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PubMed2006

Individual variability in barriers affecting people's decision to take HAART: a qualitative study identifying barriers to being on HAART.

The efficacy of highly active antiretroviral therapy (HAART) has been well documented, particularly among HIV-infected individuals with CD4 cell counts below 200/mm(3). Despite this, eligible individuals may continue to show some reluctance to use HAART. The present study explored the factors influencing patients' decision not to take HAART even though it was medically indicated according to current treatment guidelines and available at no cost to the individual. Fifteen eligible patients at an urban HIV clinic were interviewed regarding the barriers that affected their decision to decline HAART. Most participants had previous experience with antiretroviral therapy and though most believed that HAART was beneficial and felt confident that they could adhere to treatment, they did not feel HAART was the right choice for them at the present time. The Critical Incident Technique was used to identify and classify incidents participants identified as influencing their decision not to take HAART. A total of four categories emerged from the data: Medication Factors, Mood, Lack of Support, and Outcome Expectancies. The results of this study highlight the ambivalence individuals may feel when faced with the prospect of taking HAART. The extent to which each of these factors influenced their decision differed substantially among participants. Suggestions for possible clinical interventions that can be used to address these concerns are offered.

Adult↗
PubMed2004

Individual variability in herbivore-specific elicitors from the plant's perspective.

Lepidopteran larvae oral secretions and regurgitant (R), which contain a plethora of potential elicitors, are known to dramatically change a plant's wound response. We demonstrate, with a detailed microarray and secondary metabolite analysis, that the two most abundant fatty acid-amino acid conjugates (FACs) in the R of the specialist herbivore Manduca sexta (Lepidoptera, Sphingidae) can account for all measured direct (trypsin proteinase inhibitor: TPI) and indirect (cis-alpha-bergamotene) defences, the endogenous jasmonic acid burst that elicits them, and 86% of the induced transcriptional changes (89% up and 83% down) in its native host Nicotiana attenuata and hence are necessary and sufficient for the Manduca-specific modulation of the wound response. FACs were not found in eggs, but detected in larvae of all instars after their first meal. FACs were found in all regions of the alimentary canal and in the frass, but did not occur in salivary or mandibular glands, extracts of which were not active in any assay. Individual larvae differed substantially in their FAC composition and two FAC chemotypes were discernible: N-linolenoyl-L-glutamine biased R and N-linolenoyl-L-glutamate biased R. We created synthetic blends of FACs to mimic these chemical phenotypes and determined whether plants respond differently to the different R chemotypes. Micorarray and TPI analysis revealed that plants do not differentiate. N. attenuata plants use FACs from feeding caterpillars to tailor their wound responses but do not use the variability in FAC ratios to recognize attack from an individual caterpillar.

Animals↗
PubMed1992

Intra-individual variability of caffeine elimination in healthy subjects.

Caffeine is a popular test substance for assessing the activity of hepatic drug metabolizing enzymes in vivo and in vitro. A correct estimation of the relative magnitudes of intra-individual and inter-individual variations in caffeine elimination is significant for the use of the elimination parameter of caffeine to characterize the biotransformation capacity of a specific form of cytochrome P-450 (1AII) in vivo. The purpose of this study is to demonstrate the magnitudes of fluctuation of caffeine-clearance and half-life as well as inter- and intra-individual comparison in 12 healthy male subjects. Compared to the high reproducibility of caffeine decay curves in each healthy male, caffeine elimination varied more extensively between subjects. The distribution of variance amounted to: intra-individual 21.4%, inter-individual 78.6%. The knowledge of variance provided precise evidence of the sample size, which is necessary to prove previously defined differences.

Adult↗
PubMed1983

[Individual variability of the human brain (putamen)].

By means of microscopical cytoarchitectonical methods the borders of the putamen have been established and its volume has been measured in the brain of some persons of various sex and age (21 individuals, 27 hemispheres). The putamen variants are not connected with changes in the brain weight and age. The difference in the volume of the extreme variants is 3.7 times. The distribution of the variants does not contradict the hypothesis on its normality. The data obtained make to revise the principles on the proportional dependence between the external and internal structures of the brain which lie in the base for using stereotaxic atlases at any size of the human brain. An especially real threat for complications at surgical interventions performed in the human brain occurs when the most seldom variants of the putamen are present, since their parameters are not at all taken into consideration in the existing stereotaxic reference Moscow.

