The Fe content of leucocyte ferritin was low, and in all but one case the preparations contained isoferritins corresponding to those found in normal tissues or serum. Only some of the preparations contained the relatively acidic isoferritins which have been described as "carcinofoetal", but which are also present in normal heart and kidney. Ferritin from one patient contained isoferritins of lower isoelectric point than heart ferritin. These results show that there does not appear to be any specific isoelectric focusing pattern for leukaemic cells, and that assays for acidic isoferritins are unlikely to be of use in the diagnosis of leukaemia and in monitoring treatment. However, the very acidic protein found in one preparation suggests that the search for abnormal subunits of ferritin may be fruitful in acute leukaemia.

Chromatography, Ion Exchange↗
PubMed1977

Intracellular iron transport in rat intestinal epithelium: biochemical and ultrastructural observations.

Iron absorption by the rat intestinal epithelial cell has been studied by differential centrifugation of mucosal homogenates and by electron microscopic autoradiography. Autoradiography of both subcellular pellets and whole gut confirmed the biochemical findings. Mitochondria play a quantitatively significant role in iron metabolism within the epithelial cell but do not take part in the transport of iron across the cell during iron absorption.

Animals↗