Understanding the sense of smell via synthetic odors:
Manipulating synthetic optogenetic odors reveals the coding logic of olfactory perception
Edmund Chong1, Monica Moroni2, 3, Shy Shoham1, 4, 5, Stefano Panzeri2, Dmitry Rinberg1.4.
1Neuroscience Institute, NYU Langone Health, New York, NY, USA.2Neural Computation Laboratory, Istituto Italiano di Tecnologia, Rovereto, Italy.3CIMeC, University of Trento, Rovereto, Italy.4Center for Neural Science, New York University, New York, NY, USA.5Tech4Health Institute, NYU Langone Health, New York, NY, USA
How does neural activity generate perception? The spatial identities and temporal latencies of activated units correlate with external sensory features, but finding the subspace of activity that is consequential for perception, remains challenging. We trained mice to recognize synthetic odors: optogenetically-driven spatiotemporal patterns of glomerular activity in the olfactory bulb. We then performed precise spatial or temporal perturbations on trained patterns and measured how recognition changes. Changes in recognition reflect the perceptual relevance of the modified feature. We modeled recognition as the matching of glomerular activity to learned templates, and uncovered what forms a perceptually-meaningful pattern template: activation sequences ordered by latencies relative to each other, with surprisingly minimal effect of sniff. Within templates, spatially-identified glomeruli contribute additively, with larger contributions from earlier-activated glomeruli. Template matching with these perceptually-meaningful features can account for animals’ responses, with the degree of mismatch predicting changes in recognition. The model accurately generalizes to novel spatio-temporal manipulations of patterns, and produces non-linear responses that resemble the non-linear responses in the data. This is the first report to our knowledge, that not only establishes a causal role for neural activity sequences in perception, but also uncovers the perceptually-relevant coding schemes governing these sequences. Our synthetic approach reveals the fundamental logic of the olfactory code, and provides a general framework for testing links between sensory activity and perception.
Odors change when we know their names:
Mapping and Remapping the Human Olfactory Perceptual Space
Sarah Cormiea, Jason Fischer.
Johns Hopkins University, BALTIMORE, MD, USA
In visual perception, words are said “jump-start” object recognition. Similarly, learning the label seems to transform an odor – to snap its perceptual features into sharper focus. Here, we present a novel method for mapping human olfactory perceptual space. We tested whether assigning labels to everyday odors alters their perceptual similarity. Participants reported the similarity of odors by dragging and dropping icons into a circular arena on a computer screen. In Session 1, stimuli consisted of sixteen unlabeled odors from common foods (e.g. onion, carrot, grapefruit, vanilla), delivered in opaque squeeze bottles. Subjects sniffed the odors and then arranged the icons on the screen, placing icons for similar-smelling items close together and different items farther apart. In Session 2, participants performed the same task, but this time with labels on the bottles identifying the odors. In Session 3, participants performed the arrangement task based on labels alone. Perceptual similarity was reliably correlated, demonstrating shared structure in participants’ perceived relationships among odors (N=20, leave-one-out correlation = 0.45; p < 0.001). Further, the addition of labels in Session 2 altered the perceptual space in a reliable way that was not fully accounted for by a linear combination of the odor-only arrangements (Session 1) and the label-only arrangements (Session 3). Shifts in olfactory similarity space predicts that some odors will move farther apart and become more discriminable. Consistent with this hypothesis, we found improved discrimination in an odor mixture classification task with the application of labels (N=76, p = 0.041). These results suggest a reliable olfactory perceptual space that is systematically remapped with the application of labels.
The enhanced evolutionary mechanism of olfaction:
An enhanced evolutionary capacitance enables the functional expression of odorant receptors with cryptic mutations
Claire A.de March1, Kentaro Ikegami 1, 2, Maira H.Nagai 1, Soumadwip Ghosh 3, Matthew Do 1, Ruchira Sharma 1, Elise S.Bruguera1, Yueyang Eric Lu 1, Yosuke Fukutani 1, 2, Nagarajan Vaidehi 3, Masafumi Yohda2, Hiroaki Matsunami 1.
