Hemichannel-mediated inositol 1,4,5-trisphosphate (IP3) release in the cochlea: a novel mechanism of IP3 intercellular signaling.

Inositol 1,4,5-trisphosphate (IP(3)) is an important second messenger that can trigger a Ca(2+) wave prolongated between cells. This intercellular signaling was found defective in some gap junction connexin deafness mutants. In this study, the mechanism underlying IP(3) intercellular signaling in the cochlea was investigated. A gap junction channel is composed of two hemichannels. By using a fluorescence polarization technique to measure IP(3) concentration, the authors found that IP(3) could be released by gap junction hemichannels in the cochlea. The IP(3) release was increased about three- to fivefold by the reduction of extracellular Ca(2+) concentration or by mechanical stress. This incremental release could be blocked by gap junction blockers but not eliminated by a purinergic P2x receptor antagonist and verapamil, which is a selective P-glycoprotein inhibitor inhibiting the ATP-binding cassette transporters. The authors also found that IP(3) receptors were extensively expressed in the cochlear sensory epithelium, including on the cell surface. Extracellular application of IP(3) could trigger cellular Ca(2+) elevation. This Ca(2+) elevation was eliminated by the gap junction hemichannel blocker. These data reveal that IP(3) can pass through hemichannels acting as an extracellular mediator to participate in intercellular signaling. This hemichannel-mediated extracellular pathway may play an important role in long-distance intercellular communication in the cochlea, given that IP(3) only has a short lifetime in the cytoplasm.

Management of frontal sinus fractures: a review of 96 cases.

OBJECTIVES: The optimal treatment algorithm for frontal sinus fracture management remains ill-defined. The purpose of the study was to classify fracture types, review management methods, document associated injuries, and identify complications associated with various treatment options. STUDY DESIGN: The authors conducted a retrospective chart review evaluating a 13-year experience with frontal sinus fracture management. METHODS: Complete medical records of 96 frontal sinus fracture patients treated by the University of Kentucky Otolaryngology Service from 1990 to 2003 were reviewed. RESULTS: The average patient age was 39 years. Fifty percent of the fractures involved the anterior table of the frontal sinus alone, and 50% involved both anterior and posterior tables. Forty-seven percent of the injuries were managed with observation, whereas 50% of patients underwent surgical repair. In the surgical group, 60% underwent open reduction and internal fixation (ORIF), 23% had a cranialization procedure, and 17% underwent sinus obliteration. The average length of follow up was 9 months. Complications occurred in 17% of the patients (5% in the nonsurgical group and 12% in the surgical group). CONCLUSION: Our results support conservative management of nondisplaced or minimally displaced fractures based on the low complication rate seen in this series. Significant bone displacement can frequently be managed with simple ORIF. Complex fractures affecting the orbit or intracranial contents require cranialization or possibly obliteration. A subset of patients with suspected frontal sinus outflow obstruction can be considered for observation or simple ORIF with close follow up and endoscopic repair if outflow complications manifest.

The acetabular reamer: a unique tool for anterior iliac crest bone graft harvesting.

Bone grafting is often required in craniofacial reconstruction. Morselized corticocancellous bone grafts are particularly useful in applications such as filling and contouring irregular bony defects. Obtaining grafts of this consistency by traditional methods is difficult. An efficient harvesting method that can produce such grafting material in clinically useful quantities is needed. We report the use of a mechanical acetabular reamer for the purpose of harvesting a bone graft from the iliac crest.