Waseda University

This study introduces a novel method for quantifying peer interaction structures during free play in early childhood, combining triaxial accelerometer data with network analysis. Drawing on developmental psychology theories, we examined age- and sex-related differences in dyadic and triadic interactions among two- and four-year-old children. While no significant age or sex differences emerged in dyadic interactions, four-year-olds exhibited significantly more triadic configurations than two-year-olds, reflecting increased social complexity with age. No sex-based differences were found in the frequency or structure of interactions, aligning with previous findings in unstructured play settings. Our method offers objective, moment-to-moment assessments of naturalistic peer interactions and provides scalable insights into early social dynamics. These findings contribute to the theoretical understanding of peer interaction development and highlight the potential of sensor-based network approaches for studying group behavior in early childhood education contexts.

Mechanical loading induces skeletal muscle hypertrophy, however the underlying molecular mechanisms remain incompletely understood. In rodents, synergist ablation (SA) is widely used to induce hypertrophy, yet most studies focus on fast-twitch muscles, such as the plantaris (PL), because traditional ablation causes severe inflammation in slow-twitch muscles like the soleus (SOL), complicating data interpretation. Recent studies have highlighted the distinct responses of slow- and fast-twitch muscles to mechanical overload. In this study, we developed a refined rodent model of mechanical overload-induced hypertrophy targeting both slow (SOL) and fast (PL) muscles. We compared this modified partial synergist ablation (PSA) method with conventional SA and tenotomy (TT) regarding muscle hypertrophy, fiber type composition, inflammation, and regeneration. C57BL6/J male mice (16 weeks old, n = 18) were assigned to one of three surgical groups: SA, TT, and PSA. In all groups, the relative SOL weight in overloaded legs significantly increased compared to the contralateral control legs (SA: 137%; TT: 118%; PSA: 120%). Similarly, PL weight increased (SA: 145%; TT: 134%; PSA: 115%). Notably, inflammation and muscle regeneration were observed in the SOL of SA and TT groups but not in PSA group. The ratio of central nuclei to subsarcolemmal nuclei among EdU+/PCM1+ nuclei were much higher in SOL compared to those in PL among three models, suggesting distinct modality of hypertrophy in slow- and fast-muscles. These findings indicate that PSA provides a minimal inflammatory and effective approach for inducing hypertrophy in both fast and slow muscles, making it a valuable model for studying muscle adaptation.

BackgroundThis study aimed to evaluate the prevalence and potential associations among lateral ankle sprains (LAS), recurrent LAS, chronic ankle instability (CAI), and CAI by criteria for clinical practice (CAI-C). Chronic ankle instability by criteria for clinical practice is a condition that meets CAI inclusion criteria but also falls under the exclusion criteria defined by the International Ankle Consortium (IAC). Chronic ankle instability by criteria for clinical practice represents a broader clinical definition of CAI.MethodsThis study was a descriptive epidemiological study of the prevalence of LAS, recurrent LAS, CAI, and CAI-C in sports disciplines. A total of 2,175 athletes (1,522 males and 653 females) from 12 sports were surveyed using a structured questionnaire incorporating the Japanese version of the Identification of Functional Ankle Instability. Classification was based on criteria from the IAC.ResultsThe results showed that 52.9% of the participants experienced LAS, and 36.2% had a recurrence. Among those with LAS history, 68.5% had recurrent episodes. Chronic ankle instability was observed in 17.9% of athletes, and CAI-C was present in 32.6%, nearly 1.8 times more prevalent than typical CAI. In particular, the prevalence of CAI-C was more than twice that of CAI in rugby football, cheerleading, and soccer. Furthermore, 90.0% of recurrent LAS cases progressed to CAI-C. Chronic ankle instability was most prevalent in basketball and handball, whereas CAI-C was prevalent not only in these sports but also in soccer and judo, based on adjusted residuals ≥1.96.ConclusionsWe found that the number of participants with CAI-C differed from that of participants with CAI. This finding suggests that CAI may not reflect the entire clinical population with CAI conditions. Therefore, it has been suggested that it is also necessary to identify CAI-C in clinical practice. These findings underscore and support the need to consider tailored prevention programs and clinical attention to at-risk sports to reduce the long-term impact of ankle instability in athletes.Levels of Evidence:Prognostic, Level IV: case series.

