SEARCH · PubMed Health

Results for “Feature selection stability”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources

PubMed2006

Intramolecular Diels-Alder reactions of ester linked 1,3,9-decatrienes: cis/trans selectivity in thermal and Lewis acid promoted reactions of ethylene-tethered and benzo-tethered systems.

High cis (i.e., endo) diastereoselectivities are witnessed in heat-promoted intramolecular Diels-Alder (IMDA) reactions of ethylene-tethered hexadienyl acrylates. The cis stereoselectivity is improved by promotion with Et2AlCl. The first examples of Et2AlCl catalyzed intramolecular Diels-Alder reactions of ester-activated dienophiles are reported. In contrast, the corresponding benzo-tethered hexadienyl acrylates undergo moderately trans (i.e., exo) selective IMDA reactions. Very high trans stereoselection is obtained upon promotion with ATPH. The outcomes of these reactions are essentially insensitive to dienophile (C10) geometry and substitution. DFT (B3LYP/6-31+G(d)) computed cis/trans product distributions-based on Boltzmann transition structure populations-are in good agreement with the experimental results. These computational investigations provide useful insights into the origins of stereoselection in these systems. The stereoselectivity exhibited by the ethylene-tethered hexadienyl acrylates is ascribed to stabilizing secondary orbital interactions at play in the cis-transition structures (TSs). In the benzo-tethered series, this effect is overridden by stabilizing pi-conjugative interactions, between the benzo moiety and the 1,3-diene component, which are stronger in trans TSs, compared to the cis TSs. The computed TS geometries generally exhibit advanced peripheral bond forming asynchronicity, with the tether carbonyl group in conjugation with the dienophile. Such TS features significantly weaken the stereodirecting influence of terminal dienophile substituents.

Acids↗

PubMedDate not supplied

Comparative effects of interferon and hydroxyurea on bone marrow fibrosis in chronic myelogenous leukemia.

Therapy-related changes of the bone marrow fiber content remain a controversial issue in hematopathology. This conflict of opinion firstly depends on difficulties to determine the quantity of fibers exactly (semiquantitative grading, morphometry, reference to cellularity). Secondly, the appropriate selection of patients with specific monotherapies including hydroxyurea (HU) and interferon-alpha (IFN) seems to present some problems. Finally, assessment of myelofibrosis is further biased by the different endpoints of sequential examinations. The latter shortcoming can be improved upon by the calculation of the myelofibrosis progression/regression index which describes the ratio between difference of fiber density and observation time. Using strictly defined therapeutic regimens and intervals between sequential trephine biopsies a stimulating effect of IFN administration on bone marrow fibrosis in Ph1+-chronic myelogenous leukemia (CML) has been found. This result is comparable with the failure of this agent to improve myelofibrosis (and splenomegaly) in a considerable number of patients with allied subtypes of chronic myeloproliferative disorders. This is in contrast to the effect HU exerts which is a more fibrolytic or even stabilizing influence on bone marrow fibrosis. This phenomenon is readily demonstrable by the assessment of dynamic features (myelofibrosis progression index). In addition, patients showing a rapid progression of myelofibrosis during IFN and HU treatment of Ph1+-CML are generally associated with a poor risk outcome and a significant worsening of survival.

Humans↗

PubMed2006

MRI of traumatic patellar dislocation in children.

BACKGROUND: Traumatic patellar dislocations (TPD) are common injuries in children, and MRI is useful in evaluation of pediatric musculoskeletal injuries. However, no pediatric studies on the MR features of TPD have been reported. OBJECTIVE: To review the injuries after TPD in children. MATERIALS AND METHODS: Patients with clinical or radiological recognition of TPD and those with suggestive MR findings were selected. Bone, cartilage and soft-tissue injuries and patellofemoral relationships were assessed. RESULTS: A total of 26 patients (age range 10-18 years) were identified. The following injuries were seen: bone bruising of the inferomedial patella (81% of patients) and the lateral femoral condyle (81% of patients), cartilage injuries of the inferomedial patella (38% of patients) and the lateral femoral condyle (38% of patients), osteochondral fragments (42% of patients) and injuries of the medial patellar restraints (81% of patients). CONCLUSION: Pediatric manifestations of TPD seen on MRI are similar to those in adults. TPD is often occult in children. Early recognition of bone bruising of the patella and lateral femoral condyle, associated osteochondral injuries, and medial patellar stabilizer injury is important for timely diagnosis.

