Hemoperfusion by means of encapsuled charcoal for the treatment of exogenous and endogenous intoxications

The method developed by Chang for using in collodion and albumin encapsuled charcoal as artificial cells for hemoperfusion has been studied in vitro. The capacity for the absorption of more or less dialysable exogenous substances (barbiturate, Diazepam, Parathion) and an endogenous toxic metabolite (p-hydroxyphenyl acetic acid) has been examined. With the absorption unit one can eliminate 80 to 90 per cent of the initial concentration of barbiturate, Diazepam and p-hydroxyphenyl acetic acid in about 90 min, of Parathion about 50 per cent in the same time, whereas bromide and ammonia are not absorbed. Attempts to avoid regional heparinisation by the incorporation of heparin into the capsule of charcoal granules were not successful. Assuming correct preparation of the hemoperfusion system, observance of steril precoutions and regional heparinisation, the use of the "detoxication shunt" is a promising means in the treatment of severe exogenous and endogenous intoxications which are not accessible by conventional therapeutic means.     

Adsorption of amyloid beta (1-40) peptide at phospholipid monolayers

The folding of amyloid beta (1-40) peptide into beta-sheet-containing fibrils is thought to play a causative role in Alzheimer's disease. Because of its amphiphilic character, the peptide can interact with phospholipid membranes. Langmuir monolayers of negatively charged DPPS, DPPG, and DMPG, and also of zwitterionic DPPC and DMPC, have been used to study the influence of the peptide on the lipid packing and, vice versa, the influence of phospholipid monolayers on the peptide secondary structure by infrared reflection absorption spectroscopy and grazing incidence X-ray diffraction. The peptide adsorbs at the air/water (buffer) interface, and also inserts into uncompressed phospholipid monolayers. When adsorbed at the interface, the peptide adopts a beta-sheet conformation, with the long axis of these beta-sheets oriented almost parallel to the surface. If the lipid exhibits a condensed monolayer phase, then compression of the complex monolayer with the inserted peptide leads to the squeezing out of the peptide at higher surface pressures (above 30 mN m(-1)). The peptide desorbs completely from zwitterionic monolayers and negatively charged DPPG and DPPS monolayers on buffer, but remains adsorbed in the beta-sheet conformation at negatively charged monolayers on water. This can be explained in terms of electrostatic interactions with the lipid head groups. It also remains adsorbed at, or penetrating into, disordered anionic monolayers on buffer. Additionally, the peptide does not influence the condensed monolayer structure at physiological pH and modest ionic strength.     

In situ analysis of metal-oxide systems used for selective oxidation catalysis: how essential is chemical complexity?

The mode of operation of selective oxidation reactions is described by a series of chemical rules defining the catalyst and some reaction intermediates. In contrast to catalytic processes over metallic elements, little is known, however, about the atomistic details of selective oxidation. In particular, the participation of the subsurface region of the catalyst in the kinetically relevant elementary steps (Mars–van Krevelen mechanism) is not positively verified. Using in situ X-ray absorption techniques to study binary and ternary molybdenum oxides the present contribution shows that it is possible to tackle some of the problems in selective oxidation by direct experimental observation. The modification of the Mo–O local bonding interaction upon thermal reduction of MoO₃to MoO_3-x is illustrated. This was also found for mixed Mo–V oxides in which the chemical state of the vanadium seemed unaffected by the reaction but the surface Mo:V ratio varied substantially with the gas phase composition. It is further shown that the solid-state phase transformation between reduced and oxidised forms of molybdenum oxides occur so rapidly, that possibly relevant suboxide cannot be identified by ex situ phase analysis. Observation of the time-law of redox transformations showed that lattice oxygen is only available for selective oxidation if the associated solid-state transformation occurs in the kinetic regime of reaction control and not in that of diffusion control.     

Methanol oxidation over model cobalt catalysts: Influence of the cobalt oxidation state on the reactivity

X-ray photoelectron and absorption spectroscopies (XPS and XAS) combined with on-line mass spectrometry were applied under working catalytic conditions to investigate methanol oxidation on cobalt. Two cobalt oxidation states (Co₃O₄ and CoO) were prepared and investigated as regards their influence on the catalytic activity and selectivity. In addition adsorbed species were monitored in the transition of the catalyst from a non-active state, to an active one. It is shown that the surface oxidation state of cobalt is readily adapted to the oxygen chemical potential in the CH₃OH/O₂ reaction mixture. In particular, even in oxygen-rich mixtures the Co₃O₄ surface is partially reduced, with the extent of surface reduction following the methanol concentration. The reaction selectivity depends on the cobalt oxidation state, with the more reduced samples favouring the partial oxidation of methanol to formaldehyde. In the absence of oxygen, methanol effectively reduces cobalt to the metallic state, also promoting H₂ and CO production. Direct evidence of methoxy and formate species adsorbed on the surface upon reaction was found by analysing the O 1s and C 1s photoelectron spectra. However, the surface coverage of those species was not proportional to the catalytic activity, indicating that they might also act as reaction inhibitors.     

Tapping the wisdom tradition: Essential elements to mentoring students of color.

