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PubMed1985

Simultaneous monitoring of dopamine release in rat frontal cortex, nucleus accumbens and striatum: effect of drugs, circadian changes and correlations with motor activity.

Changes in homovanillic acid concentration, recorded in vivo by voltammetry with carbon-paste electrodes, were used as an index of dopamine release. With electrodes implanted in frontal cortex, nucleus accumbens and striatum, the pattern of dopamine release was monitored simultaneously in the three brain regions together with the rats' motor activity. Changes in response to the systemic administration of dopamine-receptor agonists and antagonists were used as an index of feedback control of dopamine release. The relationships between dopamine release and motor activity, as well as that between dopamine release in the different brain regions, were investigated by calculating correlation coefficients for data collected over 24-h periods. The results show that dopamine release in frontal cortex is subject to little feedback regulation, that there is no nocturnal increase and no correlation with motor activity. Dopamine release in accumbens and striatum follows a very different pattern. There was a high correlation between dopamine release in these two regions on both sides of the brain; the correlation between the accumbens and the ipsilateral striatum was the highest. Dopamine release in both regions shows evidence of considerable feedback regulation, a nocturnal increase and a high correlation with motor activity. The importance of the accumbens in relation to the level of motor activity is supported by the finding that the correlation coefficient between motor activity and dopamine release in this structure was significantly higher than that between activity and release in the striatum.

Animals↗

PubMed1994

Statistical mechanics in biology: how ubiquitous are long-range correlations?

The purpose of this opening talk is to describe examples of recent progress in applying statistical mechanics to biological systems. We first briefly review several biological systems, and then focus on the fractal features characterized by the long-range correlations found recently in DNA sequences containing non-coding material. We discuss the evidence supporting the finding that for sequences containing only coding regions, there are no long-range correlations. We also discuss the recent finding that the exponent alpha characterizing the long-range correlations increases with evolution, and we discuss two related models, the insertion model and the insertion-deletion model, that may account for the presence of long-range correlations. Finally, we summarize the analysis of long-term data on human heartbeats (up to 10(4) heart beats) that supports the possibility that the successive increments in the cardiac beat-to-beat intervals of healthy subjects display scale-invariant, long-range "anti-correlations" (a tendency to beat faster is balanced by a tendency to beat slower later on). In contrast, for a group of subjects with severe heart disease, long-range correlations vanish. This finding suggests that the classical theory of homeostasis, according to which stable physiological processes seek to maintain "constancy," should be extended to account for this type of dynamical, far from equilibrium, behavior.

Base Sequence↗

PubMed1985

Temporal correlation of some endocrine circadian rhythms in elderly subjects.

The aim of this chronobiological study was to investigate temporal correlations in the circadian patterns of 6 hormones, namely somatotrophic hormone (STH), prolactin (PRL), cortisol (F), aldosterone (ALD), insulin (IRI) and C-peptide (CP), assayed in systemic blood serum drawn at 07:00, 10:00, 13:00, 16:00, 19:00 and 22:00 h from an antecubital vein in 19 young subjects (aged 20-29 yr, comprising 10 males and 9 females; and 20 elderly subjects (aged 70-81 yr, comprising 10 males and 10 females). All subjects were sampled on a normal dietary sodium intake (120-140 mEq/24h) while following a social routine of diurnal activity (07:00-23:00) and nocturnal rest (23:00-07:00). Time-qualified data were analyzed by lead-lag correlation and by cosinor analysis. According to the lead-lag correlation findings, it would appear that the correlation which exists between several time-qualified series in young subjects is no longer present in elderly subjects. The circadian rhythms which were found to have lost their temporal correlations with advancing age were those between STH and IRI, STH and ALD, PRL and IRI, PRL and CP, and ALD and CP. It should be noted that the correlation between hormonal rhythms breaks down mainly on account of a peculiar age-related change in the magnitude of the circadian fluctuation. This chronological decline in amplitude led to the conclusion that the senescence of endocrine rhythmic functions is a biological phenomenon characterized by altered circadian variability.

Adult↗

PubMed1994

Visualization of subtle contrast-related intensity changes using temporal correlation.

