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PubMed1994

Taste perception of monosodium glutamate (MSG) in foods in young and elderly subjects.

The purpose of this study was to determine the concentrations at which young and elderly subjects were able to detect and recognize monosodium glutamate (MSG) and MSG with 0.5 mM inosine-5'-monophosphate (IMP) in various food media including meats, vegetables, and soups. The most preferred concentration levels of MSG and MSG (with IMP) in the foods were also determined. Detection thresholds for MSG (with IMP) in foods were elevated in elderly subjects compared with young subjects. The detection thresholds for elderly subjects for MSG with IMP in foods were an average of 2.8 times higher than the same detection thresholds for young subjects. The variability among subjects in the ability to detect MSG (with or without IMP) in every food was far greater than the variability found previously in water solutions, especially for young subjects. Adding 0.5 mM IMP to the MSG did not significantly affect detection thresholds in foods. However, preference scores of both young and elderly subjects were significantly higher for the MSG with IMP condition than the MSG alone condition for some foods. Optimally preferred concentration levels of MSG in foods tended to be lower than the level at which MSG is detected or recognized in the food but above the detection threshold for MSG in water. The mechanism by which MSG can be preferred at a subthreshold concentration in foods is not fully understood. One possibility is that MSG synthesizes with food chemicals and forms a new taste quality.

Adult↗
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↗
PubMedDate not supplied

Early detection of diabetic patients at risk of developing degenerative complications using electric gustometry: a five-year follow-up study.

OBJECTIVES: Taste impairment has been reported during the course of diabetes. Although a degenerative mechanism has been suspected, the natural history of taste disorders in diabetes remains unknown. The purpose of this study was to describe the five-year evolution of electric gustometry in diabetic patients compared to healthy control subjects and with reference to degenerative complications of the disease. METHODS: Electrogustometry was studied initially and after 5 years in 73 diabetic out patients and 25 control subjects. None of them had any known cause of taste impairment other than diabetes. Diabetic patients and control subjects did not differ for demographic data and confounding factors. RESULTS: After five years, the electrogustometric threshold (EGT) significantly increased (51 +/- 6 vs 95 +/- 11 microA; p < 0.001), whereas slight changes occurred in control subjects (23 +/- 4 vs 25 +/- 5 microA; NS). Frequency of electric hypogeusia (EGT > or = 100 microA) increased from 11 to 46% in diabetic patients (p < 0.001), but did not vary in control subjects (4%). EGT was not strongly associated with individual factors such as blood pressure, tobacco and alcohol consumption, but correlated with age (p < 0.001). In the diabetic group, higher EGT were observed in patients treated with insulin (p < 0.001). EGT and its changes were associated with degenerative complication (p < 0.001), but neither with metabolic control, nor with duration of diabetes. Using multivariate analyses, the strongest associations were found with peripheral neuropathy and microalbuminuria (28 to 45% of variance explained; p < 0.001). The predictive value of initial hypogeusia on neuropathy at follow-up was 88% for a positive test and 63% for a negative one. CONCLUSIONS: These results suggest that the taste nerves transduction function is impaired during the course of diabetes. This impairment is associated with an increased occurrence of degenerative complications, leading to suspect a similar pathophysiological mechanism. Electric gustometry could be an interesting test for early screening for diabetes complications.

Adolescent↗
PubMed2002

Evaluation of greater petrosal nerve function in patients with acute peripheral facial paralysis: comparison of soft palate electrogustometry and Schirmer's tear test.

