Short-term exposure to heat stress attenuates appetite and intestinal integrity in growing pigs.

Acute heat stress (HS) and heat stroke can be detrimental to the health, well-being, and performance of mammals such as swine. Therefore, our objective was to chronologically characterize how a growing pig perceives and initially copes with a severe heat load. Crossbred gilts (n=32; 63.8±2.9 kg) were subjected to HS conditions (37°C and 40% humidity) with ad libitum intake for 0, 2, 4, or 6 h (n=8/time point). Rectal temperature (Tr), respiration rates (RR), and feed intake were determined every 2 h. Pigs were euthanized at each time point and fresh ileum and colon samples were mounted into modified Ussing chambers to assess ex vivo intestinal integrity and function. Transepithelial electrical resistance (TER) and fluorescein isothiocyanate-labeled dextran (FD4) permeability were assessed. As expected, Tr increased linearly over time (P<0.001) with the highest temperature observed at 6 h of HS. Compared to the 0-h thermal-neutral (TN) pigs, RR increased (230%; P<0.001) in the first 2 h and remained elevated over the 6 h of HS (P<0.05). Feed intake was dramatically reduced due to HS and this corresponded with significant changes in plasma glucose, ghrelin, and glucose-dependent insulinotropic peptide (P<0.050). At as early as 2 h of HS, ileum TER linearly decreased (P<0.01), while FD4 linearly increased with time (P<0.05). Colon TER and FD4 changed due to HS in quadratic responses over time (P=0.050) similar to the ileum but were less pronounced. In response to HS, ileum and colon heat shock protein (HSP) 70 mRNA and protein abundance increased linearly over time (P<0.050). Altogether, these data indicated that a short duration of HS (2-6 h) compromised feed intake and intestinal integrity in growing pigs.

An anatomic basis for the communication of hypothalamic, cortical and mesolimbic circuitry in the regulation of energy balance.

Central neural control of complex feeding behaviour is likely to be influenced by a number of factors including homeostatic responses to peripheral nutrient status, cortical integration of feeding-related cues and the underlying reward value of food. We have used retrogradely transported neurotropic viruses, as tools to map chains of synaptically-connected neurons, in conjunction with neurochemical markers of feeding-related peptides to expand the blueprint of the circuitries that underlie these different components of feeding behaviour. We have identified projections to insular and anterior cingulate cortex, extending from the arcuate nucleus through synaptic relays in the lateral hypothalamic area and midline thalamic nuclei. Cortically projecting neurons from the hypothalamic arcuate nucleus were found predominantly in its lateral aspects and contained anorexigenic peptides with no representation amongst more medially-positioned neurons containing orexigenic peptides. Largely overlapping pathways were shown to project multisynaptically to the shell of the nucleus accumbens but those with origins in the arcuate nucleus had either orexigenic or anorexigenic phenotypes. Similar to the cortical projections, those relaying to the nucleus accumbens in the lateral hypothalamus contained the orexigenic peptides orexin-A and melanin-concentrating hormone in approximately 30% of cases. Common to the neural pathways directed to all three virally-injected areas were nodes of synaptic relays in the lateral hypothalamus and midline thalamic nuclei. These regions are well positioned to integrate sensory information about energy homeostasis and the reward value of food in the passage of this information to the 'ingestive cortex'.

Short-term dietary compensation in free-living adults.

Evidence suggests that compensatory behaviors operate in infants and pre-school children, such that the high variance characteristic of single eating occasions is much reduced over the day. However, the concept has not been fully explored in adults. The present within-subject, observational study investigated short-term dietary compensation patterns in fifty, weight-stable, normal weight (n=27), overweight (n=14), and obese (n=9) free-living adults (11 M, 39 F; age 30+/-11 y; BMI 26.3+/-5.9). Twenty four-hour diet recalls were obtained for 7 consecutive days, by the multi-pass technique. Each 24-h period was divided into 7 eating occasions. The coefficient of variation for energy intake was calculated for each adult, for each eating occasion, and over each 24-h period. Sub-group variability was assessed by BMI and frequency of consumption of sweetened energy-yielding beverages. The mean coefficient of variation for energy intake for the 7 eating occasions was 110.5%, compared to 28.9% for the day as a whole. Correlations between energy intakes at successive eating events were uniformly negative. No significant differences were noted in the sub-group analyses. Significantly greater variation in energy intake was noted for snacks compared to meals (P<0.0001). These data suggest that adults regulate energy intake over a 24-h period more closely than they do at individual eating occasions, similar to the pattern previously observed in children. Further studies of compensatory responses by larger sub-groups of individuals at risk for weight gain are warranted.