Contrast-enhanced magnetic resonance imaging (MRI) is a promising method for investigating the breakdown of the blood-retinal barrier (BRB). However, subtle intensity changes due to low concentrations of contrast agent can be difficult to detect without observer bias. In this study, we developed a temporal correlation method for detecting these subtle signal intensity changes. The method was evaluated in eyes with chemically induced retinal lesions of known size. A time series of MRI data were collected following i.v. administration of different doses of gadolinium-diethylaminetriaminepentaacetic acid (0.05, 0.1, 0.5 mmol/kg). These time course images were analyzed by temporal correlation to a reference enhancement curve. The reference curve was generated based on a validated theoretical enhancement curve. The temporal correlation method detected signal intensity changes in cases where the changes were too subtle to be visible on a postinjection image or a subtraction image (obtained by subtracting the precontrast image from the final image in the time course set). In addition, assessment of leakage was performed by viewing each image in the set with an eight gray-level palette. Areas of leakage identified in this manner corresponded to those identified by temporal correlation, a finding which supports the validity of the temporal correlation method. These results suggest that temporal correlation may be a time-efficient way to screen large numbers of image data sets using an objective, user-independent criterion.

Algorithms↗

PubMed2005

Photoreceptor layer features in eyes with closed macular holes: optical coherence tomography findings and correlation with visual outcomes.

PURPOSE: Study correlation between optical coherence tomography (OCT) findings and visual acuity (VA) outcomes after successful macular hole surgery (MHS). DESIGN: Retrospective cross-sectional study. METHODS: Postoperative OCT scans were analyzed in 34 eyes of 30 patients. Raw files of horizontal and vertical OCT scans were exported to Adobe Photoshop 7.0. Measured parameters included central foveal thickness, photoreceptor thickness, photoreceptor reflectivity, and relative reflectivity of photoreceptor to retinal pigment epithelium in the foveal area. Foveal configuration was subjectively graded. RESULTS: OCT scans were obtained at a median of 2 years (1 month to 10 years) postoperatively. The median visual acuity was 20/80 (20/50 to 8/200) preoperatively and 20/50 (20/20 to 5/200) postoperatively. The median foveal thickness was 198.5 micro (148 to 283). The mean (SD) photoreceptor layer thickness was 16.5 (8) micro in the 500 micro area and 17.5 (8) micro in the 1000 micro area. Mean (SD) of relative reflectivity of the photoreceptor layer was 0.60 (0.10) in both 500 micro and 1000 micro area. Postoperative VA did not correlate with foveal thickness or foveal configuration. Central (500 micro and 1000 micro) photoreceptor thickness was significantly correlated with final VA (r = .38, P = .026, each). Relative reflectivity of photoreceptors to retinal pigment epithelium in the 500 micro area was correlated with postoperative VA at a borderline significance (r = .32, P = .07). Relative reflectivity of photoreceptors to retinal pigment epithelium in the 1000 micro area was not significantly correlated with postoperative VA (r = .27, P = .12). CONCLUSION: Specific retinal features can be assessed from OCT images. Morphology and thickness of the foveal photoreceptor layer correlate well with macular function after successful MHS. Outer retinal features appear to be more important to determine postoperative visual function. Inner retinal features may be more relevant for the ophthalmoscopic appearance of anatomic closure.

Adult↗

PubMed2006

Correlation between hemifield visual field damage and corresponding parapapillary atrophy in normal-tension glaucoma.

