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PubMed1977

[Interspecies study of statistical correlations existing between the pineal gland size and weight and brain and body weight in two groups of mammals. Interspecies study of correlations between the pineal gland and brain in the rat and in man].

Network analysis procedures have been applied to study the cell patterns on the dorso medial and ventral lateral formation of the inferior colliculus of different species, i-e: Cat, Tat and Monkey. The results suggests the existence of important interspecific differences, more particularly in the primates. These differences are more obvious in the dorso medial formation. The functionnal implications of these results are discussed.

Animals↗
PubMed1976

[Cytodiagnosis of the uterine portio vaginalis according to WHO nomenclature. I. Correlative revision of cytological and histological diagnoses as quality control of selected materials. Frequency and possible reasons for the lack of correlation of cytological and histological diagnoses].

Smears from the uterine cervix have been evaluated for neoplastic changes on the basis of descriptive terms. The material was obtained by a single gynecologist using a standardized sampling technique and the results were compared with the respective histological diagnoses. Material which was found to be unsuitable for technical reasons was excluded from this study. A 98.7% agreement between cytological and histological findings was noted. Discrepancies between cytological and histological findings were essentially due to differing dysplastic changes in the deeper layers of the surface epithelium and the cervical glands, which were not sampled by the smears on the surface layer. In a few cases the discrepancies could not be explained but they disappeared after several years of observation. The practitioner should be acquainted with the nomenclature used by cytologists. In his turn, the cytologist should be familiar with the pathological anatomy of the organ in question.

Cell Biology↗
PubMed1990

Effect of self-correlation on the relation between QT interval and cardiac cycle length.

The electrocardiographic QT interval, with a wide variety of practical and theoretic applications in medicine, pharmacology, and cardiology, is critically dependent on heart rate as expressed by cycle length (RR). To account for this and permit intraindividual and interindividual comparisons of changing QT intervals, a wide variety of formulas have been offered as single rate-correcting expressions over the range of heart rates. Yet as rate rises, the QT interval occupies more and more of the cycle length, until at the highest heart rates almost the entire cycle length is QT interval, and the QT-RR correlations become largely self-correlation. To elucidate this we investigated 150 consecutive patients divided into high, mid, and low rate terciles. For the entire group, and in each tercile, we determined the level of correlation between the QT interval and cycle length (RR interval). To remove the self-correlation, we repeated the calculations, correlating QT interval with RR interval minus QT interval. For the group, correlation (r) of QT with RR was 0.65. For the high, mid, and low rate terciles, correlation fell sharply, respectively: 0.58 to 0.36 to 0.25. When the self-correlation was removed by subtracting QT from cycle length (RR-QT), all correlations were even further sharply reduced for each tercile, respectively: 0.35, 0.16, and 0.03 (the latter being virtually no correlation). We conclude that at low heart rates, when it is not being correlated with itself, the correlation between QT and RR is low; at high heart rates the higher correlation is spurious because it is mainly self-correlation.

Electrocardiography↗
PubMed1991

A meta-analysis of reported correlations between prognostic factors in breast cancer: does axillary lymph node metastasis represent biology or chronology?

A statistical overview of published results on correlations between various prognostic factors in breast cancer was undertaken. A distinction was made between clinical (or anatomical) prognostic factors--namely, axillary lymph node status and tumour size--and eight different biological prognostic factors. The latter included: tumour grade, oestrogen and progesterone receptor status, thymidine labelling index, DNA ploidy, S-phase fraction, epidermal growth factor receptor expression and c-erbB-2 gene amplification (or overexpression). 139 articles were eligible for review which reported a total of 432 individual correlations. A simple form of meta-analysis was employed: the counting method, in which the number of studies achieving a statistically significant correlation or not were counted. For each possible correlation examined, the proportion of studies showing a statistically significant correlation was calculated and an exact binomial 99% confidence interval determined for that proportion. If the 99% confidence interval included 5% (the proportion of correlations that would be expected to be statistically significant if the null hypothesis was true), it was taken as failing to exclude the null hypothesis of a zero correlation, while if it excluded 5% it was taken as rejecting the null hypothesis of a zero correlation. A broad agreement was found among published reports on the existence of a statistically significant correlation between the various biological prognostic factors in breast cancer. Of the 20 correlations examined, 18 had a 99% confidence interval excluding 5%, thus rejecting the null hypothesis of a zero correlation. On the other hand, a completely different result was obtained when reports on possible correlations between lymph node status and tumour size on the one hand and the eight biological prognostic factors on the other were analysed. Of the 16 correlations examined, 13 had a 99% confidence interval including 5%, failing to reject the null hypothesis of a zero correlation. These observations suggest the hypothesis that the prognostic influence of node status and tumour size cannot be explained by an analysis of the biology of breast cancer; and is compatible with the contention that axillary node status is merely a reflection of the relative chronological age of breast cancer.

