A comprehensive review of predictive and prognostic composite factors implicated in the heterogeneity of treatment response and outcome across disease areas.

AIM: To assess and present the current body of evidence regarding composite measures associated with differential treatment response or outcome as a result of patient heterogeneity and to evaluate their consistency across disease areas. METHODS: A comprehensive review of the literature from the last 10 years was performed using three databases (PubMed, Embase and Cochrane). All articles that met the inclusion/exclusion criteria were selected, abstracted and assessed using the NICE level-of-evidence criteria. RESULTS: Forty-nine studies were identified in the data abstraction. Approximately one-third focused on existing composite measures, and the rest investigated emerging composite factors. The majority of studies targeted patients with cancer, cardiovascular disease or psychological disorders. As a whole, the composite measures were found to be disease-specific, but some composite elements, including age, gender, comorbidities and health status, showed consistency across disease areas. To complement these findings, common individual factors found in five previous independent disease-specific literature assessments were also summarised, including age, gender, treatment adherence and satisfaction, healthcare resource utilisation and health status. CONCLUSIONS: Composite measures can play an important role in characterising heterogeneity of treatment response and outcome in patients suffering from various medical conditions. These measures can help clinicians to better distinguish between patients with high likelihood to respond well to treatment and patients with minimal chances of positive therapeutic outcomes. Herein, the individual factors identified can be used to develop novel predictive or prognostic composite measures that can be applicable across disease areas. Reflecting these cross-disease measures in clinical and public health decisions has the distinctive appeal to enable targeted treatment for patients suffering from multiple medical conditions, which may ultimately yield significant gains in individual outcomes, population health and cost-effective resource allocation.

A review of treatment response in type 2 diabetes: assessing the role of patient heterogeneity.

The response to treatment for type 2 diabetes typically varies among individuals within a study population. This variation is known as heterogeneity of treatment response. We conducted a comprehensive literature review to identify factors that account for heterogeneity of treatment response in patients treated for type 2 diabetes. Three databases (PubMed, EMBASE and Cochrane Library) were searched for articles published in the last 10 years describing investigations of factors associated with treatment response and outcomes among people with type 2 diabetes receiving pharmacological treatment. Of the 43 articles extracted and summarized, 35 (81%) discussed clinical factors, 31 (72%) described sociodemographic factors and 17 (40%) reported on comorbidity or behavioural factors. Clinical factors identified included baseline glycated hemoglobin A1c or fasting plasma glucose (FPG) levels, insulin response or sensitivity, C-peptide, body composition, adipose tissue proteins, lipid profile, plasma albumin levels and duration of disease or insulin treatment. Other factors identified included age, sex, race, socioeconomic status and comorbidities. This review identified the following research gaps: use of multiple definitions for response, few patient-reported measures and lack of evidence regarding whether factors were associated with treatment response for only specific medications or across pharmacological therapies. Furthermore, identification of factors associated with type 2 diabetes treatment response was generally a secondary objective in the research reviewed. Understanding which patient subgroups are more likely to respond to treatment and identifying factors associated with response may result in targeted treatment decisions and alter the interpretation of efficacy or effectiveness of results. In conclusion, accounting for these factors in clinical trials and when making clinical treatment decisions may improve therapy selection and individual patient outcomes.

Work impairment in bipolar disorder patients--results from a two-year observational study (EMBLEM).