PURPOSE: To evaluate the correlation between the superior or inferior half area of parapapillary atrophy (PPA) and the corresponding hemifield visual field damage (VFD) in normal-tension glaucoma. DESIGN: Cross-sectional study. METHODS: patients: One hundred nine eyes of 109 consecutive patients with normal-tension glaucoma. observation procedures: Topography parameters of the optic nerve head and PPA (zone beta) area were obtained with the Heidelberg Retina Tomograph (HRT), and VFD was evaluated with the 30 to 2 program of Humphrey Field Analyzer. The HRT parameters and PPA area were determined separately in superior and inferior half regions. main outcome measures: Partial correlation coefficients of the superior and inferior areas of PPA with refractive error, axial length, HRT parameters, and corresponding hemifield VFD. RESULTS: In simple correlation analyses, significant correlation was found between the inferior PPA area and the superior hemifield VFD (Spearman rank correlation coefficient; Rs = -0.32; P < .001) but not between the superior PPA area and the inferior hemifield VFD (Rs = 0.05; P = .6). Age, refractive error, axial length, and height variation contour were associated significantly with the total, superior, and inferior areas of PPA, respectively (P < .01). Multiple regression analyses showed that the superior PPA area was associated significantly with only axial length (P < .001), and the inferior PPA area was associated significantly with the axial length and the superior hemifield VFD (P < .001). CONCLUSIONS: In patients with normal-tension glaucoma, only the inferior half area of PPA correlated significantly with glaucomatous VFD. Axial length and myopia were associated with both the superior and inferior half areas of PPA.

Cross-Sectional Studies↗

PubMed2005

Correlation among physical impairments, pain, disability, and patient satisfaction in patients with chronic neck pain.

OBJECTIVE: To investigate the correlations among pain, physical impairments, disability, and patient satisfaction in patients with chronic neck pain. DESIGN: A longitudinal cohort study with 6-month follow-up. SETTING: Institutional practice. PARTICIPANTS: Subjects (N=218) with chronic neck pain. INTERVENTIONS: Subjects were treated with different physiotherapy modalities. MAIN OUTCOME MEASURES: Data were obtained for self-reported disability, verbal numeric pain scale, patient satisfaction, and 2 measures of physical impairments during the initial visit, at 6 weeks, and finally at 6 months. RESULTS: The correlation among 4 sets of measurements varied. Moderate correlation was noted between disability and patient satisfaction ( r range, .50-.65), and between disability and pain ( r range, .55-.63). A fair relationship was found between pain and patient satisfaction ( r range, .43-.48), but only weak relationships were found between physical impairments and pain ( r range, -.08 to -.25). The correlations tended to increase in the follow-up assessments. CONCLUSIONS: No strong correlations were found among disability, patient satisfaction, pain, and physical impairments although the correlations tended to increase in the follow-up assessments. The findings support the suggestion that clinicians should address as many relevant aspects of a presenting clinical entity as possible in the management of chronic neck pain.

Adult↗

PubMed2005

Performance in different proprioceptive tests does not correlate in ankles with recurrent sprain.

OBJECTIVE: To determine the relation between 2 proprioceptive tests, movement detection and movement discrimination, at the ankle. DESIGN: A cross-sectional descriptive study. SETTING: Research laboratory. PARTICIPANTS: Eighteen subjects with recurrent ankle inversion sprain. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Threshold to detection of movement was tested for inversion and eversion movements at 3 velocities (0.1 degrees , 0.5 degrees , 2.5 degrees /s). Movement discrimination was tested for plantarflexion and inversion movements. The tests were performed in random order, and the velocity and movements were randomized within each test paradigm. Correlations (Pearson r) were calculated between movement detection and movement discrimination. RESULTS: Correlation within each proprioceptive paradigm was poor to moderate: for movement detection, correlations among movement directions at each velocity ranged from r equal to .53 to r equal to .54; for movement discrimination correlation was r equal to .49. There was poor correlation between the scores for the 2 tasks in 10 of the 12 comparisons (r range, -.02 to -.36). CONCLUSIONS: These findings show that performance in different proprioceptive tests is not well correlated and, therefore, that general proprioceptive status cannot be inferred from assessment of a single proprioceptive test.

Adolescent↗

PubMedDate not supplied

Correlation between the CAMCOG, the MMSE, and three clock drawing tests in a specialized outpatient psychogeriatric service.

