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PubMed2004

Correlation of lung tumor motion with external surrogate indicators of respiration.

PURPOSE: To assess the correlation of respiratory volume and abdominal displacement with tumor motion as seen with X-ray fluoroscopy. Measurements throughout the patient's treatment course allowed an assessment of the interfractional reproducibility of this correlation. METHODS AND MATERIALS: Data were acquired from 11 patients; 5 were studied over multiple days. Measurements of respiratory volume by spirometry and abdominal displacement by a real-time position tracking system were correlated to simultaneously acquired X-ray fluoroscopy measurements of superior-inferior tumor displacement. The linear correlation coefficient was computed for each data acquisition. The phase relationship between the surrogate and tumor signals was estimated through cross-correlation delay analysis. RESULTS: Correlation coefficients ranged from very high to very low (0.99-0.39, p < 0.0001). The correlation between tumor displacement and respiratory volume was higher and more reproducible from day to day than between tumor displacement and abdominal displacement. A nonzero phase relationship was observed in nearly all patients (-0.65 to +0.50 s). This relationship was observed to vary over inter- and intrafractional time scales. Only 1 of 5 patients studied over multiple days had a consistent relationship between tumor motion and either surrogate. CONCLUSIONS: Respiratory volume has a more reproducible correlation with tumor motion than does abdominal displacement. If forming a tumor-surrogate prediction model from a limited series of observations, the use of surrogates to guide treatment might result in geographic miss.

Aged↗

PubMed2003

A multi-channel correlation method detects traveling gamma-waves in monkey visual cortex.

Correlations among simultaneously recorded signals are mostly analyzed pairwise and include temporal averaging. However, pairwise methods are not suitable for characterizing relationships among multiple channels for signals which vary temporally in an unpredictable way. Here we develop a time-resolved spatio-temporal correlation (STC) measure among simultaneously recorded signals. We demonstrate the capabilities of the method with artificial data sets and with multiple-channel recordings from striate cortex of awake monkeys. We concentrate on correlations in the gamma-frequency range (gamma: 30-90 Hz) because they were prominent in the analyzed recordings and gained high interest in the recent years due to their assumed role in associative processing, including perceptual binding. Former analyses of gamma-activities in visual cortex, using pairwise correlation methods, mostly revealed zero-delay correlation, indicating synchrony. In cat and monkey visual cortex this gamma-synchrony is restricted to 1.5-3.0 mm (half-height decline). However, our spatio-temporal correlation (STC)-method demonstrates for striate cortex from awake monkeys that gamma-synchrony is a local phenomenon of more global traveling plane waves that appear stimulus-induced at randomly varying orientations. These gamma-waves are coupled over much larger cortical distances (approximately 7 mm half-height decline) than the gamma-synchrony ranges obtained by pairwise correlation analyses from the same data. Our STC-method therefore suggests that the previously reported results of short-range and zero-delay correlations were often due to temporal averaging of traveling gamma-waves.

Animals↗

PubMed2004

Correlations between multiple sclerosis functional composite, expanded disability status scale and health-related quality of life during and after treatment of relapses in patients with multiple sclerosis.

The measurement of the clinical manifestations of multiple sclerosis (MS) is difficult. In the present study, we examined the changes in measurement of functions during and after pulse methylprednisolon (MP) treatment of MS exacerbations using the MSFC and EDSS. Correlation between multiple sclerosis quality of life (MSQoL)-54, EDSS and MSFC were studied. Thirty-six clinically definite MS patients were included in this study. Because of MSFC's repeating feature, we administered the tests to a control group to exclude practise effects. All patients received 1000-mg intravenous MP for 5 days, followed by tappering dose of 100-mg oral prednisolone. All three scales were assessed on day 0. EDSS and two components of MSFC (nine HPT and T25WT) were administered on the other days of pulse MP treatment. PASAT was not applied before the day 5 to exclude the practise effect. MSQoL-54 was assessed again on day 30. Mean EDSS values significantly decreased after the day 2. MSFC score improved from 0.03 +/- 1.71 on day 0 to 0.79 +/- 1.51 on day 5. Improvement continued on day 30. The mean physical health composite score increased from 66.50 +/- 9.3 on day 0 to 74.34 +/- 8.9 on day 30. Mental health composite had also a significant improvement on day 30. Correlation between the baseline overall MSFC and the EDSS was moderately strong. T25WT correlated most strongly with EDSS. Significant positive correlation was found between MSFC and both components of MSQoL-54. It is more prominent for the MSFC and physical health composite correlation. The same correlation was found for the EDSS and MSQoL-54 composites. Changes in EDSS and MSFC scores and MSQoL-54 were found significantly correlated for the overall score on day 30 compared with day 0. In conclusion, MSFC seems to be more sensitive in detecting changes in function than the EDSS. Hence, EDSS is still useful for daily routine practise. When these results combined with the significant correlation between MSFC and MSQoL-54 measures, which indicated the MSFC reflects the severity of MS as perceived by patients, MSFC seems to be the most useful scale for clinical trials.

