Induction of differentiation of cultured human promyelocytic leukemia cells by retinoids

Human promyelocytic leukemia cells (HL-60) were induced to phagocytize, reduce NBT dye(nitroblue tetrazolium), and change into forms that were morphologically similar to mature granulocytes by retinoic acid and related retinoids, but not by the pyridyl analog of retinoic acid. Induction of differentiation could be detected after 4 days of treatment of the cells with retinoic acid at as low a dose as 4 × 10^?8 M. Thus, retinoids may be used in studies on the control of cell differentiation and malignancy of human myeloid leukemia cells.     

X-ray diffraction data for (1→3)-α-d-glucan triacetate

The crystal structures of (1→3)-α-d-glucan triacetates were studied by X-ray diffraction measurements on fibre diagrams. The oriented films annealed in water at high temperature were of higher crystallinity and occurred as two crystalline polymorphs (GTA I and GTA II) depending on the samples and also the annealing temperature. All reflections in GTA I were indexed with a pseudo-orthorhombic unit cell with a = 1·753, b = 3·018 and c(fibre axis) = 1·205 nm. From the fibre repeat data coupled with the density data and the presence of only the (003) reflection on the meridian, an extended three-fold helical structure was proposed. Although some reflections in GTA II split from the layer lines, the basic unit cell was a monoclinic system with a = 1·685, b = 3·878, c (fibre axis) = 1·210 nm and γ = 112·2°. A similar three-fold structure to GTA I was proposed from the almost identical fibre repeat and the conformational analysis on (1→3)-α-d-glucan. It was concluded that, on acetylation, the d-glucan structure changed from the fully extended two-fold helix to the extended three-fold accompanied by some extent of chain shrinking.     

5'-nucleotidase from the electric ray electric lobe. Primary structure and relation to mammalian and procaryotic enzymes.

A cDNA encoding a 5'-nucleotidase was identified by screening a lambda gt10 cDNA library from the electric lobe of Discopyge ommata using a cDNA probe containing the complete open reading frame coding for the rat liver enzyme. Nucleotide sequence analysis defines an open reading frame of 577 amino acids, corresponding to a calculated molecular mass of 63,833 Da. The N-terminus of the mature protein, as determined by direct protein sequencing, is preceded by 29 amino acid residues comprising a signal peptide. The C-terminus contains a stretch of hydrophobic amino acids, considered to be cleaved on post-translational modification and exchanged for glycosylphosphatidylinositol as a membrane anchor. The predicted protein contains four potential N-linked glycosylation sites. Electric ray 5'-nucleotidase shares 61% amino acid identity with the enzymes from rat liver and human placenta, and about 23% with bacterial proteins possessing 5'-nucleotidase activity and also additional enzyme activities like UDP-glucose hydrolase. Polyclonal antibodies raised against 5'-nucleotidase from mammalian sources or the electric ray electric organ reveal mutual cross-reactivity. Interestingly, there are 5-7 domains highly conserved in procaryotes and vertebrates in enzymes exhibiting 5'-nucleotidase, 3'-nucleotidase or phosphodiesterase activity. 5'-nucleotidase isolated from Torpedo electric organ hydrolyzes UDP-glucose at 8% of the rate of AMP hydrolysis. The possible phylogenetic origin of vertebrate 5'-nucleotidase from multifunctional nucleotide hydrolases is discussed.     

Growth requirements and long-term subcultivation of bovine granulosa cells cultured in a serum-free medium

Summary We have developed an improved serum-free medium to optimize the cell growth of bovine granulosa cells. The cells on collagen-coated culture plates proliferated extensively in a nutrient medium supplemented with insulin, heparin binding growth factor-2 (HBGF-2), lipoprotein, and bovine serum albumin (BSA). The cell doubling time at logarithmic phase and final cell density at confluent cultures were equal to those of cultures grown in the presence of medium supplemented with optimal concentration (10%) of fetal bovine serum (FBS). Whereas HBGF-2 or insulin alone had a small mitogenic effect of granulosa cells, lipoprotein or BSA did not. When lipoprotein, BSA, or insulin was added together with HBGF-2, synergistic cell proliferation was observed in all combinations. Insulin or lipoprotein had an additive mitogenic stimulation of these cells in the presence of BSA. After granulosa cells were subcultivated in a serum-containing medium until three generations [8.5 cumulative population doubling level (CPDL)], subsequent subcultivation of the cells in a complete serum-free medium could be achieved up to six generations (14.4 CPDL). These results demonstrate that this serum-free medium can support the optimal cell growth and long-term subcultivation of bovine granulosa cells.     

Selective processing of proalbumin determined by site-specific mutagenesis

Rat proalbumin is cleaved at the dibasic pair Arg-Arg and converted into a mature form with Glu at the NH2 terminus. In the present study site-directed mutagenesis of the albumin cDNA was designed to generate proalbumin variants in which Glu1 was substituted with various amino acid residues. The expression plasmids constructed were transfected into COS-1 cells, and the intracellular processing of proalbumins expressed was examined by labeling experiments. Substitution of Glu1----Ser allowed the expressed proalbumin to be processed as observed for the wild-type precursor. However, replacement of Glu1 with a hydrophobic residue (Val, Leu or Ile) resulted in no processing of proalbumin, despite retaining the same cleavage signal Arg-Arg as above. The results indicate that the residue at position 1 adjacent to the dibasic pair is also important for recognition by the proalbumin-processing enzyme.     

Fungal coil formation ofRhizoctonia repens in seedlings ofGaleola septentrionalis (orchidaceae)

Protocorms or protocorms with roots of an achlorophyllous orchidGaleola septentrionalis were inoculated with isolates ofRhizoctonia repens, R. solani, andRhizoctonia spp. The seedlings were infected with eight of twelve isolates ofR. repens. Fungal coils were formed in the cells, which was suggestive of a symbiotic association. The other isolates caused soft rot or no infection to the protocorms or the protocorms with a root. Contribution No. 97, Laboratories of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Tsukuba, Ibaraki 305, Japan.     

Study on the chemical evolution of low molecular weight compounds in a highly oxidized atmosphere using electric discharges

The molecular basis for the chemical evolution of low molecular compounds was studied using electric discharges on a higly oxidized atmosphere comprised of CO₂, N₂ and H₂O. In the gas phase, O₂ and CO were formed by the decomposition of CO₂ and their yields were enhanced by the addition of N₂ to the gas mixture. It was demonstrated that H₂O suppressed the reduction of CO₂ while H₂O also had a role in producing organic compounds such as formic acid and formaldehyde. Infrared analysis of the water soluble products and the inner surface of the reaction vessel indicated the production of compounds more complex than formic acid and formaldehyde. These compounds contained the chemical bonds which were identified to be OH, CO, CN and/or CC.