1Duke University, Durham, NC, USA, 2Tokyo University of Agriculture and Technology, Tokyo, Japan. 3Beckman Research Institute of the City of Hope, Duarte, CA, USA
Odor detection begins with odorant receptors (OR), which belong to the large family of rhodopsin-like G protein-coupled receptors. In order to discriminate the vast number of volatile chemicals, the ORs repertoire gained a high functional diversity by rapidly evolving, becoming the largest sub-family of G protein-coupled receptors. The mechanism allowing this rapid evolution while conserving the functionality of the ORs remains unknown. Here, we sought to understand at a molecular level the ORs properties underlying their functional expression in olfactory sensory neurons while they remain poorly expressed in heterologous cells. Using a combination of in silico and in vitro tools, we demonstrate that the divergences from the conserved residues in this family are cryptic mutations that increase OR repertoire diversity at the expense of functionality. The divergence from conserved residues destabilizes the structure of the OR to decrease its cell surface expression in heterologous cells. The receptor transporting proteins RTP1 and RTP2 compensate this structural destabilization by promoting most ORs transport from the endoplasmic reticulum to the cell surface allowing their functional expression. We hypothesis that olfactory-specific evolutionary capacitors, such as RTP1, RTP2, and other contributors yet to be discovered, enables ORs functional cell surface expression, supporting the rapid evolution of ORs to facilitate sensory adaptation.
Decreased sense of smell leads to future depression in older US adults:
Olfactory dysfunction predicts the development of depression in older US adults
Yazan Eliyan1, Kristen E.Wroblewski2, Martha K.McClintock3, 4, Jayant M.Pinto5.
1Pritzker School of Medicine, The University of Chicago, Chicago, IL, USA.2Department of Public Health Sciences, The University of Chicago, Chicago, IL, USA.3Department of Comparative Human Development, The University of Chicago, Chicago, IL, USA.4Department of Psychology, The University of Chicago, Chicago, IL, USA.5Section of Otolaryngology-Head and Neck Surgery, Department of Surgery, The University of Chicago, Chicago, IL, USA
Olfaction is linked to mood due to neuroanatomic connections between the olfactory and limbic systems. Some (but not all) prior studies have shown that olfactory dysfunction is associated with increased depressive symptoms. However, these studies were cross-sectional and thus unable to shed light on the directionality of the relationship. We aimed to test whether impaired olfaction caused increased depressive symptoms over time. We assessed olfaction and depression in the National Social Life, Health, and Aging Project, a nationally-representative, longitudinal study of older U.S. adults. Olfactory function was measured using a validated odor identification test (5 Sniffin’ Sticks). Depressive symptoms were measured using a survey version of the validated Center for Epidemiological Studies Depression (CES-D) scale. Multivariate logistic regression models, accounting for demographics, comorbidities, alcohol use, smoking, and cognition, tested the association between olfactory dysfunction and depression. Older adults with olfactory dysfunction were more likely to have depression at baseline (OR = 1.22, 95% CI = 1.04 - 1.42). Among adults without comorbidities, those with olfactory dysfunction at baseline had increased odds of developing depression at 5- or 10-year follow-up (OR = 2.22, 95% CI = 1.13 - 4.37). Conversely, those with depression at baseline did not have significantly increased odds of developing olfactory dysfunction at 5- or 10-year follow-up, regardless of health status (OR = 1.21, 95% CI = 0.81 - 1.82). We show for the first time that olfactory dysfunction predicts the development of depression in older U.S. adults. These data support screening for depression in older adults with olfactory impairment and set the stage for disentangling the relationship between olfaction and depression.
Smelling with single cells: testing the sensitivity limits of olfaction
Precise Optical Probing of Perceptual Detection in Olfactory Circuits
Jonathan V.Gill1, 2, Gilad M.Lerman1, Hetince Zhao1, 3, Benjamin J.Stetler1, 3, Shy Shoham1, 3, 4, Dmitry Rinberg1, 2, 5.
