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At least 793 records · Page 44Linked to original sources

PubMed2000

Morphologic and biomechanical correlates with maximum bite forces in orthognathic surgery patients.

PURPOSE: The purpose of this study was to determine which factors of craniofacial morphology best predict maximum bite forces and jaw muscle strength (based on [electromyogram] EMG/force slopes) in patients selected for various orthognathic surgical procedures. These factors were then compared for their ability to separate orthognathic surgery patients by their clinical diagnosis. PATIENTS AND METHODS: Standard lateral cephalograms were taken of 121 orthognathic surgery patients (before treatment) and 80 control subjects to establish multivariate sagittal and biomechanical factors of craniofacial form. Maximum and submaximal bite forces were recorded at 8 tooth positions for each subject. EMG activity was recorded for 3 pairs of muscles (anterior temporalis, posterior temporalis, and superficial masseter) during the isometric bites. The EMG and bite force measurements were used to calculate EMG/force slopes as a measure of jaw muscle strength. The study looked for significant correlations between the morphologic factors and maximum bite force or jaw muscle strength. RESULTS: Factor analysis determined 12 sagittal and 6 biomechanical factors. However, only 3 of the sagittal and 4 of the biomechanical factors were significantly correlated with maximum bite force or jaw muscle strength. Factors reflecting jaw size were correlated with maximum bite forces and jaw muscle strength but generally did not separate patient groups. The factor most strongly correlated with maximum bite forces separated patients by their relative difference between anterior and posterior facial height. The factor for anteroposterior maxillomandibular discrepancies was not correlated with maximum bite force or jaw muscle strength. CONCLUSIONS: Many cephalometric measurements used to diagnose craniofacial deformities and to assign patients to particular orthognathic surgical procedures are not correlated with maximum bite forces or jaw muscle strength. Only measurements reflecting relative differences between anterior and posterior facial height are both strongly correlated with maximum bite force and reflect assignment of surgical procedures.

Adult↗

PubMed1998

Correlation of inflammatory cytokines with arthroscopic findings in patients with temporomandibular joint internal derangements.

PURPOSE: The goal of this study was to evaluate the presence of the inflammatory cytokines interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) within the superior temporomandibular joint (TMJ) space in patients with internal derangements and to compare these values with the pathologic findings seen arthroscopically. PATIENTS AND METHODS: Thirty patients with symptomatic TMJ dysfunction and clinical and imaging evidence of internal derangements of the TMJ were evaluated. Before entering the superior joint space with the arthroscope, 2 mL sterile saline was injected and, after 30 seconds of equilibration, was aspirated for analysis. The surgeon then performed diagnostic arthroscopy. The degree of synovitis, degeneration, percent condylar roofing, and any pathologic changes, such as perforations, were recorded. The level of total protein in each sample was ascertained, as well as the levels of IL-1 beta, IL-6, and TNF-alpha. RESULTS: Of 30 samples tested, three were discarded because of failure to gain access into the superior joint space. Of the 27 remaining samples, IL-6 showed the closest correlation with the level of acute synovitis demonstrated arthroscopically. Two of the higher IL-6 levels (167 and 324 pg/microg protein) were seen with patients with a significant disc perforation. In patients with a high degree of vascularity, IL-6 was found to be between 0 to 581 pg/microg protein with an average of 80 pg/microg protein and a median value of 43 pg/mg. These values significantly correlated with the degree of vascularity (P < or = .02). This is in comparison with the 10 remaining patients, who showed significantly fewer vascular changes arthroscopically. In these patients, the range of IL-6 was 0 to 35 pg/microg protein, with an average of 19 pg/microg protein and a median value of 14.5 pg/microg. These values significantly correlated with the smaller degree of vascularity (P < or = .02). In seven patients, the role of nonsteroidal antiinflammatory drug (NSAID) use resulted in decreased levels of IL-6, which has been noted in previous studies. In patients with higher rated redundancy of the synovial tissue, the average IL-6 level was 92 pg/microg protein, whereas the median value was 44 pg/microg protein. In patients with little or no redundant synovial tissue, an average IL-6 level of 22 pg/microg protein was present. The median value in these same joints was 15 pg/microg protein. These IL-6 values significantly correlated with the degree of redundancy (P < or = .03). The degree of degenerative change (chondromalacia, fibrillation), disc displacement (roofing), and the presence or absence of adhesions did not significantly affect the levels of IL-6 within the patients studied. The presence of IL-1 beta and TNF-alpha was not found to correlate with the arthroscopic findings in the superior joint space. CONCLUSIONS: The presence of IL-6 correlated with the degree of acute synovitis. IL-1 beta and TNF-alpha were not found in significant levels within the superior joint space. These findings correlated with those reported by other investigators. The production of IL-6 by synovial cells and its role in TMJ disease warrants further investigation.

