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PubMed1991

[A prospective study on the incidence of mercury levels in dental students. 2. Correlation analysis].

The urinary mercury levels of 49 dental students have been examined in a longitudinal study for one year. The correlation of the measured values with the number of amalgam fillings, age, sex, smoking habits, and nutrition was assessed. The urinary mercury levels did not correlate with sex and smoking habits, but there was a correlation with the number of amalgam fillings. The data obtained in our longitudinal study confirm the results of cross sectional studies: amalgam fillings contribute a measurable though small amount to urinary mercury excretion.

Adult↗
PubMedDate not supplied

Correlation analysis of pesticide use data and cancer incidence rates in California counties.

California, the leading agricultural state in the United States, has maintained a population-based cancer registry since 1988, and it also maintains a comprehensive, state-wide pesticide reporting system. Data on cancer incidence and pesticide use reporting are available, by county, for all 58 counties in California. Average annual age-adjusted cancer incidence rates (1988-1992), on a county-, sex-, and race/ethnicity-specific basis, were obtained from the California Cancer Registry (CCR), which maintains the population-based cancer registry throughout California. Pesticide use data (i.e., pounds of active ingredient applied annually in each county) were obtained from the California Department of Pesticide Regulation for 1993. Investigators used Pearson product-moment correlation coefficients (r) to correlate age-adjusted incidence rates for selected cancers with the use data for selected pesticides. For most sex- and race/ethnicity-specific groups, the correlation coefficients were very close to zero or negative in sign, indicating no correlation between pesticide use and cancer incidence. There were, however, several exceptions, particularly in Hispanic males for whom the following correlations were observed: leukemia and atrazine (r=.40), leukemia and 2,4-dichlorophenoxyacetic acid (r=.41), leukemia and captan (r=.46), atrazine and brain cancer (r=.54), and atrazine and testicular cancer (r=.41). For black males, we observed the following: atrazine and prostate cancer (r=.67) and Captan and prostate cancer (r=.49). In females, only a few of the correlations were elevated. Although most of the correlations examined in this analysis were not elevated, several of those in the Hispanic and black male populations were. These segments of the population have traditionally been employed as farm workers in California and have had the greatest potential for exposure to pesticides. This was an ecological study for which no data about exposure to pesticides at the individual level were available for analysis. In addition, no latency period was allowed between potential exposure and diagnosis with cancer. However, the results obtained in two minority groups who represented the majority of farm workers in the fields suggested that additional research studies, in which more rigorous study designs are used, should be conducted in those groups.

Age Distribution↗
PubMed2004

Time domain correlation analysis of heart rate variability in preterm neonates.

BACKGROUND AND AIM: A fuller understanding of the neural control mechanisms of heart rate during the early stages of human development would be of great value to obstetric and neonatal management. In this paper, we investigate the correlation between heart rate variability (HRV) and other physiological parameters such as blood pressure and respiration in preterm neonates with the aim of developing a numerical model to explain and predict heart rate variability. STUDY DESIGN AND SUBJECTS: All the required data are readily available for premature babies who are routinely monitored while being nursed in intensive care, and we have collected large data sets for a random group of such neonates. For the quantitative analysis of the data, we have developed a time domain correlation method, which has a number of advantages over the more commonly used power spectral analysis. We have been able to study the dynamics of the different frequency components of HRV by this method. RESULTS: Highly correlated behaviour of the different HRV components, previously observed in our work on fetal HRV, is also present in the neonate, with similar characteristic time constants. Furthermore, the correlation of high-frequency (HF) oscillations of HRV with respiration and that of low-frequency (LF) oscillations of HRV with blood pressure are demonstrated on timescales of a single oscillation. In neonates receiving artificial ventilation, the correlation between HRV and respiration depends on the type of ventilation involved and assumes opposite polarities for the two main types of equipment currently in use. CONCLUSION: We demonstrate that it is possible to analyse HRV quantitatively by calculating the relative gains and characteristic time constants for the correlated parameters and components.

