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In post-COVID-19 syndrome, clinical presentation of the nerve fiber dysfunction plays an important role. The possibility of autoantigen cross-mimicry of human coronaviruses and the peripheral nervous system needs to be investigated. The bioinformatic analysis was applied to search for possible common protein sequences located in the immunoreactive epitopes. Among the autoantigens of the human nervous system, fibroblast growth factor receptor protein 3, myelin protein P0, myelin protein P2, sodium channel protein type 9, alpha protein subunit, plexin-D1 protein and ubiquitin-carboxyl-terminal hydrolase protein of the L1 isoenzyme were selected. The original "Alignmentaj" analytical program was created. The UniProt database, Protein Data Bank, and AlphaFold databases were used. The analysis of protein sequence similarities of spike glycoproteins in human coronaviruses revealed common pentapeptides of the MERS-CoV-2 virus with the fibroblast growth factor receptor 3 and myelin protein P2. Among seasonal coronaviruses, common peptide sequences were identified in HCoV-HKU-1 virus with sodium channel protein type 9 subunit alpha and Plexin-D1, HCoV-OC43 with Plexin-D1, as well as HCoV-NL63 with Plexin-D1 and Ubiquitin carboxyl-terminal hydrolase isozyme L1. Some shared peptides belong to immunoreactive epitopes. The most important targets for the molecular similarities are the sodium channel subunits and fibroblast growth factor receptor 3, both for seasonal and highly pathogenic coronaviruses. The data obtained make it possible to identify new potential targets for the development of autoimmune reactions that may occur against the background of the infections with highly pathogenic as well as seasonal coronaviruses., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

SARS-CoV-2 infection may cause such complications as post-COVID-19 syndrome, which includes chronic fatigue, myalgia, arthralgia, as well as a variety of neurological manifestations, e.g., neuropathy of small fibers, hearing and vestibular dysfunction, and cognitive impairment. This clinical case describes a 41-year-old patient suffering from post-COVID-19 syndrome and chronic fatigue syndrome. A detailed examination was performed, including an in-depth study of peripheral and central hearing and vestibular functions, as well as small nerve fibers length and density in the skin and cornea of the eye. Contrary to expectations, no peripheral nervous system dysfunction was detected, despite the presence of dizziness and gait instability in the patient. Hearing tests (gap detection test and dichotic test) showed central auditory processing disorders. The evaluated lesion in the processing of temporal and verbal auditory information can be a significant factor contributing to additional overload of the neural activity and leading to chronic fatigue when performing daily activities in patients with CFS and post-COVID-19 complications.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic disease of unknown etiology, sharing a similar clinical presentation with the increasingly recognized post-COVID syndrome. We performed the first cross-sectional study of ME/CFS in a community population in Russia. Then we described and compared some clinical and pathophysiological characteristics of ME/CFS and post-COVID syndrome as neuroimmune disorders. Of the cohort of 76 individuals who suggested themselves as suffering from ME/CFS, 56 were diagnosed with ME/CFS by clinicians according to ≥1 of the four most commonly used case definitions. Of the cohort of 14 individuals with post-COVID-19 syndrome, 14 met the diagnostic criteria for ME/CFS. The severity of anxiety/depressive symptoms did not correlate with the severity of fatigue either in ME/CFS or in post-COVID ME/CFS. Still, a positive correlation was found between the severity of fatigue and 20 other symptoms of ME/CFS related to the domains of "post-exertional exhaustion", "immune dysfunction", "sleep disturbances", "dysfunction of the autonomic nervous system", "neurological sensory/motor disorders" and "pain syndromes". Immunological abnormalities were identified in 12/12 patients with ME/CFS according to the results of laboratory testing. The prevalence of postural orthostatic tachycardia assessed in the active orthostatic test amounted to 37.5% in ME/CFS and 75.0% in post-COVID ME/CFS (the latter was higher than in healthy controls, p = 0.02). There was a more pronounced increase in heart rate starting from the 6th minute of the test in post-COVID ME/CFS compared with the control group. Assessment of the functional characteristics of microcirculation by laser doppler flowmetry revealed obvious and very similar changes in ME/CFS and post-COVID ME/CFS compared to the healthy controls. The identified laser doppler flowmetry pattern corresponded to the hyperemic form of microcirculation disorders usually observed in acute inflammatory response or in case of systemic vasoconstriction failure.

Fibromyalgia can be defined as a chronic pain condition, affecting the musculoskeletal system, etiology and pathophysiology of which is sufficiently understudied. Despite the fact that many authors consider this entity to be a manifestation of central sensitization, and not an autoimmune disease, the high prevalence of fibromyalgia in patients with post-COVID-19 conditions requires taking a fresh look at the causes of the disease development. During the patient examination, the authors identified a combination of symptoms that occurs so often, that they can be carefully described as a clinical pattern. These manifestations include young age, female gender, joint hypermobility, the onset of pain after COVID-19, physical traumatization of one particular tendon and the development of the fibromyalgia pain syndrome during the next several weeks. As well as an increase in the titer of antinuclear antibodies and some other systemic inflammation factors. It can be assumed with great caution that local damage to the connective tissue in patients with joint hypermobility, having COVID-19 as a trigger factor can lead to the development of fibromyalgia syndrome. This article presents three clinical cases that illustrated this hypothesis.

