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PubMed2004

Characterization of nutty flavor in cheddar cheese.

The objectives of this study were to determine the volatile components responsible for the sensory perception of nutty flavor in Cheddar cheese. Cheddar cheeses with and without nutty flavors were selected by descriptive sensory analysis. Volatile aroma components from Cheddar cheeses with and without nutty flavors were isolated and characterized using solvent extraction with high vacuum distillation, dynamic headspace analysis, gas chromatography-olfactometry, and gas chromatography-mass spectrometry. More than 50 aroma-active compounds were detected in Cheddar cheeses. Consistent differences were observed between nutty and not nutty Cheddar cheeses. Strecker aldehydes were detected in higher amounts in Cheddar cheeses with nutty flavors compared with Cheddar cheeses without nutty flavors. Strecker aldehydes, dimethyl sulfide, and propionic acid were evaluated in young and aged Cheddar cheese models for nutty flavor by descriptive sensory analysis. Dimethyl sulfide and propionic acid did not contribute to nutty flavor in Cheddar cheese. The addition of Strecker aldehydes to young (<4 mo old) Cheddar cheese models resulted in nutty/malty flavor perceived by sensory analysis. When Strecker aldehydes were incorporated into aged (>9 mo old) Cheddar cheese models, nutty flavor perception increased. Strecker aldehydes contribute to nutty flavor in aged Cheddar cheese.

Aldehydes↗
PubMed2000

Development of salt-responsive neurons in the nucleus of the solitary tract.

The rodent gustatory system has become a popular and useful model for the study of brain development because of this system's protracted period of postnatal maturation and its sensitivity to subtle changes in the animal's sensory environment. The goal of this investigation was to improve our understanding of dendritic remodeling exhibited by second-order gustatory neurons by presenting a comprehensive and definitive description of the development of the dendritic architecture of taste-sensitive neurons in the rostral nucleus of the solitary tract. Extracellular and intracellular recording and intracellular labeling techniques were used to examine the structure and function of individual gustatory neurons in three groups of rats: (1) Postnatal day 13-21 (PND13-21), (2) Postnatal day 22-28 (PND22-28), and (3) Adult (postnatal day 60-90). We found that neurons that responded to all three of the salts in our taste array ("Salt Sensitive") exhibited a striking increase in the number of dendritic branch points, maximum branch order, swelling density, and spine density between the PND13-21 and PND22-28 periods. These increases were followed by a period of dendritic remodeling during which the values for all measures except spine density decreased significantly. The neurons that did not respond to all three salts exhibited no change in the number of dendritic branches, branch order, or spine density during development, but they did undergo a decrease in swelling density. We also found that there was a significant decrease in the total dendritic length and cell volume of Salt Sensitive neurons between the PND22-28 and Adult periods, whereas the cells that did not respond to all three salts exhibited an increase in dendritic length and cell volume between postnatal day 28 and adulthood. Finally, we found that the dendrites of the Adult Salt Sensitive neurons were more restricted in the rostrocaudal axis than either the PND13-21 or PND22-28 Salt Sensitive cells. In contrast, there were no significant changes in the rostrocaudal extent of the dendritic arbors of cells that did not respond to all three salts. When viewed in the context of the extant literature and our own preliminary studies that used modified salt diets, we propose that these results provide strong support for the hypothesis that there is a relationship between postnatal dendritic development (particularly remodeling) and the animal's sensitivity to salts.

Age Factors↗
PubMed1996

Functional and morphological observations on the microvascular structure of the filiform and fungiform papillae in the cat tongue.

The purpose of this study was to undertake a three-dimensional comparative observation of the microvascular cast specimen (MVCS) of the filiform papillae (FiP) and fungiform papillae (FuP) on the dorsal surface of the cat tongue. By means of the corrosive resin casting technique, the MVCS of the FiP and FuP of the cat tongue were prepared and examined in detail under the scanning electron microscope (SEM). The numerous FiP and FuP distributed sporadically among the different types of the FiP were found on the entire dorsal surface of each cat tongue. A single FiP consisted of a main process (MP) which contained a large spoon-shaped concave network process and the accessory process (AP) contained a bundle of spine-like processes, arranged in a circle at the basal margin of the MP. The FiP can be classified into five types (Type I-V) according to the shape and size of the MP and numbers of the AP. Each FuP consisted of a single MP which contained an ovoid head and many AP surrounding the basal margin of the MP. The FuP can be classified into four types (FuP I-IV) according to the shape and size of the MP and numbers of the AP. The MP of the FuP, a sense organ for taste, of the cat tongue was considered to be a transformed type from the MP of the FiP, which acquires the ability to masticate and swallow functionally.

