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Biomedical subjects

P Izadi

Publications and source records attributed to P Izadi.

8 recordsLinked to original sources
PubMed1999

Constitutive HOXA5 expression inhibits erythropoiesis and increases myelopoiesis from human hematopoietic progenitors.

The role of the homeobox gene HOXA5 in normal human hematopoiesis was studied by constitutively expressing the HOXA5 cDNA in CD34(+) and CD34(+)CD38(-) cells from bone marrow and cord blood. By using retroviral vectors that contained both HOXA5 and a cell surface marker gene, pure populations of progenitors that expressed the transgene were obtained for analysis of differentiation patterns. Based on both immunophenotypic and morphological analysis of cultures from transduced CD34(+) cells, HOXA5 expression caused a significant shift toward myeloid differentiation and away from erythroid differentiation in comparison to CD34(+) cells transduced with Control vectors (P =.001, n = 15 for immunophenotypic analysis; and P <.0001, n = 19 for morphological analysis). Transduction of more primitive progenitors (CD34(+)CD38(-) cells) resulted in a significantly greater effect on differentiation than did transduction of the largely committed CD34(+) population (P =.006 for difference between HOXA5 effect on CD34(+) v CD34(+)CD38(-) cells). Erythroid progenitors (burst-forming unit-erythroid [BFU-E]) were significantly decreased in frequency among progenitors transduced with the HOXA5 vector (P =.016, n = 7), with no reduction in total CFU numbers. Clonal analysis of single cells transduced with HOXA5 or control vectors (cultured in erythroid culture conditions) showed that HOXA5 expression prevented erythroid differentiation and produced clones with a preponderance of undifferentiated blasts. These studies show that constitutive expression of HOXA5 inhibits human erythropoiesis and promotes myelopoiesis. The reciprocal inhibition of erythropoiesis and promotion of myelopoiesis in the absence of any demonstrable effect on proliferation suggests that HOXA5 diverts differentiation at a mulitpotent progenitor stage away from the erythroid toward the myeloid pathway.

Cells, Cultured↗
PubMed1998

An in vitro model of human red blood cell production from hematopoietic progenitor cells.

Hemoglobinopathies, such as beta-thalassemias and sickle cell anemia (SCA), are among the most common inherited gene defects. Novel models of human erythropoiesis that result in terminally differentiated red blood cells (RBCs) would be able to address the pathophysiological abnormalities in erythrocytes in congenital RBC disorders and to test the potential of reversing these problems by gene therapy. We have developed an in vitro model of production of human RBCs from normal CD34(+) hematopoietic progenitor cells, using recombinant growth factors to promote terminal RBC differentiation. Enucleated RBCs were then isolated to a pure population by flow cytometry in sufficient numbers for physiological studies. Morphologically, the RBCs derived in vitro ranged from early polylobulated forms, resembling normal reticulocytes to smooth biconcave discocytes. The hemoglobin pattern in the in vitro-derived RBCs mimicked the in vivo adult or postnatal pattern of beta-globin production, with negligible gamma-globin synthesis. To test the gene therapy potential using this model, CD34(+) cells were genetically marked with a retroviral vector carrying a cell-surface reporter. Gene transfer into CD34(+) cells followed by erythroid differentiation resulted in expression of the marker gene on the surface of the enucleated RBC progeny. This model of human erythropoiesis will allow studies on pathophysiology of congenital RBC disorders and test effective therapeutic strategies.

Adult↗
PubMed1993

Comparison of buffy coat preparation to direct method for the evaluation and interpretation of bone marrow aspirates.

Bone marrow differential and French, American, British (FAB) classification of buffy coat preparation (BCP) was compared to direct method (DM) in 69 pediatric patients with various hematologic and oncologic disorders. The marrow evaluation differed significantly in 12 of 69 patients (17.4%). The differential counts were discordant in 9 out of 69 patients (13%), and the FAB classifications were discordant in 3 out of 25 patients (12%) with acute lymphoblastic leukemia (ALL). Underestimation of the percent blasts occurred with buffy coat preparation in patients with acute non-lymphoblastic leukemia (ANLL). While buffy coat preparations can facilitate morphologic evaluation in marrow malignancies, significant errors can occur in determination of the differential count. Direct smear should be used in conjunction with buffy coat smears in the evaluation of bone marrow aspirates.

Biopsy, Needle↗
PubMed1988

Comparative evaluation of the bone marrow by the volumetric method, particle smears, and biopsies in pediatric disorders.

