مرکز منطقه ای اطلاع رساني علوم و فناوري - بررسي اثرات اكسوتومي در نورونهاي حركتي نوزاد رت و تعيين مدت زمان بقاي آنان بعد از قطع عصب سياتيك

چكيده لاتين :

In this research the effects of axotomy on the spinal cord histology of neonatal rats were studied. 40 rat pups of both sexes were operated under ice-induced anesthesia within 5 days of birth. Via hypothermia and under sterile conditions, the right sciatic nerve was transected at mid-thigh level. The left side was used as a control. Operated rats were sacrificed at 3,5,7,10 and 14 days of axotomy. All animals were perfused and killed with an overdose of ether. After routine processing and embedding in paraffin, transverse serial sections were taken at 8µm from the lumbar spinal cord and stained with cresyl violet and Hematoxylin and Eosin. Moreover, the spinal cord was processed for semithin sections by perfusing the animals with 2.2% glutaradehyde in phosphate buffer, postfixed 1% osmium tetroxide and dehydrated in graded acetone followed by epoxy and resin. Slices 500-800 um thick were cut and stained with Tolidine blue. Slides were studied by superimposing an ocular grid and counting vital and nonvital motoneurons. Comparisons between counts on the right and left sides of operated animals were made. ANOVA was used to evaluate the significance of the differences between the results obtained in different periods and the neuronal loss on the operated side was determined by student r-test. Quantitative studies confirm the death of motoneurons on operated side. Mean survival rates of motoneurons in all groups was lower on the operated side and this difference was significant (P<0.01). Furthermore the mean number of live motoneurons 10 days after surgery was lower than other groups (P<0.01).There was a relation between loss of motoneurons and increase of dead cells. Microscopic observation showed nuclear changes and cytoplasmic vesicles in the spinal motoneurons. Scattered cells with a dense cytoplasm with piknotic nuclei were seen. These cells represented characteristic apoptotic features. Some motoneurons showed changes such as nuclear condensation and peripheral displacement. In conclusion, axotomy resulted in apoptotic cell death of motoneurons as well as progressive definitive time-course reduction of cell number after axotomy with a peak cell loss at day 10.