Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Individual variability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 163 records · Page 9Linked to original sources
PubMed1987

Distribution of cones in human and monkey retina: individual variability and radial asymmetry.

The distribution of photoreceptors is known for only one complete human retina and for the cardinal meridians only in the macaque monkey retina. Cones can be mapped in computer-reconstructed whole mounts of human and monkey retina. A 2.9-fold range in maximum cone density in the foveas of young adult human eyes may contribute to individual differences in acuity. Cone distribution is radially asymmetrical about the fovea in both species, as previously described for the distribution of retinal ganglion cells and for lines of visual isosensitivity. Cone density was greater in the nasal than in the temporal peripheral retina, and this nasotemporal asymmetry was more pronounced in monkey than in human retina.

Animals↗
PubMed1998

Inter-individual variability in Ca2+ signalling in platelets from healthy volunteers: effects of aspirin and relationship with expression of endomembrane Ca2+-ATPases.

Increased Ca2+ signal generation may lead to hyperactivity of platelets and contribute to thrombotic complications. Using fura-2-loaded platelets from 51 healthy volunteers, high variability was detected in the Ca2+ responses evoked by the receptor agonists, thrombin and collagen, and the inhibitor of sarco/endoplasmic reticulum Ca2+-ATPases (SERCA), thapsigargin (Tg). Oral intake of 500mg aspirin reduced the magnitude of the Ca2+ responses, and lowered the intra-individual coefficients of variance of the responses by 50%. However, the corresponding inter-individual variance coefficients were only a little influenced by aspirin intake, pointing to subject-dependent factors in Ca2+ handling that are unrelated to thromboxane formation. With each agonist, 6-9% of the subjects had platelets with relatively high Ca2+ responses (> mean + SD) both before and after aspirin intake. In 90% (9/10) of these cases the high responsiveness was confirmed in platelets obtained 6-12 months later. The Tg- but not thrombin-induced Ca2+ responses correlated inversely with the expression levels of SERCA PL/IM 430 (SERCA-3b) in platelets. After aspirin intake, the Ca2+ responses with collagen but not thrombin correlated inversely with SERCA-2b expression. These results suggest that, in the absence of potentiating effects of thromboxane, (i) the amount of PL/IM 430-recognizable SERCA may control the Ca2+ signal when SERCA-2b is specifically inhibited (with Tg), and (ii) the expression of SERCA-2b determine the collagen- but not the thrombin-evoked Ca2+ signal. Accordingly, limited Ca2+-pumping activity by low expression of one of the SERCA isoforms is likely to be one of the factors resulting in increased platelet activity towards collagen or thapsigargin but not thrombin.

Aspirin↗
PubMedDate not supplied

Intra- and inter-individual variability in measurements of biomarkers for oxidative damage in vivo: Nutrition and Breast Health Study.

Oxidative stress has been implicated in the pathogenesis of various chronic diseases, such as cancer, cardiovascular disease and inflammatory conditions, as well as in ageing. Although a number of markers are now available, little is known about the reliability of single measurements of such markers in healthy individuals. The study examined the distribution of variance for three oxidative stress markers, 8-oxo-2'-deoxyguanosine (8-oxodG), 5-hydroxymethyl-2'-deoxyuridine (5-OHmdU) and total 8-isoprostane-F2alpha, which were measured every 3-6 months over 1 year in blood and breast nipple aspirate fluid (NAF) for 103 premenopausal women. For both plasma and NAF, the between-subject variances of 8-isoprostane-F2alpha were consistently greater than the within-subject variances. Consequently, their reliability coefficients were close to the level of those for cholesterol. On the other hand, the within-subject variances were much greater than the between-subjects variances for blood 5-OHmdU, resulting in low reliability coefficients, i.e. <0.3. Overall, the reliability coefficients for blood 8-oxodG were between those of 8-isoprostane-F2alpha and 5-OHmdU, but closer to those of 8-isoprostane-F2alpha. The results suggest that the reliability of oxidative stress markers may vary considerably depending on the type of marker. Caution should be exercised in selecting markers as well as in determining the number of study subjects or the number of samples per subject in a study. There also may be ample room to optimize laboratory techniques to quantify markers of oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1991

Functional anatomy of language processing: neuroimaging and the problem of individual variability.