Bone marrow cellularity estimated by biopsy was compared to the cellularity of the aspirate particle smear and the volumetric method in two groups of children. In the first group, 101 consecutive bone marrow biopsies and aspirates were evaluated from patients with various diagnoses. In the second group, 20 patients with acute nonlymphoblastic leukemia were studied with 80 biopsies and aspirates at diagnosis and following chemotherapy. A wide discrepancy was noted between bone marrow cellularity confirmed by biopsy vs. the particle smear or the volumetric method in both groups. Neither the volumetric nor the particle method provides a good correlation of bone marrow cellularity. We also compared the volumetric method with that of the biopsy to evaluate the efficacy of the former method in detecting bone marrow infiltration by solid tumors. The volumetric method is an accurate modality of identifying solid tumor infiltration in the bone marrow.

Biopsy↗
PubMed1983

Antithrombin III progressive function: a biochemical analysis.

Antithrombin III (AT III) was isolated by two procedures using polyethylene glycol-400 (PEG) precipitation as the first stage. The PEG supernatant (PEG-sup) was applied to a heparin-affinity chromatographic system and AT III-heparin cofactor (AT III-HCF) was isolated. The PEG precipitate (PEG-ppt) was separated by a Sephacryl S-200 column. Fractions were collected and those demonstrating maximum AT III antigen and progressive thrombin inhibition were pooled and reapplied to the washed Sephacryl S-200 column. Fractions were again collected and assayed via specific antisera for AT III, alpha 1-antitrypsin (alpha 1 AG), alpha 2-macroglobulin (alpha 2 M), and alpha 1-acid glycoprotein (alpha 1 AT). AT III antigen (AT III AGN) and progressive function were confined primarily to one peak containing virtually no alpha 2 M, a low level of alpha 1 AT, and moderate quantities of alpha 1 AG. The PEG-sup, PEG-ppt, AT III-HCF, and the fraction obtained after two passes across Sephacryl S-200 (S#2) were similar in that they showed reactivity with specific AT III antisera and demonstrated heparin cofactor activity. They differed, however, in that the PEG-sup and AT III-HCF demonstrated considerably reduced progressive antithrombin function assessed over 30 min. This function was present in the PEG-ppt and S#2 fractions and this progressive activity was potentiated by EDTA. AT III two-dimensional immunoelectrophoresis (2-DIE) in the presence of heparin of both the Sephacryl and heparin-affinity purified components were very different, with the Sephacryl-purified AT III AGN showing both a fast peak and a very prominent slow-moving hump. The AT III heparin affinity fraction showed primarily a fast component. Dilution of the S#2 and PEG-ppt fractions resulted in considerable loss of the progressive activity and also the slow-moving component on 2-DIE. On the basis of these observations, it is postulated that AT III purified by PEG precipitation is in an aggregated form and that aggregate formation and dissolution is associated with AT III progressive activity.

Antithrombin III↗
PubMed1980

Inhibitory effects of interferon on mouse megakaryocytic progenitor cells in culture.

Mouse bone marrow cells were grown in plasma clots, megakaryocyte formation was stimulated with human urinary erythropoietin (Ep). The expression of megakaryocyte colony forming units (CFUM) and of single megakaryocyte forming units (M) was evaluated after seven days in culture. Usually ten times more M than CFUM were found. Megakaryocytic colony formation showed a linear dependence on cell dose from 0.5 to 2 X 10(5) cells/clot. The colony size frequency distribution exhibited a single peak in the two-cell size class, followed by a continuous decrease, suggesting that cell division may occur asynchronously in cells making up a colony. Mouse L cell interferon (IF) in doses from 10 to 1000 U/ml was included in clots together with Ep. This resulted in a biphasic, dose dependent reduction of colony formation and of single megakaryocyte formation. At all doses tested CFUM were more sensitive to IF than M. These observations are best explained by a differential inhibitory effect of IF on replication of two or more classes of megakaryocytic progenitor cells.

Animals↗
PubMed1975

Functional and metabolic studies of platelets from patients with Lesch-Nyhan syndrome.

Platelet function was investigated in three patients with the Lesch-Nyhan syndrome. Platelet count, morphology and size distribution was normal in all patients. Platelet turnover was normal. Electron microscopy did not reveal any ultrastructural abnormality. Template bleeding times were normal and prolonged after aspirin ingestion in two out of the three patients: the patient that failed to respond to the aspirin challenge also had decreased retention of platelets on a glass bead column. Biochemical studies revealed that total platelet ATP was reduced by 34% in the presence of a normal level of ADP in the storage pool. These platelets failed to incorporate radioactive hypoxanthine but did incorporate radioactive adenine to produce adenine nucleotides and a trace amount of guanine nucleotides. The results indicate that normal platelets have a functionally intact pathway for utilizing hypoxanthine as a source of preformed purine, and that the failure to salvage this purine, as in the Lesch-Nyhan syndrome, results in a decreased level of total platelet ATP. These findings suggest that platelets can function normally despite a one third reduction in total ATP content.

Adenine Phosphoribosyltransferase↗