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1.
Diabetes Obes Metab ; 24(3): 421-431, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-34747087

RESUMEN

AIM: To characterize the association between diabetes and transfusion and clinical outcomes in cardiac surgery, and to evaluate whether restrictive transfusion thresholds are harmful in these patients. MATERIALS AND METHODS: The multinational, open-label, randomized controlled TRICS-III trial assessed a restrictive transfusion strategy (haemoglobin [Hb] transfusion threshold <75 g/L) compared with a liberal strategy (Hb <95 g/L for operating room or intensive care unit; or <85 g/L for ward) in patients undergoing cardiac surgery on cardiopulmonary bypass with a moderate-to-high risk of death (EuroSCORE ≥6). Diabetes status was collected preoperatively. The primary composite outcome was all-cause death, stroke, myocardial infarction, and new-onset renal failure requiring dialysis at 6 months. Secondary outcomes included components of the composite outcome at 6 months, and transfusion and clinical outcomes at 28 days. RESULTS: Of the 5092 patients analysed, 1396 (27.4%) had diabetes (restrictive, n = 679; liberal, n = 717). Patients with diabetes had more cardiovascular disease than patients without diabetes. Neither the presence of diabetes (OR [95% CI] 1.10 [0.93-1.31]) nor the restrictive strategy increased the risk for the primary composite outcome (diabetes OR [95% CI] 1.04 [0.68-1.59] vs. no diabetes OR 1.02 [0.85-1.22]; Pinteraction  = .92). In patients with versus without diabetes, a restrictive transfusion strategy was more effective at reducing red blood cell transfusion (diabetes OR [95% CI] 0.28 [0.21-0.36]; no diabetes OR [95% CI] 0.40 [0.35-0.47]; Pinteraction  = .04). CONCLUSIONS: The presence of diabetes did not modify the effect of a restrictive transfusion strategy on the primary composite outcome, but improved its efficacy on red cell transfusion. Restrictive transfusion triggers are safe and effective in patients with diabetes undergoing cardiac surgery.


Asunto(s)
Procedimientos Quirúrgicos Cardíacos , Diabetes Mellitus , Infarto del Miocardio , Procedimientos Quirúrgicos Cardíacos/efectos adversos , Diabetes Mellitus/epidemiología , Transfusión de Eritrocitos/efectos adversos , Hemoglobinas/análisis , Humanos , Infarto del Miocardio/etiología
2.
N Engl J Med ; 379(13): 1224-1233, 2018 09 27.
Artículo en Inglés | MEDLINE | ID: mdl-30146969

RESUMEN

BACKGROUND: We reported previously that, in patients undergoing cardiac surgery who were at moderate-to-high risk for death, a restrictive transfusion strategy was noninferior to a liberal strategy with respect to the composite outcome of death from any cause, myocardial infarction, stroke, or new-onset renal failure with dialysis by hospital discharge or 28 days after surgery, whichever came first. We now report the clinical outcomes at 6 months after surgery. METHODS: We randomly assigned 5243 adults undergoing cardiac surgery to a restrictive red-cell transfusion strategy (transfusion if the hemoglobin concentration was <7.5 g per deciliter intraoperatively or postoperatively) or a liberal red-cell transfusion strategy (transfusion if the hemoglobin concentration was <9.5 g per deciliter intraoperatively or postoperatively when the patient was in the intensive care unit [ICU] or was <8.5 g per deciliter when the patient was in the non-ICU ward). The primary composite outcome was death from any cause, myocardial infarction, stroke, or new-onset renal failure with dialysis occurring within 6 months after the initial surgery. An expanded secondary composite outcome included all the components of the primary outcome as well as emergency department visit, hospital readmission, or coronary revascularization occurring within 6 months after the index surgery. The secondary outcomes included the individual components of the two composite outcomes. RESULTS: At 6 months after surgery, the primary composite outcome had occurred in 402 of 2317 patients (17.4%) in the restrictive-threshold group and in 402 of 2347 patients (17.1%) in the liberal-threshold group (absolute risk difference before rounding, 0.22 percentage points; 95% confidence interval [CI], -1.95 to 2.39; odds ratio, 1.02; 95% CI, 0.87 to 1.18; P=0.006 for noninferiority). Mortality was 6.2% in the restrictive-threshold group and 6.4% in the liberal-threshold group (odds ratio, 0.95; 95% CI, 0.75 to 1.21). There were no significant between-group differences in the secondary outcomes. CONCLUSIONS: In patients undergoing cardiac surgery who were at moderate-to-high risk for death, a restrictive strategy for red-cell transfusion was noninferior to a liberal strategy with respect to the composite outcome of death from any cause, myocardial infarction, stroke, or new-onset renal failure with dialysis at 6 months after surgery. (Funded by the Canadian Institutes of Health Research and others; TRICS III ClinicalTrials.gov number, NCT02042898 .).


