Separation and absolute configuration of the enantiomers of a degradation product of the new inhalation anesthetic sevoflurane

In a rebreathing anesthesia circuit, the inhaled anesthetic sevoflurane degrades into at least two products, termed "compound A" and "compound B." The enantiomer separation of the chiral compound B (1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane ) by capillary gas chromatography (cGC) using heptakis (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin as chiral selector was studied. With this cyclodextrin derivative diluted in the polysiloxane PS 86, an unprecedented high separation factor alpha of 4.1 (at 30 degrees C) was found. Consequently, the enantiomers of compound B were isolated by preparative GC and their specific rotations were measured. In addition, their absolute configurations were determined by X-ray crystallography. To collect the X-ray data, single crystals of both enantiomers were grown in situ on the diffractometer. The levorotatory enantiomer B(-) has the R-configuration while the dextrorotatory enantiomer B(+) has the S-configuration. The elution order of the compound B enantiomers on heptakis (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin is R before S.     

CD43 gene expression is mediated by a nuclear factor which binds pyrimidine-rich single-stranded DNA

CD43 is a leukocyte-specific surface molecule which plays an important role both in adhesion and signal transduction. We have identified a site spanning nucleotides +18 to +39 within the human CD43 gene promoter which in vitro is hypersensitive to cleavage by nuclease S1. Repeats of this region are sufficient to activate expression of a heterologous promoter in CD43-positive cell lines. Two nuclear factors, PyRo1 and PyRo2, interact with the hypersensitive site. PyRo1 is a single-stranded DNA-binding protein which binds the pyrimidine-rich sense strand. Mutation analysis demonstrates that the motif TCCCCT is critical for PyRo1 interaction. Replacement of this motif with the sequence CATATA abolishes PyRo1 binding and reduces expression of the CD43 promoter by 35% in Jurkat T lymphocytic cells and by 52% in the pre-erythroid/pre-megakaryocytic cell line K562. However, this same replacement failed to affect expression in U937 monocytic cells or in CEM T lymphocytic cells. PyRo1, therefore, exhibits cell-specific differences in its functional activity. Further analysis demonstrated that PyRo1 not only interacts with the CD43 gene promoter but also motifs present within the promoters of the CD11a, CD11b, CD11c and CD11d genes. These genes encode the α subunits of the β2 integrin family of leukocyte adhesion receptors. Deletion of the PyRo1 binding site within the CD11c gene reduced promoter activity in T lymphocytic cells by 47%. However, consistent with our analysis of the CD43 gene, the effect of this same deletion within U937 monocytic cells was less severe. That PyRo1 binds preferentially to single-stranded DNA and sequences within the CD43 and CD11 gene promoters suggests that expression of these genes is influenced by DNA secondary structure.     

The role of DNA repair processes in the repair of cytogenetic disorders. The participation of slow to repair DNA damage in the repair of cytogenetic disorders

Caffeine was used to study the kinetics of cytogenetic damages repair in Chinese hamster fibroblasts. Its half-time (90 min) was shown to correlate with that of repair of slowly repaired DNA damages. The caffeine-induced increase in the number of irreparable DNA damages, attributed to inhibition of double-strand break repair, is in a quantitative correlation with the effect of the cytogenetic damage modification.     

Na+ Influx Inhibits Neuronal Ca2+ Channels

Experiments on isolated rat brain neurons with an elevated intracellular sodium concentration (due to tetanic stimulation) demonstrated the existence of earlier unknown negative modulation of calcium channels by intracellular sodium.     

Phylogenetic position of Eulipotyphla inferred from the cDNA sequences of pepsinogens A and C

Although to date the phylogenetic position of the provisional order Eulipotyphla has been assessed by various molecular markers, it has not been conclusively clarified due to low statistical supporting values and inconsistent results. To clarify the phylogenetic position of Eulipotyphla, we cloned cDNAs for pepsinogens A and C from five mammalian species belonging to four different orders and determined their nucleotide sequences. Molecular phylogenetic analysis based on the 1st and 2nd codon positions of the protein-coding region of cDNA sequences strongly supported the close relationship between Eulipotyphla and Chiroptera. Carnivora was found to be a sister group to these two orders. The monophyly of the order Rodentia and that of the cohort Glires (Rodentia and Lagomorpha) was also shown by the present phylogenetic trees of pepsinogens.