| ObjectA 48 - kD transmembrane glycoprotein, CD - 95 ( Fas/POl ) and a 75 - kD transmembrane glycoprotein, P75 are members of the nerve growth factor receptor/TNF superfamily. They are important mediators in the apoptotic process. The implication of CD95 in the apoptosis of certain types of cells, such as activated T cells or Paneth cells, is well known. Its role is the regulation and cytotoxicity of immunol cell. P75 is an important mediator in the development of nervous system. It is a low - affinity neurotropin receptor. It might enhance TrkA bind to NGF and regulate tyrosine kinase activity. It may antiport NGF and induce apoptosis. The expression of certain genes, such as bcl - 2a, confers partial protection against the mechanisms developed by CD95. For this reason, bcl - 2a has been tested in a number of therapeutic approaches in the attempt to block the action of CD95 and limit apoptosis - mediated cell death. Other antiapoptotic strategies include the blockade of CD95 receptors or P75 or caspase inhibitors. We have studied the expression of CD95 and p75 during the early phases of SCI to further our knowledge of the presence and significance of apoptosis in injured spinal cord tissue.Materials and MethodsOne hundred and fifty S - D rats approximately weighing 250 -300 g were used for this study. Following anesthesia induced by sodium pentobarbital ,2% (25mg/kg). Fixation and sterilization, dorsal laminectomy was performed at the T9 - T11. In 50 animals, a traumatic injury was produced in exposed spinal cord by dropping a 2mm - diameter steel bar weighing 10g from a height of 5cm. The paraspinal muscles and subcutaneous tissues were subsequently closed with a No. 3-0 absorbable suture. Immediate complete paraplegia was observed in every case and persisted throughout the entire study period. The control group underwent laminectomy but not to injury. Black control underwent not to injury. In these rats, we perceived no postoperative deficits. Groups of rats were killed 30minutes, 1,3,6,24,48,72hours and 7,14,28 days after the SCI. The zone of laminectomy was removed en bloc. Then spinal cord sections were obtained from the zone of injury and processed for electron microscope and immunohistochemical studies. The sections were subjected to immunohistochemical stain by using the polyclonal antibody and to hematoxylin and eosin to evaluate postinjury tissue changes at different times. For each animal in each experimental group,four sections from the injured zone were selected at random. Using morphometry , the total number of cells in the gray and white matter ( on the basis of the number of nuclei in each histo-logical section) ,and the number of cells clearly showing positive im-munostaining for CD95 and P75 were recorded and averaged. This a-nalysis was conducted by two investigators trained in morphometrical determinations, who had no knowledge of the experimental group from which each sample was obtained. The values of CD95 and p75 positive cells were analyzed using analysis of variance, and the differences between the expression of CD95 and P75 in gray and white matter were analyzed at each time point by using the Student t - test.ResultIn the control group , histogical studies showed the features of normal spinal cord. 30 minutes after induction of SCI,severe tissue e-dema was observed in the spinal cord. Microhemorrhages, inflammatory cells and neurons showing degenerative changes such as nuclear pyknosis ,and cytoplasmic vacules were common findings. The immu-nohistochemical study showed a clear expression on small neurons from dorsal horns. Motor neurons from ventral horns also stained positive , although they were few in number. 1 hour after injury, the pathological changes were similar to those described at 30 minutes. 3 hour after injury , edema and axonal alterations were more evident in the white matter. Morphometrical studies showed that from 30 minutes to 3 hour after injury, the mean number of cells exhibiting positive immunostain-ing for CD95 was 78. 3 ± 1. 1 in histologic... |
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