Adolescent↗

PubMed1984

DNA sequence studies of simian virus 40 chromosomal excision and integration in rat cells.

Cell fusion between simian CV1 cells and the simian virus 40-transformed rat cell line 14B, which contains a single copy of integrated simian virus 40 DNA, results in chromosomal excision of viral DNA. A heterogeneous population of circular molecules containing both viral and cellular DNA is detected in the replicating pool. We present the DNA sequences across six novel junctions created by these excision events and use this information to define the parental genomic sequences involved in this form of "illegitimate" recombination. The data were analyzed to discover whether any common structural feature(s) could be detected at these sites. In each case a redundancy of either two or three base-pairs was found at the precise points of cross-over in both parental DNA molecules. The cross-over points were further distinguished by the presence of at least one copy of the sequence 5'Pyr-T-T3' in either of the homologous sequences that define the cross-over points. Additional stretches of homology are found extending from the homologous cross-over points. To explore the possibility that the selection of the cross-over sites is determined by the free energy of base-pairing, we have used the program of Zuker & Stiegler (1981) to form model heteroduplexes between single-stranded parental DNA molecules. In some cases model heteroduplexes were formed that paired the cross-over points, although these structures were of dubious thermodynamic stability. We therefore conclude that, while the redundancies at the cross-over points must play some role in these processes, other factors aside from simple base-pairing across replicating structures must also be involved. In order to expand our analysis of the recombination events that accompany transformation of rat cells by simian virus 40, we determined the DNA sequences across one of the sites on the rat genome that served as the target for the integration event that engendered the 14B line. Our analysis of this DNA showed that: (1) viral and chromosomal DNA share three base-pairs of homology at the site of cross-over; (2) the cross-over site in the rat genome is adjacent to the trinucleotide 5'Pyr-T-T3'; and (3) the homology shared by the virus and chromosome does not resemble the homology reported at another integration locus, but is similar in that it is flanked on one side by alternating purine and pyrimidine nucleotides.

Animals↗

PubMedDate not supplied

A review of cephalosporin metabolism: a lesson to be learned for future chemotherapy.

The historical background information concerning the metabolism of cephalosporins and selected other antiinfectives was reviewed as a preface to discussion concerning desacetyl-cefotaxime (dCTX), a metabolite of cefotaxime (CTX) sodium. Cephalothin and cephapirin were metabolized at the 3-position to less active desacetyl forms. However, the parent drugs and their metabolites interact in a favorable manner resulting in dominant additive or synergist inhibition of susceptible bacterial pathogens. Similarly, CTX plus dCTX have been described as being synergist in their activity against greater than 70% of Enterobacteriaceae or staphylococci and greater than 80% of anaerobic bacteria. Antagonism was rare with only two species and of no clinical significance. More recently, reported studies showed enhanced activity of CTX/dCTX against pathogens producing meningitis compared to ceftriaxone and other contemporary therapeutic agents. The dCTX compound was classified as a drug with a potency superior to a "second-generation" cephalosporin and possessed greater beta-lactamase stability against some enzymes compared to CTX. These features may explain low reported rates of superinfections and adverse side-effects, including resistance arising on chemotherapy. Physicians are cautioned to take into account the potential favorable effects of drug metabolites on antimicrobial spectrum, potency and applied pharmacokinetics. In the case of CTX/dCTX, the laboratory results for CTX will always underestimate its value or potency because of the contribution of the metabolite.

4-Quinolones↗

PubMed2005

Intra- and inter-speaker variations of formant pattern for lateral syllables in Standard Chinese.

Speech variation of speakers is a crucial issue for speaker recognition and identification, especially for forensic practice. Greater intra-speaker variation is one main reason for incorrect speaker identification in real forensic situations. Understanding the stability of acoustic parameters and their variation in speech is therefore significant for the evaluation of effective parameters for speaker identification. In this paper, all vowels in Standard Chinese including five monophthongs, eight diphthongs and four triphthongs were combined with lateral /l/. Finally, 15 lateral syllables with different tones for 10 speakers were selected and acoustically analyzed. Central frequencies of the first four formants for each syllable were measured for quantitative comparison of intra- and inter-speaker variation in order to provide a general idea of speaker variation in Standard Chinese, and finally serving for forensic application. Results show that the overall intra-speaker variation is less than the inter-speaker variation in great extent under laboratory condition though occasionally they are contrary. This supports the basis for forensic speaker identification, that is, intra-speaker variation should be less than inter-speaker variation in many acoustic features, and further validates the probability and reliability of forensic speaker identification.

