Moscow University Biological Sciences Bulletin

This is a short review concerning the problem of germ line “immortality,” which was already formulated by A. Weismann at the end of the 19th century. Over the following years, it attracted the attention of many gerontologists, who tried to understand the mechanisms of infinite transfer of genetic information from generation to generation with the help of germ cells, which, in contrast to somatic cells, avoid aging in this way. However, it remained unclear how the germ cells of women, which are in fact a population of non-dividing cells (it is similar to stationary phase aging non-subcultured cell culture), provide the mentioned immortality of the germ line. Distinguished Russian gerontologist Zh.A. Medvedev, who passed away recently, published in 1981 his brilliant work “On the Immortality of the Germ Line: Genetic and Biochemical Mechanisms. A Review,” the main points of which are relevant up to today. His paper just discusses the possible mechanisms of such “immortality.” They are analyzed in detail in the current article and can be reduced mainly to the existence of a number of barriers that, in most cases, do not allow progeny to emerge from “old” germ cells (although certain “rejuvenating” processes in the gametes still go). Therefore, children are “born young.” Some alternative approaches to explaining the immortality of the germ line are also considered. Special attention is paid to the “parental age effect” and the role of eggs and sperm cells in this phenomenon.

The spatial distribution of picocyanobacteria at the arctic longitude section passing through the shelf of the Kara, Laptev, and East Siberian seas from 58° to 168° E was studied. The average abundance of picocyanobacteria was 0.48 ± 1.2 × 10⁹ cells/m³ in the Kara Sea, 0.16 ± 0.24 × 10⁹ cells/m³ in the Laptev Sea, and 0.25 ± 0.43 × 10⁹ cells/m³ in the East Siberian Sea. The fluctuations of picocyanobacterial abundance were determined by their presence in allochthonous sources: river flow and transformed North Atlantic waters. The highest abundance was observed in the areas of the runoff influence of the Ob, Khatanga, Indigirka, and Kolyma Siberian rivers: 0.5 × 10⁹, 0.2 × 10⁹, 0.4 × 10⁹, and 1.6 × 10⁹ cells/m³, respectively. The average contribution of picocyanobacteria to the total abundance and biomass of picophytoplankton in the western part of the Kara Sea was 37 and 36%, respectively. In other regions, the average contribution of picocyanobacteria to the total abundance and biomass of phototrophic picoplankton did not exceed 7 and 6%, respectively. A highly reliable (p\( \ll \) 0.01) positive correlation between the abundance and biomass of picocyanobacteria and the water temperature (p = 0.003) was revealed in the entire dataset obtained.

The first data on the species diversity of testate amoebae of the Coco River in the provinces of Quang Nam and Da Nang (Vietnam) are presented. A total of 55 species and subspecies of testate amoebae belonging to nine genera and six families have been identified in 28 samples. Species diversity of testate amoebae in plankton is higher than in benthic samples. Centropyxis aculeata (64.3%), Netzelia wailesi (39.3%), Difflugia acuminata (32.1%), Arcella discoides scutelliformis (28.6%), and Lesquereusia modesta (28.6%) are characterized by the highest frequency of occurrence. Difflugia (25), Arcella (12), Centropyxis (5), and Netzelia (4) are the most species-rich genera. The species accumulation curve based on the entire dataset is unsaturated and is described by the equation y = 12.56N^0.46. The average species richness of testate amoebae per sample in plankton (13.0 ± 3.1) is statistically higher than in benthic samples (1.8 ± 1.5) (p < 0.001). The result of the redundancy analysis shows that the studied hydrochemical water parameters (temperature, pH, dissolved oxygen, electrical conductivity, and salinity) explain only 31.6% of the variation of testate amoeba diversity; the first and second axes explain 11 and 10.2% of this variation, respectively.

NRT1.1 nitrate transporter acts as a nitrate sensor in some plant responses. We tried to check if it may be involved in the control of cytokinin level in the plants known to be involved in the growth responses to nitrate level. The experimental objects were Arabidopsis thaliana plants of the original ecotype Columbia (Col-0) and chl1-5 mutants. The effects of the NRT1.1 gene mutation in chl1-5 plants on hormonal and growth responses to nitrogen starvation were studied. Two types of growing conditions were used: (1) plants were placed on either standard Hoagland–Arnon or modified solution, where potassium and calcium nitrates were substituted with their chlorides; (2) plants were placed on Pryanishnikov medium, where ammonium nitrate serves as the source of nitrogen and nitrogen deficiency being modeled by its withdrawal from the medium. It has been first shown that mutation of the NRT1.1 resulted in a decline in cytokinin level in the roots of chl1-5 mutants, while roots of wild type plants were longer in accordance with lower cytokinin content in them; this hormone is known to inhibit root elongation. Cytokinin content decreased in A. thaliana, Columbia ecotype, paralleled by acceleration of root elongation in response to both variants of nitrogen starvation, while chl1-5 roots responded in this way only when nitrogen was withdrawn from Pryanishnikov solution. Substitution of nitrates by chlorides in the Hoagland–Arnon solution had no effects on either chl1-5 roots’ length or cytokinin content in them. The results suggested the involvement of NRT1.1 transceptor in the control of cytokinin level and root elongation rate in the nitrate but not in ammonium starved plants, confirming the specificity of response.

