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At least 1,063 records · Page 59Linked to original sources
PubMed2004

Interactive effects of genotype, environment, and ontogeny on resistance of cucumber (Cucumis sativus) to the generalist herbivore, Spodoptera exigua.

Host-plant genotype, environment, and ontogeny all play a role in determining plant resistance to herbivory, yet little is known about the nature of the interactions among these factors. We investigated resistance of cucumber plants Cucumis sativus to the generalist herbivore Spodoptera exigua in a manipulative experiment involving three factors. In particular, we tested the effects of bitter (cucurbitacins present) vs. sweet (cucurbitacins absent) plants (genotype), with or without previous herbivory (environment), and cotyledons vs. true leaves (ontogeny). Contrary to our expectations, S. exigua growth was 54% higher on bitter plants than on sweet plants; growth was 63% higher, however, on undamaged plants compared to damaged plants, and 59% higher on true leaves compared to cotyledons. Moreover, all two-way interaction terms between genotype, environment, and ontogeny were significant. For example, S. exigua performance was higher on bitter than on sweet plants; however, this effect was strongly influenced by whether the tissue consumed was a cotyledon or true leaf and also whether it had been previously damaged. An examination of leaf nutritional chemistry revealed that some of our results could be explained by genotypic, environmental, and ontogenic differences in foliar nitrogen content. In contrast, the cucurbitacin content of plants did not appear to affect caterpillar growth. Our results provide evidence for the importance of interactions between genotype, environment, and ontogeny in determining herbivory and illustrate the value of manipulative experiments in revealing the complexities of these interactions.

Adaptation, Physiological↗
PubMed1979

Evidence for neural inhibition in bittersweet taste mixtures.

Three lines of evidence from psychophysical experiments implied that mutual suppression of bitter and sweet tastes is due to neural inhibition rather than chemical interactions in solution or competition of molecules for common receptor sites. Removal of sweetness from bittersweet mixtures caused the bitterness to increase. This was accomplished by adaptation to sucrose or by treatment with Gymnema sylvestre, neither of which affect the concentration of sucrose on the tongue. Such increases in the bitterness of mixtures, independent of the concentration of the sweet masking substance, are difficult to reconcile with suppression by means of chemical interactions. Similar dependence of suppression on perceived intensity (and independence from concentration) was observed with mixtures of phyenylthiocarbamide and sucrose. Tasters of phenylthiocarbamide showed stronger suppression of sweetness than nontasters. This result was also inconsistent with molecular interactions causing suppression, which would have resulted in the same degree of suppression for the two groups. Instead, these findings support neural explanations of mixture suppression, such as antidromic inhibition or occlusion.

Adaptation, Physiological↗
PubMed1995

A cyclic-nucleotide-suppressible conductance activated by transducin in taste cells.

Taste can be divided into four primary sensations: salty, sour, sweet and bitter. Salty and sour are directly transduced by apical channels, whereas sweet and bitter utilize cyclic nucleotide second messengers. We have shown that rod transducin is present in mammalian taste receptor cells, where it is activated by a bitter receptor and in turn activates a phosphodiesterase. Here we introduce into frog taste cells peptides derived from transducin's phosphodiesterase-interaction region, which cause an inward whole-cell current in a subset of cells. We find that the peptides' effects are reversibly suppressed by IBMX and forskolin, indicative of a transducin-activated phosphodiesterase. Cyclic nucleotides suppress the whole-cell current, indicating that cyclic nucleotides may regulate taste-cell conductance. IBMX modifies taste-cell responses to two taste stimuli, implicating phosphodiesterase in taste transduction. Submicromolar cyclic nucleotides directly suppress the conductance of inside-out patches derived from the taste-cell plasma membrane, independently of protein phosphorylation. The channels are unusual in that they are suppressed, rather than activated by cyclic nucleotides. We propose that transducin, via phosphodiesterase, decreases cyclic nucleotide levels to activate the cyclic-nucleotide-suppressible conductance, leading to Ca2+ influx and taste-cell depolarization.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Konzo associated with war in Mozambique.

