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PubMedDate not supplied

[Variability in scabies mites Sarcoptes scabiei De Geer (Acariformes, Sarcoptidae) in relation to scabies epidemiology. 1. A statistical model of female variability].

Individual variability of 235 grain mite females from Moscow and the Moscow Province was studied. The data were processed on a computer. Body proportions were used as a representative dimension index. The size of proterosomal scutellum was stable. A map of the chaetoid cover of notum is given, and its variability was studied. Statistical analysis of all signs was made. Frontal chaetoid and sejugal sections and the number of caudal chaetoids are stable. Naked, middle and abdominal chaetoid sections are the most variable. Linear sizes of naked section and the number of chaetoid sets on middle and abdominal sections correlate with the number of undeveloped chaetoids. The statistical model of variability may be useful for populational analysis of Sarcoptes forms in connection with scab epidemiology.

Animals↗
PubMed1999

Radiosensitivity of human lymphocytes in vitro correlates more with proliferative ability of cells than with the incidence of radiation-induced damages of the genome.

The purpose of this study was the estimate the extent of individual variability in radioresponse of human lymphocytes in vitro and to establish the reasons of variability. Individual variability in radiation-response was evaluated using the cytochalasin B micronucleus test among 82 healthy individuals (36 men and 46 women), of mean age 38 (range 30-48). Blood samples were irradiated with gamma (60Co) rays at a dose of 2 Gy in vitro. The yield of radiation-induced micronuclei (MN), cytochalasin blocked proliferation index (CBPI), fraction of micronucleated binucleate (BN) cells and mean incidence of MN per micronucleated BN cells at a sampling time of 72 hours were scored. Our results brought out a significant effect of gender on the level of spontaneously occurring micronuclei, the lack of statistical differences between gender in the yield of radiation-induced micronuclei and marked variability in radiation response among individuals. Likelihood of expressing hypersensitivity was correlated with ability of cells to proliferate in vitro (beta = 0.41, p < 0.000) more than with the incidence of radiation-induced micronuclei per micronucleated cell (beta = 0.20, p < 0.000).

Adult↗
PubMed2001

Characterization of diet-dependent metabolic serotypes: analytical and biological variability issues in rats.

This report, the first in a series on diet-dependent changes in the serum metabolome (metabolic serotype), describes validation of the use of high performance liquid chromatography (HPLC) separations coupled with Coulometric array detectors to characterize changes in the metabolome. The long-term aim of these studies is to improve understanding of the effects of significant variation in nutritive status on physiology and on disease processes. Initial studies focus on identifying the effects of dietary (or caloric) restriction on the redox-active components of rat serum. Identification of compounds of interest is being carried out using HPLC separations coupled with coulometric array analysis, an approach allowing simultaneous examination of nearly 1200 serum compounds. The technical and practical issues discussed in this report are related to both analytical validity (HPLC running conditions, computer-automated peak identification, mathematical compensation for chromatographic drift, etc.) and biological variability (individual variability, cohort-cohort variability, outliers). Attention to these issues suggests approximately 250 compounds in serum are sufficiently reliable, both analytically and biologically, for potential use in building mathematical models of serotype.

Animals↗
PubMed1979

[Clinical study on digoxin tablets with high bioavailability (author's transl)].

The relationship between different maintenance doses and the steady-state digoxin blood concentration was studied in 160 patients with heart failure. All patients received digoxin tablets of the same brand (Digacin). The bioavailability of this brand is 82% compared with an i.v. standard. During the treatment with daily doses of 0.2 mg and 0.3 mg average serum digoxin levels of 1.09 +/- 0.45 ng/ml and 1.33 +/- 0.53 ng/ml were measured in patients with normal renal function. The daily dose of 0.4 mg digoxin was in correlation to an average serum level of 1.75 +/- 0.81 ng/ml. 81% and 86% of all patients with normal renal function taking 0.2 or 0.3 mg digoxin every day were found to have levels in the range of 0.7 to 2.0 ng/ml. The influence of sex, age, height, body weight, maintenance dose, serum creatinine and serum potassium on the variance of the digoxin plasma levels was computed by multiple linear regression. The multiple correlation coefficient was r = 0.666, the coefficient of determination (100 r2) being 44.4%. Therefore 44.4% of the total variance could be explained by these variables. Individual variables accounted for the following percentages of the total variance: serum creatinine 29.1%; maintenance dose 14.5%; age 4.3%; and reciprocal of body weight 3.9%.