Effects of appetite, BMI, food form and flavor on mastication: almonds as a test food.

OBJECTIVES: To investigate the effects of appetitive sensations, body mass index (BMI) and physical/sensory properties of food (almonds) on masticatory indices and resultant pre-swallowing particle sizes. SUBJECTS/METHODS: Twelve lean (BMI=22.2+/-0.3) and 12 obese (BMI=34.3+/-0.6) adults. After collecting appetitive ratings, electromyographic recordings were used to assess participants' microstructure of eating for five almond products (raw, dry unsalted roasted, natural sliced, roasted salted and honey roasted) under fasted and satiated conditions. Duplicate samples were masticated to the point of deglutition and then were expectorated and size sorted. RESULTS: No statistically significant effects of BMI were detected for any of the mastication measures. Maximum and mean bite forces were greater under the fasted condition. Sliced almonds required lower bite force than did the other almond varieties. The pre-swallowing particle sizes were significantly greater for the sliced almonds than all other varieties. Both the number of chews and mastication time were negatively correlated with particle size. There were no significant effects of almond form or flavor on particle size. CONCLUSIONS: These results do not support differences in masticatory performance between lean and obese individuals, nor effects of sensory properties. Instead, the physical form of foods as well as an individuals' appetitive state may have a greater influence on masticatory behavior. The health implications of these observations warrant further investigation.

Dietary variety and its effect on food intake of elderly adults.

BACKGROUND: Older people frequently have poor food intake. This present study investigated the effect of dietary variety on food intake in younger and older people. METHODS: Eighteen young adults (mean age = 26 years) and 18 older adults (mean age = 70 years) consumed four consecutive courses of sandwiches on two occasions. In the plain treatment, each course of sandwiches was of the same type, while in the variety treatment four courses, each of a different type of sandwich, were served. Each time the participants were presented with a serving of sandwiches and asked to eat as much as they liked. RESULTS: In the plain condition, the older adult group consumed more than their young counterparts. This situation was reversed for the variety condition when the young group ate more than the older adults. Interestingly, the older adult group ate more when a variety of sandwiches was presented. This may be contrary to what is predicted by the sensory-specific satiety model of eating behaviour. CONCLUSIONS: This study suggests that presenting the older people with a varied meal may be a valid strategy to improve food intake in this group.

Identification of an immune-responsive mesolimbocortical serotonergic system: potential role in regulation of emotional behavior.

Peripheral immune activation can have profound physiological and behavioral effects including induction of fever and sickness behavior. One mechanism through which immune activation or immunomodulation may affect physiology and behavior is via actions on brainstem neuromodulatory systems, such as serotonergic systems. We have found that peripheral immune activation with antigens derived from the nonpathogenic, saprophytic bacterium, Mycobacterium vaccae, activated a specific subset of serotonergic neurons in the interfascicular part of the dorsal raphe nucleus (DRI) of mice, as measured by quantification of c-Fos expression following intratracheal (12 h) or s.c. (6 h) administration of heat-killed, ultrasonically disrupted M. vaccae, or heat-killed, intact M. vaccae, respectively. These effects were apparent after immune activation by M. vaccae or its components but not by ovalbumin, which induces a qualitatively different immune response. The effects of immune activation were associated with increases in serotonin metabolism within the ventromedial prefrontal cortex, consistent with an effect of immune activation on mesolimbocortical serotonergic systems. The effects of M. vaccae administration on serotonergic systems were temporally associated with reductions in immobility in the forced swim test, consistent with the hypothesis that the stimulation of mesolimbocortical serotonergic systems by peripheral immune activation alters stress-related emotional behavior. These findings suggest that the immune-responsive subpopulation of serotonergic neurons in the DRI is likely to play an important role in the neural mechanisms underlying regulation of the physiological and pathophysiological responses to both acute and chronic immune activation, including regulation of mood during health and disease states. Together with previous studies, these findings also raise the possibility that immune stimulation activates a functionally and anatomically distinct subset of serotonergic neurons, different from the subset of serotonergic neurons activated by anxiogenic stimuli or uncontrollable stressors. Consequently, selective activation of specific subsets of serotonergic neurons may have distinct behavioral outcomes.

