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Biomedical subjects

D A Levitsky

Publications and source records attributed to D A Levitsky.

At least 37 records · Page 2Linked to original sources
PubMed1990

Enhancement and impairment of memory retrieval by a vasopressin metabolite: an interaction with the accessibility of the memory.

A series of 3 experiments was conducted to determine the generalizability of the improved recall seen with pretest administration of vasopressin in aversively motivated tasks. The learning paradigm selected for this purpose assessed the transmission of a food preference between rats; retention intervals of 8, 10, and 14 days were used in the 3 experiments, respectively. Pretest subcutaneous injection of a vasopressin metabolite, AVP4-9, significantly improved recall under conditions in which memory was poor in vehicle-treated rats but significantly impaired memory at a time when good recall was evident in controls. These findings support the postulate that administration of vasopressin or its metabolites modulate memory retrieval processes and suggest that the nature of this effect depends on the degree of forgetting that has occurred.

Animals↗
PubMed1990

Effect of dl-fenfluramine on thermic effect of food in humans.

To determine whether dl-fenfluramine increased metabolic rate in humans, hourly indirect calorimetry measurements were made on 16 nonobese males over a 5 h period under each of four conditions: placebo/no meal, placebo/meal, 60 mg dl-fenfluramine/no meal, and 60 mg dl-fenfluramine/meal. Drug administration was double-blind and a Latin square design was used with treatments separated by 7 days. To confirm that active drug was administered when assigned, subjective sensations were measured by questionnaires administered three times during each treatment. Metabolic rate (kcal/min) during the four treatments was compared by analysis of variance over the entire 5 h and at the end of the measurement period. The 750 kcal (3140 kJ) meal increased metabolic rate over the fasting conditions (0.160 +/- 0.035 kcal/min, P less than 0.0005) and the combination of fenfluramine and meal caused a further significant increase beyond that found with placebo and meal (0.072 +/- 0.035 kcal/min, P less than 0.025). At the end of the measurement period, metabolic rate during the placebo/meal treatment had returned to the level of the fasting treatments. In contrast, during the fenfluramine/meal condition, metabolic rate was still elevated (0.173 +/- 0.04 kcal/min, P less than 0.003). The results of this study suggested that fenfluramine increased metabolic rate by potentiating the thermic effect of food.

Administration, Oral↗
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↗
PubMed1988

Comparison of the effects of psyllium and wheat bran on gastrointestinal transit time and stool characteristics.

Gastrointestinal transit time, frequency of defecation, stool weight, and stool consistency were studied in 12 subjects who were each given fiber supplements containing wheat bran, psyllium gum, a combination of wheat bran and psyllium gum, or a low-fiber control for 2 weeks. Gastrointestinal transit time was measured using four different markers: plastic pellets, chromium mordanted bran, cobalt-ethylenediamine-tetraacetic acid, and terbium oxide. The wet weight and dry weight of stools were measured, and a questionnaire accessed subjects' perceptions of the consistency of their stools. Fiber supplementation decreased transit time and increased the daily number of defecations and the wet weight and dry weight of stools. Bran had a greater effect on transit time than psyllium. Psyllium had a greater effect on the amount of water found in the stools and the total stool weight. On the days that stools were passed, 50% of the daily stool ratings were scored as "hard" when subjects received the control supplement. Less than 10% of the ratings were scored as "hard" when subjects received the high-fiber supplements. The type of marker used did not significantly affect the transit time measured.

Adult↗
PubMed1988

Enhancement of the thermic effect of food by d-fenfluramine.

Following approximately a week of daily ingestion of fenfluramine, the body weight of female rats is reduced and remains chronically suppressed for as long as treatment is continued. This chronic suppression of body weight by fenfluramine cannot be explained by the anorectic effects of fenfluramine, since food intake returns to normal after about a week. Part of this chronic suppression of body weight lies in the ability of fenfluramine to enhance the thermic effect of food. Fenfluramine ingested by a fasted rat causes no change in metabolic rate. However, following the ingestion of the meal consisting of mixed nutrients or only carbohydrates, the thermic effect of the food is significantly greater than that of the meal without fenfluramine. A similar observation was observed in humans. These observations when combined with the negligible effects of dieting as a means of controlling body weight, argue for the chronic use of fenfluramine as a therapeutic technique to produce sustained weight loss in humans.

Animals↗
PubMed1987

Effect of psyllium gum and wheat bran on spontaneous energy intake.

