5 research outputs found

    Dynamic thylakoid stacking is regulated by LHCII phosphorylation but not its interaction with PSI

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    Grana stacking in plant chloroplast thylakoid membranes dynamically responds to the light environment. These dynamics have been linked to regulation of the relative antenna sizes of PSI and PSII (state transitions), the PSII repair cycle, and the regulation of photosynthetic electron transfer. Here, we used 3D structured illumination microscopy, a subdiffraction-resolution fluorescence imaging technique, to investigate the light-intensity dependence, kinetics, reversibility, and regulation of dynamic thylakoid stacking in spinach (Spinacia oleracea) and Arabidopsis (Arabidopsis thaliana). Low-intensity white light (150 μmol photons m−2 s−1) behaved similarly to light preferentially exciting PSII (660 nm), causing a reduction in grana diameter and an increased number of grana per chloroplast. By contrast, high-intensity white light (1000 μmol photons m−2 s−1), darkness, and light preferentially exciting PSI (730 nm) reversed these changes. These dynamics occurred with a half-time of 7 to 8 min and were accompanied by state transitions. Consistent with this, the dynamics were dependent on STN7 (light-harvesting complex II [LHCII] kinase) and TAP38 (LHCII phosphatase), which are required for state transitions but were unaffected by the absence of STN8 (PSII kinase) or PSII core phosphatase (PSII phosphatase). Unlike state transitions, however, thylakoid stacking dynamics did not rely on the presence of the LHCI and PSI subunit L phospho-LHCII binding sites on PSI. Since oligomerization of thylakoid curvature protein (CURT1A) was unaffected by the absence of STN7 or TAP38, we conclude that the primary determinant of dynamic thylakoid stacking is LHCII phosphorylation

    Lateral Segregation of Photosystem I in Cyanobacterial Thylakoids

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    Photosystem I (PSI) is the dominant photosystem in cyanobacteria and it plays a pivotal role in cyanobacterial metabolism. Despite its biological importance, the native organisation of PSI in cyanobacterial thylakoid membranes is poorly understood. Here, we use atomic force microscopy (AFM) to show that ordered, extensive macromolecular arrays of PSI complexes are present in thylakoids from Thermosynechococcus (T.) elongatus, Synechococcus sp. PCC 7002 and Synechocystis sp PCC 6803. Hyperspectral confocal fluorescence microscopy (HCFM) and three-dimensional structured illumination microscopy (3D-SIM) of Synechocystis sp PCC 6803 cells visualise PSI domains within the context of the complete thylakoid system. Crystallographic and AFM data were used to build a structural model of a membrane landscape comprising 96 PSI trimers and 27,648 chlorophyll a molecules. Rather than facilitating inter-trimer energy transfer the close associations between PSI primarily maximise packing efficiency; short-range interactions with Complex I and cytochrome b6f are excluded from these regions of the membrane, so PSI turnover is sustained by long-distance diffusion of the electron donors at the membrane surface. Elsewhere, PSI-photosystem II (PSII) contact zones provide sites for docking phycobilisomes and the formation of megacomplexes. PSI-enriched domains in cyanobacteria might foreshadow the partitioning of PSI into stromal lamellae in plants, similarly sustained by long-distance diffusion of electron carriers

    Safety of hospital discharge before return of bowel function after elective colorectal surgery

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    Background: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien\u2013Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9\ub72 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4\u20137) and 7 (6\u20138) days respectively (P < 0\ub7001). There were no significant differences in rates of readmission between these groups (6\ub76 versus 8\ub70 per cent; P = 0\ub7499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0\ub790, 95 per cent c.i. 0\ub755 to 1\ub746; P = 0\ub7659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34\ub77 versus 39\ub75 per cent; major 3\ub73 versus 3\ub74 per cent; P = 0\ub7110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients

    Safety of hospital discharge before return of bowel function after elective colorectal surgery

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    © 2020 BJS Society Ltd Published by John Wiley & Sons LtdBackground: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien–Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9·2 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4–7) and 7 (6–8) days respectively (P < 0·001). There were no significant differences in rates of readmission between these groups (6·6 versus 8·0 per cent; P = 0·499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0·90, 95 per cent c.i. 0·55 to 1·46; P = 0·659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34·7 versus 39·5 per cent; major 3·3 versus 3·4 per cent; P = 0·110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients

    Safety and efficacy of non-steroidal anti-inflammatory drugs to reduce ileus after colorectal surgery

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    Background: Ileus is common after elective colorectal surgery, and is associated with increased adverse events and prolonged hospital stay. The aim was to assess the role of non-steroidal anti-inflammatory drugs (NSAIDs) for reducing ileus after surgery. Methods: A prospective multicentre cohort study was delivered by an international, student- and trainee-led collaborative group. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The primary outcome was time to gastrointestinal recovery, measured using a composite measure of bowel function and tolerance to oral intake. The impact of NSAIDs was explored using Cox regression analyses, including the results of a centre-specific survey of compliance to enhanced recovery principles. Secondary safety outcomes included anastomotic leak rate and acute kidney injury. Results: A total of 4164 patients were included, with a median age of 68 (i.q.r. 57\u201375) years (54\ub79 per cent men). Some 1153 (27\ub77 per cent) received NSAIDs on postoperative days 1\u20133, of whom 1061 (92\ub70 per cent) received non-selective cyclo-oxygenase inhibitors. After adjustment for baseline differences, the mean time to gastrointestinal recovery did not differ significantly between patients who received NSAIDs and those who did not (4\ub76 versus 4\ub78 days; hazard ratio 1\ub704, 95 per cent c.i. 0\ub796 to 1\ub712; P = 0\ub7360). There were no significant differences in anastomotic leak rate (5\ub74 versus 4\ub76 per cent; P = 0\ub7349) or acute kidney injury (14\ub73 versus 13\ub78 per cent; P = 0\ub7666) between the groups. Significantly fewer patients receiving NSAIDs required strong opioid analgesia (35\ub73 versus 56\ub77 per cent; P &lt; 0\ub7001). Conclusion: NSAIDs did not reduce the time for gastrointestinal recovery after colorectal surgery, but they were safe and associated with reduced postoperative opioid requirement
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