Abnormal adaptations to stress and impaired cardiovascular function in mice lacking corticotropin-releasing hormone receptor-2.

The actions of corticotropin-releasing hormone (Crh), a mediator of endocrine and behavioural responses to stress, and the related hormone urocortin (Ucn) are coordinated by two receptors, Crhr1 (encoded by Crhr) and Crhr2. These receptors may exhibit distinct functions due to unique tissue distribution and pharmacology. Crhr-null mice have defined central functions for Crhr1 in anxiety and neuroendocrine stress responses. Here we generate Crhr2-/- mice and show that Crhr2 supplies regulatory features to the hypothalamic-pituitary-adrenal axis (HPA) stress response. Although initiation of the stress response appears to be normal, Crhr2-/- mice show early termination of adrenocorticotropic hormone (Acth) release, suggesting that Crhr2 is involved in maintaining HPA drive. Crhr2 also appears to modify the recovery phase of the HPA response, as corticosterone levels remain elevated 90 minutes after stress in Crhr2-/- mice. In addition, stress-coping behaviours associated with dearousal are reduced in Crhr2-/- mice. We also demonstrate that Crhr2 is essential for sustained feeding suppression (hypophagia) induced by Ucn. Feeding is initially suppressed in Crhr2-/- mice following Ucn, but Crhr2-/- mice recover more rapidly and completely than do wild-type mice. In addition to central nervous system effects, we found that, in contrast to wild-type mice, Crhr2-/- mice fail to show the enhanced cardiac performance or reduced blood pressure associated with systemic Ucn, suggesting that Crhr2 mediates these peripheral haemodynamic effects. Moreover, Crhr2-/- mice have elevated basal blood pressure, demonstrating that Crhr2 participates in cardiovascular homeostasis. Our results identify specific responses in the brain and periphery that involve Crhr2.

An inverse relationship between serum immunoglobulin-G and intellectual functioning.

Serum immunoglobulin levels for IgA, IgE, IgG, and IgM were measured in 13 institutionalized, profoundly mentally retarded individuals and for 20 retarded and 29 intellectually average noninstitutionalized individuals. A significant elevation in IgG was observed for the retarded groups as compared with the intellectually average group. There was a significant inverse relationship between IgG and level of intellectual functioning. The elevated IgG is suggestive of the findings with auto-immune diseases and warrants further investigation.

Haptic attention and visual transfer by mentally retarded and nonretarded individuals.

Four mentally retarded and four nonretarded adolescents learned compound discriminations in the haptic (touch) modality using Ray's (1969) conflict-compound procedure. Reinforcement history was controlled so that prior reinforcement contingencies were unchanged for one element and reversed for the other element of a compound (two-element) stimulus during discrimination training. Consistent with Huguenin and Touchette's (1980) results in the visual modality, our retarded subjects evinced selective attention effects in posttraining tests conducted in the haptic modality. Results with nonretarded subjects similarly indicated that they had selectively attended to only one element of a conflict-compound stimulus during compound discrimination training. Visual transfer tests revealed that for most individuals the effects of conflict-compound discrimination training transferred from the haptic to visual sensory modalities. Results were discussed in terms of selectivity of attention to nonredundant stimulus elements as an effective strategy for discrimination learning rather than a perceptual deficit.

