Direct Comparison of Leaf Plasmodesma Structure and Function in Relation to Phloem-Loading Type.

The export of photosynthetically produced sugars from leaves depends on plasmodesmatal transport of sugar molecules from mesophyll to phloem. Traditionally, the density of plasmodesmata (PD) along this phloem-loading pathway has been used as a defining feature of different phloem-loading types, with species proposed to have either many or few PD between the phloem and surrounding cells of the leaf. However, quantitative determination of PD density has rarely been performed. Moreover, the structure of PD has not been considered, even though it could impact permeability, and functional data are only available for very few species. Here, a comparison of PD density, structure, and function using data from transmission electron microscopy and live-cell microscopy was conducted for all relevant cell-cell interfaces in leaves of nine species. These species represent the three principal phloem-loading types currently discussed in literature. Results show that relative PD density among the different cell-cell interfaces in one species, but not absolute PD density, is indicative of phloem-loading type. PD density data of single interfaces, even combined with PD diameter and length data, did not correlate with the intercellular diffusion capacity measured by the fluorescence loss in photobleaching method. This means that PD substructure not visible on standard transmission electron micrographs may have a strong influence on permeability. Furthermore, the results support a proposed passive symplasmic loading mechanism in the tree species horse chestnut (Aesculus hippocastanum), white birch (Betula pubescens), orchard apple (Malus domestica), and gray poplar (Populus x canescens) as functional cell coupling and PD structure differed from active symplasmic and apoplasmic phloem-loading species.

Effect of mindfulness-based stress reduction on sleep quality: results of a randomized trial among Danish breast cancer patients.

UNLABELLED: The prevalence of sleep disturbance is high among cancer patients, and the sleep problems tend to last for years after the end of treatment. As part of a large randomized controlled clinical trial (the MICA trial, NCT00990977) of the effect of mindfulness-based stress reduction (MBSR) on psychological and somatic symptoms among breast cancer patients, the aim of the current study was to evaluate the effect of MBSR on the secondary outcome, 'sleep quality'. MATERIAL AND METHODS: A total of 336 women operated on for breast cancer stage I-III 3-18 months previously were randomized to MBSR (n = 168) or treatment as usual (n = 168); both groups received standard clinical care. The intervention consisted of an eight-week MBSR program (psycho-education, meditation and gentle yoga). Sleep quality was assessed on the Medical Outcome Study sleep scale at baseline, after the intervention and at six- and 12-months' follow-up. RESULTS: The mean sleep problem scores were significantly lower in the MBSR group than in controls immediately after the intervention. Quantile regression analyses showed that the effect was statistically significant only for the participants represented by the lower percentile of change between baseline and post-intervention, i.e. those who had more sleep problems; the MBSR group had a significantly smaller increase in sleep problems than the control group. After the 12-month follow-up, there was no significant between-group effect of MBSR on sleep quality in intention-to-treat analyses. CONCLUSION: MBSR had a statistically significant effect on sleep quality just after the intervention but no long-term effect among breast cancer patients. Future trials in which participation is restricted to patients with significant sleep problems are recommended for evaluating the effect of MBSR on sleep quality.