Formation of roseoflavin from 8-amino- and 8-methylamino-8-demethyl-D-riboflavin

A synthesis of roseoflavin (RoF) by Streptomyces davawensis from 8-amino- (AF) and 8-methylamino-8-demethyl-D-riboflavin (MAF) was demonstrated. The lines of evidence are: 1) the RoF formation was increased by addition of AF or MAF to the culture, 2) [2-14C]RoF was formed by addition of [2-14C]AF or [2-14C]MAF to the culture, and the location of the 14C atom at the 2-position was demonstrated by identifying [14C]urea in the hydrolysate of the RoF, 3) [N-methyl-14C]RoF was formed by addition of [methyl-14C]methionine to the culture containing AF or MAF, and the location of the 14C atom was confirmed by the photochemical conversion of the RoF to MAF, the specific radioactivity of which was about half that of the original RoF, and by localization of the 14C atom in 1,2-dihydro-6-methyl-7-dimethylamino-2-keto-1-ribityl-3-quinoxalinecarbo xylic acid (QC), which was formed from the RoF by hydrolysis.     

Tissue 8

Tissue stress (TS) is defined as the stress which acts on atissue layer in an organ in excess of the turgor-induced tensilestress which also acts on the layer when it is isolated fromthe organ. The tensile TS in one layer of an organ is alwaysaccompanied by com-pressive TS in another layer. To calculateTS from data obtained for isolated tissue, one needs to knowthe Poisson ratios V_IKcontraction in the k-direction/extension in the i-direction for the tensile force applied in the i-direction for that tissue.Poisson ratios apply in the relationships between (i) tissueextensions caused by uniaxial stress (due to applied force)and multiaxial stress (due to turgor pressure); (ii) extensionsof tissues subjected to lateral constraint, and (iii) TSs indifferent directions. The ratios V_IW and V_WI, for the stressapplied either longitudinally (I) or in the direction of width(W), respectively, were determined for the outer tissue (OT)of sunflower hypocotyls, tulip leaves and tulip stems. The tworatios for a particular OT differed considerably. The ratiosdepended on the applied extension (strain). Knowing them, thetensile force (F₁) generating TS in the OT of an intact organcould be calculated from the longitudinal force (F_I(s)) whichwhen applied to the isolated (unconstrained laterally) OT restoredits original length. In the case of the sunflower hypocotyls,F_I(s)<F₁<1.3 F_I(s). The ratio V_Ir (r denotes the radialdirection), which was determined for segments of inner tissue,from sunflower hypocotyls and tulip stems, did not depend onthe applied stress (extension). This ratio allowed us to calculatethe relationship between the strain changes caused by equalchanges of uniaxial and multiaxial stresses: the uniaxial stresswas approximately 3-fold more efficient than the multiaxialstress. Key words: Elastic strains, Poisson ratios, tissue stresses, tissue elasticity, uni- and multiaxial stresses.     

Trisomy 8

Summary Trisomy 8, in mosaic or non-mosaic form is an extremely rare chromosomal condition in man. Liveborn subjects usually present with mental retardation, bone and joint anomalies and a variety of other physical anomalies. The mental retardation associated with the condition is, however, usually moderate compared to that found in other viable human autosomal trisomic conditions. The present report describes a trisomy 8 mosaic male subject with normal IQ and near-normal phenotype, ascertained through infertility. Chromosome studies on peripheral blood lymphocytes reveal a pure trisomy 8 constitution; cultured skin fibroblasts show 46,XY/47,XY+8 mosaicism. At meiosis, the extra No. 8 chromosome is missing from the germ line. The testicular histology indicates a germ cell maturation arrest in many spermatocytes and the patient is severely oligospermic. Biochemical studies to assay levels of glutathione reductase, a red cell enzyme, the gene for which resides in chromosome 8, show increased levels in the trisomy 8 patient compared with controls.     