Adult↗

PubMed2004

Correlations between MRI-assessed volumes of the thalamus and cortical Brodmann's areas in schizophrenia.

BACKGROUND: We compared the thalamic-cortical volumetric correlational patterns in patients with schizophrenia and normal comparison subjects, and evaluated their relations to outcome. METHODS: High-resolution MR images were acquired in patients with schizophrenia (n=106) and normal comparison subjects (n=42). Patients were divided into good-outcome (n=52) and poor-outcome (Kraepelinian, n=54) subtypes based on their ability for self-care. Correlations between the relative gray and white matter volumes of the individual cortical Brodmann's areas and five dorsoventral levels of the thalamus were assessed. RESULTS: Compared to normal subjects, schizophrenia patients lacked significant thalamic gray matter volume correlations with the prefrontal and medial temporal cortical regions in the right hemisphere, and with frontal, cingulate, posterior parietal and occipital regions in the left hemisphere, while normal white matter volume cortical-thalamic correlations along the cingulate gyrus and in the temporal lobe were not found in schizophrenia patients in both hemispheres. In contrast to both normal comparison subjects and good-outcome group, schizophrenia patients with poor outcomes showed significant bilateral gray matter volume correlations between the dorsal thalamus and ventral prefrontal cortex, while the group differences in the white matter volume correlations were mostly restricted to the cingulate arch. CONCLUSIONS: Whereas patients with schizophrenia exhibit deficiencies in cortical-thalamic correlational patterns, poor outcome is associated with abnormal interregional correlations not observed in either normal subjects or patients with good outcomes. This latter finding may be explained by a core neurodevelopmental disturbance that results in aberrant cortical-thalamic connectivity in poor-outcome schizophrenia.

Adult↗

PubMed2006

Correlation between putative indicators of primary restless legs syndrome severity.

BACKGROUND AND PURPOSE: Several methods of assessing disease severity in restless legs syndrome (RLS) have been suggested. The purpose of this study was to examine the relationship between the suggested immobilization test (SIT), the International RLS Study Group rating scale (IRLS), sleep efficiency, and periodic leg movements of sleep index (PLMI). PATIENTS AND METHODS: Forty primary RLS patients with periodic leg movements of sleep were included in this prospective study. Study procedures were all performed during the same night, beginning with IRLS administration and following with SIT and polysomnography (PSG) evaluations, in that order. SIT was composed of two parameters: SIT mean discomfort score (SIT-MDS) and SIT periodic leg movements of wakefulness index (SIT-PLMW). PSG target measures were PLMI and sleep efficiency. Pearson's correlation was used for analysis at a P<0.01 significance level. RESULTS: PSG-PLMI correlated with IRLS (r=0.462; P=0.003) and with SIT-PLMW (r=0.681; P=0.0004). A correlation was also found between IRLS and SIT-MDS (r=0.447; P=0.004), even though SIT-PLMW and IRLS did not correlate with each other (P=0.286). A negative correlation was found between PSG-PLMI and sleep efficiency (r=-0.435; P=0.005). Neither SIT nor IRLS correlated with sleep efficiency. Only SIT discomfort scores from the second half of SIT correlated with SIT-PLMW (r=0.457, P=0.004), and they had a stronger correlation with IRLS (P=0.003). CONCLUSIONS: This study attempted a much needed comprehensive evaluation of the relationship between various RLS severity indicators. Our findings support a strong role of motor dysfunction on sleep quality in RLS, as well as the potential use of SIT-PLMW as a sensitive indicator of RLS severity.

Adolescent↗

PubMed1990

Pulmonary thallium uptake: correlation with systolic and diastolic left ventricular function at rest and during exercise.

