Electron microscopy investigations of metal-support interaction effects in M/Y2O3 and M/ZrO2 thin films (M=Cu,Ni)

Model systems of the clean and pure oxides Y₂O₃ and ZrO₂, as well as Cu/Cu₂O and Ni/NiO particles embedded in the respective oxides have been used to study the reduction behavior of the oxides and the eventually associated metal-support interaction effects in oxide-supported systems. Particular emphasis has also been given to the influence of the phase transformation in ZrO₂-containing systems on metal-support interaction. Whereas Y₂O₃ has been found to be an outstandingly structurally and thermally stable oxide even upon reduction in hydrogen up to 1073 K, ZrO₂ was found to undergo a series of phase transformations from amorphous ZrO₂ to polycrystalline tetragonal ZrO₂ (∼673 K) and subsequently to monoclinic ZrO₂ (above 873 K). Both phase transformations were found to be basically dependent on gas partial pressure and annealing rate. However, substantial reduction of the oxides did not take place during the phase transformations. In turn, both Cu- and Ni-containing systems were not observed to be substantially affected by any (strong) metal-support interaction effects such as encapsulation by sub-stoichiometric oxides or reductive formation of intermetallic phases, at least up to temperatures of 1073 K. Equally, for the ZrO₂-containing systems, also the phase transformations occurring at elevated temperatures did not cause structural or thermo-chemical alterations of the Cu or Ni-particles. Differences in the metal-support interaction between Cu- and Ni-particles have only been obtained in the structural “reference” systems, that is, if supported on SiO₂. Whereas Cu/Cu₂O particles on SiO₂ are basically unaffected by the reductive treatment at elevated temperatures, a Ni₃Si₂ intermetallic phase is formed if SiO₂-supported Ni/NiO particles are treated in hydrogen at 673 K and above.     

Volatile lactones from streptomycetes arise via the antimycin biosynthetic pathway

The volatiles released by several streptomycetes were collected by using a closed-loop stripping apparatus (CLSA) and analysed by GC-MS. The obtained headspace extracts of various species contained blastmycinone, a known degradation product of the fungicidal antibiotic, antimycin A(3b), and several unknown derivatives. The suggested structures of these compounds, based on their mass spectra and GC retention indices, were confirmed by comparison to synthetic reference samples. Additional compounds found in the headspace extracts were butenolides formed from the blastmycinones by elimination of the carboxylic acid moiety. Analysis of a gene knockout mutant in the antimycin biosynthetic gene cluster demonstrated that all blastmycinones and butenolides are formed via the antimycin biosynthetic pathway. The structural variation of the blastmycinones identified here is much larger than within the known antimycins, thus suggesting that several antimycin derivatives remain to be discovered.     

No effect of creatine supplementation on oxidative stress and cardiovascular parameters in spontaneously hypertensive rats

Background

Exacerbated oxidative stress is thought to be a mediator of arterial hypertension. It has been postulated that creatine (Cr) could act as an antioxidant agent preventing increased oxidative stress. The aim of this study was to investigate the effects of nine weeks of Cr or placebo supplementation on oxidative stress and cardiovascular parameters in spontaneously hypertensive rats (SHR).

Findings

Lipid hydroperoxidation, one important oxidative stress marker, remained unchanged in the coronary artery (Cr: 12.6 ± 1.5 vs. Pl: 12.2 ± 1.7 nmol·mg^-1; p = 0.87), heart (Cr: 11.5 ± 1.8 vs. Pl: 14.6 ± 1.1 nmol·mg^-1; p = 0.15), plasma (Cr: 67.7 ± 9.1 vs. Pl: 56.0 ± 3.2 nmol·mg^-1; p = 0.19), plantaris (Cr: 10.0 ± 0.8 vs. Pl: 9.0 ± 0.8 nmol·mg^-1; p = 0.40), and EDL muscle (Cr: 14.9 ± 1.4 vs. Pl: 17.2 ± 1.5 nmol·mg^-1; p = 0.30). Additionally, Cr supplementation affected neither arterial blood pressure nor heart structure in SHR (p > 0.05).

Conclusions

Using a well-known experimental model of systemic arterial hypertension, this study did not confirm the possible therapeutic effects of Cr supplementation on oxidative stress and cardiovascular dysfunction associated with arterial hypertension.     

Use of the BioHole™ device for the creation of tunnel tracks for buttonhole cannulation of fistula for hemodialysis

Buttonhole cannulation is a method of cannulation of native arteriovenous fistulae traditionally practiced by self‐cannulators. At St Michael's Hospital, this method has been modified to allow its use in problematic fistulae by multiple cannulators. In a busy dialysis unit, the need for a few specific cannulators to establish the tunnel tracks in combination with the variable dialysis schedules creates logistical challenges. A new method of creating tunnel tracks with the use of the BioHole^? device was evaluated. Buttonhole tracks were created in 12 patients using a peg of polycarbonated material with a holder (BioHole^? kit). The peg was inserted into the path left by the hemodialysis sharp needle following the index cannulation. Four of the 12 patients had an alternate access. Buttonhole tracks were successfully created in all the patients, albeit in 2 patients, the initial attempt to establish buttonhole tracks was aborted due to complications and the procedure was rescheduled. Compared with the modified buttonhole technique, pain on cannulation following track creation was significantly less in the BioHole^? group (P<0.001). Ease of cannulation was significantly improved in the BioHole^? group (P<0.05) when compared with that in thrice‐weekly patients using the modified buttonhole technique. Hemostasis postdialysis did not differ between the study groups. The use of the BioHole^? device is effective in the creation of tunnel tracks for buttonhole cannulation, is associated with less pain, and simplifies the logistics of arranging patient and nurses' schedules.     

