A radiometric technique for the measurement of adenylosuccinate lyase

When radioactive adenylsuccinic acid (AMP-S) is metabolized to AMP and fumaric acid by the enzyme adenylsuccinate lyase (EC 4.3.2.2), a proton is released to the solvent as ³H₂O. This removal is believed to be stereospecifically identical to that catalyzed by the enzyme, l-aspartase [1–5], and therefore entails the loss of a proton from C-3 of the dicarboxylic acid moiety of the nucleotide. Advantage has been taken of this fact in the design of a facile assay for this enzyme. Adenylosuccinic acid, tritiated on C-2 and C-3 of the l-aspartase moiety, is prepared by chemical synthesis. This product is purified, lyophilized to dryness and reconstituted in a solution of unlabelled AMP-S, bringing the final concentration to 5·10^?3 M, and the final specific activity to 8.0 μCi/mol. 5-μl aliquots of this substrate are then incubated at 37°C with 5-μl aliquots of tissue extract; after an appropriate period, any tritium released to the solvent water is distilled at room temperature overnight into a 5 μl droplet of saturated aqueous KOH adherent to the lid of the sealed reaction vessel. The lid is removed and tritium thereon is measured by scintillation spectrometry. The assay, performed as prescribed, is facile, in that it permits the simultaneous estimation of the lyase activity in a large battery of samples, is not interfered with by opalescent or proteinaceous suspensions, is accurate and outstandingly sensitive.     

A novel form of vitamin B-12 and its derivatives

A new isomeric form of cobalamins is reported. The conversion of cobalamin to cobalamin′ (the new form) is achieved by substituting the benzimidazole base by a less bulky group like H₂O of CN^? and modest thermal treatment. The back conversion of adenosylcobalamin′ to the corresponding regular form occurs in the ‘base-off’ form at room temperature. It seems that the corrin ring becomes quite flexible in the ‘base-off’ form and the freer axial movement of the cobalt atom flips the corrin ring into a different conformation. The change in conformation is borne out by subtle changes in the proton magnetic resonances on the corrin ring and the base, and very marked variation in the emission Mössbauer spectra. The latter is indicative of appreciable changes in the spatial conformation in the immediate vicinity of the central metal atom.The ultraviolet-visible and infrared spectra of a cobalamin′ are indistinguishable from those of its corresponding regular form.The new conformational isomeric species is present as an impurity in all commercially available cobalamins (including pharmaceutical preparations). It raises the question whether the cobalamins′ constitute the real biologically active anti-anemic factor in humans     

Promotive effect of polyvinylpolypyrrolidone on pollen embryogenesis in Datura innoxia

Pollen embryos of Datura innoxia Mill are produced in larger numbers from anthers on agar-gelled medium containing polyvinylpolypyrrolidone than on control. The best response is observed with 0.5% polyvinylpolypyrrolidone. The effect is possibly due to adsorption of substances (phenolics) emanating from cultured anthers and inhibiting the development of pollen grains into embryos.     

Emerging Molecular Strategies for Improving Rice Drought Tolerance

Rice occupies a pre-eminent position as a food crop in the world. Its production, how- ever, entails up to 3000 liters of water per kilogram of grain produced. Such high demand makes rice prone to drought easily. Sustainable rice cultivation with limited water resources requires the deployment of a suitable strategy for better water use efficiency and improved drought tolerance. Several drought-related genes have been evaluated in rice for their mode of action in conferring drought tolerance. Manipulation of components of abscisic acid signal transduction, stomatal density, deposition of cuticular wax, and protein modification pathways are emerging as priority targets. Gene reprogramming by microRNAs is also being explored to achieve drought tolerance. Genetically dissected Quantitative Trait Loci (QTLs) and their constituent genes are being deployed to develop drought-tolerant rice varieties. Progressive research and challenges include a better understanding of crucial components of drought response and search for new targets and the deployment of improved varieties in the field.     

Intimal redox stress: Accelerated atherosclerosis in metabolic syndrome and type 2 diabetes mellitus. Atheroscleropathy

Metabolic syndrome, insulin resistance, prediabetes, and overt type 2 diabetes mellitus are associated with an accelerated atherosclerosis (atheroscleropathy). This quartet is also associated with multiple metabolic toxicities resulting in the production of reactive oxygen species. The redox stress associated with these reactive oxygen species contribute to the development, progression, and the final fate of the arterial vessel wall in prediabetic and diabetic atheroscleropathy. The prevention of morbidity and mortality of these intersecting metabolic diseases can be approached through comprehensive global risk reduction.