Paleophytogeography of the Siberian Paleofloristic Region in the Early Jurassic and First Half of the Middle Jurassic.

The results of a comparative analysis of taphofloras of the Early Jurassic and first half of the Middle Jurassic of the Siberian paleofloristic region are considered. For this time interval, a significant similarity in the systematic composition of the taphofloras of Western Siberia and Northern China is revealed. Based on the author's data and the published data, the position of the boundary in the south and southwest of the Siberian paleofloristic region and the boundary between its West Siberian and North China provinces are corrected. The refined systematic composition of paleofloras, the constant presence of numerous remains of leaves of deciduous gymnosperms in the sediments, and the sedimentological features of flora-bearing strata taken together convincingly confirm the fact that the climate throughout the entire Siberian region in the Early Jurassic and first half of the Middle Jurassic was humid with seasonal fluctuations in temperature and humidity. The paleogeographic features of the northeast of the Siberian paleofloristic region are briefly considered.

[COVID-19-associated diarrhea].

In addition to the typical clinical picture of respiratory symptoms and intoxication, the SARS-CoV-2 virus is also characterized by a gastroenterotropic effect. Diarrhea is one of the most common gastroenterological symptoms of COVID-19 and is detected, according to the various authors, in 2-49.5% of cases, including children. The presence of diarrhea aggravates the patient's clinical condition, limits the possibility of carrying out the necessary diagnostic manipulations, and complicates the selection of therapy. The article provides an overview of the scientific literature on the formation of diarrheal syndrome in patients with COVID-19. Objective. Analysis of scientific publications studying the pathogenesis, incidence, clinical features, aspects of diagnosis and therapy of diarrhea in patients with COVID-19. Material and methods. A search was made for scientific publications on the electronic resources PubMed, Google Scholar and eLIBRARY.ru. Results. The pathogenesis of diarrhea in a new coronavirus infection is complex and includes, among other things, the effect of the virus on the angiotensin-converting enzyme 2 receptors, inducing an inflammatory process in the gastrointestinal tract mucosa, neurotropic effect on the autonomic regulation of intestinal motor activity, disturbance of the colon microbiota, liver and pancreas damage. Another important pathogenetic aspect of diarrhea in COVID-19 is iatrogenic one, i.e. a side effect of drugs used in the treatment of a new coronavirus infection and its complications, and the activation of opportunistic clostridial intestinal flora against the background of antibiotic therapy. The variety of pathogenetic mechanisms of diarrheal syndrome formation allows us to speak of "COVID-associated diarrhea" as an independent clinical phenomenon characteristic for the new coronavirus infection. Mandatory diagnostic algorithm of a patient with COVID-19 and diarrhea is the fecal analysis test for toxins Cl. difficile, while the possibility of endoscopic examinations during the pandemic is limited. Compliance with the hygiene measures, diet correction and nutritional support, rational antibiotic therapy of COVID-19 complications, careful use of antiperistaltic antidiarrheal drugs, nonspecific therapy (antiviral, rehydration, adsorbents) are considered as the main therapeutic approaches for diarrheal syndrome against the background of COVID-19. The administration of probiotics and antibacterials should be considered in case of confirmed clostridial co-infection. Conclusion. Diarrhea is a frequent clinical manifestation of COVID-19 and can affect the course of the disease. The complex genesis of diarrheal syndrome requires further study of therapeutic strategies and nutritional support for patients after COVID-19.

[DNA-endonucleolysis in cell nuclei of brain and liver in patients dying from hemorrhage and after resuscitation: general patterns and differences]. / DNK-endonukleoliz v kletochnykh iadrakh mozga i pecheni pri urmiranii ot korovopoteri i posle reanimatsii: obshchie zakonomernosti i razlichiia.

Specific features of Ca2+, Mg2+ dependent DNA endonucleolysis in the nuclei of the cerebral cortex, hypothalamus and liver were investigated in mongrel anesthetized male and female dogs. The endonucleolysis was studied in different periods of long-term arterial hypotension and in postresuscitation period, with strain pUC 19 plasmids as substrate for determination of nuclear endonuclease activity. It was established that nuclear DNA-endonucleases coupled with chromatin activated earlier in brain cortical and hepatic neurons than in the hypothalamus. Changes in activity of the enzymes directly correlated with duration of CNS ischemia. Active endonucleolysis occurred in cerebral and hepatic nuclei even 3 months after the blood loss and resuscitation. Postresuscitation changes in Ca2+ and Mg2+ dependent endonucleases in cortical nuclei are phasic while in the liver their activity for three months did not differ much from that in the end of hypotension. The activity of nuclear endonucleases in the hypothalamus returned to normal after beginning of resuscitation and did not change later. The data obtained evidence for active involvement of apoptosis mechanisms in brain and liver cell degeneration in massive blood loss and in postresuscitation period including a late one.

[Effect of verapamil on the activity of Ca2+-, Mg2+-dependent endonucleases in hypothalamic cell nuclei in long-term hypovolemic shock]. / Vliianie verapamila na aktivnost' Ca2+-, Mg+-zavisimykh éndonukleas v kletochnykh iadrakh gipotalamusa pri dlitel'nom gipovolemicheskom shoke.

