Yoshii Suzuki

Mechanical stretching increases the number of cultured bone cells synthesizing DNA and alters their pattern of protein synthesis.

SummaryA simple method was devised for applying mechanical stretching to bone cell cultures. Bone cells cultured on the flexible plastic membrane of a Petriperm dish are placed over a template with a convex surface. A lead weight is then placed on top of the dish which causes the membrane and the tightly attached cells to be stretched. Mechanical stretching, applied either intermittently or continuously for a 2-hour period resulted in a 64% increase in the number of cells synthesizing DNA. Stretching the cells also significantly increased incorporation of tritiated proline and tritiated leucine. To assay the ratio of collagenous to noncollagenous protein, medium and cell layers of cultures labeled with tritiated leucine were incubated with collagenase and the digests chromatographed on PD 10 columns. The amount of collagen synthesized by stretched and unstretched cultures did not differ; but an increased synthesis of noncollagenous proteins was observed in the stretched cultures.

Influence of an intermittent compressive force on matrix protein expression by ROS 17/2.8 cells, with selective stimulation of osteopontin

The purpose of this study was to determine the response of bone cells to physical stress. Intermittent compressive force (ICF) was applied to 13 kPa to subconfluent ROS 17/2.8 cells at 18 cycles/min. After 48 h of this application, the cells were labelled with [35S]-methionine or [32PO4]. Application of ICF over this time did not alter the synthesis of type I collagen, fibronectin or bone SPARC (osteonectin) compared to that of control cells. However, the activity of alkaline phosphatase was increased 1.5-fold, and the synthesis of a 32PO4-labelled, 75-kDa phosphoprotein, recognized as osteopontin by immunoprecipitation with specific antibodies, was increased 1.4-fold. Also, an increase in osteopontin mRNA starting within 12h of ICF application was observed. The selective increase in osteopontin expression associated with ICF may be important in the remodelling of bone tissues during growth and development and in response to functional forces.

Horizontal Condylar Path in Patients with Disk Displacement with Reduction

In 32 patients with disk displacement with reduction, the condylar path in the horizontal plane during opening and closing movements of the mandible were analyzed with a computerized axiograph. The horizontal condylar tracings during opening were divided into 15 types. There was no clear relationship between the types and clinical symptoms. The specific correspondence of the types were revealed between the right and left joint. In 21 of 32 patients, the condyle on one side deviated medially, while the contralateral condyle deviated laterally at maximum opening. In most of the patients showing medio-lateral condylar deviation at maximum opening, a straight condylar path was observed from the maximum opening to the position just before the closing click. In some of the patients, the type of horizontal condylar tracing during opening was related to the displacement pattern of the disk assessed by magnetic resonance imaging (MRI).

An Analysis of Hinge Axis Translation and Rotation During Opening and Closing in Dentulous and Edentulous Subjects

In order to evaluate the influence of interocclusal environment, condylar movement was investigated by computerized axiography. The sample consisted of 50 dentulous and 50 edentulous Caucasians. The mean length of translation at maximum opening in dentulous subjects was 16 mm, while edentulous subjects showed an average of 11 mm. The mean angle of hinge axis rotation at maximum opening was 30 degrees in dentulous subjects and 17 degrees in edentulous subjects. The mean length of translation and the rotation of hinge axis in opening and closing movements was smaller in edentulous subjects than in dentulous ones. In opening and closing movement of edentulous subjects, the length of translation and the rotation value revealed no significant correlation with age or duration of upper and lower prosthesis. No significant difference was shown between edentulous and dentulous subjects on translative quantity in protrusive movement.