Lipidograma e sensibilidade à insulina em éguas Mangalarga Marchador / Lipidogram and insulin sensitivity in Mangalarga Marchador mares

A dislipidemia é um achado comum, porém não determinante, na síndrome metabólica equina (SME). O objetivo do presente trabalho foi caracterizar a dislipidemia em animais obesos com risco de SME. Para isso, 18 éguas foram alocadas em grupos, de acordo com escore corporal (EC) de 1 a 9: no grupo ideal, animais com EC de 4,5 a 5,5 (n= 6), no grupo sobrepeso, com EC de 6 a 7 (n= 6) e no grupo obeso, animais com EC de 7,5 a 9 (n= 6). Coletaram-se amostras de sangue em jejum de concentrado para determinação de triglicerídeos, colesterol total, glicemia e concentração de insulina. Valores preditivos de sensibilidade à insulina (RISQI) e de secreção ß-pancreática (MIRG) foram calculados. O grupo obeso apresentou níveis maiores em relação aos outros grupos de triglicerídeos (P=0,001) e acima do ideal em concentrações de colesterol (P=0,012). Não foi observada diferença nas concentrações plasmáticas de glicose (P=0,53), de insulina (P=0,10) ou de RISQI (P=0,46). Houve diferença entre os grupos nos valores de MIRG (P=0,048), tendo o grupo obeso obtido resultados maiores quando comparado com o grupo ideal. O aumento do EC foi associado ao aumento das concentrações plasmáticas de colesterol e triglicerídeos, o que caracteriza um estado de dislipidemia e de elevação da secreção das células ß-pancreáticas.(AU)

Increased indicators of fat metabolites are found in Equine Metabolic Syndrome (EMS) subjects, although these parameters are not included in the EMS definition described in the literature and in its diagnosis. The objective of this study was to characterize dyslipidemia in obese insulin resistant mares. 18 mares were allocated in three groups according to body condition score (BCS) in a 1 to 9 scale. In the Ideal group there were animals with BCS 4.5 to 5.5 (n= 6), in the Overweight group, the BCS were 6 to 7 (n= 6), and in the Obese group (n= 6), BCS 7.5 to 9. Concentrate fasting blood samples were taken to determine triglycerides, total cholesterol, glucose, and insulin concentrations in plasma. Insulin sensitivity proxy (RISQI) and ß-pancreatic secretion proxy (MIRG) were calculated from glucose and insulin data. The Obese group had higher triglyceride levels (P= 0.001), compared to other groups, and higher total cholesterol compared to the Ideal Group (P= 0.012). No differences in plasma glucose (P= 0.53), insulin (P= 0.10) concentrations and insulin sensitivity (RISQI: P= 0.463) were seen among groups. The Obese Group had a higher ß-pancreatic secretion (MIRG: P= 0.048) compared to the Ideal Group. The increased BCS was related to the plasma fat metabolites a higher ß-pancreatic secretion.(AU)

Influence of an n-3 long-chain polyunsaturated fatty acid-enriched diet on experimentally induced synovitis in horses.

Dietary n-3 long-chain polyunsaturated fatty acid (LCPUFA) supplementation has previously been shown to modify joint-related inflammation in several species, although information in the horse is lacking. We investigated whether dietary supplementation with n-3 LCPUFA would modify experimentally induced synovitis in horses. Twelve, skeletally mature, non-pregnant mares were randomly assigned to either a control diet (CONT) or an n-3 long-chain fatty acid-enriched treatment diet (N3FA) containing 40 g/day of n-3 LCPUFA for 91 days. Blood samples taken on days 0, 30, 60 and 90, and synovial fluid collected on days 0 and 90 were processed for lipid composition. On day 91, joint inflammation was stimulated using an intra-articular (IA) injection of 100 ng of recombinant equine IL-1beta (reIL-1ß). Synovial fluid samples taken at post-injection hours (PIH) 0, 4, 8 and 24 were analysed for prostaglandin E2 (PGE2 ), matrix metalloproteinase (MMP) activity and routine cytology. Synovium and articular cartilage samples collected at PIH 8 were analysed for gene expression of MMP 1 and MMP 13, interleukin-1beta (IL-1ß), cyclooxygenase 2 (COX-2), tumour necrosis factor-alpha and the aggrecanases, a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5. A 90-day feeding period of n-3 LCPUFA increased serum phospholipid and synovial fluid lipid compositions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) compared to CONT horses. The reIL-1ß injection caused an inflammatory response; however, there was no effect of dietary treatment on synovial fluid PGE2 content and MMP activity. Synovial tissue collected from N3FA horses exhibited lower expression of ADAMTS-4 compared to CONT horses. Despite the presence of EPA and DHA in the synovial fluid of N3FA horses, dietary n-3 LCPUFA supplementation did not modify synovial fluid biomarkers compared to CONT horses; however, the lower ADAMTS-4 mRNA expression in N3FA synovium warrants further investigation of n-3 LCPUFA as a joint therapy.

