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Linear Correlation Analysis (linear + correlation_analysis)
Selected AbstractsIntrahepatic expression of the hepatic stellate cell marker fibroblast activation protein correlates with the degree of fibrosis in hepatitis C virus infectionLIVER INTERNATIONAL, Issue 2 2002MT Levy Abstract: Background: Activated hepatic stellate cells (HSCs), recognised by their , smooth muscle actin immunoreactivity, are primarily responsible for liver fibrosis. However, the presence of , smooth muscle actin positive HSCs is not always associated with the development of liver fibrosis. Recently, other markers of human HSCs including the gelatinase fibroblast activation protein (FAP) and glial fibrillary acidic protein have been identified. Aims: We examined the relationship between the expression of these HSC markers and the severity of liver injury in patients with chronic hepatitis C virus infection. Methods: Liver tissue from 27 patients was examined using immunohistochemistry. Linear correlation analysis was used to compare staining scores with the stage and grade of liver injury. Results,Conclusions: FAP expression, seen at the tissue-remodelling interface, was strongly and significantly correlated with the severity of liver fibrosis. A weaker correlation was seen between glial fibrillary acidic protein expression and fibrosis stage. This contrasted with the absence of a relationship between , smooth muscle actin and the fibrotic score. A correlation was also observed between FAP expression and necroinflammatory score. In summary, FAP expression identifies a HSC subpopulation at the tissue-remodelling interface that is related to the severity of liver fibrosis. [source] Quantification of Alzheimer pathology in ageing and dementia: age-related accumulation of amyloid-,(42) peptide in vascular dementiaNEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 2 2006H. Lewis Clinicopathological observations suggest there is considerable overlap between vascular dementia (VaD) and Alzheimer's disease (AD). We used immunochemical methods to compare quantities of amyloid-, (A,) peptides in post mortem brain samples from VaD, AD subjects and nondemented ageing controls. Total A, peptides extracted from temporal and frontal cortices were quantified using a previously characterized sensitive homogenous time-resolved fluorescence (HTRF) assay. The HTRF assays and immunocapture mass spectrometric analyses revealed that the A,(42) species were by far the predominant form of extractable peptide compared with A,(40) peptide in VaD brains. The strong signal intensity for the peak representing A,(4,42) peptide confirmed that these N-terminally truncated species are relatively abundant. Absolute quantification by HTRF assay showed that the mean amount of total A,(42) recovered from VaD samples was approximately 50% of that in AD, and twice that in the age-matched controls. Linear correlation analysis further revealed an increased accumulation with age of both A, peptides in brains of VaD subjects and controls. Interestingly, VaD patients surviving beyond 80 years of age exhibited comparable A,(42) concentrations with those in AD in the temporal cortex. Our findings suggest that brain A, accumulates increasingly with age in VaD subjects more so than in elderly without cerebrovascular disease and support the notion that they acquire Alzheimer-like pathology in older age. [source] Spatial independent component analysis of functional MRI time-series: To what extent do results depend on the algorithm used?HUMAN BRAIN MAPPING, Issue 3 2002Fabrizio Esposito Abstract Independent component analysis (ICA) has been successfully employed to decompose functional MRI (fMRI) time-series into sets of activation maps and associated time-courses. Several ICA algorithms have been proposed in the neural network literature. Applied to fMRI, these algorithms might lead to different spatial or temporal readouts of brain activation. We compared the two ICA algorithms that have been used so far for spatial ICA (sICA) of fMRI time-series: the Infomax (Bell and Sejnowski [1995]: Neural Comput 7:1004,1034) and the Fixed-Point (Hyvärinen [1999]: Adv Neural Inf Proc Syst 10:273,279) algorithms. We evaluated the Infomax- and Fixed Point-based sICA decompositions of simulated motor, and real motor and visual activation fMRI time-series using an ensemble of measures. Log-likelihood (McKeown et al. [1998]: Hum Brain Mapp 6:160,188) was used as a measure of how significantly the estimated independent sources fit the statistical structure of the data; receiver operating characteristics (ROC) and linear correlation analyses were used to evaluate the algorithms' accuracy of estimating the spatial layout and the temporal dynamics of simulated and real activations; cluster sizing calculations and an estimation of a residual gaussian noise term within the components were used to examine the anatomic structure of ICA components and for the assessment of noise reduction capabilities. Whereas both algorithms produced highly accurate results, the Fixed-Point outperformed the Infomax in terms of spatial and temporal accuracy as long as inferential statistics were employed as benchmarks. Conversely, the Infomax sICA was superior in terms of global estimation of the ICA model and noise reduction capabilities. Because of its adaptive nature, the Infomax approach appears to be better suited to investigate activation phenomena that are not predictable or adequately modelled by inferential techniques. Hum. Brain Mapping 16:146,157, 2002. © 2002 Wiley-Liss, Inc. [source] CLIMATIC VARIABILITY ALONG A NORTH,SOUTH TRANSECT OF FINLAND OVER THE LAST 500 YEARS: SIGNATURE OF SOLAR INFLUENCE OR INTERNAL CLIMATE OSCILLATIONS?GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2008MAXIM G. OGURTSOV ABSTRACT. Statistical analysis of a multi-centennial dendrochronological proxy dataset of regional climate, constructed