Apoptosis onset and bax protein distribution in spinal motoneurons of newborn rats following sciatic nerve axotomy.
Extensive apoptosis in spinal cord motoneuron was reported to occur in the newborn following sciatic nerve axotomy. The purpose of this study was to evaluate the onset of cell death at early stages of axotomy, and the changes in Bax protein distribution pattern in the apoptotic cell. Newborn rats were divided into seven groups, axotomized at day 5 postnatal and sacrificed at the following time points: 1, 3, 6, 12, 24, 48, and 72 h after surgery. The left sciatic nerve was transected while the right side was kept as a control. Three experiments were made for morphometric, immunohistochemical, and ultrastructural studies. Morphometric study showed sustained reduction in the number of neurons in the ventral horn. Neuronal losses onset occurred at the first hour after axotomy and the highest loss occurred in the 72-h group (33.7%). The percentage of survived motoneuron (PSM) was calculated. The test of linearity showed that neuron reduction pattern was nonlinear. A nonlinear curve fitting of PSM against time showed an exponential decline in the number of neurons. Immunohistochemistry results showed three Bax protein patterns; early stage increase in Bax gene expression; Bax protein punctation; and dense Bax protein immunoreactivity (DBI). The last two can either be early or late patterns. Bax gene expression increased as early as the first hour post-axotomy and the number of Bax-positive motoneurons continued to increase throughout the time course. Ultrastructural study of the cytoplasm showed an early vacuolation in Golgi apparatus and endoplasmic reticulum that was associated by mitochondrial and nuclear changes.
Tiraihi
Taki
T
Departments of Anatomical Sciences and Pathology, School of Medical Sciences, Tarbiat Modarres University, Tehran, Iran. takialtr@modares.ac.ir
Rezaie
Mohammed Jaffer
MJ
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology*; D019771:Axotomy; D002467:Cell Nucleus / Q000648:ultrastructure; D003593:Cytoplasm / Q000502:physiology / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000648:ultrastructure; D009046:Motor Neurons / Q000378:metabolism* / Q000648:ultrastructure; D017711:Nonlinear Dynamics; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D012584:Sciatic Nerve / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*; D013997:Time Factors; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein