We employ a mechanical model of sarcomere to quantitatively investigate how adenosine triphosphate (ATP) concentration affects motor force regulation during skeletal muscle contraction. Our simulation indicates that t...We employ a mechanical model of sarcomere to quantitatively investigate how adenosine triphosphate (ATP) concentration affects motor force regulation during skeletal muscle contraction. Our simulation indicates that there can be negative cross-bridges resisting contraction within the sarcomere and higher ATP concentration would decrease the resistance force from negative cross-bridges by promoting their timely detachment. It is revealed that the motor force is well regulated only when ATP concentration is above a certain level. These predictions may provide insights into the role of ATP in regulating coordination among multiple motors.展开更多
Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and associa...Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and association (prefrontal cortex [PFC]) motor regions to the primary motor cortex (M1) during graded force tasks. It is well known that one of the major roles of the primary motor cortex (M1) is controlling motor output such as muscle force. However, it is unclear how the hoMCCs interact with M1 in regulating voluntary muscle contractions. Methods: fMRI data was acquired during graded force tasks and fMRI-based effective connectivity (EC) and muscle force analyses were performed to study the relationship between hoMCCs-M1 effective connectivity and voluntarily exerted handgrip force. Results: The results show that there is a consistent information flow from the hoMCCs to M1 under all force conditions, suggesting a hierarchical control mechanism in the brain in regulating voluntary muscle force. Only the premotor cortex exhibited a significant role in mediating the level of force production through its EC with M1 but that role diminished when the exerted force was high, suggesting perhaps a ceiling and/or fatigue effect on the EC. A flip in the direction of EC from the primary sensory cortex (S1) to the hoMCCs (PFC, SMA, and Pre) at lower force levels while at higher forces EC was observed from the hoMCCs to S1. Conclusion: The hoMCCs regulate M1 output to produce desired voluntary muscle force. Only the Pre-to-M1 connectivity strength directly correlates with the force level especially from low to moderate levels. The hoMCCs are involved in modulating higher force production likely by strengthening M1 output and downgrad<span style="font-size:12px;line-height:102%;font-family:Verdana;">ing</span><span style="font-size:12px;line-height:102%;font-family:Verdana;"> inhibition from S1 to M1.</span>展开更多
The recent outstanding issues,＂ puzzles of farmers, anxiety oflocal government and helplessness ofcentral government,＂ facing Chinese grain security, depend on the lack of national food security strategy. Therefore,...The recent outstanding issues,＂ puzzles of farmers, anxiety oflocal government and helplessness ofcentral government,＂ facing Chinese grain security, depend on the lack of national food security strategy. Therefore, we must reconstruct our national food security strategy with a cornerstone of an integrated productivity, the focus control of market regulation forces and the protection of sovereignty. By analyzing the status of integrated productivity, market regulation force and sovereign control, this essay proposes that we should change the concept from ＂ food production＂ to ＂foOd management＂, design the two systems of the interest coordination and the special safeguard, effectively improve the enthusiasm of the government＇ s undertaking work in grain-producing areas and farmers＇ farming work, firmly grasp the two initiatives of acquisition and processing of grain and operating inputs, and actively apply recommendations of the two regulators： food exports, processing and conversion.展开更多
基金supported by the National Natural Science Foundation of China (Grants 11372279, 11572285)
文摘We employ a mechanical model of sarcomere to quantitatively investigate how adenosine triphosphate (ATP) concentration affects motor force regulation during skeletal muscle contraction. Our simulation indicates that there can be negative cross-bridges resisting contraction within the sarcomere and higher ATP concentration would decrease the resistance force from negative cross-bridges by promoting their timely detachment. It is revealed that the motor force is well regulated only when ATP concentration is above a certain level. These predictions may provide insights into the role of ATP in regulating coordination among multiple motors.
文摘Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and association (prefrontal cortex [PFC]) motor regions to the primary motor cortex (M1) during graded force tasks. It is well known that one of the major roles of the primary motor cortex (M1) is controlling motor output such as muscle force. However, it is unclear how the hoMCCs interact with M1 in regulating voluntary muscle contractions. Methods: fMRI data was acquired during graded force tasks and fMRI-based effective connectivity (EC) and muscle force analyses were performed to study the relationship between hoMCCs-M1 effective connectivity and voluntarily exerted handgrip force. Results: The results show that there is a consistent information flow from the hoMCCs to M1 under all force conditions, suggesting a hierarchical control mechanism in the brain in regulating voluntary muscle force. Only the premotor cortex exhibited a significant role in mediating the level of force production through its EC with M1 but that role diminished when the exerted force was high, suggesting perhaps a ceiling and/or fatigue effect on the EC. A flip in the direction of EC from the primary sensory cortex (S1) to the hoMCCs (PFC, SMA, and Pre) at lower force levels while at higher forces EC was observed from the hoMCCs to S1. Conclusion: The hoMCCs regulate M1 output to produce desired voluntary muscle force. Only the Pre-to-M1 connectivity strength directly correlates with the force level especially from low to moderate levels. The hoMCCs are involved in modulating higher force production likely by strengthening M1 output and downgrad<span style="font-size:12px;line-height:102%;font-family:Verdana;">ing</span><span style="font-size:12px;line-height:102%;font-family:Verdana;"> inhibition from S1 to M1.</span>
文摘The recent outstanding issues,＂ puzzles of farmers, anxiety oflocal government and helplessness ofcentral government,＂ facing Chinese grain security, depend on the lack of national food security strategy. Therefore, we must reconstruct our national food security strategy with a cornerstone of an integrated productivity, the focus control of market regulation forces and the protection of sovereignty. By analyzing the status of integrated productivity, market regulation force and sovereign control, this essay proposes that we should change the concept from ＂ food production＂ to ＂foOd management＂, design the two systems of the interest coordination and the special safeguard, effectively improve the enthusiasm of the government＇ s undertaking work in grain-producing areas and farmers＇ farming work, firmly grasp the two initiatives of acquisition and processing of grain and operating inputs, and actively apply recommendations of the two regulators： food exports, processing and conversion.
