Even though the first description concerning the deportation of trophoblast cells into the maternal periphery was made by Schmorl at the turn of the 19th century, it was only in the late 20th century that the tools were developed, which permitted the enrichment of rare circulatory fetal cells (frequencies as low as 1 x 107 nucleated maternal cells). The main proponents were fluorescence-activated cell sorting (FACS) and magnetic cell sorting (MACS). Common consensus indicated that the target fetal cell of choice was the fetal erythroblast, also termed nucleated red blood cell (NRBC) because of the high prevalence of this cell in the fetal circulation (up to 50% of all nucleated fetal cells), its expression of potentially fetal-specific molecules (fetal and embryonic hemoglobin chains), and its short life span, which excluded cells from previous pregnancies from being analyzed.[1'2]
Further innovations that accelerated the pace of research in this field were the developments of fluores cent in situ hybridization (FISH) and polymerase chain reaction (PCR), both of which permit genetic analysis of individual cells. By use of these technologies, proof-of-principle studies demonstrated that fetal aneuploidies as well as single-gene Mendelian disorders, such as hemo-globinopathies, could be determined from the analysis of enriched circulatory fetal erythroblasts.[1'2]
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.