1Neuroscience Institute, New York University Langone Health, New York, NY, USA.2Center for Neural Science, New York University, New York, NY, USA.3Tech4Health Institute, New York University Langone Health, New York, NY, USA.4Department of Ophthalmology, New York University Langone Health, New York, NY, USA.5Department of Physics, New York University, New York, NY, USA
Animals are capable of detecting odorants in a single sniff, at extremely low concentrations. This ability is crucial for survival, yet it is unknown how the olfactory system supports detection at the perceptual limit. In the mouse olfactory bulb, inhalation of different odors leads to changes in the set of neurons activated, as well as when neurons are activated relative to each other (synchrony), and the onset of inhalation (latency). A key question is which features of stimulus evoked activity (e.g. rate, synchrony, or latency) are used to guide detection behavior? Here, we probed the sensitivity of mice to perturbations across each stimulus dimension using holographic two-photon (2P) optogenetic stimulation of olfactory bulb neurons, with cellular and single action potential resolution and millisecond precision. We found that mice can detect single action potentials evoked synchronously across <20 olfactory bulb neurons. Mice exhibited this sensitivity for artificial ensembles of mitral cells, as well as mixed ensembles of mitral and granule cells. Further, we discovered that detection depends strongly on the synchrony of activation across neurons, with detectability falling to near-chance levels with an imposed stimulus spread ³ 30 ms, while detection performance was minimally perturbed by changes in the latency of activation relative to inhalation. These results reveal that mice are acutely attuned to single neurons and action potentials in olfactory circuits, and that synchrony across neurons may be a critical feature supporting the perceptibility of sparse ensemble activity signals.
Factors Impacting Refreshment
Investigation of the Impact of Flavors and Alcohol Levels on Beer Refreshment Perception Using Consumer Tests
Amy Hampton, Xiaofen Du. Texas Woman's University, Denton, TX, USA
Beer is a known source of refreshment and the refreshment properties of beer likely come from a combination of different factors such as low temperature, carbonation, and alcohol. Previous studies have investigated how carbonation and temperature impact refreshment. Few studies have focused on the impact of beer flavor. The objective of this research was to investigate beer flavor and alcohol content on the perception of beer refreshment. An online survey was conducted to investigate consumer perception toward beer refreshment. Participants (n=1,050) indicted a refreshing beer was predominantly acidic in taste (lime: 51.7% of participants, lemon: 43%, orange: 40.5%, grapefruit: 35.7%), had a crisp and clean flavor profile (87.3% of participants), encompassed a cold/chilled temperature (95.4%), was carbonated (42%), and had a light flavor intensity (88.6%). A consumer test was conducted to determine if perceived refreshment was impacted by flavor (lemon, cucumber, citrus,) and/or alcohol percentage (0%, 2.5%, 5%, 7.5%). Consumers (n=326) evaluated their liking of refreshing, beer flavor, alcohol, carbonation, acidity, and bitterness attributes of formulated 12 beers using nine-point hedonic scales. Acceptance for all attributes was significantly different across all 12 samples (p<0.001). Pearson’s correlation analysis indicated that the liking of refreshing attribute strongly correlated with the liking of beer flavor, alcohol, carbonation, acidity, and bitterness. Cluster analysis (XLStat) uncovered four segments of consumers who were divided by acceptance of alcohol levels. The results of this study increased knowledge of the impact of flavors and/or alcohol content on beer refreshment perception which could guide beer development in industry.
No differences for liking or taste sensitivity after ultraprocessed and non-processed foods:
No Significant Taste Sensitivity or Preference Differences Following Ad Libitum Consumption of Ultra-Processed and Unprocessed Diets
Paule Joseph1, Alexis Franks1, Rosario Jaime-Lara1, Juen Guo2, Amber Courville2, Ciaran Forde3, Shanna Yang4, Abhrarup Roy1, Karen Taylor1, Kevin Hall2.
1NINR, Bethesda, MD, USA.2NIDDK, Bethesa, MD, USA.3Singapore Institute for Clinical Sciences, Singapore, Singapore.4NIH Clinical Center, Bethesda, MD, USA
Increases in obesity have coincided with the increased availability of ultra-processed foods (UPF). A recent study showed increased adiposity and energy intake following UPF. However, the mechanism by which UPF promote greater intake remains unclear, but changes in taste may contribute to increased intake and positive energy balance. This study explored taste sensitivity and preference and associations between taste and clinical parameters following 2 weeks on UPF or unprocessed diet(UP). In a crossover in-patient trial, 20 participants were randomized to receive UPF/UP. Taste preferences and detection thresholds were measured using comparison-tracking and forced-choice procedures respectively following each diet. Body weight and blood pressure were measured daily. Mixed model analysis was used to determine the effect of diet on patient characteristics, including BMI and blood pressure. Spearman correlations and univariate linear regressions were used to analyze taste measures by diet and taste(salt and sucrose) preference and detection thresholds. No significant differences in sweet taste(M=12.8±SD=8.20;M=13.7±SD=7.14;p=0.541) and salt taste preference (M=1.6±0.45;M=1.7±SD=0.54;p=0.997) and sweet (M=6.9±SD=5.55;M=7.0±SD=6.29;p=0.946) and salt detection thresholds(M=10.6±SD=14.80; M=10.7±SD=11.17;p=0.997) were found between the UPF and UP diets. Positive associations were found between salt taste preference, BMI(r=0.503;p=0.028) and blood pressure(r=0.588;p=0.008) following the UPF diet. This suggest that differences in eating behavior between diets unlikely arise from taste related factors. Studies are needed to clarify the mechanism by which UPF promote greater intake, and the possible relationship with taste sensitivity and preference.
