The effects of severe plastic deformation on the mechanical and corrosion characteristics of a bioresorbable Mg-ZKQX6000 alloy.

In this work, a bioresorbable Mg-ZKQX6000 (Mg-6Zn-0.6Zr-0.4Ag-0.2Ca (wt%)) alloy was severely plastically deformed via equal channel angular pressing (ECAP) according to three unique hybrid routes at low temperatures (200 °C to 125 °C). The roles of ECAP processing on microstructure, and ensuing mechanical properties and corrosion rates, are assessed. Microstructurally, ECAP induces a complex plethora of features, especially variations in grain sizes and precipitates' sizes, distributions, and morphologies for individual cases. Mechanically, ECAP generally refined grain size, resulting in ultra-high strength levels of about 400 MPa in ultimate tensile strength for several cases; however, deformation via ECAP of precipitates induced embrittlement and low elongation to failure levels. Corrosion testing, conducted in simulated bodily fluid at bodily pH levels to mimic conditions in the human body, revealed consistent corrosion rates across several techniques (mass loss, hydrogen evolution, and electrochemical impedance spectroscopy (EIS)), showing that severe plastic deformation deteriorates corrosion resistance for this material. In-situ corrosion monitoring explained that corrosion accelerated after ECAP due to the creation of heterogeneous, anodic shear zones, which exhibited dense regions of refined grains and fine precipitates. Suggestions for future design and thermomechanical processing of Mg alloys for bioresorbable orthopedic implants are provided.

Biocompatibility and degradation of LAE442-based magnesium alloys after implantation of up to 3.5years in a rabbit model.

UNLABELLED: Magnesium as basic implant material has long been the center of orthopedic research. Latest progress is achieved with a European certification and clinical use of a magnesium based compression screw. However, long term studies with implantation duration that exceed one year considerably do not exist. The present examinations analyzed the degradation progress from nine months to 3.5year after implantation of cylindrical pins into the medullary cavity of New Zealand White rabbits. Evaluation included clinical assessment, in vivo µ-computed tomography, analysis of the implants by three-point-bending and examination of the adjacent tissue by means of histology and of inner organs by mass- and optical emission spectrometry using inductively coupled plasma. Clinical acceptance was without objections in all animals. Immoderate reaction of the surrounding bone could be found in neither of the applied techniques. While in vivo µ-computed tomography showed a very slow degradation rate up to 72weeks, three-point-bending revealed a percentage loss of F(max) of 41.1% for implants after 9months implantation and 88.47% for the implant after 3.5years implantation. Although the total amounts of RE detected in the inner organs were very low, the organs of rabbits with LAE442 cylinders showed 10-20-fold increased concentrations of the alloying elements lanthanum, cerium, neodymium and praseodymium compared to animals without any implanted material. STATEMENT OF SIGNIFICANCE: This is the first animal study investigating the degradation process of a magnesium alloy in vivo for up to 3.5years. Currently available data from different other in vivo studies cover only implantation durations up to one year. Therefore, the analysis of these long-time effects in the present study is highly significant and of great interest. Comprehensive outcome achieved by different techniques was assessed. The degradation process was slow and homogenous. Maximum applied force (F(max)) reduced by 41.1% for implants after 9months and by 88.47% for the implant after 3.5years implantation. Total amounts of RE detected in the inner organs were very low; the organs of rabbits with LAE442 cylinders showed 10-20-fold increased concentrations.

A novel biodegradable frontal sinus stent (MgNd2): a long-term animal study.

