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Biomedical subjects

T M Hess

Publications and source records attributed to T M Hess.

At least 19 recordsLinked to original sources
PubMed2004

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.

Animal Welfare↗
PubMed2002

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.

Animal Feed↗
PubMed2001

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.

Adult↗
PubMed2001

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.

Adult↗
PubMed2000

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.

Adult↗
PubMed1999

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.

Adult↗
PubMed1998

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.

Adolescent↗
PubMed1998

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.

Adolescent↗
PubMed1996

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.

Adolescent↗
PubMed1994

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.

Adolescent↗
PubMed1993

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.

Adult↗
PubMed1992

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.

Aged↗
PubMed1991

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.

Adult↗
PubMed1990

Treatment of acute herpetic neuralgia. A case report and review of the literature.

Herpes zoster (shingles) is a viral infection that results from a reactivation of a dormant varicella zoster virus. It has been estimated that more than 300,000 new cases are seen in the United States each year. Several factors influence the incidence of infection, with increasing age being the most consistent. Postherpetic neuralgia is the No. 1 cause of intractable, debilitating pain in the elderly and is the leading cause of suicide in chronic pain patients over the age of 70.

Analgesia, Epidural↗
PubMed1987

Adult age differences in the perception and learning of artistic style categories.

Adult age differences in conceptual behavior were studied using informationally complex stimuli from real-world categories: paintings by two impressionist artists. In Experiment 1 we examined perceptions of category structure by having subjects sort paintings according to style similarity. Young adults were observed to depend more on abstract information in making style judgments, whereas older adults relied more on similarity in content. This resulted in different category structures between age groups, but similarity judgments in both groups appeared to correspond to actual style differences between the two artists. In Experiment 2, learning efficiency was shown to increase with a painting's category centrality, but older adults had particular trouble learning noncentral items. At transfer, both age groups were able to use abstracted central tendency information to categorize new paintings, although young adults appeared to have better access to information about specific category exemplars from acquisition. The results are generally consistent with those from studies using simpler artificial stimuli.

Adolescent↗
PubMed1987

Memory for sex-role consistent and inconsistent actions in young and old adults.

Adult age differences in the flexibility of schematic processing were examined by measuring the degree to which a dominant structure (traditional sex-role knowledge) interfered with the operation of a nondominant structure (nontraditional knowledge). In two experiments, young and old adults read statements describing a man performing actions consistent or inconsistent with a prescribed sex role in an impression-formation task. Participants in both age groups altered their processing of the actions, as indicated by reading times and trait ratings, relative to the sex role emphasized, although the effect was stronger for men than women. The expected greater recall for sex role inconsistent than consistent actions was observed only when the traditional sex role was emphasized, and not when the nontraditional role was emphasized, suggesting interference from the dominant schema at recall. However, the lack of age differences in the degree of interference observed during initial processing and recall suggests no aging effects on schematic flexibility.

Adult↗
PubMed1986

Specific exemplar retention and prototype abstraction in young and old adults.

The effects of age differences in retention of information about specific concept members on the ability to abstract central tendency information were examined. Young and older adults were presented with a series of visual patterns that were organized around a prototype. They were then presented with these same patterns plus a set of new patterns varying in prototype similarity in a recognition test. It was found that young adults retained more information about specific acquisition set exemplars, which resulted in slightly different recognition responses for new patterns. However, the recognition behavior of both young and older adults appeared to be governed by the same rules. It is suggested that the organization of conceptual information does not change with age, but the poorer retention of specific item information in older adults may result in a less complete representation.

Adolescent↗