A proposed role for copper ions in cell wall loosening

The measurement of N₂ fixation by legumes is necessary for gaining an understanding of their contributions to the N economies of agricultural and forestry systems and for their management in those systems. We report research to determine whether N₂ fixation of four of the commonly-grown ureide-producing legumes, soybean (Glycine max), cowpea (Vigna unguiculata), mungbean (V. radiata) and black gram (V. mungo), could be quantified from a single sampling and N-solute analysis of xylem sap. Data were derived from a previously-published experiment involving six genotypes of soybean at five field sites and from a second, irrigated experiment in which two genotypes of soybean, and one each of cowpea, mungbean and black gram were assessed in low- and high-nitrate soils for nodulation, yields of shoot and grain dry matter and N, and N₂ fixation using xylem solute (ureide) and ¹⁵N methods. Regression analysis of the published soybean data set indicated that the early pod-fill (R3.5 and R4) samplings for xylem sap gave estimates of percentage of plant N derived from N₂ fixation (%Ndfa) which agreed well with %Ndfa for the entire growing season obtained from ¹⁵N analysis of the shoots at R6-7. There was a marginal benefit in combining the R3.5 and R4 samplings and using the average of the two, with regression coefficients (r ²) increasing from 0.86 (R3.5 or R4 alone) to 0.92 (average of R3.5+R4). There was no additional benefit in combining R3, R3.5 and R4. In the second experiment, agreement between ¹⁵N-determined %Ndfa and either measured (R4 sampling) or calculated ureide-determined %Ndfa (R3.5 sampling) was also good (r ² of 0.73 (R4) and 0.79 (R3.5)). We conclude that seasonal %Ndfa can be accurately estimated using the xylem solute (ureide) method from a single sampling of xylem sap during early pod-fill (R3.5) and that this simplification of the protocol of the technique may encourage expanded use.     

The effects of care bundles on patient outcomes: a systematic review and meta-analysis

Background

Care bundles are a set of three to five evidence-informed practices performed collectively and reliably to improve the quality of care. Care bundles are used widely across healthcare settings with the aim of preventing and managing different health conditions. This is the first systematic review designed to determine the effects of care bundles on patient outcomes and the behaviour of healthcare workers in relation to fidelity with care bundles.

Methods

This systematic review is reported in line with the PRISMA statement for reporting systematic reviews and meta-analyses. A total of 5796 abstracts were retrieved through a systematic search for articles published between January 1, 2001, to February 4, 2017, in the Cochrane Central Register for Controlled Trials, MEDLINE, EMBASE, British Nursing Index, CINAHL, PsychInfo, British Library, Conference Proceeding Citation Index, OpenGrey trials (including cluster-randomised trials) and non-randomised studies (comprising controlled before-after studies, interrupted time series, cohort studies) of care bundles for any health condition and any healthcare settings were considered. Following the removal of duplicated studies, two reviewers independently screen 3134 records. Three authors performed data extraction independently. We compared the care bundles with usual care to evaluate the effects of care bundles on the risk of negative patient outcomes. Random-effect models were used to further explore the effects of subgroups.

Results

In total, 37 studies (6 randomised trials, 31 controlled before-after studies) were eligible for inclusion. The effect of care bundles on patient outcomes is uncertain. For randomised trial data, the pooled relative risk of negative effects between care bundle and control groups was 0.97 [95% CI 0.71 to 1.34; 2049 participants]. The relative risk of negative patient outcomes from controlled before-after studies favoured the care bundle treated groups (0.66 [95% CI 0.59 to 0.75; 119,178 participants]). However, using GRADE, we assessed the certainty of all of the evidence to be very low (downgraded for risk of bias, inconsistency, indirectness).

Conclusions

Very low quality evidence from controlled before-after studies suggests that care bundles may reduce the risk of negative outcomes when compared with usual care. By contrast, the better quality evidence from six randomised trials is more uncertain.

Trial registration

PROSPERO, CRD42016033175

     

Solubilisation of tomato fruit pectins by ascorbate: a possible non-enzymic mechanism of fruit softening

