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PubMed2004

Patterns of phenotypic covariation and correlation in modern humans as viewed from morphological integration.

Proportionality of phenotypic and genetic distance is of crucial importance to adequately focus on population history and structure, and it depends on the proportionality of genetic and phenotypic covariance. Constancy of phenotypic covariances is unlikely without constancy of genetic covariation if the latter is a substantial component of the former. If phenotypic patterns are found to be relatively stable, the most probable explanation is that genetic covariance matrices are also stable. Factors like morphological integration account for such stability. Morphological integration can be studied by analyzing the relationships among morphological traits. We present here a comparison of phenotypic correlation and covariance structure among worldwide human populations. Correlation and covariance matrices between 47 cranial traits were obtained for 28 populations, and compared with design matrices representing functional and developmental constraints. Among-population differences in patterns of correlation and covariation were tested for association with matrices of genetic distances (obtained after an examination of 10 Alu-insertions) and with Mahalanobis distances (computed after craniometrical traits). All matrix correlations were estimated by means of Mantel tests. Results indicate that correlation and covariance structure in our species is stable, and that among-group correlation/covariance similarity is not related to genetic or phenotypic distance. Conversely, genetic and morphological distance matrices were highly correlated. Correlation and covariation patterns were largely associated with functional and developmental factors, which probably account for the stability of covariance patterns.

Alu Elements↗

PubMed2003

Correlation of Bcl-2 and p53 expression in primary breast tumors and corresponding metastatic lymph nodes.

BACKGROUND: The p53 tumor suppressor gene product participated in G1 cell cycle arrest or cell death. Loss of function was associated with poor outcome in patients with breast carcinoma. bcl-2 prevented apoptosis induced by c-myc or growth factor deprivation. High bcl-2 expression in breast tumor tissue specimens appears to be associated with favorable prognostic factors. However, Bcl-2 and p53 expression in primary tumor tissue specimens versus metastatic lymph node specimens in breast carcinoma has not been studied. The current study compared Bcl-2 and p53 expression in primary breast carcinoma tissue specimens with Bcl-2 and p53 expression in axillary lymph node specimens. METHODS: Primary breast tumor and corresponding axillary metastatic lymph node tissue specimens were obtained from 60 patients with breast carcinoma. They were evaluated for the presence of Bcl-2 and p53 expression by immunohistochemistry using standard methods. RESULTS: Bcl-2 expression in primary tumor tissue specimens (53%) was correlated with Bcl-2 expression in metastatic lymph node specimens (50 %; Pearson correlation = 0.656). p53 expression in primary tumor specimens (72%) was correlated with p53 expression in metastatic lymph node specimens (60 %; Pearson correlation = 0.800). A significant inverse correlation also was found between p53 and Bcl-2 expression in primary breast tumor tissue specimens (Pearson correlation = -0.310). CONCLUSIONS: The current study suggested that Bcl-2 and p53 expression in axillary metastatic lymph node specimens is correlated with Bcl-2 and p53 expression in the primary tumor tissue specimens. The prognostic and predictive value of Bcl-2 and p53 expression in axillary lymph node metastasis in patients with breast carcinoma needs to be further evaluated in larger trials with longer follow-up.

Apoptosis↗

PubMed2005

Correlations between access to mammography and breast cancer stage at diagnosis.

BACKGROUND: There is a lack of data on the access to mammography and its relation to the incidence of early breast cancer. In this study, the authors evaluated access by correlating geographically the number of U.S. Food and Drug Administration (FDA)-certified mammography facilities and the AJCC stage of breast cancer at diagnosis by county. METHODS: Breast cancer incidence rates and stage at diagnosis were compared with the number of FDA-certified mammography facilities by county in the Surveillance, Epidemiology, and End Results reporting areas. The objective was to determine whether the number of certified facilities was associated with the percent of breast cancers diagnosed at the in situ stage. This was a multiple-group ecologic study, and counties were used as the units of analysis. RESULTS: There was a strong correlation between the number of mammography facilities and the population of a county, whereas there was no correlation between the number of mammography facilities and the land area of a county. A correlation existed between the percent of incident breast cancers that were diagnosed as in situ disease and the number of mammography facilities per 10,000 women among both whites and African Americans. CONCLUSIONS: There was an association between the number of mammography facilities and population. In counties with >/= 30,000 black and white females, 1) the percent of in situ breast cancers in black women and white women was correlated with the number of facilities per 10,000 women, indicating that population density is a factor in access for both racial groups; 2) except for 2 counties with >/= 30,000 black women, the percent of incident in situ cases was similar in both black women and white women, indicating equal access in both groups; and 3) there was a correlation between the percent in situ incidence and number of facilities per 1000 square miles in white women, but not in black women. There was a direct correlation of statewide mammography rates with the number of facilities per 1000 square miles, indicating that the rate of screening depends on availability. Maximum rates of statewide screening were achieved when there were > 15 mammography facilities per 1000 square miles.

