Starch Synthesis in Potato Tubers Is Regulated by Post-Translational Redox Modification of ADP-Glucose Pyrophosphorylase: A Novel Regulatory Mechanism Linking Starch Synthesis to the Sucrose Supply

Transcriptional and allosteric regulation of ADP-Glc pyrophosphorylase (AGPase) plays a major role in the regulation of starch synthesis. Analysis of the response after detachment of growing potato tubers from the mother plant revealed that this concept requires extension. Starch synthesis was inhibited within 24 h of tuber detachment, even though the catalytic subunit of AGPase (AGPB) and overall AGPase activity remained high, the substrates ATP and Glc-1-P increased, and the glycerate-3-phosphate/inorganic orthophosphate (the allosteric activator and inhibitor, respectively) ratio increased. This inhibition was abolished in transformants in which a bacterial AGPase replaced the potato AGPase. Measurements of the subcellular levels of each metabolite between Suc and starch established AGPase as the only step whose substrates increase and mass action ratio decreases after detachment of wild-type tubers. Separation of extracts on nonreducing SDS gels revealed that AGPB is present as a mixture of monomers and dimers in growing tubers and becomes dimerized completely in detached tubers. Dimerization led to inactivation of the enzyme as a result of a marked decrease of the substrate affinity and sensitivity to allosteric effectors. Dimerization could be reversed and AGPase reactivated in vitro by incubating extracts with DTT. Incubation of tuber slices with DTT or high Suc levels reduced dimerization, increased AGPase activation, and stimulated starch synthesis in vivo. In intact tubers, the Suc content correlated strongly with AGPase activation across a range of treatments, including tuber detachment, aging of the mother plant, heterologous overexpression of Suc phosphorylase, and antisense inhibition of endogenous AGPase activity. Furthermore, activation of AGPase resulted in a stimulation of starch synthesis and decreased levels of glycolytic intermediates

Sugar-induced increases in trehalose 6-phosphate are correlated with redox activation of ADPglucose pyrophosphorylase and higher rates of starch synthesis in Arabidopsis thaliana

Tre6P (trehalose 6-phosphate) is implicated in sugar-signalling pathways in plants, but its exact functions in vivo are uncertain. One of the main obstacles to discovering these functions is the difficulty of measuring the amount of Tre6P in plant tissues. We have developed a highly specific assay, using liquid chromatography coupled to MS-Q3 (triple quadrupole MS), to measure Tre6P in the femto-picomole range. The Tre6P content of sucrose-starved Arabidopsis thaliana seedlings in axenic culture increased from 18 to 482 pmol·g(−1)FW (fresh weight) after adding sucrose. Leaves from soil-grown plants contained 67 pmol·g(−1)FW at the end of the night, which rose to 108 pmol·g(−1)FW after 4 h of illumination. Even greater changes in Tre6P content were seen after a 6 h extension of the dark period, and in the starchless mutant, pgm. The intracellular concentration of Tre6P in wild-type leaves was estimated to range from 1 to 15 μM. It has recently been reported that the addition of Tre6P to isolated chloroplasts leads to redox activation of AGPase (ADPglucose pyrophosphorylase) [Kolbe, Tiessen, Schluepmann, Paul, Ulrich and Geigenberger (2005) Proc. Natl. Acad. Sci. U.S.A. 102, 11118–11123]. Using the new assay for Tre6P, we found that rising sugar levels in plants are accompanied by increases in the level of Tre6P, redox activation of AGPase and the stimulation of starch synthesis in vivo. These results indicate that Tre6P acts as a signalling metabolite of sugar status in plants, and support the proposal that Tre6P mediates sucrose-induced changes in the rate of starch synthesis

Prophylactic antibiotics reduce hospitalisations and cost in locally advanced head and neck cancer patients treated with chemoradiotherapy: A randomised phase 2 study

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Emotional functioning during bereavement after the death of patients with advanced cancer and associated factors

Objective: The death of a loved one is considered to be the most stressful of all life events. However, the impact of bereavement on quality of life varies between individuals. The aim of our study was to assess emotional functioning (EF), which is a domain of quality of life, of bereaved relatives after the death of their loved one and its associated factors. Method: A prospective, longitudinal, multicenter, observational study on quality of care and quality of life of patients with advanced cancer and their relatives was conducted (eQuiPe). The association between EF of relatives during bereavement and the following factors was investigated: gender, type of relationship, educational level, pre-bereavement emotional and social functioning and global quality of life, social support pre- and during bereavement, anticipatory complicated grief, support of healthcare professionals during bereavement, age of patient and bereaved relative and duration of survival after primary cancer diagnosis. Results: 150 bereaved relatives completed the bereavement questionnaire. In 41% of the bereaved relatives EF was ≤71, indicating clinically relevant low EF. Multivariable logistic regression showed that females experienced more often emotional problems (OR = 2.82). Emotional functioning pre-bereavement (OR = 0.96) and social support during bereavement (OR = 0.97) were associated with low EF during bereavement. Conclusions: Almost half of the bereaved relatives of patients with advanced cancer experienced low EF and this was associated with low EF pre-bereavement and low social support during bereavement. Support for relatives should be initiated before the patient's death. Future research is needed to investigate the impact of such support on relatives' wellbeing during bereavement

Emotional functioning during bereavement after the death of patients with advanced cancer and associated factors

Objective The death of a loved one is considered to be the most stressful of all life events. However, the impact of bereavement on quality of life varies between individuals. The aim of our study was to assess emotional functioning (EF), which is a domain of quality of life, of bereaved relatives after the death of their loved one and its associated factors. Method A prospective, longitudinal, multicenter, observational study on quality of care and quality of life of patients with advanced cancer and their relatives was conducted (eQuiPe). The association between EF of relatives during bereavement and the following factors was investigated: gender, type of relationship, educational level, pre-bereavement emotional and social functioning and global quality of life, social support pre- and during bereavement, anticipatory complicated grief, support of healthcare professionals during bereavement, age of patient and bereaved relative and duration of survival after primary cancer diagnosis. Results 150 bereaved relatives completed the bereavement questionnaire. In 41% of the bereaved relatives EF was ≤71, indicating clinically relevant low EF. Multivariable logistic regression showed that females experienced more often emotional problems (OR = 2.82). Emotional functioning pre-bereavement (OR = 0.96) and social support during bereavement (OR = 0.97) were associated with low EF during bereavement. Conclusions Almost half of the bereaved relatives of patients with advanced cancer experienced low EF and this was associated with low EF pre-bereavement and low social support during bereavement. Support for relatives should be initiated before the patient's death. Future research is needed to investigate the impact of such support on relatives' wellbeing during bereavement