across the latitudinal gradient of 1000 km, was performed. It was shown that centennial (c. 100 year), tri-decadal (27-32 year), bi-decadal (17-23 year) and decadal (9-13 year) periodicities governed the climate variability in Finland over the last five centuries. Despite the fact that many of the climatic periodicities bore great resemblance to periodicities of solar cycles, little evidence of actual solar influence on Finnish climate was found when the climate proxy records were subjected to linear correlation analysis with sunspot numbers. Highly non-linear response of Northern Fennoscandian climate to solar forcing might be a cause of this result, as well as influence of terrestrial climatic processes (e.g. effect of other forcing factors and internal dynamics of regional climate). Our results show that the presence of internal climate variability at time-scales of solar activity might distort the solar signature in climatic data and complicate its detection. [source] The influence of the tropical and subtropical Atlantic and Pacific Oceans on precipitation variability over Southern Central South America on seasonal time scalesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2004Guillermo J. Berri Abstract This paper studies the temporal and spatial patterns of precipitation anomalies over southern central South America (SCSA; 22,40°S and 54,70°W), and their relationship with the sea-surface temperature (SST) variability over the surrounding tropical and subtropical Atlantic and Pacific Oceans. The data include monthly precipitation from 68 weather stations in central,northern Argentina and neighbouring Brazil, Paraguay and Uruguay, and monthly SSTs from the NOAA dataset with a 2° resolution for the period 1961,93. We use the method of canonical correlation analysis (CCA) to study the simultaneous relationship between bi-monthly precipitation and SST variability. Before applying the CCA procedure, standardized anomalies are calculated and a prefiltering is applied by means of an empirical orthogonal function (EOF) analysis. Thus, the CCA input consists of 10 EOF modes of SST and between 9 and 11 modes for precipitation and their corresponding principal components, which are the minimum number of modes necessary to explain at least 80% of the variance of the corresponding field. The results show that November,December presents the most robust association between the SST and SCSA precipitation variability, especially in northeastern Argentina and southern Brazil, followed by March,April and May,June. The period January,February, in contrast, displays a weak relationship with the oceans and represents a temporal minimum of oceanic influence during the summer semester. Based on the CCA maps, we identify the different oceanic and SCSA regions, the regional averages of SST and precipitation are calculated, and linear correlation analysis are conducted. The periods with greater association between the oceans and SCSA precipitation are November,December and May,June. During November,December, every selected region over SCSA reflects the influence of several oceanic regions, whereas during May,June only a few regions show a direct association with the oceans. The Pacific Ocean regions have a greater influence and are more widespread over SCSA; the Atlantic Ocean regions have an influence only over the northwestern and the southeastern parts of SCSA. In general, the relationship with the equatorial and tropical Atlantic and Pacific Oceans is of the type warm,wet/cold,dry, whereas the subtropical regions of both oceans show the opposite relationship, i.e. warm,dry/cold,wet. Copyright © 2004 Royal Meteorological Society [source] Vitamin D status in female patients with primary hyperparathyroidism: does it play a role in skeletal damage?CLINICAL ENDOCRINOLOGY, Issue 1 2004Vincenzo Carnevale Summary objective, Vitamin D deficiency, even subclinical, has been considered to worsen the skeletal damage in primary hyperparathyroidism (PHPT). Our study aimed to investigate the impact of vitamin D status on skeletal involvement in PHPT. design and measurements, A cross-sectional study was designed involving 62 female patients with PHPT. Serum total calcium (tCa), phosphate (P), creatinine (Cr) and total alkaline phosphatase activity (AP), together with 24-h (uCa 24 h) and spot fasting (uCa/Cr) urinary calcium, were measured by autoanalyser; ionized calcium (iCa) was assessed by an ion-specific electrode; intact parathyroid hormone (PTH) was measured by immunoradiometric assay (IRMA) and 25-hydroxyvitamin D (25-OHD) by radioimmunoassay (RIA). Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DXA) at lumbar spine in 58 patients, and at femoral neck, Ward's triangle, greater trochanter, intertrochanteric line and total hip in 56 patients. The associations of all variables with age, 25-OHD, body mass index (BMI) and PTH were studied by linear multiple regression analysis, using progressively restricted models. results, The model including age, 25-OHD, PTH and BMI showed significant regression with BMD values. PTH, age and BMI exerted a leading role in determining such a significance, while no significant regression was found between the parameters studied and 25-OHD; this was confirmed by Pearson's linear correlation analysis. The progressively restricted models showed significant regression of BMD at femoral neck, femoral intertrochanteric line and total hip with age, BMI and PTH. BMD measured at the Ward's triangle and greater trochanter showed significant regression with age and BMI, and that measured at lumbar spine with age. conclusions, Our data indicate that in primary hyperparathyroidism patients the influence of 25-hydroxyvitamin D levels on bone mineral density, if any, was overwhelmed by the effects of parathyroid hormone excess, age and body mass index. The latter unequally affected bone mineral density of various measured sites with different composition. [source] | ||||||||||