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PubMed1981

Latent components of potentials evoked by visual stimuli in different retinal locations.

Visually evoked potentials to small patterned stimuli were recorded in an occipital row of five electrodes. The location of the flashed checkerboard stimuli of three different spatial frequencies varied in five steps from 5 degrees on the left to 5 degrees on the right hemiretina. Repeated recordings were obtained from seven healthy subjects and one Multiple Sclerosis patient. Stimulus location, electrode position and their interaction had stronger effects on the components derived from a principal components analysis than the spatial frequency. Components most significantly related to these spatial frequency or to an interaction between spatial frequency and other experimental conditions showed later peak latencies than those related to electrode position or stimulus location. This finding suggests a later or more sustained processing of pattern information. Discriminant analyses using the patient's component scores, separate principal components analysis, and the analysis of the patient's residual components all suggested major differences between the patient and the normals.

Adult↗
PubMed2004

[Content of inorganic elements of Salvia miltiorrhiza root in different area and physicochemical properties of its growing soil].

OBJECTIVE: To provide basis of environmental factors of genuine crude drug, Salvia miltiorrhiza root. METHOD: On-the-spot investigation and indoor chemical analysis were made to study the physicochemical properties of growing soil and content of inorganic elements of S. miltiorrhiza, and obtained data were analysed with SPSS 10.0 software. RESULT: S. miltiorrhiza root of high harvest area accumulated Cu and Zn. In soil principal component analysis, no principal component was obvious. So the drug has good adaptability in ecological environment of soil. CONCLUSION: Ecological environment of soil isn't leading factor in forming genuine crude S. miltiorrhiza.

China↗
PubMed2006

Use of multivariate analysis to extract latent variables related to level of production and lactation persistency in dairy cattle.

Multivariate factor analysis and principal component analysis were used to decompose the correlation matrix of test-day milk yields of 48,374 lactations of 21,721 Italian Simmental cows. Two common latent factors related to level of production in early lactation and lactation persistency, and 2 principal components associated with the whole lactation yield and persistency were obtained. Factor and principal component scores were treated as new quantitative phenotypes related to prominent features of lactation curve shape. Genetic parameters were estimated by univariate and bivariate animal models. Estimates of heritability were moderately low for both latent factors (0.13 for persistency and yield early in lactation). Heritabilities of the principal component related to total lactation yield and 305-d yield were similar (0.19 and 0.20, respectively). Finally, heritability was quite low for the principal component related to lactation persistency (0.07). Repeatabilities between lactations were about 0.27 for both latent factors, around 0.4 for the first principal component and 305-d yield, and 0.11 for the second principal component. Moderate genetic correlation among common factors (0.26) and their high genetic correlation with total lactation yield (>0.60) suggest that selection can be used to change the shape of lactation curve as well as improve yield. Scores of the second principal component can be used to genetically improve persistency while maintaining constant total lactation yield.

Analysis of Variance↗
PubMed1991

Chromatographic data for pharmacological classification of imidazol(in)e drugs.

A set of eighteen imidazol(in)e derivative drugs of various pharmacological activity were analysed under different high-performance liquid chromatographic (HPLC) conditions. Capacity factors were determined employing methanol-buffer eluents at seven volume ratios and at pH 10.9, 7.0 and 2.9. The use of an alkaline buffer was possible owing to the application of poly(butadiene)-coated alumina (PBCA) as the stationary phase. Two systems employing octadecylsilica (ODS) columns were applied, one operated at pH 7.0 and the other at pH 2.9. Capacity factors of the test solute drugs were determined in 21 chromatographic systems. All the data were subjected to chemometric analysis despite the fact that, except for the PBCA systems, only a limited range of linearity of the logarithm of capacity factor versus volume fraction of methanol in mobile phase was observed. The matrix of 21 x 18 capacity factors was statistically analysed by the principal component method. The first two principal components accounted for 80% of the variance in the capacity factors studied. The principal component object scores clearly separated the agents into groups in accordance with their pharmacological classification. It was concluded that diverse retention data can provide more information relevant to the bioactivity of solutes than just a one-dimensional hydrophobicity scale.