Asunto(s)
Procedimientos Quirúrgicos Cardíacos/mortalidad , Transfusión de Eritrocitos/métodos , Complicaciones Posoperatorias/mortalidad , Adulto , Anciano , Procedimientos Quirúrgicos Cardíacos/efectos adversos , Puente Cardiopulmonar , Causas de Muerte , Femenino , Estudios de Seguimiento , Hemoglobinas/análisis , Humanos , Estimación de Kaplan-Meier , Modelos Logísticos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/etiología , Complicaciones Posoperatorias/etiología , Insuficiencia Renal/etiología , Accidente Cerebrovascular/etiología
3.
Eur Heart J ; 41(5): 645-651, 2020 02 01.
Artículo en Inglés | MEDLINE | ID: mdl-31237939

RESUMEN

AIMS: To determine the 1-year risk of stroke and other adverse outcomes in patients with a new diagnosis of perioperative atrial fibrillation (POAF) after non-cardiac surgery. METHODS AND RESULTS: The PeriOperative ISchemic Evaluation (POISE)-1 trial evaluated the effects of metoprolol vs. placebo in 8351 patients, and POISE-2 compared the effect of aspirin vs. placebo, and clonidine vs. placebo in 10 010 patients. These trials included patients with, or at risk of, cardiovascular disease who were undergoing non-cardiac surgery. For the purpose of this study, we combined the POISE datasets, excluding 244 patients who were in atrial fibrillation (AF) at the time of randomization. Perioperative atrial fibrillation was defined as new AF that occurred within 30 days after surgery. Our primary outcome was the incidence of stroke at 1 year of follow-up; secondary outcomes were mortality and myocardial infarction (MI). We compared outcomes among patients with and without POAF using multivariable adjusted Cox proportional hazards models. Among 18 117 patients (mean age 69 years, 57.4% male), 404 had POAF (2.2%). The stroke incidence 1 year after surgery was 5.58 vs. 1.54 per 100 patient-years in patients with and without POAF, adjusted hazard ratio (aHR) 3.43, 95% confidence interval (CI) 2.00-5.90; P < 0.001. Patients with POAF also had an increased risk of death (incidence 31.37 vs. 9.34; aHR 2.51, 95% CI 2.01-3.14; P < 0.001) and MI (incidence 26.20 vs. 8.23; aHR 5.10, 95% CI 3.91-6.64; P < 0.001). CONCLUSION: Patients with POAF have a significantly increased risk of stroke, MI, and death at 1 year. Intervention studies are needed to evaluate risk reduction strategies in this high-risk population.


Asunto(s)
Fibrilación Atrial , Infarto del Miocardio , Accidente Cerebrovascular , Anciano , Fibrilación Atrial/epidemiología , Femenino , Humanos , Masculino , Infarto del Miocardio/epidemiología , Infarto del Miocardio/etiología , Complicaciones Posoperatorias/epidemiología , Factores de Riesgo , Accidente Cerebrovascular/epidemiología , Accidente Cerebrovascular/etiología
4.
N Engl J Med ; 377(22): 2133-2144, 2017 11 30.
Artículo en Inglés | MEDLINE | ID: mdl-29130845

