A simple synthesis of 3β-acetoxy-20-oxomethylpregn-5-ene and 3β-acetoxy-20-hydroxymethylpregn-5-ene

3β-Acetoxy-20-oxomethylpregn-5-ene and 3β-acetoxy-20-hydroxymethylpregn-5-ene were synthesized from (22R, 23R)-sitost-5-ene-3β,22,23-triol in 66% overall yields.     

The influence of ultrasound and constant magnetic field on gametes, zygotes, and embryos of the sea urchin

The influence of constant magnetic field, power 7 T, and ultrasound, frequency 2, 4 and 8 MHz, on gametes, fertization, embryos and larvae of the sea urchin was studied. It was shown that magnetic field breaks the process of the gamete fusion but does not influence gametes, embryos, and larvae. Ultrasound impairs the motility of spermatozoa and larvae, prevents the fertilization, and breaks the embryonic development. It is assumed that the effect of the magnetic field is connected with the response of the cortical cytoskeleton, which consists of bundles of actin microfilaments. The rearrangement of the cortical cytoskeleton occurs during the first 20 minutes after the contact of sperm with the egg. Also there is effect of magnetic fields on calcium ions, which are liberated during the first seconds after gamete contact. The effect of the ultrasound is explained by a small increase in water temperature and cavitation process, which break celluar structures.     

Morphogenetic role of the cortex in the development of twins in sea urchins

The dynamics of development of Strongylocentrotus nudus sea urchin twins has been studied after centrifugation at 2,000 g for 5 min and incubation in hypotonic medium after fertilization till formation of the first cleavage furrow. Cortex rigidity was found to correlate with the frequency of twins occurrence. The largest amount of twins forms after centrifugation and hypotonic treatment for the first 1-6 min of zygote development. The twins may be obtained at 25-40 min of development by centrifugation in the presence of cytochalasin B (1 micrograms/ml). Morphogenetic role of cortex in development of sea urchin twins has been discussed.     

Influence of neuroendocrine shifts in the pubertal period on the working memory operation in adolescents

It was found that the volume of working memory in adolescents at the initial pubertal stages (II–III) was lower than in adults. Analysis of the event-related potentials (ERPs) in various cortical areas in adolescents when they compared two successive pictures revealed specific features of neurophysiological mechanisms of visual working memory at the early pubertal stages. As compared to adult subjects, the adolescents were characterized by longer latencies and higher amplitudes of the early components of the ERPs. Certain differences were revealed in the functional organization of working memory both at the stages of stimulus fixation and in its comparison with the current information.     

Sperm ultrastructure in representatives of six bivalve families from Peter the Great Bay, Sea of Japan

The ultrastructure of sperm in seven species of bivalves, the representatives of six families, Arcidae (Anadara broughtonii, Arca boucardi), Anomiidae (Pododesmus macrochisma), Tellinidae (Macoma tokyoensis), Ostreidae (Crassostrea gigas), Myidae (Mya japonica) and Trapezidae (Trapezium liratum) is described. All the studied sperm were typical tail sperm, adapted to external insemination, which, however, had a specific structure. Differences were revealed in the form of head, acrosome structure and number of mitochondria. The studied species of the above families had their specific morphology, the Arcidae species had a bullet- or barrel-shaped head with four or five mitochondria in the middle part; the Anomiidae had conic head, the acrosome with periacrosome material and four mitochondria (a basic feature of sperm is the axial core entering periacrosome material and consisting of bundle of actin filaments); the Myidae had a curved conic head and four mitochondria; in the Tellinidae the head was bullet-shaped, the periacrosome material contained a fibril component and four mitochondria; the Trapezidae had sperm of a conic form with spherical acrosome. The spherical sperm of C. gigas were similar to sperm of Saccostrea commercialis and Crassostrea virginica, but with some distinctions in the acrosome substructure. The morphology of sperm testified to the correct attribution of the Crassostreidae family as a synonym to the Ostreidae family.     

Isotope composition of carbon and nitrogen in tissues and organs of <Emphasis Type="Italic">Betula pendula</Emphasis>

Ratios of ¹³С/¹²C and ¹⁵N/¹⁴N isotopes were identified in different parts and organs of drooping birch (Betula pendula Roth) in preforest-steppe and pine-birch forests of the Middle Urals by mass spectrometry. The data were analyzed and interpreted from the perspective of biochemical processes of carbon and nitrogen metabolism in the leaf, cambial tissue, trunk wood, branches, roots, and in the soil. The lighter isotopic composition of carbon is characteristic for the leaves, trunk cambium as well as fine (<2 mm) roots. The trunk wood is characterized by the basal trend for ¹³C enrichment. The heavier carbon isotopic composition inversely related to metabolic activity of organs and tissues, in addition, ¹³С/¹²C ratio corresponds to the nitrogen content in the organs and tissues, indicating the metabolic control of carbon fractionation in woody plants. The isotopic composition of nitrogen in the aboveground parts of the plant (leaves, trunk cambium, wood) and in the medium and fine roots was significantly depleted in ¹⁵N (δ¹⁵N varies from 0 to–3‰), while main roots (δ¹⁵N = 0.6 ‰) and soil (δ¹⁵N = 2.4–6.7‰) were more enriched. The ratio of stable isotopes of carbon and nitrogen is an integrating index of carbon and nitrogen metabolism in plants.     

Phospholipids and cholesterol of liver nuclei during artificial hypobiosis of rats

The contents of lipids in the tissue and the nuclei of liver cells during artificial hypobiosis, as well as in the nuclei of liver cells for 3 days after the cessation of cooling in rats, were studied. In the artificial hypobiosis and in the state of normothermia 24 h after the cessation of cooling, the total phospholipid content of the liver cell nuclei increased by 20% due to minor phospholipids. The levels of sphingomyelin, phosphatidylinositol, phosphatidylserine, cardiolipin, and lysophosphatidylcholine were doubled in hypobiosis and then nonmonotonically returned to the normal level within 72 h. In the state of artificial hypobiosis, the levels of fatty acids, cholesterol, and diglycerides increased by 30–40%. The state of artificial hypobiosis did not affect the level of lipids in the liver tissue of Wistar rats. The increase of the lipid content in the liver cell nuclei of Wistar rats indicates the important role of lipids in functions of the nucleus when the energy supply and protein synthesis are inhibited under conditions of artificial hypobiosis.     

Enzymatic synthesis of dimeric glycomimetic ligands of NK cell activation receptors

This work reveals new structural relationships in the complex process of the interaction between activation receptors of natural killer cells (rat NKR-P1, human CD69) and novel bivalent carbohydrate glycomimetics. The length, glycosylation pattern and linker structure of receptor ligands were examined with respect to their ability to precipitate the receptor protein from solution, which simulates the in vivo process of receptor aggregation during NK cell activation. It was found that di-LacdiNAc triazole compounds show optimal performance, reaching up to 100% precipitation of the present protein receptors, and achieving high immunostimulatory activities without any tendency to trigger activation-induced apoptosis. In the synthesis of the compounds tested, two enzymatic approaches were applied. Whereas a β-N-acetylhexosaminidase could only glycosylate one of the two acceptor sites available with yields below 10%, the Y284L mutant of human placental β1,4-galactosyltransferase-1 worked as a perfect synthetic tool, accomplishing even quantitative glycosylation at both acceptor sites and with absolute regioselectivity for the C-4 position. This work insinuates new directions for further ligand structure optimisation and demonstrates the strong synthetic potential of the mutant human placental β1,4-galactosyltransferase-1 in the synthesis of multivalent glycomimetics and glycomaterials.