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PubMed1995

Propylthiouracil tasting: determination of underlying threshold distributions using maximum likelihood.

The ability to taste low concentrations of propylthiouracil (PROP) and related bitter compounds is heritable. The current analysis determines whether the distribution of PROP taste thresholds is consistent with an additive or a dominant mode of Mendelian transmission. To that end, the lowest concentration of PROP detectable was determined for 1015 subjects and models of bi- or tri-modal distributions of PROP taste thresholds were tested. The model with the greatest likelihood had three distributions and followed an additive model of PROP taste sensitivity if the variances associated with the distributions were assumed to be equal. However, if the taste thresholds were transformed to remove skewness, or if the variances were unequal, then three- or two-distribution models were equally likely. Resolution of the mode of inheritance for bitter taste perception awaits additional family studies and the characterization of the molecular basis of taste perception for these bitter compounds.

Adolescent↗
PubMed1990

Mechanism for the bitter tasting potency of peptides using O-aminoacyl sugars as model compounds.

In order to study the role of hydrophobicity in bitter peptides, several O-aminoacyl sugars, in which amino acids or peptides were attached to the 2- and 3-position of methyl alpha-D-glucopyranoside, were synthesized and sensory analyses were carried out. It was found that the bitterness increased as the hydrophobicity of compounds increased, implying that the bitterness receptor recognizes the hydrophobicity of bitter peptides. A structure for the bitterness receptor is also discussed.

Amino Acid Sequence↗
PubMed1996

Consideration in selecting crops for the human-rated life support system: a Linear Programming model.

A Linear Programming model has been constructed which aids in selecting appropriate crops for CELSS (Controlled Environment Life Support System) food production. A team of Controlled Environment Agriculture (CEA) faculty, staff, graduate students and invited experts representing more than a dozen disciplines, provided a wide range of expertise in developing the model and the crop production program. The model incorporates nutritional content and controlled-environment based production yields of carefully chosen crops into a framework where a crop mix can be constructed to suit the astronauts' needs. The crew's nutritional requirements can be adequately satisfied with only a few crops (assuming vitamin mineral supplements are provided) but this will not be satisfactory from a culinary standpoint. This model is flexible enough that taste and variety driven food choices can be built into the model.

Crops, Agricultural↗
PubMed1991

Transduction mechanisms for the taste of amino acids.

Amino acids are important taste stimuli for a variety of animals. One animal model, the channel catfish, I. punctatus, possesses sensitive taste receptor systems for several amino acids. Neurophysiological and biochemical receptor binding studies suggest the presence of at least three receptor pathways: one is a relatively nonspecific site(s) responsive to short-chain neutral amino acids such as L-alanine (L-ALA); another is responsive to the basic amino acid L-arginine (L-ARG); still another is a low affinity site for L-proline (L-PRO). Several possible transduction pathways are available in the taste system of this animal model for these amino acids. One of these, formation of inositol trisphosphate (IP3) and cyclic AMP (cAMP), is mediated by GTP-binding regulatory proteins, while another involves ion channels directly activated by stimuli. L-ALA is a potent stimulus to cAMP and IP3 accumulation, while L-ARG at low concentrations is without effect. On the other hand, L-ARG and L-PRO, but not L-ALA, are able to activate stimulus-specific and cation-selective channels in taste epithelial membranes reconstituted in phospholipid bilayers at the tips of patch pipettes. Preliminary studies using mouse taste tissue demonstrate that monosodium-L-glutamate (MSG) did not enhance production of IP3 or cAMP. However, in reconstitution experiments using taste epithelium of mouse, conductance changes due to MSG are observed. The specificity of this channel(s) and its uniqueness have yet to be determined.

Amino Acids↗
PubMed1996

Modeling the structure of the combining site of an antisweet taste ligand monoclonal antibody NC10.14.

We report the predicted combining site structure of the monoclonal antibody fragment, NC10.14, which is specific for the superpotent sweetener, N-(p-cyanophenyl-N'-(diphenylmethyl) guanidine acetic acid, using computer-aided molecular modeling and experimental methods, such as fluorescence spectroscopy and circular dichroism. This is the first computer-aided modeling study on a lambda-chain antibody fragment. We have also identified the amino acids that are involved in ligand binding. Aromatic residues, L:91(W), L:96(W), and H:100G(Y) are predicted to make van der Waals contacts with the p-cyanophenyl moiety of the ligand. Residue H:56(K) is predicted to provide a counterion for the acetic acid moiety, and H:50(E) provides the negatively charged potential for interaction with the positive guanidinium group. We also make a comparison of the binding site architecture of NC10.14 with that of a related monoclonal antibody fragment NC6.8.

Acetates↗
PubMed1997

Curculin, a sweet-tasting and taste-modifying protein, is a non-functional mannose-binding lectin.