Adult↗

PubMed1997

Structural mimicry of a native protein by a minimized binding domain.

The affinity between molecules depends both on the nature and presentation of the contacts. Here, we observe coupling of functional and structural elements when a protein binding domain is evolved to a smaller functional mimic. Previously, a 38-residue form of the 59-residue B-domain of protein A, termed Z38, was selected by phage display. Z38 contains 13 mutations and binds IgG only 10-fold weaker than the native B-domain. We present the solution structure of Z38 and show that it adopts a tertiary structure remarkably similar to that observed for the first two helices of B-domain in the B-domain/Fc complex [Deisenhofer, J. (1981) Biochemistry 20, 2361-2370], although it is significantly less stable. Based on this structure, we have improved on Z38 by designing a 34-residue disulfide-bonded variant (Z34C) that has dramatically enhanced stability and binds IgG with 9-fold higher affinity. The improved stability of Z34C led to NMR spectra with much greater chemical shift dispersion, resulting in a more precisely determined structure. Z34C, like Z38, has a structure virtually identical to the equivalent region from native protein A domains. The well-defined hydrophobic core of Z34C reveals key structural features that have evolved in this small, functional domain. Thus, the stabilized two-helix peptide, about half the size and having one-third of the remaining residues altered, accurately mimics both the structure and function of the native domain.

Circular Dichroism↗

PubMed2006

Biomarkers of oxidative damage in human disease.

Oxidative/nitrosative stress, a pervasive condition of increased amounts of reactive oxygen/nitrogen species, is now recognized to be a prominent feature of many acute and chronic diseases and even of the normal aging process. However, definitive evidence for this association has often been lacking because of recognized shortcomings with biomarkers and/or methods available to assess oxidative stress status in humans. Emphasis is now being placed on biomarkers of oxidative stress, which are objectively measured and evaluated as indicators of normal biological processes, pathogenic processes, or pharmacologic responses to therapeutic intervention. To be a predictor of disease, a biomarker must be validated. Validation criteria include intrinsic qualities such as specificity, sensitivity, degree of inter- and intraindividual variability, and knowledge of the confounding and modifying factors. In addition, characteristics of the sampling and analytical procedures are of relevance, including constraints and noninvasiveness of sampling, stability of potential biomarkers, and the simplicity, sensitivity, specificity, and speed of the analytical method. Here we discuss some of the more commonly used biomarkers of oxidative/nitrosative damage and include selected examples of human studies.

Biomarkers↗

PubMed2000

Nuclear and cytoplasmic tau proteins from human nonneuronal cells share common structural and functional features with brain tau.

The heterogeneous family of tau proteins interacts with microtubules, actin filaments, and intermediate filaments. The tau isoforms have been shown to play a major role in neuronal polarity. However, tau-like proteins have been found in several other types of cells. Previous studies have also indicated the presence of a nuclear tau. The relationships between nuclear and cytoplasmic tau as well as the functional aspects of the nuclear tau are unknown. In this study, we demonstrate by reverse transcriptase polymerase chain reaction using specific primers that a transcript with features of neuronal tau is present in human fibroblast and Huh-7 hepatoma cell lines. Additionally, we present the first isolation and characterization of cytosolic and nuclear tau-like proteins from nonneuronal cells. Nonneuronal cytosolic tau components were isolated using the perchloric acid precipitation approach, while nuclear tau was isolated after selective extractions using high-ionic strength buffers. The cytoplasmic tau of nonneuronal cells is composed of at least three isoforms, whereas two main isoforms were detected in nuclear tau. Interestingly, the cytoplasmic and nuclear tau components exhibited the capacity to promote tubulin polymerization in vitro. Immunofluorescence studies using monoclonal anti-tau antibodies indicated a discrete distribution of tau protein in both the interphase and mitotic nucleus. In the latter, tau colocalized with the chromosomal scaffold. These studies, together with previous evidence on tau roles in modulating microtubule growth from centrosomes, and its role in the interaction patterns that stabilize the integrity of the cytoskeletal network, strongly support the idea that tau is a multifunctional protein involved in fundamental cellular processes.

