Exploring the role of lignin structure in molecular dynamics of lignin/bio-derived thermoplastic elastomer polyurethane blends.

The relaxation behavior of two lignins (Alcell organosolv, OSL, and hydroxypropyl modified Kraft, ML) and bio-based thermoplastic polyurethane (TPU) blends have been studied by Differential Scanning Calorimetry (DSC), Dynamic-Mechanical Analysis (DMA) and Dielectric Relaxation Spectroscopy (DRS). The effect of blending on the glass and local relaxation processes as a function of composition, frequency, and temperature has been assessed. The dielectric spectra were resolved into dipolar relaxations as well as conductive processes for differing blend compositions. Characteristic relaxation times, activation energies and dielectric relaxation strengths of lignin/xTPU blends were also investigated. It was found that blending suppresses the α-relaxation process of the blends compared to virgin TPU. On the other hand, while the position of the ß-relaxation was not influenced by blending, a reduction of the activation energies, Ea, of this process was observed in the lignin/xTPU blends. Finally, changes are observed in the conductivity behavior of both blends, with conductivity processes more favorable for the OSL/xTPU blends.

Molecular dynamics of carrageenan composites reinforced with Cloisite Na+ montmorillonite nanoclay.

Nanocomposites comprising biodegradable carrageenan and glycerol (KCg) as the host polymer, with different contents of natural montmorillonite (MMT) as filler, were prepared by a solution casting process. Different techniques have been used to determine the interaction/behavior among the different components of the samples such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscope (TEM) and, mainly, Dielectric relaxation spectroscopy (DRS). FTIR indicates hydrogen interaction between carrageenan matrix and silicate that is confirmed by the XRD data indicating some kind of carrageenan intercalation between the MMT layers. A rather homogenous distribution of MMT into KCg matrix were observed using transmission electron microscopy. The MMT effect on the molecular mobility at the glass transition was studied by dielectric relaxation spectroscopy. The MMT addition resulted in a slower relaxation and a wider distribution of the relaxation times. The fragility index, m, increased upon MMT incorporation, which may be attributed to a reduction in mobility chains, due to the MMT confinement of the KCg network. In addition, the apparent activation energy associated with the relaxation dynamics of the chains at Tg increased with the MMT content. The modified films developed in this paper could be used to prepare biodegradable and edible packaging films and films for biomedical applications with improved mechanical and good dielectric response.

Monitoring molecular dynamics of bacterial cellulose composites reinforced with graphene oxide by carboxymethyl cellulose addition.

Broadband Dielectric Relaxation Spectroscopy was performed to study the molecular dynamics of dried Bacterial Cellulose/Carboxymethyl Cellulose-Graphene Oxide (BC/CMC-GO) composites as a function of the concentration of CMC in the culture media. At low temperature the dielectric spectra are dominated by a dipolar process labelled as a ß-relaxation, whereas electrode polarization and the contribution of dc-conductivity dominate the spectra at high temperatures and low frequency. The CMC concentration affects the morphological structure of cellulose and subsequently alters its physical properties. X-ray diffractometry measurements show that increasing the concentration of CMC promotes a decrease of the Iα/Iß ratio. This structural change in BC, that involves a variation in inter- and intramolecular interactions (hydrogen-bonding interactions), affects steeply their molecular dynamics. So, an increase of CMC concentration produces a significantly decrease of the ß-relaxation strength and an increase of the dc-conductivity.

Biomarkers of pulmonary rejection.