Beta-caryophyllene (BCP) improves wound healing in mice:
Beta-caryophyllene improves cutaneous wound healing in mice through multiple mechanisms
Sachiko Koyama1, Anna Purk1, Manpreet Kaur1, Helena Soini1, Milos Novotny1, Keith Davis1, Cheng Kao1, Hiroaki Matsunami2, Anthony Mescher1
1Indiana University, Bloomington, IN, USA.2Duke University, Durham, NC, USA
We have a long history of actively utilizing odorants to heal or alter our physiological conditions. A variety of herbal plants’ extracts have been used to reduce stress and pain, and to promote recovery from injury or illness. Despite this long history of using herbal plant extracts, there is still a strong need of scientific evidences regarding the effects of such extracts. Beta-caryophyllene (BCP) is an odoriferous bicyclic sesquiterpene found in various herbs and spices. It has odor (activates olfactory system) and it is a ligand of cannabinoid receptor 2 (CB2). As activation of CB2 is known to have anti-inflammatory impacts, we hypothesized that BCP may affect wound healing by decreasing inflammation. Here we show that cutaneous wounds in mice treated topically with BCP enhanced re-epithelialization and increased cell proliferation. Primary cell cultures treated with BCP showed enhanced cell migration. These results suggested that the greater re-epithelialization is due to both enhanced cell proliferation and cell migration. When primary cell cultures from CB2 knockout mice were exposed to BCP, they did not show enhanced migration in chemotaxis assays, implicating this pathway, but there were no migratory differences in scratch tests suggesting involvement of other routes as well. RNA sequencing revealed large differences in gene expression between injured, BCP-treated skin and controls. Genes related to embryonic growth as well as hair follicle stem cells were up-regulated in BCP-treated tissue. Transient Receptor Potential channel genes were up-regulated in the injured skin exposed to BCP, indicating their possible involvement in the improved re-epithelialization. Our study suggests that BCP has the capacity to improve wound healing through multiple pathways.
A psychological stressor conveyed by appetite-linked neurons:
A Psychological Stressor Conveyed by Appetite-Linked Neurons
Eun Jeong Lee1, Naresh K.Hanchate1, Kunio Kondoh1, 2, Ai Phuong S.Tong1, 3, Donghui Kuang1, Andrew Spray1, Xiaolan Ye1, Linda B.Buck1.
1Fred Hutchinson Cancer Research Center, Seattle, WA, USA.2National Institute for Physiological Sciences, Okazaki, Japan.3University of Washington School of Medicine, Seattle, WA, USA
Mammals exhibit instinctive reactions to danger that include specific behaviors as well as surges in blood stress hormones that rally multiple tissues to cope with threat. Hypothalamic corticotropin releasing hormone neurons (CRHNs) control stress hormone levels, but how diverse stressors converge on CRHNs to induce stress responses is not well understood. Here, we used single cell transcriptomics to define CRHN receptors for neurotransmitters and neuromodulators and then viral tracing to localize subsets of upstream neurons expressing cognate receptor ligands. Surprisingly, one subset comprised POMC (pro-opiomelanocortin)-expressing neurons in the hypothalamic arcuate nucleus, which are linked to appetite suppression. The POMC neurons were activated by one psychological stressor, physical restraint, but not another, a predator odor. Chemogenetic activation of POMC neurons induced a stress hormone increase and their silencing inhibited the stress hormone response to physical restraint, but not predator odor. Together, these results indicate that hypothalamic POMC neurons, which are implicated in appetite suppression, also play a major role in the stress hormone response to a specific type of psychological stressor.
