Regional assignment of the genes for TK1, GALK, ALDC, and ESD on chromosome 8 in the American mink by chromosome-mediated gene transfer

Summary A panel of clones of mink-Chinese hamster somatic cell hybrids was analysed to obtain data for assigning the genes for thymidine kinase-1 (TK1), galactokinase (GALK), subunit C of aldolase (ALDC), and esterase D (ESD) to specific mink chromosomes. The results demonstrate that the genes for TK1, GALK, ALDC and ESD are syntenic and located on mink chromosome 8. Prometaphase analysis of transformed mouse cells obtained by transfer of mink genes by means of metaphase chromosomes demonstrated the presence of mink chromosome 8 fragments of different sizes in some of the independent transformants. Segregation analysis of these fragments and mink TK1, GALK, ALDC and ESD allowed us to assign the genes for TK1 and GALK to 8p24, ALDC to pter-8p25, and ESD to 8q24-8qter.     

Heterochromatin as a factor influencing X-chromosome inactivation in hybrids of the common vole (Microtinae, Rodentia)]

Expression of X-linked genes for G6PD and alpha-GAL was studied in female interspecific hybrids of Microtus. The G6PD and alpha-GAL isozymes of Microtus arvalis were found to predominate in all cases when a species carrying a heterochromatin block on the X-chromosome served as one partner of hybridization and M. arvalis containing no heterochromatin block served as another. The proportions of G6PD and alpha-GAL parental forms were approx. equal in hybrid females when both species participating in hybridization contained heterochromatin blocks on X-chromosomes. Cytological analysis for revealing active and nonactive X-chromosomes on metaphase spreads of hybrid females supports the biochemical data. Non-random inactivation of X-chromosomes carrying the heterochromatin blocks in the interspecific hybrids with M. arvalis and a random one, when both parents contain heterochromatin blocks on the X-chromosomes are supposed to be the cause for the phenomenon observed. The study provided data supporting our previous hypothesis that heterochromatin affects the X-chromosome inactivation process in interspecific hybrid voles.     

Seasonal changes in the cytochemical properties of the peritoneal mast cells in rats]

Contents of histamine, 5-hydroxytryptamine, functional state of heparinic proteoglycan have been studied in the rat peritoneal mast cells during various seasons of the year (January-February, May-June, July). In winter the mast cells have a high content of histamine and 5-hydroxytryptamine, heparinic proteoglycan of their granules is stained with both alcian blue and safranin. In summer (July) content of histamine in the mast cells is sharply decreased in comparison with that of 5-hydroxytryptamine and in May-June the content of both amines is decreased nearly to background values. Both during spring and summer periods heparinic proteoglycan of the mast cell granules is stained only with alcian blue and does not take safranin. A suggestion is made on independence of the seasonal changes of annual rhythmical pattern of histamine and 5-hydroxytryptamine contents in the mast cells. A conclusion is made concerning possible participation of the mast cell system of organs and tissues in the seasonal changes of biogenic amine levels in them.     

Binding of glucocorticoid-receptor complexes with the acceptor zones of nuclei and effect of glucocorticoids on RNA synthesis in hormone-sensitive and hormone-resistant cell populations

The binding of free radioactive glucocorticoid and the glucocorticoid-receptor complex to rat liver nuclei was studied in vitro. The binding is non-saturated and independent of preliminary injection of the "cold" hormone. In the course of DNA hydrolysis the amount of the radioactive hormone bound to the chromatin moiety in vivo remains practically unchanged relatively to the initial radioactivity of the protein. The liberation of the nuclei into a cell-free medium and the effect of DNAase I on the nuclei are associated with the redistribution of the hormone-receptor complex in the chromatin molecule and with the appearance of new, previously masked acceptor zones of the hormone binding. During the first 1-2 hours following the hormone injection the endogenous RNA-synthesizing activity of the nuclei is decreased. The increase of RNA synthesis in liver nuclei occurs not earlier than 3 hours after the injection. In Zajdela hepatoma nuclei the repression of RNA synthesis persists as long as 3 hours after the injection of dexamethasone. When RNA synthesis is determined in the nuclei in the presence of exogenous RNA-polymerase of E. coli in vitro, the increase in nuclear RNA synthesis can be observed beginning with the 30th min after the hormone injection. It is assumed that this effect is due to conformational changes in the chromatin structure, which are concomitant with the initial steps of association of the hormone-receptor complex.     

In situ proteolysis for protein crystallization and structure determination

We tested the general applicability of in situ proteolysis to form protein crystals suitable for structure determination by adding a protease (chymotrypsin or trypsin) digestion step to crystallization trials of 55 bacterial and 14 human proteins that had proven recalcitrant to our best efforts at crystallization or structure determination. This is a work in progress; so far we determined structures of 9 bacterial proteins and the human aminoimidazole ribonucleotide synthetase (AIRS) domain.     

Vacuum electron acceleration by a tightly focused,radially polarized,relativistically strong laser pulse

A test particle approach is used to solve the problem of direct electron acceleration by a short, intense, radially polarized laser pulse the focal spot diameter of which can be on the order of the laser wavelength. The fields of a tightly focused laser beam are described in terms of the Stratton-Chu integrals, with which to investigate electron acceleration when the paraxial approximation is inapplicable to laser fields. The dynamics of electron motion in a radially polarized, relativistically strong laser field is analyzed depending on the initial position of an electron in the focal region of the laser beam. The properties of the generated jets of accelerated electrons are investigated depending on the tightness of laser pulse focusing. Possible advantages of using radially polarized laser pulses for charged particle acceleration, as opposed to the use of linearly polarized ones, are discussed.     

Synthesis and luminescent properties of lanthanide homoleptic mercaptothi(ox)azolate complexes: Molecular structure of Ln(mbt)3 (Ln = Eu, Er)

The thiolate complexes of rare earth metals Ln(SR)₃ (La, HSR = 2-mercaptothiazoline (1); La, HSR = 2-mercaptobenzoxazole (2); Y, La, Sm, Eu, Tb, Gd, Er, Tm, HSR = 2-mercaptobenzothiazole (3)) were synthesized in 84-97% yield by the reactions of silylamides Ln[N(SiMe₃)₂]₃ with respective thiols. The products were characterized by elemental analysis, IR and UV/Vis spectroscopy. The structures of 3(Eu) and 3(Er) were determined by single-crystal X-ray diffraction. All obtained compounds revealed efficient luminescence in the region 400-550 nm at 293 K assigned to the ligands emission. Besides, the luminescent spectra of thiolates 3 at 77 K displayed the phosphorescent band of the ligand at 550 nm and in the cases of 3(Eu) and 3(Tb) the sets of emissions bands characteristic for Eu³⁺ and Tb³⁺ ions.