Chemical senses
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Soon after the outbreak of COVID-19, reports that smell and taste are disrupted by the illness drew the attention of chemosensory scientists and clinicians throughout the world. While other upper respiratory viruses are known to produce such disruptions, their occurrence with the deadly and highly infectious SARS-CoV-2 virus raised new questions about the nature of the deficits, their cause, and whether they might serve as indicators of the onset of the disease. ⋯ The surveys, which took different approaches and had somewhat different goals, add significant new data on the incidence and severity of smell loss in COVID-19, and the potential for olfactory dysfunction to serve as an indicator of the spread and severity of the disease. Less definitive evidence of the frequency, characteristics, and magnitude of disruptions in taste and chemesthesis point to the need for future survey studies that combine and refine the strengths of the present ones, as well as clinical studies designed to selectively measure deficits in all 3 chemosensory systems.
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In response to the COVID-19 pandemic, countries have implemented various strategies to reduce and slow the spread of the disease in the general population. For countries that have implemented restrictions on its population in a step-wise manner, monitoring of COVID-19 prevalence is of importance to guide decision on when to impose new, or when to abolish old, restrictions. We are here determining whether measures of odor intensity in a large sample can serve as one such measure. ⋯ Finally, we found that individuals progressing from reporting no symptoms to subsequently reporting COVID-19 symptoms demonstrated a large drop in olfactory performance. These data suggest that measures of odor intensity, if obtained in a large and representative sample, can be used as an indicator of COVID-19 disease in the general population. Importantly, this simple measure could easily be implemented in countries without widespread access to COVID-19 testing or implemented as a fast early response before wide-spread testing can be facilitated.
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Comparative Study
Comparison of GABA, Somatostatin, and Corticotrophin-Releasing Hormone Expression in Axon Terminals That Target the Parabrachial Nucleus.
Several forebrain areas have been shown to project to the parabrachial nucleus (PBN) and exert inhibitory and excitatory influences on taste processing. Some sources of descending input such as the central nucleus of the amygdala (CeA) might utilize somatostatin (Sst) and/or corticotrophin-releasing hormone (Crh) to influence taste processing in the PBN (Panguluri S, Saggu S, Lundy R. 2009. Comparison of somatostatin and corticotrophin-releasing hormone immunoreactivity in forebrain neurons projecting to taste-responsive and non-responsive regions of the parabrachial nucleus in rat. ⋯ To assess whether the CeA is a source of GABAergic input to the PBN, the CeA of Sst-cre mice was injected with cre-dependent enhanced yellow fluorescent protein (EYFP) virus and PBN tissue processed for GABA and EYFP expression. Again, the majority of EYFP Sst-positive axon terminals in the PBN coexpressed GABA. Together, the present results suggest that CeA neurons marked by Sst expression represent a major extrinsic source of GABAergic input to the PBN and this could underlie the predominate inhibitory effect of CeA stimulation on taste-evoked responses in the PBN.
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Comparative Study
Differences in Taste Perception and Spicy Preference: A Thai-Japanese Cross-cultural Study.
Taste perception is influenced by several factors. However, the relation between taste perception and food culture is unclear. This study compared taste thresholds between populations with different food culture, i.e. ⋯ In addition, 70% of Thai consumed spicy food weekly, whilst 80% of Japanese consumed it monthly. Our findings suggested that population with stronger spicy preference such as Thai had much poorer taste sensitivity and perception than that with milder preference like Japanese. Extensive international survey is needed to conclude the influence of food culture on taste perception.
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This study was conducted to investigate the sensory characteristics and temporal migration of hydroxyl-sanshool compounds at slight and moderate concentrations after dissolution in ethanol-water, saccharose, NaCl, and MSG via 2-AFC, time intensity (TI) and temporal dominance of sensations (TDS) methods. The pungency detection threshold (DT) was suppressed in saccharose while NaCl and MSG solutions showed no effect on pungency DT. The area under the curve (AUC) of pungency increased in NaCl and MSG solutions and decreased significantly in saccharose solution. ⋯ Low levels of pungency compounds were characterized by tingling first in the tongue tip and ending in the lips, while moderate levels of the compound produced tingling, astringency, vibrating, and numbing from the tongue tip to the bilateral sides of the tongue, lips, palate, cheek mucosa, and surface of the tongue over time. There were significant differences in the maximum rate, peak time, and duration of any dominant sensation, as well as in the duration of sensation in the lips, tongue tip, and bilateral sides of the tongue. This study provides a dynamic profile of consuming pungent food, which provides a reference not only for the design of new food products with desirable pungency, but also as a scientific basis for the application of pungent compounds within the food and catering industry.