The relevance of race, ethnicity, and culture in the mentor–mentee relationship is the essence of this article. The authors argue that diversity education for those mentoring students of color merits an additional level of required expertise in the following key areas: culture and academia, shared/assumed existential posture, racial discrimination, race and ethnic self-awareness, and relationship and process. With support from APA publications, the authors highlight specific academic and professional concerns for students of color, to work toward effective mentoring of culturally diverse students. For prospective mentors of students of color, the authors make recommendations related to engagement, instruction, and integration of personal and professional identity. Further, the authors make recommendations for the management of experiences with discrimination and the recognition of racial identity and racial awareness in the mentor–mentee relationship. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual- and organizational-level consequences of organizational citizenship behaviors: A meta-analysis.

Although one of the main reasons for the interest in organizational citizenship behaviors (OCBs) is the potential consequences of these behaviors, no study has been reported that summarizes the research regarding the relationships between OCBs and their outcomes. Therefore, the purpose of this study is to provide a meta-analytic examination of the relationships between OCBs and a variety of individual- and organizational-level outcomes. Results, based on 168 independent samples (N = 51,235 individuals), indicated that OCBs are related to a number of individual-level outcomes, including managerial ratings of employee performance, reward allocation decisions, and a variety of withdrawal-related criteria (e.g., employee turnover intentions, actual turnover, and absenteeism). In addition, OCBs were found to be related (k = 38; N = 3,611 units) to a number of organizational-level outcomes (e.g., productivity, efficiency, reduced costs, customer satisfaction, and unit-level turnover). Of interest, somewhat stronger relationships were observed between OCBs and unit-level performance measures in longitudinal studies than in cross-sectional studies, providing some evidence that OCBs are causally related to these criteria. The implications of these findings for both researchers and practitioners are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Photoinduced switching of the current through a single molecule: effects of surface plasmon excitations of the leads

The photoinduced switch of the current through a single molecule is studied theoretically by including plasmon excitations of the leads. A molecule weakly linked to two spherical nanoelectrodes is considered resulting in sequential charge transmission scheme. Taking the molecular charging energy (relative to the equilibrium lead chemical potential) to be comparable to the molecular excitation energy, an efficient current switch in a low voltage range becomes possible. A remarkable enhancement of the current is achieved due to simultaneous plasmon excitations in the electrodes. The behavior is explained by an increased molecular absorbance due to oscillator strength transfer from the electrode plasmon excitations and by a net excitation energy motion from the electrodes to the molecule.     

In vitro investigations of a novel wound dressing concept based on biodegradable polyurethane

Non-healing and partially healing wounds are an important problem not only for the patient but also for the public health care system. Current treatment solutions are far from optimal regarding the chosen material properties as well as price and source. Biodegradable polyurethane (PUR) scaffolds have shown great promise for in vivo tissue engineering approaches, but accomplishment of the goal of scaffold degradation and new tissue formation developing in parallel has not been observed so far in skin wound repair. In this study, the mechanical properties and degradation behavior as well as the biocompatibility of a low-cost synthetic, pathogen-free, biocompatible and biodegradable extracellular matrix mimicking a PUR scaffold was evaluated in vitro. The novel PUR scaffolds were found to meet all the requirements for optimal scaffolds and wound dressings. These three-dimensional scaffolds are soft, highly porous, and form-stable and can be easily cut into any shape desired. All the material formulations investigated were found to be nontoxic. One formulation was able to be defined that supported both good fibroblast cell attachment and cell proliferation to colonize the scaffold. Tunable biodegradation velocity of the materials could be observed, and the results additionally indicated that calcium plays a crucial role in PUR degradation. Our results suggest that the PUR materials evaluated in this study are promising candidates for next-generation wound treatment systems and support the concept of using foam scaffolds for improved in vivo tissue engineering and regeneration.     

Stevia rebaudiana Bertoni – Überblick über die Forschung an einer verbotenen Pflanze und derer möglichen Einsätze

Stevia rebaudiana stammt aus dem Grenzgebiet zwischen Paraguay und Brasilien. Die F?higkeit dieser Pflanze, kalorienarme sü?schmeckende Glycoside in ihren Bl?ttern zu akkumulieren, macht sie für verschiedene Anwendungen in Form eines Zuckerersatzproduktes interessant. Obwohl die Pflanze und auch die Extrakte daraus seit Jahrhunderten von der einheimischen Bev?lkerung Lateinamerikas genutzt werden, sind S. rebaudiana und diese Extrakte (Stevioside) in der EU als Lebensmittelzusatz nicht zugelassen. Ein wichtiger Aspekt ist in diesem Zusammenhang die Gew?hrleistung einer bestimmten stofflichen Zusammensetzung dieses Naturproduktes. Um externe Faktoren, die suboptimales Wachstum von S. rebaudiana bewirken und ihren endogenen Stoffwechsel beeinflussen, ausschlie?en zu k?nnen, bietet sich die Sprosskultur im Bioreaktor an, zu der in diesem Beitrag n?here Erl?uterungen gegeben werden. Die Stevioside haben durch gute Wasserl?slichkeit und Kompatibilit?t mit verschiedenen organischen S?uren von Obst und Gemüse das Potenzial u. a. im Konditorei-Gewerbe und beim Herstellen von Getr?nken eingesetzt zu werden. Vor dem Einsatz sind aber toxikologische Fragen hinreichend zu prüfen.