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Results for “Correlation analysis”

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At least 127 records · Page 7Linked to original sources
PubMed1997

[Correlation analysis of radiation effects on potential doubling time (Tpot) for human nasopharyngeal carcinoma cells].

OBJECTIVE: To understand radiation-induced cell kinetic changes of human nasopharyngeal carcinoma CNE cells and clarify cell biology basis of repopulation. METHODS: Either exponential growing stage or plateau stage human nasopharyngeal carcinoma CNE cells were measured by BrdUrd/DNA bivariate flow cytometry for phase fraction, BrdUrd labeling index, S phase duration, potential doubling time (Tpot), etc. Correlation analysis of Tpot with other kinetic parameters was made. RESULTS: (1) For exponentially growing CNE cells, shortening of Tpot after irradiation was closely correlated with increased BrdUrd labeled S phase fraction (P < 0.05), whereas no correlation was found between Tpot and other kinetic parameters measured; (2) for plateau stage CNE cells, shortening of Tpot with various radiation doses was closely correlated with decreased G0/G1 phase fraction (P < 0.05) and increased G2M phase fraction (P = 0.002), whereas no correlation was found between Tpot and other parameters measured. CONCLUSION: In a range of 0-8 Gy of irradiation, an increased accelerated repopulation rate was resulted from increasing radiation dose. Recruitment of G0 cells into cell cycle might play a major role in radiation-induced accelerated repopulation for plateau stage CNE cells, while it was contributed by an increased DNA synthesis manifested by an increased BrdUrd labeled S phase fraction for exponential growing CNE cells.

Cell Division↗
PubMed1979

[Correlation analysis of the organometric heart parameters under normal and pathological conditions].

An organometric study of 27 heart parameters normally, in hypertension, chronic nonspecific pulmonary diseases and ischemic heart disease was carried out. Significant differences in the heart weight values under normal and pathological conditions were found. A correlation analysis of the heart parameters normally and pathologically was performed revealing specific associations for each group of pathology. Increased associations were observed between heart weight values and its parts and the linear-planimetric parameters in the groups of ischemic heart disease and chronic nonspecific pulmonary diseases.

Adult↗
PubMed1986

A correlation analysis of the regional distribution of central enkephalin and beta-endorphin immunoreactive terminals and of opiate receptors in adult and old male rats. Evidence for the existence of two main types of communication in the central nervous system: the volume transmission and the wiring transmission.

By means of semiquantitative immunocytochemistry and quantitative receptor autoradiography a correlation analysis has been performed on the pre- and post-synaptic features of enkephalin and beta-endorphin immunoreactive neuron systems of the 3- and 24-month-old male rat. A parallel disappearance of enkephalin- and beta-endorphin-like immunoreactivity and of the density of mu and delta opiate receptors is shown during ageing. Furthermore, the lack of an overall correlation between the amount of pre- and post-synaptic components of the enkephalin and beta-endorphin synapses give evidence for the existence of a volume type of transmission in such systems in the telencephalic, diencephalic and mesencephalic areas analysed.

Age Factors↗
PubMed2000

Fast functional MRA using time-resolved projection MR angiography with correlation analysis.

Most recently, time-resolved 2D MRA after injection of a contrast agent bolus for various applications has been proposed. Similar to conventional digital subtraction angiography (DSA), 2D MR DSA offers the ability to observe the dilution of the bolus in the vascular system during the passage with a temporal resolution considerably below 1 sec. The purpose of this paper is to present strategies to improve the inherent low signal-to-noise ratio of 2D angiograms while retaining some temporal resolution. This can be achieved by applying algorithms for time series analysis as used in functional MRI. The significantly improved image quality is demonstrated on examples from clinical studies from bronchial MRA as well as cardiovascular MRA. In addition to the increased signal-to-noise ratio, correlation analysis leads to suppression of background signals and to a better discrimination of overlapping vessels. Further improvements in the temporal discrimination of vessels is afforded by the use of consecutive multiple contrast agent boli as demonstrated by numerical simulations and experiments.

Artifacts↗
PubMed2000

Thiopurine methyltransferase polymorphic tandem repeat: genotype-phenotype correlation analysis.