Adolescent↗

PubMed2003

Phased mirror tracing outcomes correlate with several hemisphericity measures.

Recently, subjects, separated into two large groups by the Dichotic Deafness Test (DDT), a new brain laterality measure. These were significantly correlated with groups separated by two preference-based hemisphericity-type questionnaires, the Preference Questionnaire (PrefQ) and Polarity Questionnaire (PolQ). Here, Mirror-Tracing, another potential biophysical measure of hemisphericity earlier reported to be weakly correlated with laterality, was tested using 171 subjects, the DDT, and both questionnaires. No correlations between the DDT, PrefQ, and PolQ separation methods and Mirror Tracing outcomes were found until individuals identified as having left brain affect were removed from the population. Then, robust correlations appeared for the remaining right-affect subjects alone (n=82). These correlations became even higher when the left brain affect subjects that had been removed (n=89) were "phase corrected" from a contralateral to an ipsilateral connectivity for motor dominance and then returned to the sample (n=171). These Phased Mirror-Tracing (PMT) outcomes were also significantly correlated with 10 of the 11 statements of the PolQ. Thus, PMT joins the DDT as a second performance-based measure of laterality whose outcomes significantly correlated with those of preference-based hemisphericity questionnaires.

Adult↗

PubMed2000

Neuroendocrine correlates of temperamental traits in humans.

Studies investigating temperament traits in humans and their biological correlates have found high levels of novelty seeking (NS) linked with dopaminergic system changes, and particularly a deficit of dopamine transporter. Harm avoidance and reward dependence, on the other hand, appeared to be associated, respectively with serotonin and noradrenaline changes. In the present study, we have investigated the dopaminergic (DA), serotonergic (5-HT), and noradrenergic (NE) functions in healthy volunteers by challenging the monoamine systems with the DA agonist bromocriptine, the 5-HT agonist D-fenfluramine, and the NE agonist clonidine, respectively. Parallel to this investigation, we examined the temperament traits of our subjects by measuring NS, harm avoidance (HA) and reward dependence (RD) using the 'Three-dimensional Personality Questionnaire' (TPQ). The aims of the study were to see whether or not the monoamine functions were correlated with temperament traits. Bromocriptine challenge induced a significant GH increase and a significant suppression of PRL. D-fenfluramine test significantly increased PRL and cortisol plasma levels and Clonidine test induced a significant rise in GH values. NS scores showed a significant direct correlation with brom-stimulated GH values (r=0.426, P<0.05) and a significant inverse correlation with brom-inhibited PRL values (r=-0.498, P<0.01). HA scores correlated significantly with D-fen-stimulated PRL and CORT AUCs, (PRL: r=0.424, P<0.05; CORT: r=0. 595, P<0.005). RD scores correlated positively with clon-stimulated GH values (r=0.55; F=8.6; P<0.01) and negatively with brom-inhibited-PRL AUCs (r=-0.439, P<0.05). Our data support Cloninger theory concerning the biological correlates of temperamental traits, and evidence the link between the neuroendocrine responses to dynamic challenges and stable temperament features.

Adrenergic alpha-Agonists↗

PubMed1995

Proliferative activity in breast carcinoma evaluated by BrdU and PCNA. Correlation with expression of p53, c-erbB-2, estrogen receptor and P-glycoprotein.

