The novel coronavirus variant - severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) and the disease it causes clinically (novel coronavirus disease 2019 or COVID-19) have placed medical science into a frenzy due to the significant morbidity and mortality, as well as the myriad of clinical complications developing as a direct result of infection. The most notable and one of the most severe changes in COVID-19 develops in the lungs. All cases of real-time polymerase chain reaction (rtPCR)-proved COVID-19 subjected to autopsy were withdrawn from the central histopathology archive of a single tertiary medical institution - St. Marina University Hospital - Varna, Varna, Bulgaria. Pulmonary gross and histopathology changes observed on light microscopy with hematoxylin and eosin as well with other histochemical and immunohistochemical stains were compared with the time from patient-reported symptom onset to expiration, to compare the extent and type of changes based on disease duration. A total of 27 autopsy cases fit the established criteria. All cases clinically manifested with severe COVID-19. From the selected 27 cases, n=14 were male and n=13 were female. The mean age in the cohort was 67.44 years (range 18-91 years), with the mean age for males being 68.29 (range 38-80 years) and the mean age for females being 66.54 (range 18-91 years). Gross changes in patients who expired in the first 10 days after disease onset showed a significantly increased mean weight - 1050g, compared to a relatively lower weight in patients expiring more than 10 days after symptom onset - 940g. Histopathology changes were identified as intermittent (developing independent from symptom onset and persisting) - diffuse alveolar damage with hyaline membranes - acute respiratory distress syndrome, endothelitis with vascular degeneration and fibrin thrombi; early (developing within the first week, but persisting) - type II pneumocyte hyperplasia, alveolar cell multinucleation and scant interstitial mononuclear inflammation; intermediate (developing within the late first and second weeks) - Clara cell hyperplasia and late (developing after the second week of symptom onset) - respiratory tract and alveolar squamous cell metaplasia and fibrosis. COVID-19-associated pulmonary pathology, both gross and histopathology, show a time-related dynamic with persistent early and a myriad of later developing dynamic changes in patients with severe disease. These changes underline both the severity of the condition, as well as the mechanisms and the probability of long-lasting severe complications in patients with post-COVID syndrome.

Melatonin, a basic secretory pineal gland product, is a nontoxic, multifunctional molecule. It has antioxidant and anti-apoptotic activities and protects tissues from injury. The objective of the present study was to determine the molecular mechanism of melatonin anti-apoptotic effect on gastric injury in a rat burn model. We hypothesized that melatonin gastric protection may be related to the activation of transcription erythroid 2-related factor 2 (Nrf2). Using a 30% total body surface area (TBSA) rat burn model, melatonin (10 mg/kg, i.p.) was injected immediately and 12 h after thermal skin injury. Via light immunohistochemistry, we determined the tissue level of 4-hydroxy-2-nonenal (4-HNE) as a marker of lipid peroxidation, Bcl-2 and Bax as apoptosis-related proteins, and Nrf2. Results are presented as medians (interquartile range (IQR)). Thermal trauma in burned animals, compared with the controls, increased the expression of pro-apoptotic Bax protein (1.37 (0.94–1.47)), decreased anti-apoptotic Bcl-2 protein (1.16 (1.06–1.23), p < 0.001) in epithelial cells, and elevated Bax/Bcl-2 ratios (p < 0.05). Tissue 4-HNE and Nrf2 levels were increased following severe burns (1.55 (0.98–1.61) and 1.16 (1.01–1.25), p < 0.05, respectively). Melatonin significantly decreased 4-HNE (0.87 (0.74–0.96), p < 0.01) and upregulated Nrf2 (1.55 (1.52–1.65), p < 0.001) levels. It also augmented Bax (1.68 (1.5–1.8), p < 0.001) and Bcl-2 expressions (1.96 (1.89–2.01), p < 0.0001), but reduced Bax/Bcl-2 ratios (p < 0.05). Our results suggest that experimental thermal trauma induces oxidative gastric mucosal injury. Melatonin manifests a gastroprotective effect through Nrf2 activation, lipid peroxidation attenuation, and Bax/Bcl-2 ratio modification as well.

