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At least 973 records · Page 54Linked to original sources
PubMed2004

Metal and metallothionein level in the heat-treated cytosol of gills of transplanted mussels Mytilus galloprovincialis Lmk.

A stock of mussels Mytilus galloprovincialis was transplanted over 1 year to four sites in a semi-enclosed bay in Croatia which is under the influence of various sources of pollution. The positive correlation of metal (Cd, Zn, Cu, Mn, Fe) and metallothionein (MT) tissue contents based on the analysis of heat-treated cytosol of gills with shell mass, as an indicator of mussel age, indicated to accumulation of metals, as well as the increase of MTs with mussel age. The principal component analysis (PCA) revealed that 74% of total variance of obtained results could be explained through two principal components. The first principal component was highly correlated with MT, Cd and Zn indices (metal or MT content/shell mass), and the second one with Cu, Mn, and Fe indices, as well as the gill index. High correlation of MTs with Zn and Cd is consistent with their affinity for binding to MTs.

Age Factors↗
PubMed1998

[The ecologic component of the geographic variation of the Northern Eurasian gene pool and its archaeological age].

The problem of the relationship between the state of the gene pool and population health was formulated. The subdivision into latitudinal zones, which is a characteristic feature of the northern Eurasian gene pool, was studied. This subdivision was expressed in the geographical distribution of the second principal component (PC2.G) of the total variance of 100 allelic frequencies for 34 polymorphic loci. It was suggested that this distribution of PC2.G resulted from the genetic adaptation of the population to the latitudinal zonality that is characteristic of northern Eurasia. It was also suggested that the latitudinal geographic variation was not inherent in the northern Eurasian gene pool and was younger than its total historical age. The evolutionary age of the principal components of the gene pool was estimated based on the geography of the principal components of the geographic variability of the late Paleolithic material culture, as well as the paleogeography of the Quaternary period. It was demonstrated that the first principal component of the modern gene pool was almost completely formed in the late Pleistocene; hence, its age is at least 16,000-26,000 years. The age of the second principal component (PC2.G) was estimated at less than 12,000-15,000 years; it was mostly formed in Holocene. A hypothesis was advanced that genetic adaptation occurs at the cost of population health, with the cost increasing as the evolutionary age of the genetic adaptation decreases. It was suggested that the latitudinal zonality of gene pool was accompanied by a similar zonality in the geography of morbidity as a cost of genetic adaptation.

Adaptation, Physiological↗
PubMed1997

A case-control study to identify farm factors affecting fertility of dairy herds: multivariate description of factors.

OBJECTIVES: To determine whether a multivariate model could be developed to describe farm factors affecting fertility of dairy herd and to examine the factors that determined better reproductive performance on dairy farms in New South Wales. PROCEDURE: We examined the results of a survey of breeding practices, mating policies, recording systems, timing of mating, heat detection, treatment of metritis and manager demographics of dairy farms using Principal components analysis, logistic regression and the sign test. RESULTS: Eight principal components for heat detection computed using Principal component analyses were included in the multivariate model to reflect primary and secondary heat detection signs used in the breeding decisions of managers. A final model identified three variables: optimum number of days to first service, number of people detecting heats, and age of manager which significantly influenced the risk of being in the high or low reproductive performance groups. A failure to breed at an appropriate time after calving and having more people responsible for heat detection was associated with herds with a prolonged intercalving interval. While the model provided a good fit for the data, it was not highly discriminatory. Examination of 83 management practices affecting fertility using the sign test (P = 0.01) indicated that managers of herds with good reproductive performance employed better management and breeding practices more often than managers of herds with poor reproductive performance. CONCLUSIONS: Mating cows sooner after calving and using fewer people to detect oestrus should reduce calving to conception intervals. Veterinarians investigating herd reproductive performance should consider the potential for a number of subtle failures of management to significantly impair fertility rather than limit investigations to a few factors.

Animal Husbandry↗
PubMed2003

Effect of power-frequency magnetic fields on genome-scale gene expression in Saccharomyces cerevisiae.

