Precision of Discrete and Rhythmic Forelimb Movements Requires a Distinct Neuronal Subpopulation in the Interposed Anterior Nucleus

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Sensory Agreement Guides Kinetic Energy Optimization of Arm Movements during Object Manipulation

The laws of physics establish the energetic efficiency of our movements. In some cases, like locomotion, the mechanics of the body dominate in determining the energetically optimal course of action. In other tasks, such as manipulation, energetic costs depend critically upon the variable properties of objects in the environment. Can the brain identify and follow energy-optimal motions when these motions require moving along unfamiliar trajectories? What feedback information is required for such optimal behavior to occur? To answer these questions, we asked participants to move their dominant hand between different positions while holding a virtual mechanical system with complex dynamics (a planar double pendulum). In this task, trajectories of minimum kinetic energy were along curvilinear paths. Our findings demonstrate that participants were capable of finding the energy-optimal paths, but only when provided with veridical visual and haptic information pertaining to the object, lacking which the trajectories were executed along rectilinear paths.     

Modulation of Arm Reaching Movements during Processing of Arm/Hand-Related Action Verbs with and without Emotional Connotation

The theory of embodied language states that language comprehension relies on an internal reenactment of the sensorimotor experience associated with the processed word or sentence. Most evidence in support of this hypothesis had been collected using linguistic material without any emotional connotation. For instance, it had been shown that processing of arm-related verbs, but not of those leg-related verbs, affects the planning and execution of reaching movements; however, at present it is unknown whether this effect is further modulated by verbs evoking an emotional experience. Showing such a modulation might shed light on a very debated issue, i.e. the way in which the emotional meaning of a word is processed. To this end, we assessed whether processing arm/hand-related verbs describing actions with negative connotations (e.g. to stab) affects reaching movements differently from arm/hand-related verbs describing actions with neutral connotation (e.g. to comb). We exploited a go/no-go paradigm in which healthy participants were required to perform arm-reaching movements toward a target when verbs expressing emotional hand actions, neutral hand actions or foot actions were shown, and to refrain from moving when no-effector-related verbs were presented. Reaction times and percentages of errors increased when the verb involved the same effector as used to give the response. However, we also found that the size of this interference decreased when the arm/hand-related verbs had a negative emotional connotation. Crucially, we show that such modulation only occurred when the verb semantics had to be retrieved. These results suggest that the comprehension of negatively valenced verbs might require the simultaneous reenactment of the neural circuitry associated with the processing of the emotion evoked by their meaning and of the neural circuitry associated with their motor features.     

Method for Qualitative and Quantitative Assessment of Proprioceptive Perception of Single-joint Arm Movements

The phenomenon of reproduction of the series of passive single-joint movements in the tested arm by the contralateral arm just in the course of passive movements with no visual control was studied in 35 healthy subjects and 13 post-stroke patients in order to develop a new method for objective assessment of sense of the arm motion for the detection of proprioceptive deficit and for monitoring of the changes in proprioception during rehabilitation. We examined the reproduction of flexion–extension at the elbow and wrist joints, abduction–adduction at the wrist joint and the forearm pronation–supination in both right and left arms in healthy subjects and in the affected arm in post-stroke patients. Displacements of the angles in the tested joint and a homonymous joint of the other arm were acquired by means of video recording system, goniometers, or 9-DoF inertional-magnetometric sensors. Qualitative and quantitative indicators were evaluated to assess the similarity of the passive and active movements. It has been found that the healthy subjects are able to actively reproduce the repeated passive movements at different joints of either the left or right tested arm almost simultaneously and with quite accurate reproduction of an amplitude and shape of movement. At the same time, most of post-stroke patients reproduce movements either with qualitative errors demonstrating incorrect location or wrong estimation of direction or number of repeated test movements, or with significant reduction of accuracy (increased latency or shape distortion). We proposed a method for the assessment of movement proprioception at individual joints. The procedure is easy and convenient for both physicians and patients. It does not require special heavy equipment and can easily be performed under different conditions in a wide range of patients.     

