Chemical Senses最新文献

Deuterium oxide (D2O) is water in which the heavier and rare isotope deuterium replaces both hydrogens. We have previously shown that D2O has a distinctly sweet taste, mediated by the T1R2/T1R3 sweet taste receptor. Here, we explore the effect of heavy water on T1R2 and T1R3 subunits. We show that D2O activates T1R3-transfected HEK293T cells similarly to T1R2/T1R3-transfected cells. The response to glucose dissolved in D2O is higher than in water. Mutations of phenylalanine at position 7305.40 in the transmembrane domain of T1R3 to alanine, leucine, or tyrosine impair or diminish activation by D2O, suggesting a critical role for T1R3 TMD domain in relaying the heavy water signal.

Olfactory training (OT) has been shown to be of value in the treatment of olfactory dysfunction. The present study aimed to investigate whether the efficacy of OT could be modulated with multisensory integration, attention towards odors, odor complexity, or physical activity assessed with a questionnaire. One hundred healthy participants were recruited and divided into 4 groups. Except for controls (n = 26, mean age ± SD = 36 ± 15 years) all participants performed OT 4 times a day. In the "video" group (n = 26, age 39 ± 19 years) OT was performed while watching specific and congruent video sequences. In the "counter" group (n = 24, 38 ± 17 years) participants additionally counted the number of odors 1 day per week, and in the "training only" group no additional measures were taken in addition to OT (n = 24, 38 ± 20 years). "Single-molecule" odorants or "complex mixtures" were distributed randomly for training stimulation. Sniffin' sticks tests (odor identification, odor discrimination, and odor threshold), cognitive tests, and a series of scales were measured at both baseline and after 3 months of OT. The degree of physical activity was recorded with a questionnaire. Olfactory function improved in the video and counter groups after OT, especially for odor threshold and discrimination. Yet, odor complexity and the degree of physical activity had limited effects on olfactory improvement after OT. Both multisensory interaction and attention towards odors plus OT appeared to facilitate improvement of olfactory function in healthy individuals compared with OT alone and controls, which could provide new promising treatments for clinical applications.

Olfactory studies frequently utilize odor stimuli consisting of volatiles created from liquid dilutions of various chemicals. A problem arises if the researcher relies on these liquid dilutions to extrapolate vapor concentrations based on ideal gas behavior. For most chemicals, the relationship between liquid and vapor concentration deviates from these laws of proportionality due to interactions between the chemical and the solvent. Here, we describe a method to estimate vapor-phase concentrations of diluted odorants using a photoionization detector. To demonstrate the utility of this method, we assessed the relationship between liquid-/vapor-phase concentrations for 14 odorants (7 alcohols, 1 ester, and 6 aldehydes) in 5 different solvents (water, mineral oil, diethyl phthalate, dipropylene glycol, and propylene glycol). An analysis of 7 additional esters is also included to assess how carbon chain length and functional group, interacts with these solvents (for a total of 105 odorant/solvent pairs). Our resulting equilibrium equations successfully corrected for behavioral sensitivity differences observed in mice tested with the same odorant in different solvents and were overall similar to published measurements using a gas chromatography-based approach. In summary, this method should allow researchers to determine the vapor-phase concentration of diluted odorants and will hopefully assist in more accurate comparisons of odorant concentrations across olfactory studies.

Fear and anxiety are the most frequently studied emotional states in chemosignal research. Despite differences between these two emotional states, findings from research using fear and anxiety body odors (BOs) are often treated as part of a similar phenomenon. In this article, we examine possible similarities and differences between participants exposed to fear and anxiety BOs on 2 dependent variables commonly used in chemosignals' research: (1) the activation of facial muscles in displays of fear expressions (i.e. the medial frontalis and the corrugator supercilii); and (2) the time required to discriminate between negative emotional expressions (fear, anger, and disgust) and neutral ones. Our results show that fear (vs. rest) and anxiety (vs. exercise) BOs activate the medial frontalis, suggesting that both have a similar impact on receivers' facial muscles. However, we could not replicate previous findings regarding the influence of fear BOs in discriminating negative emotional faces from neutral ones. Two additional replication attempts failed to replicate the earlier results, indicating that the results reported in the literature with this specific paradigm should be interpreted cautiously. Suggestions for future research examining possible differences between fear and anxiety BOs are advanced.

Language is often thought as being poorly adapted to precisely describe or quantify smell and olfactory attributes. In this work, we show that semantic descriptors of odors can be implemented in a model to successfully predict odor mixture discriminability, an olfactory attribute. We achieved this by taking advantage of the structure-to-percept model we previously developed for monomolecular odorants, using chemical descriptors to predict pleasantness, intensity and 19 semantic descriptors such as "fish," "cold," "burnt," "garlic," "grass," and "sweet" for odor mixtures, followed by a metric learning to obtain odor mixture discriminability. Through this expansion of the representation of olfactory mixtures, our Semantic model outperforms state of the art methods by taking advantage of the intermediary semantic representations learned from human perception data to enhance and generalize the odor discriminability/similarity predictions. As 10 of the semantic descriptors were selected to predict discriminability/similarity, our approach meets the need of rapidly obtaining interpretable attributes of odor mixtures as illustrated by the difficulty of finding olfactory metamers. More fundamentally, it also shows that language can be used to establish a metric of discriminability in the everyday olfactory space.

