| Objective To observe the difference in brachial plexus C5-T1 roots by biomechanical study and the effects of brachial plexus root rupture or avulsion injuries on the apoptosis of spinal cord grey matter anterior horn motor neuron in adult rats. Methods 20 adult Wistar rats' brachial plexus C5-T1 roots were exposed and tested by axially tensing one by one, for recording force(g)-elongation(mm); each root's initial cross-sectional area was examined by ice-slices and picture-analysis technology and corresponding stress-strain date were calculated. The stress-strain curve of each root was obtained, and biomechanical properties of the root was analyzed according to curve. Another 35 adult Wistar rats were randomly divided into three groups:normal control group(n=5),root rupture (group A,n=15) and root avulsion (group B,n=15).The latter of two groups were further subdivided into five groups according to different postoperative survival periods of 3 days,7 days, 14 days,21 days,28 days,with 3 rats each. C5-T1 level spinal cord sample was harvested at each group. (1)The number of motor neurons of anterior horn of the spinal cord was counted and morphological characteristics of apoptotic cells were observed by Hematoxylin and eosin(HE) stained sections. (2)TUNEL technique was used for detection of the apoptotic neurons, the number of apoptotic cells were summed through the 10 sight field of each section, the percentage of apoptotic cells was calculated by the ratio of the sums of apoptotic cells to general cells. Results The following biomechanical properties in rat brachial plexus roots was observed: (1)The shape of rat brachial plexus C5-T1 roots' stress-straincurve are similar to that of other peripheral nerve, but significant difference was found in quantity. (2)Each root's maximum elongation ratio ranged from 50% to 70%, elasticity scope was 30-50 percent. Among C5-T1 roots,C7 root's maximum strength, elasticity were greater than that of other. (3) C5-T1 roots'maximum tension scope was 250-500g, a significant correlation was found between maximum tension and initial cross-sectional area in C5- C7 roots. Furthermore C5- C7 roots maximum stress and strain were greater than that of C8- T1 roots. Effects of brachial plexus root injuries on the apoptosis of spinal cord motor neuron showed: (1) No apoptosis cell was detected in the control group and the group A,B s non-injury side of spinal cord;There were apoptosis cells at early time postoperatively (3 days point) in group A,B s injury side of spinal cord .(2)apoptosis percentage reached its peak at postinjury 14days with degree of 50% in group A and 7days with degree of 70% in group B, declining gradually with time.(3)Apostosis degree in group B was more than that in group A in postoperatively each group,there were statistically significant difference between the group. Conclusions (1)The rat brachial plexus roots have obvious difference in biomechanical properties and further research is needed to determine this difference in the way of anatomic construction in C5-T1 roots. (2)There were apoptosis cells at postinjury early time (3 days),moreover, which indicate that the apoptosis of the injuried neurons is highly correlated with the means of injuries,the injuries more severer, the apoptotic speed more faster, the apoptotic degree more higher. |
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