Chromatography, High Pressure Liquid↗
PubMed2003

The impact of microsatellite instability on the molecular phenotype of colorectal tumors.

Frequent microsatellite instability MSI (MSI-H) occurring in human tumors is characterized by defective DNA mismatch repair and unique clinical features. However, infrequent MSI (MSI-L) has not been attributable to any other defined molecular pathway, and its existence as a biologically distinct category has been challenged. Moreover, the global molecular phenotypes (GMPs) underlying MSI-H, MSI-L, or microsatellite-stable (MSS) tumors have never been evaluated. To evaluate the impact of MSI status on GMP and to determine the importance of MSI relative to other molecular and clinical features, cDNA microarray-derived data from 41 colon cancers were interpreted using principal components analysis. The clinically relevant principal component with the greatest impact on GMP was component 3, which distinguished MSI-H from non-MSI-H (i.e., MSI-L and microsatellite stable) tumors and was designated the MSI-H separator. Notably, MSI-L cancers were also clearly distinguished from non-MSI-L tumors by another principle component, component 10 (the "MSI-L separator"). This second finding validates the existence of MSI-L tumors as a distinct molecular phenotypic category. Thus, both components 3 and 10 reflected different aspects of MSI and helped to establish principal components analysis as a useful tool to identify and characterize distinct biological features of human malignancy.

Aged↗
PubMed1998

Multivariate examination of data from gait analysis of persons with stroke.

BACKGROUND AND PURPOSE: Gait analyses yield redundant information that often is difficult to interpret. The purpose of this study was to show how principal-component analysis can provide insight into gait data obtained from persons with stroke. SUBJECTS: Twenty male and 11 female adults who were ambulatory were studied (mean age = 60.5 years, SD = 11.8, range = 24-79; mean time since stroke = 11.4 months, SD = 15.4, range = 2.0-88.0). METHODS: Spatial data were used in a 4-segment link-segment model to calculate the kinematic and kinetic variables of gait. Principal components were constructed on the averages for 40 variables. RESULTS: The first principal component was related to speed and accounted for 40.8% of the variance. The second principal component was related to differences between the 2 limbs (symmetry) and accounted for 12.8% of the variance. The third principal component was related to adoption of a postural flexion bias and accounted for 10.2% of the variance. The fourth principal component, which was not interpretable, accounted for 6.8% of the variance. CONCLUSION AND DISCUSSION: The principal-component analysis allowed clustering of related variables and simplified the complex picture presented by the large number of variables resulting from gait analysis. Examination of variables closely related to each principal component yielded insight into the nature of the strategies used in walking and their interrelationships. The method has potential for insight into similarities and differences in gait performances arising from different pathologies and for comparing the progress of individuals with similar pathologies.

Adult↗
PubMed1995

Age estimation of adults from dental radiographs.

Previous studies have shown that with advancing age the size of the dental pulp cavity is reduced as a result of secondary dentine deposit, so that measurements of this reduction can be used as an indicator of age. The aim of the present study was to find a method which could be used to estimate the chronological age of an adult from measurements of the size of the pulp on full mouth dental radiographs. The material consisted of periapical radiographs from 100 dental patients who had attended the clinics of the Dental Faculty in Oslo. The radiographs of six types of teeth from each jaw were measured: maxillary central and lateral incisors and second premolars, and mandibular lateral incisors, canines and first premolars. To compensate for differences in magnification and angulation on the radiographs, the following ratios were calculated: pulp/root length, pulp/tooth length, tooth/root length and pulp/root width at three different levels. Statistical analyses showed that Pearson's correlation coefficient between age and the different ratios for each type of tooth was significant, except for the ratio between tooth and root length, which was, therefore, excluded from further analysis. Principal component analyses were performed on all ratios, followed by regression analyses with age as dependent variable and the principal components as independent variables. The principal component analyses showed that only the two first of them had significant influence on age, and a good and easily calculated approximation to the first component was found to be the mean of all the ratios. A good approximation to the second principal component was found to be the difference between the mean of two width ratios and the mean of two length ratios, and these approximations of the first and second principal components were chosen as predictors in regression analyses with age as the dependent variable. The coefficient of determination (r2) for the estimation was strongest when the ratios of the six teeth were included (r2 = 0.76) and weakest when measurements from the mandibular canines alone were included (r2 = 0.56). Measurement on dental radiographs may be a non-invasive technique for estimating the age of adults, both living and dead, in forensic work and in archaeological studies, but the method ought to be tested on an independent sample.