We tested sensory and secretomotor function of the greater petrosal nerve (GPN) by means of electrogustometry (EGM) of the soft palate and Schirmer's tear test in 115 patients (59 males, 56 females) with acute peripheral facial paralysis. Facial paralysis was caused by Bell's palsy in 78 cases, Ramsay Hunt syndrome in 27 cases and zoster sine herpetic lesions in 10. All patients had dysfunction of the stapedial nerve. An electrogustometer was used to test taste (GPN sensory function), and elevation of the threshold by > 6 dB on the affected side was considered abnormal. Schirmer's test was used to evaluate lacrimal (GPN secretomotor) function, which was considered abnormal when tear secretion on the affected side was < 50% of secretion on the non-affected side. Of the 78 patients with Bell's palsy, 28.2% had altered taste on the soft palate (sensory dysfunction) and 10.3% had lacrimal dysfunction, indicating that EGM of the soft palate is more sensitive than Schirmer's test for identifying dysfunction of the GPN in patients with facial paralysis due to Bell's palsy. Of the total of 115 patients, 32 (28%) had taste dysfunction and 9 (28.1%) of these 32 patients also had lacrimal dysfunction. This finding indicates that facial paralysis has different effects on the sensory and secretory nerve fibers of the GPN. The results of Schirmer's test were more closely related to the severity of, and prognosis for, facial paralysis than the results of EGM.

Acute Disease↗
PubMed2002

Reinvestigation of the chemical structure of bitter-tasting quinizolate and homoquinizolate and studies on their Maillard-type formation pathways using suitable (13)C-labeling experiments.

Very recently, application of taste dilution analysis to heated xylose/alanine solutions led to the isolation of two bitter-tasting compounds exhibiting extraordinarily low detection thresholds of 0.00025 and 0.001 mmol/kg of water, respectively. On the basis of LC-MS and NMR spectroscopy, the structures of these compounds, named quinizolate and homoquinizolate, were proposed as 1-oxo-1H,4H-quinolizinium-7-olates. Since recent experiments in our laboratory shed some doubt on the entire correctness of their structures, labeling experiments with mixtures of multiply (13)C-labeled and nonlabeled pentoses were performed to follow the joint transfer of several (13)C atoms en bloc into the bitter compounds by LC-MS and NMR isotopomer diagnosis. The site-specific visualization of the mosaics assembled from (13)C-labeled and (12)C-labeled carbon modules in both bitter compounds demonstrated the structures of quinizolate and homoquinizolate to be the previously unknown (2E)-7-(2-furylmethyl)-2-(2-furylmethylidene)-3-(hydroxymethyl)- and (2E)-7-(2-furylmethyl)-2-(2-furylmethylidene)-3,8-bis(hydroxymethyl)-1-oxo-2,3-dihydro-1H-indolizinium-6-olate.

Carbon Isotopes↗
PubMed1994

Different responsiveness of the chorda tympani and glossopharyngeal nerves to L-lysine in mice.

Differential taste responsiveness and functional role of the two taste nerves, the chorda tympani (CT) and the glossopharyngeal (GL), were studied in mice by examining neural and behavioral responses to an essential amino acid, L-lysine (Lys). Relative responses to Lys were larger in the GL than in the CT nerve. The neural threshold for the Lys response was about 2.5 log units lower in the GL (about 1.0 microM) than in the CT nerve (about 300 microM). An analysis of concentration-response relationships suggests a possibility that there are two different receptors (high and low affinity types) for Lys showing different dissociation constants. The posterior tongue region possesses both types, while the anterior region possesses only the low affinity type. Behavioral aversion threshold for Lys in intact mice, measured by use of a single bottle test, was about 1.0 microM. This threshold was the same as its neural threshold in the GL nerve. Animals whose bilateral GL nerves were sectioned showed a higher aversion threshold (about 300 microM) which was the same as the neural threshold in the CT nerve. An aversion conditioned to Lys significantly generalized to L-arginine in the intact and CT-denervated mice, and L-arginine and L-histidine in the GL-denervated mice, but the generalization pattern across various taste stimuli including the four basic taste stimuli (NaCl, HCl, quinine HCl and sucrose) did not prominently differ among the intact, the GL-denervated and CT-denervated mice. These results suggest that taste sensitivity to Lys is higher in the GL than in the CT nerve, but taste quality information for Lys conveyed by two taste nerves is not largely different.