The proliferative activity in 35 cases of breast carcinoma was evaluated by bromodeoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA) and was compared with benign breast lesion. Overexpression of p53 and c-erbB-2 oncoprotein, presence of estrogen receptor (ER) and cellular localization of multidrug resistance gene product P-glycoprotein (P-gp) were immunohistochemically examined to investigate the relation with the proliferative activity and clinicopathologic characteristics. The mean BrdU labeling index (LI) was 12.6% and PCNA labeling rate (LR) was 33.5% in breast carcinomas, and good correlation was found between them. The proliferative activity of breast carcinomas was significantly higher than that of benign lesions. The BrdU LI correlated positively with tumor size, histologic grade, TNM stage and p53 immunoreactivity, and negatively with the presence of ER. PCNA LR correlated with histologic grade and expression of p53. p53 protein was demonstrated in 43% of the breast carcinomas and correlated with proliferative activity. The extent of p53 immunoreactivity on carcinoma cells was also related to BrdU LI. c-erbB-2 oncoprotein was demonstrated in 51% of the breast carcinomas and correlated with histologic grade. ER was found in 34% of the breast carcinomas and correlated negatively with histologic grade, lymph node metastasis and TNM stage. P-gp was observed in 49% of the breast carcinomas and no correlation was found with clinicopathologic characteristics. None of the benign lesions expressed p53 protein, c-erbB-2 oncoprotein and P-gp. BrdU is a reliable standard and a more useful tool for the evaluation of proliferative activity of breast tumors. High proliferative activity, overexpression of p53 protein and the absence of ER are considered as a high grade malignancy of breast carcinoma. Expression of c-erbB-2 oncoprotein and P-gp may be related to malignant transformation of breast tumors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2001

Correlation of "in vitro" release and "in vivo" absorption characteristics of rifampicin from ethylcellulose coated nonpareil beads.

The purpose of this study was to investigate the possibility to develop different levels of correlation between in vitro dissolution parameters and in vivo pharmacokinetic parameters for three rifampicin formulations. A level A correlation of in vitro release and in vivo absorption could be obtained for individual plasma level data by means of the Wagner and Nelson method. Linear correlation could be obtained when percent dose released in vitro was plotted vs percent dose absorbed in vivo with correlation coefficients between 0.954,0.983 and 0.997 for the formulations studied. A second level correlation between mean in vitro dissolution time (MDT) and mean in vivo residence time (MRT) was performed with a correlation coefficient of 0.536,0.420 and 0.335. Finally, it was also possible to establish a good in vitro-in vivo correlation when the T(50%hrs) (time taken to release 50% of rifampicin) in vitro and C(max),T(max) or AUC in vivo were compared.

Absorption↗

PubMed2000

Correlations among evoked potential thresholds, distortion product otoacoustic emissions and hair cell loss following various noise exposures in the chinchilla.

Changes in cubic distortion product otoacoustic emissions (DeltaDPOAEs), evoked potential threshold shifts (TSs) and outer hair cell (OHC) losses were measured in a population of 95 noise-exposed chinchillas. Each animal was exposed to one of 23 different noises in an asymptotic threshold shift (ATS) producing paradigm or an interrupted noise paradigm which typically produced a toughening effect. Noises were narrow band (400 Hz) impacts with center frequencies of 0.5, 1.0, 2.0, 4.0 or 8.0 kHz presented 1 impact/s at peak SPLs of 109, 115, 121 or 127 dB. The duration of the exposures was 24 h/day for 5 days (ATS paradigm) or 6 h/day for 20 days (toughening paradigm). Based on a linear regression analysis of individual subject and group mean data, correlations among the following dependent variables were made: DeltaDPOAEs, ATS, toughening or TS recovery (TS(r)), permanent threshold shift (PTS) and OHC loss. Correlations among these metrics were generally highest for DPOAE primary frequency levels, L(1)=L(2)=70 dB. Correlation between DeltaDPOAE and TS(r) was typically low, while a considerably higher correlation was found between DeltaDPOAE and ATS. Correlations among the permanent measures of noise-induced effects, i.e. for DeltaDPOAE/PTS and DeltaDPOAE/OHC loss were typically poor when there was only a small or a moderate noise-induced effect (PTS<25 dB and DeltaDPOAE<20 dB). However, for PTS<25 dB the correlation between PTS and OHC loss was considerably better than the correlation between DeltaDPOAE and OHC loss. For more severe noise-induced changes there was generally a good correspondence between OHC loss, PTS and DeltaDPOAE metrics.

Animals↗

PubMed2000

The frequency and correlates of dyspnea in patients with advanced cancer.