Filiform papillae are “in the thick” of viscosity:
Elucidating a Potential Detection Mechanism for High-Viscosity Solutions in the Oral Cavity
Brittany L. Miles, Christopher T.Simons.
The Ohio State University, Columbus, OH, USA
Multiple modelling studies have suggested that perception of high-viscosity (η>3000cP) solutions is linked to the directional deformation of filiform papillae, although this has not been tested in humans. Thus, this study sought to further characterize the detection mechanism underpinning the perception of these solutions via psychophysical testing. We hypothesized that discrimination ability of high-viscosity solutions would be linked to filiform papillary attributes. Just-noticeable difference (JNDs) thresholds were determined for participants (n=45) using the forced-choice staircase method for viscosities of glycerin/water/carboxymethyl cellulose solutions (η=4798-12260cP). Participants evaluated solutions by pressing them against the hard palate while wearing retainers made of moldable plastic allowing for isolation of the tongue. Additionally, optical profiling was used to characterize papillary structures in tongue biopsies from the dorsal medial tongue. Papillary attributes were then related to psychophysical performance using causal analysis. Perceptual data significantly correlated to multiple filiform papillary attributes including average papillary length (R2=0.272, p<0.001) and average papillary density (R2=0.178, p=0.003). Moreover, causal analysis indicated that variation in these attributes alone explained the variation in subjects’ JND (p<0.001). This study provides insight into the tongue’s role in the perception of high-viscosity solutions. While some previous works propose filiform papillae may help discriminate varying viscosities, other studies consider the structures to be primarily vestigial. The clear association delineated here underpins the likely relevance of filiform papillae in viscosity discrimination and may indicate relevance for other texture precepts.
Autism gene affects processing of unfamiliar odors
Odor identification in novel olfactory environments is impaired in mouse model of autism
New York Institute of Technology, College of Osteopathic Medicine, Old Westbury, NY, USA
Autism spectrum disorder (ASD) has a sensory component characterized by aversion to novel stimuli as well as difficulty in identifying known stimuli in the presence of novel distractors. In fact, identification of known targets in novel backgrounds is a complex computation that challenges current machine learning algorithms. We hypothesized that such complex computation would require an intact nervous system that might be affected in ASD. We wondered if the difficulties of odor identification in novel environments would extend to the olfactory system in mouse models of autism. Here we compared the performance of C57Bl6 mice with the CNTNAP2-/- model of autism in a novel olfactory detection task. We used an “olfactory captcha” task to test the generalization capabilities in novel olfactory environments. We trained 4 head-fixed C57Bl6 mice and 4 CNTNAP2-/- mice in a go/no-go task using a training set that included a mixture of target odors and background odors that animals were familiar with. Performance was >90% after 8-10 days for both type of mice indicating that basic odor perception was spared in CNTNAP2-/- mice. We then used a test set that included novel background odors that animals have never experienced before, similar to visual captchas used to distinguish humans from computers. C57Bl6 mice were able to solve the task at 78% (p<2e-5). However, CNTNAP2 mice performed at 62% and its performance was significantly lower than C57Bl6 mice (p=0.0019). Using intrinsic optical imaging, we determined that mice performance could not be explained by a linear classifier, but mice used a sophisticated non-linear algorithm that was selectively affected in the mouse model of autism.
Reliable readout of mixture components from small populations of anterior piriform cortical neurons:
Reliable Readout of Mixture Components From Small Populations of Anterior Piriform Cortical Neurons
Sapir Penker, Tamar Licht, Dan Rokni.
Hebrew University, Jerusalem, Israel
Airborne chemicals emitted by multiple objects, mix in the air prior to reaching the nose, complicating the recognition of specific odors of interest. The olfactory system is therefore faced with the task of identifying objects in the presence of rich and often unpredictable backgrounds. Piriform cortex is thought to be the site of object recognition and scene segmentation, yet the nature of its responses to odorant mixtures is largely unknown. In this study we asked two related questions. 1) How do mixture representations relate to the representations of mixture components? And 2) Can the identity of mixture components be readout from mixture representations in piriform cortex? To answer these question, we recorded single unit activity in the piriform cortex of naïve mice while sequentially presenting single odorants and their mixtures. We find that the magnitude of piriform cortical responses increases with added mixture components, and that the responses of individual neurons are well explained by a normalization model. Finally, we show that mixture components can be identified from piriform cortical activity by pooling responses of a small population of neurons. These results suggest that piriform cortical representations are well suited to perform figure-background segmentation without the need for learning.
