Dopamine is the most abundant catecholamine in the vertebrate retina. Despite the description of retinal dopaminergic cells three decades ago, many aspects of their function in the retina remain ...unclear. There is no consensus among the authors about the stimulus conditions for dopamine release (darkness, steady or flickering light) as well as about its action upon the various types of retinal cells. Many contradictory results exist concerning the dopamine effect on the gross electrical activity of the retina reflected in electroretinogram (ERG) and the receptors involved in its action. This review summarized current knowledge about the types of the dopaminergic neurons and receptors in the retina as well as the effects of dopamine receptor agonists and antagonists on the light responses of photoreceptors, horizontal and bipolar cells in both nonmammalian and mammalian retina. Special focus of interest concerns their effects upon the diffuse ERG as a useful tool for assessment of the overall function of the distal retina. An attempt is made to reveal some differences between the dopamine actions upon the activity of the ON versus OFF channel in the distal retina. The author has included her own results demonstrating such differences.
COVID-19 and Oxidative Stress Chernyak, B. V.; Popova, E. N.; Prikhodko, A. S. ...
Biochemistry,
12/2020, Letnik:
85, Številka:
12-13
Journal Article
Recenzirano
Odprti dostop
Pathogenesis of the novel coronavirus infection COVID-19 is the subject of active research around the world. COVID-19 caused by the SARS-CoV-2 is a complex disease in which interaction of the virus ...with target cells, action of the immune system and the body’s systemic response to these events are closely intertwined. Many respiratory viral infections, including COVID-19, cause death of the infected cells, activation of innate immune response, and secretion of inflammatory cytokines. All these processes are associated with the development of oxidative stress, which makes an important contribution to pathogenesis of the viral infections. This review analyzes information on the oxidative stress associated with the infections caused by SARS-CoV-2 and other respiratory viruses. The review also focuses on involvement of the vascular endothelium in the COVID-19 pathogenesis.
Ice-edge blooms are significant features of Arctic primary production, yet have received relatively little attention. Here we combine satellite ocean colour and sea-ice data in a pan-Arctic study. ...Ice-edge blooms occur in all seasonally ice-covered areas and from spring to late summer, being observed in 77–89% of locations for which adequate data exist, and usually peaking within 20 days of ice retreat. They sometimes form long belts along the ice-edge (greater than 100 km), although smaller structures were also found. The bloom peak is on average more than 1 mg m−3, with major blooms more than 10 mg m−3, and is usually located close to the ice-edge, though not always. Some propagate behind the receding ice-edge over hundreds of kilometres and over several months, while others remain stationary. The strong connection between ice retreat and productivity suggests that the ongoing changes in Arctic sea-ice may have a significant impact on higher trophic levels and local fish stocks.
There are a number of environmental problems in the construction and disposal of solid waste landfills. One of the most important is the negative impact on the environment. The article includes the ...research findings related to content and accumulation of heavy metals such as zinc, lead, chrome and nickel in soil and plants on the territory adjacent to Shapsha Municipal Solid Waste Landfill, Shapsha settlement, Khanty-Mansiysk area, Khanty-Mansiysk Autonomous Okrug (Yugra), which is 28 km from Khanty-Mansiysk (Tyumen region, Russia). Intensity of heavy metal biological absorption was evaluated. The analysis of obtained results allowed to determine and roughly divide selected plants into two groups by their capability to accumulate heavy metals: accumulators (hyperaccumulators) that accumulate heavy metals both in case of their low and high soil content (Tussilago farfara L., Plantago major L.) and excluders that have limited input of metals to offshoots despite their high concentration in the environment (Tifolium hybridum L., Chamerion angustifolium L.). Identification of new plants prone to hyperaccumulation of heavy metals is important for efficient soil phytoremediation.
The structure and species composition of communities of 9 areas within the city of Tobolsk (Tyumen region, Russia) and its surroundings were studied. The method used to assess the quality of the ...environment consisted in determination of the fluctuating asymmetry index of the Betula pendula Roth lamina. For spatial characterization of the state of the test object and assessment of the anthropogenic load, a bioindication map was drawn up using isolines. The environmental heterogeneity of environmental conditions and the degree of deviation from the environmental optimum were revealed. During the examination of groups of individuals, insignificant fluctuations in the nature of environmental conditions from conditionally normal (I point) to critical (V points) were noted. Such fluctuations are explained by the uneven distribution of pollution sources between the compared territories. It was established that under conditions optimal for a species, the smallest level of deviations from the norm is observed, and that the territory under study is heterogeneous in terms of the fluctuating asymmetry index.
The article reflects the results of a comparative analysis of the content and accumulation of heavy metals such as chromium, lead, nickel, zinc in the thalli of Cladonia rangiferina L. in the ...anthropogenic phytocenoses of the West Siberian Subarctic, Russia. The next series of accumulations of heavy metals in descending their concentrations in soils is Zn> Pb> Cr> Ni. Analysis of the results showed that among the factors affecting the accumulation of elements, the most significant wa the distance from the highway. The content of most elements is significantly (p <0.05) related. Cladonia rangiferina L. accumulates heavy metals depending on the location of the sampling point relative to the source of pollution. The coefficient of biological absorption, as well as the biogeochemical activity of the species, varies in different areas but has the greatest value in areas close to the source of anthropogenic load.