To estimate the effect of 50 Hz magnetic-field exposure on genome-wide gene expression, the yeast Saccharomyces cerevisiae was used as a model for eukaryotes. 2D PAGE (about 1,000 spots) for protein and cDNA microarray (about 5,900 genes) analysis for mRNA were performed. The cells were exposed to 50 Hz vertical magnetic fields at 10, 150 or 300 mT r.m.s. for 24 h. As positive controls, the cells were exposed to aerobic conditions, heat (40 degrees C) or minimal medium. The 2D PAGE and microarray analyses for the positive controls showed high-confidence differential expression of many genes including those for known or unknown proteins and mRNAs. For magnetic-field exposure, no high-confidence changes in expression were observed for proteins or genes that were related to heat-shock response, DNA repair, respiration, protein synthesis and the cell cycle. Principal component analysis showed no statistically significant difference in principal components, with only insignificant differences between the magnetic-field intensities studied. In contrast, the principal components for the positive controls were significantly different. The results indicate that a 50 Hz magnetic field below 300 mT did not act as a general stress factor like heat shock or DNA damage, as had been reported previously by others. This study failed to find a plausible differential gene expression that would point to a possible mechanism of an effect of magnetic fields. The findings provide no evidence that the magnetic-field exposure alters the fundamental mechanism of translation and transcription in eukaryotic cells.

Cell Cycle↗
PubMed2000

Quantitative and kinetic evolution of wound healing through image analysis.

To define a healing function based on parameters measured on digitized images of wounds, and to use it to compare the rate of healing of two skin graft donor sites, one treated with petrolatum gauze (Pg) and the other with a topical preparation containing alginates (A). Digital photographs of donor sites (depth 0.6 mm) taken every two days between day 6 and day 12 were analyzed blind using the same algorithm, following changes in color and homogeneity. Analysis of variance was used to identify those parameters that changed during healing. The healing function was constructed using measurements made in six patients (group 1) randomly chosen from ten requiring skin grafts, and was applied and validated using data from the remaining four patients (group 2). The results given by this healing function were compared with those provided by principal component analysis. The most significant healing parameters were those measuring wound homogeneity, and our healing function reflects how these change with time. The time-dependent curves of the function calculated for groups 1 and 2 matched well enough to be considered as being derived from the same set of measurements. The results given by this healing function explained, by analogy, the meaning of the first principal component of principal component analysis. From day 6 to day 12, the healing function followed the same time-course for the Pg and A treatments, but healing was achieved significantly earlier (4 days, p < 0.03) with A. This suggests that the effect of A on wound healing is achieved in the first six days, before the visual changes from epidermalization are analyzable.

Administration, Topical↗
PubMed1987

Multidimensional scaling vs. factor analysis of Wechsler's intelligence scales.

The relations between principal component and principal factor analysis, on the one hand, and metric and nonmetric multidimensional scaling, on the other, were explored by applying all four methods to the standardization data for the WAIS-R, the WISC-R, and the WPPSI. For each of the instruments, the first component/factor was a general one that had no counterpart in the two scaling dimensions. The second component/factor and the first scaling dimension differentiated the Verbal from the Performance subtests, whereas the third component/factor and the second scaling dimension appeared to represent what has been called Freedom from Distractibility. The tendency of multidimensional scaling to remove the first general component/factor may be an undesirable feature of that method for investigating structure in the area of human abilities.

Factor Analysis, Statistical↗
PubMed2006

Diagnosis of breast cancer using diffuse reflectance spectroscopy: Comparison of a Monte Carlo versus partial least squares analysis based feature extraction technique.

BACKGROUND AND OBJECTIVE: We explored the use of diffuse reflectance spectroscopy in the ultraviolet-visible (UV-VIS) spectrum for the diagnosis of breast cancer. A physical model (Monte Carlo inverse model) and an empirical model (partial least squares analysis) based approach, were compared for extracting diagnostic features from the diffuse reflectance spectra. STUDY DESIGN/METHODS: The physical model and the empirical model were employed to extract features from diffuse reflectance spectra measured from freshly excised breast tissues. A subset of extracted features obtained using each method showed statistically significant differences between malignant and non-malignant breast tissues. These features were separately input to a support vector machine (SVM) algorithm to classify each tissue sample as malignant or non-malignant. RESULTS AND CONCLUSIONS: The features extracted from the Monte Carlo based analysis were hemoglobin saturation, total hemoglobin concentration, beta-carotene concentration and the mean (wavelength averaged) reduced scattering coefficient. Beta-carotene concentration was positively correlated and the mean reduced scattering coefficient was negatively correlated with percent adipose tissue content in normal breast tissues. In addition, there was a statistically significant decrease in the beta-carotene concentration and hemoglobin saturation, and a statistically significant increase in the mean reduced scattering coefficient in malignant tissues compared to non-malignant tissues. The features extracted from the partial least squares analysis were a set of principal components. A subset of principal components showed that the diffuse reflectance spectra of malignant breast tissues displayed an increased intensity over wavelength range of 440-510 nm and a decreased intensity over wavelength range of 510-600 nm, relative to that of non-malignant breast tissues. The diagnostic performance of the classification algorithms based on both feature extraction techniques yielded similar sensitivities and specificities of approximately 80% for discriminating between malignant and non-malignant breast tissues. While both methods yielded similar classification accuracies, the model based approach provided insight into the physiological and structural features that discriminate between malignant and non-malignant breast tissues.

