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1.
Where does Münch flow begin? Sucrose transport in the pre-phloem path.
Rockwell, FE, Gersony, JT, Holbrook, NM
Current opinion in plant biology. 2018;:101-107
Abstract
Current conceptions of sucrose export largely neglect the effect of transpiration-induced water potential gradients within leaf mesophyll, even as the mix of convection and diffusion in the pre-phloem path remains uncertain. It is also generally held that the relative importance of convection and diffusion in the pre-phloem path is controlled by the ratio of their respective mass transfer coefficients. Here, we consider pre-phloem sucrose transport in the presence of adverse water potential gradients, finding that whether convection impedes or aids sucrose delivery to the phloem is independent of the permeability of the plasmodesmata to bulk flow, and depends only on assimilation rate, path-length, and the diffusivity. For most tissues subject to transpiration, convection through plasmodesmata pushes sugar away from the phloem.
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2.
Biotechnological potential of novel glycoside hydrolase family 70 enzymes synthesizing α-glucans from starch and sucrose.
Gangoiti, J, Pijning, T, Dijkhuizen, L
Biotechnology advances. 2018;(1):196-207
Abstract
Transglucosidases belonging to the glycoside hydrolase (GH) family 70 are promising enzymatic tools for the synthesis of α-glucans with defined structures from renewable sucrose and starch substrates. Depending on the GH70 enzyme specificity, α-glucans with different structures and physicochemical properties are produced, which have found diverse (potential) commercial applications, e.g. in food, health and as biomaterials. Originally, the GH70 family was established only for glucansucrase enzymes of lactic acid bacteria that catalyze the synthesis of α-glucan polymers from sucrose. In recent years, we have identified 3 novel subfamilies of GH70 enzymes (designated GtfB, GtfC and GtfD), inactive on sucrose but converting starch/maltodextrin substrates into novel α-glucans. These novel starch-acting enzymes considerably enlarge the panel of α-glucans that can be produced. They also represent very interesting evolutionary intermediates between sucrose-acting GH70 glucansucrases and starch-acting GH13 α-amylases. Here we provide an overview of the repertoire of GH70 enzymes currently available with focus on these novel starch-acting GH70 enzymes and their biotechnological potential. Moreover, we discuss key developments in the understanding of structure-function relationships of GH70 enzymes in the light of available three-dimensional structures, and the protein engineering strategies that were recently applied to expand their natural product specificities.
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3.
Evolution of Sucrose Metabolism: The Dichotomy of Invertases and Beyond.
Wan, H, Wu, L, Yang, Y, Zhou, G, Ruan, YL
Trends in plant science. 2018;(2):163-177
Abstract
In higher plants, invertases hydrolyze sucrose (Suc), the major end product of photosynthesis, into glucose (Glc) and fructose (Fru), which are used as nutrients, energy sources, and signaling molecules for plant growth, yield formation, and stress responses. The invertase enzymes, named CWINs, VINs, and CINs, are located in the cell wall, vacuole, and cytosol, respectively. We hypothesize, based on their distinctive subcellular locations and physiological roles, that invertases may have undergone different modes during evolution with important functional implications. Here, we provide phylogenetic and functional genomic evidence that CINs are evolutionarily and functionally more stable compared with CWINs and VINs, possibly reflecting their roles in maintaining cytosolic sugar homeostasis for cellular function, and that CWINs have coevolved with the vasculature, likely as a functional component of phloem unloading.
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4.
[Iron-based Phosphate Binders for ESRD Patients].
Cozzolino, M, Mangano, M, Magagnoli, L, Di Lullo, L, Galassi, A, Brancaccio, D, Bellasi, A
Giornale italiano di nefrologia : organo ufficiale della Societa italiana di nefrologia. 2016;(4)
Abstract
Several factors influence the choice of phosphate binder for patients, including older age, male gender, post-menopause, diabetes, low bone turnover, vascular/valvular calcification and inflammation. Unlike calcium-based phosphate binders, non-calcium-based phosphate binders, such as sevelamer and lanthanum carbonate, have been able to reduce the progression of bone disease to adynamic bone among patients with CKD. New iron-based phosphate binders are now available. With multiple options available for the reduction of phosphate, the focus has been on agents that do not contain calcium. This is because it is thought that calcium itself functions as a substrate for calcification.
