持续高G对豚鼠前庭耳石器的损伤

Otolith damage induced by high sustained G in Guinea pigs

目的 研究持续高 G作用后是否会造成豚鼠耳石器的损伤 ,为航空航天活动中与此有关的问题提供实验依据。 方法 15只豚鼠随机分为 A、B、C3组 (n=5 ) ,A组给予 +10 Gy5 m in的刺激后 0 .5 h断头处死取双侧椭圆囊行扫描电镜观察 ,B组于 +10 Gy5 m in的刺激后 2 4h处死取双侧椭圆囊行扫描电镜观察 ,C组为对照组。处死前观察各组豚鼠的行为及前庭躯体和前庭眼动反射 ,并记录其持续时间 ,凡有任何一项症状者记为阳性。扫描电镜主要观察其囊斑表面耳石、毛细胞等的超微结构变化。 结果 +10 Gy作用 5 m in后 ,8只豚鼠出现了耳石器受损的阳性症状 ,主要表现为头位震颤 ,头位偏斜 ,身体侧滚 ,转圈 ,自发眼震和眼位偏斜等。其中以头位震颤发生率最高 ,持续时间最长。所有阳性症状均在 2 0 min内消失。扫描电镜可见 A组豚鼠的椭圆囊囊斑表面呈现两种性质的耳石改变 :1耳石消失 ,代之以大量新生的耳石前体——球状物 ;2耳石的变性融合 ,表现为多个耳石失去正常多棱型结构 ,融合为大的整体。另外 ,还可见广泛的毛细胞纤毛粘连 ,倒伏。B组豚鼠的椭圆囊囊斑表现为耳石膜明显增厚 ,高倍镜下显示表面大量新生的不成熟耳石分布 ,耳石的形状表现为两端钝圆膨大 ,呈哑铃型。同样可见广泛的毛细胞纤毛粘连和倒伏 ,程度?

Objective To explore if high sustained G can induce damage of the otolith organs in Guinea pigs, and provide experiment evidence for aerospace problems related to it. Methods Fifteen Guinea pigs were randomly divided into 3 groups: 2 experimental groups(group A,B) and a control group (group C). The experimentals underwent +10 Gy exposure for 5 min, and decapitated 0.5 h (group A) and 24 h (group B) later respectively. After decapitation, the utricles were prepared for scanning electron microscope(SEM) examination, the behaviour, vestibulo spinal reflex (VSR) and vestibulo ocular reflex (VOR) were observed before decapitation. Results Abnormalities of behaviour, VSR and/or VOR were found in 8/10 of the experimentals, which including head tremble, head deviation, spontaneous nystagmus, eye deviation, body roll and looping. All the symptoms disappeared within 20 min. Among them, head tremble was of the highest incidence (8/10) and the longest duration [(12±4) min]. In group A, two kinds of otoconia ultrastructure changes were observed: ①disappearance of the otoconia and appearance of the precursor of it——globe substance; ②degeneration and fusion of the otoconia, including the disappearance of its classical prism like structure and fusing into a larger one. In group B, the incrassation of the utricle macule was prominent, and a large dumb bell shaped immature otoconia was observed in a high power view. Conglutination and sloping of the hair cell cilia were observed in both group A and group B. Ultrastructure change differences between right and left utricle were non significant. Conclusions High sustained G can induce damage of the otolith organs in Guinea pigs, and its recovery is rather quick. It is suggested that damage of otolith organs may also occurred in aerospace crewmembers underwent sustained high G exposures.