BACKGROUND: Thiopurine methyltransferase (TPMT) is a genetically polymorphic enzyme that catalyzes the S-methylation of thiopurine drugs such as 6-mercaptopurine. Recently, a variable number tandem repeat (VNTR) within the TPMT promoter has been reported to "modulate" levels of this enzyme activity. METHODS: We set out to perform genotype-phenotype correlation analysis for the polymorphic TPMT tandem repeat in 1211 clinical laboratory samples in which red blood cell (RBC) TPMT activity had been measured and to compare those results with data for 279 control DNA samples. RESULTS: TPMT VNTR length varied from three to nine repeats ( *V3 to *V9), but the most common alleles were *V4 and *V5, with frequencies in the control samples of 0.54 and 0.36, respectively. The clinical laboratory samples were then stratified into those with "low," "intermediate," or "high" levels of RBC TPMT activity; that is, samples presumed to be homozygous for open reading frame (ORF)-based variant alleles, heterozygous for those alleles, or homozygous for the "wild-type" ORF sequence, respectively. TPMT VNTR genotype *V4/*V5 was associated with significantly higher RBC TPMT activity than were *V4/*V4 or *V5/*V5. Lowest activity levels were associated with genotypes that included an allele with more than 5 repeat elements. However, all of these effects were quantitatively small. Finally, there was linkage disequilibrium between VNTR allele *V5 and TPMT*3A, the most common ORF-based polymorphism associated with very low TPMT activity in white persons. CONCLUSIONS: These observations suggest that, in addition to the striking effects of ORF-based single nucleotide polymorphisms on TPMT activity, the VNTR within the 5'-flanking region of the TPMT gene also may modulate levels of RBC TPMT activity.

Adolescent↗
PubMed1994

Cross-correlation analysis of cuneothalamic interactions in the rat somatosensory system: influence of receptive field topography and comparisons with thalamocortical interactions.

1. We simultaneously recorded neuronal responses to cutaneous stimulation from matched somatotopic representations in the nucleus cuneatus and ventrobasal complex of intact, halothane-anesthetized rats. A total of 95 cuneate and 86 thalamic neurons representing hairy skin on the forelimb were activated by hair movements produced by air jets at multiple skin sites. Mean responsiveness was higher among neurons in nucleus cuneatus (34.4 spikes per stimulus) than in thalamus (23.7 spikes per stimulus), a result that was consistent with the greater proportion of "sustained" responses recorded in nucleus cuneatus (80%) than in the thalamus (62%). 2. Cross-correlation analysis of 166 pairs of cuneate and thalamic neurons showed that 56 neuron pairs displayed time-locked correlations in activity that were characterized primarily by excitatory interactions (44 pairs) or a combination of excitatory and inhibitory interactions (10 pairs). Unilateral interactions in the cuneothalamic direction (31 pairs) and reverse direction (11 pairs) were observed, as well as multiphasic interactions in both directions (14 pairs). Most excitatory interactions involved intervals of 1-7 ms between successive cuneate and thalamic discharges, whereas most inhibitory influences involved intervals > 7 ms. Connection strength, defined by the ratio of time-linked interactions to the number of cuneate discharges, varied widely among neuron pairs but was largest for interactions involving interspike intervals of < or = 15 ms. 3. The relationship between connection strength and receptive field topography was analyzed in 103 cuneate-thalamic neuron pairs. The region of skin shared by both neurons varied substantially among neuron pairs and the probability of detecting interactions increased proportionately with larger amounts of receptive field overlap. Neuron pairs with moderate (25-50%) amounts of receptive field overlap had connection strengths 3-4 times greater than neuron pairs with minimal (0-25%) overlap. Connection strength was essentially identical, however, for neuron pairs with moderate or large (> 50%) amounts of overlap. 4. Cuneate-thalamic neuron pairs displaying functional connections were usually tested at multiple peripheral sites, but only 37% (18 of 49) of these neuron pairs displayed interactions at more than one stimulation site. Stimulation at different sites altered the timing of interactions in seven neuron pairs, including three that showed timing shifts across time zero in the cross-correlation histogram. In neuron pairs displaying interactions at multiple sites, connection strengths for 67% of the cases were strongest when stimulation was delivered within the region of receptive field overlap.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Platelet aggregation in spontaneous hypertension: genetic determination and correlation analysis.

OBJECTIVE: Hyper-responsive platelets are often found in essential hypertension. It has also been suggested that in hypertensive patients platelets may serve as an easily accessible indicator of abnormalities in contractile cell function. To test these suggestions, we analysed the relationship between platelet aggregation and genetic hypertension in the rat. METHODS: Linear regression analysis of mean values of recombinant inbred strains was used to evaluate the relationship between blood pressure and ADP-induced platelet aggregation. RESULTS: ADP-induced platelet aggregation in platelet-rich plasma in spontaneously hypertensive rats (SHR) was significantly decreased compared with in normotensive Brown Norway (BN) rats. However, in recombinant inbred strains, derived from (SHR x BN) F2 hybrids, correlation analysis revealed that platelet aggregation and blood pressure are independent traits. CONCLUSIONS: The present results suggest strongly that spontaneous hypertension and platelet hypo-aggregability in SHR were linked together by chance due to drift during selective inbreeding. The absence of a correlation between the two traits also indicates that alterations in platelet function in essential hypertension, often found in population-based studies, may have to be reaffirmed in genetically better-defined situations, e.g. by pedigree analysis.

