BackgroundThe liver-derived plasma protein fetuin-A is strongly expressed during fetal life, hence its name. Fetuin-A protein is normally present in most fetal organs and tissues, including brain tissue. Fetuin-A was neuroprotective in animal models of cerebral ischemia and lethal chronic inflammation, suggesting a role beyond the neonatal period. Little is known, however, on the presence of fetuin-A in mature human brain tissue under different physiological and pathological conditions.MethodsWe studied by immunohistochemistry (IHC) the distribution of fetuin-A protein in mature human brain autopsy tissues from patients without neurological disease, patients with inflammatory brain disorders, and patients with ischemic brain lesions. To identify fetuin-A-positive cells in these tissues we co-localized fetuin-A with GFAP (astrocytes) and CD68 (macrophages, activated microglia).Results and discussionUnlike previous reports, we detected fetuin-A protein also in mature human brain as would be expected from an abundant plasma protein also present in cerebrospinal fluid. Fetuin-A immunoreactivity was increased in ischemic white matter and decreased in inflamed cerebellar tissue. Fetuin-A immunostaining was predominantly associated with neurons and astrocytes. Unlike the developing brain, the adult brain lacked fetuin-A immunostaining in CD68-positive microglia. Our findings suggest a role for fetuin-A in tissue remodeling of neonatal brain, which becomes obsolete in the adult brain, but is re-activated in damaged brain tissue. To further assess the role of fetuin-A in the mature brain, animal models involving ischemia and inflammation need to be studied.

The local heat transfer from a plane rotating disc enclosed in a casing has been studied experimentally. The disc of 800 mm diameter can be run up to 2000 min−1 at axial distances between disc and casing varied between 5 and 55 mm. Centrifugal or alternatively centripetal flow of cooling air at rates up to ṁ = 1 kg/s can be applied, both with or without an inlet swirl. With the disc rotating in a closed casing (ṁ = 0 kg/s) the influence of the characteristic dimensionless groups on the local heat transfer has been investigated. At a fixed radius, a variation of the local Reynolds Number by either speed or density results in corresponding changes of the heat transfer. However, with a variation of the radius different heat transfer-Re relations are found. In fact, the temperature distribution in the gas caused by the heat flux results in an additional influence of free convection, to be expressed by a Grashof Number. This is confirmed by a comparison of the experimental results with calculations based on Reynolds Analogy and measured friction coefficients. The discrepancies found can be explained only, if in addition to the limitations of the analogy, the influence of free convection is taken into account. Additional results of ongoing experiments concerning the influence of the geometry of the cavity between disc and casing, of the coolant flow rate and of the swirl are presented.

This staining was performed to detect fetuin-A in activated microglia. CD68 is a marker, that stains activated microglia, macrophages and monocytes. Fetuin-A and microglia were detected in paraffin sections (1 μm thickness) of formalin-fixed human brain tissue. CD68 was stained using a monoclonal mouse-anti-human antibody (Dako Cat# M0814, RRID:AB_2314148, clone KP1, dilution 1:50) and a polyclonal goat-anti-mouse Alexa Fluor® 488 conjugated secondary antibody (Thermo Fisher Scientific Cat# A-11029, RRID:AB_2534088, dilution 1:300).Fetuin-A was detected by using a monoclonal IgG2a mouse-anti-human antibody (clone MAHS-1, dilution 1.0 µg/mL), raised against purified human fetuin-A in our laboratories. Antibody binding was detected by tyramide signal amplification using a secondary biotinylated polyclonal goat-anti-mouse antibody (Dako Cat# E0433, RRID:AB_2687905, dilution 1:300) and a Tyramide Signal Amplification Kit (Life Technologies, Carlsbad, USA, T-20933). To minimize lipofuscin autofluorescence, sections were counterstained with Sudan Black (Sigma-Aldrich, Munich, Germany, 199664, dilution 0.3% in 70% ethanol, 5 minutes). Nuclei were stained with DAPI (Sigma-Aldrich, Munich, Germany D9542, dilution 0.25 µg/ml, 5 minutes). Sections were mounted with Immumount (Thermo Scientific, Waltham, USA, 9990402) and stored at 8°C in the dark.

This staining was performed to detect fetuin-A in astrocytes. Fetuin-A and astrocytes were detected in paraffin sections (1 μm thickness) of formalin-fixed human brain tissue. Glial Fibrillary Acid Antigen (GFAP) was marked by a polyclonal rabbit-anti-human antibody (Spring Bioscience Cat# E18320, RRID:AB_1661177, dilution 1:50) and a polyclonal goat-anti-rabbit Alexa Fluor® 488 conjugated secondary antibody (Thermo Fisher Scientific Cat# A-11070, RRID:AB_2534114, dilution 1:300).Fetuin-A was detected by using a monoclonal IgG2a mouse-anti-human antibody (clone MAHS-1, dilution 1.0 µg/mL), raised against purified human fetuin-A in our laboratories. Antibody binding was detected by tyramide signal amplification using a secondary biotinylated polyclonal goat-anti-mouse antibody (