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31.
32.
Krishnamoorthy V Latash ML Scholz JP Zatsiorsky VM 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2003,152(3):281-292
Movements by a standing person are commonly associated with adjustments in the activity of postural muscles to cause a desired shift of the center of pressure (COP) and keep balance. We hypothesize that such COP shifts are controlled (stabilized) using a small set of central variables (muscle modes, M-modes), while each M-mode induces changes in the activity of a subgroup of postural muscles. The main purpose of this study has been to explore the possibility of identification of muscle synergies in a postural task using the framework of the uncontrolled manifold (UCM) hypothesis employing the following three steps in data analysis: (i) Identification of M-modes: Subjects were asked to release a load from extended arms through a pulley system, resulting in a COP shift forward prior to load release. Electromyographic (EMG) activity of eleven postural muscles on one side of the body was integrated over a 100 ms interval corresponding to the early stage of the COP shift, and subjected to a principal component (PC) analysis across multiple repetitions of each task. Three PCs were identified and associated with a push-back M-mode, a push-forward M-mode and a mixed M-mode. (ii) Calculation of the Jacobian of the system, which relates changes in the magnitude of M-modes to COP shifts using regression techniques: Subjects performed three different tasks (releasing different loads at the back, voluntarily shifting body weight forward and backward, at different speeds) to verify if the relationship between magnitudes of M-modes and COP shifts is task or direction specific. (iii) UCM analysis: Three tasks were chosen (load release in the front, arm movement forward and backward) which were associated with an early shift in COP. A manifold was identified in the M-mode space corresponding to a certain average (across trials) shift of the COP and variance per degree of freedom within the UCM (VUCM) and orthogonal (VORT) to the UCM was computed. Across subjects, VUCM was significantly higher than VORT when analysis at the third step was performed using a Jacobian computed based on a set of tasks associated with a COP shift in the same direction but not in the opposite direction. This result confirms our hypothesis that the M-modes work together as a synergy to stabilize a desired shift of the COP. Forward and backward COP shifts are associated with different synergies based on the same three M-modes.An erratum to this article can be found at 相似文献
33.
Blind source separation assumes that the acquired signal is composed of a weighted sum of a number of basic components corresponding
to a number of limited sources. This work poses the problem of ECG signal diagnosis in the form of a blind source separation
problem. In particular, a large number of ECG signals undergo two of the most commonly used blind source separation techniques,
namely, principal component analysis (PCA) and independent component analysis (ICA), so that the basic components underlying
this complex signal can be identified. Given that such techniques are sensitive to signal shift, a simple transformation is
used that computes the magnitude of the Fourier transformation of ECG signals. This allows the phase components corresponding
to such shifts to be removed. Using the magnitude of the projection of a given ECG signal onto these basic components as features,
it was shown that accurate arrhythmia detection and classification were possible. The proposed strategies were applied to
a large number of independent 3s intervals of ECG signals consisting of 320 training samples and 160 test samples from the
MIT-BIH database. The samples equally represent five different ECG signal types, including normal, ventricular couplet, ventricular
tachycardia, ventricular bigeminy and ventricular fibrillation. The intervals analysed were windowed using either a rectangular
or a Hamming window. The methods demonstrated a detection rate of sensitivity 98% at specificity of 100% using nearest neighbour
classification of features from ICA and a rectangular window. Lower classification rates were obtained using the same classifier
with features from either PCA or ICA and a rectangular window. The results demonstrate the potential of the new method for
clinical use. 相似文献
34.
Müller T Ball T Kristeva-Feige R Mergner T Timmer J 《Medical & biological engineering & computing》2000,38(1):62-67
The aim is to describe a general approach to determining important electrode positions when measured electro-encephalogram
signals are used for classification. The approach is exemplified in the frame of the brain-computer interface, which crucially
depends on the classification of different brain states. To classify two brain states, e.g. planning of movement of right
and left index fingers, three different approaches are compared: classification using a physiologically motivated set of four
electrodes, a set determined by principal component analysis and electrodes determined by spatial pattern analysis. Spatial
pattern analysis enhances the classification rate significantly from 61.3±1.8% (with four electrodes) to 71.8±1.4%, whereas
the classification rate using principal component analysis is significantly lower (65.2±1.4%). Most of the 61 electrodes used
have no influence on the classification rate, so that, in future experiments, the setup can be simplified drastically to six
to eight electrodes without loss of information. 相似文献
35.
目的:获得足够量的分泌片(SC)及其相应的抗血清,用于研究SC的功能与SC在人和某些物种黏膜组织内的分布。方法:在已有的凝胶过滤和离子交换层析的基础上,进一步通过亲和层析和凝胶过滤分离纯化人的SC并进行相应的鉴定。用免疫组织化学技术检测了SC在部分小鼠组织中的表达。结果:获得了免疫纯的SC,并制备了相应的兔抗人SC的免疫血清;免疫组化显示,SC在小鼠小肠和子宫内膜处有表达。结论:利用改进的方法可以获得免疫纯的SC,进一步证实人和小鼠SC之间的交叉反应性。 相似文献
36.