Immunologic complications after lung transplantation (LT) include acute cellular rejection (ACR), antibody-mediated rejection (AMR), and most forms of chronic allograft dysfunction (CAD). ACR is an inflammatory process in which the reaction is mediated by the T-cell population. Most episodes of ACR fully recover with treatment, but repeated bouts are considered to be a risk factor for CAD. Biomarker cytokines interleukin (IL)-10, IL-15, IL-6, CCL5, CCR2 and IFNγ may play significant roles in this complication. Formerly bronchiolitis obliterans syndrome (BOS) or chronic rejection or most forms of CAD were considered to be immunologic complications not amenable therapeutic measures. CAD, the main limitation for long-term survival in LT, is characterized histologically by airway epithelial cell apoptosis and luminal fibrosis in the respiratory bronchioles causing airflow obstruction and, in some cases, lung parenchymal affectations causing restrictive lung disease. Several biomarkers have been studied in CAD, IL-6, IL-8, IL-17, IL-23, IL-13, IFN γ, and TGF ß cytokines, pH, bile acid, and tripsine of gastroesophageal reflux and toll-like receptors of innate immunity. Herein we have reviewed the literature of biomarkers involved in lung rejection.

Utility of exhaled breath condensate pH for diagnosing occupational asthma.

INTRODUCTION: The current reference standard method for diagnosing occupational asthma (OA) is specific inhalation challenge (SIC) with the suspected agent. The alternative method is serial peak expiratory flow (PEF) monitoring. Nevertheless, PEF does not have optimal sensitivity and specificity for this purpose. The aim of this study was to evaluate the utility of exhaled breath condensate (EBC) pH for the diagnosis of OA. MATERIAL AND METHODS: A prospective study was performed in 37 subjects with suspected OA. Serial PEF monitoring was carried out for 2 weeks at work and for 2 weeks off work. At the end of each period, the EBC pH and the methacholine concentration resulting in a 20% FEV(1) decrease (PC20) were measured. SIC was subsequently performed. PEF graphs were interpreted visually by 3 experienced independent readers. RESULTS: Seventeen patients tested positive with SIC. Receiver-operating characteristic curves showed that a decrease in EBC pH greater than 0.4 units during the period at work compared to the off-work period achieved the most satisfactory sensitivity (40%, CI 19.4-66.5) and specificity (90%, CI 66.9-98.2) for diagnosing OA. When EBC pH findings were added to PEF results, the diagnostic yield of PEF generally increased. Other test combinations (e.g. EBC pH plus PC20 or EBC pH plus PC20 plus PEF) did not improve diagnostic performance. CONCLUSIONS: Acidification of EBC pH at work and adding the EBC pH measurement to PEF monitoring during periods at work and off work may be useful for improving the diagnosis of OA.

Bronchoscopic balloon dilatation in the management of bronchial stenosis following lung transplantation.

BACKGROUND: Bronchial stenosis (BS) is currently found in 7-15% of lung transplantation (LT) recipients. Current treatment strategies have included Nd:Yag laser, cryotherapy, bougie dilatation and stent placement. Bronchoscopic balloon dilatation has been used as alternative treatment in a few cases with controversial results. This is a study to prospectively assess the efficacy of bronchoscopic balloon dilatation as a first step in the management of post-LT BS. METHODS: From January 1995 to December 2002, bronchoscopic balloon dilatation was evaluated as first therapeutic option in all consecutive LT patients with BS. Symptoms, pulmonary function tests, airway diameter and use of other therapeutic techniques were evaluated. RESULTS: A total of 10 out of 284 anastomed airways (3.5%) in 9 out of 152 LT patients were included in the study and follow-up lasted from 6 to 81 months. Dilatation of all but one BS met with initial success: increase of both luminal dimensions and forced vital capacity (P=0.01), and relief of symptoms. Bronchoscopic balloon dilatation long-term follow-up showed effective results in 5 out of 10 (50%) bronchial stenoses, after an average of 4 bronchoscopic balloon dilatation procedures (range 1-8). No severe complications were observed. Stent placement was required in the other 5 bronchial stenoses. CONCLUSIONS: Bronchoscopic balloon dilatation is a safe method that should be considered as first therapeutic treatment of post-LT BS. Its use avoids the need for stent placement in up to 50% of cases.

