Indentation creep testing of superalloys

Great progress has been made over the last years in high temperature nanoindentation testing and quite reliable test systems are available to operate at temperatures up to 800°C. With such systems the high temperature strength is measured via the hardness of materials. However, for high temperature materials especially the creep strength is of interest and therefore also many attempts have been undergone to probe also the creep properties with high temperature nanoindentation. In most cases pointed indenters as Berkovich or conical indenters have been used for this. A major challenge, however, then is, how the nanoindentation data are converted into uniaxial creep properties, i.e. those which are needed for constructional purposes. Although, it seems that the stress exponent can be derived quite successfully with such indenters, an evaluation of a full creep curve for materials with significant primary creep does not seem possible, since the strain a pointed indenter is inducing is fixed by the indenter shape and stays more or less constant during the whole test [1]. Please click Additional Files below to see the full abstract

Plasma levels of leptin, omentin, collagenous repeat-containing sequence of 26-kDa protein (CORS-26) and adiponectin before and after oral glucose uptake in slim adults

BACKGROUND: Adipose tissue secreted proteins are collectively named adipocytokines and include leptin, adiponectin, resistin, collagenous repeat-containing sequence of 26-kDa protein (CORS-26) and omentin. Several of these adipocytokines influence insulin sensitivity and glucose metabolism and therefore systemic levels may be affected by oral glucose uptake. Whereas contradictory results have been published for leptin and adiponectin, resistin has not been extensively investigated and no reports on omentin and CORS-26 do exist. METHODS: Therefore the plasma levels of these proteins before and 120 min after an oral glucose load were analyzed in 20 highly-insulin sensitive, young adults by ELISA or immunoblot. RESULTS: Circulating leptin was reduced 2 h after glucose uptake whereas adiponectin and resistin levels are not changed. Distribution of adiponectin and CORS-26 isoforms were similar before and after glucose ingestion. Omentin is highly abundant in plasma and immunoblot analysis revealed no alterations when plasma levels before and 2 h after glucose intake were compared. CONCLUSION: Taken together our data indicate that only leptin is reduced by glucose uptake in insulin-sensitive probands whereas adiponectin and resistin are not altered. CORS-26 was demonstrated for the first time to circulate as high molecular weight form in plasma and like omentin was not influenced by oral glucose load. Omentin was shown to enhance insulin-stimulated glucose uptake but systemic levels are not correlated to postprandial blood glucose

High temperature indentation creep and nanoindentation testing of superalloys and TiAl alloys

Measuring of the high temperature mechanical behaviour of materials by local testing has become a key task in the field of nanomechanics. However, gaining access to the application temperature of many metallic high temperature materials, which is in the range of 600°C - 1100°C, is quite difficult. In addition, creep parameters can only be determined by long time measurements, where drift influences become a severe challenge. Here we present a new approach of indentation creep testing with a flat punch indenter. For this, a thermo mechanical analyzer with very precise temperature control is used, which allows testing at temperatures up to 1200°C. A flat punch indenter with a diameter of around 10 µm allows for example local investigations of the creep properties on the dendritic scale of superalloys. This approach is also interesting to study the creep properties along the gradient of diffusion couples. Here, first test measurements on superalloys and other materials are presented and discussed. For comparison also high temperature nanoindentation measurements will be shown. Such measurements have been conducted on a multiphase titanium aluminide alloy from room temperature up to 600°C. The results show, that the hardness of the (β0+ω0)-composite phase is the highest among all phases and remains constant up to the service temperature. Both approaches of high temperature testing are compared and the prospect of these methods will be discussed

Lipopolysaccharide regulated protein expression is only partly impaired in monocytes from patients with type I diabetes