Isolation and structural characterisation of 8-O-4/8-O-4- and 8-8/8-O-4-coupled dehydrotriferulic acids from maize bran

Two new dehydrotriferulic acids were isolated from saponified maize bran insoluble fiber using Sephadex LH-20 chromatography followed by semi-preparative RP-HPLC. Based on UV-spectroscopy, mass spectroscopy and one- and two-dimensional NMR experiments, the structures were identified as 8-O-4,8-O-4-dehydrotriferulic acid and 8-8(cyclic),8-O-4-dehydrotriferulic acid. Which of the possible phenols in the initially formed 8-8-dehydrodiferulate was etherified by 4-O-8-coupling with ferulate has been unambiguously elucidated. The ferulate dehydrotrimers which give rise to these dehydrotriferulic acids following saponification are presumed, like the dehydrodiferulates, to cross-link polysaccharides. Neither dehydrotriferulic acid described here involves a 5-5-dehydrodiferulic acid unit; only the 5-5-dehydrodimer may be formed intramolecularly. However, whether dehydrotriferulates are capable of cross-linking more than two polysaccharide chains remains open. Although the levels of the isolated ferulate dehydrotrimers are lower than those of the ferulate dehydrodimers, the isolation now of three different dehydrotriferulates indicates that trimers contribute to a strong network cross-linking plant cell wall polysaccharides.     

Enantioselective synthesis of (+)-8-hydroxy-8-methylidarubicinone

An asymmetric Diels-Alder reaction methodology was employed to construct the tetracyclic structure of the anthracyclinone. A five-step sequence was needed to furnish the target (+)-8-hydroxy-8-methylidarubicinone.     

Selective fluorescence detection of 8-oxoguanosine with 8-oxoG-clamp

8-oxoguanosine, which is derived from the oxidation of guanosine (dG), is known to induce transversion mutations (G:C-->T:A) in DNA. The compounds with a small molecular weight for recognizing 8-oxoG were designed on the basis of the structure of the G-clamp, which is reported to have selective affinity toward guanosine. The G-clamp derivatives with the additional binding units toward 8-oxoG were effectively synthesized and named "8-oxoG-clamps." The 8-oxoG-clamp completely discriminated 8-oxoG from other nucleosides by fluorescence quenching.     

Transactivation of vascular endothelial growth factor receptor-2 by interleukin-8 (IL-8/CXCL8) is required for IL-8/CXCL8-induced endothelial permeability

Interleukin-8 (IL-8/CXCL8) is a chemokine that increases endothelial permeability during early stages of angiogenesis. However, the mechanisms involved in IL-8/CXCL8-induced permeability are poorly understood. Here, we show that permeability induced by this chemokine requires the activation of vascular endothelial growth factor receptor-2 (VEGFR2/fetal liver kinase 1/KDR). IL-8/CXCL8 stimulates VEGFR2 phosphorylation in a VEGF-independent manner, suggesting VEGFR2 transactivation. We investigated the possible contribution of physical interactions between VEGFR2 and the IL-8/CXCL8 receptors leading to VEGFR2 transactivation. Both IL-8 receptors interact with VEGFR2 after IL-8/CXCL8 treatment, and the time course of complex formation is comparable with that of VEGFR2 phosphorylation. Src kinases are involved upstream of receptor complex formation and VEGFR2 transactivation during IL-8/CXCL8-induced permeability. An inhibitor of Src kinases blocked IL-8/CXCL8-induced VEGFR2 phosphorylation, receptor complex formation, and endothelial permeability. Furthermore, inhibition of the VEGFR abolishes RhoA activation by IL-8/CXCL8, and gap formation, suggesting a mechanism whereby VEGFR2 transactivation mediates IL-8/CXCL8-induced permeability. This study points to VEGFR2 transactivation as an important signaling pathway used by chemokines such as IL-8/CXCL8, and it may lead to the development of new therapies that can be used in conditions involving increases in endothelial permeability or angiogenesis, particularly in pathological situations associated with both IL-8/CXCL8 and VEGF.     

Formation of 8-S-l-cysteinylguanosine from 8-bromoguanosine and cysteine

When 8-bromoguanosine was incubated with cysteine at pH 7.4 and 37 °C, a previously unidentified product was formed as a major product in addition to guanosine. The product was identified as a cysteine substitution derivative of guanosine at the 8 position, 8-S-l-cysteinylguanosine. The reaction was accelerated under mildly basic conditions. The cysteine adduct of guanosine was fairly stable and decomposed with a half-life of 193 h at pH 7.4 and 37 °C. Similar results were observed for incubation of 8-bromo-2′-deoxyguanosine with cysteine. The results suggest that 8-bromoguanine in nucleosides, nucleotides, RNA, and DNA can react with thiols resulting in stable adducts.