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1.
Neurophysiology - A model of central commands (CCs) coming to the muscles during limb movements is proposed; it is based on experimental studies of the nonlinear dynamics of muscle contraction and... 相似文献
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In tests on humans, we recorded EMG activity from the muscles flexing and extending the forearm and shoulder in the course
of realization of sequential single-joint and simultaneous two-joint movements of the upper limb. As was shown, the shoulder
muscles m. biceps brachii and m. triceps brachii are involved in flexion/extension of both elbow and shoulder joints. Central commands sent to the above muscles in the course
of a two-joint movement could be considered a superposition of the central commands coming to the same muscles in realization
of the corresponding sequential single-joint movements with the same changes in the angles of the elbow and shoulder joints.
External loadings applied in the direction of extension of the elbow and shoulder joints induced, in general, similar changes
in coordination of the activity of muscles moving the forearm and shoulder under conditions of both single-joint and two-joint
movements. These facts allow us to suppose that coordination of the muscle activity in two-joint movements depends to a greater
extent on the forces influencing limb links than on the mode of realization of the movements (two sequential single-joint
movements vs a two-joint movement corresponding to the above motor events). 相似文献
3.
Eric L. Voorn Merel A. Brehm Anita Beelen Arnold de Haan Frans Nollet Karin H. L. Gerrits 《PloS one》2014,9(7)
Objective
To assess the reliability of contractile properties of the knee extensor muscles in 23 individuals with post-polio syndrome (PPS) and 18 age-matched healthy individuals.Methods
Contractile properties of the knee extensors were assessed from repeated electrically evoked contractions on 2 separate days, with the use of a fixed dynamometer. Reliability was determined for fatigue resistance, rate of torque development (MRTD), and early and late relaxation time (RT50 and RT25), using the intraclass correlation coefficient (ICC) and standard error of measurement (SEM, expressed as % of the mean).Results
In both groups, reliability for fatigue resistance was good, with high ICCs (>0.90) and small SEM values (PPS: 7.1%, healthy individuals: 7.0%). Reliability for contractile speed indices varied, with the best values found for RT50 (ICCs>0.82, SEM values <2.8%). We found no systematic differences between test and retest occasions, except for RT50 in healthy subjects (p = 0.016).Conclusions
In PPS and healthy individuals, the reliability of fatigue resistance, as obtained from electrically evoked contractions is high. The reliability of contractile speed is only moderate, except for RT50 in PPS, demonstrating high reliability.Significance
This was the first study to examine the reliability of electrically evoked contractile properties in individuals with PPS. Our results demonstrate its potential to study mechanisms underlying muscle fatigue in PPS and to evaluate changes in contractile properties over time in response to interventions or from natural course. 相似文献4.
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Vereshchaka I. V. Gorkovenko A. V. Lehedza O. V. Abramovych T. I. Pilewska W. Zasada M. Kostyukov A. I. 《Neurophysiology》2018,50(6):466-474
Neurophysiology - Averaged EMGs were recorded from the elbow- and shoulder-operating muscles in 10 adult men during parafrontal slow test movements of the hand performed within the horizontal... 相似文献
6.
We studied coordination of central motor commands (СMCs) coming to muscles of the shoulder and shoulder belt in the course
of single-joint and two-joint movements including flexion and extension of the elbow and shoulder joints. Characteristics
of rectified and averaged EMGs recorded from a few muscles of the upper limb were considered correlates of the CMC parameters.
Special attention was paid to coordination of CMCs coming to two-joint muscles that are able to function as common flexors
(m. biceps brachii, caput breve, BBcb) and common extensors (m. triceps brachii, caput longum, TBcl) of the elbow and shoulder joints. Upper limb movements used in the tests included planar shifts of the arm from one spatial
point to another resulting from either simultaneous changes in the angles of the shoulder and elbow joints or isolated sequential
(two-stage) changes in these joint angles. As was found, shoulder muscles providing movements of the elbow with changes in
the angle of the elbow joint, i.e., BBcb and TBcl, were also intensely involved in the performance of single-joint movements in the shoulder joint. The CMCs coming to two-joint
muscles in the course of two-joint movements appeared, in the first approximation, as sums of the commands received by these
muscles in the course of corresponding single-joint movements in the elbow and shoulder joints. Therefore, if we interpret
the isolated forearm movement performed due to a change in the angle of the elbow joint as the main motor event, while the
shoulder movement is considered the accessory one, we can conclude that realization of a two-joint movement of the upper-limb
distal part is based on superposition of CMCs related to basic movements (main and accessory).