Polymeric vesicles: from drug carriers to nanoreactors and artificial organelles

One strategy in modern medicine is the development of new platforms that combine multifunctional compounds with stable, safe carriers in patient-oriented therapeutic strategies. The simultaneous detection and treatment of pathological events through interactions manipulated at the molecular level offer treatment strategies that can decrease side effects resulting from conventional therapeutic approaches. Several types of nanocarriers have been proposed for biomedical purposes, including inorganic nanoparticles, lipid aggregates, including liposomes, and synthetic polymeric systems, such as vesicles, micelles, or nanotubes. Polymeric vesicles--structures similar to lipid vesicles but created using synthetic block copolymers--represent an excellent candidate for new nanocarriers for medical applications. These structures are more stable than liposomes but retain their low immunogenicity. Significant efforts have been made to improve the size, membrane flexibility, and permeability of polymeric vesicles and to enhance their target specificity. The optimization of these properties will allow researchers to design smart compartments that can co-encapsulate sensitive molecules, such as RNA, enzymes, and proteins, and their membranes allow insertion of membrane proteins rather than simply serving as passive carriers. In this Account, we illustrate the advances that are shifting these molecular systems from simple polymeric carriers to smart-complex protein-polymer assemblies, such as nanoreactors or synthetic organelles. Polymeric vesicles generated by the self-assembly of amphiphilic copolymers (polymersomes) offer the advantage of simultaneous encapsulation of hydrophilic compounds in their aqueous cavities and the insertion of fragile, hydrophobic compounds in their membranes. This strategy has permitted us and others to design and develop new systems such as nanoreactors and artificial organelles in which active compounds are simultaneously protected and allowed to act in situ. In recent years, we have created a variety of multifunctional, proteinpolymersomes combinations for biomedical applications. The insertion of membrane proteins or biopores into the polymer membrane supported the activity of co-encapsulated enzymes that act in tandem inside the cavity or of combinations of drugs and imaging agents. Surface functionalization of these nanocarriers permitted specific targeting of the desired biological compartments. Polymeric vesicles alone are relatively easy to prepare and functionalize. Those features, along with their stability and multifunctionality, promote their use in the development of new theranostic strategies. The combination of polymer vesicles and biological entities will serve as tools to improve the observation and treatment of pathological events and the overall condition of the patient.     

Preparation, characterization, and antibacterial activity of photocured thymol-doped acrylic resins

This article describes the preparation of thymol-doped acrylic resins by photopolymerization of solutions of thymol in tripropylenglycoldiacrylic monomer. This provides an easy, energy-saving, and environmental friendly process to prepare antibacterial plastics (fulfilling most of the “green chemistry” requirements). The results demonstrate that thymol can be included in the resin even at high concentration (up to 28.6%) without affecting the photocuring reaction and losing transparency. The glass transition temperature of the doped resin decreases when the thymol content increases, as it behaves like a plasticizer with respect to the acrylic resin. As indicated by HPLC analysis, thymol can be released in liquid media at a rate that depends on the chemical nature of the liquid. Evaluation by agar diffusion assays showed an antibacterial activity on both Gram-negative and Gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli). The antibacterial activity can occur just on the plastic surface when the thymol-doped resins is applied as thin coating, while it is evident also in the surrounding agar medium for doped plastic discs, 1.2 mm thick with a concentration of thymol in the resin higher than 16.7%.     

ENGINEERING ASPECTS OF PENICILLIN G TRANSFER AND CONVERSION TO 6-AMINOPENICILLANIC ACID IN A BIOREACTOR WITH A MOBILE BED OF IMMOBILIZED PENICILLIN AMIDASE

This article presents studies on the external and internal mass transfers of penicillin G for 6-aminopenicillanic acid enzymatic production using a bioreactor with a stirred bed of immobilized penicillin amidase. By means of the substrate mass balance for a single particle of biocatalyst and considering the kinetic model adapted for competitive and noncompetitive inhibitions, specific mathematical models were developed for describing the profiles of penicillin G concentration in the outer and inner regions of biocatalyst and for estimating its mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of the mass flows are significantly influenced by the internal diffusion velocity and rate of the enzymatic conversion of substrate. These cumulated influences led to the appearance of an enzymatic inactive region near the particle center, its magnitude varying from 0 to 9.2% of the overall volume of particles.