Showing papers by "Carlo Brugnara published in 1999"
TL;DR: It is shown that Stat5 is essential for the high erythropoietic rate during fetal development, explained by a crucial role for Stat5 in EpoR's antiapoptotic signaling: it mediates the immediate-early induction of Bcl-X(L) in erythroid cells through direct binding to the B cl-X promoter.
730 citations
TL;DR: Reticulocyte Hb content level was the strongest predictor of iron deficiency and iron deficiency anemia in children and holds promise as an alternative to biochemical iron studies in diagnosis.
Abstract: ContextEarly identification of iron deficiency in children is
essential to prevent the damaging long-term consequences of this
disease. However, it is not clear which indices should be included in a
diagnostic panel for iron deficiency and iron deficiency anemia in
children.ObjectiveTo develop an effective approach for the diagnosis of
iron deficiency and iron deficiency anemia in young children.Design and SettingRetrospective laboratory analysis, carried out
over 7 weeks in 1996, using blood samples ordered by pediatricians and
sent to a large metropolitan hospital for analysis.PatientsA total of 210 children (mean [SD] age, 2.9 [2.0]
years; 120 were male) who had a lead screening test (complete blood
cell count and plasma lead level) ordered by a primary care
pediatrician.Main Outcome MeasuresLevels of hemoglobin (Hb), iron,
transferrin, transferrin saturation (Tfsat), ferritin, and circulating
transferrin receptor and reticulocyte Hb content (CHr) among patients
with and without iron deficiency, defined as Tfsat of less than 20%,
and iron deficiency anemia, defined as Tfsat of less than 20% and Hb
level of less than 110 g/L.ResultsOf the 210 subjects, 43 (20.5%) were iron deficient; 24
of these had iron deficiency anemia. Reticulocyte Hb content and Hb
levels were the only significant predictors of iron deficiency
(likelihood ratio test [LRT]=15.96; P<.001
for CHr, and LRT=6.59; P=.01
for Hb), and CHr was the only significant multivariate predictor of
iron deficiency anemia (LRT=30.43; P<.001).
Plasma ferritin level had no predictive value
(P=.97). Subjects with CHr of less than 26 pg
(optimal cutoff value based on sensitivity/specificity analysis) had
lower Hb level, mean corpuscular volume, mean corpuscular Hb level,
serum iron level, and Tfsat, and increased red blood cell distribution
width vs those with CHr of 26 pg or more (P<.001 for all).ConclusionsReticulocyte Hb content level was the strongest
predictor of iron deficiency and iron deficiency anemia in children. It
holds promise as an alternative to biochemical iron studies in
diagnosis.
224 citations
TL;DR: The hypothesis that the covalent attachment of nonimmunogenic materials (eg, mPEG) to intact RBC may have significant application in transfusion medicine, especially for the chronically transfused and/or allosensitized patient is supported.
140 citations
TL;DR: This study demonstrates adducin's importance to RBC membrane stability in vivo by creating beta-adducin null mice, which are osmotically fragile, spherocytic, and dehydrated compared with the wild type.
Abstract: Adducins are a family of cytoskeleton proteins encoded by three genes (α, β, γ). In a comprehensive assay of gene expression, we show the ubiquitous expression of α- and γ-adducins in contrast to the restricted expression of β-adducin. β-adducin is expressed at high levels in brain and hematopoietic tissues (bone marrow in humans, spleen in mice). To elucidate adducin’s role in vivo, we created β-adducin null mice by gene targeting, deleting exons 9–13. A 55-kDa chimeric polypeptide is produced from the first eight exons of β-adducin and part of the neo cassette in spleen but is not detected in peripheral RBCs or brain. β-adducin null RBCs are osmotically fragile, spherocytic, and dehydrated compared with the wild type, resembling RBCs from patients with hereditary spherocytosis. The lack of β-adducin in RBCs leads to decreased membrane incorporation of α-adducin (30% of normal) and unexpectedly promotes a 5-fold increase in γ-adducin incorporation into the RBC membrane skeleton. This study demonstrates adducin’s importance to RBC membrane stability in vivo.
122 citations
TL;DR: The mouse erythroid KCC1 cDNA and its flanking genomic regions are cloned and three anti-peptide antibodies raised against recombinant mKCC1 function as immunoblot and immunoprecipitation reagents will expedite studies of K CC1 structure-function relationships and of the pathobiology of K-Cl cotransport.