Aging↗
PubMed1976

Natural antibodies directed against murine lymphosarcoma cells: variability of level in individual mice.

Natural anti-tumor antibodies (NAA) were revealed, by a complement-dependent cytotoxicity test on el4 lymphoma cells, in the serum of C3Hf but not of C57BL mice. Hybrids between the positive C3Hf and the negative C57Bl mice were NAA producers. Individual variability of NAA level was found in C3Hf and in the hybrids. The study of mice housed in the same or in different cages and of mice belonging to the same or to different litters demonstrated a randomly distributed variability. These observations seem to exclude environmental influences on the natural immune response or genetic mutations in the C3Hf strain with the appearance of variants with different NAA content. The NAA level was age-dependent with a peak around 20-24 weeks of age. Inoculum of lymphoma cells induced an increase in the NAA level both in C3Hf and in the hybrids but not in C57Bl mice which seem therefore incapable of making guinea-pig complement-fixing NAA. The individual variability of NAA level and the stimulating effect of tumor cells support a potential role of NAA in immunosurveillance of oncogenesis.

Age Factors↗
PubMedDate not supplied

[The nature of the variability in the individual differences of the frequency characteristics of the alpha-rhythm EEG in 6- to 8-year-old children].

Behavioural genetic technique (model fitting) was used to study the genetic and environmental contributions to individual variability of power of the alpha-frequency band and its components (alpha 1 = 7.5-9.0 Hz; alpha 2 = 9.5-11.0 Hz; alpha 3 = 11.5-13.0 Hz) in different brain areas. 26 pairs of monozygotic and 22 pairs of dizygotic twins aged 6-8 years participated in EEG study. EEG was recorded from the frontal (F3, F4), central (C3, C4), temporal (T3, T4), parietal (P3, P4), and occipital (O1, O2) areas. Our study revealed that the nature of different alpha-components was different. It was found that the later in the ontogenesis a component of the alpha-frequency band became dominant in the EEG the less genetic factors contribute into the family resemblance.

Alpha Rhythm↗
PubMed1978

Remembering the person: relations of individual difference variables to memory.

Individual differences in personality and temperament variables were examined in relation to measures of simple mental performance in an attempt to determine the effects of personality on cognitive functioning in the elderly. Shorter latencies in binary decision and choice reaction times, and in recognition memory and object naming tasks were found to be associated with greater trait anxiety and experiential openness. The need to include clinical assessments of memory impairment and measures of more global cognitive abilities and styles in future research on personality and mental performance was discussed, and ways in which information on personality variables might be incorporated into programs of intervention for memory impairment in the elderly were suggested.

Adolescent↗
PubMed1990

Human photoreceptor topography.