The spontaneously hypertensive rats (SHRs) have enhanced palatability for NaCl taste as measured by the increased number of hedonic versus aversive responses to intraoral infusion (1 mL/1 min) of 0.3 M NaCl, in a taste reactivity test in euhydrated condition or after 24 h of water deprivation + 2 h of partial rehydration (WD-PR). SHRs also ingested more sucrose than normotensive rats, without differences in quinine hydrochloride intake. Here, we investigated the palatability of SHRs (n = 8-10) and normotensive Holtzman rats (n = 8-10) to sucrose and quinine sulphate infused intraorally in the same conditions that NaCl palatability was increased in SHRs. SHRs had similar number of hedonic responses to 2% sucrose in euhydrated condition (95 ± 19) or after WD-PR (142 ± 25), responses increased when compared with normotensive rats in euhydrated condition (13 ± 3) or after WD-PR (21 ± 6). SHRs also showed increased number of aversive responses to 1.4 mM quinine sulphate compared with normotensive rats, whether in euhydrated condition (86 ± 6, vs. normotensive: 54 ± 7) or after WD-PR (89 ± 9, vs. normotensive: 40 ± 9). The results suggest that similar to NaCl taste, sweet taste responses are increased in SHRs and resistant to challenges in bodily fluid balance. They also showed a more intense aversive response in SHRs to bitter taste compared with normotensives. This suggests that the enhanced response of SHRs to taste rewards does not correspond to a decreased response to a typical aversive taste.

Abundant evidence indicates that humans can communicate threat-related information to conspecifics through their body odors. However, prior research has been primarily conducted on Western (WEIRD) samples. In this study, we aimed to investigate whether threat-related information can be transmitted by individuals of East Asian descent who carry a single-nucleotide polymorphism (SNP) 538G → A in the ABCC11 gene, which significantly reduces (noticeable) body odor. To examine this, we recruited 18 self-identified male East Asian AA-homozygotes and 18 self-identified male Western individuals who were carriers of the functional G-allele. We collected samples of their fear-related and neutral body odors. Subsequently, we conducted a double-blind behavioral experiment in which we presented these samples to 69 self-identified female participants of Western Caucasian and East Asian backgrounds. The participants were asked to rate faces that were morphed between expressions of fear and disgust. Notably, despite the "odorless" phenotypical expression of the ABCC11-mutation in East Asians, their fear odor caused a perceptual fear bias in both East Asian and Caucasian receivers. This finding leaves open the possibility of universal fear chemosignaling. Additionally, we conducted exploratory chemical analysis to gain initial insights into the chemical composition of the body odors presented. In a subsequent pre-registered behavioral study (N = 33), we found that exposure to hexadecanoic acid, an abundant compound in the fear and neutral body odor samples, was sufficient to reproduce the observed behavioral effects. While exploratory, these findings provide insight into how specific chemical components can drive chemical fear communication.

The Ca2+-activated Cl¯ channel TMEM16B carries up to 90% of the transduction current evoked by odorant stimulation in olfactory sensory neurons and control the number of action potential firing and therefore the length of the train of action potentials. A loss of function approach revealed that TMEM16B is required for olfactory-driven behaviors such as tracking unfamiliar odors. Here, we used the electro-olfactogram (EOG) technique to investigate the contribution of TMEM16B to odorant transduction in the whole olfactory epithelium. Surprisingly, we found that EOG responses from Tmem16b knock out mice have a bigger amplitude compared to those of wild type. Moreover, the kinetics of EOG responses is faster in absence of TMEM16B, while the ability to adapt to repeated stimulation is altered in knock out mice. The larger EOG responses in Tmem16b knock out may be the results of the removal of the clamping and/or shunting action of the Ca2+-activated Cl¯ currents leading to the paradox of having smaller transduction current but larger generator potential.

Electrogustometry (EGM) is a practical way to test taste. It is typically performed using unipolar electrodes, with the anode on the tongue and the cathode on the hand, forearm, or neck. This results in electric current passing through nontaste tissues and adds a level of impracticality to its clinical application. We compared, using a repeated measures counterbalanced design, anodal thresholds from a unipolar electrode to those of a unique bipolar electrode in which the anode and cathode are contiguously located. Both sides of the anterior tongue were assessed in 70 subjects, as were the effects of age and sex. Nonparametric analyses were performed. The median threshold of the bipolar electrode's central disk (2.49 µA) did not differ from that of the unipolar electrode (2.96 µA) (P = 0.84). On average, older persons exhibited higher thresholds. No significant sex or tongue side effects were evident. Interestingly, when the annular (donut-shaped) bipolar electrode served as the anode, the threshold was higher than that of the other electrodes (5.19 µA; Ps < 0.001). This conceivably reflected lessened summation of activity among adjacent afferents and partial sampling of tongue regions with fewer taste buds. Correlations among all EGM thresholds were nominally higher for women than for men, ranging from 0.83 to 0.85 for women and 0.54 to 0.67 for men; all Ps < 0.001. This study validates the use of a bipolar electrode for assessing taste function, averting movement of current through nontaste-related tissues and making such testing safer and more practical.