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.

SourceResearch connectionFrom yearThrough year

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

At least 739 records · Page 41Linked to original sources

PubMed1998

Prediction of elite schoolboy 2000m rowing ergometer performance from metabolic, anthropometric and strength variables.

In 19 elite schoolboy rowers, the relationships between anthropometric characteristics, metabolic parameters, strength variables and 2000-m rowing ergometer performance time were analysed to test the hypothesis that a combination of these variables would predict performance better than either individual variables or one category of variables. Anthropometric characteristics, maximal oxygen uptake (VO2max), accumulated oxygen deficit, net efficiency, leg strength and 2000-m rowing ergometer time were measured. Body mass, VO2max and knee extension correlated with 2000-m performance time (r= -0.41, -0.43 and -0.40, respectively; P< 0.05), while net efficiency and accumulated oxygen deficit did not. Multiple-regression analyses indicated that the prediction model using anthropometric variables alone best predicts performance (R = 0.82), followed by the equation comprising body mass, VO2max and skinfolds (R = 0.80). Although the regression equations increased the predictive power from that obtained using single variables, the hypothesis that a prediction model consisting of variables from different physiological categories would predict performance better than variables from one physiological category was not supported.

Adolescent↗

PubMed2002

A prospective study of the relationship of mood and stress to pulmonary function among patients with asthma.

The purpose of this study was to examine the association of psychosocial and other variables to pulmonary function over four months. Thirty-two patients with asthma kept daily records of pulmonary function and psychosocial variables for an average of 140 days. Data on other potential covariates of pulmonary function, as assessed by peak flow meters, were also collected (e.g., allergen exposure). Sixteen subjects (50%) had significant associations between pulmonary function and psychosocial variables. Between-subjects analyses showed small but significant associations between pulmonary function and other variables. These results confirmed previous reports of individual variability in the association of psychosocial variables with pulmonary function.

Adult↗

PubMed1999

Cardiac output in four-, five-, and six-week-old broilers, and hemodynamic responses to intravenous injections of epinephrine.

Female broilers were evaluated at 4, 5, and 6 wk of age (1.2, 1.8, and 2.3 kg BW, respectively) to assess changes in cardiac output and related hemodynamics associated with BW gain, and to evaluate cardiopulmonary hemodynamic adjustments occurring secondary to i.v. injections of epinephrine (0.1 mg/ kg BW). Cardiac output increased with BW (253, 348, and 434 mL/min at 4, 5, and 6 wk, respectively) due to increases in stroke volume (0.70, 1.03, and 1.33 mL/beat) that more than compensated for reductions in heart rate (362, 337, and 328 bpm). Normalization for BW eliminated the differences in cardiac output and stroke volume. Increases in cardiac output were not associated with age- or BW-related increases in mean systemic arterial pressure (101.5, 108.6, and 108.0 mm Hg) due to corresponding reductions in total peripheral resistance (0.41, 0.32, and 0.26 relative resistance units). Epinephrine initially triggered immediate (within 90 s) threefold increases in total peripheral resistance and pulmonary vascular resistance, which, in turn, increased the systemic arterial pressure and pulmonary arterial pressure in spite of concurrent reductions in cardiac output that were associated with diminished venous return and dependent reductions in stroke volume and heart rate. Within 150 s after epinephrine injection, the systemic and pulmonary vascular resistances returned to preinjection control levels. By 300 s postinjection, stroke volume and heart rate increased, causing cardiac output to rise above preinjection control levels, which, in turn, elicited variable pulmonary arterial pressure responses apparently reflecting individual variability in the capacity for flow-dependent pulmonary vasodilation. These studies demonstrate that chronic (age- and BW-related) and acute (epinephrine-induced) changes in cardiac output in broilers reflect complex interactions among hemodynamic variables that include stroke volume, heart rate, and systemic and pulmonary vascular resistances.

Age Factors↗

PubMedDate not supplied

In vitro model for studying the effects of hemodynamics on device induced thromboembolism in human blood.