The aim of this work was to test the hypothesis that endogenous ascorbate, released into the apoplast by membrane permeabilisation early in fruit ripening, could promote the solubilisation and depolymerisation of polysaccharides, and thus contribute to fruit softening. In vitro, ascorbate (1 mM), especially in the presence of traces of either Cu²⁺ or H₂O₂, solubilised up to 40% of the total pectin from the alcohol-insoluble residue of mature-green tomato (Lycopersicon esculentum Mill.) fruit. Solubilisation was due to the action of ascorbate-generated hydroxyl radicals (^·OH), which can cause non-enzymic scission of polysaccharides. The pectins solubilised by ascorbate in vitro were polydisperse (4–1,000 kDa), partially esterified and galactose-rich. Excised pieces of living tomato fruit released ascorbate into the medium (apoplast); the ability of different tissues to do this increased in the order pericarp < placenta < locule. In all three tissues, but especially in the locule, the ability to release ascorbate increased during ripening. The Cu content of each tissue also increased during ripening, whereas neither Fe nor Mn showed a similar trend. We suggest that progressively increasing levels of Cu and ascorbate in the fruit apoplast would lead to elevated ^·OH production there and thus to non-enzymic scission of pectins during ripening. Such scission could contribute to the natural softening of the fruit. De-esterified citrus pectin was more susceptible to ascorbate-induced scission in vitro than methylesterified pectin, suggesting a possible new significance for pectin methylesterase activity in fruit ripening. In conclusion, non-enzymic mechanisms of fruit softening should be considered alongside the probable roles of hydrolases, xyloglucan endotransglucosylases and expansins.Abbreviations AIR alcohol-insoluble residue - Ara l-arabinose - DMSO dimethylsulphoxide - endo-PG endo-polygalacturonase - Gal d-galactose - GalA d-galacturonic acid - Glc d-glucose - k_·OH rate constant for reaction with the hydroxyl radical - K_av elution from Sepharose column relative to the void volume (K_av=0.0) and totally included volume (K_av=1.0) - MG mature-green - PME pectin methylesterase - Rha l-rhamnose - RR red-ripe     

Gentiobiose: a novel oligosaccharin in ripening tomato fruit

Two neutral disaccharides, gentiobiose [beta- D-Glc p-(1-->6)- D-Glc] and nigerose [alpha- D-Glc p-(1-->3)- D-Glc], were detected in tomato ( Lycopersicon esculentum Mill.) pericarp and locule. Gentiobiose was present in the locule of green fruit and ripe fruit at 0.88 and 5.8 micro mol (kg fresh weight)(-1), respectively. When vacuum-infiltrated into green tomato fruit, exogenous gentiobiose (50 or 200 micro g per fruit) hastened the initiation of ripening (as judged by colour change) by 1-3 days relative to fruit that were infiltrated with glucose or isomaltose. Nigerose plus gentiobiose was particularly effective, but nigerose alone had no significant effect. The endogenous disaccharides were found to be present in the apoplastic fluid of the fruit, compatible with a proposed intercellular signalling role. The origin and metabolic fate of the disaccharides were investigated. Phenolic esters of these disaccharides were not detectable in tomato fruit and it is therefore unlikely that the free disaccharides were formed from a pool of such esters. An alternative possible biosynthetic origin, via transglycosylation, is discussed. When [(14)C]gentiobiose was vacuum-infiltrated into unripe or ripe fruit, the disaccharide remained intact for at least 1 h but was largely degraded within 24 h. The results suggest that gentiobiose is a new, naturally occurring oligosaccharin with a rapid turnover rate.     

A pilot randomised controlled trial of negative pressure wound therapy to treat grade III/IV pressure ulcers [ISRCTN69032034

ABSTRACT: BACKGROUND: Negative pressure wound therapy (NPWT) is widely promoted as a treatment for full thickness wounds, however there is a lack of high-quality research evidence regarding its clinical and cost effectiveness. A trial of NPWT for the treatment grade III/IV pressure ulcers would be worthwhile but premature without assessing whether such a trial is feasible. The aim of this pilot randomised controlled trial was to assess the feasibility of conducting a future full trial of NPWT for the treatment of grade III and IV pressure ulcers and to pilot all aspects of the trial. METHODS: This was a two centre (acute and community), pilot randomised controlled trial. Eligible participants were randomised to receive either NPWT or Standard Care (SC) (spun hydrocolloid, alginate or foam dressings). The primary outcome measure was time to healing of the reference pressure ulcer. Secondary outcome measures included recruitment rates, frequency of treatment visits, resources used and duration of follow-up. RESULTS: 312 patients were screened for eligibility into this trial over a 12-month recruitment period and 12/312 participants (3.8%) were randomised; six to NPWT and six to SC. Only one reference pressure ulcer healed (NPWT group) during follow up (time to healing 79 days). The mean number of treatment visits per week was 3.1 (NPWT) and 5.7 (SC). 6/6 TNP and 1/6 SC participants withdrew from their allocated trial treatment. The mean duration of follow-up was 3.8 (NPWT) and 5.0 (SC) months. CONCLUSIONS: This pilot trial yielded vital information for the planning of any future full study including a projected recruitment rate, required duration of follow up and extent of research nurse support required. Data were also used to inform cost-effectiveness and value of information analyses which were conducted alongside the pilot trial.