Animals↗
PubMed2003

Georg von Békésy: visualization of hearing.

Georg von Békésy received the Nobel Prize in 1961 for his research on the functioning of the auditory system. In psychoacoustics, Békésy both extended and perfected the lines of research begun by von Helmholtz in the 19th century. First in his native Hungary and later at Harvard, Békésy used novel and imaginative devices and methods to observe and model the functioning of the inner ear. He also explored the nature of sensory inhibition by which the nervous system sharpens sensory transitions.

Auditory Perception↗
PubMed1989

Processes that contribute to radiocesium decontamination of feta cheese.

In a series of experiments, the transfer of radiocesium from ovine milk to feta cheese was investigated through modifications of the standard cheese making procedure. All variations explored showed no significant change in the percentage of radiocesium transfer and the milk-to-cheese transfer coefficient was determined as f=.79 plus/minus .04 L.kg-1. It is concluded that cesium, like the rest of the alkali metals, remains in the water phase and thus follows very closely the distribution of moisture into the products of cheese making. The possibility of radiocesium decontamination of mature feta during the customary storage of the product in brine was also explored in a second series of experiments. The theoretical model employed in the analysis of cesium transport from feta to brine is presented in the Appendix to this paper. Predictions of the model were validated by experiments. A procedure is thus proposed for decontaminating mature feta during storage through successive replacements of the storage medium. Nomograms are presented for the determination of the optimum time interval between changes of the brine and the radiocesium concentration remaining in the feta. Changes in the properties of the product induced by the proposed treatment were also investigated with respect to composition, taste, and overall quality.

Animals↗
PubMed1998

Appetitive and consummatory behaviors in the control of ethanol consumption: a measure of ethanol seeking behavior.

Models of ethanol self-administration in animals have demonstrated that ethanol can reinforce a variety of behaviors, independent of ethanol's caloric or fluid properties. However, the processes that control self-administration remain unclear. Determining factors related to ethanol seeking behavior, independent of consumption, is central to the concepts of intake regulation. The model described in this article proposes a method to separate the initial appetitive (seeking) behavior from the following consummatory (drinking) behavior to assess each behavior type. Rats were trained to lever press to gain access to a drinking tube connected to a fluid bottle containing either 10% ethanol or 3% sucrose for 20 min. When the response requirement to obtain access to the tube was increased, it was found that both solutions supported the same amount of responding (breakpoint was at approximately a fixed ratio 32 requirement), indicating equal reinforcer strength. However, regardless of the response requirement, if access to the fluids occurred, intakes were not changed. This suggests that factors besides those of reinforcer efficacy are important in controlling the size of the consummatory bout. Based on these findings, we believe that this model will be useful in determining factors related to seeking behaviors and the control of drinking bout size.

Alcohol Drinking↗
PubMed2005

The role of the NMDA receptor in alcohol relapse: a pharmacological mapping study using the alcohol deprivation effect.

Modulators of glutamate receptors especially of the N-methyl-D-aspartate receptors (NMDARs) have recently been suggested as putative pharmacotherapeutic agents in the treatment of alcohol relapse. However, at present it is not clear, which binding and modulatory sites of the NMDAR are involved in relapse behavior. We, therefore, performed a pharmacological mapping study in long-term alcohol drinking rats using the alcohol deprivation effect (ADE) as a model for relapse behavior. In a comprehensive fashion, we studied dose-response curves, employing the following selective pharmacological agents: the NMDAR competitive antagonist CGP37849, the glycine binding site antagonist L-701.324, the NR2B subunit selective antagonist ifenprodil, which acts at the polyamine binding site, the NMDAR channel blocker neramexane, and ethanol, which acts as a functional antagonist at the NMDAR. Our data show that the animals' alcohol consumption inversely correlates with the dose of ethanol administered intraperitoneally. This indicates that under the present experimental conditions alcohol intake during an ADE is an entirely pharmacologically driven behavior that is not under the control of other factors such as taste or novelty of alcohol re-exposure. The effects of the administration of the aforementioned compounds were comparable to those of ethanol, suggesting a similar pharmacological impact on relapse behavior. Repeated administration of both competitive and uncompetitive NMDAR antagonist dose-dependently suppressed alcohol consumption during ADE. In addition, ifenprodil and L-701.324 dose-dependently reduced the expression of an ADE as well. In summary, the results suggest that an inhibition of NMDAR function in general, rather than a particular interference with a specific binding site of this receptor, is sufficient for the reduction of relapse behavior.