The classical enzyme and protein markers ACP1 and GC have gained new importance because of the biological functions of their gene products. ACP1 encodes a low molecular weight enzyme which is now recognized as a phosphotyrosine phosphatase with a role in the regulation of signal transduction pathways, and GC‐globulin acts both as a transporter of vitamin D and as a plasma actin scavenger and plays a role in macrophage activation. These two polymorphisms were phenotyped for decades on the basis of electrophoretic isozyme or protein patterns; the gene structures are now known. Nucleotide substitutions determining the common alleles are close enough at each locus to be contained in one short PCR product. We have developed a simple, rapid and reliable multiplex method based on PCR and SSCP which allows the simultaneous determination of the common ACP1 and GC genotypes. 相似文献
37.
Lura Brianna Caddle Jeremy L. Grant Jin Szatkiewicz Johann van Hase Bobbi-Jo Shirley Joerg Bewersdorf Christoph Cremer Alain Arneodo Andre Khalil Kevin D. Mills 《Chromosome research》2007,15(8):1061-1073
Radiation exposure is an occupational hazard for military personnel, some health care professionals, airport security screeners,
and medical patients, with some individuals at risk for acute, high-dose exposures. Therefore, the biological effects of radiation,
especially the potential for chromosome damage, are major occupational and health concerns. However, the biophysical mechanisms
of chromosome instability subsequent to radiation-induced DNA damage are poorly understood. It is clear that interphase chromosomes
occupy discrete structural and functional subnuclear domains, termed chromosome territories (CT), which may be organized into
‘neighborhoods’ comprising groups of specific CTs. We directly evaluated the relationship between chromosome positioning,
neighborhood composition, and translocation partner choice in primary lymphocytes, using a cell-based system in which we could
induce multiple, concentrated DNA breaks via high-dose irradiation. We critically evaluated mis-rejoining profiles and tested
whether breaks occurring nearby were more likely to fuse than breaks occurring at a distance. We show that CT neighborhoods
comprise heterologous chromosomes, within which inter-CT distances directly relate to translocation partner choice. These
findings demonstrate that interphase chromosome arrangement is a principal factor in genomic instability outcomes in primary
lymphocytes, providing a structural context for understanding the biological effects of radiation exposure, and the molecular
etiology of tumor-specific translocation patterns. 相似文献
38.
Atsushi Sasaki Tsutomu Daa Kenji Kashima Shigeo Yokoyama Iwao Nakayama Shiro Noguchi 《Pathology international》1996,46(12):939-946
Forty-four thyroid carcinomas with an Insular component (JC) were reviewed from 2457 tumors diagnosed as papillary (PC) or follicular carcinoma (FC). These tumors were classified as FC with an IC (FCIC; 30 cases) and PC with an IC (PCIC; 14 cases). Both tumors were composed of solid cell nests in some areas and had a tendency toward a characteristic nuclear size: FCIC had a small nucleus and PCIC contained a nucleus of an Intermediate type or a large nucleus similar to that of PC, although there were numerous tumors with an exceptional nuclear size. The mean age and tumor diameter were the highest and largest in FCIC, respectively, followed by PCIC. Among the 44 cases, 17 patients died of the disease, two were alive with the disease and 18 were alive without the disease. From 13 clinicopathological factors, the presence of an IC, age, non-encapsulation, tumor size, vascular invasion and necrosis were found to be independent variables for actual prognosis of FC and PC based on univariate analysis followed by multtvariate analysis. The results of the present study indicate that the presence of an IC is an independent aggressive prognostic factor for patients with PC and FC. 相似文献
39.
40.
Inaccurate reporting of the absence of an endocervical (EC) component on Pap smears often results in slide rescreens, amended reports, clinician dissatisfaction, and sometimes unnecessary repeat smears. Therefore, the accuracy of reporting EC component adequacy was selected as a quality indicator for the laboratory continuous quality improvement program (CQI). The process consisted of problem identification, analysis of the situation, collection of data, implementation of solutions, and evaluation of results. The objective of the study was to determine if the accuracy of reporting EC component adequacy on Pap smears improved after application of such a program. During the first phase, 150 Pap smears originally reported with the absence of an adequate EC component and 150 smears reported with the presence of an adequate EC component were rescreened to measure the baseline accuracy of EC component adequacy reporting. The improvement process was then implemented. A cause-and-effect diagram was developed and root cause was determined. A presentation was then made to the cytology staff. Criteria for EC component adequacy were reviewed, examples were shown, and standardized marking of EC component was implemented. Following improvement actions, a second audit of 150 Pap smears reported with the absence of an adequate EC component as well as 150 smears reported with the presence of an adequate EC component was undertaken to measure change in performance in assessing EC component adequacy. For the baseline rescreening, before initiation of the CQI program, 98% accuracy was achieved with smears that were reported as adequate for EC component present. However, the accuracy with smears reported as absence of an adequate EC component was only 71%, i.e., an adequate EC component was identified in almost 1/3 of these cases on rescreen. After the implementation of improvement actions, the accuracy with smears reported with the presence of EC component remained high (98%) and the accuracy of reporting the absence of EC component was 90%. The difference of the latter before and after the implementation was statistically significant (P = 0.015, z-test). The accuracy of reporting EC component adequacy increased following the CQI process. Using reporting EC component adequacy as an example, we demonstrate that by treating clinical problems as quality control issues and applying basic quality improvement tools, a positive outcome can be effected. 相似文献