Animals↗
PubMed1990

[Correlation analysis of pulmonary shunt after resection the lung].

Thirty-three patients with performed thoracotomy and lung resection were studied by measuring changes in shunting after they had undergone the breathing of 100% O2 for 20 minutes during the operative procedure and the immediate postoperative period. The obtained values of the shunt were compared with those in the preoperative period by making a correlative analysis, with a view to examining whether the shunt values and hypoxemia during the operation and the postoperative period could be foreseen on the basis of data on the preoperative shunt. The shunt was calculated from the following equation: Qs/Qt = CcO2--CaO2/CaO2--CvO2.

Adult↗
PubMed1986

Temporal relationship of the pulsatile fluctuation of luteinizing hormone and progesterone in cattle: a time series cross-correlation analysis.

The temporal relationship between the pulsatile patterns of plasma luteinizing hormone (LH) and progesterone (P4) was studied in mid-luteal (ML) and early-pregnant (EP) dairy cows. Blood samples were collected (via external jugular vein cannulae) at 10-min intervals for 16 h in 5 ML cows (d 10 to 12 of the cycle) and for 10 h in 5 EP cows (d 52 to 56 of gestation). Concentrations of LH and P4 were determined by radioimmunoassays and a time series cross-correlation analysis was utilized to evaluate the temporal relationship between them. A pulsatile pattern was found for both hormones in both groups, and in all animals LH peaks were uniformly followed by P4 peaks. In 80% of the cows in both groups the highest cross-correlation occurred between samples LH(n) and P4 (n + 1) (n = sample number), suggesting that a lag time of about 10 min is necessary for luteal stimulation. Results from both groups demonstrate that P4 is released from the corpus luteum in a pulsatile manner and that its release is at least partially dependent upon the pulsatile pattern of plasma LH. Correlation coefficients between LH and P4 mean level, basal levels, peak frequencies and peak amplitudes obtained in both groups indicate that the conceptus alters the hypothalamic-pituitary-ovarian relationship found in the ML cows, suggesting the existence of another factor(s) acting along with LH to release P4 in EP cows.

Animals↗
PubMed1979

Canonical correlation analysis: potential for environmental health planning.

There is a challenging need to identify the relationships between environmental quality and health status. It may be especially important to be able to isolate key variables which can be consolidated into a few indices of environmental conditions as they are related to health. Such indices might be used to identifying associations among groups of variables, such as specific geographic area. The indices may also provide insights into environmental health relationships which are worthy of further epidemiological investigation. Canonical correlation analysis is a multivariate statistical technique which provides a means of identifying associations among groups of variables, such as health and environmental measures. The technique can produce weighted indices of environmental conditions as they are related to health within a city or region. This paper describes what canonical correlation is, and outlines how it might be used for these purposes. An illustrative application based on data collected for Philadelphia, Pennsylvania is also presented.

Aged↗
PubMed1977

A correlational analysis of the effects of surgical transections of three components of the MFB on ingestive behavior and hypothalamic, striatal, and telencephalic amine concentrations.

A retractable wire knife was used to transect medial or lateral components of the MFB or its lateral projections to the striatum and amygdaloid complex. All cuts produced significant depletions of NE, DA, and 5-HT from telencephalon and striatum but little or no effect on hypothalamic NE or 5-HT. Two of our cuts resulted in aphagia and adipsia, the third in hyperphagia and obesity. A detailed correlational analysis of the magnitude and direction of the behavioral and biochemical consequences of our cuts indicated that the ingestive behavior of all of our experimental animals (including animals which had been aphagic and adipsic after surgery as well as animals which were hyperphagic and obese) was positively correlated with the concentration of DA in striatum and telencephalon and negatively correlated with telencephalic 5-HT. Less consistent evidence for facilitatory noradrenergic influences on food intake was also obtained. Our results suggest that the regulation of food intake may be the result of an interaction between telencephalic serotonergic mechanisms and dopaminergic pathways which exert opposite effects on ingestive behavior.

Animals↗
PubMed1986

Quantitation of staining for amyloid in histological sections: sources of variation, correlation analysis, and interstain reproducibility.