Base Sequence↗

PubMed1990

[Ethnogenetics: adaptive structure of the gene pool of the mankind from the data on human polymorphic genetic markers].

The mean FST value as a characteristic of gene frequency changes in a random sample of polymorphic genes from population gene pool provides the best indirect estimation of selectively neutral level of genetic variability. The set of test criteria, including chi 2, F and t, can be used in order to compare F1 with F and subdivide gene sample into three subgroups, or classes of genes which are differing from each other by the degree of variation of allelic frequencies. These three classes comprise the adaptive structure of gene pool and consist of the genes which are, respectively, under stabilizing and differentiating selection pressures or neutral ones. Adaptive structures of gene pools of aboriginal human populations at the main 9 geographical regions of the World, taken together, reveal statistically significantly correlation with adaptive structure of the total gene pool of the Mankind. But the correlation is rather small and therefore, the adaptive structure of human gene pool reveals between adaptive structures, the highest is for the USSR and the lowest are for the East-Asiatic and Australian regions. The proportion of neutral to non-neutral genes is about 50% in the average, with the range of variation 40-60% in different regions. But none of the polymorphic genes so far studied reveals constant neutrality in all regional conditions of environment and at different times of evolution history of human gene pool. Its adaptive structure underwent essential transformation from the Palaeolithic till the Postpalaeolithic times, but nevertheless, among the main features of contemporary adaptive structure of human gene pool, those predominate which are of the Palaeolithic origin.

Alleles↗

PubMed2002

Optimal stimulation of the left ventricle.

Cardiac resynchronization therapy has been proposed to alleviate heart failure symptoms refractory to classic drug treatment. Potential benefits hinge on a number of key components, including judicious selection of patients likely to respond to the therapy and appropriate placement of the leads, particularly the lead responsible for left ventricular pacing. Evidence of ventricular asynchrony is an individual prerequisite for consideration of cardiac resynchronization therapy. Ventricular asynchrony can be diagnosed by recording a QRS duration >150 msec or during echocardiography, with the goal of investigating the mechanical aspect of asynchrony. The optimal left ventricular pacing site can be defined by the latest segmental contraction, which is mainly the mid-lateral wall. The first-choice technique to initiate left ventricular pacing consists of a transvenous approach via the coronary sinus tributaries. In practice, the final left ventricular pacing location also depends on highly variant coronary sinus anatomy, acceptable electrical parameters, and lead stability. Procedure-related complications, which consist mainly of coronary sinus perforation and phrenic nerve stimulation, remain low (<1%) and should decrease further with the use of new features specific to the procedure.

Cardiac Pacing, Artificial↗

PubMed1997

Enthalpy is a proper criterion for comparability of monolayer and bilayer studies: isobaric temperature scanning measurements on glycolipid monolayers.

The thermotropic behaviour of glycolipid monolayers has been studied by isobaric temperature scanning measurements to elucidate conditions under which monolayers exhibit thermodynamic and structural properties comparable to those observed in bilayers. A selection of synthetic, stereochemically pure, glyceroglycolipids with identical, ether-linked alkyl chains of 12, 14, or 16 CH2-groups has been investigated. The head groups of the glycolipids consisted of glucose, galactose, maltose, lactose or maltotriose moieties with beta-configuration of the glycosidic bond. These glycolipids were chosen to permit a quantitative characterization of three effects, (i) the role of the length of the aliphatic chains, (ii) the influence of the size of the head group, and (iii) the influence of the stereochemistry of the sugar moieties on the structure and stability of the monolayers. To probe the effects of stereochemical alterations in the glycerol moiety 2,3-O-ditetradecyl-1-O-beta-D-glucosyl-sn-glycerol (14-2,3-Glc) was compared with 1,2-O-ditetradecyl-3-O-beta-D-glucosyl-sn-glycerol (14-1,2-Glc). It has been shown that in general several features of bilayers can be obtained from monolayer studies with reasonable accuracy, provided the proper parameters are chosen. The monolayer is stabilized by elongation of the aliphatic chains of the lipids and destabilized when the monosaccharide read groups is replaced by a di-, or trisaccharide, in a similar manner as in the bilayer. The stabilizing effect that has been observed in bilayer studies, when galactose instead of glucose is introduced as head group, has also been established in the monolayer studies. This stabilizing effect is even retained in the lipids having disaccharide head groups. On the basis of these monolayer studies in connection with WAXS and SAXS measurements on multilamellar systems, we suggest that identity of transition enthalpies of the chain melting L beta-L alpha transition is an appropriate criterion for estimating molecular areas and area changes of bilayers from monolayer measurements and vice versa. However, estimates of transition temperatures are poor using the enthalpy criterion. If identity of transition temperature is introduced as criterion, glycolipid monolayers must be compressed to about 43 +/- 3 mN m-1. Under these conditions the agreement between the calculated enthalpies and structural properties of monolayers and multilayers is poor. As a general conclusion it can be emphasized that for monolayer and bilayer systems of glycolipids there exists no such parameter as a universal pressure or a universal temperature that automatically renders monolayer data identical to bilayer data. Depending on which property (transition temperatures, transition enthalpies, lateral areas and transitional area changes) one wants to extrapolate from monolayer to bilayer different lateral pressures have to be applied.