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5.
Roles of sucrose in guard cell regulation.
Daloso, DM, Dos Anjos, L, Fernie, AR
The New phytologist. 2016;(3):809-18
Abstract
The control of stomatal aperture involves reversible changes in the concentration of osmolytes in guard cells. Sucrose has long been proposed to have an osmolytic role in guard cells. However, direct evidence for such a role is lacking. Furthermore, recent evidence suggests that sucrose may perform additional roles in guard cells. Here, we provide an update covering the multiple roles of sucrose in guard cell regulation, highlighting the knowledge accumulated regarding spatiotemporal differences in the synthesis, accumulation, and degradation of sucrose as well as reviewing the role of sucrose as a metabolic connector between mesophyll and guard cells. Analysis of transcriptomic data from previous studies reveals that several genes encoding sucrose and hexose transporters and genes involved in gluconeogenesis, sucrose and trehalose metabolism are highly expressed in guard cells compared with mesophyll cells. Interestingly, this analysis also showed that guard cells have considerably higher expression of C4 -marker genes than mesophyll cells. We discuss the possible roles of these genes in guard cell function and the role of sucrose in stomatal opening and closure. Finally, we provide a perspective for future experiments which are required to fill gaps in our understanding of both guard cell metabolism and stomatal regulation.
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6.
Sucrose for analgesia in newborn infants undergoing painful procedures.
Stevens, B, Yamada, J, Ohlsson, A, Haliburton, S, Shorkey, A
The Cochrane database of systematic reviews. 2016;(7):CD001069
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Abstract
BACKGROUND Administration of oral sucrose with and without non-nutritive sucking is the most frequently studied non-pharmacological intervention for procedural pain relief in neonates. OBJECTIVES To determine the efficacy, effect of dose, method of administration and safety of sucrose for relieving procedural pain in neonates as assessed by validated composite pain scores, physiological pain indicators (heart rate, respiratory rate, saturation of peripheral oxygen in the blood, transcutaneous oxygen and carbon dioxide (gas exchange measured across the skin - TcpO2, TcpCO2), near infrared spectroscopy (NIRS), electroencephalogram (EEG), or behavioural pain indicators (cry duration, proportion of time crying, proportion of time facial actions (e.g. grimace) are present), or a combination of these and long-term neurodevelopmental outcomes. SEARCH METHODS We used the standard methods of the Cochrane Neonatal. We performed electronic and manual literature searches in February 2016 for published randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library, Issue 1, 2016), MEDLINE (1950 to 2016), EMBASE (1980 to 2016), and CINAHL (1982 to 2016). We did not impose language restrictions. SELECTION CRITERIA RCTs in which term or preterm neonates (postnatal age maximum of 28 days after reaching 40 weeks' postmenstrual age), or both, received sucrose for procedural pain. Control interventions included no treatment, water, glucose, breast milk, breastfeeding, local anaesthetic, pacifier, positioning/containing or acupuncture. DATA COLLECTION AND ANALYSIS Our main outcome measures were composite pain scores (including a combination of behavioural, physiological and contextual indicators). Secondary outcomes included separate physiological and behavioural pain indicators. We reported a mean difference (MD) or weighted MD (WMD) with 95% confidence intervals (CI) using the fixed-effect model for continuous outcome measures. For categorical data we used risk ratio (RR) and risk difference. We assessed heterogeneity by the I(2) test. We assessed the risk of bias of included trials using the Cochrane 'Risk of bias' tool, and assessed the quality of the evidence using the GRADE system. MAIN RESULTS Seventy-four studies enrolling 7049 infants were included. Results from only a few studies could be combined in meta-analyses and for most analyses the GRADE assessments indicated low- or moderate-quality evidence. There was high-quality evidence for the beneficial effect of sucrose (24%) with