SEARCH · Search PubMed

Results for “Correlation Of Data”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed1989

28 S ribosomal RNA in vertebrates. Locations of large-scale features revealed by electron microscopy in relation to other features of the sequences.

The 28 S rRNA from several vertebrate species, when examined by electron microscopy, is seen to contain regions of extensive secondary structure, as first reported for HeLa-cell 28 S rRNA by Wellauer & Dawid [(1973) Proc. Natl. Acad. Sci. U.S.A. 70, 2827-2831]. Here we correlate the locations of these regions, determined from the electron-microscopic data, with the primary structure of 28 S rRNA from human, mouse and Xenopus laevis determined by sequence analysis of rDNA. The secondary-structure features observed by electron microscopy correspond closely to phylogenetically variable G + C-rich regions that largely comprise the eukaryotic expansion segments in these three species. In most if not all cases the features can be identified with long G + C-rich helices deduced from sequence data. Correlations are given between the locations of the secondary-structure features and several 'landmark' restriction sites in 28 S rDNA. By correlating the locations of the rRNA methyl groups reported elsewhere [Maden (1988) J. Mol. Biol. 201, 289-314] with the present findings it is concluded that the rRNA secondary-structure features revealed by electron microscopy are largely or wholly unmethylated.

Animals↗

PubMed1998

Optimizing the hemodynamic performance of the DDD pacemaker: impact of the atrioventricular delay on the pulmonary venous flow pattern.

UNLABELLED: This study evaluated the impact of the atrioventricular delay (AVD) on the pulmonary venous flow pattern (PVFP). METHODS: Transthoracic Doppler PVFP were obtained during atrial and ventricular pacing at a fixed rate of 70 beats/min in 20 patients equipped with a DDD pacemaker, diastolic dysfunction linked to an impaired relaxation, a mean ejection fraction of 49%, and AV block. Two subgroups were analyzed equally: group I: seven patients with a normal ejection fraction and group II: 13 patients with decreased ejection fraction. Three different AVDs were studied: short (50 ms), intermediate (150 ms), and long (250 ms). RESULTS: As the AVD increased, the diastolic filling time and the peak atrial reverse flow wave decreased (P < 0.001). There was a decreasing D wave and no significant change in the peak velocity of the S wave. The S wave became biphasic in all patients at the longest AVD of 250 ms. The systolic (S) velocity time integral (VTI) of the pulmonary wave and the systolic/total PVF-VTI ratio increased significantly (P < 0.001). A similar response was seen in both group of patients. CONCLUSIONS: These data correlated the AVD with PVFP, supplying critical systolic information completing the diastolic data obtained from mitral Doppler patterns. These systolic measurements were especially useful for patients with heart failure and a DDD pacemaker, in order to obtain the longest diastolic filling time at the lowest atrial pressure.

Aged↗

PubMed1983

Microphotometric determination of hematocrit in small vessels.

Evaluation and calibration of a microphotometric method for hematocrit determination in microvessels of transilluminated tissues is described. This method is based on the relation of the optical density (OD) of a microvessel to its hematocrit (Hct). The following requirements of the microphotometric system appear essential: narrow-band monochromatic light source with efficient false light suppression, high numerical aperture of the objective and low numerical aperture of the condensor. We used a video system to measure the intensities of incident (Io) and transmitted (I) light. For converting of Io and I into OD values, correcting procedures were evaluated to eliminate the influence of glare, shading, and fading. The calibration procedure was performed with glass tubes of inner diameter (ID) between 13 and 68 microns perfused with red cell suspensions. A function was fitted to the data, correlating OD to ID and Hct. The standard deviation of the original data from this function is +/- 0.02 units of fractional hematocrit. The presented method allows the continuous determination of the hematocrit in a microvessel as well as the off-line evaluation of the hematocrit distribution within a microvessel network.

Animals↗

PubMed2006

Structure and function in glaucoma: The relationship between a functional visual field map and an anatomic retinal map.