This paper discusses the long-standing concepts of a participation of frontal opercular and inferior parietal cortex in high-order language processing with respect to contradictory inferences from recent positron emission tomographic (PET) activation studies (cf. Petersen et al. [49]). The main thrust of the present argument is that the technique of intersubject PET image averaging may be inappropriate due to intersubject variability. Evidence is presented which suggests that intersubject variability is at least two-fold: (i) Intraoperative stimulation has demonstrated diversity in location of language functions in the left frontal and temporoparietal association cortex; (ii) Morphometrical imaging studies have demonstrated diversity of brain shape and gyral pattern which is difficult to correct by anatomical standardization of individual brains. Both factors add noise in spatially standardized PET images and may render circumscribed high-order language foci undetectable. It is argued that PET studies of higher cognitive functions including language must focus on individual anatomo-functional organization using techniques such as intrasubject averaging.

Arousal↗
PubMed2004

LC-MS/MS analysis of dextromethorphan metabolism in human saliva and urine to determine CYP2D6 phenotype and individual variability in N-demethylation and glucuronidation.

In order to establish a fast screening method for the determination of the CYP2D6 metabolic phenotype a sensitive LC-MS/MS assay to quantify dextromethorphan (DEX) and its O-demethylated metabolite dextrorphan (DOR) in human saliva was developed with limits of quantitation of 1 pmol/ml. Saliva was provided by 170 medical students 2h after oral ingestion of 30 mg (81 micromol) dextromethorphan hydrobromide. Individual ratios of the concentrations DEX/DOR (metabolic ratio, MR(DEX/DOR)) varied more than 25,000-fold (0.03-780). Two groups comprising 156 'Extensive' and 14 'Poor Metabolizers' were clearly distinguished. For the investigation of individual differences in N-demethylation and glucuronidation, four additional metabolites of DEX, 3-methoxymorphinan (MOM), 3-hydroxymorphinan (HOM), and the two O-glucuronides (DORGlu and HOMGlu) were measured by LC-MS/MS analysis of 6-h urine of 24 volunteers. The N-demethylation reactions DEX-to-MOM and DOR-to-HOM defined by the respective MR were significantly correlated. The same holds for the glucuronidation pathways (MR(DOR/DORGlu) versus MR(HOM/HOMGlu)). The three poor CYP2D6 metabolizers excreted relatively high amounts of the parent compound DEX (up to 7 micromol), but only low amounts of glucuronides (DORGlu: 0.4-1.0 micromol; HOMGlu: 0.2-0.7 micromol). For the 21 'Extensive Metabolizers', the two glucuronides were the most abundant, with relatively little interindividual variation (DORGlu: 10-44 micromol; HOMGlu: 5-17 micromol). For the excretion of the glucuronides, two normal distributions provided the best fit, indicating that the determination of the glucuronides alone could allow assignment of the CYP2D6 metabolic phenotype.

Chromatography, Liquid↗
PubMed1985

Neutralization of individual variable antigen types in metacyclic populations of Trypanosoma brucei does not prevent their subsequent expression in mice.

The Trypanosoma brucei metacyclic population in the salivary glands of the tsetse fly displays a characteristic set of variable antigen types (VATs) which represents only a restricted part of the parasite's total VAT repertoire. After introduction into the mammalian host by fly bite, the metacyclics transform into bloodstream forms which retain expression of the metacyclic VATs. Specific antibodies, both polyvalent and monoclonal, have been used to neutralize separately 4 individual VATs from metacyclic populations. Control experiments and visual observation confirmed lysis of each VAT. On injection of the surviving trypanosomes, after washing, into mice each neutralized VAT was nevertheless expressed within a few days. Simultaneous neutralization of 2 metacyclic VATs which usually switch to one another in bloodstream infections did not prevent expression of either on subsequent injection into mice. Expression of neutralized VATs was not influenced by the antigenic composition of the population originally ingested by the tsetse fly. Metacyclic forms and their immediate successors thus appear to switch rapidly to expression of other metacyclic VATs in bloodstream populations.

Animals↗
PubMed1994

[Individual variability in the duration of the second phase of the mixed dentition].