We have measured the spatial density of cones and rods in eight whole-mounted human retinas, obtained from seven individuals between 27 and 44 years of age, and constructed maps of photoreceptor density and between-individual variability. The average human retina contains 4.6 million cones (4.08-5.29 million). Peak foveal cone density averages 199,000 cones/mm2 and is highly variable between individuals (100,000-324,000 cones/mm2). The point of highest density may be found in an area as large as 0.032 deg2. Cone density falls steeply with increasing eccentricity and is an order of magnitude lower 1 mm away from the foveal center. Superimposed on this gradient is a streak of high cone density along the horizontal meridian. At equivalent eccentricities, cone density is 40-45% higher in nasal compared to temporal retina and slightly higher in midperipheral inferior compared to superior retina. Cone density also increases slightly in far nasal retina. The average human retina contains 92 million rods (77.9-107.3 million). In the fovea, the average horizontal diameter of the rod-free zone is 0.350 mm (1.25 degrees). Foveal rod density increases most rapidly superiorly and least rapidly nasally. The highest rod densities are located along an elliptical ring at the eccentricity of the optic disk and extending into nasal retina with the point of highest density typically in superior retina (5/6 eyes). Rod densities decrease by 15-25% where the ring crosses the horizontal meridian. Rod density declines slowly from the rod ring to the far periphery and is highest in nasal and superior retina. Individual variability in photoreceptor density differs with retinal region and is similar for both cones and rods. Variability is highest near the fovea, reaches a minimum in the midperiphery, and then increases with eccentricity to the ora serrata. The total number of foveal cones is similar for eyes with widely varying peak cone density, consistent with the idea that the variability reflects differences in the lateral migration of photoreceptors during development. Two fellow eyes had cone and rod numbers within 8% and similar but not identical photoreceptor topography.

Cell Count↗
PubMed2003

Normalisation of gait EMGs: a re-examination.

The purpose of this study was to compare four different methods of normalising electromyograms (EMGs) recorded during normal gait. Comparisons were made between the amplitude, intra-individual variability and inter-individual variability of EMGs. Surface EMGs were recorded from the biceps femoris, semitendinosus, vastus lateralis and vastus medialis of ten males and two females while they walked on a treadmill at a self-selected speed. EMGs from the same muscles were subsequently recorded during isometric maximal voluntary contractions (MVCs) and concentric, isokinetic MVCs that were performed between 0.52 and 7.85 rad x s(-1) on a BIODEX dynamometer. EMGs were also recorded during eccentric, isokinetic MVCs between 0.52 and 2.62 rad x s(-1). Gait EMGs were then normalised at 2% intervals of the gait cycle by expressing them as a percentage of the following reference values: the mean (mean dynamic method) and the peak (peak dynamic method) EMG from the intra-individual ensemble average; the EMG from an isometric MVC (isometric MVC method); and the EMG from an isokinetic MVC that occurred with the same muscle action, length and velocity of musculotendinous unit as the gait EMGs (isokinetic MVC method). The isokinetic MVC method produced significantly greater (P<0.05) intra-individual variability compared to the other methods when it was measured using the variance ratio. Inter-individual variability of gait EMGs, again measured using the variance ratio, was also greatest when they were normalised using the isokinetic MVC method. The pattern and amplitude of EMGs normalised using the isometric MVC method and the isokinetic MVC method were very similar (root mean square difference and absolute difference both less than 3%). It was concluded that the isokinetic MVC method should not be adopted by gait researchers or clinicians as it does not reduce intra- or inter-individual variability anymore than existing normalisation methods, nor does it provide a more representative measure of muscle activation during gait than the isometric MVC method.

Adult↗
PubMed1986

An examination of the relation of individual difference variables to loneliness.

This study investigated the relation of five individual difference variables (extroversion, depression, self-esteem, neuroticism, and attitude toward others) to loneliness. The relative contributions of two different models that might explain these relations were examined. One model suggests that individual difference variables are related to loneliness through the mediation of social network variables; that is, individual difference variables may reduce people's motivation and/or ability to build and maintain social relationships, which in turn leads to loneliness. The second model, the cognitive bias model, states that both the individual difference variables and loneliness are influenced by the same intrapersonal, cognitive processes. Some people are prone to negative affect and tend to evaluate themselves and their relationships negatively. The relations of self-esteem, neuroticism, and depression to loneliness were hypothesized to reflect the cognitive bias model, while extroversion and attitudes toward others were hypothesized to be related to loneliness through the mediation of social network variables. Eighty-two female and 42 male adults completed measures of loneliness and the five individual difference variables, as well as an instrument assessing their social networks. The results indicated partial support for both models for each of the individual difference variables. Together, the two models did a good job of explaining the correlations of the individual difference variables and loneliness. The implications of these findings, as well as their relation to previous research, are discussed.