PURPOSE: To examine the relationship between an anatomic map relating the retinal nerve fiber layer (RNFL) distribution to the optic nerve head and a functional map derived from the interpoint correlation of raw sensitivities in visual field (VF) testing. METHODS: Previously, interpoint correlations were generated for all possible pairs of VF test points in a dataset of 98,821 Humphrey VF test results taken from the Moorfields Eye Hospital archive. The relationship between these correlations and the physical distance between the VF test point pairs was evaluated by Pearson's correlation coefficient and multiple regression analysis. The distance between the pairs of VF test points was calculated in two ways. First, the anatomic map was used to estimate the angular distance at the optic nerve head (ONH), between the RNFL bundles corresponding to the VF test points in each pair (ONHd). Second, the retinal distance between pairs of test points was calculated from the Humphrey VF template (RETd). A best-fit model for predicting functional correlation (FC) from ONHd and RETd was constructed and used to formulate a filter incorporating the anatomic-functional correlation data. RESULTS: All scatterplots showed a negative association between interpoint retinal sensitivity correlation values and distance between points: ONHd (R2 = 0.60) and RETd (R2 = 0.33). The raw sensitivity correlation values could be predicted from a multiple regression model using ONHd, RETd, and a combined interaction of ONHd and RETd (R2 = 0.75, P < 0.00001). The construction of a new filter was based on the equation FC = 0.9325 - (0.0029 . ONHd) - (0.0077 . RETd) + (0.0001 . ONHd . RETd). CONCLUSIONS: A good level of association was observed between the strength of correlation between points in the VF and the relative location of those test points in the peripheral retina and in corresponding RNFL bundles at the ONH. These results help to validate the relationship between structure and function and may be of use in the further refinement of physiologically derived VF filters to reduce measurement noise.

Glaucoma, Open-Angle↗

PubMed1995

Prothymosin alpha: in search of a function.

Prothymosin alpha is an acidic nuclear protein that is expressed at high levels in a wide variety of cell types. Accumulating data correlate prothymosin expression with alterations in the proliferative state of cells. Some data indicates that prothymosin may actually be necessary, if not sufficient, for proliferation, and that prothymosin may function in a c-myc associated pathway. Prothymosin is highly conserved through evolution suggesting a key function, however, that function remains unknown.

Animals↗

PubMed1997

Electrokinesiologic measurement of trunk sagittal mobility and lumbar erector spinae muscle activity.

Additional studies to determine intratester reliability of electrokinesiologic (EK) measures related to trunk movement and low back muscle activity are needed. EMG activity and EK records of repetitive movements at both natural and maximal speeds were computer sampled and quantified among 22 nonimpaired subjects. Significant differences were observed between group means at different speeds and trials for both kinematic and EMG measures. Predictably, maximal speed testing resulted in higher levels of EMG activity when compared to natural speed testing. Intratester reliability of measures was high at both speeds. Range of motion data correlated well between two trials for both natural and maximal speed movements, ranging from 0.81 to 0.97. Correlation of speed of movement measures ranged from 0.41 to 0.76. These data suggest that computer-analyzed EMG activity and EK signals are reliable assessment tools for trunk mobility. The application of this procedure to persons with low back pain to acquire EMG activity and mobility data appears justified.

Adolescent↗

PubMed1993

Photodynamic therapy for intracranial neoplasms: investigations of photosensitizer uptake and distribution using indium-111 Photofrin-II single photon emission computed tomography scans in humans with intracranial neoplasms.

Photodynamic therapy is being investigated as an adjuvant treatment for intracranial neoplasms. The efficacy of this therapy is based on the uptake of photosensitizer by neoplastic tissue, its clearance from surrounding brain tissue, and the timing and placement of photoactivating sources. Photofrin-II is the photosensitizer most actively being investigated. We labeled Photofrin-II with Indium-111 and studied the uptake and distribution of this agent in 20 patients with intracranial neoplasms, using single photon emission computed tomography (SPECT) with volume rendering in three dimensions. Of these patients, 16 had malignant glial tumors, 2 had metastatic deposits, 1 had a chordoma, and 1 had a meningioma. Anatomical-spatial data correlated well between the SPECT images and contrast-enhanced computed tomography or magnetic resonance images. Regions of focal uptake on SPECT images correlated with the surgical histopathological findings of the neoplasm. The kinetics of photosensitizer uptake varied according to the tumor's histological findings, the patient's use of steroids, and among patients with similar types of tumor histology. Peak ratios of target-to-nontarget tissue varied from 24 to 72 hours after injection. The study data show that, to be most effective, photodynamic therapy may need to be tailored for each patient by correlating SPECT images with anatomical data produced by computed tomography or magnetic resonance images. Photoactivating sources then can be placed, using computer-assisted stereotactics, to activate a prescribed volume of photosensitized tumor at the optimal time for treatment.

