Olfactory dysfunction in coronavirus disease

Supporting Cells ◽

Receptor Neurons ◽

Olfactory dysfunction may be the only early clinical manifestation in COVID-19 patients with no other significant signs. It is typical of the disease and can be significant for testing. The purpose of the review is to provide guidance to the otorhinolaryngologist in the problem of olfactory dysfunction in SARS-CoV-2 infection. Materials and Methods: The authors analyzed the available clinical data on the problem of olfactory dysfunction in SARS-CoV-2 infection. The data of statistics, clinical symptoms and pathogenesis were studied. Toexplain anosmia in COVID-19 patients, 4 possible mechanisms are considered: nasal congestion / nasal congestion and rhinorrhea; death of olfactory receptor neurons; infiltration of the brain and damage to the olfactorycenters; damage to the supporting cells of the olfactory epithelium. The analysis of clinical cases of patients with prolonged ansomia against the background of COVID-19 was carried out. Conclusions: Smell after COVID-19 in most cases is restored without specific treatment. There are no reports of studies in patients with long-term anosmia.

Comparison of the Nasal Olfactory Organs of Various Species of Lizardfishes (Teleostei: Aulopiformes: Synodontidae) with Additional Remarks on the Brain

International Journal of Zoology ◽

10.1155/2010/807913 ◽

2010 ◽

Vol 2010 ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

L. Fishelson ◽

D. Golani ◽

B. Galil ◽

M. Goren

Keyword(s):

Olfactory Epithelium ◽

Olfactory Receptor ◽

Adult Fish ◽

Supporting Cells ◽

Receptor Neurons ◽

Olfactory Organs ◽

Species Specific ◽

The olfactory organs of lizardfishes (Synodontidae) are situated in two capsules connected to the outside by incurrent and excurrent openings. The olfactory epithelium is in form of petal rosettes each composed of lamellae and a rephe, and bear olfactory receptor neurons, supporting cells and cells with kinocillia. The dimension of rosettes and lamellae, as well as the number of lamellae, increase with growth of the fish; until in adult fish these parameters remaine constant, species specific. In adultSynodusspp. andTrachinocephalus myopsthe rosettes are 3.5–4.0 mm long, with 5–8 lamellae, whereas inSauridaspp. they are 8.0 mm and possess up tp 22 lamellae. The number of ORN ranges from 2,600 on the smaller lamellae to 20,000 on the largest ones. The number of ORN/m of olfactory is ca. 30,000 inSauridaspp. Thus the rosettes ofS. macrolepiswith 20 lamellae possess a total of ca. 170,000 ORN, whereas those ofSy. variegatusandT. myopswith the average of six lamellae possess only ca. 50,000–65,000 ORN. The olfactory nerves lead from the rosettes to the olfactory balbs situated on the olfactory lobes. The differences among the species in olfactory organs are discussed in correlation with their distribution.

Adaptive integrate-and-fire model reproduces the dynamics of olfactory receptor neuron responses in a moth

Journal of The Royal Society Interface ◽

10.1098/rsif.2019.0246 ◽

2019 ◽

Vol 16 (157) ◽

pp. 20190246 ◽

Cited By ~ 1

Author(s):

Marie Levakova ◽

Lubomir Kostal ◽

Christelle Monsempès ◽

Philippe Lucas ◽

Ryota Kobayashi

Keyword(s):

Olfactory Receptor ◽

Time Course ◽

Olfactory Receptor Neuron ◽

Receptor Activation ◽

Response Dynamics ◽

Spike Threshold ◽

Olfactory Stimuli ◽

Receptor Neurons ◽

In order to understand how olfactory stimuli are encoded and processed in the brain, it is important to build a computational model for olfactory receptor neurons (ORNs). Here, we present a simple and reliable mathematical model of a moth ORN generating spikes. The model incorporates a simplified description of the chemical kinetics leading to olfactory receptor activation and action potential generation. We show that an adaptive spike threshold regulated by prior spike history is an effective mechanism for reproducing the typical phasic–tonic time course of ORN responses. Our model reproduces the response dynamics of individual neurons to a fluctuating stimulus that approximates odorant fluctuations in nature. The parameters of the spike threshold are essential for reproducing the response heterogeneity in ORNs. The model provides a valuable tool for efficient simulations of olfactory circuits.

Coordinating Receptor Expression and Wiring Specificity in Olfactory Receptor Neurons

10.1101/594895 ◽

2019 ◽

Cited By ~ 4

Author(s):

Hongjie Li ◽

Tongchao Li ◽

Felix Horns ◽

Jiefu Li ◽

Qijing Xie ◽

...