OBJECTIVES: To explore factors associated with work impairment at 2 years following an acute episode. METHODS: European Mania in Bipolar disorder Longitudinal Evaluation of Medication (EMBLEM) is a prospective, observational study on the outcomes of patients with a manic/mixed episode. Work impairment was measured using a Longitudinal Interval Follow-up Evaluation (slice of LIFE) item and patients were categorised with either low or high work impairment at each observation. Baseline factors associated with work impairment at 2 years were assessed using multivariate modelling. RESULTS: At baseline (n=2289), 69% of patients had high work impairment. At 2 years (n=1393), high impairment reduced to 41%. Modelling identified rapid cycling as the strongest disease-related factor associated with high work impairment at 2 years, although high work impairment at baseline had the strongest association overall. Lower levels of education, recent admissions, CGI-BP overall severity in the 12 months prior to baseline and CGI-BP mania at baseline all predicted higher work impairment. Living together in a relationship and independent housing were both significantly associated with having low work impairment at 2 years. CONCLUSIONS: Work impairment in bipolar disorder is maintained over long periods, and is strongly associated with relationship status, living conditions and various disease-related factors.

Functional impairment in patients with mania: baseline results of the EMBLEM study.

OBJECTIVES: The European Mania in Bipolar Longitudinal Evaluation of Medication (EMBLEM) is a large-scale prospective observational multicentre study to evaluate the longitudinal course of bipolar disorder and its associations with pharmacological treatment following an acute manic or mixed episode. We present an overview of the study design and patient characteristics at baseline while focusing on factors influencing work performance in the year prior to enrollment. METHODS: A total of 530 investigators across 14 European countries enrolled 3,681 patients with acute mania between December 2002 and June 2004. Longitudinal observations are ongoing until July 2006. Socio-demographic variables, psychiatric history, clinical status and information on pharmacological treatment for bipolar disorder were recorded. Items from the SLICE of LIFE were applied, including a measure of work impairment during the previous year. The distribution of the baseline characteristics was analysed with descriptive statistics. Eighteen variables were investigated as hypothesized risk factors for work impairment applying logistic regression models. RESULTS: In the previous year, 28 and 68% of patients were classified as having 'low' and 'high' work impairment, respectively. Clinical Global Impression - Bipolar Disorder (CGI-BP) overall, CGI-BP depression at baseline, rapid cycling during the previous 12 months, age between 35 and 64 years, substance abuse other than alcohol and cannabis and living without a partner or as dependent household member were significantly associated with work impairment during the previous year. CONCLUSIONS: EMBLEM is to our knowledge the largest prospective observational study assessing patients during and after an acute episode of mania. Work impairment is significant in the year prior to an acute episode of mania.

Evidence for three distinct classes of 'typical', 'psychotic' and 'dual' mania: results from the EMBLEM study.

OBJECTIVE: To describe patients included in the European Mania in Bipolar Longitudinal Evaluation of Medication (EMBLEM) study and to assess and clinically validate the presence of clinical subtypes of patients with acute mania. METHOD: The EMBLEM study is a 2-year prospective, observational study on the treatment and outcome of patients who are treated for a manic or mixed episode. Latent Class Analysis was used to define discrete groups of patients at baseline. RESULTS: Three groups were identified: 'typical mania' (59% of patients); 'psychotic mania' (27%) with more severe mania and presence of psychotic symptoms; and 'dual mania' (13%) with a high proportion of substance abuse. Patient groups differed in age of onset, social functioning and service needs. CONCLUSION: Dual mania represents a distinct and not infrequent subgroup of patients with mania. The exclusion of patients with comorbid substance problems from clinical trials creates a gap in our knowledge on treatment effectiveness.

Assessment of tidal breathing parameters in infants with cystic fibrosis.

Simple methods are needed to assess lung function in infants with cystic fibrosis (CF). This study determined the relationship between simple measurements obtained from tidal breathing with those from more complicated forced expiratory manoeuvres. Healthy infants and infants with CF were recruited from two maternity units and five specialist CF hospitals, respectively. Respiratory rate, tidal volume, minute ventilation and the tidal breathing ratio (TPTEF:TE) were measured in sedated infants and compared with forced expiratory volume in 0.4 seconds (FEV0.4) measured by the raised volume technique. Altogether, 95 healthy infants and 47 infants with CF of similar age, sex, ethnicity and proportion exposed to maternal smoking were recruited. There was no difference in TPTEF:TE and tidal volume between healthy infants and those with CF. Minute ventilation was significantly greater in infants with CF due to a mean (95% confidence interval) increase in respiratory rate of 5.8 (3.2-8.4) min(-1). Thirteen (28%) infants with CF had a respiratory rate elevated by >2 SD. However, no association between respiratory rate and FEV0.4 could be identified. Tidal breathing ratio was not useful in identifying diminished airway function in infants with cystic fibrosis. An elevated respiratory rate may be due in part to ventilation heterogeneity but is poorly predictive of diminished airway function measured by forced expiration.

