Controversy over whether pancreatic islet cells arise from adult stem or progenitor-like cells actually predates the discovery of insulin, and the recent use of islet transplantation to treat diabetes has only intensified interest in this question. Recent breakthroughs, particularly those based on Cre-loxP lineage-tracing in the mouse, have resolved some aspects of this controversy, but not all. We now know that insulin-producing Î²-cells and other islet cells derive from multipotent progenitors in the embryo, but that their maintenance and expansion in postnatal life is driven primarily by proliferation of existing differentiated cells. This appears to be true even during regeneration, and seems to apply to the exocrine acinar cells as well as islets. High-impact journals are those considered to be highly influential in their respective fields. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information.
Last date updated on July, 2014