Adult↗

PubMed1975

Correlation of in vivo collagen degradation rate with in vitro measurements.

The rate of in vitro enzymatic degradation of various materials based on collagen has been determined by a novel mechanochemical method, and has been compared with the extent of degradation resulting from subcutaneous implantation in guinea pigs. In vitro data correlate well with in vivo data. It is suggested that the simple in vitro method described is an effective means of screening a large number of materials based on collagen for their ability to resist degradation during implantation in animals.

Animals↗

PubMed1975

Path analysis of palmar ridge counts.

The methods for path analysis of family resemblance (Rao et al., '74) are employed to test hypotheses concerning the inheritance of a-b, b-c and c-d palmar ridge counts using the correlation data of Pateria ('74). Homogeneity chi-square tests of the various familial correlations provide no evidence for sex-linkage of either kind, and also suggest that maternal effects are absent. The path coefficient model employed here involves heritability (additive) and common sibling environment. Variance components show that both heritability and common environment are significant, and account for most of the variation at each of the three ridge count area; b-c has the highest heritability, significantly higher than that for a-b or c-d.

Dermatoglyphics↗

PubMedDate not supplied

Organization of simple cell responses in the three-dimensional (3-D) frequency domain.

The amplitude spectra of simple cells in areas 17 and 18 were estimated in two and three dimensions (2-D and 3-D) using drifting sinusoidal gratings. In 2-D, responses were sampled with 16 x 16 resolution in spatial and temporal frequency at the optimal orientation. In 3-D, responses were sampled with 12 x 12 x 10 resolution in spatial frequency, orientation, and temporal frequency. For 45/50 cells studied, the spatial attributes of the receptive fields (RFs) were independent of temporal frequency except for a scale factor. The five exceptions to this general finding could be described as follows: For four area 17 cells, responses in the null direction increased with temporal frequency, reducing direction selectivity. For one area 18 cell, the optimal spatial frequency increased with temporal frequency and vice versa. The 2-D discrete Fourier transform was applied to all of the estimated amplitude spectra assuming zero spatial and temporal phase. These transforms were compared with the results of first-order reverse correlations as described in the previous paper (McLean et al., 1994). Direction selective cells exhibited excitatory subregions that were obliquely oriented in space-time in both the raw correlation data and inverse transforms of the spectral data. The slopes of the subregions found in these two measures were highly correlated. Direction indices obtained from space and frequency domain measures were comparable. We demonstrate that the spectral response profiles of most simple cells are aligned with the coordinate axes in frequency domain. That is, they may be considered one-quadrant separable, suggesting that these cells are not velocity tuned per se, but are tuned for spatiotemporal frequency. The spectral bandwidth establishes the range of velocities to which these cells will respond. These findings are consistent with the one-quadrant separability constraint of linear quadrature models. We conclude that most simple cells perform as roughly linear filters in two dimensions of space and time.

Animals↗

PubMed1999

Correlation of acute and chronic defibrillation threshold with upper limit of vulnerability determined in normal sinus rhythm.

