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Biomedical subjects

B J Strupp

Publications and source records attributed to B J Strupp.

35 records · Page 2Linked to original sources
PubMed1989

Improvement of memory by a vasopressin fragment: importance of individual differences in mnemonic function.

Three studies examined the effect of AVP4-9 on memory in an appetitively motivated task (the radial maze) to ascertain the generality of the mnemonic effects seen with vasopressin analogues in avoidance paradigms. Both pre- and posttrial administration of this vasopressin fragment significantly alleviated the forgetting seen in the control condition. However, a significant relation was observed between the proficiency of the rats and the degree to which their performance was improved by the posttrial AVP4-9 treatment. The more proficient subjects did not benefit from this treatment despite the fact that their performance provided evidence of significant forgetting. This pattern of results suggests that physiological differences of animals varying in mnemonic ability may account for their disparate response to the peptide treatment. The present findings support vasopressin's putative mnemonic role but indicate that exogenous administration of vasopressinlike peptides may improve memory only in certain subgroups, and possibly only under particular testing conditions.

Animals↗
PubMed1989

Body composition and energy intake: do overweight women overeat and underreport?

The relationship between energy consumption and body composition was evaluated in 63 women by use of energy-intake values that were precisely measured in a metabolic unit and corrected for deviations from energy balance. Energy requirement for the maintenance of body weight was not significantly correlated with adiposity expressed as percent body fat. However, energy requirement was positively associated with lean mass (p less than 0.0001) whereas fat mass added no predictive value to the same multivariate regression equation. Self-reported energy intake (before the experiments) was not correlated with lean mass and was underestimated by lean subjects at least as much as by obese subjects. Discrepant findings in the literature concerning relationships between obesity and energy intake may be explained by reporting error and by the relative lean mass of obese vs nonobese women but not by systematic underreporting unique to obese subjects.

Adult↗
PubMed1988

Variation in energy intake during the menstrual cycle: implications for food-intake research.

The relationship between spontaneous energy consumption and menstrual cycle was evaluated in 23 subjects who participated in one of two independent studies. Ad libitum intakes of experimental diets were measured by food weighing and bomb calorimetry for 56 or 42 d. Comparisons were made between each woman's mean energy during the 10 d before and after the onset of menstruation. The significant decline (364 kJ, or 87 kcal) between these two 10-d intervals was smaller than but consistent with findings from previous studies of data from food journals. In a separate analysis with time-series techniques, two distinct periods of elevated intake were identified (during the midluteal and midfollicular phases) that were independent of illness and menstrual symptoms. This pattern of food intake is discussed with reference to normal hormonal fluctuations. These findings confirm that menstrual cycle is a potential confounding variable that should be controlled in research on human food intake.

Adult↗
PubMed1987

Dietary fat and the regulation of energy intake in human subjects.

The role of dietary fat in the regulation of energy intake was assessed by manipulating a conventional diet and measuring spontaneous food consumption. Twenty-four women each consumed a sequence of three 2-wk dietary treatments in which 15-20%, 30-35%, or 45-50% of the energy was derived from fat. These diets consisted of foods that were similar in appearance and palatability but differed in the amount of high-fat ingredients used. Relative to their energy consumption on the medium-fat diet, the subjects spontaneously consumed an 11.3% deficit on the low-fat diet and a 15.4% surfeit on the high-fat diet (p less than 0.0001), resulting in significant changes in body weight (p less than 0.001). A small amount of caloric compensation did occur (p less than 0.02), which was greatest in the leanest subjects (p less than 0.03). These results suggest that habitual, unrestricted consumption of low-fat diets may be an effective approach to weight control.

Adult↗
PubMed1986

Cognitive processing in anorexia nervosa. A disturbance in automatic information processing.

Anorexia nervosa patients were found to perform as well or better than control subjects on cognitive tasks that both require considerable cognitive effort and 'direct' the subject to the information that will be tested, but do more poorly than controls on tests that assess automatic or incidental processing of information. The implications of this particular pattern of cognitive alterations for theories concerning the etiology of anorexia nervosa are discussed.

Adult↗
PubMed1986

Modulation of the thermic effect of food by fenfluramine.

The thermogenic effect of fenfluramine was examined in rats following either fasting or the ingestion of a large meal. Fenfluramine did not produce a thermogenic effect in the fasting animal, but significantly potentiated the thermogenic effect of the meal. Furthermore, fenfluramine was found to produce a significant thermogenic effect when accompanied with a glucose meal, but not with one consisting of fat. These data demonstrate the importance of drug and nutrient interactions in the analysis of thermogenesis and suggest that substrate cycling may play a role in the thermogenic effect of fenfluramine.

