Experiment 1: Pregnancy Series
The relative abundance of LIF mRNA, normalized to cyclophilin, increased significantly (p = 0.002) at the time of early embryo activation compared to that during diapause (Fig. 1A). The increase in uterine LIF mRNA concentration coincided with a significant increase in weight of the paired uterine cornua (p < 0.001) from animals with blastocysts 1.2-1.6 mm in diameter (onset of early blastocyst activation, Fig. 1B). Uterine concentration of LIF mRNA remained elevated approximately twofold throughout the period of renewed embryonic development.
No cell-specific autoradiographic signals for LIF mRNA were detected in uteri of animals containing blastocysts in diapause (Fig. 2, a and b). LIF mRNA was first detectable in the glandular epithelium of uteri that contained early activated blastocysts (Fig. 2, c and d). During the final stage of blastocyst activation, LIF mRNA was also localized to the luminal epithelium of the uterus (data not shown). The intensity of the signal in the uterine glands remained relatively strong in both early (24-72 h) postattachment stage specimens examined. LIF mRNA was never localized in the myometrium. No positive signals were detected in uterine sections at any stage of pregnancy when hybridized with sense probe. buy ventolin inhalers
FIG. 1. A) Relative abundance of LIF mRNA normalized to cyclophilin (mean ± SEM) in the uterus of the spotted skunk during embryonic diapause (Delay) and early embryo activation (Early Activated), and in uteri containing fully activated blastocysts (Activated). The number of animals in each group is given in parentheses. Means denoted by different letters significantly differ from each other (p < 0.05). B) Weight of paired skunk uterine cornua (mean ± SEM) collected during the period of embryonic diapause (Delay) and early embryo activation (Early Activated), and cornua containing fully activated blastocysts (Activated). The number of animals in each group is in parentheses. Means denoted by different letters significantly differ from each other (p < 0.05).
FIG. 2. Hematoxylin- and eosin-stained section of skunk uterus that contained delayed implanting blastocysts (a). Adjacent section of the same uterus incubated with LIF antisense probe showing absence of specific autoradiographic signals at this stage of pregnancy (b). Section of skunk endometrium stained with hematoxylin and eosin. Early activated blastocysts (1.5-1.6 mm) were flushed from this uterus (c). Adjacent section of the same uterus incubated with LIF antisense probe. Note the intense localization of the probe over the uterine glands at this time (d). Bar = 100 ^m.