With a collection of dental casts from a longitudinal study of 175 orthodontically untreated probands (100 children without and 75 children with premature loss of deciduous molars and/or canines) serving as a base, the duration of the second period of mixed dentition was determined to be in relation to the probands the period of time between the gingival emergence of the first permanent buccal tooth and the full eruption of the set of teeth. The second period of mixed dentition in boys without premature loss of deciduous molars and canines lasts on an average 3.6 +/- 1.1 years and in girls 3.8 +/- 1.0 years. In cases of premature loss of deciduous molars and/or canines, the period of dentition is distinctly longer than under normal development conditions. The outside parameters (boys: Xmin = 0.9 years, Xmax = 6.2 years; girls: Xmin = 2.6 years, Xmax = 8.6 years), reflect a high degree of variability. The duration of the second period of mixed dentition is significantly affected by "the point in time of inception" and by the criteria "morphologically intact support zones" and "premature loss of deciduous molars and/or canines". Even given such data, however, it is not possible to make a sufficiently reliable prediction on an individual basis of the duration of the dentition.

Child↗
PubMed1988

Trabecular architecture in iliac crest bone biopsies: infra-individual variability in structural parameters and changes with age.

A histomorphometric study was conducted on bilateral iliac crest samples obtained at autopsy from 27 subjects who had died suddenly. Six parameters related to cancellous bone structure were measured: bone volume (BV/TV), surface density (BS/TV), surface/volume ratio (BS/BV), trabecular thickness (Tb.Th.), trabecular number (Tb.N), and trabecular separation (Tb.Sp). There were no significant differences between right and left sides in the mean values for each parameter. However, when subjects were considered individually, there was a substantial difference in the majority of cases for all parameters. The intra-individual variation (IIV) was calculated for each subject as the percentage deviation from the mean for the two sides. There was a wide range in IIV (0.05-30.27%) with a mean value of approximately 11.5% for each parameter. In males the mean IIV ranged from 9 to 11% and from 14 to 16% in females. The IIV in BV/TV was positively correlated with age. Data generated on a subsample of 15 males were used to predict patient group sizes required to detect minimum significant differences in studies involving repeat biopsies. Sample sizes of 32, 16, and 8 patients would be required for relative increments in BV/TV of 29, 36, and 46%, respectively, to be statistically significant. Tb.Sp increased significantly with age but there was no significant change in Tb.Th. This supports the view that bone loss with aging occurs primarily through a mechanism involving complete disappearance of individual trabecular plates.

Adult↗
PubMed2000

Using Shannon entropy on measuring the individual variability in the Rufous-bellied thrush Turdus rufiventris vocal communication.

We applied the information theory concepts to notes repertoire characteristics combined with temporal parameters of the Rufous-bellied thrush Turdus rufiventris song, using this particular case to test a new method of analysing quantitatively complex animal communication systems. Like most Turdus thrushes, Rufous-bellied thrushes are remarkable for their long, varied and melodious songs. For the analysis of the species repertoire, we used recordings of 44 individuals from 24 localities covering its full geographical range. We measured the repertoire size, note duration and rhythm (frequency of note utterance), and combined these parameters with the Shannon entropy values calculated for each individual. Although individuals maintain species-specific recognition capacity, we find a large variation between their song parameters and show that the information theory can be useful to analyse large and varied animal vocal repertoires. We are introducing two new parameters, temporal average entropy (E(t)) and utterance frequency average entropy (E(f)), for measuring such communication systems.

Animals↗
PubMed1992

Individual variability in the translational regulation of ribosomal protein synthesis in Xenopus laevis.

Ribosomal protein synthesis is regulated by controlling the fraction of mRNA associated with polysomes. It is known that this value changes in different developmental stages during Xenopus embryogenesis or, more generally, with changing cell growth conditions. We present here an analysis of the proportion of mRNA loaded on polysomes, carried out with probes for five different ribosomal proteins on several batches of Xenopus embryos obtained from different individuals. The results obtained indicate the existence of probe-dependent and individual differences, which reflect genetic variations in the cis- and trans-acting regulatory elements responsible for translational regulation. The fraction of ribosomal protein mRNA loaded onto polysomes can be used as an index of an individual's capacity for ribosome production.