Introduction: Hyperprolactinemia (HPRL) is known as a side effect of some antidepressants and antipsychotics. These medicines are common in treatment of schizophrenia. Thus, HPRL is often observed in schizophrenic patients. It is also known that HPRL can occur in Hashimoto's thyroiditis due to prolactoliberin effect of thyroliberin. The clinical pathophysiology of the patients with the comorbidity of schizophrenia and Hashimoto's thyroiditis, receiving antipsychotics, is of special interest. It's fair to assume that these patients have higher risks of HPRL. To analyze risks of HPRL with antipsychotic treatment, to identify an association between the antipsychotic therapy (AT) and HPRL in Hashimoto's patients receiving AT, to explore the association of HPRL and other laboratory parameters in patients with Hashimoto's thyroiditis and schizophrenia during AT., Subjects and Methods: We studied 17 patients with HT in comorbidity with schizophrenia receiving AT (mean age 46.5±12.8 years), all euthyroid or with light hypothyroidism. Different laboratory parameters such as anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG) antibodies, blood levels of thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3) and prolactin (PRL) were analysed., Results: The study revealed the high levels of PRL, anti-TPO and anti-TG autoantibodies. Thus, patients were classified into 3 groups by the degree of expected HPRL risk from the antipsychotics used: without expected risk, with low and high expected risks. The correlation analysis detected an inverse significant correlation (R=-0.51; p=0.037) between expected level of drug-associated HPRL risk and actual PRL levels in studied group. At the same time, we detected a positive significant correlation between the levels of PRL and FT4 in the groups (R=0.53; p=0.03). The correlations between the levels of PRL and other parameters such as TSH, FT3, anti-TPO, anti-TG, anti-TSH receptor antibodies were not statistically significant., Conclusions: HPRL in the group was not associated with taking of antipsychotic drugs with high expected HPRL risk. Yet, a significant positive correlation existed between the levels of PRL and FT4. Hence, in Hashimoto's thyroiditis accompanied with treated mental illness there are some non-iatrogenic stimulants of prolactogenesis. It cannot be ruled out that antipsychotics may interfere with prolactin metabolism, which creates a false effect of a positive correlation between prolactin and free thyroxine levels, in contrast to common HPRL of hypothyroidism.

The incidence of autoimmune diseases is increasing. Antinuclear antibody (ANA) testing is a critical tool for their diagnosis. However, ANA prevalence in healthy persons has increased over the last decades, especially among young people. ANA in health occurs in low concentrations, with a prevalence up to 50% in some populations, which demands a cutoff revision. This review deals with the origin and probable physiological or compensatory function of ANA in health, according to the concept of immunological clearance, theory of autoimmune regulation of cell functions, and the concept of functional autoantibodies. Considering ANA titers ≤1:320 as a serological marker of autoimmune diseases seems inappropriate. The role of anti-DFS70/LEDGFp75 autoantibodies is highlighted as a possible anti-risk biomarker for autoimmune rheumatic disorders. ANA prevalence in health is different in various regions due to several underlying causes discussed in the review, all influencing additive combinations according to the concept of the mosaic of autoimmunity. Not only are titers, but also HEp-2 IFA) staining patterns, such as AC-2, important. Accepting autoantibodies as a kind of bioregulator, not only the upper, but also the lower borders of their normal range should be determined; not only their excess, but also a lack of them or "autoimmunodeficiency" could be the reason for disorders.

The absolute sensitivity of vertebrate retinas is set by a background noise, called dark noise, which originates from several different cell types and is generated by different molecular mechanisms. The major share of dark noise is produced by photoreceptors and consists of two components, discrete and continuous. Discrete noise is generated by spontaneous thermal activations of visual pigment. These events are undistinguishable from real single-photon responses (SPRs) and might be considered an equivalent of the signal. Continuous noise is produced by spontaneous fluctuations of the catalytic activity of the cGMP phosphodiesterase. This masks both SPR and spontaneous SPR-like responses. Circadian rhythms affect photoreceptors, among other systems by periodically increasing intracellular cAMP levels ([cAMP] in ), which increases the size and changes the shape of SPRs. Here, we show that forskolin, a tool that increases [cAMP] in , affects the magnitude and frequency spectrum of the continuous and discrete components of dark noise in photoreceptors. By changing both components of rod signaling, the signal and the noise, cAMP is able to increase the photoreceptor signal-to-noise ratio by twofold. We propose that this results in a substantial improvement of signal detection, without compromising noise rejection, at the rod bipolar cell synapse., (© 2017 Astakhova et al.)

The effect of barochamber hypoxia on the local blood flow in the pigeon neostriatum caudalum, hypostriatum accessorium, ectostriatum, cerebellum cortex was studied by means of the hydrogen clearance technique. The hypoxia was shown to decrease the oxygen available in the brain tissue and to increase the blood flow. The changes were different in different brain structures. The spectral analysis of the oxygen available fluctuations revealed no regular changes in the temporal pattern of the fluctuations.