Mucormycosis is a disease caused by fungi of the Mucorales family, widespread in the environment, with pronounced angiotropism and the ability to angioinvasion, leading to thrombosis with surrounding necrosis. The main triggers for the development of mucormycosis are: immunodeficiency states, use of glucocorticosteroid drugs, decompensation of diabetes mellitus, concomitant diseases, age > 65 years. We present a clinical case of rhinocerebral mucormycosis in a 79-year-old patient against the background of uncontrolled type 2 diabetes mellitus with ketoacidosis, a condition after previous glucocorticosteroid therapy for COVID-19 (according to the severity of the disease). After suffering a new coronavirus infection caused by the SARS-CoV-2 virus, she was admitted to the hospital with complaints characteristic of mucormycosis. On the 5th day of hospital stay, the patient's condition worsened significantly, despite the correction of the therapy, and on the 12th day the patient died. According to the results of the autopsy, it was established that the rhinocerebral mucormycosis was complicated by thrombosis of the anterior and posterior left cerebral arteries with subsequent infarctions in the frontal lobe and parieto-occipital region of the brain left hemisphere, cerebral edema, which was the immediate cause of death.

The problem of fungal infections in the era of COVID-19 has acquired special significance. This infection, directly or indirectly, through the use of glucocorticoids and antibiotics in its treatment, as well as poorer self-management of chronic diseases, has led to a wide spread of risk factors for fungal diseases among people who have had a novel coronavirus infection. The article presents two cases of COVID-19-associated mycosis, more related to mucormycosis, which were diagnosed by ophthalmologists in the Volgograd region. In the first case, the severe course of rhino-orbito-cerebral form of mucormycosis required a number of surgical interventions and prolonged treatment in the intensive care unit. In the second case, the patient asked for help without signs of aggravation of the general condition, but with irreversible local manifestations. In both cases, the eyeball was removed. Morphological examination revealed aseptal ribbon hyphae of different diameters, branching mainly at right angles, more typical for fungi of the Mucorales family. Due to the severe consequences of the disease, clinicians, including ophthalmologists, need to be especially alertness in patients with the described symptoms and risk factors in the post-COVID period.

Structural changes in hippocampal fields CA1 and CA3 of the ventral part of the hippocampus were studied in 12- and 24-month-old rats (n = 20). Paraffin sections of brains were stained by the Nissl method and the proportion of shrunken neurons with cytoplasmic hyperchromatosis was determined, along with changes in the expression levels of inducible and endothelial NO synthase (iNOS, eNOS). Older rats (24 months) showed more severe signs of neuron damage in the pyramidal layer of hippocampal field CA3. An increase in the proportion of shrunken neurons with cytoplasmic hyperchromatosis was seen, with a decrease in the relative density of neurons, accompanied by pericellular edema, and cytoplasmic vacuolization. An increase in iNOS expression in neurons in the pyramidal layer of field CA3 occurred, with decreases in eNOS expression in fields CA1 and CA3 both in neurons and in vascular endotheliocytes of the microcirculatory bed, as compared with levels in 12-month-old animals.

The retinas of white male laboratory rats of two age groups (12 and 24 months; 10 animals in each group) subjected to chronic combined stress were studied. Animals were subjected to stress by simultaneous exposure to pulsatile light, loud noise, shaking, and movement restriction for 30 min/day for seven days. Controls consisted of retinas from intact rats of the same age (n = 20). Enucleated eyes from stressed and control animals were processed by standard histological methods; sections were stained by the Nissl method and with hematoxylin and eosin. Retinas from stressed animals of both age groups were characterized by decreases in the numbers of cells and deranged ordering of cell layers, most marked in the photoreceptor neuron and ganglion cell layers. Morphometric analysis demonstrated decreases in layer thicknesses and the numerical densities of cells in the retinas of stressed animals, both young (12 months) and old (24 months), as compared with control animals.

Structural changes in the ventral segment of the hippocampus and the characteristics of the expression of serine racemase were studied in rats aged 12 and 24 months exposed to combined stress. Four groups of 10 animals were formed: group 1 were control rats aged 12 months; group 2 were control rats aged 24 months; group 3 were 12-month rats subjected to 30-min stress daily for seven days; group 4 were 24-month rats subjected to stress. Stress was applied in a special apparatus consisting of six isolated sectors of identical volume and allowing the combination of different types of stress to be applied (pulsing light, loud noise, vibration). The ventral segment of the hippocampus of experimental animals showed an increase in the specific number of shrunken hyperchromic neurons in field CA3 and decreases in neuron density, accompanied by pericellular edema, cytoplasmic vacuolization, and decreased serine racemase expression in the neuropil of the radial layer of fields CA1 and CA3. Stressed animals showed changes in neurons in the pyramidal layer of field CA3, which were combined with a decrease in the level of expression of serine racemase in dendrites in the radial layer of fields CA1 and CA3, which is taken as a sign of impairment to NMDA receptor-mediated transmission of nerve spikes in the hippocampus.