The frontal sinus recess consists of anatomically narrow passages that are prone to stenosis in endonasal frontal sinus surgery for chronic sinus disease. Over the past 100 years, diverse frontal sinus stents have been developed and evaluated in clinical and animal studies. However, superinfection, formation of granulations tissue, stent dislocation and late stenosis of the duct have remained challenges and subject of debate in the literature. Currently developed biodegradable materials, including rare earth-containing magnesium alloys are promising candidates for application as temporary implant materials. The Mg 2 % wt Nd alloy (MgNd2) was used to design a nasal stent that fit the porcine anatomy. In the current study, we evaluate biocompatibility, biodegradation and functionality of a frontal sinus stent in 16 minipigs over 6 months. Intraoperative endoscopy revealed free stent lumen in all cases. Blood examination and clinical examinations indicated no systematic or local inflammation signs. The histopathology and elements analysis showed a very good biocompatibility. The µ-computed tomography-based volumetric analysis showed substantial stent degradation within 6 months. Our MgNd2 based stent appears to be a promising, solid basis for the development of a frontal sinus stent for clinical use.

MgNd2 alloy in contact with nasal mucosa: an in vivo and in vitro approach.

Biodegradable and biocompatible magnesium alloys appear to be very promising not only for temporary clinical application but also for developing deformable and degradable medical implants. This study analyzes the in vivo degradation behavior and the impact on the paranasal sinuses of the highly ductile Mg-2 wt%Nd alloy (MgNd2) in order to provide a basis for a satisfying stent system for the therapy of a chronic sinusitis. Moreover, in vitro tests were carried out on primary porcine nasal epithelial cells (PNEC). For the in vivo tests, cylindrical MgNd2 specimens were implanted into the sinus' mucosa of minipigs. During and after a total period of 180 days the long-term biodegradation and biocompatibility properties after direct contact with the physiological tissue were analyzed. Biodegradation was investigated by measuring the mass and volume losses of the MgNd2 specimens as well as by performing element analyses to obtain information about the degradation layer. The influence on the surrounding tissue of paranasal sinuses was evaluated by endoscopic and histopathological examinations of the mucosa. Here, only a locally unspecific chronic infection was found. The degradation rate showed a maximum after 45 days postsurgery and was determined to decrease subsequently. In vitro experiments using PNEC showed adequate biocompatibility of MgNd2. This study demonstrates a good in vivo biocompatibility for MgNd2 in the system of paranasal sinuses and underlines the promising properties of alloy MgNd2 for biodegradable nasal stent applications.

In vitro and in vivo corrosion of the novel magnesium alloy Mg-La-Nd-Zr: influence of the measurement technique and in vivo implant location.

For the evaluation of new magnesium-based alloys, many different in vitro and in vivo methods are used. It was the aim of the current study to perform in vitro and in vivo corrosion studies of the new alloy Mg-La-Nd-Zr for its evaluation as a promising new degradable material and to compare commonly used evaluation methods. Die casted and subsequent extruded cylindrical pins (Ø1.5 mm; length 7 mm, [Formula: see text]) were implanted subcutaneously ([Formula: see text]), intramuscular ([Formula: see text]) and intramedullary ([Formula: see text]) in female Lewis rats with a postoperative follow up of 8 weeks; subsequent µ-computed tomographical analyses (XTremeCT and µCT80) were performed as well as weight analysis prior to and after implantation. Cubes (5 mm × 4 mm × 4 mm; surface area, 1.12 cm(2); [Formula: see text]) were used for in vitro corrosion (HBSS and RPMI 1640 + 10% FBS medium) and cytocompatibility studies (L929 cells). First of all it could be stated that implant location strongly influences the in vivo corrosion rate. In particular, intramedullary implanted pins corroded faster than pins in a subcutaneous or intramuscular environment. Considering the different evaluation methods, the calculated ex vivo µCT-based corrosion rates resulted in comparable values to the corrosion rates calculated by the weight loss method, especially after chromatic acid treatment of the explanted pins. The in vitro methods used tend to show similar corrosion rates compared to in vivo corrosion, especially when a RPMI medium was used, and therefore are suitable to predict corrosion trends prior to in vivo studies. Regarding cytocompatibility, the novel magnesium alloy Mg-La-Nd-Zr showed sufficient cell viability and therefore can be considered as a promising alloy for further applications.

In vivo degradation effects of alloy MgNd2 in contact with mucous tissue.

