Thermisches Verhalten von Mono-, Bis- und Poly-2-oxazolidinonen

In connection with investigations of the thermal stability of isocyanurate and 2-oxazolidinone ring structures in cross-linked molding resins of high dimensional thermal stability, mono-, bis- and poly-2-oxazolidinones, synthesized from isocyanates and purified commercial epoxides of varying structure, have been characterized and their thermal stability in the temperatur range from 230 to 260°C has been studied. Tempering the 2-oxazolidinones under exclusion of air and moisture results in autocatalytic decomposition, increasing with the content of 2-oxazolidinone rings and with tempering time. The gaseous reaction product consisted mainly of carbon dioxide (≥94%). The residual amounts of 2-oxazolidinone and the amounts of carbon dioxide formed supplemented each other to nearly 100%. For the cleavage of the 2-oxazolidinone ring of mono-2-oxazolidinone a first order reaction was found to prevail up to about 15% conversion. The corresponding activation energy was calculated to be 130 kJ/mole. The 2-oxazolidinones investigated showed a dependence of the thermal stability upon the structure of the epoxides used. The reaction products of the 2-oxazolidinone cleavage attack the isocyanurate ring.     

Regionalization and service medicine

A comprehensive plan for perinatal regionalization in the medical facilities of the military services is advocated. Factors peculiar to military medicine which must be recognized in planning are discussed.     

Implications of orthopedic fretting corrosion particles on skeletal muscle microcirculation

Particulate corrosion and wear products of metal implants are increasingly becoming topics of interest, due to the cascade of biological and biomechanical events they induce. The impairment of skeletal muscle microcirculation by fretting corrosion particles may have profound consequences. We therefore studied in vivo leukocyte-endothelial cell interaction in skeletal muscle after confrontation with characterized titanium and stainless steel fretting corrosion particles, and compared these results with those of the bulk materials. Using the hamster dorsal skinfold chamber preparation and intravital microscopy, we could demonstrate that stainless steel induces a more pronounced inflammatory answer in contrast to the implant material titanium. However, we were not able to show a general benefit of bulk vs. debris. Overall, the study suggests that not only the bulk properties of orthopaedic implants, but also the microcirculatory implications of inevitable wear debris, may play a role in determining biocompatibility and ultimately longevity of an implant. The skinfold chamber is a feasible and versatile model for observation of the dynamic process of microvascular response after foreign-body implantation, and offers much perspective.     

Quantification of amino acids in fermentation media by isocratic HPLC analysis of their α-hydroxy acid derivatives

In this paper we describe a novel method for quantification of amino acids. First, α-hydroxy acid derivatives of amino acids were formed after reaction with dinitrogen trioxide by the van Slyke reaction. Second, the α-hydroxy acid derivatives were separated on an Aminex HPX-87H column (Bio-Rad) eluted isocratically with 5 mM H(2)SO(4) and quantified by refractive index detection. We were able to measure the reaction products of 13 of the 20 classical amino acids: glycine, l-alanine, l-valine, l-leucine, l-isoleucine, l-methionine, l-serine, l-threonine, l-asparagine, l-glutamine, l-aspartic acid, l-glutamic acid, and l-proline. We obtained linear relationships between the product peak areas and initial amino acid concentration, whereby the concentrations of these amino acids could be quantified on the basis of the quantification of their products. The method can be used to analyze amino acids in parallel with other small molecules, such as sugars or short chain fatty acids, and was used for parallel quantification of glycine, l-alanine, or l-glutamic acid, and glucose uptake in cultures of the heterotrophic dinoflagellate Crypthecodinium cohnii . The method can also be used to quantify other amines, as demonstrated by detection of Tris (2-amino-2-(hydroxymethyl)propane-1,3-diol).     

Alternative Methods for Determination of Certified Value and its Uncertainty: Case Study of Using the Gravimetric Method for Preparation of Gaseous Primary Reference Material of Ethanol in Nitrogen at the Slovak Institute of Metrology

Measurement Techniques - Gaseous mixtures of ethanol in nitrogen are prepared by the gravimetric method according to ISO 6142. The liquid component, ethanol, is added into the cylinder by the gas...     

Behead and live long or the tale of cathepsin L

In recent decades Saccharomyces cerevisiae has proven to be one of the most valuable model organisms of aging research. Pathways such as autophagy or the effect of substances like resveratrol and spermidine that prolong the replicative as well as chronological lifespan of cells were described for the first time in S. cerevisiae. In this study we describe the establishment of an aging reporter that allows a reliable and relative quick screening of substances and genes that have an impact on the replicative lifespan. A cDNA library of the flatworm Dugesia tigrina that can be immortalized by beheading was screened using this aging reporter. Of all the flatworm genes, only one could be identified that significantly increased the replicative lifespan of S.cerevisiae. This gene is the cysteine protease cathepsin L that was sequenced for the first time in this study. We were able to show that this protease has the capability to degrade such proteins as the yeast Sup35 protein or the human α‐synuclein protein in yeast cells that are both capable of forming cytosolic toxic aggregates. The degradation of these proteins by cathepsin L prevents the formation of these unfolded protein aggregates and this seems to be responsible for the increase in replicative lifespan.