Animals↗
PubMed2004

Synthesis and odour thresholds of mixed halogenated anisoles in water.

Earthy-musty off-flavour compounds in water samples are usually associated with the presence of geosmin and 2-methylisoborneol. However, the presence of 2,3,6- and 2,4,6-trichloroanisoles or other halogenated anisoles can impart objectionable tastes and odours to the water even at very low trace levels. This paper shows the synthesis of non-commercial 2,3,6- and 2,4,6- mixed chloro/bromoanisoles which can be present in bromide rich waters and could also be suspected of imparting earthy-musty off-flavours to the water. All the synthesized compounds were subjected to the flavour profile analysis (FPA) method and their odour threshold concentrations (OTC) in water were carried out giving values in the low ng/L range.

Anisoles↗
PubMed1989

Caffeine taste test for panic disorder: adenosine receptor supersensitivity.

The present study introduces a novel measure of adenosine receptor sensitivity that is based on the action of specific receptor blockers (e.g., caffeine) to potentiate the ability to detect threshold quinine concentrations. The test is used to compare gustatory adenosinergic responses to caffeine challenges in normal controls and patients with panic disorder or posttraumatic stress disorder (PTSD). Panic disorder patients had an exaggerated response to the caffeine challenge that was not found in controls or PTSD patients, although the latter had higher anxiety scores on psychometric tests. The results are related to a model in which A1-adenosine receptors up-regulate in an attempt to modulate hyperactive excitatory neuronal systems.

Adult↗
PubMed1996

A study on the efficacy of late lingual nerve repair.

The level of sensory recovery was studied in 13 consecutive patients who had undergone lingual nerve repair after a delay of 7-32 (mean 16) months since the initial injury. In all patients the damaged segment of nerve was excised and the cut ends directly apposed by 6-10 (mean 7) epineurial sutures. The final outcome was assessed 12-24 months after repair. Preoperatively none of the patients could detect light touch stimuli in the denervated area, whereas 10 patients could detect some stimuli after repair. Pin-prick was detected in 6 preoperatively and in some areas by all 13 patients after repair. Two-point discrimination thresholds decreased after repair in 10 patients and in four of these became the same as on the uninjured side. Gustatory stimuli showed that there had been some return of taste sensation in 6 patients, and there were responses to electrogustometry in 12 patients. The patients' subjective assessment of the value of repair (scale 0-10) ranged from 0-10 (median 7). These results show that most patients undergo significant and worthwhile recovery after late lingual nerve repair.

Adult↗
PubMed1982

Physiological characteristics of the solitario-parabrachial relay neurons with tongue afferent inputs in rats.

Among 180 units in the solitary tract nucleus (NTS) of rats, 34 solitario-parabrachial relay neurons (SP neurons), were identified by antidromic activation from the parabrachial nucleus. The SP neurons were classified into two groups, fast and slow, according to their antidromic latencies. The responsiveness of the SP in comparison with non-SP neurons was studied by electrical stimulation of three tongue nerves: the lingual (L), chorda tympani (CT) and glossopharyngeal (G) nerves. About half the SP neurons produced a single spike with an orthodromic latency of 2-5 ms, while about one third of them discharged more than two spikes. A few neurons gave rise to a long-lasting discharge consisting of five or six spikes. Some SP neurons were excited by stimulation of the tongue afferents with a low stimulus intensity, but other SP neurons produced spikes at only very high voltages. Fast SP cells were not differentiated from slow SP cells, except that latency of orthodromic responses to CT stimulation was significantly shorter in the former than in the latter (P less than 0.05, Mann-Whitney U-test). Locations of the SP and non-SP neurons, reconstructed histologically, indicate that they do not distribute evenly throughout the mediolateral extent at the rostral pole of the NTS, but clustered in its medial half.

Afferent Pathways↗
PubMed2004

Neuropsychological functioning associated with high-altitude exposure.

