Vol 40, No 3 (2023)

In this work, we have studied photosynthetic electron transport in chloroplasts of two “contrasting” species of Cucumis genus, the shade-tolerant species Cucumis sativus (cucumber) and the light-loving species Cucumis melo (melon). Plants were acclimated to moderate (50–125 μmole photons m⁻² s⁻¹) or high light (850– 1000 μmole photons m⁻² s⁻¹). Parameters of a fast induction of chlorophyll a fluorescence, emitted from photosystem 2 (PS2), were determined using a conventional OJIP test. For monitoring the turnover of photosystem 1 (PS1) reaction centers P⁺₇₀₀, we used electron paramagnetic resonance. The shade-tolerant (C. sativus) and light-loving (C. melo) species, acclimation to high or low light irradiation, revealed substantial difference in their response to variations of light intensity. Photosynthetic activity of shade-tolerant species C. sativus revealed higher sensitivity to light intensity during acclimation as compared to C. melo. In the course of the long-term acclimation (more than 2 months) of С. sativum to high light (≥ 500 μmole photons m⁻² m⁻¹), a photochemical activity of PS2 decreased. This was not the case, however, for leaves of C. melo. In С. sativus leaves, a decrease in photochemical activity of PS2 caused by acclimation to high light was reversible, demonstrating the recovery after the attenuation of irradiation intensity. Plants of both species acclimated to high and low light also revealed significant differences in the two-phase kinetics of redox transients. In the leaves of plants acclimated to strong light, we observed a lag-phase in the kinetics of photooxidation that could be attributed to cyclic electron transport (CET) around PS1. The ratio of the signals induced by white light and far-red light (707 nm) was higher in plants acclimated to strong light. This effect can be explained by the enhancement of CET and optimization of the energy balance at excess of light, protecting plants from oxidative stress. The data obtained are discussed in the context of the problem of photosynthesis optimization upon fluctuations of light intensity.

Cannabinoid receptors (CBRs) play a key role in various physiological processes, including neurogenesis, synaptic plasticity, immune modulation, cell apoptosis, metabolism regulation, cardiovascular and reproductive systems activity. Since activation of CBRs suppresses hyperexcitation and protect cells from death, their modulation may have therapeutic prospects in the treatment of such pathologies of the nervous system as mental disorders, epilepsy, Parkinson’s and Huntington’s disease, multiple sclerosis, spinal cord and brain injuries. This paper presents experimental data on the effects of the cannabinoid receptor agonist WIN 55,212-2 on the induced oscillations of intracellular Ca2+ concentration ([Ca2+]i) in two in vitro models of epileptiform activity. To study the neuroprotective properties of WIN 55,212-2, hyperexcitation was induced by the application of a GABA(A) receptor antagonist, bicuculline, or depolarizing doses of ammonium chloride. As experiments have shown, WIN 55,212-2 at a concentration of 100 nM and above significantly suppresses the [Ca2+]i oscillation frequency and reduces the basal [Ca2+]i level. At the same time, the amplitude of calcium oscillations also decreased in the presence of the agonist. WIN 55,212-2 at a concentration of 5 μM suppressed NH4Cl-induced [Ca2+]i oscillations in all neurons but caused a transient biphasic increase in the basal [Ca2+]i level in 20% of astrocytes. Thus, in this work, using various models of hyperexcitation of neuronal networks, we have demonstrated the potential antiepileptic effect of the cannabinoid receptor agonist WIN 55,212-2.

In this work we studied the mutual influence of multipotent mesenchymal stromal cells (MMSC) isolated from Wharton’s jelly of human umbilical cord and primary culture of hippocampal cells obtained from transgenic mice 5XFAD, used as an animal model of inherited form of Alzheimer’s disease (AD). Experimental protocols included both direct and indirect co-cultivation of MMSCs with hippocampal cells from transgenic animals. It was shown that in the conditions of indirect co-culture, the aggressive environment of cultured transgenic cells significantly decreases the survival rate and adhesiveness of MMSCs. However, preliminary priming of MMSCs with proteins YB-1 and HSP70 improved the survival and adhesive properties of MMSCs. It was also found that the interactions of MMSCs with cultured hippocampal cells depend on cell culture age. Old cultures of transgenic cells induced differentiation of MMSC into astrocytes, both during direct and indirect co-cultivation. In contrast, in young cultures of transgenic cells, during contact co-cultivation, MMSCs played the role of specific strands that promoted clustering of hippocampal cells in the culture and the formation of neurospheres. The interaction between MMSCs and neural cells occurred through gap junctions and nanotubes. Our findings expand the understanding of interactions between MMSCs and recipient cells, which allows us to revise the conditions of cellular transplantation therapy for pathological processes in the brain of AD patients.