Magnesium alloys are currently being investigated for use as resorbable biomaterials. Various applications for magnesium based implant materials have already been presented. Currently, stents and structures that sustain diseased or narrowed vessels seem to be the most promising areas. This study focuses on the use of a magnesium fluoride (MgF2 ) coated magnesium neodymium based alloy (MgNd2 ) and its use as a postsurgery stent material to avoid proliferation in the sinus region. Simple cylindrical shaped specimens were sown to the sinus' mucosa of pigs and left in place for different periods of time to investigate the long-term corrosion resistance of the alloy and its coating during direct contact with physiological tissue. Investigations made within this study explicitly focused on the corrosive behavior of the alloy in the region of a physiological sinus. Thus, losses in mass and volume, and element analyses were considered to obtain information about the specimens' corrosion performance over time. Furthermore, micrographs support the alloy specific corrosion type analyses which focus on grain boundary effects. This study demonstrates the general in vivo applicability of fluoride coated MgNd2 . The progress of corrosion was determined to be adequate and homogeneous over a total period of 180 days.

Magnesium degradation products: effects on tissue and human metabolism.

Owing to their mechanical properties, metallic materials present a promising solution in the field of resorbable implants. The magnesium metabolism in humans differs depending on its introduction. The natural, oral administration of magnesium via, for example, food, essentially leads to an intracellular enrichment of Mg(2+) . In contrast, introducing magnesium-rich substances or implants into the tissue results in a different decomposition behavior. Here, exposing magnesium to artificial body electrolytes resulted in the formation of the following products: magnesium hydroxide, magnesium oxide, and magnesium chloride, as well as calcium and magnesium apatites. Moreover, it can be assumed that Mg(2+) , OH(-) ions, and gaseous hydrogen are also present and result from the reaction for magnesium in an aqueous environment. With the aid of physiological metabolic processes, the organism succeeds in either excreting the above mentioned products or integrating them into the natural metabolic process. Only a burst release of these products is to be considered a problem. A multitude of general tissue effects and responses from the Mg's degradation products is considered within this review, which is not targeting specific implant classes. Furthermore, common alloying elements of magnesium and their hazardous potential in vivo are taken into account.

Characterization of MgNd2 alloy for potential applications in bioresorbable implantable devices.

The aim of this study is to investigate and demonstrate the mechanical and corrosive characteristics of the neodymium-containing magnesium alloy MgNd2 (Nd2), which can be used as a resorbable implant material, especially in the field of stenting applications. To determine the mechanical characteristics of Nd2, tensile and compression tests were initially carried out in the hot extruded state. Here a unique elongation ratio (~30%) of the alloy could be observed. Subsequent T5 and T6 heat treatments were arranged to reveal their effect on the alloy's strengths and elongation values. The general degradation behaviour of Nd2 in a 0.9% NaCl solution was investigated by means of polarization curves and hydrogen evolution. In addition to this, by using various in vivo parameters, a corrosion environment was established to determine the alloy's degradation in vitro. Here, the mass loss per day in (MgF(2) and Bioglass)-coated and uncoated states and the corresponding maximum forces resulting from subsequent three-point bending tests revealed slow and steady corrosion behaviour. The cell viability and proliferation tests carried out on L-929 and MSC-P5 cells also showed good results. The mechanical and corrosive characteristics determined, as well as the in vitro test results obtained within the scope of this study, led to the development and successful in vivo testing of an MgF(2)-coated Nd2 mucosa stent which was introduced as an appropriate resorbable application.

Isometric non-machine-based prevention training program: effects on the cross-sectional area of the paravertebral muscles on magnetic resonance imaging.