Blood Pressure↗
PubMed2002

Prediction of fertility by centrifugal countercurrent distribution (CCCD) analysis: correlation between viability and heterogeneity of ram semen and field fertility.

The prediction of the fertilizing ability of a sire or a given insemination dose is a primary aim in the field of artificial insemination. Centrifugal countercurrent distribution analysis (CCCD) was used to determine the relationship between some sperm parameters and the in vivo fertility rate obtained with the same sample after cervical artificial insemination. A total of 522 ewes from 26 different farms was inseminated with 53 ejaculates obtained from 25 mature Rasa aragonesa rams. Semen was diluted to 1.6 x 10(9) cells ml-1 and doses of 0.25 ml were prepared and kept at 15 degrees C until used for insemination. The same ejaculates were used for analysis of standard semen parameters and CCCD analysis. Sperm motility, concentration and viability were determined before and after CCCD. Post-CCCD parameters were derived from the analysis of the profile obtained after CCCD. The recovered viability showed the highest correlation with fertility, especially in the central chambers (V2), r = 0.415, P < 0.005). The ejaculate heterogeneity also showed a positive correlation with field fertility (r = 0.23), with a tendency towards significance (P < 0.1). The mean fertility value of all ejaculates used in this study was 46.75%, ranging from 12.5% to 75.0%. Ejaculates were classified into two categories according to their fertility: higher and lower than the mean value. Only the viability recovered in the central chambers (V2) was a parameter with a predictive capacity to discriminate between the two groups (P < 0.05). A predictive equation for field fertility with a correlation coefficient r = 0.488 and a very high level of significance (P < 0.005) was deduced by multiple analysis: PF = 6.02 + 0.069V2 + 0.315H (where PF is predictive fertility, V2 is the recovered viability in the CCCD profile central chambers and H is heterogeneity).

Animals↗
PubMed1990

Root complex and root canal system: a correlation analysis using one-rooted mandibular second molars.

The principal aim of this investigation was to verify an expected, probable correlation between certain variables, which are initially represented in the macrostructure of the root complex corresponding to the cemento-dentin junction, and certain variables that subsequently manifest themselves in the root canal system. A material consisting of 76 one-rooted, permanent mandibular second molars (M2 inf) was used. The specimens were cut at the mid-root level and all observations were made on the coronal root segment using a stereomicroscope. Relevant variables of the root complex were observed. The total macromorphologic variation of the root complex could be subdivided and classified in well-defined, distinguishable types. In accordance with the single root complex type an expected, logically deduced configuration of the root canal system was established. The relevant variables of the canal system were then recorded. Finally, the root complex morphology, as well as the expected and actually observed canal configuration, were compared type by type. In 76.3% of the teeth a good concordance could be shown between the expected and the actual canal configuration, whereas in 23.7% of the specimens there was a divergence. In 42.1% of the investigated teeth, 1 centrally localized main canal with varying cross section images, among them a C-shaped image, was found. In 30.3%, 2 main canals were found, which were often localized mesially and distally. In 23.7%, 3 main canals were observed: 1 mesiofacial, 1 mesiolingual and 1 distal. In the remaining 3.9%, 1 non-independent supernumerary canal was seen in a distolingual position.

Classification↗
PubMed2000

Brain correlates of stuttering and syllable production. A PET performance-correlation analysis.