Breast Neoplasms↗
PubMed1990

Estimation of genetic correlation: interpretation of experiments using selectively bred and inbred animals.

There is increasing interest in determining the extent to which multiple characters related to drug sensitivity are influenced by common genes. The principal method for testing for the existence of such genetic correlations has been examination of pairs of mouse or rat lines selectively bred for sensitivity or resistance to a single behavioral effect of a drug. When a pair of selected lines is found to differ significantly on some trait other than the one on which they were selected, it is commonly concluded that significant genetic correlation between the traits exists, implying the action of a common set of genes on the two responses. In addition, results from comparisons of lines of animals selected for trait X and tested for trait Y may be compared with results from lines selected for trait Y and tested for trait X. As the number of correlated responses in selected lines increases, it becomes more important to adhere to sensible, consensual guidelines for interpreting such line differences. The principles underlying phenotypic and genotypic correlational analyses with selected lines are discussed. A scheme is presented to allow standardization across laboratories of inferences about the relative strength of genetic association from experiments with selected lines. Statistical and practical experimental issues are addressed. Estimates of genetic correlations may also be derived from the correlation of mean trait values across a panel of inbred strains. Existing data have sometimes found estimates of genetic correlations made with one approach to be inconsistent with those estimated in other ways. Possible reasons for this are discussed. Finally, the relationship between phenotypic correlations and genetic correlations is discussed. Phenotypic and genetic correlations for a pair of traits may differ widely, and may even be opposite in sign. Both are characteristic of the population from which they are sampled. Phenotypic correlations estimated within selected lines may change over time, as the additive genetic variance in the selected trait is exhausted. A specific example of this phenomenon is given.

Alcoholic Intoxication↗
PubMed1990

Within-mouth correlations for indicators of the host response in gingival crevicular fluid.

Gingival crevicular fluid was collected from multiple sites in patients with chronic adult periodontitis, and analysed for the lysosomal enzymes beta-glucuronidase and arylsulphatase, the cytoplasmic enzyme lactate dehydrogenase, total IgA, IgG and IgM and the protease inhibitor alpha 2-macroglobulin. The within-mouth (intraclass) correlation coefficients were calculated to describe the relationship between samples collected from individual patients. Data collected at baseline and 3 months after root planing and scaling were analysed, as was the change between examinations. Volume of crevicular fluid demonstrated the smallest intraclass correlation coefficient (0.16 at baseline, 0.12 at 3 months; 0.11 change), while probing depth and enzyme activity had moderate intraclass correlations (i.e. 0.36, 0.36, 0.26 for beta-glucuronidase). Immunoglobulin and alpha 2-macroglobulin activity in the fluid had the strongest correlations (i.e. 0.64, 0.57, 0.65 for IgG). The correlations for anatomically related teeth within a quadrant (molar, non-molar) were equivalent to or greater than the correlation for all samples within a mouth. Examined by tooth type, the intraclass correlations for volume of crevicular fluid, probing depth, beta-glucuronidase, arylsulphatase and lactate dehydrogenase were higher for non-molar teeth. In contrast, intraclass correlations for IgA, IgG, IgM and alpha 2-macroglobulin in samples from molar teeth were either equivalent to or greater than the correlations for non-molar samples. Calculation of intraclass correlation coefficients for such data can (1) indicate the degree of variability present in multiple samples of crevicular fluid collected from individual patients, (2) provide information about the source of host mediators in the fluid, and (3) help identify appropriate sampling strategies for the fluid.

