Selective inhibition of platelet lipoxygenase by esculetin

The effects of coumarin and its derivatives on rat platelet lipoxygenase and cyclooxygenase activities were studied. Esculetin (6,7-dihydroxycoumarin) was found to inhibit the lipoxygenase more strongly than the cyclooxygenase; its concentration for 50% inhibition (IC50) was 0.65 microM for platelet lipoxygenase and 0.45 mM for platelet cyclooxygenase. Esculin (the 6-glucoside of esculetin) and umbelliferone (7-hydroxy-coumarin) also selectively inhibited the lipoxygenase, though less strongly (IC50 = 290 and 500 microM, respectively). 4-Hydroxycoumarin and coumarin had no inhibitory effect on either enzyme at concentrations up to 1 mM. The mechanism of the lipoxygenase inhibition by esculetin was non-competitive. Other antioxidants (hydroquinone, gallic acid and ascorbic acid) were less inhibitory to both enzymes and showed little selectivity.     

Paradoxical dissociation between gluconeogenic effects and glucocorticoid-receptor binding by gonadal steroids.

Estradiol and testosterone derivatives both decreased liver glycogen and impaired triamcinolone acetonide mediated gluconeogenesis in male, adrenalectomized fed rats. Neither gonadal steroid influenced binding of either glucocorticoid to its cytoplasmic receptor. Association of ³H-estradiol to liver cytoplasmic binders remained unhampered in presence of one hundredfold excess of either cortisol or triamcinolone.     

Identification of β-galactofuranosyl residues and their rapid internal motion in the Penicilliumochro-chloron cell wall probed by 13C NMR

Polysaccharides, which come into resonances in the ¹³C NMR spectrum of $\text{Penicillium}\text{ochro-chloron}$ intact mycelium and give anomeric carbon signals at 107.5 and 108.3 ppm, are associated with the cell wall. By ¹³C NMR and gas liquid chromatography analysis, it is shown that the polysaccharides are two types of β-galactofuranosyl residues, one of which has (1→2)-β-galactofuranosyl linkages. Both β-galactofuranosyl residues, which are minor cell wall components, experience rapid internal motion in the cell wall.     

Detection of PIVKA II produced by human hepatoma cells in nude mice.

A novel experimental nude mouse model, which is useful for investigation of the mechanisms of PIVKA II synthesis, was established by inoculation with PIVKA II-producing human hepatoma cells (huH-1). We have found markedly elevated levels of PIVKA II in the plasma of nude mice transplanted with huH-1 cells and increased PIVKA II content in huH-1 tumor tissues. Whereas we have not found detectable level of PIVKA II neither in the plasma nor in tumor tissues of nude mice transplanted different human hepatoma cells (HLF) which is not producing PIVKA II. Histology of the tumor tissues produced by huH-1 cells revealed a thick trabecular pattern with blood spaces.     

Analysis of Nuclear Accumulation of Influenza NP Antigen in von Magnus Virus-Infected Cells

When 1–5C-4 cells were infected with von Magnus virus derived from influenza A/RI/5⁺ virus by four successive undiluted passages in chick embryos, virus-specific proteins were synthesized but production of infectious virus was inhibited. In these cells the synthesis of viral RNA was suppressed and the nucleoprotein (NP) antigen was found predominantly in the nucleus in contrast to standard virus-infected cells in which the antigen was distributed throughout the whole cell. The intracellular location and migration of NP were determined by isotope labeling and sucrose gradient centrifugation of subcellular fractions. In standard virus-infected cells NP polypeptide was present predominantly in the cytoplasm in the form of viral ribonucleoprotein (RNP) and intranuclear RNP was detected in reduced amounts. In contrast, in von Magnus virus-infected cells NP polypeptide was present predominantly in the nucleus in a nonassembled, soluble form and the amount of cytoplasmic RNP was considerably reduced. After short-pulse labeling NP was detected exclusively in the cytoplasm in a soluble form and after a chase a large proportion of such soluble NP was seen in the nucleus. It is suggested that a large proportion of the NP synthesized in von Magnus virus-infected cells is not assembled into cytoplasmic RNP because of the lack of available RNA and the NP migrated into the nucleus and remained there.     

Glycopeptides from murine teratocarcinoma cells: structure of the determinants recognised by Griffonia simplicifolia agglutinin I and by sera from patients with ovarian germ cell tumors

High-molecular-weight glycopeptides synthesised by teratocarcinoma OTT6050 bear the binding site for Griffonia simplicifolia agglutinin I and are recognised by antibodies in the sera of patients with ovarian germ cell tumors. Digestion of the glycopeptides with endo-beta-D-galactosidase C abolished the lectin binding activity and the antigenic activity. Since the product of the enzymic digestion is alpha-D-Gal-(1----3)-D-Gal, it is concluded that the disaccharide structure is involved in the lectin binding site and the antigenic site.