Adult↗
PubMed1993

Intra- and inter-individual variations in energy expenditure of 14-15-year-old schoolgirls as determined by indirect calorimetry.

Eleven 14-15-year-old schoolgirls were investigated four times within 1 year to determine variations in energy expenditure between individuals (inter-individual variability) and within subjects (intra-individual variability). Indirect calorimetry was used to determine metabolic rates in the fasting and resting state (RMR), and during physical activities which were grouped into standardized and non-standardized activities. Analyses of variance supplied information about intra- and inter-individual variabilities of rates of energy expenditure. The mean resting metabolic rate in adolescent girls was 4.41 (SD 0.40) kJ/min. The overall coefficient of variation (9.1%) was approximately twice as high as the mean coefficient within subjects (4.3%). The reproducibility of the RMR of the girls was high (significant F value of variance analysis), even over a prolonged investigation of 1 year. This seemed to depend primarily on the constant body weight during the period of investigation. A workload of 30 W on a bicycle ergometer and walking at an individually chosen speed did not reveal significant differences between inter- and intra-individual variabilities of energy metabolic rates. However, in most non-standardized activities, e.g. relaxation at home, washing dishes and vacuum cleaning, inter-individual variability was significantly higher than intra-individual variability. There are true differences in energy expenditure rates between subjects which may be demonstrated by duplicated measurements. Conclusions on future experimental design were drawn, where differences between groups rather than between individuals are to be studied.

Adolescent↗
PubMed1980

[Individual anatomical variability of the cerebellar nuclei].

While studying the cerebellar grey nuclei in serial horizontal sections performed at the distance of 0.5 mm from each other, a considerable individual variability was revealed. For example, the denticulate nucleus, which has greater dimentions than other cerebellar nuclei, was present in all preparations in all three planes. The emboliform nucleus, which has smaller dimentions than the denticulate nucleus, varied within greater limits in all three planes, and it was rather difficult to find its permanent zone of presence. The spherical nucleus was of small dimentions and has a wide range of individual variability, therefore, it was not possible to demonstrate its permanent place in all preparations of all three planes. The tegmental nucleus, as small as the spherical nucleus in its dimentions, was permanently demonstrated only in the medial-sagittal plane, and in two other planes its position varied-within wide range.

Adult↗
PubMed2003

Staying on the job: the frontal lobes control individual performance variability.

The causes of variability of performance by individual subjects have rarely been investigated, although excessive variability or inconsistency may be a functionally significant factor for many real-life activities. Our objective was to determine whether patients with focal frontal brain lesions have excessive individual performance variability. Thirty-six patients with focal frontal (n=25) or non-frontal (n=11) lesions were compared with 12 control subjects on different measures of intra-individual variability: dispersion within a testing session; and consistency across testing sessions. Four reaction time tasks, varying in levels of complexity and based on a model of detection using feature integration, were administered. Following the first test session, 22 patients and 10 controls returned for two subsequent test sessions, which permitted the assessment of consistency of performance. Measures of abnormal dispersion of performance on these tests were observed in frontal patients only (except those with exclusively inferior medial damage). Disturbances in consistency of performance were observed primarily in patients with frontal lesions. Damage to the frontal lobes impairs the stability of cognitive performance. Damage to different frontal regions causes different profiles of abnormal variability. Fluctuations in performance of a task may underlie some of the reported difficulties in daily tasks reported by patients with frontal injuries.

Adult↗
PubMed1998

Individual differences in memory and executive function abilities during normal aging.

