During mouse mammary gland development we observed that many let-7 family members showed a peak in expression during puberty, the mature virgin stage, and early gestation, followed by a marked decrease and low levels during lactation and involution.
miR-205 (cluster 3) was strongly expressed in the basal epithelium until the mature virgin stage, showing increased expression in both luminal and basal epithelium during pregnancy and in late involution.
We found that expression of MUC1-CD in luminal epithelial cells of the mammary gland induced a mammary hyperplasia phenotype characterized by hyperbranching in the transgenic mice at prepuberty and early virgin stages.
Two miRNAs, namely let-7b and miR-205, showed specificity for the luminal and basal epithelial cell layers, respectively, during juvenile, puberty, and mature virgin stages.
For each of 23 inbred strains of P. pacificus, 20 virgin, J4 stage hermaphrodites were placed on several 100-mm plates seeded with E. coli OP50.
In all stages of MG development, no macroscopic (whole-mounts) or microscopic (HE and IHC stainings) morphological changes were observed in the MMTV-cortactin mice compared to the WT mice (Fig. 2B for L10, Fig. 4A for virgin, other stages data not shown).
By that stage, Virgin's slow coaches will be approaching Birmingham – having called at three stations already, with a dozen more to go.
Female Sprague Dawley (SD) rats (virgin and late stage pregnancy [GD 19]) were exposed to nano-TiO aerosols (173.2 ± 6.4 nm, 10.2 ± 0.46 mg/m3, 5 h) 24-h prior to experimentation leading to a single calculated deposition of 42.2 ± 1.9 μg nano- TiO2 (exposed) or 0 μg (control).
To determine the percentage of embryonic mortality, 10 J4 stage virgin hermaphrodites of each strain were transferred to single plates.
The embryo mortality was calculated by dividing the number of hatched worms by the number of eggs, and subtracting this ratio from 1. Male mating ability was assayed by placing three males along with one J4 stage virgin hermaphrodite in a 1.5 cm E. coli OP50 lawn on an agar plate.
Quantitative analysis indicated that statistically significant differences were found for the number of BrdU-positive cells between MUC1-CD transgenic mice and wild-type littermates at all three stages (virgin 8 week: 3.3±1.1% versus 1.4±0.4%, P = 0.045; 8.5 days pregnant: 7.7±0.3% versus 5.5±0.6%, P = 0.006; 13.5 days pregnant: 9.8±0.4% versus 7.4±0.6%, P = 0.005) (Fig. 4B).