Adult↗
PubMed2000

Relationships between muscle morphology and insulin sensitivity are improved after adjustment for intra-individual variability in 70-year-old men.

The purpose of this investigation was to examine to what extent variability in the muscle morphology and insulin sensitivity influence the correlation between them. Reproducibility of muscle characteristics was estimated in duplicate biopsies from the same thigh of 23 subjects from a cohort of 70-year-old men. The coefficient of variation (CV) for different characteristics of muscle morphology was between 11 and 42% in duplicate biopsies. Coefficient of variation for markers of insulin sensitivity ranged between 12 and 39%. The variability reflected by intra-class correlation ranged from 0.23 to 0.60 for muscle morphology and from 0.68 to 0.96 for estimates of insulin sensitivity. The correlation analysis between muscle morphology and insulin resistance was performed in a sample of 515 men from the cohort, correlation coefficients were calculated with (rtrue) and without (r) adjustment for intra-individual variation. Insulin sensitivity showed a positive relationship with percentage of type I fibres (rtrue=0.33, r=0.21; P < 0.0001) and capillary density (rtrue=0.43, r=0.21; P < 0. 0001) and negative correlations with percentage of type IIB fibres (rtrue=-0.35, r=-0.24; P < 0.0001). Capillary density was inversely correlated to insulin. Thus, an obvious improvement of the correlation was seen after correcting intra-individual variation. In conclusion, owing to the low degree of reproducibility of muscle morphology variables and insulin sensitivity, implying a noticeable underestimation of correlations, the r-values should be adjusted for within-subject variation in order to demonstrate a more accurate estimate of the strength of the relationships studied.

Aged↗
PubMed1989

Individual variability of amiodarone distribution in plasma and erythrocytes: implications for therapeutic monitoring.

The complexity of amiodarone disposition in blood and tissues gives rise to difficulty in determination of optimal therapeutic monitoring strategies. We have defined the within-patient variability of plasma and erythrocyte amiodarone and desethylamiodarone concentrations and electrocardiogram intervals [PR and corrected QT (QTc)] in 27 patients each sampled on three to four occasions during long-term stable amiodarone therapy. All individual repeated measurements were included in the concentration-effect analysis. The mean within-patient coefficients of variation for amiodarone and desethylamiodarone were significantly greater in erythrocytes, 46.0 and 24.5%, respectively, compared with plasma, 12.7 and 12.3%. Amiodarone and desethylamiodarone were significantly greater in erythrocytes, 46.0 and 24.5%, respectively, compared with plasma, 12.7 and 12.3%. Amiodarone and desethylamiodarone were strongly correlated (r = 0.29 p less than 0.004). There was a 10-fold variability in erythrocyte amiodarone for a given plasma level. These data emphasize the highly variable cellular distribution of amiodarone and desethylamiodarone in the same patient on stable dosage over time. Plasma amiodarone was significantly correlated with dosage (r = 0.98), and percent change in QTc, (r = 0.56, p less than 0.0001), but there was a fourfold variation in plasma amiodarone for a given QTc. Side-effect frequency was not related to plasma or erythrocyte amiodarone or desethylamiodarone concentrations. A clinically useful relationship between plasma concentration and effect could not be consistently demonstrated for amiodarone in the same individual during stable dosage.

Adult↗
PubMed1990

Individual variability in cortical organization: its relationship to brain laterality and implications to function.

The human brain and the brains of most mammals studied for this purpose demonstrate hemispheric asymmetry of gross anatomical landmarks and/or architectonic cortical subdivisions. The magnitude as well as the direction of these cortical asymmetries vary among individuals, and in some species there exist significant population directional biases. The magnitude, if not the direction, of cortical asymmetry is found to predict for relative numbers of neurons comprising a given pair of hemispheric architectonic homologues such that the more asymmetric the region is, the smaller the number of neurons. Similarly, the more asymmetric a region is, the smaller the density of interhemispheric connections and (probably) the greater the density of intrahemispheric connections. Developmentally, the decrease in the number of neurons characterizing the more asymmetrical regions appears to reflect mainly increased unilateral ontogenetic cell loss, and diminished callosal connectivity might signify increased developmental axonal pruning. These relationships between cell numbers, callosal connections, and presumed intrahemispheric relationships can be entertained to explain variability in anatomo-clinical correlations for language function and aphasia between left- and right-handers and men and women.