Our objective was to assess the correlation between (1) the Cambridge Cognitive Examination (CAMCOG) (including the Mini-Mental State Examination [MMSE]) score and three clock drawing tests (CDT) and (2) the three CDTs independently, in a specialized outpatient psychogeriatric service. One hundred and fourteen subjects completed a comprehensive evaluation and were allocated to one of the following groups: dementia of the Alzheimer's type (DAT) in 52; vascular dementia (VD) in 36; non-dementia (ND; Mood or Anxiety Disorders) in 26. When the entire sample of patients is considered, all three CDTs used were highly and significantly correlated to the MMSE score, the CAMCOG score, and to each other. In this patient population, these cognitive tests may be interchangeable for providing an initial objective measure of cognitive function. However, when the same correlations were studied in the separate diagnostic groups, in the dementia group (DAT and VD) even though the high correlations between the various CDTs themselves did not change, the correlations between the MMSE score, the CAMCOG score and the CDTs decreased, more evidently in the VD group. This trend became even more conspicuous in the ND group, where some of the above mentioned correlations became non-significant. We hypothesize that in a real clinical situation the clinician initially assumes the role of cognitive "evaluator" (in terms of the total sample) followed by the role of cognitive "monitor" (in relation to specific diagnostic groups). In the first instance, CDTs, the MMSE, and the CAMCOG might be considered interchangeable as an initial objective measure of cognitive dysfunction, while in the second role, different CDTs might be diversely used, presumably supplemented by other cognitive tests and clinical methods.

Aged↗

PubMed2004

Correlations between genomic GC levels and optimal growth temperatures are not 'robust'.

Musto et al. [FEBS Lett. 573 (2004) 73] studied the correlations between GC levels and optimal growth temperatures in 20 prokaryotic families. They reported that positive correlations are generally observed, and many of these are significant. Here, we have shown that these correlations are not "robust," i.e., correlation coefficients and/or significance of correlations can be considerably influenced by exclusion of very few (even as small as one) species from each dataset. The sensitivity of correlations is assumed as a result of high levels of bias in the family datasets. We concluded that solely based on these data, one cannot establish that GC contents of prokaryotic genomes increase as a result of growth temperature increments.

Adaptation, Physiological↗

PubMed2005

Correlations between genomic GC levels and optimal growth temperatures: some comments.

Regarding the existence of any specific correlation between optimal growth temperature and genomic GC levels, Musto et al. [FEBS Lett. 573 (2004) 73] have recently performed analysis on 20 prokaryotic families and showed that in most of the families there exists a positive correlation between these two parameters. On the basis of these results they claimed that optimal growth temperature is one of the factors that influence genomic GC composition in prokaryotes. In a subsequent article, Marashi and Ghalanbor [Biochem. Biophys. Res. Commun. 325 (2004) 381] have demonstrated that the correlation values change substantially when very few points in some of the families were excluded from the data set of Musto et al. [FEBS Lett. 573 (2004) 73]. But Marashi and Ghalanbor have not provided any reason behind this. The points excluded by Marashi and Ghalanbor are actually the outliers in the data set, which strongly affect the correlation coefficients. But the presence of outliers in large data set hardly had any effect on the correlation values. Marashi and Ghalanbor have excluded points from only those families that have small sample sizes and observed a substantial change in correlation coefficient values. Therefore, we argue that any conclusion drawn for a small sample size having outliers is always questionable. Although Musto's approach is a novel one, but to make any generalization one needs to be careful about the flawlessness in the data set.

Base Composition↗

PubMed2005

The correlation between genomic G+C and optimal growth temperature of prokaryotes is robust: a reply to Marashi and Ghalanbor.

We have recently shown that optimal growth temperature (T(opt)) is one of the factors that influence genomic GC in prokaryotes. Our results have been disputed by Marashi and Ghalanbor, who claim that the correlations we show are not "robust" because the elimination of some points (arbitrarily chosen) leads, in some families, to variations in the correlation coefficients and/or significance of correlations. Here, we test whether the correlation between T(opt) and genomic GC is robust by using two independent approaches: detection of possible outliers (using robust Mahalanobis distance) and usage of a non-parametric correlation coefficient that is not sensitive to the presence of outliers. The results presented here reinforce our previous proposal that T(opt) is correlated with genomic GC in prokaryotes.

Cytosine↗

PubMed2005

Positive correlation of serum bio-intact PTH(1-84) but not intact PTH with parathyroid gland size in hemodialysis patients.