Biomateria related thromboembolism is a complex phenomenon, affected by such variables as biomaterial surface chemistry, hemodynamics, and individual donor variations. Thus, isolation of the individual variables would greatly facilitate the understanding and inhibition of this phenomenon. A low volume in vitro model with this potential has been developed, with the initial focus on studying the influence of hemodynamics on thromboembolism (TE) in human blood. Patterned after a larger in vitro model for bovine blood used successfully in our laboratory, the smaller model directed fresh human blood in a single pass through 1/32 inch ID PVC tubing and a flow cell at 3 ml/min. The flow cell consisted of alternating abrupt expansions and contractions of cylindrical tubing that could be modified to study the effects of hemodynamic parameters on TE. Thrombus growth in the flow cell was monitored visually by transillumination microscopy. Emboli from the flow cell were detected continuously by a light-scattering microemboli detector (LSMD), and their strength was assessed by using the constant-pressure filtration (CPF) method. Preliminary studies confirmed the potential of this model. Thrombi were observed visually in the flow cell at sites of high vorticity and at flow separation and reattachment points and were also observed to embolize. Emboli were detected by the LSMD downstream of the flow cell in significantly greater numbers than upstream and were coincident with the embolization of thrombi observed visually. Emboli collected downstream of the flow cell occluded the CPF filters at 50 mm Hg, suggesting that they possessed sufficient strength to occlude microvessels. This model may be used to aid in developing a computer model of thromboembolism, which could subsequently be refined with clinical data.

Hemodynamics↗

PubMed2006

The effects of cryopreservation on the morphometric dimensions of Iberian red deer (Cervus elaphus hispanicus) epididymal sperm heads.

Computer-automated sperm-head morphometry was used in this study to determine the effects of cryopreservation on red deer sperm-head morphometry. Epididymal sperm samples were collected from 40 mature stags and were divided. One portion was diluted at room temperature in a Tris-citrate egg yolk medium, containing 6% glycerol. A microscope slide was prepared from single extended sperm samples prior to freezing. The remainder of each sample was frozen in nitrogen vapours. After thawing, sperm smears were prepared as described above. All slides were air dried and stained with Hemacolor. The sperm-head dimensions for length, width, area, perimeter and shape factor (length/width), for a minimum of 135 spermatozoa were determined for each slide by means of the Sperm-Class Analyser (SCA). Firstly, our results show that cryopreservation substantially reduced (p < 0.001) sperm motility and plasma membrane and acrosome integrities. In addition, sperm heads were significantly smaller in cryopreserved spermatozoa than in the companion extended samples for area (32.05 microm2 vs 32.56 microm2; p < 0.05), length (8.46 microm vs 8.53 microm; p < 0.0001) and shape factor (1.833 vs 1.849; p < 0.0001) for all stags. These differences were found within 29 of 40 stags (75%) for at least three of the morphometric parameters. The individual variability (CV) of sperm head measurements from extended samples was negatively correlated (p < 0.005) with the per cent of change in sperm head measurements after cryopreservation for area (r = -0.465), width (r = -0.483) and perimeter (r = -0.375). Thus, the lower the sperm head variability in the extended samples, the greater the sperm change as a consequence of the cryopreservation. These results suggest that the variability (heterogeneity) in sperm head dimensions of individual stags may be a good indicator of sperm freezability.

Acrosome↗

PubMed2006

Assessment of the relationship between neighborhood characteristics and dental caries severity among low-income African-Americans: a multilevel approach.