Five pathologists estimated with point counting the amount of amyloid in heart muscle autopsy samples from 19 patients who suffered from amyloidosis. The serial sections had been stained with 5 different methods. The different variation sources involved in a quantitative study on amyloid and the interstain reproducibility between the results given by these 5 stains were analyzed. The volume fractions of amyloid after different stains were subjected to correlation analysis. In our test system about a third (34%) of the variation was due to the point counting method. Sirius red had the lowest and Congo red the highest variation due to point counting, since Sirius red gave the most intense staining and highest volume fractions for amyloid. The volume fractions were lowest in Congo red. About 40% of the total variation was composed of the field variation. This variation includes the variation due to variation between fields, field selection and subjective intraobserver variation. Sirius red showed the smallest field variation in respect to the total variation. Congo red, on the other hand, had the highest variation. The variation caused by pure interobserver variation is presented by the difference between total variation and the calculated field variation. This was largest with Sirius red and smallest with Congo red. The pure interobserver variation accounted for about 26% of the total variation. The high reproducibility with Sirius stain is most probably due to the high volume fractions of positively stained material after this stain, not to low interobserver variation. Congo red seems to have low interobserver variation. The senior pathologists were more reliable in measuring the amyloid deposits than the junior pathologists as suggested by interstain reproducibility and variation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid↗
PubMed1998

Comparison of partial least-square method and canonical correlation analysis in a quantitative structure-retention relationship study.

The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-1-propanol and water-1-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. The relationship between retention characteristics and physicochemical parameters of solutes was elucidated by canonical correlation analysis and partial least-square regression analysis. Both methods found significant relationships between the chromatographic and physicochemical parameters, however, the results were different according to the method applied. Calculations suggested that the retention on both alumina and RP alumina layers is of mixed character, hydrophobic, electronic and steric parameters are equally involved in the retention.

1-Propanol↗
PubMed1977

Design, synthesis, and correlation analysis of 7-substituted 4-hydroxyquinoline-3-carboxylic acids as inhibitors of cellular respiration.

Fifteen 7-substituted 4-hydroxyquinoline-3-carboxylic acids have been designed to minimize covariance between the physicochemical substituent parameters: pi, MR, and sigmap. The molecules have been synthesized and evaluated for their ability to inhibit the respiration of Ehrlich ascites cells as a whole cell model and for their ability to inhibit malate dehydrogenase as an intracellular target enzyme model. Correlation analysis indicates that ascites cell inhibition is linearly related to pi and that malate dehydrogenase inhibition is linearly related to MR.

Animals↗
PubMed1976

Causal priority of social desirability over self-concept: a cross-lagged correlation analysis.

The study examined the causal relationship between social desirability (SD) and self-concept (SC). Two self-report instruments--Crandall's Children's Social Desirability Scale and the Piers-Harris Children's Self-Concept Scale--were administered before and after a 9-month therapeutic treatment designed to enhance self-concept. Subjects were 57 upper elementary pupils in a laboratory research school. Three hypotheses were proposed: (a) There is a positive correlation between SD and SC; (b) SD is more stable across time than SC; and (c) SD is causally prior to SC. Cross-lagged panel correlation analysis supported all three hypotheses. Discussion centers on a causal explanation of the distorting effect of SD upon SC scores.

Child↗
PubMed1995

Contributions of facial morphology, age, and gender to EMG activity under biting and resting conditions: a canonical correlation analysis.

Theoretical studies suggest that facial morphology may confer a mechanical advantage to particular individuals during force production, but not during rest. However, prior studies on the relationship between facial morphology and EMG suffer from various methodological limitations. We examined the hypothesis that facial morphology variables contribute significantly and meaningfully to the variance in masticatory muscle EMG when subjects produce specific levels of interocclusal force, but not when subjects are at rest. Measures of facial morphology included gonial angle, ramus height, and maxillary height, as determined from lateral cephalograms. EMG data were obtained from surface electrodes placed on masseter and temporalis sites. Subjects (N = 96) sat in a darkened, sound-attenuated room while they watched a seven-minute segment of a movie. EMG activity obtained during the last two minutes was used as a baseline period. Using the central incisors, subjects then provided five different force levels ranging from 6.5 to 48 lb in random order on a bite-force device while EMG data were collected. A canonical correlation analysis, performed on the set of predictor variables (age, gender, and facial morphology measurements) and the set of criterion variables (EMG data), showed a significant canonical correlation between the two variable sets while biting, but not at rest. Age, but not the facial morphology variables, was highly related to the canonical variate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

A spectral correlation analysis of the electrical activity of the sensorimotor cortex and the medial geniculate body in the presence of a motor polarizational dominant.

The dynamics of the changes in the structure of the coherence relationships of the electrical activity of the sensorimotor cortex and the medial geniculate body (MGB) of the rabbit in the presence of a motor polarizational dominant created by the action of a direct current anode on the region of the sensorimotor cortex were investigated by the method of spectral correlation analysis. It was demonstrated that, in addition to an increase in the components of the delta range in the interstimulus intervals in the presence of a dominant, a clear maximum in the alpha rhythm range in the electrical activity of the MGB of the "dominant" hemisphere appears in the power spectra of the electrical activity of the MGB during the action of an acoustic signal. An increase in the coherence of the delta range of the electrical activity of the MGB and of the sensorimotor cortex in the "dominant" half of the brain is manifested exclusively in the period of action of the acoustic stimulus.

Acoustic Stimulation↗