Gustatory perception of isohumulones: influence of sex and thiourea taster status

Detection thresholds for NaCl and a purified isohumulones preparationdid not differ between thiourea tasters and non-tasters. However,suprathreshold concentrations of isohumulones in water (butnot in beer) were perceived as more intense by tasters. Femaleshad significantly lower NaCl thresholds and tended to perceiveisohumulones in water as more intense.     

Taste thresholds of Japanese dental students to phenylthiocarbamide

Recognition taste thresholds for phenylthiocarbamide (PTC),a specific bitter substance, in Japanese dental students weremeasured with 372 males of 20–36 years old and 55 femalesof 20–34 years old. The mean PTC threshold in male studentswas 2.7 x 10^–5 M for tasters and 8.9 x 10^–3 M fornon-tasters. The mean threshold in female students was 2.5 x10^–5 M for tasters and 6.5 x 10^–3 M for the non-tasters.The percentage of non-tasters in a total of 427 male and femalestudents was 5.4%. There was no significant difference in non-tasterdistributions between students from the western districts ofJapan and from other districts.     

Phenylthiocarbamide taste thresholds in the population of Thailand

Summary Determination of taste thresholds for phenylthiocarbamide (PTC) in 460 healthy subjects from northern Thailand showed 9.7 percent non-tasters. There was no difference in the proportion of non-tasters between males and females but among tasters females had somewhat higher taste thresholds. In a group of 140 patients with goitre, mainly of the diffuse toxic type, the proportion of non-tasters was 4.6 percent.

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Zusammenfassung Bestimmung von Geschmacksschwellenwerten für Phenylthiocarbamid (PTC) bei 460 gesunden Probanden in Nordthailand ergab 9,7% Nichtschmecker. Es besteht kein Unterschied zwischen dem Anteil der Nichtschmecker bei männlichen und weiblichen Versuchspersonen, die letzteren hatten jedoch im allgemeinen höhere Schwellenwerte als männliche Probanden. Bei einer Gruppe von 140 Kropfpatienten, von denen die meisten eine diffuse toxische Struma hatten, fanden sich 4,6% Nichtschmecker.

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This paper contains parts of the term papers for the degree of Bachelor of Science in Medical Technology of P. B. and M. Ch.

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The Human Genetics Laboratory was established and is supported by Stiftung Volkswagenwerk.     

PROP (6-n-Propylthiouracil) tasting and sensory responses to caffeine,sucrose, neohesperidin dihydrochalcone and chocolate

The genetically determined ability to taste 6-n-propylthiouracil (PROP) has been linked with lowered acceptance of some bitter foods. Fifty-four women, aged 18-30 years, tasted and rated PROP-impregnated filter paper and seven solutions of PROP. Summed bitterness intensity ratings for PROP solutions determined PROP taster status. Respondents also tasted five sucrose and seven caffeine solutions, as well as seven solutions each of caffeine and PROP that had been sweetened with 0.3 mmol/l neohesperidin dihydrochalcone (NHDC). Respondents also rated three kinds of chocolate using 9-point category scales. PROP tasters rated caffeine solutions as more bitter than did non-tasters and liked them less. PROP tasters did not rate either sucrose or NHDC as more sweet. The addition of NHDC to PROP and caffeine solutions suppressed bitterness intensity more effectively for tasters than for non-tasters and improved hedonic ratings among both groups. PROP tasters and non-tasters showed the same hedonic response to sweetened caffeine solutions and did not differ in their sensory responses to chocolate. Genetic taste markers may have only a minor impact on the consumption of such foods as sweetened coffee or chocolate.     

Phenylthiocarbamide taste sensitivity and its relationship to growth variation

The hypothesis that there is a relationship between the tasting polymorphism and growth variation was tested on a sample of 425 Negro elementary school children. Twenty-seven non-tasters were found by testing with impregnated papers; 13 were male, 14 female, indicating no sex differences in this group. Matchedpair comparisons indicated no differences in weight, a tendency for tasters to be taller, and a stronger tendency for tasters of both sexes to be skeletally more mature. It was felt that the tendency for tasters to be taller might reflect their more advanced maturation status. The relationship to skeletal maturation might be indicative of the decreased thryoid activity found in other studies of phenylthiocarbamide tasting.     