Dyspnea is a devastating symptom in patients with advanced cancer. Unfortunately, very limited research has been done on the frequency and correlates of dyspnea in this particular patient population. The purpose of this prospective study was to assess the frequency of moderate to severe dyspnea and the correlates of dyspnea in a population of ambulatory terminally ill cancer patients. One hundred thirty-five consecutive patients attending a multidisciplinary pain clinic were tested for respiratory function (vital capacity, peak flow, maximal inspiratory pressure, and oxygen saturation). All patients gave their rating of dyspnea, anxiety, and fatigue/tiredness using visual analogue scales (VAS). Lung involvement by the tumor (primary or metastatic) was determined from the patient's chart. Moderate dyspnea occurred in 74/135 (55%) patients with terminal cancer. Lung involvement (r = 0.285, P = 0. 0009), anxiety (r = 0.306, P = 0.0003), fatigue/tiredness (r = 0.211, P = 0.0146), and vital capacity (r = -0.189, P = 0.0444) were significantly correlated with the intensity of dyspnea. Multivariate analysis demonstrated that lung involvement (P = 0.0016) and anxiety (P = 0.0027) were independently correlated with the intensity of dyspnea. In the subgroup of patients with moderate to severe dyspnea, multivariate analysis found anxiety (P = 0.0318) and maximal inspiratory pressure (P = 0.0187) to be independent correlates of the intensity of dyspnea. Dyspnea is a frequent symptom in patients with advanced cancer. The presence of cancer in the lungs, anxiety, and maximal inspiratory pressure are correlates of the intensity of dyspnea in this patient population. Possible treatments addressing low maximal inspiratory pressure and anxiety are needed, as well as further research in finding new correlates of dyspnea in advanced cancer patients.

Aged↗

PubMed2003

The prevalence and correlates of fatigue in older cancer patients.

PURPOSE: to assess the prevalence and correlates of fatigue in cancer patients aged 60 and older during outpatient treatment with chemotherapy or pamidronate. PATIENT AND METHODS: seventy-seven consecutive cancer patients with different tumors age 60+ served by the senior adult oncology program of the H. Lee Moffitt Cancer Center, were enrolled in the study. Inclusion criteria were: (1) age >-60 years; (2) histological diagnosis of malignancy; (3) no major psychiatric or neurological disorder that could interfere with the competition of the measures; (4) ability to understand and to speak English. Assessment included cognition, function, depression and fatigue. The instruments included geriatric depression scale, mini mental state examination and fatigue symptom inventory. The study used a cross-sectional design. RESULTS: Fifty-six patients (72.7%) reported fatigue at the time of the assessment; seventy-six patients (99%) in the past week. Forty patients (52%) rated their average fatigue as greater than 5. Forty-two patients (54%) reported that they felt fatigue all seven days, for any part of the day in the week before the assessment. Sixty five (84%) patients rated fatigue as interfering with their general level of activity. The fatigue disruptiveness was higher for women than for man (P<0.007). Marital status and educational level were not significantly related to fatigue severity or fatigue disruptiveness (P> or =0.33). A significant positive correlation between depressive symptoms and fatigue severity (r = 0.29, P<0.01) was recorded. Depression was also significantly related to fatigue disruptiveness (r = 0.44, P<0.01). Cognitive status was not correlated with fatigue severity or fatigue disruptiveness. A negative correlation between haemoglobin level and fatigue severity (r = -0.30, P<0.01) and between haemoglobin level and fatigue disruptiveness (r = -0.28, P<0.01) was found. Having had medical care or counselling in the past for anxiety and depression was positively correlated with fatigue disruptiveness (r = 0.29, P<0.01). CONCLUSION: Fatigue is a common symptom of older cancer patients treated with antineoplastic medical treatment. Female patient showed higher fatigue disruptiveness than male. In this study a positive correlation between depression and fatigue, and a negative correlation between haemoglobin and fatigue, were recorded.

Age Factors↗

PubMed2003

Atomic refinement with correlated solid-state NMR restraints.

