Ostracod species of the genus <em>Cytheropteron</em> from late Pleistocene-Holocene and recent sediments of the Laptev Sea (Arctic Siberia)

Sixteen species of the genus Cytheropteron from the Laptev Sea Late Pleistocene, Holocene deposits and Recent surface sediments have been described. Analysis of the literature on this subject and the collections of O.M.Lev from St. Petersburg, together with our own material from the Laptev Sea, allowed us to introduce certain changes in the taxonomy of this genus. One species Cytheropteron laptevensis Stepanova sp. nov. is described as new

Recent Ostracoda from the Laptev Sea (Arctic Siberia): Species assemblages and some environmental applications

Ostracod assemblages from coretop sediments collected at 26 localities at different depths of the Laptev Sea shelf and upper continental slope were investigated for assemblage studies. A total of 41 species belonging to 19 genera and 12 families have been identified. Three assemblages have been established that could be linked to environmental factors such as water depth, bottom salinities, water mass circulation and sea-ice transportation. The species-rich and abundant assemblages of the western and central Laptev Sea were related to the Atlantic waters occupying the upper continental slope. These include relatively deep-water forms that show clear affinities to North Atlantic and Arctic Ocean assemblages (Cytheropteron biconvexa, C. testudo, C. simplex, C. nodosoalatum, C. inflatum, C. porterae, Krithe glacialis, K. minima, Pseudocythere caudata, Polycope punctata, P. orbicularis). In the eastern middle shelf region, the assemblage is comprised of Acanthocythereis dunelmensis together with other normal marine species (Semicytherura complanata, Elofsonella concinna, Cluthia cluthae). This assemblage seems connected to the winter flaw polynya which is believed to be the main area of sediment entrainment into sea ice. The inner shelf assemblage of the southern Laptev Sea is dominated by shallow-water euryhaline species (Paracyprideis pseudopunctillata and Heterocyprideis sorbyana) with admixture of the brackish-water species Roundstonia macchesneyi. The unusual occurrence of a number of shallow-water ostracod species on the upper continental slope may be explained by ice-rafting which these ostracods are probably able to survive

Last postglacial environmental evolution of the Laptev Sea shelf as reflected in molluscan, ostracodal and foraminiferal faunas

Temporal and spatial variations in the species composition of modern and Holocene assemblages of molluscs, ostracods, and foraminifers from the Laptev Sea shelf (Arctic Siberia) have been investigated to reconstruct palaeoenvironmental changes during the last postglacial times and associated sea-level rise. Analysis of coretop sediment samples allowed to distinguish four modern assemblages. The specific habitat preferences of these species groups, such as water depth and salinity, were then used to interpret past environmental changes on the basis of two radiocarbon-dated sediment cores from the eastern middle shelf region, i.e., obtained from the Yana (51 m water depth) and Lena (45 m water depth) palaeovalleys. Despite the water depth difference of the two core sites, all downcore data document uniform fossil evidence for a gradual transformation of the Laptev Sea shelf from a terrestrial to a marine environment due to the southward transgressing sea. Three major phases have been recognized. These reflect: (1) a nearshore brackish-water environment of the initial stage of inundation (11.3–11.1 in the Yana and 11.2–10.8 cal. ka in the Lena palaeovalley); (2) a shallow inner-shelf, fluvially affected environment (11.1–10.3 and 10.8–8.2 cal. ka); (3) a modern-like marine environment which eventually became established since 10.8 and 8.2 cal. ka, depending on the specific water depth of each core site

Quantifying the Extent of North American Mammal Extinction Relative to the Pre-Anthropogenic Baseline