Calorimetry, Differential Scanning↗

PubMed1999

Expression of the voltage-gated chloride channel ClC-2 in rod bipolar cells of the rat retina.

Voltage-gated chloride channels (ClC) are highly conserved during evolution and appear to participate in a variety of physiological functions. Recently, ClC-2 was proposed to play a role in stabilizing the chloride equilibrium potential near or below the resting membrane potential in neurons expressing ligand-gated chloride channels. Because rod bipolar cells in mammalian retina express three forms of inhibitory ligand-gated chloride channels, we decided to study ClC-2 localization and function in the rat retina. RNA encoding ClC-1, -2, -3, -4, and -5 was detected by reverse transcription-PCR in the rat retina. ClC-2-specific antibodies identified protein on cell bodies and in synaptic layers. Double-immunofluorescence staining revealed that intense ClC-2 immunoreactivity colocalized with PKC-stained rod bipolar cells. Patch-clamp experiments performed with individual rod bipolar cells demonstrated the presence of a time-dependent, inwardly rectified current activated at hyperpolarizing membrane potentials. This current demonstrated selectivity for different anions (Cl(-) > I(-) > gluconate), was inhibited by Cd(2+), and was minimally reduced by 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid. These features are consistent with currents generated by ClC-2 channels. Our data indicate that functional ClC-2 channels are present in retinal rod bipolar cells and support a role for ClC-2 in maintaining Cl(-) homeostasis in neurons with ligand-gated chloride channels.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2005

[Oriented immobilization of papain on metal chelating carriers].

Based on the technology of protein separation with immobilized metal ion affinity chromatography (IMAC), a method for oriented immobilization of papain has been selected. Papain was successfully immobilized on magnetic agarose carriers. Cu2+ with iminodiacetate (IDA) was used as the chelating ligand to be correlated with the histidine on papain (His-81). The optimum immobilization conditions of enzyme were as flows: Cu2+ 0.15 x 10(-2) mol/g carriers, time was 4h, enzyme load was 30 mg/g carrier, pH was 7.0, respectively. The pH and temperature were 8.0 and 70 degrees C for immobilized enzyme. The recovery activity of immobilized enzyme was retained 68.4%. The carrier could be recovered from the spent immobilized enzyme, to be reused. After 5 times, the reimmobilization of papain on the regenerated matrix was 79.71% effective with the retention of maximum enzyme activity. The cost of carriers used for industrial applications is very important. The regenerability of carriers is therefore, relevant. The mild conditions used for immobilization, the high recovery of immobilized preparations, the stability and the regenerability of the matrix are the main features of the method reported here. All above indicate this method can be applicable and promising in enzyme immobilization field.

Catalysis↗

PubMed1997

Study of the complex between the contrast agent Iobitridol (Xenetix) and Elastase (PPE): a model for hydrophobic site protection in drug-protein interactions.

