Faculty Bibliography

Bone images of the jaws and related dental structures were obtained in 25 patients undergoing skeletal surveys. The upper and lower jaws were divided into eight quadrants to facilitate comparisons between scintigraphic image findings and the results of dental examination. Fourteen of these 25 patients had at least one jaw quadrant with a positive image. The areas of positive uptake correlated well with dental examination findings, which included healing extraction sites and common dental diseases, such as pulpal and periodontal infections and irritations from ill-fitting dentures. The potential usefulness of bone imaging as an adjunct in dental diagnosis is discussed.

We have used electron microscopy and solubility measurements to investigate the assembly and structure of purified human platelet myosin and myosin rod into filaments. In buffers with ionic strengths of less than 0.3 M, platelet myosin forms filaments which are remarkable for their small size, being only 320 nm long and 10-11 nm wide in the center of the bare zone. The dimensions of these filaments are not affected greatly by variation of the pH between 7 and 8, variation of the ionic strength between 0.05 and 0.2 M, the presence or absence of 1 mM Mg++ or ATP, or variation of the myosin concentration between 0.05 and 0.7 mg/ml. In 1 mM Ca++ and at pH 6.5 the filaments grow slightly larger. More than 90% of purified platelet myosin molecules assemble into filaments in 0.1 M KC1 at pH 7. Purified preparations of the tail fragment of platelet myosin also form filaments. These filaments are slightly larger than myosin filaments formed under the same conditions, indicating that the size of the myosin filaments may be influenced by some interaction between the head and tail portions of myosin molecules. Calculations based on the size and shape of the myosin filaments, the dimensions of the myosin molecule and analysis of the bare zone reveal that the synthetic platelet myosin filaments consists of 28 myosin molecules arranged in a bipolar array with the heads of two myosin molecules projecting from the backbone of the filament at 14-15 nm intervals. The heads appear to be loosely attached to the backbone by a flexible portion of the myosin tail. Given the concentration of myosin in platelets and the number of myosin molecules per filament, very few of these thin myosin filaments should be present in a thin section of a platelet, even if all of the myosin molecules are aggregated into filaments.