OBJECTIVES: To assess the relationship between neighborhood effects and the severity of dental caries among low-income African-Americans. METHODS: A multistage probability sample of African-American families living in the poorest 39 census tracts in Detroit was drawn. During 2002-03, cross-sectional data of a cohort that includes 1021 caregivers were collected in the first of three waves of interviews and examinations. Multilevel analyses focused on 27 neighborhood clusters and involved a combination of individual (Level-1) and neighborhood (Level-2) data including census and geocoded (address matching to census geographic areas) information. RESULTS: There is significant variation in the severity of caries between low-income neighborhood clusters. Caries severity decreases with a higher number of churches, while it increases with a higher number of grocery stores in the clusters after accounting for individual characteristics. Only 14% of the inter-individual variability in caries was explained by classical individual risk factors for this condition. CONCLUSION: Neighborhoods contribute something unique to caregivers' oral health, beyond socioeconomic position and individual risk factors. Multilevel interventions are necessary to reduce disparities among African-Americans and churches may offer a promising venue from which to conduct them.

Adolescent↗

PubMed2001

Neutron-induced adaptive response studied in go human lymphocytes using the comet assay.

This study demonstrates that cells adapted to ionizing radiation developed reduced initial DNA damage when compared to non-adapted cells. The results were obtained by subjecting in vitro irradiated whole blood from 10 healthy volunteers (including 2 A-bomb survivors carrying 1.5-2 Gy in vivo exposure) in an unstimulated condition (G0) using the comet assay. The intensity of DNA damage was assessed by computing the 'tail moment'. Adaptive response (AR) was noticed in only donor 3, as indicated by reduced tail moment when the blood samples received priming + challenging doses over a 4 h interval. The priming dose was either 0.01 Gy 137Cs gamma-rays or 0.0025 Gy 252Cf neutrons. The delivered challenging dose was either 1 Gy 60Co g-rays or 0.25 Gy 252Cf neutrons. The irradiation was conducted using the HIRRAC facility. A prior exposure to 0.0025 Gy 252Cf neutrons nullified the excess tail moment caused by 0.25 Gy neutrons given during a 4 h gap. In a similar way, 0.01 Gy 137Cs gamma-rays offered a cross-adaptive response to the neutron challenging dose. The tail moment of A-bomb survivors after in vitro irradiation was less than that of the age-matched control and, at the same time, was not influenced by the priming dose. An altered subset and the immunological status of blood after A-bomb exposure were cited as possible factors. Because AR can affect the outcome of RBE, its individual variability only emphasizes the need to have individual biodosimetry for better risk assessment, especially in planning for a long space voyage.

Adaptation, Physiological↗

PubMed2003

Genetic variation in genes associated with arsenic metabolism: glutathione S-transferase omega 1-1 and purine nucleoside phosphorylase polymorphisms in European and indigenous Americans.

Individual variability in human arsenic metabolism has been reported frequently in the literature. This variability could be an underlying determinant of individual susceptibility to arsenic-induced disease in humans. Recent analysis revealing familial aggregation of arsenic metabolic profiles suggests that genetic factors could underlie interindividual variation in arsenic metabolism. We screened two genes responsible for arsenic metabolism, human purine nucleoside phosphorylase (hNP), which functions as an arsenate reductase converting arsenate to arsenite, and human glutathione S-transferase omega 1-1 (hGSTO1-1), which functions as a monomethylarsonic acid (MMA) reductase, converting MMA(V) to MMA(III), to develop a comprehensive catalog of commonly occurring genetic polymorphisms in these genes. This catalog was generated by DNA sequencing of 22 individuals of European ancestry (EA) and 24 individuals of indigenous American (IA) ancestry. In (Italic)hNP(/Italic), 48 polymorphic sites were observed, including 6 that occurred in exons, of which 1 was nonsynonymous (G51S). One intronic polymorphism occurred in a known enhancer region. In hGSTO1-1, 33 polymorphisms were observed. Six polymorphisms occurred in exons, of which 4 were nonsynonymous. In contrast to hNP, in which the IA group was more polymorphic than the EA group, in hGSTO1-1 the EA group was more polymorphic than the IA group, which had only 1 polymorphism with a frequency > 10%. Populations representing genetic admixture between the EA and IA groups, such as Mexican Hispanics, could vary in the extent of polymorphism in these genes based upon the extent of admixture. These data provide a framework in which to conduct genetic association studies of these two genes in relevant populations, thereby allowing hNP and hGSTO1-1 to be evaluated as potential susceptibility genes in human arsenicism.

