Biology subjects

Vasiliev, A.

Publications and source records attributed to Vasiliev, A..

5 recordsLinked to original sources

bioRxiv2026

Abundance and distribution of ice-associated seals in the western Bering Sea and Sea of Okhotsk, 2012-2013

In the springs of 2012-2013, Russian Federation scientists conducted aerial surveys of ice-associated seals (including bearded, ribbon, ringed, and spotted seals) in the Sea of Okhotsk and in Russian waters of the western Bering Sea. These instrument-based surveys used a combination of thermal imaging and digital photography to detect and photograph seals basking on sea ice. Initial estimates of seal distribution and abundance from these surveys have been published in Russian journals, but did not make adjustments for observation error. In this paper, we reanalyze these data with the goal of producing spatially explicit estimates of seal abundance that properly account for incomplete detection and species classification errors. Our analysis used estimated relationships between seal abundance and habitat variables to predict abundance in unsurveyed locations, and auxiliary data on detectability to model the observation process. Under this framework, we estimated that in 2012 there were approximately 185,330 bearded seals, 68,564 ribbon seals, 272,609 ringed seals, and 226,003 spotted seals in the western Bering Sea; in 2013, these numbers were 144,105, 39,435, 203,130, and 90,501, respectively. In the Sea of Okhotsk, estimated abundance was 218,740 bearded seals, 221,228 ribbon seals, 179,893 ringed seals, and 169,870 spotted seals (2013 only). These are the first credible estimates of ice-associated seals in the Okhotsk and western Bering Seas, and should be useful for population management and for measuring how density and distribution change as a function of decreasing Arctic sea ice. Declines in seal estimates in the western Bering Sea from 2012 to 2013 mirror patterns observed in the eastern Bering Sea during concurrent U.S. surveys and could represent a decrease in abundance or a substantial decrease in pupping and molting activity.

ecology↗

bioRxiv2024

Testing various combinations of cryoprotective agents for human skin cryopreservation by vitrification method

Modern translational medicine, pharmacology and other fields require effective skin cryopreservation technology. Vitrification is promising technology for this aim. This rapid freezing technique minimizes hexagonal ice crystals formation, time of stress condition for cells in samples and dehydration both in the cytoplasm of cells and in the extracellular space. This study is aimed at finding the optimal combination of extracellular (sucrose, mannitol, polyethylene glycol and FBS) and intracellular (DMSO, glycerol, ethylene glycol) cryoprotective agents to achieve the highest viability and tissue structure preservation of skin samples after vitrification.

cell biology↗

bioRxiv2024

Abundance and distribution of ringed and bearded seals in the Chukchi Sea: a reference for future trends

Ringed (Pusa hispida) and bearded (Erignathus barbatus) seals are vulnerable to decreasing sea ice habitat in the rapidly warming Arctic. In April and May of 2016, we conducted an aerial survey over the ice-covered areas of the Chukchi Sea using thermal and color cameras to detect and count these seals on sea ice. We related the seal counts to environmental variables, and used the relationships to estimate the species distributions and abundance throughout the Chukchi Sea. We accounted for incomplete detection due to seals missed by sensors or image processing errors, behavioral responses to aircraft, or incomplete availability (i.e. seals that are in water or in snow dens on the ice, called lairs). For the latter, we used wet/dry records from satellite-linked bio-loggers, and remotely sensed snow melt dates to estimate the proportion of ringed seal individuals that were visible on ice for each day and location surveyed. To our knowledge, this is the first study where use of lairs by ringed seals has been formally addressed while estimating abundance from aerial surveys. Ringed seal abundance was estimated as [Formula] = 592,577 (95% CI: 478,448-733,929), with highest densities near Kotzebue Sound, Alaska, USA. Bearded seal abundance was estimated as [Formula] = 147,421 (95% CI: 114,155-190,380), with highest densities in broken pack ice near Bering Strait. The influence of environmental variables, such as snow depth and ice type, was consistent with prior studies of the species natural history, particularly ringed seals preference for snow of adequate depth for lairs. Our study provides the first comprehensive abundance estimates for ringed and bearded seals in the Chukchi Sea and establishes a reference for monitoring how their populations respond to Arctic warming.

ecology↗

bioRxiv2023

Testing of various protocols for human skin cryopreservation by vitrification method

Optimization of skin cryopreservation technology is an important task for translational medicine, pharmacology, and a list of other fields. One of the promising approaches is vitrification. This rapid freezing technique allows one to ensure minimal damage to the sample by equating the formation of ice crystals and dehydration both in the cytoplasm of cells and in the extracellular space. This study is aimed at finding the optimal combination of cryoprotective agents (DMSO, glycerol, sucrose and polyethylene glycol) to achieve the highest viability of skin samples after vitrification.

cell biology↗

bioRxiv2020

Sources of variation and establishment of Russian reference intervals for major hormones and tumor markers

ObjectivesA multicenter study was organized to explore sources of variation (SVs) of reference values (RVs) for 24 major immunochemistry analytes and to determine reference intervals (RIs) for the Russian population. MethodsAccording to IFCC Committee on Reference Intervals and Decision Limits (C-RIDL) protocol, 793 healthy volunteers were recruited in St. Petersburg, Moscow, and Yekaterinburg. Serum samples were tested for five tumor markers, 19 hormones and related tests by Beckman Coulters UniCel DxI 800 immunochemistry analyzer. SVs were explored using multiple regression analysis and ANOVA. Standard deviation ratio (SDR) of 0.4 was used as primary guide for partitioning RIs by gender and age. ResultsSDR for between-city difference was <0.4 for all analytes. Secondary exclusion of individuals was done under the following conditions: for female sex-hormones, those with contraceptives (8%); for CA19-9, those supposed to have negative Lewis blood-group (10.5%); for insulin, those with BMI[≥]28 kg/m2 (29.9%); for the thyroid panel, those with anti-thyroid antibodies (10.3% in males; 24.5% in females). Gender-specific RIs were required for all analytes except CA19-9, CA15-3, thyroid-related tests, parathyroid hormone, and insulin. Age-specific RIs were required for -fetoprotein and all sex-hormones except testosterone. RIs were generally derived by parametric method after Gaussian transformation using modified Box-Cox formula. Exceptions were growth hormone, estradiol, and progesterone, for which nonparametric method was required due to bimodal distribution and/or insufficient detection limit. ConclusionRIs for major hormones and tumor markers specific for the Russian population were derived based on the up-to-date internationally harmonized protocol by careful consideration of analyte-specific SVs.

biochemistry↗