We report an epidemic of konzo, symmetric spastic paraparesis associated with cassava consumption and cyanide exposure: 384 patients were treated in rehabilitation centres; the prevalence rate in a badly affected area was 30/1000. Most patients were children over 3 and women. Owing to war, communities turned to bitter cassava as their staple and took shortcuts in its processing. When the war ended, they continued to depend on inadequately processed bitter cassava. The epidemic lasted 2 years (the last year of war and the first of peace) with peaks each year during the cassava harvest. Although most cases were reported from rural inland areas, patients also came from small towns and the coast. School children had raised urinary thiocyanate and linamarin and low inorganic sulphate concentrations. Urinary thiocyanate values were lower than those previously reported in konzo epidemics, probably because we collected specimens before the cassava harvest and epidemic peak. The necessary conditions for konzo were present: intensive cultivation of bitter casava, insufficient processing, a probable high cyanide intake, and a low intake of protein-rich foods.

Adolescent↗
PubMed2002

A new whole-mouth gustatory test procedure. II. Effects of aging, gender and smoking.

Taste detection and recognition thresholds for the 4 basic tastes were measured in 670 healthy subjects using a new whole-mouth method in which test solutions of the 4 basic tastes were diluted 1:1 with distilled water successively in 13 steps. The taste thresholds were measured by spraying a 1 ml aliquot of solution into the mouth, starting with the lowest concentration, and asking the subject to swallow and note if a taste was detected and, if so, which one. The mouth was rinsed with distilled water only between different taste test solutions. Multiple comparison analysis showed a clear age-related increase in thresholds for salty, sour and bitter tastes for subjects in their eighth decade of life. From the third decade onwards, female subjects had significantly lower thresholds compared to males for sour taste in about half of the age groups and for salty and bitter tastes in some age groups. In contrast, for 18- and 19-year-old subjects, the gustatory thresholds of male subjects were lower than those of female subjects. Regarding smoking, male smokers in their third decade had significantly higher thresholds for bitter taste compared to male non-smokers in this age group.

Adolescent↗
PubMed2002

Sensitivity of three loci on the tongue and soft palate to four basic tastes in smokers and non-smokers.

The filter paper disk method was used to determine the map of the 4 tastes (sweet, salty, sour and bitter) on the tongue and soft palate in 69 healthy individuals. The equipment used for testing included filter paper disks 8 mm in diameter and taste solutions, which were sequentially diluted (in 13 stages from 80% sucrose, 12 stages from 20% NaCl, 12 stages from 8% tartaric acid and 14 stages from 4% quinine hydrochloride). The threshold at which each taste was recognized in three locations (center of the tongue tip, foliate papillae on the left side and center of the soft palate) was determined by testing increasing concentrations of each solution. We found no difference by sex for sweet taste but women were more sensitive to sour taste on the tongue tip and to salty and bitter tastes on the soft palate. No difference in taste threshold was noted at the different locations for sweet, salty or bitter tastes, but both sexes were less sensitive to sour taste on the soft palate than on the tongue tip, and in men the soft palate was even less sensitive to sour taste than the tongue root. Smoking was associated with increased (worse) taste thresholds for all four tastes, for both men and women.

Adolescent↗
PubMed2004

Taste masking technologies in oral pharmaceuticals: recent developments and approaches.

Taste is one of the most important parameters governing patient compliance. Undesirable taste is one of several important formulation problems that are encountered with certain drugs. Oral administration of bitter drugs with an acceptable degree of palatability is a key issue for health care providers, especially for pediatric patients. Several oral pharmaceuticals, numerous food and beverage products, and bulking agents have unpleasant, bitter-tasting components. So, any pharmaceutical formulation with a pleasing taste would definitely be preferred over a competitor's product and would translate into better compliance and therapeutic value for the patient and more business and profits for the company. The desire of improved palatability in these products has prompted the development of numerous formulations with improved performance and acceptability. This article reviews the earlier applications and methodologies of taste masking and discusses the most recent developments and approaches of bitterness reduction and inhibition for oral pharmaceuticals.

Administration, Oral↗
PubMed1996

A quinine-activated cationic conductance in vertebrate taste receptor cells.