Animals↗
PubMed1982

[Individual variability of the human caudate nucleus].

When establishing borders microscopically and cytoarchitectonically, the volume of the nucleus caudatus (NC) has been measured in human brains from persons of various sex and age (21 persons and 27 hemispheres). The NC volume varies greatly in some persons and it is connected neither with the brain mass, nor with the sex and age. Difference between the extreme variants is more than twice as great. Great morphological differences are supposed to demonstrate a corresponding individual functional specificity. The extreme variants occur rather seldom, cases with less range of differences prevalence. The NC asymmetry is revealed, with the right-sides (5 cases) or left-sided (1 case) prevalence. Very great individual peculiarities are revealed in relations of the form and the extent of various components of the NC: head, body and tail, as well as in the peculiar ending of the latter. Owing to the data obtained, it is necessary to revise the competency of the view on proportional dependence between the external and internal cerebral structures which make the base for using stereotaxic atlases of the human brain, since the existence of the extreme variants creates a real threat of complications in these cases at various operative interventions relying upon the reference points available.

Adult↗
PubMed1991

Individual variability in the perception of cues to place contrasts in initial stops.

Synthetic continua of two minimal pairs, BAIT-DATE and DATE-GATE, closely modeled on natural utterances by a female speaker, were presented to a group of 16 listeners for identification in full-cue and reduced-cue conditions. Grouped results showed that categorization curves for full- and reduced-cue conditions differed significantly in both contrasts. However, an averaging of results obscures marked variability in labeling behavior. Some listeners showed large changes in categorization between the full- and reduced-cue conditions, whereas others showed relatively small or no changes. In a follow-up study, perception of the BAIT-DATE contrast was compared with the perception of a highly stylized BA-DA continuum. A smaller degree of intersubject and between-condition variability was found for these less complex synthetic stimuli. The amount of variability found in the labeling of speech contrasts may be dependent on cue salience, which will be determined by the speech pattern complexity of the stimuli and by the vowel environment.

Adult↗
PubMedDate not supplied

Discrete MBL-MASP complexes show wide inter-individual variability in concentration: data from UK vs Armenian populations.

Mannan-binding lectin (MBL) circulates in plasma in complex with MBL-associated serine proteases (MASP) -1, -2 and -3 and a smaller component, MAp19. When MBL binds to the surface of foreign material (microorganisms), MASP-1, -2, -3 are activated. MASP-2 then activates the complement system. MASP-1 and -3 may activate other (unidentified) systems. MBL levels, MBL-bound MASP-1 and MBL-bound MASP-2 activities have been evaluated in healthy individuals from UK and Armenian populations. MBL-bound MASP-2 activity declines in aging (P<0.04). MBL correlates with smoking (P<0.02). There were significant differences between the two populations in MBL-bound MASP-1 activity and in MBL, but no difference in MBL-bound MASP-2 activity. When MASP activities were normalised to MBL (i.e. MASP-1 activity/MBL, MASP-2 activity/MBL), normalised MASP-2 activity in UK individuals was more than 2 fold higher than in Armenians. The difference in normalised MASP-2 activity level between these two Caucasoid populations, suggests that concentration of the MBL-(MASP-2) complex, and therefore the function of activating complement, depends not only on the quantity of MBL in serum and its oligomeric state, but also on the quantity of MASP-2 in serum. It is likely that in individuals with high MBL concentration there is excess free MBL not occupied by MASPs, particularly not by MASP-2.

Adult↗
PubMed1982

[Morphological criteria of the individual variability of the human brain].

Structural organization of the layers III and V in the cortical fields (speech area, motoring, frontal inferior parietal) of the cerebral hemispheres and the nucleus caudatus have been quantitatively studied in 4 human beings. By means of a computer, area of profile fields of neurons, total volume of all the neurons and glyocytes in the histological section (total volumetric fraction of the neurons and glia) have been calculated, as well as percentage of the neurons having various size. The material is statistically treated. Certain morphological criteria of individual peculiarities have been established in the structural organization of the cortical and subcortical formations in the human brain. Individual variants in the value of the total volumetric fraction of the neurons and glia have been revealed, as well as peculiarities in composition percent of neuronal cells in the layers III and V. Differences in the area indices of the profile fields in separate persons and in various structures have been ascertained.