Neirofiziologiya/Neurophysiology, Vol. 41, No. 1, pp. 48–56, January–February, 2009. 相似文献
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ROSITSA RAIKOVA 《Computer methods in biomechanics and biomedical engineering》2013,16(6):463-490
Abstract The purpose of this paper is an investigation of the peculiarities of biarticular muscles by means of modelling and analytical solution of the indeterminate problem. The basic model includes 10 muscle elements performing flexio/extensio in the shoulder, elbow and wrist. Four of them are biarticular muscles. Two modifications of the model with only monoarticular muscles are developed. The indeterminate problem is solved analytically using the objective criterion σciFi 2 where F( is the module of the i-th muscle force and Cj is a weight coefficient. The predicted muscle forces, joint reactions and moments are compared in-between the basic model and its two modifications for different joint angles, external loading and weight coefficients. The main conclusions are: it is impossible to formulate strict advantages of the biarticular muscles under quasistatical conditions, their peculiarities depend on limb position, external loading and neural control; in general, monoarticular muscles are more powerful than biarticular ones; the biarticular muscles fine tune muscle coordination, their control is more precise and graceful; the presence of biarticular muscles leads to an increase of the joint reactions and moments, thus stabilizing the limb. 相似文献
10.
Matthew H. Stremlau Kristian G. Andersen Onikepe A. Folarin Jessica N. Grove Ikponmwonsa Odia Philomena E. Ehiane Omowunmi Omoniwa Omigie Omoregie Pan-Pan Jiang Nathan L. Yozwiak Christian B. Matranga Xiao Yang Stephen K. Gire Sarah Winnicki Ridhi Tariyal Stephen F. Schaffner Peter O. Okokhere Sylvanus Okogbenin George O. Akpede Danny A. Asogun Dennis E. Agbonlahor Peter J. Walker Robert B. Tesh Joshua Z. Levin Robert F. Garry Pardis C. Sabeti Christian T. Happi 《PLoS neglected tropical diseases》2015,9(3)
Next-generation sequencing (NGS) has the potential to transform the discovery of viruses causing unexplained acute febrile illness (UAFI) because it does not depend on culturing the pathogen or a priori knowledge of the pathogen’s nucleic acid sequence. More generally, it has the potential to elucidate the complete human virome, including viruses that cause no overt symptoms of disease, but may have unrecognized immunological or developmental consequences. We have used NGS to identify RNA viruses in the blood of 195 patients with UAFI and compared them with those found in 328 apparently healthy (i.e., no overt signs of illness) control individuals, all from communities in southeastern Nigeria. Among UAFI patients, we identified the presence of nucleic acids from several well-characterized pathogenic viruses, such as HIV-1, hepatitis, and Lassa virus. In our cohort of healthy individuals, however, we detected the nucleic acids of two novel rhabdoviruses. These viruses, which we call Ekpoma virus-1 (EKV-1) and Ekpoma virus-2 (EKV-2), are highly divergent, with little identity to each other or other known viruses. The most closely related rhabdoviruses are members of the genus Tibrovirus and Bas-Congo virus (BASV), which was recently identified in an individual with symptoms resembling hemorrhagic fever. Furthermore, by conducting a serosurvey of our study cohort, we find evidence for remarkably high exposure rates to the identified rhabdoviruses. The recent discoveries of novel rhabdoviruses by multiple research groups suggest that human infection with rhabdoviruses might be common. While the prevalence and clinical significance of these viruses are currently unknown, these viruses could have previously unrecognized impacts on human health; further research to understand the immunological and developmental impact of these viruses should be explored. More generally, the identification of similar novel viruses in individuals with and without overt symptoms of disease highlights the need for a broader understanding of the human virome as efforts for viral detection and discovery advance. 相似文献
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Víctor Casanova Isaac Naval-Macabuhay Marta Massanella Marta Rodríguez-García Julià Blanco José M. Gatell Felipe García Teresa Gallart Carme Lluis Josefa Mallol Rafael Franco Núria Climent Peter J. McCormick 《PloS one》2012,7(12)
ADA is an enzyme implicated in purine metabolism, and is critical to ensure normal immune function. Its congenital deficit leads to severe combined immunodeficiency (SCID). ADA binding to adenosine receptors on dendritic cell surface enables T-cell costimulation through CD26 crosslinking, which enhances T-cell activation and proliferation. Despite a large body of work on the actions of the ecto-enzyme ADA on T-cell activation, questions arise on whether ADA can also modulate dendritic cell maturation. To this end we investigated the effects of ADA on human monocyte derived dendritic cell biology. Our results show that both the enzymatic and non-enzymatic activities of ADA are implicated in the enhancement of CD80, CD83, CD86, CD40 and CCR7 expression on immature dendritic cells from healthy and HIV-infected individuals. These ADA-mediated increases in CD83 and costimulatory molecule expression is concomitant to an enhanced IL-12, IL-6, TNF-α, CXCL8(IL-8), CCL3(MIP1-α), CCL4(MIP-1β) and CCL5(RANTES) cytokine/chemokine secretion both in healthy and HIV-infected individuals and to an altered apoptotic death in cells from HIV-infected individuals. Consistently, ADA-mediated actions on iDCs are able to enhance allogeneic CD4 and CD8-T-cell proliferation, globally yielding increased iDC immunogenicity. Taken together, these findings suggest that ADA would promote enhanced and correctly polarized T-cell responses in strategies targeting asymptomatic HIV-infected individuals. 相似文献
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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. 相似文献
13.