BACKGROUND: The upper limit of vulnerability (ULV) is the stimulus strength above which ventricular fibrillation cannot be induced, even when the stimulus occurs during the vulnerable period of the cardiac cycle. Determination of ULV using T-wave shocks during ventricular pacing has been shown to closely correlate with the defibrillation threshold (DFT) at ICD implantation. However, there are no data correlating ULV determined in sinus rhythm at ICD implantation, with DFT determined at implantation or during long-term follow-up. This is of clinical importance since ULV may be used to estimate DFT during ICD implantation, both during ventricular pacing or sinus rhythm. METHODS AND RESULTS: Twenty-one patients receiving a transvenous ICD system were studied prospectively. There were 16 males and 5 females, mean age 68 +/- 15 years, with mean ejection fraction 37.4 +/- 17.4%. All had structural heart disease. The ULV was defined as the lowest energy that did not induce ventricular fibrillation with shocks at 0, 20 and 40ms before the peak of the T-wave, using a step-down protocol. The initial energy tested was 15J and the lowest energy 2J. DFT was determined following a similar step-down protocol. The DFT was defined as the lowest energy that successfully defibrillated the ventricles. The linear correlation coefficient between ULV and DFT was r = 0.73 (p < 0.001). At implant, mean ULV was 9.2 +/- 5J, not statistically different from mean DFT 9.4 +/- 4J. ULV plus 5J successfully defibrillated 19 of 21 patients. During long-term follow-up of 10.1 +/- 1.8 months in eight patients, DFT was 8.8 +/- 5.8J, not significantly different than the DFT of 7.5 +/- 4.1J or ULV of 8.0 +/- 5.3 at implant. CONCLUSION: 1) When determined during normal sinus rhythm the ULV significantly correlates with DFT. 2) ULV testing might be used in lieu of standard DFT testing to confirm adequate lead placement thus minimizing or eliminating VF inductions, particularly in hemodynamically unstable patients. 3) Since ULV + 5J has a high probability of successful defibrillation in most patients, programming ICD first shock energy for VF at ULV + 5J may result in lower first shock energies compared to the standard methods of programming first shock energy at twice DFT. CONDENSED ABSTRACT: The purpose of this study was to determine if the upper limit of vulnerability (ULV) determined during normal sinus rhythm correlates with the defibrillation threshold (DFT), as has been previously shown when determined during ventricular pacing. The linear correlation coefficient between the ULV and DFT was r = 0.73 (p < 0.001). Mean ULV at implant was 9.2 +/- 5J, not statistically different from mean DFT of 0.4 +/- 4J. During long-term follow-up of 10.1 +/- 1.8 months in 8 patients, DFT was 8.75 +/- 8J, not significantly different than the DFT of 7.5 +/- 4.1J or ULV of 8.0 +/- 5.3 at implant. Shocks energies of ULV + 5J successfully defibrillated 19 of 21 patients at implant and 8 of 8 at follow-up. This study indicates that the ULV determined in normal sinus rhythm closely correlates with the DFT, and that ULV + 5J defibrillated most patients. ULV testing could be used to predict DFT and reduce or eliminate the need for DFT testing and VF induction. Programming ICD first shock energy for VF to ULV + 5J will result in lower energy than that used with standard DFT testing.

Aged↗

PubMed2001

The early pathogenesis of foot-and-mouth disease in pigs infected by contact: a quantitative time-course study using TaqMan RT-PCR.

Foot-and-mouth disease (FMD) is a highly contagious, economically important virus disease of cloven-hoofed animals. The objective of the present study was to examine the early pathogenesis of FMD in pigs by a quantitative time-course study. Under experimental conditions, recipient pigs were infected by contact with donor pigs affected by FMD. Every 24 h from day 1 to day 4 after exposure, two recipient pigs were selected randomly, killed and necropsied. A range of tissues were analysed by a quantitative TaqMan RT-PCR method and by titration of FMD virus on primary bovine thyroid cells. The titres of virus determined by assay in cell culture and calculated from the quantitative TaqMan data correlated strongly (r>0.9), thereby establishing the validity of the TaqMan calculations. The data indicated that the replication of virus in the lungs contributes only in small part to airborne virus excretion. Sites in the pharynx, trachea and nasal mucosa are probably more important in that regard. The sites of earliest virus infection and possibly replication in recipient pigs appeared to be in the pharynx (soft palate, tonsil and floor of pharynx). The data indicated that FMD virus replication in pigs is rapid and that the majority of virus amplification occurs in the skin. A model for the progression of infection is proposed, indicating initial spread from the pharyngeal region, through regional lymph nodes and via the blood to epithelial cells, resulting in several cycles of virus amplification and spread.