This article focuses on neuropsychological functioning at moderate, high, and extreme altitude. This article summarizes the available literature on respiratory, circulatory, and brain determinants on adaptation to hypoxia that are hypothesized to be responsible for neuropsychological impairment due to altitude. Effects on sleep are also described. At central level, periventricular focal damages (leuko-araiosis) and cortical atrophy have been observed. Frontal lobe and middle temporal lobe alterations are also presumed. A review is provided regarding the effects on psychomotor performance, perception, learning, memory, language, cognitive flexibility, and metamemory. Increase of reaction time and latency of P300 are observed. Reduced thresholds of tact, smell, pain, and taste, together with somesthetic illusions and visual hallucinations have been reported. Impairment in codification and short-term memory are especially noticeable above 6,000 m. Alterations in accuracy and motor speed are identified at lower altitudes. Deficits in verbal fluency, language production, cognitive fluency, and metamemory are also detected. The moderating effects of personality variables over the above-mentioned processes are discussed. Finally, methodological flaws found in the literature are detailed and some applied proposals are suggested.

Adaptation, Physiological↗
PubMed1997

Antinociceptive effects of palatable sweet ingesta on human responsivity to pressure pain.

Palatable sweet ingestion produces a morphine-like analgesia in both rats and human infants (2-5). To determine whether palatable sweet ingesta induces antinociception in human adults, 60 university students (30 men, 30 women) were exposed to a pressure algometer both before and after consuming either a sweet soft drink, filtered tap water, or nothing (Experiment 1). Pain responsivity was assessed with four pain measures: threshold, tolerance, and visual analogue scale (VAS) ratings of intensity and unpleasantness. Results showed that women who consumed either soft drink or water reported increased pain tolerance and VAS ratings at posttreatment compared with those receiving nothing. However, differences between groups were not found for men. Moreover, compared to men, women reported lower pain thresholds and tolerances and rated the pain as more intense. In Experiment 2, 40 women consumed either nothing or foods that they rated previously as palatable (chocolate-chip cookies), unpalatable (black olives), or neutral (rice cakes). Women who consumed the palatable sweet food showed increased pain tolerance compared with those receiving the unpalatable food, the neutral food, or nothing. These data constitute the first demonstration that "palatability-induced antinociception" (PIA) can occur in human adults.

Adolescent↗
PubMed1999

Combinatorial approach to flavor analysis. 2. Olfactory investigation of a library of S-methyl thioesters and sensory evaluation of selected components.

The odor characteristics of individual components present in a library comprised of S-methyl thioesters were determined independently by two laboratories using similar but not identical techniques. The odor potency was assessed by values of best estimate-GC-lower amount detected by sniffing (BE-GC-LOADS). For small and medium chain S-methyl thioesters, these values were found to increase from 6 ng for S-methyl thiobutanoate to 90 ng for S-methyl thiostearate. All assessors detected a "green", "floral", or "pineapple" odor for S-methyl thiohexanoate and described thioesters containing a 2-6 carbon chain length as "cheesy". The results of this preliminary analysis were confirmed by a more extensive study of selected compounds, namely S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, and S-methyl thiohexanoate, using a trained panel of 18 subjects. The subjects confirmed the presence of the "green" and "fruity" notes in the odor of S-methyl thiohexanoate. The analysis also revealed a significant difference in the odor of S-methyl thiopropionate relative to that of S-methyl thioacetate and S-methyl thiobutanoate. When "cheesy" characteristics were mentioned, the majority of panelists clearly associated the flavor of S-methyl thiopropionate with Camembert with almost 20% of all the descriptors given referring specifically to this cheese variety as compared to about 2 and 5% in the case of S-methyl thioacetate and thiobutanoate, respectively. Prompted by this observation, two samples of Camembert prepared from unpasteurized and pasteurized milk were analyzed and relatively large amounts of S-methyl thiopropionate were found in the former but not in the latter cheese. The results obtained in the course of this work suggest that the sensory analysis of combinatorial libraries is a useful new approach in the search for new commercial flavors and/or identification of characteristic flavors in foods.