To distinguish the neural systems of normal speech from those of stuttering, PET images of brain blood flow were probed (correlated voxel-wise) with per-trial speech-behaviour scores obtained during PET imaging. Two cohorts were studied: 10 right-handed men who stuttered and 10 right-handed, age- and sex-matched non-stuttering controls. Ninety PET blood flow images were obtained in each cohort (nine per subject as three trials of each of three conditions) from which r-value statistical parametric images (SPI¿r¿) were computed. Brain correlates of stutter rate and syllable rate showed striking differences in both laterality and sign (i.e. positive or negative correlations). Stutter-rate correlates, both positive and negative, were strongly lateralized to the right cerebral and left cerebellar hemispheres. Syllable correlates in both cohorts were bilateral, with a bias towards the left cerebral and right cerebellar hemispheres, in keeping with the left-cerebral dominance for language and motor skills typical of right-handed subjects. For both stutters and syllables, the brain regions that were correlated positively were those of speech production: the mouth representation in the primary motor cortex; the supplementary motor area; the inferior lateral premotor cortex (Broca's area); the anterior insula; and the cerebellum. The principal difference between syllable-rate and stutter-rate positive correlates was hemispheric laterality. A notable exception to this rule was that cerebellar positive correlates for syllable rate were far more extensive in the stuttering cohort than in the control cohort, which suggests a specific role for the cerebellum in enabling fluent utterances in persons who stutter. Stutters were negatively correlated with right-cerebral regions (superior and middle temporal gyrus) associated with auditory perception and processing, regions which were positively correlated with syllables in both the stuttering and control cohorts. These findings support long-held theories that the brain correlates of stuttering are the speech-motor regions of the non-dominant (right) cerebral hemisphere, and extend this theory to include the non-dominant (left) cerebellar hemisphere. The present findings also indicate a specific role of the cerebellum in the fluent utterances of persons who stutter. Support is also offered for theories that implicate auditory processing problems in stuttering.

Adult↗
PubMed2006

Correlation analysis of the beam angle dependence for elastography.

Signal decorrelation is a major source of error in the displacements estimated using correlation techniques for elastographic imaging. Previous papers have addressed the variation in the correlation coefficient as a function of the applied compression for a finite window size and an insonification angle of zero degrees. The recent use of angular beam-steered radio-frequency echo signals for spatial angular compounding and shear strain estimation have demonstrated the need for understanding signal decorrelation artifacts for data acquired at different beam angles. In this paper, we provide both numerical and closed form theoretical solutions of the correlation between pre- and post-compression radio-frequency echo signals acquired at a specified beam angle. The expression for the correlation coefficient obtained is a function of the beam angle and the applied compression for a finite duration window. Accuracy of the theoretical results is verified using tissue-mimicking phantom experiments on a uniformly elastic phantom using beam-steered data acquisitions on a linear array transducer. The theory predicts a faster decorrelation with changes in the beam or insonification angle for longer radio-frequency echo signal segments and at deeper locations in the medium. Theoretical results provide useful information for improving angular compounding and shear strain estimation techniques for elastography.

Elasticity↗
PubMed2005

Vector analysis correlating bullet trajectory to outcome after civilian through-and-through gunshot wound to the head: using imaging cues to predict fatal outcome.

OBJECTIVE: We identify radiographic imaging similarities found on head computed tomographic (CT) scans of patients with through-and-through gunshot wounds to the head with fatal outcomes. METHODS: A retrospective analysis was conducted over an 18-month period from June 2001 through December 2002. Two hundred seventeen gunshot wound patients were evaluated. Exclusion criteria included any patient with cardiopulmonary injury and instability, airway compromise, or extracranial injuries affecting prognosis. Thirty-seven patients with isolated gunshot wounds to the head were included, 10 of which were fatal. Vital signs, examination results, Glasgow coma scale (GCS) score, intracranial pressure monitoring, surgical data, days in the intensive care unit, and CT scan appearance were collected. A Cartesian xyz coordinate system was created centered on the dorsum sella. Bullet pathways on CT scans were plotted and graphed onto a standardized magnetic resonance imaging scan. RESULTS: Ten patients progressed to brain death. GCS score and pupil irregularity were associated with fatal outcome (P < 0.0001). CT scans showed that brain shift was more common in survivors. Seventy percent of nonsurvivors had minimal brain shift. A tram-track sign on CT scans correlated with fatal outcome (P = 0.005). Vector analysis of nonsurvivors showed an area of the brain approximately 4 cm above the dorsum sella that, when penetrated through the midline, led to brain death (P = 0.0006). This zone was coined the zona fatalis. CONCLUSION: We confirm that GCS score and diabetes insipidus correlated with fatal outcome. In the setting of low-velocity gunshot wounds, fatal outcome and low GCS score were associated with a tram-track sign on CT scans. Bullet passage through a particular supra-dorsum sellar transventricular zone was associated with fatal outcome.