Animals↗

PubMed2005

Long latency evoked potential database for clinical applications: justification and examples.

We summarize our experience with the clinical utility of long latency evoked potential (EP) data in clinical QEEG studies. In contrast to common wisdom, such EP data are consistent across appropriately chosen age groups. In a healthy adult population, EP data correlate consistently with independently collected psychological variables. In our pediatric referral population, EP data are of greatest and most unique value in the learning disabilities but also augment detection of abnormality in epilepsy and behavioral abnormality. Selection of subjects for a clinical database on the basis of examined medical, neurological and behavioral health, forms adequately consistent groupings for clinical utility. The use of the Z-SPM is essential for detection of EP abnormality. A minimum of three replications within a clinical study protects against chance/false positives. Also, the true data dimensionality within EP data sets is far less than the total number of variables typically collected.

Adolescent↗

PubMed1992

Occupationally induced neoplasms of the lung and pleura.

The relationship between asbestos and mesothelioma has been well delineated in the past. The epidemiologic, clinical, radiologic, and pathologic features of mesothelioma are discussed with reference to the diagnostic evaluation of asbestos-exposed patients. The extensive epidemiologic data correlating asbestos, tobacco smoke, and induction of lung carcinoma are also reviewed. These data provide a model for evaluation of other occupationally induced lung carcinogens such as organic and metallic industrial inhalants.

Humans↗

PubMed2005

Non-isotropic noise correlation in PET data reconstructed by FBP but not by OSEM demonstrated using auto-correlation function.

BACKGROUND: Positron emission tomography (PET) is a powerful imaging technique with the potential of obtaining functional or biochemical information by measuring distribution and kinetics of radiolabelled molecules in a biological system, both in vitro and in vivo. PET images can be used directly or after kinetic modelling to extract quantitative values of a desired physiological, biochemical or pharmacological entity. Because such images are generally noisy, it is essential to understand how noise affects the derived quantitative values. A pre-requisite for this understanding is that the properties of noise such as variance (magnitude) and texture (correlation) are known. METHODS: In this paper we explored the pattern of noise correlation in experimentally generated PET images, with emphasis on the angular dependence of correlation, using the autocorrelation function (ACF). Experimental PET data were acquired in 2D and 3D acquisition mode and reconstructed by analytical filtered back projection (FBP) and iterative ordered subsets expectation maximisation (OSEM) methods. The 3D data was rebinned to a 2D dataset using FOurier REbinning (FORE) followed by 2D reconstruction using either FBP or OSEM. In synthetic images we compared the ACF results with those from covariance matrix. The results were illustrated as 1D profiles and also visualized as 2D ACF images. RESULTS: We found that the autocorrelation images from PET data obtained after FBP were not fully rotationally symmetric or isotropic if the object deviated from a uniform cylindrical radioactivity distribution. In contrast, similar autocorrelation images obtained after OSEM reconstruction were isotropic even when the phantom was not circular. Simulations indicated that the noise autocorrelation is non-isotropic in images created by FBP when the level of noise in projections is angularly variable. Comparison between 1D cross profiles on autocorrelation images obtained by FBP reconstruction and covariance matrices produced almost identical results in a simulation study. CONCLUSION: With asymmetric radioactivity distribution in PET, reconstruction using FBP, in contrast to OSEM, generates images in which the noise correlation is non-isotropic when the noise magnitude is angular dependent, such as in objects with asymmetric radioactivity distribution. In this respect, iterative reconstruction is superior since it creates isotropic noise correlations in the images.

Journal Article↗

PubMed2004

Using decision forest to classify prostate cancer samples on the basis of SELDI-TOF MS data: assessing chance correlation and prediction confidence.