Earth has experienced five major extinction events in the past 450 million years. Many scientists suggest we are now witnessing a sixth, driven by human impacts. However, it has been difficult to quantify the real extent of the current extinction episode, either for a given taxonomic group at the continental scale or for the worldwide biota, largely because comparisons of pre-anthropogenic and anthropogenic biodiversity baselines have been unavailable. Here, we compute those baselines for mammals of temperate North America, using a sampling-standardized rich fossil record to reconstruct species-area relationships for a series of time slices ranging from 30 million to 500 years ago. We show that shortly after humans first arrived in North America, mammalian diversity dropped to become at least 15%–42% too low compared to the “normal” diversity baseline that had existed for millions of years. While the Holocene reduction in North American mammal diversity has long been recognized qualitatively, our results provide a quantitative measure that clarifies how significant the diversity reduction actually was. If mass extinctions are defined as loss of at least 75% of species on a global scale, our data suggest that North American mammals had already progressed one-fifth to more than halfway (depending on biogeographic province) towards that benchmark, even before industrialized society began to affect them. Data currently are not available to make similar quantitative estimates for other continents, but qualitative declines in Holocene mammal diversity are also widely recognized in South America, Eurasia, and Australia. Extending our methodology to mammals in these areas, as well as to other taxa where possible, would provide a reasonable way to assess the magnitude of global extinction, the biodiversity impact of extinctions of currently threatened species, and the efficacy of conservation efforts into the future

Boreal (Eemian) Transgression in the Northeastern White Sea Region: Multiproxy Evidence from Bychye-2 Section

Reconstructing interglacial marine environments helps us understand the climate change mechanisms of the past. To contribute to this body of knowledge, we studied a high-resolution 455 cm-thick sediment sequence of the Boreal (Eemian) marine beds directly overlying Moscovian (Saalian) moraine in the Bychye-2 section on the Pyoza River. We analyzed lithological and microfossil (foraminifers, ostracods, pollen, aquatic palynomorphs) variations at the studied site. Stratigraphical zonation is based on the local and well-established regional pollen zones, correlated with the western European pollen zones. The studied marine beds accumulated from the end of the Moscovian glacial (&gt;131 ka) until ca. 119.5 ka. We distinguished three successive phases: a seasonally sea-ice-covered, relatively deep, freshened basin in the initial rapid flooding stage (&gt;131–130.5 ka); a deep basin in the maximum flooding phase with less extensive sea ice cover (130.5–130.25 ka); and a shallow basin with reduced sea ice cover (130.25–119.5 ka). According to a pollen zone comparison with other sites, the regional glacioisostatic rebound started ca. 130 ka. The diverse warm-water assemblages of benthic foraminifers and ostracods containing typical Baltic Sea species occurred during the regression, mainly 128–124 ka, thus giving evidence for a relatively long-lasting connection between the White and Baltic Seas.</jats:p

Comparison study of the modern ostracod associations in the Kara and Laptev seas

Recent ostracod assemblages were investigated from coretop sediment samples collected in the eastern Kara Sea from water depths down to 300 m. A total of 45 species were identified, 27 of them were reported for the Kara Sea for the first time. The Kara Sea data were compared with our results on the distribution of ostracods in the eastern Laptev Sea. The spatial distribution of recent taxa and the ecological groupings demonstrate a clear relation to dominant environmental factors which range from estuarine to full-marine conditions. Four assemblages related to average summer bottom water salinities were established: (1) a freshwater assemblage from the inner estuaries of the Ob' and Yenisei rivers with salinities less than 2 and from thermokarst lagoons of the southern Laptev Sea coast with strong salinization in winter; (2) a brackishwater assemblage of the outer estuaries of the Ob' and Yenisei rivers with salinities up to 26; (3) a mixed euryhaline–marine assemblage dominated by euryhaline species Paracyprideis pseudopunctillata and Heterocyprideis sorbyana from the inner shelf river-affected zone of the Kara and Laptev seas, where salinities range between 26 and 32; (4) a taxonomically diverse marine assemblage dominated by shallow-water marine taxa from the northern parts of the Kara and Laptev shelves and upper continental slope with stable bottom environments and a salinity higher than 32. Abundant euryhaline species found at greater water depths are identified as part of an ice-rafted assemblage. They are possibly entrained into the newly formed fast ice during autumn storms and freeze-up period and then transported to the distal open-sea areas during summer

Role of vitamin D deficiency in type 2 diabetes mellitus and diabetic neuropathy development