Arsenic↗

PubMedDate not supplied

[Influence of data structure on the selection of statistic analysis methods].

In medical research, data is grouped either as per the design of the study or the selection of the sample. This structure must be taken into account in order to make correct estimates of the of the parameters and standard errors involved. This study is of the methodological type and is aimed at illustrating methods for estimating population-related methods and regression models with grouped data. For this purpose, nine variables from the First National Risk Factor and Preventive Measure Survey conducted in Cuba in 1995 are employed. The prevalence of high blood pressure is overestimated by 15% when the conventional estimators are used as compared with the weight-based and adjusted analysis. In the regression models for the body mass index based on the conventional procedures, sex, degree of schooling, degree of sedentariness, smoking habit, diastolic and systolic blood pressure were found to be significant. However, when the method taking into account the structure of conglomerates was employed, the degree of schooling and sedentariness ceased to be significant. When the random intercept model was adjusted, the 91.3% total variability was found to be explained by individual variables, the 8.7% variability being attributed to larger units. When estimating population-related parameters based on conglomerate-structure data involving inconsistent selection probabilities, the use of sample-related weights and analysis methods that take in the correlation among subjects (potential) for one same conglomerate. When adjusting regression models, it is not only important to efficiently estimate the coefficients, but rather the focus (aggregated or disaggregated) must be taken into account for modeling the problem under study.

Data Collection↗

PubMed1987

Development of dendritic spines in the Vth's layer pyramidal neurons of the rat's somatosensory cortex. A qualitative and quantitative study with the Golgi method.

Increases in the number of dendritic spines (DS) and modifications in the morphology of spines are observed through the maturation of pyramidal neurons in the somatosensory cortex of the rat. A two-fold increment in the number of spines occurs during days 15 to 30, but a 20% reduction in the overall number of DS is observed between days 30 and 90 to reach the stabilized values in the rat aged 6 months. The representation in a graph of the distribution of spines along the apical dendrite is adjusted to a curve with the maximal score lying at a distance of 200-300 microns from the cellular body. Beyond this region the number of spines decreases following a gentle descending profile. In addition, modifications in the morphology of DS occur through the development. Mushroom-shaped, stubby and short, thin spines in the 30-day-old rat replace spines with long, thin pedicles characteristic of the early developmental stages. Both variability in the density of DS and individual variability with regard to the percentage of the different types of spines on the apical dendrites are observed among neurons in the same animal even in rats 90 days old and in rats aged 6 months.

Animals↗

PubMed1986

Observations on the variability of creatinine excretion.

This paper reports the intra-individual variability of creatinine excretion under conditions of variable food intake and stress. Urine collections over 24 h were made by six subjects for 24 d in the course of an expedition to the Colombian Andes. The average coefficient of variation (CV) of day-to-day creatinine excretion was 11.4 per cent and of N excretion 28 per cent. When the outputs were averaged by 3-d period the mean CV of creatinine excretion was reduced to 5.7 per cent. It is concluded that in metabolic studies the 3-d creatinine excretion is a useful index even when food intakes and other conditions are not controlled.

Altitude Sickness↗

PubMed1983

Human monocyte chemotaxis in vitro. Influence of in vitro variables in the filter assay.

Using a modified Boyden chamber technique, variables in the cell environment were investigated and found to have a profound influence on the monocyte chemotactic responsiveness. The concentration of monocytes, pH of cell suspension, the presence of protein, the concentration and pH of cytotaxins, time allowed for migration and the temperature were all found to be critical factors for the migration response. Optimal concentrations of casein, zymosan-activated serum and N-f-methionyl-leucyl phenylalanine had equal cytotactic potency. The addition of gentamycin decreased the monocyte chemotactic responsiveness, while penicillin had no effect. Under standardized conditions the technical variability was moderate and the intra-individual variability in healthy donors was continuously less than twenty per cent.

