Том 50, № 4 (2019)

The importance of sperm DNA integrity is hard to overestimate since the quality of the genetic material in a sperm population is the key point for successful fertilization, the embryonic and subsequent development of offspring, and, therefore, the male reproductive potential. Apoptosis is essential for male gametes in the period from the time of appearance of the gonadal anlagen in the embryo to the moment of fertilization. This mechanism of programmed cell death is necessary to maintain the appropriate ratio between the germ cells and the Sertoli cells during prenatal development. The damaged cells are removed from the testicles in the adult specimens by the apoptosis pathway. A range of unfavorable effects can intensify this process. In addition, mature spermatozoa undergo apoptosis and subsequent phagocytosis in the female reproductive tract in order to prevent the inflammatory response triggered by the dead gamete destruction. The impaired process of apoptosis may cause developmental abnormalities in male gametes, infertility, and fertilization of oocyte by sperm with DNA damage followed by subsequent offspring death. Therefore, recent studies show that apoptosis is one of the main causes of sperm DNA fragmentation, which tends to become a significant problem under conditions for the widespread use of assisted reproductive technologies.

The formation of the alarm call’s time–frequency characteristics at different stages of individual development was studied on the russet ground squirrel (S. major). The hypothesis about the vocalizations of young individuals of ground squirrels being emitted at lower frequencies than those of adults was tested. The results of the study indicate a differentiated formation of the sound signal in the different sexes of the russet ground squirrel in postnatal ontogenesis. The sound signal in females is formed in the first year of life during the season of activity, whereas it is formed in males in the year following the first hibernation. In terms of the studied call parameters, the voice of adult females is higher than that of young animals of both sexes, while the voice of adult males is lower. The possible causes and significance of the identified sex and age features of the alarm call of the russet ground squirrel are discussed.

A comparative study of lipid and fatty acid status at the early stages of pink salmon’s ontogenesis has been carried out in prespawn eggs, at the stage of eye pigmentation, and in the hatched prelarvae under ecological conditions of a natural environment (Indera River, Kola Peninsula). It is shown that the high plasticity of pink salmon is due to the activation and combination of complex biochemical mechanisms at the early stages of development, providing both the sensitivity and the sustainability of the species, which contributes to the formation of the species’ high potential at high latitudes. Metabolically mature pink salmon eggs are characterized by a high level of total lipids with a high amount of the structural and energetic components that provide optimal development of the embryos. Metabolic processes are activated at the stage of eye pigmentation in autumn, which affects the changes in the spectrum of individual classes of lipids and fatty acids and their ratio indicators. The prelarvae that hatched in winter at temperatures below zero have a low content of phospholipids, triacylglycerols, and 16:1ω-7, 18:3ω-3, and 20:5ω-3 fatty acids as well as high level of cholesterol, cholesterol esters, and a ratio index of 20:4ω-6/18:2ω-6 fatty acids, while the high content of dominant 18:1ω-9 and 22:6ω-3 fatty acids remains the same. Multidirectional changes of lipid and fatty acid levels at the stage of eye pigmentation (the most sensitive stage of embryogenesis) and in pink salmon prelarvae after hatching are caused by specific processes of metabolism intensification of the developing organism.

Individual linear growth in 26 specimens of Anodonta beringiana is studied by measuring the successive annual rings on the surface of the shells. It is shown that the growth of mollusks is well described by the von Bertalanffy growth equation. The coefficients of this equation do not significantly differ between individuals, averaging k = 0.062 ± 0.011 year^–1 and L_∞ = 155.8 ± 19.5 mm. Species lifespan, calculated as a product of the growth constant k and the maximum longevity of mussels in the population, is 1.7. This value is close to the average species lifespan of other bivalve species.

A detailed study into the structural features of the multilevel antipodal complex of wheat Triticum aestivum L. embryo sac was performed at different stages of the complex’s differentiation after double fertilization. The heterogeneity of nuclei ploidy in individual antipodal complexes caused by the asynchrony of the endoreduplication rounds of the nuclear DNA was revealed. The nuclei ploidy of basal, middle, and apical layers of the complexes was measured at the early, middle, and late stages of differentiation. At the early stage of differentiation, the nuclei ploidy of the antipodal complex’s basal layer adjacent to the chalasal region of the nucellus of the embryo sac reaches 13 C, the nuclei of the apical layer cells that contact the endosperm syncytium reaches 63 C, and the nuclei of the middle layer located between the basal and apical layers reach 30 C. At the middle stage of differentiation, the nuclei ploidy in the basal layer increases to 17 C. The nuclei ploidy of the apical layer cells increases to 95 C, and nuclei ploidy of the middle layer increases to 45 C. At the stage of late differentiation, the nuclei ploidy in the basal layer increases to 24 C; the apical layer ploidy increases to 215 C; the middle layer ploidy increases to 63 C. Changes in the shape and structure of the nuclei during differentiation were revealed. They manifest themselves in heterogeneity in shape, size and structure of chromatin; the formation of individual polytene chromosomes; nuclear membrane invaginations; and the variation in the number of nucleoli. Data on the distribution and structure of cytoplasmic organelles of the antipodal cells, endoplasmic reticulum, dictyosomes, mitochondria, and microtubules at different stages of differentiation of the antipodal complexes are fundamentally new. The increased number of cytoplasmic organelles was revealed. During the differentiation, prolong cisterns of the granular reticulum are replaced by concentric rings, mitochondria and plastids of extended and cupped shape appear, and the microtubule network is rebuilt. The features of the antipodal complex’s cell structure may reflect changes in the functions of the antipodal complex during the differentiation. At the early stage, all cells of the complex perform an osmoregulatory function, and cells of different layers of the complex specialize at the middle stage of differentiation. The ploidy level of cell nuclei with polytene chromosomes reflects their functional significance in the formation of endosperm at the nuclear stage of development, and, subsequently, of normal full-fledged grain.

The mechanisms of the interaction between cells and the gravitational field are still unknown, and there are hardly any data on the effect of the gravity force on the germ cells. The objective of this work was to determine the expression levels of the genes encoding cytoskeletal proteins (beta- and gamma-actin, actin-binding proteins alpha-actinin-1 and alpha-actinin-4, beta-tubulin, and desmin) by quantitative PCR, the local level (CpG-island promoter regions of the studied genes) and the total methylation level by the restriction analysis, the content of 5-hydroxymethylcytosine by the dot blotting method, as well as the content of enzymes ensuring the establishment/maintenance of the appropriate level of methylation by the Western blotting method, in the spermatozoa of mice that were subjected for 30 days to antiorthostatic suspension and subsequent 12-h recovery. We also administrated mice with essential phospholipids (per os) and determined the parameters described above. The results suggest that antiorthostatic suspension did not lead to significant changes in the expression level of the genes encoding the actin cytoskeleton proteins in sperm; however, after 12 h of recovery, their expression increased. At the same time, the methylation of CpG islands in the promoter regions of these genes decreased. Oral administration of essential phospholipids equalized these changes. The beta-tubulin gene expression decreased after suspension, and neither the 12-h recovery nor the administration of essential phospholipids changed the situation. In general, the overall methylation level was reduced only in the 12-h recovery group, correlating with an increase in the expression level of the studied genes. At the same time, the content of methylase/demethylase did not change; however, the content of histone acetylase increased, suggesting that, under modeling microgravity conditions, the processes of chromatin modification may be involved in the change in gene expression.