Electron microscopic observation on neurodegeneration induced by brain injury newborn rats

Huiying ZHANG; Zhengrui HE; Ping ZHU; Jun GU; Lihua CHEN; Wenchao LIU; Wenlong DING

ABSTRACT

BACKGROUND:

As a result of immature brain of children and their imperfect blood brain barrier, improper clinical treatment would affect growth and development of children. It is fully important to perform further investigation on immature brain injury induced neurodegeneration.

OBJECTIVE:

To observe the ultramicrostructure of neurons in homolateral parietal cortex and hippocampus in newborn 7-day SD rat with contusion of parietal cortex.

DESIGN:

Completely randomized controlled trial.

SETTING:

Laboratories of Nerve Morphology and Cytobiology, Medical College of Shanghai Jiaotong University; Electron Microscope Room of Institute for Physiology, Chinese Academy of Science.MATERIALS The experiment was performed in Teaching and Research Section of Anatomy, Laboratories of Nerve Morphology and Cytobiology ofShanghai Second Medical University (Medical College of Shanghai Jiaotong University; Electron Microscope Room of Institute for Physiology of Chinese Academy of Science from October 2002 to June 2003. A total of 19newborn 7-day SD rats were randomly divided into experimental group, operation control group and normal control group with 15, 2 and 2 in each group respectively.

METHODS:

In experimental group, free-fall device for brain injury was used for establishing model of contusion of parietal cortex in newborn 7-day SD rat. Anesthesia and scalp incision were conducted, without using free-fall device in operation control group. But above procedures were not carried out in normal control group. The changes of ultramicrostructure were observed under transmission electron microscope after routine treatment of electron microscopic samples.MAIN OUTCOME

MEASURES:

Ultramicrostructure of neurons in homolateral parietal cortex and hippocampus.

RESULTS:

All the 19 rats entered results analysis. ① There were two sorts of morphological changes in neurons in experimental group. One was evident swelling of dendrites and bodies of neurons, accompanied with the changes of organelles. In the early stage, expansion of endoplasmic reticulum cisterna could be observed and mitochondria became compact and concentrated. Then, vacuolization of endoplasmic reticulum, progressive swelling and vacuolization of mitochondria, dissociation of polysomes from rough endoplasmic reticulum and scattering of them in cytoplasm could be seen. Changes of nucleolus presented after significant changes of cytoplasm. Nuclear chromatin clustered together under karyotheca and arranged as clockface, which were some masses with irregular contours gathering to the center. Axons were almost normal. The other was concentration of cytoplasm and nucleolus with vacuolizations of unequal size in cytoplasm. ②There was no abnormal change in neurons in homolateral parietal cortex and hippocampus both in operation control group and normal control group.

CONCLUSION:

Swelling of brain cell and concentration of cytoplasm and nucleolus after brain injury play important roles in brain injury-induced neurodegeneration of immature rats.