Exploring the relationship between forced maximal flow at functional residual capacity and parameters of forced expiration from raised lung volume in healthy infants.

The raised volume rapid thoraco-abdominal compression technique (RVRTC) is being increasingly used to assess airway function in infants, but as yet no consensus exists regarding the equipment, methods, or analysis of recorded data. The aim of this study was to explore the relationship between maximal flow at functional residual capacity (V'(maxFRC)) and parameters derived from raised lung volumes, and to address analytical aspects of the latter technique in an attempt to assist with future standardization initiatives. Forced vital capacity (FVC) from lung volume raised to 3 kPa, timed forced expiratory volumes (FEV(t)), and forced expiratory flow parameters at different percentages of expired FVC (FEF(%)) were measured in 98 healthy infants (1-69 weeks of age). V'(maxFRC) using the tidal rapid thoraco-abdominal compression (RTC) technique was also measured. The within-subject relationships and within-subject variability of the various parameters were assessed. Duration of forced expiration was < 0.5 sec in 5 infants, meaning that FEV(0.3) and FEV(0.4) were the only timed volume parameters that could be calculated in all infants during the first months of life, and even when it could be calculated, FEV(0.5) approached FVC in many of these infants. It is recommended that FEV(0.4) be routinely reported in infants less than 3 months of age. Contrary to previous reports, within subject variability of V'(maxFRC) was less than that of FEF(75) (mean CV = 6.3% and 8.9%, respectively).A more standardized protocol when analyzing data from the RVRTC would facilitate comparisons of results between centers in the future.

The association between birthweight, sex, and airway function in infants of nonsmoking mothers.

The risk of respiratory illness and death is increased in infants of low birthweight for gestational age, but the underlying physiologic mechanisms remain unclear. We examined the hypothesis that airway function is diminished in infants of low birthweight for gestational age, independent of exposure to maternal smoking. Respiratory function was measured using partial and raised volume forced expiratory maneuvers in 103 infants (> 35 wk gestation; 56 boys) not exposed pre- or postnatally to maternal smoking who, according to birthweight, were either small (SGA; n = 38) or appropriate (AGA; n = 65) for gestational age. At testing, SGA infants were of similar postnatal age (mean [SD]: SGA 6.8 [2.4] wk, AGA 5.9 [2.3] wk), but remained shorter and lighter than AGA infants. In univariate analyses, FVC, forced expired volume in 0.4 s (FEV(0.4)), and FEF(75) were significantly diminished in SGA compared with AGA infants (mean [95% CI of difference]: FVC: 127 versus 143 ml [-29, -2]; FEV(0.4): 112 versus 125 ml [-24, -2]; and FEF(75): 173 versus 203 ml s(-1) [-57, -3], respectively), but these differences were no longer significant after allowing for sex and body size. Furthermore, FEF(75) was on average 35 ml s(-1) lower in boys than girls (95% CI: -61, -8). We conclude that diminished airway function in SGA infants shortly after birth appears to be primarily mediated through impaired somatic growth.

Assessment of passive respiratory mechanics in infants: double versus single occlusion?