Alcohol Drinking↗
PubMed2005

TESS-based dose-response using pediatric clonidine exposures.

OBJECTIVE: The toxic and lethal doses of clonidine in children are unclear. This study was designed to determine whether data from the American Association of Poison Control Centers Toxic Exposure Surveillance System (TESS) could be utilized to determine a dose-response relationship for pediatric clonidine exposure. METHODS: 3,458 single-substance clonidine exposures in children <6 years of age reported to TESS from January 2000 through December 2003 were examined. Dose ingested, age, and medical outcome were available for 1550 cases. Respiratory arrest cases (n = 8) were classified as the most severe of the medical outcome categories (Arrest, Major, Moderate, Mild, and No effect). Exposures reported as a "taste or lick" (n = 51) were included as a dose of 1/10 of the dosage form involved. Dose ranged from 0.4 to 1980 (median 13) microg/kg. Weight was imputed based on a quadratic estimate of weight for age. Dose certainty was coded as exact (26% of cases) or not exact (74%). Medical outcome (response) was examined via logistic regression using SAS JMP (release 5.1). RESULTS: The logistic model describing medical outcome (P < 0.0001) included Log dose/kg (P = 0.0000) and Certainty (P = 0.045). CONCLUSION: TESS data can provide the basis for a statistically sound description of dose-response for pediatric clonidine poisoning exposures.

Accidents↗
PubMed1990

N-terminal extension of sweet peptides in relation to the structural features of peptide sweeteners.

Sweet aspartyl di- and tripeptide esters were extended toward the N-terminus in relation to the structural features of sweet peptides. The sweet peptides were designed on the basis of the receptor site model. It was found that an extension of the sweet aspartyl dipeptide esters by adding a small D-amino acid residue mostly gave sweet compounds (e.g., D-Ala-L-Asp-D-Ala-OMe), although this significantly decreased their sweetness potencies. Further extension at the N-terminus of the extended sweet tripeptide esters to yield the tetrapeptide esters resulted in a loss of the sweet taste. The N-terminal extension of sweet aspartyl tripeptide esters resulted in faintly sweet or nonsweet tetrapeptide esters. Interestingly, an analogous extension at the N-terminus of the sweet aminomalonyl dipeptide esters gave bitter compounds (e.g., D-Ala-DL-Ama-L-Phe-OMe). These results indicate that the receptor has a small space that can accomodate an additional small D-amino acid residue at the site facing the N-terminus of sweet aspartyl dipeptide esters.

Amino Acid Sequence↗
PubMed1987

Alcohol and ambience: social and environmental determinants of intake and mood.

An experiment was conducted in which 66 male subjects were given access to alcohol (20% vol.) and fruit juice to be mixed and tasted ad lib. A factorial design included social vs. solitary drinking conditions, laboratory vs. informal setting, and variable exposure to music. The amount of ethanol consumed (g/kg body weight) was used as an unobtrusive measure of preferred intake. The reciprocal relationship between mood and consumption was analyzed by LISREL. While euphoria has usually been perceived as a consequence of drinking, the only plausible fit to a LISREL model was obtained by assuming that the disposition to drink would be increased by positive mood changes occurring during the drinking session. An analogy between social drinking and adjunctive behaviour was supported, as alcohol consumption was directly affected by time-dependent environmental factors such as company and music. Since the presence of company also stimulated positive mood and alleviated boredom, consumption was precipitated by company indirectly as well as directly. These results emphasize the importance of direct as well as indirect environmental influences on spontaneous alcohol intake during social drinking.

Adult↗
PubMed1988

Altered preferences for sucrose, sodium chloride, urea and hydrochloric acid solutions in an animal model of cholestatic liver disease.

Preferences for sucrose, sodium chloride (NaCl), urea and hydrochloric acid (HCl) solutions (representing sweet, salty, bitter and sour stimuli) were examined in rats with bile duct ligation using 24-hr two-bottle choice tests. Preferences in bile duct ligated rats for sucrose and NaCl solutions were decreased relative to control animals in the initial stages following ligation (Days 1-5) and then increased in the later stages (Days 11-20). Preferences for both HCl and urea solutions were decreased briefly compared to control animals but showed no consistent pattern. The results provide the first demonstration for altered ingestive behavior in an animal model of liver disease and suggest that the bile duct ligated rat may be useful in studying mechanisms of chemosensory disturbances in human liver disease.