Black or African American↗

PubMed2002

Cervical biopsy/cytology correlation data can be collected prospectively and shared clinically.

Cervical cytology (Cy) and biopsy (Bx) correlation is used by institutions for the evaluation of their cytodiagnostic capabilities as a part of overall laboratory quality improvement (QI). However, the data obtained from correlation are not routinely included in most surgical pathology (SP) reports. Our laboratory's procedure is to include the correlation of the patient's previous (most recent) cytology smear in the surgical pathology report of all/any gynecologic surgical pathology specimens. We reviewed this process for the time period between July 1998-June 1999. Any noncorrelating cases were assigned a correlation review code by the reviewing cytopathologist: major Cy diagnostic error (DE1), minor Cy diagnostic error (DE2), Cy sampling error (Cy SE), or biopsy sampling error (Bx SE). Of 3,486 cases reviewed, 3,229 cases were satisfactory for correlation studies. Concordant results were found in 86.9%. Cy DE1 due to either Cy screening or interpretation errors or both were found in 0.2% (n = 7) of all cases, while Cy DE2 due to the same were found in 1% (n = 32). Bx SE accounted for discrepancies in 6.8% (n = 220) of all cases, while 5.1% (n = 164) of the total cases were discrepancies due to Cy SE. Follow-up Bx was available in 97.2% (n = 214) of the Bx SE, and showed 16.4% (n = 35) to be major discrepancies and 83.6% (n = 179) to be minor discrepancies. Cervical Cy/Bx correlation is useful for the evaluation of a laboratory's QI. It is also useful for the identification of either Cy or Bx SE. While QI data exist as "internal use only" documents, SE data (as part of the CC (correlation comment) included in SP reports) are vital to a specific/given patient. Bx SE was identified in 6.3% of our patients, indicating a possible need for rebiopsy. This type of QI data may be shared clinically, and may direct the management for maximum diagnostic and patient benefit.

Biopsy↗

PubMed2004

Correlations between cognitive, behavioural and psychological findings and levels of vitamin B12 and folate in patients with dementia.

BACKGROUND: Associations between low levels of folate and vitamin B12 and cognitive impairment in patients with dementia have been reported. Some studies revealed correlations between low levels of vitamin B12 and behavioural and psychological signs and symptoms of dementia (BPSD) in Alzheimer's disease (AD) patients. Given the lack of studies in frontotemporal dementia (FTD) and on folate and given the methodological shortcomings of former publications, we set up a prospective study. METHODS: At inclusion, AD (n=152) and FTD (n=28) patients underwent a neuropsychological examination. Behaviour was assessed using a battery of behavioural assessment scales. Determination of serum vitamin B12 and red cell folate levels were performed within a time frame of two weeks of inclusion. RESULTS: In both patient groups, significantly negative correlations between levels of serum vitamin B12 and red cell folate and the degree of cognitive deterioration were found. No correlations with BPSD were found in the AD patient group. In FTD patients, levels of vitamin B12 were negatively correlated with both hallucinations (p=0.022) and diurnal rhythm disturbances (p=0.036). CONCLUSIONS: The observed negative correlations between levels of vitamin B12 and folate and cognitive impairment in both AD and FTD patients, raise the possibility of a non-specific etiological role. Although levels of vitamin B12 and folate did not correlate with BPSD in AD patients, negative correlations between serum vitamin B12 levels and BPSD in FTD patients were revealed. Decreased serum vitamin B12 levels may predispose FTD patients to develop hallucinations and diurnal rhythm disturbances.

Adult↗

PubMed2002

Clock drawing test in mild and moderate dementia of the Alzheimer's type: a comparative and correlation study.

