The National Council on Radiation Protection and Measurements (NCRP) has recently published a report (Report #137) that discusses various aspects of the concepts used in radiation protection and the difficulties in measuring the radiation environment in spacecraft for the estimation of radiation risk to . Two novel dosimetric methodologies, fluence-based and microdosimetric event-based methods, are discussed and evaluated, along with the more conventional quality factor/LET method. It was concluded that for the present, any reason to switch to a new methodology is not compelling. It is suggested that because of certain drawbacks in the presently-used conventional method, these alternative methodologies should be kept in mind. As new data become available and dosimetric techniques become more refined, the question should be revisited and that in the future, significant improvement might be realized. In addition, such concepts as equivalent dose and organ dose equivalent are discussed and various problems regarding the measurement/estimation of these quantities are presented.

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This study explored EFL readers’ ability to produce a causal explanation of the text in light of their memory for causal information (CI), which is necessary for explaining the text. In L1 reading, memory for CI contributes to causal explanation, even in low-skill readers. In contrast, little is known about the relation between memory for CI and EFL readers’ actual ability to causally explain the text. In an experiment, ninety-eight university students with different L2 reading proficiency read an expository text. They took a recall test measuring memory for CI and a causal question eliciting a causal explanation of the text. The amount of the CI recalled was not significantly different between high- and low-proficiency readers. However, performance on the causal question was lower for the low-proficiency readers than for the high-proficiency readers, even when the analysis focused on the participants recalling all CI. The qualitative inspection revealed that the low-proficiency readers failed to understand the CI as a network, as a consequent of which they could not integrate the CI into one explanation. Together, the findings indicate that, in contrast to L1 readers, memory for CI is necessary but not sufficient for EFL readers to be able to produce a causal explanation.

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Ionizing radiation induces clusters of DNA damages - oxidized bases, abasic sites and strand breaks - on opposing strands within a few helical turns. Such damages have been postulated to be difficult to repair, as are double strand breaks (one type of cluster). We have shown that low doses of low and high linear energy transfer (LET) radiation induce such damage clusters in human cells. In human cells, DSB are about 30% of the total of complex damages, and the levels of DSBs and oxidized pyrimidine clusters are similar. The dose responses for cluster induction in cells can be described by a linear relationship, implying that even low doses of ionizing radiation can produce clustered damages. Studies are in progress to determine whether clusters can be produced by mechanisms other than ionizing radiation, as well as the levels of various cluster types formed by low and high LET radiation.

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Food production at the lunar base or during the manned Mars mission has recently gained significant attention. Plants such as zinnia, lettuce, thale cress, wheat, and barley have been cultured for a long duration in space. Although rice is considered a staple food for most people in the world, little research has been conducted on rice cultivation in space. Rice grains are nutrient-rich with a high content of carbohydrate, protein, and dietary fiber. Moreover, rice is a high-yield crop, and rice grains have a long shelf life. Rice symbolizes the rice-eating culture of Japan. Thus, rice should be considered as a viable Japanese food source for

. A previous report introduced a new variety, Kozonosumika, as super-dwarf rice that could be cultured in space. This rice variety is one-fourth as tall as normal varieties with approximately 20 cm plant height. We investigated its taste characteristics to determine its viability as staple food in space. Glutinous Kozonosumika and non-glutinous Hosetsuwaisei (super-dwarf varieties) and Nipponbare were cultured for sensory tests. Kozonosumika was found to be superior to Hosetsuwaisei in taste. Therefore, Kozonosumika can be a promising candidate for space cultivation because of its short height and high protein content.

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The present study explored how the interplay of text cohesion and L2 reading proficiency affects EFL readers’ text comprehension at different levels (i.e., textbase, situation models). In the experiment, a total of 100 Japanese university students read a low- or a high-cohesion expository text and performed 3 comprehension tests: a free recall test (FRT) assessing memory of explicit ideas in the text, a causal-question test (CQT) targeting understanding of relations between text events, and a problem-solving transfer test (PSTT) measuring learning from the text. Results showed that text cohesion facilitated memory of explicit text ideas regardless of readers’ L2 reading proficiency level. In contrast, a Proficiency × Cohesion interaction was found for understanding of relations in the text: high-proficiency readers benefited from the low-cohesion text, whereas low-proficiency readers performed better when reading the high-cohesion text. Finally, a proficiency effect, but no cohesion effect was observed for learning from the text. The findings suggest that text cohesion affects textbase-level comprehension more than situation-model-level comprehension, whereas L2 reading proficiency consistently influences EFL readers’ comprehension. Based on these findings, the study suggests pedagogical implications tailored to specific levels of comprehension and characteristics of the reader and text.

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This study examined how seductive details, interesting but unimportant text information, influenced expository text comprehension of Japanese EFL learners. Whereas inserting seductive details originally aims to motivate learners to read complicated expository texts, past L1 studies suggest that such information distracts their attention from the main ideas of the text. In this study, 123 Japanese university students read an expository text either with or without seductive details (the +SD vs. the -SD condition), and then completed immediate and one-week-delayed recall tasks. The results of the recall tasks showed that the learners' attention was strongly drawn to the seductive details, regardless of their English reading proficiency. However, the seductive details did not hinder the learners' comprehension of the base text and main ideas. While the seductive details did not affect the quantity of text comprehension, detailed comparisons showed that they influenced what the learners remembered from the text. These findings suggest that seductive details do not always work negatively in expository reading, and the relationships between seductive details and surrounding contexts are closely relevant to whether seductive details have positive or negative effects.