Adult↗
PubMed1992

The sequential hypothesis of sleep function. IV. A correlative analysis of sleep variables in learning and nonlearning rats.

Female adult rats were trained for a two-way active avoidance task (4 h), and allowed free sleep (3 h). Control rats (C) were left in their home cages during the acquisition period. Dural electrodes and an intraventricular cannula, implanted one week in advance, were used for EEG recording during the period of sleep and for the injection of [3H]thymidine at the beginning of the training session, respectively. Rats were killed at the end of the sleep period, and the DNA-specific activity was determined in the main brain regions and in liver. Correlations among sleep, behavioral and biochemical variables were assessed using Spearman's nonparametric method. In learning rats (L), the number of avoidances was negatively correlated with SS-W variables, and positively correlated with SS-PS variables (episodes of synchronized sleep followed by wakefulness or paradoxical sleep, respectively) and with PS variables. An inverse pattern of correlations was shown by the number of escapes or freezings. No correlations occurred in rats unable to achieve the learning criterion (NL). In L rats, the specific activity of brain DNA was negatively correlated with SS-W variables and positively correlated with SS-PS variables, while essentially no correlation concerned PS variables. On the other hand, in NL rats, comparable correlations were positive with SS-W variables and negative with SS-PS and PS variables. Few and weak correlations occurred in C rats. The data support a role of SS in brain information processing, as postulated by the sequential hypothesis on the function of sleep. In addition, they suggest that the elimination of nonadaptive memory traces may require several SS-W episodes and a terminal SS-PS episode. During PS episodes, adaptive memory traces cleared of nonadaptive components may be copied in more suitable brain sites.

Animals↗
PubMed1990

[Measuring the optic papilla with planimetry and the optic nerve head analyzer in glaucoma and suspected glaucoma. II. Correlations of the results of both methods with changes in the visual field, studied with the Octopus automatic perimeter].

Sixty-seven optic nerve heads of 40 patients with proven or suspected glaucoma were measured by planimetry and with the Rodenstock Optic Nerve Head Analyser (ONHA). The results were compared to visual field indices obtained with the Octopus program G-1. Good correlation of the results obtained by the two measurement procedures has been shown (Stürmer et al. 1989), between values for the disk area, the excavation area, and the cup/disk ratio. However, there is only weak correlation of values for the neuroretinal rim. The planimetrically measured neuroretinal rim area in the total population examined proved to be significantly correlated only with the visual field index for mean retinal sensitivity (MS; r2 = 0.106; P = 0.007) and short-term fluctuations (SF; r2 = 0.066; P = 0.036). After division of the population examined into different diagnostic groups, further statistically significant correlations between optic nerve head parameters and the various visual field indices were shown; here, the cup/disk ratio of both measurement procedures in two subgroups showed the best correlation with the visual field indices MS and mean defect (MD). Neither in the total population nor in any of the subgroups was a statistically significant correlation found between the volume of the excavation and one of the visual field indices. Comparing only the data for the temporal quadrant of the optic nerve head with the visual field did not improve the correlations. The best, i.e. highly significant, correlations were between optic nerve head parameters and the age of the patient. The correlation factors are much lower than other published data. A variety of factors could be responsible for these weak correlations: different optic nerve head configurations on the one hand, and localized or diffuse visual field defects on the other. In unselected cases it appears impossible to predict the visual field of a given optic nerve head. Both methods are suitable for follow-up, but not all anatomical configuration of the optic nerve head permit this.

Adolescent↗
PubMed1991

Fringed correlation discrimination and binaural detection.