Adult↗

PubMed1995

Complex statistical characterization of women's body measurements.

670 young Estonian female students of the Tartu University (aged 18-22 years) were examined anthropometrically (37 body measurements and 10 skinfolds). By means of multidimensional statistical analysis we found that the woman's body as a whole is a linearly well-correlated system. The leading measurements are height and weight, which account for 50% of the variability of all the other measurements, while individual variability makes up 50%. There are no other body measurements besides weight and height that can give a reliable description of the general build of a woman's body. Variations in body height-weight sizes lead to systematic changes in the length, breadth and depth measurements, circumferences and body proportions. Comparative changes of body proportions in the general contingent and in the groups of purely pyknic and leptosomic women are based on the corresponding values of their body height and weight. These findings lead to the conclusion that the anthropological whole body primary model may be a classification of women's body height and weight.

Adolescent↗

PubMed1998

Contribution of thromboxane and endomembrane Ca2+-ATPases to variability in Ca2+ signalling of platelets from healthy volunteers.

Inter-individual variability in Ca2+ signal generation was studied in platelets from 15 healthy volunteers. The possible involvement of variation in thromboxane A production and variation in sarco/endoplasmic reticulum Ca2+-ATPases (SERCAs) was investigated by using platelets isolated before and after intake of 500 mg aspirin, and by measuring the expression levels of two main SERCA isoforms (SERCA-2b and PL/IM 430-recognizable SERCA). Considerable difference in Ca2+ responses were detected after platelet stimulation with thrombin, collagen or the SERCA-2b inhibitor, thapsigargin (TG), with inter-individual coefficients of variance of 22-43% in the absence and 15-41% in the presence of aspirin. Differences in thromboxane A2 generation and SERCA expression contributed to this variability in various ways. In the absence of aspirin, the amount of formed thromboxane A2 partially explains the level of the Ca2+ response induced by TG. On the other hand, in the absence of thromboxane-dependent effects, the expression levels of SERCA-2b and SERCA PL/IM 430 were inversely related to the responses evoked by collagen and TG, respectively. None of these factors were related to the level of the thrombin-evoked Ca2+ signal.

Journal Article↗

PubMed1998

The developmental psychobiology of behavioural plasticity in mice: the role of social experiences in the family unit.

Small perturbations of young animals' sensory experience or hormonal milieu have been shown to alter ontogenetic pathways and to potentially produce huge effects on CNS functioning and behaviour later in life. From a social point of view, variables such as the expression of affiliative bonding and of playful interactions among littermates, the quantity/quality of maternal care, or episodes of maternal or sibling deprivation during critical phases in development, seem to interfere as epigenetic factors with the rigidly ordered temporal sequences of events that occur during the ontogenesis of CNS. This leads to the onset of adaptive neurodevelopmental changes, which are observable within a continuum that encompasses both "normal" individual variability and potential behavioural disorganisation, which in turn will probably be related to profound alteration in the establishment of adult social competence. The present review summarises the more recent work in mice dealing with short-term, as well as long-term modifications, in naturally occurring species-typical social and non-social responses as a function of the early manipulation of social characteristics of the family unit (such as litter gender composition and time of weaning). These analyses were carried out on infant animals, i.e. during the ontogenetic stage of the establishment of social bonding, as well as on pre-pubertal and adult mice and on lactating adult females. Critical issues, such as the respective roles of sibling-sibling and dam-offspring interactions in the shaping of "sibling effects", are also addressed. Overall, these studies indicate that, within their natural range of variation, early patterns of social stimulation are powerful determinants of subsequent behaviour of developing altricial rodents, and confirm that early social life events warrant attention because they can strongly affect neurobehavioural development. Evidence of a relationship between social events occurring during early rearing (i.e. when dramatic transitions in neuroendocrine and neurochemical CNS systems occur) and individual behavioural variability in the infant and adult response to the effects of psychostimulants abused by humans is presented. A better understanding of the mechanisms that mediate such remarkable plasticity might have great psychobiological as well as clinical importance, especially when considering the issue of vulnerability to drug abuse.

