Microscopic Temperature Control Reveals Cooperative Regulation of Actin–Myosin Interaction by Drebrin E

胎児の神経を形作る仕組みは精密な温度センサー --母体の体温維持が神経の成熟に重要であることを示唆--. 京都大学プレスリリース. 2021-11-10.Drebrin E is a regulatory protein of intracellular force produced by actomyosin complexes, that is, myosin molecular motors interacting with actin filaments. The expression level of drebrin E in nerve cells decreases as the animal grows, suggesting its pivotal but unclarified role in neuronal development. Here, by applying the microscopic heat pulse method to actomyosin motility assay, the regulatory mechanism is examined from the room temperature up to 37 °C without a thermal denaturing of proteins. We show that the inhibition of actomyosin motility by drebrin E is eliminated immediately and reversibly during heating and depends on drebrin E concentration. The direct observation of quantum dot-labeled drebrin E implies its stable binding to actin filaments during the heat-induced sliding. Our results suggest that drebrin E allosterically modifies the actin filament structure to regulate cooperatively the actomyosin activity at the maintained in vivo body temperature

Remarks on Muscle Contraction Mechanism II. Isometric Tension Transient and Isotonic Velocity Transient

Mitsui and Ohshima (2008) criticized the power-stroke model for muscle contraction and proposed a new model. In the new model, about 41% of the myosin heads are bound to actin filaments, and each bound head forms a complex MA3 with three actin molecules A1, A2 and A3 forming the crossbridge. The complex translates along the actin filament cooperating with each other. The new model well explained the experimental data on the steady filament sliding. As an extension of the study, the isometric tension transient and isotonic velocity transient are investigated. Statistical ensemble of crossbridges is introduced, and variation of the binding probability of myosin head to A1 is considered. When the binding probability to A1 is zero, the Hill-type force-velocity relation is resulted in. When the binding probability to A1 becomes finite, the deviation from the Hill-type force-velocity relation takes place, as observed by Edman (1988). The characteristics of the isometric tension transient observed by Ford, Huxley and Simmons (1977) and of the isotonic velocity transient observed by Civan and Podolsky (1966) are theoretically reproduced. Ratios of the extensibility are estimated as 0.22 for the crossbridge, 0.26 for the myosin filament and 0.52 for the actin filament, in consistency with the values determined by X-ray diffraction by Wakabayashi et al. (1994)

Ultrafast Control of Crystal Structure in a Topological Charge-Density-Wave Material

Optical control of crystal structures is a promising route to change physical properties including topological nature of a targeting material. Time-resolved X-ray diffraction measurements using the X-ray free-electron laser are performed to study the ultrafast lattice dynamics of VTe$_2$, which shows a unique charge-density-wave (CDW) ordering coupled to the topological surface states as a first-order phase transition. A significant oscillation of the CDW amplitude mode is observed at a superlattice reflection as well as Bragg reflections. The frequency of the oscillation is independent of the fluence of the pumping laser, which is prominent to the CDW ordering of the first-order phase transition. Furthermore, the timescale of the photoinduced 1$T^{\prime\prime}$ to 1$T$ phase transition is independent of the period of the CDW amplitude mode

Impact of insulin resistance on subclinical left ventricular dysfunction in normal weight and overweight/obese japanese subjects in a general community

