Fig. 5

Estrus cycle stage and surface infrared thermography (IRT). Crystal violet stain of vaginal smears for proestrus, estrus, diestrus, and metestrus cycle stages (labeled P, E, D, M respectively in the figure) are shown in (A). IRT image of a mouse using a vanadium oxide microbolometer infrared sensor thermal imaging camera is shown in (B). Thermal images displayed three temperatures: the highest temperature which imaged the periorbital/head region (red: 33.8°C), the lowest temperature which was of the cage lid (green), and the temperature at the central point of the image (white). Surface temperature of water from a mercury thermometer corresponds with temperature detected using IRT across a wide range of temperatures, (C). IRT temperature for n = 4 animals taken across the estrus cycle stage demonstrates the lowest temperature during diestrus and metestrus, (D). The cumulative distribution of temperatures for animals in proestrus-estrus (PE, filled circles) and metestrus-diestrus (open circles) shows a right shift in temperatures for animals in PE cycle stage, (E). Median temperature during PE (34.1°C, n = 13) was significantly higher than during MD (32.7°C, n = 9, *p = 0.017, Mann Whitney U), (F)