To evaluate the usefulness of newly-developed bio-intact parathyroid hormone (Bio-PTH) assay, which measures exclusively intact PTH(1-84) molecule, serum PTH level determined by Bio-PTH assay, in comparison with second-generation intact PTH (I-PTH) assay, was examined for its correlation with parathyroid gland size. Serum PTH was determined in 46 male HD patients, together with bone formation markers bone alkaline phosphatase, intact osteocalcin, N-terminal propeptide of type I collagen, and bone resorption markers deoxypyridinoline, pyridinoline, beta-crossLaps. Maximal diameter of parathyroid gland was determined with ultrasonography as the parathyroid gland size. Serum Ca and Pi correlated significantly with parathyroid gland size rationalizing our method to define parathyroid gland size. Serum Bio-PTH was correlated significantly in a positive manner with parathyroid gland size (R = 0.308, P = 0.0474), whereas serum I-PTH did not. Furthermore, parathyroid gland size did not exhibit a significant correlation with any of bone formation markers or bone resorption markers. The lack of correlation between bone markers and parathyroid gland size in HD patients may be explained by the occurrence of refractoriness of bone to PTH. In conclusion, serum Bio-PTH assay could provide a better assay than I-PTH assay to estimate parathyroid function in HD patients, due mainly to its exclusive correlation with parathyroid gland size.

Alkaline Phosphatase↗

PubMed2005

Correlation character of ionic current fluctuations: analysis of ion current through a voltage-dependent potassium single channel.

The gating of ion channels has widely been modeled by assuming the transition between open and closed states is a memoryless process. Nevertheless, the statistical analysis of an ionic current signal recorded from voltage dependence K(+) single channel is presented. Calculating the sample auto-correlation function of the ionic current based on the digitized signals, rather than the sequence of open and closed states duration time. The results provide evidence for the existence of memory. For different voltages, the ion channel current fluctuation has different correlation attributions. The correlations in data generated by simulation of two Markov models, on one hand, auto-correlation function of the ionic current shows a weaker memory, after a delayed period of time, the attribute of memory does not exist; on the other hand, the correlation depends on the number of states in the Markov model. For V(p)=-60 mV pipette potential, spectral analysis of ion channel current was conducted, the result indicates that the spectrum is not a flat spectrum, the data set from ionic current fluctuations shows considerable variability with a broad 1/f -like spectrum, alpha=1.261+/-0.24. Thus the ion current fluctuations give information about the kinetics of the channel protein, the results suggest the correlation character of ion channel protein nonlinear kinetics regardless of whether the channel is in open or closed state.

Animals↗

PubMed2005

Hierarchical clustering of the correlation patterns: new method of domain identification in proteins.

New method of identification of dynamical domains in proteins - Hierarchical Clustering of the Correlation Patterns (HCCP) is proposed. HCCP allows to identify the domains using single three-dimensional structure of the studied proteins and does not require any adjustable parameters that can influence the results. The method is based on hierarchical clustering performed on the matrices of correlation patterns, which are obtained by the transformation of ordinary pairwise correlation matrices. This approach allows to extract additional information from the correlation matrices, which increases reliability of domain identification. It is shown that HCCP is insensitive to small variations of the pairwise correlation matrices. Particularly it produces identical results if the data obtained for the same protein crystallized with different spatial positions of domains are used for analysis. HCCP can utilize correlation matrices obtained by any method such as normal mode or essential dynamics analysis, Gaussian network or anisotropic network models, etc. These features make HCCP an attractive method for domain identification in proteins.

Algorithms↗

PubMed2006

Serum HDL-C levels, log (TG/HDL-C) values and serum total cholesterol/HDL-C ratios significantly correlate with radiological extent of disease in patients with community-acquired pneumonia.