人X染色体长臂(Xq)和短臂(Xp)基因组学比较分析

X染色体发生X染色体失活 ,但是Xp基因有 30 %表现为逃逸 ,而Xq仅不到 3%。为了研究X染色体基因失活和表达逃逸发生和维持的分子机制 ,比较了Xq和XpDNA序列的RNA模拟结合强度。X染色体的核苷酸序列被分为 5 0kb一段 ,对每一段DNA做 7碱基 (7nt)字符串组合分析 (共有 4 7=16 384种组合 ) ,记录每段 5 0kbDNA中每种 7nt字符串的频率。选择生发中心B细胞中的 12 0个高表达基因 ,计算这些基因的内含子 7nt字符串的出现频率 ,称为intron 7nt,以此作为RNAs(RNA群 ,模拟细胞中RNA在小片段的总和 )。已知一段DNA序列的 7nt频率值和intron 7nt,即可以计算该DNA段与intron 7nt的结合强度。每段 5 0kbDNA与intron 7nt的结合强度取决于该DNA段与intron 7nt互补核苷酸的频率 ,互补的核苷酸序列越多 ,结合强度就越大。DNA段与intron 7nt的模拟结合强度称为RNA结合强度 ,试图模拟该段DNA可以结合的RNA小片段的总量。之所以采用 7nt字符串组合分析是考虑到连续 7个核苷酸互补则可以形成相对稳定的结合。研究发现 :1)Xp各DNA段的RNA结合强度均值显著大于Xq (P <0 0 0 1) ;2 )Xp上高结合RNA的DNA段数目显著高于Xq (P <0 0 0 1) ;3)RNA高结合DNA段形成的簇与X染色体基因表达逃逸区关联。有证据表明 ,RNA可以通过改变染色质     

Rhythmic and Blue Light-Induced Turgor Movements and Electrical Potential in the Laminar Pulvinus of Phaseolus vulgaris L.

The well-known circadian movement in Phaseolus leaves is usuallysuperimposed with small and somewhat irregular rhythmic changesof pulvinar movement. This study examines the relationship betweenthese small pulvinar movements and the membrane potential ofthe motor cell as well as the effect of light on them. Bluelight affected both the movements and potential while red andgreen lights of the same photon flux had little effect. Also,the difference in the membrane potential between the extensorand flexor cells was found to be closely related to the rhythmicturgor movement of the pulvinus. Changes in the potential differencealways preceded the movement. Sequential changes of the potentialdifference and turgor pressure in the motor cells, includingthe light-induced ones, are discussed in relation to the leafmovement. (Received August 8, 1985; Accepted November 11, 1985)     

Influence of Vibration on Motor Responses in the Upper Arm Muscles under Stationary Conditions and during Voluntary and Evoked Arm Movements under Limb Unloading Conditions

Locomotion of mammals, including humans, is based on the rhythmic activity of spinal cord circuitries. The functioning of these circuitries depends on multimodal afferent information and on supraspinal influences from the motor cortex. Using the method of transcranial magnetic stimulation (TMS) of arm muscle areas in the motor cortex, we studied the motor evoked potentials (MEP) in the upper arm muscles in stationary conditions and during voluntary and vibration-evoked arm movements. The study included 13 healthy subjects under arm and leg unloading conditions. In the first series of experiments, with motionless limbs, the effect of vibration of left upper arm muscles on motor responses in these muscles was evaluated. In the second series of experiments, MEP were compared in the same muscles during voluntary and rhythmic movements generated by left arm m. triceps brachii vibration (the right arm was stationary). Motionless left arm vibration led to an increase in MEP values in both vibrated muscle and in most of the non-vibrated muscles. For most target muscles, MEP was greater with voluntary arm movements than with vibration-evoked movements. At the same time, a similar MEP modulation in the cycle of arm movements was observed in the same upper arm muscles during both types of arm movements. TMS of the motor cortex significantly potentiated arm movements generated by vibration, but its effect on voluntary movements was weaker. These results indicate significant differences in the degree of motor cortex involvement in voluntary and evoked arm movements. We suppose that evoked arm movements are largely due to spinal rather than central mechanisms of generation of rhythmic movements.     