Currently, biological scaffolds composed of extracellular matrix (ECM) are being actively examined for the needs of regenerative medicine. ECM substrates are prepared by decellularization and used to deliver cells to damaged tissue. Native scaffolds of ECM have an advantage over bioengineered ones because ECM retains natural biologic cues that provide efficient reparative cell functions. Mesenchymal stromal cells (MSCs) have a multipotent potential of differentiation and secrete a wide range of bioactive molecules. In this regard, MSCs are valuable intermediaries for tissue repair. The ECM as a critical component of the MSCs niche modulates their functional activity, including migration, proliferation, and differentiation, and supports their potential for self-renewal. In vitro investigations would be useful in elucidation of how biological scaffolds can affect the reparative functions of MSCs. There are several different protocols for decellularization. Since ECM of various cell types differs qualitatively and quantitatively, these protocols should be optimized for each specific case. In the present study we compared the effectiveness of approach to prepare decellularized ECM (dcECM) of adipose-derived MSC (adMSC): Triton X-100/NH₄OH solution in phosphate buffered solution or H₂O, and the possibility of using dcECM after spheroids were formed. ECM-derived substrates were analyzed with immunocytochemistry and scanning electron microscopy. During long-term culture, MSСs produced a well-developed EСM, which maintained a structure close to the native one after treatment with phosphate buffered solution of Triton X‑100/NH₄OH. It was impossible to receive a uniform dcECM layer, when water solution of Triton X-100/NH₄OH was used. On the scanning electron microscopy images single fiber of ECM were revealed in this case. Fragments of ECM and cells after spheroids formation with RGD peptides were detected. Therefore, this method was not effective for obtaining dcECM of adMSCs.

Long-distance interaction plays an important role in the regulation of eukaryotic genes. Chromatin structure is involved in the process, but the role of histone modifications has not been studied. In the present work, the role of acetylation Н4K16 (Н4K16-Ac) to enhancer-promoter communication (EPC) was analyzed. This modification is associated with euchromatin and is involved in the decompaction of chromatin fibers. We have shown that the effect of H4K16-Ac on EPC in vitro depends on the level of chromatin assembly. EPC in chromatin, which lacks nucleosomes at random positions on DNA, is inhibited in the presence of H4K16-Aс. At the same time, EPC in chromatin, in which nucleosomes occupy all available positions on DNA, is somewhat stimulated in the presence of H4K16-Aс.

The study of all factors that contribute to the carbon balance in the biosphere is of paramount importance due to the current increase in carbon dioxide content in the atmosphere. This article presents data on the carbon dioxide exchange for the needles of common spruce (Picea abies L.) and Douglas fir (Pseudotsuga menziesii L.) in an urban environment (based on the example of Moscow). It is established that the warm spell in autumn 2018 contributed to the prolongation of the period of carbon dioxide uptake by coniferous trees. Our analysis into the effect of environmental factors on the needle photosynthetic activity has revealed that the intensity of photosynthesis depends only on the level of illumination. The midday increase in air temperature failed to affect the photosynthesis intensity, which is probably explained by the adaptation of the plants to low night and morning air temperatures. A regression analysis has shown that the dependence of CO₂ assimilation on illumination represented a logarithmic curve (with the approximation validity coefficient (R²) of 0.8). The effect of environmental conditions on conifer photosynthesis in autumn has proven to be species-specific. Common spruce was the most resistant to environmental factors: its photosynthetic activity was 1.4 times higher than that of Douglas fir. Calculations revealed that the level of CO₂ assimilation was 3.6 and 2.7 times higher than the light respiration level for common spruce and Douglas fir, respectively, which indicates a positive carbon dioxide exchange and an important role of coniferous trees in regulating the carbon balance of an urban ecosystem.

Aging organisms die out in accordance with the “Gompertz law,” i.e., the probability of their death increases with age. Survival curve construction is the main tool for gerontologists to study aging and test antiaging drugs. The analysis of survival curves includes obtaining some indices characterizing aging of the population, for example, the average and maximum lifespan, the mortality rate, and the aging rate. Testing geroprotectors can be correctly performed only by obtaining such curves. The dying out of stationary cell populations—bacteria, yeast, and mammalian cell cultures—also occurs in accordance with the Gompertz equation. In this regard, it is reasonable to use the construction of survival curves and their analysis to study the “aging” of non-subcultured cell cultures and testing anti-aging drugs on them. We used this approach in our experiments, due to which we were able to detect the positive anti-aging effect of the Quinton Marine Plasma on stationary phase aging culture of Chinese hamster cells.