BACKGROUND: Monocytes play an important role in innate immunity and atherosclerosis. A disturbed secretion of cytokines in lipopolysaccharide (LPS) activated monocytes from type 1 diabetes (T1D) patients has been described and may contribute to the impaired inflammatory response in these individuals. In the present study the influence of LPS on five different proteins with a function in immunity and atherosclerosis was analyzed in monocytes from controls and T1D patients. METHODS: Monocytes were isolated from controls and T1D patients and the LPS-stimulated increase of IL-6, CXCL8, monocyte chemotactic protein 1 (CCL2, MCP-1) and superoxide dismutase (SOD 2), as well as the LPS-mediated decrease of apolipoprotein E (Apo E) in primary human monocytes from controls and T1D patients was determined. RESULTS: CCL2 and IL-6 secretion in response to LPS was found significantly reduced in monocytes from T1D patients when compared to controls whereas basal CCL2 release was similar in control and T1D cells. In contrast, CXCL8 and apolipoprotein E secretion and SOD 2 expression upon LPS stimulation is similar from T1D and control monocytes. CONCLUSION: These data indicate that LPS-mediated protein expression is only partly disturbed in monocytes from T1D patients. Reduced secretion of IL-6 and CCL2 in activated monocytes of these patients may contribute to an impaired inflammatory response and vascular disease

Adiponectin-induced secretion of interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1, CCL2) and interleukin-8 (IL-8, CXCL8) is impaired in monocytes from patients with type I diabetes

BACKGROUND: Systemic adiponectin is reduced in patients with cardiovascular disease (CVD) and low adiponectin may contribute to the pathogenesis of atherosclerosis. However, circulating adiponectin is elevated in type 1 diabetes (T1D) patients, who have also a higher incidence to develop CVD. Because monocytes play an important role in atherosclerosis, we analysed the influence of adiponectin on cytokine and chemokine release in monocytes from T1D patients and controls. METHODS: Systemic adiponectin was determined in the plasma and the high-molecular weight (HMW) form of adiponectin was analysed by immunoblot. Monocytes were isolated from T1D patients and controls and the adiponectin-stimulated release of interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1, CCL2) and interleukin-8 (IL-8, CXCL8) was analysed. RESULTS: Systemic adiponectin was higher in T1D patients. Immunoblot analysis of the plasma indicate abundance of HMW adiponectin in T1D patients and controls. IL-6, CCL2 and CXCL8 secretion in response to adiponectin were found induced in monocytes from controls whereas only IL-6 was upregulated in T1D cells. The induction of IL-6 by adiponectin was abrogated by an inhibitor of the NFκB pathway. CONCLUSION: These data indicate that adiponectin-mediated induction of IL-6, CCL2 and CXCL8 is disturbed in monocytes from T1D patients and therefore elevated systemic adiponectin in T1D patients may be less protective when compared to controls

Interactions of Adiponectin and Lipopolysaccharide from Porphyromonas gingivalis on Human Oral Epithelial Cells

BACKGROUND: Periodontitis is an inflammatory disease caused by pathogenic microorganisms, such as Porphyromonas gingivalis, and characterized by the destruction of the periodontium. Obese individuals have an increased risk for periodontitis and show decreased serum levels of adiponectin. This in-vitro study was established to examine whether adiponectin modulates critical effects of lipopolysaccharide (LPS) from P. gingivalis on oral epithelial cells (OECs). METHODOLOGY/PRINCIPAL FINDINGS: The presence of adiponectin and its receptors in human gingival tissue samples and OECs was analyzed by immunohistochemistry and PCR. Furthermore, OECs were treated with LPS and/or adiponectin for up to 72 h, and the gene expression and protein synthesis of pro- and anti-inflammatory mediators, matrix metalloproteinases (MMPs) and growth factors were analyzed by real-time PCR and ELISA. Additionally, cell proliferation, differentiation and in-vitro wound healing were studied. The nuclear translocation of NFκB was investigated by immunofluorescence. Gingival tissue sections showed a strong synthesis of adiponectin and its receptors in the epithelial layer. In cell cultures, LPS induced a significant up-regulation of interleukin (IL) 1β, IL6, IL8, MMP1 and MMP3. Adiponectin abrogated significantly the stimulatory effects of LPS on these molecules. Similarly, adiponectin inhibited significantly the LPS-induced decrease in cell viability and increase in cell proliferation and differentiation. Adiponectin led to a time-dependent induction of the anti-inflammatory mediators IL10 and heme oxygenase 1, and blocked the LPS-stimulated NFκB nuclear translocation. CONCLUSIONS/SIGNIFICANCE: Adiponectin may counteract critical actions of P. gingivalis on oral epithelial cells. Low levels of adiponectin, as observed in obese individuals, may increase the risk for periodontal inflammation and destruction

Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

Identifizierung potentieller Interaktionspartner der Adiponectin Rezeptoren und Untersuchungen zur Adiponectin-induzierten Genexpression in Hepatozyten

Ziel dieser Arbeit war die Identifizierung potentieller Interaktionspartner der Adiponectin Rezeptoren und Untersuchungen zur Adiponectin induzierten Genexpression in Hepatozyten. Für fast alle Versuche wurden primäre humanen Hepatozyten verwendet, was für die Validität der Ergebnisse und deren in vivo Relevanz von entscheidender Bedeutung ist. Die Analyse der mRNA Expression von primären humanen Hepatozyten, die mit HMW-Apm stimuliert wurden, zeigte, dass ca. 300 Gene durch HMW-Apm auf mRNA Ebene reguliert werden. Die AOX1 wurde bisher meist aus pharmakologischer Sicht untersucht, weshalb über die Regulation dieses Proteins wenig bekannt ist. Es konnte gezeigt werden, dass AOX1 durch HMW-Apm und Fenofibrat über die Aktivierung von PPAR-alpha reprimiert wird. Da PPAR-alpha über die Bindung von Adiponectin an AdipoR2 reguliert wird, lässt sich sagen, dass AOX1 von HMW-Apm über AdipoR2 und PPAR-alpha reguliert wird. Die Daten zur erhöhten Expression der AOX1 in der Fettleber von Ratten müssen noch in entsprechenden humanen Proben untersucht werden. Wird dies bestätigt, eröffnen sich neue Fragen und Einblicke bezüglich des Einflusses von AOX1 auf den Stoffwechsel von Medikamenten und Xenobiotika in der verfetteten Leber. Die Erkenntnisse zur Adiponectin vermittelten Signaltransduktion werden entscheidend durch die Identifizierung des Transkriptionsfaktors HNF4-alpha als ein durch HMW-Apm reprimiertes Protein ergänzt. So konnte gezeigt werden, dass HMW-Apm neben HNF4-alpha auch dessen Zielgene ApoB, ABCB4, GLUT2 und OCT1 reprimiert. Zusätzlich wurde eine verringerte Sekretion von ApoE gefunden, die wahrscheinlich durch die verminderte Freisetzung von ApoB bedingt ist. Eine reduzierte Sekretion von ApoB-haltigen hepatischen Lipoproteinen erklärt zum Teil die negative Assoziation von systemischen Adiponectin zu LDL. Vermindertes systemisches LDL führt sekundär zu einer Erhöhung von HDL, was sich in der positiven Korrelation von Adiponectin zu HDL ausdrückt. Weiterhin konnte in dieser Arbeit das erste Mal gezeigt werden, dass AdipoR1 sowohl in primären humanen Hepatozyten als auch in hepatozytären Zelllinien exprimiert ist. In Hepatozyten wird AdipoR1 auf Proteinebene durch Fenofibrat reprimiert, während LXR/RXR Agonisten und Pioglitazon keinen Einfluss auf AdipoR1 haben. Dies legt den Schluss nahe, dass AdipoR1 in Hepatozyten kein direktes Zielgen dieser nukleären Rezeptoren ist. Mit Hilfe von in vitro translatierten und rekombinant exprimierten AdipoR2 Protein konnte gezeigt werden, dass AdipoR2, anders als in der initialen Publikation mit 35,4 kDa beschrieben, ein 43 kDa Protein ist. Die zusätzlichen 75 Aminosäuren am N-Terminus von AdipoR2 zeigen keine Homologie zu AdipoR1, während die restlichen Aminosäuren eine hohe Ähnlichkeit dazu aufweisen. In dieser Arbeit konnte weiterhin gezeigt werden, dass die Expression von AdipoR1 in der Fettleber aus Ratten unter Hochfettdiät nicht verändert ist, während die AdipoR2 mRNA induziert ist. In Mäusen mit einer durch Gallengangsligatur bedingten Leberzirrhose ist die mRNA Expression von AdipoR1 und AdipoR2 und die Menge an AdipoR1 Protein reduziert. Die Interaktion von SNTA und SNTB2 mit den C-terminalen Bereichen der beiden Adiponectin Rezeptoren stellt das interessanteste Ergebnis dieser Arbeit dar. Die Interaktion zwischen diesen Proteinen wird über die PDZ Domäne von SNTA und SNTB2 vermittelt, die wahrscheinlich