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Muscle mass is an important factor influencing the activity of daily living in older adults. We aimed to investigate whether α-actinin-3 (ACTN3) gene R577X polymorphism affects muscle mass in older Japanese women. A total of 109 women (mean±SD, 64.1 ±6.0 years) were genotyped for the R/X variant of ACTN3. Mid-thigh muscle cross-sectional area (CSA) was assessed using MRI and compared using analysis of covariance models adjusted for body weight. In addition, physical activity and protein intake were measured as the living environmental factors affecting muscle mass. The ACTN3 R577X genotype distributions of the subjects were 19,63 and 27 for the RR, RX, and XX genotypes, respectively. No differences in physical activity and protein intake were observed among the genotypes. The XX genotype showed lower thigh muscle CSA com- pared with RR&RX genotype (mean±SEM: XX: 69.1 ± 1.8cm2, RR&RX: 73.6±1.1 cm2 p<0.05). The results of the present study suggest that ACFN3 R577X polymorphism influences muscle mass in older Japanese women. [ABSTRACT FROM AUTHOR]

Myosin was isolated from two types of muscle, ordinary and dark muscles, of three species of fish living in sea water. The compositions of light chains were visualized by sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS-PAGE), and the mechanochemical activity was examined by in vitro motility and ATPase assays. Ordinary muscle myosin of either species had three species of light chain, whereas dark muscle myosin had another two species of light chain judged by SDS-PAGE. Sliding velocity of ordinary muscle myosin was in the range of 4.92–6.89 μm/s, whereas that of dark muscle myosin was in the range of 3.07–4.25 μm/s. Therefore, ordinary muscle myosin showed 1.26–1.95 times higher sliding velocity than dark muscle myosin in either species. The ratios of V max of actin-activated Mg2+-ATPase activity of ordinary to dark muscle myosins were correlated quite well to the ratios of sliding velocity. Activity of ordinary muscle myosin was comparable to that of mammalian fast muscle myosin, but that of dark muscle myosin was twice of that of mammalian slow muscle myosin. These results may reflect the essential role of fish dark muscle myosin always used in slow cruising. [ABSTRACT FROM AUTHOR]

Studies actins from five ciliate species by researchers from Japan. Significance of the circular DNA of actins cloned, sequenced and characterized by the researchers; Diversity of the actin genes obtained; Role of molecular interactions on the acceleration of the evolutionary rate of ciliate actins.

The article reports that small spines on dendrites harbor three separate pools of actin, according to researchers Naoki Honkura, Haruo Kasai and colleagues at the University of Tokyo in Japan. It is noted that trapping of one pool helps form memory which is believed to stem from long-term potentiation (LTP). It explains that the third actin pool that appeared in spines swells after repeated stimulation with glutamate. The researchers cite that calmodulin (CaM)-dependent kinase II helps cross-link the new filaments.

The article reports on a study which revealed that the transport molecule myosin-V makes a random twist as it traverses along its actin filament. The research indicated that trailing myosin head can swing in either direction as it looks for its next binding site. Researcher Toshio Yanagida of Osaka University in Japan stated that the ability of myosin-V to twist in either direction provides it better mobility.