Adult↗
PubMed1988

Chimeric heterosis in mandibular size in mice.

Morphometrical observations were carried out on the mandibles of chimeras made from the embryos of C57BL/6 and BALB/c mice to compare with the two strains and their reciprocal F1 crosses. The results of the principal component analysis indicate that the first principal component (PC1) and the second principal component (PC2) extracted might be acceptable as size and shape factors, respectively. Variations of both PC1 and PC2 were generally larger in the chimeras than in the two component strains and their F1 crosses. The mean PC1 value of the chimeras was larger than that of the two component inbred strains, and it was similar to that of F1 crosses, or slightly larger. The overall size of the mandible represented by PC1 tended to be larger in the chimeras consisting of two component cells that were approximately equivalent than in those that shifted to either cell population. The above trend was observed in both sexes. These results indicate that chimeric heterosis due to the interaction between genetically different cells (C57BL/6 and BALB/c) has some relation to mandible size. The mean PC2 value, which was accepted as shape factor, was intermediate between the two inbred strains. The mandible size (PC1) and shape (PC2) were bilaterally symmetrical, except for the shape in the female chimeras and in (C57BL/6 x BALB/c)F1.

Animals↗
PubMed1997

Preliminary study of relations between physical characteristics and psychological impressions of natural voices.

To improve the naturalness of synthesized voices, the relations between the physical characteristics of the synthesized voices and the psychological effects should be established. The authors performed a psychological evaluation using natural voices of men and women as stimuli. The method of principal component analysis was applied to intercorrelations, the numerical ratings of the evaluation, and principal components were extracted which represented aspects ordinary people use to evaluate natural voices. Pitches of the voices used in the evaluation were analyzed as samples of physical voice parameters, and the relations between the pitches and the principal components were examined. Four principal components were extracted, representing aspects to which most people were observed to pay most attention when listening to voices. A significant relation was also found between physical pitches which were standardized by sex and the perceived pitches which were introduced from the principal component scores. This finding suggests that different criteria are used for perceptions of pitches of men and women.

Adult↗
PubMed2001

[Russian genofond. Genogeography of surnames].

Surnames are traditionally used in population genetics as "quasi-genetic" markers (i.e., analogs of genes) when studying the structure of the gene pool and the factors of its microevolution. In this study, spatial variation of Russian surnames was analyzed with the use of computer-based gene geography. Gene geography of surnames was demonstrated to be promising for population studies on the total Russian gene pool. Frequencies of surnames were studied in 64 sel'sovets (rural communities; a total of 33 thousand persons) of 52 raions (districts) of 22 oblasts (regions) of the European part of Russia. For each of 75 widespread surnames, an electronic map of its frequency was constructed. Summary maps of principal components were drawn based on all maps of individual surnames. The first 5 of 75 principal components accounted for half of the total variance, which indicates high resolving power of surnames. The map of the first principal component exhibits a trend directed from the northwestern to the eastern regions of the area studied. The trend of the second component was directed from the southwestern to the northern regions of the area studied, i.e., it was close to latitudinal. This trend almost coincided with the latitudinal trend of principal components for three sets of data (genetic, anthropological, and dermatoglyphical). Therefore, the latitudinal trend may be considered the main direction of variation of the Russian gene pool. The similarity between the main scenarios for the genetic and quasi-genetic markers demonstrates the effectiveness of the use of surnames for analysis of the Russian gene pool. In view of the dispute between R. Sokal and L.L. Cavalli-Sforza about the effects of false correlations, the maps of principal components of Russian surnames were constructed by two methods: through analysis of maps and through direct analysis of original data on the frequencies of surnames. An almost complete coincidence of these maps (correlation coefficient rho = 0.96) indicates that, taking into account the reliability of the data, the resultant maps of principal components have no errors of false correlations.

Gene Pool↗
PubMed1998

[Role of school lunch in primary school education: a trial analysis of school teachers' views using an open-ended questionnaire].