Effects of two different dietary sources of long chain omega-3, highly unsaturated fatty acids on incorporation into the plasma, red blood cell, and skeletal muscle in horses.

The objective of this study was to examine the effects of different sources of dietary omega-3 (n-3) fatty acid supplementation on plasma, red blood cell, and skeletal muscle fatty acid compositions in horses. Twenty-one mares were blocked by age, BW, and BCS and assigned to 1 of 3 dietary treatments with 7 mares per treatment. Dietary treatments were: 1) control or no fatty acid supplement (CON), 2) 38 g of n-3 long chain, highly unsaturated fatty acid (LCHUFA) supplement/d provided by algae and fish oil (MARINE) containing alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA), and 3) 38 g of n-3 LCHUFA supplement/d provided by a flaxseed meal (FLAX) containing ALA. Each supplement was added to a basal diet consisting of hay and barley and was fed for 90 d. Blood samples and muscle middle gluteal biopsies were taken at d 0, 30, 60 and 90 of supplementation. Plasma, red blood cell and skeletal muscle fatty acid profiles were determined via gas chromatography. Plasma linoleic acid (LA) and ALA were at least 10 and 60% less (P < 0.01), respectively, in the MARINE compared with the FLAX and CON groups. Plasma EPA and DHA were only detected in the MARINE group, and EPA increased 40% (P < 0.001) from d 30 to 60, and DHA 19% (P < 0.01) from d 30 to 90. Red blood cell LA and ALA were not different among treatments. Red blood cell EPA and DHA were only detected in the MARINE group, where EPA increased 38% (P < 0.01) from d 30 to 60, and DHA increased 56% (P < 0.001) between d 30 and 90. Skeletal muscle LA was at least 17% less (P < 0.001) in the MARINE group compared with the other treatments. Skeletal muscle ALA was 15% less (P = 0.03) in the MARINE group compared with FLAX and CON groups. Skeletal muscle EPA was at least 25% greater (P < 0.001) in MARINE group compared with other treatments and increased (P < 0.001) by 71% from d 30 to 60. Skeletal muscle DHA was at least 57% greater (P < 0.001) in the MARINE group compared with other groups and increased (P < 0.001) by 40% between d 30 and 90. As far as the authors are aware, this is the first study to demonstrate that dietary fatty acid supplementation will affect muscle fatty acid composition in horses. Incorporation of n-3 LCHUFA into blood and muscle depends directly on dietary supply of specific fatty acids.

Single-injection glucose kinetics with compartmental modelling during rest and low-intensity exercise in horses.

REASONS FOR PERFORMING STUDY: Tools and criteria to evaluate and understand glucose metabolism are essential to optimise equine energy utilisation for exercise performance and reduced metabolic health risks. OBJECTIVES: To re-evaluate models of glucose kinetics in the horse at rest and during endurance type exercise using a single injection technique and compartmental modelling. METHODS: Twelve exercise trained Arabian geldings received a bolus of 100 µmol/kg bwt [6,6-(2) H]glucose i.v. while at rest and while running at ∼ 4 m/s on a treadmill. Tracer and tracee glucose curves from 4-150 min after the bolus dose (while the subject maintained its resting or exercising state) were described by a 2 term exponential decay curve. Compartmental modelling was performed simultaneously for each horse's resting and exercise curves using an 'exercise effect' parameter for each compartmental exchange rate during exercise. RESULTS: Exercise increased all rate constants and transport flows for glucose between compartments by 110-145% (P ≤ 0.004). Total glucose transport through the system increased from 8.9 ± 0.6 µmol/min/kg/bwt at rest to 25.0 ± 1.1 µmol/min/kg bwt during exercise (P < 0.001). Exercise decreased the volume of the primary glucose compartment by 8% (P = 0.006) and increased plasma glucose clearance rate by almost 200% (P < 0.001). Turnover times and mean residence times were decreased approximately 60% by exercise (P < 0.001), whilst turnover rates were increased 125% (P < 0.001). CONCLUSIONS: Single-injection tracer kinetics and compartmental modelling represent a valuable tool to quantify tracee availability to and use by tissue. POTENTIAL RELEVANCE: This technique could represent a beneficial tool for future studies exploring the role of glucose metabolism in equine exercise performance and metabolic disease.

