Experimental Research On Hypoxia Causing Fetal Mice Brain Injury

Objective: To observe neuronal damage degree in the fetal mice brains, which caused by undergoing hypoxia at the mid or late of the maternal mice.Method: The experimental groups were grouped into the A, B, C, D, E, F groups by different hypoxic period, gestational age when undergoing hypoxia and recovery period,.And the contol groups were grouped into the G1, G2, G3 groups by gestational age of delivery. At 12-13 days or 17 days gestation, the mice were placed into a chamber and breathed a gas mixture of 8%O₂ and 92%N₂ for 1.5, 2.5 or 3.5 hours, then moved into room air again. After 24 hours recovery, the maternal mice of the E, F groups were delivered abdominally , and the A, B, C, D groups were delivered at term. The control groups were not placed in hypoxic chamber, and the A, B, C, D groups controlled with the G3 group(delivery at term), the E group controlled with the G1 group(abdominal delivery at 13 days gestation), the F group controlled with the G2 group(abdominal delivery at 18 days gestation). To abserve the skin color and activity of the four limbs of the newborn mice delivered at term immediately, and then collect all of the fetal and newborn mice brain.To detect the fetal brains under the light microscope and electron microscope, and determine malondialdehyde(MDA) and the activities of superoxide dismutase(SOD) of the brain homogenate.Results: 1. In the control G3 group, allover the skin of all newborn mice is red , activity of the four limbs is very well. In the A, C, D groups, the newborn mice skin around the mouth and the end of the four limbs is cyanosis slightly, and activity ofthe four limbs decreased partly;In the B group, newborn mice skin allover the body is cyanosis, activity of the four limbs is decreased. 2. Morphology outcome: With HE stain, the cerebrostructure and cells of the fetal mice in the control group were normal. There were different degree changes of cerebrostructure in experiment groups. Some neurocytes pyknosised and some had necrotic changes lightly. And a few lymphocytes exuded and gliocytes proliferated in mesenchymal. Under the electron microscope, neurocyte nucleus was round, nucleolar margination, chromatin was uniformity, intracytoplasm organdie was plentiful, whose structure was clear, synapse cohere outside the cell. In experiment groups chromatin was compact, organelle was decreased and had some degeneration, cell membrane dissolved partly. 3. compared in MDA and the activities of SOD of fetal mice brain homogenate:(l)Different hypoxic period: After undergoing hypoxia at 12-13 days gestation, there was no sigmficant difference(P>0.05) between MDA in the B group (hypoxia for 3.5 hours) and that in the A group(hypoxia for 2.5 hours), but the activities of SOD in the B group was lower than that in the A group significantly (P<0.05) . After undergoing hypoxia at 17 days gestation, compared with the C group (hypoxia for 1.5 hours), MDA in the D group(hypoxia for 2.5 hours) was increased significantly (P<0.05) , while the activities of SOD in the D group was decreased significantly (P<0.05) .(2) Different gestational age when undergoing hypoxia with the same time: MDA in the D group was higher than that in the A group significantly (P<0.05) , while the activities of SOD in the D group was lower than that in the A group significantly (P<0.05) .(3) Different recovery period: Compared with the B group, MDA in the E group was no difference significantly, but the activities of SOD was significantly decreased. There was no significant difference between the F group and the D group in MDA and the activities of SOD.Conclusions: Hypoxia can result in brain injury of the fetal mice, and with the hypoxic period prolonged, brain injury become more severe. And as the hypoxic period is equal, the brain injury of the near-term fetus is more severe.