Animals↗
PubMed2001

Determination of key aroma compounds in the crumb of a three-stage sourdough rye bread by stable isotope dilution assays and sensory studies.

An investigation of the volatile fraction of a freshly prepared sourdough rye bread crumb by means of the aroma extract dilution analysis (AEDA), followed by identification experiments, revealed 22 flavor compounds in the flavor dilution (FD) factor range of 128 to 2048. Quantitations performed by stable isotope dilution assays (SIDA) and a calculation of odor activity values (OAV; ratio of concentration to odor threshold) revealed the following as contributors to the overall crumb flavor: 3-methylbutanal (malty), (E)-2-nonenal (green, fatty), (E,E)-2,4-decadienal (fatty, waxy), hexanal (green), acetic acid (sour, pungent), phenylacetaldehyde (honey-like), methional (boiled potato-like), vanillin (vanilla-like), 2,3-butandione (buttery), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (spicy), and 2- and 3-methylbutanoic acid (sweaty). Using either citrate buffer, starch, or deodorized crumb as model matrixes, the typical malty and sour rye bread crumb flavor was reproduced by adding a mixture of 20 reference odorants in the "natural" concentrations as quantitatively determined in the fresh crumb.

Bread↗
PubMed2001

Solution structure, backbone dynamics, and stability of a double mutant single-chain monellin. structural origin of sweetness.

Single-chain monellin (SCM), which is an engineered 94-residue polypeptide, has been characterized as being as sweet as native two-chain monellin. Data from gel-filtration high performance liquid chromatography and NMR has proven that SCM exists as a monomer in aqueous solution. In order to determine the structural origin of the taste of sweetness, we engineered several mutant SCM proteins by mutating Glu(2), Asp(7), and Arg(39) residues, which are responsible for sweetness. In this study, we present the solution structure, backbone dynamics, and stability of mutant SCM proteins using circular dichroism, fluorescence, and NMR spectroscopy. Based on the NMR data, a stable alpha-helix and five-stranded antiparallel beta-sheet were identified for double mutant SCM. Strands beta1 and beta2 are connected by a small bulge, and the disruption of the first beta-strand were observed with SCM(DR) comprising residues of Ile(38)-Cys(41). The dynamical and folding characteristics from circular dichroism, fluorescence, and backbone dynamics studies revealed that both wild type and mutant proteins showed distinct dynamical as well as stability differences, suggesting the important role of mutated residues in the sweet taste of SCM. Our results will provide an insight into the structural origin of sweet taste as well as the mutational effect in the stability of the engineered sweet protein SCM.

Arginine↗
PubMed1998

An artificial intelligence system for computer-assisted menu planning.

Planning nutritious and appetizing menus is a complex task that researchers have tried to computerize since the early 1960s. We have attempted to facilitate computer-assisted menu planning by modeling the reasoning an expert dietitian uses to plan menus. Two independent expert systems were built, each designed to plan a daily menu meeting the nutrition needs and personal preferences of an individual client. One system modeled rule-based, or logical, reasoning, whereas the other modeled case-based, or experiential, reasoning. The 2 systems were evaluated and their strengths and weaknesses identified. A hybrid system was built, combining the best of both systems. The hybrid system represents an important step forward because it plans daily menus in accordance with a person's needs and preferences; the Reference Daily Intakes; the Dietary Guidelines for Americans; and accepted aesthetic standards for color, texture, temperature, taste, and variety. Additional work to expand the system's scope and to enhance the user interface will be needed to make it a practical tool. Our system framework could be applied to special-purpose menu planning for patients in medical settings or adapted for institutional use. We conclude that an artificial intelligence approach has practical use for computer-assisted menu planning.

Artificial Intelligence↗
PubMed1992

The effect of d-fenfluramine on intake of carbohydrate supplements is influenced by the hydration of the test diets.