The purpose of this study was to analyze the effects of some individual variables on memory and executive function test performance in normal aging individuals. Sixty subjects (21 males and 39 females), with a mean age of 69.66 (SD = 7.09) were selected. The following neuropsychological tests were selected. The following neuropsychological tests were administered: Associative Learning and Logical Memory from the Wechsler Memory Scale (WMS) (Wechsler, 1945), Associative Memory with Semantic Enhancement Test (AMSET) (Pineda, Galeano and Giraldo, 1991), Wisconsin Card Sorting Test (WSCT) (Heaton, 1981), and Verbal Fluency (phonologic and semantic). The effects of demographic (age, education, and sex) and some individual variables (academic history, working history, physical activity, and leisure activities) were measured. Age and education effects on test scores were observed, but no sex effect was found. Working history and leisure activities established significant differences in some test scores. A multiple regression analysis was performed. Not only demographic variables, but also individual variables were associated with memory, and albeit at a lesser extend, with executive function test scores. It was emphasized that not only demographic factors, but also individual variables have a significant effect on cognitive changes observed during normal aging.

Aged↗
PubMed1983

[Individual anatomical variability of the head of the caudate nucleus and of the putamen in man].

Individual variabilities in form, size and position of the nucleus caudatus head and the putamen have been studied in the horizontal section cutting across the inferior edge of the interventricular foramen (Monro) and the posterior commissure of the cerebrum in 70 mature persons died from various diseases not connected with disorders in the brain. Variability in length, width and position of these strial structures have been estimated taking into account the size of the intercommissural lines. The investigation has demonstrated that with an increasing distance between the anterior and posterior commissures of the cerebrum, the length and width of the nucleus caudatus head and those of the putamen increase; these nuclei are observed to be pushed off the median line and approach towards the level of the anterior cerebral commissure.

Adolescent↗
PubMed1980

Individual differences in alpha rhythm responsivity: inter-task consistency and relationships to cardiovascular and dispositional variables.

Individual differences in EEG alpha rhythm responsivity were examined with respect to: (1) consistency of response across cognitive tasks; (2) relationships to cardiovascular responsivity; and (3) relationships to dispositional variables. Inter-task correlations revealed a significant degree of stability in subjects' alpha responses to four "sensory rejection" tasks: mental arithmetic, time estimation and imagining oneself as cold or warm. Individuals evidencing greater suppression of alpha activity during mental arithmetic also displayed greater heart rate increase and greater digital vasoconstriction, as well as obtaining higher scores on the Activity subscale of the EASI-III Temperament Survey and on the "Hard Striving" subscale of the Jenkins Activity Survey for Health Prediction, a measure of the Coronary-Prone Behavior Pattern. Alpha responsivity in the time estimation and warm imagery tasks was also associated with greater heart rate increase. The results suggest that alpha responsivity is related to individual differences affecting one's attentiveness or involvement in experimental tasks.

Alpha Rhythm↗
PubMed2000

Reduced variability of neoral pharmacokinetic studies in pediatric renal transplantation.

In adult renal transplant recipients the Neoral area under the curve (AUC) displays less inter- and intra-individual variability than Sandimmune, and those renal transplant recipients with reduced intra-individual variability of the AUC have a lower risk for chronic rejection. As variability of Neoral pharmacokinetic (Pk) parameters has not been investigated in pediatric renal transplant recipients, we retrospectively analyzed 453 Pk profiles in 14 pediatric patients who were switched from Sandimmune to Neoral and compared the inter- and intra-individual variability of the Pk profiles on both formulations. After the switch, we observed less inter- and intra-individual variability of AUC, the 2-h concentration, and the oral clearance. As clearance with both formulations is supposedly equal, the significantly lower intra-individual variability of oral clearance is most likely an effect of less variable absorption. While the lower inter-individual variability of the Pk parameters suggests increased success in keeping cyclosporine concentrations on target, the lower intra-individual variability leads to the hypothesis that with Neoral, a lower incidence of chronic rejection might be achieved.

Adolescent↗
PubMed1975

[Individual anatomic variability of the subthalamic nucleus in frontal sections].

The paper presents the results of studying individual variability of the shape, size and disposition of the subthalamic nucleus. Under investigation were 100 preparations. The structure was studied in serial frontal sections of the diencephalon and midbrain taken 1 mm apart. A considerable variability of the disposition of the subthalamic nucleus was revealed relative to intracerebral reference--points used in stereotaxic operations. The limits are outlined within which stereotaxical lesions should be avoided.

Aged↗