non-nutritive sucking (pacifier dipped in sucrose) or 0.5 mL of sucrose orally in preterm and term infants: Premature Infant Pain Profile (PIPP) 30 s after heel lance WMD -1.70 (95% CI -2.13 to -1.26; I(2) = 0% (no heterogeneity); 3 studies, n = 278); PIPP 60 s after heel lance WMD -2.14 (95% CI -3.34 to -0.94; I(2) = 0% (no heterogeneity; 2 studies, n = 164). There was high-quality evidence for the use of 2 mL 24% sucrose prior to venipuncture: PIPP during venipuncture WMD -2.79 (95% CI -3.76 to -1.83; I(2) = 0% (no heterogeneity; 2 groups in 1 study, n = 213); and intramuscular injections: PIPP during intramuscular injection WMD -1.05 (95% CI -1.98 to -0.12; I(2) = 0% (2 groups in 1 study, n = 232). Evidence from studies that could not be included in RevMan-analyses supported these findings. Reported adverse effects were minor and similar in the sucrose and control groups. Sucrose is not effective in reducing pain from circumcision. The effectiveness of sucrose for reducing pain/stress from other interventions such as arterial puncture, subcutaneous injection, insertion of nasogastric or orogastric tubes, bladder catherization, eye examinations and echocardiography examinations are inconclusive. Most trials indicated some benefit of sucrose use but that the evidence for other painful procedures is of lower quality as it is based on few studies of small sample sizes. The effects of sucrose on long-term neurodevelopmental outcomes are unknown. AUTHORS' CONCLUSIONS Sucrose is effective for reducing procedural pain from single events such as heel lance, venipuncture and intramuscular injection in both preterm and term infants. No serious side effects or harms have been documented with this intervention. We could not identify an optimal dose due to inconsistency in effective sucrose dosage among studies. Further investigation of repeated administration of sucrose in neonates is needed. There is some moderate-quality evidence that sucrose in combination with other non-pharmacological interventions such as non-nutritive sucking is more effective than sucrose alone, but more research of this and sucrose in combination with pharmacological interventions is needed. Sucrose use in extremely preterm, unstable, ventilated (or a combination of these) neonates needs to be addressed. Additional research is needed to determine the minimally effective dose of sucrose during a single painful procedure and the effect of repeated sucrose administration on immediate (pain intensity) and long-term (neurodevelopmental) outcomes.
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7.
Sucrose and Saccharomyces cerevisiae: a relationship most sweet.
Marques, WL, Raghavendran, V, Stambuk, BU, Gombert, AK
FEMS yeast research. 2016;(1):fov107
Abstract
Sucrose is an abundant, readily available and inexpensive substrate for industrial biotechnology processes and its use is demonstrated with much success in the production of fuel ethanol in Brazil. Saccharomyces cerevisiae, which naturally evolved to efficiently consume sugars such as sucrose, is one of the most important cell factories due to its robustness, stress tolerance, genetic accessibility, simple nutrient requirements and long history as an industrial workhorse. This minireview is focused on sucrose metabolism in S. cerevisiae, a rather unexplored subject in the scientific literature. An analysis of sucrose availability in nature and yeast sugar metabolism was performed, in order to understand the molecular background that makes S. cerevisiae consume this sugar efficiently. A historical overview on the use of sucrose and S. cerevisiae by humans is also presented considering sugarcane and sugarbeet as the main sources of this carbohydrate. Physiological aspects of sucrose consumption are compared with those concerning other economically relevant sugars. Also, metabolic engineering efforts to alter sucrose catabolism are presented in a chronological manner. In spite of its extensive use in yeast-based industries, a lot of basic and applied research on sucrose metabolism is imperative, mainly in fields such as genetics, physiology and metabolic engineering.
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8.
Understanding and manipulating sucrose phloem loading, unloading, metabolism, and signalling to enhance crop yield and food security.