Adolescent↗
PubMed2005

Determining protease activity in vivo by fluorescence cross-correlation analysis.

To date, most biochemical approaches to unravel protein function have focused on purified proteins in vitro. Whereas they analyze enzyme performance under assay conditions, they do not necessarily tell us what is relevant within a living cell. Ideally, cellular functions should be examined in situ. In particular, association/dissociation reactions are ubiquitous, but so far there is no standard technique permitting online analysis of these processes in vivo. Featuring single-molecule sensitivity combined with intrinsic averaging, fluorescence correlation spectroscopy is a minimally invasive technique ideally suited to monitor proteins. Moreover, endogenous fluorescence-based assays can be established by genetically encoding fusions of autofluorescent proteins and cellular proteins, thus avoiding the disadvantages of in vitro protein labeling and subsequent delivery to cells. Here, we present an in vivo protease assay as a model system: Green and red autofluorescent proteins were connected by Caspase-3- sensitive and insensitive protein linkers to create double-labeled protease substrates. Then, dual-color fluorescence cross-correlation spectroscopy was employed to study the protease reaction in situ. Allowing assessment of multiple dynamic parameters simultaneously, this method provided internal calibration and improved experimental resolution for quantifying protein stability. This approach, which is easily extended to reversible protein-protein interactions, seems very promising for elucidating intracellular protein functions.

Algorithms↗
PubMed2000

Spatial correlation analysis of atrial activation patterns during sustained atrial fibrillation in conscious goats.

In this study we applied both linear and nonlinear spatial correlation measures to characterize epicardial activation patterns of sustained atrial fibrillation in instrumented conscious goats. It was investigated if nonlinearity was involved in the spatial coupling of atrial regions and to what extent fibrillation was organized in the experimental model of sustained atrial fibrillation (AF) in instrumented goats. Data were collected in five goats during experiments to convert AF by continuous infusion of cibenzoline. Spatial organization during AF was quantified with the linear spatial cross correlation function and the nonlinear spatial cross redundancy which was calculated using the Grassberger-Procaccia correlation integral. Two different types of correlation were evaluated to distinguish simultaneous interaction from non-simultaneous interaction, for instance resulting from propagation of fibrillation waves. The nonlinear association length and the linear correlation length were estimated along the principal axes of iso-correlation contours in two-dimensional correlation maps of the nonlinear spatial redundancy and the linear spatial correlation function, respectively. To quantitatively assess the degree of nonlinearity, the association length was also estimated from the linearized spatial redundancy using multivariate surrogate data. The differences between the nonlinear and linearized association lengths indicated that a nonlinear component in the spatial organization of AF predominantly existed in the right atrium. The degree of organization characterized by association length along the short principal axis was higher in the right atrium (15 +/- 7 mm) than in the left atrium (8 +/- 4 mm). The spatial extension of coherent atrial patches was estimated from a surface of association equal to the area spanned by the principal axes of iso-correlation contours from the redundancy, including the effects from non-simultaneous interaction. Interpreting this area as the spatial domain of a fibrillation wavelet, the results suggest that the mapped region was activated on average by two wavelets in the left atrium and by one wavelet in the right atrium. Therefore, the activation pattern of sustained AF in goats was relatively organized, consistent with type II of AF. It is suggested that the surface of association is a measure of the number of independent wavelets present in the atria during sustained AF, and that larger association lengths result from fewer and larger reentrant circuits.

