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重力改变的幅度和持续时间以及重新适应1g对蟾鱼椭圆囊结构和功能的影响

Influence of Magnitude and Duration of Altered Gravity and Readaptation to 1 g on the Structure and Function of the Utricle in Toadfish, .

作者信息

Boyle Richard, Popova Yekaterina, Varelas Joseph

机构信息

National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA, United States.

Universities Space Research Association (USRA) Science & Technology Innovation Labs at NASA Ames Research Center, Moffett Field, CA, United States.

出版信息

Front Physiol. 2018 Oct 22;9:1469. doi: 10.3389/fphys.2018.01469. eCollection 2018.

Abstract

Gravity has remained constant during animal evolution and the neural sensory systems detecting acceleration forces have remained remarkably conserved among vertebrates. The utricular organ senses the sum of inertial force due to head translation and head tilt relative to gravitational vertical. Change in gravitational force would be expected to have profound effects on how an organism maintains equilibrium. We characterize the physiology of utricular afferents to applied accelerations in the oyster toadfish, , in normal 1 g to establish benchmarks, after 1-32-day exposures to 2.24 g (resultant) via centrifugation (hypergravity, HG), after 4- and 16-day exposures to 1.12 g (resultant), and following 1-8 days recovery to HG exposures to study re-adaptation to 1 g. Afferents were also examined during activation of efferent vestibular pathway. Centrifugation at 2.24 g included 228°/s constant angular velocity component, and thus horizontal canal afferent responses to yaw rotation were recorded as an internal control in each fish. Afferents studied after 228°/s rotation for 4 and 16 days without centripetal acceleration, called On-Center-Control, were indistinguishable from their control counterparts. Principal response to HG was an adjustment of afferent sensitivity as a function of magnitude and duration of exposure: an initial robust increase at 3-4 days followed by a significant decrease from 16 to 32 days. Initial increase observed after 4 days of HG took >4 days in 1 g to recover, and the decrease observed after 16 days of HG took >2 days to readapt to 1 g. Hair cells in striola and medial extrastriola macula regions were serially reconstructed in 3D from thin sections using transmission electron microscopy in control fish and fish exposed to 4 and 16 days of HG. Despite the highly significant differences in afferent physiology, synaptic body counts quantified in the fish were equivalent in their inter-animal variability and averages. No clear role of the efferent pathway as a feedback mechanism regulating afferent behavior to HG was found. Transfer from 1 g to HG imparts profound effects on gravitational sensitivity of utricular afferents and the accompanying transfer from the HG back to the 1 g resembles in part (as an analog) the transfer from 1 g to the micrograms.

摘要

在动物进化过程中,重力一直保持恒定,并且在脊椎动物中,检测加速力的神经感觉系统也一直保持着显著的保守性。椭圆囊器官感知由于头部平移和头部相对于重力垂直方向的倾斜而产生的惯性力总和。重力的变化预计会对生物体维持平衡的方式产生深远影响。我们对牡蛎蟾鱼椭圆囊传入神经在正常1g重力下对施加加速度的生理特性进行了表征,以建立基准,在通过离心(超重力,HG)暴露于2.24g(合力)1 - 32天后,在暴露于1.12g(合力)4天和16天后,以及在从HG暴露恢复1 - 8天后,研究重新适应1g重力的情况。在前庭传出通路激活期间也对传入神经进行了检查。2.24g的离心包括228°/秒的恒定角速度分量,因此在每条鱼中记录水平半规管传入神经对偏航旋转的反应作为内部对照。在没有向心加速度的情况下以228°/秒旋转4天和16天后研究的传入神经,称为中心控制,与它们的对照对应物没有区别。对HG的主要反应是传入神经敏感性根据暴露的大小和持续时间进行调整:在3 - 4天出现初始强劲增加,随后在16至32天显著下降。在HG暴露4天后观察到的初始增加在1g重力下需要超过4天才能恢复,在HG暴露16天后观察到的下降需要超过2天才能重新适应1g重力。使用透射电子显微镜从对照鱼和暴露于HG 4天和16天的鱼的薄切片中对纹状区和内侧纹外黄斑区的毛细胞进行了三维连续重建。尽管传入神经生理学存在高度显著差异,但在蟾鱼中量化的突触体数量在动物间的变异性和平均值方面是相当的。未发现传出通路作为调节传入神经对HG行为的反馈机制有明确作用。从1g重力转移到HG对椭圆囊传入神经的重力敏感性产生深远影响,而随后从HG转移回1g重力在一定程度上(类似地)类似于从1g重力转移到微克级重力的情况。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/59f9/6204554/9363376c07ef/fphys-09-01469-g001.jpg

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