Acute hepatic failure （AHF） is a severe liver injury accompanied by hepatic encephalopathy which causes multiorgan failure with an extremely high mortality rate, even if intensive care is provided. ...Management of severe AHF continues to be one of the most challenging problems in clinical medicine. Liver transplantation has been shown to be the most effective therapy, but the procedure is limited by shortage of donor organs. Although a number of clinical trials testing different liver assist devices are under way, these systems alone have no significant effect on patient survival and are only regarded as a useful approach to bridge patients with AHF to liver transplantation. As a result, reproducible experimental animal models resembling the clinical conditions are still needed. The three main approaches used to create an animal model for AHF are： surgical procedures, toxic liver injury and infective procedures. Most common models are based on surgical techniques （total/partial hepatectomy, complete/transient devascularization） or the use of hepatotoxic drugs （acetaminophen, galactosamine, thioacetamide, and others）, and very few satisfactory viral models are available. We have recently developed a viral model of AHF by means of the inoculation of rabbits with the virus of rabbit hemorrhagic disease. This model displays biochemical and histological characteristics, and clinical features that resemble those in human AHF. In the present article an overview is given of the most widely used animal models of AHF, and their main advantages and disadvantages are reviewed.
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 β-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.
•Combining several materials to form composites is an accepted method for improving properties.•Understanding Structure-Properties relationship is essential in the design of new materials.•Addition ...of CMC produces structural changes in the cellulose microfibrils.•Monitoring the properties of cellulose composites by addition of CMC.
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 β-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/Iβ 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 β-relaxation strength and an increase of the dc-conductivity.
: This work was undertaken to investigate whether treatment with melatonin prevents oxidative stress and changes in the expression and activity of factor erythroid 2‐related factor 2 (Nrf2)‐mediated ...antioxidant enzymes in an animal model of fulminant hepatic failure of viral origin. Rabbits were experimentally infected with 2 × 104 hemagglutination units of a rabbit hemorrhagic disease virus (RHDV) isolate and received melatonin at two concentrations of 10 mg/kg and 20 mg/kg at 0, 12 and 24 hr postinfection. Blood transaminases, blood lactate dehydrogenase, liver concentration of thiobarbituric reactive acid substances and the liver oxidized to reduced glutathione ratio significantly increased at 36 hr postinfection in infected animals. Significant decreases were found in the mRNA levels and in the liver activities of Mn‐superoxide dismutase, glutathione peroxidase and glutathione‐S‐transferase in infected rabbits. These effects were prevented by melatonin administration in a concentration‐dependent manner. Melatonin treatment was not accompanied by changes in protein levels of Kelch‐like ECH‐associating protein 1 (Keap1) but resulted in an increased protein expression of Nrf2 in the cytoplasm and the nucleus, which was confirmed by the results of Nrf2 immunostaining. Nuclear extracts from livers of melatonin‐treated rats displayed an enhanced antioxidant responsive element (ARE)‐binding activity of Nrf2. Our results suggest a potential hepatoprotective role of melatonin in fulminant hepatic failure, partially mediated through the abrogation of oxidative stress and the prevention of the decreased activity of antioxidant enzymes via the Nrf2 pathways.
•Combining several materials to form composites is an accepted method for improving properties.•Understanding Structure-Properties relationship is essential in the design of new materials.•Monitoring ...the properties of carrageenan composites by addition of MMT.
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.
Spanish in international bibliography Culebras, Jesús M
Revista española de enfermedades digestivas,
10/2015, Letnik:
107, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Comments related to a review article about percutaneous gastrostomies written by Lucendo et al. in REED.
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