Bitter taste receptors (TAS2Rs) mediate food allergy (FA):
Bitter Taste Hyper-Sensitivity to Quinine and Amarogentin Is Associated with Food Allergies
Zeping Shao1, Yun Liu2, Nadia de Jager3, Eugeni Roura1.
1Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Australia.2Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Australia.3Queensland Brain Institute, The University of Queensland, Brisbane, Australia
Food allergies have been defined as an immune response occurring soon after ingesting an otherwise innocuous, dietary protein. The activation of immune cells (i.e. T lymphocytes) occur after activation by specific peptides (referred to as epitopes) part of the amino acid sequence of the protein. Interestingly, several peptides have been identified as bitter receptor (TAS2R) agonists. For example, Gly-Phe-containing peptides have been identified as epitopes involved in peanut, tree nut, milk, and egg allergies among others. Interestingly, Gly-Phe is a high affinity ligand for TAS2R4. With the hypothesis that sensitivity to bitterants may be involved in food allergic responses, we performed sensory evaluations on 16 medically diagnosed food allergic (FA) and 16 non-food allergy (NFA) participants. Best estimate thresholds (BET) for quinine hydrochloride (quinine), amarogentin, thiamine hydrochloride (thiamine), 6-n-propylthiouracil (PROP) and caffeine were analyzed via discriminatory triangle test. The BET were significantly (P = 0.0226, one-way ANOVA) or tended to be (P = 0.0671) lower in FA group compared to NFA individuals for quinine and amarogentin, respectively. In contrast, no significant (P > 0.10) differences were observed related to the sensing of thiamine, PROP, or caffeine between the two groups. Quinine and amarogentin show high affinity to TAS2R4. Thus, it would appear that the bitter-hypersensitivity involving TAS2R4 observed in FA individuals may be related to a defensive response to avoid consumption of potential allergenic proteins. In conclusion, a significant hyper-sensitivity to bitter TAS2R4 ligands has been identified in FA compared to NFA volunteers. The potential role of TAS2R4 and other TAS2Rs in food allergies warrants further investigation.
Ethanol perception varies with thermal taste status:
Thermal taste status moderates perception of binary ethanol solutions
Margaret K Thibodeau1, Gary J Pickering1, 2, 3, 4, 5.
1Department of Biological Sciences, Brock University, St.Catharines, ON, Canada.2Cool Climate Oenology and Viticulture Institute, Brock University, St.Catharines, ON, Canada.3Department of Psychology, Brock University, St.Catharines, ON, Canada.4Charles Sturt University, Wagga Wagga, Australia.5University of the Sunshine Coast, Sippy Downs, Australia
Ethanol (EtOH), present in all alcoholic beverages, is a complex stimulus that elicits multiple gustatory and chemesthetic sensations. Alcoholic beverages also contain other tastants that significantly impact flavour, and flavour is a key driver of consumer preference and intake. Thermal taste status (TTS) is a source of individual variation across multiple flavour modalities, however suppression and enhancement phenomena have not been investigated in the context of TTS. In this study we sought to characterize the binary interactions between EtOH and four orosensory stimuli; fructose (sweet), quinine (bitter), tartaric acid (sour) and alum sulfate (astringent) and determine if/how these interactions are moderated by TTS. Female participants (21-22 thermal tasters (TT) & 16-17 thermal non-tasters (TnT)) rated the intensity of five orosensations (gLMS; sweet, sour, bitter, astringent, burning) in binary solutions of EtOH (5%, 13% or 23% v/v) + a tastant (low, medium or high). For each tastant, 3-way ANOVAs (TTS, EtOH concentration, tastant concentration) determined which factors impacted orosensory ratings. TTs rated the sweetness of fructose + EtOH solutions (F=47, p<0.001), astringency of alum sulfate + EtOH solutions (F=31, p<0.001) and sourness of tartaric acid + EtOH solutions (F=3.6, p=0.059) higher than TnTs, but not the bitterness of quinine + EtOH solutions (F=1.1, p=0.302). Further results to be reported include the indices of interaction (isobole method) which characterize the nature of the interactions between the tastants and EtOH. Overall, our results show that the orosensory advantage of TTs extends to binary and sensorially complex mixtures, with implications for alcohol preference and behaviour.