We tried to analyze synthetically teachers' view points associated with health education and roles of school lunch in primary education. For this purpose, a survey using an open-ended questionnaire consisting of eight items relating to health education in the school curriculum was carried out in 100 teachers of ten public primary schools. Subjects were asked to describe their view regarding the following eight items: 1) health and physical guidance education, 2) school lunch guidance education, 3) pupils' attitude toward their own health and nutrition, 4) health education, 5) role of school lunch in education, 6) future subjects of health education, 7) class room lesson related to school lunch, 8) guidance in case of pupil with unbalanced dieting and food avoidance. Subjects described their own opinions on an open-ended questionnaire response sheet. Keywords in individual descriptions were selected, rearranged and classified into categories according to their own meanings, and each of the selected keywords were used as the dummy variable. To assess individual opinions synthetically, a principal component analysis was then applied to the variables collected through the teachers' descriptions, and four factors were extracted. The results were as follows. 1) Four factors obtained from the repeated principal component analysis were summarized as; roles of health education and school lunch program (the first principal component), cooperation with nurse-teachers and those in charge of lunch service (the second principal component), time allocation for health education in home-room activity and lunch time (the third principal component) and contents of health education and school lunch guidance and their future plan (the fourth principal component). 2) Teachers regarded the role of school lunch in primary education as providing daily supply of nutrients, teaching of table manners and building up friendships with classmates, health education and food and nutrition education, and developing food preferences through eating lunch together with classmates. 3) Significant positive correlation was observed between "the teachers' opinion about the role of school lunch of providing opportunity to learn good behavior for food preferences through eating lunch together with classmates" and the first principal component "roles of health education and school lunch program" (r = 0.39, p < 0.01). The variable "the role of school lunch is health education and food and nutrition education" showed positive correlation with the principle component "cooperation with nurse-teachers and those in charge of lunch service" (r = 0.27, p < 0.01). Interesting relationships obtained were that teachers with longer educational experience tended to place importance in health education and food and nutrition education as the role of school lunch, and that male teachers regarded the roles of school lunch more importantly for future education in primary education than female teachers did.

Adult↗
PubMed1993

Effect of solvent on collective motions in globular protein.

Two molecular dynamics simulations on bovine pancreatic trypsin inhibitor (BPTI), have been made, one in vacuum, the other in water, in order to assess the effect of the solvent water on collective motions. Principal component analysis has been performed to determine collective modes, the principal components, which are assumed to behave as effectively independent harmonic oscillators. Projection of the protein's motion in water onto the plane defined by the first two principal components shows a clustering effect in the trajectory, absent in the vacuum trajectory. This is thought to be due to many local minima in the free energy surface caused by solute-solvent interactions. In order to assess the viscous effect of the solvent, friction coefficients for the principal components were determined by analyzing their velocity correlation functions in terms of the Langevin equation for an independent damped oscillator. Consistent with this analysis is that all modes have friction coefficients centered on the value of 47 cm-1 in a range of +/- 10 cm-1. With this friction coefficient, all modes of effective frequencies below 23.5 cm-1 display overdamped motion. By assuming the harmonic approximation for the conformational energy surface for BPTI in vacuum to be valid for BPTI in water, and treating each mode as an independent damped oscillator with a friction coefficient of 47 cm-1, the shift to higher frequencies in the water spectrum relative to the vacuum spectrum could be almost exactly reproduced, indicating this shift is due solely to the viscous effect of the solvent. By analyzing the time correlation functions of the first four principal components it is found that they can be very well described as independent damped oscillators each with a friction coefficient of 47 cm-1.

Animals↗
PubMed2006

Coordination of thumb joints during opposition.

Thumb opposition plays a vital role in hand function. Kinematically, thumb opposition results from composite movements from multiple joints moving in multiple directions. The purpose of this study was to examine the coordination of thumb joints during opposition tasks. A total of 15 female subjects with asymptomatic hands were studied. Three-dimensional angular kinematics of the carpometacarpal (CMC), metacarpophalangeal (MCP) and interphalangeal (IP) joints were obtained by a marker-based motion analysis system. Thumb opposition revealed coordination among joints in a specific direction (inter-joint coordination) and among different directions within a joint (intra-joint coordination). In particular, linear couplings existed between the flexion and pronation at the CMC joint, and between the flexion of the CMC joint and flexion of the MCP joint. Principal component analysis showed that only two principal components adequately represented the thumb opposition data of seven movement directions. A term functional degrees of freedom by virtue of principal component analysis was proposed to uncover the extent of movement coordination in functional tasks.