Elección del material de sutura idóneo en microcirugía tubárica. Estudio experimental / Selection of the ideal suture material in microsurgery. An experimental study

El presente trabajo experimental se ha realizado para establecer qué material de sutura es el más adecuado en la microcirugía tubárica, y según los resultados obtenidos establecer la validez actual de esta técnica frente a la fertilización in vitro. Se han intervenido 30 conejos de la raza New Zealand, estableciendo tres grupos de 15 trompas cada uno, con un total de 45 reanastomosis tubáricas. Las restantes 15 trompas no se intervinieron, quedando como control. El material de sutura utilizado en cada grupo ha sido poliglactin 910, nailon y polidioxanona. Hemos obtenido con la polidioxanona mejores resultados respecto a la permeabilidad tubárica, menos estenosis y adherencias respecto a los otros dos tipos de suturas, con diferencias estadísticamente significativas frente al nailon (p < 0,05), que ha producido las mayores adherencias, que supera el doble de los otros dos grupos, y granulomas de cuerpo extraño. Tanto en el estudio macroscópico como en el histológico se demuestra que las mejores suturas son las reabsorbibles frente al nailon (p < 0,05), y dentro de las reabsorbibles, los monofilamentos como la polidioxanona, y hemos de descartar el uso del nailon por su potencial adherenciógeno (AU)

[Comparison of prosthetic materials for abdominal wall reconstruction. Experimental study]. / Comparación entre materiales protésicos para reconstrucción de la pared abdominal. Estudio experimental.

To repair large abdominal deficiencies, either congenital of acquired, occasionally serious problems show up where obtaining the ideal material is concerned, in those cases where autological tissue in the right size can not be found. In this sense materials like silver, steel and tantalium darning have been used, as well as many other synthetic tissues and non porous materials like silastic. During this same period, prosthesis of reabsorbing materials have been developed and used. We present a experimental work in which we compare four prosthesic materials as there are Marlex, Silastic, polyglycolic acid and lyodura, from the clinical, biological and histopathological point of view, distinguishing the ideal material in definite pathologies.

[Acute perforated sigmoid diverticulitis in childhood]. / Diverticulitis aguda de sigma perforada en la infancia.

Colonic diverticulosis is a pathology of high incidence in normal population during the last decades of life. About 2-5 per 100 of patients admitted because of this disease are below 40 years old, and in this group of patients diverticulitis tends to be very aggressive with a high number of complications. We report a clinical case of acute perforation of sigmoid colon due to diverticulitis in a ten year old child who was treated surgically by means of resection of the sigma and primary end-to-end anastomosis. We did not find in the literature consulted any cases of this illness under twenty years of age.

The early effects of valproic acid in low doses in liver metabolism.

The effect of low doses of valproic acid (VPA), 0.6 mM in arterial blood, in liver metabolism was studied. Twenty four hour fasted rats were infused into the jugular vein with VPA at a dose of 4 mg/kg/min during 50 min. The right carotid artery was also catheterized in order to draw arterial blood samples for determining VPA concentrations and acid-base parameters. After VPA infusion, a tissue sample of liver was obtained and freeze-clamped. VPA did not change the arterial blood acid-base parameters. The liver tissue concentration of pyruvate and alanine increased in VPA group while lactate concentrations did not change. Concentration of glutamine, glutamate, malate, citrate and aspartate in the liver fell significantly. These results suggest that VPA in low doses may modify the hepatic metabolism of the rat in vivo.

Effect of valproate on lactate and glutamine metabolism by rat renal cortical tubules.

The metabolic effects of sodium valproate (VPA) on rat renal cortical tubules have been examined. When 1 or 5 mM lactate was used as substrate in the incubation medium, VPA decreased markedly the lactate uptake by the tubules. When 1 or 5 mM glutamine was used, the addition of VPA accelerated glutamine uptake, ammoniagenesis, but also stimulated markedly the accumulation of lactate and pyruvate produced from glutamine. VPA had a dose-dependent inhibitory effect on gluconeogenesis from both glutamine and lactate. With 5 mM glutamine, VPA also induced a significant accumulation of glutamate in the medium. The oxygen consumption by the tubules was diminished by 40% following VPA addition. It is concluded that VPA modifies the metabolism of rat cortical tubules by interfering with the oxidation of natural substrates and stimulates in this fashion the production of ammonia by kidney tubules.