Genetic sensitivity to bitter taste of 6-n Propylthiouracil: A useful diagnostic aid to detect early childhood caries in pre-school children

PURPOSE:

Genetic factor to bitter taste perception appears to be largely mediated by the TAS2R38 gene. The insensitivity to bitter compounds like 6-n-propylthiouracil (PROP) is mediated by this gene. PROP, a pharmacological drug used in treatment of Graves’ disease, proved to be useful tool in determining the genetic sensitivity levels to bitter and sweet taste. The purpose of this study is to show much simpler PROP sensitivity technique for the clinical examiner and its application as a diagnostic aid in Early Childhood Caries (ECC) detection among preschool children.

MATERIALS AND METHODS:

A total of 119 children belonging to the age group of 36 to 71 months of both sexes, were recruited from A. J. Institute of Dental Sciences, Mangalore (Karnataka). PROP sensitivity test was carried out to determine the inherent genetic ability to taste a bitter or sweet substance. This study used simpler scaling method to find out genetic sensitivity to bitter taste; one who tasted bitter as taster and one who was not able to differentiate/tasted like paper as non-taster. A questionnaire was provided to evaluate their dietary habits and caries experience was recorded. Collected data were tabulated and subjected to statistical analysis.

RESULTS:

In the total of 119 children the mean dmfs was definitely higher in non-taster children compared to tasters. The tasters had a mean dmfs value of 9.5120 (S.D. 7.0543) and non-tasters had a value of 7.7250 (S.D. 8.33147), which was statistically significant. The results suggested that there was increase in caries experience among the group of non-tasters as compared to tasters. Tasters tended to be sweet dislikers and non-tasters tended to be sweet likers. On the whole, tasters had a bad dentition as compared to non tasters.

CONCLUSION:

The PROP sensitivity test (filter paper test) proved to be a useful diagnostic tool in determining the genetic sensitivity levels of bitter taste. The knowledge of a child''s taste perception can help us in identifying the children who are at higher risk for ECC.     

Toxicity of the Taste Testing Compound Phenylthiocarbamide

THE genetic polymorphism in human taste acuity for phenylthiocarbamide (phenylthiourea, PTC) and related compounds is widely used in practical demonstrations at most educational levels. The Nuffield O-level biology text¹ advises that PTC papers be prepared from 0.13% PTC solution, but PTC solutions or crystals are often used to distinguish “tasters” and “non-tasters”.     

Genetic Sensitivity to 6-n-Propylthiouracil (PROP) and Hedonic Responses to Bitter and Sweet Tastes

Genetically mediated sensitivity to the bitter taste of 6-n-propylthiouracil(PROP) has been associated with greater acuity for bitter andfor some sweet tastes. Thus far, few studies have explored therelationship between PROP taste sensitivity and hedonic responsesto bitter and sweet. In this study, 87 normal-weight young womenwere divided into PROP non-tasters (n = 18), regular tasters(n = 49), and supertasters (n = 20), based on their PROP detectionthresholds and the scaling of five suprathreshold solutionsof PROP and NaCl. Non-tasters had thresholds >1.8 x 10^–4mol/l PROP. Supertasters had thresholds <3.2 x 10^–5mol/l PROP and PROP/NaCl ratios >1.70. As expected, dislikeof the bitter taste of PROP was determined by its perceivedintensity, which was greater among supertasters than among regulartasters or non-tasters. Significant correlations were observedbetween PROP taste thresholds and the sum of intensity ratings(r = –0.61) and between summed intensity and summed hedonicratings (r = –0.80). PROP taste sensitivity was weaklylinked to enhanced perception of sweet taste, but did not predicthedonic responses to sucrose or to saccharin solutions. Giventhat the dislike of PROP solutions is determined by their perceivedintensity, hedonic responses to PROP solutions may provide arapid way of screening for PROP taster status. Chem. Senses22: 27–37, 1997.     

