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Leif Carlsson

Publications and source records attributed to Leif Carlsson.

23 records · Page 2Linked to original sources
PubMed2003

Block of HERG-carried K+ currents by the new repolarization delaying agent H 345/52.

INTRODUCTION: The aim of this study was to analyze the block of HERG-carried membrane currents caused by H 345/52, a new antiarrhythmic compound with low proarrhythmic activity, in transfected mouse fibroblasts. METHODS AND RESULTS: Using the whole-cell configuration of the voltage patch clamp technique, it was demonstrated that H 345/52 concentration-dependently blocked HERG-carried currents with an IC50 of 230 nM. H 345/52 preferentially bound to the open channel with unusually rapid kinetics and was trapped by channel closure. Voltage-independent behavior of H 345/52 was observed during both square-pulse and action potential clamp protocols. In contrast, the Class III agents dofetilide (10 nM) and almokalant (250 nM) demonstrated significant membrane potential-dependent effects during square-pulse clamp protocols. When using action potential clamp protocols, voltage dependence was seen with dofetilide but not with almokalant. Mathematical simulations of human ventricular action potentials predicted that the different voltage-dependent behaviors would not produce marked variations in action potential duration prolongation patterns. CONCLUSION: We propose that block of IKr is the principal mechanism by which H 345/52 delays repolarization in human myocardium. The voltage independence of HERG/IKr block is unlikely to underlie the low proarrhythmic potential, and ancillary effects on other membrane currents must be considered.

Action Potentials↗
PubMed2003

Lhx2 expression in hematopoietic progenitor/stem cells in vivo causes a chronic myeloproliferative disorder and altered globin expression.

BACKGROUND AND OBJECTIVES: Chronic myeloproliferative disorders (CMDs) are thought to be due to mutation(s) in a single clone at the level of the hematopoietic stem cell (HSC). Such mutations and additional mutations causing progression of the disease are largely unknown. Chronic myeloid leukemia (CML) is a CMD characterized by a chromosomal translocation between chromosomes 9 and 22 creating the fusion protein BCR-ABL. This translocation has also been suggested to cause mis-expression of the LIM-homeobox gene Lhx2 in hematopoietic cells. We have previously shown that Lhx2 expression in mouse HSC generates cytokine-dependent stem cell-like cell lines that can produce long-term repopulation in stem cell-deficient mice. DESIGN AND METHODS: Since the consequences of Lhx2 expression in hematopoietic cells in vivo were unknown, mice engrafted with the stem cell-like cell lines were analyzed in detail for any pathologic changes. RESULTS: Expression of Lhx2 was maintained in vivo and most engrafted mice developed a myeloproliferative disorder characterized by splenomegaly, extramedullary hematopoiesis and anemia. The disorder was transplantable and the Lhx2-expressing cells could also cause acute leukemia. The anemia was due to both a reduced number of circulating erythrocytes and a reduced mean corpuscular hemoglobin concentration (MCHC). INTERPRETATION AND CONCLUSIONS: These observations suggest that constitutive expression of Lhx2 in hematopoietic cells causes CMD, and also that a novel cell-autonomous mechanism can contribute to anemia.

Anemia↗
PubMed2002

Runx1 is essential for hematopoietic commitment at the hemangioblast stage of development in vitro.

In this report we demonstrate a role for Runx1 (AML1) at the hemangioblast stage of hematopoietic and endothelial development in embryonic stem (ES) cell-derived embryoid bodies (EBs). Runx1 is expressed in EBs during the appearance of precursors with hemangioblast properties, the blast colony-forming cells (BL-CFCs). Cell sorting studies revealed that all BL-CFCs within EBs express Runx1. Runx1-deficient EBs consistently generate 10- to 20-fold fewer blast colonies than wild-type controls and display a complete block in definitive hematopoiesis. Despite this defect, Runx1-/- EBs and yolk sacs from mutant embryos generate normal numbers of primitive erythroid precursors. These observations clearly demonstrate that Runx1 functions early in hematopoietic development, and they support the interpretation that the primitive erythroid lineage is established early by a subset of BL-CFCs that develop in a Runx1-independent fashion.

Animals↗
PubMed2002

Hematopoietic progenitor/stem cells immortalized by Lhx2 generate functional hematopoietic cells in vivo.

Hematopoietic stem cells (HSCs) are unique in their capacity to maintain blood formation following transplantation into immunocompromised hosts. Expansion of HSCs in vitro is therefore important for many clinical applications but has met with limited success because the mechanisms regulating the self-renewal process are poorly defined. We have previously shown that expression of the LIM-homeobox gene Lhx2 in hematopoietic progenitor cells derived from embryonic stem cells differentiated in vitro generates immortalized multipotent hematopoietic progenitor cell lines. However, HSCs of early embryonic origin, including those derived from differentiated embryonic stem cells, are inefficient in engrafting adult recipients upon transplantation. To address whether Lhx2 can immortalize hematopoietic progenitor/stem cells that can engraft adult recipients, we expressed Lhx2 in hematopoietic progenitor/stem cells derived from adult bone marrow. This approach allowed for the generation of immortalized growth factor-dependent hematopoietic progenitor/stem cell lines that can generate erythroid, myeloid, and lymphoid cells upon transplantation into lethally irradiated mice. When transplanted into stem cell-deficient mice, these cell lines can generate a significant proportion of circulating erythrocytes in primary, secondary, and tertiary recipients for at least 18 months. Thus, Lhx2 immortalizes multipotent hematopoietic progenitor/stem cells that can generate functional progeny following transplantation into lethally irradiated hosts and can long-term repopulate stem cell-deficient hosts.

Animals↗