Natural Compounds as Therapeutic Agents: The Case of Human Topoisomerase IB

Natural products are widely used as source for drugs development. An interesting example is represented by natural drugs developed against human topoisomerase IB, a ubiquitous enzyme involved in many cellular processes where several topological problems occur due the formation of supercoiled DNA. Human topoisomerase IB, involved in the solution of such problems relaxing the DNA cleaving and religating a single DNA strand, represents an important target in anticancer therapy. Several natural compounds inhibiting or poisoning this enzyme are under investigation as possible new drugs. This review summarizes the natural products that target human topoisomerase IB that may be used as the lead compounds to develop new anticancer drugs. Moreover, the natural compounds and their derivatives that are in clinical trial are also commented on.     

Hide tanning with modified natural tannins

Tannin from “Acacia Mearnsii” usually called Mimosa, is largely employed in vegetal tanning of hide even if the quality of the leather is poorer than that obtained using chromium as tanning agents. However, taking into account the natural resources of this product and its reduced environmental impact, mimosa tannin has been modified to obtain leather having improved properties. Tannin was modified using formaldehyde, urea, a sulfonic acid and a sulfiting agent: The new products show a higher molecular weight than mimosa tannin but maintain a good solubility in water. Modified tannins were characterized through physicochemical and technological tests and evaluated as tanning agents. The properties of tanned leathers obtained using the new tannin products and mimosa were compared. Some of the polymers containing phenolsulfonic acid are good tannin agents, especially those with a suitable molecular weight. The technological and sensorial properties of the leather obtained using modified tannins (distension and strength of grain, tensile strength, elongation, and tear load) are better than those obtained using mimosa when an appropriate ratio of the reagents were employed. At the same time the feeling of the tanned leather was improved and the final products show fullness, elasticity, fluency, reactivity, and a thin and fine grain. Some of the tannins modified with naphtalensulfonic acid show poor tanning properties but good penetration in the leather suggesting their use as auxiliary sintans in the pretanning process. A simple procedure to prepare these modified tanning agents in the course of the tannin extraction is suggested. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Solar-powered aeration and disinfection, anaerobic co-digestion, biological CO2 scrubbing and biofuel production: the energy and carbon management opportunities of waste stabilisation ponds

Waste stabilisation pond (WSP) technology offers some important advantages and interesting possibilities when viewed in the light of sustainable energy and carbon management. Pond systems stand out as having significant advantages due to simple construction; low (or zero) operating energy requirements; and the potential for bio-energy generation. Conventional WSP requires little or no electrical energy for aerobic treatment as a result of algal photosynthesis. Sunlight enables WSP to disinfect wastewaters very effectively without the need for any chemicals or electricity consumption and their associated CO(2) emissions. The energy and carbon emission savings gained over electromechanical treatment systems are immense. Furthermore, because algal photosynthesis consumes CO(2), WSP can be utilised as CO(2) scrubbers. The environmental and financial benefits of pond technology broaden further when considering the low-cost, energy production opportunities of anaerobic ponds and the potential of algae as a biofuel. As we assess future best practice in wastewater treatment technology, perhaps one of the greatest needs is an improved consideration of the carbon footprint and the implications of future increases in the cost of electricity and the value of biogas.     

Fahr's disease and hypocalcemic syndromes. Presentation of a clinical case]

A clinical case of a man with calcification of basal ganglions (CBG) is presented. The first manifestations of this syndrome were loss of consciousness and convulsions. The potential causes of his hypocalcemia, Fahr's syndrome, myocardiopathy of hypoparathyroidism and hypocalcemia are reviewed and a study oriented to autoimmune polyendocrinopathy is performed.     