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Folic acid (FA) affect human physiology and drug metabolism. Up to now, the effect of microgravity on the pharmacokinetics of FA remains unclear. The pharmacokinetics of FA in Sprague–Dawley (SD) rats are laying a foundation for safe medicine administration of astronauts. Proteins expression of such FA metabolic enzymes as Methyltetrahydrofolate reductase (MTHFR), Cystathionine beta synthase (CBS) and Methionine synthase (MS) in a variety of organs was analyzed with Western-Blot, and mRNA expression was detected by RT-PCR. The plasma concentration–time profile of FA in normal or tail-suspended SD rats was acquired by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after oral administration of FA. Area under curve (AUC) and C_max of FA in SD rats decreased significantly with extending period of tail-suspension. In terms of expressed level of metabolic enzymes over four suspension terms, as well as the level of the corresponding mRNAs, the following regularities were found: an obvious sharp decline of MTHFR tissue in kidney, a time-dependent increase of CBS in liver tissue and duodenum tissues, the resemblance of MS fluctuation to that of CBS in tested tissues. A four-week simulated microgravity of SD rats exhibits an unequivocal diminish of bioavailability of FA, and simulated microgravity shows a varying effect on the expression of FA-metabolizing enzyme in a variety of tissues.

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Bones are important organs for body resistance against force produced by gravity, though the influence of gravity on bone development is unclear. To examine the effects of gravity on osteogenesis, medaka larvae were reared in water or gel under various conditions. For determining the effects on bone development in a state of motion, larvae were reared in water under normal gravity (1g) or hypergravity (5g) conditions. Also, to examine the direct effect of gravity on bone mineralization, larvae were embedded in low melting agarose gel containing alizarin complexone (ALC) and reared for three days under a normal gravity (1g), simulated-microgravity (s-μg) with use of a clinostat device, or 5g condition. Medaka reared in water under the 5g condition showed forward protruding jaws and spreading of the mineralized area of jaw teeth as compared to those reared under the 1g control condition. In addition, the direction of growth of the notochord in the fin region was changed upward in those reared under the 5g condition, accompanied by a part of acetylated tubulin-positive nerves also localized upward, while positive signals for DsRed, expressed by an osterix promoter, in osteoblasts were increased in the fin region. On the other hand, in medaka reared in gel, ALC signals in the fin ray of those in the s-μg condition were increased as compared to those in the 5g condition. Changes noted in medaka larvae over three days indicated osteogenesis adaptation to the specific gravity environment. The present results obtained with an experimental system are considered useful for examinations in the future regarding changes of osteogenesis, which will be needed to clarify the mechanism of the effects of gravity on bone development.

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The application of an orthostatic stress such as lower body negative pressure (LBNP) during exercise has been proposed to minimize the effects of weightlessness on the cardiovascular system and subsequently to reduce the cardiovascular deconditioning. The KAATSU training is a novel method for strength training to induce muscle strength and hypertrophy. KAATSU induces venous pooling of blood in capacitance vessels by restricting venous blood flow. Therefore, to investigate whether KAATSU can be used as an orthostatic stress, we examined the effects of KAATSU on the hemodynamic, autonomic nervous and hormonal parameters in one subject. The several parameters were measured by impedance cardiography; heart rate (HR), mean blood pressure (mBP), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and heart rate variability (HRV). These data were obtained before (pre), during and after (post) pressurization (50 and 200 mmHg) on both thighs with KAATSU mini belts, and compared with those in standing. The serum concentration of noradrenaline (NA) and vasopressin (ADH), and plasma rennin activity (PRA) were also measured. The application of 200 mmHg KAATSU decreased SV, which was almost equal to the value in standing. HR and TPR increased in a similar manner as standing with slight change of mBP. High frequency (HF_RR), a marker of parasympathetic nervous activity, decreased during both 200 mmHg KAATSU and standing, while LF_RR/HF_RR, a quantitative marker of sympathetic nervous activity, increased significantly. During KAATSU and standing, NA, PRA and ADH increased. These results indicate that the application of KAATSU on both thighs simulates systemic cardiovascular effects of orthostasis in one gravity (1G), and that KAATSU training appears to be a useful method for potential countermeasure like lower body negative pressure (LBNP) against orthostatic intolerance in space flight as well as strength training to induce muscle strength and hypertrophy.

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Exposure to radiation is one of the main concerns for space exploration by humans. By focusing deliberately on the works performed on human cells, we endeavored to review, decade by decade, the technological developments and conceptual advances of space radiation biology. Despite considerable efforts, the cancer and the toxicity risks remain to be quantified: 1) the nature and the frequency of secondary heavy ions need to be better characterized in order to estimate their contribution to the dose and to the final biological response; 2) the diversity of radiation history of each astronaut and the impact of individual susceptibility make very difficult any epidemiological analysis for estimating hazards specifically due to space radiation exposure. 3) Cytogenetic data undoubtedly revealed that space radiation exposure produce significant damage in cells. However, our knowledge of the basic mechanisms specific to low-dose, to repeated doses and to adaptive response is still poor. The application of new radiobiological techniques, like immunofluorescence, and the use of human tissue models different from blood, like skin fibroblasts, may help in clarifying all the above items.

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