Myosin light chain patterns were examined in single fibers from the extensor digitorum longus (EDL) and soleus muscles of Wistar strain rats. The fiber type composition of both muscles was also determined to estimate the relationship between myosin light chain patterns and histochemical fiber types.
The results were summarized as follows ;
1. All of single fibers from the EDL muscle was typical fast type which contained fast light chains only (fLC 1·fLC 2·fLC 3), except that there was one mixed type fiber cotaining both fast and slow light chains (fLC 1·fLC 2·sLC 1·sLC 2) .
2. There were two myosin light chain patterns in single fibers from the soleus muscle. One was typical slow type which contained slow light chains only (sLC1·sLC 2) and the other, mixed type in which fast and slow light chains coexisted. Mixed type fibers were divided into eight groups based on the light chain composition. The percentage occurence of typical slow type and mixed type fibers was 35.4% and 64.6%, respectively.
3. The average percentage of type II fibers was 94.6% in the EDL muscle 5.4% in the soleus muscle.
4. These results suggest that both fast and slow skeletal muscles contain mixed type fibers. The results further imply that in slow skeletal muscle, myosin light chain pattern of mixed type occurs not only in type II but also in type I fibers.

PURPOSE: The proposed the thoracolumbar injury classification system (TLICS) for thoracolumbar injury cites the integrity of the posterior ligamentous complex (PLC). However, no report has elucidated the severity of damage in thoracic and lumbar injury with classification schemes by presence of the PLC injury. The purpose of this study was to accurately assess the severity of damage in thoracic and lumbar burst fractures with the PLC injuries. MATERIALS AND METHODS: One hundred consecutive patients treated surgically for thoracic and lumbar burst fractures were enrolled in this study. There were 71 men and 29 women whose mean age was 36 years. Clinical and radiologic data were investigated, and the thoracolumbar injury classification schemes were also evaluated. All patients were divided into two groups (the P group with PLC injuries and the C group without PLC injuries) for comparative examination. RESULTS: Fourth-one of 100 cases showed PLC injuries in MRI study. The load sharing classification score was significantly higher in the P group [7.8+/-0.2 points for the P group and 6.9+/-1.1 points for the C group (p<0.001)]. The TLICS (excluded PLC score) score was also significantly higher in the P group [6.2+/-1.1 points for the P group and 4.0+/-1.4 points for the C group (p<0.001)]. CONCLUSION: The presence of PLC injury significantly influenced the severity of damage. In management of thoracic lumbar burst fractures, evaluation of PLC injury is important to accurately assess the severity of damage.
Adolescent ; Adult ; Aged ; Female ; Humans ; Ligaments, Articular/*injuries ; Lumbar Vertebrae/*injuries ; Magnetic Resonance Imaging ; Male ; Middle Aged ; Retrospective Studies ; Spinal Fractures/*classification/*physiopathology/surgery ; Thoracic Vertebrae/*injuries ; Young Adult