Changes of the Apoplastic pH and K+ Concentration in the Phaseolus Pulvinus in situ in Relation to Rhythmic Leaf Movements

The apoplastic pH and K⁺ concentration of the extensor of thePhaseolus primary-leaf pulvinus in relation to rhythmic leafmovements have been investigated with double-barrelled ion-sensitivemicro-electrodes. Simultaneous measurements of leaf movementand ion activities in a fine hole of the extensor in situ showedco-existence of ultradian and circadian leaf movements as wellas of ultradian and circadian pH changes in the Water Free Space(WFS) of the extensor apoplast in situ. During circadian leafmovement the H⁺ and K⁺ activities in the WFS of the extensorchange in an antagonistic manner. When extensor cells swell(upward movement of the lamina) the H⁺ activity increases fromapproximately pH 6.7 to 5.9 and the K⁺ concentration decreasesfrom approximately 50 to 10 mol m^–3 and vice versa whenextensor cells shrink. These changes in the ionic activitiesin the WFS must be correlated with large changes in the ioncontent of the DFS and thus support the hypothesis that thecell walls of pulvinar cells serve as reservoirs for K⁺ andH⁺. Key words: Phaseolus pulvinus, apoplastic ionic activities, rhythmic leaf movements, ion-sensitive micro-electrodes (double-barrelled)     

Activation of the Shoulder-Belt and Shoulder Muscles in Two-Joint Arm Movements Performed in Humans with the Action of Opposite Loadings

In tests on four volunteers, we examined coordination of central motor commands (CMCs) controlling slow two-joint movements of the arm within the horizontal plane. Current amplitudes of EMGs recorded from six muscles of the shoulder belt and shoulder and subjected to full-wave rectifying and low-frequency filtration were considered correlates of these commands. In particular, we studied the dependence of coordination of CMCs on the direction of an external force applied to the distal forearm part. As was found, coordination of CMCs significantly depends on the direction of the force flexing the elbow joint. According to our observations, EMGs of definite muscles in the case of performance of a two-joint movement can, in a first approximation, be presented as linear combinations of the EMGs recorded in the course of separate sequential single-joint movements under conditions of shifting the reference point of the hand toward the same point of the operational space as that in the two-joint movement. These data can be interpreted as confirmation of the principle of superposition of elementary CMCs in the performance of complex movements of the extremity.     

Ranging in Human Sonar: Effects of Additional Early Reflections and Exploratory Head Movements

Many blind people rely on echoes from self-produced sounds to assess their environment. It has been shown that human subjects can use echolocation for directional localization and orientation in a room, but echo-acoustic distance perception - e.g. to determine one''s position in a room - has received little scientific attention, and systematic studies on the influence of additional early reflections and exploratory head movements are lacking. This study investigates echo-acoustic distance discrimination in virtual echo-acoustic space, using the impulse responses of a real corridor. Six blindfolded sighted subjects and a blind echolocation expert had to discriminate between two positions in the virtual corridor, which differed by their distance to the front wall, but not to the lateral walls. To solve this task, participants evaluated echoes that were generated in real time from self-produced vocalizations. Across experimental conditions, we systematically varied the restrictions for head rotations, the subjects'' orientation in virtual space and the reference position. Three key results were observed. First, all participants successfully solved the task with discrimination thresholds below 1 m for all reference distances (0.75–4 m). Performance was best for the smallest reference distance of 0.75 m, with thresholds around 20 cm. Second, distance discrimination performance was relatively robust against additional early reflections, compared to other echolocation tasks like directional localization. Third, free head rotations during echolocation can improve distance discrimination performance in complex environmental settings. However, head movements do not necessarily provide a benefit over static echolocation from an optimal single orientation. These results show that accurate distance discrimination through echolocation is possible over a wide range of reference distances and environmental conditions. This is an important functional benefit of human echolocation, which may also play a major role in the calibration of auditory space representations.     

Rhythmic control of activity and sleep by class B1 GPCRs

Abstract

Members of the class B1 family of G-protein coupled receptors (GPCRs) whose ligands are neuropeptides have been implicated in regulation of circadian rhythms and sleep in diverse metazoan clades. This review discusses the cellular and molecular mechanisms by which class B1 GPCRs, especially the mammalian VPAC2 receptor and its functional homologue PDFR in Drosophila and C. elegans, regulate arousal and daily rhythms of sleep and wake. There are remarkable parallels in the cellular and molecular roles played by class B1 intercellular signaling pathways in coordinating arousal and circadian timekeeping across multiple cells and tissues in these very different genetic model organisms.     