RESUMEN

BACKGROUND: The effect of a restrictive versus liberal red-cell transfusion strategy on clinical outcomes in patients undergoing cardiac surgery remains unclear. METHODS: In this multicenter, open-label, noninferiority trial, we randomly assigned 5243 adults undergoing cardiac surgery who had a European System for Cardiac Operative Risk Evaluation (EuroSCORE) I of 6 or more (on a scale from 0 to 47, with higher scores indicating a higher risk of death after cardiac surgery) to a restrictive red-cell transfusion threshold (transfuse if hemoglobin level was <7.5 g per deciliter, starting from induction of anesthesia) or a liberal red-cell transfusion threshold (transfuse if hemoglobin level was <9.5 g per deciliter in the operating room or intensive care unit [ICU] or was <8.5 g per deciliter in the non-ICU ward). The primary composite outcome was death from any cause, myocardial infarction, stroke, or new-onset renal failure with dialysis by hospital discharge or by day 28, whichever came first. Secondary outcomes included red-cell transfusion and other clinical outcomes. RESULTS: The primary outcome occurred in 11.4% of the patients in the restrictive-threshold group, as compared with 12.5% of those in the liberal-threshold group (absolute risk difference, -1.11 percentage points; 95% confidence interval [CI], -2.93 to 0.72; odds ratio, 0.90; 95% CI, 0.76 to 1.07; P<0.001 for noninferiority). Mortality was 3.0% in the restrictive-threshold group and 3.6% in the liberal-threshold group (odds ratio, 0.85; 95% CI, 0.62 to 1.16). Red-cell transfusion occurred in 52.3% of the patients in the restrictive-threshold group, as compared with 72.6% of those in the liberal-threshold group (odds ratio, 0.41; 95% CI, 0.37 to 0.47). There were no significant between-group differences with regard to the other secondary outcomes. CONCLUSIONS: In patients undergoing cardiac surgery who were at moderate-to-high risk for death, a restrictive strategy regarding red-cell transfusion was noninferior to a liberal strategy with respect to the composite outcome of death from any cause, myocardial infarction, stroke, or new-onset renal failure with dialysis, with less blood transfused. (Funded by the Canadian Institutes of Health Research and others; TRICS III ClinicalTrials.gov number, NCT02042898 .).


Asunto(s)
Procedimientos Quirúrgicos Cardíacos , Transfusión de Eritrocitos/métodos , Adulto , Anciano , Procedimientos Quirúrgicos Cardíacos/efectos adversos , Procedimientos Quirúrgicos Cardíacos/mortalidad , Puente Cardiopulmonar , Femenino , Hemoglobinas/análisis , Mortalidad Hospitalaria , Humanos , Unidades de Cuidados Intensivos , Análisis de Intención de Tratar , Tiempo de Internación , Masculino , Persona de Mediana Edad , Infarto del Miocardio/etiología , Atención Perioperativa , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/mortalidad , Insuficiencia Renal/etiología , Accidente Cerebrovascular/etiología
5.
J Mol Diagn ; 26(5): 323-336, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38360211

RESUMEN

Trypanosomatids, including Trypanosoma and Leishmania species, present significant medical and veterinary challenges, causing substantial economic losses, health complications, and even fatalities. Diagnosing and genotyping these species and their genotypes is often complex, involving multiple steps. This study aimed to develop an amplicon-based sequencing (ABS) method using Oxford Nanopore long-read sequencing to enhance Trypanosomatid detection and genotyping. The 18S rDNA gene was targeted for its inter-species conservation. The Trypanosomatid-ABS method effectively distinguished between 11 Trypanosoma species (including Trypanosoma evansi, Trypanosoma theileri, Trypanosoma vivax, and Trypanosoma rangeli) and 6 Trypanosoma cruzi discrete typing units (TcI to TcVI and TcBat), showing strong concordance with conventional methods (κ index of 0.729, P < 0.001). It detected co-infections between Trypanosomatid genera and T. cruzi, with a limit of detection of one parasite per mL. The method was successfully applied to human, animal, and triatomine samples. Notably, TcI predominated in chronic Chagas samples, whereas TcII and TcIV were found in the acute stage. Triatomine vectors exhibited diverse Trypanosomatid infections, with Triatoma dimidiata mainly infected with TcI and occasional TcBat co-infections, and Rhodnius prolixus showing TcI and TcII infections, along with T. rangeli co-infections and mixed TcII infections. Animals were infected with T. vivax, T. theileri, and T. evansi. The ABS method's high resolution, sensitivity, and accuracy make it a valuable tool for understanding Trypanosomatid dynamics, enhancing disease control strategies, and enabling targeted interventions.