mit den PDZ Bindemotiven am C-Terminus von AdipoR1 und AdipoR2 wechselwirken. Es konnte nachgewiesen werden, dass die beiden Rezeptoren so in der Membran orientiert sind, dass der C-Terminus intrazellulär und der N-Terminus extrazellulär liegt. Die Interaktion mit SNTB2 und AdipoR1 oder AdipoR2 wurde durch die Stimulation mit HMW-Apm verstärkt, während die Maskierung der PDZ Bindedomäne der beiden Rezeptoren zu einem Verlust der Interaktion führt. Die funktionelle Bedeutung dieser Interaktion wurde mit siRNA Experimenten untersucht. Die Reduktion von SNTA durch siRNA führte zu einer Induktion von AdipoR1 auf Proteinebene, während der Knock-down von STNB2 zu einer Reduktion von AdipoR1 resultierte. Funktionell führte die Reduktion von SNTA und SNTB2 zu keiner Veränderung im Signalweg von Adiponectin über AdipoR2. Der Knock-down von SNTB2 reduzierte den Effekt von Adiponectin über AdipoR1, während die Reduktion von SNTA zu einer tendenziellen Verstärkung des Adiponectin Effekts über AdipoR1 führte. Dies deutet auf eine antagonistische Wirkung von SNTA und SNTB2 in der Funktion von AdipoR1 hin. Um zu klären ob diese Interaktion auch in vivo von Bedeutung ist, wurden in Kooperation mit Marvin Adams die Lebern von SNTA-/-, SNTB2-/- und SNTA/B2-/- Knock-out Tieren untersucht. Ähnlich wie in den siRNA Experimenten führte das Fehlen von SNTA zu einer Induktion von AdipoR1, während die Defizienz von SNTB2 in einer Reduktion von AdipoR1 resultierte. Die Menge an AdipoR2 war im Gegensatz zu den SNTA-/- Mäusen, wo keine Veränderung von AdipoR2 zu beobachten ist, in den SNTB2-/- Mäusen reduziert. In den SNTA/B2-/- Doppel-Knock-out Tieren war AdipoR2 reduziert, während AdipoR1 Protein in der gleichen Menge enthalten war wie in den WT Tieren. In der metabolischen Charakterisierung zeigten die SNTA-/- und SNTB2-/- Tiere eine gestörte Glukosetoleranz, wohingegen die SNTA/B2-/- Tiere eine normale Gluksoetoleranz aufwiesen. Zusätzlich lag in den SNTB2-/- Tieren eine verringerte Insulinsensitivität vor. Dies unterstützt die in vitro Daten aus den siRNA Experimenten, dass SNTA und SNTB2 gegenteilige Effekte auf den Glukosestoffwechsel ausüben und dass das gleichzeitige Fehlen von SNTA und SNTB2 diese antagonistischen Effekte kompensiert

Adiponectin, a key adipokine in obesity related liver diseases

Non-alcoholic fatty liver disease (NAFLD) comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), and progressive liver fibrosis is considered the most common liver disease in western countries. Fatty liver is more prevalent in overweight than normal-weight people and liver fat positively correlates with hepatic insulin resistance. Hepatic steatosis is regarded as a benign stage of NAFLD but may progress to NASH in a subgroup of patients. Besides liver biopsy no diagnostic tools to identify patients with NASH are available, and no effective treatment has been established. Visceral obesity is a main risk factor for NAFLD and inappropriate storage of triglycerides in adipocytes and higher concentrations of free fatty acids may add to increased hepatic lipid storage, insulin resistance, and progressive liver damage. Most of the adipose tissue-derived proteins are elevated in obesity and may contribute to systemic inflammation and liver damage. Adiponectin is highly abundant in human serum but its levels are reduced in obesity and are even lower in patients with hepatic steatosis or NASH. Adiponectin antagonizes excess lipid storage in the liver and protects from inflammation and fibrosis. This review aims to give a short survey on NAFLD and the hepatoprotective effects of adiponectin