The chincona alkaloid quinine is known to be a bitter tasting substance for various vertebrates. We examined the effects of quinine on isolated taste receptor cells from the bullfrog (Rana catesbeiana). Membrane currents were recorded by whole-cell recording, while quinine hydrochloride was applied extracellularly from a puffer pipette. At the resting potential (-77 +/- 9 mV, mean +/- SD, n = 49 cells), taste cells generated inward currents in response to quinine stimulation (> 1 mM), indicating a depolarizing response in the taste cells. Two types of current responses were observed; a newly found quinine-activated cationic conductance and a previously reported blocking effect of quinine on K+ conductances. The cationic current was isolated from the K+ current by using a Cs(+)-containing patch pipette. The relative permeabilities (Pion) of the quinine-activated cationic conductance were: PNa/PK/PCs = 1:0.5:0.42. The quinine dose-response relation was described by the Hill equation with the K1/2 of 3.6 mM and Hill coefficient of 5.3. When extracellular [Ca2+] (1.8 mM) was reduced to nominally free, the conductance was enhanced by about sixfold. This property is consistent with observations on quinine responses recorded from the gustatory nerve, in vivo. The quinine-induced cationic current was decreased with an application of 8-bromo-cAMP. We conclude that the bitter substance quinine activates a cation channel in taste receptor cells and this channel plays an important role in bitter taste transduction.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1985

Gustation as a determinant of ingestion: methodological issues.

To better characterize the relationship between taste function and dietary intake, measures of taste sensitivity, perceived intensity and preference for sweet (sucrose) and bitter (urea) stimuli were assessed in 35 healthy adults using aqueous and food tastants. Observations were then correlated with the proportions of calories contributed by carbohydrate, protein, fat and foods characterized by subjects as predominantly sweet or bitter on 7-day diet records. No significant association was noted among single measures of taste function and any of the five intake parameters, although taste profiles comprised of multiple taste ratings accounted for approximately a third of the variance in sweet and bitter calorie consumption. Levels of nutrient intake could not be predicted at better than chance levels using taste responses. Taste function plays a subordinate role to other determinants of food and nutrient intake, although taste profiles may facilitate the prediction of preferred tastes of diets.

Adolescent↗
PubMed1995

The influence of genetic taste markers on food acceptance.

Genetically mediated sensitivity to the bitter taste of phenylthiocarbamide (PTC) and 6-n-propylthiouracil (Prop) has long been associated with enhanced sensitivity to other sweet and bitter compounds. New studies suggest that tasters and supertasters of Prop may also differ from notasters in their taste preferences and in their patterns of food rejection and food acceptance. One question is whether the acceptability of bitter-tasting vegetables is influenced by Prop taster status. Cruciferous vegetables are among the major dietary sources of potentially chemoprotective agents in cancer control, and their consumption is reported to alter cancer risk. Strategies aimed at dietary change in individuals or groups should consider the role of genetic taste markers and their potential influences on food preferences and dietary habits.

Alcoholism↗
PubMed2005

TAS2R38 (phenylthiocarbamide) haplotypes, coronary heart disease traits, and eating behavior in the British Women's Heart and Health Study.

BACKGROUND: Variation in the perception of bitter tastes has been associated with eating behavior, body composition, and cardiovascular disease. Recent observations have implicated 2 common haplotypes of TAS2R38 in the determination of bitter compound-tasting ability. OBJECTIVE: The objectives of the study were to examine, in the British Women's Heart and Health Study cohort, any association between TAS2R38 haplotypes, coronary heart disease (CHD), CHD risk factors, and eating behavior and to examine whether the associations allow for estimation of the effects of variation in diet on the etiology of common disease. DESIGN: We conducted a cross-sectional study of relations between TAS2R38 haplotypes and CHD, CHD risk factors, and eating behavior in 3383 women from 23 British towns. RESULTS: Genotyping at P49A and V262A in TAS2R38 (rs713598 and rs1726866) allowed construction of all 4 possible haplotypes. The 2 most common haplotypes corresponded with previously identified haplotypes related to bitter compound-tasting ability. No substantial evidence of association was found between these haplotypes and CHD (odds ratio for taste-defining haplotypes: 0.97; 95% CI: 0.78, 1.2), body mass index (difference between means of taste-defining haplotypes: -0.084; 95% CI: -0.45, 0.29), or a series of physiologic and dietary characteristics. A marginally lower risk of diabetes was observed among those with the nontaster haplotype than among those with the taster haplotype (odds ratio: 0.69; 95% CI: 0.48, 1.00). CONCLUSION: TAS2R38 status was not an important determinant of CHD, related risk factors, or eating behavior in the British Women's Heart and Health Study sample.