Asunto(s)
Enfermedad de Chagas , Coinfección , Secuenciación de Nanoporos , Trypanosoma cruzi , Humanos , Animales , Genotipo , ARN Ribosómico 18S/genética , Enfermedad de Chagas/parasitología , Trypanosoma cruzi/genética
6.
Nat Commun ; 14(1): 1850, 2023 04 03.
Artículo en Inglés | MEDLINE | ID: mdl-37012236

RESUMEN

During an infection the immune system produces pathogen-specific antibodies. These antibody repertoires become specific to the history of infections and represent a rich source of diagnostic markers. However, the specificities of these antibodies are mostly unknown. Here, using high-density peptide arrays we examined the human antibody repertoires of Chagas disease patients. Chagas disease is a neglected disease caused by Trypanosoma cruzi, a protozoan parasite that evades immune mediated elimination and mounts long-lasting chronic infections. We describe a proteome-wide search for antigens, characterised their linear epitopes, and show their reactivity on 71 individuals from diverse human populations. Using single-residue mutagenesis we revealed the core functional residues for 232 of these epitopes. Finally, we show the diagnostic performance of identified antigens on challenging samples. These datasets enable the study of the Chagas antibody repertoire at an unprecedented depth and granularity, while also providing a rich source of serological biomarkers.


Asunto(s)
Enfermedad de Chagas , Trypanosoma cruzi , Humanos , Trypanosoma cruzi/genética , Epítopos , Especificidad de Anticuerpos , Ensayo de Inmunoadsorción Enzimática , Enfermedad de Chagas/parasitología , Antígenos de Protozoos/genética , Anticuerpos , Américas , Anticuerpos Antiprotozoarios
7.
PLoS Negl Trop Dis ; 17(8): e0011542, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37556493

RESUMEN

BACKGROUND: Trypanosoma cruzi, the agent of Chagas disease, displays a highly structured population, with multiple strains that can be grouped into 6-7 evolutionary lineages showing variable eco-epidemiological traits and likely also distinct disease-associated features. Previous works have shown that antibody responses to 'isoforms' of the polymorphic parasite antigen TSSA enable robust and sensitive identification of the infecting strain with near lineage-level resolution. To optimize the serotyping performance of this molecule, we herein used a combination of immunosignaturing approaches based on peptide microarrays and serum samples from Chagas disease patients to establish a deep linear B-cell epitope profiling of TSSA. METHODS/PRINCIPLE FINDINGS: Our assays revealed variations in the seroprevalence of TSSA isoforms among Chagas disease populations from different settings, hence strongly supporting the differential distribution of parasite lineages in domestic cycles across the Americas. Alanine scanning mutagenesis and the use of peptides of different lengths allowed us to identify key residues involved in antibody pairing and the presence of three discrete B-cell linear epitopes in TSSAII, the isoform with highest seroprevalence in human infections. Comprehensive screening of parasite genomic repositories led to the discovery of 9 novel T. cruzi TSSA variants and one TSSA sequence from the phylogenetically related bat parasite T. cruzi marinkellei. Further residue permutation analyses enabled the identification of diagnostically relevant or non-relevant substitutions among TSSA natural polymorphisms. Interestingly, T. cruzi marinkellei TSSA displayed specific serorecognition by one chronic Chagas disease patient from Colombia, which warrant further investigations on the diagnostic impact of such atypical TSSA. CONCLUSIONS/SIGNIFICANCE: Overall, our findings shed new light into TSSA evolution, epitope landscape and modes of recognition by Chagas disease patients; and have practical implications for the design and/or evaluation of T. cruzi serotyping strategies.


