Biomedical subjects

David A Schroeder

Publications and source records attributed to David A Schroeder.

4 recordsLinked to original sources

PubMed2006

Myeloid lineage progenitors give rise to vascular endothelium.

Despite an important role in vascular development and repair, the origin of endothelial progenitors remains unknown. Accumulating evidence indicates that cells derived from the hematopoietic system participate in angiogenesis. However, the identity and functional role of these cells remain controversial. Here we show that vascular endothelial cells can differentiate from common myeloid progenitors and granulocyte/macrophage progenitors. Endothelial cells derived from transplanted bone marrow-derived myeloid lineage progenitors expressed CD31, von Willebrand factor, and Tie2 but did not express the hematopoietic markers CD45 and F4/80 or the pericyte markers desmin and smooth muscle actin. Lineage tracing analysis in combination with a Tie2-driven Cre/lox reporter system revealed that, in contrast to bone marrow-derived hepatocytes, bone marrow-derived endothelial cells are not the products of cell fusion. The establishment of both hematopoietic and endothelial cell chimerism after parabiosis demonstrates that circulating cells can give rise to vascular endothelium in the absence of acute radiation injury. Our findings indicate that endothelial cells are an intrinsic component of myeloid lineage differentiation and underscore the close functional relationship between the hematopoietic and vascular systems.

Animals↗

PubMed2005

Prosocial behavior: multilevel perspectives.

Current research on prosocial behavior covers a broad and diverse range of phenomena. We argue that this large research literature can be best organized and understood from a multilevel perspective. We identify three levels of analysis of prosocial behavior: (a) the "meso" level--the study of helper-recipient dyads in the context of a specific situation; (b) the micro level--the study of the origins of prosocial tendencies and the sources of variation in these tendencies; and (c) the macro level--the study of prosocial actions that occur within the context of groups and large organizations. We present research at each level and discuss similarities and differences across levels. Finally, we consider ways in which theory and research at these three levels of analysis might be combined in future intra- and interdisciplinary research on prosocial behavior.

Altruism↗

PubMed2003

Transplanted adult hematopoietic stems cells differentiate into functional endothelial cells.

During early embryogenesis, blood vessels and hematopoietic cells arise from a common precursor cell, the hemangioblast. Recent studies have identified endothelial progenitor cells in the peripheral blood, and there is accumulating evidence that a subset of these cells is derived from precursors in the bone marrow. Here we show that adult bone marrow-derived, phenotypically defined hematopoietic stem cells (c-kit+, Sca-1+, lineage-) give rise to functional endothelial cells. With the exception of the brain, donor-derived cells are rapidly integrated into blood vessels. Durably engrafted endothelial cells express CD31, produce von Willebrand factor, and take up low-density lipoprotein. Analysis of DNA content indicates that donor-derived endothelial cells are not the products of cell fusion. Self-renewal of stem cells with hematopoietic and endothelial cell potential was revealed by serial transplantation studies. The clonal origin of both hematopoietic and endothelial cell outcomes was established by the transfer of a single cell. These results suggest that adult bone marrow-derived hematopoietic stem cells may serve as a reservoir for endothelial cell progenitors.

Animals↗

PubMed2003

Justice within social dilemmas.

The defining feature of social dilemma situations is the inherent conflict faced by those involved: should one act in his or her own individual best interest or sacrifice a measure of one's personal payoff to help maximize the joint payoff of the group as a whole? In such dilemmas, those making individualistic and defecting choices are always at a competitive advantage relative to those who choose to cooperate. One seemingly inevitable consequence of the resulting resource allocation asymmetry is that it must challenge and threaten the cooperator's sense of fairness and justice, and it is the reaction of those caught in social dilemmas to this injustice and unfairness that is the focus of this article. We examine how justice processes-distributive justice, procedural justice, restorative justice, and retributive justice-operate in social dilemmas. Within this examination, we consider ideas from classic and contemporary conceptual analyses of justice to provide a broader context within which to understand social dilemmas and the roles that justice plays as people strive to ensure fair outcomes for themselves and for others. We conclude with the proposal of a 4-stage, sequential model of justice in social dilemmas that posits groups move between the types of justice concerns when unfair and unsatisfactory outcomes (e.g., inequitable resource allocations, violations of agreed-on allocation rules, intentional and egregious exploitation of the group) cause members to "recognize the necessity" for change to ensure fair and just outcomes for all.

Conflict, Psychological↗