Tokai Gakuin University

Oxidative stress increases with aging and may influence both sleep physiology and gut microbial activity. Molecular hydrogen, produced by intestinal fermentation, acts as an endogenous antioxidant and can be measured noninvasively in exhaled breath. However, age- and sex-related differences in nocturnal changes of breath hydrogen remain unclear. We analyzed breath hydrogen and methane levels in 166 healthy adults aged 20-85 years. Participants self-collected end-alveolar breath samples at home before sleep and immediately after waking. Breath hydrogen and methane levels were determined by gas chromatography. The older group (n= 91) showed significantly lower breath hydrogen levels after waking compared with the non-older group (n= 75), despite no differences before sleep. No significant sex-related differences were observed. The older group also reported more frequent nocturnal awakenings. These findings suggest that age-related changes in hydrogen dynamics may be associated with sleep-related physiological processes. The overnight change in breath hydrogen was significantly greater in the older group compared with the non-older group, indicating a larger overnight reduction in hydrogen levels in older adults. No significant differences in breath methane levels were observed between groups. Age-related alterations in gut microbiota, gastrointestinal motility, and redox balance may contribute to reduced morning hydrogen levels. Breath hydrogen measurement represents a simple, noninvasive biomarker for assessing physiological changes associated with aging and sleep.

Cytochalasin D (CytoD) is widely used to inhibit actin polymerization, but the underlying regulatory mechanism is unclear. We addressed this using Total Internal Reflection Fluorescence (TIRF) microscopy. Our time course depolymerization assay of individual actin filaments showed that CytoD tightly caps the barbed end, with an estimated Km value for inhibition of 4.1 nM and a duration time of ~1 min. Consistently, in polymerization assays, CytoD at concentrations near the Km value completely suppressed barbed end elongation. Interestingly, at lower concentrations, CytoD acted as a leaky capper, allowing actin monomer addition by rapidly binding to and dissociating from barbed ends. We interpreted this contradictory behavior as arising from differences in binding modes: capping one strand (fast dissociation) or both strands (slow dissociation). CytoD severs actin filaments at micromolar levels, a concentration range commonly used in cell biological studies. Although the severing rate is slower than cofilin, the frequency is higher, resulting in the fragmentation of filaments into shorter pieces. Severing activity was suppressed by inorganic phosphate or cofilin. We determined the crystal structure of CytoD bound to filamentous conformation (F-form) actin and found that CytoD fits better in the hydrophobic cleft of F-form actin than in the monomeric conformation actin, explaining the preferential binding towards barbed end subunits. The structure further indicates that CytoD prevents barbed end depolymerization by stabilizing the terminal subunits in the F-form, which is supported by our MD simulations. Collectively, our results demonstrate how CytoD regulates actin dynamics at the molecular level. ### Competing Interest Statement The authors have declared no competing interest.