Animals↗
PubMed2006

[Correlation analysis between diabetic retinopathy and early atherosclerotic changes in adolescents with type 1 diabetes -- preliminary report].

OBJECTIVE: Recent studies have shown a correlation between advanced diabetic retinopathy and late stages of atherosclerosis. There are no findings on a possible relation between diabetic retinopathy and diseases of the cardiovascular system at their earliest stage in young people with diabetes type 1. The purpose of the study was to analyze a correlation between diabetic retinopathy and early atherosclerotic changes in adolescents with type 1 diabetes. RESEARCH DESIGN AND METHODS: The study included 28 adolescents aged 17.6+/-1.4 years suffering from type 1 diabetes mellitus for 7.9+/-3.1 years, the mean age of the disease onset - 9.5+/-3.7 years, a mean level of HbA1c - 8.6+/-1.9%. Eight patients with developing simple retinopathy, were separated from the whole group of young people. First control group consisted of the remaining patients with type 1 diabetes chosen with regard to age and sex, without disease complications. Second control group consisted of 11 healthy young people. The function of endothelium by measuring the brachial artery dilatation -- FMD and the intima-media complex thickness of the common carotid arteries were evaluated ultrasonographically. RESULTS: Young people with retinopathy had higher systolic pressure: 133+/-19 mmHg in comparison with patients without complications: 117+/-14 mmHg (p<0.05) and healthy people: 115+/-8 mmHg (p<0.05). All patients with diabetes showed significantly lower FMD (7.6+/-5.1%, p<0.05). In the group with retinopathy, FMD equaled 7.8+/-4.1% (p=0.04) and in the group without retinopathy - 7.6+/-5.5% (p<0.05) in comparison with 12.1+/-5.1% in healthy volunteers. Significantly higher IMT was found in all patients with diabetes in comparison with healthy young people: 0.49+/-0.06 vs. 0.42+/-0.03 mm (p<0.001). Patients with retinopathy had a significantly higher value of IMT in comparison not only with controls but also with patients without complications: 0.56+/-0.06 vs. 0.47+/-0.03 mm (p<0.001). CONCLUSIONS: 1. Young people with type 1 diabetes had a significantly impaired function of endothelium and higher IMT in comparison with healthy young people. 2. Adolescents with retinopathy were characterized by significantly higher values of systolic arterial blood pressure when compared to patients without complications 3. Higher IMT was found in patients with diabetic retinopathy in comparison with patients without complications, which may suggest that macrovascular changes are more advanced in case of complications than in patients without retinopathy.

Adolescent↗
PubMed1978

[Correlative analysis in the study of enzyme-ligand interactions].

A comprehensive study on enzyme ligand interactions by QSAR techniques is discussed. Thirteen correlation equations are presented which relate activity of 1086 ligands of isolated chloroplasts, chymotrypsin, dihydrofolate reductase, xanthine oxidase and guanine deaminase to their chemical structures. Two kinds of space within and on the surface of an enzyme are defined by means of pi and MR constants. Emphasis is put on the use of indicator variables as a means of rationalizing special enzyme-ligand interactions. The use of such studies for drug development is discussed.

Chloroplasts↗
PubMed2001

A utility analysis correlation with visual acuity: methodologies and vision in the better and poorer eyes.

