Enhancing beneficial antioxidants in fruits: a plant physiological perspective

The aim of this review is to present an outline of the physiological perspectives of beneficial antioxidant production in fruit. The drive to enhance the consumption of fruit and vegetables in the human diet is linked with positive effects of beneficial antioxidants impacting on health promotion. We briefly outline our physiological understanding of environmental processes which induce the production of reactive oxygen species and how antioxidants prevent plant cellular damage. More specifically, we describe the impact that environmental stresses, such as drought and radiation, have on the production of endogenous antioxidants and how these stresses can be incorporated into novel experimental crop growing systems to achieve high antioxidant concentrations in fruits. This includes in particular the use of irrigation application techniques and enhanced light reflectance to increase the concentrations of bioactive compounds such as ellagic acid and ascorbic acid.     

Magnetic resonance imaging (MRI) as a method for determination of freezing injury in strawberry crowns

In an experiment with controlled freezing, strawberry plants were exposed to 0, ?8, ?12, ?16 and ?20°C at a freeze and thaw rate of 2 °C/hour in March/April 1996. Crowns from the cultivar ‘Korona’ were examined using magnetic resonance imaging (MRI), showing a gradual increase of signal intensity from the centre of the crowns, as a result of the temperature drop, which might be caused by lipids. The increase in signal intensity was in accordance with the tissue browning of crowns, which increased substantially when the temperature dropped below ?12 °C. A similar reaction was shown in a field experiment comparing wintercovered and not wintercovered strawberry plants. The plants which had been exposed to temperatures between ?10 and ?16 °C were severely injured. This demonstrates that MRI has a potential as an objective method to determine freeze injury in the field, by «calibrating» the MRI instrument to freezing profiles in controlled experiments.     

Novel root-fungus symbiosis in Ericaceae: sheathed ericoid mycorrhiza formed by a hitherto undescribed basidiomycete with affinities to Trechisporales

Ericaceae (the heath family) are widely distributed calcifuges inhabiting soils with inherently poor nutrient status. Ericaceae overcome nutrient limitation through symbiosis with ericoid mycorrhizal (ErM) fungi that mobilize nutrients complexed in recalcitrant organic matter. At present, recognized ErM fungi include a narrow taxonomic range within the Ascomycota, and the Sebacinales, basal Hymenomycetes with unclamped hyphae and imperforate parenthesomes. Here we describe a novel type of basidiomycetous ErM symbiosis, termed 'sheathed ericoid mycorrhiza', discovered in two habitats in mid-Norway as a co-dominant mycorrhizal symbiosis in Vaccinium spp. The basidiomycete forming sheathed ErM possesses clamped hyphae with perforate parenthesomes, produces 1- to 3-layer sheaths around terminal parts of hair roots and colonizes their rhizodermis intracellularly forming hyphal coils typical for ErM symbiosis. Two basidiomycetous isolates were obtained from sheathed ErM and molecular and phylogenetic tools were used to determine their identity; they were also examined for the ability to form sheathed ErM and lignocellulolytic potential. Surprisingly, ITS rDNA of both conspecific isolates failed to amplify with the most commonly used primer pairs, including ITS1 and ITS1F + ITS4. Phylogenetic analysis of nuclear LSU, SSU and 5.8S rDNA indicates that the basidiomycete occupies a long branch residing in the proximity of Trechisporales and Hymenochaetales, but lacks a clear sequence relationship (>90% similarity) to fungi currently placed in these orders. The basidiomycete formed the characteristic sheathed ErM symbiosis and enhanced growth of Vaccinium spp. in vitro, and degraded a recalcitrant aromatic substrate that was left unaltered by common ErM ascomycetes. Our findings provide coherent evidence that this hitherto undescribed basidiomycete forms a morphologically distinct ErM symbiosis that may occur at significant levels under natural conditions, yet remain undetected when subject to amplification by 'universal' primers. The lignocellulolytic assay suggests the basidiomycete may confer host adaptations distinct from those provisioned by the so far investigated ascomycetous ErM fungi.     

Morphine-induced increase in D-1 receptor regulated signal transduction in rat striatal neurons and its facilitation by glucocorticoid receptor activation: Possible role in behavioral sensitization

One month (but not 1–3 days) after intermittent morphine administration, the hyperresponsiveness of rats toward the locomotor effects of morphine and amphetamine was associated with an increase in dopamine (DA) D-1 receptor-stimulated adenylyl cyclase activity and enhanced steady state levels of preprodynorphin gene expression in slices of the caudate/putamen and nucleus accumbens. Such an enduring increase in postsynaptic D-1 receptor efficacy also occurred in cultured γ-aminobutyric acid (GABA) neurons of the striatum obtained from rats prenatally treated with morphine. Interestingly, in vitro glucocorticoid receptor activation in these cultured striatal neurons by corticosterone potentiated this neuroadaptive effect of prior in vivo morphine exposure. Since activation of glucocorticoid receptors by corticosterone did not affect D-1 receptor functioning in cultured neurons of saline-pretreated rats, prior intermittent exposure to morphine (somehow) appears to induce a long-lasting state of corticosterone hyperresponsiveness in striatal neurons. Therefore, DA-sensitive striatal GABA neurons may represent common neuronal substrates acted upon by morphine and corticosterone. We hypothesize that the delayed occurrence of these long-lasting morphine-induced neuroadaptive effects in GABA/dynorphin neurons of the striatum is involved in the enduring nature of behavioral sensitization to drugs of abuse and cross-sensitization to stressors. Special issue dedicated to Dr. Eric J. Simon.