OBJECTIVES: (a) To compare two different clock drawing tests (CDTs) in mild and moderate dementia of the Alzheimer's type (DAT); (b) To examine presumed correlation between these CDTs and some demographic, cognitive and activities of daily living (ADL) variables in mild and moderate DAT. METHODS: Cross-sectional study. Psychogeriatric outpatient clinic. 49 DAT patients, total; 26-mild, 23-moderate, mean age 77.8 and 80.6, respectively. Evaluations included the Mini-Mental State Examination (MMSE), the Cambridge Cognitive Examination (CAMCOG), the Instrumental Activities of Daily Living Scale (IADL), and a Basic Activities of Daily Living (BADL)-dressing subscale. Severity of dementia was determined with the Clinical Dementia Rating (CDR). Each clock was blindly scored by the same investigator, according to Shulman's and Freedman's methods. RESULTS: Mild and moderate DAT groups were similar in age, gender and education. Performance on Shulman's clock was similar between groups while moderate DAT subjects performed significantly worse on Freedman's clock compared to mild DAT patients. Both clocks correlated highly in mild and moderate DAT. CDT scores correlated significantly with age and education only in mild DAT. Neither clock correlated with ADLs in either stage of dementia severity. CDTs correlated with the MMSE score, and the CAMCOG score in mild DAT, and only with the CAMCOG score in moderate DAT. These correlations were still significant after controlling for age and education. CONCLUSIONS: Different aspects of cognition and dementia severity are reflected depending on how a clock drawing is scored. Some scoring systems may have greater sensitivity than others in monitoring progression of cognitive deterioration. Correlation between different CDTs and the variables studied (demographic, cognitive, ADLs), when present, is not ubiqitous and changes with the dementia severity.

Activities of Daily Living↗

PubMed2004

Assessment by monte carlo simulation of thermodynamic correlation of retention times in dual-column temperature programmed comprehensive two-dimensional gas chromatography.

The correlation of retention times in comprehensive two-dimensional gas chromatography caused by correlation of enthalpy and entropy changes between two stationary phases, methylsilicone and poly(ethylene glycol), was examined using commercial GC software and in-house Monte Carlo simulation. The enthalpy change, deltaH0, and entropy change, deltaS0, of 93 compounds were predicted from isothermal one-dimensional gas chromatograms predicted by the software. These values then were mimicked by Monte Carlo simulation, which removed the strong correlation of deltaH0 and modest correlation of deltaS0 between the two phases. Retention times in a comprehensive two-dimensional gas chromatogram (GC x GC) and in simulations of it were predicted for typical dual-capillary temperature-programmed conditions using the actual, correlated values of deltaH0 and deltaS0 and their uncorrelated Monte Carlo counterparts, respectively. The uncorrelated deltaH0 and deltaS0 values caused the retention-time range of the simulations' second dimension to expand substantially beyond that in the GC x GC. Other simulations were developed using a restricted range of uncorrelated deltaH0 and deltaS0 values to mimic more closely the retention-time range of the GC x GC's second dimension. The intervals between nearest neighbor retention-time coordinates were calculated in both the latter simulations and the GC x GC. The intervals were larger in the simulations than in the GC x GC because the former contained uncorrelated coordinates and the latter contained correlated ones, which clustered along or near the diagonal. The retention times in the first dimension of the GC x GC were Poisson distributed, as assessed by statistical-overlap theory. In contrast, the two-dimensional reduced retention-time coordinates in the GC x GC were not Poisson distributed, because retention times were correlated. However, the reduced retention-time coordinates in the simulations were Poisson distributed.

Journal Article↗

PubMed2003

Baseline abdominal pressure and valsalva leak point pressures-correlation with clinical and urodynamic data.