Animals↗
PubMed1976

[Individual variability in human requirements for food stuffs and energy and nutritional norms].

The regular modifications in man's need of energy and protein substances primarily under the effect of a variety of factors are investigated. Emphasis is laid on the broad limits of individual variations in terms of alimentary requirements of people, and on a number of facts suggesting that in some ses the regularity of variations is by no means clarified. The problem of the minimum energy expenditure required by the organism is dealt with, underscoring the role played in this respect by basic metabolism values, and by the maximum energetic potential. The problem of the influence of deficient feeding and immobilization on man's need of alimentary substances is also discussed, as well as the issue of optimal protein balance level in the organism, considered as a level securing to the organism the optimal possibilities of metabolic adaptation to external milieu effects.

Adult↗
PubMed1998

[Precise DNA cytometry: investigation of individual variability in animal genome size].

The variability of genome size was studied in animal populations and in cell populations of different animal species by means of DNA flow cytometry with the precision level of several tenths of percent. For populations of frog Rana esculenta and laboratory mouse lines C57B1 and CBA the analysis was made with cells of different tissues: erythrocytes for R. esculenta, splenocytes for mice and haploid cells of testes for both species. The results of DNA cytometry, obtained with cells of different species, were shown to be correlated, which indicates the objectivity of individual intrapopulation differences in the genome size recorded with DNA flow cytometry. The level of variability (expressed as CV) was 0.3-0.4% for the population of frogs, and 0.2-0.3% for mouse lines. The analysis of genome size variability in cell populations of different animal species revealed a relationship between the variability level and the genome size: the coefficient of variance of the peak of DNA histogram was inversely related to the square root of genome size. The latter effect may be explained by fluctuations of a measured multicomponent object, but it is still unclear whether these fluctuations could be related to the genome size or to pecularities of chromatin structure. It is concluded that the method of flow DNA cytometry may be effective for studying individual differences in the genome size.

Animals↗
PubMedDate not supplied

Individual variability in Tyr-Gly-Gly formation from enkephalin hydrolysis in mouse plasma.

We examined the effects of captopril (an angiotensin-converting enzyme inhibitor) and phosphoramidon (a selective enkephalinase inhibitor) on Tyr-Gly-Gly production during Met-enkephalin hydrolysis in plasma samples taken from individual outbred Swiss-Webster and inbred C57BL/6J and DBA/2J mice. Discriminant analysis procedures identified three distinct plasma profiles of Tyr-Gly-Gly production in all strains of mice: a captopril-sensitive/phosphoramidon-insensitive profile, a captopril-insensitive/phosphoramidon-sensitive profile, and a moderate captopril and phosphoramidon sensitivity profile. The abilities of captopril and phosphoramidon to inhibit Tyr-Gly-Gly production in the same mouse plasma sample were highly inversely correlated (r = -0.938). Plasma of Swiss-Webster mice whose cages and bedding had been changed 24 h prior to sample collection was significantly more likely to exhibit the captopril-sensitive/phosphoramidon-insensitive profile than the plasma of mice whose cages/bedding had not been changed for at least 5 days. The results suggest that environmental novelty may dramatically alter the activity of a plasma dipeptidyl carboxypeptidase system, and thereby regulate behavioral and physiological responses to novel experiences.

Amino Acid Sequence↗
PubMed1985

Intra-individual variability in postural blood pressure in the elderly.