A new specific ageusia: some humans cannot taste L-glutamate

A new specific ageusia was found in human subjects for monosodium L-glutamate (MSG). Four tests were successively applied to discriminate non-tasters and hypotasters from tasters. (i) NaCl and MSG thresholds, and (ii) suprathreshold sensitivity were evaluated using the up-and-down procedure. Only 73% of 109 subjects common to both tests demonstrated a sensitivity for MSG significantly higher than their sensitivity to NaCl, and hence a specific sensitivity to L-glutamate. The remaining 27% who showed no significant difference in sensitivity to MSG and NaCl solutions were considered as putative hypotasters. (iii) Perception profiles (time-intensity) for MSG and NaCl were tested in 58 subjects and appeared significantly different in 47 tasters (81%). This technique helped in identifying among putative hypotasters of tests 1 and 2 a few tasters who perceived equal intensity for isoconcentration of NaCl and MSG but who could discriminate isomolar solutions on other cues. Thus, 19% of subjects, for whom no significant differences were found between MSG and NaCl time-intensity profiles, remained in the hypotaster group. (iv) A discrimination task including 24 triangular presentations per subject of NaCl and MSG 29 mM applied to the eight most severe hypotasters showed that two subjects at least (two of 58; 3.5%) could not discriminate between both stimuli. Moreover, these subjects probably perceived identical sensations for MSG and NaCl solutions. The six other hypotasters (10.3%) could discriminate both stimuli at the limit of significance. None of these eight subjects were able to identify the typical umami taste in 29 mM MSG.     

Physical growth and development, neurological maturation, and behavioral functioning in two Ecuadorian Andean communities in which goiter is endemic. II. PTC taste sensitivity and neurological maturation

PTC (phenylthiocarbamide) taste sensitivity was correlated with a measure of visual-motor maturation in children six to 15 years of age in two Ecuadorian Andean communities in which goiter (enlargement of the thyroid gland) and cretinism are endemic. The children in one population received injections of iodine in oil IM in 1966 while the children in the other population did not. The correlations between PTC taste sensitivity and visual-motor maturation were significant in both sex groups in the non-iodized population, but not in the iodized population. There was also a significant increase in taste sensitivity with age in the non-iodized, but not the iodized, population. The data support the hypothesis that the sensitive “tasters” of PTC limit their ingestion of naturally occurring goitrogens and are at an adaptive advantage with respect to the less sensitive “tasters” and “non-tasters” in this area in which iodine intake is low and the consumption of food crops containing naturally occurring goitrogens is high.     

Effect of high altitude on sensitivity to the taste of phenylthiocarbamide

Sensitivity to the taste of phenylthiocarbamide (PTC) was studied using the Harris-Kalmus method in healthy human volunteers at sea level and then subsequently at an altitude of 3500 m over a period of 3 weeks, after which they were brought back to sea level. Blood sugar, insulin and blood cortisol levels were estimated weekly. The results indicated that, out of 51 subjects studied, 26 (55%) were PTC tasters at sea level. Eight of those unable to taste PTC at sea level tested as tasters at high altitude, and 2 of them reverted to being non-tasters on return to sea level. In the blood, an increase in cortisol and blood insulin levels was seen without any significant change in sugar levels. All the changes recorded at high altitude tended to return to basal values after re-induction to sea level. The study suggests that high-altitude hypoxia in some way, possibly involving changes in hormonal profile among other factors, causes an alteration in sensitivity to the taste of PTC, resulting in some of the individuals shifting to lower PTC sensitivity. Received: 24 November 1999 / Accepted: 25 January 2000     

Taste perception for phenylthiocarbamide and food choice--a Hungarian twin study

A total of 98 MZ and 67 like sexed DZ adult twin pairs were studied for taste sensitivity to P.T.C. The MZ pairs were also tested for their food favoritism. A P.T.C. screening test showed a concordance in "tasting" or "non-tasting", within the MZ versus the DZ pairs. For the comparison of food choices of the P.T.C. tasters and non-tasters (members of MZ pairs) a quantity called "Tastership Test Point" (TTP) was constructed. Based on an analysis of the TTP values it may be suggested that taste sensitivity to P.T.C. and food preferences are not completely unrelated characters. These results serve as a contribution to the authors' previous findings obtained in Hungarian adolescents.     

The influence of temperature on the threshold values of primary tastes

The threshold values of taste substances are influenced by severalfactors. To learn about the effect of the temperature on stimulus,recognition and terminal thresholds, these threshold valueswere determined for sucrose, sodium chloride, caffeine, quininehydrochloride, citric and tartaric acid at temperatures of 10,20, 40 and 60°C in a panel of 19 tasters. The individualvalues were found to vary over a wide range, resulting in arelatively large standard deviation of the mean threshold values.A temperature-dependence was found for the stimulus and recognitionthresholds which was different for the different taste substances.The stimulus and recognition thresholds are lowest in the temperaturerange of 20 to 40°C. The threshold values increase withincreasing temperature, and except for citric acid, significantand highly significant differences existed particularly between20 and 60°C, whereas statistically verifiable results couldnot be obtained between 10 and 20°C. There was no verifiabletemperature dependence either for the terminal thresholds. Theterminal thresholds were found to lie rather in a relativelynarrow concentration range and to be largely independent ofthe temperature. The results suggest that in warm dishes andbeverage more taste substances are required to produce the sametaste intensity. A dependence of the individual thresholds uponage, sex and smoking habits could not be found.     