AIMS: To characterize the factors contributing to changes in baseline abdominal pressure (P(abd)) and the correlation between DeltaVLPP, VLPP(tot), and other clinical and urodynamic variables. METHODS: Two hundred sixty-four female patients who had undergone an anti-incontinence procedure between February 1994 and October 1999 were retrospectively reviewed. The urodynamics performed for each patient included abdominal and vesical pressures measured in a standardized manner with the patient sitting upright and the pressure sensors maintained at the level of the symphysis pubis. VLPP was determined at bladder volumes of 200 mL during a gradually increasing Valsalva maneuver. RESULTS: Baseline P(abd) varied between 10 and 55 cm H(2)O (mean, 32.7 +/- 8.8) and were significantly correlated with patient weight (P<0.001) and with patient body mass index (P<0.001). Baseline P(abd) was not found to be correlated with patient age, Baden and Walker Classification of the grading of pelvic floor prolapse, degree of incontinence (determined by the number of pads used per day), or prior surgical procedures for stress incontinence. Higher baseline P(abd) were significantly correlated with the peak abdominal pressure reached during the Valsalva maneuver (P<0.0001) and with VLPP(tot) (P<0.0001) but not with DeltaVLPP. Higher VLPP(tot) significantly correlated with decreased age (P=0.004), less severe incontinence (P=0.004), higher peak Valsalva pressure (P<0.0001), and the ability to increase abdominal pressure for a longer period of time (time to peak P(abd) during Valsalva). VLPP(tot) and DeltaVLPP had similar statistical correlation with all the clinical variables examined and neither could predict the outcome of any anti-incontinence surgery. By using a VLPP of 60 cm H(2)O as a cutoff to differentiate severe ISD from GSUI, 211 (67.4%) of the patients would be categorized as having ISD according to their DeltaVLPP compared with only 106 (40.1%) by using the VLPP(tot). CONCLUSIONS: Baseline P(abd) varies considerably among patients, is correlated with patient weight and habitus. In addition, it varies with both the ability to be increased for longer periods of time and with VLPP(tot). Looking at VLPP(tot) and DeltaVLPP will result in a different categorization of the type of incontinence in at least 25% of patients and, thus, affect the physician's selection of an anti-incontinence procedure for an individual patient.

Abdomen↗

PubMed1995

Spontaneous bursting and long-lived local correlation in normal and denervated tectum of goldfish.

The formation of fine retinotopic order by growing optic fibers in the goldfish is thought to be mediated by the correlated firing of optic fibers from neighboring retinal ganglion cells. Although the activity of the tectal cells must also be important for this activity-dependent refinement, few studies have analyzed the pattern and local correlation of the intrinsic activity of tectal neurons and the effect of denervation on this activity. To address this issue, spontaneous (nonoptic driven) activity was analyzed and cross-correlograms were computed between individual tectal neurons using single and double electrode extracellular recordings. Recordings were made in normally innervated tectum in which the contribution of optic activity was eliminated by short-term intraocular blockade with tetrodotoxin and in denervated tecta in which the optic nerve had been severed several weeks prior. Several observations were relevant to activity-dependent refinement: First, coupling between neighboring tectal cells is weak. Second, the time duration for local correlation is relatively long, as long as 200 ms. Third, tectal neurons exhibit spontaneous bursting. Fourth, denervation increased the level of spontaneous activity in the tectum. The increased spontaneous activity and bursting following denervation implies that tectal neurons are more excitable when optic fibers are beginning to reinnervate the tectum. This could make it possible for optic fibers to drive tectal neurons at a time when their input to individual neurons is severely weakened by a lack of spatial convergence. The weak coupling between tectal cells and the consequent long-time constant for correlated activity implies a constraint on the duration of correlated retinal activity that is used for activity-dependent refinement. Since optic fibers likely need to detect the postsynaptic activity of a local group of tectal neurons, rather than that of a single neuron, the long tectal time constant means that retinal activity need not be correlated with precision much better than 200 ms because the postsynaptic circuitry cannot generate shorter correlations.

Animals↗

PubMed2006

Nuchal translucency measurements are highly correlated in both mono- and dichorionic twin pairs.

OBJECTIVES: To establish the distribution of serological and ultrasound first-trimester Down syndrome markers in twins and identify correlations of significance for risk calculation. METHODS: Nuchal translucency (NT), PAPP-A and betahCG data were extracted from 181 twin pregnancies (31 mono- and 150 dichorionic) with a normal outcome. All pregnancies were consecutively and prospectively included and examined in the Copenhagen First-Trimester Study. The variance of the sum and the difference of log MoM NT values in twin pairs was used to calculate the correlation. RESULTS: The serological markers did not correlate and were nearly twice the value seen in singleton pregnancies with a median PAPP-A MoM of 2.14 and a median free betahCG MoM of 2.06. Chorionicity was not found to influence the level of biochemical markers. In all twin pairs (r = 0.343, p < 0.001, F-test), as well as mono- (r = 0.404, p = 0.011, F-test) and dichorionic twins (r = 0.316, p < 0.001, F-test) there was a significant correlation between log MoM NT in each pair. CONCLUSION: As the NT values of fetuses in subsequent pregnancies from the same woman do not correlate, the correlation between NTs in twins reflects that the NT is influenced by placental and maternal factors specific for the particular pregnancy, for example, nutrient supply or vascularisation. The correlation may be useful to improve the precision of the prenatal risk assessment for Down syndrome in first-trimester twin pregnancies. The serological markers were elevated in the examined twins as previously described.