Braun, DM, Wang, L, Ruan, YL
Journal of experimental botany. 2014;(7):1713-35
Abstract
Sucrose is produced in, and translocated from, photosynthetically active leaves (sources) to support non-photosynthetic tissues (sinks), such as developing seeds, fruits, and tubers. Different plants can utilize distinct mechanisms to transport sucrose into the phloem sieve tubes in source leaves. While phloem loading mechanisms have been extensively studied in dicot plants, there is less information about phloem loading in monocots. Maize and rice are major dietary staples, which have previously been proposed to use different cellular routes to transport sucrose from photosynthetic cells into the translocation stream. The anatomical, physiological, and genetic evidence supporting these conflicting hypotheses is examined. Upon entering sink cells, sucrose often is degraded into hexoses for a wide range of metabolic and storage processes, including biosynthesis of starch, protein, and cellulose, which are all major constituents for food, fibre, and fuel. Sucrose, glucose, fructose, and their derivate, trehalose-6-phosphate, also serve as signalling molecules to regulate gene expression either directly or through cross-talk with other signalling pathways. As such, sugar transport and metabolism play pivotal roles in plant development and realization of crop yield that needs to be increased substantially to meet the projected population demand in the foreseeable future. This review will discuss the current understanding of the control of carbon partitioning from the cellular to whole-plant levels, focusing on (i) the pathways employed for phloem loading in source leaves, particularly in grasses, and the routes used in sink organs for phloem unloading; (ii) the transporter proteins responsible for sugar efflux and influx across plasma membranes; and (iii) the key enzymes regulating sucrose metabolism, signalling, and utilization. Examples of how sugar transport and metabolism can be manipulated to improve crop productivity and stress tolerance are discussed.
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9.
A review of sucroferric oxyhydroxide for the treatment of hyperphosphatemia in patients receiving dialysis.
Bousher, A, Al-Makki, A, Sutton, J, Shepler, B
Clinical therapeutics. 2014;(12):2082-2093
Abstract
PURPOSE Sucroferric oxyhydroxide is the newest phosphate binder to receive US Food and Drug Administration approval for patients on dialysis. The purpose of this review is to critically evaluate the studies that have been conducted with this medication and determine where it may fit in the clinician's overall treatment plan for hyperphosphatemia in patients with chronic kidney disease. METHODS Literature searches were performed in the PubMed database and www.ClinicalTrials.gov using the search terms sucroferric oxyhydroxide, and PA21 phosphate binder. Limits were set to include only clinical trials performed in human subjects. FINDINGS Four completed clinical trials and 3 ongoing studies were identified. Completed clinical trials included Phase I, Phase II, and Phase III studies that all demonstrated the ability of sucroferric oxyhydroxide to lower serum phosphorus concentrations. One study compared sucroferric oxyhydroxide with sevelamer and reported no statistically significant difference in serum phosphorus-lowering ability. The ongoing trials are evaluating sucroferric oxyhydroxide for long term use, in peritoneal dialysis patients, and compared with calcium-based phosphate binders. IMPLICATIONS Sucroferric oxyhydroxide is an effective phosphate binder for chronic kidney disease patients receiving hemodialysis and may offer an advantage in terms of pill burden. Gastrointestinal side effects are similar to those of current phosphate binders. Advantages of other phosphate binders (ie, the lipid- and uric acid-lowering abilities of sevelamer) may outweigh the pill burden benefits of sucroferric oxyhydroxide.
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10.
Oral sucrose for pain control in nonneonate infants during minor painful procedures.
McCall, JM, DeCristofaro, C, Elliott, L
Journal of the American Association of Nurse Practitioners. 2013;(5):244-52
Abstract
PURPOSE To provide information regarding the effective use of oral sucrose as an analgesic for immunization and venipuncture procedures in the older infant. DATA SOURCES Evidence-based literature including original clinical trials, reviews, and clinical practice guidelines. CONCLUSIONS Most infants are exposed to multiple minor painful procedures during the first year of life. Oral sucrose solution in a 24% concentration at a dose of 2 mL approximately 2 min prior to the painful procedure has been shown effective in reducing pain during immunizations and venipuncture in the outpatient setting in infants aged 1-12 months old. IMPLICATIONS FOR PRACTICE Oral sucrose solution should be used as a pain reduction intervention in infants up to 12 months of age undergoing minor painful procedures. Its proven effectiveness as an analgesic, low rate of minor adverse events, ease of administration, and excellent availability make sucrose a good choice for this purpose. Additional research is needed regarding dose response in different infant age groups, optimal concentration of sucrose solution, need for multiple sucrose dosing, adjustment for multiple painful procedures, and addition of optimal nonpharmacologic interventions as a combination approach.