Post-COVID-19 condition is not only a question of persistent symptoms: structured screening including health-related quality of life reveals two separate clusters of post-COVID.

PURPOSE: Some patients experience long-term sequelae after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, despite a present post-COVID condition, defined as "any symptom lasting longer than 12 weeks," only a subset of patients search for medical help and therapy. METHOD: We invited all adults with a positive real-time polymerase chain reaction (RT-PCR) for SARS-CoV-2 between March 2020 and September 2021 (n = 4091) in the city of Jena to answer a standardized questionnaire including demographic information, the course of the acute infection and current health status. K-means-clustering of quality of life (QoL) was used to explore post-COVID subgroups. RESULTS: A total of 909 participants at a median interval of 367 (IQR 291/403) days after acute infection were included in the analysis. Of those, 643 (70.7%) complained of having experienced persistent symptoms at the time of the survey. Cluster analysis based on QoL revealed two subgroups of people with persistent post-COVID symptoms. Whereas 189/643 participants (29.4%) showed markedly diminished QoL, normal QoL was detected in 454/643 individuals (70.6%). CONCLUSION: Despite persistent symptoms being reported by nearly three quarters of participants, only one-third of these described a significant reduction in QoL (cluster 1), whereas the other two-thirds reported a near-normal QoL (cluster 2), thus indicating a differentiation between "post-COVID disease" and "post-COVID condition". The prevalence of clinically relevant post-COVID disease was at least 20.7%. Health policies should focus on this subset.

Evidence for accessory chemosensory cells in the adult human nasal cavity.

The existence of functionally relevant accessory olfactory organs in humans is still a matter of controversy. A vomeronasal organ (VNO) with sensory and non-sensory epithelia exists only in macrosmatic mammals. A similar structure is regularly observed in humans during fetal development. The postnatal persistence of a VNO like epithelial duct has been described in about 10 %. Here we studied tissue samples of nasal mucosa from adults. In all individuals we found epithelial cells in the lower part of the nasal septum which exhibited morphological features of sensory neurons and which showed immunostaining for olfactory marker protein OMP. These cells were interposed by ciliated cells, goblet cells and small intraepithelial capillaries. Only occasionally we found such cells within a morphologically defined epithelial duct. A clear separation of sensory and non-sensory epithelia could not be observed. In most cases we found OMP positive groups of cells either in epithelial cavities or just embedded in respiratory epithelium. With RT-PCR we could confirm the presence of OMP encoding mRNA thus supporting the idea of intrinsic expression of this protein in the nasal mucosa. We conclude that accessory chemosensory structures are regularly conserved in adult humans in the approximate anatomical location of the VNO of microsmatic animals. Their functional importance is yet to be determined.

Steroidal pheromones and their potential target sites in the vomeronasal organ.

Steroids are important olfactory signals in most mammalian species. The vomeronasal organ has been suspected to be the primary target of pheromones. In rat vomeronasal sensory neurons express steroid binding proteins and nuclear receptors. Some binding globulins were found also in single ciliated cells of the non-sensory vomeronasal epithelium. Immunoelectron microscopy revealed VDR in olfactory microvilli and DPB in apical membrane protrusions of supporting sells within the sensory epithelium. Pilot behavioral studies with dogs showed increased sniffing duration upon exposure to low concentrations of vitamin D while higher concentrations were less effective. It has been shown that vitamin D has pheromone-like properties in lizards. Our histochemical and behavioral observations indicate that the mammalian vomeronasal organ may be a vitamin D target. Olfactory functions of vitamin D involve most likely rapid membrane mediated effects rather than actions through nuclear receptors.

Estrogen receptors and sex hormone binding globulin in neuronal cells and tissue.

Estrogens exert a critical influence on neuronal tissues and cells. As demonstrated in many clinical studies, estrogens are neuroprotective to the extent that they improve prognosis for women with neurodegenerative diseases. Unfortunately, we still do not know exactly how these effects are mediated. Fifty years ago the first estrogen receptor was found, but since then many other new pathways of estrogen action have been identified. This review describes several of these pathways of estrogen effects and provides some conclusions and correlations about these as determined by recent studies with nerve growth factor differentiated rat pheochromocytoma cell line.