Does usefulness of potassium supplementation depend on speed?

REASONS FOR PERFORMING STUDY: Electrolyte mixtures given to counter sweat loss usually contain abundant potassium. However, increases in plasma [K+] occur with exercise and supplementation may further increase plasma levels, potentially increasing the risk of neuromuscular hyperexcitability and development of adverse clinical sequellae. This proposition requires study. OBJECTIVES: To compare effects of a K-rich electrolyte supplement (EM+K) to a K-free one (EM-K) on plasma [K+], [Ca++] and acid-base status during an endurance incremental exercise test on the treadmill. METHODS: The test consisted of 3 bouts (simulating loops in an endurance race) of 12 km performed at 6, then 7, then 8 m/sec with 25 min rest stops (S1, S2) between loops on 13 endurance trained Arabian horses (7 EM-K, 6 EM+K). Electrolytes were supplied orally 60 mins before exercise (Pre) and at each stop. Blood samples were taken before exercise and during exercise, each S and 120 mins of recovery (R). Blood was analysed for pH, PCO2, packed cell volume (PCV), plasma [Na+], [K+], [Cl-], [Ca++], glucose, and lactate [La-]; plasma [H+] and osmolality (osm) were calculated. The dietary cation anion difference (DCAD) was calculated to be -27 meq/dose EM-K and 109 meq in EM+K, respectively. RESULTS: Plasma [H+] decreased during the 6 and 7 m/sec loops, increased during the 8 m/sec loop, and returned to Pre at S1, S2 and R. Plasma [K+] was higher at 8 m/sec and plasma [Ca++] was overall lower in the EM+K group compared to EM-K. Other findings included higher overall PCV, overall glucose, and [La-] during the 8 m/sec loop (P<0.040) in EM+K compared to EM-K horses. CONCLUSIONS: EM+K supplementation leads to higher plasma [K+] increasing the risk of neuromuscular hyperexcitability during exercise. Acute effects of a lower DCAD in EM-K may have led to higher plasma [Ca++]. Potassium-rich electrolytes may have triggered the release of epinephrine, contributing to higher PCV, glucose release and increased lactate production. POTENTIAL RELEVANCE: Lower plasma [K+] and higher plasma [Ca++] with EM-K supplementation may help reduce the risk of conditions associated with neuromuscular hyperexcitability occurring especially during higher speeds in endurance races.

Glucose dynamics during exercise: dietary energy sources affect minimal model parameters in trained Arabian geldings during endurance exercise.

REASONS FOR PERFORMING STUDY: Glucose regulation is critical for health and exercise performance. OBJECTIVES: To quantify the effects of exercise and diet on insulin sensitivity (SI), glucose effectiveness (Sg), acute insulin response to glucose (AIRg) and disposition index (DI) in horses. METHODS: This study applied the minimal model of glucose and insulin dynamics to exercise-trained Arabian geldings during rest or constant moderate-intensity exercise after 8 weeks adaptation to feeds high in sugar and starch (SS, n = 6) or fat and fibre (FF, n = 6). Horses underwent 2 frequently sampled i.v. glucose tolerance tests (FSIGT). For both tests, a resting basal sample was collected, followed by an i.v. dose of 600 mg/kg bwt glucose defining 0 min of the test. Insulin (0.01 iu/kg bwt) was administered 20 min post glucose for each test. Resting horses were sampled for 240 min. The exercise FSIGT began after each horse had warmed-up for 25 min on the treadmill at which point they had reached the speed representing 60% of their predetermined lactate breakpoint maintained for the rest of the FSIGT. Exercising horses were sampled identically to rest, but for only 150 min post glucose. RESULTS: Exercise increased (P<0.008) SI, Sg and DI and decreased AIRg in all horses. Overall, horses adapted to FF tended to have higher SI (P = 0.070) and DI (P = 0.058). During exercise, FF horses tended to have higher (P< or =0.085) SI and DI, than SS horses and these variables tended to be increased more (P< or =0.075) by exercise in FF horses than SS horses. CONCLUSIONS: Insulin and glucose dynamics adjust during exercise, increasing plasma glucose uptake, presumably to meet demand by contracting skeletal muscle. Trained horses adapted to a high fat diet showed greater metabolic adjustment during exercise than trained horses adapted to a high starch and sugar diet, potentially allowing them to better meet energy demands. POTENTIAL RELEVANCE: Nutrition and exercise impact glucose and insulin dynamics, potentially influencing health and performance.