Biomechanical Phenomena↗
PubMed2004

Measurement of continuity of care in cardiac patients: reliability and validity of an in-person questionnaire.

BACKGROUND: Breaks in continuity of care occur during the care of patients with cardiac conditions, such as congestive heart failure (CHF) and atrial fibrillation (AF), during their hospitalization, the discharge process or follow-up care. Recently, to measure continuity of care for such patients, a comprehensive questionnaire was developed to reflect the cardiac patient's perspective on multifaceted aspects of continuity of care. OBJECTIVE: To examine the psychometric properties of an in-person interview questionnaire for the measurement of continuity of care in patients recently hospitalized with CHF or AF. METHODS: The Heart Continuity of Care Questionnaire (HCCQ) was administered to 350 cardiac patients (176 with CHF and 174 with AF) at least six months after discharge from hospitals in two urban centres. The questionnaire was assessed by item and principal components analysis. Factors derived from principal components analysis were assessed for internal consistency and construct validity against variables of comorbidity, health status and symptom severity. RESULTS: A principal components analysis produced three subscales. These subscales were internally consistent, and demonstrated construct validity through expected correlations with other variables and theoretical constructs. CONCLUSION: The present study supports the reliability and validity of the HCCQ for measuring continuity of care. The HCCQ subscales correspond to the theoretical components of continuity of care that have been proposed, namely relational, informational and management continuity. The HCCQ subscales may be of value for identifying problems in continuity of care and for evaluating interventions aimed at improving continuity of care for cardiac patients after hospital discharge.

Adult↗
PubMed1998

Tissue inhibitors of metalloproteinases level and collagenase activity in gingival crevicular fluid: the relevance to periodontal diseases.

OBJECTIVES: To provide an overall assessment of levels of tissue inhibitors of metalloproteinases (TIMPs), collagenase activities, and of immuno-reactivities for matrix metalloproteinases (MMP)-1 and -8 in gingival crevicular fluid (GCF) obtained from healthy subjects, and gingivitis and periodontitis patients, and to analyse the relationships between periodontal tissue destruction and the GCF components in periodontal diseases by principal component analysis. MATERIALS AND METHODS: GCF was sampled with sterile paper strips from 10 gingivitis and 11 periodontitis patients. Ten volunteers served as clinically healthy controls. TIMP-1 and -2 protein amounts in GCF were measured by ELISA, and active and APMA-activatable collagenase activities were determined by functional assays using image-analysis after SDS-PAGE. RESULTS: GCF TIMP-1 level and both active and latent collagenase activities were significantly higher in the diseased groups than in the healthy group. TIMP-2 was detectable in only 29% of all subjects (mean: 2.06 ng). Western blot analysis showed that MMP-8 was the major interstitial collagenase in the GCF of the diseased groups. Principal component analysis using clinical parameters and the GCF components has indicated components one to three account for 87% of total variation when evaluating the relevance of their measurements to periodontal diseases. CONCLUSIONS: We conducted the functional and immunological characterization of MMPs and TIMPs in the GCF of periodontally diseased patients. Principal component analysis indicated components one to three explaining 87% of total variation, and further suggested that higher collagenase activity (especially in active collagenase) would be an important marker in evaluating the pathogenesis of periodontitis. Consequently, these observations may have significant therapeutic and diagnostic implications.

Adult↗
PubMed2003

Increases in regional subarachnoid CSF without apparent cortical gray matter deficits in schizophrenia: modulating effects of sex and age.