The single breath or occlusion technique (SOT) is widely used to assess passive respiratory mechanics in infants, but depends on various underlying assumptions. Recently, it has been proposed that such measurements could be internally validated by performing two brief airway occlusions during the same expiration. The aim of this study was to evaluate the use of the double occlusion technique (DOT) using a new commercially available program (Jaeger MasterScreen BabyBody Erich Jaeger GmbH, Würzburg, Germany). Paired measurements of respiratory system compliance (Crs) and resistance (Rrs) using both SOT and DOT were obtained in 18 healthy sedated infants (age range 4-41 weeks, weight 2.7-9.9 kg). There was close agreement between both methods of assessing Crs in all infants, the mean within-subject difference (95% confidence interval (CI)) for DOT-SOT being -0.06 (-0.55- +0.42) mL x kPa(-1) x kg(-1). By contrast, estimates of Rrs,DO were on average 20% lower than those for Rrs,SO, (mean within-subject difference (95% CI) being -0.67 (-1.04- -0.31) kPa x L(-1) x s; p<0.01). The relatively lower values obtained for Rrs,DO may reflect the higher mean lung volume at which it was calculated. Further work is required to investigate the clinical and epidemiological relevance of this new approach, and whether there are any advantages of using both techniques when assessing passive mechanics in infants.

Passive respiratory mechanics: the occlusion techniques.

The aim of this position paper is to define quality control and acceptance criteria for measuring passive respiratory mechanics in infants using the occlusion techniques to ensure that valid results are obtained. These guidelines cover numerous aspects including: 1) terminology and definitions; 2) equipment; 3) data acquisition; 4) data handling and analysis; 5) reporting of results. Adherence to these guidelines should ensure that measurement of passive respiratory mechanics in infants in different lung function laboratories could be performed with an acceptable degree of safety, precision, and reproducibility. This will facilitate multi-centre collection of data and performance of clinical investigations.

Influence of jacket placement on respiratory compliance during raised lung volume measurements in infants.

SUMMARY. Recent introduction of the raised lung volume rapid thoraco-abdominal compression (RVRTC) technique for measuring forced expiratory maneuvers in infants provides the potential opportunity to assess respiratory mechanics simultaneously by using multiple linear regression (MLR) of the relaxed breaths preceding jacket inflation to force expiration. This study was undertaken to investigate whether data obtained from raised lung volume are influenced by placement of the rapid thoraco-abdominal compression (RTC) squeeze jacket. Paired measurements of tidal volume (V(T)) and respiratory rate (RR) during tidal breathing, and of inflation volume (V(inf)), respiratory system compliance (C(rs)), and resistance (R(rs)) during passive lung inflations were made in 60 (30 male) healthy term infants with and without a fastened, but uninflated RTC jacket in place. Jacket placement was associated with a significant reduction (P < 0.0001) in weight-corrected V(inf) [-1.86 (95% confidence interval, -2.46, -1.27) mL.kg(-1)] and C(rs) [-0.77 (-1.04, -0.49) mL.kPa(-1).kg(-1)]. This represented a reduction in weight-corrected C(rs) from 9.00 to 8.24 mL.kPa(-1).kg(-1), with the fall being >10% in 42% of infants studied. There was no significant change in R(rs) or weight-corrected V(T). If passive respiratory mechanics are to be measured during raised lung volume maneuvers, they should be performed prior to the jacket being fastened, unless considerable care is taken with each infant to ensure that the jacket does not restrict chest wall movement during maximum inflation.

Serine esterase (BLT-esterase) activity in murine splenocytes is increased with exercise but not training.

