Prozessoptimierung des SLM-Prozesses mit hoch-reflektiven und thermisch sehr gut leitenden Materialien durch systematische Parameterfindung und begleitende Simulationen am Beispiel von Silber

Additive Manufacturing durch Aufschmelzen von Metallpulvern hat sich auf breiter Front als Herstellverfahren, auch für Endprodukte, etabliert. Besonders für die Variante des Selective Laser Melting (SLM) sind Anwendungen in der Zahntechnik bereits weit verbreitet und der Einsatz in sensitiven Branchen wie der Luftfahrt ist in greifbare Nähe gerückt. Deshalb werden auch vermehrt Anstrengungen unternommen, um bisher nicht verarbeitete Materialien zu qualifizieren. Dies sind vorzugsweise Nicht-Eisen- und Edelmetalle, die sowohl eine sehr hohe Reflektivität als auch eine sehr gute Wärmeleitfähigkeit aufweisen – beides Eigenschaften, die die Beherrschung des Laser-Schmelzprozesses erschweren und nur kleine Prozessfenster zulassen. Die Arbeitsgruppe SLM des Lehr- und Forschungsgebietes Hochleistungsverfahren der Fertigungstechnik hat sich unter der Randbedingung einer kleinen und mit geringer Laserleistung ausgestatteten SLM Maschine der Aufgabe gewidmet und am Beispiel von Silber die Parameterfelder für Einzelspuren und wenig komplexe Geometrien systematisch untersucht. Die Arbeiten wurden von FEM Simulationen begleitet und durch metallographische Untersuchungen verifiziert. Die Ergebnisse bilden die Grundlage zur schnellen Parameterfindung bei komplexen Geometrien und bei Veränderungen der Zusammensetzung, wie sie bei zukünftigen Legierungen zu erwarten sind. Die Ergebnisse werden exemplarisch auf unterschiedliche Geometrien angewandt und entsprechende Bauteile gezeigt.

Gastropod Seed Dispersal: An Invasive Slug Destroys Far More Seeds in Its Gut than Native Gastropods

Seed dispersal is one of the most important mechanisms shaping biodiversity, and animals are one of the key dispersal vectors. Animal seed dispersal can directly or indirectly be altered by invasive organisms through the establishment of new or the disruption of existing seed dispersal interactions. So far it is known for a few gastropod species that they ingest and defecate viable plant seeds and consequently act as seed dispersers, referred to as gastropodochory. In a multi-species experiment, consisting of five different plant species and four different gastropod species, we tested with a fully crossed design whether gastropodochory is a general mechanism across native gastropod species, and whether it is altered by the invasive alien slug species Arion lusitanicus. Specifically, we hypothesized that a) native gastropod species consume the seeds from all tested plant species in equal numbers (have no preference), b) the voracious invasive alien slug A. lusitanicus – similarly to its herbivore behaviour – consumes a higher amount of seeds than native gastropods, and that c) seed viability is equal among different gastropod species after gut passage. As expected all tested gastropod species consumed all tested plant species. Against our expectation there was a difference in the amount of consumed seeds, with the largest and native mollusk Helix pomatia consuming most seeds, followed by the invasive slug and the other gastropods. Seed damage and germination rates did not differ after gut passage through different native species, but seed damage was significantly higher after gut passage through the invasive slug A. lusitanicus, and their germination rates were significantly reduced.

P450 oxidoreductase deficiency: a new disorder of steroidogenesis affecting all microsomal P450 enzymes

Combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase activities was first described in 1985; however the genes for P450c17 and P450c21 in these patients lack mutations. In 1986 we postulated that this disorder might be due to mutations in P450 oxidoreductase (POR), the flavoprotein that donates electron to these and all other microsomal P450 enzymes, but this hypothesis was not tested until the POR gene sequence became available through the genome database. We found five POR missense mutations in our first four patients. In vitro assays of the activities of these mutations showed that the standard assay of POR activity, reduction of cytochrome c, correlated poorly with the patients' phenotypes, but that assays of POR-supported 17alpha-hydroxylase and 17,20 lyase activities correlated well. POR deficiency is a new disorder of adrenal and gonadal steroidogenesis that affects all microsomal cytochrome P450 enzymes, hence may have important implications for genetic differences in drug metabolism.

Lack of Host Gut Microbiota Alters Immune Responses and Intestinal Granuloma Formation during Schistosomiasis

Fatalities from schistosome infections arise due to granulomatous, immune-mediated responses to eggs that become trapped in host tissues. Schistosome-specific immune responses are characterized by initial Th1 responses and our previous studies demonstrated that Myd88-deficient mice failed to initiate such responses in vivo. Paradoxically, schistosomal antigens fail to stimulate innate cells to release pro-inflammatory cytokines in vitro. Since S. mansoni infection is an intestinal disease, we hypothesized that commensal bacteria could act as bystander activators of the intestinal innate immune system to instigate Th1 responses. Using a broad spectrum of orally-administered antibiotics and antimycotics we analyzed schistosome-infected mice that were simultaneously depleted of gut bacteria. After depletion there was significantly less inflammation in the intestine which was accompanied by decreased intestinal granuloma development. In contrast, liver pathology remained unaltered. In addition, schistosome-specific immune responses were skewed and fecal egg excretion was diminished. This study demonstrates that host microbiota can act as a third partner in instigating helminth-specific immune responses.