Orthostatic hypotension, an age-related phenomenon, has been associated with hypertension and body weight variability. To evaluate the relative contributions of blood pressure elevation and abnormalities in extracellular volume regulation to orthostatic hypotension, elderly institutionalized subjects (mean age = 87 +/- 7 years), taking no cardiovascular medications, underwent measurement of body weight (n = 15) and first morning supine and standing blood pressures (n = 19), 12-13 times per subject over a 2-4 week period. There was a wide day-to-day variability in postural systolic blood pressure change (coefficient of variation = 533%) and a strong negative correlation between each day's postural change in systolic blood pressure and basal supine blood pressure (r = -0.55, P less than 0.0001). There was no association between postural blood pressure change and heart rate response or body weight changes, which were very small over the duration of the study (coefficient of variation = 0.6%). Elderly individuals have intact homeostatic mechanisms for the control of standing pressure when basal blood pressure is normal. Postural hypotension in the elderly is a variable phenomenon related to elevations in basal blood pressure.

Age Factors↗
PubMed1981

[Individual variability of associations between acrocentrics (author's transl)].

We studied the quantitative and qualitative variation of associations between acrocentric chromosomes in four subjects on a period of ten months; results show a definite tendency of association in a same subject, tendency which is reproducible and clear. Even though each individual has a determined rate of associations, the number of associated chromosomes and the number of associations themselves do not vary with months. Furthermore, associations do not appear at random; indeed, they have a wide spectrum of variations from one subject to the other but if we take the subjects individually, their associative rate concerning each chromosome do not change with months. Therefore, the phenomenon of association could be viewed as a biological characteristic of each individual.

Adult↗
PubMed2003

Chromosomal radiosensitivity: a study of the chromosomal G(2) assay in human blood lymphocytes indicating significant inter-individual variability.

The G(2) chromosomal radiosensitivity assay is a technically demanding assay. To ensure that it is reproducible in our laboratory, we have examined the effects of storage and culture conditions by applying the assay to a group of healthy controls and determined the extent of intra- and inter-individual variations. Nineteen different individuals provided one or more blood samples resulting in a total of 57 successful tests. Multiple cultures from a single blood sample showed no statistically significant difference in the number of chromatid type aberrations between cultures. A 24h delay prior to culturing the lymphocytes did not significantly affect the induced G(2) score. Intra-individual variation was not statistically significant in seven out of nine individuals. Inter-individual variation was highly statistically significant (P<0.001), indicating that there is a real difference between individuals in the response to radiation using this assay.

Adult↗
PubMedDate not supplied

Effects of clinical and individual variables on quality of life in chronic renal failure patients.

BACKGROUND: The purpose of this study was to assess the effects of baseline characteristics of patients, chronic renal failure and its treatment on quality of life. METHODS: To investigate the health status we used a questionnaire, the SF-36, during individual interviews. The study involved i) a cross-sectional observational stage, lasting from 1 Sept. 1997 to 30 April 1999, on all the patients undergoing conservative treatment, hemodialysis, peritoneal dialysis and kidney transplantation in district of Ravenna, and ii) a longitudinal stage, when the subjects were administered two questionnaires at an interval of at least 16 months. The quality of life data collected during the cross-sectional stage were analyzed to establish any correlations between age, type of treatment of chronic renal failure and hemoglobin levels. Patients under dialysis were also examined for any interference caused by the center where dialysis was done. RESULTS: Multivariate analysis on the data collected during the cross-sectional stage showed that chronic renal failure treatment and age affected the quality of life scores for the following parameters: physical activity, bodily pain, general health and vitality (age was inversely related to the scores). Transplanted patients and those on conservative treatment enjoyed the best overall quality of life, followed by those on peritoneal dialysis and those on hemodialysis. The physical domain scores were strongly associated with age, hemoglobin and diabetes. Multivariate analysis of the longitudinal study indicated that the interval between the beginning and the end of the observation period, age and diabetes greatly influenced quality of life. CONCLUSIONS: The data confirmed that age and diabetes have a strong influence on the quality of life and that the long period of treatment, with the absence of any prospect of resolving the clinical situation, has a negative effect on the quality of life in uremic patients.

Aged↗
PubMedDate not supplied

Inter-individual variability in blood/air partitioning of volatile organic compounds and correlation with blood chemistry.