Quantified pulmonary 201-thallium uptake, assessed as pulmonary/myocardial ratios (PM) and body surface area-corrected absolute pulmonary uptake (Pc), was determined from single photon emission computed tomography studies in 22 normal subjects and 46 consecutive patients with coronary artery disease (CAD). By means of equilibrium radionuclide angiography (ERNA), ejection fraction (EF), peak ejection rate (PER) in end-diastolic volume (EDV/sec) and peak filling rate (PFR) in EDV/sec and stroke volume (SV/sec) units, PFR/PER ratio, and time to peak filling rate (TPFR) in milliseconds were computed at rest and during exercise (n = 35). Left ventricular response to exercise was assessed as delta EF, relative delta EF, delta EDV, and delta ESV. In normal subjects the PM ratios showed significant inverse correlation with PER at rest and with EF, PER, and PFRedv during exercise. For the left ventricular response to exercise, delta ESV showed significant correlation with the PM ratios. The body surface area-corrected pulmonary uptake values showed no correlation with any of the variables. In patients with CAD the PM ratios and Pc uptake showed significant inverse correlation with EF, PER, PFRedv and to exercise EF, exercise PER, and exercise PFRedv. For the left ventricular response to exercise, delta EF showed significant inverse correlation with the PM ratios but not with the Pc uptake. Neither in normal subjects nor in patients with CAD did any of the independent diastolic variables show significant correlation with the PM ratios or Pc values. Thus pulmonary thallium uptake is correlated with systolic left ventricular function at rest and during exercise in normal subjects and in patients with CAD but not with diastolic function. In normal subjects delta ESV and in patients with CAD, delta EF showed correlation with pulmonary thallium uptake.

Adult↗

PubMed1999

Static and pulsatile blood pressure correlates of left ventricular structure and function in black and white young adults: the CARDIA study.

OBJECTIVE: To determine the unbiased relative strength of the association of static (systolic and diastolic) and pulsatile (pulse pressure) blood pressure components with left ventricular mass and function. BACKGROUND: Blood pressure is correlated with left ventricular mass; however, the unbiased relative strength of static and pulsatile blood pressure components with left ventricular mass and function is unknown in young adults. METHODS: Cross-sectional analyses of 3918 young adult participants at 4 community-based CARDIA clinical centers during 1990 and 1991. RESULTS: Left ventricular mass positively correlated (P <.01) with systolic, diastolic, and pulse pressure in all ethnicity-sex groups except for diastolic blood pressure in white men (P =.19). The association rank ordered as systolic blood pressure > pulse pressure > diastolic blood pressure except in white men, in whom pulse pressure and systolic blood pressure reversed positions in this hierarchy. Systolic blood pressure was the third and fourth strongest independent correlate of left ventricular mass in men and women, respectively. Body mass index, followed by height, was the strongest correlate of left ventricular mass in both sexes. Left ventricular wall thickness/chamber radius ratio positively correlated with diastolic and systolic blood pressure (women only) (P <.05) but not with pulse pressure. In all groups, stroke volume positively correlated (P <.05) with pulse pressure but was unrelated to static blood pressure measures, except for systolic blood pressure in black men. Left ventricular mass and the ventricular wall thickness/chamber radius ratio were greater in blacks compared with whites. CONCLUSIONS: Although systolic blood pressure was consistently the strongest unbiased blood pressure correlate of left ventricular mass, this relation varied by ethnicity and sex. Pulse pressure correlated with favorable left ventricular function and geometry, suggesting an opposite meaning to the ominous prognosis of wide pulse pressure in hypertensive, older adults.

Adolescent↗

PubMed2003

Correlation between posterior capsule opacification and visual function before and after Neodymium: YAG laser posterior capsulotomy.

PURPOSE: To investigate the correlation between visual acuity, contrast sensitivity, and contrast sensitivity with glare source (glare sensitivity), and the degree of posterior capsule opacification (PCO) before and after neodymium:yttrium-aluminum-garnet (Nd:YAG) laser posterior capsulotomy. DESIGN: Prospective interventional case series. METHODS: Eighty-four patients (90 pseudophakic eyes) scheduled to undergo Nd:YAG laser capsulotomy were recruited. Visual acuity and contrast sensitivity with and without the presence of a circular glare source (using the contrast glare tester) were measured before and after Nd:YAG laser capsulotomy. The PCO density value was measured using a Scheimpflug videophotography system. The visual functions were statistically correlated with the PCO value. RESULTS: Before Nd:YAG laser capsulotomy, strong correlation existed between the PCO value and visual acuity (r = 0.728). Contrast sensitivity and glare sensitivity were also weakly correlated with the PCO value, but the correlation coefficients were smaller than that of visual acuity. After Nd:YAG laser capsulotomy, mean visual acuity, contrast sensitivity, and glare sensitivity at all visual angles improved significantly (P <.0001). After capsulotomy, no significant correlation was found between visual acuity, contrast sensitivity, or glare sensitivity and the PCO value. CONCLUSIONS: Before Nd:YAG laser capsulotomy, visual functions correlated significantly with the degree of PCO. Specifically, visual acuity has a stronger association with PCO than does contrast sensitivity or glare sensitivity and therefore should be considered to reflect most accurately the degree of PCO. After capsulotomy, these visual functions improve markedly and no longer have a significant correlation with PCO.

