Fig. 2. Morphology of the mammary gland and transgenic expression. Mammary glands from transgenic mice (A-I) and wild-type littermates (A'-I') isolated at day 10 (A,A',D,D'), day 13 (B,B',E,E') and day 16 of pregnancy (C,C',F,F'), and day 1 of lactation (G-I,G'-I') from lines WBK6414 and WBK6426. Haematoxylin and eosin staining of tissue sections (A-C,A'-C', G,H,G'H') and whole-mount haematoxylin staining (I,I') revealed reduced lobuloalveolar development of the mammary glands of transgenic mice compared with wild-type littermates. Immunohistochemistry using an antibody against the myc epitope tag in the transgene construct (antibody signal shown in black) (D-F, D'-F') reveals transgene expression at 10P (D, arrows) and 12P (E, arrows), but not at 16P (F). Note fragmented, apoptotic cells associated with transgene expression at 12P (E, arrows). Nontransgenic littermates (D'-F') show no specific antibody signal, and arrows in E' illustrate nonspecific antibody trapping in blood vessels. Bars, 25 µm (D-F,D'-F'); 100 µm (A-C,A'-C',H,H'); 500 µm (G,G',I,I').

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