| Objective: To evaluate the effects of different kinds of oxygen therapies on cerebral pathology and apoptosis of the fetal rats following ischemic-hypoxia.Methods: Twenty-five 17-day-old pregnant rats were randomized divided into two groups: 20 rats in ischemic-hypoxia group ,5 rats in sham operated group. The intrauterine ischemic-hypoxia model was established by clamping both of the uterine artery for 15 minutes. Then the ischemic-hypoxia group was randomized divided into four groups including non-given oxygen grou,low-concentration interrupted oxygen given group,high-concentration interrupted oxygen given group and low-concentration persistent oxygen given group. Each group had five pregnant rats. From the 18th to the 20th pregnant day, the low-concentration interruptted oxygen given group was given 37% oxygen by 30 minutes one time, three times daily; the high-concentration interrupted oxygen given group was given 84% oxygen, by 15 minutes one time, for a 5-minute interval, twice; persistent oxygen given group was continuously given 37% oxygen for 8 hours. On the 21th pregnant day, all rats received caesarean section and the cerebral tissue were obtained, which were determined by the HE stain, electron microscope and TUNEL respectively.Results: (1) Pathology in the cerebral tissue:①After the HE stain, all of the cerebral tissue of non-given oxygen group appeared angio-hyperemia, confused structure, part of the neuron swelling, central type Nissl body dissolved, part of the nucleus pycnosis, nucleolus diminution or even disappearance, colloid cell nodule formed. The cerebral tissues of the two different interrupted oxygen given groups had clear layers, no obvious degeneration or necrosis. But the cerebral cortex of low-concentration persistent oxygen given group appeared angio-hyperemia, confused structure, as the same as the non-given oxygen group. Pathological score: non-given oxygen group (1.36±0.57) and low-concentration persistent oxygen given group (1.49±0.68 ) are significantly higher than those of the sham operated group (0.70±0.27) , low-concentration interrupted oxygen given group ( 0.73±0.25 ) and high-concentration interrupted oxygen given group (0.76±0.29) (P<0.001); but there was no statistical difference between the non-oxygen given group and the low concentration oxygen given group, the different concentration oxygen given groups, the high concentration oxygen given group and the sham operated group, the low-concentration interrupted oxygen given group and the sham operated group respectively (P>0.05).②Electron microscope in the cerebral tissue: in the non-given oxygen and the low- concentration persistent oxygen given group, there were confused nucelus double membrane, nucleus pycnosis or dissolved nucleus, and extensive mitochondrion; in the two interrupted oxygen given groups, there were clear nucelus double membrane, plentiful organelle, uniform chromatin, no obvious changes of mitochondrion and endoplasmic reticulum. Density of mitochondrion: sham operated group(45.39±13.01 um-3),non-given oxygen group(36.03±12.05um-3), low-concentration persistent oxygen given group(42.10±10.33 um-3), high-concentration interrupted oxygen given group(41.78±10.27 um-3), low-concentration persistent oxygen given group(38.23±11.90 um-3), and there were no statistical difference between groups(P > 0.05). Volume of mitochondrion: non-given oxygen group (5.78±1.69×10-4um3) and low-concentration persistent oxygen given group (6.93±1.72×10-4um3) were significantly higher than those of the sham operated group (3.16±1.18×10-4um3) , low-concentration interrupted oxygen given group (3.23±1.25×10-4um3) and high-concentration interrupted oxygen given group (3.36±1.41×10-4um3) (P<0.001); but there were no statistical difference between the sham operated group and the low-concentration interrupted oxygen given group,the sham operated group and the high-concentration interrupted oxygen given group, the different interrupted oxygen given groups, and the low-concentration persistent oxygen given group and non-given oxygen group(P>0.05).(2)The apoptosis of the neurocytes: in the sham operated group and the interrupted oxygen group given groups, there were little apoptosis neurocyte. The apoptosis of the neurocytes in the sham operated group might be associated with the physiological death. The apoptosis neurocyte of non-given oxygen group and the low-concentration persistent oxygen group increased obviously. Percentages of the positive cells determined by TUNEL: non-given oxygen group (32.78±9.92%) and low-concentration persistent oxygen given group (48.52±11.49% ) were significantly higher than the sham operated group (15.63±7.02% ) , low-concentration interrupted oxygen given group (16.85±8.04%) and high-concentration interrupted oxygen given group (16.55±8.07%) (P<0.001). The low-concentration persistent oxygen given group increased significantly than those of the non-given oxygen group(P<0.001). there was no statistical difference between the non-oxygen given group and the low concentration oxygen given group, the different concentration oxygen given groups, the high concentration oxygen given group and the sham operated group, the low-concentration interrupted oxygen given group and the sham operated group respectively (P>0.05). Conclusion: (1) In the cerebral tissue of fetal rats following intrauterine ischemia-hypoxia, obvious change of the pathology and apoptosis of neurocyte showed that the intrauterine ischemic-hypoxia in the gestation period could cause brain damage. (2) Low-concentration interrupted and high-concentration interrupted oxygen therapy could protect cerebral tissue from intrauterine ischemic-hypoxia brain damage, but low-concentration persistent oxygen therapy could aggravate the brain damage.
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