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Nutrient tasting and signaling mechanisms in the gut V. Mechanisms of immunologic sensation of intestinal contents.

Immune perception of intestinal contents reflects a functional dualism with systemic hyporesponsiveness to dietary antigens and resident microflora (oral tolerance) and active immune responses to mucosal pathogens. This facilitates optimal absorption of dietary nutrients while conserving immunologic resources for episodic pathogenic challenge. Discrimination between dangerous and harmless antigens within the enteric lumen requires continual sampling of the microenvironment by multiple potential pathways, innate and adaptive recognition mechanisms, bidirectional lymphoepithelial signaling, and rigorous control of effector responses. Errors in these processes disrupt mucosal homeostasis and are associated with food hypersensitivity and mucosal inflammation. Mechanisms of mucosal immune perception and handling of dietary proteins and other antigens have several practical and theoretical implications including vaccine design, therapy of systemic autoimmunity, and alteration of enteric flora with probiotics.

Animals↗

Perception of chemotherapy side effects cancer versus noncancer patients.

PURPOSE: This study was conducted to identify and compare perceptions regarding the disruption in quality of life caused by chemotherapy side effects in patients with cancer receiving chemotherapy and in noncancer, chemotherapy-naive patients. DESCRIPTION OF STUDY: One hundred forty-six patients with cancer and 224 patients without cancer completed two instruments to assess the perceived magnitude of 41 physical and psychosocial chemotherapy side effects. Instrument 1 used a 5-point Likert scale (1 = not at all; 2 = a little bit; 3 = somewhat; 4 = quite a bit; and 5 = very much) to summarize patient responses to the question, "How much did or would each of the following side effects of chemotherapy bother you?" Instrument 2 was a serial ranking questionnaire that asked patients to select the 10 most bothersome side effects to numerically rank the top five. An index of the relative magnitude of chemotherapy side effects was calculated for each instrument. RESULTS: For patients with cancer, loss of hair 50%), changes in taste (46%), constantly being tired (42%), affects work duties (39%), changes in smell perception (35%) were most frequently perceived as bothering them "quite a bit" or "very much." Nausea and vomiting were ranked 11th and 22nd, respectively. With instrument 2, the five side effects perceived as most troublesome were, in decreasing order: nausea, loss of hair, constantly tired, vomiting, and changes in the way things taste. For noncancer patients, those factors potentially bothersome "quite a bit" or "very much" were: financial hardship (82%), hardship on family (78%), vomiting (73%), shortness of breath (70%), and ability to perform work duties (69%). Via instrument 2, the top five side effects, in decreasing order were: vomiting, hardship on family, loss of hair, financial hardship, nausea, having to move close to a treatment center. CLINICAL IMPLICATIONS: Noncancer, chemotherapy-naive patients perceived most chemotherapy-associated side effects as having greater impact on the quality of life than did cancer patients who had received chemotherapy. These findings can be used to direct patient education, education of the public, specific materials concerning cancer chemotherapy. The expertise of various members of the healthcare team can maximize the patient's comprehension of the adverse effects of the treatment options. The physician's knowledge of the overall treatment plan can assist in patient understanding; oncology pharmacists nurses are in a unique position to educate patients their families regarding potential chemotherapy side effects.

Adult↗

The receptors and coding logic for bitter taste.

The sense of taste provides animals with valuable information about the nature and quality of food. Bitter taste detection functions as an important sensory input to warn against the ingestion of toxic and noxious substances. T2Rs are a family of approximately 30 highly divergent G-protein-coupled receptors (GPCRs) that are selectively expressed in the tongue and palate epithelium and are implicated in bitter taste sensing. Here we demonstrate, using a combination of genetic, behavioural and physiological studies, that T2R receptors are necessary and sufficient for the detection and perception of bitter compounds, and show that differences in T2Rs between species (human and mouse) can determine the selectivity of bitter taste responses. In addition, we show that mice engineered to express a bitter taste receptor in 'sweet cells' become strongly attracted to its cognate bitter tastants, whereas expression of the same receptor (or even a novel GPCR) in T2R-expressing cells resulted in mice that are averse to the respective compounds. Together these results illustrate the fundamental principle of bitter taste coding at the periphery: dedicated cells act as broadly tuned bitter sensors that are wired to mediate behavioural aversion.