Asunto(s)
Enfermedad de Chagas , Trypanosoma cruzi , Humanos , Estudios Seroepidemiológicos , Enfermedad de Chagas/epidemiología , Antígenos de Protozoos , Péptidos , Epítopos de Linfocito B/genética , Anticuerpos Antiprotozoarios
8.
Bioresour Technol ; 318: 124050, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32889118

RESUMEN

Enzymatic hydrolysis of three pre-treated lignocellulosic biomasses -LCB- (wheat straw-WS-, corn stover-CSV- and cardoon stems -CS-) is studied. These biomasses were pre-treated by two methods: diluted sulfuric acid and acid ethanol-water extraction at six severity levels (H values). Pretreated solid fractions were hydrolyzed with commercial enzyme cocktails at standard conditions. A first-order kinetic fractal model was fitted to the experimental results. This model accurately describes the hydrolysis of all biomasses at all pre-treatment conditions studied. The results show that the formal first-order kinetic constant k depends on the biomass nature. The hydrolysis rate increases as the pre-treatment severity does, while the fractal exponent value h decreases. With these pre-treatments, and in terms of k and h, WS is highly reactive and, at medium H with EW pretreatment, highly accessible; CSV has a low reactivity and high accessibility and CS has the lowest reactivity and an increasing accessibility as severity rises.


Asunto(s)
Celulasa , Biomasa , Fractales , Hidrólisis , Lignina
9.
J Biotechnol ; 292: 32-38, 2019 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-30668958

RESUMEN

The stabilization effects on a novel commercial ß-glucosidase preparation from Aspergillus fumigatus during saccharification of ethanol-water pretreated wheat straw were analysed in comparison to this enzyme stability during cellobiose hydrolysis. For this purpose, the kinetics of ß-glucosidase residual activity during cellobiose hydrolysis from 40 till 70 °C were studied, resulting in the fitting of a first-order partial deactivation model. Furthermore, a subsequent fitting of a kinetic model including this first-order deactivation equation and a Michaelis-Menten equation with double competitive inhibition by glucose and uncompetitive inhibition by cellobiose to released glucose was successful. Finally, global enzyme deactivation and prospective deactivation of enzyme remaining in the liquid phase were evaluated during wheat straw hydrolysis at 50 °C as a relevant saccharification process. Results suggest that the presence of a solid substrate dramatically reduces the global deactivation rate of the enzyme and, in addition, there is no loss the stability of the enzyme in the liquid phase along the saccharification process, even for 72 h.


Asunto(s)
Aspergillus fumigatus/enzimología , Proteínas Fúngicas/metabolismo , Temperatura , Triticum , beta-Glucosidasa/metabolismo , Celobiosa/metabolismo , Estabilidad de Enzimas , Etanol , Glucosa/metabolismo , Hidrólisis , Cinética , Agua
10.
Bioresour Technol ; 280: 396-403, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-30784989

RESUMEN

Liquor recycle in lignocellulosic biomass fractionation with ethanol-water has been studied. Runs have been carried out in a 6 L tank reactor with liquor recirculation. The liquors obtained in six successive fractioning operations have been analyzed together with the solid phase remnant. Experimental results revealed that the number of re-uses reduces solids recovery (from 52.2 to 42.6%) and cellulose recovery (from 28.1 to 23.3%) with minor or no effect on the hemicelluloses and lignin removal. The more remarkable effect is an increase of the glucose yield (from 76.7 to 95.3% after enzymatic hydrolysis during 72 h). The accumulation of acetic acid in the spent liquors (until 1.3 g/L) seems to be responsible of the higher enzymatic hydrolysis yield, from 76.3 (first use) to 87.7% (fifth re-use). Liquor re-use is effective to improve the sustainability of the pre-treatment obtaining a cellulose-rich solid easy to hydrolysate to sugars reducing energy consumption.


Asunto(s)
Bebidas Alcohólicas , Biomasa , Lignina/metabolismo , Ácido Acético/metabolismo , Fraccionamiento Químico/métodos , Etanol , Glucosa/metabolismo , Hidrólisis , Agua
11.
Bioresour Technol ; 268: 592-598, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30138871

RESUMEN

A physico-chemical kinetic model for the hydrolysis of pre-treated corn stover is proposed. This model takes into account two reactions in series, the hydrolysis of cellulose to cellobiose and the production of glucose from cellobiose. Experiments have been carried out with an industrial enzymatic cocktail from Trichoderma reesei containing endo and exoglucanases and a very low activity of ß-glucosidase. Kinetic parameters were calculated by fitting the proposed model to experimental data of cellulose and glucose concentrations with time. The kinetic parameters fulfilled all relevant statistical and physical criteria. The kinetic model has been validated with published saccharification data regarding differently pre-treated corn stover and enzymatic cocktail, in this case with a very high ß-glucosidase activity (as it is common in modern industrial cellulase cocktails). In both cases, the kinetic model proposed could be fitted very appropriately to cellulose hydrolysis data.