Genetic variation in Nigeria. I. The genetics of phenylthiourea tasting ability.

Phenylthiourea (PTC) taste sensitivity thresholds have been measured for 2,013 Nigerians using a modified sorting technique. The frequency of non-tasters was observed to be 12.5% and the t gene frequency was 0.354. There was a significant difference between the sexes at the 0.01 level for the overall population. However, when the data are analyzed according to the geographical origin of the subject, the sex difference is found only in one of three geographical regions. Also, there may be geographical influences on PTC taste sensitivity, although this was not statistically significant. The estimates reported in this population differ considerably from some of the previously published estimates for black populations.     

Bitter taste perception in Neanderthals through the analysis of the TAS2R38 gene

The bitter taste perception (associated with the ability or inability to taste phenylthiocarbamide) is mediated by the TAS2R38 gene. Most of the variation in this gene is explained by three common amino-acid polymorphisms at positions 49 (encoding proline or alanine), 262 (alanine or valine) and 296 (valine or isoleucine) that determine two common isoforms: proline–alanine–valine (PAV) and alanine–valine–isoleucine (AVI). PAV is the major taster haplotype (heterozygote and homozygote) and AVI is the major non-taster haplotype (homozygote). Amino acid 49 has the major effect on the distinction between tasters and non-tasters of all three variants. The sense of bitter taste protects us from ingesting toxic substances, present in some vegetables, that can affect the thyroid when ingested in large quantities. Balancing selection has been used to explain the current high non-taster frequency, by maintaining divergent TAS2R38 alleles in humans. We have amplified and sequenced the TAS2R38 amino acid 49 in the virtually uncontaminated Neanderthal sample of El Sidrón 1253 and have determined that it was heterozygous. Thus, this Neanderthal was a taster individual, although probably slightly less than a PAV homozygote. This indicates that variation in bitter taste perception pre-dates the divergence of the lineages leading to Neanderthals and modern humans.     

Marked Increase in PROP Taste Responsiveness Following Oral Supplementation with Selected Salivary Proteins or Their Related Free Amino Acids

The genetic predisposition to taste 6-n-propylthiouracil (PROP) varies among individuals and is associated with salivary levels of Ps-1 and II-2 peptides, belonging to the basic proline-rich protein family (bPRP). We evaluated the role of these proteins and free amino acids that selectively interact with the PROP molecule, in modulating bitter taste responsiveness. Subjects were classified by their PROP taster status based on ratings of perceived taste intensity for PROP and NaCl solutions. Quantitative and qualitative determinations of Ps-1 and II-2 proteins in unstimulated saliva were performed by HPLC-ESI-MS analysis. Subjects rated PROP bitterness after supplementation with Ps-1 and II-2, and two amino acids (L-Arg and L-Lys) whose interaction with PROP was demonstrated by ¹H-NMR spectroscopy. ANOVA showed that salivary levels of II-2 and Ps-1 proteins were higher in unstimulated saliva of PROP super-tasters and medium tasters than in non-tasters. Supplementation of Ps-1 protein in individuals lacking it in saliva enhanced their PROP bitter taste responsiveness, and this effect was specific to the non-taster group.¹H-NMR results showed that the interaction between PROP and L-Arg is stronger than that involving L-Lys, and taste experiments confirmed that oral supplementation with these two amino acids increased PROP bitterness intensity, more for L-Arg than for L-Lys. These data suggest that Ps-1 protein facilitates PROP bitter taste perception and identifies a role for free L-Arg and L-Lys in PROP tasting.     

