Adaptive responses of wild mungbean (Vigna radiata ssp sublobata) to photo-thermal environment. II. Growth, biomass, and seed yield

The leaf growth, dry matter production, and seed yield of 11 wild mungbean ( Vigna radiata ssp. sublobata) accessions of diverse geographic origin were observed under natural and artificial photoperiod temperature conditions, to determine the extent to which genotypic differences could be attributed to adaptive responses to photo-thermal environment. Environments included serial sowings in the field in SE Queensland, complemented by artificial photoperiod extension and controlled-environment growth rooms. Photo-thermal environment influenced leaf growth, total dry matter production ( TDM), and seed yield directly, through effects of ( mainly cool) temperature on growth, and indirectly, through effects on phenology. In terms of direct effects, leaf production, leaf expansion, and leaf area were all sensitive to temperature, with implied base temperatures higher than usually observed in cultivated mungbean ( V. radiata ssp. radiata). Genotypic sensitivity to temperature varied systematically with accession provenance and appeared to be of adaptive significance. In terms of the indirect effects of photo-thermal environment, genotypic and environmental effects on TDM were positively related to changes in total growth duration, and harvest index was negatively related to the period from sowing to flowering, similar to cultivated mungbean. However, seed yield was positively related to the duration of reproductive growth, reflecting the indeterminate growth habit of the wild accessions. As a consequence, the wild accessions are more responsive to favourable environments than typically observed in cultivated mungbean, which is determinate in habit. It is suggested that the introduction of the indeterminate trait into mungbean from the wild subspecies would increase the responsiveness of mungbean to favourable environments, analogous to that of black gram ( V. mungo). Although the wild subspecies appeared more sensitive to cool temperature than cultivated mungbean, it may provide a source of tolerance to the warmer temperatures experienced during the wet season in the tropics.

Ataxia-telangiectasia: chronic activation of damage-responsive functions is reduced by alpha-lipoic acid

Cells from patients with the genetic disorder ataxia-telangiectasia (A-T) are hypersensitive to ionizing radiation and radiomimetic agents, both of which generate reactive oxygen species capable of causing oxidative damage to DNA and other macromolecules. We describe in A-T cells constitutive activation of pathways that normally respond to genotoxic stress, Basal levels of p53 and p21(WAF1/CIP1), phosphorylation on serine 15 of p53, and the Tyr15-phosphorylated form of cdc2 are chronically elevated in these cells. Treatment of A-T cells with the antioxidant alpha -lipoic acid significantly reduced the levels of these proteins, pointing to the involvement of reactive oxygen species in their chronic activation. These findings suggest that the absence of functional ATM results in a mild but continuous state of oxidative stress, which could account for several features of the pleiotropic phenotype of A-T.

Developing biodegradable mulch films from starch-based polymers

This paper examines the development of starch-based plastics for use as biodegradable mulch film. A variety of starch-based polymers are blended with high performance biodegradable polyester polymers in order to determine the applicability of films to be processed on a film blowing line and to perform well in mulch film field trials. The process of material formulation, film blowing processing and scale-up and performance properties are highlighted for a successful material. Insights into future developments of starch-derived biodegradable polymers are given.

Spermine modulation of the glutamate(NMDA) receptor is differentially responsive to conantokins in normal and Alzheimer's disease human cerebral cortex

The pharmacology of the N -methyl-d-aspartate (NMDA) receptor site was examined in pathologically affected and relatively spared regions of cerebral cortex tissue obtained at autopsy from Alzheimer's disease cases and matched controls. The affinity and density of the [H-3]MK-801 binding site were delineated along with the enhancement of [H-3]MK-801 binding by glutamate and spermine. Maximal enhancement induced by either ligand was regionally variable; glutamate-mediated maximal enhancement was higher in controls than in Alzheimer's cases in pathologically spared regions, whereas spermine-mediated maximal enhancement was higher in controls in areas susceptible to pathological damage. These and other data suggest that the subunit composition of NMDA receptors may be locally variable. Studies with modified conantokin-G (con-G) peptides showed that Ala(7)-con-G had higher affinity than Lys(7)-con-G, and also defined two distinct binding sites in controls. Nevertheless, the affinity for Lys(7)-con-G was higher overall in Alzheimer's brain than in control brain, whereas the reverse was true for Ala(7)-con-G. Over-excitation mediated by specific NMDA receptors might contribute to localized brain damage in Alzheimer's disease. Modified conantokins are useful for identifying the NMDA receptors involved, and may have potential as protective agents.