A Mathematical Model of the Stability Control of Human Thorax and Pelvis Movements During Walking

A mathematical model is developed to study the human thorax and pelvis movements in the frontal plane during normal walking. The model comprises of two-link base-excited inverted pendulums with one-degree of rotational freedom for each link. Since the linear motion of the pelvis has a significant effect on the upper body stability, this effect is included in the model by having a base point moving in the frontal plane in a general way. Furthermore, because the postural stability is the primary requirement of normal human walking, the control law is developed based on Lyapunov's stability theory, which guarantees the stability of the pendulum system around the up-right position. To evaluate the model, the simulation results, including the angular displacement of each link and the torque applied on each link, are compared with those from gait measurements. It is shown that the simulation results match those from gait measurements closely. These results suggest that the proposed model can provide a useful framework for analysis of postural control mechanisms.     

Purification of Transthyretin by High Performance Affinity Chromatography from Human Plasma

Abstract

The partial purification of human transthyretin (TTR) by high performance affinity chromatography with the help of other separation techniques is described in the present paper. A new affinity medium was prepared with a monosized (ca. 10μM particle size) macroporous resin as the support and thyroxine (T₄) as the ligand. The purification of TTR was carried out in a few simple steps involving serum precipitation, anion exchange, Thyroxine affinity chromatography and gel filtration. The overall yield was 29% and the refined TTR contained less than 2% impurities as analyzed by RP-HPLC. When TTR was administrated to the culture medium DMEM of liver tumor strain SMMC-7721, a true inhibition of cell growth (ca. 50%) was observed as an actual decrease in cell number over time.     

Dynamics of Inter-heavy Chain Interactions in Human Immunoglobulin G (IgG) Subclasses Studied by Kinetic Fab Arm Exchange

Interdomain interactions between the CH3 domains of antibody heavy chains are the first step in antibody assembly and are of prime importance for maintaining the native structure of IgG. For human IgG4 it was shown that CH3-CH3 interactions are weak, resulting in the potential for half-molecule exchange (“Fab arm exchange”). Here we systematically investigated non-covalent interchain interactions for CH3 domains in the other human subclasses, including polymorphisms (allotypes), using real-time monitoring of Fab arm exchange with a FRET-based kinetic assay. We identified structural variation between human IgG subclasses and allotypes at three amino acid positions (Lys/Asn-392, Val/Met-397, Lys/Arg-409) to alter the strength of inter-domain interactions by >6 orders of magnitude. Each substitution affected the interactions independent from the other substitutions in terms of affinity, but the enthalpic and entropic contributions were non-additive, suggesting a complex interplay. Allotypic variation in IgG3 resulted in widely different CH3 interaction strengths that were even weaker for IgG3 than for IgG4 in the case of allotype G3m(c3c5*/6,24*), whereas G3m(s*/15*) was equally stable to IgG1. These interactions are sufficiently strong to maintain the structural integrity of IgG1 during its normal life span; for IgG2 and IgG3 the inter-heavy chain disulfide bonds are essential to prevent half-molecule dissociation, whereas the labile hinge disulfide bonds favor half-molecule exchange in vivo for IgG4.     

Micropurification of Two Human Cerebrospinal Fluid Proteins by High Performance Electrophoresis Chromatography

Abstract: Using C8 reversed-phase HPLC in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we have fractionated proteins contained in human CSFs obtained from patients with schizophrenic disorders. When these proteins were electrophoretically blotted onto polyvinylidene difluoride membrane for direct N-terminal amino acid sequencing, several CSF proteins were identified; these included albumin, transferrin, apolipoprotein A-l, β₂-microglobulin, and prealbumin. We have also identified two structurally related human CSF proteins designated cerebrin 28 (M_r 28,000) and cerebrin 30 (M_r 30,000) that have an N-terminal amino acid sequence of NH₂-APPAQVSVQPNF and NH₂-APEAQVSVQPLFXQ, respectively. Comparison of these sequences with existing database at Protein Identification Resource (R 32.0), GenBank (R 72.0), SWISS-PROT (R 22.0), and EMBL (R 31.0) indicated that they are unique proteins. These proteins were subsequently purified by high performance electrophoresis Chromatography (HPEC) using an Applied Biosystems 230A HPEC system. A specific polyclonal antibody was prepared and an ELISA was established for cerebrin 30. It was noted that HPEC is a powerful tool to purify microgram quantities of proteins from human, rabbit, and rat CSFs. Using such a system, we have been able to micropurify as many as 10 proteins simultaneously in a single experiment because the elution of proteins occurred strictly according to their molecular weights. More importantly, we routinely obtained a recovery of >90%. The potential use of this technology for micropurification of proteins was discussed.