The Life and Death of a Taste Cell:
The Life and Death of a Taste Cell
Courtney E Wilson1, 2, 3, Yannick K Dzowo1, 2, Ruibiao Yang1, 2, Robert S Lasher1, 2, Thomas E Finger1, 2.
1University of Colorado School of Medicine Department of Cell and Developmental Biology, Aurora, CO, USA.2Rocky Mountain Taste and Smell Center, Aurora, CO, USA.3University of Colorado School of Medicine Department of Otolaryngology, Aurora, CO, USA
Taste buds undergo continuous cell turnover throughout life. Our understanding of the processes and signals involved in taste cell replacement has advanced greatly in the past decade. How taste cells die and exit the bud, however, has received scant attention. Using serial EM images of murine taste buds, we identified cells that appear to be in various stages of cell death, based on their ultrastructural features. These cells display morphological characteristics of apoptosis: reduced cell volume, changes in heterochromatin organization within the nuclei, nuclear fragmentation, golgi body degradation, and cell fragmentation. Dying cells tend to lie near the edge of the taste bud, often abutting “edge” cells at the border between the taste bud and the surrounding epithelial tissue. From this observation, we suggest that taste cells migrate outward from the longitudinal center of the taste bud over the course of their lives. Dying cells also tend to be wrapped by Type I cells, which in some cases appear to be in the process of engulfing the dying cell or fragments that have separated from the dying cell. We propose that Type I cells act as non-specialized phagocytes during the programmed death of a neighboring cell. Our serial EM datasets only capture a snapshot of time in the taste bud. Cells caught in the process of cell death are relatively rare. For example, in a single taste bud, we found evidence of only 2 apoptotic cells in a total population of ~100 taste cells. Since the lifespan of the average taste cell is 10-15 days, over 10% of the cells should be dying every day. We therefore conclude that morphological apoptosis occurs rapidly in the taste bud.
Cranberry polyphenols and individual differences in salivary proteins :
Salivary Protein Response to and Recovery from Cranberry-derived Polyphenol Exposure: Methodological Insight From A Time-Course Study
Neeta Y Yousaf1, Melania Melis2, Mariano Mastinu2, Cristina Contini3, Tiziana Cabras3, Iole T Barbarossa2, Beverly J Tepper1.
1Department of Food Science and Center for Sensory Sciences and Innovation, Rutgers University, New Brunswick, NJ, USA.2Department of Physiology, University of Cagliari, Cagliari, Italy.3Department of Biochemistry, University of Cagliari, Cagliari, Italy
Astringency is a tactile sensation which is often experienced when dietary polyphenols interact with salivary proteins. Although it is standard practice in astringency research to provide breaks in between stimuli, there is limited consensus over the amount of time needed to restore the oral environment to baseline levels. Here we examined salivary protein levels after exposure to 20 ml of a model stimulus (cranberry polyphenol extract, 0.75 g/L CPE) or unsweetened cranberry juice, CJ over a 10 min period. Whole saliva from healthy subjects (n=60) was collected at baseline and after 5 and 10 mins following either stimulus. Salivary proteins of five families (basic proline-rich proteins (bPRPs), acidic proline-rich proteins (aPRPs), Histatins, Statherin, & Cystatins) were identified from whole saliva by HPLC-ESI-IT-MS and quantified using the area of the extracted ion current (XIC) peaks. In comparison to baseline (resting), both stimuli caused salivary protein levels to rise, although CJ elicited a more robust response than CPE. Levels of all proteins (except two bPRPs) rose after stimulation with CJ, remained high at 5 mins (p<0.0007-0.0001) and did not return to baseline even at 10 mins (p<0.05-0.0001). In comparison, CPE increased the levels of aPRPs, and selected Cystatins & Histatins (p<0.04-0.0099) at 5 mins, which generally did not return to baseline even at 10 mins. Differences in bPRP levels with respect to gender and PROP taster status were observed after stimulation with both CJ and CPE. These data show that the oral environment may need more than 10 minutes to reset after an astringent stimulus, which is far longer than the typical break used in sensory studies. These findings will inform sensory methodology and will be discussed in the context of interindividual differences.