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Ulrich Neumann

Publications and source records attributed to Ulrich Neumann.

9 recordsLinked to original sources
PubMed2006

Sialic acid is a receptor determinant for infection of cells by avian Infectious bronchitis virus.

The importance of sialic acid for infection by avian Infectious bronchitis virus (IBV) has been analysed. Neuraminidase treatment rendered Vero, baby hamster kidney and primary chicken kidney cells resistant to infection by the IBV-Beaudette strain. Sialic acid-dependent infection was also observed with strain M41 of IBV, which infects primary chicken kidney cells but not cells from other species. In comparison with Influenza A virus and Sendai virus, IBV was most sensitive to pre-treatment of cells with neuraminidase. This finding suggests that IBV requires a greater amount of sialic acid on the cell surface to initiate an infection compared with the other two viruses. In previous studies, with respect to the haemagglutinating activity of IBV, it has been shown that the virus preferentially recognizes alpha2,3-linked sialic acid. In agreement with this finding, susceptibility to infection by IBV was connected to the expression of alpha2,3-linked sialic acid as indicated by the reactivity with the lectin Maackia amurensis agglutinin. Here, it is discussed that binding to sialic acid may be used by IBV for primary attachment to the cell surface; tighter binding and subsequent fusion between the viral and the cellular membrane may require interaction with a second receptor.

Animals↗
PubMed2004

Tumor-associated CD75s gangliosides and CD75s-bearing glycoproteins with Neu5Acalpha2-6Galbeta1-4GlcNAc-residues are receptors for the anticancer drug rViscumin.

The anticancer drug rViscumin, currently under clinical development, has been shown in previous studies to be a sialic acid specific ribosome inactivating protein (RIP). Comparative binding assays with the CD75s-specific monoclonal antibodies HB6 and J3-89 revealed rViscumin to be a CD75s-specific RIP due to identical binding characteristics toward CD75s gangliosides. The receptor gangliosides are IV6nLc4Cer, VI6nLc6Cer, and the newly characterized ganglioside VIII6nLc8Cer, all three carrying the Neu5Acalpha2-6Galbeta1-4GlcNAc motif. To elucidate the clinical potential of the rViscumin targets, CD75s gangliosides were determined in several randomly collected gastrointestinal tumors. The majority of the tumors showed an enhanced expression of CD75s gangliosides compared with the unaffected tissues. The rViscumin binding specificity was further investigated with reference glycoproteins carrying sialylated and desialylated type II N-glycans. Comparative Western blots of rViscumin and ricin, an rViscumin homologous but galactoside-specific RIP, revealed specific recognition of type II N-glycans with CD75s determinants by rViscumin, whereas ricin failed to react with terminally sialylated oligosaccharides such as CD75s motifs and others. This strict binding specificity of rViscumin and the increased expression of CD75s gangliosides in various tumors suggest this anticancer drug as a promising candidate for an individualised adjuvant therapy of human tumors.

Antibodies, Monoclonal↗
PubMed2004

Mistletoe lectin I is a sialic acid-specific lectin with strict preference to gangliosides and glycoproteins with terminal Neu5Ac alpha 2-6Gal beta 1-4GlcNAc residues.

Mistletoe lectin I (ML-I) is a type II ribosome-inactivating protein, which inhibits the protein biosynthesis at the ribosomal level. ML-I is composed of a catalytically active A-chain with rRNA N-glycosidase activity and a B-chain with carbohydrate binding specificities. Using comparative solid-phase binding assays along with electrospray ionization tandem mass spectrometry, ML-I was shown to preferentially bind to terminally alpha2-6-sialylated neolacto series gangliosides from human granulocytes. IV(6)Neu5Ac-nLc4Cer, VI(6)Neu5Ac-nLc6Cer, and VIII(6)Neu5Ac-nLc8Cer were identified as ML-I receptors, whereas the isomeric alpha2-3-sialylated neolacto series gangliosides were not recognized. Only marginal binding of ML-I to terminal galactose residues of neutral glycosphingolipids with a Galbeta1-4Glc or Galbeta1-4GlcNAc sequence was determined, whereas a distal Galalpha1-4Gal, GalNAcbeta1-3Gal, or GalNAcbeta1-4Gal disaccharide did not bind at all. Among the glycoproteins investigated in Western blot and microwell adsorption assays, only those carrying Neu5Acalpha2-6Galbeta1-4GlcNAc residues, exclusively, predominantly, or even as less abundant constituents in an assembly with Neu5Acalpha2-3Galbeta1-4GlcNAc-terminated glycans, displayed high ML-I binding capacity. From our data we conclude that (i) ML-I has to be considered as a sialic acid- and not a galactose-specific lectin and (ii) neolacto series gangliosides and sialoglycoproteins with type II glycans, which share the Neu5Acalpha2-6Galbeta1-4GlcNAc terminus, are true ML-I receptors. This strict preference might help to explain the immunostimulatory potential of ML-I toward certain leukocyte subpopulations and its therapeutic success as a cytotoxic anticancer drug.

Adsorption↗
PubMed2003

Lectin histochemistry of the lymphoid organs of the chicken.