Aged↗

PubMed2002

Probing the endocytic pathway in live cells using dual-color fluorescence cross-correlation analysis.

Fluorescence (auto)correlation spectroscopy (FCS) has developed into a widely used method for investigating molecular dynamics and mobility of molecules in vitro and in vivo. Dual-color cross-correlation, an extension of this technique, also assesses the concomitant movement of two spectrally distinguishable fluorescent molecules and has therefore proven superior to autocorrelation analysis to study interactions between different molecular species in solution. Here we explore the benefits of cross-correlation analysis when applied to live cells, by demonstrating its potential in analyzing endocytic processes. Bacterial cholera toxin (CTX) was labeled with Cy2 and Cy5 dyes on different subunits of the same holotoxin. Along the endocytic pathway, positive cross-correlation between the A and B subunits was first preserved, later followed by a loss in cross-correlation upon their separation in the Golgi. Furthermore, endocytosis of a mixture of only Cy2- and only Cy5-labeled holotoxins also gave rise to cross-correlation. Our results suggest that cross-correlation may be used to recognize whether different cargoes use the same endocytic pathway. Additionally, we show that cross-correlation is applicable to two-dimensional membrane diffusion. CTX bound to GM1-containing artificial giant unilamellar vesicles was diffusible, whereas CTX bound to the plasma membrane was immobile on the FCS time-scale, possibly because of raft-association of GM1.

Animals↗

PubMed1987

Correlation between histopathological, clinical and biochemical parameters in S-antigen-induced experimental autoimmune uveitis in guinea-pigs.

Footpad immunization with purified bovine retinal S-antigen in complete Freund's adjuvant was used to induce experimental allergic uveitis in 32 guinea-pigs. Thirteen animals immunized only with complete Freund's adjuvant were used as controls. Ninety-three point seven per cent of the animals immunized with S antigen developed clinical experimental allergic uveitis while none of the controls had any clinical manifestation of uveitis. Histopathological analysis in the experimental group revealed mono- and polymorphonuclear cell infiltration in the choroid, ciliary body and iris. Simultaneous disruption of the outer segment of photoreceptor cell layer was also noticed. For the anterior segment of the eye there was a strong correlation between the histopathological grading and the clinical grading. For the posterior segment this correlation was, however, poor. Histopathological changes in the eye were correlated with the clinical grading and biochemical parameters (phospholipase A2, prostaglandin E2, leukotriene C4, proteins and myeloperoxidase) measured from aqueous humour, serum samples and ciliary body-iris homogenate. Protein and phospholipase A2 levels in the aqueous humour correlated well with the histological grading of the anterior segment of the eye. The myeloperoxidase activity, measured from ciliary body-iris homogenate, also correlated with the inflammatory cell infiltration in the anterior segment. Leukotriene C4 and prostaglandin E2 levels in aqueous humour did not correlate with the histopathological, or with the clinical grading, although elevated mean values were recorded in eyes having uveitis. Gamma glutamyl transpeptidase, measured in the serum, had a poor correlation with the histological grading for the anterior segment. All other parameters, measured in serum, did not correlate with the histopathological or the clinical grading. Histopathological changes in the anterior uvea are thus reflected by elevated protein and phospholipase A2 levels in aqueous humour as well as by myeloperoxidase activity in ciliary body-iris homogenate.

Animals↗

PubMed2001

Serum insulin-like growth factor-I (IGF-I) does not correlate positively with isometric strength, fatigue, and quality of life in post-polio syndrome.