Animals↗

[Psychophysics of sweet taste. I. Goals and methods of investigation].

With a view to the solution of problems concerned with the consumer's acceptance of foods in which saccharose had been substituted, a discussion is opened on psychologic and physiologic aspects of the measurability of sensory stimulus-sensation relations. The classic method for measuring taste is the determination of the taste discrimination threshold which is also termed least discernible difference. In the lat years, the discrimination threshold has been determined and calculated mainly as the mean concentration (stimulus) difference resulting from the distribution of the tasters according to their efficiency (probit analysis). In contrast, the new method, which is described in detail, is based on the dependence of the probability of a perception of difference upon the intensity which is linear and represents the initial course of a stimulus-response curve. Differences in efficiency in the group of tasters, which is assumed to be homogeneous, are included in the variance of difference frequencies found. The control of the course of the test by sequential analysis and the binomial weighting of the probabilities obtained allow to perform calculations of the discrimination threshold which are largely free from systematic errors; this discrimination threshold is defined as the concentration difference that engenders the arbitrarily defined alternative probability of Pa = 0.75. To minimize the risk of overrating the measurement result, it is suggested to calculate in addition, on the basis of the binomial distribution, the confidence limits of the discrimination threshold. Furthermore, the constant stimulus method for determining the perception of two stimulus intensities of different sweetening agents is adapted, as to performance and calculation, to the new aspects in discrimination threshold determination.

Consumer Behavior↗

Pungent qualities of sanshool-related compounds evaluated by a sensory test and activation of rat TRPV1.

The detection threshold and taste characteristics of sanshools were examined by sensory evaluation, after isolating four sanshools (alpha-, beta-, gamma-, and delta-), and two hydroxy sanshools (alpha- and beta-) from the pericarp of Japanese pepper. The Scoville unit (SU) values of the four sanshools were in the range of 80,000-110,000, while those of hydroxy sanshools were 3-5 fold lower than corresponding sanshools. The pungent qualities of each sanshool were different. Burning and tingling were predominantly perceived and lasted for the longest time with alpha-sanshool. Burning and fresh for gamma-sanshool, and tingling and numbing for hydroxy alpha-sanshool were perceived. Tests on the activation of rat TRPV1 were also performed. All of them were weak agonists. Among them, gamma-sanshool was the most potent agonist, although its EC50 value of 5.3 microM was 230 fold higher than that of capsaicin. These results indicate that it would be difficult to explain the pungent quality of each sanshool simply in terms of TRPV1 activation.

Adult↗

Use it or lose it: molecular evolution of sensory signaling in primates.

Sensory organs provide key and, in many cases, species-specific information that allows animals to effectively forage, find mates, and avoid hazards. The primary sensors for the vertebrate senses of vision, taste, and smell are G-protein-coupled receptors (GPCRs) expressed by sensory receptor cells that initiate intracellular signal transduction cascades in response to activation by appropriate stimuli. The identification of sensory GPCRs and their related downstream transduction components from a variety of species has provided an essential tool for understanding the molecular evolution of sensory systems. Expansion of the number of genes encoding sensory GPCRs has, in some cases, expanded the repertoire of signals that animals detect, allowing them to occupy new niches, while, in other cases, evolution has favored a reduction in the repertoire of receptors and their cognate signal transduction components when these signals no longer provide a selective advantage. This review will focus on recent studies that have identified molecular changes in vision, smell, taste, and pheromone detection during primate evolution.

Animals↗

Fish-odor syndrome presenting as dysosmia.