OBJECTIVE: The authors investigated the modulating effects of biological sex and age on regional decreases in cortical gray matter and increases in subarachnoid CSF in 25 patients with chronic schizophrenia and 28 group-matched healthy comparison subjects. METHOD: Computational cortical pattern-matching methods were employed to measure the local proportions of gray matter and subarachnoid CSF at thousands of homologous cortical surface locations in each subject using high-resolution magnetic resonance images. Principal-component analysis reduced tissue proportion values obtained at each cortical surface point into component scores for each subject. Principal-component analysis scores were used as dependent variables in statistical analyses that included diagnosis, age, and sex as predictor variables. To reveal more regional changes in tissue proportions, statistical differences in gray matter and CSF were compared at each cortical surface location and mapped in three dimensions. RESULTS: Principal-component analyses revealed main effects of diagnosis, sex, and age for the CSF increases seen in the schizophrenia patients, in male subjects, and in association with age. Significant diagnosis-by-age, diagnosis-by-sex, and diagnosis-by-sex-by-age interactions were also observed, revealing CSF increases in male patients at younger ages. Statistical maps showed regional increases in subarachnoid CSF in association with the above effects. For cortical gray matter measurements, only main effects of age were observed. CONCLUSIONS: Regionally specific increases in sulcal and subarachnoid CSF occur during adulthood and appear prematurely in male schizophrenia patients. Cortical gray matter reductions show aging effects but are below the threshold of significance in schizophrenia.

Adult↗
PubMed2004

PCA in studying coordination and variability: a tutorial.

OBJECTIVE: To explain and underscore the use of principal component analysis in clinical biomechanics as an expedient, unbiased means for reducing high-dimensional data sets to a small number of modes or structures, as well as for teasing apart structural (invariant) and variable components in such data sets. DESIGN: The method is explained formally and then applied to both simulated and real (kinematic and electromyographic) data for didactical purposes, thus illustrating possible applications (and pitfalls) in the study of coordinated movement. BACKGROUND: In the sciences at large, principal component analysis is a well-known method to remove redundant information in multidimensional data sets by means of mode reduction. At present, principal component analysis is starting to penetrate the fundamental and clinical study of human movement, which amplifies the need for an accessible explanation of the method and its possibilities and limitations. Besides mode reduction, we discuss principal component analysis in its capacity as a data-driven filter, allowing for a separation of invariant and variant properties of coordination, which, arguably, is essential in studies of motor variability. METHODS: Principal component analysis is applied to kinematic and electromyographic time series obtained during treadmill walking by healthy humans. RESULTS: Common signal structures or modes are identified in the time series that turn out to be readily interpretable. In addition, the identified coherent modes are eliminated from the data, leaving a filtered, residual pattern from which useful information may be gleaned regarding motor variability. CONCLUSIONS: Principal component analysis allows for the detection of modes (information reduction) in both kinematic and electromyographic data sets, as well as for the separation of invariant structure and variance in those data sets. RELEVANCE: Principal component analysis can be successfully applied to movement data, both as feature extractor and as data-driven filter. Its potential for the (clinical) study of human movement sciences (e.g., diagnostics and evaluation of interventions) is evident but still largely untapped.

Algorithms↗
PubMed2004

Multiplicative neural noise can favor an independent components representation of sensory input.

Arguments have been advanced to support the role of principal components (e.g., Karhunen-Loéve, eigenvector) and independent components transformations in early sensory processing, particularly for color and spatial vision. Although the concept of redundancy reduction has been used to justify a principal components transformation, these transformations per se do not necessarily confer benefits with respect to information transmission in information channels with additive independent identically distributed Gaussian noise. Here, it is shown that when a more realistic source of multiplicative neural noise is present in the information channel, there are quantitative benefits to a principal components or independent components representation for Gaussian and non-Gaussian inputs, respectively. Such a representation can convey a larger quantity of information despite the use of fewer spikes. The nature and extent of this benefit depend primarily on the probability distribution of the inputs and the relative power of the inputs. In the case of Gaussian input, the greater the disparity in power between dimensions, the greater the advantage of a principal components representation. For non-Gaussian input distributions with a kurtosis that is super-Gaussian, an independent components representation is similarly advantageous. This advantage holds even for input distributions with equal power since the resulting density is still rotationally asymmetric. However, sub-Gaussian input distributions can lead to situations where maximally correlated inputs are the most advantageous with respect to transmitting the greatest quantity of information with the fewest number of spikes.

Models, Neurological↗