To evaluate the stage of the estrous cycle by visual observation, each mouse was held by the tail with the forepaws resting on a cage lid. The vaginal opening of each female was evaluated based on the criteria described by Champlin, et al. A digital image of each mouse was taken using a DSCF707 Cyber-shot digital camera (Sony, Japan). Additional lighting was supplied for photographs by fiber optic lights (Fiber Lite MI-150, Dolan-Jenner Industries, Boxborough, MA).
When evaluating stage of the estrous cycle using the visual method, it is important to always evaluate animals in the same area with respect to room lighting. The table or workstation should always face the same direction and there should be sufficient light available. The light source is also important to consider because it can change the perceived color of vaginal tissues and make evaluation difficult. Portable lights can be purchased and attached to workstations and moved as needed. However, LED lights should be avoided because they have a purple hue that makes visual detection challenging. Battery operated 4W fluorescent lamps (Maverick, Edison, NJ) were used in the vivarium for this study. In the laboratory, 32W Sylvania Octron fluorescent ceiling lights (Sylvania, Danvers, MA) were used for lighting.
The vaginal opening of mice in proestrus is characterized by swollen, moist, pink tissue. The opening is wide and there are often wrinkles or striations along the dorsal and ventral edges. As the mouse enters estrus the vaginal opening becomes less pink, less moist, and less swollen. Metestrus is characterized by a vaginal opening that is not open wide, not swollen, and white cellular debris may be visible. In diestrus, the vaginal opening is small and closed with no tissue swelling.
When evaluating stage of the estrous cycle using the visual method, it is important to always evaluate animals in the same area with respect to room lighting. The table or workstation should always face the same direction and there should be sufficient light available. The light source is also important to consider because it can change the perceived color of vaginal tissues and make evaluation difficult. Portable lights can be purchased and attached to workstations and moved as needed. However, LED lights should be avoided because they have a purple hue that makes visual detection challenging. Battery operated 4W fluorescent lamps (Maverick, Edison, NJ) were used in the vivarium for this study. In the laboratory, 32W Sylvania Octron fluorescent ceiling lights (Sylvania, Danvers, MA) were used for lighting.
The vaginal opening of mice in proestrus is characterized by swollen, moist, pink tissue. The opening is wide and there are often wrinkles or striations along the dorsal and ventral edges. As the mouse enters estrus the vaginal opening becomes less pink, less moist, and less swollen. Metestrus is characterized by a vaginal opening that is not open wide, not swollen, and white cellular debris may be visible. In diestrus, the vaginal opening is small and closed with no tissue swelling.
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