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© 2016 Elsevier Ireland Ltd Background Side-population (SP) cells, identified by their capacity to efflux Hoechst dye, are highly enriched for stem/progenitor cell activity. They are found in many mammalian tissues, including mouse heart. Studies suggest that cardiac SP (CSP) cells can be divided into SCA1+/CD31−, SCA1+/CD31+and SCA1−/CD31−CSP subpopulations. SCA1+/CD31−were shown to be cardiac and endothelial stem/progenitors while SCA1+/CD31+CSP cells are endothelial progenitors. SCA1−/CD31−CSP cells remain to be fully characterized. In this study, we characterized SCA1−/CD31−CSP cells in the adult mouse heart, and investigated their abilities to proliferate, differentiate and migrate in vitro and in vivo. Methods and results Using fluorescence-activated cell sorting, reverse transcriptase/polymerase chain reaction, assays of cell proliferation, differentiation and migration, and a murine model of myocardial infarction we show that SCA1−/CD31−CSP cells are located in the heart mesenchyme and express genes characteristic of stem cells and endothelial progenitors. These cells were capable of proliferation, differentiation, migration and vascularization in vitro and in vivo. Following experimental myocardial infarction, the SCA1−/CD31−CSP cells migrated from non-infarcted areas to the infarcted region within the myocardium where they differentiated into endothelial cells forming vascular (tube-like) structures. We further demonstrated that the SDF-1α/CXCR4 pathway may play an important role in migration of these cells after myocardial infarction. Conclusions Based on their gene expression profile, localization and ability to proliferate, differentiate, migrate and vascularize in vitro and in vivo, we conclude that SCA1−/CD31−CSP cells may serve as endothelial progenitor cells in the adult mouse heart.

Are subjects sensitive to the frequency of parts of the same whole in the same way that they are sensitive to instances of the same category? Subjects read a randomised list of words and then estimated how many words on the list had belonged to particular groups, e.g. parts of a bird, or kinds of bird. Groups of words were either parts of the same whole, e.g. feathers, beak, wing, or members of the same category, e.g. robin, sparrow, eagle. Subjects were asked, either, "How many parts of a (bird) did you see?" or "How many kinds of (bird) did you see?". Half of the subjects expected the frequency estimation task, whereas for the other half, who performed a distractor task during encoding, the task was unexpected. In Experiment 1 subjects saw either parts of kinds. Sensitivity to frequency did not differ for parts and kinds nor as a function of whether the frequency estimation test was expected. In Experiment 2 subjects saw both parts and kinds belonging to the same superordinates, e.g. parts of birds and kinds of birds, and were asked to estimate the frequency of both types of groupings for each superordinate. The results were the same as in Experiment 1. In addition, subjects were able to separate the frequency of parts and kinds of the same superordinate. The results suggest that, in frequency estimation, part-of and kind-of associations can function similarly, and that the mechanism responsible for frequency estimation is sensitive to the type of association.

This study investigated the possibility that systematic differences exist between the perceptions resulting from the use of two different heptic modes to know the same object. In each of three experiments 24 male and female college students chose visual comparison stimuli to match the length of haptically presented standard stimuli. In each experiment significantly smaller visual matches were made when the length of the haptic standard was perceived by holding it between the thumb and index finger than when the haptic standard was perceived by stroking it from end to end with the index finger. Experiment 1 established a significant difference (p less than .05) using a horizontal visual comparison. Experiment 2 replicated this effect (p less than .001) using vertical visual comparisons. Experiment 3 again replicated the effect (p less than .001) with visual comparisons and ruled out the possibility that the effect was due to the orientation of the haptic stimuli.