Akiko Uematsu Mie Matsui Chiaki Tanaka Tsutomu Takahashi Kyo Noguchi Michio Suzuki Hisao Nishijo 《PloS one》2012,7(10)
Knowledge of amygdalar and hippocampal development as they pertain to sex differences and laterality would help to understand not only brain development but also the relationship between brain volume and brain functions. However, few studies investigated development of these two regions, especially during infancy. The purpose of this study was to examine typical volumetric trajectories of amygdala and hippocampus from infancy to early adulthood by predicting sexual dimorphism and laterality. We performed a cross-sectional morphometric MRI study of amygdalar and hippocampal growth from 1 month to 25 years old, using 109 healthy individuals. The findings indicated significant non-linear age-related volume changes, especially during the first few years of life, in both the amygdala and hippocampus regardless of sex. The peak ages of amygdalar and hippocampal volumes came at the timing of preadolescence (9–11 years old). The female amygdala reached its peak age about one year and a half earlier than the male amygdala did. In addition, its rate of growth change decreased earlier in the females. Furthermore, both females and males displayed rightward laterality in the hippocampus, but only the males in the amygdala. The robust growth of the amygdala and hippocampus during infancy highlight the importance of this period for neural and functional development. The sex differences and laterality during development of these two regions suggest that sex-related factors such as sex hormones and functional laterality might affect brain development. 相似文献
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《基因组蛋白质组与生物信息学报(英文版)》2020,18(2):140-149
Mosaic variants resulting from postzygotic mutations are prevalent in the human genome and play important roles in human diseases. However, except for cancer-related variants, there is no collection of postzygotic mosaic variants in noncancer disease-related and healthy individuals. Here, we present MosaicBase, a comprehensive database that includes 6698 mosaic variants related to 266 noncancer diseases and 27,991 mosaic variants identified in 422 healthy individuals. Genomic and phenotypic information of each variant was manually extracted and curated from 383 publications. MosaicBase supports the query of variants with Online Mendelian Inheritance in Man (OMIM) entries, genomic coordinates, gene symbols, or Entrez IDs. We also provide an integrated genome browser for users to easily access mosaic variants and their related annotations for any genomic region. By analyzing the variants collected in MosaicBase, we find that mosaic variants that directly contribute to disease phenotype show features distinct from those of variants in individuals with mild or no phenotypes, in terms of their genomic distribution, mutation signatures, and fraction of mutant cells. MosaicBase will not only assist clinicians in genetic counseling and diagnosis but also provide a useful resource to understand the genomic baseline of postzygotic mutations in the general human population. MosaicBase is publicly available at http://mosaicbase.com/ or http://49.4.21.8:8000. 相似文献
15.
