Properties and serum levels of pregnancy-associated variant of human transcortin

The amino acid composition, N- and C-terminal amino acid sequences, and the basic physicochemical and immunochemical properties of the recently discovered pregnancy-associated molecular variant of human transcortin (Strel'chyonok, O.A., Avvakumov, G.V. and Akhrem, A.A. (1984) Carbohydr. Res. 134, 133-140) have been found to be identical to those of transcortin from normal donor serum. This suggests the identity of polypeptide moieties of the two glycoproteins. The transcortin variant has a lower isoelectric point (3.5-4.1) than normal transcortin (3.6-4.2), and different electrophoretic mobility in low-porosity polyacrylamide gel (one band versus two for normal transcortin). These differences can be reasonably explained by different organization of the carbohydrate moieties of these glycoproteins due to diverse post-translational modification of a single polypeptide chain. The levels of transcortin variant in the maternal venous serum throughout normal gestation (447 donors in all) and on the fifth day after delivery, as well as in umbilical cord serum and extracts of term placenta, have been measured by a radioimmune assay. Analysis of the data obtained allowed us to conclude that the biosynthesis of pregnancy-associated transcortin variant occurs in some organ of the maternal organism rather than in the feto-placental system, and it is a characteristic of pregnancy as a unique physiological state of the female organism rather than a phenomenon caused by individual features of certain women. We assume that the transcortin variant takes part in the guided transport of corticosteroids and/or progestins into some tissues that develop in the course of gestation.     

Skeletal Ultrastructure in some Tubuliporine Cyclostome Bryozoans

The ultrastructure of the calcareous skeleton is described in twenty–one species of recent tubuliporine cyclostome bryozoans, using field emission SEM. The succession of skeletal fabrics in interior walls may be classified into four different fabric suites. The first–formed part of the calcitic skeleton in all species for which it has been observed is a precursory fabric of tiny, wedge–shaped crystallites. This is succeeded in about half of the species studied by a fabric of transverse fibres, followed by foliated fabric and often semi–nacre (fabric suite 1). Most of the remaining species lack transverse fibres and have interior walls largely comprising semi–nacre (fabric suite 2). A few species have skeletons consisting of predominantly distally–oriented, irregularly or regularly foliated fabric (fabric suite 3). A single species has a skeleton of proximally–oriented foliated fabric (fabric suite 4). Basal exterior walls in all species have a precursory fabric of tiny wedge–shaped crystallites without a strong preferred orientation, deposited directly upon the organic cuticle, followed by a layer of planar spherulitic structure, which in turn is succeeded by a similar fabric to that developed in the interior wall of the species concerned. Outermost layers of frontal exterior walls exhibit one of the following combinations of three fabrics: an outer layer of (1) finely granular or wedge–shaped crystallites; a thin dense granular layer followed by (2) distally accreting planar spherulitic fabric., or (3) obliquely accreting planar spherulitic fabric growing partly towards the midline of the frontal wall. Terminal diaphragms usually have outer layers dominated by planar spherulitic ultrastructure with centripetal growth directions. The fabric suites present in tubuliporines encompass most known fabrics found in the other cyclostome suborders and support the notion that this species–rich suborder occupies a central position in cyclostome evolution.     

Stable isotopes in fish otoliths discriminate between lagoonal and oceanic residents of Taiaro Atoll (Tuamotu Archipelago, French Polynesia)

 The fully enclosed Taiaro lagoon is hypersaline (42.5 psu) and non-tidal; constant salinity and water level result from strong evaporation balanced by low percolation through the lagoon floor. Seawater can flow over the atoll rim during exceptionally high seas and may then replenish lagoonal communities with propagules of oceanic origin. The distinctive water chemistry of the lagoon suggests a possible way of identifying these immigrants. We established this potential by analysing stable isotopes of carbon and oxygen in the recent growth layers of otoliths of two adult reef fishes, Chaetodon ulietensis and Acanthurus triostegus, collected from both sides of the atoll rim. Fish from the two locations were discriminated by their isotopic signatures, suggesting that analysis of the microchemical signatures deposited during the larval development could be used in future work to determine which individuals and species complete their life-cycles in this unusual lagoon. Accepted: 28 August 1997     

Effect of menthol on human temperature sensitivity

Application of 1% methol, which, along with cold, activates specific thermosensitive ionic channels, changes the number of functioning cold receptors on the skin of the forearm similarly to the cold exposure test; however, it does not affect the number of heat receptors and does not significantly change the threshold of cold sensation. Group variants of responses to menthol that indicate individual differences in the sensitivity of skin receptors to the effects of methol and cold have been found. The results obtained give grounds to suggest that, from the variant of response to menthol (a decrease, increase, or absence of changes in the number of functioning cold receptors 5 min after menthol application), it is possible to predict specific features of response to cold.     

Lipase-catalyzed transamidation of non-activated amides in organic solvent

A novel biocatalytic reaction of transamidation of non-activated amides with amines is reported. Among 45 different lipolytic and proteolytic enzymes tested, only the lipase from Candida antarcticawas able to catalyze this reaction. The reaction proceeded with up to ca. 80% conversion in anhydrous methyl tert-butyl ether and worked with both N-substituted and unsubstituted amides. The biocatalytic transamidation is an equilibrium process and, therefore, higher conversions to the desired amide were achieved by using increased concentrations of the amine nucleophile.     

Photolabeling of brain membrane proteins by lysergic acid diethylamide

³H-Lysergic acid diethylamide (³H-LSD) is irreversibly incorporated into bovine caudate membranes during ultraviolet light illumination. The incorporated radioligand apparently forms a covalent bond with a sub-population of the membrane proteins. Although the photolabeling pattern differs significantly from the Coomassie blue staining pattern on SDS gels, the photolabeling is apparently not specific for LSD binding sites associated with neurotransmitter receptors. ³H-LSD photolabeling can occur during prolonged exposure of membrane samples to room lighting and thus may introduce artifacts into receptor binding assays.