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PubMed1998

Low dimensionality of supraspinally induced force fields.

Recent experiments using electrical and N-methyl-D-aspartate microstimulation of the spinal cord gray matter and cutaneous stimulation of the hindlimb of spinalized frogs have provided evidence for a modular organization of the frog's spinal cord circuitry. A "module" is a functional unit in the spinal cord circuitry that generates a specific motor output by imposing a specific pattern of muscle activation. The output of a module can be characterized as a force field: the collection of the isometric forces generated at the ankle over different locations in the leg's workspace. Different modules can be combined independently so that their force fields linearly sum. The goal of this study was to ascertain whether the force fields generated by the activation of supraspinal structures could result from combinations of a small number of modules. We recorded a set of force fields generated by the electrical stimulation of the vestibular nerve in seven frogs, and we performed a principal component analysis to study the dimensionality of this set. We found that 94% of the total variation of the data is explained by the first five principal components, a result that indicates that the dimensionality of the set of fields evoked by vestibular stimulation is low. This result is compatible with the hypothesis that vestibular fields are generated by combinations of a small number of spinal modules.

Animals↗
PubMedDate not supplied

Finger ridge-count variability in sub-Saharan Africa.

Mean finger ridge-count data were obtained, primarily from literature sources, for 31 male and 24 female sub-Saharan African samples. The 10 finger ridge-counts and total ridge-count were used as independent variables in a multiple regression analysis, latitude and longitude serving in turn as the dependent variables. The results show that it is not the magnitude of the ridge-counts themselves that is important, but rather contrasts between groups of digits. The most important geographically patterned variation in ridge-counts consists of contrasts between digits 4 and 5 and digits 2 and 3. South and south-east African populations are characterized by low contrasts, west Africans by high contrasts and, south-west Africans are intermediate. The geographical patterning of the contrast agrees well with known patterns of gene flow into and within the continent as determined by serological genes. Principal components analysis was also carried out to determine whether within-group components corresponding to the geographically relevant between-group variation could be identified. The third, fourth and fifth components drew the same types of contrasts between the groups of digits identified in the multiple regression analysis, but they were relatively unimportant. The geographically important principal components would have been overlooked in a traditional multivariate analysis of finge ridge-counts, since the analysis would have been dominated by pattern size. We conclude that finger ridge-counts are potentially very useful in population studies, but account must be taken of their multicomponent nature.

Africa, Southern↗
PubMed2007

Staff attitudes towards working with drug users: development of the Drug Problems Perceptions Questionnaire.

AIM: To evaluate the psychometric properties of an adaptation of the Alcohol and Alcohol Problems Perceptions Questionnaire to measure the attitudes of staff to working with drug users (the DDPPQ). DESIGN: Postal survey: a questionnaire was mailed to participants on two occasions. SETTING: A large urban National Health Service (NHS) mental health service. PARTICIPANTS: A stratified random sample of medical staff, clinical psychologists, occupational therapists and nurses (n = 672) who work within generic mental health, adolescent psychiatry, forensic psychiatry and alcohol and drug services. Response rate at Time 1 was 56% and 68% at Time 2. MEASUREMENTS: A structured demographic questionnaire; individual item and total scores for the DDPPQ administered on two occasions 4 weeks apart; data relating to the content validity of the instrument. FINDINGS: A principal component analysis confirmed the DDPPQ's construct validity and participants confirmed its content validity. Following analysis of the instrument's test-retest reliability and its principal component structure it was reduced to a 20-item scale. Its five subscales related to role adequacy, role support, job satisfaction, role-specific self-esteem and role legitimacy. CONCLUSION: The refined DDPPQ was shown to be a valid and reliable tool which can be used to measure attitudes of people in relation to working with drug users.

Alcoholism↗
PubMed2004

Assessing undergraduate palliative care education: validity and reliability of two scales examining perceived efficacy and outcome expectancies in palliative care.