Animals↗
PubMed1985

A mnemonic role for vasopressin: the evidence for and against.

This review critically evaluates the animal and human research concerning vasopressin's putative mnemonic role. Weaknesses in the interpretations of the early animal experiments as well as the implications of the later inconsistent findings are discussed. It is concluded that both the initial enthusiasm and the subsequent skepticism concerning this hypothesized role were premature. This conclusion applies equally to the human research. A review of these studies reveals that almost all of the negative reports involved cognitively-impaired individuals. The relatively few studies that have been conducted concerning vasopressin's effects in unimpaired human subjects are consistent with the hypothesis that vasopressin does affect cognition, though both the mechanism of action and the specific cognitive processes which are altered have yet to be elucidated.

Animals↗
PubMed1984

PKU, learning, and models of mental retardation.

Experimental phenylketonuria was induced in male rats by daily injections of alpha-methylphenylalanine and phenylalanine on postnatal Days 3-31. Beginning at 8 weeks of age, the animals were subjected to a test of observational learning followed by a test of latent learning (two tests of "advantageous" learning). The animals subjected to the PKU treatment early in life showed significant learning deficits in both tests. The importance of these studies lies in the fact that unlike conventional tests of learning, tests of advantageous learning are sensitive to the kinds of biological insults which cause mental retardation in humans. This differential sensitivity evident in studies of animal models of cognitive pathology is analogized to the areas of dysfunction which characterize human mental retardation. Suggestions for the development of appropriate models of intellectual development are made.

Animals↗
PubMed1983

Early brain insult and cognition: a comparison of malnutrition and hypothyroidism.

The effects of two biological insults, hypothyroidism and malnutrition, incurred during pre- and postnatal development were compared using a newly developed test of observational learning in rats. Whereas early hypothyroidism produced a significant impairment in observational learning in recovered rats, no indication of any impairment was observed in rats recovered from early malnutrition. These results are important in that they demonstrate that tests of advantageous learning such as observational learning are sensitive to the kinds of early biological insult that lead to permanent cognitive impairment in humans. Moreover, these data further support the concept that the cognitive impairment observed during periods of malnutrition in humans and animals is not permanent.

Animals↗
PubMedDate not supplied

Deficient cumulative learning: an animal model of retarded cognitive development.

Biological insults that produce profound mental retardation (MR) in humans have generally been found to produce little cognitive dysfunction in animal models. Based on the fact that impaired transfer of learning is one of the hallmark characteristics of mentally retarded humans, we proposed that this discrepancy may largely reflect the common use of a single learning task as the critical cognitive index rather than an assessment of cumulative learning. Consistent with this hypothesis, rats exposed to prenatal hyperphenylalaninemia (a model of maternal PKU) evidenced significant impairment when tested on a series of 10 problems designed to allow for positive transfer of learning. This same treatment, however, did not alter learning rate of the individual tasks that comprised this series when presented singly to experimentally naive animals. Deficient transfer of learning contributed significantly to the impairment observed in the maternal PKU group. These results support the hypothesis that the assessment of cumulative learning is an important component of animal models of impaired cognitive development.

Acoustic Stimulation↗
PubMedDate not supplied

An in-depth analysis of lead effects in a delayed spatial alternation task: assessment of mnemonic effects, side bias, and proactive interference.

This study examined the effects of chronic postweaning lead (Pb) exposure in Long-Evans rats on a series of spatial alternation tasks. All tasks were administered in automated testing chambers, with a nosepoke as the critical response. While neither Pb-exposed group (median blood lead levels: 19 and 39 micrograms/dl, respectively) was impaired in learning the alternation rule, both groups performed more poorly than controls on the alternation task with variable intertrial delays (0, 10, 20, and 40 s). The deficit was constant across delays, arguing against memory dysfunction. Analyses of the responses on individual trials shed further light on the impaired and spared processes in the Pb-exposed rats. First, these analyses revealed stronger side biases in the higher exposure group. One interpretation is that these animals experienced impatience when the longer delays were included, making it more difficult for them to inhibit a prepotent response to a preferred side. In contrast, these trial-by-trial analyses revealed that several other factors-retention interval, semantic proactive interference, and temporal discriminability-exerted similar effects on performance in the control and lead-exposed animals. The use of logistic regression for these trial-by-trial analyses provided a means of simultaneously assessing the influence of several variables on performance, a significant advantage when there is confounding or interactions between variables.