A three-dimensional model of curculin, a sweet-tasting and taste-modifying protein from the fruits of Curculigo latifolia, was built from the X-ray coordinates of GNA, a mannose-binding lectin from snowdrop (Galanthus nivalis). The three mannose-binding sites present in GNA were found in curculin but are devoid of mannose-binding activity as shown by docking experiments performed with mannose. Some regions well exposed on the surface of the three-dimensional model of curculin could act as epitopes responsible for the sweet-tasting properties of this protein.

Amino Acid Sequence↗
PubMed1993

Neural mechanisms of taste aversion learning.

When ingestion of a taste stimulus is paired with internal malaise the animal remembers the taste and rejects its ingestion thereafter. A model of neural substrate for this conditioned taste aversion (CTA) is presented on the basis of our recent experiments. To establish the CTA in rats, 0.01 M saccharin was paired with i.p. injection of 0.15 M LiCl. Behavioral lesion experiments by means of ibotenic acid showed that the parabrachial nucleus (PBN), medial thalamus (MT), and lateral part of the amygdala (LPA) were crucial to establish the CTA. c-fos immunoreactivity studies showed that ingestion of saccharin induced a remarkable activation of the central lateral (cl) subnucleus of the PBN in normal rats, however, rats with the CTA to saccharin showed c-fos neurons in the ventral lateral (vl) subnucleus of the PBN. These findings suggest that the recipient zone for saccharin taste switches from the cl to vl subnuclei after acquisition of a CTA. The taste pathway from the vl subnucleus to the LPA through the MT may be a neural substrate for taste aversion learning. The switching may result from a plastic change involving long-term potentiation and depression due to a convergence of the taste input of saccharin and general visceral information of LiCl injection.

Animals↗
PubMed1990

Individual differences in taste, body weight, and depression in the "helplessness" rat model and in humans.

The helplessness paradigm is used extensively in basic stress research and is an experimental model of clinical depression. In Experiment 1, exposure to unsignaled, inescapable shock resulted in finickiness about drinking a weak quinine solution, as previously reported. In contrast, exposure to escapable shock resulted in marked individual differences in finickiness that were predicted by prestress body weight. A more sensitive index of finickiness was used in Experiment 2, and a correlation between body weight and finickiness was observed in nonshocked rats. In Experiment 3, measures of quinine reactivity and body weight predicted depressive symptomatology in a nonclinical human sample. Although research in the helplessness paradigm usually focuses on environmental determinants of distress, the paradigm may help identify and explain individual differences in, or intrinsic modulation of, stress and depression.

Adolescent↗
PubMed2001

Increased histone acetyltransferase and lysine acetyltransferase activity and biphasic activation of the ERK/RSK cascade in insular cortex during novel taste learning.

Changes in gene expression are thought to be involved in neuronal plasticity associated with learning and memory. Although acetylation of lysine residues on histones by histone acetyltransferases (HAT) is an obligatory component of transcription, HAT activity has been largely ignored in studies of the nervous system. We developed a new model for studying novel taste learning using novel solid food presentation to nondeprived animals. Using this behavioral paradigm, we investigated short- and long-term regulation of lysine acetyltransferase activity and the ERK/mitogen-activated protein kinase (MAPK)/RSK cascade in insular cortex, a CNS region known to be crucial for the formation of novel taste memories. We observed that novel taste learning elicited biphasic (acute and long-lasting) activation of two distinct lysine acetyltransferase activities along with the ERK/MAPK cascade in insular cortex. In vitro studies revealed that the ERK cascade could regulate the lysine acetylation of a 42 kDa lysine acetyltransferase substrate, suggesting a causal relationship between ERK activation and lysine acetyltransferase activity in insular cortex. Overall, our studies reveal an unanticipated long-lasting activation of insular cortex signal transduction cascades in novel taste learning. Furthermore, our studies suggest the hypothesis that acute and long-term ERK activation and lysine-histone acetyltransferase activation may play a role in regulating gene expression in single-trial learning and long-term memory formation.

Acetylation↗
PubMed1993

Perceptual integration in heterogeneous taste percepts.

When mixtures of dissimilar tasting compounds are perceived, specific taste sensations are integrated into a percept. Four models are evaluated that were designed to predict the total taste intensity of a mixture percept from the total taste intensities of the unmixed components or from the specific taste intensities of the components within the mixture percept. The predictions of the two dominant component models are inferior to those made by the two other models. Predictions made by the vector summation model are accurate, but the model contains theoretical weaknesses that make it an invalid psychological integration model. The sum of sensations model predicts total intensity with an accuracy similar to the vector summation model, but it is more parsimonious. Furthermore, it can account for all of the empirical phenomena observed.

Citrates↗
PubMed1980

Interaction of alpha-L-aspartyl-D-phenylalanine methyl ester with the receptor site of the bitter taste.

The analysis of the structure-activity relationship previously performed on the sweet L,L isomer of Asp-Phe-OMe was extended to the bitter L,D diastereoisomer. A combination of NMR measurements and of an original method of PEM calculations gives a description of the conformational state of the L,D isomer that can be effectively used to study the interaction with a previously proposed model of the bitter taste receptor site.