Results are reported from a series of binaural detection and interaural correlation discrimination experiments at 500 Hz. The experiments include fringed correlation discrimination in which the correlation change is restricted to a narrow (38 Hz) target band of frequencies and the reference correlation is maintained in a fringe band of frequencies. This experiment is designed to be analogous to a detection experiment with a narrow-band target; in both cases the correlation changes only inside the target band. A simplified theoretical framework is used to compare the results of the detection and correlation discrimination experiments. Results are consistent with the notion that binaural detection and interaural correlation discrimination are effected by a common mechanism when the reference correlation is unity (as in the NoS pi case). When the reference correlation is zero (as in the NuSo case), detection performance is significantly better than predicted from the measured ability to discriminate interaural correlation.

Attention↗
PubMed1992

The correlation between lupus anticoagulant and autoantibodies.

The presence of a positive lupus anticoagulant (LA) has recently been associated with reproductive failure. LA positivity and reproductive failure have also been associated with autoantibody abnormalities, especially antiphospholipid autoantibodies. Because the correlation between LA and autoantibody positivity has remained controversial, we retroactively investigated 326 sera of patients with reproductive failure for correlation between lupus anticoagulant and 15 autoantibodies separately for IgG, IgM, and IgA isotypes. LA by TTI and APTT correlated significantly (p less than 0.0001). Among 18 antiphospholipid isotypes, 6 (33%) correlated significantly with TTI, 5 (28%) with APTT, and 3 (17%) both with TTI and APTT. Among 15 isotypes to histone subfractions, 4 (27%) correlated significantly to TTI, 3 (20%) to APTT, and 2 (13%) to both LA assay methods. Of 12 isotypes to antipolynucleotide antibodies, 2 (17%) correlated significantly to TTI, 1 (8%) to APTT, and none to both assay methods. The correlation between LA and autoantibodies was less striking among LA-positive than LA-negative sera. LA by both TTI and APTT was primarily found to correlate with IgG and IgA autoantibodies. This occurs in decreasing frequency to phospholipids, histones, and polynucleotides. At abnormal levels of LA (by either method) the correlation with autoantibody levels is less pronounced and appears closer with IgM autoantibodies to histones and polynucleotides than antibodies to phospholipids. We conclude that the correlation between LA and autoantibodies, especially antiphospholipid antibodies, is less pronounced than often reported in the literature. Patients suspected to suffer from reproductive failure due to abnormal autoimmunity have to be screened not only with LA and/or selected antiphospholipid autoantibodies, but with a more comprehensive autoantibody profile.

Autoantibodies↗
PubMed1992

Correlating magnetic resonance imaging with the biochemical content of the normal human intervertebral disc.

Magnetic resonance imaging was used to determine the T2 relaxation times of prepared proteoglycan solutions and of normal human intervertebral disc tissue from the annulus fibrosus (AF) and nucleus pulposus (NP). The collagen, proteoglycan, and water contents of the disc tissue samples were determined by biochemical assays after they were scanned. Correlations among 1/T2, collagen, proteoglycan, and water contents of the tissue samples and among 1/T2, water, and proteoglycan contents of the proteoglycan solutions were calculated. A moderate negative correlation between 1/T2 and water content was noted for the tissue samples, and a very high negative correlation was found between 1/T2 and water content for the proteoglycan solutions. The very high positive correlation between 1/T2 and proteoglycan content of the proteoglycan solutions is probably due to this negative correlation between 1/T2 and water content. There was no significant correlation between 1/T2 and proteoglycan content of the tissues. The moderate positive correlation between 1/T2 and collagen content is probably due to the high negative correlation between collagen content and water content. No significant correlation was found between the collagen and proteoglycan contents of the tissues. Thus it appears that the data confirm previous reports in the literature that the collagen of the disc tissue functions to control its water content.

Adult↗
PubMed1992

Correlations of developmental end points observed after 2,4,5-trichlorophenoxyacetic acid exposure in mice.