PURPOSE: The purpose of this study was to determine potential effects of isometric non-machine-based training on the cross-sectional area (CSA) of the paravertebral muscles in volunteers who were participants in a prevention program. An increase in the CSA of back muscles after various machine-based exercises have been reported but non-machine-based training programs have not been adressed before. MATERIALS AND METHODS: In the study 14 volunteers, who were participants of a company internal prevention program, underwent a magnetic resonance (MR) examination before and after a 3 months training program to improve back muscle strength. The MRI protocol consisted of T1-weighted and T2-weighted images aligned to the intervertebral disc spaces. The CSAs of the erector spinae and quadratus lumborum muscles were assessed twice by 2 operators at the levels L3/4, L4/5 and L5/S1. RESULTS: Out of 14 subjects 11 completed the training. The recorded CSA values exhibited an intrarater and intrarater correlation coefficient ranging from 0.949 to 0.989. There was an increase in CSA in all subjects after the training period (mean increase 8%). CONCLUSIONS: A 3-month isometric training program is sufficient to effect measurable increases in back muscles volume. The study demonstrated the usefulness of MRI to quantify such changes as a measure of training efficacy and compliance into the training program. These results represent a rationale for further studies to determine the effect of different training methods on the CSA of back muscles and to correlate structural changes with clinical symptoms in chronic low back pain syndrome.

[Study of plant lectins from Viscum album using monoclonal antibodies]. / Issledovanie rastitel'nykh lektinov iz omely beloi s pomoshch'iu monoklonal'nykh antitel.

Monoclonal antibodies (monAT) against both native (TA5, TB12) and denatured (TB33, TB35) plant toxin ML1 from Viscum album have been obtained. The interaction of monAT against native toxin with its isoforms ML2 and ML3 was investigated. It was shown that monAT TA5 to A-chain of ML1 toxin cross-reacted with ML2 and ML3 isoforms. TA5 did not inhibit enzyme activity of A-chain in cell-free rabbit reticulocyte system. It was shown that monAT TB12 reacted with galactose-binding site of B-subunit. Both monAT had no cross-reactions with plant toxin ricin. The binding constants for TA5 with ML1, ML2, ML3 respectively were 4.3.10(7) M-1, 1.2.10(7) M-1, and 0.3.10(7) M-1. The binding constants for TB12 were 2.10(7) M-1 with ML1 toxin, and more than 10(6) M-1 with ML2 and ML3. The nature of heterogeneity in ML toxin family is discussed. Test-systems for ML1 determination in different V. album extracts are suggested.

[Incomplete spontaneous esophageal rupture - a variant of the Mallory-Weiss and Boerhaave syndrome?]. / Inkomplette spontane Osophagusruptur - eine Variante des Mallory-Weiss-bzw. des Boerhaave-Syndroms?

Belching and severe vomiting may lead in association with gastro-oesophageal prolapse to a variety of lesions within the gastro-oesophageal junction. Incarceration of the prolapse, diffuse hemorrhage from the prolapsed mucosa, longitudinal lacerations (Mallory-Weiss syndrome), intramural hematoma and spontaneous rupture (Boerhaave syndrome) are the most common complications. Based on 4 cases of incomplete rupture of the oesophagus we would like to draw attention to a disorder with mediastinal emphysema or pneumopericardium following severe vomiting. It is postulated that air escapes from a mucosal tear in the terminal oesophagus into the mediastinum. Conservative treatment seems justified.

Differences in toxicity and antigenicity between mistletoe lectin I and viscotoxin A 3.

In contrast to mistletoe lectin I (ML I), viscotoxin A 3 does not inhibit protein synthesis in cell-free systems. From the immunological studies it is concluded that ML I and viscotoxin do not share identical structural domains.

The lectins from Agaricus edulis. Isolation and characterization.

2 lectins from the mushroom Agaricus edulis were isolated, after heating the crude extract at 75 degrees C, by ion exchange chromatography and gel chromatography using QAE-Sephadex A-50 and Sephadex G75. Some hemagglutinating and physicochemical properties of the agglutinins are reported.

Chemical modification studies on the D-galactopyranosyl binding lectin from the mistletoe Viscum album L.

The role of amino, sulfhydryl, disulfide, carboxyl, phenolic, imidazole and indole groups on the agglutination of human erythrocytes by the lectin from Viscum album has been determined using specific chemical modification techniques. The results indicate that tyrosine residues participate in the hemagglutination reaction. Subunits of the lectin possess only reduced hemagglutinating ability.