Aspartame↗
PubMed1999

The effect of flavor principles on willingness to taste novel foods.

E. Rozin and P. Rozin have suggested that one of the functions of "flavor principles" (the distinctive seasoning combinations which characterize many cuisines) is to facilitate the introduction of novel staple foods into a culture by adding sufficient familiarity to decrease the neophobia ordinarily produced by a new food. We tested this idea experimentally, predicting that the addition of a familiar flavor principle to a novel food would increase individuals>> willingness to taste it, in comparison to their willingness to taste the same food in the absence of the flavor principle. Since people have little reluctance to approach familiar foods, addition of a familiar flavor principle to a familiar food should have little effect on willingness to taste it. In a pilot study, subjects selected from a list, a sauce which was high in familiarity and liking for them. They then rated their willingness to taste one novel and one familiar food with the sauce and one of each with no sauce. Subjects did not actually see any foods-the familiar and novel foods were simply described-and they were aware that they would not actually be tasting any foods. In the study proper, subjects rated their willingness to try each of the four food/sauce combinations described above. In this study, they actually saw the foods they were rating and were under the impression their ratings would determine what they would taste later in the study. In both studies, the addition of a familiar sauce to a novel food increased subjects>> willingness to taste it (in comparison to the same food with no sauce) while the addition of a sauce to a familiar food either had no effect or decreased subjects>> willingness to taste it. In the pilot study, the "flavor principle" effect interacted with subjects>> levels of food adventurousness.

Adolescent↗
PubMed1988

Magnetic field effects on dental amalgam in divers welding and cutting electrically underwater.

Divers have for some years been complaining about a metallic taste in the mouth while electrically welding and cutting underwater. This paper reports on results from an assessment of this problem. It was hypothesized that the magnetic fields arising from the welding or cutting current could correlate with the reported symptoms. The intraoral magnetic flux density was calculated to 1.15 mT, at 650 ADC, in a normal cutting situation. This was verified in vivo. This magnetic field was shown to contain an AC component that is a candidate for inducing secondary currents in the oral tissues and restorative materials. Five submerged divers exposed to a magnetic field of 0.35 mT did not report any metallic taste. Magnetophosphenes were reported by 1 diver. (Magnetophosphenes are luminous impressions due to excitement of the retina by a magnetic field in addition to or in place of impingement of light rays.) Only a slight shielding effect to magnetic fields was observed due to a copper-brass helmet. An in vitro model for exposure of dental amalgams to magnetic fields was designed. Recommendations for decreasing the magnetic field surrounding the diver in practical work is given.

Adult↗
PubMed1992

Intracellular free calcium concentrations in single taste receptor cells in the guinea pig.

Single, viable taste receptor cells were isolated from the tongue of the guinea pig by enzymatic digestion and mechanical dissociation. The cells could be classified into flask, spindle and intermediate shapes. The intracellular free calcium ion concentrations [(Ca2+)i] of these cells were determined using the Ca2+ sensitive dye fura-2 and digital imaging microscopy. All types of cells produced an irreversible increase in (Ca2+)i upon addition of Ca2+ ionophore ionomycin (1 microM) and denatonium (10 microM). There was no evidence of any increase in (Ca2+)i in the taste receptor cells in nominally Ca2+ free solution, and when stimulated by denatonium (10 microM). When 3 mM CaCl2 was added, the (Ca2+)i remarkably increased. This would suggest that the (Ca2+)i increase in the presence of denatonium mainly depended on calcium influx from the extracellular space. There was no increase in case of high potassium (50 mM and 150 mM) or saccharose (1 mM and 5 mM) stimulation. The hypothesis that the increase in (Ca2+)i controls biochemical mechanisms related to the bitter taste transduction process is worthy of further study.

Animals↗
PubMed1985

Targets of learned food aversions in humans.

In order to determine whether some nutrients are more salient targets than others for the development of learned taste aversions a large group of normal human subjects were surveyed about their experiences with such aversions. The targets of these spontaneously occurring food aversions were identified and classified into general food categories. A prominent category for human aversions proved to be foods which were protein sources. This finding was similar to our observations in the clinical setting as well as those we have obtained using an animal model. It suggests that taste and/or postingestive properties of protein foods may make them particularly salient targets for food aversion learning.

Animals↗
PubMed1982

Alcohol and taste-mediated learning.

Taste-mediated learning is relevant to the alcohol consumption patterns of animals. This review concludes that taste aversion learning has thus far prevented development of an animal model of alcoholism. The presence of a taste cue, lack of control over alcohol administration, and high alcohol concentrations or dosages all facilitate the development of alcohol aversions. There is little evidence that taste preference learning is involved in the development of alcohol dependence. Data from taste-mediated learning research with animals are consistent with drinking patterns of human alcoholics.

Alcohol Drinking↗