Adult↗
PubMed1991

[Inter- and intra-individual variability of pharmacokinetic parameters for contraceptive steroids].

Serum levels of ethinylestradiol (E2) and levonorgestrel (LNG) have been determined in 10 volunteers of similar age after administration of 1 tablet of the oral contraceptives Gravistat and Ediwal, respectively, each containing 0.05 mg E2 and 0.125 mg LNG, using a cross over design. The studies were carried out at intervals of 4 weeks, within the follicular phase of the menstrual cycle and under standardized conditions. Wide variations were observed between the women in the calculated pharmacokinetic parameters, while there was a relatively close correspondence between the intra-individually obtained values, except for one case.

Adult↗
PubMed2006

Use of isotope ratio mass spectrometry to detect doping with oral testosterone undecanoate: inter-individual variability of 13C/12C ratio.

The metabolic effect of multiple oral testosterone undecanoate (TU) doses over 4 weeks was assessed in seven voluntary men. The protocol was designed to detect accumulation of the substance by choosing the appropriate spot urines collections time and to study the urinary clearance of the substance after weeks of treatment. Urines were analysed by a new GC/C/isotope ratio mass spectrometry (IRMS) method to establish the delta(13)C-values of testosterone metabolites (androsterone and etiocholanolone) together with an endogenous reference compound (16(5alpha)-androsten-3alpha-ol). The significant differences in inter-individual metabolism following TU intake was illustrated by large variations in delta(13)C-values of both T metabolites (maximum Deltadelta(13)C-values = 5.5 per thousand), as well as by very stable longitudinal T/E profiles and carbon isotopic ratios in the first hours following administration. According to T/E ratios and delta(13)C-values, the washout period after 80 mg TU intake was less than 48 h for all subjects and no accumulation phenomenon was observed upon chronic oral administration.

Administration, Oral↗
PubMed1993

Morphometric evaluation of neurophysin-immunoreactivity in the human brain: pronounced inter-individual variability and evidence for altered staining patterns in schizophrenia.

The neurohypophyseal peptides vasopressin and oxytocin have a variety of well documented behavioural effects. Accordingly, terminals and receptors that respectively contain or bind these peptides have been identified throughout the central nervous system (CNS) in experimental animals. In this study we have mapped the distribution of neurophysin I and II-immunoreactive structures in the human CNS. Neurophysins are portions of the precursor proteins for vasopressin and oxytocin, and are found specifically in structures that contain these peptides. In addition, we have quantitatively compared neurophysin neurons and fibers in the brains of individuals with no history of neurologic or psychiatric abnormality, and in brains of patients dying with psychotic illness categorized as schizophrenia. These latter brains were collected prior to the advent of pharmacologic treatment and were available from the Vogt collection. Our findings show wide variations of morphometric values obtained for neurophysin-stained structures in different CNS regions in normal subjects, but provide evidence for abnormal values in certain brain areas in untreated schizophrenia, in the hypothalamic paraventricular nucleus, internal pallidal segment and substantia nigra. These findings suggest that the function of vasopressin and/or oxytocin may be disturbed in these brain regions in schizophrenia. Further investigation will be required to establish whether these differences contribute to, or are a consequence of the disease mechanism.

Adult↗
PubMed1980

Species specificity and individual variability of sea urchin sperm H2B histones.

Total histones from the sperms and embryos of the sea urchins Paracentrotus lividus, Arbacia lixula, Psammechinus microtuberculatus and Sphaerechinus granularis hae been fractionated into the component molecules by electrophoretic analyses in SDS, in urea-acetic acid and in Triton-urea-acetic acid. Sperm H2B histones are in all cases different from those of the corresponding embryonic chromatins. Each sea urchin species has distinctive variants of the sperm H2B histones that are fractionated by electrophoresis in SDS acrylamide gel into two to four components forming a new class of lower mobility. This analytical method shows that individuals of the same species have different assortments of the H2B components. Electrophoretic analyses in Triton-urea also show multiple components for H2B but the patterns are similar in the different individuals.

Animals↗