Animals↗

PubMed2002

Extensive individual differences in brain activations associated with episodic retrieval are reliable over time.

The localization of brain functions using neuroimaging techniques is commonly dependent on statistical analyses of groups of subjects in order to identify sites of activation, particularly in studies of episodic memory. Exclusive reliance on group analysis may be to the detriment of understanding the true underlying cognitive nature of brain activations. In the present study, we found that the patterns of brain activity associated with episodic retrieval are very distinct for individual subjects from the patterns of brain activity at the group level. These differences go beyond the relatively small variations due to cyctoarchitectonic differences or spatial normalization. We quantify this individual variability by cross-correlating volumes of brain images. We demonstrate that individual patterns of brain activity are reliable over time despite their extensive variability. We suggest that varied but reliable individual patterns of significant brain activity may be indicative of different cognitive strategies used to produce a recognition response. We believe that individual analysis in conjunction with group analysis may be critical to fully understanding the relationship between retrieval processes and underlying brain regions.

Adult↗

PubMed2006

Interpreting disparate responses to cancer therapy: the role of human population genetics.

Increasingly, investigators are recognizing differences in tumor biology, drug metabolism, toxicity, and therapeutic response among different patient populations receiving anticancer agents. These observations provide exciting opportunities to identify the factors most important for predicting individual variability in pharmacologically relevant phenotypes and consequently for personalizing the delivery of cancer therapy. Although pharmacogenomic differences may explain some of these disparities, rigorous investigation of both genetic and nongenetic differences is important to identify the variables most important for optimal selection and dosing of treatment for an individual patient. For example, pharmacogenetic tests currently used in cancer therapy, such as genotyping UGT1A1 to reduce the incidence of severe toxicity of irinotecan and sequencing epidermal growth factor receptor from tumors to identify somatic mutations conferring sensitivity to tyrosine kinase inhibitors, were developed without initial identification of interpopulation differences. Although interpopulation variability in toxicity and efficacy of these agents has been observed, the basis for these population differences remains only partially explained. Here, we review concepts of human population genetics to inform interpretations of disparate drug effects of cancer therapy across patient populations. Understanding these principles will help investigators better design clinical trials to identify the variables most relevant to subsequent individualization of a cancer therapy.

Antineoplastic Agents↗

PubMed1988

Spontaneous variability and circadian distribution of ectopic activity in patients with malignant ventricular arrhythmia.

Day to day variability of ventricular ectopic activity was analyzed in 45 patients with a history of malignant ventricular tachyarrhythmias who underwent two successive 24 h periods of ambulatory electrocardiographic (ECG) monitoring in the absence of antiarrhythmic drugs; 26 were male and 19 female, with a mean age of 56 years (range 15 to 76). The total number of single ventricular premature beats, couplets and ventricular tachycardia beats and runs on days 1 and 2 demonstrated a consistent overall correlation (r = 0.76 to 0.84). Individual variability was evaluated by regression analysis with determination of 95% confidence limits. The minimal decrease in arrhythmia density necessary to distinguish true drug effect from spontaneous variability was 64% for single ventricular premature beats, 83% for couplets, 90% for ventricular tachycardia runs and 93% for ventricular tachycardia beats. To meet the criteria for arrhythmia aggravation, the arrhythmia density had to increase by 400, 877, 1,500 and 2,400%, respectively. Multivariate analysis disclosed an inverse relation between day to day arrhythmia variability and baseline arrhythmia density and age. Variability was more pronounced in patients with coronary artery disease but was not influenced by the type of presenting arrhythmia or left ventricular function. The diurnal distribution of arrhythmias and heart rate followed a distinct circadian pattern. These data indicate that, despite good group reproducibility, spontaneous arrhythmia variability in individuals is substantial, necessitating standards to define both drug effect and arrhythmia aggravation.

Adolescent↗