Induction of cytochrome P450 enzymes in primary equine hepatocyte culture

In this study, we established cell culture conditions for primary equine hepatocytes allowing cytochrome P450 enzyme (CYP) induction experiments. Hepatocytes were isolated after a modified method of Bakala et al. (2003) and cultivated on collagen I coated plates. Three different media were compared for their influence on morphology, viability and CYP activity of the hepatocytes. CYP activity was evaluated with the fluorescent substrate 7-benzyloxy-4-trifluoromethylcoumarin. Induction experiments were carried out with rifampicin, dexamethasone or phenobarbital. Concentration-response curves for induction with rifampicin were created. Williams' medium E showed the best results on morphology and viability of the hepatocytes and was therefore used for the following induction experiments. Cells cultured in Dulbecco's Modified Eagle Medium were not inducible. Incubation with rifampicin increased the CYP activity in two different hepatocyte preparations in a dose dependent manner (EC50=1.20 μM and 6.06 μM; Emax=4.1- and 3.4-fold induction). No increase in CYP activity was detected after incubation with dexamethasone or phenobarbital. The hepatocyte culture conditions established in this study proved to be valuable for investigation of the induction of equine CYPs. In further studies, other equine drugs can be evaluated for CYP induction with this in vitro system.

Genetic variation in genes for the xenobiotic-metabolizing enzymes CYP1A1, EPHX1, GSTM1, GSTT1, and GSTP1 and susceptibility to colorectal cancer in Lynch syndrome.

Individuals with Lynch syndrome are predisposed to cancer due to an inherited DNA mismatch repair gene mutation. However, there is significant variability observed in disease expression likely due to the influence of other environmental, lifestyle, or genetic factors. Polymorphisms in genes encoding xenobiotic-metabolizing enzymes may modify cancer risk by influencing the metabolism and clearance of potential carcinogens from the body. In this retrospective analysis, we examined key candidate gene polymorphisms in CYP1A1, EPHX1, GSTT1, GSTM1, and GSTP1 as modifiers of age at onset of colorectal cancer among 257 individuals with Lynch syndrome. We found that subjects heterozygous for CYP1A1 I462V (c.1384A>G) developed colorectal cancer 4 years earlier than those with the homozygous wild-type genotype (median ages, 39 and 43 years, respectively; log-rank test P = 0.018). Furthermore, being heterozygous for the CYP1A1 polymorphisms, I462V and Msp1 (g.6235T>C), was associated with an increased risk for developing colorectal cancer [adjusted hazard ratio for AG relative to AA, 1.78; 95% confidence interval, 1.16-2.74; P = 0.008; hazard ratio for TC relative to TT, 1.53; 95% confidence interval, 1.06-2.22; P = 0.02]. Because homozygous variants for both CYP1A1 polymorphisms were rare, risk estimates were imprecise. None of the other gene polymorphisms examined were associated with an earlier onset age for colorectal cancer. Our results suggest that the I462V and Msp1 polymorphisms in CYP1A1 may be an additional susceptibility factor for disease expression in Lynch syndrome because they modify the age of colorectal cancer onset by up to 4 years.

Cardiolipin biosynthesis and remodeling enzymes are altered during development of heart failure.

Cardiolipin (CL) is responsible for modulation of activities of various enzymes involved in oxidative phosphorylation. Although energy production decreases in heart failure (HF), regulation of cardiolipin during HF development is unknown. Enzymes involved in cardiac cardiolipin synthesis and remodeling were studied in spontaneously hypertensive HF (SHHF) rats, explanted hearts from human HF patients, and nonfailing Sprague Dawley (SD) rats. The biosynthetic enzymes cytidinediphosphatediacylglycerol synthetase (CDS), phosphatidylglycerolphosphate synthase (PGPS) and cardiolipin synthase (CLS) were investigated. Mitochondrial CDS activity and CDS-1 mRNA increased in HF whereas CDS-2 mRNA in SHHF and humans, not in SD rats, decreased. PGPS activity, but not mRNA, increased in SHHF. CLS activity and mRNA decreased in SHHF, but mRNA was not significantly altered in humans. Cardiolipin remodeling enzymes, monolysocardiolipin acyltransferase (MLCL AT) and tafazzin, showed variable changes during HF. MLCL AT activity increased in SHHF. Tafazzin mRNA decreased in SHHF and human HF, but not in SD rats. The gene expression of acyl-CoA: lysocardiolipin acyltransferase-1, an endoplasmic reticulum MLCL AT, remained unaltered in SHHF rats. The results provide mechanisms whereby both cardiolipin biosynthesis and remodeling are altered during HF. Increases in CDS-1, PGPS, and MLCL AT suggest compensatory mechanisms during the development of HF. Human and SD data imply that similar trends may occur in human HF, but not during nonpathological aging, consistent with previous cardiolipin studies.