Watanabe Masahiko, Nakahara Yuichi, Sakashita Tetsuya, Kikawada Takahiro, Fujita Akihiko, Hamada Nobuyuki, Horikawa Daiki D, Wada Seiichi, Kobayashi Yasuhiko, Okuda Takashi
Anhydrobiosis Research Unit, National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan.
J Insect Physiol. 2007 Jun;53(6):573-9. doi: 10.1016/j.jinsphys.2007.02.008. Epub 2007 Mar 6.
High tolerance against various extreme environments exhibited by some anhydrobionts might be due to being almost completely desiccated, a state where little or no chemical reactions occur. We have shown that anhydrobiotic larvae of Polypedilum vanderplanki have higher tolerance against both high- and low-linear energy transfer (LET) radiation than hydrated larvae. It is of great interest to know how the desiccating larvae gain radiation tolerance. We therefore examined effects of high-LET radiation on four kinds of larvae: (1) normal hydrated (intact) larva, (2) intermediates between the anhydrobiotic and normal hydrated state, (3) almost completely dehydrated (anhydrobiotic) larvae, and (4) immediately rehydrated larvae that are assumed to have a similar molecular profile to anhydrobiotic larvae. The intermediates and immediately rehydrated larvae survived longer after high-LET radiation than intact larvae, indicating that radiation tolerance could be enhanced even in hydrated larvae. Physiological changes toward anhydrobiosis, e.g. accumulation of protectants or increasing damage repair capacity, correlate with improved radiation tolerance in hydrated larvae. In addition, almost complete desiccation further enhanced radiation tolerance, possibly in a different way from the hydrated larvae.
一些隐生生物对各种极端环境表现出的高耐受性可能是由于它们几乎完全脱水，处于一种很少或几乎没有化学反应发生的状态。我们已经表明，范氏摇蚊的隐生幼虫比水合幼虫对高、低传能线密度（LET）辐射都具有更高的耐受性。了解脱水幼虫如何获得辐射耐受性非常有趣。因此，我们研究了高LET辐射对四种幼虫的影响：（1）正常水合（完整）幼虫，（2）处于隐生状态和正常水合状态之间的中间态幼虫，（3）几乎完全脱水的（隐生）幼虫，以及（4）假定具有与隐生幼虫相似分子特征的立即复水幼虫。中间态幼虫和立即复水幼虫在高LET辐射后比完整幼虫存活时间更长，这表明即使在水合幼虫中，辐射耐受性也可以提高。向隐生状态的生理变化，例如保护剂的积累或损伤修复能力的增强，与水合幼虫辐射耐受性的提高相关。此外，几乎完全脱水进一步增强了辐射耐受性，其方式可能与水合幼虫不同。
