Figure 1

Morphological changes of the tympanic membrane and inflammatory cell infiltration in mouse AOM. Visualization of the tympanic membrane was performed on normal animal and days 1, 2, 3, 7, and 14 post-injection, and photographs were taken at the time of sacrifice under a rigid 4-mm diameter, 0°-angled endoscope. (a–f) Tympanic membranes in PBS injected ears as the control group. (b) Tympanic membrane thickening was only seen on day 1.Then returned to transparency more quickly and the perforation had healed by days 3–5 (c,d). With no congestion or oedema seen in control group. (g–l) Tympanic membranes in Streptococcus pneumoniae (10⁹cfu/ml, 5 μl) injected ears. (h) Tympanic membranes started thickening on day 1. The changes in the tympanic membranes peaked at days 3 and 5 (i,j). White arrows showed expanded blood vessels. (k) All of the pathologic changes began to return to normal starting from day 7. (l) On day 14, the membranes were back to normal; in some of them, scars and small calcifications were visible. (m–r) H&E staining of the bullaes after Streptococcus pneumoniae caused mouse AOM. Inflammatory cells were observed to have accumulated in the middle ear cavity on days 1, 3, and 5 (n,o,p), particularly on day 1. Asterisks show the infiltrated cells. ET, Eustachian tube; MEC, middle ear cavity.