Ganglion cells are the output retinal neurons that convey visual information to the brain. There are ~20 different types of ganglion cells, each encoding a specific aspect of the visual scene as ...spatial and temporal contrast, orientation, direction of movement, presence of looming stimuli; etc. Ganglion cell functioning depends on the intrinsic properties of ganglion cell’s membrane as well as on the excitatory and inhibitory inputs that these cells receive from other retinal neurons. GABA is one of the most abundant inhibitory neurotransmitters in the retina. How it modulates the activity of different types of ganglion cells and what is its significance in extracting the basic features from visual scene are questions with fundamental importance in visual neuroscience. The present review summarizes current data concerning the types of membrane receptors that mediate GABA action in proximal retina; the effects of GABA and its antagonists on the ganglion cell light-evoked postsynaptic potentials and spike discharges; the action of GABAergic agents on centre-surround organization of the receptive fields and feature related ganglion cell activity. Special emphasis is put on the GABA action regarding the ON–OFF and sustained–transient ganglion cell dichotomy in both nonmammalian and mammalian retina.
The rapid Arctic summer sea ice reduction in the last decade has lead to debates in the maritime industries on the possibility of an increase in cargo transportation in the region. Average sailing ...times on the North Sea Route along the Siberian Coast have fallen from 20 days in the 1990s to 11 days in 2012–2013, attributed to easing sea ice conditions along the Siberian coast. However, the economic risk of exploiting the Arctic shipping routes is substantial. Here a detailed high-resolution projection of ocean and sea ice to the end of the 21st century forced with the RCP8.5 IPCC emission scenario is used to examine navigability of the Arctic sea routes. In summer, opening of large areas of the Arctic Ocean previously covered by pack ice to the wind and surface waves leads to Arctic pack ice cover evolving into the Marginal Ice Zone. The emerging state of the Arctic Ocean features more fragmented thinner sea ice, stronger winds, ocean currents and waves. By the mid 21st century, summer season sailing times along the route via the North Pole are estimated to be 13–17 days, which could make this route as fast as the North Sea Route.
•A high-resolution projection for the Arctic Ocean in the 21st century is examined.•Future navigability of the Arctic sea routes and sailing times are assessed.•Increased wind and waves transform pack ice into fragmented Marginal Ice Zone.•Arctic transit shipping saves time and fuel but may add to Arctic warming.•Forecasting requirements for the new emerging state of the Arctic are discussed.
This study presents a framework to simulate dynamic recrystallization (DRX) in hexagonal closed packed (HCP) metals and alloys using crystal plasticity based finite element model (CPFEM) coupled with ...a probabilistic cellular automata (CA) approach, as applied to Mg alloys. The CPFEM takes as input the microstructural information from experimental measurements and computes local dislocation density evolution corresponding to active deformation modes. DRX proceeds via nucleation of new grains and their subsequent growth. A new nucleation criterion based on local mismatch in dislocation density is implemented in the model. Nucleation sites are defined solely from the local inhomogeneouty of dislocation density within a grain or across grain boundaries. Cellular automata model with probabilistic state switching rule predicts the growth of viable nucleation sites with high misorientation angle depending on the difference in the stored energy of the nucleus and the stored energy of the surrounding matrix. State switching probability rule is based on the velocity of the grain boundary between the nucleus and the matrix grains. The new approach is validated with recrystallization data on AZ31 sheets. The model captures both the microscopic (texture) and the macroscopic (stress–strain response) properties during DRX.
Most future projections forecast significant and ongoing climate change during the 21st century, but with the severity of impacts dependent on efforts to restrain or reorganise human activity to ...limit carbon dioxide (CO2) emissions. A major sink for atmospheric CO2, and a key source of biological resources, the World Ocean is widely anticipated to undergo profound physical and – via ocean acidification – chemical changes as direct and indirect results of these emissions. Given strong biophysical coupling, the marine biota is also expected to experience strong changes in response to this anthropogenic forcing. Here we examine the large-scale response of ocean biogeochemistry to climate and acidification impacts during the 21st century for Representative Concentration Pathways (RCPs) 2.6 and 8.5 using an intermediate complexity global ecosystem model, MEDUSA-2.0. The primary impact of future change lies in stratification-led declines in the availability of key nutrients in surface waters, which in turn leads to a global decrease (1990s vs. 2090s) in ocean productivity (−6.3%). This impact has knock-on consequences for the abundance of the low trophic level biogeochemical actors modelled by MEDUSA-2.0 (−5.8%), and these would be expected to similarly impact higher trophic level elements such as fisheries. Related impacts are found in the flux of organic material to seafloor communities (−40.7% at 1000 m), and in the volume of ocean suboxic zones (+12.5%). A sensitivity analysis removing an acidification feedback on calcification finds that change in this process significantly impacts benthic communities, suggesting that a~better understanding of the OA-sensitivity of calcifying organisms, and their role in ballasting sinking organic carbon, may significantly improve forecasting of these ecosystems. For all processes, there is geographical variability in change – for instance, productivity declines −21% in the Atlantic and increases +59% in the Arctic – and changes are much more pronounced under RCP 8.5 than the RCP 2.6 scenario.
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