PubMed Health⌕ Search

Biomedical subjects

B Vaisman

Publications and source records attributed to B Vaisman.

8 recordsLinked to original sources
PubMed2004

Dental treatment for children with chronic idiopathic thrombocytopaenic purpura: a report of two cases.

Idiopathic thrombocytopaenic purpura (ITP) is the most common acquired bleeding disorder occurring in previously healthy children. The condition is benign and self-limiting, with a high possibility of recovery. Only 15-30% of children with acute ITP develop the chronic form. Clinically, ITP presents with petechiae, ecchymoses, haematomas, epistaxis, haematuria, mucocutaneous bleeding, and occasionally, haemorrhage into tissues. Oral manifestations include spontaneous gingival bleeding, petechiae or haematomas of the mucosa, tongue or palate. Two paediatric case reports are described concerning female patients diagnosed with chronic ITP. Oral findings and dental procedures are described. Standard dental treatment was performed with a platelet count higher than 50,000/mm3. The importance of adequate dental plaque control techniques in order to prevent inflammation, potential bleeding and infection in these patients is emphasized. The paediatric dentist must be aware of the clinical appearance of ITP in order to recognize the condition and successfully manage the patient.

Child↗
PubMed2000

Ferritin expression in maturing normal human erythroid precursors.

We studied the expression of H- and L-ferritin subunits at sequential stages of maturation of normal human erythroid precursors. The erythroid cells developed in liquid culture and were purified immunomagnetically before analysis. It was found that the content of both ferritin subunits decreased exponentially with maturation: the decrease was rapid when cellular haemoglobin was low, and it slowed down when the haemoglobin was increased. This mode of decline was especially pronounced for the L-subunits. The H-/L-subunit ratio did not change significantly during the investigated period. The synthesis of both subunits was equal at each given developmental stage, and declined significantly with maturation. However, this decline was just slightly faster than that of total protein synthesis. The data indicated that the degradation of H- and L-ferritin also declined as maturation proceeded. No decrease was observed in mRNA levels of either ferritin subunit. Thus, the ferritin content and turnover were maximal at the beginning of haemoglobin accumulation and diminished later. As the rate of ferritin turnover determines the rate of incorporation and release of its iron, the results presented suggest that ferritin mediates cellular iron transport and donates iron for haem synthesis, mainly at the beginning of haemoglobin accumulation. The synthesis of both ferritin subunits is regulated during erythroid maturation at the post-transcriptional level.

Cell Division↗
PubMed1999

Regulation of intracellular iron metabolism in human erythroid precursors by internalized extracellular ferritin.

Human erythroid precursors grown in culture possess membrane receptors that bind and internalize acid isoferritin. These receptors are regulated by the iron status of the cell, implying that ferritin iron uptake may represent a normal physiologic pathway. The present studies describe the fate of internalized ferritin, the mechanisms involved in the release of its iron, and the recognition of this iron by the cell. Normal human erythroid precursors were grown in a 2-phase liquid culture that supports the proliferation, differentiation, and maturation of erythroid precursors. At the stage of polychromatic normoblasts, cells were briefly incubated with (59)Fe- and/or (125)I-labeled acid isoferritin and chased. The (125)I-labeled ferritin protein was rapidly degraded and only 50% of the label remained in intact ferritin protein after 3 to 4 hours. In parallel, (59)Fe decreased in ferritin and increased in hemoglobin. Extracellular holoferritin uptake elevated the cellular labile iron pool (LIP) and reduced iron regulatory protein (IRP) activity; this was inhibited by leupeptin or chloroquine. Extracellular apoferritin taken up by the cell functioned as an iron scavenger: it decreased the level of cellular LIP and increased IRP activity. We suggest that the iron from extracellular is metabolized in a similar fashion by developing erythroid cells as is intracellular ferritin. Following its uptake, extracellular ferritin iron is released by proteolytic degradation of the protein shell in an acid compartment. The released iron induces an increase in the cellular LIP and participates in heme synthesis and in intracellular iron regulatory pathways.

Cell Differentiation↗
PubMed1999

The cellular labile iron pool and intracellular ferritin in K562 cells.

The labile iron pool (LIP) harbors the metabolically active and regulatory forms of cellular iron. We assessed the role of intracellular ferritin in the maintenance of intracellular LIP levels. Treating K562 cells with the permeant chelator isonicotinoyl salicylaldehyde hydrazone reduced the LIP from 0.8 to 0.2 micromol/L, as monitored by the metalo-sensing probe calcein. When cells were reincubated in serum-free and chelator-free medium, the LIP partially recovered in a complex pattern. The first component of the LIP to reappear was relatively small and occurred within 1 hour, whereas the second was larger and relatively slow to occur, paralleling the decline in intracellular ferritin level (t1/2= 8 hours). Protease inhibitors such as leupeptin suppressed both the changes in ferritin levels and cellular LIP recovery after chelation. The changes in the LIP were also inversely reflected in the activity of iron regulatory protein (IRP). The 2 ferritin subunits, H and L, behaved qualitatively similarly in response to long-term treatments with the iron chelator deferoxamine, although L-ferritin declined more rapidly, resulting in a 4-fold higher H/L-ferritin ratio. The decline in L-ferritin, but not H-ferritin, was partially attenuated by the lysosomotrophic agent, chloroquine; on the other hand, antiproteases inhibited the degradation of both subunits to the same extent. These findings indicate that, after acute LIP depletion with fast-acting chelators, iron can be mobilized into the LIP from intracellular sources. The underlying mechanisms can be kinetically analyzed into components associated with fast release from accessible cellular sources and slow release from cytosolic ferritin via proteolysis. Because these iron forms are known to be redox-active, our studies are important for understanding the biological effects of cellular iron chelation.

