DNA analysis was performed by PCR followed by agarose gel electrophoresis in order to examine the method’s effectiveness for the human-cell contamination of returned samples in an astrobiology project (the Tanpopo mission). The effect of aerogel fragments on cell-derived DNA detection was investigated by focusing on Alu elements—primate-specific short interspersed sequences. A human cell-contaminated model of aerogel was prepared, and as a result, ca. 240 cells attached to the hydrophobic aerogel fragments were detected. No false positive was measured, indicating that our method is useful for evaluating the human contamination of aerogel returned from the Tanpopo mission.

Human astronauts follow a fixed prebreathing protocol consisting of 100% hyperoxia exposure repeated several times weekly before conducting the extravehicular activities in interplanetary space. However, despite astronaut exposure to both space radiation and hyperoxia, which have different biological effects on cells, the combinatorial effects on aging and longevity is unknown. Here, we evaluated the interactive effects on aging using Caenorhabditis elegans exposed to short-term ⁶⁰Co γ-ray irradiation and hyperoxia. Thus, combined treatment extended the lifespan by approximately 10-15% in wild-type worms compared with irradiation only. Moreover, we found that the interaction induced not only the expression of antioxidant genes via insulin/IGF-1 signaling and the reduction of mitochondrial ROS, but also the activation of DNA damage repair system and sirtuin homologue genes during aging. Despite short-term irradiation of low linear energy transfer (LET) radiation such as γ-ray inducing transiently transcriptional inactivation of most genes, the levels of genes expression were recovered under hyperoxia during aging, at least partially. These findings in the C. elegans, showing that genetic transcriptional and mitochondrial dynamics depend on the interaction of low LET radiation with hyperoxia to consequently boost longevity, suggest some intracellular molecular targets to protect astronauts in space.

Growth and development, and polar auxin transport in epicotyls of etiolated pea (Pisum sativum L. cv Alaska) seedlings grown under hypergravity conditions produced by centrifugation were studied. Seeds were allowed to germinate and grow under various magnitude of hypergravity conditions for 3.5 days in the dark. Hypergravity at up to 50 G had little effect on epicotyl elongation growth, but increasing gravity force up to 300 G resulted in a reduction of elongation growth, the reduction at 100 G and 200 G being ca. 30% and 50% of control, respectively. Although expressions of genes playing an important role in polar auxin transport, auxin efflux carrier PsPINs and influx carrier PsAUX1, were not affected by hypergravity conditions, polar auxin transport activities of the epicotyls were substantially reduced, those at 100 G and 200 G being ca. 80% and 60% of control, respectively. In addition, close relationships between inhibition of elongation growth and polar auxin transport of the epicotyls were observed. These results suggest that hypergravity-regulated polar auxin activity is involved in inhibition of elongation growth of epicotyls of etiolated pea seedlings. The mechanisms to regulate elongation growth and polar auxin transport are discussed.