OBJECTIVES AND BACKGROUND: To determine if serum insulin-like growth factor-I (IGF-I) levels are associated with strength, body mass index (BMI), fatigue, or quality of life in post-poliomyelitis syndrome (PPS). PPS is likely due to a distal disintegration of enlarged post-polio motor units as a result of terminal axonal sprouting. Age-related decline in growth hormone and IGF-I (which support terminal axonal sprouts) is proposed as a contributing factor. METHODS: As part of the North American Post-Poliomyelitis Pyridostigmine Study (NAPPS), baseline data on maximum voluntary isometric contraction (MVIC), BMI, subjective fatigue (fatigue severity scale, Hare fatigue symptom scale), health-related quality of life (short form health survey-36; SF-36), and serum IGF-I levels were gathered on 112 PPS patients. Pearson correlation coefficients were calculated to evaluate the association between serum IGF-I and MVIC in 12 muscles, BMI, two fatigue scales, and SF-36 scale scores. RESULTS: There is a significant inverse correlation of IGF-I levels with MVIC in left ankle dorsiflexors (r=-0.30, P<0.01), and left and right knee extensors (r=-0.22, -0.25, P=<0.01, 0.01), but no significant correlations in other muscles. When men and women were evaluated separately, inverse correlations of IGF-I levels with MVIC were found only in men. IGF-I correlated inversely with BMI (r=-0.32, P=0006) and age (r=-0.32, P=0.0005). IGF-I did not correlate with the fatigue or SF-36 scales. CONCLUSIONS: In this exploratory study, we found that contrary to our expectations, IGF-I did not correlate positively with strength. IGF-I correlated negatively with strength in several lower extremity muscles, BMI, and age. IGF-I is likely not an important factor in the pathogenesis of fatigue and in determining quality of life in PPS, but its role on strength should be studied further.

Adult↗

PubMed2003

Correlations of new markers of bone formation and resorption in kidney transplant recipients.

Renal osteodystrophy is a common complication of chronic renal failure and renal replacement therapy. Successful kidney transplantation reverses many of these abnormalities, but the improvement is often incomplete. The evaluation of renal osteodystrophy in everyday practice is based on noninvasive measurements. Taking this into consideration the aim of the present study was to assess new markers of bone metabolism: serum CrossLaps degradation products of C-terminal telopeptides of type I collagen tartrate-resistant acid phosphatase (TRAP) and bone-specific alkaline phosphatase (bALP), as well as their correlations with bone mineral disease (BMD) in kidney transplant recipients. Twenty-six patients (aged 26 to 54 years) receiving a triple immunosuppressive regimen with stable graft function were enrolled in the study. Serum parathormone (PTH) osteocalcin type collagen C-terminal peptides (ICTP), and procollagen type I carboxyterminal extension peptide (PICP) concentrations were measured by radioimmunoassay (RIA), Serum CrossLaps, bALP, beta2-microglobulin, TRAP 5b by enzyme-linked immunoassay (ELISA), and deoxypyridinoline (DPD) in urine immunochemiluminescence. BMD, as measured by dual-energy X-ray absorptiometry (DEXA), correlated negatively with markers of bone formation (bALP, osteoclacin, and PICP) and resorption (TRAP, ICTP, and beta2-microglobulin). The only positive correlation was between urine DPD and BMD at the femoral neck. Interestingly, BMD correlated negatively with CsA concentration. TRAP 5b correlated positively with serum creatinine, ALP, bALP, osteocalcin, iPTH, ICTP, and serum beta2-microglobulin, and negatively with CsA concentration, and azathioprine and prednisone dose. DPD did not correlate with any parameters. Serum CrossLaps correlated with markers of both bone formation and resorption. Because TRAP and serum CrossLaps correlated with markers of both bone formation and or resorption, additional studies are needed to establish the value of these markers of bone resorption to assess renal osteodystrophy.

Adult↗

PubMed1998

Quantitative electroencephalographic correlates of cerebral blood flow in patients with chronic subdural hematomas.

