Euglena gracilis and its close relative Astasia longa show a pronounced negative gravitactic behavior. Many experiments revealed that gravitaxis is most likely mediated by an active physiological mechanism. The goal of the present study was to examine elements in the sensory transduction by means of inhibitors of gravitaxis and the intracellular calcium concentration during short microgravity periods. During the course of six parabolic flights (ESA 31th parabolic flight campaign and DLR 6th parabolic flight campaign) the effects of trifluoperazine (calmodulin inhibitor), caffeine (phosphodiesterase inhibitor) and gadolinium (blocks mechano-sensitive ion channels) was investigated. Due to the extreme parabolic flight maneuvers of the aircraft alternating phases of 1.8 x g(n) (about 20 s) and microgravity (about 22 s) were achieved (g(n): acceleration of Earth's gravity field). The duration of the microgravity periods was sufficient to detect a loss of cell orientation in the samples. In the presence of gadolinium impaired gravitaxis was found during acceleration, while caffeine-treated cells showed, compared to the controls, a very precise gravitaxis and faster reorientation in the 1.8 x g(n) period following microgravity. A transient increase of the intracellular calcium upon increased acceleration was detected also in inhibitor-treated samples. Additionally, it was found that the cells showed a higher calcium signal when they deviated from the vertical swimming direction. In the presence of trifluoperazine a slightly higher general calcium signal was detected compared to untreated controls, while gadolinium was found to decrease the intracellular calcium concentration. In the presence of caffeine no clear changes of intracellular calcium were detected compared to the control.

中文翻译：

---

在抛物线飞行过程中研究了Astasia longa中的引力信号转导元件。

Euglena gracilis及其近亲Astasia longa表现出明显的负引力行为。许多实验表明，引力作用很可能是由活跃的生理机制介导的。本研究的目的是在短微重力时期通过重力抑制剂和细胞内钙浓度检查感觉转导中的元素。在六次抛物线飞行过程中（ESA第31次抛物线飞行运动和DLR第6次抛物线飞行运动），研究了氟氟拉嗪（钙调蛋白抑制剂），咖啡因（磷酸二酯酶抑制剂）和（（阻断机械敏感离子通道）的作用。由于飞机的极端抛物线飞行机动，因此实现了1.8 xg（n）（约20 s）和微重力（约22 s）的交替阶段（g（n）：地球重力场的加速度）。微重力周期的持续时间足以检测样品中细胞取向的丧失。在acceleration存在下，在加速过程中发现了引力受损，而与对照相比，咖啡因处理的细胞显示出非常精确的引力和在微重力作用下的1.8 xg（n）时间内更快的重新定向。在抑制剂处理的样品中，随着加速度的增加，细胞内钙的瞬时增加也被检测到。另外，发现当细胞偏离垂直游泳方向时它们显示出较高的钙信号。与未处理的对照组相比，在三氟拉嗪的存在下，检测到的总体钙信号略高，而g则降低了细胞内钙的浓度。