The solid pseudopapillary tumor (SPT) is a rare pancreatic lesion that usually affects young and middle-aged patients and has a female predominance and low malignant potential. The exact histogenesis of this tumor is still unclear. We present the case of a 60-year-old female patient with occasional abdominal pain. Positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) revealed a tumor mass in the pancreatic tail. Distal pancreatectomy and splenectomy were performed. The result from the pathology report was solid pseudopapillary neoplasm (SPN). The patient underwent four cycles of adjuvant chemotherapy with gemcitabine, which she tolerated well without complaints. A control computed tomography (CT) scan and PET/CT of the abdomen (five months after the operation) showed a cystic lesion suspicious for local recurrence in the pancreatic tail during the follow-up period. The patient underwent a second surgery operation. Subsequent histological examination showed chronic indurative pancreatitis, areas with steatonecrosis, lipogranulomas, and fibrosis without evidence of relapse. SPT is a rare pancreatic tumor that most commonly affects young women. Although the tumor has locally aggressive characteristics, the prognosis is excellent after surgical excision. Our case emphasizes that this tumor can occur not only in young women but also in older patients. Chronic granulomatous inflammation and indurative pancreatitis can sometimes mimic a relapse on CT and PET/CT image tests.

Metabolic syndrome is a disorder of energy metabolism characterized by persistently high prevalence and significant medical and economic burden on society. An effective animal model that closely replicates the key features of the syndrome in humans is essential for evaluating therapeutic strategies aimed at improving health outcomes. High-calorie diet-induced animal models of metabolic syndrome are preferred by many research groups for studying its pathogenesis, prevention and therapy. However, there are numerous variations in the types and proportions of carbohydrates and/or fats in the diets used. In 2015, our research team developed a diet-induced model of metabolic syndrome in young adult male Wistar rats that was based on adding 17% animal fat and 17% fructose to the standard rat chow and 10% fructose to the drinking water. This model reliably induced the morphometric and biochemical alterations that represent the core diagnostic features of the syndrome in humans. Since its initial introduction, we have utilized the high-fat high-fructose diet-induced model of metabolic syndrome/obesity in ten experimental studies. The current paper provides a protocol for applying the model, presents its repeatability and discusses the variability in the morphometric, biochemical, histopathological, immunohistochemical, and behavioral data of 10 experimental studies on Wistar rats.

Paraganglioma is a tumour lesion of neuroectodermal origin that occurs at various places in the human body, but is rarely observed in the spinal cord. Usually, it presents in the lumbar region (cauda equine and filum terminal) as a slow-growing painless tumour mass that causes local compression.We present a 53-year-old man with chronic low back pain, difficulty in walking, and impotence. The magnetic resonance study showed a tumour lesion suspicious for ependymoma. Surgical excision was performed and the result from the intraoperative frozen section was also ependymoma due to the presence of pseudorosettes structures. After the surgery, a thorough histological examination of the specimen revealed an encapsulated formation composed of ovoid and spindle-shaped cells with eosinophilic to light cytoplasm, with rounded nuclei with finely dispersed chromatin. An arrangement of cells in the form of pseudorosettes – ependymoma-like features was found in a large area of the tumour. Immunohistochemically, it was proved that the tumour was paraganglioma, not ependymoma.Paraganglioma is a rare tumour in the spinal cord and it should be distinguished from other tumours normally observed in this area like ependymomas by using immunohistochemical stains.

Background/Objective: Metabolic dysfunction-associated fatty liver disease (MAFLD) is defined by the presence of hepatic steatosis, and is associated with obesity, diabetes, and other metabolic alterations. Feeding rats with a high-fat high-fructose (HFHF) diet is a reproducible experimental model of obesity/metabolic syndrome and the related MAFLD. Aronia melanocarpa, Rosa canina, and Alchemilla vulgaris are polyphenol-rich plants with proven health benefits. The aim of this study was to reveal the effects of four Aronia melanocarpa-based fruit juices (AMBFJs) in HFHF-fed rats. Methods: The AMBFJs were AM20 and AM60 (produced from aronia berries at 20 °C and 60 °C, respectively), AMRC (aronia juice with Rosa canina), and AMAV (aronia juice with Alchemilla vulgaris). Male Wistar rats were allocated to 6 groups. Except for the Control, the rest of the groups were fed an HFHF diet for 60 days. Throughout the experiment, each of the AMBFJs was administered to one HFHF-fed group. Results: HFHF-fed rats had an increased calorie intake on the background of increased liquid and decreased food consumption. At the end of the experiment, they had similar body weights, slightly increased fat indices, increased levels of blood lipids and liver enzymes, as well as typical histopathological changes in liver and adipose tissue. AMBFJs-treated animals showed improvement in most of these parameters, especially in triglyceride levels, liver enzymes, and the histopathological changes in the liver and fat. AMAV, the juice with the highest polyphenolic content, had the highest effect on adiposity. Conclusion: In HFHF-fed rats, AMBFJs exerted beneficial effects on MAFLD probably due to their polyphenolic ingredients.