O. V. Lebedev

The buccohypophyseal canal is an ancestral vertebrate trait maintained by modulation in sonic hedgehog signaling

BackgroundThe pituitary gland is formed by the juxtaposition of two tissues: neuroectoderm arising from the basal diencephalon, and oral epithelium, which invaginates towards the central nervous system from the roof of the mouth. The oral invagination that reaches the brain from the mouth is referred to as Rathke’s pouch, with the tip forming the adenohypophysis and the stalk disappearing after the earliest stages of development. In tetrapods, formation of the cranial base establishes a definitive barrier between the pituitary and oral cavity; however, numerous extinct and extant vertebrate species retain an open buccohypophyseal canal in adulthood, a vestige of the stalk of Rathke’s pouch. Little is currently known about the formation and function of this structure. Here we have investigated molecular mechanisms driving the formation of the buccohypophyseal canal and their evolutionary significance.ResultsWe show that Rathke’s pouch is located at a boundary region delineated by endoderm, neural crest-derived oral mesenchyme and the anterior limit of the notochord, using CD1, R26R-Sox17-Cre and R26R-Wnt1-Cre mouse lines. As revealed by synchrotron X-ray microtomography after iodine staining in mouse embryos, the pouch has a lobulated three-dimensional structure that embraces the descending diencephalon during pituitary formation. Polarisfl/fl; Wnt1-Cre, Ofd1-/- and Kif3a-/- primary cilia mouse mutants have abnormal sonic hedgehog (Shh) signaling and all present with malformations of the anterior pituitary gland and midline structures of the anterior cranial base. Changes in the expressions of Shh downstream genes are confirmed in Gas1-/- mice. From an evolutionary perspective, persistence of the buccohypophyseal canal is a basal character for all vertebrates and its maintenance in several groups is related to a specific morphology of the midline that can be related to modulation in Shh signaling.ConclusionThese results provide insight into a poorly understood ancestral vertebrate structure. It appears that the opening of the buccohypophyseal canal depends upon Shh signaling and that modulation in this pathway most probably accounts for its persistence in phylogeny.

Nitration of imidazoles with various nitrating agents

The nitration of imidazole and its derivatives has been studied. The action of sulfuric-nitric nitrating mixture on imidazole and its nitro derivatives has given di- and trinitroimidazoles. The action of a mixture of nitric acid and acetic anhydride on the mononitroimidazoles has given the corresponding N-nitro derivatives, and some of their properties have been studied.

Synthesis of 2-monofunctionalized 2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones

New (1R*,5S*)-2-R-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-diones containing the terminal carboxy or hydroxy group in the substituent R were synthesized by cyclocondensation of 4,5-dihydroxyimidazolidin-2-one with 1-R-ureas. Single-crystal X-ray diffraction analysis showed that 2-carboxyethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione crystallizes as a racemate.

The nitration of iodoimidazoles

Treatment of iodoimidazoles with nitric acid of various concentrations results in replacement of the iodine atoms by nitro groups, including those in the 2-position, which is not activated towards electrophilic substitution in acid media. The use of a nitric acid- sulfuric acid nitrating mixture also results in the replacements of the iodine atom in the 4(5)position.

Chemico-Pharmaceutical Analysis of the Biologically Active Substances Albicar

Methods for analysis of Albicar substance as required for assessment of the quality of this medicinal substance for standardization purposes were developed and verified.

Oxidative macrocyclocondensation of 3,4-diaminofurazan and 4,4′-diamino-3,3′-azofurazan with dibromoisocyanurate. Crystal structures of hexa- and octadiazenofurazan macrocycles

The oxidative cyclocondensation of 3,4-diaminofurazan and 4,4′-diamino-3,3′-azofurazan with dibromoisocyanurate afforded macrocyclec polydiazenofurazans. The reaction can be directed towards the formation of both the four-membered cycle alone or the three-, six-, and eight-membered macrocycles.

Middle Famennian (Upper Devonian)Chondrichthyans and Sarcopterygians from Oryol region; Central Russia

Abstract The middle Famennian vertebrate localities of Central Russia yielded new micro- and macroremains of the chondrichthyansTuberospina nataliae nov. gen. et sp. and Symmorium sp.; struniiforms Strunius cf. rolandi Gross and Pycnacanthus fischeri nov. sp.; porolepiform ?Glyptolepis dellei Gross . The osteolepiform taxa Cryptolepis grossi Vorobyeva and ?Glyptopomus bystrowi Gross ; known before from the studied localities; are revised. A new family Pycnacanthidae nov. fam. is established on the ground of peculiar parasymphysial teeth fusion. Preliminary conodont dating is carried out based on local zonation.

Synthesis of (1,2,3-triazol-1-yl)furazans. 2. Reaction of azidofurazans with morpholinonitroethene

We have studied the 1,3-dipolar cycloaddition of azidofurazans to morpholinonitroethene and prepared 1,2,3-triazoles with furazan ring in position 1 and NO2 group at position 4.

Novel method for synthesis of 3,4:7,8:11,12:15,16-tetrafurazano-1,2,5,6,9,10,13,14-octaazacyclohexadeka-1,3,5,7,9,11,13,15-octaene and its crystal structure

We have established the formation of a tetradiazenofurazan macrocycle as a result of intramolecular oxidative cyclization of 4,4′-bis(4-aminofurazanyl-3-azo)-3,3′-azofurazan and have studied its crystal structure.

REACTIONS OF SULFONAMIDES WITH 4,5-DIHYDROXYIMIDAZOLIDIN-2-ONES

The interaction of sulfonamides with 4,5-dihydroxyimidazolidin-2-ones was studied for the first time. The earlier unknown 4,4′-sulfonyldiiminobis(1,3-dialkylimidazolidin-2-ones) and 4(5)-aryl(alkyl)-sulfonyliminoimidazolidin-2-ones were synthesized. A probable pathway of the reaction was proposed. 1,3-Diethyl-4,5-dihydroxyimidazolidin-2-one was isolated and described.