Algorithms↗

PubMed1997

Correlations of Adsorption Energies with Physical and Structural Properties of Adsorbate Molecules

The purpose of this work is to find a suitable method to correlate Henry's law adsorption energies such as the isosteric heat or the gas-solid interaction energy. Available adsorption energies for a total of 63 gases distributed among five adsorbents-a zeolite, a silica gel, a carbon black, and two microporous carbons adsorbents were correlated with the boiling point, a critical constant ratio involving critical temperature and critical pressure, the log of the octanol-water partition coefficient, and molecular structural energy. In the structural approach each gas molecule is considered to be composed of a series of structural units that each make a fixed contribution to the total molecular adsorption energy. Multiple regression analyses were done for each of the five adsorbent systems using the four main correlation methods. The method based on the structural units of a molecule and its dipole moment was found to give a 0.99 correlation coefficient for all five gas-solid systems. This structural method was superior to correlations based on boiling points, critical constants, partition coefficients, and various combinations of other physical properties that were also examined. Since there has been a variety of interest in either predicting the energy of adsorption or extent of adsorption for specific adsorbate-adsorbent pairs, our correlation results could be useful in future quantitative structure-activity relationship (QSAR) correlations of adsorption. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

PubMed2000

Cross-correlated relaxation for the measurement of angles between tensorial interactions.

Theory,experimental aspects, and use in structure calculation of cross-correlated relaxation rates measured on zero- and double-quantum coherences in liquid state NMR are presented. The relative size of the interaction depends on the projection angle between the two tensorial interactions. The tensorial interaction can be either a dipolar interaction or a chemical shift anisotropy relaxation mechanism (CSA). Effects of additional sources of relaxation on the cross-correlated relaxation rates are analyzed. Also, an easy-to-use formalism is given to manipulate different cross-correlated relaxation interactions. The application addresses measurement of the backbone angle psi in a protein by measuring dipole((15)N-(1)H)-dipole((13)C(alpha)-(1)H(alpha)) and CSA((15)N)-dipole((13)C(alpha)-(1)H(alpha)) cross-correlated relaxation rates. It is shown that ambiguities due to the 3 cos(2)θ-1 dependence of one cross-correlated relaxation rate can be overcome by measuring additional cross-correlated relaxation rates. The use of cross-correlated relaxation rates is demonstrated in structure calculations.

Anisotropy↗

PubMed1998

The Effect of Correlation between Price and Quality on Consumer Choice.

According to the price-expectancy model of consumer choice, consumers evaluate products by comparing the actual price with a reference or expected price determined from (a) product's quality and (b) the price-quality correlation of the product category. Choices between hypothetical products of beer are used to test the model against a model without a reference price. Consistent with the price-expectancy model, product preferences varied with the subjective correlation between price and quality: the relative preference for higher priced/higher quality products over lower priced/lower quality products increased as the subjective correlation increased. For some pairs, the correlation between price and quality created a preference reversal across contexts: the higher priced/higher quality product was chosen over the lower priced/lower quality product in the higher correlational context, but the lower priced/lower quality product was chosen over the higher priced/higher quality product in the lower correlational context. An additional study provided evidence that the price-quality correlation affects reference price, rather than reference quality, formation. Copyright 1998 Academic Press.

Journal Article↗

PubMed2002

Variation of proposed correlation indices of cerebrovascular reactivity with change of arteriolar diameter.