Background Insulin resistance carries increased risk of heart failure, although the pathophysiological mechanisms remain unclear. LV global longitudinal strain (LVGLS) assessed by speckle-tracking echocardiography has emerged as an important tool to detect early LV systolic abnormalities. This study aimed to investigate the association between insulin resistance and subclinical left ventricular (LV) dysfunction in a sample of the general population without overt cardiac disease. Methods We investigated 539 participants who voluntarily underwent extensive cardiovascular health check including laboratory test and speckle-tracking echocardiography. Glycemic profiles were categorized into 3 groups according to homeostatic model assessment of insulin resistance (HOMA-IR): absence of insulin resistance (HOMA-IR  − 16.65%). Results Forty-five (8.3%) participants had DM and 66 (12.2%) had abnormal HOMA-IR. LV mass index and E/e′ ratio did not differ between participants with and without abnormal HOMA-IR, whereas abnormal HOMA-IR group had significantly decreased LVGLS (− 17.6 ± 2.6% vs. − 19.7 ± 3.1%, p < 0.05). The prevalence of impaired LVGLS was higher in abnormal HOMA-IR group compared with normal HOMA-IR group (42.4% vs. 14.0%) and similar to that of DM (48.9%). In multivariable analyses, glycemic abnormalities were significantly associated with impaired LVGLS, independent of traditional cardiovascular risk factors and pertinent laboratory and echocardiographic parameters [adjusted odds ratio (OR) 2.38, p = 0.007 for abnormal HOMA-IR; adjusted OR 3.02, p = 0.003 for DM]. The independent association persisted even after adjustment for waist circumference as a marker of abdominal adiposity. Sub-group analyses stratified by body mass index showed significant association between abnormal HOMA-IR and impaired LVGLS in normal weight individuals (adjusted OR 4.59, p = 0.001), but not in overweight/obese individuals (adjusted OR 1.62, p = 0.300). Conclusions In the general population without overt cardiac disease, insulin resistance carries independent risk for subclinical LV dysfunction, especially in normal weight individuals

The start-up of thermophilic anaerobic digestion of municipal solid waste

Thermophilic anaerobic digestion of municipal solid wastes (MSW) was conducted for 6 weeks in a lab-scale semi-continuous digester for investigating the start-up operation of anaerobic digestion treating MSW. The feedstock was a mixture of simulated food waste, paper waste, and in some cases, cow manure. Organic loading rate (OLR) was adjusted 1.14 ～ 4.00 gVS/kg-sludge/day to biogas production. At the initial stage of thermophilic anaerobic digestion, pH value gradually increased from 8.2 to 8.3 on 17th day from start-up. Free-ammonia concentration in the digester also gradually increased from 361.6 to 412.5 ppm. On 17th day, inhibition of free-ammonia occurs, and biogas generation stopped. After gas generation stopped on day 17, pH and free-ammonia concentration were adjusted to the proper level by adding paper and deionized water. As a result, gas generation restarted on day 21. Then the amount of food waste charged in the digester was decreased and that of paper waste was increased to adjust the total amount of nitrogen invested in the digester. Afterwards, pH value was settled around 7.8, and a stable digestion was achieved till the end of experiment. Inhibition of free-ammonia could be suppressed by adjusting the amount of nitrogen invested in the digester.都市ごみ（MSW）の高温嫌気性消化発酵（メタン発酵）立ち上げ時の実験条件を調べるために，半連続発酵方法を用いて６週間（１期：１～20日，２期：21～46日）メタン発酵が行われた。生ごみ，紙ごみ，そして牛ふん（立ち上げ時）を混合して発酵原料として供試した。有機物負荷量を，1.14～4.00 VS（有機物濃度）/kg-sludge/dayに調製した。高温（52℃）メタン発酵の初期段階（実験開始から17日目）で，発酵液のpHは8.2から8.3に増加し，遊離アンモニア阻害が生じ，バイオガス生成は停止した。17日目以降，紙ごみとイオン交換水を用いて発酵液のpHと遊離アンモニア濃度を適性値に調整した。その結果， 21日目以降，ガス生成が再び始まった。発酵液の全窒素濃度を調整するために，生ごみ量を減らし，紙ごみ量を増やして原料を供給して発酵試験を進めた。pHは7.8付近を推移，試験終了まで安定的に発酵が行われた。遊離アンモニアによる阻害は，発酵液における窒素量を制御することにより抑えられると考えられる