Adipose Tissue↗
PubMed1990

Development of feature detectors by self-organization. A network model.

We present a two-layered network of linear neurons that organizes itself as to extract the complete information contained in a set of presented patterns. The weights between layers obey a Hebbian rule. We propose a local anti-Hebbian rule for lateral, hierarchically organized weights within the output layer. This rule forces the activities of the output units to become uncorrelated and the lateral weights to vanish. The weights between layers converge to the eigenvectors of the covariance matrix of input patterns, i.e., the network performs a principal component analysis, yielding all principal components. As a consequence of the proposed learning scheme, the output units become detectors of orthogonal features, similar to ones found in the brain of mammals.

Color Perception↗
PubMed2002

Multivariate analysis of the ecoregion delineation for aquatic systems.

The ecoregion concept is a popular method of understanding the spatial distribution of the environment', however, it has yet to be adequately demonstrated that the environment is distributed in accordance with these bounded units. In this paper, we generated a testable hypothesis based on the current usage of ecoregions: the ecoregion classification will allow for discrimination between lakes of different water quality. The ecoregion classification should also be more effective better than a comparably scaled classification based on political boundaries, land-use class, or random grouping. To test this hypothesis we used the Environmental Monitoring and Assessment Program (EMAP) lake water chemistry data from the northeast United States. The water chemistry data were reduced to four components using principal component analysis. For comparison to an optimal grouping of these data we used K-means cluster analysis to define the extent at which these lakes could be segregated into distinct classes. Jackknifed discriminant analysis was used to determine the classification rate of ecoregions, the three alternative spatial classification methods, and the clustering algorithm. The classification based on ecoregions was successful for 35% of the lakes included in this study, in comparison to the clustered groups accuracy of 98%. These results suggest that the large scale spatial distribution of ecosystem types is more complicated than that suggested by the present ecoregion boundaries. Further tests of ecoregion delineations are needed and alternative large-scale management strategies should be investigated.

Algorithms↗
PubMed2006

A(max) is the best a-wave measure for classifying Abyssinian cat rod/cone dystrophy.

AIM: To see if any a-wave measure segregated normal cats from those affected by a recessively inherited Abyssinian rod/cone dystrophy more efficiently than a(max) to scotopic I(max). METHOD: A-waves to electroretinograms (ERGs) evoked by a 4 cd x s/m(2) scotopic flash were extracted from 241 ERG sessions using 108 cats. They were either wild type or from an affected Abyssinian stock. Fourty four were bred by back-crossing to have a 50% probability of being affected. Most were diagnosed by retinal appearance or by the pattern of loss in a long protocol ERG. Eight were still unclassified. The diagnostic efficiency of amplitudes at 7, 8, 9, and 10 ms and a(max), of a(max) peak time, age at testing, and the main components of principal components factor analysis were compared by scaling their ability to segregate affected and normal cats. RESULTS: Variance and overlap between the groups both decreased as time along the a-wave increased. The loading of each animal on the largest factor also gave considerable overlap. There was a small absolute separation between groups when a(max) itself was used. Age and peak time were uncorrelated with disease. The light intensity used could be calculated to be equivalent to one sufficient for about 75% of full saturation in man. CONCLUSION: A(max) is a simple measure that is already in routine clinical use. When the flash is very bright and the animal fully dark adapted, this single measure is the most efficient sign of this rod/cone degeneration and possibly of all degenerations involving rods.

Animals↗
PubMed1991

The quantitative extraction and topographic mapping of the abnormal components in the clinical EEG.