We describe a patient who had perceived an unpleasant odor or taste for at least 20 years. Several other physicians had unsuccessfully treated her for infections, mucus membrane dryness and inflammation, chronic tonsillitis, and psychiatric disorders. Her workup at the State University of New York Health Science Center at Syracuse Olfactory Referral Center included a thorough history, examinations (including endoscopic studies of her nose, pharynx, and lungs), roentgenograms, taste testing, olfactory testing, and selective anesthesia of her chemosensory areas. The perception occurred only during exhalation, and appeared to be binasal. These findings, together with her morning mucus sample having a strong fishlike odor, prompted us to suspect a metabolic problem. Further testing at the Monell-Jefferson Chemosensory Clinical Research Center, Philadelphia, Pa, confirmed that she had trimethylaminuria. It is important to consider this and other treatable conditions when evaluating individuals with olfactory complaints.

Adult↗

Gustatory reaction time to various salt solutions in human adults.

Reaction times and perceived intensities to various concentrations of 12 salt solutions were measured in 53 human adults. The reaction time (T) decreased and the perceived intensity (S) increased with increasing concentration (C) of each salt applied to the anterior dorsal tongue. The relationships between T and S, T and logS, T and C, and T and logC are well described by experimental formulae of rectangular hyperbola for all the 12 salt solutions. Effects of cross-adaptation with 0.1 M NaCl on the reaction times to various salt solutions were also examined. Changes of the perceived intensity of salt solutions were calculated based on the formulae using the amount of increase or decrease in reaction times after the cross-adaptation. The theorectical values thus obtained were highly significantly correlated with the psychophysical values reported by previous workers.

Adaptation, Physiological↗

Color affects perceived odor intensity.

In Experiment 1, some odorous solutions (e.g., strawberry) were rated as smelling stronger when colored (e.g., red) than when colorless. Experiment 2 showed this effect to be due to a perceptual change rather than a response to experimental demand characteristics. Experiment 3 showed that the color-induced increase in odor intensity is not due to subjects' preexperimental experience with particular color-odor combinations, because the increase occurred with novel ones. We conclude that color induces a weak olfactory percept that combines with odorant-induced percepts. The effect may be due to conditioning or may be the result of residual intersensory neural connections left over from infancy.

Adult↗

Effect of color on judgments of food aroma and flavour intensity in young and elderly adults.

The hypothesis was tested that subjects' judgments of food aroma and flavour strength will be increasingly influenced by food color as the chemosensory differences between foods become less apparent. Elderly (n = 24) and young (n = 22) adults were presented with pairs of food samples and instructed to indicate which sample had the more intense aroma or flavor. The chemosensory discriminations varied in difficulty, and the color of the food pairs was also manipulated so that either they were similarly colored, or the color strength differed so that it was either positively or inversely correlated with flavour strength. Overall, the results failed to support the hypothesis that color alters the perceived intensity of the food aroma or flavor. There was a weak trend toward a greater number of errors among sample pairs that varied in color, especially when color strength was inversely related to flavor strength. Elderly and young adult groups did not differ in chemosensory ability or in their responses to food color differences, although the elderly adults were significantly more certain of the accuracy of their chemosensory judgments.

Adult↗

Color preference and food choice among children.

The effects of color on children's food choices were investigated. Subjects were 120 children who were equally distributed among each of the combinations of age (5 vs. 9 years old), sex (male vs. female), food type (3 types of candies), and color (red, green, yellow, and orange) in a counterbalanced, factorial, analysis-of-variance design with repeated measures on subjects. A significant main effect for color indicated that children preferred foods that were red, green, orange, and yellow, in that order. Interpretation of this main effect was not interfered with by main effects or interaction terms involving age, sex, or food type, which served as alternative rival hypotheses.

Candy↗

The Espinet and the perceptual learning effects in flavour aversion conditioning: do they depend on a common inhibitory mechanism?