Asunto(s)
Eliminación de Residuos , Zea mays , Celulasa , Explosiones , Hidrólisis , Vapor
12.
Bioresour Technol ; 270: 449-456, 2018 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-30245314

RESUMEN

Ethanol-water (EW) and diluted sulfuric acid (DSA) pre-treatment have been studied for lignocellulosic biomass (corn stover, Cynara cardunculus L. stems and wheat straw). Both pre-treatments have been compared taken into account: solids recovery, glucans recovery, xylans removed, delignification and glucose yield. In all cases, the amount of energy involved has been taken as a criterion for sustainability. In general terms, EW is more efficient to remove lignin and DSA more appropriate to hydrolysate xylans. The combined effect of delignification and xylans removal is responsible for the improvement in the enzymatic cellulose hydrolysis. Under conditions of moderate-low energy inputs, EW pre-treatment yields better results than DSA with glucose yields in the range of 50-60% for EW pre-treated corn stover and cardoon stems; while wheat straw pulps reach up to 80%. So, multiple raw materials biorefinery needs a previous study to fit the type and conditions of the pre-treatment to each feedstock.


Asunto(s)
Cynara/metabolismo , Triticum/metabolismo , Zea mays/metabolismo , Biomasa , Celulosa/metabolismo , Cynara/efectos de los fármacos , Etanol/farmacología , Hidrólisis , Lignina/farmacología , Ácidos Sulfúricos/farmacología , Triticum/efectos de los fármacos , Agua/farmacología , Xilanos/metabolismo , Zea mays/efectos de los fármacos
13.
Bioresour Technol ; 256: 178-186, 2018 May.
Artículo en Inglés | MEDLINE | ID: mdl-29438918

RESUMEN

The fractionation of wheat straw by ethanol-water (EW) pre-treatment was studied regarding its main operating conditions: time, temperature, L/S ratio and ethanol percentage were optimized by using an orthogonal experimental design (Taguchi). Afterwards, diluted sulfuric acid (DSA) hydrolysis and EW treatments have been compared in terms of energy consumption and yield of a cellulosic solid residue able to be enzymatically hydrolyzed to glucose. Experimental results show that temperature is the only variable of EW with a significant effect on the quality of the pretreated solids. EW pre-treatment of wheat straw is more effective than DSA hydrolysis due to its higher capacity of delignification. Moreover, a high glucose yield (80%) can be obtained by enzymatic hydrolysis of a solid pretreated with a moderate energy input EW (160 °C, 45 min) while wheat straw needs of a higher energy input during DSA to produce a similar yield of glucose after saccharification.


Asunto(s)
Etanol , Triticum , Fermentación , Hidrólisis , Ácidos Sulfúricos , Agua
14.
Bioengineering (Basel) ; 4(4)2017 Nov 28.
Artículo en Inglés | MEDLINE | ID: mdl-29182575

RESUMEN

The effect of the addition of two [4-butyltrimethylammonium]-xylan chloride polyelectrolytes (BTMAXs) on bacterial cellulose (BC) was evaluated. The first strategy was to add the polyelectrolytes to the culture medium together with a cell suspension of the bacterium. After one week of cultivation, the films were collected and purified. The second approach consisted of obtaining a purified and homogenized BC, to which the polyelectrolytes were added subsequently. The films were characterized in terms of tear and burst indexes, optical properties, surface free energy, static contact angle, Gurley porosity, SEM, X-ray diffraction and AFM. Although there are small differences in mechanical and optical properties between the nanocomposites and control films, the films obtained by BC synthesis in the presence of BTMAXs were remarkably less opaque, rougher, and had a much lower specular gloss. The surface free energy depends on the BTMAXs addition method. The crystallinity of the composites is lower than that of the control material, with a higher reduction of this parameter in the composites obtained by adding the BTMAXs to the culture medium. In view of these results, it can be concluded that BC-BTMAX composites are a promising new material, for example, for paper restoration.