BACKGROUND: In several studies, it was shown that there was a marked decrease in serum levels of HDL-C during infection and inflammation in general. In particular, a decrease in the level of serum HDL-C was also shown in pneumonia. Correlations between inflammatory markers such as acute phase proteins, cytokines and serum HDL-C levels were shown. However, there are no studies indicating a correlation between serum HDL-C levels and the radiological extent of the disease (RED) in community-acquired pneumonia (CAP). AIM: We hypothesized that there could be a relationship between serum HDL-C levels and RED in CAP. MATERIALS AND METHODS: A case-controlled study, including 97 patients with CAP and 45 healthy subjects, was performed. Chest X-rays of CAP patients were scored for RED, and correlations were investigated between RED scores, serum lipid parameters, the erythrocyte sedimentation rate (ESR) and serum albumin levels. RESULTS: The mean serum HDL-C level was lower in CAP patients than in controls. A significant and negative correlation between RED scores (REDS) and serum HDL-C levels was detected (r = -0.64, P = 0.0001). There were also significant correlations between REDS and other lipid parameters. Significant correlations between ESR and serum HDL-C levels and between ESR and other serum lipid parameters were also found. CONCLUSION: It appears that serum HDL-C levels are generally lower in CAP cases than in healthy controls. Serum HDL-C levels and serum albumin levels might decrease and serum total cholesterol/HDL-C ratios and log (TG/HDL-C) values might increase proportionally with RED in CAP patients. These results might have some significance for individuals having long-standing and/or recurrent pneumonia and other cardiovascular risk factors.

Adolescent↗

PubMed2007

Bronchiectasis: correlation of high-resolution CT findings with health-related quality of life.

AIM: To evaluate the relationship between the severity of bronchiectatic diseases, as evident on high-resolution computed tomography (HRCT) and the patient's quality of life measured using the St George's Respiratory Questionnaire (SGRQ). METHODS AND MATERIALS: Forty-six patients (25 women, 21 men, mean age: 63 years) with bronchiectatic disease as evident on recent HRCT examinations were recruited. Each patient completed the SGRQ and underwent respiratory function tests. HRCT findings were blindly and independently scored by two radiologists, using the modified Bhalla scoring system. The relationships between HRCT scores, SGRQ scores and pulmonary function tests were evaluated. RESULTS: The patients' total CT score did not correlate with the SGRQ scores. However, patients with more advanced disease on HRCT, significantly differed in their SGRQ scores from patients with milder bronchiectatic disease. A significant correlation was found between the CT scores for the middle and distal lung zones and the activity, impacts and total SGRQ scores. No correlation was found between CT scores and respiratory function test indices. However, a significant correlation was found between the SGRQ scores and most of the respiratory function test indices. CONCLUSION: A correlation between the severity of bronchiectatic disease as expressed in HRCT and the health-related quality of life exists in patients with a more severe bronchiectatic disease but not in patients with mild disease. Such correlation depends on the location of the bronchiectasis in the pulmonary tree.

Adult↗

PubMed2006

Psychosocial correlates of substance use in adolescence: a cross-national study in six European countries.

AIMS: To examine the psychosocial correlates of substance use among adolescents in six European countries. DESIGN: Cross-sectional school population survey (ESPAD) based on standardized methodological procedures. SETTING: High schools in six European countries: Bulgaria, Croatia, Greece, Romania, Slovenia and UK. PARTICIPANTS: Representative samples of a total sample of 16,445 high school students whose 16th birthday fell in the year of data collection. MEASUREMENTS: Anonymous self-administered questionnaire. Self-reported substance use was measured by core items on tobacco, alcohol, marijuana and any illegal drug use. Psychosocial correlates included scales of self-esteem, depression, anomie and antisocial behavior, and items pertaining to family, school and peers. FINDINGS: Logistic regression analyses for each potential correlate adjusted for country, taking into account the clustered sample, showed statistically significant associations with each substance use variable separately, in almost every case. Particularly strong associations were found between smoking and going out most evenings and having many friends who smoke, while cannabis and illegal drugs were strongly correlated with having friends or older siblings who used these substances. The self-esteem scale score was not correlated with substance use. Anomie and antisocial behavior were more strongly associated than depression with substance use. In the case of depression, anomie and most of the other items examined, associations were stronger for girls than for boys. CONCLUSION: The present cross-national study identified correlates of legal and illegal substance use which extend outside specific countries, providing grounds to believe that they can be generalized. They provide evidence for the need to address both the use of the gateway drugs and deviant behavior in conjunction with environmental risk factors when designing and implementing preventive interventions in schools.

Adolescent↗