Region-specific irradiation system with heavy-ion microbeam for active individuals of Caenorhabditis elegans

Abstract

Radiation may affect essential functions and behaviors such as locomotion, feeding, learning and memory. Although whole-body irradiation has been shown to reduce motility in the nematode Caenorhabditis elegans, the detailed mechanism responsible for this effect remains unknown. Targeted irradiation of the nerve ring responsible for sensory integration and information processing would allow us to determine whether the reduction of motility following whole-body irradiation reflects effects on the central nervous system or on the muscle cells themselves. We therefore addressed this issue using a collimating microbeam system. However, radiation targeting requires the animal to be immobilized, and previous studies have anesthetized animals to prevent their movement, thus making it impossible to assess their locomotion immediately after irradiation. We developed a method in which the animal was enclosed in a straight, microfluidic channel in a polydimethylsiloxane chip to inhibit free motion during irradiation, thus allowing locomotion to be observed immediately after irradiation. The head region (including the central nervous system), mid region around the intestine and uterus, and tail region were targeted independently. Each region was irradiated with 12 000 carbon ions (12C; 18.3 MeV/u; linear energy transfer = 106.4 keV/μm), corresponding to 500 Gy at a φ20 μm region. Motility was significantly decreased by whole-body irradiation, but not by irradiation of any of the individual regions, including the central nervous system. This suggests that radiation inhibits locomotion by a whole-body mechanism, potentially involving motoneurons and/or body-wall muscle cells, rather than affecting motor control via the central nervous system and the stimulation response.

Space Radiation Biology for “Living in Space”

“…The heavy-ion microbeam at QST-Takasaki is able to irradiate cultured cells and small model animals with a HZE. Therefore, this facility has contributed to the analysis of radiation effects of HZE to cultured cells from the viewpoint of single-ion-hit effects [62] and bystander effects [63][64][65], as well as analyzed the effects of local HZE radiation on the whole body using the nematode Caenorhabditis elegans [66,67] and Medaka fish [68]. Moreover, at QST-Takasaki, the development of a new microbeam beamline that generates a finer beam spot than the current system is taking place [69].…”

“…BioMed Research International functions are important for space missions. The effects of high-LET radiation exposure on several behaviors including muscle movements have been investigated using the nematode C. elegans [66,67,69,153,154], which is an experimental model organism and a powerful tool to study the effects of radiation. In this animal, locomotion, including forward and backward movements and turns, is carried out by 95 body wall muscle cells, for which the fate of each cell from its birth to death can be easily determined.…”

“…In this animal, locomotion, including forward and backward movements and turns, is carried out by 95 body wall muscle cells, for which the fate of each cell from its birth to death can be easily determined. Locomotion (motility) of adult C. elegans on an agar plate without food was reported to decrease in a dose-dependent manner immediately after whole-body irradiation was administered using both high-LET radiation ( 12 C, 18.3 MeV/u, LET = 113 keV/μm) [67,153] and low-LET radiation ( 60 Co γ-rays) [155]. The RBE ratio of high-LET radiation relative to low-LET radiation for inhibition of locomotion was 1.4 [153].…”

“…Moreover, the results of region-specific irradiation showed that motility was not reduced significantly by irradiation of any of the individual tissues in a ∅ 20 μm region, including the CNS, intestines, and tail. This suggests that radiation reduces loco-motion by a whole-body mechanism, potentially involving motor neurons and/or body wall muscle cells, rather than affecting motor control via the CNS and the stimulation response [67].…”

Heavy-Ion Microbeams for Biological Science: Development of System and Utilization for Biological Experiments in QST-Takasaki

“…We identified a suitable buffer solution to maintain good worm conditions in the channel. Using this method, irradiating a specific region of C. elegans with the exact number of heavy ions is now possible as well as analyzing the immediate response on locomotive activity [23][24][25].…”