Cellular interactions within the immune system are in part mediated via the carbohydrate-rich coat of the cell membrane, the glycocalyx, of which the terminal carbohydrate residues are of particular functional importance. Thus, these carbohydrate residues from thymus, bursa of Fabricius, spleen and bone marrow of 2- and 30-day-old chickens were investigated by lectin histochemistry. In the thymus, mannose as well as N-acetyl-glucosamine (glcNAc)-specific lectins labelled macrophages, epithelial reticulum cells and lymphocytes within the cortex. In the bursa of Fabricius, the brush border of the lining epithelium, the macrophages and the endothelium were labelled by mannose-specific lectins. The follicle-associated epithelium was labelled by a broad spectrum of lectins. Epithelial cells that separated the cortex from the medulla and large mononuclear cells in the cortex were only being labelled by N-acetyl-galactosamine (galNAc)-specific and glcNAc-specific lectins, respectively. In the spleen, lymphocytes of the peri-ellipsoid lymphocyte sheaths and macrophages of the red pulp were labelled by lectins of nearly all sugar specificities. In general, glycotopes of these organs were more intensively labelled in the 2-day-old chicken than in the 30-day-old chicken, indicating changes in glycotope expression during post-hatching development. Thus, cells of the avian immune system are as rich and diverse in their lectin binding sites as their mammalian counterparts, indicating that similar carbohydrate lectin interactions between cells and matrices take place in birds as well.

Acetylglucosamine↗
PubMed2003

3D tooth shape from radiographs using thin-plate splines.

Current methods to produce 3-dimensional tooth root models involve conversion from radiographic means (computed tomography) or creation using computer-assisted design (CAD) software. The former lacks detail while the second is manually fabricated and can bear little resemblance to the original. Thin-plate splines have been used in morphometrics to define changes of shape between subjects of the same species. Herein, we use thin-plate splines to deform a 3D geometric prior model of a tooth to match 2D patient radiographs, producing a "best-fit" patient specific 3D geometric polygonal mesh of the tooth.

Humans↗
PubMed2003

The virtual craniofacial patient: 3D jaw modeling and animation.

In this paper, we present new developments in the area of 3D human jaw modeling and animation. CT (Computed Tomography) scans have traditionally been used to evaluate patients with dental implants, assess tumors, cysts, fractures and surgical procedures. More recently this data has been utilized to generate models. Researchers have reported semi-automatic techniques to segment and model the human jaw from CT images and manually segment the jaw from MRI images. Recently opto-electronic and ultrasonic-based systems (JMA from Zebris) have been developed to record mandibular position and movement. In this research project we introduce: (1) automatic patient-specific three-dimensional jaw modeling from CT data and (2) three-dimensional jaw motion simulation using jaw tracking data from the JMA system (Zebris).

Computer Simulation↗
PubMed2002

Preferential binding of the anticancer drug rViscumin (recombinant mistletoe lectin) to terminally alpha2-6-sialylated neolacto-series gangliosides.

Production of biochemically defined recombinant mistletoe lectin was achieved by cloning and separate expression of the single catalytically active A-chain and the B-chain with carbohydrate binding properties in Escherichia coli, yielding an active heterodimeric protein named rViscumin (Eck et al. [1999] Eur. J. Biochem., 265, 788-797). Employing solid phase binding assays, rViscumin was shown to preferentially bind to terminally alpha2-6-sialylated neolacto-series gangliosides IV(6)Neu5Ac-nLc4Cer, VI(6)Neu5Ac-nLc6Cer, and VIII(6)Neu5Ac-nLc8Cer isolated from human granulocytes. Only marginal binding of rViscumin to galactose-terminated neutral GSLs was determined, whereas reinvestigation of ricin specificity demonstrated this lectin as a galactose-binding protein. Human promyelotic HL-60 cells exhibited an IC(50) value (half maximum cytotoxicity) of 1.16 pM and human bladder carcinoma 5637 cells of 12.1 pM rViscumin; CHO-K1 cells were resistant to rViscumin treatment up to a concentration of 5.26 nM tested. Quantification of the predominant receptor ganglioside IV(6)Neu5Ac-nLc4Cer by means of a specific anti-Neu5Acalpha2-6Galbeta1-4GlcNAc-R antibody revealed 3.68 x 10(6) and 1.54 x 10(6) receptor molecules per HL-60 and 5637 cell, respectively; CHO-K1 cells were negative, lacking alpha2-6-sialylated gangliosides. The data imply a direct correlation of rViscumin cytotoxicity and the expression of receptor ganglioside. Moreover, CHO-K1 cells were rendered susceptible toward rViscumin cytotoxicity after exogenous application of human granulocyte gangliosides. Thus, (1) rViscumin has to be considered as a sialic acid-specific rather than a galactose-specific type II ribosome-inactivating protein, and (2) neolacto-series gangliosides with Neu5Acalpha2-6Galbeta1-4GlcNAc-terminus are true functional and physiologically relevant rViscumin receptors.

Animals↗
PubMedDate not supplied

Expressive facial animation synthesis by learning speech coarticulation and expression spaces.

Synthesizing expressive facial animation is a very challenging topic within the graphics community. In this paper, we present an expressive facial animation synthesis system enabled by automated learning from facial motion capture data. Accurate 3D motions of the markers on the face of a human subject are captured while he/she recites a predesigned corpus, with specific spoken and visual expressions. We present a novel motion capture mining technique that "learns" speech coarticulation models for diphones and triphones from the recorded data. A Phoneme-Independent Expression Eigenspace (PIEES) that encloses the dynamic expression signals is constructed by motion signal processing (phoneme-based time-warping and subtraction) and Principal Component Analysis (PCA) reduction. New expressive facial animations are synthesized as follows: First, the learned coarticulation models are concatenated to synthesize neutral visual speech according to novel speech input, then a texture-synthesis-based approach is used to generate a novel dynamic expression signal from the PIEES model, and finally the synthesized expression signal is blended with the synthesized neutral visual speech to create the final expressive facial animation. Our experiments demonstrate that the system can effectively synthesize realistic expressive facial animation.

Artificial Intelligence↗