Moreover as a unique characterization tool, tuning the occupation energy of the quantum dot allows controlled groundstate parity changes in the ring, enabling a toggling between Φ0 and 2Φ0 periodicity.
To directly address the issue of whether parity changed the proportion of cells in the mammary epithelium with stem/progenitor cell capacity, a series of limiting dilution transplant experiments was carried out comparing the ability of cells isolated from parous animals and AMV animals to repopulate a cleared mouse mammary fat pad.
To determine whether parity might change the CD24 Sca-1 CD49flowow cytometry profile of mammary cells and, in particular, whether changes might occur to the CD24+/Low Sca-1 CD49fHigh stem-cell-enriched population, mammary cell preparations from parous and AMV animals were stained for expression of these markers and were analysed by flow cytometry.
Despite the small size of the analyzed region (270 nt), missense changes are more likely to be detected in the E reading frame than silent changes (at least significantly at time points 1 and 3; table 5), whereas parity of changes seems the rule within the D reading frame (table 5).
These early parity-induced changes of gene expression and dynamics of mammary stem/progenitor cells were caused primarily by a decrease in the proportion of hormone-sensitive and Wnt4-secreting luminal epithelial cells [ 6, 7].
Additional studies are underway to compare gene expression patterns in mammary tissues from parous and nulliparous mice, rats, and women with parity-induced changes in gene expression that are evolutionarily conserved.
The protective effect of an early full-term pregnancy is a well established phenomenon; in contrast, the molecular and cell-specific mechanisms that govern parity-specific changes in the mammary gland have not been well described.
To evaluate the mouse as a suitable model for these parity-related changes, Sivaraman and coworkers [ 17] repeated their experiments using BALB/c mice, and were able to recapitulate their findings from the E+P-treated Wistar Furth rat.
Furthermore, numerous parity-induced changes in gene expression have been identified in genome-wide expression profiles of entire lobular breast tissues of women or entire mammary glands of rats and mice [ 8- 10].