In three experiments rats were given short or long preexposure (4 or 10 sessions) to two compound flavours, AX and BX, according to an intermixed or a blocked schedule. Following preexposure, aversion conditioning trials were given with AX as the conditioned stimulus (CS). In Experiments 1 and 2, retardation and summation tests were then carried out to assess the inhibitory properties of B (an Espinet procedure). In Experiment 3, test trials evaluated generalization from AX to BX (the standard perceptual learning procedure). The results showed that B performed as an inhibitor of the unconditioned stimulus (US; an Espinet effect) only after long intermixed preexposure, whereas a reliable perceptual learning effect was observed both after short and after long preexposure. The observation that B had no detectable inhibitory properties after short preexposure casts doubt on the suggestion that inhibitory learning is responsible for perceptual learning after brief exposure to AX and BX.

Animals↗

The effect of sweeteners on perceived viscosity.

Two different sweeteners, sucrose and aspartame, were matched in perceived sweetness intensity. These solutions were thickened with carboxymethylcellulose to six different viscosity levels. Sucrose and aspartame appeared to decrease perceived viscosity of the solutions at a specific sweetener concentration, at all viscosity levels. However, in a second similar experiment with three viscosity levels and seven sucrose concentrations no effect of sucrose concentration on perceived viscosity was found. Reasons for these conflicting results are discussed. No definite conclusions about the effect of sweeteners on perceived viscosity can as yet be drawn.

Adult↗

Sensory evaluation of mixtures of maltitol or aspartame, sucrose and an orange aroma.

The suitability of Beidler's mixture equation for mixtures of sucrose and maltitol as well as for mixtures of sucrose and aspartame was examined in the presence of an orange aroma. The mean scores for the attribute sweet remained constant for each combination of sucrose and maltitol and for each combination of sucrose and aspartame. Therefore, Beidler's mixture equation can be used to choose combinations of sucrose and maltitol and of sucrose and aspartame giving the same sweetness. Quantitative descriptive analysis of different solutions indicated that the flavour profiles of sucrose and maltitol did not differ significantly at a constant concentration of orange aroma. However, flavour profiles of solutions with increasing aspartame concentrations (but constant aroma levels) showed significantly higher scores for the attributes sour, chemical and aftertaste. Addition of orange aroma provided the different solutions with a more distinct flavour. The mean scores for the attributes orange, sour, fruity and aftertaste increased significantly for most of the sucrose-maltitol mixtures. This effect of orange aroma was even more pronounced in solutions containing combinations of sucrose and aspartame. Further comments on the attribute aftertaste showed similar terms for the different solutions, the most often mentioned being orange, sour, fruity and chemical for solutions containing the orange aroma. The aftertaste of solutions containing relatively more aspartame was mainly described as sweet and chemical.

Adult↗

Understanding soft drink consumption among female adolescents using the Theory of Planned Behavior.

This study identified factors that influence regular soda consumption among 707 female students, aged 13-18 years, attending North Los Angeles County public high schools. Participants completed a group-administered Theory of Planned Behavior-based questionnaire. Almost all of the participants, 96.3%, reported that they currently drink soda; 50.1% reported drinking 2 glasses of soda or more per day during the past year. Students reported drinking regular soda more than diet soda and reported drinking phosphoric acid-containing soda more than non-phosphoric acid-containing soda. Attitude, subjective norm and perceived behavioral control had statistically significant positive associations with intention, and were each significant predictors of intention to drink regular soda and together explained 64% of its variance. The strongest predictor was attitude, followed by perceived behavioral control and subjective norm. Our results suggest that efforts to reduce soda consumption among female adolescents should include parents and friends. It is also important that soda should not be excessively available at home or widely accessible to teenagers at schools. Healthy eating messages for adolescents need to be developed and incorporated into existing and future campaigns to reinforce the perception that there are other healthier drinks that quench thirst and that taste good as well.

Adolescent↗