Electric Field Assisted Microfluidic Platform for Generation of Tailorable Porous Microbeads as Cell Carriers for Tissue Engineering

Injection of cell‐laden scaffolds in the form of mesoscopic particles directly to the site of treatment is one of the most promising approaches to tissue regeneration. Here, a novel and highly efficient method is presented for preparation of porous microbeads of tailorable dimensions (in the range ≈300–1500 mm) and with a uniform and fully interconnected internal porous texture. The method starts with generation of a monodisperse oil‐in‐water emulsion inside a flow‐focusing microfluidic device. This emulsion is later broken‐up, with the use of electric field, into mesoscopic double droplets, that in turn serve as a template for the porous microbeads. By tuning the amplitude and frequency of the electric pulses, the template droplets and the resulting porous bead scaffolds are precisely produced. Furthermore, a model of pulsed electrodripping is proposed that predicts the size of the template droplets as a function of the applied voltage. To prove the potential of the porous microbeads as cell carries, they are tested with human mesenchymal stem cells and hepatic cells, with their viability and degree of microbead colonization being monitored. Finally, the presented porous microbeads are benchmarked against conventional microparticles with nonhomogenous internal texture, revealing their superior performance.     

Linear segmented polyurethanes: I. A kinetics study

This work investigates the two‐step polymerization between methylene diphenyl diisocyanate (MDI), two different poly(tetramethylene oxide) macrodiols, and 1,4‐butanediol (BD) as chain extender. At the end of the prepolymerization, the reaction mixture contains MDI in excess and a prepolymer with isocyanate end group. Then, BD and a solvent (tetrahydrofuran) were added to start the finishing stage under nominal stoichiometric equilibrium. The reaction was analyzed by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance (¹H‐NMR), and size exclusion chromatography. ¹H‐NMR was employed to follow global concentrations of unreacted isocyanate end groups and internal urethane groups. This information enabled to estimate the following “effective” rate constants: k₁ = 1.07 × 10^?3 L mol^?1 s^?1 for the prepolymerization; and k₂ = 1.94 × 10^?4 L mol^?1 s^?1 for the finishing stage. These values are subject to errors caused by biases introduced in the recipe, in the measurements, in the reaction conditions, in the quality of reagents, and in the reaction mechanism assumptions. Such errors also explain the dispersion of the published rate constants values. The ¹H‐NMR measurements also enabled to estimate the evolution (with extent of reaction) of the number‐average number of structural units along the prepolymerization and finishing stages; and such estimates reasonably verify Flory's classical expressions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45747.     

HARD TURNING PLUS GRINDING–A COMBINATION TO OBTAIN GOOD SURFACE INTEGRITY IN AISI O1 TOOL STEEL MACHINED PARTS

The establishment of adequate machining guidelines requires the study of several factors (residual stresses, roughness, hardness, microstructural changes, etc.) that define the surface integrity generated in the part by a machining operation. This work studies the surface integrity generated in AISI O1 tool steel by four hard turning (conventional, laser assisted, MQL and conventional with worn tool) and two grinding (production and finishing) processes, as well as by a combined machining process (conventional hard turning + finishing grinding). Hard turning generates tensile stresses and strong structural changes in the machined surface while grinding causes compressive stresses and negligible structural changes. Below the surface, grinding generates slightly tensile or nearly null stresses whereas turning generates strong compressive stresses. The results obtained show that an optimum machining process would imply the combination of hard turning plus a slight final grinding.     

Edible films from mucilage of Cereus hildmannianus fruits: Development and characterization

Mucilages are heteropolysaccharides with rich monosaccharide composition. They are capable of forming films that are brittle and fragile, and in order to obtain flexible materials, plasticizers must be added. The present study aims to evaluate the physicochemical properties of mucilage‐based films produced with Cereus hildmannianus and different glycerol concentrations by the casting technique. Transparent and yellowish films were obtained by the addition of glycerol, which also improved handleability, evidenced by increased elongation, and reduced tensile strength and Young's modulus. Thermal gravimetric analysis and differential thermal analysis revealed that glycerol presence reduced the thermal stability, showing the influence of a plasticizer over the polymer structure. Water absorption capacity and contact angle were reduced with the increase of plasticizer concentration; on the other hand, the water vapor permeability increased, as expected, due to the hydrophilic nature of glycerol. The results indicated the potential application of C. hildmannianus mucilage as a promising material to produce edible films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45223.