A method is described which seems to be effective for extracting the abnormal components from the clinical EEG. The approach involves the use of a set a spatial patterns which are common to recorded and 'normal' EEGs and which can account for maximally different proportions of the combined variances in both EEGs. These spatial factors are used to decompose the EEG into orthogonal temporal wave forms which can be judged by the expert electroencephalographer to be abnormal, normal or of artifactual origin. The original EEG is then reconstructed using only the abnormal components and principal component analysis is used to present the spatial topography of the abnormal components. The effectiveness of the method is discussed along with its value for localization of abnormal sources. It is suggested, in conclusion, that the approach described may be optimal for interpretation of the clinical EEG since it allows what is best in terms of quantitative analysis of the EEG to be combined with the best that is available in terms of expert qualitative analysis.

Brain↗
PubMed2005

Surface-enhanced Raman scattering imaging of single living lymphocytes with multivariate evaluation.

This paper is aimed to show the possibility to determine individual organic compounds introduced into single living cells with surface-enhanced Raman spectroscopy (SERS). Surface enhancement was achieved with gold colloids that were allowed to diffuse into lymphocytes. An introduced analyte, rhodamine 6G, could be imaged together with for example nucleotides and amino acids of the cell. Multivariate evaluation of surface-enhanced Raman images proved to be a powerful tool for the separation of spectral information of various intracellular components. The principal component analysis (PCA) enabled identification of spectra containing different chemical information and separation of the spectral contribution of rhodamine 6G from the complex cellular matrix.

Cell Biology↗
PubMed1983

Quantitative structure-activity relationships employing independent quantum chemical indices.

Derivation of quantitative structure-activity relationships between pharmacological potencies and the electronic structure of molecules may often result in chance correlations, because of the large number of quantum chemical indices. Interrelationships between the parameters complicate the interpretation of the results. Quantum chemical indices of benzylamines, tetracyclines, and 1,4-benzodiazepines were transformed into mutually independent components using principal component analysis. The number of essential components was 3, 4, and 3, respectively. The computational efforts needed to develop multivariate linear regression equations between these components and the pharmacological activities were reduced, since the regression coefficients were not affected by the inclusion of new parameters. In each example, the first component, which accounted for the highest part of the total sample variance in the electronic structure, was the most important one in determining pharmacological activity. It seems that besides the electrostatic forces, charge transfer also affected the inhibitory potencies of benzylamines.

Amines↗
PubMed1997

Application of near-infrared reflectance spectrometry in the study of atopy. Part 1. Investigation of skin spectra.

An investigation into the existence of spectral differences and differences in response in terms of water and lipid content between normal and atopic skin is described. Since NIR radiation penetrates complex structured matrices down to a depth of 0.15-0.20 mm, it is evident that the method lends itself to spectral detection of skin components down to the deepest level. First the reproducibility of readings made with the instrument was tested and it was also checked whether the use of the probe caused changes in skin equilibrium due to occlusion. Analysis of the NIR spectra did not enable normal and atopic subjects to be distinguished unequivocally but provided important information on the use of NIR spectrometry in these subjects and insights into the stratum corneum. Although the responses of water and lipid structures could not be read directly from the spectra, it was possible to decompose the global spectral information into components by principal components analysis. It was possible to observe a fraction of variance associated in different ways with water.

Female↗
PubMed2003

Nondestructive discrimination of ivories and prediction of their specific gravity by Fourier-transform Raman spectroscopy and chemometrics.

Fourier-transform (FF) Raman spectroscopy and chemometrics were used for nondestructive analysis of ivories. The discrimination of five kinds of ivories, two subspecies of African elephant, mammoth, hippopotamus, and sperm whale, was investigated, and a calibration model for predicting their specific gravity was developed. FT-Raman spectra were measured in situ for them and chemometrics analyses were carried out for the 3050-350 cm(-1) region. The five kinds of ivories were clearly discriminated from each other on the scores plots of two or three principal components (PCs) obtained by principal component analysis (PCA). The loadings plot for PC 1 shows that the discrimination relies on the content ratio of organic collagenous protein and inorganic hydroxyapatite of ivories. The loadings plot for PC 2 shows that bands due to the CH3 and CH2 stretching modes of the protein also play a role in the discrimination. Using partial least squares regression (PLSR), we developed a calibration model that predicts the specific gravity of the ivories from the FT-Raman spectra. The correlation coefficient and root mean square error of cross validation (RMSECV) of this model were 0.980 and 0.024, respectively.