Animals↗
PubMedDate not supplied

Effects of chronic lead exposure on learning and reaction time in a visual discrimination task.

Long-Evans rats exposed chronically to lead (Pb) acetate (0, 75, or 300 ppm) were tested as adults on an automated, three-choice visual discrimination task as part of a larger study designed to elucidate the cognitive effects of developmental Pb exposure. Median adult BPb levels for the groups were <5, 20, and 36 microgram/dl. The pattern of results suggested a linear effect, with increasing lead dose producing progressively slower learning and an increased incidence of "impaired" individuals. This latter measure proved to be slightly more sensitive than the former, suggesting individual differences in susceptibility to Pb neurotoxicity. Additional analyses revealed that the impairing effect of Pb was seen in both the chance and post-chance learning phases, indicating that the deficit was not limited to (but could include) attentional function. Reaction time on incorrect trials was reduced in the 300-ppm group, whereas no Pb effect was seen for correct trials. The present findings suggest that chronic developmental Pb exposure produces an associative deficit as well as a tendency to respond rapidly, but does not affect information-processing speed.

Animals↗
PubMedDate not supplied

Attention as a target of intoxication: insights and methods from studies of drug abuse.

A symposium was convened to discuss recent developments in the assessment of attention and the effects of drugs and toxic chemicals on attention at the 17th annual meeting of the Behavioral Toxicology Society on May 1, 1999, in Research Triangle Park, NC. Speakers addressed issues including the methodology of assessing cognitive function, the neurobiology of specific aspects of attention, the dual roles of attention as a target of intoxication and as a mediating variable in the development of addiction to psychoactive drugs, the changes in attention that accompany neuropsychological disorders of schizophrenia, senile dementia of the Alzheimer type and attention deficit hyperactivity disorder, and potential therapies for these disorders. This article provides an overview of the objectives of the symposium, followed by summaries of each of the talks given.

Animals↗
PubMedDate not supplied

Early lead exposure produces lasting changes in sustained attention, response initiation, and reactivity to errors.

The present study tested the hypothesis that early lead (Pb) exposure causes lasting attentional dysfunction. Long-Evans dams were fed Pb-adulterated water during gestation and/or lactation; the offspring were tested as adults. The results of a visual discrimination task revealed no Pb effects on learning rate or information-processing speed. However, lasting effects of the early Pb exposure were seen in the subsequent vigilance tasks, particularly in the final task in which onset of the visual cue and cue duration varied randomly across trials. Exposure during both gestation and lactation impaired response initiation. In addition, animals exposed to Pb during lactation only or lactation+gestation committed significantly more omission errors than controls under two specific conditions: (1) trials in which a delay was imposed prior to cue presentation and (2) trials that followed an incorrect response. The pattern of treatment differences indicated that early Pb exposure produced lasting impairment of sustained attention and increased reactivity to errors. Both effects may contribute to the cognitive impairment, problematic classroom behaviors, and increased delinquency associated with early Pb exposure in children. These findings also demonstrate that the developmental timing of the exposure determines the pattern of effects. Thus, conclusions regarding whether or not a particular cognitive or affective function is impaired or spared by early Pb exposure must be limited to the specific timing and intensity of exposure.

Administration, Oral↗
PubMedDate not supplied

Enduring effects of early lead exposure: evidence for a specific deficit in associative ability.

Long-Evans dams were exposed to Pb acetate in the drinking water during both gestation and lactation, or lactation only. This report presents the results of an automated, olfactory, serial reversal task administered to the adult offspring. Although overall learning rate was not significantly affected by Pb exposure, analyses of specific phases of the learning process revealed that all three exposed groups required significantly more trials than controls to reach criterion from the point at which perseverative responding to the previously correct cue ended. These in-depth analyses revealed that the reversal learning impairment of the Pb-exposed animals was not due to a deficit in inhibiting responses to the previously correct cue, the mechanism commonly assumed to underlie impaired reversal learning. Instead, the analyses revealed that two other independent Pb effects were responsible for the prolonged postperseverative learning period: a response bias and an impaired ability to associate cues and/or actions with affective consequences. The contribution of these two factors varied as a function of the timing and intensity of the Pb exposure. It is hypothesized that the Pb-induced associative deficit may reflect lasting damage to the amygdala and/or nucleus accumbens, which comprise a system thought to modulate the process by which environmental cues acquire affective significance.

Animals↗