BACKGROUND: Medical students have traditionally received little education in palliative care. However, in 1999, as part of a revised medical curriculum, Year 4 undergraduates at Liverpool University participated in a 2-week programme of education in palliative care. To assess the effect of the education programme, 2 assessment scales were identified: the Self-efficacy in Palliative Care Scale (SEPC) (assessing efficacy in communication, patient management and multiprofessional teamworking) and the Thanatophobia Scale (assessing attitudes towards palliative care). The aim of this study was to examine the psychometric properties of these scales. METHODS: The scales were examined by 5 palliative care doctors for content validity and appropriate wording. Following this, the SEPC and Thanatophobia Scales were completed by the undergraduates (n = 139) prior to and after completion of the education programme. RESULTS: Both scales were analysed independently on pre- and post-test scores. Cronbach's alphas of 0.84-0.85 and 0.92-0.95 were recorded, respectively, indicating high reliability. Varimax rotated principal components analysis of the SEPC Scale suggested 3 distinct factors, as theoretically expected, with high factor loadings of 0.45-0.89 at pre- and post-test. Principal components analysis of the Thanatophobia Scale suggested only 1 factor underlies the scale, as theoretically expected. All 7 items had high factor loadings of 0.60-0.81 at pre- and post-test. CONCLUSIONS: The results suggest that the SEPC and Thanatophobia Scales are valid and reliable assessment scales that may be of use when evaluating the impact of an education programme.

Curriculum↗
PubMed1988

Further studies on the resolution of human mercapt- and nonmercaptalbumin and on human serum albumin in the elderly by high-performance liquid chromatography.

High-performance liquid chromatographic (HPLC) analysis of human serum albumin (HSA) on Asahipak GS-520 showed at least two peaks, the principal component corresponding to human mercaptalbumin (HMA) and the secondary one to nonmercaptalbumin (HNA). HPLC analysis of HSA on Asahipak ES-520 N showed three peaks, the principal component corresponding to HMA, the secondary one to HNA having mixed disulfide with cysteine or glutathione and the tertiary one to HNA oxidized higher than mixed disulfide. Two kinds of rapid HPLC for the resolution of HSA into HMA and HNA were developed by the present authors. Using these HPLC, the present authors found a significant decrease in the fraction of HMA in the elderly.

Aged↗
PubMed1982

Digital dermatoglyphics of the Samaritans.

Analysis of digital dermatoglyphics in a sample of 109 Samaritans in Cholon, Israel, suggests in several quantitative measures reduction in variance by comparison with the limited data available from populations elsewhere. Such reduction would be expected in an inbred population. It is not clear whether this is due to Samaritan inbreeding, or is a general feature of Middle-East populations. The Samaritans tend toward the extreme of the Middle-East range of pattern frequencies, but are not grossly different in any of the conventional descriptive dermatoglyphic variables. Principal component analysis suggests slight differences in eigenvalues and differing distributions of the eigenvectors over the digits but, despite some random fluctuation due to sample size, the principal components observed in other populations are also detectable in the Samaritans.

Consanguinity↗
PubMed2001

Multispectral imaging of tablets in blister packaging.

This experiment tested the hypothesis that using near-infrared (IR) imaging spectrometry on tablets through blister packs permits the identification and composition of multiple individual tablets to be determined simultaneously. Aspirin was selected for this study because its breakdown mechanism is well understood. Near-IR cameras were used to collect thousands of spectra simultaneously from a field of packaged aspirin tablets. Tablets were selected by a principal component analysis selection algorithm. Graphs of the columns of the transformation matrix showed that salicylic acid and acetylsalicylic acid in the samples were modeled by the principal components. The bootstrap error-adjusted single-sample technique chemometric-imaging algorithm was used to draw probability-density contour plots that revealed tablet composition. Choice of color was used to represent constituent identity, whereas intensity represented concentration. The percentage of usable pixels in the indium antimonide (InSb) array was 99.9%. The SEP was 0.06% of the tablet mass for both water uptake and salicylic acid production. The number of tablets that a typical near-IR camera can currently analyze simultaneously was also estimated to be approximately 1300.

Aspirin↗
PubMed1999

[Genogeographic analysis of subdivided population. The Adyge gene pool in the Caucasian gene pool system].