Emergence of Cooperation in a Bio-Inspired Multi-Agent Simulation of Army Ants

This paper presents a multi-agent simulation inspired from army ants. Several studies have been conducted on Bio-inspired methods such as the idea presented in this paper; especially, social insect’s cooperation has been widely discussed in Artificial Intelligence circles. Interestingly, researchers in biology have discovered the fact that army ants dig holes or gulfs in the route from a food source to the nest. This is a behavior helps to optimize the food gathering performance of the ants. We have noted that this behavior is sometimes useful in engineering applications. The purpose of this study is to understand this biological behavior by creating a computer simulation

Effects of an automated stride assistance system on walking parameters and muscular glucose metabolism in elderly adults

Objective: To identify the effects of an automated stride assistance system (SAS) on walking scores and muscle activities in the lower extremities of elderly people.Methods: Seven healthy elderly men (73-81 years) participated in this study. Subjects walked continuously at a constant speed for 50 min on a treadmill with and without the SAS, which is a device to control the walk ratio (step length/cadence) and to add support power to the thigh during walking. A step counter equipped with an infrared device was used to record walking data. The average speeds during treadmill walking were 2.89-3.82 km/h without the SAS and 3.03-4.03 km/h with the SAS. Positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG) evaluation of glucose metabolism were conducted on each subject twice after walking with and without the SAS.Results: Walk ratio, walking speed and step length were significantly improved in all subjects by the SAS, while cadence was significantly decreased by the SAS in all subjects except one. The SAS did not have a significant effect on glucose metabolism of the muscles of the lower extremities. There were no significant correlations between change in walking speed and change in SUV values in each muscle without the SAS and with the SAS. In contrast, significant correlations between walking speed and SUV uptake were shown in gluteus minimus (r = -0.929), hip related muscles (r = -0.862), soleus (r = -0.907), and medial gastrocnemius (r = -0.952) without the SAS. In with the SAS condition, there were significant correlations in gluteus medius (r = -0.899), hip related muscles (r = -0.819), and medial gastrocnemius (r = -0.817) in the elderly subjects.Conclusions: The SAS increases walking scores in elderly people without increasing energy consumption of lower-extremity muscles. The elderly subjects with low walking speed showed higher glucose metabolism in hip related muscles and triceps surae. Thus, this association suggested that decreased walking speed in elderly adults have higher metabolic cost in these muscle regions

Effects of exercise on brain activity during walking in older adults: a randomized controlled trial

Abstract Background Physical activity may preserve neuronal plasticity, increase synapse formation, and cause the release of hormonal factors that promote neurogenesis and neuronal function. Previous studies have reported enhanced neurocognitive function following exercise training. However, the specific cortical regions activated during exercise training remain largely undefined. In this study, we quantitatively and objectively evaluated the effects of exercise on brain activity during walking in healthy older adults. Methods A total of 24 elderly women (75–83 years old) were randomly allocated to either an intervention group or a control group. Those in the intervention group attended 3 months of biweekly 90-min sessions focused on aerobic exercise, strength training, and physical therapy. We monitored changes in regional cerebral glucose metabolism during walking in both groups using positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG). Results All subjects completed the 3-month experiment and the adherence to the exercise program was 100%. Compared with the control group, the intervention group showed a significantly greater step length in the right foot after 3 months of physical activity. The FDG-PET assessment revealed a significant post-intervention increase in regional glucose metabolism in the left posterior entorhinal cortex, left superior temporal gyrus, and right superior temporopolar area in the intervention group. Interestingly, the control group showed a relative increase in regional glucose metabolism in the left premotor and supplemental motor areas, left and right somatosensory association cortex, and right primary visual cortex after the 3-month period. We found no significant differences in FDG uptake between the intervention and control groups before vs. after the intervention. Conclusion Exercise training increased activity in specific brain regions, such as the precuneus and entorhinal cortices, which play an important role in episodic and spatial memory. Further investigation is required to confirm whether alterations in glucose metabolism within these regions during walking directly promote physical and cognitive performance. Trial registration UMIN-CTR ( UMIN000021829 ). Retrospectively registered 10 April 2016