The effect of a treadmill exercise bout (30 m/min, 4 degrees slope, 30 min) or 9 weeks of training (18 m/min, 0 degrees slope, 45 min/day, 5 x/week) on splenic natural killer cell activity (NKCA) and BLT-esterase activity was studied in adult C3/He male mice. These immune parameters were assessed in mice who had been injected i.p. 24 h before sacrifice with saline or poly I:C, an interferon inducer and activator of killer cells in vivo. Acutely exercised mice pretreated with saline had an increase in NKCA and BLT-esterase activity 5 minutes after cessation of exercise relative to values at rest. The frequency of asialo GM1 positive splenocytes did not differ in the saline injected, acutely exercised mice compared to values obtained before exercise. Animals pretreated with poly I:C did not differ in their NKCA or BLT-esterase activity as a function of time. Trained mice injected with saline had a significant increase in the in vitro splenic NKCA and in the frequency of splenocytes positive for asialo GM1 compared with sedentary controls. However, BLT-esterase activities did not differ by training status. Pretreatment with poly I:C augmented NKCA in all groups of mice and abolished the significant effects observed with acute exercise or training on fresh natural killer cells. These results indicate that the increase in splenic natural killer cell activity immediately after acute exercise is accompanied by an increase in the activity of the granule lytic enzyme, BLT-esterase, presumably involved in delivery of the 'lethal hit'.(ABSTRACT TRUNCATED AT 250 WORDS)

Status of allogeneic bone marrow transplantation in childhood in the GDR.

Of 25 HLA-identical, MLC negative transplants 10 patients had acute lymphoblastic leukaemia (ALL), 8 acute nonlymphoblastic leukaemia (ANLL), 3 severe aplastic anaemia, 2 malignant histiocytosis, 1 patients neuroblastoma and 1 Fanconi anaemia. 3 HLA nonidentical, MLC positive transplants were performed, two children had malignant infantile osteopetrosis and 1 child had a severe combined immunodeficiency disease. Patients with ALL and ANLL received cyclophosphamide and single dose total body irradiation. 3 patients received fractionated TBI. The results for the allogeneic group overall indicate that the actuarial disease free survival rate is 0.62. 16 of 25 patients are in continuous complete remission (CCR) periods of 3-78 months posttransplant. All three transplanted children with severe aplastic anaemia alive disease-free for periods of 21-81 months. 10 patients with ALL were transplanted (2 in first remission for high risk ALL, 8 in second remission). 7 of 10 patients are alive and disease-free (CCR rate 0.67). 8 patients underwent BMT for ANNL while in first remission in 7 patients and in third partial remission in 1 patient. 4 of 8 patients are alive and disease-free for periods of 25-56 months (CCR rate 0.50). 1 patient with neuroblastoma stage IV survives 24 months, 1 child with Fanconi anemia died on day +25 of GVHD and septicaemia. 1 of the 2 patients transplanted for malignant histiocytosis relapsed 3 months posttransplant, 1 patient is alive and disease-free 5 months posttransplant. In none of the HLA-nonidentical and MLC positive transplantations T-cell depleted marrow engrafted.

Transplantation of major AB0-incompatible bone marrow: removal of red cells by dextrane sedimentation.

The elimination of erythrocytes by dextran sedimentation is a useful method to prevent haemolytic complications after AB0-incompatible bone marrow transplantation. The procedure presented here lasts only 1.5-2 hours, is high reproducible and safe in respect of infections. The mean recovery of nucleated cells amounted to 94%. The contamination with erythrocytes is low (recovery 1.1%). We have never seen haemolytic reactions during 7 AB0-incompatible bone marrow transplantations.

Triethanolamine, tris, hepes, and cytosine arabinoside show neuritogenic activity in cultured chick embryo ganglia.

Neuritogenesis, which occurs to a slight extent in chick embryo ganglia maintained under standard conditions and which is maximally stimulated by nerve growth factor, also was enhanced by presence in the medium of buffers (triethanolamine, Tris, and Hepes) and cytosine arabinoside and by the passage of direct electric current. The major effect of the buffers probably was to remove protons from cell membranes, that of the current to produce accelerated movement of ions through membranes of the ganglionic cells, and that of cytosine arabinoside to decrease the numbers of nonneural cells by inhibiting DNA synthesis. The buffers were neuritogenically ineffective on nerve growth factor-sensitive PC12 pheochromocytoma cells in culture. Media from ganglia in which triethanolamine or passage of electric current had elicited outgrowth of neurites produced no observable effect on PC12 cells under our experimental conditions. Current data fit the hypothesis that, whereas nerve growth factor exerts direct neuritogenic effects on neurons, the other treatments affect neural-nonneural interactions, possibly by way of gap junctions or changes in direct physical contact, so as to disinhibit inherent neural neuritogenic potential and/or to stimulate it.