BACKGROUND: We have observed that the reduction in cerebral blood flow (CBF) of patients with chronic subdural hematomas is always most pronounced in the thalamus and has a linear correlation with the degree of brain deformity caused by the compression from the hematoma. When the brain is markedly displaced by a hematoma, electroencephalography (EEG) shows delta waves in the frontal region. We theorized that the flow reduction begins in the thalamus, spreading throughout the hemisphere as displacement progresses. METHODS: We measured CBF using the xenon/computed tomography (CT) method in 10 patients with chronic subdural hematomas who had hemiparesis and/or a mental disturbance and radiographic evidence of a midline shift or herniation. We correlated their flow reductions with topographic encephalograms. RESULTS: Flow reductions were more pronounced in the thalamus than in the hemisphere and cortex. Slow waves dominated over fast waves, especially in the frontopolar and frontal regions bilaterally. Flow values correlated negatively with the presence of delta and theta waves and positively with that of alpha and beta waves. On the side of the hematoma, the brain wave activity correlated significantly with thalamic flow, and the correlation was greater than with the hemispheric or cortical flow. Thalamic flow correlated more consistently with delta and alpha waves in the central, temporal, and occipital regions, and with beta waves in the frontopolar, frontal, and central regions. On the nonhematoma side, the correlation between brain wave activity and hemispheric flow was significant and greater than with cortical or thalamic flow. CONCLUSIONS: The correlation of EEGs with thalamic flow, which was maximally reduced, seems to substantiate the concept that the thalamus is primarily injured by brain distortion due to the compression from hematoma and that the remote areas are secondarily deactivated by a transneural depression ("diaschisis") originating from the dysfunctioning thalamus. Thalamic involvement seems to be the cause of the neurologic dysfunction and the abnormal EEG activity in chronic subdural hematomas.

Aged↗

PubMed2003

American Urological Association Symptom Index for lower urinary tract symptoms in women: correlation with degree of bother and impact on quality of life.

OBJECTIVES: To determine first whether the American Urological Association Symptom Index (AUASI) correlates with the degree of bother caused by lower urinary tract symptoms (LUTS) in women and whether the association varies with a woman's age and continent status; and second, whether the AUASI and degree of bother caused by symptoms correlate with a woman's quality of life (QOL) and whether the association varies with a woman's age and continent status. LUTS occur in women and may produce significant bother and affect their QOL. The AUASI has been used to evaluate LUTS in female patients; however, its correlation with the degree of bother and QOL has not been clearly established in women. METHODS: The charts of 1232 women who completed the AUASI, as well as the Symptom Problem Index and global QOL question, were reviewed. Spearman's rank order correlation was computed to assess the correlation between the AUASI and Symptom Problem Index. It was also computed after stratifying the women's age and continence status (continent versus incontinent). A linear regression model was applied, with the AUASI and Symptom Problem Index as the response variables and QOL as the continuous explanatory variable. RESULTS: The mean age was 54.6 years. Six hundred women (49%) were incontinent. Spearman's rank order showed a strong correlation between symptoms and problems caused by symptoms (0.858, P <0.0001). The correlation existed throughout various age groups and was independent of coexisting incontinence. The symptoms correlated with QOL in a similar pattern. CONCLUSIONS: The AUASI accurately described LUTS in women and, as with men, is a good indicator of the degree of bother and affect on QOL.

Adolescent↗

PubMed2001

Trial to trial variability in either stimulus or action causes apparent correlation and synchrony in neuronal activity.

In this report we show that the observed inter-neuronal correlation reflects a superposition of correlations associated with the intrinsic correlation between neurons, and correlations associated with variability in the stimuli presented to, or the actions performed by, the subject. We argue that the effects of either stimulus or action variability on the observed correlation, though generally ignored, can be substantial. Specifically, we demonstrate how observed correlations are effected by trial to trial variability in either stimulus or action. In addition, assuming that all relevant stimuli and actions are known, we outline a method for eliminating their effects on the observed correlation. It is also shown that tuning of correlations to a stimulus or an action might be a direct consequence of variability in that stimulus or action, even in the absence of any modulation of direct inter-neuronal interaction. The effects of stimulus and action variability should therefore be carefully considered when designing and interpreting experiments involving multi-neuronal recordings.

Action Potentials↗

PubMed1992

Correlation of end-tidal CO2 to cerebral perfusion during CPR.