In vitro blood/air partition coefficients (KB/A) for acetone, 1,1,1-trichloroethane, toluene, and styrene were measured in blood samples from 73 human subjects and correlated with blood chemistry parameters (hematocrit, total cholesterol, serum triglycerides, serum albumin, total plasma proteins, Na+, K+, Cl-, and HCO3-). Statistically significant inter-individual variation existed in KB/A between some subjects. Substitution of group or generic in vitro KB/A values for values determined in some individuals could introduce errors of up to 50%. However, most subjects could be well represented by group averages (mean +/- SD; acetone, 301 +/- 22; 1,1,1-trichloroethane, 6.0 +/- 0.8; toluene, 19 +/- 3; styrene, 62 +/- 10). The KB/A values for acetone, 1,1,1-trichloroethane and toluene were normally distributed. The data for styrene appeared to deviate from a normal distribution and may have been bimodal. The KB/A values for the two structurally related compounds, toluene and styrene, were strongly correlated within individuals, while the KB/A values for compounds with less structural similarity, such as acetone and styrene, were poorly correlated. At most, 15% of the variation in KB/A among individuals could be explained by variation in the measured blood chemistry parameters. When the entire sample group was considered, blood chemistry parameters were not significantly correlated with KB/A for any compound. The KB/A of 1,1,1-trichloroethane was significantly correlated with the concentration of cholesterol and triglycerides in females. Sex was a significant grouping variable for the correlation of albumin concentration with the KB/A of styrene. Age was not a significant correlation variable. Blood chemistry parameters which previously have been correlated with KB/A in small sample groups do not appear to be significantly correlated in our larger sample group.

Acetone↗
PubMed2000

Five-year intra-individual variability in C-reactive protein levels in a Japanese population-based study: the Jichi Medical School Cohort Study at Yamato, 1993-1998.

C-reactive protein (CRP) is an acute-phase reactant that is related to future cardiovascular events. However, little is known about the long-term intra-individual stability of CRP in community residents. The 5-year intra-individual correlation of CRP levels was examined in the Jichi Medical School Cohort Study in Japan. CRP measurements were obtained in 1993 and in 1998 from 388 presumptively healthy individuals aged 30-69 years at baseline. The Pearson's correlation coefficient of CRP between baseline and follow-up measurements was 0.43 (95% confidence interval (CI): 0.34-0.51). Additional analyses by sex and smoking status at baseline revealed similar coefficients. The correlation coefficient of CRP was lower than that of other classical risk factors, such as body-mass index (BMI), blood pressure, and total and high-density lipoprotein (HDL) cholesterol. A subgroup of individuals with higher levels of CRP at both baseline and follow-up measurements had higher BMI, hemoglobin Alc, and plasma fibrinogen, and lower levels of HDL-cholesterol than others, even after adjusting for age, sex, and smoking status in a multiple logistic model. In conclusion, the stability of CRP levels was statistically significant in a long-term population-based study. A subgroup with higher levels of CRP who had an aggregation of cardiovascular risk factors was identified by the 2 measurements.

Adult↗
PubMed1989

Individual variability in the blood pressure response to intravenous phenylpropanolamine: a pharmacokinetic and pharmacodynamic investigation.

The intersubject variability in blood pressure response to 0.44 mg/kg intravenous phenylpropanolamine (d,l-norephedrine) was studied in 10 normal subjects. A phenylpropanolamine or placebo infusion was administered over 45 minutes on separate days according to a double-blind, balanced protocol. Blood pressure increased by 24 +/- 13/16 +/- 7 mm Hg (systolic/diastolic, mean +/- SD) after the phenylpropanolamine infusion and was statistically different from the placebo infusion response (7 +/- 5/8 +/- 3 mm Hg). Phenylpropanolamine infusions were terminated early in two subjects (hyperresponders) after 0.31 and 0.23 mg/kg because of excessive increases in blood pressure (52/30 and 34/21 mm Hg, respectively). The hyperresponders had the lowest peak serum phenylpropanolamine concentrations. These data suggest that considerable intersubject variability exists in the blood pressure response to intravenous phenylpropanolamine. A pharmacokinetic basis for the variability in response to racemic phenylpropanolamine was not observed. A relationship did not exist within the group between blood pressure effect and serum concentration but did exist within each subject. Therefore phenylpropanolamine's blood pressure effect in an individual cannot be predicted solely from a serum concentration of racemic drug.

Adult↗