Antioxidant supplementation and subsequent oxidative stress of horses during an 80-km endurance race.

This study tested the development of oxidative stress and the effects of antioxidant supplementation in an 80-km ride. A precompetition survey revealed that no competitor would participate without vitamin E supplementation; therefore, 46 horses were paired for past performances and randomly assigned to two groups of 23 each for 3 wk of supplementation before the ride. One group (E) was orally supplemented with 5,000 IU of vitamin E per day; the other group (E+C) received that dose of vitamin E plus 7 g/d of vitamin C. Blood samples, temperature, and heart rate were taken the day before the race, at 21 and 56 km during the ride, at completion, and after 20 min of recovery. Plasma was assayed for lipid hydroperoxides, alpha-tocopherol, total ascorbate, albumin, creatine kinase (CK), and aspartate aminotransferase (AST). Total glutathione and glutathione peroxidase activity were determined in red blood cells and white blood cells. Thirty-four horses completed the race, 12 horses (six in E and six in E+C) did not finish for reasons including lameness, metabolic problems, and rider option. Plasma ascorbate was higher (P = 0.045) in the E+C group than in the E group. Other than ascorbate, neither antioxidant status nor CK and AST activities were affected by supplementation with E+C vs. E. Red blood cell glutathione peroxidase, white blood cell total glutathione, lipid hydroperoxides, CK, and AST increased, and red blood cell total glutathione and white blood cell glutathione peroxidase activity decreased with distance (P < 0.001). Positive correlations were found for plasma lipid hydroperoxides on CK (r = 0.25; P = 0.001) and AST (r = 0.33; P < 0.001). These results establish an association between muscle leakage and a cumulative index of oxidative stress.

Speed associated with plasma pH, oxygen content, total protein and urea in an 80 km race.

To test the hypothesis that endurance performance may be related quantitatively to changes in blood, we measured selected blood variables then determined their reference ranges and associations with speed during an 80 km race. The plan had 46 horses in a 2 x 2 factorial design testing a potassium-free electrolyte mix and a vitamin supplement. Blood samples were collected before the race, at 21, 37, 56 and 80 km, and 20 min after finishing, for assay of haematocrit, plasma pH, pO2, pCO2, [Na+], [K+], [Ca++], [Mg++], [Cl-], lactate, glucose, urea, cortisol, alpha-tocopherol, ascorbate, creatine kinase, aspartate amino transferase, lipid hydroperoxides, total protein, albumin and creatinine, and erythrocyte glutathione and glutathione peroxidase. Data from 34 finishers were analysed statistically. Reference ranges for resting and running horses were wide and overlapping and, therefore, limiting with respect to evaluation of individual horses. Speed correlations were most repeatable, with variables reflecting blood oxygen transport (enabling exercise), acidity and electrolytes (limiting exercise) and total protein (enabling then, perhaps, limiting). Stepwise regressions also included plasma urea concentration (limiting). The association of speed with less plasma acidity and urea suggests the potential for fat adaptation and protein restriction in endurance horses, as found previously in Arabians performing repeated sprints. Conditioning horses fed fat-fortified and protein-restricted diets may not only improve performance but also avoid grain-associated disorders.

Aging and social expertise: the impact of trait-diagnostic information on impressions of others.

