The Consequential Validity of Student Ratings: What do Instructors Really Think?

This study investigates instructors’ perceptions about strengths and weaknesses of a student ratings instrument employed in their university. The sample consisted of 357 instructors in a major Canadian university where each term students are required to complete an evaluation at the end of every course. Qualitative analyses of their written responses indicate that most instructors held negative views about the ratings instrument, administration procedures, and use of results. They also reported concerns about biasing factors and the negative effect that ratings have on instructors. Few instructors provided positive comments about the validity of the ratings, the utility of ratings for the user groups, accountability, student representation, and cost efficient administration procedures. Moreover, only 25% considered ratings useful for improving teaching effectiveness

Aberrant α-Adrenergic Hypertrophic Response in Cardiomyocytes from Human Induced Pluripotent Cells

Cardiomyocytes from human embryonic stem cells (hESC-CMs) and induced pluripotent stem cells (hiPSC-CMs) represent new models for drug discovery. Although hypertrophy is a high-priority target, we found that hiPSC-CMs were systematically unresponsive to hypertrophic signals such as the α-adrenoceptor (αAR) agonist phenylephrine (PE) compared to hESC-CMs. We investigated signaling at multiple levels to understand the underlying mechanism of this differential responsiveness. The expression of the normal α1AR gene, ADRA1A, was reversibly silenced during differentiation, accompanied by ADRA1B upregulation in either cell type. ADRA1B signaling was intact in hESC-CMs, but not in hiPSC-CMs. We observed an increased tonic activity of inhibitory kinase pathways in hiPSC-CMs, and inhibition of antihypertrophic kinases revealed hypertrophic increases. There is tonic suppression of cell growth in hiPSC-CMs, but not hESC-CMs, limiting their use in investigation of hypertrophic signaling. These data raise questions regarding the hiPSC-CM as a valid model for certain aspects of cardiac disease. In this article, Fo¨ldes and colleagues show that hiPSC-derived cardiomyocytes are relatively unresponsive to α-adrenergic hypertrophic signals compared to hESC cardiomyocytes. The main difference in hiPSC-CMs that accounts for the defective response is the suppression of growth by tonic antihypertrophic pathways. Superficial similarities in phenotype between cardiomyocytes derived from hESCs or hiPSCs may mask complex differences in signaling

Cardiac mesenchymal stem cells promote fibrosis and remodeling in heart failure: Role of PDGF signaling

Heart failure (HF) is characterized by progressive fibrosis. Both fibroblasts and mesenchymal stem cells (MSCs) can differentiate into pro-fibrotic myofibroblasts. MSCs secrete and express platelet-derived growth factor (PDGF) and its receptors. We hypothesized that PDGF signaling in cardiac MSCs (cMSCs) promotes their myofibroblast differentiation and aggravates post-myocardial infarction left ventricular remodeling and fibrosis. We show that cMSCs from failing hearts post-myocardial infarction exhibit an altered phenotype. Inhibition of PDGF signaling in vitro inhibited cMSC-myofibroblast differentiation, whereas in vivo inhibition during established ischemic HF alleviated left ventricular remodeling and function, and decreased myocardial fibrosis, hypertrophy, and inflammation. Modulating cMSC PDGF receptor expression may thus represent a novel approach to limit pathologic cardiac fibrosis in HF

Evidence for the Involvement of Sphingosine-1-Phosphate in the Homing and Engraftment of Hematopoietic Stem Cells to Bone Marrow

The α-chemokine stromal-derived factor 1 (SDF-1), which binds to the CXCR4 receptor, directs migration and homing of CXCR4+ hematopoietic stem/progenitor cells (HSPCs) to bone marrow (BM) stem cell niches. Nevertheless, it is also known that CXCR4-/- fetal liver-derived hematopoietic stem cells engraft into BM and that blockade of CXCR4 by its antagonist AMD3100 does not prevent engraftment of HSPCs. Because of this finding of SDF-1-CXCR4-independent BM homing, the unique role of SDF-1 in HSPC homing has recently been challenged. While SDF-1 is the only chemokine that chemoattracts HSPCs, other chemoattractants for these cells have recently been described, including the bioactive phosphosphingolipid sphingosine-1-phosphate (S1P). To address the potential role of S1P in homing of HSPCs to BM, we performed hematopoietic transplants into mice deficient in BM-expressed sphingosine kinase 1 (Sphk1-/-) using hematopoietic cells from normal control mice as well as cells from mice in which floxed CXCR4 (CXCR4fl/fl) was conditionally deleted. We observed the presence of a homing and engraftment defect in HSPCs of Sphk1-/- mice that was particularly profound after transplantation of CXCR4-/- BM cells. Thus, our results indicate that BM-microenvironment-expressed S1P plays a role in homing of HSPCs. They also support the concept that, in addition to the SDF-1-CXCR4 axis, other chemotactic axes are also involved in homing and engraftment of HSPCs

Cardiomyocyte-restricted overexpression of extracellular superoxide dismutase increases nitric oxide bioavailability and reduces infarct size after ischemia/reperfusion

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