Life threatening behavior: analysis and intervention. Summary and discussion of special issues.

This chapter summarizes issues relevant to analyzing and treating LTB. This is a difficult area in which to conduct research and develop functional interventions; however, it is important to the welfare and dignity of those afflicted with LTB. This chapter has suggested the development of a unified approach to the study and treatment of LTB. We should view LTB as a system or class of systems (composed of multiple behavioral components) rather than isolated incidences of maladaptive behavior. It has been shown that the various classes of LTB have common ground, including 1) theoretical orientation; 2) intervention techniques; and 3) future research strategies. Finally, because many of the factors controlling the occurrence of LTB are unknown, research should be directed toward those factors. Once these factors are understood and effective treatment methods and procedures are established, it will be necessary to conduct direct and systematic replications to establish empirical validity and generality (Sidman, 1960).

Analysis of rocking behavior.

Operant conditioning techniques were applied to the study of stereotyped body-rocking movements. Six mentally retarded children were tested individually in a fully automated situation under the following conditions: (a) free operant baseline; (b) intense auditory stimulation; (c) variable-interval (VI) and fixed-ratio (FR) reinforcement schedules; (d) differential reinforcement of low rate (DRL); (e) differential reinforcement of other behaviors (DRO); and (f) noncontingent reinforcement. The results indicated: (a) intense auditory stimulation increased the rate of rocking movements in four of six subjects; (b) VI and FR schedules generated curves that are representative of these schedules; (c) DRL schedules decelerated high-rate rocking; (d) DRO schedules eliminated high-rate rocking; (e) noncontigent reinforcement increased variability and resulted in decreased rate of responding. In conclusion, the data support the hypothesis that body-rocking movements in the mentally retarded are an operant and reflect the established characteristics of reinforcement schedules and operant controls.

A nonvocal system for teaching retarded children to read and write.

This study investigated the development of nonvocal teaching of reading and writing in severely retarded children. Fourteen subjects were selected who demonstrated limited communication skills, and were randomly placed into two groups. Group A received training procedures utilizing abstract plastic symbols which were arbitrarily assigned to represent specific words. The training program was divided into three phases. Phase I consisted of training left to right sequencing of four color--coded forms; Phase II consisted of training of matching symbols to stimulus pictures; and Phase III consisted of training of fading from symbols to printed words. The subjects completing this training program demonstrated the ability to learn selected reading and writing skills, i.e., they learned to sequence an article, subject noun, auxiliary verb, and verb. They also demonstrated functional semantic comprehension of five nouns and five verbs. Thirteen subjects finished the communication training program in less than four months with a mean training of 7 hours and 55 minutes. This is approximately 2 hours of training a month per subject to learn these skills. The data showed that Group B (rebuses) required fewer trials than Group A (abstract symbols) to meet criterion for Phase II, matching symbols to stimulus pictures. This suggests that Group B subjects may have had a meaningful association for the rebus signs which generalized to stimulus pictures. Group A (abstract symbols) required fewer trials than Group B (rebuse) to meet criterion for Phase 111, matching printed words to stimulus pictures. This indicates that perhaps Group A's training with abstract symbols positively affected learning to read printed words. The success of the visual nonvocal treatment program with the severely retarded is encouraging. Indeed, this is a different and viable approach in teaching communication skills (reading and writing) to the retarded.

Chlorpromazine: direct measurement of differential behavioral effect.

A retarded child with a high stereotyped rocking rate was conditioned to pull a ball on a reinforcement schedule in which the fixed ratio aof rewarded to nonrewarded responses was 100. Results show no rocking movements during ball-pulling; but when ball-pulling was on extinction, rocking returned to its original rate. Chlorpromazine blocked rocking movements during extinction, but had no effect on ball-pulling. Delivery of one free reinforcer was sufficient to reinstate ball-pulling after extinction, but the stimulus properties of the free reinforcer were not affected by the drug.