The biochemical and ultrastructural effects of tunicamycin and D-glucosamine in L1210 leukemic cells

Tunicamycin was found to specifically inhibit the incorporation of a number of sugars into L1210 leukemia cell glycoproteins. This inhibition of glyco-protein biosynthesis led to a cessation of cell growth which was reversible in a dose-dependent and time-dependent manner. After removal of the antibiotic from L1210 cell cultures resumption of sugar incorporation preceded that of thymidine incorporation and the recovery of cell growth. The treatment of cells with tunicamycin resulted in a significant increase in the intracellular pool of UDP-N-acetylglucosamine which occurred concurrently with alterations in cell ultrastructure including distentions of the endoplasmic reticulum and nuclear membranes. Similar ultrastructural changes and increases in the intracellular pools of UDP-sugars were observed in L1210 cells exposed to 5 mM D-glucosamine, which suggested that the antiproliferative effects of tunicamycin may be related to the accumulation in the endoplasmic reticulum of one or more nucleotide sugar precursors of asparagine-linked glycoprotein biosynthesis. However, the biological effects of tunicamycin could be distinguished from those caused by D-glucosamine. Exposure of L1210 cells to tunicamycin resulted in specific alterations in the biochemical composition of the plasma membrane and in the inhibition of cellular agglutination by wheat germ agglutinin which were not apparent following exposure to equitoxic concentrations of the aminosugar. These studies, together with those which demonstrated that recovery of the cellular capacity to synthesize glycoproteins was obligatory for the recovery of cellular proliferation in tunicamycin-treated cells, suggested that inhibition of the synthesis of glycoproteins was the major factor limiting L1210 leukemic cell proliferation.     

Schistosoma mansoni adult microsomal antigens, a serologic reagent. I. Systematic fractionation, quantitation, and characterization of antigenic components

A systematic and quantitative search was conducted to identify and isolate a serologically pertinent antigen with high specific activity and low cross-reactivity from adult worms of Schistosoma mansoni. Adult worms of S. mansoni quickly thawed from liquid N2 temperatures were disrupted by controlled homogenization in isotonic buffered sucrose. Differential centrifugation of the homogenate yielded three particulate and one soluble fractions: the 480 x G pellet (nuclear), the 7650 x G pellet (mitochondrial), the 360,000 x G pellet (microsomal), and the 360,000 x G supernatant (cytosol). Quantitative analysis indicated a major concentration of specific antigenic activities in the microsomal fraction. Further purifications of the urea-solubilized, n-butanol-treated microsomal particles by gel filtration and ionic-exchange chromatography resulted in a microsomal antigen (MAMA) possessing high specific activity and low cross-reactivity. The final purification post-ionic exchange chromatograph showed a 30-fold increase of specific antigen activity over that of the cytosol fraction. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunotransfer blot by the "Western blot" technique (EITB) indicated specific antigenic activities in association with several different m.w. bands (heterogeneous m.w. by extrapolation = 4.3 to 11.9 x 10(6), 2.0 x 10(5), and 2.0 x 10(4) daltons) of the MAMA fraction. When compared with other reported serologic antigens, MAMA showed substantially higher specific activity and lower cross-reactivity.     

A dihedral angle-vicinal proton coupling constant correlation for the α–β bond of amino acid residues

A coupling constant-dihedral angle correlation for the H? Cα? Cβ? H system of amino acid residues in peptides has been derived from a set of model compounds covering the full range of dihedral angles. The expression obtained, J = 11.0 cos₂ θ ?1.4 cos θ + 1.6 sin₂θ, is close to those already used in pmr studies of peptide conformation, and provides a firmer foundation for them. A factor limiting the precision of this and other “Karplus relations” is illustrated.     

IS SUICIDE PREVENTABLE?

Among 500 cases of suicide analyzed in Stockholm, fewer than a third were associated with depression. Most forms of psychiatric disease were represented. Nevertheless, most persons give some warning before attempting suicide, and these warnings should be the signal for preventive action. Centers with trained personnel could prevent many suicides, if the potential victims were recognized and referred early enough. Laymen too should be educated to recognize potential suicide and help avert it.     

Allescheria boydii and Aspergillus fumigatus Skin Test Antigens

May, Lewis K. (Woman's Medical College of Pennsylvania, Philadelphia), Ralph A. Knight, and H. William Harris. Allescheria boydii and Aspergillus fumigatus skin test antigens. J. Bacteriol. 91:2155-2157. 1966.-Protein and polysaccharide fractions were extracted from culture filtrates of Allescheria boydii and Aspergillus fumigatus by the methods of Seibert and of Heidelberger, and injected intradermally into guinea pigs previously infected with these fungi. The diameter of erythema and induration was determined at 8, 24, and 48 hr. The protein and polysaccharide antigens yielded specific skin reactions in homologously infected guinea pigs. Erythema appeared at 8 hr with both the protein and polysaccharide antigens. At this time, the polysaccharide skin tests showed erythema and a central blanched wheal. A similar wheal was not observed with the protein. The erythema of the polysaccharide reaction began fading at 24 hr, whereas the protein reaction remained unchanged through 48 hr with both antigens. In guinea pigs, the area of erythema was more constant and thus easier to measure than was induration.