Representative photographs and micrographs for each stage of the estrous cycle were obtained following these steps: 1. a preliminary observation was made about the stage of the estrous cycle by assessing the vaginal opening of each mouse, 2. the stage of the estrous cycle was verified by vaginal cytology, 3. stage of estrous cycle was confirmed by mating mice overnight and checking for ovulation the following morning as described later.
These steps can also be used to learn the visual method and train the eye to identify each stage. Proestrus and estrus are easier to identify by visual observation than metestrus and diestrus. Coat color and skin pigmentation can make it more challenging to evaluate some strains. It is easier to observe changes in agouti and albino strains than in black strains where changes to the vaginal opening are more subtle.
These steps can also be used to learn the visual method and train the eye to identify each stage. Proestrus and estrus are easier to identify by visual observation than metestrus and diestrus. Coat color and skin pigmentation can make it more challenging to evaluate some strains. It is easier to observe changes in agouti and albino strains than in black strains where changes to the vaginal opening are more subtle.
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