A gene geographic analysis of the indigenous population of the Caucasian historical cultural province was carried out with a set of genetic markers extensively studied in the Adyges (39 alleles of 18 loci): AB0, ACP, C3, FY, GC, GLO, HP, KEL, LEW, MN, MNS, P, PGD, PGM1, RH-C, RH-D, RH-E, and TF. Genetic information on 160 Caucasian populations was used (on average, 65 populations per locus). A synthetic map of the first principal component clearly showed a division into two gene geographic provinces: Northern Caucasus and Transcaucasia. The component significantly differed across the Greater Caucasian Ridge. One of the major regions of extreme values corresponded to the Adyge region. A map of the second component revealed two poles, Northwestern (the Adyges) and Caspian, in gene pool variation of the Caucasian population. The analysis of the maps and the space of principal components showed that the Adyge population is an important component of the Caucasian gene pool. A map of genetic distance from all Caucasian populations to the Adyges showed that the north Caucasian populations (excluding the Ossetes) are the most genetically similar to the Adyges, while Georgians from the Kolkhida Valley and Azerbaijanians from the lowlands near the Caspian Sea and highland steppes are the most genetically remote from the Adyges. The genetic diversity (GST x 10(2)) of the entire Caucasian gene pool was studied. The average diversity of subpopulation within a Caucasian ethnos was GS-E = 0.81, the diversity of ethnoses within a linguistic family was GE-L = 0.83, and the diversity of linguistic families was GL-T = 0.58. The race classification of the Caucasian populations (GS-E = 0.81, GS-R = 0.80, GR-T = 0.76) proved to be more genetically informative than the linguistic one. The major parameters of the Adyges (total diversity HT = 0.364, heterozygosity HS = 0.361, and subpopulation diversity within the ethnos GS-E = 0.69) were similar to those averaged over the entire Caucasian population. A comparison with the same set of genetic markers showed that the interethnic diversity in the Caucasian region was lower than in the other north Eurasian regions (GS-E was 1.24 in the European region, 1.42 in the Ural region, 1.27 in Middle Asia, and 3.85 in Siberia).

Gene Pool↗
PubMed1998

Translation, adaptation, and validation of the SF-36 Health Survey for use in Japan.

Development of the Japanese SF-36 was completed in two phases: Phase 1: Japanese version 1.1 was produced according to International Quality of Life Assessment (IQOLA) project guidelines, but some results of psychometric tests were unexpected. First, scores varied little across physical-functioning items. Second, using factor analysis, we could not clearly distinguish the scales designed to measure the "physical" component of quality of life from those designed to measure the "mental" component. Phase 2: Focus-group discussions revealed that limited had often been interpreted as limited by a doctor. Therefore, is difficult to do was used instead (version 1.2). Results of two surveys indicated that version 1.2 yields scores that are reliable by internal consistency and test-retest standards and yields two principal components. In Japan, however, the pattern of correlations between some scales and the principal components differs from that in the United States. Iterative use of qualitative and quantitative methods was very important in developing the Japanese SF-36.

Cross-Cultural Comparison↗
PubMed1976

Intensity and rate functions of cochlear and brainstem evoked responses to click stimuli in man.

The complex of five waves, which are the responses to click stimuli of the auditory nerve and the brainstem auditory nuclei, were recorded in ten human subjects by means of earlobe and scalp electrodes. The rate of the stimuli was varied from 5/s to 80/s and their intensity was varied over a 70 dB intensity range in order to study the rate and intensity functions of each of the response components. With increasing click intensity, the amplitude of the first wave (generated by the auditory nerve) increased proportionally while the amplitudes of the later waves (generated by the brainstem auditory nuclei) reached their maximum amplitudes at intermediate click levels (saturation), and at high intensities occasionally even decreased in amplitude. The latency of each of the waves decreased by similar amounts as the intensity was increased. With increasing click rates, the amplitude of the first wave decreased the most, while there were smaller effects on the amplitude of the later waves. There was no effect of click rate on the latency of the first wave, but the latency of the later waves increased with click rate, the effect being greater on the later waves. In the rate functions, the latency change of a wave was greater than that of the waves preceding it (accumulative effect). These results are explained by overlapping convergence and divergence in the ascending auditory pathway. These results support the notion that the principal component of each wave is activated by the principal component of the previous wave. These results may explain the relative ease with which several workers record the fourth wave of the complex, and their preference for this response.

Auditory Pathways↗
PubMedDate not supplied

Levels of PCDD/Fs in soil samples in the vicinity of a municipal solid waste incinerator.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in 24 soil samples collected near a municipal solid waste incinerator (Tarragona, Catalonia, Spain). Soil samples were obtained at various sites within 1.5 km from the stack. Total PCDD/F concentrations ranged from 0.225 to 5.80 ng TEQ/kg dry matter (d.m.) with a median value of 0.799 ng TEQ/kg and a mean value of 1.080 ng TEQ/kg. No remarkable PCDD/F contamination was found. The results were consistent and even lower than those reported in other international studies. Principal Component Analysis and hierarchical cluster analysis were used to compare these soil samples with a set of 10 additional samples collected outside the influence of the plant. Principal Component and hierarchical cluster analyses of soils in the vicinity of the incinerator provide patterns of PCDD/Fs quite similar from those obtained in soils collected far from the influence of that facility.

Benzofurans↗
PubMed2002

Quantitative variations in the pathology of 11 cases of variant Creutzfeldt-Jakob disease (vCJD).