The purpose of this study was to examine the relationship between proposed correlation indices of cerebrovascular reserve and corresponding changes of cerebrovascular reserve as measured by changes of pial arteriolar diameter. Mild and severe physiologic challenge was produced in piglets by appropriate ventilation with foreign gas mixture and altered alveolar ventilation. Intracranial pressure (ICP), arterial blood pressure (ABP), and video micrometer recordings of pial arteriolar diameter were made. Serial values of ICP and ABP were used to compute the Correlation Coefficient index (Corrx) and the Pressure Reactivity Index (PrX). For the 10 mild physiologic challenge experiments, correlations between percent change index (% delta Corrx and % delta PrX) and percent change of pial arteriolar diameter (% delta dia.) induced by mild challenges (n = 40) were 0.51 (p < .005) and 0.097 (p n.s.) respectively. For 8 asphyxia experiments, serial values with respect to time of the correlation indices were correlated with % delta dia. obtained before, during induction and recovery. The grand mean (n = 8) correlation values (+/- S.D.) of the Corrx and PrX were 0.76 (+/- 0.18, p < .025) and 0.21 (+/- 0.38, p n.s.) respectively. In contrast to the PrX index, changes of the Corrx index significantly correlated with changes of pial arteriolar diameter. However, Corrx and PrX were simultaneously high only during a state of maximum dilation. These findings suggest that sudden salient increases of the Corrx and PrX indices induced by physiologic challenge are indicative of vigorous dilatory response of the cerebral arterioles and loss of cerebrovascular reserve.

Animals↗

PubMed1991

The inappropriateness of conventional use of the correlation coefficient in assessing validity and reliability of dietary assessment methods.

Accuracy and precision of nutritional data are crucial in estimating effects in nutritional epidemiology. Because it is known that such data are usually flawed, studies have been designed to estimate both the validity of diet assessment methods in measuring "true" diet and the reliability of these methods in providing nutrient data that are at least reproducible. In these studies, validity and reliability have often been gauged by computing correlation coefficients between two or more estimates of diet and testing the coefficient's departure from 0. We propose that the correlation coefficient may be inappropriate in these studies as a measure of association. If correlation coefficients are presented, we suggest that one should also present confidence intervals and test the departure of the coefficient from approximately 1 rather than 0. We have examined this approach using dietary data from various studies. We have computed 95% confidence intervals of the correlation coefficients and have tested H0:rho = 0.95 as an approximation of rho = 1.00. In all of the studies selected, comparisons produced correlation coefficients statistically significantly different from both 0.95 and 0. Due to the dependence of the correlation coefficient on factors unique to individual studies, it is recommended that other techniques be used to assess agreement between nutrient scores derived in reliability or validation studies. Viable options include linear regression, analyses of the standard deviations of the differences between scores, and examinations of the intraclass correlation coefficient.

Diet↗

PubMed1996

The estrous cycle and the olivo-cerebellar circuit. I. Contrast enhancement of sensorimotor-correlated cerebellar discharge.

Neuromodulation of Purkinje (Pnj) cell responses by monoamines and estrous hormones is well characterized in the cerebellum at the cellular level, but not at the level of neuronal circuits in the awake behaving animal. In the present study, simultaneous recordings of up to 16 single neurons from within the olivo-cerebellar circuit were obtained through chronically implanted microwire electrode bundles: arrays of Pnj cell like neurons (Pnj cln) in the paravermal cerebellum and neurons within the afferent source of its climbing fiber input, the rostral dorsal accessory olive (rDAO), were recorded simultaneously across 3-20 consecutive estrous cycles during constant or variable speed treadmill locomotion performance tasks. Over 90% of Pnj cln recorded during treadmill locomotion exhibited significant increases (80%) or decreases (10%) in activity correlated with the stance phase of locomotion. In contrast, cells from the rDAO increased activity during speed changes or when the rat failed to maintain the treadmill speed (position slip). On the night of behavioral estrus, which is triggered by elevations in circulating levels of 17 beta-estradiol and progesterone, the magnitude of both increases and decreases in stance-correlated Pnj cln activity increased by 85-115%. These results are consistent with our previous findings that 17 beta-estradiol and progesterone enhance excitatory and inhibitory responses of single Pnj cells to locally applied glutamate and GABA, respectively. This dual enhancement of both excitatory and inhibitory effects, apparently paradoxical at the cellular level, produced a marked heightening of the contrast of the neural population "signal" at the neuronal ensemble level. Furthermore, the stance-correlated discharge of Pnj cln during estrus preceded that during diestrus by approximately 120 ms. Frame-by-frame video analysis also suggested that the swing phase of the step cycle was shortened on estrus compared with diestrus (low hormone state). In addition, rDAO discharge correlated with speed change or position slip was also significantly increased (P < 0.05) on the night of behavioral estrus versus diestrus. Thus, estrus was associated with changes in both the amplitude and the timing of Pnj cln and rDAO discharge correlated with specific behavioral events. These estrous-associated changes in Pnj cell activity were well correlated (r = 0.84) with faster responses to random changes in treadmill speed, a motor performance task. Together, these findings suggest that the increases in the contrast of stance-correlated Phj cln discharge observed following peak circulating levels of sex steroid hormones are associated with improved motor performance on a randomly moving treadmill.

