Immunocytochemical localization of apolipoprotein A-I using polyclonal antibodies raised against the formaldehyde-modified antigen

The preparation of cells for electron microscopy, in particular the fixation and embedding routine, influences the antigenicity, often resulting in a markedly reduced labelling intensity. To overcome the difficulties associated with fixation-induced changes in antigenicity, we produced antibodies against pre-fixed human apolipoprotein (apo) A-I. Purified apo A-I was fixed with 4% formaldehyde and was used to raise polyclonal antibodies in rabbits. The antiserum was purified by protein-A-Sepharose followed by affinity chromatography with the fixed antigen coupled to vinylsulphone-activated agarose. The specificity of the antibodies was ascertained by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis against different fixed and unfixed lipoproteins. In ELISA, the reaction of the antibodies was markedly enhanced with the fixed antigen, indicating that the antibodies were directed against epitopes characteristically modified by the fixation. The efficacy of the antibodies for light and electron microscopy was tested on HepG2 cells and on human liver cells. When HepG2 cells were exposed to anti-apo A-I antibodies followed by a secondary FITC-labelled antibody, fluorescence was found intracellularly in distinct regions. Electron microscopy revealed that the endoplasmic reticulum, and in particular the trans elements of the Golgi complexes, were the main compartments stained for apo A-I both in HepG2 cells, as shown by the immunoperoxidase technique, and in human hepatocytes, as shown by the protein-A-gold technique on ultrathin cryosections. The findings demonstrate the potential of using antibodies to fixed antigens as a strategy to overcome impaired localization due to fixation in cytochemistry at the light microscopic and electron microscopic levels.     

Fast segmentation of range images into planar regions by scan line grouping

A novel technique is presented for rapid partitioning of surfaces in range images into planar patches. The method extends and improves Pavlidis' algorithm (1976), proposed for segmenting images from electron microscopes. The new method is based on region growing where the segmentation primitives are scan line grouping features instead of individual pixels. We use a noise variance estimation to automatically set thresholds so that the algorithm can adapt to the noise conditions of different range images. The proposed algorithm has been tested on real range images acquired by two different range sensors. Experimental results show that the proposed algorithm is fast and robust.     

Ultrasonic dispersion and attenuation near the liquid-gas critical point of4He

We describe sound velocity and acoustic attenuation measurements at several frequencies between 0.5 and 5 MHz along the critical isochore of ⁴ He immediately above the critical pointT _c. The dispersion is obtained with respect to the velocity measurements by Barmatz taken at 1.8 kHz along the critical isochore. The dispersion and attenuation results are analyzed following the theory of Kawasaki and using the more recent modifications resulting from the Fixman-Mistura approach as described by Garland and co-workers. We have determined the critical exponent for the correlation length divergence to be v=0.66±0.04 and found good internal consistency between certain constants appearing in the theoretical expressions for both sound dispersion and attenuation. These experimentally determined constants are compared with those calculated from other experiments. Deviations in the observed acoustic properties from the predicted ones are discussed. They are similar to those found in acoustic experiments and in light scattering experiments near the critical point of Xe.     

Einfluß der Kaltverformung auf das Zeitstand- und Kriechverhalten einiger warmfester austenitischer Stähle

Zeitstandversuche an den Stählen X 10 NiCrAITi 32 20, X 8 CrNiMoNb 16 16 und X 10 NiCrMoTiB 15 15 bei 650 °C bis zu 6 000 h nach dem Lösungsglühen und anschließender Kaltverformung zwischen 0 und 60%. Einfluß der Kaltverformung auf die Zeitstandfestigkeit und die niedrigste Kriechgeschwindigkeit. Zeitbruchdehnung und -einschnürung in Abhängigkeit von der Kaltverformung. Licht- und elektronenmikroskopische Untersuchung der Ausscheidungsvorgänge und der Änderungen des Versetzungsnetzwerks. Zusammenhang zwischen der Erniedrigung der Kriechgeschwindigkeit und dem Kohlenstoffgehalt.     

Eine Heliumkühlvorrichtung zur Verwendung in Werkstoffprüfmaschinen

Anwendungsmöglichkeiten einer Heliumkühlvorrichtung und Erprobung einer solchen Vorrichtung. Gründe für ihre gute Wirksamkeit. Spannung-Dehnung-Kurve einer Kupferzugprobe bei 4 K. Vorteile der Krafteinleitung über Zug- und Druckstäbe. Verwendbarkeit für Zug-, Biege- und Bruchmechanikversuche.     

Die remissionsspektralphotometrische Bestimmung von Trigonellin und Coffein in Kaffee

Zusammenfassung Es wird eine Methode zur quantitativen Bestimmung von Trigonellin und Coffein in Röst- und Pulverkaffee mittels Remissions-Spektralphotometrie nach dünnschicht-chromatographischer Trennung beschrieben. Die störenden, braunen Bestandteile werden an DEAE-Cellulose selektiv abgeschieden. Pulverkaffees enthalten 0,8–1,5% Trigonellin, Roh- und Röstkaffees 0,5–1,0%.

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Determination of trigonellin and coffein in coffee by reflection spectrophotometry

Summary A procedure is described to determine trigonellin and coffein in roasted coffees and instant products by reflection spectrophotometry after separation by thin layer chromatography. The disturbing brown ingredients are separated selectively on DEAE-cellulose. Instant coffees contain 0,8–1,5% trigonellin, green and roasted coffees 0,5–1,0%.