King-Ting Lim Yasmin Abu Hanifah Mohd Yasim Mohd Yusof Kwai-Lin Thong 《Indian journal of microbiology》2012,52(4):593-600
Methicillin sensitive Staphylococcus aureus is an important bacterial pathogen associated with hospital- and community-acquired infections leading to endocarditis, skin tissue infection and pneumonia. The objective of this study was to determine both the genetic characteristics of methicillin-sensitive S. aureus (MSSA) strains, and the occurrence of virulence factors produced by S. aureus strains isolated from UMMC and healthy students in the University from year 2009. Out of 429 nasal swab samples, 67 were MSSA. The prevalence of 21 different virulence genes among 67 Malaysian clinical and community MSSA strains was determined by PCR, and their genetic features were assessed by PCR-RFLP of coa gene, agr types, spa typing and PFGE. The five predominant virulence genes were ica (79 %), efb and fnbA (61 % each), sdrE (57 %) and hlg (45 %). Toxin genes (enterotoxin, etd and pvl) were significantly more common (P < 0.05) in clinical strains compared to community strains. Three agr genotypes were observed: agr type I (45 %), agr type III (25 %) and agr type II (19 %). All 67 MSSA strains were distinguished into 26 profiles by PCR-RFLP of coa, 55 pulsotypes and 21 spa types. Four novel spa types (t7312, t7581, t7582 and t7583) were observed. In conclusion, different virulence profiles were observed in MSSA strains in Malaysia where toxin genes were more prevalent among clinical strains. No correlation between DNA profiles (coa-RFLP, PFGE and spa) and virulotypes was observed. The Malaysian MSSA strains from clinical and community sources were genetically diverse and heterogeneous. 相似文献
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Mihai Bragaru C. P. van Wilgen Jan H. B. Geertzen Suzette G. J. B. Ruijs Pieter U. Dijkstra Rienk Dekker 《PloS one》2013,8(3)
Introduction
Although individuals with lower limb amputation may benefit from participation in sports, less than 40% do so.Aim
To identify the barriers and facilitators that influence participation in sports for individuals with lower limb amputation.Design
Qualitative study.Participants
Twenty six individuals with lower limb amputation, all originating from the Dutch provinces of Groningen and Drenthe, of which 13 athletes.Methods
Semi-structured interviews were used to gather information. Following thematic analysis, emerging themes were organized in three categories Technical, Social and Personal.Results
Sport was perceived as enjoyable activity that would help participants to become and stay healthy, improve the number of social contacts, reduce phantom pain and decrease daily tension. Inadequate facilities, problematic transportation, trivialization from others, poor health and lack of motivation or the lack of a sports partner were barriers commonly mentioned by non-athletes. Remarkably, while all athletes were successful prosthetic users, the majority chose to participate in sports for which prosthesis was neither required nor needed.Conclusions
Each individual with lower limb amputation needs to be counselled according to the barriers and facilitators he/she personally experiences. Athletes appeared to be more proactive in searching for a solution and also appeared less discouraged by failing. 相似文献18.
We examined the peculiarities of central coordination of motor commands coming to the muscles of the shoulder belt and shoulder
in the course of generation of targeted isometric efforts by the arm. The dependence of these commands on changes in the effort
direction and position of the forearm within the working space were analyzed. The intensity of the central commands was estimated
according to the amplitudes of rectified and averaged EMGs recorded from the corresponding muscles. Sector diagrams of EMG
activity of the above muscles depending on the direction of the effort vector, EV, were plotted [1]. Preferential sectors
of activity where the efforts were formed due to activation of definite functional muscle groups were identified. As was found,
the direction of these sectors depends significantly on the EV orientation. Differences between the patterns of coactivation
of the examined muscles were demonstrated. Organization of the motor commands under conditions of creation of extensor efforts
is distinguished by a more complex pattern than that related to flexor efforts. In the former case, the activity of extensor
muscles is accompanied by more significant activation of the flexors. 相似文献
19.
Characterising Upper Limb Movements in Huntington's Disease and the Impact of Restricted Visual Cues
Jessica Despard Anne-Marie Ternes Bleydy Dimech-Betancourt Govinda Poudel Andrew Churchyard Nellie Georgiou-Karistianis 《PloS one》2015,10(8)
Background
Voluntary motor deficits are a common feature in Huntington''s disease (HD), characterised by movement slowing and performance inaccuracies. This deficit may be exacerbated when visual cues are restricted.Objective
To characterize the upper limb motor profile in HD with various levels of difficulty, with and without visual targets.Methods
Nine premanifest HD (pre-HD), nine early symptomatic HD (symp-HD) and nine matched controls completed a motor task incorporating Fitts'' law, a model of human movement enabling the quantification of movement timing, via the manipulation of task difficulty (i.e., target size, and distance between targets). The task required participants to make reciprocal movements under cued and blind conditions. Dwell times (time stationary between movements), speed, accuracy and variability of movements were compared between groups.Results
Symp-HD showed significantly prolonged and less consistent movement times, compared with controls and pre-HD. Furthermore, movement planning and online control were significantly impaired in symp-HD, compared with controls and pre-HD, evidenced by prolonged dwell times and deceleration times. Speed and accuracy were comparable across groups, suggesting that group differences observed in movement time, variability, dwell time and deceleration time were evident over and above simple performance measures. The presence of cues resulted in greater movement time variability in symp-HD, compared with pre-HD and controls, suggesting that the deficit in movement consistency manifested only in response to targeted movements.Conclusions
Collectively, these findings provide evidence of a deficiency in both motor planning, particularly in relation to movement timing and online control, which became exacerbated as a function of task difficulty during symp-HD stages. These variables may provide a more sensitive measure of motor dysfunction than speed and/or accuracy alone in symp-HD. 相似文献20.
Han Gil Seo Nam-Jong Paik Shi-Uk Lee Byung-Mo Oh Min Ho Chun Bum Sun Kwon Moon Suk Bang 《PloS one》2015,10(6)