Energy intake, fecal energy output, and gastrointestinal symptoms were measured in 12 females who consumed either approximately 23 g/d supplementary fiber or a 4 g/d fiber control. Fiber supplements were crackers containing psyllium gum, wheat bran, or a combination of the two fiber sources. After 1 wk on the control cracker, subjects consumed the three high-fiber crackers and the control cracker for 2-wk periods in a balanced design. Gum and combination supplements gave increased bloating and flatulence. Increase in abdominal pain was reported with gum supplement. Mean daily fecal energy was 96 kcal/d with control crackers and was increased by 63 kcal with high-fiber crackers. Gum and combination supplements significantly decreased intake of digestible energy by 153 and 115 kcal/d, respectively. This suppression was not dependent upon fiber intolerance. Wheat bran supplement had no effect on energy intake.

Adult↗
PubMed1987

Mean transit time measurement by analysis of a single stool after ingestion of multicolored plastic pellets.

Mean transit time (MTT) was measured in 12 females and served as a standard to evaluate the validity of different methods of estimating transit by analysis of a single stool (SST). Each subject consumed three different fiber supplements and a low-fiber control for 14-d periods. On days 4-8 of each period, subjects were given 20 plastic pallets, which varied in color each day. SST was calculated using from two to five sets of colored pellets and different criteria for designation of the stool to be analyzed were compared. Results indicate that the following modifications in the SST method originally proposed by Cummings and Wiggins will result in improved prediction of MTT: 1) Increase the days of dosing from 3 to 6.2) Collect for study the first stool passed 3 h after the last dosing. 3) Include all pellets identified in the selected stool in the SST calculation.

Defecation↗
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

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↗
PubMed1985

Eating in the laboratory: is it representative?

The degree to which caloric intake of food consumed in a laboratory setting can approximate caloric intake measured under free-living conditions was assessed in the present study. Four men and four women of normal body weight weighed and recorded their food intake for four days (period 1) during which they were eating in their normal home environment. On the following week (period 2) which also lasted 4 days, the subjects consumed all their food in a laboratory setting. Based upon the findings that no significant change in body weight occurred during either period of the study, that no significant difference in paired caloric intake was observed between period 1 and period 2, and that a highly significant intraclass correlation coefficient, ri = .80 (p less than .005) existed between period 1 and period 2, it was concluded that food consumed in a laboratory setting is a reasonable approximation of caloric intake as measured under free-living conditions.

Adult↗
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↗
PubMed1983

Lithium chloride and avoidance of novel places.

Rats were exposed to a distinctive chamber (chamber A, part of a two-chamber apparatus), which was novel for half of the rats but familiar for the other half. Each rat was subsequently injected with lithium chloride or saline. In a test trial conducted 24 hr later, all rats were given a choice between chamber A and a second chamber (B), which was novel for all rats. The main result was that the group made familiar with chamber A and then given lithium showed a significant preference for that side or an avoidance of the novel side, a "spatial neophobia." A second experiment confirmed the spatial neophobia effect and demonstrated that it was not dependent on the particular conditioning procedure used in the first experiment. The spatial neophobia effect was related to similar effects in the taste aversion literature, and to the results of research on lithium-induced decreases in exploratory behavior.

Animals↗
PubMed1982

Insensible weight loss as an indicator of metabolic rate.

Insensible weight loss has been used in large animals as an index of metabolic rate. By using the microprocessor controlled electronic balance to minimize the effects of movement, the feasibility of utilizing insensible weight loss as an estimate of metabolic rate in the rat is considered in terms of convenience and accuracy. Using various metabolic stimulants, a high correlation between insensible weight loss and metabolic rate was obtained. Moreover, a calculation is described that corrects for respiratory water loss and results in even higher correlations. These findings support the use of insensible weight loss as an indicator of metabolic rate in controlled situations for small animals.

Animals↗
PubMed1982

Spillage behavior and thiamin deficiency in the rat.

Food spillage, food intake and body weight of four groups of adult rats were monitored daily as they were fed varying responses of deficient, marginal, or high thiamin (B) diet. Food spillage was a more sensitive index of the dietary B1 then either food intake or body weight change. Animals fed the deficient B1 diet exhibited the greatest levels of food spillage followed by the animals fed the marginal B1 diet. Hypophagia and weight loss occurred only among animals fed the marginal B1 diet. Feeding the high B1 diet to animals previously given the deficient and marginal B1 diets completely eliminated the excessive food spillage, and food intake and body weight returned to control levels. These data support the use of spillage behavior as a useful screening tool for detecting behavioral effects of inadequate nutrient intake or chemical intoxication.

Animals↗