15.
Bioresour Technol ; 220: 110-116, 2016 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-27566519

RESUMEN

Enzymatic hydrolysis of corn stover was studied at agitation speeds from 50 to 500rpm in a stirred tank bioreactor, at high solid concentrations (20% w/w dry solid/suspension), 50°C and 15.5mgprotein·gglucane(-1). Two empirical kinetic models have been fitted to empirical data, namely: a potential model and a fractal one. For the former case, the global order dramatically decreases from 13 to 2 as agitation speed increases, suggesting an increment in the access of enzymes to cellulose in terms of chemisorption followed by hydrolysis. For its part, the fractal kinetic model fits better to data, showing its kinetic constant a constant augmentation with increasing agitation speed up to a constant value at 250rpm and above, when mass transfer limitations are overcome. In contrast, the fractal exponent decreases with rising agitation speed till circa 0.19, suggesting higher accessibility of enzymes to the substrate.


Asunto(s)
Ácidos/metabolismo , Celulosa/metabolismo , Modelos Teóricos , Zea mays/enzimología , Zea mays/metabolismo , Reactores Biológicos , Celulasa , Fractales , Hidrólisis , Cinética
16.
Bioresour Technol ; 216: 28-35, 2016 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-27233094

RESUMEN

The effect of fluid dynamic conditions on enzymatic hydrolysis of acid pretreated corn stover (PCS) has been assessed. Runs were performed in stirred tanks at several stirrer speed values, under typical conditions of temperature (50°C), pH (4.8) and solid charge (20% w/w). A complex mixture of cellulases, xylanases and mannanases was employed for PCS saccharification. At low stirring speeds (<150rpm), estimated mass transfer coefficients and rates, when compared to chemical hydrolysis rates, lead to results that clearly show low mass transfer rates, being this phenomenon the controlling step of the overall process rate. However, for stirrer speed from 300rpm upwards, the overall process rate is controlled by hydrolysis reactions. The ratio between mass transfer and overall chemical reaction rates changes with time depending on the conditions of each run.


Asunto(s)
Biomasa , Lignina/química , Eliminación de Residuos/métodos , Zea mays/química , Celulosa/química , Hidrodinámica , Hidrólisis
17.
Appl Spectrosc ; 70(9): 1537-45, 2016 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-27129363

RESUMEN

A new method was developed to study how the oil and cyan pigments of cold-set ink are distributed in newspaper thickness. The methodology involved laboratory printing followed by delamination of the printed paper. The unprinted side, printed side, and resulting layers were analyzed using attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR). Three commercial newspapers and black and cyan cold-set inks were chosen for the study. Attenuated total reflection Fourier transform infrared spectroscopy enabled the proportion of oil and cyan pigment on the printed surface and throughout the sheet thickness to be measured. Oil percentage was evaluated as the area increment of the region from 2800 cm(-1) to 3000 cm(-1) The relative amount of cyan pigment was determined as the area of the absorption band at 730 cm(-1) The ink oil was found mainly below half the paper thickness, whereas the pigment was detected at the layers closer to the printed surface, at a depth penetration of less than 15 µm (20% of thickness). Distribution of these two components in paper thickness depended on the type of cold-set ink, the amount of ink transferred, and the newspaper properties.

18.
Carbohydr Polym ; 116: 173-81, 2015 Feb 13.
Artículo en Inglés | MEDLINE | ID: mdl-25458287

RESUMEN

Bacterial cellulose (BC) synthesized by Gluconacetobacter sucrofermentans CECT 7291 seems to be a good option for the restoration of degraded paper. In this work BC layers are cultivated and purified by two different methods: an alkaline treatment when the culture media contains ethanol and a thermal treatment if the media is free from ethanol. The main goal of these tests was the characterization of BC layers measured in terms of tear and burst indexes, optical properties, SEM, X-ray diffraction, FTIR, degree of polymerization, static and dynamic contact angles, and mercury intrusion porosimetry. The BC layers were also evaluated in the same terms after an aging treatment. Results showed that BC has got high crystallinity index, low internal porosity, good mechanical properties and high stability over time, especially when purified by the alkaline treatment. These features make BC an adequate candidate for degraded paper reinforcement.