Keyword(s):

Olfactory Receptor ◽

Olfactory Receptors ◽

Receptor Expression ◽

Unique Combination ◽

Axon Targeting ◽

Transcriptional Regulatory ◽

Receptor Neurons ◽

Transcriptional Regulatory Mechanisms ◽

The ultimate function of a neuron is determined by both its physiology and connectivity, but the transcriptional regulatory mechanisms that coordinate these two features are not well understood1–4. The Drosophila Olfactory receptor neurons (ORNs) provide an excellent system to investigate this question. As in mammals5, each Drosophila ORN class is defined by the expression of a single olfactory receptor or a unique combination thereof, which determines their odor responses, and by the single glomerulus to which their axons target, which determines how sensory signals are represented in the brain6–10. In mammals, the coordination of olfactory receptor expression and wiring specificity is accomplished in part by olfactory receptors themselves regulating ORN wiring specificity11–13. However, Drosophila olfactory receptors do not instruct axon targeting6, 14, raising the question as to how receptor expression and wiring specificity are coordinated. Using single-cell RNA-sequencing and genetic analysis, we identified 33 transcriptomic clusters for fly ORNs. We unambiguously mapped 17 to glomerular classes, demonstrating that transcriptomic clusters correspond well with anatomically and physiologically defined ORN classes. We found that each ORN expresses ~150 transcription factors (TFs), and identified a master TF that regulates both olfactory receptor expression and wiring specificity. A second TF plays distinct roles, regulating only receptor expression in one class and only wiring in another. Thus, fly ORNs utilize diverse transcriptional strategies to coordinate physiology and connectivity.

Cyclic-nucleotide–gated cation current and Ca2+-activated Cl current elicited by odorant in vertebrate olfactory receptor neurons

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1613891113 ◽

2016 ◽

Vol 113 (40) ◽

pp. 11078-11087 ◽

Cited By ~ 14

Author(s):

Rong-Chang Li ◽

Yair Ben-Chaim ◽

King-Wai Yau ◽

Chih-Chun Lin

Keyword(s):

Cyclic Nucleotide ◽

Olfactory Receptor ◽

Signal Amplification ◽

Time Course ◽

Cation Current ◽

Nonselective Cation Channels ◽

Predominant Component ◽

Receptor Neurons ◽

Olfactory transduction in vertebrate olfactory receptor neurons (ORNs) involves primarily a cAMP-signaling cascade that leads to the opening of cyclic-nucleotide–gated (CNG), nonselective cation channels. The consequent Ca2+ influx triggers adaptation but also signal amplification, the latter by opening a Ca2+-activated Cl channel (ANO2) to elicit, unusually, an inward Cl current. Hence the olfactory response has inward CNG and Cl components that are in rapid succession and not easily separable. We report here success in quantitatively separating these two currents with respect to amplitude and time course over a broad range of odorant strengths. Importantly, we found that the Cl current is the predominant component throughout the olfactory dose–response relation, down to the threshold of signaling to the brain. This observation is very surprising given a recent report by others that the olfactory-signal amplification effected by the Ca2+-activated Cl current does not influence the behavioral olfactory threshold in mice.

Ca2+-activated Cl current predominates in threshold response of mouse olfactory receptor neurons

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1803443115 ◽

2018 ◽

Vol 115 (21) ◽

pp. 5570-5575 ◽

Cited By ~ 6

Author(s):

Rong-Chang Li ◽

Chih-Chun Lin ◽

Xiaozhi Ren ◽

Jingjing Sherry Wu ◽

Laurie L. Molday ◽

...

Keyword(s):

Olfactory Receptor ◽

Signal Amplification ◽

Behavioral Threshold ◽

Olfactory Transduction ◽

Threshold Response ◽

Axonal Projections ◽

Cl Channels ◽

Receptor Neurons ◽

In mammalian olfactory transduction, odorants activate a cAMP-mediated signaling pathway that leads to the opening of cyclic nucleotide-gated (CNG), nonselective cation channels and depolarization. The Ca2+ influx through open CNG channels triggers an inward current through Ca2+-activated Cl channels (ANO2), which is expected to produce signal amplification. However, a study on an Ano2−/− mouse line reported no elevation in the behavioral threshold of odorant detection compared with wild type (WT). Subsequent studies by others on the same Ano2−/− line, nonetheless, found subtle defects in olfactory behavior and some abnormal axonal projections from the olfactory receptor neurons (ORNs) to the olfactory bulb. As such, the question regarding signal amplification by the Cl current in WT mouse remains unsettled. Recently, with suction-pipette recording, we have successfully separated in frog ORNs the CNG and Cl currents during olfactory transduction and found the Cl current to predominate in the response down to the threshold of action-potential signaling to the brain. For better comparison with the mouse data by others, we have now carried out similar current-separation experiments on mouse ORNs. We found that the Cl current clearly also predominated in the mouse olfactory response at signaling threshold, accounting for ∼80% of the response. In the absence of the Cl current, we expect the threshold stimulus to increase by approximately sevenfold.

