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. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.
Germ cells are the only type of cell that can transmit all genomic information to the next generation. Such cells have unique characteristics, being not only germline-competent but also serving as stem cells. In Caenorhabditis elegans and Drosophila, germ cell lineages are predetermined. In contrast, in mammals, primordial germ cells, which are precursors of germ cells, are induced from multipotentepiblasts via extra-embryonic signaling. In avian species, however, the means by which germ cells are defined remain to be elucidated. Manipulation of germ cells is valuable in studies on germline development and in production of valuable cell lines. In birds, which lack germline-competent stem cells, genomic modulation of germ cells might serve to generate genetically modified poultry for both commercial applications and basic research. (Tae Sub Park, HyungChul Lee, DeivendranRengaraj and Jae Yong Han, Germ Cell, Stem Cell, and Genomic Modification in Birds)
Last date updated on September, 2014