In various diseases, there is an increased production of the free radicals needed to carry out certain physiological processes but their excessive amounts can cause oxidative stress and cell damage. Enzymes play a major role in the transformations associated with free radicals. One of them is nitric oxide synthase (NOS), which catalyzes the formation of nitric oxide (NO). This enzyme exists in three forms (NOS1, NOS2, NOS3), each encoded by a different gene. The following work presents the most important information on the NOS isoforms and their role in the human body, including NO synthesis in various tissues and cells, intercellular signaling and activities supporting the immune system and regulating blood vessel functions. The role of NOS in pathological conditions such as obesity, diabetes and heart disease is considered. Attention is also paid to the influence of the polymorphisms of these genes, encoding particular isoforms, on the development of these pathologies and the role of NOS inhibitors in the treatment of patients.

The ongoing COVID-19 pandemic has significantly limited social contacts, thus contributing to deepening isolation. Therefore, SARS-CoV-2 exerted on humanity not only a physical impact but also a psychological one, often increasing the feeling of stress. The long-term effects of such a state could include the management of depression, so our study aimed to analyze groups of medical students in different periods of the pandemic (at the beginning of the pandemic, after half a year of the pandemic, after one year of the pandemic) in order to assess the impact of this situation on coping with stress. The impact of the pandemic on the development of stress factors such as alcohol consumption and smoking was also studied. The level of physical activity in the context of coping with an uncertain situation was also assessed. The impact of the above-mentioned factors on the behavior of students, including the Mini-COPE questionnaire, AUDIT test, the Fagerström test and the IPAQ questionnaire was analyzed. It has been shown that as the pandemic and the lockdown progressed, patients consumed more often or larger amounts of alcohol, smoked more cigarettes, and levels of physical activity decreased. All these factors may have had some impact on the deterioration of coping with stress among the respondents, which would indicate that the COVID-19 pandemic significantly contributed to an increase in the sense of stress among the students.

Kidney transplantation (KTx) is the best treatment method for end-stage kidney disease. KTx improves the patient’s quality of life and prolongs their survival time; however, not all patients benefit fully from the transplantation procedure. For some patients, a problem is the premature loss of graft function due to immunological or non-immunological factors. Circulating cell-free DNA (cfDNA) is degraded deoxyribonucleic acid fragments that are released into the blood and other body fluids. Donor-derived cell-free DNA (dd-cfDNA) is cfDNA that is exogenous to the patient and comes from a transplanted organ. As opposed to an invasive biopsy, dd-cfDNA can be detected by a non-invasive analysis of a sample. The increase in dd-cfDNA concentration occurs even before the creatinine level starts rising, which may enable early diagnosis of transplant injury and adequate treatment to avoid premature graft loss. In this paper, we summarise the latest promising results related to cfDNA in transplant patients.