Action of histamine on eustachian tube function.

INTRODUCTION: The role of allergy in eustachian tube dysfunction is controversial. In this study, allergy was simulated by exposure to histamine, and eustachian tube function testing was performed in an experimental rat model. METHODS: Ventilatory function was assessed by measuring passive opening and closing pressures of the eustachian tube after challenge with either transtympanic or intranasal histamine. The mucociliary clearance time of the tubotympanum was assessed by observing dye transport from the middle ear to the nasopharynx after challenge with either transtympanic histamine or control solution. RESULTS: There was a statistically significant increase in passive opening and closing pressures with transtympanic histamine versus intranasal histamine. In addition, mucociliary clearance times of the tubotympanum after transtympanic histamine showed a statistically significant increase when compared with those after transtympanic control solution. CONCLUSIONS: Transtympanic histamine exposure causes eustachian tube dysfunction in the rat by increasing passive opening and closing pressures of the eustachian tube and impairing mucociliary clearance time.

Bone ingrowth to implant surfaces in an inflammatory arthritis model.

Many studies have shown enhanced bone apposition to implants coated with hydroxyapatite, but the optimum implant texture, especially in abnormal trabecular bone, is unclear. The purpose of this project was to evaluate the histological and mechanical properties of cylindrical implants with three different surface textures that were placed in the cancellous bone of the distal femur of the rabbit after the production of an inflammatory knee arthritis. The three implant surfaces included a beaded surface (Group A), a beaded surface coated with hydroxyapatite (Group B), and a smooth surface coated with hydroxyapatite (Group C). The right knees of 36 rabbits were injected with carrageenan twice a week for 2 weeks. Then bilateral implantations were performed, with 12 rabbits in each group receiving identical implants in the right and left knees. The rabbits were killed 6 weeks after surgery. Mechanical (push-out test) and histomorphometric analyses were performed to determine the quality and quantity of bone ingrowth. In Group A, there was virtually no direct contact (a 20-60-microm clearance) between the bone and the beaded surfaces. Direct contact between the bone and the implant surfaces was seen in Groups B and C. The thickness and number of trabeculae were smaller on the arthritic side than on the control side for all groups but were not different between groups for either the control or the arthritic side. Mechanical testing showed that the shear strength of the interface was weaker on the arthritic side in all groups. The results suggest that inflammatory arthritis induced by carrageenan may influence the quality of local bone (osteopenic changes) and hence compromise the bone apposition and mechanical stability of the interface between the implant and bone.

Morphological and mechanical study on the effects of experimentally induced inflammatory knee arthritis in rabbit long bones.

Inflammatory knee arthritis was induced by intraarticular injection of carrageenan twice a week for a total of 6 weeks in New Zealand White rabbits and the effects of the arthritis on the morphological and mechanical properties of the adjacent femur and tibia were evaluated 8 weeks after the first injection. Carrageenan-induced knee arthritis resulted in severe osteopenic changes and a dramatic decrease in bone strength of the entire ipsilateral femur and tibia, including the femoral head and distal tibia, but not the contralateral femur and tibia and the remote humerus. The osteoporotic changes of the adjacent bones of the inflammatory arthritic knee are the basis for the reduced mechanical strength of these bones. These findings may have clinical significance with regard to the mechanisms and consequences of osteoporotic changes in patients with rheumatoid arthritis.