Abstract: Although K-Cl cotransporter (KCC1) mRNA is expressed in many tissues, K-Cl cotransport activity has been measured in few cell types, and detection of endogenous KCC1 polypeptide has not yet been re...
86 citations
TL;DR: It is concluded that protein 4.2 is important in the maintenance of normal surface area in RBCs and for normal RBC cation transport.
Abstract: Protein 4.2 is a major component of the red blood cell (RBC) membrane skeleton. We used targeted mutagenesis in embryonic stem (ES) cells to elucidate protein 4.2 functions in vivo. Protein 4. 2-null (4.2(-/-)) mice have mild hereditary spherocytosis (HS). Scanning electron microscopy and ektacytometry confirm loss of membrane surface in 4.2(-/-) RBCs. The membrane skeleton architecture is intact, and the spectrin and ankyrin content of 4. 2(-/-) RBCs are normal. Band 3 and band 3-mediated anion transport are decreased. Protein 4.2(-/-) RBCs show altered cation content (increased K+/decreased Na+)resulting in dehydration. The passive Na+ permeability and the activities of the Na-K-2Cl and K-Cl cotransporters, the Na/H exchanger, and the Gardos channel in 4. 2(-/-) RBCs are significantly increased. Protein 4.2(-/-) RBCs demonstrate an abnormal regulation of cation transport by cell volume. Cell shrinkage induces a greater activation of Na/H exchange and Na-K-2Cl cotransport in 4.2(-/-) RBCs compared with controls. The increased passive Na+ permeability of 4.2(-/-) RBCs is also dependent on cell shrinkage. We conclude that protein 4.2 is important in the maintenance of normal surface area in RBCs and for normal RBC cation transport.
84 citations
TL;DR: The characteristics of membrane-associated PP1 and PP2A are consistent with a role for both phosphatases in K-Cl cotransport activation in human erythrocytes and response to changes in ionic strength and cell size.
Abstract: Activation of K-Cl cotransport is associated with activation of membrane-bound serine/threonine protein phosphatases (S/T-PPases). We characterize red blood cell S/T-PPases and K-Cl cotransport act...
81 citations
TL;DR: In this paper, the effect of hydroxyurea (HU), clotrimazole (CLT), magnesium oxide (Mg), and combined CLT+Mg therapies on the erythrocyte characteristics and their response to chronic hypoxia in a transgenic sickle mouse (SAD) model was examined.
54 citations
TL;DR: In this paper, the authors showed that cell dehydration mediated by Ca2+-activated K+ channels plays an important role in the pathogenesis of sickle cell disease in mice.
Abstract: Cell dehydration mediated by Ca2+-activated K+ channels plays an important role in the pathogenesis of sickle cell disease. CD-1 mouse erythrocytes possess a Ca2+-activated K+ channel (Gardos chann...
52 citations
TL;DR: The data suggest that the increased activity of KCI cotransport in beta-thal red blood cells is mediated by the deposition of membrane free iron, a mechanism that may be attenuated by deferiprone therapy.
34 citations
TL;DR: Hb A and Hb S seem to affect in different manners the functional properties of K-Cl cotransport, especially in erythrocyte ghosts prepared with the gel column method to contain minimal amounts of Hb.
Abstract: K-Cl cotransport is abnormally active in erythrocytes containing positively charged hemoglobins such as Hb S (SS: β6 Glu → Val) or Hb C (CC: β6 Glu → Lys). The relatively younger age of erythrocytes in these diseases cannot completely account for the increased K-Cl cotransport activity. It has been suggested that these positively charged Hb may interact with the K-Cl cotransport system or one of its regulators and induce changes in its functional activity. We report here data on the volume- and pH-dependence of K-Cl cotransport in ghosts obtained from normal and sickle erythrocytes, and on the effect of addition of either Hb A or Hb S before resealing. In erythrocyte ghosts prepared with the gel column method to contain minimal amounts of Hb, (white ghosts, WG), K-Cl cotransport has similar magnitude in normal and sickle erythrocytes, is not inhibited by alkaline pH and it is volume-independent. Addition of low concentrations of Hb A to WG from normal erythrocytes decreases the magnitude of K-Cl cotransport and restores its volume dependency, but not its pH sensitivity. Addition of Hb S to WG from either normal or sickle erythrocytes restores the volume-dependent component of K-Cl cotransport and increases the magnitude of flux mediated by this transporter. Thus, Hb A and Hb S seem to affect in different manners the functional properties of K-Cl cotransport.