Based on the tripartite influence model, this longitudinal study investigated the relationship between body talk and the internalization of ideal body images, mainly focusing on female university students. It was hypothesized that negative fat talk and positive body talk would interact with exposure to thin-ideal images on the internet to influence the internalization of the thin ideal, leading to body fat dissatisfaction among women. This study also tested the hypothesis that negative muscle talk—a form of body talk focusing on dissatisfaction with one’s muscularity—would be associated with the internalization of athletes’ bodies, which corresponds to a toned or mesomorphic physique, among women. We conducted a two-wave longitudinal study over a 4-week interval with female (n = 386, mean age = 19.22 years) and male students (n = 216, mean age = 19.62 years) who completed self-report measures assessing frequency of body talk, the internalization of the thin ideal or athletes’ bodies, exposure to thin-ideal images on the internet, and body dissatisfaction. Path analyses conducted separately by gender revealed no significant interaction between baseline body talk and exposure to thin-ideal images in predicting the internalization of the thin ideal four weeks later. However, exposure to thin-ideal images directly predicted increased internalization of the thin ideal for both genders after controlling for baseline levels. Exposure to thin-ideal images indirectly predicted body fat dissatisfaction through increased thin-ideal internalization among women. Additionally, baseline negative muscle talk was associated with increased internalization of athletes’ bodies for women only. Among men, baseline negative fat talk was positively related to the subsequent internalization of athletes’ bodies. Negative fat talk and positive body talk did not moderate the effect of exposure to thin-ideal images on the internalization of the thin ideal. In contrast, exposure to thin-ideal images emerged as a significant factor in promoting the internalization of the thin ideal. Among women, negative muscle talk promoted the internalization of athletes’ bodies. These findings may advance future research in eating disorder pathology and media psychology. This study focused on the influence of three types of body talk: negative fat talk, which involves statements like “I feel so fat” to express dissatisfaction with body fat; negative muscle talk, reflecting frustration about not being muscular enough; and positive body talk, which reflects acceptance of one’s body and related lifestyle habits. A survey of 602 university students indicated that whether women engaged in negative fat talk was not associated with a subsequent increase in the internalization of the culturally promoted thin ideal (thin-ideal internalization) four weeks later. In contrast, women who were exposed to more thin-ideal depictions of the female body online were more likely to have greater thin-ideal internalization, which in turn increased their body fat dissatisfaction. Additionally, women who engaged more in negative muscle talk showed a greater increase in the internalization of athletes’ bodies, that is, a toned or muscular physique. Unlike women, men who engaged more in negative fat talk showed a greater increase in the internalization of athletes’ bodies. These findings revealed that, in addition to exposure to thin-ideal depictions, long known to increase body image concerns, engaging in body talk also contributes to these concerns.

This study evaluated the reliability and validity of the Japanese version of the Body Talk Scale (BTS), designed to measure negative fat talk, negative muscle talk, and positive body talk. The study also explored the longitudinal associations between each body talk category and body dissatisfaction. We conducted two separate studies among university students in Japan. Separate confirmatory factor analyses for female and male data indicated that the initially proposed three-factor model demonstrated an acceptable fit, whereas the bi-factor model provided a better fit. The Japanese BTS showed good construct validity, acceptable to adequate internal consistency, and test-retest reliability within 2 weeks. A four-week longitudinal study involving 386 women and 216 men (mean age = 19.22 and 19.62, respectively) revealed that negative fat talk predicted an increase in the discrepancy between the thin ideal body image and the actual body image among women. In contrast, positive body talk was linked to reduced body dissatisfaction and body image discrepancy in women. There were no such significant associations in men. These findings support the use of the Japanese BTS as a valuable instrument for future research on the intrapersonal and interpersonal effects of various types of body talk.

This study examined informative and uninformative anchoring effects on judgments of learning (JOLs), focusing on two hypotheses: the optimistic/pessimistic and differential-scaling hypotheses. The optimistic/pessimistic hypothesis states that anchoring information changes subjective confidence in memory, whereas the differential-scaling hypothesis states that anchoring information elicits a scaling bias in the conversion process of subjective internal confidence into scale JOLs (i.e., 0-100% responses). Experiment 1 focused on binary JOLs (i.e., Yes/No predictions). The results confirmed that the informative anchoring effect occurred (i.e., binary JOLs in the high anchor condition were higher than those in the low anchor condition), whereas the uninformative anchoring effect did not. Experiment 2 evaluated whether the difference in response scales between anchoring information and JOLs elicited the anchoring effect, demonstrating that the informative anchoring effect occurred when different response scales were used for the anchoring information (i.e., the number of words correctly recalled) and JOLs (i.e., 0-100% scale), and the uninformative anchoring effect did not. Experiment 3 examined whether the uninformative anchoring effect can be explained by numeric priming rather than scaling bias, demonstrating that anchoring information unrelated to test performance using a 0-100% scale did not elicit the uninformative anchoring effect. These findings suggest that the informative anchoring effect supports the optimistic/pessimistic hypothesis, whereas the uninformative anchoring effect supports the differential-scaling hypothesis. Thus, the nature of anchoring information affects the process of forming JOLs. Specifically, the uninformative anchor elicits only scaling bias, whereas the informative anchor changes subjective confidence in memory.