Aged↗
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↗
PubMed1996

Responses of primate taste cortex neurons to the astringent tastant tannic acid.

In order to advance knowledge of the neural control of feeding, we investigated the cortical representation of the taste of tannic acid, which produces the taste of astringency. It is a dietary component of biological importance particularly to arboreal primates. Recordings were made from 74 taste responsive neurons in the orbitofrontal cortex. Single neurons were found that were tuned to respond to 0.001 M tannic acid, and represented a subpopulation of neurons that was distinct from neurons responsive to the tastes of glucose (sweet), NaCl (salty), HCl (sour), quinine (bitter) and monosodium glutamate (umami). In addition, across the population of 74 neurons, tannic acid was as well represented as the tastes of NaCl, HCl quinine or monosodium glutamate. Multidimensional scaling analysis of the neuronal responses to the tastants indicates that tannic acid lies outside the boundaries of the four conventional taste qualities (sweet, sour, bitter and salty). Taken together these data indicate that the astringent taste of tannic acid should be considered as a taste quality, which receives a separate representation from sweet, salt, bitter and sour in the primate cortical taste areas.

Animals↗
PubMed2003

Taste sensitivities to PROP and PTC vary independently in mice.

Mammals use common mechanisms to detect, transduce and process taste stimulus information. For example, they share families of receptors that respond to amino acids, and sweet- and bitter-tasting stimuli. Nonetheless, it also clear that different species exhibit unique taste sensitivities that may reflect specific genetic variations. In humans, sensitivities to the chemically similar, bitter-tasting compounds 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC) are heritable and strongly correlated, suggesting a common genetic basis. However, it is unknown whether PROP and PTC taste sensitivities are similarly correlated in mice. Here we report that PROP and PTC taste sensitivities vary independently between two inbred strains of mice. In brief-access taste tests C3HeB/FeJ (C3) and SWR/J (SW) mice possess similar taste sensitivity to PTC, while SW mice are significantly more sensitive to PROP than are C3 mice. In two-bottle preference tests, however, SW mice display greater aversion to both compounds. This discrepancy may be explained by the observation that SW mice consumed taste solutions at a greater rate during the intake test than did C3 mice. Therefore, PTC avoidance is correlated with the amount of PTC consumed in the intake tests rather than the concentration of PTC tested. These findings suggest that post-ingestive factors play a significant role in PTC avoidance during intake tests and highlight an important advantage of brief-access tests over intake tests in resolving the gustatory and post-ingestive contributions to taste-related behaviors. Most strikingly, these results demonstrate that in mice, unlike in humans, PTC and PROP taste sensitivities vary independently, thereby suggesting a subtle functional diversity of bitter-taste mechanisms across mammalian species.

Animal Feed↗
PubMed2004

Incidental learning and memory for three basic tastes in food.

Forty three subjects were invited under the pretence that they would take part in an experiment on hunger feelings. They came without having eaten anything that morning and received a standard breakfast containing orange juice, cream cheese on crackers and yoghurt. These products were later (when subjects returned after scoring hunger feelings during the day) used as targets amidst a set of distractors varied by adding or subtracting different amounts of two basic tastes. Orange juice was varied in sweetness and bitterness, cream cheese in sourness and bitterness and yoghurt in sweetness and sourness. The changes were made comparable by using just noticeable differences, determined in preliminary experiments with other subjects, as units of change. Two measurements of memory were compared, an absolute (indicating which were the targets) and a relative one (indicating whether the targets and distractors were more, less or equally pleasant, sweet, sour, bitter or salty as the item eaten at breakfast). Both methods showed incidental learning, but relative memory was superior. Memory differed between tastes and was partly product dependent. These experiments suggest that taste memory is tuned to detect novel and potentially dangerous stimuli rather than to remember features of earlier experienced stimuli with great precision.