Chromatography, Gas↗
PubMedDate not supplied

Sodium chloride preference and recognition threshold in normotensive subjects on high and low salt diet.

Young adult volunteers were placed on two week periods of high and low-salt diets following dietetic counselling and using normally available foodstuffs. Changes in sodium recognition threshold, salivary and urinary electrolytes and preference for NaCl, NaCl/KCl (1:1) mix and monosodium glutamate were measured during the high- and low-salt diet periods and during two-week control periods with subjects on their usual diet. Sodium preference was defined as the sodium concentration of unsalted tomato juice following ad libitum addition of a sodium salt till the most preferred taste was achieved. Subjects served as their own controls across the dietary periods in a cross-over design. While sodium excretion on the low-salt diet was significantly less than at on the high-salt diet, there were no significant changes in blood pressure, sodium recognition threshold, body weight or salivary electrolytes between these dietary periods. There was a significant increase in preference for NaCl, NaCl/KCl mix and monosodium glutamate on the high-salt diet when compared to the low-salt diet period. In all dietary periods less sodium was added to the unsalted tomato juice with monosodium glutamate than with NaCl/KCl and less sodium was added with the NaCl/KCl mix than with the NaCl. This study demonstrates that relatively short periods of increased sodium intake result in an increase in sodium preference in the absence of changes in salivary electrolytes or recognition threshold.

Adult↗
PubMed1992

The effect of neonatal capsaicin treatment on gustatory behavior in the albino rat.

Small-diameter fibers present in gustatory peripheral nerves have historically been suspected of relaying information about the bitter quality of a taste stimulus. Neonatally injected capsaicin irreversibly destroys a proportion of unmyelinated C- and some A delta-fibers. Consummatory responses to increasing concentrations of quinine and other chemical solutions following neonatal capsaicin injection were compared to those of untreated and vehicle-injected control Sabra albino rats. Capsaicin-treated rats significantly increased their withdrawal thresholds to noxious, CO2 laser-generated heat pulses verifying treatment effectiveness. Furthermore, neonatal capsaicin treatment diminished sensitivity to pungent capsaicin solutions in mature rats. However, there were no group differences in quinine intake, suggesting that the full array of unmyelinated fibers associated with taste buds is not essential for the transmission of bitter taste. Capsaicin-treated animals showed a significant reduction in intake of normally highly preferred sodium chloride and sucrose concentrations. These results were probably not due to loss of peripheral unmyelinated afferent fibers per se, but rather to secondary central changes.

Animals↗
PubMed1998

Development and genetics of glutamate taste preference.

The sodium salt of glutamic acid, monosodium glutamate (MSG), and certain other amino acids and ribonucleotides impart a unique taste sensation often called 'umami.' We have been studying preference for umami substances in two systems: inbred mice and human infants. In 48-hr tests, C57BL/6J (C57) mice exhibit a lower preference threshold for MSG than do 129/J mice. Moreover, C57 mice show a greater preference across a wide range of concentrations and, at high (e.g., 300-600 mM) concentrations, consume greater amounts of MSG. To examine whether the strain difference in MSG preference might be related to a similar strain difference in preference for sucrose and other sweeteners, as might be suggested from studies with rats, preferences for MSG and sucrose in the second (F2) generation were examined. Preferences for sucrose and for MSG were not positively correlated in the F2 indicating that these strain differences depend on different genes. For human adults, unlike mice, the taste of aqueous MSG is not palatable. Our studies of human infants also indicate that MSG alone is not preferred to plain water, but, when it is added to soup, the soup plus MSG is preferred to soup alone. Ongoing studies are designed to determine whether simple mixtures of MSG with other tastants, in particular NaCl, are preferred to water alone, NaCl alone, and MSG alone.

Adult↗