Animals↗

PubMed1995

Fractal correlation in human H-reflex.

The amplitude of the H-reflex has been known to have considerable variability even if the intensity of the stimulation is held constant. However, previous studies largely ignored the time-dependent profile of this variability. Recent mathematical analyses have shown that some seemingly irregular biological signals have fractal properties. A fractal time series is characterized by the property of self-similarity (self-affinity), and has long-range time correlation. The aim of this study was to investigate the question of whether the fluctuation of H-reflex was fractal with strong time-correlation. Soleus H-reflexes were evoked in five healthy subjects at two levels of stimulation intensity [1.2 MT (motor threshold) and 0.9 MT] every 1 s and 1050 successive amplitudes of H-wave and M-wave were recorded twice. The sequences of the H-wave and the M-wave amplitudes were analyzed by "coarse graining spectral analysis" to calculate the percentage of random fractal components in the sequences (%Fractal) and the spectral exponent beta. The %Fractal values of both sequences were above 90% [H-wave: 93.3 +/- 2.3% (1.2 MT), 91.6 +/- 3.1% (0.9 MT); M-wave: 94.3 +/- 3.3%; mean +/- SD]. Nonflat power spectra of the fractal components were observed for the H-wave sequences regardless of the stimulation intensity [beta = 0.75 +/- 0.26 (1.2 MT), 0.80 +/- 0.39 (0.9 MT)], indicating that the sequences were strongly time correlated. On the other hand, the M-wave sequences had a flatter spectrum (beta = 0.26 +/- 0.14) which was close to uncorrelated white noise. These results indicated that: (1) the fractal correlation found in the H-wave sequences was caused neither by the conduction through nerve fibers nor by the transmission at the neuromuscular junction, because the M-wave sequence had a significantly weaker time correlation, and (2) antidromic impulses in a motor nerve induced by the stimulation made a minor contribution to the generation of fractal correlation in the H-wave sequences, because it was preserved when the stimulation intensity was below MT. It was suggested that the fractal correlation in human H-reflex was generated at the synaptic connections to alpha-motoneurons in the spinal cord.

Adult↗

PubMed1988

Semiquantifying regional cerebral blood flow by 123I-amphetamine (IMP) SPECT in cerebrovascular disorders: correlations with CBF indices by 133Xe inhalation method.

To examine the capacity of detecting regional cerebral blood flow (rCBF) disturbances in stroke, measurements with 133Xe inhalation and 123I-amphetamine (IMP) SPECT were performed within 1-2 days in 19 patients. IMP SPECT images in transverse sections consisting of outer and inner areas were correlated with 32 regions of 133Xe rCBF. 133Xe rCBF was assessed by ISI, CBF15, and F1. Inter hemispheric ratio correlation showed outer IMP uptake correlated better with 133Xe CBF indices than the inner one. With higher ratios of 133Xe rCBF. IMP uptake ratios were variable, suggesting less usefulness of this parameter in evaluation of mild ischemia. Values of IMP in outer regional hypo and hyperemic areas correlated better with those of 133Xe rCBF than the inner ones. In regional ratios of hypo and hyperemic areas from hemispheric mean, outer IMP uptake correlated with 133Xe CBF indices, reflecting regional disturbances of fast clearing tissue perfusion. Regression lines between ratios in 133Xe CBF and IMP uptake were located below one to one correlation, and dissociated more for hyperemic regions. IMP SPECT correlated better with 133Xe rCBF for tissues with reduced perfusion but underestimated hyperemic regions as measured with the 133Xe method. The data suggest outer cerebral IMP uptake evaluated by SPECT could reflect flow disturbances in the brain cortex.

Adult↗