Synergistic effects of the myc and ras oncogenes on ganglioside synthesis by BALB/c 3T3 fibroblasts

The effects of oncogene activation on glycosphingolipid (GSL) synthesis by a mouse fibroblast clonal cell line were studied. A transfectant that expressed the activated ras gene showed a definite change in the composition of acidic GSLs, probably an increase in polysialoganglioside, while one that expressed the myc gene showed only a slight change. Neither transfectant grew in soft agar. However, another transfectant, which expressed both the myc and ras genes, and grew in soft agar, showed a more dramatic increase in the acidic GSL component. Thus, activations of the myc and ras oncogenes have a synergistic effect on GSL synthesis during transformation.     

Establishment of a nucleoside-specific suppressor T cell line from SLE prone (NZB/NZW)F1 mice

A long-term cultured suppressor T cell line (GTS-124) was established from an autoimmune mouse strain, (NZB X NZW)F1, by a two-part procedure: a) B/W F1 mice were made tolerant to guanosine (G) by administration of a tolerogen, the G-modified copolymer of D-glutamic acid and D-lysine (G-D-GL); and b) the spleen cells obtained from tolerant mice were repeatedly stimulated with mitomycin C-treated G-modified syngeneic spleen cells. The GTS-124 cells suppressed the secondary in vitro response to G-keyhole limpet hemocyanin (G-KLH) but did not suppress the response to unrelated antigens, sheep erythrocytes (SRBC), or trinitrophenyl-KLH (TNP-KLH). The expression of Thy-1 antigen on the cell surface of GTS-124 was demonstrated by flow cytometry. Growth of GTS-124 cells was dependent on IL 2. To determine whether GTS-124 cells could suppress the response to nucleosides other than G, KLH coupled with four nucleosides (adenosine [A], G, cytidine [C], and thymine riboside [T]) collectively (AGCT-KLH) was first used as the antigen in the assay system. The PFC response to the individual nucleosides (anti-A, -G, -C, and -T PFC) were effectively inhibited by GTS-124 cells, suggesting that the GTS-124 cells mediated cross-suppression toward all four nucleosides. A more stringent cross-suppression test was conducted by using only the T moiety bound to KLH (T-KLH) as antigen. The results showed that GTS-124 cells were capable of suppressing the T-specific response. The cross-suppression could be seen after repeated selection on a G-BSA-coated dish. These results provide direct evidence that the suppressor T cells induced by in vitro stimulation with G-modified self can indeed suppress the response to nucleosides other than G.     

Purification and properties of rat liver globotriaosylceramide synthase, UDP-galactose:lactosylceramide alpha 1-4-galactosyltransferase

The enzyme which catalyzes the transfer of galactose from UDP-galactose to lactosylceramide (LacCer) was obtained in a 32,000-fold purified and apparently homogeneous form from rat liver by a procedure involving affinity chromatography on UDP-hexanolamine-Sepharose and LacCer-Sepharose. The enzyme is composed of two nonidentical subunits whose apparent molecular weights are 65,000 and 22,000. Methylation and hydrolysis of the product formed by incubation of the enzyme with UDP-galactose and [3H]LacCer yielded 2,3,6-tri-O-methyl-[3H]galactose, indicating that a galactose residue was introduced to position C-4 of the terminal galactose of the LacCer. The product also specifically reacted with monoclonal antibody directed to globotriaosylceramide (Gal alpha 1-4Gal beta 1-4Glc beta 1-1Cer). This indicates that the purified enzyme is exclusively alpha 1-4-galactosyltransferase. Studies on substrate specificity indicate that the purified enzyme is highly specific for the synthesis of GbOse3Cer and is clearly distinct from the enzymes responsible for the formation of iGbOse3Cer (Gal alpha 1-3Gal beta 1-4Glc-Cer) and blood group-B substance, which possess alpha 1-3 galactosidic linkages at the nonreducing termini. The enzyme is also distinct from the alpha 1-4-galactosyltransferase which catalyzes the formation of galabiaosylceramide (Gal alpha 1-4Gal beta 1-1Cer) and IV4Gal-nLacOse4 (P1 antigen). These studies represent the first report of the properties of a highly purified alpha-galactosyltransferase catalyzing the transfer of sugar residues to glycolipids.     

Heterophile antibodies to rabbit erythrocytes in human sera and identification of the antigen as a glycolipid

Normal human sera contain heterophile hemagglutinins to rabbit erythrocytes which are different from anti-B isoantibody and other heterophile antibodies such as Hanganutziu-Deicher antibody or Paul-Bunnell antibody. The antigen to this antibody was purified from rabbit erythrocyte stroma, and identified as pentaglycosyl ceramide, Gal(alpha 1-3)Gal(beta 1-4)GlcNAc(beta 1-3)Gal(beta 1-4)Glc-Cer.     

Characterization of N-glycolyneuraminic acid-containing glycosphingolipids from a Marek's disease lymphoma-derived chicken cell line, MSB1, as tumor-associated heterophile Hanganutziu-Deicher antigens

Heterophile, Hanganutziu-Deicher (HD) antigen-active N-glycolylneuraminic acid-containing glycosphingolipids (GSLs) were detected as tumor-associated foreign antigens of a Marek's disease lymphoma-derived cell line, MSB1, by enzyme-immunoassay with chicken antibody against N-glycolylneuraminyl-lactosylceramide (anti-NeuGc-LacCer). At least three species of HD antigen-active GSLs were detected by two-dimensional thin-layer chromatography (TLC) combined with enzyme-immunoassay. The reactivities of the GSLs with anti-NeuGc-LacCer, their behaviors on two-dimensional TLC and the results of an endo-beta-galactosidase digestion study indicated that these three GSLs were NeuGc-LacCer (NeuGc alpha 2-2Gal beta 1-4Glc-Cer), NeuGc-nLcOse4Cer (NeuGc alpha 2-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer) and NeuGc-nLcOse6Cer (NeuGc alpha 2-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer).     