Long-term serial cultivation of arterial and capillary endothelium from adult bovine brain.

Cerebrovascular endothelial cells from adult bovine brain were carried successfully in long-term, serial culture. Endothelial cells were obtained from the middle and anterior cerebral arteries and from capillaries isolated from grey matter of the cerebral cortex or caudate nucleus. Capillary cells were found to grow best in RPMI 1640 with 20% fetal bovine serum. They did not require tumor-conditioned medium or matrix-coated surfaces, although fibronectin was used to enhance the initial plating efficiency of the primary cultures. The same conditions were used to support satisfactory growth of arterial endothelial cells; however they did not grow as rapidly as the cells. Retention of endothelial-specific characteristics were shown for capillary-derived cells carried up to Passage 28, arterial-derived cells up to Passage 11, and after frozen storage of both types of cultured cells. Cultures of both arterial and capillary cells stained positively for Factor VIII antigen, exhibited a nonthrombogenic surface, and produced prostacyclin in response to arachidonic acid. Arterial endothelial cells produced more prostacyclin than capillary endothelium. The capillary cells had a unique tendency to assume a ringlike morphology after subculture and sometimes formed capillarylike networks of cell cords in dense cultures. When cultured in a three-dimensional plasma clot, capillary and arterial endothelial cells, but none of the other cell types studied, organized into tubelike structures reminiscent of capillary formation in vivo. The availability of long-term cultures of cerebrovascular endothelial cells provides an opportunity to compare properties of arterial and capillary endothelium from the same tissue and to investigate such processes as angiogenesis and blood-brain barrier induction.

Membrane anomalies in Huntington's disease fibroblasts.

Plasma membranes, microsomes, and mitochondria were isolated from paired, passage number matched, cultured human fibroblasts. The cells were obtained from skin biopsies of Huntington's disease (HD) subjects and from sex and age matched controls. All fibroblasts were cultured in identical media for three to seven passages. Enrichment of surface marker enzymes such as Na+,K+-ATPase indicated a 10-fold purification of the isolated plasma membrane. The specific activity of Na+,K+-ATPase was 62 and 82% greater in the crude homogenate and isolated plasma membrane, respectively, of HD fibroblasts than in control fibroblasts. The specific activity of plasma membrane Na+,K+-ATPase was correlated with lipid composition and with membrane structure as determined by measurement of the rotational relaxation time and limiting anisotropy of fluorescence probe molecules. Major alterations in the structure of the plasma membranes in HD fibroblasts were not noted. The rotational relaxation time and limiting anisotropy of 1,6-diphenyl-1,3,5-hexatriene and of trans-parinaric acid were not significantly different between the plasma membrane, microsomes, or mitochondria of HD versus those of control fibroblasts. trans-Parinaric acid demonstrated the coexistence of fluid and solid domains in all three subcellular membrane fractions of the normal and HD skin fibroblasts. Lastly, both trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene displayed characteristic breakpoints in Arrhenius plots of absorbance corrected fluorescence in plasma membranes, microsomes, and mitochondria. In all cases, similar breakpoint temperatures, indicative of phase alterations, were noted near 20 degrees and 30 degrees C. These breakpoints were unaltered in HD. In summary, the data do not support the concept of major membrane structural defects in HD.

Sex and age alter plasma membranes of cultured fibroblasts.