OBJECTIVE: To ascertain the correlation between visual acuity levels and ophthalmic utility values obtained using time tradeoff and standard gamble utility analysis methodologies. METHODS: Three hundred twenty-five consecutive patients with visual loss to 20/40 or less in at least one eye with predominantly vitreoretinal pathology were evaluated in a cross-sectional fashion using a standardized testing methodology to obtain ophthalmic time tradeoff and standard gamble utility values. Spearman correlation coefficients were employed to correlate the utility values with visual acuity in better seeing and poorer seeing eyes. RESULTS: The Spearman correlation coefficient for time tradeoff utility values and vision in the better seeing eye was 0.455 (p < 0.001), while that for time tradeoff utility values and visual acuity in the poorer seeing eye was 0.268 (p < 0.001). The coefficient for standard gamble utility values and the better seeing eye was 0.371 (p < 0.001), while that for standard gamble utility values and vision in the poorer seeing eye was 0.250 (p < 0.001). CONCLUSIONS: There is a greater correlation between ophthalmic utility values and vision in the better seeing eye, as versus vision in the poorer seeing eye. Time tradeoff ophthalmic utility values demonstrate a greater correlation with vision in the better seeing eye than do standard gamble utility values.

Aged↗
PubMed1980

[Cross-correlation analysis of the impulse activity of spinal locomotor center neurons].

Crosscorrelation analysis of neuronal impulse activity of spinal locomotor centres was performed on thalamic immobilized cats. No correlation was observed at small time intervals (time displacement of one spike train with respect to another did not exceed 54 ms during plotting the crosscorrelation histogram) both at rest and during generation of efferent discharges. Impulse trains of neurons could correlate only at large time intervals (maximum of time displacement of one spike train relative to another was not less than 4-8 s). A weak correlative dependence was found at large time intervals (4-8 s) between the current mean frequency of a neuron and the intensity of discharge in a motor nerve. No correlation was found between the changes in momentary frequency of a neuron and the intensity of discharge in a motor nerve. Possible reasons for the absence of correlation dependence at a small time interval and its presence at a large time interval are discussed.

Animals↗
PubMed1988

On the independence of physical and nominal codes: a correlational analysis.

In studies of college students, normal children at three grades, and learning-disabled children, physical and nominal matching procedures were highly correlated, (range .72-.96). In each instance, expected time differences favoring physical matches were replicated. Comparable results were found with both tachistoscopic and paper-and-pencil methods. In two studies where relevant data were available, correlations were not significantly attenuated when the effects of motor speed were partialled out. The results challenge the premise that nominal and physical matching measures are empirically independent, invalidate their application as measures of independent types of information processing, and help explain inconsistent findings in hemispheric specialization research.

Adolescent↗
PubMed1983

Cross-correlation analysis of the response of units in the dorsal spinocerebellar tract (DSCT) to muscle stretch and contraction.

Activity of DSCT units was cross-correlated with stimuli evoking gastrocnemius-soleus muscle stretch or contraction in order to investigate the muscle receptor input to DSCT. The most potent stimulus was generally muscle contraction, and the most common response one of inhibition. The similarity in response of many units to stretch, contraction and nerve simulation suggests that Golgi tendon organs are prominent source of input to DSCT, and that much of this input is inhibitory.

Action Potentials↗
PubMed1996

Correlation analysis between bladder cancer and cigarette smoking in various countries.

Cigarette smoking is considered to be a risk factor of bladder cancer. We investigated the relationship between bladder cancer mortality rates and cigarette smoking prevalence in various countries, and examined whether only the difference of smoking prevalence could explain the difference of mortality rates of bladder cancer in each country or not. The age-adjusted mortality rates from bladder cancer were high in European countries and low in Asian countries. The sex ratios ranged between 2 to 6 in most of the countries. For 20 countries, the mortality rate from bladder cancer was not correlated with the cigarette smoking prevalence. However, when the analysis was restricted to 16 countries in Europe, North America and Oceania (Caucasians), the correlation coefficients between them were high, being 0.68 (p < 0.01) in males and 0.49 (0.05 < p < 0.1) in females. In both Japan and the United States, cigarette smoking prevalence declined while the incidence of bladder cancer increased in males, both being stable in females. Race might be considered to be a strong risk factor of bladder cancer, followed by the prevalence of cigarette smoking. It is necessary to follow the changes of incidence rates of bladder cancer in the future to evaluate the influence of cigarette smoking.

Age Factors↗