Individual differences in perception of bitterness from capsaicin, piperine and zingerone

It was recently shown that in some subjects capsaicin can evoke bitterness as well as burning and stinging, particularly in the circumvallate (CV) region of the tongue. Because perception of bitterness from capsaicin is characterized by large individual differences, the main goal of the present study was to learn whether people who taste capsaicin as bitter also report bitterness from structurally similar sensory irritants that are known to stimulate capsaicin-sensitive neurons. The irritancy and taste of capsaicin and two of its most commonly studied congeners, piperine and zingerone, were measured in individuals who had been screened for visibility of, and reliable access to, the CV papillae. Approximately half of these individuals reported tasting bitterness from all three irritants when the stimuli were swabbed directly onto the CV papillae. Concentrations that produced similar levels of burning sensation across subjects also produced similar (though lower) levels of bitter taste. These results are consistent with the hypothesis that capsaicin and its congeners stimulate bitterness via a common sensory receptor that is distributed differentially among individuals. Additionally, bitter tasters rated gustatory qualities (but not burning and stinging) slightly but significantly higher than did bitter non-tasters, which suggests that perception of capsaicin bitterness is associated with a higher overall taste responsiveness (but not chemesthetic responsiveness) in the CV region.     

Bitter taste study in a sardinian genetic isolate supports the association of phenylthiocarbamide sensitivity to the TAS2R38 bitter receptor gene

Recently, a major locus on chromosome 7q was found in association with the taste sensitivity to phenylthiocarbamide (PTC) in humans. This region contains the TAS2R38 gene that encodes a member of the TAS2R bitter taste receptor family. Three SNPs within this gene demonstrated a strong association with taster status in Utah families and in an additional sample of 85 unrelated individuals. We studied a small isolated village in eastern Sardinia and carried out a genome-wide scan to map the genetic basis of PTC perception in this population. We performed both qualitative and quantitative PTC-taste linkage analysis. Qualitative analysis was carried out by defining a cut-off from the bimodal distribution of the trait and classifying subjects as tasters and non-tasters (75 and 25%, respectively). Linkage analysis on 131 subjects belonging to a unique large multi-generation pedigree comprising 239 subjects confirmed significant evidence for linkage at 7q35 also in our population. Haplotype analyses of the three SNPs inside the PTC gene allowed us to identify only two haplotypes that were associated with the non-taster phenotype (80% AVI homozygous) and to taster phenotype (40% PAV homozygous and 56% PAV/AVI heterozygous). Sex, age and haplotype effect explained 77.2 % of the total variance in PTC sensitivity.     

Genetic analysis of a complex trait in the Utah Genetic Reference Project: a major locus for PTC taste ability on chromosome 7q and a secondary locus on chromosome 16p

The ability to taste phenylthiocarbamide (PTC) shows complex inheritance in humans. We obtained a quantitative measure of PTC tasting ability in 267 members of 26 large three-generation families that were part of a set of CEPH families that had been used for genetic mapping. Significant bimodality was found for the distribution of age and gender adjusted scores (P<0.001), with estimated means of 3.16 (SD=1.80) and 9.26 (SD=1.54). Using the extensive genotyping available in these families from the genetic mapping efforts, we performed a genome scan by using 1324 markers with an average spacing of 4 cM. Analyses were first carried out with a recessive genetic model that has traditionally been assumed for the trait, and a threshold score of 8.0 delineating tasters from non-tasters. In this qualitative analysis, the maximum genome-wide lod score was 4.74 at 246 cM on chromosome 7; 17 families showed segregation of the dichotomous PTC phenotype. No other lod scores were significant; the next highest score was on chromosome 10 (lod=1.64 at 85 cM), followed by chromosome 3 (lod=1.29 at 267 cM). Because PTC taste ability exhibited substantial quantitative variation, the quantitative trait was also analyzed by using a variance components approach in SOLAR. The maximum quantitative genome-wide lod score was 8.85 at 246 cM on chromosome 7. Evidence for other possible quantitative loci was found on chromosomes 1 (lod=2.31 at 344 cM) and 16 (lod=2.01 at 14 cM). A subsequent two-locus whole-genome scan conditional on the chromosome 7 quantitative trait locus identified the chromosome 16 locus (two-locus lod=3.33 at 14 cM).     

Comparison of bitterness of caffeine and quinine by a time - intensity procedure

Temporal bitterness sequences elicited by four equi-bitter concentrationsof caffeine and quinine were evaluated by a time – intensityprocedure. For both compounds, the increase in bitterness intensitywas highly correlated with an increased duration of aftertaste,although the time to maximum intensity did not change. For equi-bittersolutions, the duration of aftertaste was influenced by thespecific tastant, and was longer for caffeine. Caffeine eliciteda faster maximum rate of onset and slower maximum rate of decayof bitterness. Only one significant difference between subjectswho were sensitive to l-phenyl-2-thiourca (PTC) and those whowere non-tasters was found. Tasters rated the maximum intensityof quinine solutions higher than non-tasters.