The orientation data provided by solid-state NMR can provide a great deal of structural information about membrane proteins. The quality of the information provided is, however, somewhat degraded by sign degeneracies in measurements of the dipolar coupling tensor. This is reflected in the dipolar coupling penalty function used in atomic refinement, which is less capable of properly restraining atoms when dipolar sign degeneracies are present. In this report we generate simulated solid-state NMR data using a variety of procedures, including back-calculation from crystal structures of alpha-helical and beta-sheet membrane proteins. We demonstrate that a large fraction of the dipolar sign degeneracies are resolved if anisotropic dipolar coupling measurements are correlated with anisotropic chemical shift measurements, and that all sign degeneracies can be resolved if three data types are correlated. The advantages of correlating data are demonstrated with atomic refinement of two test membrane proteins. When refinement is performed using correlated dipolar couplings and chemical shifts, perturbed structures converge to conformations with a larger fraction of correct dipolar signs than when data are uncorrelated. In addition, the final structures are closer to the original unperturbed structures when correlated data are used in the refinement. Thus, refinement with correlated data leads to improved atomic structures. The software used to correlate dipolar coupling and chemical shift data and to set up energy functions and their derivatives for refinement, CNS-SS02, is available at our web site.

Algorithms↗

PubMed2002

Correlation between spectral EEG parameters and intelligence test variables in school-age children.

OBJECTIVES: The objective of the study was to investigate the relationship between the degree of intelligence and spectral electroencephalographic (EEG) parameters and to find out which EEG variables are relevant for this correlation. METHODS: Bipolar 1 min EEG recordings were derived for the fronto-central and parieto-occipital leads from 155 clinically healthy 10-year-old children in vigilance state awake with eyes closed. Relative spectral power parameters were calculated by Fast Fourier Transform. Two-group t tests according to the score values of the 'WISC-R' intelligence test as well as univariate and multiple correlation analyses between spectral and intelligence test variables were carried out. RESULTS: A statistically significant positive correlation of the intelligence test variables with the spectral alpha power and a significant negative correlation with the spectral power of lower frequency bands was observed. Predicting the spectral parameters by means of intelligence test variables, significant multiple correlation coefficients were revealed in the frequency ranges: 0.5-1.5, 3.0-5.0 and 9.0-10.5 Hz. The highest significance (P<0.0001) was found for the spectral value at 9.0 Hz. CONCLUSIONS: The results of t tests and correlation analyses confirm the strong relationship between spectral EEG parameters and the degree of intelligence indicating that the 'EEG recordings do reflect intellectual abilities'. It may be supposed that the amount of the intelligence quotient is correlated with the degree of EEG maturation and thus reflects the active number of synapses and the degree of differentiation of the neuronal controlling system.

Alpha Rhythm↗

PubMed2001

Statistical two-dimensional correlation spectroscopy: its theory and applications to sets of vibrational spectra.

The present study aims at developing a new form of two-dimensional (2D) correlation spectroscopy, statistical 2D correlation spectroscopy. Statistical 2D spectroscopy differs from the widely used generalized 2D correlation spectroscopy in that the former abstracts spectral features by pretreatment and by 2D maps that are limited by the correlation coefficients in the range from 1 to -1. In this paper, the theory of the new 2D method is briefly described, and then its applications are discussed to reveal spectral and concentration features of artificial model spectra, infrared spectra of polycondensation of bis(hydroxyethyl terephthalate) measured on-line, and short-wave near-infrared spectra of raw milk. The results are analyzed thoroughly and compared with those from generalized 2D correlation spectroscopy and partial least-squares loadings and scores. The most significant advantage of statistical 2D correlation spectroscopy is that the 2D correlation spectra are easy to calculate and are purely mathematical in nature, thereby eliminating any subjective involvement of an experimenter, while the inherent weakness of the method lies in its sensitivity to the noise.

Journal Article↗

PubMed1986

Chloroplast coupling factor 1: dependence of rotational correlation time on polypeptide composition.

Time-resolved fluorescence depolarization measurements were made on chloroplast coupling factor 1 (CF1) labeled with pyrenylmaleimide. Rotational correlation times were determined for native CF1, for CF1 lacking epsilon and/or delta polypeptides, and for activated enzyme. The rotational correlation time measured is characteristic of the rotation of the entire enzyme. Removal of the delta polypeptide resulted in a 25% smaller rotational correlation time, although the delta polypeptide contributes less than 5% of the mass of CF1. Removal of the epsilon polypeptide was without effect. Simultaneous removal of delta and epsilon polypeptides produced a 30% smaller rotational correlation time. Activation of CF1 ATPase by incubation with dithiothreitol reduced the rotational correlation time by 15% relative to that of the latent enzyme. The rotational correlation time of CF1 with delta and epsilon polypeptides removed is essentially that expected for a spherical molecule, whereas the other forms of the enzyme can be approximated as ellipsoids of revolution; the axial ratio of the latent enzyme is estimated from the rotational correlation time and the intrinsic viscosity. These data indicate that the delta polypeptide significantly alters the shape of the enzyme and that a conformational change accompanies dithiothreitol activation of the enzyme.