Antagonism in olfactory receptor neurons and its implications for the perception of odor mixtures

eLife ◽

10.7554/elife.34958 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 38

Author(s):

Gautam Reddy ◽

Joseph D Zak ◽

Massimo Vergassola ◽

Venkatesh N Murthy

Keyword(s):

Olfactory Receptor ◽

Natural Environments ◽

Inhibitory Mechanisms ◽

Odor Mixtures ◽

Sensory Pathway ◽

Receptor Neurons ◽

The Brain ◽

Antagonistic Interactions

Natural environments feature mixtures of odorants of diverse quantities, qualities and complexities. Olfactory receptor neurons (ORNs) are the first layer in the sensory pathway and transmit the olfactory signal to higher regions of the brain. Yet, the response of ORNs to mixtures is strongly non-additive, and exhibits antagonistic interactions among odorants. Here, we model the processing of mixtures by mammalian ORNs, focusing on the role of inhibitory mechanisms. We show how antagonism leads to an effective ‘normalization’ of the ensemble ORN response, that is, the distribution of responses of the ORN population induced by any mixture is largely independent of the number of components in the mixture. This property arises from a novel mechanism involving the distinct statistical properties of receptor binding and activation, without any recurrent neuronal circuitry. Normalization allows our encoding model to outperform non-interacting models in odor discrimination tasks, leads to experimentally testable predictions and explains several psychophysical experiments in humans.

Immunopathology of olfactory mucosa following injury to the olfactory bulb

The Journal of Laryngology & Otology ◽

10.1017/s0022215100114483 ◽

1990 ◽

Vol 104 (12) ◽

pp. 959-964 ◽

Cited By ~ 6

Author(s):

Mayumi Inamitsu ◽

Tadashi Nakashima ◽

Takuya Uemura

Keyword(s):

Head Injury ◽

Olfactory Bulb ◽

Olfactory Receptor ◽

Neuron Specific Enolase ◽

Olfactory Dysfunction ◽

Olfactory Mucosa ◽

Marker Protein ◽

Olfactory Marker Protein ◽

Receptor Neurons

AbstractRemoval of the olfactory bulb was performed on rats in an attempt to elucidate the processes of olfactory dysfunction following head injury. Degeneration and regeneration of the olfactory mucosa were examined, histopathologically and immunohistochemically. We used antisera to olfactory marker protein (OMP) and neuron specific enolase (NSE) as a marker of the mature olfactory receptor neurons. Following rapid degeneration after bulbectomy, the olfactory receptor neurons regenerated. OMP and NSE containing cells re-appeared 49 days later. However, the cell population of the neuroepithelium did not revert to the numbers observed in the non-operated neuroepithelium, even three months later. The lack of a connection between regenerated axons and the olfactory bulb may result in immature neuronal replacement and reduce the number of olfactory receptor neurons.

Goggatomy: a Method for Opening Small Cuticular Compartments in Arthropods for Physiological Experiments

10.1101/053298 ◽

2016 ◽

Author(s):

Alan R. Kay ◽

Davide Raccuglia ◽

Jon Scholte ◽

Elena Loukianova ◽

Christopher Barwacz ◽

...

Keyword(s):

Drosophila Melanogaster ◽

Olfactory Receptor ◽

Plasma Membranes ◽

Antennal Segment ◽

Direct Access ◽

Sense Organs ◽

Supporting Cells ◽

The Third ◽

Receptor Neurons

AbstractMost sense organs of arthropods are ensconced in small exoskeletal compartments that hinder direct access to plasma membranes. We have developed a method for exposing live sensory and supporting cells in such structures. The technique uses a viscous light cured resin to embed and support the structure, which is then sliced with a sharp blade. We term the procedure a ‘goggatomy’, from the Khoisan word for a bug, gogga. To demonstrate the utility of the method we show that it can be used to expose the auditory chordotonal organs in the second antennal segment and the olfactory receptor neurons in the third antennal segment of Drosophila melanogaster, preserving the transduction machinery. The procedure can also be used on other small arthropods, like mites, Daphnia, mosquitoes, wasps and ants to expose a variety of cells.