Two studies were conducted to examine the bases for age differences in the construction of social inferences. In each study, adults aged from 20 to 80 years were presented with an impression formation task in which they first read brief behavioral descriptions of fictitious people and then made a trait inference and likability judgment about each person. Results were generally consistent with previous findings in showing that aging was associated with an increase in the weighting of trait-diagnostic information in making trait attributions. In addition, the pattern of age effects was only minimally affected by situational factors that have been known to influence the use of trait-diagnostic information. The findings are interpreted as demonstrating an aging-related increase in social expertise in which knowledge regarding the underlying bases for the behaviors of others has been translated in specific procedural knowledge.

The selective removal of phosphorus from soil: is event size important?

Data from the Woburn Erosion Reference Experiment (Bedfordshire, UK) were used to test the hypothesis that losses of phosphorus (P) in small erosion events are as great as those in infrequent large events, and to examine the effect of storm characteristics on the selective enrichment of P in eroded sediment. For almost every plot event in the period 1988 to 1994, the clay-sized fraction of the sediment was enriched compared with the soil of the plots. There was more variation in clay enrichment for smaller erosion events than for larger ones. The clay and P contents of the sediment were strongly correlated (p < 0.01), and there was a wider range of P concentrations in the sediment derived from small events than in that from large events. However, individual events resulting in small soil losses (< 100 kg) did not account for greater P losses than larger events (> 100 kg). The greater frequency of smaller events, combined with the likelihood of higher P concentrations in the sediment, therefore accounted for a greater proportion of the P lost over the 6-yr period than the infrequent large events. Phosphorus concentrations generally increased with increasing peak discharge and decreased with increasing event duration. For the same return period, P losses were generally greater from plots cultivated up and down the slope than from those cultivated across the slope. Overall, our results suggest that small erosion events should be controlled to prevent P contamination of surface waters and that the most effective means of doing this are by the introduction of minimal tillage techniques and across-slope cultivations.

Motivation and representational processes in adulthood: the effects of social accountability and information relevance.

The role of motivation in determining age differences in social representations was examined. Adults aged 20 to 83 years were given an impression formation task that attempted to manipulate motivation by varying the characteristics of the target and the extent to which participants would be held accountable for their impressions. It was hypothesized that increasing age would be associated with greater selectivity in the use of available cognitive resources to support the construction of accurate representations. Support for this hypothesis was obtained when trait inferences and recall were examined. Specifically, older adults made more accurate trait inferences and recalled more information when the target was similar in age or they were held accountable for their impressions. In contrast, younger adults demonstrated similar levels of accuracy across conditions. The fact that these effects were observed when cognitive resources was controlled suggests a motivational effect that is independent of age differences in cognitive ability.

Motivational and cognitive influences on affective priming in adulthood.

This research examined age differences in the impact of affective primes on judgments about neutral stimuli. When participants were unaware that the primes had been presented, age differences were nonexistent, with individuals of all ages producing likability judgments consistent with the valence of the prime. In contrast, when awareness of the primes was maximized, prime influences were virtually nonexistent in the youngest participants, but prime influences increased with participants' age. In addition, the impact of the primes was differentially affected by an individual's need for simple structure. Need for structure did not influence the performance of young and middle-aged participants, but prime effects increased with need in the oldest participants. It is argued that the stronger predictive validity of need for structure with age is due to aging-related changes in personal resources (both social and cognitive) and/or a closer mapping of individual characteristics onto need with age. Regardless of source, the results argue for closer consideration of motivational factors in determining age differences in performance.

Trait diagnosticity versus behavioral consistency as determinants of impression change in adulthood.

Age differences in the types of processing associated with impression change were examined. Young, middle-aged, and older adults formed an impression of a target based on a short vignette that described either positive or negative characteristics in 1 of 2 domains (ability vs. morality). Impression change was examined after presentation of additional behavioral information that was inconsistent with the original vignette. Replicating previous findings, younger adults changed their impressions in response to the consistency of the new information with the initial target description. In contrast, impression change in the 2 older groups was based on the trait diagnosticity of the original and new information, suggesting greater use of inferential, knowledge-based processing with age. The results indicate that qualitative difference exist in impression change processes, with different-aged individuals considering different types of information when constructing and updating social representations.

Aging and impression formation: the impact of processing skills and goals.

Two studies assessed age differences in representations and judgments about people. Our specific interest was in examining how presumed age-related changes in processing efficiency and motivation affected performance in an impression formation task. Consistent with age-related declines in processing efficiency, we found that increasing age was associated with: (a) no change in the processing of evaluative information; (b) less use of specific traits to organize impressions; (c) poorer memory for behavioral information, especially when it contradicted expectations; and (d) less systematic relationships between memory and judgments. We also found, however, that more meaningful task goals and a focus on individual behaviors resulted in reduced age differences in the nature of representations about the target person.