Background: Extracellular vesicles (EVs) released from skeletal muscle mediate metabolic communication via microRNAs (miRNAs). While both circadian rhythms and exercise influence metabolism, the joint modulation of the muscle-derived EV miRNA landscape by circadian rhythms and chronic exercise remains undefined, particularly under the metabolic stress of obesity. Methods: Employing a 2 × 2 factorial design (Phase: ZT3 vs. ZT15; Condition: sedentary vs. exercise; ZT, Zeitgeber Time), EV-enriched fractions were isolated from ex vivo quadriceps muscle (QUA) cultures of high-fat diet-fed mice following an 8-week treadmill training regimen using polymer-based precipitation, and comprehensive miRNA profiling was performed by small RNA sequencing. Results: Principal component analysis (PCA) revealed that circadian phase accounted for a greater proportion of global variance in EV miRNA profiles than exercise. Differential expression analysis identified miR-1a-3p and miR-1b-5p as upregulated across both composite phase and exercise contrasts; however, condition-specific analyses indicated that this signal was primarily driven by the sedentary-phase comparison (ZT15-sed vs. ZT3-sed), in which the miR-29 family was also prominently co-upregulated, rather than constituting independent phase and exercise effects; this phase-associated signature was absent in the corresponding exercise-condition comparison. Exploratory functional enrichment of experimentally validated targets revealed phase-preferential association with metabolic and iron-heme pathways, whereas exercise-associated miRNAs mapped to signaling, inflammatory, and transcription-related networks. Conclusions: Circadian phase was the dominant contributor to global variance in muscle-derived EV-enriched miRNA profiles in obesity, as reflected by the phase-associated separation along principal component 1 (PC1, 33.47% of total variance), with exercise introducing context-dependent adaptive modulation. This study provides a foundational basis for investigating the temporal regulation of muscle secretome dynamics under high-fat diet conditions, highlighting temporal specificity as a key dimension in EV-mediated exercise physiology research.

Abstract Lean-burn engines emit low CO2, but produce high NOx, and conventional three-way catalysts cannot purify NOx from oxygen-rich exhaust gases. NOx storage reduction (NSR) is effective but typically requires fuel-consuming “rich spikes”. We investigated an NSR process in an electric field, achieving effective NOx reduction under low-temperature (473 K) lean conditions. We developed a 0.1wt%Pd/0.5wt%Pt−16wt%BaO/CeO2 catalyst, where trace Pd addition suppressed C3H6 over-oxidation and enhanced its efficiency as a reductant. Applying an electric field (6 mA) significantly increased the conversion of stored NOx to N2 from 3.0% to 45.1%. This system offers a promising pathway for efficient NOx purification in hybrid vehicles by utilising surplus electricity rather than additional fuel.

This paper examines how risk preferences differ over goods and in-kind monetary rewards, such as gift cards. I conduct an experiment in which control subjects allocate self-selected Amazon.com goods over uncertain states, whereas treated subjects allocate temporally-restricted Amazon.com credit instead. Under perfect information, I prove allocations would be theoretically identical between these groups without assumptions on utility form or risk preferences. In practice, subjects demonstrate considerable differences, with credit allocations 4 times more likely to be riskless. Using an information treatment where subjects browse Amazon.com for an extended time, I find no evidence that price or product uncertainty explains these differences. An additional experiment demonstrates these differences do not exist in a risk-free environment requiring real effort in exchange for credit or goods, further indicating the differences are not driven by uncertainty regarding the utility value of monetary credit.

BackgroundAlcohol and caffeine have distinct pharmacological effects, yet they are often consumed in overlapping everyday contexts (e.g., social gatherings and shared leisure time). The psychological factors that may contribute to such overlap remain unclear. This study explores associations between motives for alcohol and caffeine consumption.MethodsThis study obtained Internet survey data from nonproblem alcohol drinkers in Japan aged 20–39 years (N = 325). Correlation analysis was conducted between the scores for the Drinking Motives Questionnaire-Revised (DMQ-R) and the Motives for Caffeine Consumption Questionnaire (MCCQ). Additionally, the study conducted an exploratory, person-centered cluster analysis based on DMQ-R and MCCQ subscale scores to descriptively summarize combined motive patterns, and compared external variables, including subscale scores from the Ten Item Personality Inventory (TIPI) and the Cognitive Emotion Regulation Questionnaire (CERQ), between the resulting clusters.ResultsAmong the significant positive correlation coefficients between the subscale scores for the DMQ-R and MCCQ, the largest was between conformity (DMQ-R) and social (MCCQ). Exploratory cluster analysis yielded two motive-profile clusters. The cluster characterized by relatively higher social-motive profiles showed lower neuroticism and higher openness (TIPI), as well as lower scores on several CERQ subscales (self-blame, acceptance, rumination, putting into perspective, and catastrophizing).ConclusionThe findings suggest that motives for alcohol and caffeine consumption may be associated, particularly with respect to social-context motives, and that personality traits and cognitive emotion regulation strategies may be associated with individual differences in these motive patterns.