PURPOSE: The concept of Hydrophilic Sphere Stabilization, or Hydrophobic Shielding, has been postulated in the synthesis of biocompatible contrast agents in vascular imaging. To improve the safety of these polyiodinated agents, interactions with protein hydrophobic sites in biomacromolecules should be kept as low as possible. In order to evaluate the level of interactions with proteins, we have selected the serine proteinase Elastase, in presence of Iobitridol (Xenetix), as a model. METHODS: The complex between Iobitridol and Pancreatic Porcine Elastase was investigated by X-ray diffraction techniques, on saturated monocrystals, using the synchrotron radiation at 0.98A. RESULTS: In contrast to Iohexol, which displays several interactions including one in the active site, Iobitridol is unable to interact directly with elastase. Only one partially occupied site is found in between two molecules of the crystal packing. CONCLUSIONS: The validation of the "hydrophobic shielding" concept, which was at the origin of the design of the Iobitridol molecule, has been proven to be an essential feature in minimizing in vivo protein interactions.

Animals↗

PubMed2001

Threading structural model of the manganese-stabilizing protein PsbO reveals presence of two possible beta-sandwich domains.

The manganese-stabilizing protein (PsbO) is an essential component of photosystem II (PSII) and is present in all oxyphotosynthetic organisms. PsbO allows correct water splitting and oxygen evolution by stabilizing the reactions driven by the manganese cluster. Despite its important role, its structure and detailed functional mechanism are still unknown. In this article we propose a structural model based on fold recognition and molecular modeling. This model has additional support from a study of the distribution of characteristics of the PsbO sequence family, such as the distribution of conserved, apolar, tree-determinants, and correlated positions. Our threading results consistently showed PsbO as an all-beta (beta) protein, with two homologous beta domains of approximately 120 amino acids linked by a flexible Proline-Glycine-Glycine (PGG) motif. These features are compatible with a general elongated and flexible architecture, in which the two domains form a sandwich-type structure with Greek key topology. The first domain is predicted to include 8 to 9 beta-strands, the second domain 6 to 7 beta-strands. An Ig-like beta-sandwich structure was selected as a template to build the 3-D model. The second domain has, between the strands, long-loops rich in Pro and Gly that are difficult to model. One of these long loops includes a highly conserved region (between P148 and P174) and a short alpha-helix (between E181 and N188)). These regions are characteristic parts of PsbO and show that the second domain is not so similar to the template. Overall, the model was able to account for much of the experimental data reported by several authors, and it would allow the detection of key residues and regions that are proposed in this article as essential for the structure and function of PsbO.

Algorithms↗

PubMedDate not supplied

Force analysis of the belly gutter and Capener splints.

In the management of hand injuries resulting from trauma or diseases like rheumatoid arthritis, hand therapists often design static and dynamic splints to rest and protect joints, provide stability, and enhance joint motion. However, the literature provides little help in analyzing the forces of a splint acting on a digit. This paper studies the forces generated by two different finger splints acting on the proximal interphalangeal joint (PIP) of the finger. The principles of force analysis are based on the Fess and Philips model of mechanics. Factors that affect the resultant forces generated by each splint design are identified, and the properties of each splint are discussed. Although the force generated by the two types of splints may vary only slightly, special features of each splint should be seriously taken into consideration in clinical application.

Contracture↗

PubMed1999

Long-term intra-individual variability of the background EEG in normals.

OBJECTIVES: Forty-five healthy adult volunteers underwent repeated qEEG examinations with retest intervals 25-62 months in order to investigate the long-term intra-individual variability of several qEEG features such as, absolute and relative power, power asymmetry, coherence, mean and peak frequency and entropy. Prior to any computations all parameters were transformed to Z-scores on the basis of a normal database. METHODS: Correlation coefficients were used to test the effect of the time on the test-retest differences. Correlation coefficients were also computed between baseline and retest values, as a measure of intra-individual stability, to make our results comparable to most literature data. By computing the standard deviations for test-retest differences, the intra-individual variabilities of the examined parameters were obtained in the unit of inter-individual variability of normal population. The same calculations were carried out with values obtained from the odd and even numbered epochs of the same EEG sections. This way, that portion of the intra-individual variability was estimated that might be introduced even by chance only when the epochs were selected randomly from the same section of EEG conforming to selection criteria. RESULTS: As for our results, further increase of test-retest differences with time after 25 months might be so insignificant that it could not be demonstrated in our test material. The long-term intra-individual variability for most parameters, especially for total absolute power and alpha mean frequency, was less than the inter-individual variability in the normal population. The moment-to-moment variability was least in the case of the absolute power. CONCLUSIONS: Estimates for intra-individual variability expressed this way in Z-scores might easily be used in the follow-up of patients even for a few years.

Adult↗