Age-related priming effects in social judgments.

Two experiments investigated adult age differences in the impact of previously activated (and thus easily accessible) trait-related information on judgments about people. The authors hypothesized that age-related declines in the efficiency of controlled processing mechanisms during adulthood would be associated with increased susceptibility to judgment biases associated with such information. In each study, different-aged adults made impression judgments about a target, and assimilation of these judgments to trait constructs activated in a previous, unrelated task were examined. Consistent with the authors' hypotheses, older adults were likely to form impressions that were biased toward the primed trait constructs. In contrast, younger adults exhibited greater awareness of the primed information and were more likely to correct for its perceived influence, especially when distinctive contextual cues regarding the source of the primes were available.

Acquisition of prototype-based information about social groups in adulthood.

Two experiments examined adult age differences in the ability to acquire prototype-based information about a fictitious social group. Young and older adults were presented with 60 descriptions of people who varied in their similarity to a prototypical group member along 12 (Experiment 1) or 10 (Experiment 2) feature dimensions. The prototype represented either an arbitrary combination of features or a coherent set of features based on evaluative content. Younger adults generally performed better than the older adults in learning the arbitrary prototype, whereas age differences were absent or in favor of the older adults when the prototype consisted of evaluatively consistent features. The authors argue that the results can be explained by the age-related variations in the reliance on automatic processing mechanisms and the congruence of these processes with the demands of the task across prototype conditions.

Adult age differences in impression change processes.

Three experiments examined the factors influencing impression change in young and older adults. In each study, Ss formed an impression of a fictitious target person and then read additional behavioral information that varied in its consistency with this initial impression. On the basis of previous work, older adults were expected to be less likely than younger adults to integrate new, inconsistent information in the schema-based memory representation, which would result in less impression change. No support for this prediction was found; instead, young and older adults varied in their weighting of different types of information (e.g., negative behaviors), which subsequently affected their impressions and memory for specific behavioral information. These results highlight the importance of considering the impact of age differences in implicit theories about behavior on social cognition.

Aging and memory for schematically vs taxonomically organized verbal materials.

Two experiments examined age differences in the effects of type of organization on recall of verbal materials. Young and older adults studied a list of simple verb-noun phrases that were organized either taxonomically by categories or schematically by activities, and then were tested for recall. Relative to taxonomic organization, schematic organization was found to facilitate recall in both age groups, although the effect of organization was only present for the older adults when explicit organizational cues were presented. The enhancement associated with schematic organization was attributed to the additional temporal and causal connections between items. These associations were assumed to be responsible for the facts that, relative to taxonomic organization, schematic organization was associated both with more correspondence between input and output orders and with more items being retrieved the first time an activity or category grouping was accessed at recall.

Schema-based retrieval processes in young and older adults.

Through two experiments we examined the extent to which the memory performance of different-aged adults was dependent upon the conceptual relationship between the to-be-remembered information and the perspective adopted at retrieval. In both studies, young and old adults read a story from one of two perspectives. They then recalled the story twice: first from the perspective taken at reading and then again from the alternative perspective. It was found that memory performance in both age groups was related to the relevance of the story information to the recall perspective. In addition, the interaction between recall perspective and the relevance of the story units was similar across age groups. This suggests that young and older adults are similarly dependent upon schema-based relations in aiding recall, at least when the memory task has a heavy emphasis on conceptually driven retrieval processes.

Adult age differences in explanations and memory for behavioral information.

Age differences in the effects of knowledge-based expectations on both the use of integrative memory processes and recall were examined. In the context of an impression-formation task, young and older adults were presented with lists containing behaviors that varied in consistency with attributed personality traits. Younger adults recalled trait-inconsistent behaviors better than consistent ones, but older adults exhibited no such consistency effect. The age difference in performance was related to the younger adults' spontaneously producing more explanations for inconsistent behaviors. Explanations are assumed to facilitate access to such information by establishing associations with other behavioral information residing in memory. When age differences in the use of explanation-based processing were controlled, the age differences in the effects of consistency on memory were eliminated.