Asunto(s)
Celulosa/química , Papel , Celulosa/aislamiento & purificación , Celulosa/metabolismo , Etanol/química , Gluconacetobacter/metabolismo , Calor , Porosidad , Espectroscopía Infrarroja por Transformada de Fourier , Viscosidad , Difracción de Rayos X
19.
Int J Cardiol ; 93(2-3): 189-95, 2004 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-14975546

RESUMEN

BACKGROUND: Although impaired cardio-vagal response characterizes full-blown Chagas' disease, this feature among otherwise healthy T. cruzi serology carriers (SERO[+]) requires confirmation. The purpose of this study was to determine whether abnormal cardio-vagal responses were different among SERO[+] subjects with varying ECG alterations. METHODS: We assessed cardio-vagal reflex response in 57 randomly selected healthy blood donors (36 SERO[+], 15 with ECG rhythm/conduction abnormalities). The following cardiac autonomic tests were performed: (1) short-term heart rate variability (HRV), (2) Deep breathing test (DBT), (3) cold face test, (4) cold pressor test (CPT), (5) Valsalva maneuver, and (6) baroreflex sensitivity after administration of nitroprusside (BRS-NTP) and phenylephrine (BRS-PNP). RESULTS: Overall, SERO[+] subjects had 161/324 (49.7%) abnormal responses, compared to 41/189 (21.7%) in SERO[-] (p<0.001). Similar rates were found in SERO[+] according to ECG status (68/135, 50.4% in ECG[+] and 93/189, 49.2% in ECG[-], p=0.836). Covariate-adjusted pooled odd ratios (95%CI) for abnormal responses compared to SERO[-] were: 2.73 (1.71-4.35) for SERO[+], and 2.63 (1.63-4.34) for SERO[+]/ECG[-] (p<0.001). BRS-NTP, CPT and DBT individually showed significant differences between SERO[-] and SERO[+] groups. Conversely, ECG changes among SERO[+] were not associated with a significant excess of autonomic abnormality either overall (OR=1.09, 95%CI: 0.67-1.78, p=0.719) or by any individual test. CONCLUSIONS: Early cardio-vagal dysfunction was documented in SERO[+] subjects regardless of ECG status. Cardiac autonomic evaluation may be useful for identification of subclinical disease in SERO[+] subjects.


Asunto(s)
Sistema Nervioso Autónomo/fisiopatología , Cardiomiopatía Chagásica/fisiopatología , Trypanosoma cruzi/aislamiento & purificación , Adulto , Animales , Barorreflejo/fisiología , Donantes de Sangre , Cardiomiopatía Chagásica/diagnóstico , Electrocardiografía , Femenino , Corazón/inervación , Humanos , Masculino , Nervio Vago/fisiología
20.
Bioresour Technol ; 167: 186-91, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-24980031

RESUMEN

Steam explosion and steam pre-treatment have proved capable of enhancing enzymatic saccharification of lignocellulosic materials. However, until now, these methods had not been compared under the same operational conditions and using the same raw material. Both pre-treatments lead to increased yields in the saccharification of Eucalyptus globulus; but results have been better with steam pre-treatments, despite the more accessible surface of exploded samples. The reason for this finding could be enzymatic inhibition: steam explosion causes a more extensive extraction of hemicelluloses and releases a greater amount of degradation products which can inhibit enzymatic action. Enzymatic inhibition is also dependent on the amount and chemical structure of lignin, which was also a contributing factor to the lower enzymatic yields obtained with the most severe pre-treatment. Thus, the highest yields (46.7% glucose and 73.4% xylose yields) were obtained after two cycle of steam treatment, of 5 and 3 min, at 183°C.


Asunto(s)
Biotecnología/métodos , Metabolismo de los Hidratos de Carbono , Celulasa/metabolismo , Eucalyptus/metabolismo , Vapor , Glucosa/análisis , Lignina/aislamiento & purificación , Xilanos/aislamiento & purificación , Xilosa/análisis
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