The effect of d-fenfluramine on carbohydrate intake in the rat has been investigated using a dietary paradigm in which a pure carbohydrate supplement is presented in addition to the normal balanced chow diet. This experimental strategy has been used as an alternative to the macronutrient selection model in an attempt to increase the sensitivity of the measurement of drug effects on carbohydrate intake. This issue is important because of the postulated theoretical relationship between brain serotonin (5-HT) and carbohydrate intake. The effect of d-fenfluramine was dependent upon the texture and density of the supplement (hydrated vs. non-hydrated) and upon the nature of the carbohyhdrate employed - either sucrose (sweet-tasting) or Polycose (bland-tasting). Selective carbohydrate suppression, by d-fenfluramine, was detected (as predicted by the 5-HT/carbohydrate theory) but only under specific environmental conditions, namely hydrated chow supplemented with dry Polycose. Therefore, suppression of carbohydrate may depend, not on any inherent biological link between carbohydrate consumption and brain 5-HT activity, but on a shift in relative preference for the diet choices available.

Journal Article↗
PubMed2001

Motivation for alcohol assessed by multiple variable interval schedule behaviour: effects of reward size and alcohol cues.

Altered motivation for drugs of abuse is a central feature of most definitions of drug dependence and the impact of drug-related cues on motivation is of current interest. However, since most studies of cue-reactivity have not used behavioural measures of motivation, their results are often difficult to interpret in motivational terms. In the current paper we describe two experiments in which a behavioural technique, based on multiple variable interval (VI) schedules of reinforcement, was used to study motivation for alcohol in human subjects. In both experiments, subjects attended for several sessions and, during each session, were exposed to a 6-ply VI schedule (values ranged from 1 to 720 s), during which they earned points that were later exchanged for a preferred beer or lager. In Experiment 1 the procedure was validated by showing that changes in the magnitude of reinforcement altered behaviour appropriately. In Experiment 2 we found evidence that the presence of an alcohol-related cue increased the value of alcohol rewards. The results are discussed with reference to a model for the behavioural effects of drug-related cues in triggering relapse and a number of problems we found in using the multiple variable interval schedule procedure.

Adult↗
PubMed1998

Food intake in free-feeding and energy-deprived lean rats is mediated by the neuropeptide Y5 receptor.

The new neuropeptide Y (NPY) Y5 receptor antagonist CGP 71683A displayed high affinity for the cloned rat NPY Y5 subtype, but > 1, 000-fold lower affinity for the cloned rat NPY Y1, Y2, and Y4 subtypes. In LMTK cells transfected with the human NPY Y5 receptor, CGP 71683A was without intrinsic activity and antagonized NPY-induced Ca2+ transients. CGP 71683A was given intraperitoneally (dose range 1-100 mg/kg) to a series of animal models of high hypothalamic NPY levels. In lean satiated rats CGP 71683A significantly antagonized the increase in food intake induced by intracerebroventricular injection of NPY. In 24-h fasted and streptozotocin diabetic rats CGP 71683A dose-dependently inhibited food intake. During the dark phase, CGP 71683A dose-dependently inhibited food intake in free-feeding lean rats without affecting the normal pattern of food intake or inducing taste aversion. In free-feeding lean rats, intraperitoneal administration of CGP 71683A for 28 d inhibited food intake dose-dependently with a maximum reduction observed on days 3 and 4. Despite the return of food intake to control levels, body weight and the peripheral fat mass remained significantly reduced. The data demonstrate that the NPY Y5 receptor subtype plays a role in NPY-induced food intake, but also suggest that, with chronic blockade, counterregulatory mechanisms are induced to restore appetite.

Animals↗
PubMed1997

Flavor characteristics of glutathione in raw and cooked foodstuffs.

The flavor of glutathione (gamma-L-glutamyl-L-cysteinylglycine, GSH) was examined by several sensory evaluations. The measurement of a point of subjective equality (PSE) showed that the peptide increases the flavor characteristics but did not affect the intensity of basic tastes, such as sweetness, saltiness, sourness, and umami. However, the threshold value of GSH decreased significantly in an umami solution containing 0.05% each of monosodium glutamate (MSG) and disodium inosinate (IMP). This suggests that GSH interacts with the umami substance and has a certain effect on the flavor. GSH had a characteristic kokumi flavor, such as continuity, mouthfulness, and thickness in the umami solution as well as in a model beef extract constructed from analyzed components at a concentration of 0.02% w/v. Some foodstuffs, including meat, were found to contain GSH above its threshold value, which implicates the contribution of GSH to the flavor. The thermal degradation study suggested that a part of GSH have changed into its disulfide, pyroglutamic acid (PCA), and cyclocysteinylglycine in cooked foodstuffs.

Cooking↗