Читать книгу Pathology of Genetically Engineered and Other Mutant Mice - Группа авторов - Страница 83

Stages of mouse development are defined in terms of major events in four dimensions: length, width, breadth, and time (Figure 5.1). Specific stages typically are assigned using the Theiler staging (TS) system based on visible anatomic landmarks [11, 15, 29, 31, 32]. Timing for each event varies by up to 12 hours among strains with different genetic backgrounds [33, 34]. Furthermore, the developmental stages in any litter differ by between 10 to 24 hours for the oldest and youngest embryos (Figure 5.2) [2, 11, 33]. Accordingly, developmental stage is not equal to developmental age for prenatal mice. In utero age is assigned as either “days post coitum” (dpc) or as “gestational day” (GD, often referred to as “embryonic day” [E]). When using the GD (or E) timing convention, it is imperative that investigators note whether the day of conception is counted as GD0 or GD1 since this choice will dramatically impact the times assigned to developmental landmarks. The convention used in this chapteris that the presence of a vaginal plug is designated as 0 dpc (or GD0).