Quantitative variations in the density and distribution of the vacuolation ('spongiform change'), surviving neurons, and prion protein (PrP) deposits were studied in eight brain regions from 11 cases of variant Creutzfeldt-Jakob disease (vCJD). Principal components analysis (PCA) was used to study the similarities and differences between cases and to identify the neuropathological variables which could best account for these variations. Two principal components (PC) were extracted from the data accounting in total for 93.4% of the variance; the majority of the variance (90%) being associated with PC1. Some clustering of the 11 cases in relation to PC1 and PC2 was evident. The densities of the vacuolation in the occipital cortex and the molecular layer of the cerebellum were positively and negatively correlated, respectively, with PC1. No significant variation between cases was associated with PrP deposition. These data suggest that vCJD cases have a consistent neuropathological profile characterised by the presence of vacuolation, neuronal loss and PrP deposition in the form of florid and non-florid deposits. However, there are quantitative variations between cases in the development of the vacuolation especially affecting the occipital cortex and cerebellum.

Journal Article↗
PubMed1998

Axial synergies in parkinsonian patients during voluntary trunk bending.

During upper trunk movements, the axial kinematic synergies (opposite movements of upper and lower segments) preserve the balance by minimizing the antero-posterior center of gravity (CG) shift due to the movement. Forward and backward upper trunk movements were analyzed in a population of parkinsonian patients (PD) that were subject to falling, in order to determine whether an impaired control of the kinematic synergies might explain the falling. Ten PD (stage III-IV of the Hoehn and Yahr classification; Hoehn MM, Yahr MD. Parkinsonism: onset, progression and mortality. Neurology 1967;17;427-432) were compared to seven age-matched control subjects (CS). Kinematic analysis and force platform recordings were carried out. Principal Component (PC) analysis was performed to measure the coupling between hip, knee and ankle joint angles during the movement. (1) In both PD and CS, the first principal component (PC1) was found to account for 98% or more of the joint angles changes, which indicates that there exists a strong coupling between the angles during the movement; however, the part of the movement not accounted for by PC1 was twice as high in PD as in CS. (2) The intertrial variability between the angle ratios was about twice as high in PD as in CS. (3) The absolute value of the antero-posterior CG shift occurring during the movement significantly increased in PD in the case of backward movements, both fast and slow. (4) As a high correlation was found between actual CG shift and its estimation based on the observed interjoint coordination, the increased CG shift in PD was related to unproper set of ratios between joint angles. It was concluded that the control of the kinematic synergy is preserved on the whole in PD, with an increased variability and unproper set of the ratios between joint angular changes. This may lead to CG shifts to beyond the support surface, especially in backward bending. Copyright 1998 Elsevier Science B.V.

Journal Article↗
PubMed2004

In situ spectral monitoring of mRNA translation in embryonic stem cells during differentiation in vitro.

Raman microspectroscopy was used to determine biochemical markers during the differentiation of embryonic murine stem cells (mES) in vitro. Such markers are useful to determine the differentiation status of ES cells cultured on biomaterials. Raman spectra of mES cells as undifferentiated, spontaneously differentiated (4 days), and differentiated cells via formation of embryoid bodies (16, 20 days) were analyzed. Unsupervised hierarchical cluster analysis and principal component analysis were used to determine biochemical differences between mES cells in various states of differentiation. The undifferentiated cells were characterized by high scores of the first principal component (PC1, 49% variance). Similarity between the PC1 loading and the Raman spectrum of RNA indicated a high concentration of RNA in mES cells compared to differentiated cells. The ratio between the peak areas of RNA and proteins was used as a measure of mRNA translation. Using the same peak area ratio, it was possible to differentiate even between mES as undifferentiated and in early stages of differentiation (4 days). These findings were correlated with biological studies reporting high levels of nontranslated mRNA during early embryonic development. Therefore, the RNA translation obtained from the Raman spectra can be used as marker of differentiation state of mES cells.

Animals↗
PubMedDate not supplied

Combined MEDV-GA-MLR method for QSAR of three panels of steroids, dipeptides, and COX-2 inhibitors.