Experiments on anesthetized non-inbred 8-17 kg b.w.dogs have demonstrated that cerebral ischemia consequent to 4-hour hypovolemic shock activates Ca(2+)-, Mg(2+)-dependent endonucleases in cell nuclei of the hypothalamus. Intravenous injection of calcium channels blocker verapamil (Orion) in a dose 0.1 mg/kg 30 min before blood loss prevents activation of the above endonucleases and makes it possible to avoid internucleosome fragmentation of genome DNA.

[The neurochemical, molecular and ultrastructural mechanisms of the formation of latent postresuscitation encephalopathy]. / Neirokhimicheskie, molekuliarnye i ul'trastrukturnye mekhanizmy formirovaniia skrytoi postreanimatsionnoi éntsefalopatii.

The content of total RNA and DNA, activity of Ca2+, Mg(2+)-dependent DNA endonuclease, and ultrastructural changes in nerve tissue cells were examined in the brain cortex of narcotized dogs 1 to 3 months after a 4-hour hemorrhagic shock (arterial pressure 40 mm Hg). A new variant of reconstruction of cell membranes and organelles formed by them was revealed, developing in the brain neurons in the course of adaptation during the first-third months of the postshock period. Evidently, the molecular base of development of an atypical variant of cell structure rearrangement in the remote period after shock is the internucleosomal fragmentation of a part of the DNA of nerve cells resultant from DNA endonucleolysis and subsequent information disintegration of a cell as a system. This distorts the process of biosynthesis of supramolecular ensembles, specifically, of nerve cell biomembranes.

[Significance of DNA endonucleases in the pathogenesis of ischemic lesion of the brain during massive hemorrhage]. / Znachenie DNK-éndonukleoliza v patogeneze ishemicheskogo porazheniia mozga pri massivnoi krovopotere.

Experiments on dogs exposed to hemorrhagic shock demonstrated a direct relationship between the duration of arterial hypertension and activities of Ca(2+)-Mg(2+)-dependent DNA-endonucleases in the cellular nuclei of the cerebral cortex. Appreciable differences in the kinetics of accumulation of acid-soluble products of DNA chromatin in the cellular nuclei of the cerebral cortex were detected: chromatin DNA degradation was the most rapid in the nervous tissue of dogs exposed to 6 h hemorrhagic shock. Verapamil, a Ca blocker, injected to animals 30 min before massive hemorrhage in a dose of 0.1 mg/kg, reliably reduced the activities of Ca(2+)--Mg(2+)-dependent endonucleases of the cellular nuclei of the cerebral cortex by the 4th h of hemorrhagic shock. The detected physicochemical changes in the chromatin DNA of the cerebral cortex cellular nuclei and a progressive increase of activities of Ca(2+)--Mg(2+)-dependent endonucleases during a prolonged hemorrhagic shock are by their nature close to the phenomenon of genomic programmed cellular death.

[Molecular and cellular mechanisms of ischemic damage of the brain in hemorrhagic shock]. / Molekuliarnye i kletochnye mekhanizmy ishemicheskogo povrezhdeniia mozga pri gemorragicheskom shoke.

General lightening of caryoplasma, the appearance of destructive areas in which electron-optic density was undetectable, ruptures in chromatin chains, changes in the nature of structural organization of euchromatic areas at the expense of density redistribution have been found in the nuclei of brain cortex oligodendrogliocytes and astrocytes by electron microscopy of caryoplasma of the nuclei from light neurons during experiments on anesthetized adult mongrel dogs weighing 9 to 26 kg recovered after a 4-hour hemorrhagic shock (BP 40 mm Hg). The nuclei of dark neurons and oligodendrogliocytes had matrix structure similar to control. The nuclei of astrocytes had marked matrix lightening with the formation of large zones in which electron-optic density was undetectable. It is evident that the degree of chromatin destruction in different neurons was not identical in hemorrhagic shock and depended on the functional neuronal activity. It has been established that there is a significant increase in the activity of nuclear Ca2+, Mg(2+)-depended endonucleases associated with chromatin and irreversibly cleaving ds- and ss-chromatin DNA chains. We believe that an increase in Ca2+, Mg(2+)-depended DNA-endonuclease activity should be considered an important pathogenetic factor in destructive processes that take place in the nuclei of brain cortex neurons in severe hemorrhagic shock.

Effect of hemorrhagic shock duration on the activity of nuclear Ca2+/Mg(2+)-dependent DNA-endonucleases in canine cerebral cortex.

A direct correlation between the duration of arterial hypotension (40 mmHg) and the activity value of nuclear Ca2+/Mg(2+)-dependent DNA-endonucleases was revealed in dogs exposed to hemorrhagic shock. Thus, an increase in the activity of endonucleases was significant after 2 h of arterial hypotension. During that period there activity amounted to 4149 +/- 295 units/mg of protein instead of 2839 +/- 231 units/mg protein in the control (P < 0.01). With the prolonged hemorrhagic shock, the activity of DNA-endonucleases continued to increase. By 4 h of hemorrhagic shock it reached 5021 +/- 443 units/mg protein and by 6 h, 8661 +/- 338 units/mg protein which was three times the control values (P < 0.01). An electron-microscopic study of the structure of neuron nuclei karioplasm showed that by 2-4 h of hemorrhagic shock some neurons showed reduced chromatin content, and the nuclear matrix had clarified with the formation of electron-translucent empty zones. We think that the sharp increase in the nuclear endonuclease activity and the subsequent endonucleolysis can be regarded as a pathogenetic factor in the destructive processes taking place in the nuclei of cortex neurons during prolonged periods of hemorrhagic shock.