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Role of Tumor Cell Membrane in Hyperthermia
Published in Leopold J. Anghileri, Jacques Robert, Hyperthermia In Cancer Treatment, 2019
The bilayer of lipids (Figure 1) is the geometrical pattern which best fits the energetic requirement needed to obtain stable arrangement of the lipids normally found in membranes and in the presence of an aqueous environment. This simple model has been used to formulate the unit membrane model,6 where proteins are layered on a continuous lipid bilayer and the membrane is stabilized by noncovalent bonds perpendicular to the plane of the bilayer: these bonds are essentially accomplished by polar interactions between ionic groups in the polypeptide chains and groups of opposite charges in the phospholipids. This type of interaction makes possible a dynamic lateral, structural organization within the bilayer and lateral phase separations resulting in domains consisting of only one or a few components.7
The Study of the Effect of UV-C Radiation on the Current–Voltage Characteristics of Chitosan Membranes
Published in Pandit B. Vidyasagar, Sagar S. Jagtap, Omprakash Yemul, Radiation in Medicine and Biology, 2017
Ni Nyoman Rupiasih, Made Sumadiyasa, Putu Erika Winasri
This chapter presents a study in which the effect of UV-C radiation on the characteristics of the current–voltage (I–V) curve in a chitosan membrane was studied. The membrane used was chitosan membrane 2%. Irradiation was done at ambient temperature in air media. The membranes were irradiated for short time intervals, e.g., 10, 20, 40, and 60 min, and some of them were kept without irradiation, which were used as a control. The ion transport experiments were carried out using a cell membrane model that was composed of two compartments. The electrolyte solution used was NaCl with concentrations of 0.1 and 10 mM and the applied currents were 19–24 μΑ with increment of 0.5 μA. The potential difference was measured using a pair of Activon AEP calomel electrodes. All measurements were conducted at room temperature. The results obtained that the current–voltage curves of both groups, i.e., control and irradiated membranes, showed the ohmic behavior (region I). The increasing exposure time caused an increase in potential difference across the membrane, which led to a decrease in the membrane conductivity. It also decreased the water uptake capability of the membrane. The results indicate that a very short UV-C irradiation (10 min) was able to change the ionic transport properties and the water uptake of chitosan membrane, which increased with increase in time.
Freeze-Fracture Images
Published in Sek Wen Hui, Freeze-Fracture Studies of Membranes, 1989
Sek Wen Hui, Pedro Pinto da Silva
The principal problem in Branton’s laboratory was to locate the fracture plane of membranes. He had proposed that membranes were split along a hydrophobic interior,10 a hypothesis that ran against that of Mohr and Mühlethaler11 (reviewed in Reference 2), who argued that fracture followed the surface of membranes. Branton had advanced his hypothesis based on the morphological interpretation of specimens impregnated in glycerol, freeze-fractured, and then subjected to a period of sublimation (“etching”). This approach proved less than convincing, in part, because it appeared circular (new rules of interpretation were used to formulate new rules of interpretation) and because, should membrane splitting occur, it implied a membrane model that failed to align itself with any of the then prevailing models of membrane structure: on one side Daneilli,12 Robertson,13 and all of those who proposed biological membranes as comprised of planar bilayers of amphipatic lipids coated with adsorbed proteins; on the other, those who held that biomembranes were planar aggregates of lipoprotein structures (among these Sjostrand,14 Green and Fleischer,15 Benson and Singer,16 and others, many working with mitochondrial membranes).
A hybrid model to evaluate the impact of active uptake transport on hepatic distribution of atorvastatin in rats
Published in Xenobiotica, 2020
Priyanka Kulkarni, Ken Korzekwa, Swati Nagar
The aim of this study was to evaluate the utility of a semi-physiological hybrid model to study the effect of active uptake transport on intracellular and plasma ATV disposition. Specifically, the impact of liver in distribution of ATV was studied. For the first time, the explicit membrane model for the liver was combined with a compartmental pharmacokinetic (PK) model for the rest of the body. In vivo PK studies for ATV were conducted in male Sprague Dawley rats in presence and absence of the active uptake inhibitor, rifampicin (RIF). Intravenous dosing was utilized to evaluate the distribution and elimination of ATV, and to eliminate the processes of oral absorption and first-pass hepatic and intestinal metabolism from subsequent modeling efforts. The compartmental mammillary model and semi-physiological hybrid models were separately fit to the plasma concentration-time data. The role of the liver as a distributing organ in addition to an eliminating organ was examined by comparison of the distribution parameters from the compartmental mammillary model and the semi-physiological hybrid model.
Lipidomic analysis of cancer cells cultivated at acidic pH reveals phospholipid fatty acids remodelling associated with transcriptional reprogramming
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Lorena Urbanelli, Sandra Buratta, Mariantonia Logozzi, Nico Mitro, Krizia Sagini, Rossella Di Raimo, Donatella Caruso, Stefano Fais, Carla Emiliani
The role of pH on the structure and dynamics of membrane lipids has been investigated on membrane model systems. Studies reported that low pH enhances membrane thickness, influences spontaneous curvature and induces head group protonation40,41. However, when cells are adapted to grow at low pH, only the external leaflet must adapt physically to an elevated H+ concentration, whereas the rest of the cell membranes must adapt to support this growth condition without being directly exposed to low pH. ER and plasma membrane show differences in their lipid composition, as sterols and sphingolipids are present at a low percentage in the ER and their abundance increase in the route to the Golgi and the plasma membrane42. Similarly, phospholipids are more saturated at the plasma membrane than at the ER. For this reason, further insight on the phospholipid composition of specific cell fractions is needed to understand the role of phospholipid remodelling towards longer and unsaturated acyl chains in cells exposed to a low extracellular pH, as the function of specific subcellular organelle biomembranes could be affected.
Comparative study between lutein and its liposomal form on cisplatin-induced retinal injury in rabbits
Published in Cutaneous and Ocular Toxicology, 2019
Amal E. Ibrahim, Medhat W. Shafaa, Mahmoud H. Khedr, Rawda F. Rashed
In this study, we reported the properties of a liposomal form of lutein developed in order to reduce the retinal toxicity of cisplatin. The antioxidant activity of lutein after liposome encapsulation was not only associated with their chemical reactivity but also with their incorporation efficiencies into liposomal membrane and modulating effects on the membrane properties [25]. Liposomes are artificial membranous vesicles formed by phospholipids bilayers. Liposomes have long been receiving a lot of care due to their biocompatibility and appealing ability to carry both hydrophobic and hydrophilic compounds. Liposomes are used as a membrane model, because of their similarity with the bilayer structure of natural membranes. The similarity between the liposomes and membrane bilayer core makes liposomes a very valuable means to explore the significance of carotenoids-membrane interactions.