Adult↗
PubMed2004

Treatment of irritable bowel syndrome with herbal preparations: results of a double-blind, randomized, placebo-controlled, multi-centre trial.

BACKGROUND: Herbal medications have been used in many countries for the treatment of patients with irritable bowel syndrome. Controlled data supporting the efficacy of these treatments in patients with irritable bowel syndrome are lacking. AIM: To assess the efficacy and safety of a commercially available herbal preparation (STW 5) (nine plant extracts), the research herbal preparation STW 5-II (six plant extracts) and the bitter candytuft mono-extract in patients with irritable bowel syndrome. METHODS: Two hundred and eight patients with irritable bowel syndrome were recruited after standardized diagnostic work-up into a double-blind, placebo-controlled, multi-centre trial and were randomly assigned to receive one of four treatments: commercially available herbal preparation STW 5 (n = 51), research herbal preparation STW 5-II (n = 52), bitter candytuft mono-extract (n = 53) or placebo (n = 52). The main outcome variables were the changes in total abdominal pain and irritable bowel syndrome symptom scores. RESULTS: Two hundred and three patients completed the trial. STW 5 and STW 5-II were significantly better than placebo in reducing the total abdominal pain score (intention-to-treat: STW 5, P = 0.0009; STW 5-II, P = 0.0005) and the irritable bowel syndrome symptom score (intention-to-treat: STW 5, P = 0.001; STW 5-II, P = 0.0003) at 4 weeks. There were no statistically significant differences between the bitter candytuft mono-extract group and the placebo group (P = 0.1473, P = 0.1207). CONCLUSIONS: The commercially available herbal preparation STW 5 and its research preparation STW 5-II are both effective in alleviating irritable bowel syndrome symptoms.

Abdominal Pain↗
PubMed1993

Degradation and debittering of a tryptic digest from beta-casein by aminopeptidase N from Lactococcus lactis subsp. cremoris Wg2.

The mode of action of purified aminopeptidase N from Lactococcus lactis subsp. cremoris Wg2 on a complex peptide mixture of a tryptic digest from bovine beta-casein was analyzed. The oligopeptides produced in the tryptic digest before and after aminopeptidase N treatment were identified by analysis of the N- and C-terminal amino acid sequences and amino acid compositions of the isolated peptides and by on-line liquid chromatography-mass spectrometry. Incubation of purified peptides with aminopeptidase N resulted in complete hydrolysis of many peptides, while others were only partially hydrolyzed or not hydrolyzed. The tryptic digest of beta-casein exhibits a strong bitter taste, which corresponds to the strong hydrophobicity of several peptides in the tryptic digest of beta-casein. The degradation of the "bitter" tryptic digest by aminopeptidase N resulted in a decrease of hydrophobic peptides and a drastic decrease of bitterness of the reaction mixture.

Amino Acid Sequence↗
PubMed1973

Preparation of antimicrobial compounds by hydrolysis of oleuropein from green olives.

Oleuropein, an intensely bitter glucoside, was isolated from green olives. Hydrolysis products obtained from oleuropein in sufficient quantity for further tests were: (i) beta-3,4-dihydroxyphenylethyl alcohol prepared by acid hydrolysis of oleuropein; (ii) elenolic acid obtained by methanolysis of oleuropein, isolation of the intermediate acetal, and subsequent acid hydrolysis; and (iii) oleuropein aglycone formed by the action of beta-glucosidase on the parent glucoside. Mass spectral verification of the isolated compounds and ultraviolet absorption data are given. Oleuropein and its aglycone had similar threshold levels for detection of bitterness, whereas elenolic acid and beta-3,4-dihydroxyphenylethyl alcohol were not judged to be bitter.

Anti-Infective Agents↗