Calcium-Transporting ATPases↗

PubMed1998

Time-resolved fluorescence anisotropy of HIV-1 protease inhibitor complexes correlates with inhibitory activity.

The tryptophan time-resolved fluorescence intensity and anisotropy of the HIV-1 protease dimer is shown to be a quick and efficient method for the conformational characterization of protease inhibitor complexes. Four fluorescence lifetimes were needed to adequately describe the fluorescence decay of the two tryptophan residues, W6 and W42, per protease monomer. As a result of the wavelength dependence of the respective amplitudes, the 2.06 ns and the 4.46 ns decay constants were suggested to be the intrinsic fluorescence lifetimes of the more solvent-exposed W6 and the less exposed W42 residues, respectively. Analysis of the fluorescence anisotropy decay yielded a short correlation time of 250 ps corresponding to local chromophore motions, and a long correlation time of 12.96 ns resulting from overall rotation of the protease enzyme. Fluorescence lifetimes and rotational correlation times changed when inhibitors of the HIV-1 protease were added. The effects of 11 different inhibitors including statine-derived, hydroxyethylamine-derived, and 2 symmetrical inhibitors on the protease fluorescence dynamics were investigated. Inhibitor binding is shown to induce an increase of the mean fluorescence lifetime taumean, an increase of the short rotational correlation time phi1, as well as a decrease of the long rotational correlation time phi2. The mean rotational correlation time phimean was identified as the global dynamic parameter for a given molecular complex, which correlates with the inhibitor dissociation constant Ki, and therefore with the activity of the inhibitor.

Fluorescence Polarization↗

PubMed1999

Correlation of acute and chronic defibrillation threshold with upper limit of vulnerability determined in normal sinus rhythm.

BACKGROUND: The upper limit of vulnerability (ULV) is the stimulus strength above which ventricular fibrillation cannot be induced, even when the stimulus occurs during the vulnerable period of the cardiac cycle. Determination of ULV using T-wave shocks during ventricular pacing has been shown to closely correlate with the defibrillation threshold (DFT) at ICD implantation. However, there are no data correlating ULV determined in sinus rhythm at ICD implantation, with DFT determined at implantation or during long-term follow-up. This is of clinical importance since ULV may be used to estimate DFT during ICD implantation, both during ventricular pacing or sinus rhythm. METHODS AND RESULTS: Twenty-one patients receiving a transvenous ICD system were studied prospectively. There were 16 males and 5 females, mean age 68 +/- 15 years, with mean ejection fraction 37.4 +/- 17.4%. All had structural heart disease. The ULV was defined as the lowest energy that did not induce ventricular fibrillation with shocks at 0, 20 and 40ms before the peak of the T-wave, using a step-down protocol. The initial energy tested was 15J and the lowest energy 2J. DFT was determined following a similar step-down protocol. The DFT was defined as the lowest energy that successfully defibrillated the ventricles. The linear correlation coefficient between ULV and DFT was r = 0.73 (p < 0.001). At implant, mean ULV was 9.2 +/- 5J, not statistically different from mean DFT 9.4 +/- 4J. ULV plus 5J successfully defibrillated 19 of 21 patients. During long-term follow-up of 10.1 +/- 1.8 months in eight patients, DFT was 8.8 +/- 5.8J, not significantly different than the DFT of 7.5 +/- 4.1J or ULV of 8.0 +/- 5.3 at implant. CONCLUSION: 1) When determined during normal sinus rhythm the ULV significantly correlates with DFT. 2) ULV testing might be used in lieu of standard DFT testing to confirm adequate lead placement thus minimizing or eliminating VF inductions, particularly in hemodynamically unstable patients. 3) Since ULV + 5J has a high probability of successful defibrillation in most patients, programming ICD first shock energy for VF at ULV + 5J may result in lower first shock energies compared to the standard methods of programming first shock energy at twice DFT. CONDENSED ABSTRACT: The purpose of this study was to determine if the upper limit of vulnerability (ULV) determined during normal sinus rhythm correlates with the defibrillation threshold (DFT), as has been previously shown when determined during ventricular pacing. The linear correlation coefficient between the ULV and DFT was r = 0.73 (p < 0.001). Mean ULV at implant was 9.2 +/- 5J, not statistically different from mean DFT of 0.4 +/- 4J. During long-term follow-up of 10.1 +/- 1.8 months in 8 patients, DFT was 8.75 +/- 8J, not significantly different than the DFT of 7.5 +/- 4.1J or ULV of 8.0 +/- 5.3 at implant. Shocks energies of ULV + 5J successfully defibrillated 19 of 21 patients at implant and 8 of 8 at follow-up. This study indicates that the ULV determined in normal sinus rhythm closely correlates with the DFT, and that ULV + 5J defibrillated most patients. ULV testing could be used to predict DFT and reduce or eliminate the need for DFT testing and VF induction. Programming ICD first shock energy for VF to ULV + 5J will result in lower energy than that used with standard DFT testing.

