348 research outputs found

    Possible adsorption sites of cellulases on crystalline cellulose

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    AbstractThe possible adsorption sites of cellulases on crystalline cellulose were investigated by molecular graphic representation of a crystal of cellulose and estimation of the accessibility of the various glycosidic bonds to enzymatic attack. The results show that only certain glycosidic bonds of certain surface cellulose chains are susceptible to enzymatic hydrolysis. These preferential sites correlate well with previous electron microscopy observations of the adsorption sites of 1,4-β-D-glucan cellobiohydrolase I (CBHI) from Trichoderma reesei on Valonia cellulose

    Structural modifications and thermal transitions of standard maize starch after DIC hydrothermal treatment

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    International audienceStandard maize starch was hydrothermally treated by Instantaneous Controlled Pressure Drop (DIC) process at three pressure levels (1, 2 and 3 bar) corresponding to the temperatures of 100, 122 and 135 C (at 13–27% moisture), respectively. The structural effects of various hydrothermal conditions were examined with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. In order to understand the changes that occur during DIC treatment, melting endotherms of native maize starch at various moisture contents were determined. The gelatinization temperatures of DIC treated standard maize starch increased with DIC treatment. The transition temperatures (To, Tp) are closely related to the combined effect of pressure and processing time. At approximately 10 min of processing time, To and Tp were 65.7 and 72.3, 68.8 and 73.6 C, 74.8 and 79.8 C for pressure levels of 1, 2 and 3 bar, respectively (against 63.1 and 69.6 C for native starch). DIC treatment narrowed the gelatinization temperature range and decreased gelatinization enthalpy (DH), as the severity of processing conditions increased. DH decreased from 11.4 J g1 (native) to 11.0 (1 bar), 9.0 (2 bar) and 1.7 J g1 (3 bar) for treated maize starch during approximately 10 min. Relative crystallinity of hydrothermally treated starch decreased with increasing DIC conditions. The A-type crystalline pattern was progressively lost (at pressure level P2 bar) and substituted by the Vh-type X-ray diffraction pattern, corresponding to the formation of amylose–lipid complexes. For severe DIC conditions (pressure level of 3 bar), the substitution was completed. Microscopic observations revealed progressive loss of the birefringence of DIC treated starch granules except at low pressure (1 bar), while the integrity of starch granules was preserved for all the conditions. These modifications that reveal important changes in the crystalline organization of the starch granules are related to their functional properties

    Physico-chemical characterisation of sago starch

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    The physico-chemical characteristics of various sago starch samples from South East Asia were determined and compared to starches from other sources. X-ray diffraction studies showed that all the sago starches exhibited a C-type diffraction pattern. Scanning electron microscopy showed that they consist of oval granules with an average diameter around 30 μm. Proximate composition studies showed that the moisture content in the sago samples varied between 10.6% and 20.0%, ash between 0.06% and 0.43%, crude fat between 0.10% and 0.13%, fiber between 0.26% and 0.32% and crude protein between 0.19% and 0.25%. The amylose content varied between 24% and 31%. The percentage of amylose obtained by colourimetric determination agreed well with the values obtained by fractionation procedures and potentiometric titration. Intrinsic viscosities and weight average molecular weight were determined in 1M KOH. Intrinsic viscosity for amylose from sago starches varied between 310 and 460 ml/g while for amylopectin the values varied between 210 and 250 ml/g. The molecular weight for amylose was found to be in the range of 1.41×106 to 2.23×106 while for amylopectin it was in the range of 6.70×106 to 9.23×106. The gelatinisation temperature for the sago starches studied varied between 69.4°C and 70.1°C. The exponent ‘a’ in the Mark–Houwink equation and the exponent ‘α’ in the equation Rg=kMα was found to be 0.80 and 0.58, respectively for amylose separated from sago starch and these are indicative of a random coil conformation. Two types of pasting properties were observed. The first was characterised by a maximum consistency immediately followed by sharp decrease in consistency while the second type was characterised by a plateau when the maximum consistency was reached

    Change in Sleep Quality of Residents the Night Before High-Fidelity Simulation: Results From a Prospective 1-Year National Survey.

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    peer reviewed[en] OBJECTIVE: The stress level of participants in high-fidelity simulation stems from various factors but may result in anticipatory anxiety causing sleep disturbances during the night prior to simulation. The objective of this survey was to determine the change in sleep quality of residents during the night prior to the simulation. METHODS: The survey was proposed for 1 year to all residents at the beginning of the simulation, in 10 simulation centres. The questionnaire combined demographics and the Leeds Sleep Evaluation Questionnaire using visual analogue scales divided into 4 sleep qualitative domains. The primary outcome was the prevalence of sleep disturbance (>10 mm on 1 domain). Secondary outcomes were the prevalence of severe sleep disturbance (>25 mm), as well as qualitatively and quantitatively reported explanatory sleep parameters. RESULTS: Among respondents, 66% [95% CI: 63 to 69] of residents had more than 10 mm and 27% [95% CI: 24 to 30] had more than 25 mm of sleep disturbance. Residents with a sleep disturbance of more than 10 mm had fewer hours of sleep (6.4 [standard deviation=1.8] vs 7.3 [standard deviation=1.3], difference: -0.9 [95% CI: -1.1 to -0.7]; P < .0001), with a higher number of night-time awakenings (1.3 [standard deviation=1.5] vs 0.7 [standard deviation=0.9], difference: 0.6 [95% CI: 0.4 to 0.8]; P < .0001). CONCLUSION: Among residents participating in the simulation, a high prevalence of change in sleep quality during the night before the simulation was noted. Strategies to help residents achieve better sleep prior to simulation should be explored

