Dose-dependent regulation of macrophage differentiation by mos mRNA in a human monocytic cell line.

The proto-oncogene c-mos was expressed during differentiation of the human monocytic cell line U937 into macrophages. To investigate a possible role of the mos oncogene, we introduced the v-mos gene under an inducible promoter, MT-I, into U937 cells. The v-mos transformed cells expressed mos mRNA at an amount proportional to the concentration of Zn2+ ions. The induction of the v-mos gene caused growth inhibition and macrophage differentiation in these cells. The differentiation of v-mos transformed monocytes into macrophages required continuous expression of the v-mos gene. The extent of expression of phenotypic characteristics of macrophages, such as phagocytosis, cell surface antigens and typical morphology, depends on the amount of mos mRNA present. We were therefore able to demonstrate that the expression of only one oncogene, mos, determines monocyte differentiation into macrophages.     

VP-16-induced nucleotide pool changes and poly(ADP-ribose) synthesis: the role of VP-16 in interphase death

Exposure of human promyelocytic leukemia cell line (HL-60) to VP-16 resulted in accumulation of DNA strand breaks. Concomitantly, intracellular NAD levels fell at 1 h, followed by declines in ATP at 2 h and in GTP, CTP, and UTP at 3 h. Furthermore, marked morphological changes, such as loss of microvilli or bleb formation, appeared at 4 h and cell death by 8-10 h. The addition of an inhibitor of poly(ADP-ribose) polymerase, 3-aminobenzamide (5 mM), theophylline (2 mM), or thymidine (1 mM), prevented these sequential reductions of nucleotide pools and cell death. In fact, the activation of poly(ADP-ribose) synthesis was detectable within a few hours after treatment with VP-16, although it was smaller than that induced by N-methyl-N'-nitro-N-nitrosoguanidine. These results may suggest the possible role of activation of poly(ADP-ribosyl)ation in VP-16-induced nucleotide pool changes and subsequent interphase death.     

Biosynthesis, processing and half-life of P-glycoprotein in a human multidrug-resistant KB cell

The biosynthesis, processing, and half-life of the drug efflux pump, P-glycoprotein, were studied in human multidrug-resistant KB (KB-C2) cells selected for resistance to colchicine. An antibody directed against a synthetic oligopeptide corresponding to the amino-acid sequence (Glu-393-Lys-408) of P-glycoprotein from human mdr1 cDNA was prepared in rabbits. With immunoblotting and immunoprecipitation, we detected a 140-170 kDa protein in KB-C2 cells but not in parental sensitive KB cells. KB-C2 cells made a 125 kDa precursor that was slowly processed (t1/2 = 45 min) to the mature form of 140-150 kDa. The processing rate of P-glycoprotein was slower than that of low-density lipoprotein receptor. We detected another 160-180 kDa smear band, which might be a completely denatured form of P-glycoprotein. With immunoblotting, a minor band of high molecular mass (greater than 500 kDa) was also detected and this form increased after the cells were treated with chemical cross-linker, 1,5-difluoro-2,4-dinitrobenzene. The half-life of P-glycoprotein was long; no significant loss of P-glycoprotein was observed within 24 h after synthesis. Cells treated with tunicamycin produced a 120 kDa form of P-glycoprotein which was no longer processed but showed stability similar to that of the mature 140-150 kDa form. Agents that reverse multidrug resistance, phorbol ester and transport substrate did not affect the stability of P-glycoprotein.     

The systematic position ofAsplenium cardiophyllum (Aspleniaceae)

Asplenium cardiophyllum is a morphologically unusual species with simple leaves and anastomosing venation, and is often placed in the segregate genusBoniniella. To determine its systematic position, character comparisons were made of vascular anatomy, raphides in leaf epidermis, chromosome number and perispore of this species and those ofAsplenium sect.Hymenasplenium. Asplenium cardiophyllum conforms with sect.Hymenasplenium in its dorsiventral dictyostele, the presence of raphides, a chromosome number of 2n=156 (x=39), and lophate peristore with spinulate projections on the lumina. We therefore propose to includeA. cardiophyllum in that section. Dedicated to the memory of the late Professor Kunio Mitui.     

Structural heterogeneity regarding local Shwartzman activity of lipid A

The relation of chemical structure to local Shwartzman activity of lipid A preparations purified by thin-layer chromatography from five bacterial strains was examined. Two lipid A fractions from E. coli F515--Ec-A2 and Ec-A3--exhibited strong activity, similar to that of previous synthetic E. coli-type lipid A (compound 506 or LA-15-PP). The Ec-A3 fraction contained a component that appeared to be structurally identical to compound 506, and the main component of Ec-A2 fraction was structurally similar to compound 506 except that it carried a 3-hydroxytetradecanoyl group at the C-3' position of the backbone in place of a 3-tetradecanoyloxytetradecanoyl group. Free lipid A (12 C) and purified lipid A fractions, Ec-A2 (12 C) and Ec-A3 (12 C), respectively, obtained from bacteria grown at 12 C, exhibited activity comparable to Ec-A2 or Ec-A3. In these preparations, a large part of the 3-dodecanoyloxytetradecanoyl group might be replaced by 3-hexadecenoyloxytetradecanoyl group. Salmonella minnesota R595 free lipid A also contained at least two active lipid A components as seen in E. coli lipid A, but the third component corresponding to the synthetic Salmonella-type lipid A (compound 516 or LA-16-PP) exhibited low activity. A lipid A fraction, Cv-A4 from Chromobacterium violaceum IFO 12614, which was proposed to have two acyloxyacyl groups at the C-2 and C-2' positions with other acyl groups, exhibited weaker activity than the free lipid A or LPS. The purified lipid A fractions from Pseudomonas diminuta JCM 2788 and Pseudomonas vesicularis JCM 1477 contained an unusual backbone with 2,3-diamino-2,3-dideoxy-D-glucose disaccharide phosphomonoester, and these lipid A (Pd-A3 and Pv-A3) exhibited strong activity comparable to the E. coli lipid A. Thus, the present results show that the local Shwartzman reaction can be expressed by partly different lipid A structures in both hydrophilic backbone and fatty acyl residues; when they have the same backbone the potency varies markedly depending on the structure of the acyl residues.     

The effects of guanine and cytosine variation on dinucleotide frequency and amino acid composition in the human genome

Summary One hundred twelve human DNA sequences were analyzed with respect to dinucleotide frequency and amino acid composition. The variation in guanine and cytosine (G+C) content revealed: (1) at 2–3 and 3-1 doublet positions CG discrimination is attenuated at high G+C, but TA disfavor is enhanced, and (2) several amino acids are subject to G+C change. These findings have been reported in part for collections of sequences from various species. The present study confirms that in a single organism-the human-the G+C effects do exist. Aspects of the argument that connects G+C with protein thermal stability are also discussed.