Human skin fibroblasts were taken from age-matched male and female subjects. The cells were then cultured under identical conditions and passage-number matched. Plasma membranes were isolated and membrane enzyme activities, lipid composition, and structure of isolated plasma membranes were measured in order to determine the presence of significant sex differences in human fibroblast membrane properties. The results indicated that plasma membranes from normal female subjects had a 1.6-fold and 3.6-fold higher cholesterol/phospholipid ratio and oleic acid (18:2) content than normal male subjects. The limiting anisotropy and the rotational relaxation time of fluorescence probe molecules such as trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene in the plasma membranes was not significantly different from fibroblasts of male versus female normal subjects. The total activity of plasma membrane (Na+, K+)-ATPase was significantly higher in female than male normal subjects. A potential 'membrane structural disorder', Huntington's disease, was confirmed in fibroblast membranes from male but not from female Huntington's disease subjects. The possibility that Huntington's disease was a 'premature membrane aging' phenomenon was considered. A comparison of plasma membrane enzymes, lipids, and structure from old and young Huntington's disease subjects did not show differences consistent with accelerated membrane aging as explaining the molecular basis for the disease. The age-dependent differences noted in aged Huntington's disease subjects: increased phosphatidylcholine/phosphatidylethanolamine ratio and sphingomyelin + lysophosphatidylcholine content of fibroblast plasma membranes were not significantly altered when compared to normal age-matched controls. However, (Na+, K+)-ATPase activity was significantly enhanced in fibroblast plasma membranes of older Huntington's disease subjects unlike those of control subjects. In conclusion, sex and age differences in membrane properties of cultured cells represent important potential variables in the elucidation of human genetic disorders that may be membrane-related.

Age-related alterations in cultured human fibroblast membrane structure and function.

Membrane enzyme activities, lipid composition, and fluorescence probe characteristics in isolated plasma membranes, microsomes and mitochondria of cultured human fibroblasts were used to determine if structural alterations occurred as a function of donor age. The cells were sex matched and allowed to undergo approximately 8 population doublings under identical culture conditions. Plasma membrane (Na+, K+)-ATPase, microsomal NADPH cytochrome c reductase, and mitochondrial succinate cytochrome c activities showed variation as a function of increasing donor age but these changes were not statistically significant. At the same time the cholesterol/phospholipid molar ratio was unaltered in plasma membranes, decreased 50% in microsomes, and unchanged in mitochondria with increasing donor age. The phosphatidylcholine/phosphatidylethanolamine ratio increased in all three membrane fractions with increasing age of the fibroblast donor. The ratio of unsaturated/saturated fatty acids decreased in the phospholipids of microsomes but not of plasma membranes or mitochondria. The structural properties of the membranes were determined with two different fluorescence probe molecules, trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene. These probe molecules indicated that the fluorescence lifetime and/or fluorescence polarization of the trans-parinaric acid probe decreased in microsomes, mitochondria, and in the plasma membrane, such that the limiting anisotropy, indicative of restrictions to probe motions, was significantly lower (high fluidity) with increasing subject age in plasma membranes, microsomes and mitochondria. The trans-parinaric acid fluorescence lifetime displayed two components in plasma membranes, microsomes, and mitochondria, a finding consistent with the coexistence of fluid and solid membrane lipid areas in the cultured human fibroblast subcellular membranes. The trans-parinaric acid partitioned preferentially into solid membrane areas. The limiting anisotropy of 1,6-diphenyl-1,3,5-hexatriene, a fluorescent probe that partitioned almost equally into different lipid domains, was also decreased in microsomes and mitochondria with increasing donor age. In contrast, 1,6-diphenyl-1,3,5-hexatriene indicated a small increase in limiting anisotropy (0.219 vs 0.195) in plasma membranes. Arrhenius plots of trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene absorbance-corrected fluorescence in plasma membranes, microsomes and mitochondria demonstrated characteristic breakpoints near 20 degrees C and 30 degrees C. These breakpoints were not altered as a function of age.(ABSTRACT TRUNCATED AT 400 WORDS)