    Starch Plastic Packaging and Agriculture Applications

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    Paper constitutes the most important material in the United States for packaging and containers largely because of its low cost and wide availability (WPO, 2008). It is also perceived as a sustainable material because it is derived from plants and is recycled at a very high percentage (62%) (EPA, 2010). Plastic ranks as the second most used packaging material in the United States. Plastics can provide transparency, greater moisture protection, and various mechanical properties that are superior to paper packaging. Consequently, some types of plastic packaging continue to grow faster than other packaging materials (WPO, 2008). In contrast to paper, only 7% of plastic generated as waste is recycled. This explains why more plastics ultimately end up in landfills than paper or any other packaging material (EPA, 2010). Plastic processors worldwide are becoming increasingly aware that environmentally sustainable packaging has become mainstream. It can no longer be considered only a niche market that can be ignored or given token attention. Informed consumers are demanding sustainable packaging; state and local governments are mandating it; and now, even the largest retailers are building it into the foundation of their marketing strategies (Deligio, 2009; Wood, 2010)

    Kinin B1 Receptor Enhances the Oxidative Stress in a Rat Model of Insulin Resistance: Outcome in Hypertension, Allodynia and Metabolic Complications

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    BACKGROUND: Kinin B(1) receptor (B(1)R) is induced by the oxidative stress in models of diabetes mellitus. This study aims at determining whether B(1)R activation could perpetuate the oxidative stress which leads to diabetic complications. METHODS AND FINDINGS: Young Sprague-Dawley rats were fed with 10% D-Glucose or tap water (controls) for 8-12 weeks. A selective B(1)R antagonist (SSR240612) was administered acutely (3-30 mg/kg) or daily for a period of 7 days (10 mg/kg) and the impact was measured on systolic blood pressure, allodynia, protein and/or mRNA B(1)R expression, aortic superoxide anion (O(2)(*-)) production and expression of superoxide dismutase (MnSOD) and catalase. SSR240612 reduced dose-dependently (3-30 mg/kg) high blood pressure in 12-week glucose-fed rats, but had no effect in controls. Eight-week glucose-fed rats exhibited insulin resistance (HOMA index), hypertension, tactile and cold allodynia and significant increases of plasma levels of glucose and insulin. This was associated with higher aortic levels of O(2)(*-), NADPH oxidase activity, MnSOD and catalase expression. All these abnormalities including B(1)R overexpression (spinal cord, aorta, liver and gastrocnemius muscle) were normalized by the prolonged treatment with SSR240612. The production of O(2)(*-) in the aorta of glucose-fed rats was also measured in the presence and absence of inhibitors (10-100 microM) of NADPH oxidase (apocynin), xanthine oxidase (allopurinol) or nitric oxide synthase (L-NAME) with and without Sar[D-Phe(8)]des-Arg(9)-BK (20 microM; B(1)R agonist). Data show that the greater aortic O(2)(*-) production induced by the B(1)R agonist was blocked only by apocynin. CONCLUSIONS: Activation of kinin B(1)R increased O(2)(*-) through the activation of NADPH oxidase in the vasculature. Prolonged blockade of B(1)R restored cardiovascular, sensory and metabolic abnormalities by reducing oxidative stress and B(1)R gene expression in this model

    The kallikrein–kinin system in diabetic nephropathy

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    Diabetic nephropathy is the major cause of end-stage renal disease worldwide. Although the renin-angiotensin system has been implicated in the pathogenesis of diabetic nephropathy, angiotensin I-converting enzyme (ACE) inhibitors have a beneficial effect on diabetic nephropathy independently of their effects on blood pressure and plasma angiotensin II levels. This suggests that the kallikrein-kinin system (KKS) is also involved in the disease. To study the role of the KKS in diabetic nephropathy, mice lacking either the bradykinin B1 receptor (B1R) or the bradykinin B2 receptor (B2R) have been commonly used. However, because absence of either receptor causes enhanced expression of the other, it is difficult to determine the precise functions of each receptor. This difficulty has recently been overcome by comparing mice lacking both receptors with mice lacking each receptor. Deletion of both B1R and B2R reduces nitric oxide (NO) production and aggravates renal diabetic phenotypes, relevant to either lack of B1R or B2R, demonstrating that both B1R and B2R exert protective effects on diabetic nephropathy presumably via NO. Here, we review previous epidemiological and experimental studies, and discuss novel insights regarding the therapeutic implications of the importance of the KKS in averting diabetic nephropathy
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