The MEDV-13, molecular electronegativity distance vector based on 13 atomic types, has at best 91 descriptors. It is impossible to indirectly use multiple linear regression (MLR) to derive a quantitative structure-activity relationship (QSAR) model. Although principal component regression (PCR) or partial least-squares regression (PLSR) can be employed to develop a latent QSAR model, it is still difficult how to determine the principal components (PCs) and depict the physical meaning of the PCs. So, a genetic algorithm (GA) is first employed to select an optimal subset of the descriptors from original MEDV-13 descriptor set. Then MLR is utilized to build a QSAR model between the optimal subset and the biological activities of three sets of compounds. For 31 benchmark steroids, a 5-descriptor QSAR model (M1) between the corticosteroid-binding globulin (CBG) binding affinity of the steroids and 5-descriptor subset is developed. The root-mean-square error of estimations (RMSEE) and the correlation coefficient of estimations (r) between the CBG binding affinity (BA) observed and the BA estimated by M1 are 0.422 and 0.9182, respectively. The root-mean-square error of predictions (RMSEP) and the correlation coefficient of predictions (q) between the BA observed and the BA predicted by leave-one-out cross validations are 0.504 and 0.8818, respectively. For 58 dipeptides inhibiting angiotensin-converting enzyme (ACE), a 5-variable QSAR model (M2) between the pIC(50) of peptides and 5-descriptor subset is derived. The M2 has a high quality with RMSEE = 0.339 and r = 0.9398 and RMSEP = 0.370 and q = 0.9280. For 16 indomethacin amides and esters (ImAE) inhibiting cyclooxygenase-2 (COX-2), a 6-variable QSAR model (M3) with RMSEE = 0.079 and r = 0.9839 and RMSEP = 0.151 and q = 0.9413 is built.

Cyclooxygenase 2↗
PubMed1984

Effects of a lacto-ovo vegetarian diet on serum concentrations of cholesterol, triglyceride, HDL-C, HDL2-C, HDL3-C, apoprotein-B, and Lp(a).

The effect of intervention with a lacto-ovo vegetarian diet on serum concentrations of cholesterol, triglyceride, total high-density lipoprotein cholesterol (HDL-C), HDL2-C, HDL3-C, low-density lipoprotein cholesterol, apoprotein-B, apoprotein-HDL, and Lp(a) was studied in 19 men and 17 women. Most weekday meals were obtained from a single source and dietary records were completed to assess the changes in nutrient intakes. Blood was collected in the 6th wk of each dietary period. Because of strong correlations between many of the changes in nutrient intakes, principal component (factor) analysis was used followed by stepwise multiple regression analysis to identify associations between changes in diet and changes in lipid, lipoprotein or apoprotein levels. Three principal components accounted for 92.0% of the variation in lipid levels: factor 1 represented an increase in saturated fat, total fat, monounsaturated fat, cholesterol, and energy intake: factor 2 represented an increase in fiber and polyunsaturated fat, and decrease in protein intake; factor 3 an increase in total carbohydrate, complex carbohydrate, and energy intake. Where a change in a variable was significantly associated with change in diet, one factor appeared primarily responsible for the change; total cholesterol (factor 2, p = 0.034); triglyceride (factor 3, p = 0.005); apo-HDL (factor 1, p = 0.014); HDL2-C (factor 2, p = 0.023), HDL3-C (factor 3, p = 0.015). A borderline significant association was seen for total HDL-C (factor 2, p = 0.055).

Alcohol Drinking↗
PubMed2002

Modeling and estimation problems in the turtle visual cortex.

The goal of this paper is to verify that position and velocity of a spot of light incident on the retina of a turtle are encoded by the spatiotemporal dynamics of the cortical waves they generate. This conjecture is examined using a biophysically realistic large-scale computational model of the visual cortex implemented with the software package, GENESIS. The cortical waves are recorded and analyzed using principal components analysis and the position and velocity information from visual space is mapped onto an abstract B-space, to be described, using the coefficients of the principal components expansion. The likely values of the position/velocity are estimated using standard statistical detection methods.

Algorithms↗
PubMed1999

Use of the functional assessment measure (FIM+FAM) in head injury rehabilitation: a psychometric analysis.

OBJECTIVES: The drive to measure outcome during rehabilitation after brain injury has led to the increased use of the functional assessment measure (FIM+FAM), a 30 item, seven level ordinal scale. The objectives of the study were to determine the psychometric structure, internal consistency, and other characteristics of the measure. METHODS: Psychometric analyses including both traditional principal components analysis and Rasch analysis were carried out on FIM+FAM data from 2268 assessments in 965 patients from 11 brain injury rehabilitation programmes. RESULTS: Two emergent principal components were characterised as representing physical and cognitive functioning respectively. Subscales based on these components were shown to have high internal consistency and reliability. These subscales and the full scale conformed only partially to a Rasch model. Use of raw item ratings, as opposed to transformed ratings, to produce summary scores for the two subscales and the full scale did not introduce serious distortion. CONCLUSION: The full FIM+FAM scale and two derived subscales have high internal reliability and the use of untransformed ratings should be adequate for most clinical and research purposes in comparable samples of patients with head injury.

Activities of Daily Living↗