This report reviews three categories of precursor cells present within adults. The first category of precursor cell, the epiblast-like stem cell, has the potential of forming cells from all three embryonic germ layer lineages, e.g., ectoderm, mesoderm, and endoderm. The second category of precursor cell, the germ layer lineage stem cell, consists of three separate cells. Each of the three cells is committed to form cells limited to a specific embryonic germ layer lineage. Thus the second category consists of germ layer lineage ectodermal stem cells, germ layer lineage mesodermal stem cells, and germ layer lineage endodermal stem cells. The third category of precursor cells, progenitor cells, contains a multitude of cells. These cells are committed to form specific cell and tissue types and are the immediate precursors to the differentiated cells and tissues of the adult. The three categories of precursor cells can be readily isolated from adult tissues. They can be distinguished from each other based on their size, growth in cell culture, expressed genes, cell surface markers, and potential for differentiation. This report also discusses new findings. These findings include the karyotypic analysis of germ layer lineage stem cells; the appearance of dopaminergic neurons after implantation of naive adult pluripotent stem cells into a 6-hydroxydopamine-lesioned Parkinson's model; and the use of adult stem cells as transport mechanisms for exogenous genetic material. We conclude by discussing the potential roles of adult-derived precursor cells as building blocks for tissue repair and as delivery vehicles for molecular medicine.

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The purpose of this study was to evaluate the patentcy rates and physiological effectiveness of angioplasty and stenting as a primary therapy for superficial femoral (SFA), popliteal (POP), and tibial (TIB) arterial occlusive disease. Seventy-eight patients had stents placed in the infra-inguinal vessels between January 1, 2001, and July 31, 2004. We collected data on patient demographics, symptoms, as well as pre- and postprocedure ankle-brachial index (ABI) and angio-graphic findings. Patency rates at 6 months, 12 months, and 24 months were analyzed by life table methods. Thirty-one men and 47 women had a mean age of 68 years (range 36–94 years). Risk factors included diabetes in 50 per cent, hypertension in 79 per cent, smoking in 41 per cent, and end-stage renal disease in 10 per cent. The indications for intervention were claudication in 52 per cent and limb salvage in 48 per cent of patients. Stents were placed in the SFA in 54 patients (69%), in the POP in 15 patients (18%), and in the TIB artery in 6 patients (8%). Average follow-up was 11.2 months. The mean postprocedural increase in ABI was 0.29. The 6-month, 1-year, and 2-year primary patency rates were 83 per cent, 58 per cent, and 47 per cent, respectively. Limb salvage was achieved in 66 per cent of patients treated for limb-threatening ischemia. There was one major and three minor complications. Stenting of the infra-inguinal vessels has a low morbidity, high success rate, and acceptable patency and limb-salvage rates.