Animals↗
PubMed2004

Non-destructive analysis of the two subspecies of African elephants, mammoth, hippopotamus, and sperm whale ivories by visible and short-wave near infrared spectroscopy and chemometrics.

Visible (VIS) and short-wave near infrared (SW-NIR) spectroscopy was used for non-destructive analysis of ivories. VIS-SW-NIR (500-1000 nm) spectra were measured in situ for five kinds of ivories, that is two subspecies of African elephants, mammoth, hippopotamus, and sperm whale. Chemometrics analyses were carried out for the spectral data from 500 to 1000 nm region. The five kinds of ivories were clearly discriminated from each other on the scores plot of two principal components (PCs) obtained by principal component analysis (PCA). It was noteworthy that the ivories of the two subspecies of African elephants were discriminated by the scores of PC 1. The loadings plot for PC 1 showed that the discrimination relies on the intensity changes in bands due to collagenous proteins and water interacting with proteins. It was found that the scores plot of PC 2 is useful to distinguish between the ivories of the two subspecies of African elephants and the other ivories. We also developed a calibration model that predicted the specific gravity of five kinds of ivories from their VIS-SW-NIR spectral data using partial least squares (PLS)-1 regression. The correlation coefficient and root mean square error of cross validation (RMSECV) of this model were 0.960 and 0.037, respectively.

Animals↗
PubMed2002

The usefulness of amplified fragment length polymorphism markers for taxon discrimination across graduated fine evolutionary levels in Caribbean Anolis lizards.

Fine-level taxon discrimination is important in biodiversity assessment and ecogeographical research. Genomic markers are often required for studies on closely related taxa, however, most existing mitochondrial and nuclear markers require prior knowledge of the genome and are impractical for use in small conservation projects. This study describes the application of amplified fragment length polymorphism (AFLP) to discriminate at four progressively finer evolutionary levels of Caribbean Anolis lizards from the central Lesser Antilles. AFLP is shown to be a rapid and effective method for discriminating between species. Separation increases with primer pair number and choice of primer combination appears to be noncritical. Initial population-level results show markedly less discriminatory power. A screening technique for the identification of population informative markers combining principal component and principal coordinate analyses is presented and assessed. Subsequent results show selected conspecific AFLP data to be remarkably congruent with those of mitochondrial DNA, microsatellite and morphological markers. The use of AFLP as a low-cost nuclear marker in species-level taxon discrimination is supported, whereas population level application demands further consideration.

Animals↗
PubMed1997

Longitudinal dietary changes between 1984-5 and 1991-2 in British adults: association with socio-demographic, lifestyle and health factors.

The study aimed to examine dietary changes and their associations with demographic, lifestyle and health variables in a random sample of British adults. The Health and Lifestyle Survey of 1984-5 (HALS1) identified four main dietary components by principal component analysis from food frequency data. Comparison of the HALS1 dietary component scores with those of the follow-up survey of 1991-2 (HALS2) for the same individuals revealed increases on component 1 (high weightings for fresh fruit, salads, 'brown' bread, fruit juice and green vegetables but low weightings for chips, fried food and processed meat). There were substantial decreases on component 2 (high weightings for puddings/pies, cake, potatoes, biscuits, preserves, pulses and meat), small increase on component 3 (high weightings for crisps, soft drinks and chips) and increases on component 4 (high weightings for confectionery, biscuits and cake and low weightings for vegetables of all kinds). Except for women on component 3 the changes were all significant, P < 0.001. Unadjusted score changes were smallest in elderly respondents for all components. Differences in score changes between groups were based on an analysis of covariance adjusting for the HALS1 score. On component 1 the largest score increases were associated with non-manual groups, improvements in lifestyle and good health. For component 2 the greatest changes in score were associated with changes in household size, smoking habit and heavy drinking. Score increases on component 3 were also associated with heavy drinking, whilst the largest rises on component 4 were amongst the non-manual, the non-drinkers and the non-smokers and, for women only, those who had few malaise symptoms or who lived in Scotland. The results show that there have been overall dietary changes and that changes have been associated with longitudinal alterations in socio-demographic, lifestyle and health circumstances.

Adult↗