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Late Pleistocene permafrost of the Yedoma type constitutes a valuable paleo-environmental archive due to the presence of numerous and well-preserved floral and faunal fossils. The study of the fossil Yedoma inventory allows for qualitative and quantitative reconstructions of past ecosystem and climate conditions and variations over time. Here, we present the results of combined paleo-proxy studies including pollen, chironomid, diatom and mammal fossil analyses from a prominent Yedoma cliff on Sobo-Sise Island in the eastern Lena Delta, NE Siberia to complement previous and ongoing paleo-ecological research in western Beringia. The Yedoma Ice Complex (IC) cliff on Sobo-Sise Island (up to 28 m high, 1.7 km long) was continuously sampled at 0.5 m resolution. The entire sequence covers the last about 52 cal kyr BP, but is not continuous as it shows substantial hiatuses at 36–29 cal kyr BP, at 20–17 cal kyr BP and at 15–7 cal kyr BP. The Marine Isotope Stage (MIS) 3 Yedoma IC (52–28 cal kyr BP) pollen spectra show typical features of tundra–steppe vegetation. Green algae remains indicate freshwater conditions. The chironomid assemblages vary considerably in abundance and diversity. Chironomid-based TJuly reconstructions during MIS 3 reveal warmer-than-today TJuly at about 51 cal kyr BP, 46-44 and 41 cal kyr BP. The MIS 2 Yedoma IC (28–15 cal kyr BP) pollen spectra represent tundra-steppe vegetation as during MIS 3, but higher abundance of Artemisia and lower abundances of algae remains indicate drier summer conditions. The chironomid records are poor. The MIS 1 (7–0 cal kyr BP) pollen spectra indicate shrub-tundra vegetation. The chironomid fauna is sparse and not diverse. The chironomid-based TJuly reconstruction supports similar-as-today temperatures at 6.4–4.4 cal kyr BP. Diatoms were recorded only after about 6.4 cal kyr BP. The Sobo-Sise Yedoma record preserves traces of the West Beringian tundra-steppe that maintained the Mammoth fauna including rare evidence for woolly rhinoceros’ presence. Chironomid-based TJuly reconstructions complement previous plant-macrofossil based TJuly of regional MIS 3 records. Our study from the eastern Lena Delta fits into and extends previous paleo-ecological Yedoma studies to characterize Beringian paleo-environments in the Laptev Sea coastal region.

No abstract

We studied changes in the stability of the genome in cells of two brain regions (prefrontal cortex and hippocampus), as well as in the bone marrow of rats with a hereditary high and low thresholds of excitability of the nervous system (strains HT and LT, respectively) after prolonged exposure with emotional-pain stressor. To study the reactivity of the brain cells genome, phosphorylated histone -H2AX (-H2AX phospho Ser139) was used. The level of mitotic disturbances in bone marrow cells was also assessed. Between the animals of the control groups, there were no interstrain differences in the studied parameters. Stress exposure increases the immunoreactivity to -H2AX phospho Ser139 of the prefrontal cortex cells and the level of chromosomal aberrations in bone marrow cells in animals of both strains. In cells of the dentate gyrus of the hippocampus, a specific increase in immunoreactivity to -H2AX phospho Ser139 was revealed in rats of the low-excitable HT strain. The relationship between the reaction of cells of this zone of hippocampus to the stressor exposure with the hereditary level of excitability of the nervous system of animals is discussed.

The effects of long-term mental and pain stress on H3Ser10 histone phosphorylation in neurons of the the sensorimotor corex and midbrain reticular formation were studied 24 h, 2 weeks, and 2 months after exposure of rats differing by the nervous system excitability. Rats with high excitability threshold exhibited higher basal level of H3Ser10 histone phosphorylation in the midbrain reticular formation neurons than rats with low excitability threshold. The sensorimotor cortical neurons of the two strains did not differ by this parameter. Stress led to a significant increase in the counts of immunopositive neuronal nuclei in rats with low excitability threshold: the parameter increased significantly in the sensorimotor cortex 24 h after exposure and normalized in 2 weeks after neurotization. In the midbrain reticular formation of this rat strain stress stimulated H3Ser10 histone phosphorylation after 24 h and after 2 weeks; the parameter normalized after neurotization in 2 months. Hence, genetically determined level of the nervous system excitability was essential for the basal level of neuron phosphorylation and for the time course of this process after long-term exposure to mental and pain stress, depending on the brain structure. A probable relationship between H3Ser10 histone phosphorylation process and liability to obsessive compulsive mental disorders in humans was discussed.

Stress plays an important role in the pathogenesis of anxiety and depressive disorders. Neuroinflammation is considered as one of the mechanisms by which stress alters the molecular and cellular plasticity in the nervous tissue and thus entails CNS dysfunction. The contribution of genetically determined features of the nervous system to the development of post-stress neuroinflammation has not been sufficiently studied. In this study, the dynamics of post-stress changes in mRNA levels of the il-1 β and tnf genes encoding proinflammatory cytokines interleukin-1 beta (IL-1β) and tumor necrosis factor (TNF) were evaluated in the blood and brain of two rat strains with high and low excitability thresholds of the nervous system (HT and LT, respectively). Changes in IL-1β and TNF mRNA levels were assessed by real-time PCR 24 h, 7, 24 and 60 days after long-term long-term emotional and painful stress in the blood and three brain structures involved in the development of post-stress pathology (prefrontal cortex, hippocampus, amygdala). In highly excitable LT rats, IL-1β mRNA level in the hippocampus and amygdala increased compared to the control 24 days after stress termination, while in low-excitable HT animals, an increase in the level of IL-1β mRNA was only detected in the hippocampus at the same time point. TNF mRNA level did not change in any of the rat strains at any of the post-stress time points. Genetically determined excitability of the nervous system is a promising marker of individual stress vulnerability, as manifested in post-stress disorders associated with developmental and time-course features of neuroinflammation.

Long-term effects of chronic emotional and pain stress on histone H3 phosphorylation by serine 10 in hippocampal CA3 neurons were examined 24 h, 2 weeks, and 2 months after termination of the stress procedure in 2 rat strains differing by excitability of the nervous system. The low excitable rats with high threshold (HT) of excitability were characterized by a high baseline level of histone H3 phosphorylation in comparison with the high excitable rats with low threshold (LT) of excitability. The long-term emotional and pain stress significantly changed the number of positive immune cells in highly excitable rats: this parameter increased in 24 h and 2 weeks after the stress, but returned to the control level in 2 months. In contrast, stress did not affect histone H3 phosphorylation in low excitable rats. Thus, long-term (up to 2 weeks) changes in histone H3 phosphorylation were reveled in rat hippocampal CA3 neurons, which depended on genetically determined functional status of the nervous system.

We studied the effects of prenatal emotional painful stress on numerical density of neurons and characteristics of heterochromatin in developing and mature hippocampus of rats with different excitability of the nervous systems. It was shown that prenatal stress reduces the numerical density of neurons in hippocampal CA3 field in 24-day-old and adult (3 months) low excitable animals and chromocenter area in cells of developing hippocampus in embryos of both strains. The difference in chromocenter areas in offspring of stressed females was retained on postnatal day 24.