Deferoxamine↗
PubMed1999

Isolation of large and pure samples of human erythroid precursors at different stages of maturation using immunomagnetic separation of cells from liquid cultures.

The two-phase liquid culture, which supports the development of human erythroid progenitors into hemoglobin-containing orthochromatic normoblasts, provides high yield of erythroblasts with synchronized development. However, other cell types are also present in the culture. In the present report, we used immunomagnetic separation for the purification of the developing erythroid precursors. At different stages of the culture, aliquots of the cells were incubated with anti-glycophorin A, B monoclonal antibodies, followed by anti-mouse IgG-coated magnetic beads, and separated by a magnet. In mature cultures, all isolated glycophorin-positive cells contained hemoglobin, as indicated by their staining with benzidine. All glycophorin-negative cells were benzidine negative. In earlier cultures, morphological examination and measurements of hemoglobin content showed that the erythroid precursors could be isolated at different stages of maturation. Thus, the combination of the liquid culture procedure with the immunomagnetic separation technique permitted to obtain large samples of pure erythroid cells, which were synchronized at subsequent stages of maturation. The method enables comprehensive studies of developing erythroid cells from normal donors as well as from patients with various disorders of erythropoiesis.

Blood Proteins↗
PubMed1999

An ELISA for the H-subunit of human ferritin which employs a combination of rabbit poly- and mice monoclonal antibodies and an enzyme labeled anti-mouse-IgG.

We describe a sensitive ELISA for measuring the H-type subunit of human ferritin. A high detection sensitivity was attained by the use of antibodies from different species and an enzyme-conjugated secondary antibody. It consisted of a sandwich assay using a solid phase coated with a rabbit polyclonal antibody for human ferritin from term placenta and a soluble monoclonal antibody for human H-ferritin, followed by a secondary anti-mouse immunoglobulin (Ig)G conjugated to beta-galactosidase. The assay was calibrated with purified recombinant human H-ferritin from E. coli. The colorigenic chlorophenol red beta-D-galactopyranoside and the fluorogenic 4-methyl-umbelliferyl-beta-D-galactopyranoside substrates were used with similar outcome. The described method permits the measurement of human H-ferritin at a concentration ranging from 0.1 to 100 micrograms/l (or 20-20,000 pg per 200 microliters sample) and is accurate at a concentration as low as 0.3 microgram/l. The coefficient of variation of the assay was 6.05-10.3% and the recovery of H-ferritin added to cell lysates was 105.8 +/- 7.52%. Depending on the H-ferritin content of the cell line tested, only 600 to 60,000 cells of different human cell lines were needed to measure their H-ferritin content.

Animals↗
PubMed1997

Utilization of intracellular ferritin iron for hemoglobin synthesis in developing human erythroid precursors.

Ferritin (Ft) plays an important role in cellular iron metabolism. It can store substantial amounts of iron in a nontoxic soluble form. However, its ability to donate iron for cellular needs, in particular for hemoglobin (Hb) synthesis in human erythroid cells, is still controversial. We studied the role of intracellular Ft-iron in Hb synthesis and the involvement of lysosomal proteolysis in iron release from Ft. Ft-iron release and its subsequent incorporation into heme was investigated in normal human erythroid precursors developing in culture. Dual staining flow cytometry with antibody (Ab)-specific for Ft and for Hb showed a decrease in cellular Ft content in erythroid cells during their maturation. Cellular Ft-iron participation in heme synthesis was studied by labeling cells with 59Fe. Cells were incubated with 59Fe-labeled human diferric transferrin (Tf), then chased, and intracellular radioiron distribution between Ft and Hb was determined on subsequent days by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and/or Ft immunoprecipitation and heme extraction. On day 6, most of the 59Fe accumulated in Ft. Thereafter, a progressive decrease of radioiron in Ft and a corresponding increase of the label in Hb was observed. Inhibition of heme synthesis with succinylacetone caused radioiron to remain in Ft and prevented its redistribution. Addition of unlabeled diferric Tf to the culture medium did not prevent radioiron from appearing in Hb. Chloroquine repression of lysosomal function prevented radio-iron redistribution between Ft and Hb. Inhibition of proteolysis by chymostatin and/or leupeptin led to Ft-protein accumulation in the cells and also prevented radioiron transfer from Ft to Hb. The results of the present study suggest that intracellular Ft donates iron for heme synthesis and that proteolytic Ft degradation in a lysosomal-like compartment is necessary for iron release and its transfer to heme.

Autoradiography↗