Acceleration of chromosome aberrations in senescence-accelerated strains of mice

Age-related changes in the frequency of chromosome aberrations were examined using bone marrow cells of senescence-accelerated strains of mice (SAM). An accelerated senescence-prone strain, SAM-P/1, showed a striking increase in the frequency of chromosome aberrations, from age 3 to 8 months, whereas an accelerated senescence-resistant strain, SAM-R/1, at the same ages showed only a slight increase. Both these strains were derived from the same ancestral strain (AKR/J). The rate of increase of chromosome aberration frequency paralleled the advancement of senescence in both strains. These observations suggest that there are genetic factors which closely relate to chromosomal instability and acceleration of the senescence processes.     

Congenitally defective aldosterone biosynthesis in humans: the involvement of point mutations of the P-450C18 gene (CYP11B2) in CMO II deficient patients.

The gene for steroid 18-hydroxylase (P-450C18) has been recently assigned to encode corticosterone methyl oxidases Type I and Type II which were previously postulated to catalyze the final two steps in the biosynthesis of aldosterone in humans. Molecular genetic analysis of the P-450C18 gene is three patients from three different families affected with CMO II deficiency has indicated that a point mutation of CGG----TGG (181Arg----Trp) in exon 3 and one of GTG----GCG (386Val----Ala) in exon 7 occur exclusively in the gene of the patients. Analysis of PCR products by restriction enzymes (HapII and HphI) has indicated that the patients are homozygous and the unaffected parent is heterozygous for both mutations, in accordance with the established concept that CMO II deficiency is inherited in an autosomal recessive manner. These data clearly provide the molecular genetic basis for the characteristic biochemical phenotype of CMO II clinical variants.     

Antigen of "serum sickness" type of heterophile antibodies in human sera: indentification as gangliosides with N-glycolylneuraminic acid.

Antigen of “serum-sickness” type of heterophile antibodies in pathologic human sera was purified from equine and bovine erythrocyte stroma. The chemical nature of this antigen was glycosphingolipids with N-glycolylneuraminic acid. The antigen of equine erythrocytes was identified as hematoside with N-glycolylneuraminic acid, GlNeu(α, 2–3)Gal(β, 1–4)Glc(β,1-1) ceramide and the antigen of bovine erythrocytes was N-glycolylneuraminyl-paragloboside, GlNeu (α,2–3)Gal(β,1–4)GlcNAc(β,1–3)Gal(β,1–4)Glc(β,1-1) ceramide. The results indicate that “serum-sickness” antibodies react with a common disaccharide moiety of non-reducing end of the both glycosphingolipids.     

Fluctuations in pulmonary fibrin decomposing activities (plasmin and non-plasmin activities) in an endotoxin DIC model in rats

Non-plasmin fibrinolysis enzyme was extracted from the lung and spleen of conventional rats (Thrombos. Haemostas., 1979), although the enzyme was not found in germfree rats, suggesting the possibility that the enzyme may participate in the defence mechanism of the body. The present study was made in an attempt to determine the behavior of non-plasmin fibrinolysis enzyme of the lung tissue in the DIC model of conventional rats induced by a single injection of bacterial endotoxin. The plasminogen-activator activity of the lung tissue, and the fibrinogen level, platelet count, urea nitrogen and plasminogen-activator activity in the blood were also measured. Examination of the lung tissue in the DIC rats indicated a remarkable increase in non-plasmin fibrinolysis activity and a disappearance of plasminogen-activator activity. Inhibitor studies using t-AMCHA and DFP demonstrated that the increased non-plasmin fibrinolysis activity was not derived from activated plasmin, but from serine protease. The disappearance of plasminogen-activator activity in the lung and increase of plasminogen-activator activity in the blood suggested a release of the activator from the lung into the blood due to the endotoxin injection.     

Isolation and some properties of copper-binding proteins found in a copper-resistant strain of yeast

Copper-binding proteins were extracted from a copper-resistantstrain of Saccharomyces cerevisiae which was obtained by repeatedsubculturing in a copper-containing medium. They were separatedinto three types through purification steps such as salt fractionation,gel filtration and preparative polyacrylamide gel electrophoresis.They resembled each other in amino acid composition. Acidicamino acids, lysine, serine, glycine and half-cystine constituteda large part of the protein, with a small amount of hydrophobicamino acids. Aromatic amino acids and methionine were almostabsent. The molecular weight of the components was estimatedto be about 10,000 by Sephadex gel filtration and electrophoresison polyacrylamide gel (slope method). Absorption spectra ofthe components exhibited a broad band at 275 nm, but none inthe visible region, thus resembling that of copper-thionein.Moreover, the absorption band at 275 nm changed markedly onaddition of Ag⁺, Hg2⁺, CN^– or H₂O₂, which are well knownas thiol reagents. These components were abo produced in theparent cells, if they could grow in a copper-containing medium.Based the results of experiments using various culture conditionsand some other yeast species, a possible role of the componentsis discussed. (Received July 13, 1976; )