A large-scale developmental toxicology study of 2,4,5-trichlorophenoxyacetic acid was conducted in four inbred strains and one outbred strain of mice. The most significant developmental effects observed were reduced fetal weight and increased incidences of cleft palate (malformation) and prenatal death (deaths/resorptions). The correlation coefficients among the proportion of deaths/resorptions, proportion of malformations, average fetal weights, and number of viable fetuses were investigated, with each variable measured on a per-litter basis. Generally, the correlation coefficients between average fetal weight and number of viable fetuses were negative for the control and low-dose groups in the C57BL/6, C3H/He, and BALB/c strains. Overall, the correlation coefficients between proportion of malformations and number of viable fetuses were not significant. The correlation coefficients between proportion of malformations and average fetal weight were negative for all but one case. The correlations were weak in the control and low-dose groups, in which the malformation rates were very low, and were strong in the high-dose groups. The correlation coefficients between proportion of deaths/resorptions and proportion of malformations were generally positive at the high doses; some negative correlations were observed in control and low-dose groups. The correlation coefficients between proportion of deaths/resorptions and average fetal weight were negative for the A/JAX and CD-1 strains. In summary, the strongest relationship observed was the negative correlation between fetal weight and malformation.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1989

Electroencephalographic correlates of blood flow and oxygen metabolism provided by positron emission tomography in patients with cerebral infarction.

Quantitative EEG data were analyzed statistically with respect to cortical cerebral blood flow (CBF) and oxygen metabolism (CMRO2) measured by positron emission tomography in 47 patients with unilateral cerebral infarction. Relative value of the square root of average power was used as a percentage power fraction (PPF) for each frequency category. Power ratio index (PRI) was calculated by dividing the combined delta-PPF and theta-PPF by the combined alpha-PPF and beta-PPF. Delta-PPF, theta-PPF and PRI correlated negatively with regional CBF (rCBF) and CMRO2 (rCMRO2) whereas alpha-PPF and beta-PPF correlated positively. In the acute stage, delta-PPF, alpha-PPF and PRI correlated with rCBF at all but the frontopolar region whereas the correlation with rCMRO2 was poor. Alpha-PPF and PRI correlated also with rCMRO2 in the frontal, central, parietal and occipital regions while delta-PPF correlated with rCBF only in the parietal and occipital regions in the subacute stage. In the chronic stage, all EEG quotients correlated significantly with both rCBF and CMRO2 in the central and parietal regions. In the frontopolar region, only the theta-PPF correlated with rCBF throughout. In the comparison of hemispheric mean values, the correlations were always closer for the affected hemisphere than for the contralateral hemisphere. Although hemispheric mean CBF and CMRO2 were significantly lower in patients with cortical infarcts on CT than in those with small subcortical infarcts, there was no significant difference in the EEG data between the 2 groups.

Brain↗
PubMed2026

Consistent and idiosyncratic pleiotropy in shaping genetic correlations.

Pleiotropy, the phenomenon where a single mutation influences multiple phenotypic traits, creates genetic correlations that can constrain evolutionary trajectories. Yet genetic correlations differ in their persistence: some remain stable over long evolutionary timescales, whereas others change rapidly across generations or environments. One explanation is that similar values of genetic correlation, rG, can arise from different pleiotropic architectures: broadly aligned effects across many loci, or disproportionate covariance contributions from a few large effect loci. Motivated by the distinction between vertical and horizontal pleiotropy, here, we develop a bivariate marker effect framework for recombinant mapping populations that separates candidate large covariance contributors from the polygenic background correlation, rD. We define rD as the correlation among marker effects after trimming markers with unusually large covariance contributions. rD is a trait-pair summary of how consistently small and moderate effect markers align across the genome; high rD is expected when many perturbations propagate through shared developmental, physiological, causal, or geometric structure. Applying this framework to high-dimensional yeast single-cell morphology, we show that trait pairs with similar rG can differ substantially in rD, and that a small number of candidate outlier regions can strongly influence some marker effect correlations. We then test whether rD predicts the environmental stability of genetic correlations under geldanamycin-mediated Hsp90 perturbation. Trait pairs with stronger rD show smaller absolute changes in rG. These results suggest that genetic correlations supported by a strong polygenic marker effect background are more environmentally stable than correlations shaped primarily by a few large covariance contributors.

Genetic Pleiotropy↗