Aged↗

PubMedDate not supplied

Redundancy and synergy arising from pairwise correlations in neuronal ensembles.

Multielectrode arrays allow recording of the activity of many single neurons, from which correlations can be calculated. The functional roles of correlations can be revealed by measures of the information conveyed by neuronal activity; a simple formula has been shown to discriminate the information transmitted by individual spikes from the positive or negative contributions due to correlations (Panzeri et al., 1999). Here, this analysis, previously applied to recordings from small ensembles, is developed further by considering a model of a large ensemble, in which correlations among the signal and noise components of neuronal firing are small in absolute value and entirely random in origin. Even such small random correlations are shown to lead to large possible synergy or redundancy, whenever the time window for extracting information from neuronal firing extends to the order of the mean interspike interval. In addition, a sample of recordings from rat barrel cortex illustrates the mean time window at which such "corrections" dominate when correlations are, as often in the real brain, neither random nor small. The presence of this kind of correlations for a large ensemble of cells restricts further the time of validity of the expansion.

Action Potentials↗

PubMed2001

Correlations between in vitro effects of preparations of interferon and its inducers on blood cells in patients with multiple sclerosis.

We studied in vitro production of interferon-alpha and interferon-gamma by peripheral blood leukocytes from 15 patients with multiple sclerosis. The priming effects of interferon preparations weakly correlated with interferon-alpha production by leukocytes from patients with multiple sclerosis, but negatively correlated with interferon-gamma production. The effects of interferon inducers in most cases positively correlated with its spontaneous production. We found a weak positive correlation between the priming effect of natural interferon-alpha and the effect of recombinant interferons. There were positive or strong positive correlations between the effects of recombinant interferons on leukocytes from patients with multiple sclerosis. The relationship between the effects of medicinal interferon inducers and interferon preparation varied from negative to strong positive correlations. These data suggest that correlation analysis can be used for dynamic control and elaboration of methods for combined immunotherapy of multiple sclerosis with various interferon preparations or interferon and its inducers.

Acridines↗

PubMed1997

Testing for heterogeneity among phenotypic correlations: a comparison of methods using Monte Carlo simulations.

Heterogeneous phenotypic correlations may be suggestive of underlying changes in genetic covariance among life-history, morphology, and behavioural traits, and their detection is therefore relevant to many biological studies. Two new statistical tests are proposed and their performances compared with existing methods. Of all tests considered, the existing approximate test of homogeneity of product-moment correlations provides the greatest power to detect heterogeneous correlations, when based on Hotelling's z*-transformation. The use of this transformation and test is recommended under conditions of bivariate normality. A new distribution-free randomisation test of homogeneity of Spearman's rank correlations is described and recommended for use when the bivariate samples are taken from populations with non-normal or unknown distributions. An alternative randomisation test of homogeneity of product-moment correlations is shown to be a useful compromise between the approximate tests and the randomisation tests on Spearman's rank correlations: it is not as sensitive to departures from normality as the approximate tests, but has greater power than the rank correlation test. An example is provided that shows how choice of test will have a considerable influence on the conclusions of a particular study.

Journal Article↗