Mouse middle ear ion homeostasis channels and intercellular junctions.

Hypothesis: The middle ear contains homeostatic mechanisms that control the movement of ions and fluids similar to those present in the inner ear, and are altered during inflammation.

Background: The normal middle ear cavity is fluid-free and air-filled to allow for effective sound transmission. Within the inner ear, the regulation of fluid and ion movement is essential for normal auditory and vestibular function.

Steroid control of acute middle ear inflammation in a mouse model.

Objective: To investigate steroids for their potential for therapeutic approaches to control otitis media. Glucocorticoids and mineralocorticoids have differential effects on inflammation and fluid absorption, but little is known of their control of middle and inner ear manifestations of acute otitis media.

Design: Both glucocorticoid (prednisolone and dexamethasone) and mineralocorticoid (aldosterone and fludrocortisone) steroids were investigated for their ability to reduce inflammatory symptoms in a mouse otitis media model.

Gram-negative pathogen Klebsiella oxytoca is associated with spontaneous chronic otitis media in Toll-like receptor 4-deficient C3H/HeJ mice.

Conclusion: This report confirms the presence of gram-negative Klebsiella bacteria in the middle ear of the C3H/HeJ mouse by culture, polymerase chain reaction (PCR), and electron microscopy. Identification of the bacterial pathogen supports the C3H/HeJ mouse as an excellent model for spontaneous chronic otitis media and its effects on the middle and inner ear.

Objectives: The C3H/HeJ mouse has a single amino acid substitution in its Toll-like receptor 4, making it insensitive to endotoxin and suppressing initiation of the innate immune system.

Intratympanic injection of dexamethasone: time course of inner ear distribution and conversion to its active form.

Hypothesis: Intratympanically injected dexamethasone 21-phosphate is converted to its active form dexamethasone in the inner ear and follows the distribution of the glucocorticoid receptor.

Background: Although dexamethasone is routinely delivered intratympanically for hearing loss, we know little of its inner ear pharmacokinetics. Dexamethasone 21-phosphate is the pharmaceutical compound available for injection, but it must be converted to its biologically active form (dexamethasone) to bind to the glucocorticoid receptor.