STUDY OBJECTIVE: A number of studies have demonstrated a correlation between end-tidal carbon dioxide (ETCO2), cardiac output, and return of spontaneous circulation in experimental animals and in patients undergoing closed-chest CPR. Our study attempted to correlate ETCO2 to cerebral blood flow during cardiac arrest. DESIGN: Sixteen piglets were anesthetized, intubated, and instrumented for cerebral blood flow studies. An ultrasonic flow probe was placed on both internal carotid arteries for continuous flow measurements. The animal was fibrillated, and closed-chest CPR was begun. Continuous ETCO2 measurements were obtained and compared with simultaneous internal carotid, cardiac output, and cerebral blood flow measurements. MEASUREMENTS AND MAIN RESULTS: Correlations between ETCO2 and carotid and cerebral blood flow were determined using Pearson's method. The correlation between ETCO2 and total internal carotid flow was .58 (P = .01, Bonferroni's adjusted P = .30). Correlation between ETCO2 and cerebral blood flow was .64 (P = .01, Bonferroni's adjusted P = .09). A partial correlation coefficient for ETCO2 versus cardiac output was .70, whereas it was only .30 for ETCO2 versus cerebral blood flow. CONCLUSION: Partial correlation coefficients suggest that ETCO2 correlates with cerebral blood flow when changes in cerebral blood flow parallel changes in cardiac output.

Animals↗

PubMed1981

Reconstruction of imperfectly ordered zinc-induced tubulin sheets using cross-correlation and real space averaging.

Large negatively-stained two-dimensional tubulin arrays induced by incubation with zinc were examined using electron microscopy. When Fourier methods are applied for the reconstruction, the resolution depends critically on the order of these arrays. The real space cross-correlation method as described in this paper, however, can be satisfactorily applied to disordered arrays. The method involves selection of a small area which is used as a reference to locate correlation peaks in other regions. In this way the locations of various unit cells are determined, often at points which deviate from the exact lattice. The unit cells at their determined locations are averaged, and the average is used as an improved reference in another search for correlation peaks. The process can be iterated to refine the reference and improve the correlation mapping. If necessary, poorly correlating unit cells can be ignored in the averaging, and rotational as well as translational corrections can be considered; but neither of these steps were found to be necessary in the studies on the zinc-induced tubulin sheets reported here. When both correlation and Fourier methods were compared for the same areas of selected sheets, the two methods gave comparable results for relatively well ordered regions, but the correlation images were superior for the more poorly ordered regions. In addition, even for the relatively well ordered regions the correlation images revealed some details that were lacking in the simple Fourier reconstructions but did appear in more extensive studies involving three-dimensional reconstruction. A direct comparison of the efficacy of real space and Fourier space reconstruction methods is presented using disordered model data.

Fourier Analysis↗

PubMed2003

Correlated multisecond oscillations in firing rate in the basal ganglia: modulation by dopamine and the subthalamic nucleus.

Previous studies from this laboratory have shown that many neurons in the basal ganglia have multisecond (<0.5 Hz) periodicities in firing rate in awake rats. The frequency and regularity of these oscillations are significantly increased by systemically injected dopamine (DA) agonists. Because oscillatory activity should have greater functional impact if shared by many neurons, the level of correlation of multisecond oscillations was assessed by recording pairs of neurons in the globus pallidus and substantia nigra pars reticulata in the same hemisphere, or pairs of globus pallidus neurons in opposite hemispheres in awake, immobilized rats. Cross-correlation (90-180 s lags) and spectral analysis were used to characterize correlated oscillations. Thirty-eight percent of pairs recorded in baseline (n=50) demonstrated correlated multisecond oscillations. Phase relationships were near 0 or 180 degrees. DA agonist injection significantly increased the incidence of correlation (intra- and interhemispheric) to 94% (n=17). After DA agonist injection, phase relationships of globus pallidus/substantia nigra neuron pairs were exclusively concentrated near 180 degrees, and phases of interhemispheric pairs of globus pallidus neurons were concentrated near 0 degrees. After subthalamic nucleus lesion (n=8), the incidence of correlated multisecond oscillations (or of multisecond oscillations per se) was not changed, although the consistent phase relationship between the globus pallidus and substantia nigra pars reticulata was disrupted. Subthalamic lesion also blocked apomorphine-induced decreases in oscillatory period and increases in oscillation amplitude, and significantly attenuated apomorphine-induced changes in mean firing rate. The data demonstrate that multisecond oscillations in the basal ganglia can be correlated between nuclei, and that DA receptor activation increases the level of correlation and organizes internuclear phase relationships at these multisecond time scales. While the subthalamic nucleus is not necessary for generating or transmitting these slow oscillations, it is involved in DA agonist-induced modulation of mean firing rate, oscillatory period, and internuclear phase relationship. These data further support a role for DA in modulating coherent oscillatory activity in the basal ganglia, and for the subthalamic nucleus in shaping the effects of DA receptor stimulation on basal ganglia output.

Animals↗