Type 2 diabetes mellitus (DM) is a global epidemic associated with severe vascular complications development. Diabetic neuropathy is the most common chronic complication of DM that worsens patients&rsquo; life quality and prognosis. Therefore, studies dealing with DM and diabetic neuropathy underlying mechanisms are extremely relevant. The review discusses current views on vitamin D role in glucose metabolism and inflammatory processes. It is reported that vitamin D deficiency can contribute to insulin resistance development, and change in vitamin D receptor activity or extra- and intracellular calcium concentration due to vitamin D deficiency can affect pancreatic &beta;-cells function and lead to decrease in insulin production. Key pathogenic mechanisms of diabetic neuropathy as well as possible relationship between vitamin D deficiency and neuropathy development are in focus of this review. Results of recent clinical trials regarding vitamin D supplementation in patients with DM are also discussed. The presented data suggest that vitamin D deficiency can be considered as a non-classical risk factor for the development of not only DM but its complications as well

ОПРЕДЕЛЕНИЕ БРОМИДА ЦЕТИЛТРИМЕТИЛАММОНИЯ ФОТОМЕТРИЧЕСКИМ МЕТОДОМ ЗА СЧЕТ АГРЕГАЦИИ С КАРБОЦИАНИНОВЫМ КРАСИТЕЛЕМ

It was found that the commercial carbocyanine dye IR-783 containing sulfo groups forms aggregates with cetyltrimethylammonium bromide (CTAB) in a slightly alkaline medium yielding a new absorption band, a change in the solution color from blue to yellow (Dl = 350 nm), and a change in the fluorescence intensity in the near-IR region. CTAB was determined by the photometric method  by photographing the reaction mixture in a 96-well plate with a smartphone camera or in a Camag visualizer. The difference between the intensities of the red and blue channels (R – B), corresponding to the yellow color, was used as an analytical signal. The linear range in an aqueous solution is (3 – 25)·10–6 M, the detection limit is 1.6·10–6 M, and the relative standard deviation is 2–5%. The determination is not affected with a number of non-ionic surfactants, inorganic salts and polymers; the anionic surfactants interfere. Other cationic surfactants also give analytical signals, but with different sensitivities. The characteristics of the literature method for the determination of CTAB based on the Coomassie brilliant blue G-250 dye and the proposed method are comparable. A sample of CTAB-containing lysing buffer solution was analyzed.Keywords: cetyltrimethylammonium, cationic surfactants, carbocyanine dye, aggregation, photometry DOI: http://dx.doi.org/10.15826/analitika.2022.26.3.004 Irina A. Stepanova, Anna V. Shik, Evgenii V. Skorobogatov, Anatasiya A.Bartoshevich, Mikhail K. BeklemishevDepartment of Chemistry, Lomonosov Moscow State University,Russian Federation, 119991, GSP-1, Moscow, Leninskie gory, 1, building 3Обнаружено, что коммерческий карбоцианиновый краситель IR-783, содержащий сульфогруппы, в слабощелочной среде образует агрегаты с бромидом цетилтриметиламмония (ЦТАБ) с появлением новой полосы поглощения, изменением цвета раствора с синего на желтый (Dl = 350 нм) и изменением интенсивности флуоресценции в ближней ИК области. ЦТАБ определяли фотометрическим методом, фотографируя реакционную смесь в 96-луночном планшете камерой смартфона или в визуализаторе Camag. В качестве аналитического сигнала использовали разность интенсивностей красного и синего каналов (R – B), соответствующую желтому цвету. Диапазон определяемых концентраций в водном растворе составляет (3 – 25)·10–6 М, предел обнаружения 1.6·10–6 М, относительное стандартное отклонение 2–5 %. Определению не мешает ряд неионных ПАВ, неорганических солей и полимеров, мешают анионные ПАВ. Другие катионные ПАВ также дают сигналы, но с разной чувствительностью. Характеристики литературной методики определения ЦТАБ на основе красителя кумасси бриллиантовый синий G-250 и предлагаемой сопоставимы. Проанализирован образец лизирующего буфера, содержащего ЦТАБ.Ключевые слова: цетилтриметиламмоний, катионные поверхностно-активные вещества, карбоцианиновый краситель, агрегация, фотометрияDOI: http://dx.doi.org/10.15826/analitika.2022.26.3.00