Apoptosis: mode of cell death induced in T cell leukemia lines by dexamethasone and other agents

Glucocorticoids can mediate the destruction of thymocytes and T cell-derived leukemia cells through a mechanism known as apoptosis. The characteristic feature of apoptosis is fragmentation of DNA at internucleosomal linkers through the activity of a specific endonuclease. In this study, an attempt was made to compare dexamethasone-induced apoptosis in two T cell-derived human leukemia lines (CEM-C1 and CEM-C7) to the cell killing brought about by selected cytotoxic agents. In the CEM-C7 cell line (dexamethasone-sensitive), apoptosis was induced not only by dexamethasone but by actinomycin D, cycloheximide, and 25-OH cholesterol. In the CEM-C1 cell line (dexamethasone-resistant) cycloheximide, 25-OH cholesterol, or cell starvation could induce apoptosis. It appears that in leukemic cells apoptosis may be induced by a variety of unrelated toxic agents and is not limited to glucocorticoids.     

A novel Z-structure for poly d(GC).poly d(GC)

A novel zig-zag (Z) structure is proposed for poly d(GC).poly d(GC). The proposed model closely resembles the crystal structure of d(CG)₃.     

Isolation and characterisation of cathepsin-B from bovine pancreas

A simple procedure for the isolation of cathepsin-B from bovine pancreas employing ammonium sulphate fractionation, DEAE cellulose chromatography and Sephadex G-200 gel filtration is described. The purified enzyme gave a single band on polyacrylamide gel electrophoresis. The molecular weight as determined by gel filtration of the enzyme was 26,850. ItsK _m andV _max values were 12.8 mM and 0.303 Μmol/min/mg, respectively. TheK _i for iodoacetamide was 0.16 mM.     

A robust KASP marker for selection of four pairs of linked leaf rust and stripe rust resistance genes introgressed on chromosome arm 5DS from different wheat genomes

Molecular Biology Reports - Stripe rust and leaf rust are among the most devastating diseases of wheat, limiting its production globally. Wheat wild relatives harbour genetic diversity for new...     

Xanthomonas sontii sp. nov., a non-pathogenic bacterium isolated from healthy basmati rice (Oryza sativa) seeds from India

Antonie van Leeuwenhoek - We report three yellow-pigmented, Gram-negative, aerobic, rod-shaped, motile bacterial isolates designated as PPL1T, PPL2, and PPL3 from healthy basmati rice seeds....     

Mapping of flag smut resistance in common wheat

Flag smut, caused by Urocystis agropyri, has been a problem in wheat production, but its incidence has declined with the use of resistant varieties and seed dressing. Diamondbird, an Australian wheat cultivar that carries high levels of resistance to flag smut, was crossed with susceptible Chinese landrace TH3929 and a doubled haploid (DH) population was developed. A linkage map comprising 386 markers was used for detection of genomic regions controlling flag smut resistance. Composite interval mapping identified five quantitative trait loci (QTL) with significant effects for flag smut resistance. QTL QFs.sun-3AL, QFs.sun-6AS, QFs.sun-1BL and QFs.sun-5BS were contributed by Diamondbird. Although TH3929 was susceptible, it contributed a minor QTL QFs.sun-3AS. QTL QFs.sun-3AL and QFs.sun-6AS were detected in both seasons and each explained more than 17 % of the variation in flag smut response. Other QTL QFs.sun-3AS, QFs.sun-1BL and QFs.sun-5BS explained 5–10 % of the phenotypic variation. DH lines that showed low flag smut levels carried combinations of three or more QTL. This is the first report on chromosomal location of flag smut resistance in a modern common wheat cultivar.     

Molecular Weight Dependence of Exciton Diffusion in Poly(3‐hexylthiophene)

A joint experimental and theoretical study of singlet exciton diffusion in spin‐coated poly(3‐hexylthiophene) (P3HT) films and its dependence on molecular weight is presented. The results show that exciton diffusion is fast along the co‐facial π–π aggregates of polymer chromophores and about 100 times slower in the lateral direction between aggregates. Exciton hopping between aggregates is found to show a subtle dependence on interchain coupling, aggregate size, and Boltzmann statistics. Additionally, a clear correlation is observed between the effective exciton diffusion coefficient, the degree of aggregation of chromophores, and exciton delocalization along the polymer chain, which suggests that exciton diffusion length can be enhanced by tailored synthesis and processing conditions.     

A Nanosecond Molecular Dynamics Study of Antiparallel d(G)7 Quadruplex Structures: Effect of the Coordinated Cations

Abstract

Nanosecond scale molecular dynamics simulations have been performed on antiparallel Greek key type d(G₇) quadruplex structures with different coordinated ions, namely Na⁺ and K⁺ ion, water and Na⁺ counter ions, using the AMBER force field and Particle Mesh Ewald technique for electrostatic interactions. Antiparallel structures are stable during the simulation, with root mean square deviation values of ～ 1.5 Å from the initial structures. Hydrogen bonding patterns within the G-tetrads depend on the nature of the coordinated ion, with the G-tetrad undergoing local structural variation to accommodate different cations. However, alternating syn-anti arrangement of bases along a chain as well as in a quartet is maintained through out the MD simulation. Coordinated Na+ ions, within the quadruplex cavity are quite mobile within the central channel and can even enter or exit from the quadruplex core, whereas coordinated K⁺ ions are quite immobile. MD studies at 400K indicate that K⁺ ion cannot come out from the quadruplex core without breaking the terminal G-tetrads. Smaller grooves in antiparallel structures are better binding sites for hydrated counter ions, while a string of hydrogen bonded water molecules are observed within both the small and large grooves. The hydration free energy for the K⁺ ion coordinated structure is more favourable than that for the Na⁺ ion coordinated antiparallel quadruplex structure.