Class prediction using "omics" data is playing an increasing role in toxicogenomics, diagnosis/prognosis, and risk assessment. These data are usually noisy and represented by relatively few samples and a very large number of predictor variables (e.g., genes of DNA microarray data or m/z peaks of mass spectrometry data). These characteristics manifest the importance of assessing potential random correlation and overfitting of noise for a classification model based on omics data. We present a novel classification method, decision forest (DF), for class prediction using omics data. DF combines the results of multiple heterogeneous but comparable decision tree (DT) models to produce a consensus prediction. The method is less prone to overfitting of noise and chance correlation. A DF model was developed to predict presence of prostate cancer using a proteomic data set generated from surface-enhanced laser deposition/ionization time-of-flight mass spectrometry (SELDI-TOF MS). The degree of chance correlation and prediction confidence of the model was rigorously assessed by extensive cross-validation and randomization testing. Comparison of model prediction with imposed random correlation demonstrated biologic relevance of the model and the reduction of overfitting in DF. Furthermore, two confidence levels (high and low confidences) were assigned to each prediction, where most misclassifications were associated with the low-confidence region. For the high-confidence prediction, the model achieved 99.2% sensitivity and 98.2% specificity. The model also identified a list of significant peaks that could be useful for biomarker identification. DF should be equally applicable to other omics data such as gene expression data or metabolomic data. The DF algorithm is available upon request.

Decision Support Techniques↗

PubMed2003

Comparison between aromatase inhibitors and sequential use.

The biochemical efficacy of aromatase inhibitors and inactivators in vivo may be determined by two types of methods; by measuring plasma or tissue estrogen levels, or assessment of the conversion of the androgen substrate (in practice, androstenedione) into estrogens (estrone) by the use of tracer methods. While methods to determine plasma and tissue estrogens are limited through lack of sensitivity required to measure the very low concentrations recorded in postmenopausal women on treatment with these compounds, measurement of in vivo aromatization is an extensive procedure, applicable to a limited number of patients only. While we may correlate the mean level of aromatase inhibition achieved with different compounds to clinical efficacy, data correlating individual estrogen suppression to clinical outcome among patients treated with a specific compound is limited. The now well-characterized phenomenon of lack of cross-resistance between non-steroidal aromatase inhibitors and steroidal aromatase inactivators are likely due to biochemical effects not related to differences in total body aromatase inhibition.

Aromatase Inhibitors↗

PubMed2003

Can periodic limb movement disorder be diagnosed without polysomnography? A case-control study.

OBJECTIVES: (1) To determine whether clinical information can predict the presence of periodic limb movement disorder (PLMD). (2) To examine whether clinical data correlate with PLMD severity. METHODS: Sixty-one adult patients (48 males and 13 females, aged 55.1+/-14.1 years) with PLMD (without a clinical diagnosis of restless legs syndrome) were compared with 61 control patients without PLMD (43 males and 18 females, aged 49.6+/-16.1 years) in this case-control study. All patients completed a detailed questionnaire which included (1) demographics, (2) sleep complaints, (3) medical disorders, (4) use of medication, nicotine, and caffeine, and (5) history of nocturnal motor/sensory leg symptoms. All patients underwent standard polysomnography. RESULTS: The PLMD and control groups were similar in the prevalence of insomnia, hypersomnia, diabetes, peripheral neurologic disorders, anemia, spinal disease, antidepressant medication use, smoking, caffeine intake, and leg pain. Compared with the control group, the PLMD group reported more leg kicks (28% vs. 5%, P<0.001) and more crawling or aching sensations in legs (28% vs. 11%, P=0.023). The logistic regression analysis showed that only age (P=0.044), leg kicks (odds ratio (OR) 12.70, 95% confidence interval (CI) 2.80-57.63, P=0.001), and crawling or aching in legs (OR 5.23, 95% CI 1.16-23.44, P=0.029) were significantly related to the presence of PLMD. The positive predictive value of leg kicks in the diagnosis of PLMD was 85% and the negative predictive value was 57%. Within the PLMD group, only age correlated positively with the PLM-index (r=0.47, P<0.001). Both the PLM-index and the PLM arousal-index were negatively correlated with sleep efficiency on polysomnography (P=0.005 and P=0.006, respectively). CONCLUSIONS: Clinical data are not sufficiently predictive of the presence of PLMD to rule in or rule out the diagnosis. Polysomnography is required for establishing the diagnosis of PLMD in patients with insomnia or hypersomnia.

Case-Control Studies↗